Improved stern structure for propeller support for single- or multi-propeller ships

Abstract

The invention relates to an aft support structure for a ship propeller, applicable to single- or multi-propeller ships, wherein said aft structure comprises a support (10) for the ship propeller, said support (10) being positioned aft of the propeller (21) and configured to support a boss (17) integral with the support (10) itself and housing a propeller bearing (19) to allow rotation of a propeller hub (22) of the propeller (21), the support (10) having a hydrodynamically streamlined section aligned with a rudder blade (15) to reduce vortex formation and resistance to ship advancement, characterized in that said support (10) is separate from the said rudder (15).

Description

[0001] Title:

[0002] "IMPROVED STERN STRUCTURE FOR PROPELLER SUPPORT FOR SINGLE- OR MULTI-PROPELLER SHIPS”

[0003] FIELD OF THE INVENTION the present invention relates to an improved stem structure for propeller support for single- or multi-propeller ships.

[0004] PRIOR ART

[0005] As is known, numerous factors are involved in the calculation of a ship’s fuel consumption, as stated by naval hydrodynamics theory.

[0006] A brief description of these factors is provided below:

[0007] □ CH hourly fuel consumption= PB x CS (kg / kWh)

[0008] □ PB Brake power required to propel the ship at speed V

[0009] □ CS = Specific hourly consumption

[0010] □ PB = PE / qP

[0011] □ PE = Rt x V Effective power = power required by the ship without the propeller to advance at speed V

[0012] □ Rt Total resistance of the ship without propeller

[0013] □ qP = (qH x qB) x (qm x qS) Total propulsion efficiency = (qH x qO x qR) x (qm x qS)

[0014] □ qH Hull efficiency

[0015] □ qO Isolated propeller efficiency, Open water

[0016] □ qB = qO x qR Efficiency behind hull, Behind

[0017] □ qR Relative rotational efficiency

[0018] □ qM Mechanical efficiency

[0019] □ qS Shafting and bearing efficiency

[0020] The parameter of greatest interest in the final formulation of PB for the present invention is essentially one: qB, the efficiency behind the hull.

[0021] As indicated in the formulation above: qB = qO x qR, where qR is essentially a reduction in propeller efficiency behind the hull compared to the isolated propeller efficiency qO, which is determined through computational fluid dynamics and experimental tests using a mechanically similar model, driven by a motor under full experimental control with the propeller immersed in water moving axially uniformly relative to it.

[0022] See Figure 1 , which illustrates the flow of fluid filaments at the propeller disk for a single-propeller ship.

[0023] The European patent application EP No. 88830294.0 had identified the wake and vortices produced by what is located upstream of the propeller or propellers as the main cause of the reduction in propeller or propellers efficiency, which, instead of being in a uniform flow as in experimental tests or appropriate fluid-dynamic calculations, works or work in a flow having radial and tangential velocity components of the fluid filaments that impair its optimal functioning.

[0024] Indeed, the non-uniform ity of the flow is mainly due to what is located in front of the propeller: the stem forms of the hull in single-propeller ships and, to a lesser extent, in multi-propeller ships that have simple-arm or V-shaped propeller-support structures, which in any case are smaller than the stern forms of single-propeller ships.

[0025] In this previous patent application, which illustrates the possibility that controllable- pitch propellers may be managed by a fluid-dynamic system allocated within the structure supporting the propeller weight and mechanically connected to the rudder, the possibility is considered that the rudder shaft is guided, in its lower part, by a system called a “calcagnolo", forming part of the single structure considered.

[0026] This solution, despite its undoubted benefits, due to its design involving a single support structure for both the rudder and the propeller, does not prevent that, in the event of impacts against foreign objects on one of its parts, a repercussion of the damage may occur on other parts, aggravating possible negative effect.

[0027] It can indeed be easily noted that, with the solution identified in patent application EP No. 88830294.0, by examining its peculiar geometry and construction (also visible in Figure 2 of patent application EP No. 88830294.0), damage may be caused even to components of the same solution that have not been in direct contact with foreign objects.

