GB2279712A - An oscillation damper arrangement - Google Patents

Abstract

An oscillation damper arrangement (1), e.g. for a belt tensioner or a vehicle suspension, comprises a composite (7) positioned between and in frictional engagement with relatively movable first and second bodies (5) (6). Composite (7) is comprised of relatively flexible and rigid materials, the flexible material constituting a matrix (14) which may not be continuous, supporting a plurality of elements (15) of relatively rigid material such as fibres, monofilaments, flakes, plates and the like which may be discrete or interconnected, such that relative sliding of at least one of the first and second bodies (5) (6) to the surface (8) (9) of the composite associated with one half cycle of the oscillatory movement can cause the elements (15) to reversibly move outwardly and distort the surface of the composite. Distortion of the surface of the composite during the half cycle modifies the coefficient of friction of that surface and the pressure between the contacting surfaces so that the relative movement is more highly resisted thereby during the one half cycle than the other. <IMAGE>

Description

An Oscillation Damper Arrangement This invention relates to an oscillation damper arrangement and particularly to an oscillation damper arrangement providing damping characteristics which differ in the two opposite directions of oscillatory motion, herein referred to as asymmetric damping. This invention relates especially, but not exclusively, to an oscillation damper arrangement for use in the motor vehicle manufacturing industry.

Oscillation dampers have a wide range of application in many engineering and mechanical fields, one such field being that of the automotive industry where dampers are employed in suspension systems and in drive belt tensioning devices for example.

While the damping of oscillations is often desirable to rapidly stabilize the operation of a drive system destabilized by fluctuating loads and other disturbing influences, it is, to this end, often desirable to dampen the effect of the destabilizing forces to which the system is subjected, more strongly than that of the forces of reaction derived from the system itself which tend to toward restoring stability.

In this connection, a damper arrangement is proposed in USA patent specification 4583962 which includes a one-way clutch mechanism and an additional friction-type damping mechanism.

The one-way clutch is aimed at permitting normal damped movements in one direction, consistent with drive belt tensioning, but only limited movement in the opposite direction. As regards the additional damping mechanism; any asymmetric damping provided by this is totally dependent upon differences occurring between the respective forces applied to the frictionally engaged surfaces for the opposite directions of relative movement.

A further proposal is made in USA patent specification 4725260 which employs a strap and a ring which are arranged such that they form a band brake which is aimed at providing a greater resistance to relative frictional sliding in one direction than in the other. This is achieved by causing the band to tighten on the ring for relative movement in the one direction, which tightening is relaxed for relative movement in the other direction.

The above proposals, while offering means whereby a degree of asymmetric damping may be achieved, describe means which are complex, cumbersome and totally dependent upon a difference occurring between the forces applied to the frictionally engaged surfaces for the opposing directions of relative movement respectively.

According to the present invention there is provided an oscillation damper arrangement comprising a first body and a second body having first and second surfaces respectively which are in frictional relationship with one another which bodies are mounted to permit the first and second surfaces to be urged towards sliding relative to one another by a tendency for oscillatory movement between the first and second bodies, wherein the frictional relationship is via a composite having at least one surface in frictional contact with at least one of the first surface and the second surface respectively, the composite being comprised of relatively flexible and rigid materials, the flexible material constituting a matrix supporting a plurality of elements of the relatively rigid material said elements being arranged in the composite such that relative sliding of at least one of the first and second surfaces to the said at least one surface of the composite respectively associated with one half cycle of the oscillatory movement can cause the elements to reversibly move and outwardly distort the said at least one surface of the composite to enhance damping of said movement during said one half cycle.

