Improved dampers

Abstract

A piston-cylinder damper having a cylinder containing a damping fluid. The damper is operable to perform a compression stroke and a return stroke. A piston rod is engageable with a piston assembly and a return arrangement. A sealing element is axially movable relative to the piston rod so that the sealing arrangement is operable to engage with the piston assembly and the return arrangement so that the sealing arrangement engages only with the piston assembly during the compression stroke and engages only with the return arrangement during the return stroke.

Description

Technical Field

[0001] The present invention relates to a damper. Background Art

[0002] It is becoming increasingly common to include dampers in furniture items to assist in closing drawers and doors. There is a need to try to reduce the size of said dampers. However, it is essential to maintain high damping performance. It is also important to ensure the reliability of the dampers.

[0003] A known damper is disclosed in GB2498747. The damper comprises a piston assembly, which is shown in situ in Figures 1 and 3 and enlarged in Figures 2 and 4. The piston assembly comprises an upper flange and a lower flange (see features 14a, 14b). The outer diameter of the upper and lower flanges is slightly smaller than the inner diameter of the cylinder bore. Therefore, the piston assembly can move freely in the cylinder along its longitudinal axis. This also means that there is a small gap between the flange and the cylinder, forming a passage for the damping fluid to circulate between the upper and lower chambers.

[0004] The upper flange is axially spaced from the lower flange, and an O-ring is disposed in the space therebetween. The O-ring is in sealing engagement with the cylinder bore but not with the piston assembly. The piston assembly has a hole therethrough that enables a fluid communication passage to be formed between the upper chamber and the lower chamber.

[0005] In operation, the assembly is usually in the position shown in Figure 1, with the piston rod of the assembly fully extended from the cylinder. When the distal end of the piston rod is hit by, for example, a closing door, this will cause the piston rod to force the piston assembly to move toward the closed end of the cylinder against the bias of the spring. At the same time, the upper flange (feature 14a) will move to engage with the O-ring, thereby closing the fluid path between the upper flange and the cylinder. Thus, the only remaining path for the damping fluid to flow from the lower chamber to the upper chamber is through the gap between the counterbore in the piston assembly and the inner end of the piston rod. This restricted flow of the damping fluid between the two chambers provides a damping limiting force for the movement of the piston rod. When the force on the distal end of the piston rod dissipates, the piston rod will return to its extended position by the spring bias force acting on the piston assembly. This movement causes the O-ring to move from engaging with the upper flange (feature 14a) to engaging with the lower flange (feature 14b). In this position, a greater degree of fluid communication is opened between the two chambers. This greatly reduces the flow of damping fluid across the piston assembly, thus meaning that there is almost no effective damping resistance in the return movement of the piston rod.

[0006] Improvements to the above designs would be advantageous. It would be particularly advantageous to be able to make a damper that is more compact in length and diameter while still maintaining a high level of damping capacity. Summary of the invention

[0007] According to the present invention, there is provided a piston-cylinder damper having a cylinder containing a damping fluid, operable to perform a compression stroke and a return stroke, the damper comprising:

[0008] A piston rod engageable with a piston assembly and a return device, wherein the sealing element is axially movable relative to the piston rod so that the sealing device is operable to engage with the piston assembly and the return device so that the sealing device only engages with the piston assembly during a compression stroke and only engages with the return device during a return stroke.

[0009] This arrangement reduces the overall length of the damper by making the piston assembly smaller. During the return stroke, the piston assembly does not need to force the sealing device back to its starting position. Therefore, relative to the previous arrangement, the piston assembly can include a reduced length.

[0010] Furthermore, in known prior art arrangements, the piston assembly, the sealing means and the return flange (feature 14b) are all mounted on the piston rod. This can lead to coaxial problems with heavy use, which may require replacement of the damper unit. Therefore, the piston assembly needs to have a certain diameter. In the present arrangement, only the piston assembly is mounted on the piston rod, so the diameter of the damper can be reduced.

