Marine propulsion unit

Abstract

According to an embodiment, a marine propulsion unit is described. The marine 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.

Description

MARINE PROPULSION UNITTECHNICAL FIELD

[0001] Embodiments of the present invention relate to a marine propulsion unit. Further embodiments relate to a method of maintaining a marine propulsion unit.BACKGROUND

[0002] Marine propulsion units provide an efficient way to propel marine vessels. Different concepts for marine propulsion units are available, which typically prioritise specific operating properties of the marine propulsion system. In particular, azimuthing propulsion units provide an efficient manner to propel marine vessels. 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. In some marine vessels, a shaft-line configuration of propulsion units may be preferred. In particular, the thrust may be provided by a motor arranged within the hull of the marine vessel and a propeller connected to the motor via a shaft-line.

[0003] Maintaining marine propulsion units, particularly azimuthing propulsion units, commonly requires dry-docking, which is a time-consuming process. Thus, dry-docking a marine vessel to maintain the marine 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, marine propulsion units, particularly azimuthing propulsion units, that provide a high efficiency, durability and maintainability, in particular in view of the restricted amount of space available within a hull of the marine propulsion unit or the pod, are desired. Marine propulsion units, such as azimuthing propulsion units, with reduced maintenance efforts are desired.DISCLOSURE OF THE INVENTION

[0004] In the view of the foregoing, the present invention is directed to a marine propulsion unit and a method of maintaining a marine propulsion unit. The marine propulsion unit is preferably an azimuthing propulsion unit.

[0005] According to an aspect of the present invention, marine propulsion unit is provided. The marine 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. The marine propulsion unit further comprises a DE inner bearing arranged between the DE outer shaft and the DE inner shaft. The DE outer shaft of the marine propulsion unit comprises a hatch.

[0006] According to another aspect, the marine propulsion unit according to any of the embodiments described herein is an azimuthing propulsion unit.

[0007] According to another aspect of the present invention, a method of maintaining of a marine 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 marine propulsion unit; and accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft.

[0008] According to some embodiments, the marine propulsion unit, preferably the azimuthing propulsion unit, is configured to propel a marine vessel. 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 marine vessels. 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-handlingtug 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 or marine vessels having an ice-class by a classification society. In some embodiments, the marine vessel may comprise navy or coast guard vessels. In some embodiments, the marine vessel may comprise submarine vessels or unmanned remotely operated underwater vehicles (ROVs).

[0009] The marine vessel typically comprises a hull. In some embodiments, the hull of the marine vessel comprises a hull of the marine propulsion unit. In some embodiments, the hull of the marine propulsion unit is a pod. In some embodiments, the pod of the marine propulsion unit, and particularly 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 of the marine vessel defines a vessel interior and a vessel exterior. Space confined by the hull and configured to be isolated from sea water may be defined as the vessel interior. Space outside the hull, and in particular the sea, may be defined as the vessel exterior. Typically, the vessel interior is substantially free of sea water and substantially dry.

[0010] In some embodiments, the marine vessel may comprise a plurality of marine propulsion units, such as azimuthing propulsion units. In particular, the marine vessel may comprise 2, 3, 4, or more marine propulsion units. Typically, each of the plurality of marine propulsion units may be controlled separately. In some embodiments, the marine vessel may comprise a single marine propulsion unit, particularly a single azimuthing propulsion unit, and more particularly with a single pod. In some embodiments, at least one marine propulsion unit, such as the azimuthing propulsion unit, may be combined with one or more further marine propulsion unit on a single marine vessel. Where two or more marine propulsion units are present, the marine propulsion units may be the same or different marine propulsion units. For example, the marine vessel can have two azimuthing propulsion units, two shaft-line marine propulsion units, or one azimuthing propulsion unit and one shaft-line marine propulsion unit.

[0011] Typically, the pod of the marine propulsion unit, particularly the azimuthing propulsion unit, comprises a pod hull. The pod may be configured to be rotatably attachedto the hull of the marine vessel, particularly at the bottom of the hull of the marine vessel. The pod may be rotated about a substantially vertical rotation axis of the azimuthing propulsion unit. In particular, the pod may 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. In other embodiments, the pod of the marine propulsion unit is fixed to the hull of the marine vessel.

