GB2612342A

GB2612342A - Rubber in compression coupling

Info

Publication number: GB2612342A
Application number: GB2115537.9A
Authority: GB
Inventors: Richards Paul; Griffiths Gavin; Estrada Eduardo
Original assignee: Renold PLC
Current assignee: Renold PLC
Priority date: 2021-10-28
Filing date: 2021-10-28
Publication date: 2023-05-03
Also published as: GB202115537D0

Abstract

A coupling (2, fig 1), for a marine vessel, comprises an outer member (4), an inner member 8 and a plurality of radial interdigitated projections 10, 16 that project from the outer member 4 and from the inner member 8. A rubber buffer element comprises first and second buffer element portions 22, 24, linked by an extension portion 26 having a second surface 58, and configured to be received in a plurality of spaces 66. The extension portion 26 is spaced apart from the projections 10, 16 and is configured to buffer relative radial movement of the inner member 8 and the outer member (4). The extension portion 26 may be reinforced by a mesh formed of a fabric and/or of a metallic material embedded in the extension portion 26. Inner and outer members 8, (4) may be made of a metallic material or non-metallic materials such as carbon fibre, glass reinforced plastic etc.

Description

Rubber in Compression Coupling

Field of Invention

The present invention relates to a coupling. The present invention also relates to an assembly including such a coupling, and to a marine vessel including such a coupling.

The present invention also relates to a buffer element for a coupling.

Background

Couplings are used to connect rotary components such that the torque and rotational speed is transferred from one rotary component to another. Couplings typically comprise a first member coupled to a first rotary component and a second member coupled to a second rotary component.

Radial misalignment occurs in couplings when an inner member and an outer member move with respect to one another in the radial direction. Radial misalignment is undesirable because it can result in damage to the components of the coupling. Radial misalignment may occur, for example, because of an impact to the system or apparatus, such as a vehicle, of which the coupling forms a part.

It is an object of the present invention to provide a coupling that at least partially addresses one or more problems associated with existing systems whether identified herein or otherwise.

Summary

In a first aspect of the invention there is provided a coupling comprising an outer member, an inner member and a plurality of radial projections that project from the outer member and from the inner member. The projections of the outer member are interdigitated with the projections of the inner member to define a plurality of spaces. The coupling further comprising a buffer element. The buffer element comprises a first buffer element portion configured to be received in a first space of the plurality of spaces and an extension portion located radially adjacent to a projection of the plurality of projections. The extension portion is configured to buffer relative radial movement of the inner member and the outer member.

The extension portion is configured to be located radially adjacent to a projection of the plurality of projections. As such, in the assembled condition, the extension portion is located radially adjacent to a projection of the plurality of radial projections. In such an assembled condition, the extension portion is disposed between an end of a projection and a respective one of the outer member and the inner member. The extension portion being located radially adjacent to a projection of the plurality of projections may refer to the extension portion being radially spaced apart from the projection, or the extension portion adjoining, abutting, or otherwise being in contact with the projection. In addition, the extension portion may be adjacent to a projection of the plurality of projections during normal use of the coupling.

The term 'normal use' may be understood to refer to use of the coupling where the outer member and the inner member are generally radially aligned with respect to one another.

The radial projections of the inner member may be referred to as radially outward projections. The radial projections of the outer member may be referred to as radially inward projections. The radial projections of the inner member preferably radially overlap with the radial projections of the outer member.

The coupling may be an elastic coupling. The coupling may be a flexible coupling. The coupling may be a compression coupling. Therefore, the coupling is able to withstand torsional vibration.

The outer member may be the driven member of the coupling. The inner member may be the driven member of the coupling. The term driven member may be understood to mean the member of the coupling to which a load is applied.

The outer member may comprise a body. The body of the outer member may be annular. The plurality of radially inward projections may project from the body of the outer member. The inner member may define a body. The body of the inner member may be annular. The outer member comprises a plurality of radially inwardly projecting projections. The inner member comprises a plurality of radially outwardly projecting projections. The plurality of radially outward projections may project from the body of the inner member. The number of radially inward projections may be equal to the number of radially outward projections.

The plurality of projections being interdigitated may be understood to mean that the projections of the outer member are interdigitated with the projections of the inner member. This does not necessarily require radial overlap, but in embodiments, the projections on respective inner and outer members are preferably radially overlapped.

The extension portion may circumferentially overlap at least one radially inward projection and/or at least one radially outward projection. The radially inward projections may be radially overlapped with the radially outward projections.

The first buffer element portion may be generally cylindrical. The first buffer element portion may comprise a first axial end region and a second axial end region. The first axial end region and/or the second axial end region may be generally frustoconical. The width of the first axial end region and/or the second axial end region may taper in the axial direction.

Since the extension portion is configured to buffer relative movement of the inner member and outer member in the radial direction, the radial stiffness of the coupling increases during a radial misalignment event. This reduces the maximum radial displacement of the outer member and the inner member relative to one another and therefore reduces the likelihood of the outer member and inner member coming into direct contact with one another. Because of this, the likelihood of damage to the coupling during a radial misalignment event is advantageously reduced.