[0011] Preferably, the return means comprises a spring. Preferably, the spring engages the piston rod directly or indirectly via a support member. By actively engaging the return means with the sealing means, rather than directly with the piston assembly, the damper may be constructed to have a reduced length.

[0012] Preferably, the return means is in contact engagement with the piston rod during compression and return strokes. The piston rod is engaged with the piston assembly, but there is no engagement between the piston assembly and the return means. A sealing means is maintained between the return means and the piston assembly. The sealing means is maintained in a floating arrangement, with the return means and the piston assembly being the limits of its path of travel.

[0013] Preferably, the piston assembly comprises a bore therethrough. Particularly preferably, the piston assembly comprises a flow channel substantially surrounding the bore. The flow channel may be on the side of the piston assembly facing the piston rod. Alternatively, the flow channel may be on the side of the piston assembly facing the return means. By providing a flow channel of such dimensions, the travel path of the damping fluid during the compression stroke is long relative to the overall length of the damper.

[0014] Preferably, the piston assembly includes a counterbore located around the hole. The piston rod may include a flange operable to cooperate with the counterbore.

[0015] In a preferred arrangement, both sides of the piston assembly may include flow channels. Specifically, the flow channel may be provided on the side of the piston assembly facing the piston rod, and the second flow channel may be provided on the side of the piston assembly facing the return device.

[0016] Preferably, the sealing device is an O-ring. In one embodiment, the O-ring may include one or more protrusions to allow the O-ring to bend or deform during the return stroke. In a further preferred arrangement, the O-ring may include grooves located on either side of the one or more protrusions. Such grooves help the O-ring to bend or deform.

[0017] Alternatively, the piston assembly may include one or more protrusions. In this case, the O-ring, which may be of standard design, may flex during the compression stroke.

[0018] The O-ring is not mounted on the piston assembly. Therefore, the hole through the piston assembly can have a reduced diameter.

[0019] According to a second aspect of the invention, there is provided a piston assembly comprising a first face operable to engage with a piston rod and a second face operable to engage with a return device, wherein the first face comprises a first flow channel. The piston can be used with a damper. When the damper is compressed, the flow channel provides a path for the damping fluid to travel.

[0020] Preferably, the piston assembly includes a bore therethrough. Preferably, the bore is defined by the inner surface. Also preferably, the first face includes a counterbore.

[0021] Preferably, the first flow passage substantially surrounds the aperture. Also preferably, the first flow passage is located within the counterbore. Further preferably, the first flow passage includes a portion that passes through an inner surface of the piston assembly.

[0022] Preferably, the second face comprises a second flow channel.Preferably, the second flow channel substantially surrounds the aperture.

[0023] Preferably, the first and second flow channels are connected by a through hole. By providing two communicating flow channels, a long fluid path for the damping fluid can be provided. However, since the fluid path includes two full-circumferential paths located on both sides of the piston assembly, the overall length of the piston assembly can be reduced. This allows the damper to be made smaller.

[0024] Preferably, the first face and the second face of the piston assembly are connected by a peripheral surface. In a preferred arrangement, the peripheral surface may include one or more grooves.

[0025] According to a third aspect of the invention, there is provided a piston cylinder damper operable to perform a compression stroke and a return stroke, the damper comprising: a piston rod; a piston assembly, and a return device, wherein the piston rod and the return device are operable to engage independently of the piston assembly in the compression and return strokes.

[0026] Preferably, the return means comprises a spring. Also preferably, a portion of the piston rod is operable to pass through a hole in the piston assembly and directly engage the spring.

[0027] In another embodiment, the return device and the piston rod may be engaged by a support member. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the present invention more easily understood, specific embodiments thereof will now be described in conjunction with the following drawings.

[0029] FIG. 1 shows a cross section of a damper of a first embodiment, illustrating the compression stroke.

[0030] FIG. 2 shows a cross section of the damper of FIG. 1 along line AA.