[0012] Typically, the hull of the marine propulsion unit or the pod comprises a hull cap at a first end of the hull of the marine propulsion unit or pod and a propeller unit, in particular a pushing or pulling propeller unit, attached to a second end of the hull of the marine propulsion unit or pod. The first end of the hull of the marine propulsion unit or pod may also be described as a non-driving end (NDE), and the second end of the hull of the marine propulsion unit or pod may also be described as a driving end (DE), of the hull of the marine propulsion unit or pod. The propeller unit typically rotates about a rotation axis of the propeller unit. The rotation axis of the propeller unit may be substantially perpendicular to the vertical rotation axis of the azimuthing propulsion unit.

[0013] In some embodiments, the marine propulsion unit comprises at least one shaft-line marine propulsion unit. Typically, in the shaft-line marine propulsion unit, the electric motor, particularly the contra-rotating electric motor, is arranged within the hull of the marine vessel. The electric motor may be connected to the propeller unit via a shaft-line. The propeller unit is typically arranged at a stem of the marine vessel. Particularly, the propeller unit is typically arranged at a skeg of the marine vessel. Typically, for a shaft-line marine propulsion unit, a stem-facing side of the marine propulsion unit may be described as a driving end, DE, side of the marine propulsion unit. Typically, for a shaft-line marine propulsion unit, a vessel-center facing side of the marine propulsion unit may be described as non-driving end, NDE, side of the marine propulsion unit.

[0014] 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 may also bedescribed as front propeller and the inner shaft propeller may be described as the rear propeller; and vice versa for a pulling propeller unit. In particular, for the azimuthing propulsion unit, 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.

[0015] Typically, the propeller unit comprises a contra rotating propeller unit. In particular, the outer shaft propeller may be configured to rotate in a first direction, particularly about the rotation axis of the propeller unit, and the inner shaft propeller may 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 may rotate clockwise and the inner shaft propeller may rotate counterclockwise, or vice versa, about the same rotation axis. In some embodiments, the outer shaft propeller and the inner shaft propeller of the contra rotating propeller unit are arranged adjacent to each other. In some embodiments, the outer shaft propeller and the inner shaft propeller of the contra rotating propeller unit are arranged at opposite ends of the hull of the marine propulsion unit or of a pod in which the marine propulsion unit is arranged. In other words, the contra rotating propeller unit may be arranged in a push-pull-configuration. A contra rotating propeller unit may advantageously allow for a higher hydrodynamic efficiency than other propeller concepts, in particular with respect to single propellers.

[0016] 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 may be different from the first number. The outer shaft propeller may comprise 3, 4, 5, 6, or 8 first blades. The inner shaft propeller may 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 may comprise the same number of blades, in particular3, 4, 5, 6, or 8 first and second blades, respectively. The outer shaft propeller and / or the inner shaft propeller may each be manufactured as a monoblock or in components, as a built-up propeller.

[0017] 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 or within the hull of the marine vessel, particularly the hull of the marine propulsion unit. Particularly, the electric motor is mechanically connected to the propeller gearlessly and / or without a clutch. 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 may be identical to the drive shaft of the propeller unit or may 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 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 may be driven by the same electric motor.

[0018] 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 may 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 may be a permanent magnet rotor or an externally excited synchronous rotor.

[0019] In some embodiments, the drive shaft of the propeller 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. In some embodiments, the outer shaft and / or the inner shaft may comprise at least one shaft coupling. In particular, the outer shaft and / or the inner shaft comprising at least one shaft coupling advantageously allows to modularly adapt the marine propulsion unit to the marine vessel. Exemplarily, a length of the shaft may beadapted dependent on a size of the marine vessel. 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.

[0020] Typically, the inner shaft is supported by a drive end, DE, inner bearing and a nondrive end, NDE, inner bearing. Typically, the outer shaft is supported by a drive end, DE, outer bearing and a non-drive end, NDE, outer bearing. For a push-pull-configuration, no non-drive end is present. Thus, in the push-pull-configuration a first bearing may be considered as a drive end bearing and a second bearing may be considered as non-drive end bearing. In other words, the terms non-drive end and drive end merely act to distinguish bearings by their bearing location. The NDE inner bearing and / or the NDE outer bearing may each comprise an axial bearing and a radial bearing, particularly within the same bearing housing. Employing a contra rotating electric motor may advantageously allow to drive the contra rotating propeller with a single electric motor gearlessly. Thereby, a more compact and efficient drive train may be provided.