[0028] EP1368227 describes a hybrid propulsion system for ships that employs at least one pair of contra-rotating propellers, combining a main combustion engine and an electric motor to achieve high overall efficiency. Propulsion is provided by a fixed-pitch front propeller and a controllable-pitch rear propeller.

[0029] This document contemplates a propeller system composed of a rear controllable-pitch propeller driven by an internal shaft and a front fixed-pitch propeller driven by an external shaft coaxial with the first, wherein the propellers are supported as follows: for the internal shaft, by a bearing housed within the front fixed-pitch propeller, and for the external shaft, by a bearing housed in the traditional stem structure with skeg. The controllable-pitch propeller driven by the internal shaft of the propeller line may also be supported by a bearing sustained by an isolated support arm, which is connected to the stem frame that, in this case, is mechanically integrated into the structure supporting the rudder body. It is not indicated the means for easy assembly and disassembly of this solution nor the precautions necessary to ensure the absence of disturbances caused by the excessive proximity of the propeller blades to the new -type support structure.

[0030] US 2,931 ,443 essentially describes a system for adjusting the pitch of naval controllable-pitch propellers (CPP). The propeller hub, which houses the hydraulic system for the controllable blades, is mounted on a fixed non-rotating support element that allows the passage of hydraulic lines; this fixed support contains a bearing and extends vertically from the stem of the ship. This bearing supports the weight of the controllable-pitch propeller and the shaft, essentially serving as a guide for the aft part of the propeller hub. The support element appears completely isolated and not integrated with the rudder structure. It's incomprehensible either the means for easy assembly and disassembly of the propeller or the precautions necessary to ensure the absence of disturbances caused by the excessive proximity of the propeller blades to the new-type support structure.

[0031] JP 2012121370 A describes a propulsion system for ships focused on the design of the propeller shaft support structure, with the primary objective of reducing the hydrodynamic resistance generated by conventional supports. The propeller shaft extends aft from a non-visible hull of the ship, indicated as single-propeller, on which the propeller is mounted, and is supported by a support bracket that holds the aft end of the shaft connected to the propeller hub. The hull is incorrectly described as having a profile that extends downward from bow to stem. The bearing that supports the weight of the propeller and its shaft appears to have the same longitudinal dimension as the support bracket, and this support bracket may be mechanically connected to the rudder structure. It is not indicated the means for easy assembly and disassembly of this solution nor the precautions necessary to ensure the absence of disturbances caused by the excessive proximity of the propeller blades to the new-type support structure. DE 38 08 710 A1 describes a propulsion system for ships using a single propeller, or two contra-rotating propellers arranged in succession at the stern. The configuration of the vertical stern support, which sustains the weight of the single propeller or the two contra-rotating propellers, is such that the support element, the bearing of the shaft or shaft system, is positioned with a longitudinal dimension equal to that of the support containing it, on its forward side, while the aft side integrates the rudder blade. It is not indicated the means for easy assembly and disassembly of this solution nor the precautions necessary to ensure the absence of disturbances caused by the excessive proximity of the propeller blades to the new-type support structure.

[0032] CN 205168803 U describes the problems of conventional ship deck structures and states that steel decks in some contexts have been replaced with FRP (fiber-reinforced plastic) decks to exploit the greater corrosion resistance and extend the service life of the hull.

[0033] An object of the present invention is therefore to create a stem propeller support structure capable of better withstanding impacts on any of its parts — steering and propulsion components — without repercussions on other parts, and moreover, to minimize the losses in propeller efficiency behind the hull, qB.

[0034] According to the invention, the value of qB is significantly and positively modified by the inventive solution described below.

[0035] Consequently, the value of qP is also positively affected.

[0036] It is important to note that the present improved invention fully achieves the benefits highlighted in European patent application EP No. 88830294.0.

[0037] That document had indeed identified the wake and vortices generated by what is located upstream of the propeller or propellers as the main cause of reduction in propeller efficiency, which, instead of being in a uniform flow as in experimental tests or appropriate fluid-dynamic calculations, work in a flow having axial, radial, and tangential velocity components of the fluid filaments that impair its optimal functioning. Depending on the solutions under consideration, reductions in qP of approximately 2- 4% can be estimated, which directly impact the power values involved and, consequently, the fuel consumption.

