GB2293641A - Shock absorber - Google Patents

Abstract

A shock absorber comprising: a body tube 12; first and second end closure members 16, 17 to define a working volume; a piston 23 to fluid tightly separate first and second volumes 27, 28 within the working volume; at least one flow channel in the piston providing for the flow of fluid F from the first to the second volume; a valve to control the flow of fluid along the flow channel; regulating means to provide for the valve to establish flow at a value between a maximum and a minimum flow value; a piston rod 30 having a first end section serving to link the piston rod to the piston to enable the piston rod to be rotated about its longitudinal axis relative to the piston while preventing relative logitudinal movement; the first end being linked to the regulating means to operate the valve; the piston rod extending outside the body member allowing for reciprocation of the piston rod relative to the body tube; and an end unit retained on, and adapted for rotation about, longitudinal axis of the piston rod so that the end unit can be aligned relative to the first closure member. <IMAGE>

Description

SHOCK ABSORBER FOR A SUSPENSION UNIT This invention relates to a shock absorber for a suspension unit. It is particularly, though not exclusively, concerned with a suspension unit for a ground engaging wheel of a land vehicle. A conventional suspension unit is made up of a combination of a shock absorber and a coil spring connected in parallel between a vehicle and wheel. In operation the shock absorber serves to dampen oscillation of the spring caused by linear motion of the wheel relative to the vehicle. Current designs of shock absorber comprise a piston mounted for reciprocation within a body. A piston rod extends outside the body and on use the piston body is attached to the vehicle and the piston rod to ground engaging wheel of the vehicle. Displacement of the piston results in displacement of a working fluid (liquid or gas) within the body around a working fluid circuit.

By using an appropriate combination of shock absorber and spring characteristics a preferred ride characteristic for the vehicle can be obtained.

In designing a suspension unit for a motor car or a motor bike for competitive use it is necessary to distinguish between the behaviour of the unit when subject to compression ('bump') and when free to expand ('rebound'). Earlier attempts to provide a practical suspension unit with independent control of bump and rebound behaviour were not invariably successful or consistent in operation. Such units tended to be complicated and expensive to manufacture.

In use they did not provide for ready modification of bump and rebound since access to any built-in adjustment involved the vehicle being at rest and the dismantling of components of the suspension unit.

In what follows it should be understood that the shock absorber can be used for any type of vehicle as part of a suspension for a ground engaging vehicle.

According to a first aspect of the present invention there is provided a shock absorber comprising: a) a body tube having a longitudinal axis; b) a first closure member for a first end of the body tube and a second closure member for the other end of the tube to the first end; the combination of the tube and the first and second closure members serving to define a working volume; c) a piston adapted for reciprocation within the working volume to fluid tightly separate a first and second volume within the working volume; at least one first flow channel in the piston providing for the flow of fluid from the first volume to the second volume; a first valve to control the flow of fluid along the first flow channel or channels; a first regulating means to provide for the first valve to establish flow along the channel or channels at a value between a maximum and a minimum flow value; d) a piston rod having a longitudinal axis co-axial with, or parallel to, the longitudinal axis of the body tube; the piston rod having a first end section and a second end section; the first end section serving to link the piston rod to the piston to enable the piston rod to be rotated about its longitudinal axis relative to the piston while preventing relative logitudinal movement between rod and the piston; the first end being linked to the regulating means so as to provide for operation of the valve associated with the regulating means by rotation of the rod about its longitudinal axis relative to the piston; relative rotation of the piston rod in a first direction about the longitudinal axis of the piston rod serving to increase flow along the channel; relative rotation of the piston rod in a second direction about the longitudinal axis of the piston rod serving to reduce flow along the channel; the piston rod extending outside the body member by way of a pressure seal in the second closure member so as to locate the second end outside the body member while allowing for reciprocation of the piston rod relative to the body tube; and f) an end unit retained on, and adapted for rotation about, longitudinal axis of the piston rod so that the end unit can be aligned relative to the first closure member.

