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Title:
DAMPER ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2014/060776
Kind Code:
A1
Abstract:
A damper assembly has a chain, a first mounting element and a second mounting element. The chain has a longitudinal axis and comprising a plurality of links pivotally interconnected by transverse articulation elements. It has a straight configuration in which the links are substantially aligned in a linear direction, and has at least one resilient member configured to force adjacent links of the chain to articulate out of the straight configuration. The first and second mounting elements are each attached to the chain and are movable relative to one another between a first position and a second position, and are arranged to urge the chain towards the straight configuration when they are moved towards the second position.

Inventors:
CHRISTMAS, Michael Charles (55 Berkshire Drive, WoolstonWarrington, Cheshire WA1 4EY, GB)
PYPER, Torquil Edmund (Benmor, Duns Tew RoadHempton, Oxfordshire OX15 0QZ, GB)
Application Number:
GB2013/052731
Publication Date:
April 24, 2014
Filing Date:
October 18, 2013
Export Citation:
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Assignee:
RENOLD PLC. (Styal Road, Wythenshawe, Greater Manchester M22 5WL, GB)
International Classes:
F16F7/00; F16G13/06
Foreign References:
JPH07172786A1995-07-11
DE1087413B1960-08-18
GB1020087A1966-02-16
Attorney, Agent or Firm:
MARKS & CLERK (1 New York Street, Manchester, Greater Manchester M1 4HD, GB)
Download PDF:
Claims:
CLAIMS

1. A damper assembly comprising:

a chain having a longitudinal axis and comprising a plurality of links pivotally interconnected by transverse articulation elements, the chain having a straight configuration in which the links are substantially aligned in a linear direction and at least one resilient member configured to force adjacent links of the chain to articulate out of the straight configuration, and

a first mounting element and a second mounting element each attached to the chain, the mounting elements being movable relative to one another between a first position and a second position and being arranged to urge the chain towards the straight configuration when they are moved towards the second position.

2. A damper assembly according to claim 1 wherein the resilient member is a flexible elongate resilient member threaded along at least part of the length of the chain.

3. A damper assembly according to claim 1 or 2 wherein the chain is located within a reservoir that is arranged to contain damping fluid. 4. A damper assembly according to any preceding claim wherein the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston, the piston being slidably received within the cavity.

5. A damper assembly according to claim 4 wherein the piston defines a piston cavity therein.

6. A damper assembly according to claim 5 wherein the chain is at least partially received within the piston cavity. 7. A damper assembly according to claim 6 wherein one portion of the chain is attached to the piston, and another portion of the chain is attached to the first mounting element via a protrusion projecting through an aperture in the piston.

8. A damper assembly according to any one of claims 4-7 wherein the mounting element cavity and the piston co-operatively form a piston pump mechanism arranged to displace a damping fluid. 9. A damper assembly according to claim 8 wherein the piston pump mechanism is arranged to displace damping fluid into the piston cavity.

10. A damper assembly according to any preceding claim wherein the damper assembly further comprises a housing unit with a housing unit cavity, the first mounting element being slidably received within the housing unit cavity.

1 1. A damper assembly according to claim 10, when dependent on claim 8 or 9, wherein the piston pump mechanism is arranged to displace damping fluid into the housing unit cavity.

12. A damper assembly according to any preceding claim comprising two counterposed second mounting elements

13. A damper assembly according to claim 12, when dependent on any preceding claim incorporating claim 4, wherein each of the second mounting elements comprises a piston, both pistons being received within the mounting element cavity.

14. A damper assembly according to claim 12 or 13 wherein the chain is attached to the first mounting element at a first location along its longitudinal axis, and is attached to each of the second mounting elements at locations along its longitudinal axis that are on opposite sides of the first location.

15. A damper assembly according to any one of claims 12-14 wherein the two counterposed second mounting elements are connected such that their relative movement is restricted.

16. A damper assembly according to any preceding claim wherein the chain comprises one or more extensions configured to increase the resistance to motion of the chain due to drag.

17. A damper assembly according to claim 16 wherein the extensions are configured to co-operatively define one or more voids between neighbouring extensions, the shape of each of said voids being variable according to the configuration of the chain. 18. A damper assembly according to claim 17 wherein at least some of the extensions are shaped to maintain a predetermined clearance with neighbouring extensions when the chain articulates out of the straight configuration.

19. A damper assembly according to any preceding claim comprising a plurality of said chains comprised within a chain assembly, wherein:

each of the plurality of chains runs between a first connection bracket and a second connection bracket of the chain assembly;

the first and second connection brackets are movable between a first position and a second position and are arranged to urge each of the chains towards the straight configuration when they are moved towards the second position;

the first and second mounting elements of the damper assembly are arranged to urge each chain towards the straight configuration by urging the first and second connection brackets towards their second position. 20. A damper assembly according to claim 19 wherein each of said chains defines an articulation plane within which the links can pivot, and the plurality of chains are positioned whereby their respective articulation planes are substantially parallel.

21. A damper assembly according to claim 19 wherein each of said chains defines an articulation plane within which the links can pivot, and at least two of said chains are positioned whereby their respective articulation planes are non-parallel.

22. A damper assembly according to any one of claims 19-21 wherein the chain assembly further comprises a damper sub-assembly configured to damp movement of the first and second connection brackets relative to one another.

23. A damper assembly according to claim 22 wherein the damper sub-assembly comprises an elongate piston extending between the first and second connection brackets, and at least one of the first and second connection brackets defines a fluid cavity within which the piston is slidably received, relative movement of the first and second connection brackets causing the piston to slide within the fluid cavity.

24. A damper assembly according to claim 22 or 23 wherein the damper sub-assembly comprises a deformable bladder which defines a fluid cavity therein, relative movement of the first and second connection brackets causing the bladder to change shape, thereby changing the shape of the fluid cavity.

25. A damper assembly according to claim 23 or 24 wherein the chain assembly comprises a duct in fluid communication with the fluid cavity or cavities.

26. A damper assembly according to any one of claims 19-25 wherein the chain assembly further comprises a resiliently deformable element configured to be deformed by relative movement of the first and second connection brackets.

27. A damper assembly according to claim 26 wherein the resiliently deformable element is configured to be deformed by movement of the first and second connection brackets towards the first position. 28. A damper assembly according to claim 26 or 27 wherein the resiliently deformable element is configured to be deformed by movement of the first and second connection brackets towards the second position.

29. A damper assembly according to any one of claims 19-28 wherein the chain assembly further comprises an alignment structure positioned to prevent at least two of the chains from contacting each other.

Description:
Damper Assembly

The present invention relates to a damper assembly of the kind that may be used, for example, in automotive suspension systems.

Conventional damper assemblies for automotive suspension utilise a coil spring connected in parallel with a cylinder and piston. When the damper assembly is disturbed by the application of a load, the spring is deformed and the piston moves within the cylinder. The deformed spring provides a restorative force, urging the damper back to its default position, and movement of the piston displaces fluid within the cylinder, dissipating energy and bringing about a damping effect. In such damper assemblies, failure of the coil spring can lead to the damper assembly failing catastrophically under load. This, in turn, can cause damage to other components, for instance in the case of a vehicle suspension system the vehicle chassis or bodywork may impact the ground.

It is one object of the present invention to provide an improved or alternative damper assembly. According to a first aspect of the present invention there is provided a damper assembly comprising: a chain having a longitudinal axis and comprising a plurality of links pivotally interconnected by transverse articulation elements, the chain having a straight configuration in which the links are substantially aligned in a linear direction and at least one resilient member configured to force adjacent links of the chain to articulate out of the straight configuration, and a first mounting element and a second mounting element each attached to the chain, the mounting elements being movable relative to one another between a first position and a second position and being arranged to urge the chain towards the straight configuration when they are moved towards the second position.

One advantage of the present invention is that it can allow the portion of the damper assembly which provides the restorative force, and the portion which brings about the damping effect, to be at least partially independent of one another. This can be advantageous in providing a degree of redundancy. For instance, if the resilient member were weaker than the chain, then any failure of the former would not be catastrophic since load applied to the damper assembly could still be carried by the chain. A second advantage arises in that the components of the damper assembly moving over each other (and/or being deformed) can provide inherent damping capabilities as outlined below. In contrast, a conventional coil spring offers very little inherent damping. Further, the extent of inherent damping may be selectively varied by virtue of the configuration and geometry of the chain and resilient member, and/or the use of lubricant and/or damping fluid (or lack thereof).

The chain may be a roller-bush chain. Where the chain is a roller bush chain, the resilient member may bear against one or more of the rollers. One or more rollers may be attached to or integral with the resilient member.