[0031] Fig. 3 shows a cross section of the damper of the first embodiment, illustrating the return stroke.

[0032] FIG. 4 shows a cross section of the damper of FIG. 1 along line BB.

[0033] FIG. 5 shows an example of a support member that may comprise a portion of a return arrangement.

[0034] FIG. 6 shows an example of a sealing arrangement.

[0035] FIG. 7 shows a first view of the piston assembly.

[0036] FIG. 8 shows a second view of the piston assembly of FIG. 7 .

[0037] Fig. 9 A cross section of a damper of a second embodiment is shown, illustrating the compression stroke.

[0038] Figure 10 shows Fig. 9 Cross section of the damper along line AA.

[0039] FIG. 11 shows a return device according to a second embodiment.

[0040] Fig.12 A first view of another piston assembly is shown.

[0041] Fig.13 Shows Fig.12 A second view of the piston assembly.

[0042] FIG. 14 shows a cross-section of the damper of the third embodiment, illustrating the compression stroke.

[0043] FIG. 15 shows a cross section of the damper of FIG. 14 along line BB.

[0044] FIG. 16 shows a return device according to a third embodiment.

[0045] Figure 17 shows a cross section of a damper of a fourth embodiment, showing the compression stroke.

[0046] FIG. 18 shows a cross section of the damper of FIG. 17 along line AA.

[0047] FIG. 19 shows a return device according to a fourth embodiment.

[0048] FIG. 20 shows another sealing arrangement.

[0049] Fig.20a A variation of the sealing arrangement of FIG. 20 is shown.

[0050] Fig.20b Another piston assembly is shown.

[0051] Figure 21 shows a cross section of a damper of a fifth embodiment, showing the compression stroke.

[0052] FIG. 22 shows a cross section of the damper of FIG. 21 along line AA.

[0053] FIG. 23 shows a supporting device according to a fifth embodiment.

[0054] Fig.24 A first view of another piston assembly is shown.

[0055] Fig.25 Shows Fig.24 A second view of the piston assembly.

[0056] Figure 26 shows a cross section of the damper of the sixth embodiment, showing the return stroke.

[0057] FIG. 27 shows a return device according to a sixth embodiment.

[0058] FIG. 28 shows a first view of the piston assembly.

[0059] FIG. 29 illustrates a second view of the piston assembly of FIG. 28 .

[0060] FIG. 30 shows a cross section of the damper of FIG. 26 along line BB.

[0061] Figure 31 shows a cross section of the damper of the seventh embodiment, showing the compression stroke.

[0062] FIG. 32 shows a return device according to a seventh embodiment.

[0063] FIG. 33 shows a first view of the piston assembly.

[0064] FIG. 34 illustrates a second view of the piston assembly of FIG. 33 .

[0065] FIG. 35 shows a cross section of the damper of FIG. 31 along line BB. DETAILED DESCRIPTION

[0066] Figures 1 and 3 show a linear piston cylinder damper 1. The damper 1 includes a cylinder 10 that accommodates a piston rod 12 and a piston assembly 14. The cylinder 10 typically has a circular cross-section and is closed at one end. The cylinder contains a damping fluid, such as oil or silicone. The piston rod 12 is mounted to perform linear reciprocating movement relative to the cylinder 10 along its longitudinal axis x. The free end 16 of the piston rod 12 extends out of the cylinder 10 from the other end of the cylinder 10, which is closed by a cover assembly 18. The cover assembly 18 provides support for the slidable mounting of the piston rod 12 and has suitable seals to prevent the damping fluid from leaking out of the cylinder 10.

[0067] The piston assembly 14 includes a central bore therethrough. The central bore includes an inner surface 56.

[0068] The piston rod 12 extends into the interior of the cylinder 10, and the inner end 20 of the piston rod 12 engages with the piston assembly 14 inside the cylinder 10. The inner end 20 of the piston rod 12 is received in a counterbore 22 of the piston assembly 14.