According to a first preferred version of the first aspect the body tube has a noncircular internal cross section and the piston has a complementary outside periphery complementing the non-circular cross-section.

According to a second preferred version of the first aspect of the present invention the body tube has a circular internal cross section; the piston has a complementary outside periphery.

According to a third preferred version of the present invention or any preceding preferred version thereof there is provided in the piston at least one second flow channel providing for the flow of fluid from the second volume to the first volume; a second valve to control the flow of fluid along the second channel or channels; a second regulating means providing for operation of the second valve to provide a range of obturation to flow in the second flow channel between a maximum and a minimum flow value; the first end of the piston rod being linked to the piston so as to enable the piston rod to be rotated about its longitudinal axis relative to the body member while preventing relative logitudinal movement between rod and body member; and linked to the second regulating means so as to provide for operation of the valve associated with the second regulating means by rotation of the rod about its longitudinal axis relative to the piston body member; such that relative rotation of the piston rod in a first direction about the longitudinal axis of the piston rod serving to cause the second valve to act to increase obturation to flow in the or each second flow channel; and relative rotation of the piston rod in a second direction about the longitudinal axis of the piston rod serving to cause the second valve to act to reduce obturation to flow in the or each second flow channel.

According to a fourth preferred version of the first aspect of the present invention or any preceding preferred version thereof the piston rod encloses a drive rod co-axial with the piston rod; the first end section of the piston rod being linked to one regulating means; the drive rod having a first end section and a second end section; the first end section of the drive rod serving to link the drive rod to the other regulating means the drive rod extending outside the body member by way of the piston rod so as to locate the second end of the drive rod outside the body member; the first end section of the drive rod being linked to the other regulating means so as to provide for operation of the valve associated with that regulating means by rotation of the drive rod about its longitudinal axis relative to the piston body member; relative rotation of the drive rod in a first direction about the longitudinal axis of the drive rod serving to cause the valve to act to increase obturation to flow in the flow channel; relative rotation of the drive rod in a second direction about the longitudinal axis of the drive rod serving to cause the valve to act to reduce obturation in the flow channel.

According to a fifth preferred version of the present invention or any preceding preferred version thereof there is provided a regulating means for pressure in the first volume comprising: a) a pressurisable auxiliary chamber located outside the working volume and linked: (i) to provide for fluid flow from the first volume to the auxiliary chamber by way of a third flow channel; (ii) to prove for fluid flow from the auxiliary chamber to the second chamber by way of a fourth flow channel; (iii) to provide for fluid flow from the auxiliary chamber to the second volume by way of a fifth flow channel; b) a third valve to control the flow of fluid along the third channel; c) a fourth valve to control the flow of fluid along the fourth channel.

According to a sixth preferred version of first aspect of the present invention or the first, second third or fourth preferred versions thereof the body tube is surrounded by a further tube to define a pressurisable annul us which forms the auxiliary chamber.

According to a seventh preferred version of the first aspect of the present invention or o the fifth or sixth preferred versions thereof the auxiliary chamber contains a pressurised bladder adapted to vary the volume of the auxiliary chamber in response to working pressure therein.

According to an eighth preferred version of the first aspect of the present invention or the fifth, sixth or seventh preferred versions thereof wherein a first bleed adjuster provides for flow bleed adjustment between the first volume and the auxiliary chamber; and a second bleed adjuster provides for flow bleed adjustment between the second volume and the auxiliary chamber According to a ninth preferred version of the first aspect of the present invention in a shock absorber according to the fifth preferred version the auxiliary chamber comprises a pressure vessel mounted apart from the body tube and linked to it by means of a pressure duct. Typically the auxiliary chamber comprises a loading volume isolated from the working volume by a piston defining a pressure tight slidable boundary therebetween and a pressurisable line communicating with the loading volume.The pressurisable line can extend through the first closure member.

According to an eleventh preferred version of the first aspect of the present invention or any preceding preferred version thereof the piston rod is rotatable relative to the body member by means of a bevel drive incorporated in the end unit.