[0038] BRIEF SUMMARY OF THE INVENTION

[0039] These and other objects are achieved by a stem propeller support structure for a ship, applicable to single- or multi-propeller ships, wherein said stem structure comprises a vertical support, either simple or with a V-shaped bracket, for the ship propeller. Said support is positioned aft of the propeller and is configured to support, with a projection integral with the support and having appropriate longitudinal and diametral dimensions, the housing of the propeller and shaft support bearing, and to ensure the proper distance between said support and the propeller blades. A propeller-supporting bearing is housed within to allow rotation of the propeller hub. The support has a section hydrodynamically streamlined with a rudder blade and may be positioned aft of the propeller(s) to reduce vortex formation and the ship’s resistance to forward motion. The propeller support is mechanically separate from the rudder and constitutes an independent support element, which can be installed and removed autonomously relative to the rudder structure, supporting the entire weight of the propeller and the aft portion of the propeller hub and its shaft.

[0040] This solution can be used for ships with conventional multi-propeller propulsion systems, both with and without a central propeller. In the case of a central propeller, this solution also allows for a substantial modification of the stern hull forms.

[0041] The present invention offers numerous advantages, among which several relevant aspects are highlighted here.

[0042] The structural separation of the “rudder” function from the “propeller” function eliminates or significantly reduces, in the event of damage due to accidental contact of the rudder and / or propeller and / or propeller shaft with foreign objects of any kind, at sea or in a dry dock, possible damage repercussions to adjacent structures due to distance and, consequently, the absence of direct contact. This distance can be selected based on calculations related to deformations caused by impacts, which arises between the rudder arrangement and the propeller support arrangement described herein.

[0043] The solutions proposed within the context of the present invention allow, based on assumed impact values — for example, contact between the rudder blade and a quay at speed V — to calculate the minimum clearance necessary between the rudder support structure and the propeller support structure to effectively prevent further damage.

[0044] The present improvements according to the invention, indeed, confirming the advantages highlighted in European patent application EP No. 88830294.0, are able to further enhance its already considerable benefits: - by improving the engineering characteristics; it is in fact evident that the design and construction of the structures proposed in the present invention are easier, being less bulky and less complex, and therefore more readily manufacturable and installable compared to the structure shown in Figure 2 of European patent application EP No. 88830294.0. Indeed, the construction and installation, particularly for ships of considerable size, of structures as described in EP No. 88830294.0 pose significant engineering and production challenges, taking into account the need to perform mechanical work on various parts of the single-piece structure and the difficulty of achieving the necessary alignments with the internal reinforcement structures and the propeller shaft exit from the hull;

[0045] - by significantly simplifying the structure identified as part 12 in Figure 2 of European patent application EP No. 88830294.0;

[0046] - by reducing possible interactions between the components necessary to achieve the same objectives as in European patent application EP No. 88830294.0. The two essential elements for ship functionality, namely the propulsion element — propeller — and the maneuvering element — rudder — do not belong, in the present invention, to a single structure as in that patent application, but are suitably separated from each other with distances that can be properly calculated based on assumptions regarding the position and magnitude of loads resulting from accidental impact. The result of such calculations may be that there is no interaction between the two structures;

[0047] - all of the above without introducing design or regulatory complications.

[0048] Further features of the invention may be deduced from the dependent claims.

[0049] BRIEF DESCRIPTION OF THE FIGURES

[0050] Further features and advantages of the invention will be evident from the following description, provided by way of example and not limitation, with reference to the figure illustrated in the accompanying drawing, wherein:

[0051] - Figure 1 illustrates the flow of fluid filaments at the propeller disk for a single-propeller ship;

[0052] - Figure 2 illustrates a stem support structure for the propeller, improved for singlepropeller ships or for the central propeller of multi-propeller ships, according to a first embodiment of the invention;

[0053] - Figure 3 illustrates a stem support structure for the propeller, improved for singlepropeller ships or for the central propeller of multi-propeller ships, according to a further embodiment of the invention; - Figure 4 illustrates a stern support structure for the propeller, improved for singlepropeller ships or for the central propeller of multi-propeller ships, according to a third embodiment of the invention;

[0054] - Figure 5 illustrates a stem support structure for the propeller, improved for singlepropeller ships or for lateral propellers of multi-propeller ships, according to a fourth embodiment of the invention; and

[0055] - Figure 6 illustrates a stern support structure for the propeller, in the case of singlepropeller ships and a support structure as in Figure 2 according to the invention, during operations in a dry dock.

