BACKGROUND

[0001] Disclosed herein is a novel suspension module, particularly, a suspension module that may be retro-fitted, or incorporated as part of a suspension assembly. Such suspension assemblies may be used, for example, as vibration isolation mounts for a driver cabin in off-road vehicles.

[0002] Suspension units need to conform to specific functional requirements with regard to their capacity for absorbing vibration energy, and also to specific structural requirements so as to allow them to be fitted into a confined space, while maintaining capacity to withstand all operating load conditions. It is an ongoing desire to reduce the size of suspension units. Great Britain Patent Publication No. 2,242,958 discloses an elastomeric mounting of a type suitable for a vehicle cab suspension, providing good isolation of certain frequencies, but is not good for isolating sudden, shock motions. PCT Patent Publication No. 2004/097246 is directed to a vibration damping system for multi-directional shock protection.

[0003] A problem with these known damping systems is that they actively damp vibrations under all conditions, i.e., large and small amplitude vibrations at all and any frequencies. Under some vibration conditions, this detracts from the effective functioning of the elastomeric device, which can compromise the performance. [0004] Another problem with existing suspension units is that they may have been designed for vehicles or cabins without roll over protection structures (ROPS). If a vehicle is retro-fitted with a roll over protection structure or with a ROPS cabin, the suspension system may require a corresponding re-design.

[0005] However, it is costly to replace entire suspension assemblies designed for a specific environment.

[0006] As shown in Fig. 1 , a suspension device as known in the prior art is designed to moderate the transmission of vibrations from a chassis plate 10 to a plate 20. Plate 20 may be, for example, part of a bracket for a driver cabin. The suspension device of Fig. 1 comprises two axisymmetric elastomeric bodies 30 and 40 with an axial through hole for receiving a mounting bolt 50. The upper and lower elastomeric bodies are located one above and one below a mounting hole in a chassis plate 10. The elastomeric bodies are fixed to the chassis plate 10 by the bolt 50. The plate 20 is fixed to the upper elastomeric body by the same bolt 50. The damping behavior is determined by the properties of the elastomeric bodies 30, 40.

SUMMARY

[0007] Various embodiments of the design discussed herein have been devised to alleviate the afore-mentioned problems.

[0008] Accordingly, there is disclosed herein a suspension module and a damper for use in the suspension module, the damper comprising: an inner member and an outer member, one of said members being provided for mounting to a supporting body and the other of said members being provided for mounting to a suspended body, the inner member traversing axially through a fluid-tight chamber formed between the inner member and an inner wall of the outer member, the chamber containing damper fluid; a piston axially displaceable in the chamber with respect to said inner and outer members; a permanent passage through which the damper fluid can pass from one side of the piston to the other; one of said members having a pair of abutment surfaces, one on each side of the piston, and spaced apart by a distance larger than the thickness of the piston; wherein when the piston is part way between the abutment surfaces, an auxiliary passage is open through which the damper fluid can pass from one side of the piston to the other, said auxiliary passage having an area for passage of the damper fluid that is greater than that of said permanent passage, and wherein said auxiliary passage is blocked by the piston when it abuts against either one of said abutment surfaces. Various embodiments may comprise features described below.

[0009] Specific embodiments shall now be described with reference to the Figures, in which: [0010] Fig. 1 shows a cross-section of a suspension device as known in the prior art, installed in situ.

[001 1] Fig. 2 shows a schematic cross-sectional view of an embodiment of a damper, in its rest position.

[0012] Fig. 3 shows a cross-section of a suspension module incorporating the damper of Fig. 2, in its rest position. [0013] Fig. 4 shows a schematic cross-sectional view of another embodiment of a damper, in its rest position.

[0014] Fig. 5 shows a cross-sectional view of the damper of Fig. 4 in a housing, in its rest position, for assembly in a suspension module. [0015] Fig. 6 shows a cross-sectional view of another embodiment of a damper, in its rest position.

