Marine propeller shaft seal

Abstract

Marine propeller shaft seal with annular rotor coupled to the shaft. The rotor has a ceramic face that interfaces a stationary carbon stator to form a sealing interface. The ceramic face is formed from silicon carbide and retained within a metallic portion of the rotor. A rubber bellow connects the stator to an adapter and includes a concertina section to accommodate axial variation. Snap-fit and press-fit joints form interlocking formations to secure the bellow to the stator. A hose barb penetrates the stator and bellow to deliver water for lubrication and cooling while securing components together. A sleeve further secures the bellow to the stator. The seal offers compact installation, tolerance to shaft misalignment, and extended service life in marine environments..

Description

Marine Propeller Shaft SealField of the Invention

[0001] The present invention relates to marine sealing systems, and more particularly to a propeller shaft seal for marine vessels configured to provide a watertight interface between a rotating propeller shaft and a stationary hull structure.Background of the Invention

[0002] A propeller shaft seal is a component in marine vessels, designed to prevent water from entering the hull where the propeller shaft exits the boat. In typical marine environments, maintaining a watertight barrier around the rotating shaft is essential to preserve vessel integrity and operational safety.

[0003] Conventional shaft seal arrangements often rely on mechanical face seals or packing glands. Mechanical face seals generally comprise a rotating ring mounted to the shaft and a stationary ring mounted to the hull or stern tube. However, many of these designs suffer from premature wear due to suboptimal material pairings, particularly when exposed to the high loads, continuous rotation, and temperature fluctuations typical in marine settings. This can lead to accelerated degradation of sealing surfaces, reduced service intervals, and increased maintenance demands.

[0004] Packing glands, while simple and inexpensive, commonly permit a degree of controlled leakage to maintain lubrication and prevent overheating. This not only introduces continuous moisture into the bilge but also necessitates frequent adjustment and eventual replacement of the packing material. Furthermore, such arrangements are often bulky and may not accommodate shaft misalignment or vibration effectively, leading to uneven wear and reduced sealing reliability.

[0005] Another limitation observed in existing designs is the complexity of installation and servicing, which may require precise alignment of components and intricate securing mechanisms. In some cases, the size and arrangement of components contribute to spatial inefficiency, presenting challenges in tight engine compartments or retrofit installations.

[0006] These disadvantages have prompted continued interest in more robust, low- maintenance sealing solutions capable of accommodating dynamic shaft conditions while maintaining effective exclusion of water over prolonged service intervals .

[0007] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.Summary of the Disclosure

[0008] The disclosed marine propeller shaft seal comprises an annular rotor defining a central bore configured to receive a propeller shaft therethrough, the rotor including a ceramic face arranged to rotate with the shaft. A carbon stator having a flat face interfaces against the ceramic face of the rotor to form a sealing interface, with the stator configured to remain stationary relative to the shaft. This configuration provides a robust and durable sealing interface that accommodates rotary motion while maintaining sealing integrity. This particular interface pairing has demonstrated performance benefits when compared with conventional arrangements. For example, unlike elastomeric or polymer-based contact faces, which tend to deform and degrade rapidly under load and elevated temperatures, the ceramic-carbon interface maintains dimensional stability and sealing effectiveness over extended use. Similarly, arrangements employing metal sealing faces such as bronze or stainless steel often exhibit greater friction and are susceptible to galling or scoring under continuous rotation — issues not observed with the present configuration. Compared to packing gland systems, which inherently allow leakage and require routine maintenance, the disclosed seal provides a substantially dry, maintenance-reduced solution better suited to modern marine applications.

[0009] In preferred embodiments, the rotor comprises a metallic portion configured to retain a ceramic annular disc. This metallic portion may define an annular recess that accommodates the ceramic disc therein, ensuring structural support for the ceramic component and protecting its edges from mechanical damage. This arrangement facilitates precise positioning and exposure of the ceramic sealing face while maintaining overall integrity under dynamic loads.

[0010] The radial width of the ceramic face may exceed that of the flat face of the stator, providing a wider sealing interface. This broader contact area can help distribute contact pressure more evenly, reducing localised wear and improving resistance to lateral movement or vibration-induced misalignment.

[0011] In preferred embodiments, the ceramic face is formed from silicon carbide. The selection of silicon carbide for the ceramic face followed evaluation of various candidate materials including alumina and zirconia-based ceramics. While these alternatives offer some degree of hardness and corrosion resistance, they were found to exhibit limitations in thermal conductivity, fracture toughness, or long -term wear performance under the dynamic and corrosive conditions typical of marine shaft environments. In contrast, silicon carbide demonstrated a more favourable balance of structural integrity, thermal dissipation, and resistance to abrasive wear when paired with a carbon stator. This enhanced compatibility not only contributed to a more stable sealing interface during shaft misalignment and vibration but also reduced the incidence of microcracking and surface degradation observed in other ceramic materials over time. As such, the implementation of silicon carbide as the ceramic sealing face was found to further enhance the operational lifespan, reliability, and performance consistency of the seal in service.