[0056] DETAILED DESCRIPTION OF THE FIGURES

[0057] The invention will now be described with initial reference to Figure 2, in which a stem support structure for the propeller, improved for single- or multi-propeller ships for any type and use, is shown according to one embodiment of the invention and generally indicated by reference numeral 10.

[0058] The propeller support structure 10 comprises a support having a section hydrodynamically aligned with the rudder blade 15.

[0059] This stem structure 10 is positioned aft of the propeller 21 and serves to support a boss 17 integral with it, within which a propeller bearing 19 is housed, allowing the hub 22 of the propeller 21 to rotate.

[0060] The stem structure 10 is suitably connected to the hull structures.

[0061] The new design of the stem support structure, illustrated in Figure 2 as a single-arm support for the propeller bearing positioned aft of the propeller for single-propeller ships, is such that no lower support structure for the rudder 15 and its associated shaft is provided within the stem structure.

[0062] In particular, according to an important aspect of the invention, the support 10 for the propeller 21 is separated from the rudder 15.

[0063] This improved structure is also applicable to multi-propeller ships without modification of the stem hull forms as generally used today.

[0064] The embodiment shown in Figure 2 is essentially realized through the hydrodynamic and structural design of a rudder 15, which can be defined as a “flag-type” rudder.

[0065] The design and construction technology of the rudder are therefore exactly the same as those normally in use today, thereby eliminating the engineering considerations that would otherwise be required: drawings, calculations, experimental tests, vibration checks, etc., as would be necessary with the solution described in European patent application EP No. 88830294.0.

[0066] The same simplifications mentioned above — drawings, calculations, experimental tests, vibration checks, etc. — are also achieved for all aspects concerning the new- type structure shown in Figure 2.

[0067] Indeed, it is easier to design, engineer, and construct compared to the solution proposed in European patent application EP No. 88830294.0, as it only has to perform the single function of supporting the propeller bearing 19 and its associated shaft.

[0068] Considering ship dimensions, speed, propeller size, shaft line dimensions, and the distance between the propeller bearing and the shaft-seal bearing on the hull, the structure of the invention can be realized using bent and welded plate solutions or forged solutions with subsequent mechanical machining.

[0069] The materials used and their surface treatments may be those typical of naval structures of this type.

[0070] In general, the materials should have the following characteristics:

[0071] Corrosion resistance: to withstand exposure to saltwater or freshwater;

[0072] Tensile strength: to resist hydrostatic pressures;

[0073] Toughness: to absorb stresses from collisions with other ships, mooring structures, or submerged objects such as logs or ice;

[0074] Weldability: essential for robust assembly of the various parts of a ship;

[0075] Flexibility and formability: must be adaptable to the different shapes of naval components, from hulls to decks and superstructures.

[0076] As an example, steels such as AH36, DH36, and EH36, commonly used in shipbuilding, or their equivalents, may be used.

[0077] For the installation, inspection, and removal of the propeller bearing 19, suitable provisions and appropriate mechanical machining may be provided.

[0078] Depending primarily on the propeller 21 size, suitable access hatches with locking devices may be provided to allow insertion of tools for installation or removal of the bearing 19 itself and for its inspection when the propeller 21 is in its operational position.

[0079] For the installation, inspection, and removal of the propeller hub 22, the same design and technical measures currently used in the prior art solutions for the installation and removal of the propeller 21 , after disassembly and reassembly of the removable outer shaft section 20, will be employed. Appropriate appendages, such as brackets, rings, etc., will be installed in the necessary number and positions on the hull to facilitate and simplify all operations of installation, inspection, and removal of the final shaft section 20, the propeller 21 with its hub 22, and the propeller bearing 19 during construction or maintenance in a dry dock.

[0080] The structure 10 is adequately supported by internal hull structures: longitudinal and transverse reinforcements connected to the hull frames, and suitable local increases in hull plating thickness in the relevant area.