The resilient member may be connected to one of the mounting elements. For example, it may be attached to the first or second mounting element at one end. Alternatively, the resilient member may be attached to the chain. For instance, it may be attached at one end of the chain and/or resilient member, at both ends of the chain and/or resilient member, or at an intermediate location along the length of the chain and/or resilient member. When the chain is subjected to a tensile load (i.e. is urged towards the straight configuration) by the mounting elements, the links tend towards the straight configuration but are resisted by the resilient member, which may deflect as a consequence. The resilient member is arranged such that when the tensile load is removed it returns to its original shape.

The resilient member applies a reactive force to the chain when the chain is subjected to a tensile load, by virtue of it being deflected and its resilience. The tensile load forces the chain links to move towards the straight configuration but the reactive force of the resilient member acts on the chain (and preferably on individual chain links) so as to resist such movement.

The resilient member thus acts in a manner analogous to a spring. The reactive force may act in the manner of a spring constant in that it may change in proportion to the tensile load applied. It may change in a linear or non-linear relationship. The magnitude of the reactive force may be dependent on a combination of the configuration and geometry of the resilient member and the mechanism of the chain elements. In one embodiment the resilient member acts like a constant-force spring such that the force it exerts over its range of motion is a constant. The resilient member may provide a degree of damping by virtue of movement of the links relative to the resilient member, the friction between the two providing sufficient energy losses to achieve effective damping. Alternatively or in addition, damping may be designed into the chain by virtue of the resilient member comprising a suitable elastomeric material that absorbs some of the energy (such as an elastomeric polymer). The member may wholly comprise such a material or may be made in part from such material. For example, the resilient member may comprise a core material and an elastomeric polymer coating, such as, for example, nitrile rubber or other synthetic rubber copolymer. The core material may be any suitable material that has sufficient stiffness such as a metal. One example is steel and preferably a spring steel. Instead or in addition, the chain may have rollers made from a suitable elastomeric damping material such as a polymeric damping material. The material may be injection mouldable. The size and/or thickness of the rollers may vary along the length of the chain in order to provide different damping characteristics along the chain. Alternatively or in addition, the material of the rollers may vary along the length of the chain.

The chain may be disposed between guide members for guiding movement of the chain.

The chain may be substantially enclosed within the damper assembly. For example, it may be contained in a space provided in one of the mounting elements or in a space co-operatively provided by more than one of the mounting elements. Alternatively, the chain may be only partially enclosed or may be in an exposed position.

The resilient member may be a resilient elongate flexible member threaded along at least part of the length of the chain. One advantage of such an arrangement is that if the resilient member breaks, in some embodiments it can be retained in position by the chain, at least for a period of time, allowing any intact portions of the resilient member to continue to offer a restorative force (albeit at a reduced effectiveness). Instead, the resilient member may take the form of a resilient elongate flexible loop held within the chain, or may take the form of an elastomeric block held within the chain. Alternatively, it may take any other suitable form and be in any other suitable position, for instance it may be a resilient elongate flexible which is not threaded along at least part of the length of the chain. Alternatively, the resilient member may take the form of a resilient elongate flexible member, but not be threaded between the chain links. In either case, it may be deflected into an undulating form as the chain links articulate towards the straight configuration, and tend towards the straight, linear configuration (but may be prevented from being perfectly straight by virtue of the chain links).

The damper assembly may have a plurality of resilient members disposed in a side-by- side relationship. This may be advantageous in that the resilient members moving against one another may increase energy dissipation, thereby improving the damping capability of the assembly.

The chain may be located within a reservoir that is arranged to contain damping fluid. The reservoir may contain damping fluid. Damping fluid is any fluid (liquid or gas) which exhibits sufficient viscosity to be useful in dissipating kinetic energy applied to it, such as natural or synthetic oil or grease, or water. The damping fluid may be manufactured from viscous synthetic oil, and/or have a viscosity in the region of 30,000-70,000 cSt and preferably around 50,000 cSt. The reservoir may be partially of completely filled with damping fluid. Alternatively, the damper assembly may have no such reservoir. In this case no damping fluid may be present in contact with the chain, or one or more moving parts of the chain may be coated with damping fluid. The moving parts may be one or more selected from the group comprising the links, rollers, pins, bushes or the resilient member. The presence of damping fluid in contact with the chain, whether it is in a reservoir or as a coating on parts of the chain itself, may increase the damper constant of the assembly. The damping fluid may also function as a lubricant, and/or have the effect of reducing the noise of the chain in use.

In one embodiment of the invention, the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston, the piston being slidably received within the cavity. The mounting element cavity and the piston may be of complementary shape. Each may be cylindrical (of circular or ovoid cross-section), prismatic, or of any other suitable shape. One or more sealing members may be interposed between the piston and the mounting element cavity. The mounting element cavity and the piston may define a common longitudinal axis along which they are movable relative to one another. The longitudinal axis of the chain (when it is in the straight configuration) may or may not be in line with or parallel to the common longitudinal axis of the mounting element cavity and piston.

In the above embodiment, the piston may define a piston cavity therein. The piston cavity may be fully enclosed, substantially fully enclosed or only partially enclosed, by the piston or by the piston and other components. It may be cylindrical (of circular or ovoid cross-section), prismatic, or of any other suitable shape. Alternatively, the piston may be solid.

In an embodiment where the piston defines a piston cavity, the chain is at least partially received within the piston cavity. Where the chain is only partially received within the piston cavity it may be partially exposed, or may be partially received within another component (for example the mounting element cavity). Alternatively, the chain may be in a fully exposed position, and/or may be fully or partially received in a different component of the damper assembly (such as the mounting element cavity). In the above embodiment one portion of the chain may be attached to the piston, and another portion of the chain attached to the first mounting element via a protrusion projecting through an aperture in the piston. Where the mounting element cavity and the piston define a common longitudinal axis along which they are movable relative to one another, the protrusion may project substantially radially through the aperture in the piston, and/or the aperture may be in the form of an elongate slot substantially parallel with the common longitudinal axis of the mounting element cavity and piston. The protrusion may be a pin extending through an aperture in a chain link.

Alternatively, in the above embodiment the damper assembly may further comprise a plug slidably received within the piston cavity, one portion of the chain being attached to the piston and another portion of the chain being attached to the plug. The plug may be of complementary shape to the piston cavity. It may be cylindrical, prismatic, or of any other suitable shape. There may be one or more sealing members interposed between the plug and the piston cavity. Where the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston slidably received within the mounting element cavity, the mounting element cavity and the piston may co-operatively form a piston pump mechanism arranged to displace a damping fluid. The damper assembly may contain damping fluid arranged to be displaced by the piston pump mechanism. In embodiments where the chain is located within a reservoir of damping fluid, the damping fluid in the reservoir and damping fluid displaced by the piston pump may or may not be of the same composition. Where the fluid is of the same composition, the fluid in the reservoir may or may not be displaced by the piston pump.

Where the damper assembly includes a piston cavity, the piston pump mechanism may be arranged to displace damping fluid into the piston cavity.

The damper assembly may further comprise a housing unit with a housing unit cavity, the first mounting element being slidably received within the housing unit cavity.

Where a damper assembly has a housing unit and a piston pump mechanism, the piston pump mechanism may be arranged to displace damping fluid into the housing unit cavity.

In one embodiment, the damper assembly comprises two counterposed second mounting elements. The two counterposed second mounting elements may or may not be substantially identical to one another and/or substantially mirror images of each other.

Where the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston, in the above embodiment each of the second mounting elements may comprise a piston, both pistons being received within the mounting element cavity. Alternatively, the damper assembly may comprise more than one mounting element cavity and the pistons may be received within different mounting element cavities.

In the above embodiment, the chain may be attached to the first mounting element at a first location along its longitudinal axis, and attached to each of the second mounting elements at locations along its longitudinal axis that are on opposite sides of the first location. The first location may or may not be substantially equidistant from the points at which the second mounting elements are attached. Alternatively, the damper assembly may have separate chains attached to each of the second mounting elements.

In the above embodiment, the two counterposed second mounting elements may be connected such that their relative movement is restricted. The second mounting elements may be substantially prevented from moving relative to one another. Alternatively, each of the second mounting elements may be free to move independently of the other.

In a damper assembly according to the first aspect of the invention the chain may comprise one or more extensions configured to increase the resistance to motion of the chain due to drag. The extensions may induce drag in air, or in a damping fluid surrounding the chain. The extensions may be in the form of plates, which may each be attached to a link of the chain and be positioned substantially orthogonally to it. Alternatively, they may take any other suitable shape (for instance they may take the form of elongate members or arrays thereof), may be attached in any other suitable way and/or may be in any other suitable orientation.

