Azimuthing propulsion unit

Abstract

An azimuthing propulsion unit (1000) comprising a motor and a propeller, in particular a contra rotating motor (1) and a contra rotating propeller (9, 10) driven by the contra rotating motor.

Description

[0001] AZIMUTHING PROPULSION UNIT

[0002] TECHNICAL FIELD

[0003] Embodiments of the present invention relate to an azimuthing propulsion unit. Further embodiments relate to a method for operating an azimuthing propulsion unit.

[0004] BACKGROUND

[0005] Azimuthing propulsion units provide an efficient way to propel marine vessels.

[0006] Further, azimuthing propulsion units allow for an improved maneuverability of marine vessels. In azimuthing propulsion units, at least one marine propeller attached to a rotatable pod provides thrust. A direction of the thrust may be controlled via a rotation of the rotatable pod. In typical azimuthing propulsion units, at least one electric motor driving the at least one marine propeller is integrated in the pod.

[0007] Azimuthing propulsion units that provide a high efficiency, durability and maintainability are desired.

[0008] SUMMARY

[0009] The invention is defined by the independent claims. The dependent claims define further embodiments of the invention.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings relate to embodiments of the disclosure and are described in the following:

[0012] Fig OA schematically illustrates an azimuthing propulsion unit according to the embodiments described herein;

[0013] Fig OB schematically illustrates an azimuthing propulsion unit according to the embodiments described herein;

[0014] Fig OC schematically illustrates an azimuthing propulsion unit according to the embodiments described herein;

[0015] FIG 1A schematically illustrates a cross-section of an isometric view of an azimuthing propulsion unit according to the embodiments described herein;FIG IB illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein;

[0016] FIG 1C illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein;

[0017] FIG ID illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein;

[0018] FIG IE illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein; and

[0019] FIG IF illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein.

[0020] Fig 2A schematically illustrates an azimuthing propulsion unit according to the embodiments described herein;

[0021] Fig 2B schematically illustrates a cross-section of an isometric view of an azimuthing propulsion unit according to the embodiments described herein;

[0022] Fig 2C schematically illustrates a cross-section of an isometric view of an azimuthing propulsion unit according to the embodiments described herein;

[0023] Fig 2D illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein;

[0024] Fig 2E illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein;

[0025] Fig 2F illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein; and

[0026] Fig 2G illustrates a flow chart of a method of maintaining an azimuthing propulsion unit according to the embodiments described herein.

[0027] FIG 3 A schematically illustrates a sealing unit inside an azimuthing propulsion unit according to the embodiments described herein;FIG 3B schematically illustrates a sealing unit inside an azimuthing propulsion unit according to the embodiments described herein

[0028] FIG 3C schematically illustrates a method for servicing a sealing unit inside an azimuthing propulsion unit according to the embodiments described herein.

[0029] FIG 4A schematically shows an NDE side of the azimuthing propulsion unit with a bearing unit according to some embodiments described herein;

[0030] FIG. 4B schematically shows a bearing unit for an azimuthing propulsion unit according to some embodiments described herein;

[0031] FIG. 4C schematically shows a bearing unit for an azimuthing propulsion unit according to some embodiments described herein and the transfer of forces therein;

[0032] FIG. 4D schematically shows a perspective view of a bearing unit at the NDE side of an azimuthing propulsion unit according to some embodiments described herein;

[0033] Fig. 4E schematically shows an enlarged view of Fig. 4A; and,

[0034] Fig. 4F schematically shows a flow chart of a method for supporting shafts in an azimuthing propulsion unit according to some embodiments described herein.

[0035] FIG 5A schematically illustrates a marine propulsion unit with a slip-ring cooling system according to embodiments described herein;

[0036] FIG 5B schematically illustrates a marine propulsion unit with an enlarged view of the slipring housing;

[0037] FIG. 5C schematically illustrates the dual rotor electric motor in a cross-sectional view with the air channel arrangement;

[0038] FIG 5D schematically illustrates the position of the air channel arrangement along the outer rotor with an enlarged view;

[0039] FIG 5E schematically illustrates a method of cooling a slip-ring arrangement in a marine propulsion unit.

[0040] FIG 6A schematically illustrates a cross-sectional view of a dual rotor electric motor of a marine propulsion unit according to the embodiments described herein;FIG 6B schematically illustrates a detail of a marine propulsion unit according to the embodiments described herein;

[0041] FIG 6C schematically illustrates a detail of a marine propulsion unit according to the embodiments described herein;

[0042] FIG 6D schematically illustrates a method of cooling a contra rotating motor of a marine propulsion unit according to embodiments described herein.

[0043] FIG 7A schematically illustrates an embodiment of the invention in sectional view;

[0044] FIG 7B schematically illustrates a different embodiment of the invention in sectional view;

[0045] FIG 7C schematically illustrates a different embodiment of the invention in sectional view;

[0046] FIG 7D schematically illustrates a different embodiment of the invention in sectional view;

[0047] FIG 7E schematically illustrates a method for the assembly of the azimuthing propulsion unit;

[0048] FIG 7F schematically illustrates a first modification of the method for the assembly of the azimuthing propulsion unit;

[0049] FIG 7G schematically illustrates a second modification of the method for the assembly of the azimuthing propulsion unit.

[0050] DETAILED DESCRIPTION OF EMBODIMENTS

[0051] The expression “in one embodiment”, “in some embodiments”, “according to an embodiment”, “according to embodiments”, “in a typical embodiment”, “according to typical embodiments”, “typically”, etc., refer to general teachings of preferred embodiments which are combinable, if not otherwise explicitly stated and not mutually exclusive. Said expressions are therefore not intended as explicitly listing a specific delimited combination of features. Features of embodiments of the present disclosure are therefore combinable with other features and embodiments described herein.

[0052] According to some embodiments, the azimuthing propulsion unit is configured to propel a marine vessel. In particular, the marine vessel can comprise at least one azimuthing propulsion unit according to embodiments described herein. The marine vessel as described herein comprises seagoing or inland marine vessels. In particular, the marine vessel comprises ships and boats. In some embodiments, the marine vessel comprises merchant ships, in particular for transportinggoods. In particular, the marine vessel can comprise a container vessel, a Ro-Ro or car carrier, a tanker or shuttle tanker, a liquid natural gas (LNG) carrier or a floating storage, and regasification unit. In some embodiments, the marine vessel comprises ferries, in particular single- and double-ended ferries, cruise ships, water buses, yachts. In some embodiments, the marine vessel comprises offshore energy vessels, in particular service operation vessels (SOVs), cable laying vessels (CLVs), foundation installation vessels (FIVs), offshore construction (OCVs) and support vessels (OSVs), platform supply vessels (PSVs), and anchor-handling tug supply vessels (AHTS). In some embodiments, the marine vessel comprises research and survey vessels or other special purpose vessels, such as dredgers, heavy lift vessels, or towboats. In some embodiments, the marine vessel comprises ice-going marine vessels, in particular icebreakers. In some embodiments, the marine vessel can comprise navy or coast guard vessels.

[0053] The marine vessel typically comprises a hull. A pod of the azimuthing propulsion unit is attached to the hull of the marine vessel, in particular at the bottom of the hull. Typically, the hull defines a vessel interior and a vessel exterior. Space confined by the hull and configured to be isolated from sea water is typically defined as the vessel interior. Space outside the hull, and in particular the sea, is typically defined as the vessel exterior. Typically, the vessel interior is substantially free of sea water and substantially dry.

[0054] In some embodiments, the marine vessel can comprise a plurality of azimuthing propulsion units. In particular, the marine vessel can comprise 2, 3, 4, or more azimuthing propulsion units. Typically, each of the plurality of azimuthing propulsion units is controlled separately. In some embodiments, the marine vessel can comprise a single azimuthing propulsion unit with a single pod. In some embodiments, one typical azimuthing propulsion unit can be combined with one or more further marine propulsion unit, e.g. one or more further azimuthing propulsion units or other propulsions, in a single marine vessel.

[0055] Typically, the azimuthing propulsion unit comprises a pod with a pod hull. The pod is configured to be rotatably attached to the hull of the marine vessel, particularly at the bottom of the hull of the marine vessel. The pod is typically rotatable about a substantially vertical rotation axis of the azimuthing propulsion unit. In particular, the pod can be rotated by at least 270°, at least 315° or at least 360° about the substantially vertical rotation axis of the azimuthing propulsion unit. In typical embodiments, the rotation of the pod about the substantially vertical rotation axis of the azimuthing propulsion unit is not restricted, in particular not mechanically restricted.Typically, the pod comprises a hull cap at a first end of the pod and a propeller unit, in particular a pushing or pulling propeller unit, attached to a second end of the pod. The first end of the pod can also be described as a non-driving end (NDE), and the second end of the pod can also be described as a driving end (DE), of the pod. The propeller unit typically rotates about a rotation axis of the propeller unit. The rotation axis of the propeller unit can be substantially perpendicular to the vertical rotation axis of the azimuthing propulsion unit.

[0056] In typical embodiments, the propeller unit comprises an outer shaft propeller and an inner shaft propeller. Typically, the outer shaft propeller is arranged closer to the hull than the inner shaft propeller. In a pushing propeller unit, the outer shaft propeller can also be described as front propeller and the inner shaft propeller can be described as the rear propeller; and vice versa for a pulling propeller unit. In particular, the outer shaft propeller is arranged closer to the vertical rotation axis than the inner shaft propeller. Typically, the outer shaft propeller and the inner shaft propeller are arranged adjacent to each other. The outer shaft propeller and the inner shaft propeller rotate about the rotation axis of the propeller unit.

[0057] Typically, the propeller unit comprises a contra rotating propeller unit. In particular, the outer shaft propeller can be configured to rotate in a first direction, particularly about the rotation axis of the propeller unit, and the inner shaft propeller can be configured to rotate in a second direction opposite to the first direction, particularly about the rotation axis of the propeller unit. In other words, the outer shaft propeller can rotate clockwise and the inner shaft propeller can rotate counterclockwise, or vice versa, about the same rotation axis. A contra rotating propeller unit can advantageously allow for a higher hydrodynamic efficiency than other propeller concepts, in particular with respect to single propellers.

[0058] In some embodiments, the outer shaft propeller has a first diameter and the inner shaft propeller has a second diameter with the second diameter being different from the first diameter, particularly the first diameter being larger than the second diameter. Typically, the outer shaft propeller comprises a first number of first blades and the inner shaft propeller comprises a second number of second blades. Typically, the second number can be different from the first number. The outer shaft propeller can comprise 3, 4, 5, 6, or 8 first blades. The inner shaft propeller can comprise 3, 4, 5, 6, or 8 second blades. In some embodiments, the outer shaft propeller comprises one more first blade than the inner shaft propeller comprises second blades. Exemplarily, the outer shaft propeller comprises 6 first blades and the inner shaft propeller comprises 5 second blades. In some embodiments, the outer shaft propeller and the inner shaft propeller can comprise the same number of blades, in particular 3, 4, 5, 6, or 8 first and second blades, respectively. The outer shaft propellerand / or the inner shaft propeller can each be manufactured as a monoblock or in components, as a built-up propeller.

[0059] Typically, the propeller unit is driven by an electric motor. Typically, the electric motor has a power of at least 100 kW, at least 1 MW, at least 2 MW, at least 5 MW, at least 10 MW or at least 15 MW. The electric motor is typically arranged within the pod. Particularly, the electric motor is mechanically connected to the propeller gearlessly. Typically, a rotation axis of the electric motor is identical to the rotation axis of the propeller unit. In particular, an output shaft of the electric motor can be identical to the drive shaft of the propeller unit or can be gearlessly connected to a drive shaft of the propeller unit. The output shaft of the electric motor typically is coaxial to the drive shaft of the propeller unit, in typical embodiments, for a propeller unit comprising a single shaft propeller, the shaft propeller can be driven by the electric motor. In typical embodiments, for a propeller unit comprising an outer shaft propeller and an inner shaft propeller, in particular for the contra rotating propeller unit, the outer shaft propeller and the inner shaft propeller can be driven by the same electric motor.

[0060] The electric motor typically comprises a rotating electric motor. A rotor is configured to rotate about a rotation axis of the electric motor. Typically, the rotation axis of the electric motor can be coaxially arranged with the rotation axis of the propeller unit. Typically, the electric motor is a synchronous electric motor. Typically, the rotor comprises windings to be supplied with an electric current for the operation of the electric motor. The inner rotor can be permanent magnet rotor or an externally excited synchronous rotor.

[0061] The electric motor typically comprises a contra rotating electric motor. In particular, the contra rotating electric motor comprises a dual rotor electric motor with an outer rotor and an inner rotor configured to rotate in opposite directions about a rotation axis of the electric motor. Typically, the rotation axis of the electric motor can be coaxially arranged with the rotation axis of the propeller unit. Typically, the electric motor is a synchronous electric motor. Typically, the outer rotor comprises windings to be supplied with an electric current for the operation of the electric motor. The inner rotor can be a permanent magnet rotor or an externally excited synchronous rotor.

[0062] In some embodiments, the drive shaft of the propeller unit comprises a single shaft. Typically, the drive shaft can rotate about the rotation axis of the electric motor. Typically, the shaft is supported in the pod by a drive end, DE, inner bearing and a non-drive end, NDE, inner bearing. The NDE inner bearing and / or the NDE outer bearing can each comprise an axial bearing and a radial bearing, particularly within the same bearing housing. Employing a rotating electric motor canadvantageously enable driving the rotating propeller with a single electric motor deal gearlessly. Thereby, a more compact and efficient drive train can be provided.

[0063] In typical embodiments, the drive shaft of the propeller unit comprises an outer shaft and an inner shaft. The outer shaft and the inner shaft are typically coaxially arranged. Typically, the outer rotor drives the outer shaft. The outer shaft is typically mechanically connected to the outer shaft propeller gearlessly. Typically, the inner rotor drives the inner shaft. The inner shaft is typically mechanically connected to the inner shaft propeller gearlessly. Typically, the inner shaft is arranged inside the outer shaft; in other words, an inside radius of the outer shaft exceeds an outside radius of the inner shaft. The inner shaft and the outer shaft rotate about the same rotation axis, and in particular about the rotation axis of the electric motor. Typically, the inner shaft is supported in the pod by a drive end, DE, inner bearing and a non-drive end, NDE, inner bearing. Typically, the outer shaft is supported in the pod by a drive end, DE, outer bearing and a non-drive end, NDE, outer bearing. The NDE inner bearing and / or the NDE outer bearing can each comprise an axial bearing and a radial bearing, particularly within the same bearing housing. Employing a contra rotating electric motor can advantageously allow to drive the contra rotating propeller with a single electric motor gearlessly. Thereby, a more compact and efficient drive train can be provided.

[0064] Embodiments described herein for azimuthing propulsion system may be applicable for marine propulsion systems, and particularly applicable for non-azimuthing pod propulsion systems.

[0065] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield a further embodiment. It is intended that the description includes such modifications and variations. In the figures, elements can be depicted with exaggerated dimensions to improve the comprehensibility of the detailed description of embodiments. In particular, relations of lengths and widths of components shown can be distorted. Further, some elements can be depicted with enlarged dimensions while other elements in the same figure are depicted, relatively, with reduced dimensions.

[0066] FIG OA schematically illustrates an azimuthing propulsion unit 1000 according to typical embodiments described herein. The azimuthing propulsion unit 1000 of Fig. 0A comprises a dualrotor electric motor 1. The dual rotor electric motor 1 can also be described as contra rotating electric motor. The dual rotor electric motor 1 is typically arranged substantially horizontally and substantially centrally within the azimuthing propulsion unit 1000. Particularly, the dual rotor electric motor 1 is arranged within a pod 30 of the azimuthing propulsion unit 1000.

[0067] Typically, the dual rotor electric motor 1 comprises an inner rotor 2 and an outer rotor 3. The inner rotor 2 is arranged within the outer rotor 3. Inner rotor 2 and outer rotor 3 are arranged coaxially with respect to each other. The inner rotor 2 and the outer rotor 3 are configured to rotate about a rotation axis 50. The rotation axis 50 is a longitudinal axis of the azimuthing propulsion unit 1000. The inner rotor 2 drives an inner shaft propeller 10 and the outer rotor 3 drives an outer shaft propeller 9. The outer shaft propeller 9 and the inner shaft propeller 10 are arranged coaxially and rotate about the rotation axis 50. The outer shaft propeller 9 and the inner shaft propeller 10 form a contra rotating propeller unit. In the embodiment of Fig. 0A, the outer shaft propeller 9 and the inner shaft propeller 10 substantially have the same diameter. In embodiments not shown in Fig.

[0068] 0A the outer shaft propeller 9 can have a diameter different from the diameter of the inner shaft propeller 10. Exemplarily, the outer shaft propeller 9 can have a diameter of at least 6 m, exemplarily of 6.1 m, and the inner shaft propeller 10 can have a diameter of at most 6 m, exemplarily of 5.575 m.

[0069] The outer rotor 3 of the dual rotor electric motor 1 typically comprises a perforated tube 4, as shown in the typical embodiment of Fig. 0A. The perforated tube 4 mechanically supports the outer rotor winding and comprises a plurality of openings. The plurality of openings of the perforated tube 4 are configured to pass air from an exterior of the dual rotor electric motor 1 into an interior of the dual rotor electric motor 1, and vice versa. Warm air, particularly heated by the dual rotor electric motor 1, can pass from an air gap 23 between the inner rotor 2 and the outer rotor 3 through the perforated tube to an annular air channel 14.

[0070] Typically, the perforated tube 4 transmits a torque of the outer rotor 3 to outer rotor end flanges 5, 6. A non-drive end, NDE, outer rotor end flange 5 connects the perforated tube 4 to an NDE outer shaft 47. A drive end, DE, outer rotor end flange 6 connects the perforated tube 4 to a DE outer shaft 7. The DE outer shaft 7 transmits the torque of the outer rotor 3 to the outer shaft propeller 9. For example, the DE outer shaft 7 is mechanically coupled to the outer rotor 3. The outer shaft propeller 9 comprises a plurality of first blades 21, of which two are visible in Fig. 0A. The inner rotor 2 is connected to an NDE inner shaft 48 and to a DE inner shaft 8. For example, the DE inner shaft 8 is mechanically coupled to the inner rotor 2 and / or the NDE inner shaft 48 is mechanically coupled to the inner rotor 2. The DE inner 8 shaft transmits the torque of the inner rotor 2 to theinner shaft propeller 10. The inner shaft propeller 10 comprises a plurality of second blades 22, of which two are visible in Fig. 0A. In the embodiment of Fig. 0A, the outer shaft propeller 9 and the inner shaft propeller 10 are arranged in a pulling configuration. In particular, the first blades 21 and the second blades 22 are configured to operate in a pulling mode.

[0071] Typically, the NDE inner shaft 48 is supported in the pod 30 by an NDE inner bearing 42. The NDE outer shaft 47 is supported in the pod 30 by an NDE outer bearing 41. The NDE outer bearing 41 and the NDE inner bearing 42 typically comprise an oil seal, respectively. The DE outer shaft 7 is supported in the pod 30 by a DE outer bearing 11. The DE inner shaft 7 is supported in the DE outer shaft 8 by a DE inner bearing 12. The DE outer bearing 11 and the DE inner bearing 12 typically comprise an oil and a water seal, respectively. The oil seal can prevent oil from exiting the pod 30. The water seal can prevent water from entering the pod 30.

[0072] Typically, the dual rotor electric motor 1 is provided with electric energy via a slip ring unit 19. The slip ring unit 19 is typically arranged on the non-drive end side of the dual rotor electric motor 1 and in particular to contact the NDE outer shaft 47 as shown in Fig. 0A. The NDE outer shaft 47 and the NDE outer rotor end flange 5 are configured to electrically connect the slip ring unit 19 to the dual rotor electric motor 1. The slip ring unit 19 comprises at least one sliding contact to transmit electricity from power supply cables 20 to the dual rotor electric motor 1 and particularly to the outer rotor 3 of the dual rotor electric motor 1. From the outer rotor 3, electricity is provided to windings of the dual rotor electric motor 1. The power supply cables 20 provide electrical power from a marine vessel, and in particular from a power supply of the marine vessel to the dual rotor electric motor 1 via the slip ring unit 19. The slip ring unit 19 comprises a slip ring unit housing 39. The slip ring unit housing 39 separates the slip ring unit 19 from a further interior of the pod 30 and in particular is configured to prevent dust generated inside the slip ring unit 19, in particular generated by the at least one sliding contact of the slip ring unit 19, from escaping to the interior of the pod 30.

[0073] Typically, inside the pod 30 of the azimuthing propulsion unit 1000, air is circulated. The azimuthing propulsion unit 1000 comprises a cooling air unit 16. In the embodiment of Fig. 0A, the cooling air unit 16 is arranged within a hull of a marine vessel. In the typical embodiment shown in Fig. 0A, the cooling air unit 16 comprises an air fan 17 to circulate air. The cooling air unit 16 typically comprises a heat exchanger 18. Through the heat exchanger 18, warm air entering the heat exchanger 18 from the pod 30 is cooled with heat being at least partially transferred to a cooling agent of the heat exchanger 18. The cooling air unit 16 provides cool air to the dual rotor electric motor 1 via a DE ingoing air channel 31 and an NDE ingoing air channel 32 in the pod 30.The DE ingoing air channel 31 is physically separated from an outgoing air channel 33 by an DE air channel separating wall 34 in Fig. OA. The NDE ingoing air channel 32 is physically separated from the outgoing air channel 33 by an NDE air channel separating wall 35 in Fig. OA. Typically, the outgoing air channel 33 substantially extends in the center of the pod 30 and in particular along a vertical central axis of the pod 30. Air passing through the DE ingoing air channel 31 and / or the NDE ingoing air channel 32 passes through openings of the perforated tube 4 and / or the outer rotor end flanges 5, 6 into an interior of the dual rotor electric motor 1. Within the dual rotor electric motor 1, the air can be heated by the dual rotor electric motor 1, in particular when in operation. The air can exit the dual rotor electric motor 1 via openings of the perforated tube 4 towards the annular air channel 14. The annular air channel 14 is connected to the outgoing air channel 33.

[0074] In some embodiments according to Fig. OB, the azimuthing propulsion unit 1000 is configured to operate in a pushing mode. In particular, the first blades 21 and the second blades 22 are configured to operate in a pushing mode.

[0075] In Fig. 0C, a side view of the azimuthing propulsion unit 1000 of the embodiment of Fig. 0B is schematically shown.

[0076] The present disclosure is in particular directed at improving efficiency, durability and maintainability of an azimuthing propulsion unit, providing synergistic solutions that in particular improve an access and a servicing and / or maintenance of the azimuthing propulsion unit.

[0077] In some embodiments, the present disclosure provides an improved access of a drive end inner bearing, for example providing at least one hatch.

[0078] In some embodiments, the present disclosure provides an improved access of a drive end outer distal seal.

[0079] In some embodiments, the present disclosure provides an improved sealing unit for an azimuthing propulsion unit and / or an improved servicing of a sealing unit.

[0080] In some embodiments, the present disclosure provides a bearing unit for an improved supporting of shafts in an azimuthing propulsion unit that provide in particular an easy maintenance.

[0081] In some embodiments, an improved cooling of a slip ring arrangement is provided that simplifies the slip-ring cooling and reduces required components, improving the reliability and reducing the need for maintenance.An improved cooling of a contra rotating motor is furthermore provided. A non-drive end shaft is furthermore provided.

[0082] 1. IMPROVING ACCESS TO A DRIVE END INNER BEARING

[0083] Maintaining azimuthing propulsion units commonly requires dry-docking, which is a timeconsuming process. Thus, dry-docking a marine vessel to maintain the azimuthing propulsion units requires for the marine vessel to be taken out of service in order for maintenance procedures, routine or not, to be undertaken. Therefore, azimuthing propulsion units that provide a high efficiency, durability and maintainability, in particular in view of the restricted amount of space available in the pod, are desired. Azimuthing propulsion units with reduced maintenance efforts might be desired.

[0084] According to some embodiments of the present disclosure, an azimuthing propulsion unit comprising a rotatable drive end (DE) inner shaft; a rotatable DE outer shaft, wherein the DE inner shaft runs at least partially within the DE outer shaft; and a DE inner bearing arranged between the DE outer shaft and the DE inner shaft; wherein the DE outer shaft comprises a hatch, is provided.

[0085] According to some embodiments of the present invention, a method of maintaining of an azimuthing propulsion unit according to any of the embodiments described herein is provided. The method comprises: opening a hatch of a DE outer shaft of the azimuthing propulsion unit; and accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft.

[0086] In some embodiments, the azimuthing propulsion unit comprises a rotatable drive end (DE) inner shaft, a rotatable DE outer shaft, wherein the DE inner shaft runs at least partially within the DE outer shaft, and a DE inner bearing arranged between the DE outer shaft and the DE inner shaft, wherein the DE outer shaft comprises at least one hatch.

[0087] The azimuthing propulsion unit described herein can permit the azimuthing propulsion unit to be maintained without requiring the marine vessel to be dry-docked. Dry docking a marine vessel is a time and resource consuming process which ultimately adversely affects an efficiency of the marine vessel.

[0088] According to some embodiments, the at least one hatch can be, for example, configured to provide access to the DE inner bearing. According to some embodiments, the at least one hatch can be, for example, configured to be accessed by a user from within the azimuthing propulsion unit. In order for the hatch to provide sufficient access to the DE inner bearing, the hatch can be of a definedshape and size. For example, the hatch can be any of the following shapes, but not limited to: a rectangle, a circle, a triangle, a rhombus, a pentagon, a hexagon, etc. For example, the hatch can be rectangular with a length of at least 0.2 m and / or up to 1.5 m, preferably at least 0.3 m or at least 0.4 m and / or up to 0.6 m or up to 0.5 m, and a width of at least 0.1 m and / or up to 0.8 m, preferably at least 0.3 m and / or up to 0.5 m or up to 0.4 m. In a further example, the hatch 302 is circular with a diameter of at least 0.2 m and / or up to 1.5 m, preferably at least 0.3 m and / or up to 0.7 m.

[0089] The DE outer shaft can comprise, for example, two hatches, three hatches, four hatches, five hatches, etc. The azimuthing propulsion unit comprising two or more hatches can comprise two or more of the same hatch, two or more different hatches, or a combination thereof. For example, wherein the azimuthing propulsion unit comprises four hatches, each of the four hatches can be of a different shape and size, the same shape and size, or a combination thereof. In typical embodiments, the at least one hatch comprises at least one seal. In particular, the at least one seal is a hatch seal. The at least one hatch seal can prevent fluid, such as lubricating oil, from exiting a contained volume.

[0090] The at least one hatch can be configured to permit the user to access the DE inner shaft from within the azimuthing propulsion unit. The hatch can be configured to permit the user to access a region between the DE inner shaft and the DE outer shaft. For example, the user can access the DE inner bearing from within the azimuthing propulsion unit through the at least one hatch. The at least one hatch can be opened and / or removed to gain access to the region between the DE inner shaft and the DE outer shaft. For example, the at least one hatch can be opened through a push-to-unlock mechanism. For example, the at least one hatch can be opened by removing at least one fixing mechanism, such as a screw. The at least one hatch can be reused. For example, the at least one hatch can be opened and closed any number of times, for example, 20 times, 50 times, 100 times, 500 times, or more.

[0091] The at least one hatch can permit for maintenance to be done on the DE inner shaft and / or the DE outer shaft from within the azimuthing propulsion unit. The maintenance can include checking, preparing, removing, replacing, adding, or any combination thereof of the components in the drive end of the azimuthing propulsion unit.

[0092] According to some embodiments described herein, the DE inner bearing comprises inner bearing pads. According to some embodiments described herein, the DE inner bearing comprises an inner roller bearing. According to some embodiments described herein, the DE inner bearing comprisesan inner bearing pad and / or an inner roller bearing. The DE inner bearing and / or the inner bearing pads can be arranged distally in relation to the at least one hatch. According to typical embodiments, the DE inner bearing is a segmented bearing. For example, the DE inner bearing comprises two or more inner bearing pads, for example 3 bearing pads, 5 bearing pads, 8 bearing pads, 12 bearing pads, or any predefined number of bearing pads. The inner bearing pads can be arranged around the DE inner shaft, and in particular around an entire circumference of the DE inner shaft. The inner bearing pads can be configured to be displaced along the DE inner shaft. The inner bearing pads can be slide bearing pads. The inner bearing pads can be configured to be slid along the DE inner shaft.

[0093] Typically, the DE inner bearing and / or inner bearing pads can be displaced proximally, and in particular, proximally towards the at least one hatch. The DE inner bearing and / or inner bearing pads can be displaced continuously or in intervals. The DE inner bearing and / or inner bearing pads can be displaced axially by a predetermined distance, for example, in line with the at least one hatch. The DE inner bearing and / or inner bearing pads can be displaced axially by a distance determined by the user, for example, 0.3 m. The DE inner bearing and / or inner bearing pads can be displaced according to the maintenance procedure taking place.

[0094] According to some embodiments described herein, the azimuthing propulsion unit can further comprise a DE inner distal seal. The DE inner distal seal can be arranged between the DE inner shaft and the DE outer shaft. The DE inner distal seal can be arranged towards a drive end, and in particular the drive and of the azimuthing propulsion unit. The DE inner distal seal can comprise at least one water seal and / or at least one lubricant seal. For example, the DE inner distal seal can prevent water from entering into the azimuthing propulsion unit and / or can prevent lubricant, for example oil, from exiting the azimuthing propulsion unit. The DE inner distal seal can prolong the lifespan of the azimuthing propulsion unit and / or can prevent on environment from being contaminated.

[0095] Typically, the DE inner distal seal can be displaced proximally, and in particular, proximally towards the at least one hatch. The DE inner distal seal can be displaced continuously or in intervals. The DE inner distal seal can be displaced axially by a predetermined distance, for example, in line with the at least one hatch. The DE inner distal seal can be displaced axially by a distance determined by the user, for example, 0.3 m. The DE inner distal seal can be displaced according to the maintenance procedure taking place.According to some embodiments described herein, the azimuthing propulsion unit can further comprise a DE inner proximal seal. The DE inner proximal seal can be arranged between the DE inner shaft and the DE outer shaft. The DE inner proximal seal can be arranged towards the NDE. In typical embodiments, the DE inner proximal seal can be arranged distally to the at least one hatch. The DE inner proximal seal can comprise at least one seal. For example, the DE inner proximal seal comprises 2, 3, 4, 5, 6, 8, 10, or any number of seals. The DE inner proximal seal can comprise at least one oil seal. For example, the DE inner proximal seal can prevent lubricant from leaving at least one desired region.

[0096] Typically, the DE inner proximal seal can be displaced distally, and in particular, distally towards the at least one hatch. The DE inner proximal seal can be displaced continuously or in intervals. The DE inner proximal seal can be displaced by a predetermined distance, for example, in line with the at least one hatch. The DE inner proximal seal can be displaced by a distance determined by the user, for example, 0.3 m. The DE inner proximal seal can be displaced according to the maintenance procedure taking place.

[0097] Typically, the DE inner distal seal and / or the DE inner proximal seal can comprise two or more seals. The DE inner distal seal and / or the DE inner proximal seal can be attached to at least the DE inner shaft. For example, the DE inner distal seal and / or the DE inner proximal seal can be attached to the DE inner shaft and the DE outer shaft.

[0098] According to some embodiments described herein, the azimuthing propulsion unit can further comprise a pod, wherein the pod comprises a pod hull. The pod can permit for the DE inner bearing and / or the DE inner bearing pads and / or the DE inner distal seal and / or the DE inner proximal seal to be maintained from within the azimuthing propulsion unit. This can be beneficial in that, for example, for the DE inner bearing and / or the DE inner bearing pads and / or the DE inner distal seal and / or the DE inner proximal seal to be maintained without requiring the azimuthing propulsion unit and over the marine vessel to be dry-docked. This can for example, reduce time required for maintenance and / or permit for an increase in maintenance opportunities available. For example, the marine vessel can be docked at a port as part of its schedule and the DE inner bearing and / or the DE inner bearing pads and / or the DE inner distal seal and / or the DE inner proximal seal can be maintained during this time at the port. For example, the user can enter the azimuthing propulsion unit through a vessel interior of the marine vessel, and can proceed to accessing any of the aforementioned components.According to some embodiments described herein the azimuthing propulsion unit can further comprise a DE outer bearing. In some embodiments, the DE outer bearing can comprise an outer bearing pad. According to some embodiments described herein, the DE outer bearing comprises an outer roller bearing. According to some embodiments described herein, the DE outer bearing comprises an outer bearing pad and / or an outer roller bearing. The DE outer bearing and / or the outer bearing pads can be arranged distally in relation to the at least one hatch. According to typical embodiments, the DE outer bearing is a segmented bearing. For example, the DE outer bearing comprises two or more outer bearing pads, for example 3 bearing pads, 5 bearing pads, 8 bearing pads, 12 bearing pads, or any predefined number of bearing pads. The outer bearing pads can be arranged around the DE outer shaft, and in particular around an entire circumference of the DE outer shaft. The outer bearing pads can be configured to be displaced along the DE outer shaft. The outer bearing pads can be slid. The outer bearing pads can be configured to be slid along the DE outer shaft. The DE outer bearing and / or outer bearing pads can be displaced radially from the DE outer shaft. In typical embodiments, the DE outer bearing and / or outer bearing pads can be slid and / or displaced radially.