[0081] These reinforcements may be equivalent in number and type to those used for the support of existing rudder structures, stabilizing fins, or azimuthal propulsion devices. No special design or construction practices are required, as existing frames, transverse floors, reinforced longitudinal stringers, or, if necessary, additional elements may be used.

[0082] The structure 10 of the invention has surfaces streamlined with the rudder blade 15 to avoid vortices that cause resistance to ship advance and reduced rudder performance. These profiles, which do not interfere with the rudder blade 15 in its extreme rotational positions, can be formed by suitable shaping of structure 10 or added to the structure with appropriately shaped panels connected to structure 10.

[0083] Figure 3 illustrates a propeller support stem structure, improved for single-screw ships or for the central propeller of multi-screw ships, according to a further embodiment of the invention.

[0084] The structure 10 comprises a support having a section hydrodynamically streamlined with the rudder blade 15.

[0085] The stem structure 10 is positioned aft of the propeller 21 and serves to support a boss 17 fixed thereto, in which a propeller bearing 19 is housed. The hub 22 of the propeller 21 rotates within said bearing, such that the structure supports the weight of the aft section of the shaft, the hub 22, and the propeller 21 .

[0086] The stem structure 10 is suitably connected to the hull structures.

[0087] In Figure 3, the rudder 15 is supported by a rudder support element 30, conveniently separated and profiled from the aforementioned support structure 10, and suitably connected to the hull. In an appropriate position, it houses a bearing 35 supporting the rudder shaft against radial loads.

[0088] The improved variant of Figure 3 is also applicable to multi-propeller ships without modifying the stem form of hulls as generally used today. The improved variant of Figure 3 is essentially realized by:

[0089] - the hydrodynamic and design sizing of the propeller 21 arrangement and its guide and support structures, identical to those of the embodiment in Figure 2;

[0090] - the drawing and hydrodynamic and structural design of a rudder which, for particular reasons of size, choice of construction material, or other considerations, is provided with a rudder support element 30 (see Figure 3) that houses a rotation system of the rudder shaft 15 in the form of a heel bearing 35.

[0091] The presence, not shown in the drawing, of a lower surface of the rudder blade 15, positioned forward of the rudder shaft and intended to compensate for the forces when heeling the rudder, can also be easily considered. Such a compensating surface may conveniently be located beneath the structure 17 in Figure 3.

[0092] Essentially, the rudder support element 30 of the rudder 15, external to the hull, must be dimensioned taking into account:

[0093] - the hydrodynamic forces generated by the rudder blade in various steering positions of the ship and transmitted from the shaft to the support structure;

[0094] - the requirement for resistance to possible impacts, with magnitude and point of application as determined during the design phase;

[0095] - the internal hull rudder support structure;

[0096] - the possible presence of a bearing connected to the above-mentioned support element, suitable for operation in seawater or freshwater, allowing the rudder to rotate and supporting its total or partial weight; such bearing may include appropriate lubrication and / or greasing devices;

[0097] - a bearing, rigidly connected to the heel bearing 35, which allows rotation of the rudder shaft while preventing radial movements of the shaft. This bearing must be suitable for immersion in seawater or freshwater.

[0098] The design and manufacturing technology of the rudder are therefore similar to those commonly used today, but specifically adapted to the novelty of the present invention. The same considerations as above also apply to the new-type structure identified in Figure 3.

[0099] Indeed, it is easier to design, engineer, and construct compared to the solution proposed in European Patent Application EP No. 88830294.0 and prior art, since it is solely intended to support the propeller bearing and its shaft.

[0100] Considering ship dimensions, speed, propeller size, shaft line dimensions, and the distance between the propeller bearing and the shaft bearing on the hull, both the structure 10 and the rudder support element 30 of rudder 15 can be made using bent and welded plate solutions or forged solutions, with subsequent machining. The materials used and their surface treatment will be those typical of naval structures of this type.

[0101] For the assembly, inspection, and disassembly of the propeller bearing 19, appropriate measures and mechanical operations can be provided for this purpose.