The extension portion may be spaced apart from the projection of the plurality of projections.

Preferably, the extension portion is spaced apart from the projection of the plurality of projections during normal use. Preferably, the extension portion is spaced apart from the projection of the plurality of projections in the radial direction. It will be appreciated that in cases where the coupling is subject to shocks or otherwise is radially misaligned, the extension portion may come into contact with a projection. In this way, the stiffness of the coupling in the radial direction is increased and resists the shock or misalignment. Where the extension portion is in contact with a projection in normal use, in the event of a shock or other radial misalignment, the projection presses the extension portion, thereby providing additional resistance to the misalignment.

Where the extension portion does not contact the projection of the plurality of projections, normal operation of the coupling is advantageously unaffected by the presence of the extension portion. When there is misalignment, an end of the projection of the plurality of projections interacts with the extension portion to increase the radial stiffness and resist the misalignment. Additionally or alternatively, the extension portion prevents or reduces contact between an end of a protrusion and an outer or inner member.

At least part of the extension portion may extend tangentially from the first buffer element portion.

Advantageously, this reduces the magnitude of stress concentrations that may be present at the region where the extension portion is connected to the first buffer element portion and second buffer element portion. The extension portion may be connected to or form part of the first buffer element portion.

The coupling may further comprise a reinforcing structure. The reinforcing structure may be at least partially embedded in the extension portion.

The reinforcing structure may be a mesh. The reinforcing structure may be referred to as a reinforcing mesh. The mesh may be formed of a fabric and/or metallic material. The extension portion may be the only part of the buffer element that is provided with a reinforcing structure.

In addition or alternative to being embedded in the extension portion, the reinforcing structure may be embedded in the first buffer element portion. Where the reinforcing structure is embedded in the first buffer element portion, the reinforcing structure of the first buffer element portion may be integrally formed with the reinforcing structure of the extension portion.

Where the coupling comprises a reinforcing structure, that is preferably embedded in the extension portion, the extension portion is advantageously strengthened. Strengthening the extension portion advantageously reduces the likelihood of the extension portion being severed and/or torn during use.

The buffer element may be positioned such that the extension portion is in a radially inner position.

The phrase radially inner position may be understood as referring to the extension portion of each buffer element being positioned, in the radial direction, between the inner member and a radially inner projection of the outer member. In the radially inner position, the extension portion is located radially inwards of a radially inward projection of the plurality of radially inward projections of the outer member.

It will be appreciated that the reverse condition is also contemplated where the buffer element is positioned such that the extension portion is in a radially outer position.

In embodiments, the coupling includes at least one extension portion in a radially inner position and at least one extension portion in a radially outer position.

The coupling may further comprise a radial gap. The radial gap may be located between a radial projection of the outer member and the extension portion of the buffer element.

The inner member may comprise a body. The shape of the extension portion of the buffer element may generally correspond with the shape of the body of the inner member.

The buffer element may be positioned such that the extension portion is in a radially outer position.

The phrase radially outer position may be understood as referring to the extension portion of each buffer element being positioned, in the radial direction, between a the body of the outer member and a radially outer projection of the inner member.

The coupling may further comprise a radial gap. The radial gap may be located between a radial projection of the inner member and the extension portion of the buffer element.

The outer member may comprise a body. The shape of the extension portion of the buffer element generally corresponds with the shape of the body of the outer member.

The hardness of the material of the extension portion may be greater than the hardness of the material of the first buffer element portion and/or of the second buffer element.

Advantageously, this improves the performance of each portion of the buffer element, and therefore the coupling as a whole.

The buffer element may further comprise a second buffer element portion. The second buffer element portion may be received in a second space of the plurality of spaces. The extension portion may connect the first buffer element portion to the second buffer element portion.

Any of the features discussed above in relation to the first buffer element portion may be applied to the second buffer element portion. This includes any combination of features. The second buffer element portion need not be identical to the first buffer element portion.

The first buffer element portion, the second buffer element portion and the extension portion may be formed as a unitary body. The first buffer element portion, the second buffer element portion and the extension portion may be integrally formed with one another.

One of the first buffer element portion and the second buffer element portion may be referred to as the lead buffer element portion and the other one may be referred to as the trailing buffer element portion. The lead buffer element portion may be understood to refer to the buffer element portion that is ahead, in the circumferential direction, in the direction that the coupling is rotating. Under normal operating conditions, the load that the trailing block is subject to is insignificant as compared to the load that the lead block is subject to.

Advantageously, the extension portion connecting the first buffer element portion to the second buffer element portion reduces the likelihood of the trailing buffer element portion, which may be either the first buffer element portion or the second buffer element portion, from migrating out of position during operation of the coupling.

At least part of the extension portion may extend tangentially from the second buffer element portion.

The extension portion may be separately formed from the first buffer element portion and/or from the second buffer element portion. The extension portion may be connected to the first buffer element portion and/or to the second buffer element portion by any suitable means.