According to a preferred embodiment of the present invention there is provided an oscillation damper arrangement comprising a first body and a second body having first and second surfaces respectively which are in frictional relationship with one another, which bodies are mounted to permit the first and second surfaces to be urged towards sliding relative to one another by a tendency for oscillatory movement between the first and second bodies, wherein the frictional relationship is via a composite having at least one surface in frictional contact with at least one of the first surface and the second surface respectively, the composite being comprised of relatively flexible and rigid materials, the flexible material constituting a matrix supporting a plurality of elongate elements of the relatively rigid material, said elements being arranged such that their longitudinal axes are nonparallel to the said at least one surface and such that they extend from the said at least one surface into the composite with their longitudinal axes in a direction having a component substantially aligned with the direction of relative sliding of at least one of the first and second surface to the said at least one surface respectively associated with one half cycle of the oscillatory movement.

By means of this invention, an oscillation damping arrangement may be constructed which does not totally depend upon or alternatively necessarily rely upon, a difference occurring between the forces applied to the frictionally engaged surfaces for the opposing directions of relative movement respectively, to enable it to exhibit asymmetrical damping. Further, the oscillation damping arrangement of this invention may provide enhanced asymmetrical damping and yet be of simple and economic construction.

The oscillation damping arrangement of this invention may find application in motor vehicle suspension systems, belt tensioners including conveyor belt tensioners and drive-belt tensioners and any other like dynamic mechanical or engineering field.

The first and second bodies of the damping arrangement of this invention may be such that the first and second surfaces are flat or curved. For example, the first and second surfaces may be in frictional relationship in a common substantially flat plane, in parallel substantially flat planes or over a common arc or concentric arcs. In the latter cases of arcuate frictional relationship, the tendency for oscillatory movement between the bodies may be of a rotary or torsional nature or indeed of a linear nature such as may occur between a piston and a cylinder for example.

The mounting of the first and second bodies should be such as to permit the first and second surfaces to be urged towards sliding relative to one another and preferably such that the forces maintaining the frictional relationship of the surfaces may be varied, by variable spring tension for example, more preferably such as to be higher for one direction of relative sliding of the surfaces than for the other. It is preferred that the forces are higher for the direction of relative sliding of the surfaces in which higher damping is required.

The frictional relationship of the first and second surfaces with one another via the composite may be direct if at least one of the first and second surfaces comprises the surface of the composite. However, it is preferred that the frictional relationship is indirect such that the composite is positioned between the first and second surfaces and especially such that opposite surfaces of the composite are in frictional contact with the first and second surface respectively.

A surface of the composite which is in frictional contact with the first or second surface, preferably has a corresponding shape. Thus, it is preferred that two surfaces in frictional contact are both flat or both correspondingly curved for example. It will be appreciated that two surfaces in frictional contact may be tapered to permit adjustment of their mutual frictional relationship according to load and wear for example. Further, it will be appreciated that a surface for use in frictional contact with another may be textured to modify its frictional or heat dissipation properties, for example.

The composite employed in the oscillation damper arrangement of the preferred embodiment of this invention is comprised of a flexible material constituting a matrix, which is not necessarily a continuous matrix throughout the composite, and elongate elements of relatively rigid material supported by the matrix. The flexible matrix material may be a plastics material or a natural or synthetic rubber, is preferably of a compressibly resilient nature and preferably also has resistance to degradation by frictional heat in use. Some reversible softening by frictional heat however may be beneficial in some applications for example if progressively increasing damping is desired. The flexible material is preferably such that it can be moulded or cast in forming the matrix. Examples of flexible materials are polyethylene (high, medium or low, including linear low, density), polybutadiene, polyisoprene, butyl rubber and neoprene and include flexible materials which are in the cross-linked or cured stated in the composite.

The relatively rigid material employed in the preferred embodiment comprises elongate elements arranged in the composite such that their longitudinal axes are non-parallel to a surface of a composite in frictional contact with the first or second surface and such that they extend from that surface of the composite into the composite with their axes in a direction having a component substantially aligned with the direction of the relative sliding of the first and second surfaces. The relatively rigid material may comprise a metal, plastics, glass or carbon for example and is preferably such that the elongate elements retain their integrity when subjected to deflection in the composite in use. A plastics material is preferred and particularly a plastics material which substantially retains its rigidity when the composite is subjected to frictional heat in use; high softening nylon or polyethylene terephthalate may be used for example.