[0069] A collar 24 on the inner end 20 of the piston rod 12 provides an annular reaction surface to help distribute loads transmitted to the piston assembly 14. The collar 24 may be integrally formed with the piston rod 12, such as by stamping, or it may be formed separately and attached by suitable means.

[0070] The piston assembly may include a counterbore 22 operable to receive a collar 24 of the piston rod 12. This helps provide lateral support to the inner end of the piston rod and guide it to reciprocate along the axis x. However, the counterbore is optional, and it is contemplated that the piston rod 12 may engage a flush surface of the piston assembly 14. By providing a piston assembly 14 that presents a substantially flat surface to the piston rod 12, a shorter piston assembly 14 may be provided.

[0071] The portion of the piston rod 12 that advances from the collar 24 is referred to as the piston rod pin 26. The piston rod pin 26 is shaped to be able to pass through a hole in the piston assembly 14.

[0072] The piston assembly 14 divides the interior of the cylinder into two independent chambers, namely the left chamber A and the right chamber B in FIG. 1 , and includes a passage for controlling the flow of damping fluid between them. The outer diameter of the piston assembly 14 is slightly smaller than the inner diameter of the cylinder 10. Therefore, the piston assembly 14 can move freely along its longitudinal axis in the cylinder 10. The piston assembly 14 has grooves 28 on its outer surface to help the damping fluid flow between the chambers. These grooves are shown in FIGS. 7 and 8 .

[0073] When the free end 16 of the piston rod 12 is subjected to an impact tending to compress the damper, the impact force will be transmitted through the collar 24 of the piston rod 12 to the piston assembly 14 thereby driving it into the cylinder 10. This will cause the piston assembly 14 to engage sealingly with the seal 30. In the present embodiment, the seal 30 is an O-ring. This effectively seals the gap around the outside of the piston assembly 14. In other words, the passage around the periphery of the piston assembly is closed to the damping fluid, leaving the passage through the piston assembly 14 as the only possible path for the damping fluid to flow out of the left chamber A. By controlling the amount of restriction presented by the passage, the flow through the piston assembly 14 can be adjusted to provide the desired amount of damping resistance to be generated by the damper 1 for the inward movement of the piston rod 12. This is the compression stroke of the damper 1.

[0074] During the return stroke, i.e. when the piston rod 12 moves outwardly, the seal 30 will move out of engagement with the piston assembly 14, thereby opening an additional path for fluid flow around the outside of the piston assembly 14 through the groove 28. This is a larger path, which means that the fluid can freely return to the left chamber B quickly and substantially without any damping resistance.

[0075] The return stroke is assisted by providing a return device 32. In the present case, the return device 32 may include a spring 32 that directly or indirectly engages the piston rod pin 26. The embodiment shown in Figures 1 to 8 includes a return device 32 that includes a spring 32 and a support member 34. The spring 32 is arranged to force the support member 34 to move towards the end cap 18.

[0076] The support member 34 of this embodiment comprises a cylindrical body 36 having four ribs 38 extending axially therefrom. This arrangement is shown in Figure 5. There could be more or fewer ribs, but four ribs 38 provide the best stability and performance.

[0077] In known arrangements, the piston assembly retains a seal between the first and second members, one of which engages the seal during the respective compression and return strokes. However, in the present invention, the piston group 14 engages the seal 30 only during the compression stroke. Here, during the compression stroke, the piston rod pin 26 engages the cylindrical body 36 of the support member 34 through the diameter of the O-ring 30. The O-ring 30 is engaged by the piston assembly 14. The O-ring 30 is spaced a distance X1 from the rib 38 of the support member 34. This distance is the minimum movement of the O-ring between the compression stroke and the return stroke.

[0078] Furthermore, since the O-ring 30 is not held on the piston assembly 14, the diameter of the hole through which the O-ring 30 passes can be made smaller. This can reduce the overall diameter of the damper 1.