According to a twelfth preferred version of the first aspect of the present invention and in particular the fourth preferred version thereof the drive rod is rotatable relative to the body member by means of a bevel drive incorporated in the end unit.

According to a second aspect of the present invention there is provided a vehicle having ground engaging wheels attached to the vehicle by means of a shock absorber according to the first aspect hereof.

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings which are longitudinal sections of shock absorbers of which: Figures 1 and 2 are longitudinal sections of a first embodiment; Figure 3 is a detail of a part of Figures 1 and 2 together with plan views of individual components; Figures 4 and 5 are longitudinal sections of a second embodiment; Figure 6 is a detail plan view of a part of Figures 4 and 5; and Figures 7 and 8 are of a third embodiment.

Many of the components described in relation to the three embodiments are similar in form and function. Consequently to avoid repetition in the description a component described in connection with Figure 1 is given a reference numeral which is repeated for any subsequent embodiment in which it appears.

First Embodiment (Figures 1, 2 and 3) Shock absorber 11 includes a body tube 12 which has a bore 12' which is of oval cross-section over length 13 and of circular internal cross-section over end lengths 14, 15. The body tube 12 has a longitudinal axis of syrnmetry Al. In this case the working fluid is an oil.

First end closure 16 and second end closure 17 serve to enclose pressurisable volumes within the shock absorber 11. These comprise a first working volume working volume 27, second working volume 28 and a loading volume 21 separated from the first volume 27 by a loading piston L. Pressure tube 20 provides for the application of pressurised fluid to the interior of loading volume 21 as will be described hereafter. First end closure 16 provides an eye 19 whereby one end of the shock absorber 11 is mounted on a vehicle.

Piston 23 will now be described in more detail with particular reference to Figure 3.

Piston 23 is made up of a body 24 (plan view 24') having a longitudinal axis A2. The body 24 has an external periphery 25 in which is mounted a peripheral hydraulic seal 26 whereby the body 24 can slide within the bore 12' so as to pressure tightly isolate first volume 27 and second volume 28. The periphery 25 complements the non-circular bore 12' of the body tube 12 so that the piston 23 is incapable of rotation about axis Al relative to the tube 12 on rotation of the piston rod 30 (as could arise with a piston and bore combination of circular cross section).

Piston 23 is mounted on first end 29 of piston rod 30. First end 29 is provided with four progressively stepped portions D1, D2, D3 and D4 of reducing diameter compared with the main diameter D of the rod 30.

Portion D1 receives end plate 32 (plan view 32'), regulator 33 (plan view 33'), coil spring 34, (plan view 34') and spring washer 35 (plan view 35'). The portion D1 is threaded to receive corresponding threaded bore 32A on end plate 32 and threaded bore 33A on regulator 33.

Portion D2 receives body 24 so that it seats on abutment 36 and is held there by mean of circlip 37 (plan view 37') which seats in peripheral slot 38. An O-ring 39 (plan view 39') provides for a fluid tight seal between the body 24 and the rod 30.

Portion D3 receives spring washer 40 (plan view 40') coil spring 41 (plan view 41'), regulator 42 (plan view 42') and end plate 43 (plan view 43'). The portion D3 is threaded to receive corresponding threaded bore 42A on regulator 42 and threaded bore 43A on end plate 43.

Portion D4 is threaded to receive retaining nut 44 (plan view 44') which is tightened down onto abutment 45 between portions D3 and D4 to retain piston 23 on piston rod 30.

The body 24 (plan view 24') is through pierced by an outer ring 46 of flow channels (typically channel 47), an inner ring 48 of flow channels (typically channel 49), and aligning bores 50, 51. The bores 50, 51 serve to align, respectively, dowels 52, 53 which on the assembled piston serve to space the end plate 32 and end plate 43.

Regulator 33 is provided with sliding bores 54, 55 and regulator 42 is provided with sliding bores 56, 57 to enable the regulators to be driven towards one another or drawn apart from one another by rotation of the rod 30 relative to the body 24 as will be described later. To this end portions D1, D3 are threaded with oppositely handed threads as are the regulators 33, 42. Typically regulator 33 in moving to the right (as viewed in Figure 3) compresses spring 34 so increasing the loading applied by the spring 34 to the spring washer 35.