The elements may be in the form of fibres, monofilaments, flakes, plates, and the like, which may be discrete or interconnected by way of a mesh-like, fan-like or other shaped structure.

The longitudinal axis of an elongate element of the preferred embodiment has the maximum longitudinal symmetry of the element about it.

The production of the elongate elements is preferably such that a degree of crystalline or molecular orientation of the material structure is achieved in the longitudinal direction, to enhance physical properties, in known manner.

The selection of the flexible and relatively rigid materials for use in the composite is preferably such that the two materials will bond with one another in the formation of the composite and whereby such bond will be retained in use of the composite. To this end, it may be necessary for the elements to be treated, for example by application of electrical or chemical surface oxidation treatments and/or by applying a key-coat or tie layer, such that the flexible matrix material will bond more readily to the elements in the composite. Such treatments are well known.

It will be appreciated that the elongate elements of the preferred embodiment, extending into the composite with their axes in a direction having a component substantially aligned with the direction of the relative sliding of the first and second surfaces, will have their axes inclined to a surface of the composite in frictional contact with the first or second surface. The angle of inclination may be from 1 to 89 , for example, preferably 5 to 85 more preferably 50e to 85. It is preferred that at least a majority of the elongate elements have axes inclined at the same angle. If the surface of the composite is curved, the angle of inclination is taken to be the angle between the axis of the elongate element and the plane of a tangent to the surface of the composite where the axis cuts that surface. It is preferred that the axes of the elements are inclined in planes respectively which both lie in the direction of relative sliding of the first and second surfaces and are perpendicular to a surface of the composite in frictional contact with the first or second surface.

It is preferred that the direction of extent of at least a majority of the axes of the elongate elements of the preferred embodiment into the composite has a component substantially in the direction of relative sliding of the first or second surface to the at least one surface of the composite respectively, associated with the half cycle of the oscillatory movement for which relatively high damping is required.

It will be appreciated that the oscillation damper arrangement of the present invention may comprise more than one first and/or second bodies and/or composite and indeed may include additional other surfaces in frictional contact with one another.

Figure 1 is a sketch of a plan view of an oscillation damper arrangement according to the present invention and incorporated in a drive belt tensioner.

Figure la is a sketch of a sectional elevational view of the oscillation damper arrangement shown in Figure 1.

Figure 2 is a sketch of an enlargement of a portion of the composite of the oscillation damper arrangement shown in Figure la and shows an effect of frictional forces on the composite in use at one surface.

Figure 3 is a sketch showing in part an alternative composite for use in the arrangement shown in Figure 1.

Figure 4 is a sketch showing in part a further alternative composite for use in the arrangement shown in Figure 1.

Figure 5 is a sketch of an enlargement of a portion of the composite shown in Figure 4 and showing the effect of frictional surface forces on the composite in use at one surface.

Figure 6 is a sketch of a perspective view in part of a composite similar to that shown in Figure 4 but having elements extending into the composite from only one surface.

Figure 7 is a sketch of an enlarged portion of the composite shown in Figure 6 and showing the effect of surface frictional forces on the composite in use at one surface.

Figure 8 is a sketch illustrating schematically a method for manufacturing the composite shown in Figure 1.

Figure 8a is a sketch illustrating schematically the method illustrated in Figure 8, but in cross-section.

In the drawings in which like numbers correspond, Figure 1 shows an oscillation damper arrangement indicated generally by 1 incorporated in a drive belt tensioner 2. The tensioner 2 is mounted to solid base 3 in pivotal manner about the axis y of bolt 4 via cast and machined aluminium cylindrical components 5 and 6 the facing surfaces of which may slide relative to one another with the flanged cylindrical composite 7 positioned in between having opposite surfaces 8 and 9 in frictional contact with surfaces of the components 5 and 6 respectively. The tensioner 2 is provided with the bearing mounted pulley 10 which may contact the belt of a belt drive system (not shown) in use.