The coupling may comprise a plurality of buffer elements.

Each buffer element of the plurality of buffer elements may comprise any combination of features described above with respect to the buffer element.

In a second aspect of the invention there is provided a buffer element for a coupling. The buffer element comprising a first buffer element portion configured to be received in a first space of the coupling. The buffer element further comprising an extension portion. The extension portion is configured to be located radially adjacent to a projection of the coupling. The extension portion is further configured to buffer relative radial movement of an inner member and an outer member of the coupling. As such, according to the second aspect of the invention, there is provided a buffer element for a coupling comprising a first buffer element portion and a circumferentially extending extension portion extending from a surface of the buffer element.

The buffer element may comprise any combination of features described above in relation to the buffer element of the coupling of the first aspect of the invention.

In a third aspect of the invention there is provided an assembly comprising a coupling according to the first aspect of the invention, a first rotatable body and a second rotatable body. The first rotatable body is coupled to the inner member and the second rotatable body is coupled to the outer member.

The first rotatable body may be a shaft. The first rotatable body may be a flywheel. The second rotatable body may be a shaft. The second rotatable body may be a flywheel.

In a fourth aspect of the invention there is provided a marine vessel comprising a coupling according to the first aspect of the invention and/or an assembly according to the third aspect of the invention.

Brief Description of the Drawings

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a coupling according to an embodiment of the present invention; Figure 2 shows a perspective view of a buffer element of the coupling of Figure Figure 3 shows a plan view of a buffer element of Figure 2; Figure 4 shows a perspective view of the buffer element Figure 2; Figure 5 shows a side view of the buffer element of Figure 2; and Figure 6 shows a detail view 'A' of the coupling of Figure 1.

Detailed Description

Referring first to Figure 1, a coupling 2 is depicted. The coupling 2 can be used to connect a first shaft, or flywheel, (not shown) to a second shaft, or flywheel, (not shown). The coupling 2 can transfer a torque of at least 100kNm. In some embodiments, the coupling 2 can transfer a torque of at least 300kNm. In some embodiments, the coupling 2 can transfer a torque of at least 500kNm. The coupling 2 defines a coupling axis 3. Throughout this description, the terms 'axial direction', 'axially' and the like will be used to refer to the direction of the coupling axis 3. The coupling 2 comprises an outer member 4 and an inner member 8. The outer member 4 is located radially outwards the inner member 8. The inner member 8 is located radially inwards of the outer member 4. The outer member 4 is generally annular. The outer member 4 defines an outer radius R. The outer radius R may be referred to as the outer radius of the coupling. The inner member 8 is generally annular. It will be appreciated that in other, non-depicted, embodiments the outer member 4 and the inner member 8 can be any other suitable shape.

The outer member 4 defines a body 5. The body 5 of the outer member 4 is generally annular. The outer member 4 comprises a plurality of radially inward projections 10 (only one of the radially inward projections is labelled in Figure 1). The plurality of radially inward projections 10 project from the body 5 of the outer member 4. The inner member 8 defines a body 7. The body 7 of the inner member is generally annular. The inner member 8 comprises a plurality of radially outward projections 16 (only one of the radially inward projections is labelled in Figure 1). The plurality of radially outward projections 16 project from the body 7 of the inner member 8.

The plurality of radially inward projections 10 of the outer member 4 are radially spaced apart from the body 7 of the inner member 8. The plurality of radially outward projections 16 of the inner member 8 are radially spaced apart from the body 5 of the outer member 4. The plurality of radially inward projections 10 of the outer member 4 are radially overlapped with the plurality of radially outward projections 16 of the inner member 8. Since the projections 10, 16 of the members 4, 8 of the coupling 2 are radially overlapped, the coupling is a fail-safe coupling. That is to say, the projections 10, 16 can engage one another in the event that the buffers fail. The plurality of radially inward projections 10 of the outer member 4 are interdigitated with the plurality of radially outward projections 16 of the inner member 8. The interdigitation of the radially inward projections 10 with the radially outward projections defines a plurality of spaces 66 (only one of which is labelled in Figure 1), as will be discussed in more detail below.

In the depicted embodiment, the outer member 4 comprises eight radially inward projections 10, although it will be appreciated that outer members having different numbers of radially inward projections are explicitly considered. The invention is not specifically limited to the depicted number of projections. The inner member 8 comprises eight radially outward projections 16. Again, it will be appreciated that this number is for example only and other numbers of projections are explicitly considered. Therefore, the number of radially inward projections 10 of the radially outer member 4 is equal to the number of radially outward projections 16 of the inner member 8. It will be appreciated that in other, non-depicted, embodiments, the number of radially inward projections 10 of the radially outer member 4 can be different to the number of radially outward projections 16 of the inner member 6.