[0012] To accommodate potential misalignment or shaft eccentricities, the stator may define a bore having an inner diameter that exceeds the bore of the rotor. This overbore arrangement allows the stator to float radially around the shaft, mitigating the effects of vibration or misalignment and preserving the sealing engagement over time.

[0013] In certain embodiments, a rubber bellow may be arranged to exteriorly overlap the stator, with interlocking formations provided between the bellow and stator. For example, an internal groove in the bellow may receive an external collar on the stator, forming a snap-fit connection. Alternatively or additionally, overlapping longitudinal collars may form a press-fit joint. These features provide a secure and resilient mechanical interface that facilitates rapid installation and resists separation under dynamic operating conditions.

[0014] The bellow and stator may thus be configured to define adjacent snap-fit and press-fit joints, which act complementarily to enhance both mechanical retention and sealing function. Such configurations can simplify assembly, reduce the need for adhesives or mechanical fasteners, and help ensure long-term structural integrity.

[0015] The bellow may also include a concertina section to permit axial length variation during operation, accommodating thermal expansion, flexing of the hull, or propeller shaft movement without compromising the seal.

[0016] In some arrangements, a hose barb penetrates through the bellow and the stator to provide a coolant and lubrication path. This dual-penetration design can serve to both secure the components and introduce a fluid stream at the interface, thereby improving thermal management and reducing wear at the sealing surface.

[0017] The stator may define a tapered edge, such as a frustrotriangular profile in radial cross-section, with the bellow extending to a base of this tapered edge. This configuration not only enhances sealing efficiency but also reduces the overall axial length of the seal, enabling installation in spatially constrained environments.

[0018] A metallic sleeve may be used to secure the bellow to the stator, optionally defining an aperture through which the hose barb may pass. The sleeve may further include interlocking formations, such as internal features that mate with corresponding exterior formations on the bellow, enhancing mechanical stability and helping maintain concentricity around the shaft.

[0019] The rotor may further comprise one or more O-rings disposed within the central bore to seal against the propeller shaft, minimising internal leakage along the shaft body. Threaded holes may also be provided in the rotor to receive set screws, facilitating secure attachment of the rotor to the shaft while enabling straightforward installation and removal.

[0020] In preferred embodiments, the carbon stator is configured to float radially relative to the shaft to compensate for minor misalignment or eccentric motion, improving reliability and reducing the potential for localised stress or interface failure.

[0021] These features, when combined, provide a versatile and compact sealing assembly for marine propeller shafts that offers reduced maintenance demands,enhanced resistance to environmental wear, and reliable long-term operation under dynamic loading and movement conditions.

[0022] Other aspects of the invention are also disclosed.Brief Description of the Drawings

[0023] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0024] Figure 1 shows a perspective cross-sectional view of marine propeller shaft seal in accordance with a preferred embodiment.Description of Embodiments

[0025] Figure 1 illustrates a marine propeller shaft seal 100 that includes an annular rotor 101 having a ceramic face 102 and a carbon stator 103 arranged to bear against the ceramic face. The ceramic is preferably silicon carbide. The annular rotor 101 defines a central bore 104 for a propeller shaft and carries interior O-rings 105 that seal directly against the shaft. Threaded holes 106 receive set screws to secure the rotor 101 to the shaft.

[0026] The rotor 101 may incorporate a metallic portion 107, such as marine-grade stainless steel, that retains a ceramic annular disc 108. The metallic portion 107 defines an annular recess 109 in which the disc 108 is housed while leaving the ceramic face 102 exposed for co-operation with the stator 103.

[0027] The stator 103 may present a tapered edge 1 10 that is frustro-triangular in radial cross-section and provides a flat sealing face for engagement with the ceramic face 102. Preferably, the ceramic face 102 is wider than the stator’s flat face, so the radial width of the disc 108 exceeds that of the stator 103, enhancing the sealing interface.

[0028] To accommodate shaft misalignment or vibration, the stator 103 can be overbored relative to the shaft, such that the inner diameter of the stator bore exceeds that of the rotor bore. A rubber bellow 1 1 1 may be connected between the stator 103 and an adapter 1 12; the bellow 1 1 1 may have a distal portion engaging the stator103, a proximal portion engaging the adapter 1 12, and a concertina section that allows axial length variation in service. Hose clamps 126 may secure the proximal portion to the adapter 1 12.

[0029] The distal portion of the bellow 1 1 1 preferably overlaps and substantially envelops the stator 103, thereby shortening the overall length of the seal 100. As shown, the bellow 1 1 1 extends approximately to the base of the tapered edge 1 10. Interior formations on the bellow 1 1 1 may interlock with exterior formations on the stator 103: for example, a snap-fit joint in which an external collar 1 13 on the stator engages an internal groove 1 14 in the bellow. A complementary press-fit joint can also be provided in the form of overlapping longitudinal collars 1 15. Preferably, the seal 100 incorporates both a snap-fit joint 1 16 and a press-fit joint 1 17 positioned adjacent one another to reinforce mechanical retention and sealing performance.