The tensioner 2 is provided with a coiled spring 11 the ends of which are positively located on an extension of the base 3 at 12 and on an extension to cylindrical component 5 at 13. The action of the spring 11 is to resist an anticlockwise movement of pulley 10 and its bearing mounting about axis y. If pretensioned, the spring would urge the pulley 10 and its bearing mounting to move in a clockwise direction about axis y and in such circumstances the tensioner 2 may be employed to maintain a pre-set tension in a drive belt passed under and in contact with the pulley 10.

The frictional contact between the two opposite surfaces of cylindrical composite 7 and surfaces of cylindrical components 5 and 6 offer damping type resistance to movement of the pulley 10 and its bearing mounting about axis y. The level of this damping type resistance is dependent upon the nature of the surfaces in frictional contact and the force with which they are urged towards one another. As may be better appreciated by reference to Figure la; a movement of pulley 10 and bearing mounting in the direction indicated by the arrow and consistent with tensioning the spring 11, gives rise to increased surface pressure on one side of axis y. This is due to reactions of the ends of spring 11 causing a tangential force on the surfaces of the composite 7. Any relaxing of the spring 11 will correspondingly reduce this increased surface pressure. Since the frictional resistance is proportional to the pressure, it will be seen, that on this basis alone a degree of asymmetric damping may be achieved. However, composite 7 is comprised of a flexible plastics material 14 such as polyethylene in the form of a cylindrically shaped matrix and supporting a plurality of monofilaments 15 of a relatively more rigid plastics material such as nylon (eg nylon 6,6). The monofilaments 15 extend between the surfaces of the composite 7 and into the composite 7 with their longitudinal axes inclined to tangents to the respective curved surfaces of the composite 7 in frictional contact with the surfaces of the components 5 and 6 at angles o (see Figure 2) in the region of 50 to 85 and in a direction having a component in the direction of relative sliding of the respective surfaces of the components 5 and 6 to the respective surfaces of the composite 7 in which relatively high damping is required. That is to say, the monofilaments are arranged to extend into the composite with their axes in a direction having a component in the direction of anti-clockwise rotation of the surface of component 5 relative to the surface of the composite 7 which is in frictional contact. It will be seen that the direction of the axes of the monofilaments at the other surface of the composite which is in frictional contact with component 6 has a component in the direction of relative clockwise rotation of the surface of the component 6 to the surface of the composite. It will be appreciated that in reality in this instance it is the composite 7 that moves in an anti-clockwise direction to the component 6 which is stationary and that, however expressed, the movement is relative. A cylindrical bush of for example nylon may be positioned between the spring and the component 6 to assist movements of the spring.

It will be appreciated that the opposite surfaces of the composite 7 and the surfaces of components 5 and 6 may be provided with slight conical tapers to permit adjustment of their frictional relationship according to load and wear.

Figure 2, which illustrates an enlargement of a portion of the composite shown in Figure la, shows how frictional forces at a surface of composite 7 can affect the nature of that surface in use. The broken lines in Figure 2 indicate the boundaries of the composite 7 in the normal unstressed state. It will be seen that frictional contact of say the surface of component 5 (not shown) or of component 6 (not shown) under a pressure N with the surface 16 of the composite 7, with relative movement in the direction of force F can, at sufficiently high values of N and F, cause a distortion of at least some of the monofilaments 15 by an amount ds with consequent compression of the flexible material 14 behind those monofilaments 15 which are caused to project above the normal boundary level. This monofilament distortion and material compression expends energy and can give rise to a distortion of the surface of the composite 7 illustrated by the solid line 16a.