[0079] Figures 2 and 4 show a cross section of the support member 34. As will be appreciated, the shape of the support member 34 and its engagement with the seal 30 allows damping fluid to pass easily during the return stroke. As can be seen in Figure 3, during the return stroke, there is a distance Y1 between the O-ring 30 and the piston assembly 14. Because the damping fluid can easily pass between the O-ring 30 and the ribs 38 of the support member 34, this distance can be kept short relative to known arrangements.

[0080] As shown in Figure 7, the piston assembly 14 presents a flow channel 40 that allows damping fluid to flow between the two chambers of the damper 1 when the piston assembly 14 is engaged with the O-ring 30. The flow channel 40 also includes a chamfered channel that generally surrounds the main bore through the piston assembly 14. The flow channel 40 includes a flow passage 58 located in the inner surface 56 of the piston assembly 14. The chamfered channel terminates at an outlet that allows the damping fluid to flow from chamber A to chamber B. The stroke length of the damping fluid is therefore longer than in a conventional arrangement, so a physically shorter damper can be achieved; the fluid is still forced to follow a path, but the path is maintained within the relatively short piston assembly with the flow channel 40 surrounding the bore.

[0081] It will therefore be appreciated that the size of the damper 1 can be reduced by providing at least one of a full circumferential groove around the bore of the piston assembly and a return means engaging the piston rod 12 independently of the piston assembly 14. Together these two concepts provide a significant size reduction.

[0082] Figures 9 to 13 A second embodiment is shown, which has many similarities to the first embodiment and these similarities will not be described in detail.

[0083] In this embodiment, the return means comprises a spring 32 which engages directly with the piston rod pin 26. An example is shown in Figure 11. The spring 32 comprises an annular portion 42 which engages with the seal 30 during the return stroke, and a protruding portion 44 which engages with the piston rod pin 26. Fig. 9 The protrusion is shown so that during the compression stroke, a distance X2 is maintained between the annular portion of the spring 42 and the seal 30. This defines the range of movement of the O-ring between the compression stroke and the return stroke. In known arrangements, the O-ring is mounted on the piston assembly, so a piston assembly of larger physical dimensions is required. By allowing the O-ring to float with the piston assembly 14 and the return device 32, the overall length of the damper can be reduced.

[0084] The difference of the piston assembly 14 is that the flow passage 40 is located on the side pointing to the left chamber. The flow path has an inlet near the inner bore of the piston assembly and an outlet near one of the grooves on the outer edge of the piston assembly 14. During the compression stroke, the piston assembly 14 is pushed against the O-ring 30. Thus, the only path for the damping fluid is through the flow path and then through the groove on the piston assembly into the right chamber. It should be understood that the piston assemblies of Figures 7 and 8 can be used in this embodiment.

[0085] Figures 14 to 16 show a third embodiment. In this arrangement, the spring 32 includes a tapered portion 46 formed by the coil of the spring, which acts as a protrusion in the second embodiment. The diameter of the tapered portion 46 is smaller than the diameter of the hole through the O-ring 30. The diameter of the remaining spring coils is larger than the hole diameter of the O-ring 30. The tapered portion has a sufficient length to maintain a distance X3 between the O-ring 30 and the first of the remaining spring coils. Such a distance is sufficient to allow the damping fluid to return from chamber B to chamber A during the return stroke.

[0086] During the return stroke, the tapered portion of the spring 32 allows the damping fluid to flow freely through the hole in the seal 30 and over the spring 32 back into the chamber A.

[0087] This embodiment can be used as shown in Figures 7 and 8 or Fig.12 and 13 The piston assembly 14 is shown.

[0088] Also, in this embodiment, by allowing the O-ring 30 to float between the return device and the piston assembly during operation, the damper 1 can be made smaller in size relative to the prior art.