[0099] The DE inner bearing and the DE outer bearing can be coupled. For example, the DE inner bearing and the DE outer bearing can be fluidly coupled. For example, the DE inner bearing can comprise a DE inner bearing chamber and the DE outer bearing can comprise a DE outer bearing chamber. In particular, the DE inner bearing chamber and the DE outer bearing chamber can be fluidly coupled. In typical embodiments, the DE outer shaft comprises at least one bore to fluidly couple the DE inner bearing and the DE outer bearing. The at least one bore can be through the DE outer shaft. Typically, the at least one bore is radially through the DE outer shaft. The fluid coupling can comprise a lubricant, such as grease and / or oil. The DE inner bearing and the DE outer bearing can be arranged coaxially to the rotation axis. The DE outer bearing can at least partially overlap the DE inner bearing. For example, the DE outer bearing and / or the outer bearing pads can be displaced proximally. In particular, the DE outer bearing and / or the outer bearing pads can be displaced axially. The DE outer bearing and / or the outer bearing pads can be displaced axially and proximally along the DE outer shaft. The outer bearing pads can comprise slide bearing pads.

[0100] The DE inner bearing and / or the inner bearing pads and / or the DE outer bearing and / or the outer bearing pads can be configured to be individually displaced and / or changed. The DE inner bearing can be rotated with respect to the DE inner shaft, the DE outer shaft, or both. For example, a gliding layer is between the DE inner bearing and the DE inner shaft, the DE outer shaft, or both. The DE inner bearing can be rotated along the DE inner shaft, the DE outer shaft, or both. The DE outer bearing can be rotated with respect to the DE outer shaft, the DE outer bearing housing, or both.For example, a gliding layer is between the DE outer bearing and the DE outer shaft, the DE outer bearing housing, or both. The DE outer bearing can be rotated along the DE outer shaft, the DE outer bearing housing, or both.

[0101] The azimuthing propulsion unit described herein can enable inner bearing and seal change in a contra rotating propeller. For example, the azimuthing propulsion unit described herein can enable maintenance without removing at least one propeller and / or driving conditions.

[0102] According to some embodiments described herein, a method of maintaining an azimuthing propulsion unit is provided. The method of maintaining the azimuthing propulsion unit described herein comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit; and accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft. Typically, the method of maintaining the azimuthing propulsion unit can be performed within the azimuthing propulsion unit described herein. In particular, the method of maintaining the azimuthing propulsion unit can be performed without requiring for the azimuthing propulsion unit and / or a marine vessel to be dry-docked.

[0103] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit can further comprise, after accessing the DE inner bearing to the hatch, displacing the DE inner bearing. The method can comprise releasing the DE inner bearing. In particular, releasing the DE inner bearing can occur prior to displacing the DE inner bearing. For example, the DE inner bearing can be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner bearing can enable the displacing of the DE inner bearing. For example, the method comprises displacing the DE inner bearing towards the motor, preferably without removing a portion through the hatch. For example, the method comprises displacing the DE inner bearing at least partially through the hatch. For example, the method comprises displacing the entire DE inner bearing through the hatch.

[0104] Typically, displacing the DE inner bearing can comprise removing the DE inner bearing through the hatch. For example, removing the DE inner bearing can comprise proximally displacing the DE inner bearing to a position in line with the hatch. Upon displacing the DE inner bearing to the position in line with the hatch, the method can comprise extracting the DE inner bearing, in particular extracting the DE inner bearing through the hatch. Typically, displacing the DE inner bearing comprises displacing the DE inner bearing to a service position. When the DE inner bearing is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE inner bearing. For example, servicing the DE inner bearingcan comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner bearing can be for the entire DE inner bearing or at least a portion thereof. For example, servicing the DE inner bearing comprises servicing at least one wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due for service. Typically, servicing the DE inner bearing is through the hatch. Typically, servicing the DE inner bearing is performed within the hatch. Typically, servicing the DE inner bearing is performed outside the hatch.

[0105] Typically, displacing the DE inner bearing can comprise axially displacing the DE inner bearing a distance of at least 0.1 m, 0.2 m, 0.3 m, up to 1.5 m, or any distance therebetween. For example, displacing the DE inner bearing can comprise displacing the DE inner bearing within a region between the DE inner shaft and the DE outer shaft.

[0106] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing the DE inner bearing and / or replacing the DE inner bearing, and in particular with a new DE inner bearing and / or at least a new portion thereof.

[0107] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit can further comprise, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch, and displacing the DE inner distal seal. Typically, displacing the DE inner bearing comprises displacing the DE inner distal seal to a service position. The service position can be proximal to the at least one hatch. Typically, displacing the DE inner bearing comprises partly or completely displacing the DE inner bearing through the at least one hatch. Typically, displacing the DE inner bearing comprises displacing the DE inner distal seal to a service position and partly or completely displacing the DE inner bearing through the at least one hatch. The method can comprise releasing the DE inner distal seal. In particular, releasing the DE inner distal seal can occur prior to displacing the DE inner distal seal. For example, the DE inner distal seal can be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner distal seal can enable the displacing of the DE inner distal seal.

[0108] Typically, displacing the DE inner distal seal can comprise removing the DE inner distal seal through the hatch. For example, removing the DE inner distal seal can comprise proximally displacing the DE inner distal seal to a position in line with the hatch. Upon displacing the DE inner distal seal to the position in line with the hatch, the method can comprise extracting the DE inner distal seal, in particular extracting the DE inner distal seal through the hatch. Typically, displacing the DE inner distal seal comprises displacing the DE inner distal seal to a serviceposition. When the DE inner distal seal is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE inner distal seal. For example, servicing the DE inner distal seal can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner distal seal can be for the entire DE inner distal seal or at least a portion thereof. For example, servicing the DE inner distal seal comprises servicing at least one wearable part. Typically, a seal, such as a lip seal, is a wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due for service. Typically, servicing the DE inner distal seal is through the hatch. Typically, servicing the DE inner distal seal is within the hatch. Typically, servicing the DE inner distal seal is outside the hatch.

[0109] Typically, displacing the DE inner distal seal can comprise axially displacing the DE inner distal seal a distance of at least 0.1 m, 0.2 m, 0.3 m, up to 3 m, or any distance therebetween. For example, displacing the DE inner distal seal can comprise displacing the DE inner distal seal within a region between the DE inner shaft and the DE outer shaft.

[0110] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing the DE inner distal seal and / or replacing the DE inner distal seal, and in particular with a new DE inner distal seal and / or at least a new portion thereof.

[0111] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit can further comprise accessing a DE inner proximal seal through the hatch, and displacing the DE inner proximal seal. The method can comprise releasing the DE inner proximal seal. In particular, releasing the DE inner proximal seal can occur prior to displacing the DE inner proximal seal. For example, the DE inner proximal seal can be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner proximal seal can enable the displacing of the DE inner proximal seal.

[0112] Typically, displacing the DE inner proximal seal can comprise removing the DE inner proximal seal through the hatch. For example, removing the DE inner proximal seal can comprise distally displacing the DE inner proximal seal to a position in line with the hatch. Upon displacing the DE inner proximal seal to the position in line with the hatch, the method can comprise extracting the DE inner proximal seal, in particular extracting the DE inner proximal seal through the hatch. Typically, displacing the DE inner proximal seal comprises displacing the DE inner proximal seal to a service position. When the DE inner proximal seal is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE inner proximalseal. For example, servicing the DE inner proximal seal can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner proximal seal can be for the entire DE inner proximal seal or at least a portion thereof. For example, servicing the DE inner proximal seal comprises servicing at least one wearable part. Typically, a seal, such as a lip seal, is a wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due for service. Typically, servicing the DE inner proximal seal is performed through the hatch. Typically, servicing the DE inner proximal seal is within the hatch. Typically, servicing the DE inner proximal seal is performed outside the hatch.

[0113] Typically, displacing the DE inner proximal seal can comprise axially displacing the DE inner proximal seal a distance of at least 0.1 m, 0.2 m, 0.3 m, up to 3 m, or any distance therebetween. For example, displacing the DE inner proximal seal can comprise displacing the DE inner proximal seal within a region between the DE inner shaft and the DE outer shaft.

[0114] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing the DE inner proximal seal and / or replacing the DE inner proximal seal, and in particular with a new DE inner proximal seal and / or at least a new portion thereof.

[0115] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, can comprise axially displacing along the DE inner shaft. For example, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, can comprise sliding, in particular axially, along the DE inner shaft. For example, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, can comprise rotating, preferably rotating to displace the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, the DE outer shaft, the DE inner shaft, or any combination thereof.

[0116] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit, comprises an azimuthing propulsion unit which comprises: a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof. The method typically further comprises displacing any of a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof. For example, displacing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof, can comprise axially displacing along the DE outer shaft and / or sliding along the DE outer shaft and / or radially displacing from the DE outer shaft. Typically, displacing the DE outer proximal seal, the DE outer bearing, the DE outerdistal seal, or any combination thereof, comprises displacing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof to a service position. When the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof. For example, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof can be for the entire DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof, or at least a portion thereof. For example, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof comprises servicing at least one wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due for service. Typically, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is through the hatch. Typically, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is within the hatch. Typically, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is outside the hatch.

[0117] The method of maintaining the azimuthing propulsion unit can comprise servicing the DE inner proximal seal and / or the DE inner distal seal. The method of maintaining the azimuthing propulsion unit can comprise repairing and / or replacing the DE inner proximal seal and / or the DE inner distal seal. Repairing and / or replacing the DE inner proximal seal and / or the DE inner distal seal can occur after accessing the DE inner proximal seal and / or the DE inner distal seal, and in particular, after releasing and displacing the DE inner proximal seal and / or the DE inner distal seal.

[0118] Typically, the DE inner distal seal and / or the DE inner proximal seal comprise sealing elements. Sealing elements can comprise sealing lips. Typically, the sealing elements the DE inner distal seal and / or the DE inner proximal seal is replaced, displaced and / or serviced with the respective seal staying in place, after moving the respective seal to a service position or without removing the respective seal from the DE inner shaft. Typically, sealing elements are handled as described without necessarily displacing and / or servicing the entire DE inner distal seal and / or the entire DE inner proximal seal.In typical embodiments, the method comprises displacing the DE inner distal seal and / or the DE inner proximal seal. In typical embodiments, the method comprises servicing the DE inner distal seal and / or the DE inner proximal seal. In typical embodiments, the method comprises displacing the sealing elements of the DE inner distal seal and / or the DE inner proximal seal. In typical embodiments, the method comprises servicing the sealing elements of the DE inner distal seal and / or the DE inner proximal seal. For example, the DE inner distal seal and / or the DE inner proximal seal comprises a seal ring. For example, the DE inner distal seal and / or the DE inner proximal seal comprises a seal housing. The seal housing can comprise housing rings. The seal housing is typically configured to hold the sealing elements. Typically, servicing comprises cutting the seal rings.

[0119] In typical embodiments, the method comprises proximally and / or distally displacing the seal housing. The method typically comprises proximally and / or distally displacing with respect to the DE inner bearing housing. The method typically comprises displacing the seal housing to the hatch. In particular, the method comprises displacing the seal housing to the hatch on the DE outer shaft. The method typically comprises servicing the seal housing. Servicing the seal housing typically comprises dismantling the housing rings. Typically, the housing rings are not removed through the hatch. Dismantling the housing rings typically comprises detaching from one another. Typically, the method comprises displacing sealing lips. Typically, the method comprises removing the sealing lips. Typically, displacing and / or removing the sealing lips is after dismantling the housing rings. In typical embodiments, the method comprises replacing the sealing lips. In typical embodiments, the method comprises repairing the sealing lips. In typical embodiments, the method comprises installing new sealing lips. In typical embodiments, the method comprises bonding and / or joining the sealing lips. In typical embodiments, the method comprises bonding to one another. Typically, bonding is done through the at least one hatch. Typically, in case of elastomer seals, chemicals such as glue, compression, and heat are used in bonding. In typical embodiments, the method comprises joining the sealing lips on the DE shaft. Typically, in case of polyurethane seals, bonding and / or joining comprises heating two ends of the seal ring and pressing the two ends together. In typical embodiments, the method comprises assembling the seal housing. In typical embodiments, the method comprises re-assembling the seal housing. In typical embodiments, the method comprises assembling the housing rings.

[0120] Typically, the DE inner shaft and / or the DE outer shaft can be supported. Supporting the DE inner shaft and / or the DE outer shaft can provide more room to manipulate the remaining components in the azimuthing propulsion unit.Typically, a user can perform the method of maintaining the azimuthing propulsion unit described herein. For example, the user can open the hatch and can access the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal. The user can further perform the displacing of the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal. For example, the user can reach into the region accessible through the at least one hatch, and can displace any of the aforementioned components and / or subsidies thereof. The user can perform the opening of the hatch and / or the displacing of the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal using their labour and / or tools. For example, the user can employ at least one rod, threaded bar, grappling tool, and / or any tool suitable for releasing and displacing the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal.

[0121] For example, the user can access the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal. The user can further perform the displacing of the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal. The user can perform the displacing of the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal using their labour and / or tools. For example, the user can employ at least one rod, threaded bar, grappling tool, and / or any tool suitable for releasing and displacing the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal.

[0122] Embodiments of the present invention provide azimuthing propulsion units, in particular azimuthing propulsion units with an improved drive end shaft structure enabling inner bearing and seal change. With exemplary embodiments, the bearings and / or the seals might undergo maintenance and / or might be changed without it being mandatory to bring the vessel into a dry dock. For example, before removing the seals, shafts might be sealed against the water with some temporary seals applied from the waterside of the pod hull of the pod to allow a seal change whilst the vessel is in a swimming condition.

[0123] FIG. 1 A schematically illustrates a cross-section of an isometric view of an azimuthing propulsion unit 1000 according to typical embodiments described herein. The azimuthing propulsion unit 1000 comprises a pod 30 and a pod hull 300. A rotatable drive end (DE) inner shaft 8, runs at least partially within a DE outer shaft 7. A DE inner bearing 12 is arranged between the DE outer shaft 7 and the DE inner shaft 8. The DE outer shaft 7 comprises a hatch 302.

[0124] The exemplary azimuthing propulsion unit 1000 of Fig. 1A as described herein can permit the azimuthing propulsion unit 1000 to be maintained without requiring the marine vessel to benecessarily dry-docked. Dry docking a marine vessel is a time and resource consuming process which ultimately adversely affects an efficiency of the marine vessel.

[0125] The hatch 302 is configured to provide access to the DE inner bearing 12. The hatch 302 is, for example, configured to be accessed by a user from within the azimuthing propulsion unit 1000. In order for the hatch 302 to provide sufficient access to the DE inner bearing 12, the hatch 302 typically has substantially the size of a man-hole.

[0126] The embodiment of Fig. 1A comprises the DE inner bearing 12 with inner bearing pads 312. For example, the DE inner bearing 12 can comprise two or more inner bearing pads 312. The inner bearing pads 312 are arranged around the DE inner shaft 8, and in particular around an entire circumference of the DE inner shaft 8.

[0127] The embodiment of Fig. 1 A comprises a DE inner distal seal 304, wherein the DE inner distal seal 304 is arranged between the DE inner shaft 8 and the DE outer shaft. , The DE inner distal seal 304 is arranged towards a drive end (DE) of the azimuthing propulsion unit 1000.

[0128] The exemplary azimuthing propulsion unit 1000 of Fig. 1A comprises a DE inner proximal seal 306, wherein the DE inner proximal seal 306 is arranged between the DE inner shaft 8 and the DE outer shaft. The DE inner proximal seal 306 is arranged towards a non-drive end (NDE) of the azimuthing propulsion unit 1000.

[0129] The azimuthing propulsion unit 1000 shown in Fig. 1A comprises a DE outer bearing 11. As with typical embodiments, the DE outer bearing 11 comprises outer bearing pads 511.

[0130] The DE inner bearing 12 and the DE outer bearing 11 are arranged coaxially on the rotation axis 50. In the exemplary embodiment of Fig. 1A, the DE outer bearing 11 is at least partially overlapping the DE inner bearing 12.

[0131] FIG. IB illustrates a flow chart of a method 350 of maintaining an azimuthing propulsion unit according to the embodiments described herein. The method 350 comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit 352. The method 350 comprises accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft 354.

[0132] FIG. 1C illustrates a flow chart of a method 350 of maintaining an azimuthing propulsion unit according to the embodiments described herein. The method 350comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit 352. The method 350comprises accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft 354. The method 360further comprises, after accessing the DE inner bearing the hatch, displacing the DE inner bearing 356.

[0133] FIG. ID illustrates a flow chart of a method 350of maintaining an azimuthing propulsion unit according to the embodiments described herein. The method 350comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit 352. The method 350comprises accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft 354. The method 350further comprises, after accessing the DE inner bearing the hatch, displacing the DE inner bearing 356. The method 350further comprises, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch, and displacing the DE inner distal seal 358.

[0134] FIG. IE illustrates a flow chart of a method 350of maintaining an azimuthing propulsion unit according to the embodiments described herein. The method 350comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit 352. The method 350comprises accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft 354. The method 350further comprises, after accessing the DE inner bearing the hatch, displacing the DE inner bearing 356. The method 350further comprises, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch, and displacing the DE inner distal seal 358. The method 350, further comprising, accessing a DE inner proximal seal arranged between the DE outer shaft and a DE inner shaft 359.

[0135] FIG. IF illustrates a flow chart of a method 350 of maintaining an azimuthing propulsion unit according to the embodiments described herein. The method 350 comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit 352. The method 350 comprises accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft 354. The method 350 further comprises, after accessing the DE inner bearing the hatch, displacing the DE inner bearing 356. The method 350 further comprises, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch, and displacing the DE inner distal seal 358. The method 350, further comprising, accessing a DE inner proximal seal arranged between the DE outer shaft and a DE inner shaft 359. The method 350, wherein the azimuthing propulsion unit comprises a DE outer bearing, a DE outer distal seal, a DE outer proximal seal, or any combination thereof, the method 350 further comprising displacing any of: a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof (360).

[0136] Embodiments of the present disclosure therefore provide an azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprisinga rotatable drive end (DE) inner shaft (8);

[0137] a rotatable DE outer shaft (7), wherein the DE inner shaft (8) runs at least partially within the DE outer shaft (7); and

[0138] a DE inner bearing (12) arranged between the DE outer shaft (7) and the DE inner shaft (8);

[0139] wherein the DE outer shaft (7) comprises at least one hatch (302).

[0140] In some embodiments, the hatch (302) is configured to provide an access to the DE inner bearing (12).

[0141] In some embodiments, the hatch (302) is configured to be accessed by a user from within the azimuthing propulsion unit (1000).

[0142] In some embodiments, the DE inner bearing (12) comprises at least one inner bearing pad (312).

[0143] In some embodiments, the azimuthing propulsion unit (1000) further comprises a DE inner distal seal (304), wherein the DE inner distal seal (304) is arranged between the DE inner shaft (8) and the DE outer shaft (7), and wherein the DE inner distal seal (304) is arranged towards a drive end.

[0144] In some embodiments, the azimuthing propulsion unit (1000) further comprises a DE inner proximal seal (306), wherein the DE inner proximal seal (306) is arranged between the DE inner shaft (8) and the DE outer shaft (7), and wherein the DE inner proximal seal (306) is arranged towards a non-drive end.

[0145] In some embodiments, the azimuthing propulsion unit (1000) further comprises a pod (30), wherein the pod (30) comprises a pod hull (300).

[0146] In some embodiments, the azimuthing propulsion unit (1000) further comprises a DE outer bearing (11), wherein the DE outer bearing (11) preferably comprises at least one outer bearing pad.

[0147] In some embodiments, the DE inner bearing (12) and the DE outer bearing (11) are arranged coaxially to a rotation axis (50), in particular the DE outer bearing (11) is at least partially overlapping the DE inner bearing (12).

[0148] Embodiments of the present disclosure further provide a method (350) of maintaining an azimuthing propulsion unit, particularly the azimuthing propulsion unit according to the present disclosure, the method comprising:opening a hatch of a drive end (DE) outer shaft of the azimuthing propulsion unit (352); and

[0149] accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft (354).

[0150] In some embodiments, the method further comprises, after accessing the DE inner bearing through the hatch: displacing the DE inner bearing (356).

[0151] In some embodiments, the method further comprises, after displacing the DE inner bearing:

[0152] accessing a DE inner distal seal through the hatch; and

[0153] displacing the DE inner distal seal (358).

[0154] In some embodiments, the method further comprises:

[0155] accessing a DE inner proximal seal arranged between the DE outer shaft and a DE inner shaft; and

[0156] displacing the DE inner proximal seal (359).

[0157] In some embodiments, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, further comprises axially displacing along the DE inner shaft.

[0158] In some embodiments, the method further comprises: displacing any of a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof (360).

[0159] 2. IMPROVING ACCESS TO A DRIVE END OUTER DISTANT SEAL

[0160] Maintaining azimuthing propulsion units commonly requires dry-docking, which is a timeconsuming process. Thus, dry-docking a marine vessel to maintain the azimuthing propulsion units requires for the marine vessel to be taken out of service in order for maintenance procedures, routine or not, to be undertaken. Therefore, azimuthing propulsion units that provide a high efficiency, durability and maintainability, in particular in view of the restricted amount of space available in the pod, are desired. Azimuthing propulsion units with reduced maintenance efforts might be desired.

[0161] 1The present disclosure provides, an azimuthing propulsion unit comprising a rotatable drive end (DE) shaft, a DE outer bearing arranged between the DE shaft and the DE outer bearing housing, wherein the DE outer bearing is configured to be displaced, and wherein the DE outer bearing comprises outer bearing pads; and a DE outer distal seal, wherein the DE outer distal seal is configured to be accessed from within the azimuthing propulsion unit, is provided.

[0162] The present disclosure further provides, a method of maintaining of an azimuthing propulsion unit according to any of the embodiments described herein is provided. The method comprises: accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit; accessing a DE outer bearing arranged between a DE shaft and a DE outer bearing housing; and accessing a DE outer distal seal.

[0163] In some embodiments, the azimuthing propulsion unit for a vessel comprises a rotatable drive end (DE) shaft. The DE shaft is typically hollow. Some embodiments comprise a solid DE shaft. Typically, the azimuthing propulsion unit comprises a DE outer bearing arranged between the DE shaft and the DE outer bearing housing. The DE outer bearing is typically configured to be displaced. The DE outer bearing can comprise outer bearing pads. Typically, the azimuthing propulsion unit comprises a DE outer distal seal, the DE outer distal seal is typically configured to be accessed from within the azimuthing propulsion unit. The DE outer distal seal is typically arranged distally with respect to the DE outer bearing. The DE outer distal seal is typically arranged in contact with the DE shaft, the DE outer bearing housing, or a combination thereof. The DE outer distal seal can, for example, prevent water from entering the azimuthing propulsion unit, prevent lubricant such as oil or grease from exiting the azimuthing propulsion unit, or a combination thereof. The DE outer distal seal is typically a water and / or lubricant seal. The DE outer distal seal is typically arranged between an inner portion of the DE outer bearing housing and an outer portion of the DE shaft. The DE outer distal seal is typically arranged in contact with the inner portion of the DE outer bearing housing and the DE shaft, in particular, the outer portion of the DE shaft.

[0164] The outer bearing pads are typically configured to be displaced axially and / or radially, and / or the DE outer distal seal is configured to be displaced axially and / or radially.

[0165] For example, the outer bearing pads are configured to be displaced axially along the DE outer shaft. In particular, the outer bearing pads are configured to be displaced proximally. The outer bearing pads are typically configured to slide. In particular, the outer bearing pads are configured to be slid by a user. For example, the outer bearing pads are slid proximally by the user along theDE outer shaft. Typically, the outer bearing pads are configured to be displaced axially. In particular, the outer bearing pads are configured to be displaced axially, and not along the DE outer shaft. For example, a gap is between the outer bearing pads and the DE outer shaft. For example, a film such as a protective film and / or sliding film is between the outer bearing pads and the DE outer shaft.

[0166] For example, the DE outer distal seal is configured to be displaced axially along the DE outer shaft. In particular, the DE outer distal seal is configured to be displaced proximally. The DE outer distal seal is typically configured to slide. In particular, the DE outer distal seal is configured to be slid by a user. For example, the DE outer distal seal is slid proximally by the user along the DE outer shaft. Typically, the DE outer distal seal is configured to be displaced axially. In particular, the DE outer distal seal is configured to be displaced axially, and not along the DE outer shaft. For example, a gap is between the DE outer distal seal and the DE outer shaft. For example, a film such as a protective film and / or sliding film is between the DE outer distal seal and the DE outer shaft.

[0167] The outer bearing pads are typically configured to be displaced radially and / or the DE outer distal seal is configured to be displaced radially. For example, the outer bearing pads are configured to be displaced radially from the DE outer shaft. In particular, the outer bearing pads are configured to be displaced radially outwards. The outer bearing pads are typically configured to be extracted from the DE outer bearing housing. In particular, the outer bearing pads are configured to be displaced and / or extracted by a user. For example, the outer bearing pads are displaced and / or extracted radially outwards from the DE outer bearing housing by the user. In particular, the outer bearing pads can be displaced and / or extracted from the DE outer bearing housing through at least one hatch in the DE outer bearing housing.

[0168] For example, the DE outer distal seal is configured to be displaced radially from the DE outer shaft. In particular, the DE outer distal seal is configured to be displaced radially outwards. The DE outer distal seal is typically configured to be extracted from the DE outer bearing housing. In particular, the DE outer distal seal is configured to be displaced and / or extracted by a user. For example, the DE outer distal seal is displaced and / or extracted radially outwards from the DE outer bearing housing by the user. In particular, the DE outer distal seal is can be displaced and / or extracted from the DE outer bearing housing through the at least one hatch in the DE outer bearing housing.Typically, the DE outer distal seal is arranged between the DE shaft and the DE outer bearing housing. The DE outer distal seal is typically arranged towards a propeller mounted on the DE shaft, i.e. more distal with respect to the motor. The DE outer distal seal can be in contact with an enclosed environment within the azimuthing propulsion unit and / or an outside environment, such as water. The DE outer bearing housing can be a single unit or comprising any number of units. The DE outer bearing housing can comprise 2, 3, 4, 5, 6, 8, or any number of housing units.

[0169] In some embodiments, the azimuthing propulsion unit comprises a DE outer proximal seal. The DE outer proximal seal is typically arranged between the DE shaft and the DE outer bearing housing. The DE outer proximal seal is typically more proximal to the motor compared to the DE outer distal seal. The DE outer proximal seal is typically arranged on the DE shaft, the DE outer bearing housing, or a combination thereof. The DE outer proximal seal is typically arranged between a proximal portion of the DE outer bearing housing and an outer portion of the DE shaft. The DE outer proximal seal is typically arranged in contact with the proximal portion of the DE outer bearing housing, the outer portion of the DE shaft, or a combination thereof.

[0170] Typically, the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal are replaceable from within a pod hull of the pod of the azimuthing propulsion unit. For example, the DE outer distal seal, and / or the DE outer proximal seal are configured to be replaced from within the azimuthing propulsion unit. In particular, the DE outer distal seal, and / or the DE outer proximal seal are configured to be replaced from within the pod hull. For example, the DE outer distal seal, and / or the DE outer proximal seal are replaceable from a proximal region. For example, the proximal region is towards the motor of the azimuthing propulsion unit. For example, the user can access the proximal region to maintain the DE outer distal seal, and / or the DE outer proximal seal. This can be beneficial in reducing the time required for a maintenance procedure as the user can access the DE outer distal seal, and / or the DE outer proximal seal in less time than having to access these components from outside the azimuthing propulsion unit.

[0171] Typical embodiments of the azimuthing propulsion unit described herein can permit the azimuthing propulsion unit to be maintained without requiring the marine vessel to be dry-docked. Dry docking a marine vessel is a time and resource consuming process which ultimately adversely affects an efficiency of the marine vessel. Typical azimuthing propulsion units as described herein can be maintained from within the respective azimuthing propulsion unit. The azimuthing propulsion units described herein can provide the benefit of not requiring accessing, for example, the DE outer distal seal mandatorily from outside the azimuthing propulsion unit. It should beunderstood, that an access from the outside is still possible with typical embodiments as described herein.

[0172] Typically, the azimuthing propulsion unit is a contra rotating propeller azimuthing propulsion unit. For example, the DE shaft is a DE outer shaft. In particular, the rotatable DE shaft is be a rotatable DE outer shaft.

[0173] In typical embodiments, the azimuthing propulsion unit comprises a rotatable drive end (DE) inner shaft, a rotatable DE outer shaft, wherein the DE inner shaft runs at least partially within the DE outer shaft. Typically, the DE outer shaft comprises one or more hatches. Typically, the azimuthing propulsion unit comprises a DE inner bearing. The DE inner bearing is typically arranged between the DE outer shaft and the DE inner shaft.

[0174] According to some embodiments, the at least one hatch can be, for example, configured to provide access to the DE inner bearing. Typically, the DE inner bearing is accessible through the at least one hatch. According to typical embodiments, the at least one hatch can be, for example, configured to be accessed by a user from within the azimuthing propulsion unit. In order for the hatch to provide sufficient access to the DE inner bearing, the hatch can be of a defined shape and size. For example, the hatch can be any of the following shapes, but not limited to: a rectangle, a circle, a triangle, a rhombus, a pentagon, a hexagon, etc. For example, the hatch can be rectangular with a length of at least 0.2 m and / or up to 1.5 m, preferably at least 0.3 m and / or up to 0.6 m, and a width of at least 0.1 m and / or up to 0.8 m, preferably at least 0.3 m and / or up to 0.5 m. In a further example, the hatch 302 is circular with a diameter of at least 0.2 m and / or up to 1.5 m, preferably at least 0.3 m and / or up to 0.7 m.

[0175] The DE outer shaft can comprise, for example, two hatches, three hatches, four hatches, five hatches, etc. The azimuthing propulsion unit comprising two or more hatches can comprise two or more of the same hatch, two or more different hatches, or a combination thereof. For example, wherein the azimuthing propulsion unit comprises four hatches, each of the four hatches can be of a different shape and size, the same shape and size, or a combination thereof. In typical embodiments, the at least one hatch comprises at least one seal. In particular, the at least one seal is a hatch seal. The at least one hatch seal can prevent fluid, such as lubricating oil, from exiting a contained volume.

[0176] The at least one hatch can be configured to permit the user to access the DE inner shaft from within the azimuthing propulsion unit. The hatch can be configured to permit the user to access a region between the DE inner shaft and the DE outer shaft. For example, the user can access the DE innerbearing from within the azimuthing propulsion unit through the at least one hatch. The at least one hatch might be a hatch including a cover. For example, the hatch can be opened and / or removed to gain access to the region between the DE inner shaft and the DE outer shaft. For example, the at least one hatch can be opened through a push-to-unlock mechanism. For example, the at least one hatch can be opened by removing at least one fixing mechanism, such as a screw. The at least one hatch can be reused. For example, the at least one hatch can be opened and closed any number of times, for example, 20 times, 50 times, 100 times, 500 times, or more. In some embodiments, the at least one hatch is an opening through the DE outer shaft without a cover.

[0177] The at least one hatch can permit for maintenance to be done on the DE inner shaft and / or the DE outer shaft from within the azimuthing propulsion unit. The maintenance can include checking, preparing, removing, replacing, adding, or any combination thereof of the components in the drive end of the azimuthing propulsion unit.

[0178] According to some embodiments described herein, the DE inner bearing comprises inner bearing pads. According to some embodiments described herein, the DE outer bearing comprises generally a bearing. For example, the DE outer bearing comprises an outer roller bearing. According to some embodiments described herein, the DE outer bearing comprises outer bearing pads and / or outer roller bearings. The DE inner bearing and / or the inner bearing pads can be arranged distally in relation to the at least one hatch. According to typical embodiments, the DE inner bearing is a segmented bearing. For example, the DE inner bearing comprises two or more inner bearing pads, for example 3 bearing pads, 5 bearing pads, 8 bearing pads, 12 bearing pads, or any predefined number of bearing pads. The inner bearing pads can be arranged around the DE inner shaft, and in particular around an entire circumference of the DE inner shaft. The inner bearing pads can be configured to be displaced along the DE inner shaft. The inner bearing pads can be slide bearing pads. The inner bearing pads can be configured to be slid along the DE inner shaft.

[0179] Typically, the DE inner bearing and / or inner bearing pads can be displaced proximally, and in particular, proximally towards the at least one hatch. The DE inner bearing and / or inner bearing pads can be displaced continuously or in intervals. The DE inner bearing and / or inner bearing pads can be displaced axially by a predetermined distance, for example, in line with the at least one hatch. The DE inner bearing and / or inner bearing pads can be displaced axially by a distance determined by the user, for example, 0.3 m. The DE inner bearing and / or inner bearing pads can be displaced according to the maintenance procedure taking place.According to some embodiments described herein, the azimuthing propulsion unit can further comprise a DE inner distal seal. The DE inner distal seal can be arranged between the DE inner shaft and the DE outer shaft. The DE inner distal seal can be arranged towards a drive end, and in particular the drive and of the azimuthing propulsion unit. The DE inner distal seal can comprise at least one water seal and / or at least one lubricant seal. For example, the DE inner distal seal can prevent water from entering into the azimuthing propulsion unit and / or can prevent lubricant, for example oil, from exiting the azimuthing propulsion unit. The DE inner distal seal can prolong the lifespan of the azimuthing propulsion unit and / or can prevent on environment from being contaminated.

[0180] Typically, the DE inner distal seal can be displaced proximally, and in particular, proximally towards the at least one hatch. The DE inner distal seal can be displaced continuously or in intervals. The DE inner distal seal can be displaced axially by a predetermined distance, for example, in line with the at least one hatch. The DE inner distal seal can be displaced axially by a distance determined by the user, for example, 0.3 m. The DE inner distal seal can be displaced according to the maintenance procedure taking place.