Distortion of the surface of composite 7 modifies the coefficient of friction of that surface to increase it and also increases the pressure N between the contacting surfaces whereby the force F required to cause relative movement of component 5 (or 6) to composite 7 is increased and any such movement correspondingly resisted. At sufficiently low values of N and F, clearly the composite 7 is permitted to resume its unstressed state.

If the direction of force F in Figure 2 is reversed, it will be seen that there will be little or no tendency for the monofilaments to distort to expend energy and no tendency for the monofilaments 15 to distort to project above the normal boundary of the composite 7 whereby the surface of composite 7 may be relatively unaffected.

Thus it will be seen that any tendency for component 5 to move anti-clockwise relative to composite 7 and for composite 7 to move anti-clockwise relative to component 6 will tend towards increasing the tension in spring 11 to cause an increase in the pressure N. Conversely any tendency for component 5 to move in a clockwise direction will cause a decrease in the pressure N. Accordingly, at sufficiently high levels of N, pre-set or attained, the presence of the composite 7 gives greatly increased resistance to movement of component 5 in the anti-clockwise direction than in the clockwise direction and thereby greatly enhanced asymmetric damping.

Figure 3 shows in part and in end elevation, an alternative composite for use in the arrangement shown in Figure 1 and la and wherein the monofilaments 15 are interconnected by webs 17 both circularly as shown and longitudinally (not shown) of the flanged cylindrical composite. The function of this alternative composite is comparable to that of composite 7 described above.

Figure 4 shows in part and in end elevation a further alternative composite for use in the arrangement shown in Figures 1 and la and wherein as best seen in Figure 5, the elongate elements 18 are part of a more complex structure comprised of the relatively rigid material. The elements 18 (and similarly 181) extend into the composite 19 with their longitudinal axes at relatively shallow angles 8 to the surface(s) of the composite 19. It will be seen that the elements 18 and 181 extend into the composite 19 with their longitudinal axes extending into the composite in directions of opposite effective sense and the function of the composite 19 as a whole will therefore be different from that of the composite 7 of Figures 1 and la, but the function of the respective elements 18 and 181 will be similar to one another as now explained with reference to Figure 5 and elements 18.

Figure 5 shows elements 18 to be part of a more complex structure comprised of the relatively rigid material which structure includes aligned ramps 20. The elements 18 are supported by the ramps 20 and by the surrounding flexible material 14. It will be seen that frictional contact of the surface of composite 19 with, say, the surface of component 6 (not shown) under a pressure N with relative movement of component 6 effectively in the direction of force F, can, at sufficiently high values of N and F cause movement of element 18 relative to the ramp 20 to a position shown in dotted outline. Such movement along the ramp 20 expends energy and causes element 18 to extend above the unstressed surface of composite 19 and also to otherwise modify the surface of composite 19 by compression and distortion of the flexible material 14 as shown at 21. Thus the coefficient of friction of the surface of composite 19 is modified and also the pressure N between contacting surfaces is increased whereby the force F required to cause relative movement of the composite 19 relative to component 6 is increased and any such movement correspondingly resisted. At sufficiently low values of N and F, the composite 19 is permitted to resume its unstressed state.

It will be seen that elements 18 have their longitudinal axes extending into the composite with a component in opposite direction to the effective relative sliding of the component 6 to composite 19 for relatively high damping.

If the direction of force F in Figure 5 is reversed, it will be seen that there will be relatively no tendency for elements 18 to be caused to extend above the surface or for compression and distortion of the flexible material 14 to occur. Accordingly, relative movement between the composite 19 and component 6 will be resisted less in that direction.

It will be appreciated that the function of elements 181 and ramps 201 of Figure 4 will be similar to that of elements 18 and ramps 20. However, as indicated above, because the elements 18 and 181 extend into the composite 19 with their longitudinal axes extending in directions of opposite effective sense, the function of the composite 19 in the arrangement of Figures 1 and la in place of composite 7 would be different. Hence, anti-clockwise rotation of the component 5 relative to composite 19 would be resisted by their surfaces certainly no more than clockwise rotation.