[0102] For the assembly, inspection, and disassembly of the propeller hub 22, the same design and technical measures currently used in prior art solutions can be employed for the assembly / disassembly of propeller 21 following the assembly / disassembly of the removable outer section 20 of its shaft.

[0103] Appropriate appendages, such as brackets, rings, etc., can be mounted in the required number and positions on the hull to facilitate and simplify all operations for mounting, inspecting, and disassembling the final part of shaft 20, propeller 21 with its hub 22, and propeller bearing 19 during construction or in a dry dock.

[0104] The stem structure and the rudder support element can be adequately supported by internal hull structures: longitudinal and transverse reinforcements connected to the hull frames, and appropriate increases in hull plate thickness in the relevant area.

[0105] The stern structure features hydrodynamically streamlined surfaces aligned with the rudder blade 15, in order to prevent vortices that generate resistance to the ship’s advance and reduce the rudder’s efficiency.

[0106] These profiles, which do not interfere with the rudder blade in its extreme rotation positions, can be formed by appropriately shaping structure 10, or they can be added to the structure with suitably shaped panels attached to it.

[0107] Figure 4 illustrates a stem support structure for the propeller, optimized for singlepropeller ships or the central propeller of multi-propeller ships, according to a third embodiment of the invention.

[0108] In this variant, the support structure 10 for the propeller shaft 20 features a two-arm V- shaped configuration 10’, 10” forming a strut, suitably shaped, which connects the propeller bearing support 19 to the appropriate hull surfaces located above the said bearing 19 on the right and left of the ship’s symmetry plane S in the case of singlepropeller ships or the central propeller of multi-propeller ships.

[0109] In the case of multiple propellers positioned on the right and left of the ship’s symmetry plane S, the two V-shaped struts 10’, 10” are placed above the corresponding propeller 21 , as shown in Figure 5, which illustrates a stem support structure for the propeller, optimized for single- or multi-propeller ships, according to a fourth embodiment of the invention.

[0110] In this embodiment, for ships with multiple propellers positioned to the right and left of the ship’s symmetry plane S, the rudder 15 can, depending on appropriate engineering choices, also be designed without a rudder shaft support bearing, as already indicated in the embodiment of Figure 2.

[0111] The purpose of the embodiments shown in Figures 4 and 5 is to prevent or address vibration issues and / or increased structural reinforcement requirements for the propeller shaft support, which is designed and constructed with the two V-shaped struts 10’, 10” connected at the bottom to the propeller bearing support 19 and at the top to corresponding areas of the hull.

[0112] The structures shown in Figures 4 and 5 serve the sole function of supporting the propeller bearing 19 and its shaft.

[0113] There are no particular design or construction difficulties, as a similar arrangement — with the struts positioned forward of the propeller, which would disturb the fluid flow and reduce propeller efficiency — is commonly used for twin-propeller ship solutions.

[0114] The rudder 15, in terms of its dimensions and type, can be installed either with a configuration as shown in Figures 4 or 5, similar to that of Figure 3, or with a configuration identical to that of Figure 2.

[0115] Considering the ship dimensions, speed, number and size of propellers, propeller shaft dimensions, and the distance between the propeller bearing and the stem shaft seal, this structure, together with the associated rudder support structure, can be constructed using bent and welded plates or a forged solution, with subsequent mechanical processing.

[0116] The materials and surface treatments used will be those typical of naval structures of this type.

[0117] For the installation, inspection, and removal of the propeller bearing 19, appropriate design measures and mechanical operations may be provided. Similarly, for the installation, inspection, and removal of the propeller hub, the same design and technical measures currently used in conventional solutions for propeller mounting on its shaft can be applied.

[0118] Suitable appendages, such as brackets, rings, etc., can be installed in the required number and positions on the hull to facilitate and simplify all operations for the installation, inspection, and removal of the propeller shaft end, the propeller with its hub, and the propeller bearing 19 during construction or in a dry dock.

[0119] All structures will be adequately supported by internal hull structures: longitudinal and transverse reinforcements connected to the hull frames and appropriate increases in hull plate thickness in the two areas affected by the V-shaped struts 10’, 10”.