The outer member 4 and the inner member 8 can be made of any suitable material. The outer member 4 and the inner member 8 are made of the same material. However, it will be appreciated that the outer member 4 and the inner member 8 need not be made of the same material. The outer member 4 and/or the inner member 8 can be made of a metallic material. Suitable metallic materials include but are not limited to cast iron, steel or aluminium. The outer member 4 and/or the inner member 8 can be made of a nonmetallic material. Suitable non-metallic materials include but are not limited to plastics, carbon fibre, glass-reinforced plastic or another suitable fibre-impregnated material. It will be appreciated that the material from which the outer member 4 and the inner member 8 are made of should be suitable for the torque that the coupling is intended to transfer.

The width of the outer member 4 is greater than the width of the inner member 8. In other, non-depicted embodiments, the widths of the width of the outer member 4 and the inner member 8 can be equal. In some, non-depicted, embodiments, the width of the inner member Scan be greater than the width of the outer member 4.

The coupling 2 further comprises a plurality of buffer elements 18 (only one of the buffer elements is labelled in Figure 1). In use, the buffer elements the plurality of buffer elements 18 absorb at least partially a torsional vibration that is applied to the coupling 2 by a shaft (not shown in Figure 1). Therefore, the coupling 2 is a flexible coupling. The coupling 2 can also be referred to as an elastic coupling. The buffer elements of the plurality of buffer elements 18 define the stiffness of the coupling 2. In particular, the plurality of buffer elements 18 define the rotational stiffness of the coupling 2. Rotational stiffness can be described as the angle that the coupling 2 turns through when a given load is applied to the coupling. Since the coupling 2 rotates during use, the dynamic stiffness of the coupling 2 determines whether the coupling is suitable for a particular application. In other words, the dynamic stiffness of the coupling 2 determines whether the coupling will be able to absorb vibrations sufficiently during use. The buffer elements of the plurality of buffer elements 18 can be made of any suitable material. For example, the buffer elements may be made of a rubber material. Different portions of each buffer element may be made of different materials, as will be discussed in more detail below.

Referring to Figure 2, a buffer element 18a of the plurality of buffer elements 18 is depicted. The following description of the buffer element 18a applies to the other buffer elements of the plurality of buffer elements 18 of the coupling. However, the buffer elements of the plurality of buffer elements 18 need not be identical to one another, and each buffer element of the plurality of buffer elements can comprise any suitable combination of features described with respect to the buffer element 18a.

The buffer element 18a comprises a first buffer element portion 22. The first buffer element portion 22 defines an axial length. The buffer element 18a comprises a second buffer element portion 24. The second buffer element portion 24 defines an axial length.

The axial length of the first buffer element portion 22 is generally equal to the second buffer element portion 24. However, the axial length of the first buffer element portion 22 may be greater than or less than the axial length of the second buffer element portion. The buffer element 18a comprises an extension portion 26. The extension portion 26 may be referred to as an extension buffer portion. The extension portion 26 extends between the first buffer element portion 22 and the second buffer element portion 24.

The extension portion 26 is connected to the first buffer element portion 22. The extension portion 26 is connected to the second buffer element portion 24. The extension portion 26 may be referred to as a connection portion. The extension portion 26 may be in the form of a substantially flat protrusion extending from an outer surface of the buffer element portion 22, 24. The extension portion 26 preferably extends from an outer surface of the buffer element portion 22, 24 at an angle that is other than perpendicular. In the depicted embodiment, the extension portion 26 extends from an outer surface of the buffer element portion 22, 24 such that it connects the two buffer element portions 22, 24 to form a space therebetween that is approximately the same depth as the diameter of the buffer element portions 22, 24. In this way, an outer face of the extension portion 26 can complement the curvature of the respective inner member 4 or outer member 8. As such, an inward projection 10 or an outward projection 16 can be received within the space formed by the buffer element portions 22, 24 and the extension portion 26, and there is only a small space or no space formed on the side opposite to the side on which the inward projection or outward projection is received. If there were a large space on the opposite side to the side on which the inward projection or outward projection is received, in the event of a shock causing the inward or outward projection to impinge on the extension portion 26, the extension portion 26 may be stretched and could potentially fail, for example if the extension portion extended perpendicularly from the surface of the buffer element portions and thereby formed to equally sized spaces for receiving the protrusions. In the depicted embodiment, the extension portion 26 is configured to lie against the respective inner or outer member so that in the event of shock, it is pressed against the inner or outer member and thereby supported by the inner or outer member to avoid over-stretching of the extension portion 26. It will be appreciated that the extension portion 26 may be able to accommodate at least some stretching.