[0021] In some embodiments, the marine propulsion unit, and particularly the contrarotating motor, the drive shaft and the propeller unit, may form a single propulsion unit. Exemplarily, the single propulsion unit may be mounted into the pod or into the vessel interior as a single propulsion unit. In some embodiments, the drive shaft, the contra-rotating motor, the DE bearing and the NDE bearing, and a slip ring unit may be arranged within a frame structure, in other words arranged within a capsule structure. The capsule structure may advantageously allow to mount at least part of the marine propulsion unit as a single unit into the pod or the vessel interior. The capsule structure may advantageously reduce an assembly effort and / or assembly time during the building process of the marine vessel. Typically, the marine propulsion unit is connected to the vessel hull via the capsule structure. In some embodiments, the marine propulsion unit is connected to the pod via the capsule structure. Particularly, the capsule structure is configured to transmit at least 75% or at least 90% of a propulsion force of the marine propulsion unit to the marine vessel.

[0022] In some embodiments, the marine 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.

[0023] The marine propulsion unit described herein may permit the marine 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.

[0024] According to some embodiments, the at least one hatch may be, for example, configured to provide access to the DE inner bearing. According to some embodiments, the at least one hatch may be, for example, configured to be accessed by a user from within the marine propulsion unit. In order for the hatch to provide sufficient access to the DE inner bearing, the hatch may be of a defined shape and size. For example, the hatch may 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 may 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 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.

[0025] The DE outer shaft may comprise, for example, two hatches, three hatches, four hatches, five hatches, etc. The marine propulsion unit comprising two or more hatches may comprise two or more of the same hatch, two or more different hatches, or a combination thereof. For example, wherein the marine propulsion unit comprises four hatches, each of the four hatches may 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 may prevent fluid, such as lubricating oil, from exiting a contained volume.

[0026] The at least one hatch may be configured to permit the user to access the DE inner shaft from within the marine propulsion unit. The hatch may be configured to permit the user to access a region between the DE inner shaft and the DE outer shaft. For example, the usermay access the DE inner bearing from within the marine propulsion unit through the at least one hatch. The at least one hatch may 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 may be opened through a push-to-unlock mechanism. For example, the at least one hatch may be opened by removing at least one fixing mechanism, such as a screw. The at least one hatch may be reused. For example, the at least one hatch may 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.

[0027] The at least one hatch may permit for maintenance to be done on the DE inner shaft and / or the DE outer shaft from within the marine propulsion unit. The maintenance may include checking, preparing, removing, replacing, adding, or any combination thereof of the components in the drive end of the marine propulsion unit.

[0028] 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 comprises an inner bearing pad and / or an inner roller bearing. The DE inner bearing and / or the inner bearing pads may 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 may be arranged around the DE inner shaft, and in particular around an entire circumference of the DE inner shaft. The inner bearing pads may be configured to be displaced along the DE inner shaft. The inner bearing pads may be slide bearing pads. The inner bearing pads may be configured to be slid along the DE inner shaft.

[0029] Typically, the DE inner bearing and / or inner bearing pads may be displaced proximally, and in particular, proximally towards the at least one hatch. The DE inner bearing and / or inner bearing pads may be displaced continuously or in intervals. The DE inner bearing and / or inner bearing pads may 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 may be displaced axially by a distance determined by the user, for example,0.3 m. The DE inner bearing and / or inner bearing pads may be displaced according to the maintenance procedure taking place.

[0030] According to some embodiments described herein, the marine propulsion unit may further comprise a DE inner distal seal. The DE inner distal seal may be arranged between the DE inner shaft and the DE outer shaft. The DE inner distal seal may be arranged towards a drive end, and in particular the drive and of the marine propulsion unit. The DE inner distal seal may comprise at least one water seal and / or at least one lubricant seal. For example, the DE inner distal seal may prevent water from entering into the marine propulsion unit and / or may prevent lubricant, for example oil, from exiting the marine propulsion unit. The DE inner distal seal may prolong the lifespan of the marine propulsion unit and / or may prevent on environment from being contaminated.

[0031] Typically, the DE inner distal seal may be displaced proximally, and in particular, proximally towards the at least one hatch. The DE inner distal seal may be displaced continuously or in intervals. The DE inner distal seal may be displaced axially by a predetermined distance, for example, in line with the at least one hatch. The DE inner distal seal may be displaced axially by a distance determined by the user, for example, 0.3 m. The DE inner distal seal may be displaced according to the maintenance procedure taking place.