[0181] According to some embodiments described herein, the azimuthing propulsion unit can further comprise a DE inner proximal seal. The DE inner proximal seal can be arranged between the DE inner shaft and the DE outer shaft. The DE inner proximal seal can be arranged towards the NDE. In typical embodiments, the DE inner proximal seal can be arranged distally to the at least one hatch. The DE inner proximal seal can comprise at least one seal. For example, the DE inner proximal seal comprises 2, 3, 4, 5, 6, 8, 10, or any number of seals. The DE inner proximal seal can comprise at least one oil seal. For example, the DE inner proximal seal can prevent lubricant from leaving at least one desired region.

[0182] Typically, the DE inner proximal seal can be displaced distally, and in particular, distally towards the at least one hatch. The DE inner proximal seal can be displaced continuously or in intervals. The DE inner proximal seal can be displaced by a predetermined distance, for example, in line with the at least one hatch. The DE inner proximal seal can be displaced by a distance determined by the user, for example, 0.3 m. The DE inner proximal seal can be displaced according to the maintenance procedure taking place.

[0183] Typically, the DE inner distal seal and / or the DE inner proximal seal can comprise two or more seals. The DE inner distal seal and / or the DE inner proximal seal can be attached to at least the DEinner shaft. For example, the DE inner distal seal and / or the DE inner proximal seal can be attached to the DE inner shaft and the DE outer shaft.

[0184] According to some embodiments described herein, the azimuthing propulsion unit can further comprise a pod, wherein the pod comprises a pod hull. The pod can permit for the DE inner bearing and / or the DE inner bearing pads and / or the DE inner distal seal and / or the DE inner proximal seal to be maintained from within the azimuthing propulsion unit. This can be beneficial in that, for example, for the DE inner bearing and / or the DE inner bearing pads and / or the DE inner distal seal and / or the DE inner proximal seal to be maintained without requiring the azimuthing propulsion unit and over the marine vessel to be dry-docked. This can for example, reduce time required for maintenance and / or permit for an increase in maintenance opportunities available. For example, the marine vessel can be docked at a port as part of its schedule and the DE inner bearing and / or the DE inner bearing pads and / or the DE inner distal seal and / or the DE inner proximal seal can be maintained during this time at the port. For example, the user can enter the azimuthing propulsion unit through a vessel interior of the marine vessel, and can proceed to accessing any of the aforementioned components.

[0185] According to some embodiments described herein the azimuthing propulsion unit can further comprise a DE outer bearing. The DE outer bearing can comprise outer bearing pads. The DE outer bearing and / or the outer bearing pads can be arranged distally in relation to the at least one hatch. According to typical embodiments, the DE outer bearing is a segmented bearing. For example, the DE outer bearing comprises two or more outer bearing pads, for example 3 bearing pads, 5 bearing pads, 8 bearing pads, 12 bearing pads, or any predefined number of bearing pads. The outer bearing pads can be arranged around the DE outer shaft, and in particular around an entire circumference of the DE outer shaft. The outer bearing pads can be configured to be displaced along the DE outer shaft. The outer bearing pads can be slide bearing pads. The outer bearing pads can be configured to be slid along the DE outer shaft. The DE outer bearing and / or outer bearing pads can be displaced radially from the DE outer shaft. In typical embodiments, the DE outer bearing and / or outer bearing pads can be slid and / or displaced radially.

[0186] The DE inner bearing and the DE outer bearing can be coupled. For example, the DE inner bearing and the DE outer bearing can be fluidly coupled. For example, the DE inner bearing can comprise a DE inner bearing chamber and the DE outer bearing can comprise a DE outer bearing chamber. In particular, the DE inner bearing chamber and the DE outer bearing chamber can be fluidly coupled. In typical embodiments, the DE outer shaft comprises at least one bore to fluidly couple the DE inner bearing and the DE outer bearing. The at least one bore can be through the DE outershaft. Typically, the at least one bore is radially through the DE outer shaft. The fluid coupling can comprise a lubricant, such as grease and / or oil. The DE inner bearing and the DE outer bearing can be arranged coaxially on the rotation axis. The DE outer bearing can at least partially overlap the DE inner bearing. For example, the DE outer bearing and / or the outer bearing pads can be displaced proximally. In particular, the DE outer bearing and / or the outer bearing pads can be displaced axially. The DE outer bearing and / or the outer bearing pads can be displaced axially and proximally along the DE outer shaft. The outer bearing pads can comprise slide bearing pads.

[0187] The DE inner distal seal and the DE outer distal seal can be coupled. For example, the DE inner distal seal and the DE outer distal seal can be fluidly coupled. For example, the DE inner distal seal can comprise a DE inner distal seal chamber and the DE outer distal seal can comprise a DE outer distal seal chamber. In particular, the DE inner distal seal chamber and the DE outer distal seal chamber can be fluidly coupled. The fluid coupling can comprise a lubricant, such as grease and / or oil, and / or water.

[0188] The DE inner bearing and / or the inner bearing pads and / or the DE outer bearing and / or the outer bearing pads can be configured to be individually displaced and / or changed. The DE inner bearing can be rotated with respect to the DE inner shaft, the DE outer shaft, or both. For example, a gliding layer is between the DE inner bearing and the DE inner shaft, the DE outer shaft, or both. The DE inner bearing can be rotated along the DE inner shaft, the DE outer shaft, or both. The DE outer bearing can be rotated with respect to the DE outer shaft, the DE outer bearing housing, or both. For example, a gliding layer is between the DE outer bearing and the DE outer shaft, the DE outer bearing housing, or both. The DE outer bearing can be rotated along the DE outer shaft, the DE outer bearing housing, or both.

[0189] The azimuthing propulsion unit described herein can enable inner bearing and seal change in a contra rotating propeller. For example, the azimuthing propulsion unit described herein can enable maintenance without removing at least one propeller and / or driving conditions.

[0190] According to some embodiments described herein, a method of maintaining an azimuthing propulsion unit is provided. The method of maintaining an azimuthing propulsion unit may concern any of the embodiments described herein. Typical methods of maintaining the azimuthing propulsion unit comprise accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit; and accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing; displacing the DE outer bearing; and accessing a DE outer distal seal from within the pod hull.Accessing the DE outer distal seal typically comprises accessing the DE outer distal seal arranged between the DE shaft and the DE outer bearing housing. The DE outer distal seal is typically accessed upon accessing the DE outer bearing. For example, a user accessing the DE outer distal seal is accessing the DE outer bearing prior to accessing the DE outer distal seal. Typically, the user accessing the DE outer distal seal is accessing the DE shaft prior to accessing the DE outer bearing. Accessing the DE outer distal seal can comprise accessing a distal region with respect to the DE outer bearing.

[0191] Typically, the method of maintaining the azimuthing propulsion unit comprises releasing and displacing a DE outer proximal seal prior to accessing the DE outer bearing. For example, releasing the DE outer proximal seal comprises loosening and / or removing at least one joining mechanism such as a screw and / or nut and bolt, overcoming at least one tolerance fit, and / or releasing at least one joining point. Displacing the DE outer proximal seal typically comprises axially displacing in a typically proximal direction. For example, displacing the DE outer proximal seal comprises axially displacing the DE outer proximal seal along the DE shaft, typically towards a motor of the azimuthing propulsion unit, which is typically the proximal direction. In particular, displacing the DE outer proximal seal comprises axially displacing the DE outer proximal seal proximally along the DE shaft. The DE outer proximal seal can be displaced partly or completely. The method of maintaining the azimuthing propulsion unit can comprise repairing and / or replacing the DE outer proximal seal. Repairing and / or replacing the DE outer proximal seal can occur after accessing the DE outer proximal seal, and in particular, after releasing and displacing the DE outer proximal seal. In typical embodiments, at least one seal is present to prevent water from entering the azimuthing propulsion unit.

[0192] Typically, the DE outer distal seal and / or the DE outer proximal seal comprise sealing elements. Sealing elements can comprise sealing lips. Typically, the sealing elements the DE outer distal seal and / or the DE outer proximal seal is replaced, displaced and / or serviced with the respective seal staying in place, after moving the respective seal to a service position or without removing the respective seal from the DE outer shaft. Typically, sealing elements are handled as described without necessarily displacing and / or servicing the entire DE outer distal seal and / or the entire DE outer proximal seal.

[0193] In typical embodiments, the method comprises displacing the DE outer distal seal and / or the DE outer proximal seal. In typical embodiments, the method comprises servicing the DE outer distal seal and / or the DE outer proximal seal. In typical embodiments, the method comprises displacing the sealing elements of the DE outer distal seal and / or the DE outer proximal seal. In typicalembodiments, the method comprises servicing the sealing elements of the DE outer distal seal and / or the DE outer proximal seal. For example, the DE outer distal seal and / or the DE outer proximal seal comprises a seal ring. For example, the DE outer distal seal and / or the DE outer proximal seal comprises a seal housing. The seal housing can comprise housing rings. The seal housing is typically configured to hold the sealing elements.

[0194] In typical embodiments, the method comprises proximally displacing the seal housing. The method typically comprises proximally displacing with respect to the DE outer bearing housing. The method typically comprises displacing the seal housing to the hatch. In particular, the method comprises displacing the seal housing to the hatch on the DE shaft. The method typically comprises servicing the seal housing. Servicing the seal housing typically comprises dismantling the housing rings. Typically, the housing rings are not removed through the hatch. Dismantling the housing rings typically comprises detaching from one another. Typically, the method comprises displacing sealing lips. Typically, the method comprises removing the sealing lips. Typically, displacing and / or removing the sealing lips is after dismantling the housing rings. In typical embodiments, the method comprises replacing the sealing lips. In typical embodiments, the method comprises repairing the sealing lips. In typical embodiments, the method comprises installing new sealing lips. In typical embodiments, the method comprises bonding and / or joining the sealing lips. In typical embodiments, the method comprises bonding to one another. In typical embodiments, the method comprises joining the sealing lips on the DE shaft. In typical embodiments, the method comprises assembling the seal housing. In typical embodiments, the method comprises reassembling the seal housing. In typical embodiments, the method comprises assembling the housing rings.

[0195] Methods of maintaining the azimuthing propulsion unit may comprise displacing the DE outer bearing after accessing the DE outer bearing, and displacing the DE outer distal seal after accessing the DE outer distal seal. For example, displacing the DE outer bearing comprises releasing the DE outer bearing. Displacing the DE outer distal seal typically comprises releasing the DE outer distal seal. The method of maintaining the azimuthing propulsion unit permits for maintaining the azimuthing propulsion unit from within the azimuthing propulsion unit.

[0196] In some embodiments, displacing any of the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises axially displacing along the DE shaft and / or radially displacing from the DE shaft. For example, axially displacing the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises displacing in a proximal direction. For example, radially displacing the DE outer bearing, the DEouter distal seal, the DE outer proximal seal, or any combination thereof, comprises displacing through at least one hatch in the DE outer bearing housing. For example, radially displacing the DE outer proximal seal allows for axially displacing the DE outer bearing. For example, radially displacing the DE outer bearing allows for axially and / or radially displacing the DE outer distal seal.

[0197] Typically, axially moving or displacing the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises, axially moving or displacing the DE outer bearing, the DE outer distal seal, or the DE outer proximal seal to a service position. For example, the service position can be in a proximal location with respect to the DE outer bearing housing. For example, the service position can be between the DE outer bearing housing and a motor of the azimuthing propulsion unit. In typical embodiments, the service position is in a location between the DE outer bearing housing and a motor of the azimuthing propulsion unit, and in particular, the location is proximal to the DE outer bearing housing and distal to the motor. For example, the service position for the DE outer bearing, the DE outer distal seal, or the DE outer proximal seal can be the same for each, different for each, or a combination thereof. The service position might also be a removal position or might be named as a removal position.

[0198] Typically, methods of maintaining a typical CRP azimuthing propulsion unit as described herein comprises displacing any of: a DE inner proximal seal arranged proximally between the DE inner shaft and the DE outer shaft, a DE inner bearing arranged between the DE inner shaft and the DE outer shaft, a DE inner distal seal arranged distally between the DE inner shaft and the DE outer shaft, or any combination thereof, through a hatch in the DE outer shaft.

[0199] Typical methods comprise removing any of a DE inner proximal seal, a DE inner bearing, a DE inner distal seal, or any combination thereof, through at least one hatch. The at least one hatch can be on the DE shaft.

[0200] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing and / or replacing any of: the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, the DE inner distal seal, the DE inner bearing, the DE inner distal seal, and in particular with a new component and / or at least a new portion thereof.

[0201] Typically, a user can perform the method of maintaining the azimuthing propulsion unit described herein. For example, the user is accessing the DE shaft from the interior of the pod hull of the azimuthing propulsion unit. For example, the user is releasing and / or displacing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof, using atleast one hand and / or at least one tool. The user can perform the method of maintaining the azimuthing propulsion unit described herein by accessing the azimuthing propulsion unit through a vessel interior.

[0202] According to some embodiments described herein, a method of maintaining an azimuthing propulsion unit is provided. The method of maintaining the azimuthing propulsion unit described herein comprises opening a hatch of a DE outer shaft of the azimuthing propulsion unit; and accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft. Typically, the method of maintaining the azimuthing propulsion unit can be performed within the azimuthing propulsion unit described herein. In particular, the method of maintaining the azimuthing propulsion unit can be performed without requiring for the azimuthing propulsion unit and / or a marine vessel to be dry-docked.

[0203] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit can further comprise, after accessing the DE inner bearing to the hatch, displacing the DE inner bearing. The method can comprise releasing the DE inner bearing. In particular, releasing the DE inner bearing can occur prior to displacing the DE inner bearing. For example, the DE inner bearing can be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner bearing can enable the displacing of the DE inner bearing. For example, the method comprises displacing the DE inner bearing towards the motor, preferably without removing a portion through the hatch. For example, the method comprises displacing the DE inner bearing at least partially through the hatch. For example, the method comprises displacing the entire DE inner bearing through the hatch.

[0204] Typically, displacing the DE inner bearing can comprise removing the DE inner bearing through the hatch. For example, removing the DE inner bearing can comprise proximally displacing the DE inner bearing to a position in line with the hatch. Upon displacing the DE inner bearing to the position in line with the hatch, the method can comprise extracting the DE inner bearing, in particular extracting the DE inner bearing through the hatch. Typically, displacing the DE inner bearing comprises displacing the DE inner bearing to a service position. When the DE inner bearing is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE inner bearing. For example, servicing the DE inner bearing can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner bearing can be for the entire DE inner bearing or at least a portion thereof. For example, servicing the DE inner bearing comprises servicing at least one wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due forservice. Typically, servicing the DE inner bearing is through the hatch. Typically, servicing the DE inner bearing is within the hatch. Typically, servicing the DE inner bearing is outside the hatch.

[0205] Typically, displacing the DE inner bearing can comprise axially displacing the DE inner bearing a distance of at least 0.1 m, 0.2 m, 0.3 m, up to 1.5 m, or any distance therebetween. For example, displacing the DE inner bearing can comprise displacing the DE inner bearing within a region between the DE inner shaft and the DE outer shaft.

[0206] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing the DE inner bearing and / or replacing the DE inner bearing, and in particular with a new DE inner bearing and / or at least a new portion thereof.

[0207] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit can further comprise, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch, and displacing the DE inner distal seal. Typically, displacing the DE inner bearing comprises displacing the DE inner distal seal to a service position. The service position can be proximal to the at least one hatch. Typically, displacing the DE inner bearing comprises partly or completely displacing the DE inner bearing through the at least one hatch. Typically, displacing the DE inner bearing comprises displacing the DE inner distal seal to a service position and partly or completely displacing the DE inner bearing through the at least one hatch. The method can comprise releasing the DE inner distal seal. In particular, releasing the DE inner distal seal can occur prior to displacing the DE inner distal seal. For example, the DE inner distal seal can be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner distal seal can enable the displacing of the DE inner distal seal.

[0208] Typically, displacing the DE inner distal seal can comprise removing the DE inner distal seal through the hatch. For example, removing the DE inner distal seal can comprise proximally displacing the DE inner distal seal to a position in line with the hatch. Upon displacing the DE inner distal seal to the position in line with the hatch, the method can comprise extracting the DE inner distal seal, in particular extracting the DE inner distal seal through the hatch. Typically, displacing the DE inner distal seal comprises displacing the DE inner distal seal to a service position. When the DE inner distal seal is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE inner distal seal. For example, servicing the DE inner distal seal can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner distal seal can be for the entire DE inner distal seal or at least a portion thereof. For example, servicing the DE inner distal seal comprisesservicing at least one wearable part. Typically, a seal, such as a lip seal, is a wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due for service. Typically, servicing the DE inner distal seal is through the hatch. Typically, servicing the DE inner distal seal is within the hatch. Typically, servicing the DE inner distal seal is outside the hatch.

[0209] Typically, displacing the DE inner distal seal can comprise axially displacing the DE inner distal seal a distance of at least 0.1 m, 0.2 m, 0.3 m, up to 3 m, or any distance therebetween. For example, displacing the DE inner distal seal can comprise displacing the DE inner distal seal within a region between the DE inner shaft and the DE outer shaft.

[0210] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing the DE inner distal seal and / or replacing the DE inner distal seal, and in particular with a new DE inner distal seal and / or at least a new portion thereof.

[0211] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit can further comprise accessing a DE inner proximal seal through the hatch, and displacing the DE inner proximal seal. The method can comprise releasing the DE inner proximal seal. In particular, releasing the DE inner proximal seal can occur prior to displacing the DE inner proximal seal. For example, the DE inner proximal seal can be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner proximal seal can enable the displacing of the DE inner proximal seal.

[0212] Typically, displacing the DE inner proximal seal can comprise removing the DE inner proximal seal through the hatch. For example, removing the DE inner proximal seal can comprise distally displacing the DE inner proximal seal to a position in line with the hatch. Upon displacing the DE inner proximal seal to the position in line with the hatch, the method can comprise extracting the DE inner proximal seal, in particular extracting the DE inner proximal seal through the hatch. Typically, displacing the DE inner proximal seal comprises displacing the DE inner proximal seal to a service position. When the DE inner proximal seal is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE inner proximal seal. For example, servicing the DE inner proximal seal can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner proximal seal can be for the entire DE inner proximal seal or at least a portion thereof. For example, servicing the DE inner proximal seal comprises servicing at least one wearable part. Typically, a seal, such as a lip seal, is a wearable part. The at least one wearable part can be defined as any part whichneeds to be serviced, and / or is due for service. Typically, servicing the DE inner proximal seal is through the hatch. Typically, servicing the DE inner proximal seal is within the hatch. Typically, servicing the DE inner proximal seal is outside the hatch.

[0213] Typically, displacing the DE inner proximal seal can comprise axially displacing the DE inner proximal seal a distance of at least 0.1 m, 0.2 m, 0.3 m, up to 3 m, or any distance therebetween. For example, displacing the DE inner proximal seal can comprise displacing the DE inner proximal seal within a region between the DE inner shaft and the DE outer shaft.

[0214] Typically, the method of maintaining the azimuthing propulsion unit can further comprise installing the DE inner proximal seal and / or replacing the DE inner proximal seal, and in particular with a new DE inner proximal seal and / or at least a new portion thereof.

[0215] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, can comprise axially displacing along the DE inner shaft. For example, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, can comprise sliding, in particular axially, along the DE inner shaft. For example, displacing any of the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, can comprise rotating, preferably rotating to displace the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, the DE outer shaft, the DE inner shaft, or any combination thereof.

[0216] According to some embodiments described herein, the method of maintaining the azimuthing propulsion unit, comprises an azimuthing propulsion unit which comprises: a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof. The method typically further comprises displacing any of a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof. For example, displacing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof, can comprise axially displacing along the DE outer shaft and / or sliding along the DE outer shaft and / or radially displacing from the DE outer shaft. Typically, displacing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof, comprises displacing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof to a service position. When the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is at the service position, the method of maintaining the azimuthing propulsion unit typically comprises servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, orany combination thereof. For example, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof can comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof can be for the entire DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof, or at least a portion thereof. For example, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof comprises servicing at least one wearable part. The at least one wearable part can be defined as any part which needs to be serviced, and / or is due for service. Typically, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is through the hatch. Typically, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is within the hatch. Typically, servicing the DE outer proximal seal, the DE outer bearing, the DE outer distal seal, or any combination thereof is outside the hatch.

[0217] The method of maintaining the azimuthing propulsion unit can comprise servicing the DE inner proximal seal and / or the DE inner distal seal. The method of maintaining the azimuthing propulsion unit can comprise repairing and / or replacing the DE inner proximal seal and / or the DE inner distal seal. Repairing and / or replacing the DE inner proximal seal and / or the DE inner distal seal can occur after accessing the DE inner proximal seal and / or the DE inner distal seal, and in particular, after releasing and displacing the DE inner proximal seal and / or the DE inner distal seal.

[0218] Typically, the DE inner distal seal and / or the DE inner proximal seal comprise sealing elements. Sealing elements can comprise sealing lips. Typically, the sealing elements the DE inner distal seal and / or the DE inner proximal seal is replaced, displaced and / or serviced with the respective seal staying in place, after moving the respective seal to a service position or without removing the respective seal from the DE inner shaft. Typically, sealing elements are handled as described without necessarily displacing and / or servicing the entire DE inner distal seal and / or the entire DE inner proximal seal.

[0219] In typical embodiments, the method comprises displacing the DE inner distal seal and / or the DE inner proximal seal. In typical embodiments, the method comprises servicing the DE inner distal seal and / or the DE inner proximal seal. In typical embodiments, the method comprises displacing the sealing elements of the DE inner distal seal and / or the DE inner proximal seal. In typical embodiments, the method comprises servicing the sealing elements of the DE inner distal seal and / or the DE inner proximal seal. For example, the DE inner distal seal and / or the DE innerproximal seal comprises a seal ring. For example, the DE inner distal seal and / or the DE inner proximal seal comprises a seal housing. The seal housing can comprise housing rings. The seal housing is typically configured to hold the sealing elements. Typically, servicing comprises cutting the seal rings.

[0220] In typical embodiments, the method comprises proximally and / or distally displacing the seal housing. The method typically comprises proximally and / or distally displacing with respect to the DE inner bearing housing. The method typically comprises displacing the seal housing to the hatch. In particular, the method comprises displacing the seal housing to the hatch on the DE shaft. The method typically comprises servicing the seal housing. Servicing the seal housing typically comprises dismantling the housing rings. Typically, the housing rings are not removed through the hatch. Dismantling the housing rings typically comprises detaching from one another. Typically, the method comprises displacing sealing lips. Typically, the method comprises removing the sealing lips. Typically, displacing and / or removing the sealing lips is after dismantling the housing rings. In typical embodiments, the method comprises replacing the sealing lips. In typical embodiments, the method comprises repairing the sealing lips. In typical embodiments, the method comprises installing new sealing lips. In typical embodiments, the method comprises bonding and / or joining the sealing lips. In typical embodiments, the method comprises bonding to one another. Typically, bonding is done through the at least one hatch. Typically, in case of elastomer seals, chemicals such as glue, compression, and heat are used in bonding. In typical embodiments, the method comprises joining the sealing lips on the DE shaft. Typically, in case of polyurethane seals, bonding and / or joining comprises heating two ends of the seal ring and pressing the two ends together. In typical embodiments, the method comprises assembling the seal housing. In typical embodiments, the method comprises re-assembling the seal housing. In typical embodiments, the method comprises assembling the housing rings.

[0221] Typically, the DE inner shaft and / or the DE shaft can be supported. Supporting the DE inner shaft and / or the DE shaft can provide more room to manipulate the remaining components in the azimuthing propulsion unit.

[0222] Typically, a user can perform the method of maintaining the azimuthing propulsion unit described herein. For example, the user can open the hatch and can access the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal. The user can further perform the displacing of the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal. For example, the user can reach into the region accessible through the at least one hatch, and can displace any of the aforementioned components and / or subsidies thereof. The user can perform the opening of thehatch and / or the displacing of the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal using their labour and / or tools. For example, the user can employ at least one rod, threaded bar, grappling tool, and / or any tool suitable for releasing and displacing the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal.

[0223] For example, the user can access the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal. The user can further perform the displacing of the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal. The user can perform the displacing of the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal using their labour and / or tools. For example, the user can employ at least one rod, threaded bar, grappling tool, and / or any tool suitable for releasing and displacing the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal.

[0224] Embodiments of the present invention provide azimuthing propulsion units, in particular azimuthing propulsion units with an improved drive end shaft structure enabling inner bearing and seal change. With exemplary embodiments, the bearings and / or the seals might undergo maintenance and / or might be changed without it being mandatory to bring the vessel into a dry dock. For example, before removing the seals, shafts might be sealed against the water with at least one temporary seal applied from the waterside of the pod hull of the pod to allow a seal change whilst the vessel is in a swimming condition. For example, the azimuthing propulsion unit comprises at least one temporary seal. In particular, the at least one temporary seal is configured to be activated on demand.

[0225] In Fig. 2A, a side view of an exemplary azimuthing propulsion unit 500 with a single shaft and a single propeller is shown. The exemplary azimuthing propulsion unit 500 shown in Fig.2A can comprise similar parts as the exemplary embodiments of Figs. 0A - 0C, however, only a single shaft is present, which single shaft might be driven by a single motor with a typically fixed stator.

[0226] Fig. 2B schematically illustrates a cross-section of an isometric view of an azimuthing propulsion unit 500 according to typical embodiments described herein, the exemplary azimuthing propulsion unit 500 of Fig. 2B comprises a pod 30 and a pod hull 300. A rotatable drive end (DE) shaft 7 runs longitudinally in a driving direction.

[0227] The typical azimuthing propulsion unit 500 shown in Fig. 2B comprises a DE outer bearing 11. As with typical embodiments, the DE outer bearing 11 comprises outer bearing pads 51 land a DEouter bearing housing 510. Illustrated in the embodiment of Fig. 2B is a hatch 520 in the outer bearing housing 510. The hatch 520 can provide access to the DE outer bearing 11 and / or the outer bearing pads 511 and typically allows for the radial displacement of the DE outer bearing 11 and / or the outer bearing pads 511.

[0228] The exemplary embodiment of Fig, 2B comprises a DE outer distal seal 504, wherein the DE outer distal seal 504 is arranged between the DE shaft 7 and the DE outer bearing housing 510. The DE outer distal seal 504 is arranged towards a drive end (DE) of the azimuthing propulsion unit 500.

[0229] The exemplary azimuthing propulsion unit 500 of Fig. 2B comprises a DE outer proximal seal 506, wherein the DE outer proximal seal 506 is arranged between the DE shaft 7 and the DE outer bearing housing 510. The DE outer proximal seal 506 is arranged towards a motor of the azimuthing propulsion unit 500. The DE outer proximal seal 506 is typically arranged on an outer portion of the DE shaft 7 and on a proximal portion of the DE outer bearing housing 510. Especially in embodiments with the proximal seal in L-shape, the DE proximal seal 506 is in contact with both the DE outer shaft and the DE outer bearing housing.

[0230] FIG. 2C schematically illustrates a cross-section of an isometric view of an azimuthing propulsion unit 1000 according to typical embodiments described herein. The azimuthing propulsion unit 1000 comprises a pod 30 and a pod hull 300. Typically, a rotatable drive end (DE) inner shaft 8 runs at least partially within a DE outer shaft 7. As with further typical embodiments, a DE inner bearing 12 is arranged between the DE outer shaft 7 and the DE inner shaft 8. The DE outer shaft 7 typically comprises a hatch 302, preferably with at least the size of a man-hole or a size which allows access to an inside of the DE outer shaft.

[0231] The exemplary azimuthing propulsion unit 1000 of Fig. 2C as described herein can be maintained without requiring the marine vessel to be necessarily dry-docked. Dry docking a marine vessel is a time and resource consuming process which ultimately adversely affects an efficiency of the marine vessel.

[0232] The hatch 302 of the exemplary azimuthing propulsion unit 1000 of Fig. 2C is configured to provide access to the DE inner bearing 12. The hatch 302 is, for example, configured to be accessed by a user from within the azimuthing propulsion unit 1000. In order for the hatch 302 to provide sufficient access to the DE inner bearing 12, the hatch 302 typically has substantially the size of a man-hole or greater.The exemplary embodiment of Fig. 2C comprises the DE inner bearing 12 with inner bearing pads 312. For example, the DE inner bearing 12 can comprise two or more inner bearing pads 312. The inner bearing pads 312 are arranged around the DE inner shaft 8, and in particular around an entire circumference of the DE inner shaft 8.

[0233] The embodiment of Fig. 2C comprises a DE inner distal seal 304, wherein the DE inner distal seal 304 is arranged between the DE inner shaft 8 and the DE outer shaft. The DE inner distal seal 304 is arranged towards a drive end (DE) of the azimuthing propulsion unit 1000.

[0234] The exemplary azimuthing propulsion unit 1000 of Fig. 2C comprises a DE inner proximal seal 306, wherein the DE inner proximal seal 306 is arranged between the DE inner shaft 8 and the DE outer shaft. The DE inner proximal seal 306 is arranged towards a non-drive end (NDE) of the azimuthing propulsion unit 1000.

[0235] The exemplary azimuthing propulsion unit 1000 shown in Fig. 2C comprises a DE outer bearing 11. As with typical embodiments, the DE outer bearing 11 comprises outer bearing pads 511.

[0236] The DE inner bearing 12 and the DE outer bearing 11 are arranged coaxially on the rotation axis 50. In the exemplary embodiment of Fig. 2C, the DE outer bearing 11 is at least partially overlapping the DE inner bearing 12.

[0237] Fig. 2D illustrates a flow chart of a method 550 of maintaining an azimuthing propulsion unit according to typical embodiments described herein. The exemplary method 550 comprises accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit 552. The method 550 comprises accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing 554. The method 550 comprises accessing a DE outer distal seal 356.

[0238] Fig. 2E illustrates a flow chart of a method 550 of maintaining an azimuthing propulsion unit according to typical embodiments described herein. The exemplary method 550 of Fig. 2E comprises accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit 552. The method 550 comprises accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing 554. The method 550 comprises accessing a DE outer distal seal 356. The method 550 comprises releasing and displacing a DE outer proximal seal prior to accessing the DE outer bearing 558.

[0239] Fig. 2F illustrates a flow chart of a method 550 of maintaining an azimuthing propulsion unit according to some embodiments described herein. The exemplary method 550 of Fig. 2F comprises accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsionunit 552. The method 550 comprises accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing 554. The method 550 comprises accessing a DE outer distal seal 356. The method 550 comprises releasing and displacing a DE outer proximal seal prior to accessing the DE outer bearing 558. The method 550 comprises displacing the DE outer bearing after accessing the DE outer bearing, and displacing the DE outer distal seal after accessing the DE outer distal seal 559.

[0240] Fig. 2G illustrates a flow chart of a method 550 of maintaining an azimuthing propulsion unit according to typical embodiments described herein. The exemplary method 550 of Fig. 2G comprises accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit 552. The method 550 comprises accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing 554. The method 550 comprises accessing a DE outer distal seal 356. The method 550 comprises releasing and displacing a DE outer proximal seal prior to accessing the DE outer bearing 558. The method 550 comprises displacing the DE outer bearing after accessing the DE outer bearing, and displacing the DE outer distal seal after accessing the DE outer distal seal 559. The method 550, wherein the azimuthing propulsion unit further comprises a hatch in the DE shaft, wherein the DE shaft is a DE outer shaft of a contra rotating propeller (CRP) azimuthing propulsion unit, wherein the CRP azimuthing propulsion unit further comprises: a rotatable DE inner shaft, which runs at least partially within the DE outer shaft, a DE inner bearing, a DE inner proximal seal, and a DE inner distal seal, the method further comprising displacing and / or removing any of: a DE inner proximal seal arranged proximally between the DE inner shaft and the DE outer shaft, a DE inner bearing arranged between the DE inner shaft and the DE outer shaft , a DE inner distal seal arranged distally between the DE inner shaft and the DE outer shaft, or any combination thereof, through the hatch (560).

[0241] Embodiments of the present disclosure further provide an azimuthing propulsion unit (1000) for a vessel, the azimuthing propulsion unit (1000) comprising:

[0242] a rotatable drive end (DE) shaft (7);

[0243] a DE outer bearing housing (510);

[0244] a DE outer bearing (11) arranged between the DE shaft (7) and the DE outer bearing housing (510), wherein the DE outer bearing (11) is configured to be displaced, and wherein the DE outer bearing (11) comprises outer bearing pads (511); anda DE outer distal seal, wherein the DE outer distal seal is configured to be accessed from within the azimuthing propulsion unit.

[0245] In some embodiments, the azimuthing propulsion unit is a contra rotating propeller (CRP) azimuthing propulsion unit and the DE shaft is a DE outer shaft of the azimuthing propulsion unit, and the azimuthing propulsion unit (1000) further comprises a rotatable DE inner shaft (8), which runs at least partially within the DE outer shaft (7).

[0246] In some embodiments, the outer bearing pads are configured to be displaced axially and / or the DE outer distal seal is configured to be displaced axially.

[0247] In some embodiments, the DE outer distal seal (504) is arranged between the DE shaft (7) and the DE outer bearing housing (510).

[0248] In some embodiments, the azimuthing propulsion unit (1000) further comprises a DE outer proximal seal (506), wherein the DE outer proximal seal (506) is arranged between the DE shaft (7) and the DE outer bearing housing (510).

[0249] In some embodiments, the DE outer bearing (11), the DE outer distal seal (504), and / or the DE outer proximal seal (506) is replacable from within a pod hull (300) of a pod (30) of the azimuthing propulsion unit (1000).

[0250] In some embodiments, the DE outer shaft (7) comprises a hatch (302), which is configured to provide an access to a space between the DE outer shaft (7) and the DE inner shaft (8).