The hardness of the extension portion 26 is generally equal to the hardness of the first buffer element portion 22 and of the second buffer element portion 24. However, the hardness of the extension portion 26 may be greater than the hardness of the first buffer element portion 22 and of the second buffer element portion 24. The elastic modulus of the extension portion 26 is generally equal to the elastic modulus of the first buffer element portion 22 and of the second buffer element portion 24. However, the elastic modulus of the extension portion 26 may be greater than the elastic modulus of the first buffer element portion 22 and of the second buffer element portion 24.The hardness of the first buffer element portion 22 is generally equal to the hardness of the second buffer element portion 24. However, the hardness of the first buffer element portion 22 may be greater than the hardness of the second buffer element portion 24, or vice versa. The elastic modulus of the first buffer element portion 22 is generally equal to the elastic modulus of the second buffer element portion 24. However, the elastic modulus of the first buffer element portion 22 may be greater than the elastic modulus of the second buffer element portion 24, or vice versa. The extension portion 26 may be reinforced. The extension portion 26 may be reinforced by a reinforcing structure. The reinforcing structure may be a reinforcing mesh embedded in the extension portion 26. The reinforcing mesh may be formed of a fabric and/or of a metallic material. The first buffer element portion 22 and/or the second buffer element portion 24 may be reinforced. The first buffer element portion 22 and/or the second buffer element portion 24 may be reinforced by a reinforcing structure. The first buffer element portion 22 and the second buffer element portion 24 may be reinforced by embedding a reinforcing mesh in the first buffer element portion and/or the second buffer element portion. The reinforcing mesh may be formed of a fabric and/or of a metallic material. The reinforcement of the first buffer element portion 22 and of the second buffer element portion 24 may be the same as, or may differ from, the reinforcement of the extension portion 26. Where the extension portion 26 and the first buffer element portion 22 and/or the second buffer element portion 24 the reinforcement structure of the first buffer element portion and/or of the second buffer element portion may be integral with the reinforcement structure of the extension portion.

Referring now to Figure 3, the first buffer element portion 22 comprises a first end region 28. The first buffer element portion 22 comprises a second end region 30. The first buffer element portion 22 comprises a central region 32. The central region 32 defines an axial length. The central region 32 is generally cylindrical. However, the central region 32 can be any suitable shape. The central region 32 is located axially between the first end region 28 and the second end region 32. The central region 32 defines an external surface 33. The surface 33 may be referred to as an engagement surface of the central region 32.

The first end region 28 adjoins the central region 32. The first buffer element portion 22 comprises a first end surface 34. The first end surface 34 defines a first absolute end surface, in the axial direction, of the first buffer element portion 22. The first end surface 34 forms a part of the first end region 28. The diameter of the central region 32 is greater than the diameter of the first end surface 34. The first end region 28 is tapered. The first end region 28 being tapered facilitates assembly of the buffer element 18a into the coupling. The first end region 28 comprises a first radiused portion 37. The first radiused portion 37 adjoins the central region 32. The first end region 28 comprises a second radiused portion 38. The second radiused portion 38 adjoins the first end surface 34. The first end region 28 comprises a chamfered portion 40. The chamfered portion 40 is disposed axially between the first radiused portion 37 and the second radiused portion 38. In other, non-depicted, embodiments, the first end region may comprise a single radiused portion extending from the central region of the first buffer element portion to the first end surface of the first buffer element portion. In other, non-depicted, embodiments, the first end region may comprise a single chamfered portion extending from the central region of the first buffer element portion to the first end surface of the first buffer element portion. The shape of the end region 28 reduces the likelihood of the first buffer element portion 22 being damaged or misaligned during assembly into a coupling. In particular, the radii provided to the end region 28 reduce the likelihood of a radially inward projection of the outer member (not depicted in Figure 3) and/or a radially outward projection of the inner member (not depicted in Figure 3) cutting into the first buffer element portion 22.

The second end region 30 adjoins the central region 32. The first buffer element portion 22 comprises a second end surface 36. The second end surface 36 defines a second absolute end surface, in the axial direction, of the first buffer element portion 22 in the axial direction. The second end surface 36 is opposed to the first end surface 34. The second end surface 36 forms a part of the second end region 30. The diameter of the central region 32 is greater than the diameter of the second end surface 36. The second end region 30 is tapered. The second end region 30 being tapered facilitates assembly of the buffer element 18a into the coupling. The second end region 30 comprises a first radiused portion 42. The first radiused portion 42 adjoins the central region 32. The second end region 30 comprises a second radiused portion 44. The second radiused portion 44 adjoins the second end surface 36. The second end region 30 comprises a chamfered portion 46. The chamfered portion 46 is disposed axially between the first radiused portion 42 and the second radiused portion 44. In other, non-depicted, embodiments, the second end region may comprise a single radiused portion extending from the central region of the first buffer element portion to the second end surface of the first buffer element portion. In other, non-depicted, embodiments, the second end region may comprise a single chamfered portion extending from the central region of the first buffer element portion to the second end surface of the first buffer element portion.

The second buffer element portion 24 is generally identical to the first buffer element portion 22. Therefore, the above description of the first buffer element portion 22 applies to the second buffer element portion 24. Like numerals, provided with a dash ('), for the features of the first buffer element portion 22 will be used for the second buffer element portion 24 throughout the remainder of this description. In other, non-depicted, embodiments, the second buffer element portion may differ from the first buffer element portion and may comprise any combination of features described with respect to the first buffer element portion. In further, non-depicted, embodiments, the second buffer element portion need not be provided, as will be discussed in more detail below.