DETAILED DESCRIPTION

[0016] Fig. 2 shows a schematic cross-sectional view of a damper 100 for use in an exemplary suspension module. The damper 100 comprises an inner member 1 10 traversing axially through an outer member 200. One of the members 1 10 is provided to be mounted to a first body (e.g., a bracket of a cabin). The other of the members 200 is provided to be mounted to a second body (e.g., chassis plate 10 of Fig. 1 ) to which the first body is to be mounted. One of the first and second bodies generates vibration energy and it is desired to minimize the amount of vibration energy transferred from the vibration-generating body to the other body.

[0017] The inner member 1 10 comprises a rigid tube with a through hole to receive a mounting bolt. This facilitates the mounting of the inner member 1 10 to existing assembly geometries using a bolt. However, the inner member may have a different shape. For example, the inner member may be a strut with mounting means provided on one or both ends of the strut.

[0018] As shown in Fig. 3, the outer member 200 may be provided in the form of a cartridge to be provided within a housing 210. A modular assembly comprising a separate cartridge and housing increases the design freedom. This facilitates the integration of suspension units within existing designs, for instance for retro-fitting. However, use of a separate cartridge is not essential for the principles to be described herein.

[0019] Further shown in Fig. 2 is the inner surface 190 of the member 200, comprising upper and lower circumferential rims 192, 194. The rims facilitate

manufacture, e.g., in the embodiment described below the rims provide a secure seat for a press-fitted diaphragm. In an embodiment, the rims 192, 194 are means of tethering the flexible diaphragms. For example, the rims may be folded inwards and wrapped around the outer edges of the diaphragms. The rims 192, 194 may be integral to the outer member 200. For instance, the rims may be formed by wrapping the walls over.

[0020] The inner member 1 10 comprises a pair of abutment surfaces, shown here in the form of upper and lower flanges 1 12, 1 14 on its outer circumference. The purpose of these abutment surfaces will be explained below. The flanges 1 12, 1 14 are spaced apart from each other by a distance that is less than the space between the rims 192, 194. Therefore, it is possible to align the pair of flanges 1 12, 1 14 about midway between the upper and lower rims 192, 194 when the inner member 1 10 is inserted in the outer member 200. However, it will be appreciated that the axial position of the inner member 100 relative to the outer member 200 will depend on the applied static load.

[0021] Between the inner member 1 10 and the outer member 200 a fluid-tight chamber 150 is defined. As shown in the embodiment of Fig. 2, the inner and outer members are connected by an upper diaphragm 122 and a lower diaphragm 124. The upper diaphragm 122 is attached to the upper rim 192 and the upper flange 1 12.

Correspondingly, the lower diaphragm 124 is attached to the lower rim 194 and the lower flange 1 14. However, the diaphragms may be attached directly to the outer member 200. The attachment of the diaphragms is fluid-tight. For example, a sufficiently fluid-tight characteristic may be achieved by a press-fit. Thereby, the fluid- tight chamber 150 is defined as the volume enclosed by the outer surface of inner member 1 10, by the inner surface of outer member 200, and by the upper and lower diaphragms 122, 124.

[0022] The fluid-tight chamber 150 contains damper fluid. A filling port may be provided in the inner or outer member to allow damper fluid to be filled into the fluid- tight chamber 150. Preferably, the damper fluid completely fills the fluid-tight chamber 150. Preferably, the damper fluid is suitable for operation at a range of temperatures between about -25°C to +50°C. Preferably, the damper fluid is not corrosive to the components that it comes into contact with. Preferably, the damper fluid has a viscosity of at least 1 ,000 centistokes (cSt) at 25°C.

[0023] The diaphragms 122, 124 comprise a flexible material allowing displacement of the inner member 1 10 relative to the outer member 200 while providing a fluid-tight envelope for the chamber with the total volume of the fluid-tight chamber 150 being maintained independent of said relative displacement.