[0089] 17 to 20 show a fourth embodiment. In this embodiment, the return device 32 includes a spring 32 that directly engages the O-ring 30. The O-ring 30 includes a pair of protrusions or sockets 48 that enable the flat side 50 of the O-ring 30 to deform. The sockets 48 face the return spring 32 and engage with the return spring 32, so that the O-ring 30 deforms during the return stroke, thereby making it easier for the damping fluid to flow from the first chamber A to the second chamber B. The sockets 48 extend from the surface 54 of the O-ring 32 that faces the return device. A variation of this O-ring 30 is shown in FIG. Fig.20a As shown. The grooves 52 are provided on either side of the socket 48. This arrangement promotes deformation of the O-ring 30 during the return stroke. This embodiment can be used as shown in Figures 7 and 8 or Fig.12 and 13 The piston assembly 14 is shown.

[0090] A spacing X4 is provided between the return device 32 and the return-facing surface 54 of the O-ring 30 . This distance is the working range of the O-ring 30 .

[0091] This arrangement differs from the previous embodiment in that the return means 32 does not directly engage the piston rod pin 26. The provision of a profiled O-ring allows the O-ring to flex during the return stroke and thereby provide the necessary return passage for the damping fluid.

[0092] Another variation of this embodiment is Fig.20b . This figure shows a deformed piston assembly 14. In this arrangement, two protrusions 60 are provided on the surface of the piston assembly, which, in use, faces the return device 32. This arrangement will conveniently cooperate with a standard O-ring, such as the O-ring shown in FIG. 6. In this arrangement, the O-ring bends during the compression stroke due to its interaction with the protrusions 60 located on the piston assembly 14. It will be understood that the O-ring will remain unbent during the return stroke of the damper 1. The O-ring bends over the protrusions 60, thereby sealing the passage for the damping fluid on the outer surface of the piston assembly 14. Therefore, the only way for the damping fluid to travel from chamber A to chamber B during the compression stroke is through the flow channel 40 provided on the piston assembly. To further assist in sealing in the compression stroke, two extended chamfers 62 are also provided, which seal the inner diameter of the O-ring during the compression stroke. In order to ensure adequate sealing, the width of the chamfers 62 must be greater than the width of the protrusions 60. This arrangement is advantageous because it allows assembly with a standard O-ring assembly.

[0093] A fifth embodiment is shown in FIGS. 21 to 23 . In this embodiment, the return device 32 comprises a spring 32 and a support member 34. The support member comprises a cylindrical body 36 and four ribs 38. The ribs 38 may be more or less. The cylindrical body 36 may comprise a hole that may receive a protrusion from the spring 32.

[0094] Figure 22 shows a cross section of the support member. This embodiment can be used as shown in Figures 7 and 8 or Fig.12 and 13 The piston assembly 14 is shown.

[0095] FIG. 21 shows the compression stroke of the damper 1. The piston rod pin 26 engages with the body 36 of the support member 34. A gap X5 is maintained between the O-ring and the rib 38 of the support member 34. The gap constitutes the travel path of the O-ring between the compression and return strokes. In the return stroke, the O-ring will engage with the rib 38 of the support member and will provide a gap corresponding to X5 between the O-ring 30 and the piston assembly 14. This allows the damping fluid to have a larger path between chamber B and chamber A because the damping fluid can flow through the groove 28 on the outer surface of the piston assembly 14.

[0096] In all embodiments, the piston assembly 14 engages a seal 30, typically an O-ring, during the compression stroke. During the return stroke, the O-ring 30 disengages from the piston assembly 14. The return device 32 engages the O-ring 30 during the return stroke. In prior art arrangements, the return device would engage the piston assembly, which in turn would engage the seal.