[0032] According to some embodiments described herein, the marine propulsion unit may further comprise a DE inner proximal seal. The DE inner proximal seal may be arranged between the DE inner shaft and the DE outer shaft. The DE inner proximal seal may be arranged towards the NDE. In typical embodiments, the DE inner proximal seal may be arranged distally to the at least one hatch. The DE inner proximal seal may 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 may comprise at least one oil seal. For example, the DE inner proximal seal may prevent lubricant from leaving at least one desired region.

[0033] Typically, the DE inner proximal seal may be displaced distally, and in particular, distally towards the at least one hatch. The DE inner proximal seal may be displaced continuously or in intervals. The DE inner proximal seal may be displaced by a predetermined distance, for example, in line with the at least one hatch. The DE inner proximal seal may be displaced by a distance determined by the user, for example, 0.3 m.The DE inner proximal seal may be displaced according to the maintenance procedure taking place.

[0034] Typically, the DE inner distal seal and / or the DE inner proximal seal may comprise two or more seals. The DE inner distal seal and / or the DE inner proximal seal may be attached to at least the DE inner shaft. For example, the DE inner distal seal and / or the DE inner proximal seal may be attached to the DE inner shaft and the DE outer shaft.

[0035] According to some embodiments described herein, the marine propulsion unit may further comprise a hull of the marine propulsion unit or a pod, wherein the pod comprises a pod hull. The hull of the marine propulsion unit or the pod may 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 marine propulsion unit. This may 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 marine propulsion unit and over the marine vessel to be dry-docked. This may for example, reduce time required for maintenance and / or permit for an increase in maintenance opportunities available. For example, the marine vessel may 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 may be maintained during this time at the port. For example, the user may enter the marine propulsion unit through a vessel interior of the marine vessel, and may proceed to accessing any of the aforementioned components.

[0036] According to some embodiments described herein the marine propulsion unit may further comprise a DE outer bearing. In some embodiments, the DE outer bearing may 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 may 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 anypredefined number of bearing pads. The outer bearing pads may be arranged around the DE outer shaft, and in particular around an entire circumference of the DE outer shaft. The outer bearing pads may be configured to be displaced along the DE outer shaft. The outer bearing pads may be slid. The outer bearing pads may be configured to be slid along the DE outer shaft. The DE outer bearing and / or outer bearing pads may be displaced radially from the DE outer shaft. In typical embodiments, the DE outer bearing and / or outer bearing pads may be slid and / or displaced radially.

[0037] The DE inner bearing and the DE outer bearing may be coupled. For example, the DE inner bearing and the DE outer bearing may be fluidly coupled. For example, the DE inner bearing may comprise a DE inner bearing chamber and the DE outer bearing may comprise a DE outer bearing chamber. In particular, the DE inner bearing chamber and the DE outer bearing chamber may 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 may be through the DE outer shaft. Typically, the at least one bore is radially through the DE outer shaft. The fluid coupling may comprise a lubricant, such as grease and / or oil. The DE inner bearing and the DE outer bearing may be arranged coaxially to the rotation axis. The DE outer bearing may at least partially overlap the DE inner bearing. For example, the DE outer bearing and / or the outer bearing pads may be displaced proximally. In particular, the DE outer bearing and / or the outer bearing pads may be displaced axially. The DE outer bearing and / or the outer bearing pads may be displaced axially and proximally along the DE outer shaft. The outer bearing pads may comprise slide bearing pads.

[0038] The DE inner bearing and / or the inner bearing pads and / or the DE outer bearing and / or the outer bearing pads may be configured to be individually displaced and / or changed. The DE inner bearing may 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 may be rotated along the DE inner shaft, the DE outer shaft, or both. The DE outer bearing may 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 DEouter bearing may be rotated along the DE outer shaft, the DE outer bearing housing, or both.

[0039] The marine propulsion unit described herein may enable inner bearing and seal change in a contra rotating propeller. For example, the marine propulsion unit described herein may enable maintenance without removing at least one propeller and / or driving conditions.

[0040] According to some embodiments described herein, a method of maintaining a marine propulsion unit is provided, particularly the marine propulsion unit described herein. In typical embodiments, the method of maintaining the marine propulsion unit comprises maintaining an azimuthing propulsion unit. The method of maintaining the marine propulsion unit described herein comprises opening a hatch of a DE outer shaft of the marine 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 marine propulsion unit may be performed within the marine propulsion unit described herein. In particular, the method of maintaining the marine propulsion unit may be performed without requiring for the marine propulsion unit and / or a marine vessel to be dry-docked.