[0024] While the inner and outer members are rigid, the diaphragms 122, 124 are flexible to allow multi-axial displacement of the inner member 1 10 relative to the outer member 200. Further, the diaphragms 122,124 should ensure that there is minimal volumetric change in response to hydraulic pressure of the damper fluid.

[0025] Although the diaphragms 122, 124 need not be press-fitted to the flanges 122, 124, this arrangement provides a secure seat of the diaphragms. The flanges 122, 124 also provide a defined seat which can facilitate alignment of the individual components during assembly of the device.

[0026] As shown in Fig. 2, in the rest position the flanges 1 12, 1 14 are mid-way between the rims 192, 194 and thus urge the diaphragms into an inclined orientation within a perimeter defined by the outer member 200. This arrangement allows each diaphragms to bulge outward, e.g., in response to axial displacement of the inner member 1 10.

[0027] A piston 130 is provided within the chamber 150 in the space between the pair of flanges 1 12, 1 14. The piston is shown in the form of an annular piston plate comprising an outer circumference 132 and an inner circumference 134. The outer diameter of the piston 130 is only slightly smaller than the inner diameter of outer member 200, and allows a sliding engagement with the inner surface. Thereby, the piston 130 defines within the chamber 150 an upper compartment and a lower compartment. The piston plate 130 as shown further provides a permanent fluid passage 160 allowing fluid communication between the upper and lower compartment. The permanent fluid passage 160 may be comprised within the piston 130, e.g., in the form of one or more apertures or on the form of one or more radially extending grooves.

[0028] Preferably, the inner and outer members 1 10, 200 are axisymmetric, and thus the chamber 150 may be described as having a generally annular or toroidal volume. In such an arrangement the piston is generally circular and able to rotate about the inner member 1 10. However, embodiments may have other geometries of irregular or polygonal cross-section, e.g., octagonal or hexagonal cross-section, and correspondingly shaped piston. Thereby, rotation of the piston relative to the inner member 1 10 is restricted.

[0029] The inner circumference 134 of the piston plate 130 is smaller than the circumference of the flanges 1 12, 1 14. As such, there is an annular overlap of the piston and the opposing axial ly-facing surfaces of the flanges 1 12, 1 14. Further, the piston 130 has a thickness smaller than the space between the flanges. This allows the piston 130 to be axially displaced relative to both the inner member 1 10 and the outer member 200. In general terms, the flanges provide abutment surfaces which limit the axial travel of the piston. In the embodiment described here, the abutment surfaces are provided by the opposing axially-facing surfaces of the flanges 1 12, 1 14. However, the abutment surfaces may be provided differently. E.g., the abutment surfaces may be formed integral with the outer or inner member.

[0030] In the embodiment of Fig. 2, the inner circumference 134 of piston plate 130 is larger than the outer circumference of the inner member 1 10. When the piston 130 is positioned part-way between the flanges, an auxiliary fluid passage 170 is thus open allowing fluid communication between the upper and lower compartments of the chamber 150. The area for passage of the damper fluid of the auxiliary fluid passage 170 is greater than, and in many applications substantially greater than, the area for passage of the damper fluid of the permanent fluid passage 160. When the piston plate 130 abuts either the upper or the lower flange, the auxiliary fluid passage 170 is blocked. This restricts the total area available for fluid passage to just the permanent fluid passage 170.