The extensions may be configured to co-operatively define one or more voids between neighbouring extensions, the shape of each of said voids being variable according to the configuration of the chain. At least some of the extensions may be shaped to maintain a predetermined clearance with neighbouring extensions when the chain articulates out of the straight configuration. For instance, some extensions may be provided with a convex shape configured to maintain a particular clearance with neighbouring extensions of a flat shape. As another example, all the extensions may have convex surfaces which are shaped to maintain a predetermined clearance with the convex surfaces of adjacent extensions. By utilising this latter arrangement, the volume of each void can be maintained at a substantially constant level when the chain articulates out of the straight configuration. The damper assembly may comprise a plurality of said chains comprised within a chain assembly, wherein:

each of the plurality of chains runs between a first connection bracket and a second connection bracket of the chain assembly;

the first and second connection brackets are movable between a first position and a second position and are arranged to urge each of the chains towards the straight configuration when they are moved towards the second position;

the first and second mounting elements of the damper assembly are arranged to urge each chain towards the straight configuration by urging the first and second connection brackets towards their second position.

The first and second mounting elements of the damper assembly may be attached to the second and first connection brackets respectively, or vice versa. Each chain may be attached to the first and second connection brackets. First and second ends of each chain may be attached to the first and second connection brackets respectively.

Each of the plurality of chains may be different, or one or more of the plurality may be substantially identical to one another. For instance, if one of the chains comprises one or more of the features described above, each of the other chains may or may not also comprise those features. Two or more of the chains may be positioned substantially parallel to one another when the first and second connection brackets are in the second position. Each of said plurality of chains may define an articulation plane within which the links can pivot, and the plurality of chains may be positioned whereby their respective articulation planes are substantially parallel.

All of the plurality of the chains may be so positioned. For the avoidance of doubt, reference to planes being parallel is intended to include their being coplanar.

Alternatively, and at least two of said chains may be positioned whereby their respective articulation planes are non-parallel.

All of the plurality of chains may be positioned such that none are parallel to each other. The chain assembly may further comprise a damper sub-assembly configured to damp movement of the first and second connection brackets relative to one another. The damper sub-assembly may be configured to damp movement of the connection brackets towards the first position and/or towards the second position. The damper sub-assembly may take any suitable form. For instance, it may be a dashpot, a piston pump, an electromagnetic damper, an elastomeric component which dissipates energy through hysteresis.

The damper sub-assembly may comprise an elongate piston extending between the first and second connection brackets, and at least one of the first and second connection brackets defines a fluid cavity within which the piston is slidably received, relative movement of the first and second connection brackets causing the piston to slide within the fluid cavity.

Both the first and second connection brackets may define fluid cavities within which the piston is slidably received. The damper sub-assembly may comprise a deformable bladder which defines a fluid cavity therein, relative movement of the first and second connection brackets causing the bladder to change shape, thereby changing the shape of the fluid cavity.

The change of shape of the fluid cavity in the bladder may be a change in geometric shape (for instance a change in aspect ratio) and/or a change in volume.

The chain assembly may comprise a duct in fluid communication with the fluid cavity or cavities. The duct may run through one or both of the connection brackets, or may be positioned in any other suitable location. For instance, where the chain assembly comprises a piston the duct may run through the piston.

The chain assembly may further comprise a resiliently deformable element configured to be deformed by relative movement of the first and second connection brackets. The resiliently deformable element may be an elastomeric component such as a tube, sheet or block, or it may be a spring such as a coil spring, leaf spring or Belleville washer. Alternatively, it may take any other suitable form.

The resiliently deformable element is configured to be deformed by movement of the first and second connection brackets towards the first position.

Alternatively or in addition, the resiliently deformable element may be configured to be deformed by movement of the first and second connection brackets towards the second position.

The chain assembly may further comprise an alignment structure positioned to prevent at least two of the chains from contacting each other.

The alignment structure may be positioned to prevent all the plurality of chains from contacting each other.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a chain of a damper assembly according to a first embodiment of the invention;

Figures 2a-2c are cross-sectional side views of the chain of figure 1 in different configurations;

Figures 3a-3c are cross-sectional side views of a damper assembly according to a first embodiment of the invention, in different configurations;

Figure 4 is a cross-sectional side view of a modification of the damper assembly of the first embodiment;

Figure 5 is a cross-sectional side view of a further modification of the damper assembly of the first embodiment;

Figure 6 is a cross-sectional side view of a damper assembly according to a second embodiment of the invention;

Figure 7 is a cross-sectional side view of a damper assembly according to a third embodiment of the invention; Figure 8 is a side view of a modification of the third embodiment of the invention, shown in partial cross-section;

Figures 9a and 9b are side and perspective views respectively of a damper assembly according to a fourth embodiment of the invention, shown in partial cross-section;

Figure 10 is a perspective view of a chain suitable for use in the invention;

Figures 1 1 a-1 1c are side views of the chain of figure 10;

Figure 12 is a side view of another chain suitable for use in the invention;

Figure 13 is a side view of a further chain suitable for use in the invention;

Figure 14 is a cross-sectional side view of another modification of the first embodiment of the invention;

Figure 15 is a cross-sectional side view of a further modification of the first embodiment of the invention;

Figure 16 is a cross-sectional side view of an additional modification of the first embodiment of the invention;

Figure 17 is a schematic side-view of a damper assembly according to a fifth embodiment of the invention;

Figure 18 is a perspective view of a first embodiment of a chain assembly for use as part of a damper assembly according to any of the preceding embodiments;

Figure 19 is a side view of the chain assembly of Figure 18;

Figure 20 is a front view of the chain assembly of Figure 18;

Figure 21 is a perspective view of a modification of the chain assembly of Figure 18;

Figure 22 is a perspective cutaway view of a second embodiment of a chain assembly for use as part of a damper assembly according to any of the preceding embodiments;

Figure 23 is a perspective cutaway view of a modification of the chain assembly of Figure 22;

Figure 24 is a perspective cutaway view of a modification of the chain assembly of Figure 23; and

Figure 25 is a perspective cutaway view of a modification of the chain assembly of Figure 24.

Referring now to figure 1 of the drawings, a chain 1 of a damper of a first embodiment of the invention is a roller bush chain, although it is to be understood other chain types may be used. The roller bush chain 1 comprises a plurality of inner link assemblies 2 that are interconnected along the length of the chain by outer link plates 4 such that the inner link assemblies can articulate relative to each other. Each inner link assembly 2 comprises a pair of opposed spaced inner link plates 6 connected together by a pair of bushes 8 (most of which are hidden in figure 1 ) extending perpendicularly to the plates 6. Each of the inner link plates 6 has a pair of spaced apertures 10 in which the ends of the pair of bushes 8 are received. Each of the opposed inner link plates 6 is mounted in a friction or interference fit on the ends of the bushes 8 in a fixed relationship and a rotatable cylindrical roller 12 is supported on each bush 8 between the inner link plates 6.

The outer link plates 4 are of similar configuration to the inner link plates 6 but with smaller apertures 14 and are arranged to connect together adjacent inner link assemblies 2. A given outer link plate 4 overlaps with adjacent inner link assemblies 2 such that each of its apertures 14 is aligned with a corresponding aperture 10 in the inner link assembly 2 and is connected to the inner link assemblies 2 by pins 16 that pass through the aligned apertures 10, 14 and are received in the bushes 8. The apertures 10 in the inner link assemblies 2 are sized such that the assemblies are free to rotate on the pins 16 but the outer link plates 4 are fixed to the pins 16. More specifically, the apertures 14 in the outer link plates 4 are sized such that the edge of the plate around them is an interference or friction fit with the pins 16.

The chain 1 further comprises a resilient member which in this embodiment is in the form of an elongate flexible member 20 that is threaded through the inner link assemblies 2, along the length of the chain, in a sinuous formation. The elongate flexible member 20 is made of any suitable resilient material that is elastically deformable in a direction substantially perpendicular to its longitudinal axis in the manner shown in figure 2. It is able to move relative to the chain 1 , although in order to prevent the elongate flexible member 20 working free of engagement with the chain it may be loosely connected to the chain at each end, or otherwise retained as outlined below.

In this arrangement the elongate flexible member 20 is threaded through the chain 1 such that it alternately passes over and under successive rollers 12 of the chain (in other embodiments however, it may be arranged to miss one or more rollers, for instance it may pass over and under successive pairs of rollers). This can be seen most clearly in figures 2a-2c in which the member is shown in solid line for clarity. The resilient member 20 is designed such that in the undeformed state it tends towards a straight (linear) configuration (without undulations along its length), as shown in figure 2a. As a result the chain links 2, 4 are forced to articulate on the pins 16 and the chain 1 adopts a zig-zag configuration, i.e. a non-straight configuration, in which the link assemblies 2 are disposed at an angle to the outer link plates 4. Thus the inner link assemblies 2 on each side of a pin 14 (which defines an articulation axis) are forced to move in opposite directions resulting in contraction of the chain length compared to when it is in a straight configuration.