[0041] According to some embodiments described herein, the method of maintaining the marine propulsion unit may further comprise, after accessing the DE inner bearing to the hatch, displacing the DE inner bearing. The method may comprise releasing the DE inner bearing. In particular, releasing the DE inner bearing may occur prior to displacing the DE inner bearing. For example, the DE inner bearing may be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner bearing may 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.

[0042] Typically, displacing the DE inner bearing may comprise removing the DE inner bearing through the hatch. For example, removing the DE inner bearing may 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 maycomprise 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 marine propulsion unit typically comprises servicing the DE inner bearing. For example, servicing the DE inner bearing may comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner bearing may 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 may 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.

[0043] Typically, displacing the DE inner bearing may 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 may comprise displacing the DE inner bearing within a region between the DE inner shaft and the DE outer shaft.

[0044] Typically, the method of maintaining the marine propulsion unit may 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.

[0045] According to some embodiments described herein, the method of maintaining the marine propulsion unit may 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 may 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 may comprise releasing the DE inner distal seal. In particular, releasing the DE inner distal seal may occur prior to displacing the DE inner distal seal. For example, the DE inner distal seal may be securedbetween the DE inner shaft and the DE outer shaft. Releasing of the DE inner distal seal may enable the displacing of the DE inner distal seal.

[0046] Typically, displacing the DE inner distal seal may comprise removing the DE inner distal seal through the hatch. For example, removing the DE inner distal seal may 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 may 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 marine propulsion unit typically comprises servicing the DE inner distal seal. For example, servicing the DE inner distal seal may comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner distal seal may 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 may 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.

[0047] Typically, displacing the DE inner distal seal may 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 may comprise displacing the DE inner distal seal within a region between the DE inner shaft and the DE outer shaft.

[0048] Typically, the method of maintaining the marine propulsion unit may 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.

[0049] According to some embodiments described herein, the method of maintaining the marine propulsion unit may further comprise accessing a DE inner proximal seal through the hatch, and displacing the DE inner proximal seal. The method may comprise releasing the DE inner proximal seal. In particular, releasing the DE inner proximal seal may occur priorto displacing the DE inner proximal seal. For example, the DE inner proximal seal may be secured between the DE inner shaft and the DE outer shaft. Releasing of the DE inner proximal seal may enable the displacing of the DE inner proximal seal.

[0050] Typically, displacing the DE inner proximal seal may comprise removing the DE inner proximal seal through the hatch. For example, removing the DE inner proximal seal may 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 may 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 marine propulsion unit typically comprises servicing the DE inner proximal seal. For example, servicing the DE inner proximal seal may comprise: repairing, replacing, installing, removing, or any combination thereof. In particular, servicing the DE inner proximal seal may 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 may 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.

[0051] Typically, displacing the DE inner proximal seal may 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 may comprise displacing the DE inner proximal seal within a region between the DE inner shaft and the DE outer shaft.

[0052] Typically, the method of maintaining the marine propulsion unit may 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.

[0053] According to some embodiments described herein, the method of maintaining the marine propulsion unit, displacing any of the DE inner bearing, the DE inner distal seal, theDE inner proximal seal, or any combination thereof, may 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, may 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, may 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.

[0054] According to some embodiments described herein, the method of maintaining the marine propulsion unit, comprises an marine 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, may 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 marine 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 may 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 may 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 may 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 distalseal, 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.

[0055] The method of maintaining the marine propulsion unit may comprise servicing the DE inner proximal seal and / or the DE inner distal seal. The method of maintaining the marine propulsion unit may 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 may 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.

[0056] Typically, the DE inner distal seal and / or the DE inner proximal seal comprise sealing elements. Sealing elements may 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.

[0057] 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 may comprise housing rings. The seal housing is typically configured to hold the sealing elements. Typically, servicing comprises cutting the seal rings.

[0058] In typical embodiments, the method comprises proximally and / or distally displacing the seal housing. The method typically comprises proximally and / or distallydisplacing 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 reassembling the seal housing. In typical embodiments, the method comprises assembling the housing rings.

[0059] Typically, the DE inner shaft and / or the DE outer shaft may be supported. Supporting the DE inner shaft and / or the DE outer shaft may provide more room to manipulate the remaining components in the marine propulsion unit.

[0060] Typically, a user may perform the method of maintaining the marine propulsion unit described herein. For example, the user may open the hatch and may access the DE inner bearing, the DE inner distal seal, and / or the DE inner proximal seal. The user may 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 may reach into the region accessible through the at least one hatch, and may displace any of the aforementioned components and / or subsidies thereof. The user may 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 theirlabour and / or tools. For example, the user may 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.