[0031] Fig. 3 shows an embodiment in which the damper 100 of Fig. 2 is

incorporated into a suspension unit akin to that shown in Fig. 1 . Only one mounting plate 10 is shown for simplicity. In Fig. 3, the damper 100 is provided in the form of a cartridge seated in a housing 210. Fig. 3 shows two elastomeric bodies 230 and 240 similar to those in Fig. 1 . The upper body 230 is provided above the mounting plate 10. In contrast to Fig. 1 , the Fig. 3 also shows a damper 100 mounted between the lower elastomeric body 240 and the mounting plate 10. The geometry of the upper body 230 does not need to be modified to accommodate damper 100. Thus, the damper 100 can be incorporated without great difficulty. Of course, Fig. 3 provides only one example for incorporating a damper into a suspension module into a known suspension assembly. [0032] It is understood that the provision of the outer member 200 in the form of a cartridge to be fitted into a housing 210 is optional, and that the outer member 200 may be the housing itself. In that case, components that are described herein with reference to the outer member 200 wall would be understood to refer to the housing 210. [0033] Now turning to Figs. 4 and 5, there is shown a schematic cross-sectional view of a damper 300 for use in a suspension module in accordance with the present invention. Damper 300 is an embodiment comprising two pistons. Multi-piston embodiments, including the two-piston embodiment shown in Fig. 4, may provide an even better degree of control over the damping behavior and over the displacement behavior of the suspension module.

[0034] The damper 300 comprises an inner member 310 traversing axially through an outer member 400. Akin to the damper 100, one of the inner and outer members is provided to be mounted to a first body. The other of the inner and outer member is provided to be mounted to a second body to which the first body is to be mounted. [0035] As shown in Fig. 4, the inner member 310 comprises a rigid tube with a through hole to receive a mounting bolt, to allow the inner member 310 to be mounted to a suspension module. As set forth above in relation to inner member 1 10, the inner member 310 may have a different shape.

[0036] The outer member 400 is provided in the form of a cartridge to be provided within a housing 410 (shown in Fig. 5).

[0037] The member 400 is a generally cylindrical tube whose inner surface defines an inner surface 390. The member 400 comprises two circumferential rims 392 and 394, one on the upper end of the member 400 and the other provided at the lower end of the member 400. The circumferential rim 392 that is provided at the upper end of the member 400 provides a secure seat for a press-fitted diaphragm 322. Likewise, the circumferential rim 394 at the lower end provides a secure seat for a press-fitted diaphragm 324. The attachment of the diaphragms is fluid-tight. As used herein, "upper" and "lower" refer to the orientation of Figs. 4 and 5. The damper 300 may be installed in any orientation, for instance in an orientation in which the circumferential rim 392 faces down and the circumferential rim 394 faces up, or, alternatively, horizontally or at an inclined angle. [0038] The inner member 310 comprises, on its outer surface, a series of edges, located partway between the upper and lower end of the inner member 310. As shown in Fig. 4, the edges comprise an upper edge 302, a lip 303, and a lower edge 304. The inner member 310 comprises a series of pairs of abutment surfaces provided by an upper flange 312, a center flange 313, and a lower flange 314. The upper flange 312 is positioned on the upper edge 302, the center flange 313 is positioned on the lip 303, and the lower flange 314 is positioned on the lower edge 304. It will be apparent that the upper edge 302, the lip 303, and the lower edge 304 are optional features that facilitate the axial positioning of the flanges. [0039] As used herein, "center" refers to a position of a feature relative to corresponding upper and lower features and typically partway between the

corresponding upper and lower features, but does not require a feature to be exactly centered.

[0040] The upper flange 312 and the center flange 313 provide a first pair 316 of abutment surfaces. The abutment surfaces of the first pair 316 are constituted by the face of the upper flange 312 that faces the center flange 313, and by the face of the center flange 313 that faces the upper flange 312. Likewise, the center flange 313 and the lower flange 314 provide a second pair 318 of abutment surfaces, wherein the abutment surfaces of the second pair 318 are constituted by the face of the center flange 313 that faces the lower flange 314, and by the face of the lower flange 314 that faces the center flange 313.

[0041] As shown in Fig. 4, the spacing between the flanges 312 and 313, as well as the spacing between the flanges 313 and 314, is less than the spacing between the circumferential rims 392 and 394. Thereby, the center flange 313 may assume a rest position about half-way between the circumferential rims 392 and 394.