However, anti-clockwise rotation of composite 19 relative to component 6 under sufficiently high values of N and F would be resisted by their surfaces to a greater extent than clockwise rotation.

It will be appreciated that a composite such as composite 19 having outer and inner elements 18 and 181 having axes extending in directions of opposite effective sense may provide adaptability for enhanced damping in one direction or the other depending the selection of composite surface used in relative movement.

Figure 6 shows a composite 22 similar to that shown in Figure 4 but having elements extending into the composite from only one surface. Figure 6 also shows the end flange 23 common to the composites of Figures 1 to 5 and shown in Figure 1. It will be seen that the elements 18 and ramps 20 as in Figure 4 extend along the length of the cylindrical composite 22.

Figure 7 is similar to Figure 5 and shows elements 24 and aligned ramps 25 with the elements 24 being interconnected so as to provide greater potential movement relative to the ramps 25 from which they are initially spaced. The broken line outline indicates the positions of the elements 24 when displaced by amounts dx and dy by the influence of force F and pressure N associated with the frictional contact of a surface with the surface of the composite 26.

Figures 8 and 8a illustrating schematically a method for manufacturing the composite shown in Figure 1, show an injection mould cavity 27 fed with flexible material in molten state via injection nozzle 28 and the bore 29 of male mould tool 30 having multiple radially arranged injection ports 31 (two only shown in Figure 8 and three only shown in Figure 8a). The female mould tool defining the outer shape of the flanged composite to be produced includes a circular mould plate 32 provided with holes 33 which are non-radial, as best seen in Figure 8a, deviating from the radial direction by 90-8 ie in the region of 50 to 400 and which communicate with the mould cavity 27. The holes 33 are provided with guillotine sharp edges where they terminate at the mould cavity 27. The mould plate 32 with which is associated a mould cavity end plug (not shown) is designed to permit die plate 34 and tool 30 to be rotated about its axis as indicated by the arrow R. The process is operated by closing the mould cavity 27 and inserting monofilaments into the cavity 27 via holes 33 so that they extend across the cavity in alignment with the longitudinal axes of holes 33 which they closely fit. The monofilaments are of nylon (eg nylon 6,6) which is a relatively rigid material compared with low density polyethylene, the flexible material to be used in the composite to be produced. Low density polyethylene in molten state is then injected into the cavity 27 via the nozzle 28, bore 29 and ports 31 to surround the monofilaments and fill the cavity 27. The mould plate 32 is then cooled (via coolant channels, not shown) and thereby the composite formed in the cavity 27 cooled. Die plate 34 together with male tool 30 and the composite formed in the cavity 27 are then rotated together through a small angle relative to the mould plate 32 about their common axis to shear off the monofilaments at the surface of the composite in guillotine-like fashion. The mould plate 32 and die plate 34 are then separated and the composite stripped off the male tool 30 with shearing of the sprues from ports 31.

In Figure 8, the holes 33 are shown regularly spaced along the length of the mould cavity 27. Clearly they could be randomly spaced. As shown in Figure 8a the peripheral spacing of holes 3 may be irregular.

The composite thus produced may be machine finished to texture the inside and/or outside surfaces of the cylindrical portion. This may be to texture the surface in addition to any texture in-moulded in the moulding process.

It will be appreciated that on removal of the formed composite from the mould cavity 27 in the above described process, the mould plate 32 and the die plate 34 are brought together again whereupon the cycle of operations may be repeated.

It will be understood that the above described process may be modified by replacing holes 33 with slots similarly angled to guide strips of nylon into the cavity 27, the strips being orientated with the longer cross-sectional dimension parallel with the axis of the cavity.

Composites having elongate elements which extend longitudinally of the composite may be produced by continuous co-extrusion techniques, a continuous coextrusion being cut into sections. If a composite so produced is required to have an end flange, this may be subsequently moulded on in an injection moulding process in which a composite section is employed as an insert.