[0030] A hose barb 1 18 may supply cooling and lubrication water. The hose barb may include a tube 1 19 for hose connection and a tubular base 120 that threads into an aperture 121 in the stator 103. In the preferred embodiment, the hose barb 1 18 passes through both the bellow 1 1 1 and the stator 103, thereby drawing these components together. In embodiments, the hose barb 1 18 may be plastic.

[0031] A metallic sleeve 122 may be fitted over the bellow 1 1 1 to clamp it to the stator 103. The sleeve 122 can include a side aperture 123 aligned with the hose barb 1 18, allowing the barb to pass through the sleeve, the bellow, and the stator in a single operation that secures the entire assembly. Interior sleeve formations 124 may interlock with exterior bellow formations 125, further enhancing concentricity and structural stability.

[0032] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the aboveteachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

Claims

Claims1 . A marine propeller shaft seal comprising: an annular rotor defining a central bore configured to receive a propeller shaft therethrough, the rotor comprising a ceramic face arranged to rotate with the shaft; and a carbon stator having a flat face arranged to interface against the ceramic face of the rotor to define a sealing interface, the carbon stator being configured to remain stationary relative to the shaft.

2. The marine propeller shaft seal as claimed in claim 1 , wherein the rotor comprises a metallic portion configured to retain a ceramic annular disc.

3. The marine propeller shaft seal as claimed in claim 2, wherein the metallic portion defines an annular recess configured to accommodate the ceramic annular disc therein.

4. The marine propeller shaft seal as claimed in claim 1 , wherein the ceramic face comprises silicon carbide.

5. The marine propeller shaft seal as claimed in claim 1 , wherein a radial width of the ceramic face exceeds a radial width of the flat face of the stator.

6. The marine propeller shaft seal as claimed in claim 1 , wherein an inner diameter of a bore defined by the stator exceeds an inner diameter of the central bore defined by the rotor.

7. The marine propeller shaft seal as claimed in claim 1 , further comprising a rubber bellow arranged to exteriorly overlap the stator, wherein an interior formation of the bellow interlocks with an exterior formation of the stator.

8. The marine propeller shaft seal as claimed in claim 7, wherein the exterior formation of the stator comprises an external collar, and the interior formation of the bellow comprises an internal groove that receives the external collar.

9. The marine propeller shaft seal as claimed in claim 7, wherein the interlocking formations are configured to engage along a longitudinal axis defined by the seal.

10. The marine propeller shaft seal as claimed in claim 9, wherein the interlocking formations comprise overlapping, longitudinally oriented collars.1 1 . The marine propeller shaft seal as claimed in claim 1 , further comprising a rubber bellow connected to the stator, wherein the bellow and stator define adjacent snap-fit and press-fit joints.

12. The marine propeller shaft seal as claimed in claim 1 , further comprising a rubber bellow connected to the stator, and a hose barb penetrating through the rubber bellow and the stator.

13. The marine propeller shaft seal as claimed in claim 1 , wherein the stator defines a tapered edge, and the rubber bellow extends to a base of the tapered edge.

14. The marine propeller shaft seal as claimed in claim 1 , further comprising a rubber bellow overlapping the stator and a sleeve configured to secure the bellow to the stator.

15. The marine propeller shaft seal as claimed in claim 14, further comprising a hose barb penetrating the rubber bellow, the sleeve, and the stator.

16. The marine propeller shaft seal as claimed in claim 14, wherein an interior formation of the sleeve interlocks with an exterior formation of the bellow.

17. The marine propeller shaft seal as claimed in claim 1 , further comprising a rubber bellow arranged to exteriorly overlap the stator and wherein the rubber bellow comprises a concertina section configured to accommodate axial length variation during operation.

18. The marine propeller shaft seal as claimed in claim 1 , wherein the rotor comprises at least one O-ring disposed within the central bore for sealing engagement with the propeller shaft.

19. The marine propeller shaft seal as claimed in claim 1 , wherein the rotor comprises threaded holes for receiving set screws to secure the rotor to the propeller shaft.

20. The marine propeller shaft seal as claimed in claim 1 , wherein the carbon stator is configured to float radially relative to the shaft to compensate for misalignment or vibration.

21. A method of sealing a propeller shaft in a marine vessel, the method comprising: mounting an annular rotor onto a propeller shaft, the rotor defining a central bore and comprising a ceramic face configured to rotate with the shaft; positioning a carbon stator with a flat face to interface against the ceramic face of the rotor to form a sealing interface, the stator being arranged to remain stationary relative to the shaft; and securing a rubber bellow to the stator such that the stator is at least partially enclosed by the bellow, wherein the bellow provides axial compliance and sealing integrity during operation.

22. A marine propulsion system comprising: a propeller shaft; and a marine propeller shaft seal comprising: an annular rotor mounted to the propeller shaft and comprising a ceramic face configured to rotate with the shaft; and a carbon stator having a flat face arranged to interface against the ceramic face of the rotor to form a sealing interface, the stator being stationary with respect to the shaft.

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