[0042] The upper diaphragm 322 is attached by a press-fit to a circumferential rim 311 of the upper flange 312. Likewise, the lower diaphragm 324 is attached to a circumferential rim 315 of the lower flange 314. The attachment of the upper diaphragm 322 to the upper flange 312 and of the lower diaphragm 324 to the lower flange 314 is fluid-tight. Of course, the diaphragm may be attached to the inner member and the outer member by other mechanisms, provided that these mechanisms result in a fluid- tight attachment. For instance, these may include adhesive and/or sealants, or a rubber seal that is integral with the diaphragm and can be held in place with a clip.

[0043] Thus, the inner member 310, the outer member 400 and the diaphragms 322 and 324 define a fluid-tight chamber 350. Like the fluid-tight chamber 150 described above, the fluid-tight chamber 350 contains damper fluid. The damper fluid may be filled into the chamber 350 via a filling port (not shown). Preferably, the damper fluid is suitable for operation at a range of temperatures between about -25°C to +50°C. Preferably, the damper fluid is not corrosive to the components that it comes into contact with. Preferably, the damper fluid has a viscosity of at least 1 ,000 centistokes (cSt) at 25°C.

[0044] As described above with reference to diaphragms 122 and 124, the upper and lower diaphragms 322, 324 are flexible and allow the inner member 310 to be displaced relative to the outer member 400, while providing a fluid-tight envelope for the chamber 350. The total volume of the fluid-tight chamber 350 can be maintained independent of relative displacement. The flexibility of the diaphragms 322, 324 also allows multi-axial displacement of the inner member 310 relative to the outer member 400.

[0045] As shown in Fig. 4, the upper diaphragm 322 is attached at the chamber- facing sides of the circumferential rims 392 and 31 1 , and the lower diaphragm 324 is attached to the chamber-facing sides of the circumferential rims 394 and 315. For each diaphragm, the width between its inner circumference and its outer circumference is larger than the spacing between the rims to which each diaphragm is attached. Thus, each diaphragm is, in the rest position, urged into an arc. The arc faces into the fluid- tight chamber 350. This arrangement is used when it is necessary to reduce the risk that a diaphragm is caught between the circumferential rims and the corresponding flange during movement of the inner member 310 relative to the outer member 400. However, in other embodiments the diaphragm may arc convex to the rims, i.e., so as to protrude outward, away from the fluid-tight chamber 350.

[0046] The embodiment of Fig. 4 comprises two pistons, a first piston 330A and a second piston 330B. Each piston 330A and 330B corresponds to the piston 130 described above. Thus, the first piston 330A comprises an outer circumference 332A and an inner circumference 334A. The second piston 330B comprises an outer circumference 332B and an inner circumference 334B. The outer circumferences 334A and 334B are slightly smaller than the circumference of the inner surface 390 of the outer member 400, thus allowing sliding engagement with the inner surface 390.

[0047] The first piston 330A and the second piston 330B divide the fluid-tight chamber 390 into a series of compartments. The embodiment of Fig. 4 has an upper compartment 352 defined between the upper diaphragm 322 and the first piston 330A, a center compartment 354 between the first piston 330A and the second piston 330B, and a lower compartment 35 between the second piston 330B and the lower diaphragm 324. [0048] The first piston 330A and the second piston 330B each comprise one or more apertures (not shown in Fig. 4) to provide a fluid passage between the

compartments of the fluid-tight chamber 350. I.e., the one or more apertures of the piston 330A provide a fluid passage between the upper compartment 352 and the center compartment 354, and the one or more apertures of the piston 330B provide a fluid passage between the center compartment 354 and the lower compartment 356.

As shown in Fig. 4, the inner member 310 and the outer member 400 are axisymmetric and both the first piston 330A and the second piston 330B are generally circular.

Nevertheless, other geometries may be used, as set forth with reference to piston 130.