[0120] The surfaces of the V-shaped struts 10’, 10” are hydrodynamically streamlined, as shown in Figures 4 and 5, to prevent vortices that would cause resistance to the ship’s advance and reduced rudder efficiency.

[0121] The structures described can be made of steel, cast iron, bronze, or other materials suitable for use in seawater or freshwater, using manufacturing methods such as forging, casting, or plate bending and welding.

[0122] The dimensions and geometries of the described structures can be symmetric or asymmetric to account for specific flow patterns of the fluid filaments downstream of the propeller.

[0123] It is envisaged that a section of the propeller shaft 20, from its exit from the hull to the propeller hub, is of a removable type to allow possible disassembly or reassembly of the propeller and / or the corresponding bearing without requiring further adjustments of the internal shaft line within the hull.

[0124] Appropriate inspection, cleaning, and bearing check hatches are provided in suitable positions.

[0125] As shown in Figure 6, the above-mentioned support structures can also be dimensioned for use during dry-docking operations 100, serving as support for the ship’s weight on suitable blocks 110.

[0126] A skilled person in the field, in order to meet specific and contingent requirements, may make further modifications and variants to the present invention, all of which remain within the scope of protection of the invention as defined by the following claims.

Claims

CLAIMS1. Stern support structure for a ship propeller, for single- or multi-propeller ships, wherein said stern structure comprises a support (10) for the ship propeller, wherein the said support (10) is positioned aft of the propeller (21 ) and is configured to support a boss (17) integral with the support (10) itself, within which a propeller bearing (19) is housed to allow the rotation of a propeller hub (22) of the propeller (21 ). The support (10) has a section hydrodynamically streamlined with a rudder blade (15), which may be supported only by its rotation shaft without other support elements and positioned aft of the support (10), in order to reduce the formation of vortices and the ship’s resistance to forward motion, characterized in that the said propeller support (10) is separate from the said rudder (15), constituting an independent support element, autonomously installable and removable with respect to the rudder structure (15), and supports the entire weight of the propeller (21 ) and the aft portion of the propeller hub (22) of the propeller (21 ).

2. Stem support structure for a ship propeller according to claim 1 , characterized in that it comprises a separate support element (30) for the rudder (15), said separate support element (30) for the rudder (15) including a bearing (35) suitable for operation in a water environment and configured to support radial loads of the rudder shaft (15).

3. Stem support structure for a ship propeller according to claim 1 , characterized in that said support structure comprises two V-shaped arms (10’, 10”), said arms being positioned symmetrically with respect to a longitudinal axis, said arms being connected to the propeller bearing (19) and to the hull of the ship, and configured to prevent vibration issues and to increase the stability of the propeller support structure.

4. Stem support structure for a ship propeller according to claim 3, characterized in that the two V-shaped arms (10’, 10”) are positioned symmetrically with respect to the ship's plane of symmetry (S).

5. Stem support structure for a ship propeller, according to any of the preceding claims, characterized in that it is applicable to ships without a central propeller without modifying the stem shape of the hull, comprising a support (10) with a hydrodynamically streamlined section in order to minimize resistance and improve the maneuverability of the rudder (15).

6. Stem support structure for a ship propeller, according to any of the preceding claims, characterized in that it comprises appendages and supports, brackets and rings, fixedto the hull to facilitate the assembly, disassembly, and maintenance operations of the propeller shaft bearing (19) and the propeller hub (22).

7. Support structure for a ship propeller shaft, according to any of the preceding claims, characterized in that it comprises a removable propeller shaft section (20) to allow the assembly and disassembly of the propeller shaft bearing (19) and the propeller (21 ) without having to move the entire internal shaft line of the ship.

8. Aft support structure for a ship propeller, according to any of the preceding claims, characterized in that the structure (10) is made of bent and welded plate or by forging followed by subsequent machining.

9. Aft support structure for a ship propeller according to claim 1 , characterized in that the support (10) comprises materials having corrosion resistance, tensile strength, toughness, weldability, and flexibility, such as AH36, DH36, EH36 steel or equivalents, to withstand the marine environment.

10. Aft support structure for a ship propeller according to any of the preceding claims, characterized in that said aft support structure can be designed, constructed, and used in a dry dock as a support for the weight of the ship.

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