The arrangement allows the chain 1 to behave in the manner of a spring in that a load applied to the chain in a direction that tends to straighten the chain, such that the link plates 4, 6 are moved towards a straight configuration, is resisted by the elongate flexible member 20. As the load increases the chain 1 is forced towards the straight configuration and the undulating form of the flexible member 20 increases, thereby offering greater resistance to the load. This is shown in figure 2b. The resistance operates in the manner of a spring force i.e. the force the member exerts on the chain links is proportional to its deflection. When the load has reached a magnitude such that the chain is pulled to the straight configuration, as shown in figure 2c, the flexible member 20 will not deflect any further and the load is carried entirely through the chain links, thus providing a hard stop. A graph of load plotted against deflection would show a curve that is initially steep but which flattens out. In some embodiments the resilient member may be compressed by the chain links in a direction transverse to its length such that its thickness is reduced.

The resilient elongate flexible member 20 may be made from any suitable flexible material such as for example, a polymer, steel, a synthetic or natural fibrous material, or a composite material. It is resilient such that it springs back to its original linear form once the load is removed. The chain 1 is thus designed such that elongate flexible member 20 has sufficient stiffness to force the chain links 2, 4 to articulate and to resist straightening of the chain links. The member may be rectangular or any other shape that would conveniently pass along the length of the chain in the manner described above. The member may be a unitary, continuous piece or it may be discontinuous i.e. it may comprise a plurality of pieces placed at different locations along the length of the chain. In the latter instance the pieces may be disposed at selected strategic locations so as to provide a variable stiffness characteristic along the chain length. This chain 1 may have inherent damping capabilities owing to losses in energy that occur as a result of the elongate flexible element 20 sliding over the rollers 12 as the chain flexes. The damping characteristics could be improved if the resilient elongate flexible member 20 is manufactured wholly or partly from a suitable polymeric damping material. In one example the entire member 20 is made from a polymeric damping material having suitable characteristics to provide the required damping whilst also having the capacity to carry the load applied to the chain. One example is an injection mouldable polymer such as, for example, a thermoplastic polyester elastomer. A commercially available product of this kind is available from Dupont under the trade mark Hytel ®. As an alternative, the resilient elongate flexible member 20 may comprise a core of suitable material such as spring steel (for example) to which a suitable elastomeric polymer coating is applied (e.g. a nitrile rubber or other synthetic rubber copolymer).

A damper assembly according to a first embodiment of the invention is shown in figures 3A-3C. The damper assembly of the first embodiment has a chain 1 as described above, a first mounting element 22 and a second mounting element 24. The first mounting element 22 and the second mounting element 24 are movable relative to one another between a first position, as shown in figure 3a, to a second position, as shown in figure 3c. Figure 3b shows the mounting elements 22, 24 in an intermediate position.

In this embodiment the first mounting element takes is in the shape of an elongate cylindrical cup of substantially uniform wall thickness, in other words it is in the shape of a substantially uniform cylindrical tube with one closed end and one open end. The internal space within the first mounting element 22 forms a mounting element cavity 28. The second mounting element 24 takes the form of a piston 26, which is slidably received within the mounting element cavity 28. The piston of this embodiment is in the shape of a closed-ended cylindrical tube of substantially constant cross section. The internal space within the piston 26 defines a piston cavity 30. The chain 1 is received fully within the piston cavity 30, which forms a reservoir which contains damping fluid and holds it in contact with the chain. The chain 1 is connected at one end to the piston 26 by a protrusion 32 in the form of a cylindrical peg which is received within a bush 8 of the chain (which allows the adjacent link to pivot about the protrusion). The chain 1 is connected at the other end to the first mounting element 22 via another protrusion 34, also in the form of a cylindrical peg received within a bush 8. The peg 34 projects from the surface of the mounting element cavity 28, through an aperture 36 in the piston. In this embodiment the aperture is in the form of a slot which is parallel to the common axis of the piston 26 and cavity 28 (that is to say the axis about which the piston and cavity are movable relative to one another).

The damper assembly of the first embodiment is arranged to damp compressive forces (in the vertical direction from the perspective of figure 3). With no such force applied, the behaviour of the chain is dominated by the action of the resilient elongate flexible member 20. The chain therefore adopts the zig-zag configuration discussed above, due to the links 2, 4 being forced to articulate around the pins 16 by the resilient elongate flexible member 20. In such a configuration the axial length of the chain decreases. This urges the protrusions 32, 34 towards each other, biasing the mounting elements 22, 24 to the first position (shown in figure 3A).

When a compressive force is applied, the first and second mounting elements 22, 24 are forced towards the second position (shown in figure 3C), against the bias of the chain 1 that is provided by the resilient elongate flexible member 20. As the mounting elements 22, 24 move towards the second position, the piston 26 moves further inside the mounting element cavity 28, taking with it projection 32, and the slot 36 travels across the projection 34. Since projection 34 is fixed to the first mounting element 22 and projection 32 moves with the piston 26, this movement results in the projections 32, 34 being moved further apart, stretching the chain 1 and moving it towards the straight configuration (forcing the resilient elongate flexible member to deform and undulate). In this embodiment when the mounting elements 22, 24 are in the second position the chain is in the straight configuration. In other embodiments however, when the mounting elements are in the second position the chain may not reach the straight configuration (for instance it may only reach the configuration shown in figure 3b, i.e. a partially-straight configuration). As outlined above as the extension of the chain increases, the resistive force generated by the resilient elongate flexible member 20 also increases. If the compressive force is relatively low, therefore, the mounting elements 22, 24 will only move part way to the second position and the chain will reach a configuration nearer to the straight configuration but not fully straight, as shown in figure 3b.

If the compressive force is relatively large, however, the biasing force from the chain 1 will be insufficient to counteract it. The mounting elements 22, 24 will therefore move to the second position and (in this embodiment) the chain will reach the straight configuration. The chain reaching the straight configuration will provide the 'hard stop' discussed above.

Movement of the mounting elements 22, 24 between the first and second positions undergoes a damping action by virtue of energy being dissipated by friction between the rollers 12 and the resilient elongate flexible member 20 (as well as hysteresis in embodiments where the resilient elongate flexible member and/or the rollers are elastomeric). Further damping is provided by the energy dissipated by displacement of the damping fluid as the chain 1 articulates towards/away from the straight configuration. When such a damping fluid is present between surfaces that would otherwise come into contact with one another, it requires a significant amount of energy to move those surfaces relative to each other. Further, in embodiments such as the first embodiment where the chain is in a reservoir of damping fluid, movement of the chain links acts to 'stir' the damping fluid, dissipating further energy. The amount of force required and therefore the amount of the damping effect can be controlled by suitable selection of the components of the damping fluid, e.g. the oil components of a grease. The higher the molecular weight of the oil the greater the internal shear resistance of the grease. The damping fluid may also have the effect of reducing the noise of the chain in use, e.g. by acting as a lubricant. A grease which may be suitable for use as a damping fluid is commercially available from Nye Lubricants Inc. of Fairhaven, Massachusetts, USA. It is thought that a such a damping grease having a base kinematic viscosity (at 25 °C) of around 50,000 cSt (0.05 m 2 /s) would be appropriate for most applications.

Figure 4 shows a modification of the first embodiment in which the piston 26 is formed from two piston portions 40, 42, and the damper assembly has sealing members 44 interposed between the piston 26 and the mounting element 22. In this embodiment the sealing members 44 are disposed in annular grooves in the piston 26. The sealing members 44 prevent leakage of damping fluid from the piston cavity 30 (though a minimal amount may escape into the annular clearance between the piston 26 and the first mounting element 22), or leakage of air into the piston cavity 30. They also seal the mounting element cavity 28, creating a gas pocket 45 in the portion of the mounting element cavity which is not occupied by the piston 26. In this modification the second mounting element 24 (in this case the piston 26) is received entirely within the first mounting element 22 and compressive force is applied to it through an aperture 46 in the first mounting element, as denoted by arrow 48. The piston portions 40, 42 are not mechanically joined together, but are prevented from separating by the enclosed damping fluid. The damping fluid is incompressible therefore without the introduction of air (which is prevented by the sealing members 44) the piston portions 40, 42 can only be separated by a force large enough to produce a vacuum in the piston cavity 30. Further, when the damper assembly is under load the two piston portions 40, 42 are held together by the virtue of the compressive force (arrow 48) urging piston portion 42 towards piston portion 40, and the resistive force from the chain urging piston portion 40 towards piston portion 42 (through protrusion 32). The piston 26 being made from multiple sections may simplify the manufacturing and/or assembly processes of the damper assembly, and as outlined above the sealing members 44 assist in the prevention of leaks. Further, the provision of the gas pocket 45 provides the damper assembly with additional resistance to compression, as movement of the piston 26 further into the mounting element cavity 28 compresses the gas in the gas pocket 45, which in turn provides a restorative force acting to push the piston outwards again. The extent of this restorative force can be controlled by suitable selection of the volume of the gas pocket 45, and the pressure of the gas contained therein for a given displacement of the piston 26 (for example the gas pocket could be filled with pressurised gas during construction of the assembly). Though the gas pocket of this damper assembly is located in the mounting element cavity, other embodiments may have one or more gas pockets for the same purpose in the same or in any other suitable locations.