[0251] In some embodiments, the hatch (302) is configured to provide an access to a DE inner bearing (12) being arranged between the DE inner shaft (8) and the DE outer shaft (7); preferably wherein the DE inner bearing (12) comprises inner bearing pads (312) being configured to be accessed through the hatch (302).

[0252] In some embodiments, the DE inner bearing (12) and the DE outer bearing (11) are arranged coaxially on a rotation axis (50), wherein the DE outer bearing (11) is at least partially overlapping the DE inner bearing (12).

[0253] Embodiments of the present disclosure further provide a method (550) of maintaining an azimuthing propulsion unit, particularly the azimuthing propulsion unit according to the present disclousre; the method comprising:accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit (552);

[0254] accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing (554);

[0255] displacing the DE outer bearing; and

[0256] accessing a DE outer distal seal (556) from within the pod hull.

[0257] In some embodiments the method further comprises releasing and displacing a DE outer proximal seal prior to accessing the DE outer bearing (558).

[0258] In some embodiments the method further comprises displacing the DE outer bearing after accessing the DE outer bearing, and / or displacing the DE outer distal seal after accessing the DE outer distal seal (559).

[0259] In some embodiments, displacing any of the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises axially displacing along the DE shaft and / or radially displacing from the DE shaft.

[0260] In some embodiments, axially displacing the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises, axially displacing the DE outer bearing, the DE outer distal seal, or the DE outer proximal seal to a service position.

[0261] In some embodiments, the DE shaft of the azimuthing propulsion unit is a DE outer shaft of a contra rotating propeller (CRP) azimuthing propulsion unit, the CRP azimuthing propulsion unit further comprising:

[0262] a hatch in the DE outer shaft; a rotatable DE inner shaft, which runs at least partially within the DE outer shaft; a DE inner bearing arranged between the DE inner shaft and the DE outer shaft; a DE inner proximal seal arranged proximally between the DE inner shaft and the DE outer shaft; and / or a DE inner distal seal arranged distally between the DE inner shaft and the DE outer shaft;

[0263] and the method further comprises:

[0264] displacing any of: the DE inner proximal seal, the DE inner bearing, the DE inner distal seal, or any combination thereof, through the hatch (560).

[0265] 3. SEALING UNIT FOR AN AZIMUTHING PROPULSION UNITAzimuthing propulsion units that provide a high efficiency, durability and maintainability, in particular in view of the restricted amount of space available in the pod, are desired. Such azimuthing propulsion units can comprise an inner shaft and an outer shaft. An efficient, durable and maintainable sealing unit to seal an outside of the pod from an inside of the pod can be required. Embodiments of the present disclosure relate to such sealing units. Typically, embodiments of the present disclosure can fluidly connect an inner shaft sealing and an outer shaft sealing. Particularly, fluid can be transferred between the inner shaft sealing inside the outer shaft and the outer shaft sealing outside the outer shaft.

[0266] In the view of the foregoing, the present disclosure is directed to a sealing unit for an azimuthing propulsion unit and a method for servicing a sealing unit in an azimuthing propulsion unit.

[0267] According to some embodiments of the present disclosure, a sealing unit for an azimuthing propulsion unit is provided.

[0268] According to some embodiments of the present disclousre, a method for servicing of a sealing unit in an azimuthing propulsion unit according to any of the embodiments described herein is provided.

[0269] In some embodiments, an azimuthing propulsion unit comprises a rotatable inner shaft and a rotatable outer shaft. The inner shaft runs at least partially within the outer shaft. The outer shaft runs at least partially within a sealing housing of a pod. A sealing unit for such an azimuthing propulsion unit comprises a plurality of chamber systems, an inner shaft sealing and an outer shaft sealing. Each chamber system of the plurality of chamber systems comprises an inner shaft seal chamber, an outer shaft seal chamber and a passage through the outer shaft fluidly connecting the inner shaft seal chamber and the outer shaft seal chamber. The inner shaft sealing seals the inner shaft seal chambers of the plurality of chamber systems. The outer shaft sealing seals the outer shaft seal chambers of the plurality of chamber systems.

[0270] Typically, a plurality can be understood as at least one, particularly one or more. For example, a plurality of chamber systems can be understood as at least one chamber system, particularly one or more chamber systems.

[0271] In some embodiments, the outer shaft can be a DE outer shaft and the inner shaft can be a DE inner shaft.Typically, the fluid connection of the inner chamber and the outer chamber of a chamber system enables fluid transportation between the inner chamber and the outer chamber. Particularly, fluid can be transported through the outer shaft to the inner chamber of each chamber system.

[0272] In some embodiments, the inner shaft sealing can seal an inside of the outer shaft from an outside of the pod. The outer shaft sealing can seal an inside of the pod from the outside of the pod. Particularly, outside of the pod can be understood as outside the exterior of the pod, outside the hull of the vessel and / or the vessel exterior. Particularly, inside of the outer shaft can be understood as the space inside the outer shaft and / or the space between the outer shaft and the inner shaft.

[0273] In some embodiments, the inner shaft sealing can comprise an inner composure, an outer composure and a plurality of inner sealing elements. Typically, the inner composure, the outer composure and the inner sealing elements can be serviced and / or replaced separately from each other.

[0274] In some embodiments, the inner composure of the inner shaft sealing can be a seal liner and the outer composure of the inner shaft sealing can be a seal housing. The seal liner can rotate with the inner shaft. An inner static sealing between the seal liner and the inner shaft can seal the inside of the outer shaft from the outside of the pod. The seal housing can rotate with the outer shaft. An outer static sealing between the seal housing and the outer shaft can seal the inside of the outer shaft from the outside of the pod.

[0275] In some embodiments, the outer composure of the inner shaft sealing can be a seal liner and the inner composure of the inner shaft sealing can be a seal housing. The seal liner can rotate with the outer shaft. An outer static sealing between the seal liner and the outer shaft can seal the inside of the outer shaft from the outside of the pod. The seal housing can rotate with the inner shaft. An inner static sealing between the seal housing and the inner shaft can seal the inside of the outer shaft from the outside of the pod.

[0276] Typically, the inner composure of the inner shaft sealing and the outer composure of the inner shaft sealing and / or the inner sealing elements can be serviced individually, e.g. replaced individually. For example, the inner sealing elements and / or the seal liner may experience larger wear in comparison to the seal housing.

[0277] In some embodiments, the outer shaft sealing can comprise an inner composure, an outer composure and a plurality of outer sealing elements. Typically, the inner composure, the outercomposure and the outer sealing elements can be serviced and / or replaced separately from each other.

[0278] In some embodiments, the inner composure of the outer shaft sealing can be a seal liner and the outer composure of the outer shaft sealing can be a seal housing. The seal liner can rotate with the outer shaft. An inner static sealing between the seal liner and the outer shaft can seal the inside of the pod from the outside of the pod. The seal housing can be comprised by the sealing housing. An outer static sealing between the seal housing and the sealing housing can seal the inside of the pod from the outside of the pod.

[0279] In some embodiments, the outer composure of the outer shaft sealing can be a seal liner and the inner composure of the outer shaft sealing can be a seal housing. The seal liner can be comprised by the sealing housing. An outer static sealing between the seal liner and the sealing housing can seal the inside of the pod from the outside of the pod. The seal housing can rotate with the outer shaft. An inner static sealing between the seal housing and the outer shaft can seal the inside of the pod from the outside of the pod.

[0280] Typically, the inner composure of the outer shaft sealing and the outer composure of the outer shaft sealing and / or the outer sealing elements can be serviced individually, e.g. replaced individually. For example, the outer sealing elements and / or the seal liner may experience larger wear in comparison to the seal housing.

[0281] Typically, the plurality of inner sealing elements seals the plurality of inner shaft seal chambers and the plurality of outer sealing elements seals the plurality of outer shaft seal chambers. The inner sealing elements and / or the outer sealing elements can be sealing lips.

[0282] In some embodiments, a least one passage, particularly each passage, through the outer shaft can comprise an inner groove. The inner groove can be in at least one of: the inside of the outer shaft; and / or the inner shaft sealing. Particularly, the inner groove can be in an outer composure of the inner shaft sealing.

[0283] Typically, the inner groove of a chamber system provides a constant fluid connection between the inner shaft seal chamber of the chamber system and the outer shaft seal chamber of the chamber system. Particularly, the inner groove of the chamber system provides a constant fluid connection between the inner shaft seal chamber of the chamber system and the channels of the chamber system through the outer shaft.In some embodiments, an inner groove can be sealed by at least one inner groove sealing element. The inner groove sealing element(s) can typically prevent leakage between the inner grooves. Particularly, each inner groove sealing element can be a static ring and / or a sealing ring.

[0284] In some embodiments, at least one passage, particularly each passage, through the outer shaft can comprise an outer groove. The outer groove can be in at least one of: the outside of the outer shaft; and / or the outer shaft sealing. Particularly, the outer groove can be in the inner composure of the outer shaft sealing.

[0285] Typically, the outer groove of a chamber system provides a constant fluid connection between the inner shaft seal chamber of the chamber system and the outer shaft seal chamber of the chamber system. Particularly, the outer groove of the chamber system provides a constant fluid connection between the outer shaft seal chamber of the chamber system and the channels of the chamber system through the outer shaft.

[0286] In some embodiments, an outer groove can be sealed by at least one outer groove sealing element. The outer groove sealing element(s) can typically prevent leakage between the outer grooves. Particularly, each outer groove sealing element can be a static ring and / or a sealing ring.

[0287] In some embodiments, at least one passage, particularly each passage, through the outer shaft can comprise a plurality of channels through the outer shaft fluidly connecting the inner shaft seal chamber and the outer shaft seal chamber, particularly the inner shaft seal chamber and the outer shaft seal chamber of one chamber system.

[0288] In some embodiments, at least one passage, particularly each passage, through the outer shaft can comprise a plurality of channels through the outer shaft fluidly connecting the inner groove and the outer groove.

[0289] In some embodiments, a plurality of channels through the outer shaft can typically provide an improved fluid connection between the inner shaft seal chamber of a chamber system and the outer shaft seal chamber of the chamber system. Particularly, a plurality of channels through the outer shaft can typically provide an improved fluid connection between the inner groove of a chamber system and the outer groove of the chamber system.

[0290] In some embodiments, at least one passage, particularly each passage, through the outer shaft can comprise at least one hole, drilled through the outer shaft. Particularly, each channel of the plurality of channels of each passage through the outer shaft can comprise a hole, drilled through the outer shaft.In some embodiments, drilling a hole through the outer shaft provides a simple method to create a channel, a plurality of channels and / or a passage through the outer shaft of an appropriate size and / or at an appropriate location.

[0291] In some embodiments, the plurality of chamber systems can comprise a proximate chamber system. The proximate chamber system can be fluidly connected to an oil reservoir. Particularly, oil can be transferred from the oil reservoir to the proximate chamber system.

[0292] Typically, oil can be transferred from the oil reservoir to the inner shaft seal chamber through the outer shaft seal chamber and the passage through the outer shaft. Particularly, oil can be transferred from the proximate chamber system to the oil reservoir. Typically, oil can be transferred from the inner shaft seal chamber to the oil reservoir through the outer shaft seal chamber and / or the passage through the outer shaft.

[0293] Typically, the pressure inside the proximate chamber system is adjustable. Particularly the pressure inside the proximate chamber system is adjustable by adjusting the pressure inside the oil reservoir. Particularly, the sealing properties of the sealing unit can be improved by optimizing the pressure inside the proximate chamber system.

[0294] In some embodiments, the plurality of chamber systems can comprise a distant chamber system. Particularly, the distant chamber system can be free from oil. Typically, oil contamination of water leaking in the distant chamber system can be avoided.

[0295] In some embodiments, the plurality of chamber systems can comprise an intermediate chamber system. The intermediate chamber system can be fluidly connected to an air reservoir, particularly to a pressurized air reservoir.

[0296] Particularly, air can be transferred from the air reservoir, particularly the pressurized air reservoir, to the intermediate chamber system. Typically, air can be transferred from the air reservoir, particularly the pressurized air reservoir, to the inner shaft seal chamber through the outer shaft seal chamber and the passage through the outer shaft.

[0297] Particularly, air, leakage oil and / or leakage water can be transferred from the intermediate chamber system to the air reservoir, particularly the pressurized air reservoir. Typically, air, leakage oil and / or leakage water can be transferred from the inner shaft seal chamber to the air reservoir, particularly the pressurized air reservoir, through the outer shaft seal chamber and / or the passage through the outer shaft. Typically, air, leakage oil and / or leakage water can be transferred from the inner shaft seal chamber to an outlet reservoir, particularly an outlet reservoir of the air reservoir,particularly of the pressurized air reservoir, through the outer shaft seal chamber and / or the passage through the outer shaft.

[0298] Typically, the pressure inside the intermediate chamber system is adjustable. Particularly the pressure inside the intermediate chamber system is adjustable by adjusting the pressure inside the air reservoir, particularly the pressurized air reservoir. Typically, the sealing properties of the sealing unit can be improved by adjusting the pressure inside the intermediate chamber system.

[0299] Typically, leakage oil and / or leakage water can be removed from the intermediate chamber system. Typically, oil contamination of the distant chamber system can be avoided and / or water contamination of the proximate chamber system can be avoided. Particularly, the intermediate chamber system can seal the proximate chamber system from the distant chamber system.

[0300] In some embodiments, the air reservoir, particularly the pressurized air reservoir, can be fluidly connected to a compressor. In some embodiments, the air reservoir, particularly the pressurized air reservoir, can be a compressor. In some embodiments, the air reservoir, particularly the pressurized air reservoir, can be a pressurized air network, particularly a pressurized air network of a vessel.

[0301] In some embodiments, the proximate chamber system can be the chamber system of the plurality of chamber systems closest to a motor. The motor can be configured to drive the inner shaft and / or the outer shaft. The motor can be a dual rotor electric motor. The distant chamber system can be the chamber system of the plurality of chamber systems farthest from the motor. The intermediate chamber system can be a chamber system of the plurality of chamber systems between the proximate chamber system and the distant chamber system.

[0302] In some embodiments, the plurality of chamber systems can comprise a proximate chamber system, a distant chamber system and an intermediate chamber system. The proximate chamber system can be fluidly connected to an oil reservoir and the intermediate chamber system can be fluidly connected to an air reservoir, particularly a pressurized air reservoir.

[0303] Particularly, water from outside of the pod may leak inside the distant chamber system. The intermediate chamber system may seal the distant chamber system from the proximate chamber system. Typically, contamination of the distant chamber system with oil can be avoided. Typically, contamination of the proximate chamber system with water can be avoided.

[0304] In some embodiments, the plurality of chamber systems can comprise at least four chamber systems. At least two chamber systems of the plurality of chamber systems can be fluidlyconnected to an oil reservoir and / or at least one chamber system of the plurality of chamber systems can be fluidly connected to an air reservoir, particularly a pressurized air reservoir.

[0305] In some embodiments, each chamber system of the plurality of chamber systems can contain at least one of: (a) oil; (b) air; and / or (c) leakage fluid. Typically, the air can be pressurized air. Typically, the leakage fluid can be oil leaked from a neighboring chamber system and / or water leaked from outside the pod.

[0306] In some embodiments, each fluid connection of a chamber system of the plurality of chamber systems with a reservoir can comprise a supply groove. The supply groove can be in at least one of: the sealing housing; and / or the outer shaft sealing.

[0307] In some embodiments, each fluid connection of a chamber system of the plurality of chamber systems with a reservoir can comprise at least one supply channel. Each supply channel can fluidly connect the chamber system with the reservoir. Typically, at least one supply channel can be an inlet supply channel and at least one supply channel can be an outlet supply channel. Typically, fluid can be transferred from the reservoir to the chamber system through the inlet supply channel. Typically, fluid can be transferred from the chamber system to the reservoir through the outlet supply channel.

[0308] In some embodiments, a reservoir can comprise an inlet reservoir. Typically, fluid can be transferred from the inlet reservoir to a chamber system of the plurality of chamber systems through at least one inlet supply channel. Typically, the inlet reservoir can provide fresh / ready-to-use fluid to a chamber system.

[0309] In some embodiments, a reservoir can comprise an outlet reservoir. Typically, fluid can be transferred from a chamber system of the plurality of chamber systems to the outlet reservoir through at least one outlet supply channel. Typically, the outlet reservoir can receive used fluid, e.g. contaminated fluid such as oil-contaminated water, water-contaminated oil, oil-contaminated air and / or water-contaminated air.

[0310] In some embodiments, a supply groove can be sealed by at least one supply groove sealing element. Particularly, each outer groove sealing element can be a static ring and / or a sealing ring. Typically, the supply groove(s) provide(s) a constant fluid connection between the outer shaft seal chamber(s) and the supply channel(s).

[0311] In some embodiments, the propulsion unit can further comprise an inner bearing and an outer bearing. The inner bearing can be inside an inner bearing chamber between the inner shaft and theouter shaft. The outer bearing can be inside an outer bearing chamber between the outer shaft and the bearing housing. The sealing unit can further comprise an inner bearing sealing and an outer bearing sealing. The inner bearing sealing can seal the inside of the pod from the inner bearing chamber. The outer bearing sealing can seal the inside of the pod from the outer bearing chamber.

[0312] In some embodiments, the inner bearing can be a DE inner bearing and the outer bearing can be a DE outer bearing.

[0313] In some embodiments, the inner bearing chamber and / or the outer bearing chamber can be filled with oil.

[0314] In some embodiments, the bearing housing and the sealing housing can be connected. Particularly, the bearing housing and the sealing housing can be provided in a combined bearing and sealing housing.

[0315] Typically, oil from inside the inner bearing chamber can be prevented from leaking inside the pod by the inner bearing sealing. Typically, oil from inside the outer bearing chamber can be prevented from leaking inside the pod by the outer bearing sealing.

[0316] In some embodiments, the inner bearing chamber and the outer bearing chamber can be fluidly connected. Typically, oil can be supplied from an oil reservoir to the inner bearing chamber through the outer bearing chamber.

[0317] In some embodiments, the inner shaft sealing can seal the outside of the pod from the inner bearing chamber. The outer shaft sealing can seal the outside of the pod from the outer bearing chamber. Typically, oil from inside the inner bearing chamber and / or from inside the outer bearing chamber can be prevented from leaking to the outside of the pod. Typically, water from the outside of the pod can be prevented from leaking inside the inner bearing chamber and / or the outer bearing chamber.

[0318] An embodiment describes a method for servicing a sealing unit in an azimuthing propulsion unit. The propulsion unit comprises a rotatable inner shaft and a rotatable outer shaft, wherein the inner shaft runs at least partially within the outer shaft and wherein the outer shaft runs at least partially within a sealing housing of a pod. The sealing unit is a sealing unit according to any embodiment described herein. The method for servicing the sealing unit comprises: providing a service sealing arrangement, wherein the service sealing arrangement seals the inner shaft sealing from the outside of the pod; dismounting, at least partially, through a hatch provided in the outer shaft, an inner bearing between the inner shaft and the outer shaft; dismounting, at least partially, the inner shaftsealing through the hatch; servicing the inner shaft sealing; mounting the serviced inner shaft sealing through the hatch; and mounting the inner bearing through the hatch.

[0319] In some embodiments, the service sealing arrangement can be a pneumostop sealing arrangement.

[0320] In some embodiments, dismounting, at least partially, the inner bearing can comprise moving, at least partially, the inner bearing along a rotation axis of the inner shaft to provide access to the inner shaft sealing through the hatch.

[0321] In some embodiments, servicing the inner shaft sealing can comprise: replacing at least one inner sealing element of the inner shaft sealing; and bonding the new inner sealing element(s). Typically, bonding the new inner sealing element can provide a continuous sealing element around the entire circumference of the inner shaft.

[0322] Typically, the inner shaft sealing of the sealing unit in the azimuthing propulsion unit can be serviced without removing the azimuthing propulsion unit from the water. Particularly, the inner shaft sealing of the sealing unit in the azimuthing propulsion unit can be serviced without the use of a dry dock and / or without removing the vessel from the water.

[0323] In some embodiments, the service sealing arrangement can seal the outer shaft sealing from the outside of the pod. The method can further comprise: dismounting, at least partially, an outer bearing between the outer shaft and the bearing housing; dismounting, at least partially, the outer shaft sealing; servicing the outer shaft sealing; mounting the serviced outer shaft sealing; and mounting the outer bearing.

[0324] In some embodiments, the service sealing arrangement can comprise a service sealing to seal the inner shaft sealing and the outer shaft sealing from the outside of the pod. In some embodiment, the service sealing arrangement can comprise an inner service sealing to seal the inner shaft sealing from the outside of the pod. In some embodiments, the service sealing arrangement can comprise an outer service sealing to seal the outer shaft sealing from the outside of the pod. In some embodiments, the service sealing arrangement can comprise the inner service sealing and the outer service sealing. Typically, the inner service sealing and the outer service sealing may be activated and / or deactivated at the same time, particularly through the same mechanism.

[0325] In some embodiments, servicing the outer shaft sealing can comprise: replacing at least one outer sealing element of the outer shaft sealing; and bonding the new outer sealing element(s). Typically, bonding the new outer sealing element can provide a continuous sealing element around the entire circumference of the outer shaft.In some embodiments, the method can further comprise: dismounting, at least partially, an outer bearing sealing, wherein the outer bearing sealing seals the inside of the pod from the outer bearing chamber; and mounting the outer bearing sealing. Typically, dismounting the outer bearing sealing provides access to the outer bearing.

[0326] Typically, the outer shaft sealing of the sealing unit in the azimuthing propulsion unit can be serviced without removing the azimuthing propulsion unit from the water. Particularly, the outer shaft sealing of the sealing unit in the azimuthing propulsion unit can be serviced without the use of a dry dock and / or without removing the vessel from the water.

[0327] In some embodiments, the method can further comprise: mounting an inner spacer ring arrangement between the inner shaft and the outer shaft. The inner spacer ring arrangement can define the location of the inner shaft sealing, particularly of the inner sealing elements, the outer composure of the inner shaft sealing and / or the inner composure of the inner shaft sealing, along the rotation axis of the inner shaft.

[0328] The inner spacer ring arrangement can comprise a first inner spacer ring and / or a second inner spacer ring. The first inner spacer ring can engage with the inner shaft, particularly with a shaft shoulder of the inner shaft, and the inner shaft sealing, particularly the inner composure of the inner shaft sealing. The second inner spacer ring can engage with the outer shaft, particularly with a shaft shoulder of the outer shaft, and the inner shaft sealing, particularly the outer composure of the inner shaft sealing.

[0329] Typically, the location of the inner shaft sealing, the inner composure of the inner shaft sealing, the outer composure of the inner shaft sealing and / or the inner sealing elements along the rotation axis of the inner shaft can be changed be replacing a mounted inner spacer ring arrangement with a replacement inner spacer ring arrangement. The mounted inner spacer ring arrangement, particularly the first inner spacer ring and / or the second inner spacer ring of the mounted inner spacer ring arrangement, can have a different thickness, particularly a thickness in the direction of the rotation axis of the inner shaft and the outer shaft, compared to the thickness, particularly a thickness in the direction of the rotation axis of the inner shaft and the outer shaft, of the replacement inner spacer ring arrangement, particularly the first inner spacer ring and / or the second inner spacer ring of the replacement inner spacer ring arrangement.

[0330] Typically, by changing the location of the inner shaft sealing, of the inner composure of the inner shaft sealing, of the outer composure of the inner shaft sealing and / or of the inner sealing elements along the rotation axis of the inner shaft, the inner shaft sealing, the inner composure of the innershaft sealing, the outer composure of the inner shaft sealing and / or the inner sealing elements can be relocated to a location on the inner shaft with less wear. Typically, by changing the location of the inner composure of the inner shaft sealing and / or the location of the outer composure of the inner shaft sealing the inner composure of the inner shaft sealing can be relocated compared to the outer composure of the inner shaft sealing (or vice versa). Particularly, the inner sealing elements can be relocated relative to the inner composure of the inner shaft sealing or the outer composure of the inner shaft sealing to a location with less wear on the inner composure of the inner shaft sealing or the outer composure of the inner shaft sealing.

[0331] In some embodiments, the method can further comprise: mounting an outer spacer ring arrangement between the outer shaft and the sealing housing. The outer spacer ring arrangement can define the location of the outer shaft sealing, particularly of the outer sealing elements, the outer composure of the outer shaft sealing and / or the inner composure of the outer shaft sealing, along the rotation axis of the outer shaft.

[0332] The outer spacer ring arrangement can comprise a first outer spacer ring and / or a second outer spacer ring. The first outer spacer ring can engage with the outer shaft, particularly with a shaft shoulder of the outer shaft, and the outer shaft sealing, particularly the inner composure of the outer shaft sealing. The second outer spacer ring can engage with the sealing housing, particularly with a shoulder of the sealing housing, and the outer shaft sealing, particularly the outer composure of the outer shaft sealing.

[0333] Typically, the location of the outer shaft sealing, of the inner composure of the outer shaft sealing, of the outer composure of the outer shaft sealing and / or of the outer sealing elements on the outer shaft can be changed be replacing a mounted outer spacer ring arrangement with a replacement outer spacer ring arrangement. The mounted outer spacer ring arrangement, particularly the first outer spacer ring and / or the second outer spacer ring of the mounted outer spacer ring arrangement, can have a different thickness, particularly a thickness in the direction of the rotation axis of the inner shaft and the outer shaft, compared to the thickness, particularly a thickness in the direction of the rotation axis of the inner shaft and the outer shaft, of the replacement outer spacer ring arrangement, particularly the first outer spacer ring and / or the second outer spacer ring of the replacement outer spacer ring arrangement.

[0334] Typically, by changing the location of the outer shaft sealing, of the inner composure of the outer shaft sealing, of the outer composure of the outer shaft sealing and / or of the outer sealing elements along the rotation axis of the outer shaft, the outer shaft sealing, the inner composure of the outershaft sealing, the outer composure of the outer shaft sealing and / or the outer sealing elements can be relocated to a location on the outer shaft with less wear. Typically, by changing the location of the inner composure of the outer shaft sealing and / or the outer composure of the outer shaft sealing the inner composure of the outer shaft sealing can be relocated compared to the outer composure of the outer shaft sealing (or vice versa). Particularly, the outer sealing elements can be relocated relative to the inner composure of the outer shaft sealing or the outer composure of the outer shaft sealing to a location with less wear on the inner composure of the outer shaft sealing or the outer composure of the outer shaft sealing.

[0335] FIG 3A schematically illustrates an exemplary sealing unit inside an azimuthing propulsion unit 1000. The sealing unit 1000 comprises a plurality of chamber systems, an inner shaft sealing 810 and an outer shaft sealing 820. Each chamber system of the plurality of chamber systems comprises an inner chamber 817a, 817b, 817c, an outer chamber 827a, 827b, 827c and a passage through the outer shaft 7 fluidly connecting the inner chamber 817a, 817b, 817c and the outer chamber 827a, 827b, 827c. The inner shaft sealing 810 is arranged between the inner shaft 8 and the outer shaft 7. The inner shaft sealing 810 can seal the inner chambers 817a, 817b, 817c of the plurality of chamber systems. The outer shaft sealing 820 is arranged between the outer shaft 7 and the sealing housing 801. The outer shaft sealing 820 seals the outer chambers 827a, 827b, 827c of the plurality of chamber systems.

[0336] The inner shaft sealing 810 typically comprises an inner composure 811, an outer composure 813 and a plurality of inner sealing elements 815. For example, each inner sealing element 815 of the plurality of inner sealing elements 815 composed by the inner shaft sealing 810 is a sealing lip.

[0337] The outer shaft sealing 820 typically comprises an inner composure 821, an outer composure 823 and a plurality of outer sealing elements 825. For example, each outer sealing element 825 of the plurality of outer sealing elements 825 composed by the outer shaft sealing 820 is a sealing lip.

[0338] Each passage through the outer shaft 7 typically comprises an inner groove 835a, 835b, 835c. The inner groove 835a, 835b, 835c is in the inside of the outer shaft 7. Alternatively, the inner groove 835a, 835b, 835c can be in the inner shaft sealing 810 and / or the inner groove 835a, 835b, 835c can be in the outer composure 813 of the inner shaft sealing 810. Typically, the inner groove 835a, 835b, 835c can be in the inside of the outer shaft 7 and in the inner shaft sealing 810.Each passage through the outer shaft 7 typically comprises an outer groove 833a, 833b, 833c. The outer groove 833a, 833b, 833c is in the outside of the outer shaft 7. Alternatively, the outer groove 833a, 833b, 833c can be in the outer shaft sealing 820 and / or the outer groove 833a, 833b, 833c can be in the inner composure 821 of the outer shaft sealing 820. Typically, the outer groove 833a, 833b, 833c can be in the outside of the outer shaft 7 and in the outer shaft sealing 820.

[0339] Each passage through the outer shaft 7 comprises a plurality of channels 831a, 83 lb, 831c through the outer shaft 7 fluidly connecting one of the inner shaft seal chambers 817a, 817b, 817c and one of the outer grooves 827a, 827b, 827c.

[0340] A proximate chamber system comprises the outer shaft seal chamber 827a, the inner shaft seal chamber 817a, the outer groove 833a, the inner groove 835a and the channel 831a.

[0341] An intermediate chamber system comprises the outer shaft seal chamber 827b, the inner shaft seal chamber 817b, the outer groove 833b, the inner groove 835b and the channel 831b.

[0342] A distant chamber system comprises the outer shaft seal chamber 827c, the inner shaft seal chamber 817c, the outer groove 833c, the inner groove 835c and the channel 831c.

[0343] Each chamber system of the plurality of chamber systems can be fluidly connected to a reservoir. Each fluid connection comprises a supply groove 843 in the sealing housing 801 and / or each fluid connection comprises a supply groove 843 in the outer shaft sealing 820 and / or each fluid connection comprises a supply groove 843 in the outer composure 823 of the outer shaft sealing 820. At least two (only one is shown) supply channels 841 fluidly connect the chamber system and the reservoir. Particularly, each supply channel 841 fluidly connects the supply groove 843 and the reservoir.

[0344] In FIG 3 A the proximate chamber system is connected to an oil reservoir (not shown) by the supply groove 843 and at least two (only one is shown) supply channels 841.

[0345] The intermediate chamber system can be connected to an air reservoir, particularly a pressurized air reservoir, by a supply groove and at least one supply channels (not shown). The distant chamber system can be connected to a reservoir by a supply groove and at least one supply channels (not shown).

[0346] The inner shaft sealing 810 typically seals further inner shaft seal chambers 817d, 817e. The outer shaft sealing 820 typically seals further outer shaft seal chambers 827d, 827e. In someembodiments, the further inner shaft seal chambers 817d, 817e and the further outer shaft seal chambers 827d, 827e are not fluidly connected.

[0347] In some embodiments, the inner shaft sealing can seal at least one further inner shaft seal chamber. In some embodiments, the outer shaft sealing can seal at least one further outer shaft seal chamber. In some embodiments, the inner shaft sealing can seal X further inner shaft seal chamber(s). X may be any number equal to or larger than 1. In some embodiments, the outer shaft sealing can seal Y further outer shaft seal chamber(s). Y may be any number equal to or larger than 1. In some embodiments, X may equal Y. In some embodiments, X may be different than Y.

[0348] FIG 3B schematically illustrates an exemplary sealing unit inside an azimuthing propulsion unit 1000. The sealing unit 1000 comprises a plurality of chamber systems, an inner shaft sealing 810 and an outer shaft sealing 820. Each chamber system of the plurality of chamber systems comprises an inner chamber 817a, 817b, 817c, an outer chamber 827a, 827b, 827c and a passage through the outer shaft 7 fluidly connecting the inner chamber 817a, 817b, 817c and the outer chamber 827a, 827b, 827c. The inner shaft sealing 810 is arranged between the inner shaft 8 and the outer shaft 7. The inner shaft sealing 810 can seal the inner chambers 817a, 817b, 817c of the plurality of chamber systems. The outer shaft sealing 820 is arranged between the outer shaft 7 and the sealing housing 801. The outer shaft sealing 820 seals the outer chambers 827a, 827b, 827c of the plurality of chamber systems.

[0349] The inner shaft sealing 810 typically comprises an inner composure 811, an outer composure 813 and a plurality of inner sealing elements 815. For example, each inner sealing element 815 of the plurality of inner sealing elements 815 composed by the inner shaft sealing 810 is a sealing lip.

[0350] The outer shaft sealing 820 typically comprises an inner composure 821, an outer composure 823 and a plurality of outer sealing elements 825. For example, each outer sealing element 825 of the plurality of outer sealing elements 825 composed by the outer shaft sealing 820 is a sealing lip.

[0351] Each passage through the outer shaft 7 typically comprises an inner groove 835a, 835b, 835c. The inner groove 835a, 835b, 835c is in the inside of the outer shaft 7. Alternatively, the inner groove 835a, 835b, 835c can be in the inner shaft sealing 810 and / or the inner groove 835a, 835b, 835c can be in the outer composure 813 of the inner shaft sealing 810. Typically, the inner groove 835a, 835b, 835c can be in the inside of the outer shaft 7 and in the inner shaft sealing 810.

[0352] Each passage through the outer shaft 7 typically comprises an outer groove 833a, 833b, 833c. The outer groove 833a, 833b, 833c is in the outside of the outer shaft 7. Alternatively, the outer groove833a, 833b, 833c can be in the outer shaft sealing 820 and / or the outer groove 833a, 833b, 833c can be in the inner composure 821 of the outer shaft sealing 820. Typically, the outer groove 833a, 833b, 833c can be in the outside of the outer shaft 7 and in the outer shaft sealing 820.