This washer 35 serves to obturate the inner ring 48 of flow channels. With increasing pressure applied to the washer 35 by spring 34 the passage of fluid flow through the flow channels in ring 48 from the first chamber 27 to second chamber 28 is increasingly resisted. In the reverse situation with regulator 33 moving to the left (as viewed in Figure 3) relieves spring 34 so reducing the loading applied by the spring 34 to the spring washer 35. In this way flow through flow channels in ring 48 meets with less resistance. It will be appreciated that flow through channels in ring 48 from the second volume 28 to first volume 27 is very small since flow in this direction tends to drive the washer 35 down to cover the flow channels in ring 48.

A corresponding situation arises for regulator 42. When moved to the left (as viewed in Figure 3) spring 41 is compressed so increasing the loading applied by the spring 41 to the spring washer 40. This washer 40 serves to obturate the outer ring 46 of flow channels. With increasing pressure applied to the washer 40 by spring 41 the passage of fluid flow through the flow channels in ring 46 from the second chamber 28 to first chamber 27 is increasingly resisted. In the reverse situation with regulator 42 moving to the left (as viewed in Figure 3) the loading on spring 41 is reduced so reducing the loading applied by the spring 41 to the spring washer 40.In this way flow through flow channels in ring 46 meets with less resistance. it will be appreciated that flow through channels in ring 46 from the first volume 27 to second volume 28 is very small since flow in this direction tends to drive the washer 40 down to cover the flow channels in ring 46.

To provide for a simultaneous change in loading on both spring washers 35, 40 (and so a simultaneous change in the opening and closing characteristics of the shock absorber 11) the piston rod 30 is rotated relative to piston 23. This is provided for firstly by piston 23 having a body 24 of non-circular cross section lying in a corresponding complementary non-circular bore 12'. Rotation of piston rod 30 is achieved by way of a first bevel gear 60 at outer end 61 of piston rod 30. End unit 62 is retained on end 61 by a ball race 63 which allows for the ready rotation of the end unit 62 relative to piston rod 30 (even when under load) while preventing longitudinal motion of end unit 62 relative to piston rod 30. The end unit 62 incorporates a securing eye 64 whereby the shock absorber 11 is secured to a wheel mounting of the vehicle.A second bevel gear 65 is mounted within the unit 62 for rotation by knob 66. The first bevel gear 60 and second bevel gear 65 intermesh. This enables the piston rod 30 to be readily rotated relative to piston 23 by rotation of knob 66. Since the piston 23 cannot rotate when the piston rod 30 is rotated rotation of the rod 30 results in the simultaneous displacement of the regulators 33, 42 either towards or away from one another. As a result the loading of springs 34, 41 applied to spring washers 35, 40 is changed so changing both the bump and rebound characteristics of the shock absorber 11.

Figure 1 shows the oil flow during a compression (bump) operation of the shock absorber 11 when the overall length of the shock absorber between eye 19 and eye 64 is reducing. In this operation the piston 23 is moving to the right with the size of second volume 28 increasing (and so its internal pressure decreasing) and that of first volume 27 decreasing (and so its internal pressure increasing). As a consequence there is a flow F of working fluid from first volume 27 to second volume 28 by way of inner ring 48 of flow channel in piston body 24. The loading applied to spring washer 35 by spring 34 governs the resistance to flow to working fluid through the inner ring 48. The greater the resistance to this flow on this bump operation the greater the resistance of the shock absorber to compression.The loading volume 21 is pressurised from an external pressure reservoir by pressure inlet 20 to an extent necessary to preload the piston L (which tends to move in the direction of arrow L' and so establish the minimum size of first volume 27.