With continued reference to Figure 3, the extension portion 26 comprises a first end region 48. The extension portion 26 comprises a second end region 50. The extension portion comprises a central region 52. The central region 52 is located axially between the first end region 48 and the second end region 50. The extension portion 26 comprises a first end surface 53. The first end surface 53 defines a first absolute end surface, in the axial direction, of the extension portion 26. The extension portion 26 comprises a second end surface 54. The second end surface 54 defines a second absolute end surface, in the axial direction, of the extension portion 26. The extension portion 26 defines an axial length. The axial length of the extension portion 26 is generally equal to the axial length of the central region 32 of the first buffer element portion 22. The axial length of the extension portion 26 is generally equal to the axial length of the central region 32' of the second buffer element portion 24. In other, non-depicted, embodiments, the axial length of the extension portion may be less than or greater than the axial length of the central region of the first buffer element portion and/or of the central region of the second buffer element portion.

The extension portion 26 further comprises a first surface 56. The first surface 56 extends between the first end surface 53 and the second end surface 54. Referring now to Figure 4, the extension portion further comprises a second surface 58. The second surface is opposed to the first surface (not visible in Figure 4).

Referring now to Figure 5. The first surface 56 of the extension portion 26 comprises a planar portion 60. The first surface 56 comprises a first radiused portion 62. The first radiused portion 62 adjoins the first buffer element portion 22. The first radiused portion 62 adjoins the planar portion 60. The first surface comprises a second radiused portion 64. The second radiused portion 64 adjoins the second buffer element portion 24. The second radiused portion 64 adjoins the planar portion 60. In other, non-depicted embodiments, the planar portion need not be provided. Where the first surface does not include the planar portion, the first surface may comprise a single continuous radiused portion that adjoins both the first buffer element portion and the second buffer element portion. Alternatively, the first surface may comprise a first radiused portion and a second radiused portion that adjoin one another and each adjoin a respective one of the first buffer element portion and the second buffer element portion. As a further alternative, the first surface may comprise a planar portion that adjoins both the first buffer element portion and the second buffer element portion.

The first surface 56 extends tangentially from the first buffer element portion 22. In particular, the first radiused portion 62 of the first surface 56 extends tangentially from the external surface 33 of the central region 32 of the first buffer element portion 22. The first surface 56 extends tangentially from the second buffer element portion. In particular, the second radiused portion 64 of the first surface 56 extends tangentially from the external surface 33' of the central region 32' of the second buffer element portion 24.

The second surface 58 adjoins the first buffer element portion 22. The second surface 58 adjoins the second buffer element portion 24. The second surface 58 is concave. The second surface 58 defines a radius. In other, non-depicted, embodiments, the second surface may be convex. In other, non-depicted, embodiments, the second surface may define a single planar surface. The second surface 58 extends tangentially from the first buffer element portion 22. In particular, the second surface 58 extends tangentially from the external surface 33 of the central region 32 of the first buffer element portion 22. The second surface 58 extends tangentially from the second buffer element portion. In particular, the second surface 58 extends tangentially from the external surface 33' of the central region 32' of the second buffer element portion 24.

The extension portion 26 defines a radial thickness. The radial thickness of the extension portion 26 is the distance, in the radial direction, from the first surface 56 to the second surface 58. The radial thickness of the extension portion 26 varies in the circumferential direction. The extension portion 26 defines a minimum radial thickness.

A gap 59 is defined between the first buffer element portion 22 and the second buffer element portion 24. The gap 59 extends in both the radial and circumferential directions. The gap 59 may be referred to as a space, or as a projection receiving gap or space.

The gap 59 is configured to receive a radially inward projection 10 of the outer member 4 or a radially outward projection 16 of the inner member 6.

Figure 6 shows region 'A' of Figure 1. As can be seen from Figure 6, a plurality of spaces 66 (only one of the spaces is labelled in Figure 6) are defined by the coupling 2. Each space of the plurality of spaces 66 is defined between a radially inward projection of the plurality of radially inward projections 10 and an adjacent radially outward projection of the plurality outward projections 16. The first buffer element portion 22 of each buffer element 18 is received in a respective space of the plurality of spaces 66. The first buffer element portion 22 of each buffer element 18 is engaged by a radially inward projection of the plurality of radially inward projections 10 and by a radially outward projection of the plurality of radially outward projections 16. The second buffer element portion 24 of each buffer element 18 is received in a respective space of the plurality of spaces 66. The second buffer element portion 24 of each buffer element 18 is engaged by a radially inward projection of the plurality of radially inward projections 10 and by a radially outward projection of the plurality of radially outward projections 16. The space of the plurality of spaces 66 that the first buffer element portion 22 is received in is adjacent to the space of the plurality of spaces that the second buffer element portion 24 is received in.