[0353] Each passage through the outer shaft 7 comprises a plurality of channels 831a, 83 lb, 831c through the outer shaft 7 fluidly connecting one of the inner shaft seal chambers 817a, 817b, 817c and one of the outer shaft seal chambers 827a, 827b, 827c.

[0354] A proximate chamber system comprises the outer shaft seal chamber 827a, the inner shaft seal chamber 817a, the outer groove 833a, the inner groove 835a and the channel 831a.

[0355] An intermediate chamber system comprises the outer shaft seal chamber 827b, the inner shaft seal chamber 817b, the outer groove 833b, the inner groove 835b and the channel 831b.

[0356] A distant chamber system comprises the outer shaft seal chamber 827c, the inner shaft seal chamber 817c, the outer groove 833c, the inner groove 835c and the channel 831c.

[0357] Each chamber system of the plurality of chamber systems can be fluidly connected to a reservoir. Each fluid connection comprises a supply groove 843 in the sealing housing 801 and / or each fluid connection comprises a supply groove 843 in the outer shaft sealing 820 and / or each fluid connection comprises a supply groove 843 in the outer composure 823 of the outer shaft sealing 820. At least two (only one is shown) supply channels 841 fluidly connect the chamber system and the reservoir. Particularly, each supply channel 841 fluidly connects the supply groove 843 and the reservoir.

[0358] In FIG 3B the proximate chamber system is connected to an oil reservoir (not shown) by the supply groove 843 and at least two (only one is shown) supply channels 841.

[0359] The intermediate chamber system can be connected to an air reservoir, particularly a pressurized air reservoir, by a supply groove and at least one supply channels (not shown).

[0360] The inner shaft sealing 810 typically seals further inner shaft seal chambers 817d, 817e. The outer shaft sealing 820 typically seals further outer shaft seal chambers 827d, 827e. In some embodiments, the further inner shaft seal chambers 817d, 817e and the further outer shaft seal chambers 827d, 827e are not fluidly connected.

[0361] The azimuthing propulsion unit 1000 comprises an inner bearing 12 and an outer bearing 11. The inner bearing 12 can be a DE inner bearing 12. The outer bearing 11 can be a DE outer bearing 12. The inner bearing 12 is arrange inside an inner bearing chamber 851 between the inner shaft 8 andthe outer shaft 7. The outer bearing 11 is arranged inside an outer bearing chamber 853 between the outer shaft 7 and the bearing housing 803. The inner bearing chamber 851 and the outer bearing chamber 853 are fluidly connected by a bearing channel 859.

[0362] A hatch 860 is provided inside the outer shaft 7. The hatch 860 can provide access to the inside of the outer shaft 7.

[0363] FIG 3C schematically illustrates a method for servicing a sealing unit inside an azimuthing propulsion unit 1000. The method comprises: providing 891 a service sealing; dismounting 892, at least partially, an inner bearing 12; dismounting 893, at least partially, an inner shaft sealing 810; servicing 894 the inner shaft sealing 810; mounting 895 the serviced inner shaft sealing 810; and mounting 896 the inner bearing 12. The service sealing can seal the inner shaft sealing 810 and the outer shaft sealing 820 from the outside of the pod 30. The inner bearing 12 between the inner shaft 8 and the outer shaft 7 can be dismounted 891 through a hatch 860 provided in the outer shaft 7. The inner shaft sealing 810 can be dismounted 893, at least partially, through the hatch 860. The serviced inner shaft sealing 810 can be mounted 895 through the hatch 860. The inner bearing 12 can be mounted 896 through the hatch 860.

[0364] Some embodiments of the present disclosure provide a sealing unit for an azimuthing propulsion unit (1000), the propulsion unit (1000) comprising a rotatable inner shaft (8) and a rotatable outer shaft (7), wherein the inner shaft (8) runs at least partially within the outer shaft (7) and wherein the outer shaft (7) runs at least partially within a sealing housing (801) of a pod (30),

[0365] the sealing unit comprising:

[0366] - a plurality of chamber systems, wherein each chamber system comprises an inner shaft seal chamber (817a, 817b, 817c), an outer shaft seal chamber (827a, 827b, 827c) and a passage through the outer shaft fluidly connecting the inner shaft seal chamber (817a, 817b, 817c) and the outer shaft seal chamber (827a, 827b, 827c);

[0367] - an inner shaft sealing (810) between the inner shaft (8) and the outer shaft (7), wherein the inner shaft sealing (810) seals the inner shaft seal chambers (817a, 817b, 817c) of the plurality of chamber systems; and

[0368] - an outer shaft sealing (820) between the outer shaft (7) and the sealing housing (801), wherein the outer shaft sealing (820) seals the outer shaft seal chambers (827a, 827b, 827c) of the plurality of chamber systems.In some embodiments, the inner shaft sealing (810) seals an inside of the outer shaft (7) from an outside of the pod (30); and / or wherein the outer shaft sealing (820) seals an inside of the pod (30) from the outside of the pod (30).

[0369] In some embodiments,

[0370] - the inner shaft sealing (810) comprises an inner composure (811), an outer composure (813) and a plurality of inner sealing elements (815); and / or

[0371] - the outer shaft sealing (820) comprises an inner composure (821), an outer composure (823) and a plurality of outer sealing elements (825).

[0372] In some embodiments, at least one passage through the outer shaft (7) comprises an inner groove (835a, 835b, 835c), and wherein the inner groove (835a, 835b, 835c) typically is in at least one of: the inside of the outer shaft (7); and / or the inner shaft sealing (810).

[0373] In some embodiments, at least one passage through the outer shaft (7) comprises an outer groove (833a, 833b, 833c), and wherein the outer groove (833a, 833b, 833c) typically is in at least one of: the outside of the outer shaft (7); and / or the outer shaft sealing (820).

[0374] In some embodiments, at least one passage through the outer shaft (7) comprises a plurality of channels (831a, 831b, 831c) through the outer shaft (7) fluidly connecting the inner shaft seal chamber (817a, 817b, 817c) and the outer shaft seal chamber (827a, 827b, 827c).

[0375] In some embodiments, the plurality of chamber systems comprises:

[0376] - a proximate chamber system, wherein the proximate chamber system is fluidly connected to an oil reservoir;

[0377] - a distant chamber system; and

[0378] - an intermediate chamber system, wherein the intermediate chamber system is fluidly connected to an air reservoir.

[0379] In some embodiments, each chamber system of the plurality of chamber systems contains at least one of:

[0380] - oil;

[0381] - air; and / orleakage fluid.

[0382] In some embodiments, each fluid connection of a chamber system of the plurality of chamber systems to a reservoir comprises:

[0383] - a supply groove (843) in at least one of: the sealing housing (801); and the outer shaft sealing (820).

[0384] In some embodiments, each fluid connection of a chamber system of the plurality of chamber systems to a reservoir comprises:

[0385] - at least one supply channels (841) fluidly connecting the chamber system and the reservoir.

[0386] In some embodiments, the propulsion unit (1000) further comprises:

[0387] - an inner bearing (12) inside an inner bearing chamber (851) between the inner shaft (8) and the outer shaft (7); and

[0388] - an outer bearing (11) inside an outer bearing (853) chamber between the outer shaft (7) and a bearing housing (803);

[0389] and the sealing unit further comprises:

[0390] - an inner bearing sealing (855), wherein the inner bearing sealing (855) seals the inside of the pod (30) from the inner bearing chamber (851);

[0391] - an outer bearing sealing (857), wherein the outer bearing sealing (857) seals the inside of the pod (30) from the outer bearing chamber (853).

[0392] In some embodiments, the inner bearing chamber (851) and the outer bearing chamber (853) are fluidly connected.

[0393] In some embodiments,

[0394] - the inner shaft sealing (810) seals the outside of the pod (30) from the inner bearing chamber (851); and / or

[0395] - the outer shaft sealing (820) seals the outside of the pod (30) from the outer bearing chamber (853).

[0396] Embodiments of the present disclosure further provide a method for servicing a sealing unit,typically for servicing a sealing unit according to the present disclosure, in an azimuthing propulsion unit (1000), the propulsion unit (1000) comprising a rotatable inner shaft (8) and a rotatable outer shaft (7), wherein the inner shaft (8) runs at least partially within the outer shaft (7) and wherein the outer shaft (7) runs at least partially within a sealing housing (801) of a pod (30), the method comprising:

[0397] - providing (891) a service sealing arrangement, wherein the service sealing arrangement seals the inner shaft sealing (810) from the outside of the pod (30);

[0398] - dismounting (892), at least partially, through a hatch (860) provided in the outer shaft (7), an inner bearing (12) between the inner shaft (8) and the outer shaft (7);

[0399] - dismounting (893), at least partially, the inner shaft sealing (810) through the hatch (860);

[0400] - servicing (894) the inner shaft sealing (810);

[0401] - mounting (895) the serviced inner shaft sealing (810) through the hatch (860); and

[0402] - mounting (896) the inner bearing (12) through the hatch (860).

[0403] In some embodiments, the service sealing arrangement seals the outer shaft sealing (820) from the outside of the pod (30);

[0404] and the method further comprises:

[0405] - dismounting, at least partially, an outer bearing (11) between the outer shaft (7) and a bearing housing (803);

[0406] - dismounting, at least partially, the outer shaft sealing (820);

[0407] - servicing the outer shaft sealing (820);

[0408] - mounting the serviced outer shaft sealing (820); and

[0409] - mounting the outer bearing (11).

[0410] 4. BEARING UNIT FOR AN AZIMUTHING PROPULSION UNIT

[0411] In known azimuthing propulsion systems, the ship has to go to the dry dock for repair and maintenance of the elements of an azimuthing propulsion system. This comes with high costs and loss of operation time of the complete ship. For instance, the shaft(s) of an azimuthing propulsionsystem is / are supported by bearings, which are prone to wear and are to be replaced or repaired from time to time. Thus, the bearings within the pod of the azimuthing propulsion unit are one cause for the ship to be stopped and undergo maintenance actions.

[0412] Azimuthing propulsion units that provide a high efficiency, durability and maintainability, in particular in view of the restricted amount of space available in the pod, are desired. In particular, a good and uncomplicated maintainability of the pod and the elements in the pod, such as the bearings, leads to reduced costs of operation of an azimuthing propulsion unit. It is therefore desirable to provide a bearing unit for the azimuthing propulsion unit considering the small space within the pod, and enabling easy maintenance, repair and replacement of the bearings in the azimuthing propulsion unit.

[0413] In the view of the foregoing, the present disclosure is directed to a bearing unit for an azimuthing propulsion unit, an azimuthing propulsion unit comprising a bearing unit and a method of supporting an inner shaft and an outer shaft in an azimuthing propulsion unit for an azimuthing propulsion unit.

[0414] According to some embodiments of the present disclosure, a bearing unit for an azimuthing propulsion unit is provided. The azimuthing propulsion unit includes a rotatable inner shaft and a rotatable outer shaft, wherein the inner shaft runs at least partially within the outer shaft. The bearing unit includes: a bearing arrangement including at least one axial bearing (especially axial bearings) for the inner shaft and the outer shaft, wherein the bearing arrangement is configured for supporting at least a part of the inner shaft and the outer shaft; and a bearing housing for housing the bearing arrangement and the part of the inner shaft and the outer shaft to be supported by the bearing arrangement. The bearing arrangement is configured for allowing a transfer of axial forces between the outer shaft and the inner shaft. According to embodiments described herein, an azimuthing propulsion unit including a bearing unit as described herein is provided.

[0415] With the bearing unit according to embodiments described herein, the shafts of the azimuthing propulsion unit can be supported in a space-saving arrangement and, at the same time, the maintenance, repair and replacement of parts of the bearing arrangement, or parts of / at the bearing housing is facilitated.

[0416] Typically, the bearing arrangement includes a first axial bearing between the inner shaft and the outer shaft for allowing the transfer of axial forces between the inner shaft and the outer shaft. In some embodiments, the bearing arrangement includes the first axial bearing between the inner shaft and the outer shaft, a second axial bearing arranged between a bearing housing wall and theinner shaft, and a third axial bearing arranged between a bearing housing wall and the outer shaft. The arrangement of the axial bearings between the shafts as well as a common placement of the axial bearing(s) for both shafts allows for an efficient, space-saving, and compact arrangement of the bearings used for the shafts of the azimuthing propulsion unit.

[0417] In some embodiments, the bearing housing includes at least one hatch or opening for reaching into the inside of the bearing housing. Especially, the at least one hatch is configured for allowing access to the axial bearing(s), maintenance of the axial bearing(s) and replacement of the axial bearing(s) of the bearing arrangement for the inner shaft and the outer shaft. Additionally, or alternatively, the at least one hatch allows for access to the housing for allowing maintenance, repair or replacement of the radial bearing(s) and / or other elements within, at or near the bearing housing (such as seals and the like). This facilitates the maintenance, repair and replacement of elements within the pod of the azimuthing propulsion unit, and saves time and costs.

[0418] According to some embodiments, the bearing unit may inlcude an oil seal. In particular, the oil seal may be located between the inner shaft and the outer shaft, especially between a flange of the inner shaft and a flange of the outer shaft. In some embodiments, the oil seal may be located under (inside) the first bearing. Especially, the oil seal may be removable throug the at least one hatch. More specifically, the first bearing may be removed at least partly to open up a maintenance route / space for maintenance, repair or exchange of the oil seal, especially via hatch. In some embodiments, the oil seal may include an oil seal housing. According to some embodiments, the oil seal housing part can be fastened to one of the inner shaft and the outer shaft, or both (or the respective flanges of the shafts). Typically, the oil seal may contain elastic lips seals against liner.

[0419] According to some embodiments described herein, at least one of the axial bearings (and / or, optionally, at least one of the radial bearings) of the bearing arrangement is a pad bearing. A pad bearing provides a reliable function with a simple design. In some embodiments, the pad bearing can easily be removed from the bearing housing due to its simple design and uncomplicated montage possibilities.

[0420] According to embodiments described herein, an azimuthing propulsion unit is provided including a bearing unit according to embodiments described herein. Especially, the azimuthing propulsion unit is configured for allowing access of a person to a hatch of the bearing housing of the bearing unit. The azimuthing propulsion unit with the bearing unit according to embodiments described herein, enables an easy access to the complete bearings of the shafts of the NDE side of the azimuthing propulsion unit.According to another aspect of the present disclosure, a method of supporting an inner shaft and an outer shaft in an azimuthing propulsion unit according to any of the embodiments described herein is provided, wherein the azimuthing propulsion unit includes the inner shaft and the outer shaft and wherein the inner shaft runs at least partially within the outer shaft. The method includes providing a bearing arrangement and a bearing housing for housing the bearing arrangement, the bearing arrangement including at least one axial bearing for the inner shaft and the outer shaft; and arranging the axial bearing of the bearing arrangement for allowing a transfer of axial forces between the outer shaft and the inner shaft.

[0421] According to some embodiments described herein, arranging the axial bearings for a transfer of axial forces between the outer shaft and the inner shaft includes arranging a first axial bearing between the inner shaft and the outer shaft. In some embodiments, which may be combined with other embodiments described herein, arranging the first axial bearing between the inner shaft and the outer shaft includes utilizing a bearing pad mounted between the inner shaft and the outer shaft. This may provide a compact, reliable, and cost-efficient solution for supporting both shafts of the azimuthing propulsion unit. Furthermore, the transfer of axial forces between the inner shaft and the outer shaft is enabled by the one axial bearing between the two shafts.

[0422] Typically, the method according to some embodiments described herein may include accessing the bearing arrangement (or other elements, such as oil seals, and the like) within the bearing housing through a hatch or opening. In particular, the method according to embodiments described herein, may include performing repair, maintenance, and / or replacement of the bearing arrangement through the at least one hatch or opening. Accessing the inside of the bearing housing through a hatch, which is - in turn - accessible from the inside of the pod of the azimuthing propulsion unit, facilitates maintenance and repair, and safes time and costs for the maintenance and repair. In some embodiments, the bearing unit may include an oil seal, which may especially be located between the inner shaft and the outer shaft, or their flanges. Typically, the method may include removing the oil seal from the bearing unit through the at least one hatch. According to some embodiments, which may be combined with other embodiments described herien, the method may inlcude removing the first bearing (being e.g. designed as a pad bearing) at least partly to open up a maintenance route / space for maintenance, repair or exchange of the oil seal, especially via hatch. In some embodiments, the oil seal may include an oil seal housing. According to some embodiments, the oil seal housing part can be fastened on the inner and / or outer shaft, or on or into one (or both) of the flanges of the inner shaft and the outer shaft.The NDE inner shaft 48 and the NDE outer shaft 47 are supported by a bearing unit 40. In some embodiments, the bearings for the NDE inner shaft and for the NDE outer shaft can be configured so that the axial (and, eventually, radial bearings) for both shafts may be fitted into the same bearing housing. Typically, the bearing unit 40 (and / or the bearing arrangement of the bearing unit) typically comprises an oil seal, respectively.

[0423] The DE outer shaft 7 is supported in the pod 30 by a DE outer bearing 11. The DE inner shaft 7 is supported in the DE outer shaft 8 by a DE inner bearing 12. The DE outer bearing 11 and the DE inner bearing 12 typically comprise an oil and water seal, respectively.

[0424] Fig. 4A shows a partial view of an azimuthing propulsion unit and, especially, the NDE side according to some embodiments described herein. In Fig. 4A, the bearing unit 40 is shown including a bearing arrangement 401 and a bearing housing 407. Typically, the bearing housing may at least partly be filled with an lubricant, such as oil. In some embodiments, the bearing(s) of the bearing arrangement 401 are lubricated, such as oil lubricated. The bearing arrangement 401 includes bearings 402 to 406 for supporting both the inner shaft 48 and the outer shaft 47. Typically, the outer shaft 47 may include a flange 471, especially at the end of the outer shaft 47. In some embodiments, the NDE side of the outer shaft may be the part of the outer shaft to be supported by the bearing arrangement. In some embodiments, the outer shaft 47 may have a substantially L-like shape for providing the flange 471 at the end of the outer shaft 47. According to some embodiments, the inner shaft 48 may include a flange 481 extending from the inner shaft 48. In some embodiments, the NDE side of the inner shaft may be the part of the inner shaft to be supported by the bearing arrangement. In some embodiments, the flange 471 of the outer shaft 47 and / or the flange 481 of the inner shaft 48 may be integrally formed with the rest of the respective shaft. Alternatively, or additionally, the flange 471 and / or the flange 481 may be connected to the rest of the respective outer shaft, e.g. by screws, bolts, mortise joints, some kind of tongue and groove arrangement, or the like.

[0425] According to some embodiments, the flange 471 of the outer shaft 47 and / or the flange 481 of the inner shaft 48 may extend from the surface of the part of the respective shaft, which runs substantially parallel to the rotation axis, from about 100 mm to about 400 mm, more typically from about 150 mm to about 350 mm, and even more typically from about 200 mm to about 300mm in radial direction. Typically, the extension of the flange 471 of the outer shaft 47 and / or the flange 481 of the inner shaft 48 in axial direction may be between about 50 mm to about 400 mm, more typically between about 100 mm and about 350 mm, and even more typically between about 150 mm and about 300 mm. According to some embodiments, the flanges 471 and 481 maybe arranged and configured with respect to each other for enabling the montage of two shafts and / or for enabling the montage of the common axial bearing at one of the flanges, e.g. by one flange extending the other flange slightly in radial direction.

[0426] Typically, the bearing unit 40 is adapted and configured for supporting the flange 471 of the outer shaft 47 and the flange 481 of the inner shaft 48.

[0427] The bearing unit 40 includes a bearing arrangement 401 including bearings for supporting the inner shaft 48 and the outer shaft 47. In some embodiments, the bearings of the bearing arrangement 401 are configured and placed for supporting the inner shaft 48 and the outer shaft 47 by supporting the flange 481 of the inner shaft 48 and the flange 471 of the outer flange 47. According to embodiments described herein, the bearing arrangement 401 may include one or more axial bearings 402, 403, 404 for the inner shaft 48 and the outer shaft 47. According to some embodiments, which may be combined with other embodiments described herein, the bearing arrangement 401 may include radial bearings 405, 406 for the inner shaft 48 and the outer shaft 47 of the azimuthing propulsion unit.

[0428] Fig. 4B shows a schematic view of the bearing arrangement 401 according to some embodiments described herein. The bearing arrangement 401 includes a first axial bearing 403 between the inner shaft 48 and the outer shaft 47 (or between the flange 481 of the inner shaft 48 and the flange 471 of the outer shaft 47). In the embodiment exemplarily shown in Fig. 4B, the bearing arrangement 401 further includes a second axial bearing 402 arranged between a first bearing housing wall 408 and the inner shaft 48 (or the flange 481 of the inner shaft), and a third axial bearing 404 arranged between a second bearing housing wall 409 and the outer shaft 47 (or the flange 471 of the outer shaft). Typically, the first bearing housing wall 408 and the second bearing housing wall 409 may extend substantially perpendicular to the axis of rotation 50 of the inner shaft 48 and the outer shaft 47. The bearing arrangement 401 shown in Fig. 4B may further include a radial bearing 405 for the inner shaft 48 and a radial bearing 406 for the outer shaft 47. Typically, the location of the radial bearing may be different in other embodiments.

[0429] According to embodiments described herein, the bearing arrangement 401 is configured for allowing a transfer of axial forces between the outer shaft 47 and the inner shaft 48 (or, particularly, the flange 471 of the outer shaft 47 and the flange 481 of the inner shaft 48). For instance, a first axial bearing 403 is provided between the inner shaft and the outer shaft for enabling a transfer of the axial forces between the shafts.Fig. 4C shows the situation of a transfer of axial forces between the flange 481 of the inner shaft and the flange 471 of the outer shaft by arrows 415. The arrows 415 of Fig. 4C show a transfer of axial forces between the shafts in both directions. According to some embodiments, a transfer of axial forces between the two shafts may be beneficial for the stability of the drive chain of the azimuthing propulsion unit. The axial load of the two shafts may be described as being bundled or merged when using a bearing unit as described in embodiments described herein, and the bearing arrangement of the bearing unit allows for a combined axial load sharing. Typically, a combined axial load sharing enables the distribution of the load, especially the weakening of load peaks. The distributed load may relieve the single shafts and may prevent damage on one of the shafts. The bearing arrangement 401 shown in Fig. 4C may further include a radial bearing 405 for the inner shaft 48 and a radial bearing 406 for the outer shaft 47.

[0430] Typically, the inner shaft and the outer shaft and the bearing arrangement as described in embodiments herein, are arranged within the bearing housing for a combined axial load sharing. According to some embodiments, the first axial bearing 403 may be configured to carry thrust loads from one shaft. The second and third bearing 402 (or 404) may be configured to carry thrust loads from both shafts.

[0431] Typically, for enabling a transfer of axial forces between two shafts in an azimuthing propulsion unit, the location and the distance of the inner shaft to the outer shaft may be considered (and, especially, the location and the distance between the flange 471 of the outer shaft and the flange 481 of the inner shaft). Typically, the inner shaft and the outer shaft are positioned dependent on each other in axial direction, in particular by the first axial bearing. Typically, the inner shaft and the outer shaft share one axial bearing, namely the first axial bearing 403. In some embodiments, the inner shaft and the outer shaft share one axial bearing for enabling the transfer of axial forces (and, especially, for realizing the combined axial load sharing). Typically, the bearing arrangement (in particular the first axial bearing 403) provides support for the combined axial load sharing of the inner shaft and the outer shaft.

[0432] According to some embodiments described herein, the arrangement of the inner shaft and the outer shaft with respect to each other and the arrangement of the first axial bearing allows for a space saving arrangement of the shafts as well as a space saving arrangement of the bearing unit. The compact design of the bearing unit and the positioning of the shafts to each other for a space saving arrangement further allows the bearing unit to be easily (and commonly) maintained.According to some embodiments, the bearings as described herein, may be pad bearings, but may also be rolling bearing, or plain bearings, or any combination of the different bearing types for the different bearing locations. In one embodiment, the radial bearing(s) may be slide bearings / pad bearings. In some examples, the bearings of the bearing arrangement may be chosen as useful or appropriate for the bearing unit. For instance, in some embodiments, the radial bearings of the bearing arrangement according to some embodiments described herein may be rolling bearings, while the axial bearings (or at least one of them) may be (a) pad bearing(s). In some embodiments, which may be combined with other embodiments described herein, some components of the axial bearing may be partitioned (e.g. in replaceable sectors) for facilitating a removal of the axial bearing out of the bearing housing. Typically, the top (at one or both sides) of the pad bearing may be a slide bearing. According to some embodiments, a pad bearing may be composed of multiple pads (such as two or more pads), or pad layers. According to some embodiments, a pad bearing as described herein may be designed as useful or suitable for the application in the bearing arrangement according to embodiments described herein. For instance, a pad bearing may include sector pieces, may be substantially round shaped, may include a slide bearing housing, a bearing ring, a slide guide, sliding segments, segment carrier and the like, and / or may be equipped with spring elements.

[0433] According to some embodiments, the axial bearing(s), such as bearing pads, and especially the first axial bearing 403, may be mounted to the inner shaft or the outer shaft by a fixation means. In some embodiments, the axial bearing(s), especially first bearing 403, is mounted and configured in a non-rotating way. For instance, the axial bearing(s), especially the first bearing 403, may be fastened to the bearing housing. Typically, the axial bearing(s) may be fastened to a shaft by a bolt connection, a screw connection, a form-fit connection (such as a fishtail connection), and the like.

[0434] According to some embodiments, which may be combined with other embodiments described herein, the bearing unit as described herein may include a misalignment compensation mechanism in the axial bearing(s), especially the first axial bearing 403. For instance, elastic (spring) elements (e.g. a disk spring) may be used as a misalignment compensation mechanism.

[0435] Typically, the design of the axial bearing, the fixation means for the at least one axial bearing, the arrangement of the bearings within the housing, the housing geometry, the arrangement of the flanges of the inner shaft and the outer shaft may be arranged so as to enable a maintenance person to lift up the axial bearing in the case of maintenance, repair, or replacement. For instance, the bearing arrangement and the bearing housing may be designed so that substantially no barrier (or at least only a removable barrier) is present when lifting an axial bearing out of the housing.According to embodiments described herein, the bearing unit as referred to herein is a bearing unit for an azimuthing propulsion unit. According to some embodiments, the bearing unit may be adapted or configured for an azimuthing propulsion unit by choosing for instance the size, the material, the strength, the type, the location, the arrangement, the shape and further properties for the use in an azimuthing propulsion unit. For instance, the size of the bearing unit may be adapted to the above listed sizes of the shafts. In another example, the material and / or the strength may be chosen according to the expected load appearing in an azimuthing propulsion unit having e.g. the above named examples of propeller power, and so on. In some embodiments, the housing of the bearing unit may be adapted to be mounted in a pod of an azimuthing propulsion unit. The housing may for instance be adapted by configuring the size, the shape, the mounting features, the seals, and the like for the use in a pod of an azimuthing propulsion unit. In some embodiments, which may be combined with other embodiments described herein, the bearing unit may be adapted for an azimuthing propulsion unit by choosing the properties of the bearings of the bearing arrangement for the shafts of an azimuthing propulsion unit (e.g. regarding size, strength and the like). Typically, the bearing unit may be adapted for the montage in a pod of an azimuthing propulsion unit (e.g. by respective fixation means, montage features, fulfilled shape requirements, and the like) and may especially be configured for a better maintenance and repair possibilities, e.g. by hatches as described in detail below.

[0436] In one embodiment, the bearing unit provides for a defined axial distance between the inner shaft 48 (or its flange 481) and the outer shaft 47 (or its flange 471), especially via the geometrical conditions of the bearing arrangement and the bearing housing. For instance, the bearing unit provides an axial distance between the inner shaft and the outer shaft within the bearing housing of between typically about 50 mm and about 250 mm, more typically between about 80 mm and about 200 mm, and even more typically between about 100 mm and about 170mm.

[0437] Typically, the bearings of the bearing arrangement and the bearing housing provide at least partly a substantially ring-like shape surrounding parts (such as flanges) of the inner shaft and the outer shaft.

[0438] A property being denoted with “substantially” herein may be understood as the property including small or minor deviations. For instance, the term “substantially ring-shaped” may be understood that the ring may have small interruptions from the strict closed ring shape. In another example, a “substantially L-like shape” may look like an “L” but may include deviations from the rectangular angles in an “L” of about typically 15%, more typically of about 10%, and even more typically ofabout 5%. The same may be valid for expressions like “substantially parallel”, “substantially perpendicular”, and the like.

[0439] Fig. 4D shows a partial, perspective view of the bearing unit 40 arranged at the NDE side of an azimuthing propulsion unit. Fig. 4D shoes a bearing unit 40 according to embodiments descried herein including a bearing housing 407 having bearing housing walls 408, 409, and 410 (as can exemplarily be seen in Fig. 4D). Typically, the bearing housing 407 is adapted for housing the bearing arrangement 401 including one or more bearings for the inner shaft 48 and the outer shaft 47, and for housing the parts (especially the flanges 471 and 481) of the inner shaft 48 and the outer shaft 47 to be supported by the bearing arrangement 401. In some embodiments, the bearing housing 407 may be adapted for holding one or more of the bearings of the bearing arrangements, and withstanding the forces exerted by the bearings of the bearing arrangement 401. According to some embodiments, the bearing housing being adapted for housing parts of the inner shaft 48 and the outer shaft 47 and / or adapted for holding bearings of the bearing arrangement may include adapting the size of the housing, the shape of the housing, the properties of the material of the housing, the stability and the statics of the housing, and the like. Especially, the strength and statics of the bearing housing may be adapted to be able to hold a bearing, or counter the forces provided by the bearing, e.g. in a case, where a bearing is (partly) fixed to a bearing housing wall.

[0440] According to some embodiments, which may be combined with other embodiments described herein, the bearing housing may have a length in axial direction from about 500 mm to about 2000 mm. According to some embodiments, the bearing housing may have a width in radial direction from about 300 mm to about 1500 mm cm.

[0441] The inner shaft 48, the flange 481 of the inner shaft, the outer shaft 47, the flange 471 of the outer shaft 47, the bearing housing 407 having bearing housing walls 408, 409, and 410 can exemplarily be seen in Fig. 4D. Typically, the bearing housing walls 408 and 410 extend substantially perpendicular to the rotation axis of the inner shaft and the outer shaft, and bearing housing wall 411 extends (at least partly) substantially parallel to the rotation axis of the inner shaft and the outer shaft. In some embodiments, bearing housing wall 409 extending substantially parallel to the rotation axis may be denoted as a kind of ceiling of the bearing housing.

[0442] According to some embodiments, the bearing housing wall 409, which may also be denoted as the ceiling of the bearing housing, may include one or more hatches or opening. In Fig. 4D, two hatches 411 and 412 are exemplarily shown in the bearing housing wall 409. The hatches in the bearing housing wall may be configured for reaching into the inside of the bearing housing. Forinstance, the size of the one or more hatches may be adapted for allowing access to the bearings of the bearing arrangement, and especially for allowing maintenance and / or replacement of the bearings of the bearing arrangement through the one or more hatches. Fig. 4D exemplarily shows two hatches 411 and 412; however, the number of the hatches or opening may be more than two, such as three or four, or may be dependent on the number and position of the bearings within the bearing housing, or may be less than two, such as one single hatch or opening. According to some embodiments, the size of the one or more hatches or opening may be adapted to the number. For instance, a single hatch or opening may be larger than three hatches or opening.

[0443] In some embodiments described herein, the center axial bearing, e.g. the first axial bearing 403, may be removed, by a hatch in the bearing housing wall 409 (the ceiling), e.g. through hatch 411 as shown in Fig. 4D. According to some embodiments, which may be combined with other embodiments described herein, other bearings, such as radial bearings, or thrust side pads (e.g. bearings 402, 404) may be removed through a hatch in the bearing housing wall 409, and / or from a hatch in the axial, or side direction (such as one or more hatches in the bearing housing walls 408 and / or 410). According to some embodiments, which may be combined with other embodiments described herein, the at least one hatch may be located on a radial surface of the bearing housing (so that the bearing pads can e.g. be radially removed). Alternatively or additionally the at least one hatch may be located on an axial side surface of the bearing housing (so that the pads can be moved axially, for instance).

[0444] In some embodiments, a hatch of the bearing housing may be provided by a removable wall of the bearing housing, such as bearing housing wall 409, or 410 to access the bearing arrangement within the bearing housing. Typically, the removable bearing housing wall may be fixed to the rest of the bearing housing by fixation means, e.g. screws, bolts, form-fit connections, or the like.

[0445] According to some embodiments, which may be combined with other embodiments described herein, the bearing housing may be adapted to include, or may include one or more seals, especially oil seals for the bearings. Typically, the one or more hatches in the bearing housing wall enables servicing of the oil seal, e.g. by the position and / or the size of the hatch.

[0446] The oil seal 430 (shown e.g. in Fig. 4A, and in an enlarged view in Fig. 4E) may be located between shaft flanges 481 and 471. Typically, the oil seal 430 may be located under (inside) the first bearing 403. The first bearing (being e.g. designed as a pad bearing) may be removed at least partly to open up a maintenance route / space for maintenance, repair or exchange of the oil seal, especially via hatch 411 (in particular, wear parts can be changed and bonded). In some embodiments, theoil seal may include an oil seal housing. According to some embodiments, the oil seal housing part can be fastened into one of the flanges 471, 481, or both. In some embodiments (in particular additionally or alternatively), the seal housing may be attached to either (or may stand in connection to both) of the inner shaft 48 and the outer shaft 47. Typically, the oil seal may contain elastic lips seals against liner.