[0097] Fig.24 and Fig.25 Another piston assembly 14 is shown in . This piston assembly 14 can be used in any of the above embodiments. The piston assembly 14 includes a flow channel 40 on each face. Therefore, a first flow channel located on the face that engages with the piston assembly 14 and a second flow channel that engages with the return device 32 are provided. By providing two flow channels 40, the travel length of the damping fluid in the compression stroke is increased. The two flow channels 40 are connected by a through hole 66. Therefore, the damping fluid is forced to flow around the two flow channels during the compression stroke. Thereby, a high level of damping can be achieved with a relatively short damper.

[0098] Both the full circumferential groove / flow channel and the floating O-ring concept enable a reduction in the size of the damper 1. When these two concepts are used together, the size (length and diameter) of the damper can be significantly reduced.

[0099] By allowing the return means to engage directly or indirectly with the piston rod, the O-ring is enabled to float between positions on the compression and return strokes.

[0100] Two further embodiments (sixth and seventh) will now be described in conjunction with Figures 26 to 35. Where possible, the same reference numerals as in the previous embodiments have been used. Features that perform the same function as previously described will not be repeated.

[0101] The sixth embodiment is shown in Figures 26 to 30. As previously described, a return device 32, a sealing device, a piston assembly 14 and a piston rod 12 are provided. In this embodiment, the piston rod includes a flange 24, which is operable to engage with the piston assembly 14. The portion operable to engage with the return device 32 can be referred to as a piston rod pin 26.

[0102] The return means comprises a spring, one end of which is adapted to include a socket 70. The socket 70 comprises a bar adapted from a spring, which bar is operable to engage the piston rod pin 26.

[0103] The difference from the previous embodiment is that the piston rod pin 26 extends beyond the position of the O-ring 30 during the damping stroke.

[0104] It will be noted from FIGS. 28 and 29 that the piston assembly 14 includes a first groove 72 etched into the wall of the hole through the piston assembly 14 and a second semicircular force limiting groove 74 (as shown in FIG. 29 ) surrounding the hole of the piston assembly. This is similar to the arrangement shown in FIGS. 7 and 8 . In this embodiment, the piston assembly 14 includes two further grooves 76 configured to increase the return flow of the damping fluid in the return stroke of the damper. A cross-section of the piston assembly is shown in FIG. 30 . The first groove 72 and the two further grooves 76 are visible.

[0105] In this embodiment, the piston assembly is configured to float between the damping stroke and the return stroke in a manner similar to the sealing device in the previous embodiment. During the damping stroke, the flange 24 on the piston rod 12 engages with the piston assembly 14 and pushes the piston assembly and the sealing device against the return device 32. The damping fluid is forced to flow from chamber A to chamber B through the first groove 72 and the second semi-circular force-limiting groove 74. During the return stroke, the return device 32 pushes the piston rod 12 (through the piston rod pin 26) out of the damper housing. Because the piston rod pin 26 is longer than the O-ring 30 and the piston assembly 14, both components can slide relative to the piston rod pin 26. In this way, as shown in Figure 26, a gap G is created between the piston assembly and the flange. Thus, the damping fluid can flow between the piston assembly and the flange through the additional groove.

[0106] In a variation, the O-ring 30 and the piston assembly 14 may be fixed together. One option is to glue them together, or the piston assembly may have an integral retaining device.

[0107] A seventh embodiment is shown in FIGS. 31 to 35 . In this arrangement, the piston assembly 14 is adapted to include an elongated portion 78 for extending the piston rod pin 26. In this arrangement, the return device 32 engages the elongated portion 78. The flange 24 of the piston rod 12 remains engaged with the piston assembly 14 throughout the damping and return strokes. In this arrangement, the O-ring 30 can float between positions along the elongated portion 78 in the manner described in the previous embodiments.

[0108] As shown in FIG. 34 , the piston assembly 14 includes a first groove 72 etched into the wall of the hole through the piston assembly 14 and a second semi-circumferential force limiting groove 74 surrounding the hole of the piston assembly. During the compression stroke (damping stroke), the flange 24 on the piston rod 12 engages the piston assembly 14 and pushes it against the return device. The damping fluid is forced to flow from chamber A to chamber B through the first groove 72 and the second semi-circumferential force limiting groove 74. The piston assembly engages the O-ring 30 to ensure that the damping fluid does not flow across the piston assembly; all the damping fluid is forced through the first and second grooves 72 and 74.