[0049] The inner circumference 334A is smaller than the outer circumference of the first pair 316 of abutment surfaces, and the thickness of the first piston 330A is less than the space between the abutment surfaces of the first pair 316. Likewise, the inner circumference 334B is smaller than the outer circumference of the second pair 318 of abutment surfaces, and the thickness of the second piston 330B is less than the space between the abutment surfaces of the second pair 318. Thus, each piston 330A and 330B may be displaced axially, but the axial travel is limited between their respective abutment surfaces.

[0050] As can be appreciated, while the abutment surfaces in Fig. 4 are provided in the form of flanges 312, 313, and 314 on the inner member 310, they may be provided on the outer member 400, or integral with the inner member 310 or outer member 400. [0051] The inner circumferences 334A and 334B of the first and second pistons are larger than the outer circumference of the inner member 310. Thus, if either piston 330A or 330B is positioned partway between its respective abutment surfaces, auxiliary fluid passages are open. The first auxiliary fluid passage 370A connects, via the space between the first pair 316 of abutment surfaces, the upper compartment 352 with the center compartment 354. The first auxiliary fluid passage 370A is blocked when the first piston 330A abuts against either of the abutment surfaces of the first pair 316. The second auxiliary fluid passage 370B connects, via the space between the second pair 318 of abutment surfaces, the center compartment 354 with the lower compartment 356. The second auxiliary fluid passage 370B is blocked when the second piston 330B abuts against either of the abutment surfaces of the second pair 318.

[0052] When an auxiliary passage is blocked by a piston, fluid cannot pass through the auxiliary passage from the one side of the piston to the other side of the piston.

However, the permanent fluid passage in the piston will allow fluid to pass from the one side of the piston to the other side of the piston. This will be the case independently for either or both the first piston 330A and the second piston 330B, i.e., one piston may be moving while the other piston blocks the auxiliary passage. [0053] As in the embodiment of Fig. 2, the area for passage of the damper fluid through the auxiliary passages 370A and 370B may be greater than, and may be substantially greater than, the area for passage of the damper fluid through the permanent fluid passage.

[0054] Fig. 5 shows an embodiment in which the damper 300 of Fig. 4 is

incorporated into a housing 410. With the housing 410, the damper 300 may be incorporated, as a cartridge, in a suspension unit in the manner shown in Fig. 3.

[0055] Fig. 6 shows a multi-piston embodiment of a damper 500 similar to the two- piston embodiment of Fig. 4. The damper 500 comprises an outer member 600 which forms part of a housing. Thus, damper 500 does not need to be inserted into a housing. Outer member 600 is a generally cylindrical tube comprising a first aperture 602 and a second aperture 604. A flange 606 is provided around the outer circumference of the first aperture 602. The flange 606 is designed to fit in a retainer 608. The retainer 608 is generally annular and comprises radially spaced apart through holes 610 and a shoulder 612 extending around its inner circumference. The shoulder 612 is shaped to accommodate the flange 606. To install the damper 500 in a suspension unit, the damper 500 with the cylindrical body 600 is placed in position. The retainer 608 is slotted over the cylindrical body 600 and can be fixed to a structure using the through holes 610. The damper 500 is held in place by the physical engagement of the flange 606 and the shoulder 612.

[0056] By way of this arrangement, different geometries and through hole configurations for retainer 608 may be provided without difficulty. [0057] The second aperture 604 comprises a circumferential edge 614 in which an annular base plate 616 is seated. The annular base plate 616 can be inserted after assembly of the damper 500, which facilitates manufacture of the inner components of the damper 500. The inner surface of the outer member 600 comprises two inner circumferential edges 618, 620 to locate and retain two outer circumferential rims 592 and 594. The upper edge 618 is provided for the outer upper circumferential rim 592 and the lower edge 620 is provided for the outer lower circumferential rim 594. The circumferential edges 618, 620 facilitate axial positioning but are optional.