[0061] For example, the user may access the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal. The user may further perform the displacing of the DE outer bearing, the DE outer distal seal, and / or the DE outer proximal seal. The user may 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 may 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.

[0062] Embodiments of the present invention provide marine propulsion units, in particular marine 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 hull of the marine vessel to allow a seal change whilst the vessel is in a swimming condition.BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings relate to embodiments of the disclosure and are described in the following:Fig. la schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. lb schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. 1c schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. Id schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. le schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. If schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. 1g schematically illustrates a marine propulsion unit according to the embodiments described herein;Fig. 2 schematically illustrates a cross-section of an isometric view of a marine propulsion unit according to the embodiments described herein;Fig. 3 illustrates a flow chart of a method of maintaining a marine propulsion unit according to the embodiments described herein;Fig. 4 illustrates a flow chart of a method of maintaining a marine propulsion unit according to the embodiments described herein;Fig. 5 illustrates a flow chart of a method of maintaining a marine propulsion unit according to the embodiments described herein;Fig. 6 illustrates a flow chart of a method of maintaining a marine propulsion unit according to the embodiments described herein; andFig. 7 illustrates a flow chart of a method of maintaining a marine propulsion unit according to the embodiments described herein.DETAILED DESCRIPTION OF EMBODIMENTS

[0064] 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 ofexplanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment may 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 may 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 may be distorted. Further, some elements may be depicted with enlarged dimensions while other elements in the same figure are depicted, relatively, with reduced dimensions.

[0065] Fig. la through Fig. Id schematically illustrate a marine propulsion unit, particularly an azimuthing propulsion unit 1000, according to typical embodiments described herein. In Fig. le through Fig. 1g, a marine propulsion unit, particularly a shaftline marine propulsion unit 2000, is schematically illustrated.

[0066] The azimuthing propulsion unit 1000 of Fig. la comprises a dual rotor electric motor 1. The dual rotor electric motor 1 may 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 hull of the marine propulsion unit or a pod 30 of the azimuthing propulsion unit 1000.

[0067] 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. la, the outer shaft propeller 9 and the inner shaft propeller 10 substantially have the same diameter. In embodiments not shown in Fig. la the outer shaft propeller 9 may have a diameter different from the diameter of the inner shaft propeller 10. Exemplarily, the outershaft propeller 9 may have a diameter of at least 6 m, exemplarily of 6.1 m, and the inner shaft propeller 10 may have a diameter of at most 6 m, exemplarily of 5.575 m.

[0068] 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. la. 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, may 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.

[0069] 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. la. 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 the inner shaft propeller 10. The inner shaft propeller 10 comprises a plurality of second blades 22, of which two are visible in Fig. la. In the embodiment of Fig. la, 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.

[0070] The NDE inner shaft 48 is supported in the hull of the marine propulsion unit or the pod 30 by an NDE inner bearing 42. The NDE outer shaft 47 is supported in the hull of the marine propulsion unit or 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 hull of the marine propulsion unit or 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 bearing12. The DE outer bearing 11 and the DE inner bearing 12 typically comprise an oil and a water seal, respectively. The oil seal may prevent oil from exiting the hull of the marine propulsion unit or the pod 30. The water seal may prevent water from entering the hull of the marine propulsion unit or the pod 30.

[0071] 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. la. 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 hull of the marine propulsion unit or 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 hull of the marine propulsion unit or the pod 30.

[0072] Inside the hull of the marine propulsion unit or the pod 30 of the marine propulsion unit, particularly the azimuthing propulsion unit 1000, air is circulated. The marine propulsion unit, particularly the azimuthing propulsion unit 1000, comprises a cooling air unit 16. In the embodiment of Fig. la, the cooling air unit 16 is arranged within a hull of a marine vessel. In the typical embodiment shown in Fig. la, 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 hull of the marine propulsion unit or 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 hull of the marine propulsion unit or the pod 30. The DE ingoing air channel 31 is physically separated from an outgoing air channel 33 by an DE air channelseparating wall 34 in Fig. la. 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. la. Typically, the outgoing air channel 33 substantially extends in the center of the hull of the marine propulsion unit or the pod 30 and in particular along a vertical central axis of the hull of the marine propulsion unit or 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 may be heated by the dual rotor electric motor 1, in particular when in operation. The air may 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.

[0073] In Fig. lb, 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. In Fig. 1c, a side view of the azimuthing propulsion unit 1000 of the embodiment of Fig. lb is schematically shown.