The extension portion 26 of each buffer element 18 engages the body 7 of the inner member 8. In particular, the second surface 58 of the extension portion 26 of each buffer element 18 engages the body 7 of the inner member 8. The shape of the second surface 58 generally corresponds with the portion of the body 7 of the inner member 8 that the second surface engages. At least part of the first buffer element portion 22 and of the second buffer element portion 24 can also engage the body of the inner member 8. This configuration can be referred to as the extension portion 26 of each buffer element 18 being in a radially inner position.

In the radially inner position, the gap (not visible in Figure 6-a radially inward projection 10 is received in the gap) of each buffer element 18 receives a respective radially inward projection of the plurality of radially inward projections 10. At least part of the first buffer element portion 22 and at least part of the second buffer element portion 24 of the buffer element 18 engages the radially inward projection that is received by the gap 59. The radially inward projection is spaced apart from the extension portion 26. In particular, the radially inward projection is spaced apart from the extension portion 26 in the radial direction. In particular, the radially inward projection is spaced apart from the first surface 56 of the extension portion 26 in the radial direction. During normal use, the radially inward projection does not contact the extension portion 26. The term 'normal use' may be understood to refer to use of the coupling 2 while the outer member 4 is generally radially aligned with the inner member 8.

A misalignment event may occur during use of the coupling 2. The misalignment event may involve a translational misalignment and/or an angular misalignment of the coupling 2, which may collectively be referred to as a radial misalignment. The misalignment event may also involve an axial misalignment of the coupling. The term 'translational misalignment' may be understood to mean that the central axis of the outer member 4 and of the inner member 8 of the coupling 2 are not coincident with one another. This may be due to a translation of the central axes of the outer member 4 and the inner member 8 relative to one another. The term 'angular misalignment' may be understood to mean that an angle is defined between the central axis of the outer member 4 and of the inner member 8 of the coupling 2. That is to say, the central axis of the outer member 4 and of the inner member 8 of the coupling may be non-parallel. The term 'axial misalignment' may be understood to mean that at least one of the outer member 4 and the inner member 8 moves relative to the other in the direction of the coupling axis 3. A radial misalignment event may occur, for example, if the system or apparatus, such as a vehicle, that the coupling 2 forms a part of is subject to an impact. During a radial misalignment event, the radial separation between the radially inward projections of the plurality of radially inward projections 10 of the outer member 4 and the body 7 of the inner member 8 may reduce. Alternatively or additionally, the radial separation between the radially outward projections of the plurality of radially outward projections 16 of the inner member 8 and the body 5 of the outer member 4 may reduce.

The radial separation between the radially inward projections of the plurality of radially inward projections 10 of the outer member 4 and the body 7 of the inner member 8 may be such that, in the absence of the extension portion 26, one or more of the radially inward projections of the plurality of radially inward projections 10 contacts the body 7 of the inner member 8, and/or one or more of the radially outward projections of the plurality of radially outward projections 16 contacts the body 5 of the outer member 4. This is undesirable because the body 5 of the outer member 4, the body 7 of the outer member 8 and/or the one or more projections that contact the respective body 5, 7 can become damaged by such contact. The extension portion 26 of the present coupling 2 advantageously reduces the likelihood of such damage. This is because the extension portion 26 acts to buffer movement of the inner member 4 and the outer member 8 relative to one another. In particular, the extension portion 26 acts to buffer relative radial movement of the inner member 4 and the outer member 8. Since the extension portion 26 is radially spaced apart from the radially outward projection, the impact of the extension with the characteristics of the coupling 2 during normal operating conditions is reduced relative to if the extension portion were to contact the radially outward projection during normal operation.

The extension portion 26 also contributes towards maintaining a trailing buffer element portion of the first buffer element portion 22 and the second buffer element portion 24 correctly located within the space of the plurality of spaces 66 that it is received in. The trailing buffer element portion is the one of the first buffer element portion 22 and the second buffer element portion 24 that is unloaded during operation of the coupling 2.

The one of the first buffer element portion 22 and the second buffer element portion 24 that is loaded during operation of the coupling 2 is referred to as the lead buffer element portion. Which of the first buffer element portion 22 and the second buffer element portion 24 is the trailing buffer element portion and which is the lead buffer element portion is determined by which of the outer member 4 and the inner member 8 is connected to a driven component. The driven component may be, for example, the drive shaft of an engine (not shown in the figures). If the outer member 4 is connected to a driven component then the second buffer element portion 24 is the trailing buffer element portion and the first buffer element portion 22 is the lead buffer element portion. If the inner member 8 is connected to a driven component then the first buffer element portion 22 is the trailing buffer element portion and the second buffer element portion 24 is the lead buffer element portion. Because the extent to which the trailing buffer element is loaded is insignificant, the trailing buffer element portion can be susceptible to moving within the space of the plurality of spaces 66 that it is received in. The trailing buffer element portion can even begin to move into an adjacent space of the plurality of spaces.

Since the extension portion 26 is connected to the first buffer element portion 22 and to the second buffer element portion 24, the extension portion 26 is advantageously able to help retain the trailing buffer element portion in a correct position.