Figure 2 shows the oil flow during a rebound operation of the shock absorber 11 when the overall length of the shock absorber between eye 19 and eye 46 is increasing. In this operation the piston 24 is moving to the left with the size of first volume 27 increasing (and so its internal pressure decreasing to an extent depending on the loading applied by piston L.). The volume of second volume 28 decreasing (and so its internal pressure increasing). As a consequence there is a flow G of working liquid from second volume 28 to first volume 27 by way of outer ring 46 of flow channels through the piston body 24. The loading applied to spring washer 40 by spring 41 governs the resistance to flow to working fluid through the outer ring 46.The greater the resistance to this flow on this rebound operation the greater the resistance of the shock absorber to expansion resulting from the action of the spring associated with the shock absorber in the suspension unit.

Figures 4. 5 and 6 This embodiment shows a shock absorber 71 which functions in a similar way to the first embodiment described in connection with Figures 1 and 2 but differs from the first embodiment in that the unit is self contained and does not require an external source of pressure to pre-load the first volume.

Body tube 72 with bore 71' is of oval cross section over length 73 and of circular cross section over end lengths 74, 75. The body tube 72 has a longitudinal axis of symmetry A3. The working fluid is again oil.

First end closure 76 and second end closure 77 serve to pressure tightly locate body tube 72 coaxially with a circular section outer tube 78 which provides an approximately annular volume 79 between the body tube 72 and outer tube 78.

The first end closure 76 is equipped with a stub 80 enabling the shock absorber to be mounted on a vehicle.

Piston 81, piston rod 82 and end unit 83 are identical in form and function to piston 24, piston rod 30 and end unit 62 described in connection with Figure 3.

Consequently no substantial further description of their form or function is made here.

Piston 81 serves to divide the inner volume of body tube 72 into first volume 84 and second volume 85. Working disc 86 serves to control flow of working fluid between the first volume 84 and annular volume 79. To this end the working disc 86 (see Figure 6) is pierced by a central bore 87 which is closes by a disc valve 88 seated on lip 89 surrounding the bore 87. The disc valve is pressed in place on the lip 89 by way of one end of a coil spring 90 whose other end is located by a ring washer 91. The working disc 86 is further provided with a ring 92 of flow channels (typically flow channel 93) which are partially obscured by a spring washer 94 mounted on face 95 of working disc 86 facing into the first volume 84.

Annular volume 79 serve to house a bladder 96 which is pressurised so that a pre-loaded pressure can be established in the annular volume on filling the shock absorber when the minimum operating pressure to be readily established in first volume 84.

Figure 4 shows oil flow during a compression (bump) operation of the shock absorber 71 when the overall length of the shock absorber is reducing. In this circumstance the piston 81 is moving to the right with the size of second volume 85 increasing (and so its internal pressure decreasing) and that of first volume 84 decreasing (and so its internal pressure increasing). As a consequence their is a flow F1 of working oil from the first volume 84 to the second volume 85 by way of an inner ring of flow channels in the piston body of piston 81 corresponding to the description in Figure 3 relating to flow F, inner ring 48 of flow channels in piston body 24.In addition there is a further flow F2 of working oil from first volume 84 to annular volume 79 through bore 87 when disc valve 88 lifts from lip 89 due to the pressure differential established across the working disc. Displaced oil in flow F2 passes into annular volume 79 by way of annular passage 98. Bladder 96 is prepressurised so that in the event the pressure in the annular volume 79 increase the volume of bladder 96 will reduce.

Figure 5 shows the oil flow during a rebound operation of the shock absorber 71 when the overall length of the shock absorber is increasing. In this operation the piston 81 is moving from right to left with the size of the first volume 84 increasing. The volume of the second volume is decreasing (and so its internal pressure increasing). As a consequence there is a flow G1 of working fluid from the second volume 85 by way of an outer ring of flow channels in piston body of piston 81 corresponding to the description in Figure 3 relating to flow G and outer ring 46 of flow channels in piston body 24. In addition there is a further flow G2 of working oil from annular volume 79 and along annular passage into first volume 84 byway of annular flow passages 92 in working disc 86.In this case a pressure differential acts to cause washer 94 to lift from working disc 86 due to the pressure differential established across the working disc.