[0447] In some embodiments described herein, a bearing housing as referred to herein may be understood as an element housing at least one bearing and the parts to be supported by the bearing. In one example, the bearing housing may for instance house the flange 481 of the inner shaft and the shaft 471 of the outer shaft 47 at least partially and at least one (axial) bearing between the shafts. According to some embodiments, the bearing housing may be a separate housing within the hull of the pod of the azimuthing propulsion unit. In some embodiments, the bearing housing may (at least partially) be integrally formed in the hull of the pod of the azimuthing propulsion unit. For instance, one or more walls of the bearing housing may be provided by the hull of the pod of the azimuthing propulsion unit. In some embodiments, the bearing housing being at least partially integrated into the hull of the pod may provide access to the bearing arrangement within the bearing housing e.g. by removing one of the walls of the bearing housing.

[0448] Some embodiments provide a bearing unit as described herein in an azimuthing propulsion unit. In some embodiments, the azimuthing propulsion unit, which the bearing unit according to embodiments described herein is provided in, may include a motor (preferably an electric motor, and still preferably a dual electric motor), and an inner shaft and an outer shaft (which are preferably both driven by the motor). The azimuthing propulsion unit, which the bearing unit according to embodiments described herein is provided in, may further include a propeller unit including an outer shaft propeller connected (and especially driven by) the outer shaft, and an inner shaft propeller connected (and preferably driven by) the inner shaft. Typically, the drive chain of the azimuthing propulsion unit, which the bearing unit according to embodiments is provided in, includes a driven end (DE), which is the end, where the propeller unit is arranged, and a non-driven end (NDE) on the end of the drive chain opposite to the propeller unit. According to some embodiments described herein, the bearing unit as described in embodiments herein may be arranged at the NDE side of the drive chain of the azimuthing propulsion unit.

[0449] Typically, the azimuthing propulsion unit, which the bearing unit according to embodiments is provided in, or which the bearing unit according to embodiments described herein is adapted for, may be an azimuthing propulsion unit as described herein above, e.g. with respect to Figs. OA, OB, and / or OC.According to some embodiments described herein, an azimuthing propulsion unit having a bearing unit as described in embodiments herein is described. Typically, the azimuthing propulsion unit may be an azimuthing propulsion unit as described in detail above, especially with respect to Figs. OA, OB, and / or OC.

[0450] As mentioned above, the bearing housing may have one or more hatches for reaching into the inside of the bearing housing. Likewise, the pod of the azimuthing propulsion unit having a bearing unit according to embodiments described herein, may provide a space for a person to reach to the one or more hatches of the bearing housing of the bearing unit. For instance, the pod of the azimuthing propulsion unit may include one or more defined paths for a person to repair, maintain, or replace the elements within the pod, e.g. the bearing unit. In some embodiments, the pod of the azimuthing propulsion unit with the bearing unit according to embodiments described herein may have a height in the inside to allow repair, maintenance, and replacement may be performed in an ergonomic way. In some embodiments, the pod may be adapted for allowing at least an arm of a maintenance person to reach to the bearing housing.

[0451] According to some embodiments described herein, a method of supporting an inner shaft and an outer shaft in an azimuthing propulsion unit is provided. Fig. 4F shows a schematic flow diagram of the method 420 as described in embodiments herein. Typically, the azimuthing propulsion unit includes the inner shaft and the outer shaft, wherein the inner shaft runs at least partially within the outer shaft. According to some embodiments, which may be combined with other embodiments described herein, the azimuthing propulsion unit, whose shafts are supported in the herein described method may for instance be an azimuthing propulsion unit as described above, especially with respect to Figs. OA, OB and / or OC.

[0452] As can be seen in Fig. 4F, the method 420 includes in box 421 providing a bearing arrangement 401 and a bearing housing 407 for surrounding or housing the bearing arrangement. Typically, the bearing arrangement used in the method according to embodiments described herein may be a bearing arrangement of a bearing unit as described in embodiments above. Especially, the bearing arrangement may include one or more axial bearings (402; 403; 404) for the inner shaft 48 and the outer shaft 47. In some embodiments, the bearing arrangement may include one or more radial bearings (405; 406) for the inner shaft 48 and the outer shaft 47. Typically, the axial and / or radial bearings being arranged may include one or more pad bearings as described in embodiments above. According to some embodiments, providing a bearing arrangement in a bearing housing may include providing support for the bearings in the bearing housing, such as a fixture, a receptacle, an area foreseen (and maybe preprocessed) for the bearing of the bearing unit to rest,and the like. Especially, bearing housing walls 408 and 409 may be adapted and / or prepared for providing a contact area for the axial bearings of the bearing arrangement. In some embodiments, providing the bearing arrangement and the bearing housing may include providing the bearing arrangement at least partially in the bearing housing, e.g. by using pre-mounted elements in the bearing housing.

[0453] In box 422, the method according to embodiments described herein includes arranging the axial bearings (402; 403; 404) of the bearing arrangement 401 for allowing a transfer of axial forces between the outer shaft 47 and the inner shaft 48 of the azimuthing propulsion unit. For instance, at least one axial bearing 403 may be arranged between the inner shaft 48 and the outer shaft 48, or their flanges 471 and 481, respectively. In some embodiments, the bearing arrangement is used in the method according to embodiments described herein for allowing a combined axial load sharing. In some embodiments, the method may include bundling or merging the axial load of the two shafts.

[0454] According to some embodiments, which may be combined with other embodiments described herein, the method includes accessing the bearing arrangement 401 within the bearing housing 407 through at least one hatch 411, 412. In particular, the method according to embodiments described herein may include performing repair, maintenance, and / or replacement of the bearing arrangement 401, and / or other parts in, at or near the bearing housing (such as e.g. oil seals) through the one or more hatches.

[0455] According to some embodiments, for performing repair, maintenance, and / or replacement of the bearing, the bearing (such as an axial bearing pad) may be removed from the bearing housing. Typically, the compression between the two flanges of the inner shaft and the outer shaft around the bearing (such as the axial bearing pad) may be loosened for removing the bearing. This may be denoted as an ’’opening of axial gap.” The loosening of the compression or the opening of an axial gap may be done via external jack-up or any force excerted by auxiliary equipment outside the bearing housing in some embodiments.

[0456] According to embodiments described herein, the bearing unit as described herein, the azimuthing propulsion unit including a bearing unit as described herein and the method for supporting shafts in an azimuthing propulsion unit as described herein allows for the montage of a bearing arrangement with a low space consumption within the pod of an azimuthing propulsion unit. Typically, the bearing unit according to embodiments described herein enables a reliable function with fewest possible parts. Additionally, the bearing unit according to embodiments describedherein allows for an easy maintenance, repair, and exchange of the parts within, at or near the bearing housing, and spares time and cost for the maintenance, repair, or replacement.

[0457] This written description uses examples to describe the subject matter herein, including the best mode, and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

[0458] The bearing unit 40 and the bearing arrangement 401 may correspond to or may be used to replace bearing 41 and / or bearing 42 according to embodiments of the present disclosure.

[0459] Embodiments of the present disclosure provide a bearing unit (40) for an azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprising a rotatable inner shaft (48) and a rotatable outer shaft (47), wherein the inner shaft (48) runs at least partially within the outer shaft (47),

[0460] the bearing unit (40) comprising:

[0461] A bearing arrangement (401) comprising at least one axial bearing (402-404) for the inner shaft (48) and the outer shaft (47), wherein the bearing arrangement is configured for supporting at least a part of the inner shaft (48) and the outer shaft (47); and,

[0462] A bearing housing (407) for housing the bearing arrangement (401) and the part (471; 481) of the inner shaft (48) and the outer shaft (47) to be supported by the bearing arrangement (401);

[0463] wherein the bearing arrangement (401) is configured for allowing a transfer of axial forces between the outer shaft (47) and the inner shaft (48).

[0464] In some embodiments, the bearing arrangement (401) comprises a first axial bearing (403) between the inner shaft (48) and the outer shaft (47) for allowing the transfer of axial forces between the inner shaft (48) and the outer shaft (47).

[0465] In some embodiments, the bearing arrangement (401) comprises the first axial bearing (403) between the inner shaft (48) and the outer shaft (48), a second axial bearing (402) arranged betweena bearing housing wall (408) and the inner shaft (48), and a third axial bearing (404) arranged between a bearing housing wall (409) and the outer shaft (47).

[0466] In some embodiments, the bearing housing (407) comprises at least one hatch (411; 412) for reaching into the inside of the bearing housing (407).

[0467] In some embodiments, the at least one hatch (411; 412) is configured for allowing access to one of the axial bearings (402; 403; 404), maintenance of the axial bearings (402; 403; 404) and / or replacement of the axial bearings (402; 403; 404) of the bearing arrangement (401) for the inner shaft (48) and the outer shaft (47).

[0468] In some embodiments, at least one of the axial bearings (402; 403; 404) of the bearing arrangement is a pad bearing.

[0469] Embodiments of the present disclosure further provide a bearing unit according to embodiments of the present disclosure in an azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprising a dual electric motor (1), the inner shaft (48) and the outer shaft (47), at least one of the inner shaft (48) and the outer shaft (47) being driven by the dual electric motor (1), a propeller unit comprising an outer shaft propeller (9) and an inner shaft propeller (10), wherein the inner shaft propeller (10) is driven by the inner shaft (48) and the outer shaft propeller (9) is connected to the outer shaft (47), and wherein the drive chain of the azimuthing propulsion unit (1000) comprises a driven end (DE), which is the end, where the propeller unit is arranged, and a non-driven end (NDE) on the end of the drive chain opposite to the propeller unit.

[0470] In some embodiments, the bearing unit (401) is arranged at the NDE side of the drive chain of the azimuthing propulsion unit (1000).

[0471] Embodiments of the present disclosure further provide an azimuthing propulsion unit (1000) comprising a bearing unit (40) according to embodiments of the present disclosure..

[0472] In some embodiments, the bearing housing (407) has at least one hatch (411; 412) for maintenance, repair and replacement of the bearing arrangement (401) or parts of the bearing arrangement, and wherein the azimuthing propulsion unit (1000) is configured for allowing access of a person to the at least one hatch (411; 412).

[0473] Embodiments of the present disclosure further provide a method (420) of supporting an inner shaft (48) and an outer shaft (47) in an azimuthing propulsion unit (1000), the azimuthing propulsionunit (1000) comprising the inner shaft (48) and the outer shaft (47), wherein the inner shaft (48) runs at least partially within the outer shaft (47), the method comprising:

[0474] o Providing (421) a bearing arrangement (401) and a bearing housing (407) for housing the bearing arrangement, the bearing arrangement comprising at least one axial bearing (402; 403; 404) for the inner shaft (48) and the outer shaft (47); and,

[0475] o Arranging (422) the axial bearing (402; 403; 404) of the bearing arrangement (401) for allowing a transfer of axial forces between the outer shaft (47) and the inner shaft (48).

[0476] In some embodiments, arranging (422) the axial bearings (402; 403; 404) for a transfer of axial forces between the outer shaft (47) and the inner shaft (48) comprises arranging a first axial bearing (403) between the inner shaft (48) and the outer shaft (47).

[0477] In some embodiments, arranging the first axial bearing (403) between the inner shaft (48) and the outer shaft (47) comprises utilizing a bearing pad mounted between the inner shaft (48) and the outer shaft (47).

[0478] In some embodiments, the bearing housing (407) comprises at least one hatch (411; 412) and the method further comprises: accessing the bearing arrangement (401) within the bearing housing (407) through the at least one hatch (411; 412); and, in particular, performing repair, maintenance, and / or replacement of the bearing arrangement (401) through the at least one hatch (411; 412).

[0479] In some embodiments, providing the bearing unit (40) comprises mounting the bearing unit (40) in an azimuthing propulsion unit (1000), especially in an azimuthing propulsion (1000) unit according to any of claims 9 and 10.

[0480] 5. COOLING OF A SLIP-RING ARRANGEMENT

[0481] For an efficient marine propulsion unit, contra rotating propellers may be employed. For driving a contra rotating propeller, a contra rotating electric motor can be suitable that employs slip-rings. However, it is required that the slip-rings operate reliably and with a seldom need for maintenance.

[0482] In the view of the foregoing, the present disclosure is directed to a marine propulsion unit and a method for cooling a slip-ring arrangement in the marine propulsion unit.According to embodiments of the present disclosure, a marine propulsion unit with a slip-ring cooling system and a contra rotating motor having an inner rotor and an outer rotor is provided. The marine propulsion unit comprises a slip-ring housing and a slip-ring assembly arranged within the slip-ring housing, wherein the slip-ring assembly comprises at least one slip-ring element being in contact to the outer rotor. Furthermore, an air channel arrangement is provided which comprises a first position being connected to the slip-ring housing and a second position. The marine propulsion unit further comprises an air fan device configured to generate a cooling airflow that flows from the first position to the second position of the air channel arrangement creating a negative pressure within the slip-ring housing. The marine propulsion unit further includes an outflow filter unit arranged at the second position of the air channel arrangement for filtering the cooling airflow exiting the air channel arrangement.

[0483] According to embodiments aspect of the present disclosure, a marine vessel comprising a marine propulsion unit according to any of the embodiments described herein is provided.

[0484] According to embodiments of the present disclosure, a method for cooling a slip-ring arrangement in a marine propulsion unit with a contra rotating motor having an inner rotor and an outer rotor is provided. The method for cooling a slip-ring arrangement includes cooling a slip-ring assembly within a slip-ring housing by generating a negative pressure in an air channel arrangement connected by a first position to the slip-ring housing, wherein a cooling airflow flows from the first position to a second position of the air channel arrangement. The method further includes filtering the cooling airflow exiting the second position of the air channel arrangement by an outflow filter unit.

[0485] In some embodiment, the marine propulsion unit comprises a slip-ring cooling system for cooling a slip-ring unit, particularly for cooling a slip-ring arrangement. The slip-ring cooling system includes a slip-ring housing and a slip-ring assembly arranged within the housing. Typically, the slip-ring assembly comprises at least one slip-ring element which is in contact to the outer rotor. Furthermore, an air channel arrangement is provided, which includes a first position being connected to the slip-ring housing and a second position. An air fan device is provided which is configured to generate a cooling airflow that flows from the first position to the second position of the air channel arrangement creating a negative pressure within the slip-ring housing. Furthermore, an outflow filter unit is included which is arranged at the second position of the air channel arrangement for filtering the cooling airflow exiting the air channel arrangement.Typically, the slip-ring housing can be understood as a casing which is configured to accommodate the slip-ring assembly separately in the pod. The slip-ring housing is configured to prevent dust, in particular carbon dust to enter the interior of the pod. Typically, a slip-ring element includes a sliding contact, in particular brushing means fixed in the slip-ring housing which are configured to transfer electrical power, signal or data to a corresponding slip-ring arranged on the outer surface of the outer rotor by contacting the corresponding slip-ring element. It can also be understood, that the corresponding slip-ring may arranged on the outer shaft of the outer rotor. The air channel arrangement can be, for example, understood as a continuous air channel in which air can flow from the first position to the second position in a closed setting. In particular, the air channel arrangement is typically airtight in between the first position and the second position. In other words, the air channel arrangement is configured to enable air flowing between the first end and the second end of the air channel arrangement without mixing with surrounding air of the contra rotating motor.

[0486] The air fan device, for example, can be arranged near the second position outside of the air channel arrangement. The air fan device may be configured to draw in air from the second position of the air channel arrangement thereby generating the cooling airflow. Furthermore, the air fan device can also be arranged within the air channel arrangement to blow out air towards the second position of the air channel arrangement. In particular, the air fan device can also include one or more air fan elements which are arranged outside and / or inside of the air channel arrangement and are configured to generate the cooling airflow. It can also be understood that, the air fan device is configured to generate a pressure difference between the slip-ring housing and the outer environment of the slip-ring housing by generating the cooling air flow. The term “creating negative pressure within the slip-ring housing” could also be interpreted as creating a vacuum within or inside the slip-ring housing.

[0487] Typically, the outflow filter unit is an air filter configured to filter out dirt particles from the cooling airflow exiting the air channel arrangement. The outflow filter unit can include, for example, a dust filter, a particle filter, a soot filter or similar air filters. Typically, the outflow filter unit is configured to filter the entire cooling air flow before it exits the second position of the air channel. In other words, the outflow filter unit is configured to completely cover the second position of the air channel arrangement. The outflow filter unit may be a replaceable outflow filter unit. A replaceable outflow filter unit can be understood as an outflow filter unit which is detachably arranged at the second position of the air channel arrangement. Furthermore, the outflow filter unit may be freely accessible from the interior of the pod to be replaceable.In some embodiments, the cooling airflow is part of a motor cooling airflow of a motor cooling system before the cooling airflow enters the slip-ring housing. The cooling airflow maybe be merged with the motor cooling airflow before entering the slip-ring housing. It can also be understood, that the cooling airflow is diverted from the motor cooling airflow by entering the slip-ring housing. Thereby no separate cooling airflow upstream of the slip-ring housing is required, which simplifies the operation of the slip-ring cooling system by allowing the use of components that are already provided for the motor cooling airflow. Typically, at least 1%, at least 2%, at least 5% or at least 10% of the motor cooling airflow is entering the slip-ring housing.

[0488] In some embodiments, the cooling airflow is part of a motor cooling system after the cooling airflow exits the second position of the air channel arrangement. The cooling airflow maybe be merged with the motor cooling airflow after exiting the second position of the air channel arrangement, in particular after exiting the outflow filter unit. It can also be understood, that the cooling airflow is merged with the motor cooling airflow downstream of the second position of the air channel arrangement. Thereby no separate cooling airflow downstream of the second position of the air channel arrangement is required, which also simplifies the operation of the slipring cooling system by allowing the use of components, like heat exchangers or further filter means, that are already provided for the motor cooling airflow.

[0489] In some embodiments, the marine propulsion unit further includes an inflow filter unit at the slipring housing for the slip-ring assembly. The inflow filter unit is configured to filter air entering the slip-ring housing. The inflow filter unit maybe integrated in the slip-ring housing. The inflow filter unit may also be arranged at an opening in the slip-ring housing. According to embodiments more than one inflow filters units can be provided. Typically, the inflow filter unit is an air filter configured to filter out dirt particles from a motor cooling airflow entering the slip-ring housing. The inflow filter unit can include, for example, a dust filter, a particle filter, a soot filter or similar air filters. Typically, the inflow filter unit is configured to filter the most of the air entering the slip-ring housing. In other words, the inflow filter unit can be configured to filter at least 85%, at least 90%, at least 95% or at least 99% of the air entering the slip-ring housing. According to embodiments the inflow filter unit can be configured to filter all air entering the slip-ring houses. The inflow filter unit can be a replaceable inflow filter unit. A replaceable inflow filter unit can be understood as an inflow filter unit which is detachably arranged at the slip-ring housing. Furthermore, the inflow filter unit may be freely accessible from the outside and / or the inside of the slip-ring housing in order to be easily replaceable.In some embodiments, the marine propulsion unit includes a set of seals at both ends of the slipring assembly at the slip-ring housing and the outer rotor to seal the slip-ring housing against the outside. In particular, the set of seals are configured to seal the slip-ring housing in an area between the slip-ring housing and an outer surface of the outer rotor. The area between the slip-ring housing and the outer surface of the outer rotor can also be understood as the outer rotor shaft interface. Typically, the set of seals are configured to seal the slip-ring housing in an area between the slipring housing and the outer shaft of the outer rotor. According to embodiments, at least two seals in a row are provided at one corresponding end of the slip-ring assembly. It could also be understood that the set of seals separating the air inside the slip-ring housing from the air outside the slipring housing. The seals can be configured as shaft seals arranged at the slip-ring housing, which are pressed against the outer surface of the outer rotor to enable sealing. In particular, the shaft seals can be pressed against the outer surface of the outer shaft of the outer rotor. The set of seals can prevent the dust generated by the at last one slip-ring element, when the contra rotating motor is in operation, to exit the slip-ring housing. Furthermore, the set of seals are configured to be accessible from inside the slip-ring housing and / or from outside the slip-ring housing within the pod.

[0490] In some embodiments, the set of seals includes at least one lip seal and / or a least one labyrinth seal. Typically, the at least one lip seal can be configured as a soft seal, lip-type seal, strut seals, hydraulic seals or radial shaft seals, for example. Typically, the at least one labyrinth seal can be configured as a smooth-slot labyrinth seal. According to embodiment, the at least one labyrinth seal includes one or more seal chambers. According to embodiments, at least two lip seals in a row are provided at one corresponding end of the slip-ring assembly. According to embodiments, at least one of the two lip seals in a row is arranged in an opposite alignment the other one of the at least two lip seals to further improve the sealing effect. Providing at least one labyrinth seal has the advantage that there is reduced wear in the sealing which improves the sealing effect for the slip-ring housing and reduces the need for replacement.

[0491] In some embodiments, an air barrier is provided by instrumentation air within at least one seal. The instrumentation air may be used to pressurize the at least one seal to create an air barrier inside the at least one seal. The instrumentation air can be, for example, supplied by a compressed air reservoir near the slip-ring housing The instrumentation air can also be fed through a compressed air piping from the vessel to the slip-ring housing. Instrumentation air can include any gaseous substance like, normal air or inert gas like noble gas or gaseous nitrogen. Typically, instrumentation air can be supplied by compressed air which is free from contaminates such as moisture and particulates. Typically, instrumentation air can be understood as filtered air.Providing an air barrier, in particular a pressurized air barrier within at least one seal can further enhance the sealing effect of the at least one seal. According to embodiments, an air barrier can be provided in all seals at the slip-ring housing by instrumentation air.

[0492] In some embodiments, the slip-ring housing includes a top part accommodating the slip-ring arrangement and a bottom part which is connected to the first position of the air channel arrangement. The top part is situated at a higher altitude as the bottom part. In other words, the bottom part of the slip-ring housing is arranged below the outer rotor, wherein the top part is arranged above the outer rotor, in particular above the outer shaft of the outer rotor. The dust or debris generated by the slip-ring assembly tend to fall down in the bottom part of the slip-ring housing by gravity and by the cooling airflow, since the first position of the air channel arrangement is connected to the bottom part of the slip-ring housing. Furthermore, the dust or debris tends also to move downwards, since the cooling airflow flows from the top part to the bottom part of the slip ring housing. According to some embodiments, the bottom part of the slip ring housing can be larger than the top part of the slip ring housing. Typically, the ratio of the top part to the bottom part by volume-% can be at least 40%, or at least, 30%, or at least 20% or lower. The bottom part being larger than the top part can facilitate the cleaning of the dust and debris accumulating inside the bottom part, for example, by a cleaning device and / or by a personal.

[0493] In some embodiments, the bottom part of the slip-ring housing includes dust collecting means. Dust collecting means can include, for example, pockets, collection containers, mesh structures or similar. Providing collecting means at the bottom part of the slip-ring housing can make the cleaning process easier. Furthermore, it might prevent the majority of the dust to enter the air channel arrangement through the first position of the air channel arrangement.

[0494] In some embodiments, the air channel arrangement runs, at least in sections, along the longitudinal axis of the outer rotor, and / or wherein the air channel arrangement runs, at least in sections, around the circumference of the outer rotor. This allows a compact and space saving design for the air channel arrangement in the pod. According to some embodiments, parts of the air channel arrangement can be arranged within the motor cooling system along the longitudinal axis of the outer rotor. According to some embodiments, parts of the air channel arrangement can be arranged within the motor cooling system around the circumference of the outer rotor. Typically, the longitudinal axis can also be regarded as rotation axis of the electrical motor.

[0495] In some embodiments, the air fan device is part of a motor cooling system. It allows to provide just one air fan device to operate both the motor cooling system and the slip-ring cooling system.According to embodiments, the air fan device of the motor cooling system can be arranged near the second position outside of the air channel arrangement. It can also be understood, that the air fan device is configured to propel air of the motor cooling system and of the cooling airflow simultaneously, e. g. by suction.

[0496] In some embodiments, the first position of the air channel arrangement is situated at a lower altitude than the second position of the air channel arrangement. Thus, dust particle rather tends to accumulate near the first position of the air channel arrangement due to gravity. This can also reduce the filter load of the outflow filter unit at the second position which can increase the cleaning intervals and thus ensures more reliable operation of the outflow filter unit. According to embodiments, the vertical distance between the first position and the second position can be at least 2m, or at least 3m, or at least 5m or more than 7m.

[0497] The marine propulsions units described herein, and particularly the azimuthing propulsion units described herein, may be employed in a marine vessel. In particular, the marine vessel may comprise at least one marine propulsion unit according to embodiments described herein. Propelling a marine vessel using a marine propulsion unit according to embodiments described herein may improve maneuverability and efficiency of the marine vessel.

[0498] The method for cooling a slip-ring arrangement in a marine propulsion unit with a contra rotating motor having an inner rotor and an outer rotor is provided. The method includes cooling a slipring assembly within a slip-ring housing by generating a negative pressure in an air channel arrangement which is connected by a first position to the slip-ring housing, wherein a cooling airflow flows from the first position to a second position of the air channel arrangement. The method for cooling a slip-ring arrangement further includes filtering the cooling airflow exiting the second position of the air channel arrangement by an outflow filter unit.

[0499] According to some embodiments, the method for cooling the slip-ring arrangement further includes filtering the cooling airflow which enters the slip-ring housing by an inflow filter.

[0500] Embodiment of the present disclosure provide a marine propulsion unit, particularly azimuthing propulsion unit, with an improved slip-ring cooling system for cooling the slip-ring assembly in the slip-ring housing. In particular, the cooling airflow in the air channel arrangement is able to either cool the slip-ring assembly and to create a negative pressure within the slip-ring housing. This negative pressure ensures that carbon dust generated through friction of the at least one slipring element in operation hardly escape the slip-ring housing. Furthermore, the outflow filter unit arranged at the second position of the air channel arrangement can prevent dust, in particularcarbon dust, from entering the pod, whereby other components in the pod, like the contra rotating motor for example, can be protected from the dust. Additionally, the cleaning and the replacement of the outflow filter unit can be done from inside of the propulsion system without dry docketing the vessel.

[0501] Fig. 5 A schematically illustrates a marine propulsion unit 1000 according to typical embodiments described herein. Similar to embodiment of Fig. 1 the marine propulsion unit 1000 comprises the cooling air unit 16. The cooling air unit 16 is arranged within a hull of a marine vessel. In the typical embodiment shown in Fig. 5 A, the cooling air unit 16 comprises an air fan 17 to circulate air. The cooling air unit 16 typically comprises a heat exchanger 18. By the heat exchanger 18, warm air entering the heat exchanger 18 from the pod 30 is cooled with heat being at least partially transferred to a cooling agent of the heat exchanger 18. The cooling air unit 16 provides cool air to the dual rotor electric motor 1 via a DE ingoing air channel 31 and an NDE ingoing air channel 32 in the pod 30. The DE ingoing air channel 31 is physically separated from an outgoing air channel 33 by an DE air channel separating wall 34 in Fig. 5A. The NDE ingoing air channel 32 is physically separated from the outgoing air channel 33 by an NDE air channel separating wall 35 (not shown) in Fig. 5 A.

[0502] A motor cooling airflow 232 which is indicated by the arrow pointing downwards at an angle, flows from the NDE ingoing air channel 32 into the slip-ring housing 19 via an inflow filter unit 235 as shown in Fig. 5 A. The inflow filter unit 235 is configured to filter the air of the motor cooling airflow 232 to prevent dirt, or dust, like oil particle, entering the slip-ring housing 19. The air of the cooling airflow 232 entering the slip-ring housing 19 is configured to cool the slip-ring assembly 240 arranged inside the slip-ring housing 19. Upstream of the slip-ring housing 19 the motor cooling airflow 232 is merged with a cooling airflow 250 before the cooling airflow 250 enters the slip-ring housing 19 via the inflow filter unit 235. In other words, the motor cooling airflow 232 includes the cooling airflow 250 upstream of the slip-ring housing 19. The cooling airflow 250 absorbs the heat generated by the slip-ring assembly 240 and flows through a bottom part 222 of the slip-ring housing 19. Furthermore, the cooling airflow 250 generates a negative pressure inside the slip-ring housing 19. The cooling airflow 250 exits the slip-ring housing 19, in particular the bottom part 222 of the slip-ring housing 19 at a first position 255 of an air channel arrangement 260.

[0503] The air channel arrangement 260 is separated from the outgoing air channel 33. The air channel arrangement 260 directs the cooling airflow 250 around the dual rotor electric rotor 1, not shownin Fig. 5A. The cooling airflow flows within the air channel arrangement 260 towards a second position 257 of the air channel arrangement 260. At the second position 257 an outflow filter 265 is provided which fully covers the air channel arrangement 260. The cooling airflow 250 which exits the air channel arrangement 260 is filtered by the outflow filter 265 to prevent dust, e. g. carbon dust generated by the slip-ring assembly 240 to enter the pod 30. Typically, the cooling airflow 250 is generated by means of suction which is provided by the air fan 17. According to embodiments, the cooling airflow 250 is merged again, after exiting the outflow filter 265, with the heated motor cooling airflow 232b downstream of the dual rotor electric rotor 1.

[0504] Fig. 5B schematically illustrates a marine propulsion unit with an enlarged view of the slip-ring housing 19. According to embodiments, the slip-ring assembly 240 is accommodated within the slip-ring housing 19. The slip-ring assembly 240 includes 3 slip-ring elements 240a, 240b, 240c. Each slip element 240a, 240b, 240c, includes brushing means 242 which are in contact with a corresponding slip-ring 243 arranged on the outer surface of the outer shaft 47 of the outer rotor 3 for transmitting power to the outer rotor 3. The slip-ring assembly 240 is arranged in a top part 221 of the slip-ring housing 19. Due to abrasion of the brushing means 242 sliding at the slip-rings 243 carbon dust is generated inside the slip ring housing 19. To prevent the carbon dust from escaping the slip-ring housing 19, seals 245 at both end of the slip-ring assembly 240 are provided which seal the air inside the slip-ring housing 19 from the air outside of the slip-ring housing 19. The seals 245 are arranged at the slip-ring housing 19 and are pressed against the outer surface of outer rotor 3 to seal the area between the outer rotor 3 and the slip-ring housing 19. In particular, the seals 245 are pressed against the NDE outer shaft 47 of the outer rotor 3. According to embodiments, the slip-rings 243 can be mounted on a sleeve layer included at the outer surface of the outer shaft 47, wherein the seals 245 are pressed against the sleeve layer of the outer shaft 47 to seal the air within the slip-ring housing 19 from the air outside the slip-ring housing 19.

[0505] Furthermore, the carbon dust is prevented from escaping the slip-ring housing 19, since the slipring housing 19 is provided with negative pressure generated by the cooling airflow 250. The slipring housing 19 includes a bottom part 222 which is arranged below the outer rotor 3. According to embodiments, the bottom part 222 is larger than the top part 221 of the slip-ring housing. Furthermore, due to gravity the carbon dust lower itself down to the bottom part 222 where it can accumulate. Likewise, the carbon dust is carried down to the bottom part 222 by the cooling airflow 250. In particular, larger carbon dust particles tend to remain in the bottom part, wherein lighter carbon dust particles tend to be carried by the cooling airflow 250 out of the bottom part 222 into the air channel arrangement 260. As already described for Fig. 5A, the cooling airflow 250 enters the slip-ring housing 19 by the inflow filter unit 235 and exits the slip-ring housing 19at the first position 255 of the air channel arrangement 260. A first section 260a connected to the first position 255 of the air channel arrangement 260 runs along the longitudinal axis of the outer rotor 3. A second section, not shown, arranged downstream of the first section 260a runs around the circumference of the outer rotor 3.

[0506] In Fig. 5C, the dual rotor electric motor 1 is shown in a cross-sectional view. In Fig. 5C, the cross-sectional view along a plane perpendicular to the rotating axis 50 of Fig. 0A at a central position of the dual rotor electric motor 1 is shown. The dual rotor electric motor 1 is arranged within the pod 30 of the marine propulsion system. Between a wall of the pod 30 and the dual rotor electric motor 1, the second section 260b of the air channel arrangement 260 is provided. The first section 260a of the air channel arrangement 260 running along the longitudinal axis of the out rotor is connected to the second section 260b which runs around the circumference of the outer rotor of the air channel arrangement. In other words, the second section 260b of the air channel arrangement 260 is ring-shaped. Furthermore, the second section of 260b runs within the motor cooling system but is separated from it. In other words, the second section 260b is enclosed on both sides along the longitudinal direction by the motor cooling system. Furthermore, the cooling airflow 250 is not merged with the motor cooling airflow in the first section 260a and the second section 260b of the air channel arrangement 260. The first section 260a is separated from motor cooling system by its outer walls 262a. Furthermore, the second section 260b is separated from the motor cooling system by an annular separating wall 262b.

[0507] The inner rotor 2 of the dual rotor electric motor 1, having a free space 124 between poles of the inner rotor 2 for air passing along the inner rotor 2, is arranged within the outer rotor 3. Between the inner rotor 2 and the outer rotor 3, an air gap 23 is present. The outer rotor 3 comprises an outer rotor winding installed in an outer rotor core. The outer rotor core comprises cooling air slots 125 arranged in a radial direction to allow air to flow from the inner rotor 2 and the outer rotor winding towards the outgoing air channel 33 (not shown) via the perforated tube 4. The perforated tube 4 is connected with the outer rotor 3 via a plurality of axial beams 114. The perforated tube 4 comprises a plurality of radial openings 104. Particularly, the perforated tube 4 comprises a plurality of first openings connected to the at least one ingoing air channel (not shown in Fig. 3) and a plurality of second openings 105 connected to the outgoing air channel 33 (not shown).