[0109] The elongated portion 78 of the piston assembly comprises means 80 for allowing the damping fluid to enter the first groove 72. In the example shown, the means 80 comprises a cutout in the elongated portion 78.

[0110] During the return stroke, the O-ring is forced away from the piston assembly (ie it can float towards the return means) so that damping fluid can flow over the piston assembly with the aid of grooves 28. These are similar to the grooves 28 shown in the embodiment described in conjunction with Figures 7 and 8.

[0111] In the two embodiments described in conjunction with Figures 26-35, the second groove 74 does not need to be full-circumferential. The length of the groove 74 defines the damping force. The longer the groove, the greater the damping force. For example, if a smaller force is required, a short linear groove can be provided.

[0112] The foregoing embodiments are provided to aid understanding and many modifications and variations are possible within the scope of the appended claims.

Claims

1. A piston-cylinder damper having a cylinder containing a damping fluid, operable to perform a compression stroke and a return stroke, the damper comprising: a piston rod engageable with a piston assembly and a return arrangement, wherein a sealing arrangement is axially movable relative to the piston rod such that the sealing arrangement is operable to engage with the piston assembly and the return arrangement such that the sealing arrangement engages only with the piston assembly during the compression stroke and engages only with the return arrangement during the return stroke; wherein the piston assembly comprises a central bore and the first flow passage substantially surrounds the bore, wherein the return means comprises a spring engaged directly with the piston rod or indirectly via a support member, and Wherein, the sealing device is an O-ring.

2. The damper according to claim 1, wherein: The return device is in contacting engagement with the piston rod during the compression and return strokes.

3. The damper according to claim 1, wherein: The piston assembly includes a first face operable to engage the piston rod and a second face operable to engage the return device.

4. The damper according to claim 3, wherein: The piston assembly includes a counterbore operable to receive the piston rod.

5. The damper according to claim 3, wherein: The first flow passage is on a first face of the piston assembly.

6. The damper according to any one of claims 3 to 5, wherein: The piston assembly further includes a second flow passage on the second face.

7. The damper according to claim 1, wherein: The O-ring includes one or more protrusions to allow the O-ring to flex or deform during the return stroke.

8. The damper according to claim 1, wherein: The piston assembly includes an elongated portion for extending the piston rod.

9. The damper according to claim 8, wherein: The sealing means is retained on the elongated portion and is operable to move along the elongated portion between limits defined by the piston assembly and the return means, depending on whether the damper assembly is performing a compression stroke or a return stroke.

10. The damper according to claim 9, wherein: The return means directly or indirectly engages the elongate portion during the compression and return strokes.

11. A piston-cylinder damper operable to perform a compression stroke and a return stroke, the damper comprising: Piston rod; Piston assembly, and Return device, wherein the piston rod and the return means are operable to engage independently of the piston assembly during the compression and return strokes, Wherein, the return device comprises a spring, and The piston assembly includes a bore therethrough, and wherein a portion of the piston rod is operable to pass through the bore and directly engage the spring.

12. A piston cylinder damper, comprising: A piston rod, the piston rod comprising a flange and a piston rod pin; Return device; Sealing device; and Piston assembly, wherein the length of the piston rod pin is greater than the total length of the sealing device and the piston assembly when compared along the main axis of the damper, and wherein the piston rod pin engages with the return device during both the compression stroke and the return stroke, and the sealing device and the piston assembly are operable to float relative to the return device and the piston rod.

13. The piston-cylinder damper according to claim 12, wherein: The sealing means is an O-ring.

14. The damper according to claim 1, 11 or 12, wherein: The return means comprises a lever operable to engage the piston rod directly or via an elongated portion.

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