Figure 7 and 8 This embodiment shows a shock absorber 101 which functions in a similar way to the second embodiment described in connection with Figures 4 and 5. To avoid repetition items in Figures 7 and 8 similar in form and function to those in Figures 4 and 5 are given similar reference numerals with the addition of an apostrophe in Figures 7 and 8.

Apart from the similarities between the second and third embodiments the third embodiment provides over and above the second embodiment additional control of the bump and rebound characteristics. This is done in two ways: by providing bleed channels and controls for oil flow within the shock absorber; and by providing for flow control adjustment through the piston so that control of the bump and rebound characteristics can be carried out separately.

Shock absorber 101 has a body tube 72' with a bore 71" of oval cross section with a longitudinal axis of symmetry A3'.

First end closure 102 and second end closure 103 serve to pressure tightly locate body tube 72' coaxially with a circular section outer tube 78' which provides an approximately annular volume 79' between body tube 72' and outer tube 78'.

Piston 81' and end unit 83' are identical in form and function to piston 24 and end unit 62 described in connection with Figure 2. No further description of their form and function is made here. In addition piston rod 104 is similar to earlier rods 30, 82 except that it provides for separate control of the bump and rebound characteristics imposed by the piston 105. Piston rod 104 can be rotated by way of flats 106 cut in the sides of the rod 104 near the end unit 62'.

However rod 104 only regulates operation of the spring valve acting on the flow channels 107 in piston body 108 corresponding to (see Figure 3) valve 40 acting on rebound flow channels 46).

To regulate operation of the spring valve acting on the flow channels 109 corresponding to (see Figure 3) valve 35 acting on flow channels 48 use is made of a drive rod 110 mounted coaxially with piston rod 104. Outboard end 111 of drive rod 110 is fitted with a first bevel gear 112 which is rotatable by means of knob 113 driving second bevel gear 114. Inboard end 115 of drive rod 110 regulates the spring valve. By providing for separate adjustment of compression and rebound flows through the piston body 108 a wider range of operating adjustment is made available.

In addition to separate regulation for the piston flow channels further channels and bleed means are provided apart from those through the piston.

In end unit 103 there is provided a passage 117 linking the second volume 85' to annular volume 79'. Flow along this passage 117 is regulated by a bleed adjuster 119 positioned for easy access on the outside of the end unit 103.

In end unit 102 there is provided passage 120 which is connected to passage 121 through working disc 122. The passage 120 contains a bleed adjuster 123 so that flow along passage 120 between the first volume 84' and the annular channel 79' can be readily controlled outside the end unit 102.

Figure 7 shows oil flow during compression (bump) operation of the shock absorber 101. In this case piston 81' is moving to the right with the size of second volume 85' increasing (and so its internal pressure decreasing) and that of first volume 84' decreasing ()and so its internal pressure increasing). As a consequence there are flows: Fl' through the piston from first volume 84' to second volume 85' corresponding to flow F1 described earlier in connection with Figure 4; F2' through from first volume 84' to annular volume 7Y through bore 87' when disc valve 88' lifts; and F3 along passage 120 from the first volume to the annular volume effectively bypassing the disc valve 88'.

The last flow, F3, provides an ability to fine tune the response of the shock absorber during a compression stroke.

Figure 8 shows the oil flow during a rebound operation of the shock absorber 101. In this case the piston 81' is moving to the left with the size of the first volume 84' increasing. The size of the second volume 85' is decreasing (and so its internal pressure increasing). As a consequence there are oil flows: G1 from the second volume 85' by way of the outer ring of flow channels in piston body of piston 81' corresponding to the description in Figure 3 relating to flow G and outer ring 46 of flow channels in piston body 24; and G2 from annular volume 79' and along annular passage 98 into first volume 84' by way of annular flow passages 92' in working disc 86'.

The last flow, G2, provides an ability to fine tune the response of the shock absorber during a rebound stroke.

A common feature of all three embodiments is the need for heat dissipation.