Claims (15)

1. An oscillation damper arrangement comprising a first body and a second body having first and second surfaces respectively which are in frictional relationship with one another which bodies are mounted to permit the first and second surfaces to be urged towards sliding relative to one another by a tendency for oscillatory movement between the first and second bodies, wherein the frictional relationship is via a composite having at least one surface in frictional contact with at least one of the first surface and the second surface respectively, the composite being comprised of relatively flexible and rigid materials, the flexible material constituting a matrix supporting a plurality of elements of the relatively rigid material said elements being arranged in the composite such that relative sliding of at least one of the first and second surfaces to the said at least one surface of the composite respectively associated with one half cycle of the oscillatory movement can cause the elements to reversibly move and outwardly distort the said at least one surface of the composite to enhance damping of said movement during said one half cycle.

2. An oscillation damper arrangement as claimed in Claim 1 wherein the composite is comprised of relatively flexible and rigid materials, the flexible material constituting a matrix supporting a plurality of elongate elements of the relatively rigid material, said elements being arranged such that their longitudinal axes are non-parallel to the said at least one surface and such that they extend from the said at least one surface into the composite with their longitudinal axes in a direction having a component substantially aligned with the direction of relative sliding of at least one of the first and second surface to the said at least one surface respectively associated with one half cycle of the oscillatory movement.

3. An oscillation damper arrangement as claimed in either of Claim 1 or Claim 2 wherein forces which maintain the frictional relationship of the first and second surfaces may be varied.

4. An oscillation damper arrangement as claimed in Claim 3 wherein the forces may be varied to be higher for the direction of relative sliding of the surfaces in which higher damping is required.

5. An oscillation damper arrangement as claimed in any one of the preceding claims wherein the composite is positioned between the first and second surfaces.

6. An oscillation damper arrangement as claimed in any one of the preceding claims wherein a surface of the composite in frictional contact with the first surface or second surface has a corresponding shape.

7. An oscillation damper arrangement as claimed in any one of the preceding claims wherein the flexible matrix material is of compressibly resilient nature.

8. An oscillation damper arrangement as claimed in any one of the Claims 2 to 7 wherein the elongate elements have a degree of crystalline or molecular orientation in the longitudinal direction.

9. An oscillation damper arrangement as claimed in any one of Claims 2 to 8 wherein the elongate elements are treated such that the flexible matrix material will bond more readily to the elements.

10. An oscillation damper arrangement as claimed in any one of Claims 2 to 9 wherein the elongate elements extending into the composite have their longitudinal axes inclined to a surface of the composite in frictional contact with the first or second surface at an angle in the range of 50 to 850 preferably in the range of 500 to 850.

11. An oscillation damper arrangement as claimed in any one of Claims 2 to 10 wherein the majority of the elongate elements extending into the composite have their longitudinal axes inclined to a surface of the composite in frictional contact with the first or second surface at the same angle.

12. An oscillation damper arrangement as claimed in any one of Claims 2 to 11 wherein the elongate elements extending into the composite have their longitudinal axes inclined in planes respectively which both lie in the direction of relative sliding of the first and second surfaces and are perpendicular to a surface of the composite in frictional contact with the first and second surface.

13. An oscillation damper arrangement as claimed in any one of Claims 2 to 12 wherein at least a majority of the longitudinal axes of the elongate elements extend into the composite in a direction having a component substantially in the direction of relative sliding of the first or second surface to the at least one surface of the composite respectively, associated with the half cycle of the oscillatory movement for which relatively high damping is required.

14. An oscillation damper arrangement as claimed in any one of the preceding claims wherein the tendency for oscillatory movement between the first and second bodies is of a rotary or torsional nature.

15. An oscillation damper arrangement as claimed in any one of the preceding claims substantially as described herein with reference to the accompanying drawings.