[0074] In Fig. Id, the azimuthing propulsion unit 1000 is arranged in a push-pull-configuration. In particular, in Fig. Id, the outer shaft propeller 9 and the inner shaft propeller 10 are arranged at opposite ends of the hull of the marine propulsion unit or the pod 30. The outer shaft propeller 9 acts as a pushing propeller and the inner shaft propeller 10 acts as a pulling propeller. In embodiments not shown in the figures, the inner shaft propeller may act as the pushing propeller and the outer shaft propeller may act as the pulling propeller.

[0075] In Fig. le and Fig. If, a marine propulsion unit 2000 is schematically illustrated. The marine propulsion unit 2000 is arranged within the hull 2100 of the marine vessel. Particularly, the marine propulsion unit 2000 is arranged in a shaft-line configuration with the dual rotor electric motor 1 being arranged within the hull 2100 of the marine vessel. Similar to the azimuthing propulsion unit 1000, as shown in Fig. la - 1c, the marine propulsion unit 2000 comprises the dual rotor electric motor 1, a drive shaft connecting the dual rotor electric motor 1 to the propeller unit with the outer shaft propeller 9 and the inner shaft propeller 10. The outer shaft propeller 9 and the inner shaft propeller 10 are arranged at a skeg of the hull 2100 of the vessel. Generally, the drive shaft, the dual rotor electricmotor 1, the outer shaft propeller 9 and the inner shaft propeller 10, the DE and NDE bearings 41, 42 and the slip ring unit 19 of the marine propulsion unit 2000 may be arranged similar or substantially identical to the azimuthing propulsion unit as shown in Fig. la - 1c.

[0076] In Fig. le, the marine propulsion unit 2000 comprises a motor block 2050. Within the motor block 2050, the drive shaft, the dual rotor electric motor 1, the DE and NDE bearings 41, 42 and the slip ring unit 19 of the marine propulsion unit 2000 are arranged. The motor block 2050 comprises an outgoing air channel 33 and, typically, a DE ingoing air channel and an NDE ingoing air channel (not explicitly shown in Fig. le). In embodiments not shown in the Figures, the marine propulsion unit may comprise an axial air cooling. Particularly, for the axial air cooling, air may enter the dual rotor electric motor 1 from a DE side and exit the dual rotor electric motor 1 from an NDE side or vice versa. The outgoing air channel 33 and the ingoing air channels are connected to the cooling air unit 16. Typically, the cooling air unit 16 is arranged outside the motor block 2050. In some embodiments (not shown in the Figures), particularly for a large motor block 2050, the cooling air unit 16 may be arranged inside the motor block 2050. The motor block 2050 follows a contour of the hull 2100 of the vessel. Particularly, the motor block 2050 forms a skeg of the hull 2100 of the vessel. The motor block 2050 is typically welded to the hull 2100 at a welding area 61.

[0077] In Fig. If, the marine propulsion unit 2000 comprises a marine propulsion unit housing 2010. Within the marine propulsion unit housing 2010, the drive shaft, the dual rotor electric motor 1, the slip ring unit 19 and the NDE bearings 41, 42 are arranged. The marine propulsion unit housing 2010 is configured to be inserted in the hull 2100 via the skeg of the hull 2100.

[0078] In Fig. 1g, the dual motor electric motor 1, the slip ring unit 19 and the NDE bearings 41, 42 are arranged within the hull of the marine vessel. The dual rotor electric motor 1 is connected to the contra rotating propeller 9, 10 via the drive shaft. In Fig. 1g, the drive shaft is longer that in the embodiments shown in Fig. le and If. Particularly, the drive shaft may have a length of at least 5 times a length of the dual rotor electric motor 1. In part, the drive shaft extends outside the hull of the marine vessel as an exposed shaft. The driveshaft is supported by support bearings 45, 46. In the hull, the dual motor electric motor 1, the slip ring unit 19 and the DE and NDE bearings 41, 42 are accessible for maintenance.

[0079] FIG 2 schematically illustrates a cross-section of an isometric view of a marine propulsion unit, such as an azimuthing propulsion unit 1000, according to typical embodiments described herein. The marine propulsion unit, such as the azimuthing propulsion unit 1000, comprises a hull of the marine propulsion unit or 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.

[0080] The exemplary azimuthing propulsion unit 1000 of Fig. 2 as described herein may permit the marine propulsion unit, particularly the azimuthing propulsion unit 1000, to 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.