Repeated operation of a shock absorbers results in the generation of a considerable amount of heat. Displacement of the working fluid involved helps to distribute such heat throughout flow paths in the shock absorber. However to improve overall dissipation it is necessary that body tube 12 (Figures 1, 2 and 7), 72 (Figures 4 and 5) and 72' (Figures 7 and 8) and the outer tubes 78 (Figures 4 and 5) and 78' (Figures 7 and 8) should be capable of conducting heat from the interior of the shock absorber to the outside. To this end the tubes are fabricated from non-metallic composite materials those involving carbon fibre are particularly appropriate. The chosen material is selected for strength, lightness and the ability to take a range of finishes.

The embodiments show a shock absorber where adjustments to bump and / or return characteristics can be applied readily from outside the shock absorber by rotation of the piston rod or of a shaft within the piston rod. By way of example a bevel drive was used to rotate the piston rod or a drive shaft within the piston rod. It will be understood such rotation could be applied remotely by way of a drive system by a user or passenger in the vehicle involved. This could be of particular use in setting up or fine tuning a vehicle such as a car or motor bike for a competitive event.

The shock absorber the subject of the present invention when applied to each wheel of a four wheeled vehicle results in a set of shock absorbers which can be adjusted as a set to promote a particular type of ride or behaviour.

Typically the steered wheels of such a vehicle can be equipped with an embodiment of the invention so that the shock absorber of the outside wheel in a turn is stiffened and the shock absorber of the inside wheel softened to reduce a tendency of the vehicle to roll outwardly.

The described embodiments refer to the use of a non-circular piston so that rotation of the piston rod will not result in rotation of the piston. However a similar effect can be achieved with a circular piston to which the piston rod is linked but in a position offset from the centre of the geometric centre of the piston. In such an embodiment rotation of the piston will still result in relative rotation of the piston rod relative to the piston without causing rotation of the piston. Consequently such relative movement can be used to impart a control input to a valve associated with the piston as described in the exemplary embodiments.

Claims (16)

1A shock absorber comprising: a) a body tube having a longitudinal axis; b) a first closure member for a first end of the body tube and a second closure member for the other end of the tube to the first end; the combination of the tube and the first and second closure members serving to define a working volume;

c) a piston adapted for reciprocation within the working volume to fluid tightly separate a first and second volume within the working volume; at least one first flow channel in the piston providing for the flow of fluid from the first volume to the second volume; a first valve to control the flow of fluid along the first flow channel or channels; a first regulating means to provide for the first valve to establish flow along the channel or channels at a value between a maximum and a minimum flow value; d) a piston rod having a longitudinal axis co-axial with, or parallel to, the longitudinal axis of the body tube; the piston rod having a first end section and a second end section; the first end section serving to link the piston rod to the piston to enable the piston rod to be rotated about its longitudinal axis relative to the piston while preventing relative logitudinal movement between rod and the piston; the first end being linked to the regulating means so as to provide for operation of the valve associated with the regulating means by rotation of the rod about its longitudinal axis relative to the piston; relative rotation of the piston rod in a first direction about the longitudinal axis of the piston rod serving to increase flow along the channel; relative rotation of the piston rod in a second direction about the longitudinal axis of the piston rod serving to reduce flow along the channel; the piston rod extending outside the body member by way of a pressure seal in the second closure member so as to locate the second end outside the body member while allowing for reciprocation of the piston rod relative to the body tube; and f) an end unit retained on, and adapted for rotation about, longitudinal axis of the piston rod so that the end unit can be aligned relative to the first closure member.

2 A shock absorber as claimed in Claim 1 wherein the body tube has a non-circular internal cross section and the piston has a complementary outside periphery complementing the non-circular cross-section.

3 A shock absorber as claimed in Claim 1 wherein the body tube has a circular internal cross section; the piston has a complementary outside periphery.