A further modification of the first embodiment is shown in figure 5. As well as a piston 26, the second mounting element 24 has an outer casing member 50 which is concentric with the piston 26 and defines an annular clearance therewith, the clearance receiving the first mounting element 22. Also, in this modification the mounting elements 22, 24 are arranged so that the slot 36 remains sealed by the surface of the mounting element cavity 28, preventing leakage of damping fluid from the piston cavity 30 (such an arrangement would preferably have one or more sealing members positioned around the slot 36, though these are not shown in the diagram). The piston 26 and mounting element cavity 28 function as a piston pump. As a compressive load forces the piston 26 further into the mounting element cavity 28, the piston displaces damping fluid contained in the mounting element cavity 28. The damping fluid is forced out of the cavity 28 through an aperture 52 in the first mounting element 22, and into an auxiliary receptacle (not shown). When the compressive load is removed and the piston partially withdraws from the cavity under action of the chain 1 , the displaced fluid is sucked back from the auxiliary receptacle (not shown) into the mounting element cavity 28 through the aperture 52. This pumping of damping fluid can increase the damping capabilities of the device.

Figure 6 shows a second embodiment of the invention. Like the first embodiment, the second embodiment has a chain 1 of the type described previously, and first and second mounting elements 22, 24 which are movable from a first position to a second position relative to one another. Figure 6 shows the mounting elements 22, 24 in an intermediate position between the first and second positions.

As in the first embodiment, the second mounting element 24 takes the form of a piston 26, which is slidably received within a mounting element cavity 28 defined by the first mounting element 22. Unlike the first embodiment, the piston of the second embodiment is solid (i.e. does not define a cavity). It also has a projection 58 which protrudes from the mounting element cavity 28. In this embodiment the chain is fully enclosed within the damper assembly by virtue of it being positioned within the mounting element cavity 28. The mounting element cavity 28 in this embodiment acts as the reservoir for damping fluid.

The damper assembly of the second embodiment has a housing unit 54 with a housing unit cavity 55. The first mounting element 22 is slidably received within the housing unit cavity 55. It will be noted that the housing unit 54 is similar in appearance to the first mounting element of the first embodiment, and the first mounting element 22 of the second embodiment is similar in appearance to the piston of the first embodiment. The first mounting 22 element has an aperture 53, which provides fluid communication between the mounting element cavity 28 and the piston cavity housing unit cavity 55. As with the first embodiment, the chain 1 is connected at one end to the piston 26 by a protrusion 32, and the other end of the chain is connected to the first mounting element 22 by a protrusion 34. Again, both protrusions take the form of cylindrical pegs received within a bush 8 of the chain. In the second embodiment, moving the mounting elements 22, 24 to the first position requires the piston 26 to be moved outwards within the mounting element cavity 28, away from the first mounting element 22. This can be achieved e.g. by applying a tensile force between the piston 26 and the housing unit 54, or by applying a compressive force between the first mounting element 22 and the housing unit. If a tensile force is applied between the piston 26 and the housing unit 54 (e.g. if the piston is pulled downwards from the perspective of figure 6, with the housing unit held stationary), the piston moves away from the housing unit, sliding within the mounting element cavity 28. This decreases the pressure in the mounting element cavity 28, which decreases the pressure in the housing unit cavity 55, which in turn sucks the first mounting element 22 further into the housing unit 54. If on the other hand a compressive force is applied between the first mounting element 22 and the housing unit 54 (e.g. if the first mounting element 22 is pushed upwards from the perspective of figure 6, with the housing unit 54 held stationary), the first mounting element moves towards the housing unit 54, sliding within the housing unit cavity 55. This increases the pressure in the housing unit cavity 55, which increases the pressure in the mounting unit cavity 28, which in turn forces the piston 26 outwards along the mounting element cavity. In either case, first and second mounting units 22, 24 are forced to move in opposite directions, i.e. away from each other. This moves the protrusions 32, 34 away from each other, stretching the chain 1 towards the straight configuration. The stretched chain urges the mounting elements 22, 24 to the first position, as described previously.

The second embodiment provides damping as described above, with energy being dissipated by friction between the rollers 12 and the resilient elongate flexible member 20 (and potentially by hysteresis as outlined previously), and by displacement of the damping fluid by the chain 1 as it articulates towards/away from the straight configuration. Further energy is dissipated by the piston 26 and mounting element cavity 28 functioning as a piston pump, in this case displacing damping fluid between the mounting element cavity 28 and the housing unit cavity 55.

In the second embodiment both the first mounting element 22 and the piston 26 (via the projection 58) both protrude from the housing unit cavity 55. They are therefore both accessible for the application of force, allowing the damper to work either in tension (e.g. by moving the piston 26 relative to the housing unit 54) or in compression (e.g. by moving the first mounting element 22 relative to the first housing unit). In other embodiments however, the piston 26 or the first mounting element 22 may be flush with or recessed within the mouth of the housing unit cavity 55 so that the damper functions only in tension or compression. For instance, the piston may not be provided with a projection.

It is to be understood that the relationship between movement of the piston 26 and movement of the first mounting element 22 is linked by the sizes of the mounting element cavity 28 and the housing unit cavity 55. For instance, the stroke length of the assembly (i.e. the total displacement which can be accommodated before reaching the 'hard stop') when compressive load is applied between the first mounting element 22 and the housing unit 54 could be decreased by narrowing the mounting element cavity 28. By doing so, the amount of damping fluid displaced from the housing unit cavity 55 by moving the first mounting element 22 a particular amount would constitute a larger proportion of the total volume of the mounting element cavity 28. The piston 26 would therefore have to move further within the mounting element cavity to accommodate this fluid, which would stretch the chain to a greater extent and mean that it reached the straight configuration sooner.

Figure 7 shows a third embodiment of the invention. Like the first and second embodiments, the third embodiment has a first mounting element 22 with a mounting element cavity 28, and a chain 1 of the type described above. In this embodiment it is the mounting element cavity 28 which acts as a reservoir that contains damping fluid and within which the chain 1 is received. The damper assembly of the third embodiment has two identical counterposed second mounting elements 24a, 24b, either one of which can be moved to a second position with respect to the first mounting element 22. Each second mounting element 24a, 24b comprises a piston 26a, 26b. Both pistons 26a, 26b are slidably received within the mounting element cavity 28. The chain 1 is attached at one end to piston 26a by protrusion 60a, and at the other end to piston 26b by protrusion 60b. The chain is also attached to the first mounting element 22 via a protrusion 62 that projects from the surface of the mounting element cavity 28. The point along the longitudinal axis of the chain 1 at which the first mounting element 22 is attached is between the points at which the second mounting elements 24a, 24b are attached. In other words, the points along the longitudinal axis of the chain at which the second mounting elements 24 are attached are on opposite sides of the point at which the first mounting element 22 is attached. The damper assembly of the third embodiment can function in tension or compression, with force being applied between the first mounting element 22 and one of the second mounting elements 24a, 24b. For example, if compressive force was applied between the first mounting element 22 and the second mounting element 24b, the piston 26b would move upwards (from the perspective of figure 7) relative to the first mounting element, moving deeper into the mounting element cavity 28. This moves the protrusion 60b and the protrusion 62 closer together, causing the portion of chain between them to contract (i.e. to move further from the straight configuration). Since the portion of the mounting element cavity 28 between the two pistons 26a, 26b is filled with (incompressible) damping fluid, as the piston 26b moves deeper into the mounting element cavity 28 the counterposed piston 26a is forced outwards (i.e. upwards from the perspective of figure 7) by the damping fluid. This moves the first mounting element 22 and the other second mounting element 24a (i.e. the second mounting element which is not being acted on by the compressive force) to the second position, increasing the distance between the protrusion 62 and the protrusion 60a, stretching the portion of chain between them (i.e. urging it towards the straight configuration).

If, on the other hand, a tensile force was applied between the first mounting element 22 and the second mounting element 24b, the piston 26b would move downwards (from the perspective of figure 7) relative to the first mounting element 22, moving outwards within the mounting element cavity 28. This moves the first mounting element 22 and the second mounting element 24b (i.e. the first mounting element being acted on by the tensile force) to the first position. This in turn moves the protrusion 60b and the protrusion 62 further apart, causing the portion of chain between them to be stretched (i.e. to move towards the straight configuration). Since the portion of the mounting element cavity 28 between the two pistons 26a, 26b is filled with (incompressible) damping fluid, as the piston 26b moves outwards within the mounting element cavity 28 the counterposed piston 26a is sucked deeper into the cavity (i.e. downwards from the perspective of figure 7). This decreases the distance between the protrusion 62 and the protrusion 60a, contracting the portion of chain between them (i.e. urging it further from the straight configuration).