[0508] Fig. 5D schematically illustrates the air channel arrangement 260 a long the outer rotor 3 with an enlarged view with respect to Fig. 5C. The first section 260a of the air channel arrangement 260 runs between the pod 30 and the dual electric motor 1. The first section 260a runs along the longitudinal axis of the rotor and is connected with the second section 260b of the air channelarrangement 260. The first section 260a runs perpendicular to the second section 260b. In the perspective of Fig. 5D the outer walls 262a can also be considered as the end portions of the first section 260a where the first section 260a leads into the second section 260b of the air channel arrangement 260. Accordingly, the cooling airflow 250 runs a long the longitudinal axis within the first section 260a and is than deflected in a circumferential direction of the outer rotor within the second section 260b.

[0509] Fig. 5E shows a method 280 for cooling a slip-ring arrangement in a marine propulsion unit with a contra rotating motor having an inner rotor and an outer rotor. The method 280 comprises cooling 282 a slip-ring assembly within a slip-ring housing by generating a negative pressure in an air channel arrangement connected by a first position to the slip-ring housing, wherein a cooling airflow flows from the first position to a second position of the air channel arrangement and filtering 284 the cooling airflow exiting the second position of the air channel arrangement by an outflow filter.

[0510] The marine propulsion unit according to embodiments of the present disclosure may be the azimuthing propulsion unit according to embodiments of the present disclosure.

[0511] Embodiments of the present disclosure provide a marine propulsion unit with a slip-ring cooling system and a contra rotating motor having an inner rotor and an outer rotor, comprising:

[0512] a slip-ring housing;

[0513] a slip-ring assembly arranged within the slip-ring housing;

[0514] wherein the slip-ring assembly comprises at least one slip-ring element being in contact to the outer rotor;

[0515] an air channel arrangement comprising a first position being connected to the slip-ring housing and a second position;

[0516] an air fan device configured to generate a cooling airflow that flows from the first position to the second position of the air channel arrangement creating a negative pressure within the slip-ring housing; and

[0517] an outflow filter unit arranged at the second position of the air channel arrangement for filtering the cooling airflow exiting the air channel arrangement.

[0518] In some embodiments, the cooling airflow is part of a motor cooling airflow of a motor cooling system before the cooling airflow enters the slip-ring housing.In some embodiments, the cooling airflow is part of a motor cooling airflow of a motor cooling system after the cooling airflow exits the second position of the air channel arrangement.

[0519] In some embodiments, the marine propulsion unit further comprises an inflow filter unit at the slip-ring housing of the slip-ring assembly.

[0520] In some embodiments, the marine propulsion unit further comprises a set of seals at both ends of the slip-ring assembly at the slip-ring housing and the outer rotor, to seal the slip ring housing against the outside.

[0521] In some embodiments, the set of seals comprises at least one lip seal and / or at least one labyrinth seal.

[0522] In some embodiments, an air barrier is provided by instrumentation air within at least one seal. In some embodiments, the slip-ring housing comprises a top part accommodating the slip-ring arrangement and a bottom part which is connected to first position of the air channel arrangement. In some embodiments, the bottom part of the slip-ring housing comprises dust collecting means. In some embodiments, the air channel arrangement runs, at least in sections, along the longitudinal axis of the outer rotor, and / or wherein the air channel arrangement runs, at least in sections, around the circumference of the outer rotor.

[0523] In some embodiments, the air fan device is part of a motor cooling system.

[0524] In some embodiments, the first position of the air channel arrangement is situated at a lower altitude than the second position of the air channel arrangement.

[0525] Embodiments of the present disclosure further provide a marine vessel comprising a marine propulsion unit according to the present disclosure.

[0526] Embodiments of the present disclosure further provide a method for cooling a slip-ring arrangement in a marine propulsion unit with a contra rotating motor having an inner rotor and an outer rotor, comprising:

[0527] Cooling a slip-ring assembly within a slip-ring housing by generating a negative pressure in an air channel arrangement connected by a first position to the slip-ring housing, wherein a cooling airflow flows from the first position to a second position of the air channel arrangement; and filtering the cooling airflow exiting the second position of the air channel arrangement by an outflow filter.

[0528] In some embodiments, the method further comprises: filtering the cooling air flow entering the slip-ring housing by an inflow filter.6. COOLING OF A MARINE PROPULSION UNIT

[0529] To propel marine vessels, marine propulsion units with a high efficiency and maneuverability are desired. Azimuthing propulsion units may generally provide marine propulsion units with a high efficiency and maneuverability. In azimuthing propulsion units, at least one marine propeller attached to a rotatable pod provides thrust. A direction of the thrust may be controlled via a rotation of the rotatable pod. In typical azimuthing propulsion units, at least one electric motor driving the at least one marine propeller is integrated in the pod.

[0530] For an efficient marine propulsion unit, contra rotating propellers may be employed. For driving a contra rotating propeller, a contra rotating electric motor can be suitable. However, reliable and efficient cooling systems for the contra rotating motor are required.

[0531] In the view of the foregoing, embodiments of the present disclosure are directed to a marine propulsion unit and a method of cooling a contra rotating motor of a marine propulsion unit.

[0532] According to embodiments of the present disclosure, a marine propulsion unit with a motor air cooling system and a contra rotating motor having an inner rotor and an outer rotor is provided. The contra rotating motor comprises a perforated tube with a plurality of radial openings, the perforated tube being configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor winding. The motor air cooling system comprises at least one ingoing air channel and at least one outgoing air channel. The ingoing air channel is connected to the outgoing air channel via at least some of the plurality of radial openings of the perforated tube.

[0533] According to embodiments of the present disclosure, a marine vessel comprising a marine propulsion unit according to any of the embodiments described herein is provided.

[0534] According to embodiments of the present disclosure, a method of cooling a contra rotating motor with an outer rotor and an inner rotor of a marine propulsion unit is provided. The contra rotating motor comprises a perforated tube configured to transmit a torque of the outer rotor to a propeller unit and configured to support an outer rotor winding. The method comprises providing cooling air to the contra rotating motor and drawing the cooling air from the contra rotating motor via the perforated tube.

[0535] According to some embodiments, the marine propulsion unit is configured to propel a marine vessel. Typically, the marine propulsion unit comprises an azimuthing marine unit. In particular, the marine vessel may comprise at least one marine propulsion unit according to embodiments described herein. The marine vessel as described herein comprises seagoing or inland marinevessels. In particular, the marine vessel comprises ships and boats. In some embodiments, the marine vessel comprises merchant ships, in particular for transporting goods. In particular, the marine vessel may comprise a container vessel, a Ro-Ro or car carrier, a tanker or shuttle tanker, a liquid natural gas (LNG) carrier or a floating storage and regasification unit. In some embodiments, the marine vessel comprises ferries, in particular single- and double-ended ferries, cruise ships, water buses, yachts. In some embodiments, the marine vessel comprises offshore energy vessels, in particular service operation vessels (SOVs), cable laying vessels (CLVs), foundation installation vessels (FIVs), offshore construction (OCVs) and support vessels (OSVs), platform supply vessels (PSVs), and anchor-handling tug supply vessels (AHTS). In some embodiments, the marine vessel comprises research and survey vessels or other special purpose vessels, such as dredgers, heavy lift vessels or towboats. In some embodiments, the marine vessel comprises ice-going marine vessels, in particular icebreakers. In some embodiments, the marine vessel may comprise navy or coast guard vessels.

[0536] In some embodiments, the marine propulsion unit comprises a motor air cooling system, particularly for cooling the contra rotating motor. The motor air cooling system typically comprises at least one ingoing air channel and at least one outgoing air channel. In some embodiments, the motor air cooling system comprises one ingoing air channel or two ingoing air channels. In some embodiments, the number of ingoing air channels may be different from the number of outgoing air channels, and particularly the number of outgoing air channels may exceed the number of ingoing air channels. Typically, an ingoing air channel may be defined as an air channel through which the air of the motor cooling system passes prior to interacting with the motor, in particular prior to cooling the motor. Typically, an outgoing air channel may be defined as an air channel through which the air of the motor cooling system passes subsequent to interacting with the motor, in particular subsequent to cooling the motor. However, in some embodiments, a direction of the air flow may be reversible. Particularly, an air channel may be both an ingoing air channel and an outgoing air channel, depending on an operation of the motor air cooling system.

[0537] Typically, the contra rotating motor comprises a perforated tube. The perforated tube may substantially have a cylinder shape, particularly with a cage-like structure. In some embodiments, the perforated tube may, at least in part, form an outer contour of the contra rotating motor. The perforated tube is configured to transmit a torque of the outer rotor to the propeller unit. The perforated tube supports an outer rotor winding of the outer rotor. Particularly, the outer rotor winding is connected to the perforated tube. In some embodiments, the outer rotor comprises a plurality of axial beams between a core of the outer rotor winding and the perforated tube. Inparticular, the outer rotor may comprise at least 3, at least 6, at least 12, or at least 24 axial beams. Typically, the axial beams are arranged parallel to an axis, particularly the rotating axis, of the perforated tube. Typically, the plurality of axial beams is arranged substantially parallel with respect to each other. The plurality of axial beams is typically configured to transmit a torque from the outer rotor core, which particularly accommodates the windings, to the perforated tube. The plurality of axial beams are configured to allow air to flow from an interior of the motor, particularly via radial slots in a core of the outer rotor winding of the outer rotor, towards the perforated tube, and particularly towards the radial openings in the perforated tube. The core of the outer rotor winding typically is a steel core.

[0538] The perforated tube typically comprises a plurality of radial openings. Exemplarily, the perforated tube may comprise at least 6, at least 12, at least 24, at least 50, at least 72, at least 100, or at least 200 radial openings. Typically, the plurality of radial openings are substantially quadratically with rounded comers. In some embodiments, the plurality of radial openings are substantially oval, and particularly round, or substantially triangular. Oval or triangular openings may advantageously alter the strength of the perorated tube. In some embodiments, the plurality of radial openings is arranged substantially symmetrical, particularly with respect to at least one axis of the perforated tube. In some embodiments, the plurality of radial openings may be arranged according to a pattern, particularly according to a quadratical or a triangular pattern. The plurality of radial openings may be arranged substantially rotational symmetrically about the rotational axis of the perforated tube. Rotational symmetry may particularly comprise a n-fold rotational symmetry with n being any natural number exceeding 1, and particularly exceeding 2. The plurality of radial openings may be arranged substantially mirror symmetrically, particularly with respect to a plane perpendicular to the rotational axis of the perforated tube.

[0539] In typical embodiments, the plurality of radial openings cover at least 10%, at least 20%, at least 25%, at least 35%, at least 50%, at least 70%, or at least 80% of a side surface of the perforated tube. Typically, the plurality of radial openings cover at most 90% of a side surface of the perforated tube. In particular, the plurality of radial openings cover at least 25% and at most 90 % of as side surface of the perforated tube. In some embodiments, the side surface of the perforated tube may comprise the area of the perforated tube in which the radial openings are arranged.

[0540] In typical embodiments, the plurality of openings is equally spaced with respect to each other in at least one dimension and particularly with respect to two dimensions. Exemplarily, the plurality of openings is equally spaced with respect to a radial and / or an axial dimension. In some embodiments, the plurality of openings may be equally spaced in a first direction and may bearranged with a decreasing distance in a second dimension, in particular towards the center of the perforated tube. The plurality of openings may be considered as equally spaced when neighboring openings have the same distance from each other in at least one dimension. A spacing of the plurality of openings may be advantageously adapted to a heat generation distribution of the electric motor and / or to an air flow within the electric motor. Particularly, the spacing of the plurality of openings may be adapted to ensure a substantially homogeneous cooling effect in the electric motor and / or to avoid hot spots.

[0541] The ingoing air channel is connected to the outgoing air channel via the perforated tube. Particularly, the ingoing air channel is connected to the outgoing air channel via at least some of the plurality of radial openings of the perforated tube. Typically, the plurality of radial openings comprises first openings connected to the at least one ingoing air channel and comprises second openings connected to the at least one outgoing air channel. The motor air cooling system is arranged such that at least part of the air from the at least one ingoing air channel enters the contra rotating motor via the first openings and exits the contra rotating motor via the second openings. Typically, the at least one outgoing air channel is connected to at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the plurality of radial openings. In other words, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the plurality of radial openings are second openings. Particularly, air passing through the motor and exiting the motor may exit the perforated tube through at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the plurality of radial openings.

[0542] Typically, the at least one ingoing air channel is connected to at least 2%, at least 5%, at least 10%, at least 20% or at least 40% of the plurality of radial openings. In other words, at least 2%, at least 5%, at least 10%, at least 20% or at least 40% of the plurality of radial openings are first openings. The at least one ingoing air channel is typically connected to at most 50% or at most 60% of the plurality of radial openings. In other words, at most 50% or at most 60% of the plurality of radial openings are first openings. Particularly, air provided by the motor air cooling system and entering the motor may enter the motor via the perforated tube through at least 2%, at least 5% or at least 10%, at least 20% or at least 40% and / or at most 50% or at most 60% of the plurality of radial openings.

[0543] In typical embodiments, each of the plurality of radial openings is connected to either the at least one ingoing air channel or the at least one outgoing air channel. In other words, for each of the plurality of radial openings, cooling air provided by the motor air cooling system either enters theelectric motor via the radial opening or exits the electric motor via the radial opening. Typically, each of the plurality of radial openings either is a first opening or a second opening.

[0544] Typically, the first openings and the second openings are separated by at least one air slot separating wall between the air slots and the perforated tube. The at least one air slot separating wall is configured to ensure that air entering via the first openings passes through the outer rotor, and particularly through the radial air slots in the outer rotor core, prior to exiting the outer rotor via the second openings. The at least one air slot separating wall is substantially perpendicular to the rotation axis of the perforated tube.

[0545] Typically, the motor propulsion unit comprises an outer rotor air sealing for sealing a gap between the outer rotor, which rotates in operation, and a stationary part, exemplarily a motor housing. The outer rotor air sealing may advantageously prevent air passing from the ingoing air channel to the outgoing air channel without passing the outer rotor. Particularly, the outer rotor air sealing may reduce an air fan power required to cool the motor. The outer rotor air sealing typically comprises a small gap, a labyrinth seal or a soft seal.

[0546] Typically, the outer rotor is connected to the outer shaft via at least one outer rotor end flange. The at least one outer rotor end flange typically comprises at least one flange opening. Particularly, the at least one outer rotor end flange comprises a plurality of flange openings, exemplarily at least 3 flange openings, at least 5 flange openings or at least 8 flange openings. Typically, the plurality of flange openings are arranged symmetrically, particularly according to an n-fold rotational symmetry with n being a natural number exceeding 1 or 2. The at least one flange opening typically extends substantially parallel to the rotational axis of the perforated tube. Typically, at least some of the at least one flange opening, particularly all of the at least one flange opening, are connected to the at least one ingoing air channel. Typically, at least part of the air entering the motor enters the motor through the at least one flange opening. Particularly, at least 2%, at least 5%, at least 10% or at least 20% of the air entering the motor enters the motor through the at least one flange opening.

[0547] Typically, the outer rotor is connected on both axial ends to the outer shaft via an outer rotor end flange. Particularly, the outer rotor is connected to the drive end (DE) outer shaft via a DE outer rotor end flange and is connected to the non-drive end (NDE) outer shaft via the NDE outer rotor end flange. In typical embodiments, the NDE outer rotor end flange and the DE outer rotor end flange both comprise at least one flange opening and are both connected to at least one ingoing air channel. Typically, an amount of air flowing into the motor via the at least one flange opening ofthe NDE outer rotor end flange and via the at least one flange opening of the DE outer rotor end flange varies by at most 5%, at most 10% or at most 20%. A similar air flow through the outer rotor end flange on both axial ends of the outer rotor may advantageously enable a homogenous air flow through the motor and a homogenous cooling of the motor.

[0548] In typical embodiments, a majority of the air passing through the at least one ingoing air channel enters the outgoing air channel via the perforated tube. In some embodiments, a part of the air passing thought the at least one ingoing air channel may be configured to cool other elements of the marine propulsion unit, exemplarily a slip ring unit. Typically, the air passing through the at least one ingoing air channel may be divided prior to reaching parts of the marine propulsion unit to be cooled. Exemplarily, the air passing through the at least one ingoing air channel may be divided prior to reaching the motor and the slip ring unit. In some embodiments, different parts of the motor air cooling system may be separated by one or more filters, in particular to reduce or to avoid contamination of different parts of the marine propulsion unit by the air passing through the motor air cooling system. In some embodiments, different parts of the motor air cooling system may be cooled subsequently. In other words, after cooling a first part of the marine propulsion unit, air is used to cool a second part of the marine propulsion unit, particularly prior to reaching an air cooling stage, such as a heat exchanger.

[0549] Typically, at least 80%, at least 90%, at least 95% or at least 99% of air passing through the at least one ingoing air channel enters the at least one outgoing air channel via the perforated tube. Ensuring a high fraction of the air, particularly of the volume of the air, passing through the perforated tube may advantageously allow an efficient cooling of the motor and may reduce a required air fan power.

[0550] In typical embodiments, the motor air cooling system is configured to first guide air along an axial direction of the perforated tube and subsequently in a radial direction of the perforated tube. In particular, air may enter the perforated tube via at least one flange opening and / or via radial openings of the plurality of radial openings adjacent to the outer rotor end flanges and may exit the perforated tube radially via radial openings of the plurality of radial openings, particularly arranged towards the center of the perforated tube.

[0551] Typically, the motor air cooling system is preferably configured such that the temperature of the air remains substantially identical in axial direction. Substantially identical may comprise a temperature difference in axial direction being at most 5%, at most 10% or at most 15% of the lowest temperature of air in the motor. In some embodiments, the motor air cooling system maycomprise at least one temperature sensor, particularly a plurality of temperature sensors. Typically, the motor air cooling system may control an air flow, exemplarily by controlling an air fan setting or an air fan power, based upon at least one temperature signal of the at least one temperature sensor. In some embodiments, the motor air cooling system may comprise deflection or control shields to control an air flow within the motor to provide a substantially identical temperature of the air in axial direction. The flection or control shields may be fixed or controllable.

[0552] The at least one temperature sensor may comprise a physical temperature sensor, exemplarily a thermometer, or a virtual temperature sensor extrapolating a temperature from non-temperature sensor data, exemplarily motor performance data, being provided to a controller, exemplarily an air fan controller.

[0553] Typically, the motor air cooling system is arranged such that air from the ingoing air channel enters the perforated tube at a first axial position of the perforated tube and exits the perforated tube at a second axial position of the perforated tube, with the second axial position being closer to a center of the perforated tube than the first axial position. The center of the perforated tube may particularly be at an axial center, or at a middle axial length of the perforated tube. Particularly, within the perforated tube, air flows substantially axially from the first axial position to the second axial position. The first axial position may be associated with a position of the at least one outer rotor end flange and / or with radial openings of the plurality of radial openings being connected to the at least one ingoing air channel. The second axial position may be associated with radial openings of the plurality of radial openings being connected to the at least one outgoing air channel. The motor air cooling system being configured such that air enters the perforated tube at a first axial position and exits the perforated tube at a second axial position with the second axial position being closer to the center of the perforated tube than the first axial position may advantageously be associated with a balanced temperature distribution in the motor, and / or may advantageously be associated with sealings, bearings or flanges not being heated by the air already having passed though the motor. However, in some embodiments, the motor cooling system may be arranged in reverse, particularly such that the air enters the perforated tube at the second axial position and exits the perforated tube at the first axial position. For some embodiments, a heating of components of the marine propulsion unit may be desired and air exiting the perforated tube may be employed to achieve such a heating effect.

[0554] Typically, the motor air cooling system is configured to guide air along an axial direction of the perforated tube for ensuring an at least substantially equal convective heat transfer along the axial direction of the perforated tube from the inner rotor and / or the outer rotor to the air.Typically, the motor air cooling system is arranged such that air from the at least one ingoing air channel enters the contra rotating motor via the at least one flange opening and exits the contra rotating motor via at least part of the plurality of radial openings, particularly through the second radial openings. In some embodiments, the direction of the air flow may be reversed. Thus, the air may enter the contra rotating motor via at least part of the plurality of radial openings and exits the contra rotating motor via the at least one flange opening.

[0555] Typically, the motor air cooling system is arranged such that a first part of the air entering the motor enters the motor via the at least one flange opening and a second part of the air enters the motor via at least part of the plurality of radial openings, particularly via the first radial openings. In some embodiments, a majority of the air enters the motor via at least part of the plurality of radial openings, particularly via the first radial openings. Exemplarily, at least 60%, at least 70% or at least 80% of the air enters the motor via at least part of the plurality of radial openings, particularly via the first radial openings. In some embodiments, the ratio of the air entering via the at least one flange opening and via at least part of the plurality of radial openings may be variable, and particularly controllable.

[0556] In some embodiments, the marine propulsion unit comprises at least one air channel separating wall. The at least one air channel separating wall may separate the at least one ingoing air channel and the at least one outgoing air channel. Particularly, the at least one air channel separating wall ensures that the air passes through the components to be cooled, in particular through the motor and the perforated tube and / or the slip ring unit. In some embodiments, the at least one air channel separating wall may be configured to separate different streams of the ingoing air. Exemplarily, part of the ingoing air may be separated to cool the motor while another part of the ingoing air is separated to cool the slip ring unit. The at least one air channel separating wall may further avoid leaking of the closed loop air cooling system or contamination of the air within the closed loop air cooling system.

[0557] Typically, the motor air cooling system further comprises an air fan and a heat exchanger. The air fan is typically configured to propel air through the motor air cooling system. Particularly, the air fan may provide cooling air to the contra rotating motor and may draw the cooling air from the contra rotating motor via the perforated tube, particularly after cooling the contra rotating motor. Typically, the air fan is configured to generate an overpressure in the ingoing air channel and a negative pressure in the outgoing air channel.Typically, the heat exchanger may be configured to cool the air of the motor air cooling system, particularly to remove heat received from the components of the marine propulsion unit, exemplarily from the motor. The heat exchanger may comprise a gas-to-liquid heat exchanger. In some embodiments, the air may be cooled using sea water, either directly or indirectly.

[0558] Typically, the air fan and / or the heat exchanger is arranged within a hull-integrated section of the marine propulsion unit, and particularly of the azimuthing propulsion unit. In other words, the air fan and / or the heat exchanger is typically arranged within the main contour of the hull of the marine vessel. Particularly, the air fan and / or the heat exchanger is not integrated in the pod of the azimuthing propulsion unit. In some embodiments, the heat exchanger may be integrated in the pod of the azimuthing propulsion unit with the air fan not being integrated in the pod of the azimuthing propulsion unit.

[0559] Typically, the motor air cooling system is a closed loop air cooling system. Particularly, air within the motor air cooling system is cycled multiple times through the motor air cooling system. In some embodiments, the motor air cooling system is an open air cooling system. In some embodiments, the motor air cooling system may comprise a conditioning system for physical or chemical properties of the air, exemplarily for dehumidifying the air within the motor air cooling system. Typically, the motor air cooling system comprises a filter for filtering the air in the motor air cooling system. The filter may particularly be configured to filter dust or oil residues in the air.

[0560] The marine propulsions units described herein, and particularly the azimuthing propulsion units described herein, may be employed in a marine vessel. In particular, the marine vessel may comprise at least one marine propulsion unit according to embodiments described herein. Propelling a marine vessel using a marine propulsion unit according to embodiments described herein may improve maneuverability and efficiency of the marine vessel.

[0561] Typically, cooling a contra rotating motor with an outer rotor and an inner rotor of a marine propulsion unit, and in particular of an azimuthing marine propulsion unit, with the contra rotating motor comprising a perforated tube configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor winding, comprises providing cooling air to the contra rotating motor and drawing the cooling air from the contra rotating motor via the perforated tube. Providing cooling air to the contra rotating motor and drawing the cooling air from the contra rotating motor typically comprises operating an air fan in a closed loop air cooling system.

[0562] Embodiments of the present disclosure provide marine propulsion units, particularly azimuthing propulsion units, with an improved cooling of the contra rotating motor and an improvedefficiency. In particular, a homogeneous and efficient cooling of the contra rotating motor allows to operate the motor at higher power levels, with smaller motor dimensions and shields further components of the marine propulsion system from heat. In particular, embodiments of the present disclosure ensure an effective cooling of both the inner rotor and the outer rotor.

[0563] In Fig. 6A, the dual rotor electric motor 1 is shown in a cross-sectional view. In Fig. 6A, the cross-sectional view along a plane perpendicular to the rotating axis 50 of Fig. 0A at a central position of the dual rotor electric motor 1 is shown. The dual rotor electric motor 1 is arranged within the pod 30 of the marine propulsion system. Between a wall of the pod 30 and the dual rotor electric motor 1, the annular air channel 14 is present. Through the annular air channel 14, the air exiting the dual rotor electric motor 1, and particularly exiting the outer rotor 3, may pass to the outgoing air channel 33. At the position of the cross-sectional view of Fig. 2, air inside the dual rotor electric motor 1 may exit the dual rotor electric motor 1 towards the outgoing air channel 33. The inner rotor 2 of the dual rotor electric motor 1, having a free space 124 between poles of the inner rotor 2 for air passing along the inner rotor 2, is arranged within the outer rotor 3. Between the inner rotor 2 and the outer rotor 3, an air gap 23 is present. The outer rotor 3 comprises an outer rotor winding installed in an outer rotor core. The outer rotor core comprises cooling air slots 125 arranged in a radial direction to allow air to flow from the inner rotor 2 and the outer rotor winding towards the outgoing air channel 33 via the perforated tube 4. The perforated tube 4 is connected with the outer rotor 3 via a plurality of axial beams 114. The perforated tube 4 comprises a plurality of radial openings 104. Particularly, the perforated tube 4 comprises a plurality of first openings connected to the at least one ingoing air channel (not shown in Fig. 6A) and a plurality of second openings 105 connected to the outgoing air channel 33.

[0564] In some embodiments, particularly at axial positions towards the axial ends of the dual rotor electric motor 1, air may enter the dual rotor electric motor 1 through the radial openings. A cross-sectional view at such a position (not shown in the figures) could resemble the cross-sectional view shown in Fig. 2 with the air flow being inverted. Geometrical relations described for the cross-sectional view of Fig. 2 may thus be applicable to axial positions towards the axial ends of the dual rotor electric motor 1 as well.

[0565] In Fig. 6B, a detail of a marine propulsion unit according to embodiments described herein in a longitudinal cross-section. In Fig. 3, part of the dual rotor electric motor is shown. The inner rotor 2 and the outer rotor 3 rotate about the rotational axis 50, particularly in opposite directions. The inner rotor 2 is connected to the drive end shaft 8. The outer rotor 3 is connected to the perforatedtube 4 via a plurality of axial beams (not shown in Fig. 3). The perforated tube 4 is configured to transmit the torque via the drive end outer rotor end flange 6 to the drive end outer shaft 7. The drive end outer rotor end flange 6 comprises at least one flange opening 106. The at least one flange opening 106 is configured to allow air entering from the at least one ingoing air channel into the dual rotor electric motor. The perforated tube 4 comprises a plurality of first openings 104 connected to the at least one ingoing air channel and a plurality of second openings 105 connected to the outgoing air channel. The outer rotor comprises the outer rotor winding 101 and the outer rotor core 103. The outer rotor core 103 comprises a plurality of cooling air slots 125 arranged in a radial direction to allow air to flow between the outer rotor winding 101 and the perforated tube 4. From the first openings 104, air can flow through the plurality of cooling air slots 125 to the outer rotor winding 101 and the inner rotor 2. An air sealing 131 is arranged between the perforated tube 4 and the outer rotor core 103 to separate the first openings 104 and the second openings 105. Between the static ingoing air channel and outgoing air channel and the rotatable perforated tube 4, an outer rotor air sealing 110 is arranged. The outer rotor air sealing 110 may be connected to the at least one air channel separating wall (not shown in Fig. 3). The outer air sealing 110 comprises a small gap.

[0566] Fig. 6C shows a detail of the marine propulsion system, in particular the dual rotor electric motor 1, in a side view. The inner rotor is connected to the DE inner shaft 8 and the NDE inner shaft 48. The outer rotor is connected to the perforated tube 4. The perforated tube 4 transmits the torque of the outer rotor to the DE outer shaft 7 via the DE outer rotor end flange 6. The perforated tube 4 transmits the torque of the outer rotor to the NDE outer shaft 47 via the DE outer rotor end flange 5. The DE outer rotor end flange 5 comprises a plurality of flange openings 106. The plurality of flange openings 106 are arranged substantially symmetrical around a rotation axis of the perforated tube 4 and / or the dual rotor electric motor 1. The perforated tube 4 comprises a plurality of radial openings. The plurality of radial openings comprises a plurality of first openings 104 and a plurality of second openings 105. In the embodiments of Fig. 4, the plurality of radial openings are substantially quadratically with rounded corners. In the embodiments of Fig. 6C, the plurality of radial openings are arranged in a substantially rectangular, and particularly quadratical, pattern.

[0567] Fig. 6D shows a method 190 of cooling a contra rotating electric motor, or a dual rotor electric motor, with an outer rotor and an inner rotor, of a marine propulsion unit. The method comprises providing 192 cooling air to the contra rotating motor and drawing 194 the cooling air from the contra rotating motor via the perforated tube.The marine propulsion unit according to embodiments of the present disclosure may be the azimuthing propulsion unit according to embodiments of the present disclosure.

[0568] Embodiments of the present disclosure provide a marine propulsion unit (1000) with a motor air cooling system and a contra rotating electric motor (1) having an inner rotor (2) and an outer rotor (3), wherein

[0569] the contra rotating motor comprises a perforated tube (4) with a plurality of radial openings (104, 105), the perforated tube being configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor winding;

[0570] the motor air cooling system comprises at least one ingoing air channel (31, 32) and at least one outgoing air channel (33); and

[0571] the at least one ingoing air channel is connected to the at least one outgoing air channel via at least some of the plurality of radial openings of the perforated tube.

[0572] In some embodiments,

[0573] the propeller unit comprises a contra rotating propeller (9, 10);

[0574] the inner rotor is configured to drive an inner shaft (8, 48) connected to an inner shaft propeller (10) of the contra rotating propeller; and

[0575] the outer rotor is configured to drive an outer shaft (7, 47) connected to an outer shaft propeller (9) of the contra rotating propeller.

[0576] In some embodiments,

[0577] the outer rotor is connected to the outer shaft via at least one outer rotor end flange (5, 6), and

[0578] the at least one outer rotor end flange comprises at least one flange opening (106).

[0579] In some embodiments, the perforated tube comprises at least 50 radial openings.

[0580] In some embodiments

[0581] the plurality of radial openings is arranged substantially symmetrically with respect to the perforated tube; and / orthe plurality of radial openings is equally spaced with respect to each other in at least one dimension.

[0582] In some embodiments, the plurality of radial openings cover at least 20% of a side surface of the perforated tube.

[0583] In some embodiments, the outer rotor comprises a plurality of radial slots (125) in a core (103) of the outer rotor winding (101).

[0584] In some embodiments, the outer rotor comprises a plurality of axial beams (114) between a core of the outer rotor winding and the perforated tube.

[0585] In some embodiments, at least 80% of air passing through the at least one ingoing air channel enters the at least one outgoing air channel via the perforated tube.

[0586] In some embodiments,

[0587] the motor air cooling system is configured to first guide air along an axial direction of the perforated tube and subsequently in a radial direction of the perforated tube, and

[0588] wherein the motor air cooling system is preferably configured such that a temperature of the air remains substantially identical in axial direction.

[0589] In some embodiments, the motor air cooling system is arranged such that air from the at least one ingoing air channel enters the contra rotating motor via the at least one flange opening and exits the contra rotating motor via at least part of the plurality of radial openings.

[0590] In some embodiments,

[0591] the plurality of radial openings comprises first openings (104) connected to the at least one ingoing air channel and comprises second openings (105) connected to the at least one outgoing air channel; and

[0592] the motor air cooling system is arranged such that at least part of the air from the at least one ingoing air channel enters the contra rotating motor via the first openings and exits the contra rotating motor via the second openings.

[0593] In some embodiments,

[0594] the motor air cooling system further comprises an air fan (17) and a heat exchanger (18);the air fan and the heat exchanger are arranged within a hull-integrated section of the marine propulsion unit; and

[0595] the motor air cooling system is a closed loop air cooling system.

[0596] Embodiments of the present disclosure further provide a marine vessel comprising a marine propulsion unit according to embodiments of the present disclosure.

[0597] Embodiments of the present disclosure further provide a method (190) of cooling a contra rotating electric motor with an outer rotor and an inner rotor of a marine propulsion unit, the contra rotating motor comprising a perforated tube configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor w...

Claims

CLAIMS1. An azimuthing propulsion unit comprising a motor and a propeller, in particular a contra rotating motor and a contra rotating propeller driven by the contra rotating motor.

2. The azimuthing propulsion unit of claim 1, comprising:a rotatable drive end (DE) inner shaft (8);a rotatable DE outer shaft (7), wherein the DE inner shaft (8) runs at least partially within the DE outer shaft (7); anda DE inner bearing (12) arranged between the DE outer shaft (7) and the DE inner shaft (8);wherein the DE outer shaft (7) comprises at least one hatch (302).

3. The azimuthing propulsion unit of any of claims from 1 to 2, comprising:a rotatable drive end (DE) shaft (7);a DE outer bearing housing (510);a DE outer bearing (11) arranged between the DE shaft (7) and the DE outer bearing housing (510), wherein the DE outer bearing (11) is configured to be displaced, and wherein the DE outer bearing (11) comprises outer bearing pads (511); anda DE outer distal seal, wherein the DE outer distal seal is configured to be accessed from within the azimuthing propulsion unit;wherein the azimuthing propulsion unit is a contra rotating propeller (CRP) azimuthing propulsion unit and wherein the DE shaft is a DE outer shaft of the azimuthing propulsion unit, the azimuthing propulsion unit (1000) further comprising a rotatable DE inner shaft (8), which runs at least partially within the DE outer shaft (7).