In other, non-depicted, embodiments, one of more of the plurality of buffer elements may be positioned in a radially outer portion. In the radially outer position, the extension portion of each buffer element engages the body of the outer member. In particular, the second surface of the extension portion of each buffer element engages the body of the outer member. The shape of the second surface of the one or more buffer elements that are placed in a radially outer position generally corresponds with the shape of the body of the portion of the outer that the second surface engages. Buffer elements having extension portions with convex second surfaces may be used for the buffer elements that are placed in a radially outer position. At least part of the first buffer element portion and of the second buffer element portion can also engage the body of the outer member.

In the radially outer position, the gap of each buffer element receive a respective radially outward projection of the plurality of radially outward projections. At least part of the first buffer element portion and at least part of the second buffer element portion of the buffer element engages the radially outward projection that is received by the gap. The radially outward projection is spaced apart from the extension portion. In particular, the radially outward projection is spaced apart from the extension portion in the radial direction. In particular, the radially outward projection is spaced apart the first surface of the extension portion in the radial direction. During normal use, the radially outward projection does not contact the extension portion.

In some, non-depicted, embodiments, the buffer elements of the plurality of buffer elements only comprise a first buffer element portion. Where the buffer elements of the plurality of buffer elements comprise only a first buffer element portion, the buffer elements may be arranged alternatively in the radially inner position and the radially outer position. Advantageously, this may further protect the inner member and/or the outer member from damage during a radial misalignment event.

In some, non-depicted, embodiments, only one buffer element of the plurality of buffer elements comprising an extension portion as described herein may be provided. Where only one buffer element comprising an extension portion is provided, the remaining spaces of the plurality of spaces can receive buffer elements of any suitable shape.

In some, non-depicted, embodiments, the coupling may further comprise one or more further members that is located radially inwards of and/or radially outwards of the inner and/or outer member of the coupling. In these embodiments, the coupling may define one or more intermediate members. The intermediate members may comprise both a plurality of radially inward projections and a plurality of radially outward projections.

In some, non-depicted, embodiments, two buffer element portions of adjacent buffer elements of the plurality of buffer elements may be received in a single space of the plurality of spaces. Where this is the case, the buffer element portions of adjacent buffer elements may be formed to be of complementary shape. Therefore, once the two buffer elements are received in the coupling, the two buffer element portions together occupy the space.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. The depicted embodiments of the present invention are in order to assist in the understanding of the invention, which is defined in the appended claims.

Claims

CLAIMS: 1. A coupling comprising: an outer member; an inner member; and a plurality of radial projections that project from the outer member and from the inner member; wherein the projections of the outer member are interdigitated with the projections of the inner member to define a plurality of spaces; the coupling further comprising a buffer element, the buffer element comprising: a first buffer element portion configured to be received in a first space of the plurality of spaces; and an extension portion located radially adjacent to a projection of the plurality of projections, wherein the extension portion is configured to buffer relative radial movement of the inner member and the outer member.
2. The coupling of claim 1, wherein the extension portion is spaced apart from the projection of the plurality of projections.
3. The coupling of claim 1 or claim 2, wherein at least part of the extension portion extends tangentially from the first buffer element portion.
4. The coupling of any preceding claim, further comprising a reinforcing structure, the reinforcing structure being at least partially embedded in the extension portion.
5. The coupling of any preceding claim, wherein the buffer element is positioned such that the extension portion is in a radially inner position.
6. The coupling of claim 5, further comprising a radial gap, the radial gap being located between a radial projection of the outer member and the extension portion of the buffer element.
7. The coupling of claim 5 or claim 6, wherein the inner member comprises a body and wherein the shape of the extension portion of the buffer element generally corresponds with the shape of the body of the inner member.
8. The coupling of any of claims 1 to 4, wherein the buffer element is positioned such that the extension portion is in a radially outer position.
9. The coupling of claim 8, further comprising a radial gap, the radial gap being located between a radial projection of the inner member and the extension portion of the buffer element.
10. The coupling of any of claims 7 to 9, wherein the outer member comprises a body and wherein the shape of the extension portion of the buffer element generally corresponds with the shape of the body of the outer member.
11. The coupling of any preceding claim, wherein the buffer element further comprises a second buffer element portion, the second buffer element portion being received in a second space of the plurality of spaces, and wherein the extension portion connects the first buffer element portion to the second buffer element portion.
12. The coupling of claim 11, wherein at least part of the extension portion extends tangentially from the second buffer element portion.
13. The coupling of any preceding claim, further comprising a plurality of buffer elements.
14. A buffer element for a coupling, the buffer element comprising: a first buffer element portion configured to be received in a first space of the coupling; an extension portion that is configured to be located radially adjacent to a projection of the coupling and is configured to buffer relative radial movement of an inner member and an outer member of the coupling.
15. An assembly comprising: a coupling according to any of claims 1 to 13, a first rotatable body and a second rotatable body; wherein the first rotatable body is coupled to the inner member and the second rotatable body is coupled to the outer member.
16. A marine vessel comprising a coupling according to any of claims 1 to 13 and/or an assembly according to claim 15.