In any event, when a force is applied to the damper assembly one of the second mounting elements 24a, 24b is moved to the first position relative to the first mounting element 22, which leads to one portion of the chain being stretched (i.e. moved towards the straight configuration) and another being contracted (i.e. moved away from the straight configuration). The stretched portion of chain provides a biasing force which urges the first mounting element 22 and second mounting element (the one which was moved towards the second position relative to the first mounting element by the applied force) towards the first position again. As the entire chain articulates (be it towards or away from the straight configuration), dissipating energy through friction and displacement of damping fluid, the whole chain contributes to the damping effect of the assembly.

In the third embodiment the movement of the counterposed second mounting elements 24a, 24b is restricted by the damping fluid, which (due to its incompressible nature) prevents any change in volume of the space in the mounting element cavity 28 between the two pistons 26a, 26b. Figure 8 shows a variation of the third embodiment in which the two second mounting elements 24a, 24b are physically joined by a connecting body 64. In this embodiment the connecting body 64 is integral to both the counterposed second mounting elements 24a, 24b, though in other embodiments it may be a separate component to one or both of them. The connecting body 64 and the second mounting elements 24a, 24b co-operatively define the reservoir of connecting fluid in which the chain 1 is positioned. This arrangement functions in the same fashion as the third embodiment, except that while in the third embodiment the second mounting elements 24a, 24b can be moved apart relative to one another by exerting a force large enough to induce a vacuum in the reservoir, in this arrangement the second mounting elements can only be moved relative to one another by exerting a force of sufficient magnitude to physically deform the connecting body 64. As outlined above, part of the damping capabilities of the above embodiments result from motion of the chain dissipating energy by displacing damping fluid. Figures 9a and 9b show a fourth embodiment of the invention. This embodiment is identical to the second embodiment except that the piston 26 is recessed within the mounting element cavity 28 rather than having a projection protruding from it, and the chain 1 has a plurality of extensions 66. The extensions 66 are arranged to project from the chain 1 to increase the resistance to motion of the chain that is offered by the damping fluid. In other words, they increase the volume of damping fluid which is displaced by articulation of the chain 1 , increasing the aerodynamic drag of the chain as it moves. This increased drag increases the extent to which the damping effect of the assembly is proportional to the acceleration it experiences (i.e. magnitude of the force applied), which is particularly desirable in vehicle suspension systems. In this embodiment each outer link plate 4 has one extension 66, which is in the form of a substantially flat plate projecting orthogonally from the outer link plate to which it is attached and is connected to the outer link plate by a flange 67.

Figure 10 shows a chain 1 for use in the invention which also has extensions 66. In this arrangement the chain 1 is formed from two lengths 1 a, 1 b of roller bush chain (each with its own resilient elongate flexible member 20a, 20b) connected together in parallel. The two lengths 1 a, 1 b are joined together via common outer link plates 68, arranged alternately with standard roller bush chain outer link plates 4. The extensions 66 are arranged such that they co-operatively define a plurality of voids 70 along the length of the chain. In this embodiment the voids 70 are formed by virtue of the extensions 66 being arranged two different orientations (horizontal or vertical from the perspective of figure 10). As shown in more detail in figures 1 1 a-1 1c, as the chain 1 articulates out of the straight configuration (which is shown in figure 1 1 a) the voids 70 change in shape and volume. The same is true when the chain articulates towards the straight configuration. This further increases the extent to which damping fluid is displaced (and therefore the damping capabilities of a damper assembly in which such a chain is mounted). A development of the above chain is shown in figure 12. In this arrangement each of the extensions 66 is shaped to maintain minimal clearance between it and the neighbouring extensions 66 with which it defines a void 70 as the chain articulates. The extensions have either a flat interface surface 71 or a convex interface surface 72. In both cases the extensions have a flat rear surface 73. The flat and convex interface surfaces 71 , 72 are shaped and positioned such that as the chain 1 articulates to or from the straight orientation, the edges 74 of the flat interface surfaces 71 sweep across the convex interface surfaces 72, maintaining a substantially constant clearance. As a minimal clearance is maintained between the extensions 66 which form each void 70, as the chain articulates little damping fluid can pass between adjacent extensions (i.e. little damping fluid can move into or out of the voids in the plane shown in figure 12). The fluid must therefore take a more convoluted route to and from the voids 70, which further increases the energy dissipation (and thus damping) offered by the system.

Figure 13 shows a further development of this chain (with the extensions not shown). While in the chains described above the resilient elongate flexible member is threaded along the chain, in this arrangement the chain has a plurality of resilient flexible loop members 76 housed within the chain 1 which act to urge it away from the straight configuration. In a further arrangement these loop-shaped resilient elongate flexible members may be replaced by elastomeric blocks.

It will be appreciated that in embodiments with a resilient elongate flexible member threaded along at least part of the length of the chain, in use the resilient elongate flexible member may move along the longitudinal axis of the chain under the influence of repeated contact with the moving rollers (or other components of the chain). It may therefore be preferable to include retaining means for restricting movement of the resilient member along the chain. Figure 14 shows a modification of the damper assembly of the first embodiment, in which the resilient elongate flexible member 20 is attached at one end 77 to one of the mounting elements 22, 24. In this case, it is attached to the piston 26 of the second mounting element 24, due to it being joined to the surface of the piston cavity 30.

Figure 15 shows a further modification of the first embodiment in which the resilient elongate flexible member 20 of the chain 1 is restrained in its axial movement relative to the chain. In this arrangement the resilient elongate flexible member has a hooked portion 78 at each end. The hooked portions 78 are configured to hook onto respective rollers 12 of the chain 1 to restrict axial movement of the resilient elongate flexible member 20 along the chain 1 . In this arrangement the hooked end portions 78 are spaced apart just enough for the chain 1 to reach the straight configuration. In other arrangements however, they may be spaced more closely together (for example so as to prevent the chain reaching the straight configuration) or may be spaced further apart (for example to provide a degree of leeway or to allow for less stringent manufacturing tolerances).

It will be appreciated that in embodiments where the resilient member protrudes from one or both ends of the chain, the extent to which it protrudes will be dependent on the configuration of the chain. In some situations it may be preferable to include one or more retainer lugs. Figure 16 shows a further modification of the first embodiment which includes a pair of retainer lugs 84a, 84b, each mounted to a surface of the piston cavity 30. Each retainer lug 84a, 84b has an aperture 86a, 86b within which a respective end 77a, 77b of the resilient member 20 is received. Each aperture 86a, 86b terminates in a base 88a, 88b. As the chain articulates, the ends 77a, 77b of the resilient member 20 move within the apertures 86a, 86b (but the retainer lugs 84a, 84b are of sufficient length that the ends of the resilient member are not completely withdrawn from the apertures at any point). The retainer lugs 84a, 84b therefore restrain the lateral movement of the ends 77a, 77b of the resilient member 20. Further, the bases 88a, 88b are positioned to restrain the axial movement of the resilient member 20, preventing it from working free of the chain and/or being damaged or damaging other components.

While in this arrangement the retainer lugs 84a, 84b are both fixed to the piston 26, in other arrangements they may be arranged differently. For instance, the lower (from the perspective of figure 16) retainer lug 84b may be fixed relative to the projection 34, so that each retainer lug is in a constant axial position relative to its respective end of the chain.

Though the above embodiments all describe damper assemblies which can work in compression, as these are particularly suitable for use as shock absorbers in vehicle suspension systems, in other applications a damper assembly according to the invention may be designed to work solely in tension. A schematic diagram of one such arrangement, a fifth embodiment of the invention, is shown in figure 17. The fifth embodiment has a first mounting element 22 with a mounting element cavity 28, and a second mounting element 24 with a piston 26 slidably received within the mounting element cavity. The piston 26 of the fifth embodiment has a plurality of apertures 80. The chain 1 (which is shown as a spring in the schematic diagram of figure 16, but may be a chain of any of the embodiments above or may be any other suitable chain) is located within the mounting element cavity 28, which functions as a reservoir for damping fluid. The chain 1 is attached at one end to the mounting element cavity 28 of first mounting element 22, and attached at the other end to the piston 26 of the second mounting element 24.

When a tensile force is applied to the damper assembly between the first and second mounting elements 22, 24 (e.g. if the second mounting element 24 is moved downwards from the perspective of figure 17 with the first mounting element 22 held stationary), the mounting elements 22, 24 move to the second position. The piston 26 slides outwards within the mounting element cavity 28 and stretches the chain 1 towards the straight configuration. The stretched chain provides a restorative force to bias the mounting elements 22, 24 back towards the first position and its articulation provides damping, as outlined above. In addition, as the piston 26 moves, the damping fluid within the mounting element cavity 28 in the path of the piston is displaced and forced through the piston through the apertures 80. This increased displacement of damping fluid may increase the damping capabilities of the assembly. To increase the displacement of damping fluid yet further, the chain 1 may be positioned adjacent one or more baffle members (not shown) arranged to restrict entry of damping fluid into the voids, and/or exit of damping fluid therefrom, from a particular direction.