[0081] 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 marine propulsion unit, particularly 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.

[0082] The embodiment of Fig. 2 comprises the DE inner bearing 12 with inner bearing pads 312. For example, the DE inner bearing 12 may 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.

[0083] The embodiment of Fig, 2 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.

[0084] The exemplary azimuthing propulsion unit 1000 of Fig. 2 comprises a DE inner proximal seal 306, wherein the DE inner proximal seal 306 is arranged between the DE innershaft 8 and the DE outer shaft. The DE inner proximal seal 306 is arranged towards a nondrive end (NDE) of the azimuthing propulsion unit 1000.

[0085] The azimuthing propulsion unit 1000 shown in Fig. 2 comprises a DE outer bearing 11. As with typical embodiments, the DE outer bearing 11 comprises outer bearing pads 511.

[0086] 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. 2, the DE outer bearing 11 is at least partially overlapping the DE inner bearing 12.

[0087] FIG. 3 illustrates a flow chart of a method 350 of maintaining a marine propulsion unit such as an azimuthing propulsion unit according to the embodiments described herein. The method 350 comprises opening a hatch of a DE outer shaft of the marine propulsion unit 352. The method 350 comprises accessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft 354.

[0088] FIG. 4 illustrates a flow chart of a method 350 of maintaining a marine propulsion unit such as an azimuthing propulsion unit according to the embodiments described herein. The method 350 comprises opening a hatch of a DE outer shaft of the marine 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 360 further comprises, after accessing the DE inner bearing the hatch, displacing the DE inner bearing 356.

[0089] FIG. 5 illustrates a flow chart of a method 350of maintaining a marine propulsion unit such as an azimuthing propulsion unit according to the embodiments described herein. The method 350comprises opening a hatch of a DE outer shaft of the marine 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.

[0090] FIG. 6 illustrates a flow chart of a method 350of maintaining a marine propulsion unit such as an azimuthing propulsion unit according to the embodiments described herein. The method 350comprises opening a hatch of a DE outer shaft of the marine propulsion unit352. 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.

[0091] FIG. 7 illustrates a flow chart of a method 350 of maintaining a marine propulsion unit such as an azimuthing propulsion unit according to the embodiments described herein. The method 350 comprises opening a hatch of a DE outer shaft of the marine 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 marine 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).

[0092] While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the appended claims.

Claims

CLAIMS1. A marine propulsion unit (1000, 2000), the marine propulsion unit (1000, 2000) 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).

2. The marine propulsion unit (1000) of claim 1, wherein the marine propulsion unit is an azimuthing propulsion unit.

3. The marine propulsion unit (1000, 2000) of any of claims 1 or 2, wherein the hatch (302) is configured to provide an access to the DE inner bearing (12).

4. The marine propulsion unit (1000, 2000) of claim 3, wherein the hatch (302) is configured to be accessed by a user from within the marine propulsion unit (1000).

5. The marine propulsion unit (1000, 2000) of any of claims 1 to 4, wherein the DE inner bearing (12) comprises at least one inner bearing pad (312).

6. The marine propulsion unit (1000, 2000) of any of claims 1 to 5, 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.

7. The marine propulsion unit (1000, 2000) of any of claims 1 to 6, 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.

8. The marine propulsion unit (1000, 2000) of any of claims 1 to 7, further comprising a hull of the marine propulsion unit.

9. The marine propulsion unit (1000, 2000) of any of claims 1 to 8, further comprising a DE outer bearing (11), wherein the DE outer bearing (11) preferably comprises at least one outer bearing pad.

10. The marine propulsion unit (1000, 2000) of claim 9, 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).

11. A method (350) of maintaining an marine propulsion unit, particularly the marine propulsion unit according to any of claims 1 to 10; the method comprising:opening a hatch of a drive end (DE) outer shaft of the marine propulsion unit (352); andaccessing a DE inner bearing arranged between the DE outer shaft and a DE inner shaft (354).

12. The method of claim 11, comprising, after accessing the DE inner bearing through the hatch: displacing the DE inner bearing (356).

13. The method of claim 12, comprising, after displacing the DE inner bearing, accessing a DE inner distal seal through the hatch; anddisplacing the DE inner distal seal (358).

14. The method of any of claims 11 to 13, 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).

15. The method of any of claims 11 to 14, 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.

16. The method of any of claims 11 to 15, further comprising displacing any of: a DE outer proximal seal, a DE outer bearing, a DE outer distal seal, or any combination thereof (360).

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