4. The azimuthing propulsion unit of any of claims from 1 to 3, comprising a rotatable DE inner shaft (8) and a rotatable outer shaft (7), wherein the inner shaft (8) runs at least partially within the outer shaft (7) and wherein the outer shaft (7) runs at least partially within a sealing housing (801) of a pod (30),and further comprising a sealing unit, the sealing unit comprising:a plurality of chamber systems, wherein each chamber system comprises an inner shaft seal chamber (817a, 817b, 817c), an outer shaft seal chamber (827a, 827b, 827c) and a passage throughthe outer shaft fluidly connecting the inner shaft seal chamber (817a, 817b, 817c) and the outer shaft seal chamber (827a, 827b, 827c);an inner shaft sealing (810) between the inner shaft (8) and the outer shaft (7), wherein the inner shaft sealing (810) seals the inner shaft seal chambers (817a, 817b, 817c) of the plurality of chamber systems; andan outer shaft sealing (820) between the outer shaft (7) and the sealing housing (801), wherein the outer shaft sealing (820) seals the outer shaft seal chambers (827a, 827b, 827c) of the plurality of chamber systems.

5. The azimuthing propulsion unit of any of claims from 1 to 4 comprising a rotatable inner shaft (48) and a rotatable outer shaft (47), wherein the inner shaft (48) runs at least partially within the outer shaft (47),and further comprising a bearing unit, the bearing unit comprising:a bearing arrangement (401) comprising at least one axial bearing (402-404) for the inner shaft (48) and the outer shaft (47), wherein the bearing arrangement is configured for supporting at least a part of the inner shaft (48) and the outer shaft (47); and,a bearing housing (407) for housing the bearing arrangement (401) and the part (471; 481) of the inner shaft (48) and the outer shaft (47) to be supported by the bearing arrangement (401);wherein the bearing arrangement (401) is configured for allowing a transfer of axial forces between the outer shaft (47) and the inner shaft (48).

6. The azimuthing propulsion unit of claim 5, wherein the bearing housing (407) has at least one hatch (411; 412) for maintenance, repair and replacement of the bearing arrangement (401) or parts of the bearing arrangement, and wherein the azimuthing propulsion unit (1000) is configured for allowing access of a person to the at least one hatch (411; 412).

7. The azimuthing propulsion unit of any of claims from 1 to 6, with a slip-ring cooling system and a contra rotating motor having an inner rotor and an outer rotor, further comprising:a slip-ring housing;a slip-ring assembly arranged within the slip-ring housing;wherein the slip-ring assembly comprises at least one slip-ring element being in contact to the outer rotor;an air channel arrangement comprising a first position being connected to the slip-ring housing and a second position;an air fan device configured to generate a cooling airflow that flows from the first position to the second position of the air channel arrangement creating a negative pressure within the slip-ring housing; andan outflow filter unit arranged at the second position of the air channel arrangement for filtering the cooling airflow exiting the air channel arrangement;and wherein the cooling airflow is part of a motor cooling airflow of a motor cooling system before the cooling airflow enters the slip-ring housing.

8. The azimuthing propulsion unit of claim 7, whereinthe cooling airflow is part of a motor cooling airflow of a motor cooling system after the cooling airflow exits the second position of the air channel arrangement.

9. The azimuthing propulsion unit of any of claims from 1 to 8 (1000) with a motor air cooling system and a contra rotating electric motor (1) having an inner rotor (2) and an outer rotor (3), whereinthe contra rotating motor comprises a perforated tube (4) with a plurality of radial openings (104, 105), the perforated tube being configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor winding;the motor air cooling system comprises at least one ingoing air channel (31, 32) and at least one outgoing air channel (33); andthe at least one ingoing air channel is connected to the at least one outgoing air channel via at least some of the plurality of radial openings of the perforated tube;wherein at least 80% of air passing through the at least one ingoing air channel enters the at least one outgoing air channel via the perforated tube.

10. The azimuthing propulsion unit of any of claims from 1 to 9, comprising a dual rotor electric motor (1), the dual rotor electric motor (1) comprising an outer rotor (3) and an inner rotor (2) arranged coaxially within the outer rotor (3); the azimuthing propulsion unit (1000) further comprising:a rotatable inner shaft (48) coupled to the inner rotor (2); anda rotatable outer shaft (47) coupled to the outer rotor (3), wherein the inner shaft (48) runs at least partially within the outer shaft (47);and wherein the inner shaft (48) comprises a distal inner segment (620) and a proximal inner segment (610).

11. A method for operating and / or maintaining and / or mounting and / or servicing an azimuthing propulsion unit, in particular the azimuthing propulsion unit of any of claims from 1 to 10, the method comprising in particular maintaining the azimuting propulsion unit and / or mounting the azimuthing propulsion unit.

12. The method of claim 11, comprisingcomprising:opening a hatch of a drive end (DE) outer shaft of the azimuthing propulsion unit (352); andaccessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft (354).

13. The method of any of claims from 11 to 12, further comprising:accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit (552);accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing (554);displacing the DE outer bearing; andaccessing a DE outer distal seal (556) from within the pod hull.

14. The method of any of claims from 11 to 13, further comprising:providing an outer shaft (47) with a hollow cross section; andproviding an inner shaft (48); wherein the inner shaft (48) comprises a distal inner segment (620) and a proximal inner segment (610), wherein the method further comprises:inserting at least one of or both of the distal inner segment (620) and the proximal inner segment (610) into the outer shaft (47); andcoupling the distal inner segment (620) to the proximal inner segment (610).

15. A marine vessel comprising an azimuthing propulsion unit according of any of claims from 1 to 10.

16. An azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprising:a rotatable drive end (DE) inner shaft (8);a rotatable DE outer shaft (7), wherein the DE inner shaft (8) runs at least partially within the DE outer shaft (7); anda DE inner bearing (12) arranged between the DE outer shaft (7) and the DE inner shaft (8);wherein the DE outer shaft (7) comprises at least one hatch (302).

17. The azimuthing propulsion unit (1000), wherein the hatch (302) is configured to provide an access to the DE inner bearing (12).

18. The azimuthing propulsion unit (1000) of claim 17, wherein the hatch (302) is configured to be accessed by a user from within the azimuthing propulsion unit (1000).

19. The azimuthing propulsion unit (1000) of any of claims 16 to 18, wherein the DE inner bearing (12) comprises at least one inner bearing pad (312).

20. The azimuthing propulsion unit (1000) of any of claims 16 to 19, further comprising a DE inner distal seal (304), wherein the DE inner distal seal (304) is arranged between the DE inner shaft (8) and the DE outer shaft (7), and wherein the DE inner distal seal (304) is arranged towards a drive end.

21. The azimuthing propulsion unit (1000) of any of claims 16 to 20, further comprising a DE inner proximal seal (306), wherein the DE inner proximal seal (306) is arranged between the DE inner shaft (8) and the DE outer shaft (7), and wherein the DE inner proximal seal (306) is arranged towards a non-drive end.

22. The azimuthing propulsion unit (1000) of any of claims 16 to 21, further comprising a pod (30), wherein the pod (30) comprises a pod hull (300).

23. The azimuthing propulsion unit (1000) of any of claims 16 to 22, further comprising a DE outer bearing (11), wherein the DE outer bearing (11) preferably comprises at least one outer bearing pad.

24. The azimuthing propulsion unit (1000) of claim 23, wherein the DE inner bearing (12) and the DE outer bearing (11) are arranged coaxially to a rotation axis (50), wherein the DE outer bearing (11) is at least partially overlapping the DE inner bearing (12).

25. A method (350) of maintaining an azimuthing propulsion unit, particularly the azimuthing propulsion unit according to any of claims 16 to 24; the method comprising:opening a hatch of a drive end (DE) outer shaft of the azimuthing propulsion unit (352); andaccessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft (354).

26. The method of claim 25, comprising, after accessing the DE inner bearing through the hatch: displacing the DE inner bearing (356).

27. The method of claim 26, comprising, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch; anddisplacing the DE inner distal seal (358).

28. The method of any of claims 25 to 27, comprising, accessing a DE inner proximal seal arranged between the DE outer shaft and a DE inner shaft; anddisplacing the DE inner proximal seal (359).

29. The method of any of claims 25 to 28, wherein displacing any of: the DE inner bearing, the DE inner distal seal, the DE inner proximal seal, or any combination thereof, comprises axially displacing along the DE inner shaft.

30. The method of any of claims 25 to 29, further comprising displacing any of: a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof31. An azimuthing propulsion unit (1000) for a vessel, the azimuthing propulsion unit (1000) comprising:a rotatable drive end (DE) shaft (7);a DE outer bearing housing (510);a DE outer bearing (11) arranged between the DE shaft (7) and the DE outer bearing housing (510), wherein the DE outer bearing (11) is configured to be displaced, and wherein the DE outer bearing (11) comprises outer bearing pads (511); and a DE outer distal seal, wherein the DE outer distal seal is configured to be accessed from within the azimuthing propulsion unit.

32. The azimuthing propulsion unit (1000) of claim 31, wherein the azimuthing propulsion unit is a contra rotating propeller (CRP) azimuthing propulsion unit and wherein the DE shaft is a DE outer shaft of the azimuthing propulsion unit, the azimuthing propulsion unit (1000) further comprising a rotatable DE inner shaft (8), which runs at least partially within the DE outer shaft (7).

33. The azimuthing propulsion unit (1000) of claim 31 or 32, wherein the outer bearing pads are configured to be displaced axially and / or the DE outer distal seal is configured to be displaced axially.

34. The azimuthing propulsion unit (1000) of any of the claims from 31 to 33, wherein the DE outer distal seal (504) is arranged between the DE shaft (7) and the DE outer bearing housing (510).

35. The azimuthing propulsion unit (1000) of any of the claims from 31 to 34, further comprising a DE outer proximal seal (506), wherein the DE outer proximal seal (506) is arranged between the DE shaft (7) and the DE outer bearing housing (510).

36. The azimuthing propulsion unit (1000) of any of the claims from 31 to 35, wherein the DE outer bearing (11), the DE outer distal seal (504), and / or the DE outer proximal seal (506) is replacable from within a pod hull (300) of a pod (30) of the azimuthing propulsion unit (1000).

37. The azimuthing propulsion unit (1000) of any of the claims 32 to 36, wherein the DE outer shaft (7) comprises a hatch (302), which is configured to provide an access to a space between the DE outer shaft (7) and the DE inner shaft (8).

38. The azimuthing propulsion unit (1000) of claim 37, wherein the hatch (302) is configured to provide an access to a DE inner bearing (12) being arranged between the DE inner shaft (8) and the DE outer shaft (7); preferably wherein the DE inner bearing (12) comprises inner bearing pads (312) being configured to be accessed through the hatch (302).

39. The azimuthing propulsion unit (1000) of claim 38, wherein the DE inner bearing (12) and the DE outer bearing (11) are arranged coaxially on a rotation axis (50), wherein the DE outer bearing (11) is at least partially overlapping the DE inner bearing (12).

40. A method (550) of maintaining an azimuthing propulsion unit, particularly the azimuthing propulsion unit according to any of claims from 31 to 39; the method comprising: accessing a DE shaft from an interior of a pod hull of a pod of the azimuthing propulsion unit (552);accessing a DE outer bearing arranged between the DE shaft and a DE outer bearing housing (554);displacing the DE outer bearing; andaccessing a DE outer distal seal (556) from within the pod hull.

41. The method (550) of claim 40, further comprising releasing and displacing a DE outer proximal seal prior to accessing the DE outer bearing (558).

42. The method (550) of any of claims 40 or 41, further comprising, displacing the DE outer bearing after accessing the DE outer bearing, and / or displacing the DE outer distal seal after accessing the DE outer distal seal (559).

43. The method (550) of any of claims 40 to 42, wherein displacing any of: the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises axially displacing along the DE shaft and / or radially displacing from the DE shaft.

44. The method (550) of claim 43, wherein axially displacing the DE outer bearing, the DE outer distal seal, the DE outer proximal seal, or any combination thereof, comprises, axially displacing the DE outer bearing, the DE outer distal seal, or the DE outer proximal seal to a service position.

45. The method (550) of any of claims 40 to 44, wherein the DE shaft of the azimuthing propulsion unit is a DE outer shaft of a contra rotating propeller (CRP) azimuthing propulsion unit, the CRP azimuthing propulsion unit further comprising:a hatch in the DE outer shaft; a rotatable DE inner shaft, which runs at least partially within the DE outer shaft; a DE inner bearing arranged between the DE inner shaft and the DE outer shaft; a DE inner proximal seal arranged proximally between the DE inner shaft and the DE outer shaft; and / or a DE inner distal seal arranged distally between the DE inner shaft and the DE outer shaft; the method further comprising:displacing any of: the DE inner proximal seal, the DE inner bearing, the DE inner distal seal, or any combination thereof, through the hatch (560).

46. A sealing unit for an azimuthing propulsion unit (1000), the propulsion unit (1000) comprising a rotatable inner shaft (8) and a rotatable outer shaft (7), wherein the inner shaft (8) runs at least partially within the outer shaft (7) and wherein the outer shaft (7) runs at least partially within a sealing housing (801) of a pod (30),the sealing unit comprising:- a plurality of chamber systems, wherein each chamber system comprises an inner shaft seal chamber (817a, 817b, 817c), an outer shaft seal chamber (827a, 827b, 827c) and a passage through the outer shaft fluidly connecting the inner shaft seal chamber (817a, 817b, 817c) and the outer shaft seal chamber (827a, 827b, 827c);- an inner shaft sealing (810) between the inner shaft (8) and the outer shaft (7), wherein the inner shaft sealing (810) seals the inner shaft seal chambers (817a, 817b, 817c) of the plurality of chamber systems; and- an outer shaft sealing (820) between the outer shaft (7) and the sealing housing (801), wherein the outer shaft sealing (820) seals the outer shaft seal chambers (827a, 827b, 827c) of the plurality of chamber systems.

47. A sealing unit according to claim 46, wherein the inner shaft sealing (810) seals an inside of the outer shaft (7) from an outside of the pod (30); and / or wherein the outer shaft sealing (820) seals an inside of the pod (30) from the outside of the pod (30).

48. A sealing unit according to any of claim from 46 to 47,- wherein the inner shaft sealing (810) comprises an inner composure (811), an outer composure (813) and a plurality of inner sealing elements (815); and / or- wherein the outer shaft sealing (820) comprises an inner composure (821), an outer composure (823) and a plurality of outer sealing elements (825).

49. A sealing unit according to any of claim from 46 to 48, wherein at least one passage through the outer shaft (7) comprises an inner groove (835a, 835b, 835c), and wherein the inner groove (835a, 835b, 835c) typically is in at least one of: the inside of the outer shaft (7); and / or the inner shaft sealing (810).

50. A sealing unit according to any claim of claims from 46 to 49, wherein at least one passage through the outer shaft (7) comprises an outer groove (833a, 833b, 833c), and wherein the outer groove (833a, 833b, 833c) typically is in at least one of: the outside of the outer shaft (7); and / or the outer shaft sealing (820).

51. A sealing unit according to any of claims from 46 to 50, wherein at least one passage through the outer shaft (7) comprises a plurality of channels (831a, 83 lb, 831c) through the outer shaft (7) fluidly connecting the inner shaft seal chamber (817a, 817b, 817c) and the outer shaft seal chamber (827a, 827b, 827c).

52. A sealing unit according to any of claims from 46 to 51, wherein the plurality of chamber systems comprises:- a proximate chamber system, wherein the proximate chamber system is fluidly connected to an oil reservoir;- a distant chamber system; and- an intermediate chamber system, wherein the intermediate chamber system is fluidly connected to an air reservoir.

53. A sealing unit according to any of claims from 46 to 52, wherein each chamber system of the plurality of chamber systems contains at least one of:- oil;- air; and / or- leakage fluid.

54. A sealing unit according to any of claims from 46 to 53, wherein each fluid connection of a chamber system of the plurality of chamber systems to a reservoir comprises:- a supply groove (843) in at least one of: the sealing housing (801); and the outer shaft sealing (820).

55. A sealing unit according to any of claims from 46 to 54, wherein each fluid connection of a chamber system of the plurality of chamber systems to a reservoir comprises:- at least one supply channels (841) fluidly connecting the chamber system and the reservoir.

56. A sealing unit according to any of claims from 46 to 55, the propulsion unit (1000) further comprising:- an inner bearing (12) inside an inner bearing chamber (851) between the inner shaft (8) and the outer shaft (7); and- an outer bearing (11) inside an outer bearing (853) chamber between the outer shaft (7) and a bearing housing (803);the sealing unit further comprising:- an inner bearing sealing (855), wherein the inner bearing sealing (855) seals the inside of the pod (30) from the inner bearing chamber (851);- an outer bearing sealing (857), wherein the outer bearing sealing (857) seals the inside of the pod (30) from the outer bearing chamber (853).

57. A sealing unit according to claim 56, wherein the inner bearing chamber (851) and theouter bearing chamber (853) are fluidly connected.

58. A sealing unit according to any of the two previous claims,- wherein the inner shaft sealing (810) seals the outside of the pod (30) from the inner bearing chamber (851); and / or- wherein the outer shaft sealing (820) seals the outside of the pod (30) from the outer bearing chamber (853).

59. A method for servicing a sealing unit, typically for servicing a sealing unit according to any of claims 1 to 13, in an azimuthing propulsion unit (1000), the propulsion unit (1000) comprising a rotatable inner shaft (8) and a rotatable outer shaft (7), wherein the inner shaft (8) runs at least partially within the outer shaft (7) and wherein the outer shaft (7) runs at least partially within a sealing housing (801) of a pod (30), the method comprising:- providing (891) a service sealing arrangement, wherein the service sealing arrangement seals the inner shaft sealing (810) from the outside of the pod (30);- dismounting (892), at least partially, through a hatch (860) provided in the outer shaft (7), an inner bearing (12) between the inner shaft (8) and the outer shaft (7);- dismounting (893), at least partially, the inner shaft sealing (810) through the hatch (860); - servicing (894) the inner shaft sealing (810);- mounting (895) the serviced inner shaft sealing (810) through the hatch (860); and - mounting (896) the inner bearing (12) through the hatch (860).

60. A method according to the previous claim, wherein the service sealing arrangement seals the outer shaft sealing (820) from the outside of the pod (30);the method further comprising:- dismounting, at least partially, an outer bearing (11) between the outer shaft (7) and a bearing housing (803);- dismounting, at least partially, the outer shaft sealing (820);- servicing the outer shaft sealing (820);- mounting the serviced outer shaft sealing (820); and- mounting the outer bearing (11).

61. Bearing unit (40) for an azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprising a rotatable inner shaft (48) and a rotatable outer shaft (47), wherein the inner shaft (48) runs at least partially within the outer shaft (47),the bearing unit (40) comprising:A bearing arrangement (401) comprising at least one axial bearing (402-404) for the inner shaft (48) and the outer shaft (47), wherein the bearing arrangement is configured for supporting at least a part of the inner shaft (48) and the outer shaft (47); and,A bearing housing (407) for housing the bearing arrangement (401) and the part (471; 481) of the inner shaft (48) and the outer shaft (47) to be supported by the bearing arrangement (401);wherein the bearing arrangement (401) is configured for allowing a transfer of axial forces between the outer shaft (47) and the inner shaft (48).

62. The bearing unit according to claim 61, wherein the bearing arrangement (401) comprises a first axial bearing (403) between the inner shaft (48) and the outer shaft (47) for allowing the transfer of axial forces between the inner shaft (48) and the outer shaft (47).

63. The bearing unit according to any of claims from 61 to 62, wherein the bearing arrangement (401) comprises the first axial bearing (403) between the inner shaft (48) and the outer shaft (48), a second axial bearing (402) arranged between a bearing housing wall (408) and the inner shaft (48), and a third axial bearing (404) arranged between a bearing housing wall (409) and the outer shaft (47).

64. The bearing unit according to any of claims from 61 to 63, wherein the bearing housing (407) comprises at least one hatch (411; 412) for reaching into the inside of the bearing housing (407).

65. The bearing unit according to claim 64, wherein the at least one hatch (411; 412) is configured for allowing access to one of the axial bearings (402; 403; 404), maintenance of the axial bearings (402; 403; 404) and / or replacement of the axial bearings (402; 403; 404) of the bearing arrangement (401) for the inner shaft (48) and the outer shaft (47).

66. The bearing unit according to any of claims from 61 to 65, wherein at least one of the axial bearings (402; 403; 404) of the bearing arrangement is a pad bearing.

67. The bearing unit according to any of claims from 61 to 66 in an azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprising a dual electric motor (1), the inner shaft (48) and the outer shaft (47), at least one of the inner shaft (48) and the outer shaft (47) being driven by the dual electric motor (1), a propeller unit comprising an outer shaft propeller (9) and an inner shaft propeller (10), wherein the inner shaft propeller (10) is driven by the inner shaft (48) and the outer shaft propeller (9) is connected to the outer shaft (47), and wherein the drive chain of the azimuthing propulsion unit (1000) comprises a driven end (DE), which is the end, where the propeller unit is arranged, and a non-driven end (NDE) on the end of the drive chain opposite to the propeller unit.

68. The bearing unit according to claim 67, wherein the bearing unit (401) is arranged at the NDE side of the drive chain of the azimuthing propulsion unit (1000).

69. Azimuthing propulsion unit (1000) comprising a bearing unit (40) according to any of claims 61 to 66.

70. Azimuthing propulsion unit according to claim 69, wherein the bearing housing (407) has at least one hatch (411; 412) for maintenance, repair and replacement of the bearing arrangement (401) or parts of the bearing arrangement, and wherein the azimuthing propulsion unit (1000) is configured for allowing access of a person to the at least one hatch (411; 412).

71. Method (420) of supporting an inner shaft (48) and an outer shaft (47) in an azimuthing propulsion unit (1000), the azimuthing propulsion unit (1000) comprising the inner shaft (48) and the outer shaft (47), wherein the inner shaft (48) runs at least partially within the outer shaft (47), the method comprising:o Providing (421) a bearing arrangement (401) and a bearing housing (407) for housing the bearing arrangement, the bearing arrangement comprising at least one axial bearing (402; 403; 404) for the inner shaft (48) and the outer shaft (47); and, o Arranging (422) the axial bearing (402; 403; 404) of the bearing arrangement (401) for allowing a transfer of axial forces between the outer shaft (47) and the inner shaft (48).

72. The method according to claim 71, wherein arranging (422) the axial bearings (402; 403; 404) for a transfer of axial forces between the outer shaft (47) and the inner shaft (48) comprises arranging a first axial bearing (403) between the inner shaft (48) and the outer shaft (47).

73. The method according to claim 72, wherein arranging the first axial bearing (403) between the inner shaft (48) and the outer shaft (47) comprises utilizing a bearing pad mounted between the inner shaft (48) and the outer shaft (47).

74. The method according to any of claims 71 to 73, wherein the bearing housing (407) comprises at least one hatch (411; 412) and wherein the method further comprises: accessing the bearing arrangement (401) within the bearing housing (407) through the at least one hatch (411; 412); and, in particular, performing repair, maintenance, and / or replacement of the bearing arrangement (401) through the at least one hatch (411; 412).

75. The method according to any of claims 71 to 74, wherein providing the bearing unit (40) comprises mounting the bearing unit (40) in an azimuthing propulsion unit (1000), especially in an azimuthing propulsion (1000) unit according to any of claims 9 and 10.

76. A marine propulsion unit with a slip-ring cooling system and a contra rotating motor having an inner rotor and an outer rotor, comprising:a slip-ring housing;a slip-ring assembly arranged within the slip-ring housing;wherein the slip-ring assembly comprises at least one slip-ring element being in contact to the outer rotor;an air channel arrangement comprising a first position being connected to the slip-ring housing and a second position;an air fan device configured to generate a cooling airflow that flows from the first position to the second position of the air channel arrangement creating a negative pressure within the slip-ring housing; andan outflow filter unit arranged at the second position of the air channel arrangement for filtering the cooling airflow exiting the air channel arrangement.

77. The marine propulsion unit according to claim 76, wherein the cooling airflow is part of a motor cooling airflow of a motor cooling system before the cooling airflow enters the slip-ring housing.

78. The marine propulsion unit according to claim 76 or 77, whereinthe cooling airflow is part of a motor cooling airflow of a motor cooling system after the cooling airflow exits the second position of the air channel arrangement.

79. The marine propulsion unit according any of claim 76 to 78, further comprising an inflow filter unit at the slip-ring housing of the slip-ring assembly.

80. The marine propulsion unit according to any of claim 76 to 79, further comprising a set of seals at both ends of the slip-ring assembly at the slip-ring housing and the outer rotor, to seal the slip ring housing against the outside.

81. The marine propulsion unit according to claim 80, whereinthe set of seals comprises at least one lip seal and / or at least one labyrinth seal.

82. The marine propulsion unit according to any of claims 80 to 81, whereinan air barrier is provided by instrumentation air within at least one seal.

83. The marine propulsion unit according to any of claims 76 to 82, whereinthe slip-ring housing comprises a top part accommodating the slip-ring arrangement and a bottom part which is connected to first position of the air channel arrangement.

84. The marine propulsion unit according to claim 83, whereinthe bottom part of the slip-ring housing comprises dust collecting means.

85. The marine propulsion unit according to any of claims 76 to 84, whereinthe air channel arrangement runs, at least in sections, along the longitudinal axis of the outer rotor, and / or wherein the air channel arrangement runs, at least in sections, around the circumference of the outer rotor.

86. The marine propulsion unit according to any of claims 76 to 85,wherein the air fan device is part of a motor cooling system.

87. The marine propulsion unit according to any of claims 76 to 86, whereinthe first position of the air channel arrangement is situated at a lower altitude than the second position of the air channel arrangement.

88. A marine vessel comprising a marine propulsion unit according to any of claims from 76 to 87.

89. A method for cooling a slip-ring arrangement in a marine propulsion unit with a contra rotating motor having an inner rotor and an outer rotor, comprising:Cooling a slip-ring assembly within a slip-ring housing by generating a negative pressure in an air channel arrangement connected by a first position to the slip-ring housing, wherein a cooling airflow flows from the first position to a second position of the air channel arrangement; and filtering the cooling airflow exiting the second position of the air channel arrangement by an outflow filter.

90. The method for cooling a slip-ring arrangement according to claim 89, further comprising:Filtering the cooling air flow entering the slip-ring housing by an inflow filter.

91. A marine propulsion unit (1000) with a motor air cooling system and a contra rotating electric motor (1) having an inner rotor (2) and an outer rotor (3), whereinthe contra rotating motor comprises a perforated tube (4) with a plurality of radial openings (104, 105), the perforated tube being configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor winding;the motor air cooling system comprises at least one ingoing air channel (31, 32) and at least one outgoing air channel (33); andthe at least one ingoing air channel is connected to the at least one outgoing air channel via at least some of the plurality of radial openings of the perforated tube.

92. The marine propulsion unit of claim 91, whereinthe propeller unit comprises a contra rotating propeller (9, 10);the inner rotor is configured to drive an inner shaft (8, 48) connected to an inner shaft propeller (10) of the contra rotating propeller; andthe outer rotor is configured to drive an outer shaft (7, 47) connected to an outer shaft propeller (9) of the contra rotating propeller.

93. The marine propulsion unit of any of the claims from 91 to 92, whereinthe outer rotor is connected to the outer shaft via at least one outer rotor end flange (5, 6), andthe at least one outer rotor end flange comprises at least one flange opening (106).

94. The marine propulsion unit of any of claims from 91 to 93, wherein the perforated tube comprises at least 50 radial openings.

95. The marine propulsion unit of any of the claims from 91 to 94, whereinthe plurality of radial openings is arranged substantially symmetrically with respect to the perforated tube; and / orthe plurality of radial openings is equally spaced with respect to each other in at least one dimension.

96. The marine propulsion unit of any of claims from 91 to 95, wherein the plurality of radial openings cover at least 20% of a side surface of the perforated tube.

97. The marine propulsion unit of any of claims from 91 to 96, wherein the outer rotor comprises a plurality of radial slots (125) in a core (103) of the outer rotor winding (101).

98. The marine propulsion unit of any of claims from 91 to 97, wherein the outer rotor comprises a plurality of axial beams (114) between a core of the outer rotor winding and the perforated tube.

99. The marine propulsion unit of any of claims from 91 to 98, wherein at least 80% of air passing through the at least one ingoing air channel enters the at least one outgoing air channel via the perforated tube.

100. The marine propulsion unit of any of claims from 91 to 99, whereinthe motor air cooling system is configured to first guide air along an axial direction of the perforated tube and subsequently in a radial direction of the perforated tube, andwherein the motor air cooling system is preferably configured such that a temperature of the air remains substantially identical in axial direction.

101. The marine propulsion unit of any of claims from 91 to 100, wherein the motor air cooling system is arranged such that air from the at least one ingoing air channel enters the contra rotating motor via the at least one flange opening and exits the contra rotating motor via at least part of the plurality of radial openings.

102. The marine propulsion unit of any of claims from 91 to 101, whereinthe plurality of radial openings comprises first openings (104) connected to the at least one ingoing air channel and comprises second openings (105) connected to the at least one outgoing air channel; andthe motor air cooling system is arranged such that at least part of the air from the at least one ingoing air channel enters the contra rotating motor via the first openings and exits the contra rotating motor via the second openings.

103. The marine propulsion unit of any of claims from 91 to 102, whereinthe motor air cooling system further comprises an air fan (17) and a heat exchanger (18); the air fan and the heat exchanger are arranged within a hull-integrated section of the marine propulsion unit; andthe motor air cooling system is a closed loop air cooling system.

104. A marine vessel comprising a marine propulsion unit according to any of claims from 91 to 103.

105. A method (190) of cooling a contra rotating electric motor with an outer rotor and an inner rotor of a marine propulsion unit, the contra rotating motor comprising a perforated tube configured to transmit a torque of the outer rotor to a propeller unit and to support an outer rotor winding, the method comprising:providing (192) cooling air to the contra rotating motor; anddrawing (194) the cooling air from the contra rotating motor via the perforated tube.

106. An azimuthing propulsion unit (1000) comprising a dual rotor electric motor (1), the dual rotor electric motor (1) comprising an outer rotor (3) and an inner rotor (2) arranged coaxially within the outer rotor (3); the azimuthing propulsion unit (1000) further comprising:a rotatable inner shaft (48) coupled to the inner rotor (2); anda rotatable outer shaft (47) coupled to the outer rotor (3), wherein the inner shaft (48) runs at least partially within the outer shaft (47);and wherein the inner shaft (48) comprises a distal inner segment (620) and a proximal inner segment (610).

107. An azimuthing propulsion unit (1000) according to claim 106, wherein the outer shaft (47) comprises a distal outer segment (640) and a proximal outer segment (630).

108. An azimuthing propulsion unit (1000) according to any of claim from 106 to 107, wherein at least one of the inner shaft (48) and outer shaft (47) comprises a dismountable flange, wherein the dismountable flange forms a segment of the respective shaft.

109. An azimuthing propulsion unit (1000) according to any of claims from 106 to 108, wherein the distal inner segment (620) and the proximal inner segment (610) are releasably joint together.

110. An azimuthing propulsion unit (1000) according to any of claims from 106 to 109, wherein the proximal inner segment (610) comprises a proximal inner flange (612).

111. An azimuthing propulsion unit (1000) according to any of claims from 106 to 110, wherein the distal inner segment (620) comprises a distal inner flange (622).

112. An azimuthing propulsion unit (1000) according to claim 107 to 111, whereinthe proximal outer segment (630) comprises a proximal outer flange (5); and the distal outer segment (640) comprises a distal outer flange (642).

113. An azimuthing propulsion unit (1000) according to claim 112, whereinthe proximal outer flange (5) is coupled to the outer rotor (3); andthe proximal inner flange (612) is coupled to the inner rotor (2).

114. An azimuthing propulsion unit (1000) according to any of claims from 106 to 113, wherein the inner shaft (48) comprises a section with a hollow cross section (679).

115. An azimuthing propulsion unit (1000) according to any of claims from 106 to 114, wherein at least one integral ring shaped component (699) is mounted onto a surface of the outer shaft and is located in between the proximal outer flange (5) and the distal outer flange (642).

116. An azimuthing propulsion unit (1000) according to any of claims from 106 to 115, comprising an enclosed volume (660), which is defined as the volume in between the inner shaft (48) and the outer shaft (47) and a bearing housing (665); and wherein the enclosed volume (660) is sealed.

117. A method for mounting an azimuthing propulsion unit (1000), preferably an azimuthing propulsion unit (1000) according to any of the claims 106 - 116, comprising:providing an outer shaft (47) with a hollow cross section; andproviding an inner shaft (48); wherein the inner shaft (48) comprises a distal inner segment (620) and a proximal inner segment (610), wherein the method further comprises:inserting at least one of or both of the distal inner segment (620) and the proximal inner segment (610) into the outer shaft (47); andcoupling the distal inner segment (620) to the proximal inner segment (610).

118. A method according to claim 117, wherein providing the outer shaft (47) comprises providing a distal outer segment (640) and a proximal outer segment (630); and wherein the method further comprises:coupling the distal outer segment (640) to the proximal outer segment (630) to form the outer shaft (47), before coupling the distal inner segment (620) to the proximal inner segment (610).

119. A method according to claim 118, wherein the method further comprises:mounting an integral ring shaped component (699) onto the outer shaft (47), before coupling the distal outer segment (640) to the proximal outer segment (630).

120. A method according to any of the claims 118 to 119 further comprising:coupling the proximal inner segment (610) to an inner rotor (2) of a dual rotor electric motor (1) using an inner rotor connection (681); andcoupling the proximal outer segment (630) to an outer rotor (3) of the dual rotor electric motor (1) using an outer rotor connection (683).

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