In damper assemblies for some applications, the required resistance to extension may be beyond what can practically be achieved with a single chain. In such circumstances a chain assembly may be utilised. Figures 18-20 show a first embodiment of a chain assembly for use as part of a damper assembly according to any of the preceding embodiments. The chain assembly 1 12 has six chains 1 14 each of which is attached at one end to a first connection bracket 1 16 and at the other end to a second connection bracket 1 18. In the chain assembly 1 12 shown in Figure 18 each chain 1 14 is substantially the same as the chain shown in Figure 1 , but wherein the resilient flexible elongate member 120 of each chain 1 14 passes underneath two successive pins 122 (and rollers 124) before passing between adjacent pins to the opposite side where it passes over the next two successive pins 1 12 (and rollers 124).

The chains 1 14 are arranged in two rows of three, with an alignment structure 128 positioned between the rows. The alignment structure 128 is loosely received within recesses 130 in the connection brackets 1 16, 1 18, so that it is able to move to a certain extent within them (see Figure 19). The alignment structure 128 being positioned between the two rows of chains 1 14 acts to prevent any of the chains from coming into contact with each other, which could significantly increase wear and reduce service life of the assembly 1 12. In this arrangement the chains 1 14 are positioned such that they run substantially parallel to one another when in the straight configuration. However, in other arrangements this may not be the case.

Each chain 1 14 of the chain assembly 1 12 is a roller bush chain, as described previously. As such, each chain 1 14 defines an articulation plane within which its links can articulate about their respective pins 122. The articulation plane of each chain 1 14 is substantially perpendicular to its pins 122. In this arrangement, the chains 1 14 are positioned so that their articulation planes are parallel. As such, the entire chain assembly 1 12 can articulate within a plane that is parallel to the articulation planes of the chains 1 14, in a manner akin to a single chain. The articulation of the chain assembly 1 12 is limited, however, by the alignment structure 128. The loose fit of the alignment structure 128 in the recesses 130 permits movement to a certain extent, beyond which the alignment structure will brace against the walls of the recesses 30 and prevent any further articulation.

The chains 1 14 are connected to the connection brackets 1 16, 1 18 by rivets 126, about which the adjacent link plates (i.e. the distal link plates of the chains 1 14) can rotate. Each connection bracket 1 16, 1 18 also has a rivet 127 which may provide a mounting point for attaching that connection bracket to a first or second mounting element (not shown) of a damper assembly. In this arrangement the first and second connection brackets 1 16, 1 18 are substantially identical. One of the connection brackets 1 16, 1 18 is attached to the first mounting element of the damper assembly and the other connection bracket 1 16, 118 is attached to the second mounting element, such that movement of the mounting elements towards the second position moves the connection brackets 1 16, 1 18 towards a second position (described in more detail below), which urges each chain 1 14 towards the straight configuration. Since the mounting elements are attached to the connection brackets 116, 1 18 and the connection brackets 1 16, 1 18 are attached to the first and second ends of the chains 1 14, the mounting elements are attached to the first and second ends of chains 114 via the connection brackets 1 16, 1 18.

For example, where the chain assembly is part of the damper assembly according to the first embodiment (see Figures 3A-3C), the first connection bracket 1 16 of the chain assembly 112 may be attached to the second mounting element (24 in Figures 3A-3C) by positioning the chain assembly such that the protrusion (32 in Figures 3A-3C) is accommodated in the first connection bracket 1 16 in place of the rivet 127. Similarly, the second connection bracket 1 18 of the chain assembly 1 12 may be attached to the first mounting element (22 in Figures 3A-3C) by positioning the chain assembly such that the protrusion (34 in Figures 3A-3C) is accommodated in the second connection bracket 1 18 in place of the rivet 127.

Figures 18-20 show the chain assembly 1 12 with the connection brackets 1 16, 1 18 in a first position. As stated above, movement of the mounting elements towards the second position moves the connection brackets 1 16, 1 18 directly apart from one another towards a second position. This movement of the connection brackets 1 16, 1 18 towards the second position urges each chain 1 14 towards the straight configuration. As described previously, the chains 1 14 resist being stretched towards the straight configuration. They therefore act to urge the connection brackets 1 16, 1 18 (and therefore the mounting elements) back towards the first position when moved therefrom. Since moving the connection brackets 1 16, 1 18 towards the second position stretches six chains 1 14 in parallel, the resistance to extension provided by the chain assembly 1 12 is six times that of a single chain 114. Other arrangements may have any number of chains 1 14 (i.e. two or more chains), allowing the resistance to extension to be tailored to a specific application. The chain assembly 1 12 may comprise a plurality of the chains described in relation to the damper assemblies of the above embodiments. The chains may be identical, or may differ (for instance one of the chains may be of the form described in relation to one of the embodiments, and another may be of the form described in relation to a different embodiment).

The chain assembly 1 12 may be used as part of any of the damper assemblies of the above described embodiments.

Figure 21 shows a modification of the arrangement of Figures 18-20. In this arrangement, the chains 14 are of reduced length, each having only three pairs 132 of link plates (as opposed to five in the above arrangement). In addition, though in the arrangement of Figures 18-20 the resilient elongate flexible member 120 of each chain 1 14 is positioned so that it urges the central portion of that chain outwards, in this arrangement it is positioned to urge the central portion of the chain inwards. As such, the overall size of the chain assembly 1 12 is reduced, allowing it to be used in smaller spaces. Figure 22 shows a second embodiment of the chain assembly. Again, it has a first connection bracket 1 16 and a second connection bracket 1 18 connected by a plurality of chains 1 14 and movable between said first position (as shown in Figure 22) and said second position. In this case however, there are three chains 1 14 (two of which are visible in Figure 22), and each chain is positioned so that its articulation plane is non- parallel to the articulation planes of each of the other chains. More particularly, the chains 1 14 are positioned substantially circumferentially around the longitudinal axis of the assembly 1 12, and are evenly spaced so that each chain 1 14 is positioned with its articulation plane at an angle of 60 degrees with the articulation planes of the other two chains. At least two of the chains 1 14 (in this case all of the chains) being arranged with non-parallel articulation planes may provide the chain assembly 1 12 with increased torsional and/or lateral rigidity in comparison with arrangements where all the chains 114 are positioned so that their articulation planes are parallel. In other words, the chain assembly of this embodiment has increased resistance to torsional forces applied (for instance between the connection brackets 1 16, 1 18) about its longitudinal axis in comparison to the embodiment of Figures 18-20. In addition, because the articulation planes of the chains 1 14 are non-parallel the chain assembly of this embodiment has increased resistance to bending along its longitudinal axis.

The chain assembly 1 12 of this arrangement also comprises a damper sub-assembly 134 which provides additional damping to that supplied by the chains (as described previously). The damper sub-assembly 134 comprises a piston 136 comprised within the first connection bracket 1 16, which is slidably received in a fluid cavity 138 provided in the second connection bracket 1 18. Sealing elements may be provided between the piston 136 and fluid cavity 138, though these are not shown in Figure 22. As the connection brackets 1 16, 1 18 move between the first and second positions, the piston slides within the fluid cavity 138, changing the volume thereof. The piston 136 of the first connection bracket 1 16 being received within the fluid cavity 138 of the second connection bracket 1 18 also provides additional structural support to the chain assembly 1 12.

In this arrangement the fluid cavity 138 is connected to a duct 140a in the first connection bracket 1 16 (the duct in this case running through the piston 136) and connected to a duct 140b in the second connection bracket 1 18. In this arrangement the fluid cavity 138 is filled with damping fluid in the form of grease, and the ducts 140a, 140b are each connected to a bulk source of this grease (such as a reservoir provided by a damper assembly, in which case the entire chain assembly may be positioned within the reservoir and the ducts may simply be left open). The piston 136 and fluid cavity 138 cooperatively form a piston pump mechanism. Movement of the piston 136 deeper into the fluid cavity 138 (i.e. when the connection brackets 1 16, 1 18 move towards the first position) forces grease out of the cavity 138 and into the bulk source through one or both of the ducts 140a, 140b. Similarly, the piston being moved outwards from within the fluid cavity 138 (i.e. when the connection brackets 1 16, 1 18 move towards the second position) sucks grease into the cavity 138 through one or both of the ducts 140a, 140b. In other arrangements, the fluid cavity 138 may enclose a sealed volume of gas, allowing the piston 136 and fluid cavity 140 to function as an air damper.