4 A shock absorber as claimed in Claim 1 or Claim 2 wherein there is provided in the piston at least one second flow channel providing for the flow of fluid from the second volume to the first volume; a second valve to control the flow of fluid along the second channel or channels; a second regulating means providing for operation of the second valve to provide a range of obturation to flow in the second flow channel between a maximum and a minimum flow value; the first end of the piston rod being linked to the piston so as to enable the piston rod to be rotated about its longitudinal axis relative to the body member while preventing relative logitudinal movement between rod and body member; and linked to the second regulating means so as to provide for operation of the valve associated with the second regulating means by rotation of the rod about its longitudinal axis relative to the piston body member; such that relative rotation of the piston rod in a first direction about the longitudinal axis of the piston rod serving to cause the second valve to act to increase obturation to flow in the or each second flow channel; and relative rotation of the piston rod in a second direction about the longitudinal axis of the piston rod serving to cause the second valve to act to reduce obturation to flow in the or each second flow channel.

5 A shock absorber as claimed in any preceding claim wherein the piston rod encloses a drive rod co-axial with the piston rod; the first end section of the piston rod being linked to one regulating means; the drive rod having a first end section and a second end section; the first end section of the drive rod serving to link the drive rod to the other regulating means the drive rod extending outside the body member by way of the piston rod so as to locate the second end of the drive rod outside the body member; the first end section of the drive rod being linked to the other regulating means so as to provide for operation of the valve associated with that regulating means by rotation of the drive rod about its longitudinal axis relative to the piston body member; relative rotation of the drive rod in a first direction about the longitudinal axis of the drive rod serving to cause the valve to act to increase obturation to flow in the flow channel; relative rotation of the drive rod in a second direction about the longitudinal axis of the drive rod serving to cause the valve to act to reduce obturation in the flow channel.

6 A shock absorber as claimed in any preceding claim wherein there is provided a regulating means for pressure in the first volume comprising: a) a pressurisable auxiliary chamber located outside the working volume and linked: (i) to provide for fluid flow from the first volume to the auxiliary chamber by way of a third flow channel; (ii) to prove for fluid flow from the auxiliary chamber to the second chamber by way of a fourth flow channel; (iii) to provide for fluid flow from the auxiliary chamber to the second volume by way of a fifth flow channel; b) a third valve to control the flow of fluid along the third channel;

c) a fourth valve to control the flow of fluid along the fourth channel.

7 A shock absorber as claimed in Claim 1, 2, 3, 4 or 5 wherein the body tube is surrounded by a further tube to define a pressurisable annulus which forms the auxiliary chamber.

8 A shock absorber as claimed in Claim 6 or Claim 7 wherein the auxiliary chamber contains a pressurised bladder adapted to vary the volume of the auxiliary chamber in response to working pressure therein.

9 A shock absorber as claimed in Claim 6 or Claim 7 or Claim 8 wherein a first bleed adjuster provides for flow bleed adjustment between the first volume and the auxiliary chamber; and a second bleed adjuster provides for flow bleed adjustment between the second volume and the auxiliary chamber

10 A shock absorber as claimed in Claim 6 wherein the auxiliary chamber comprises a pressure vessel mounted apart from the body tube and linked to it by means of a pressure duct.

11 A shock absorber as claimed in Claim 6 wherein the auxiliary chamber comprises a loading volume isolated from the working volume by a piston defining a pressure tight slidable boundary therebetween and a pressurisable line communicating with the loading volume.

12 A shock absorber as claimed in Claim 11 wherein the pressurisable line extends through the first closure member.

13 A shock absorber as claimed in any preceding claim wherein the piston rod is rotatable relative to the body member by means of a bevel drive incorporated in the end unit.

14 A shock absorber as claimed in Claim 5 and in any subsequent claim to Claim 5 when dependent on Claim 5 wherein the drive rod is rotatable relative to the body member by means of a bevel drive incorporated in the end unit.

15 A shock absorber as hereinbefore described with reference to Figures 1 and 2; or Figure 3 and 4; or Figures 5 or 6 of the accompanying drawings.

16 A vehicle equipped with a shock absorber as claimed in any preceding claim.