The arrangement of Figure 22 also differs from that of Figures 18-20 in that the connection brackets 1 16, 1 18 have threaded ports 142 rather than rivets (127 in Figures 18-20) for attaching the first and second connection brackets 1 16, 1 18 to the first and second mounting elements 22, 24 respectively of the damper assembly. Alternatively the first and second brackets 1 16, 118 may be attached to the second and first mounting elements 22, 24 respectively. Figure 23 shows a modification of the chain assembly of Figure 22. In this case the piston 136 is not part of either connection bracket 1 16, 1 18, but is slidably received in fluid cavities 138a, 138b in each of them. As in the arrangement of Figure 22 each connection bracket 1 16, 1 18 has a duct 140a, 140b connected to its fluid cavity 138a, 138b, but in this case the ducts 140a, 140b are positioned radially rather than longitudinally. In addition, the piston 136 contains a further duct 140c which connects the two fluid cavities 138a, 138b.

The piston 136 and each of the fluid cavities 138a, 138b co-operatively form piston pump mechanisms as described above. Moving the connection brackets 1 16, 1 18 towards the second position pulls the piston 136 outwards from within one or both of the fluid cavities 138a, 138b, sucking grease into the or each cavity through its associated duct 140a, 140b (and potentially from one fluid cavity to the other through the duct 140c in the piston 136). Similarly, moving the connection brackets 1 16, 1 18 towards the first position pushes the piston 136 deeper into one or both of the fluid cavities 138a, 138b, forcing grease out of the or each cavity through its associated duct 140a, 140b (and potentially from one fluid cavity to the other through the duct 140c in the piston 136).

The arrangement of Figure 23 also comprises chains 1 14 of increased length. The chain assembly 1 12 therefore comprises an alignment structure 128 to prevent the chains 1 14 touching as described previously. In this case, the alignment structure 128 takes the form of an enlarged section of the piston 136, providing a section of large enough radius to space apart the middle portions of the chains 1 14 and prevent them touching.

Figure 24 shows a modification of the arrangement of Figure 23. In this case, the piston 136 of the damper sub-assembly 134 is not provided with an alignment structure (128 in Figure 23) since the chains 1 14 will not touch each other due to their being relatively short and due to the resilient elongate flexible member 120 being positioned to urge the middle portions of the chains 1 14 outwards (i.e. away from each other). In this arrangement, a resiliently deformable element in the form of a coil spring 144 is positioned around the piston, between the first and second connection brackets 1 16, 118 and attached thereto. The spring 144 is at its natural length when the connection brackets 1 16, 1 18 are in the first position, therefore moving the connection brackets apart (i.e. towards the second position) stretches the spring and causes it to urge them back together (towards the first position). Similarly, moving the connection brackets 1 16, 1 18 closer together (beyond the first position) compresses the spring and causes it to urge them apart (towards the first position). The spring 144 therefore works with the chains 1 14 in providing additional resistance to extension of the chain assembly 1 14, and also allows the assembly 1 12 to resist compressive loads.

In other arrangements, the spring 144 may only act in tension to supplement the restorative force from the chains 1 14, or may only act in compression so as to allow the assembly 1 12 to react to compressive loads (in which case the spring may simply be held between the connection brackets 1 16, 188, rather than being attached thereto). Further, though in this arrangement no alignment structure is needed, in other arrangements this may be included as well. For instance, the spring 140 may be of diameter sufficient to allow it to function as an alignment structure as described in relation to Figure 23.

Figure 25 shows a modification of the chain assembly of Figure 24. In this spring assembly 1 12 the damper sub-assembly 134 takes the form of a deformable bladder 146 which defines a bifurcated fluid cavity 138 therein. The bladder 146 is attached to each connection bracket 1 16, 1 18 so that relative movement of the connection brackets changes the shape of the bladder, which in turn changes the shape of the fluid cavity 138. For example, moving the connection brackets 1 16, 1 18 towards the second position stretches the bladder axially (vertically from the perspective of Figure 25). In this case, the bladder 146 is shaped so that deforming it not only changes the shape of the fluid cavity 138, but also changes the volume of the fluid cavity. The bladder can therefore function as a pump for damping fluid such as grease, as outlined in relation to Figure 22. For instance, moving the connection brackets 1 16, 1 18 together deforms the bladder 146 and reduces the volume of the fluid cavity 138, forcing grease out of the cavity through one or both of the ducts 140a, 140b, and moving them apart increases the volume of the fluid cavity, sucking grease back into it. The bladder may instead pump another fluid such as a gas, however due to gas being of lower viscosity than grease the damping effect may be reduced. The chain assembly 1 12 of Figure 25 may instead provide damping by displacing fluid by changing the shape of the fluid cavity 138, without the volume of the cavity necessarily changing. For instance, the cavity 138 may be filled with grease and sealed (for instance by inserting plugs into the ducts 140a, 140b). Deformation of the bladder 146 (and thus of the cavity 138) would dissipate energy by forcing the grease within the cavity 134 to move within the cavity to conform to its new shape. As another example, the fluid cavity 138 may be a sealed pocket of gas such as air, allowing it to function as an air damper.

As an additional point, it is to be noted that if the bladder 146 is made of a resiliently deformable material, and/or if the fluid cavity comprises a sealed volume of compressible fluid (i.e. gas), the bladder may also constitute a resiliently deformable element as described in relation to Figure 24.

It will be appreciated that numerous modifications to the above described designs may be made without departing from the scope of the invention as defined in the appended claims. For example, in embodiments with a resilient elongate flexible member that is threaded along at least part of the length of the chain, the particular manner in which it is threaded may vary depending on the application. Moreover, for any of the embodiments covered by the claims the rollers (where present) may be made from a polymeric damping material to improve the damping performance of the chain. The material may be injection mouldable for ease of manufacture. In one embodiment the material may be Nylon 6 but many other options would be readily appreciated by the skilled person. The size and/or thickness of the rollers may vary along the length of the chain in order to provide different damping characteristics along the chain. Alternatively, the material of the rollers may vary along the length of the chain to achieve the same effect.

It is to be appreciated that the invention may utilise different forms of chain such as a chain without rollers or bushes, or a chain comprising link plate and pins only such as a leaf chain (e.g. a fork lift truck chain) or a Galle chain. In some instances where there are multiple strands of link plates arranged in parallel along the width of the chain, selected link plates may be removed from the chain to accommodate a resilient elongate flexible member. Moreover, the inner link assembly may take any suitable form including moulded from a plastics material.

While in the described embodiments the first mounting element, second mounting element(s), mounting element cavity, housing unit, housing unit cavity, piston(s) and piston cavity are all cylindrical in shape, in other embodiments one or more of them may be any other suitable shape. For instance one or more of them may be oval, triangular, square, hexagonal or octagonal in cross-section.

In some embodiments of the invention it may be advantageous to provide one or more abutment surfaces to restrict relative motion between two components. Such abutment surfaces may restrict the relative motion between any two of a/the first mounting element, second mounting element, piston, housing unit, or two or more portions of one of said components. It may be particularly advantageous to provide the damper assembly of the second embodiment of the invention with abutment surfaces so as to prevent the piston from being entirely withdrawn from the mounting element cavity. For the avoidance of doubt, reference above to the 'ends' of the chain being attached to components of the damper assembly should not be construed as limiting. Arrangements in which the chain is a continuous loop that is attached to the mounting elements at two points, and arrangements in which a length of chain is attached to the mounting elements at locations other than its ends, are intended to fall within the scope of the invention. Similarly, though the chain is defined as having a 'straight' configuration, it is to be appreciated that in practice the links of a chain may be incapable of reaching substantial alignment (such as if the force from the resilient member is sufficient that the chain would deform or snap under load before reaching the straight configuration).

Although in the above damper assemblies with two counterposed second mounting elements the relative motion of the second mounting elements is substantially prevented, in some applications it may be preferable for them to be partially or entirely free to move independently. For instance, it may be preferable in some situations to change the damping fluid between the pistons of the third embodiment from a grease to a gas. This would provide a degree of autonomy of the second mounting elements but still restrict their motion up to a point. Alternatively, the damping fluid may be replaced by a (vented) space. The two second mounting elements would then be entirely independent and the damper assembly would function as a pair simple tension dampers. Furthermore, though figures 6 and 7 show damper assemblies where a single chain is connected to the first mounting element and to both the second mounting elements, in other embodiments one piece of chain may be attached to the first mounting element and one of the second mounting elements, and separate piece of chain may be attached to the first mounting element and the other of the second mounting elements.

For the avoidance of doubt, although in the described embodiments of chain assemblies the connection brackets are moved towards the second position by moving them directly apart, in other embodiments they may be movable towards the second position in any other suitable fashion. For instance, they may be moved towards the second position by rotation, pivoting, and/or movement towards and/or tangentially relative to one another, instead or in addition to movement away from one another.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. It should be understood that while the use of words such as "preferable", "preferably", "preferred" or "more preferred" in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.