[0058] Further, the inner member 510, which corresponds to the inner members 1 10 and 310, is provided around its outer surface with a series of circumferential edges 501 , 502, 503, 504, and 505. These edges are optional and need not be present in every embodiment. However, one or more circumferential edges facilitate the axial positioning of components that are mounted on the inner member as set forth below.

[0059] Two inner circumferential rims 596 and 598 are located at near the upper and lower end of the inner member 510. An upper diaphragm 522 is mounted to the outer upper circumferential rim 592 and the inner upper circumferential rim 596.

Likewise, a lower diaphragm 524 is mounted to the inner lower circumferential rim 594 and the inner lower circumferential rim 598.

[0060] The inner upper circumferential rim 596 is located at the circumferential edge 501 , whereas the inner lower circumferential rim 598 is located at the circumferential edge 505. Three flanges, an upper flange 512, a center flange 513, and a lower flange 514, are located at the circumferential edges 502, 503, and 504, respectively.

[0061 ] It is understood that the upper, center, and lower flanges 512, 513, and 514 provide abutment surfaces in the manner described for the flanges 312, 313, and 314 of the embodiment of Fig. 4. [0062] Likewise, an upper compartment 552 is defined between the upper diaphragm 522 and a piston 530A, a center compartment 554 is defined between the piston 530A and a piston 530B, and a lower compartment 556 is defined between the piston 530B and the lower diaphragm 524. The compartments are in fluid communication via permanent fluid passages in the pistons 530A and 530B.

[0063] The axial spacing of the circumferential edges 501 , 502, 503, 504, and 505 on the inner member 510 can be designed as required to provide a desired spacing between the flanges 512, 513, 514 and/or between the inner circumferential rims 596, 598.

[0064] The volume of the upper compartment 552, the center compartment 554, and the lower compartment 556 can be designed by choosing an appropriate spacing between the circumferential edges 501 , 502, 503, 504, and 505 at the design stage. [0065] It is understood that in embodiments in which the abutment surfaces are not provided in the form of a pair of flanges, the inner circumference 134 of the piston 130, or the inner circumferences 334A, 330B of the pistons 330A, 330B, may be smaller than the outer circumference of inner member 1 10, 310, or 510, respectively. E.g., the abutment surfaces may be provided by a circumferential groove on inner member 1 10, 310, or 510, in which case the piston 130, pistons 330A or 330B, or pistons 530A or 530B respectively, may have a degree of axial travel within the groove. In such a configuration, the inner circumference 134 (or 334A or 334B) of the piston 130, 330A, 330B, 530A, or 530B may be smaller than the outer circumference of the inner member 1 10, 310, or 510, respectively, and larger than the inner circumference of the groove, to provide the auxiliary passage within the groove.

[0066] In operation, at rest or under a normal vibration load, the inner member 1 10, 310, 510 may be displaced axially relative to the outer member 200, 400, 600 with relatively small amplitudes or speeds of displacement. While the auxiliary fluid passage 170 is open, a fluid transfer is facilitated between the upper and lower compartment, and the piston 130 can assume a position half-way, or centralized, between the flanges 1 12, 1 14. The self-centralizing effect is achieved with reference to the inner member 1 10 while allowing the piston 130 to be axially decoupled from the inner member 1 10.

[0067] Likewise, in an embodiment with multiple pistons 330A and 330B or 530A and 530B, while both the auxiliary fluid passages 370A and 370B are open, the fluid transfer is facilitated between the series of compartments 352, 354, 356, or 552, 554, 556. This provides a self-centralizing effect for each piston plate 330A, 330B with reference to the respective first or second pair 316, 318 of abutment surfaces on the inner member. E.g., the first piston plate 330A (or 530A) is self-centralizing between the first pair 316 of abutment surfaces, and the second piston plate 330B (or 530B) is self-centering between the second pair 318 of abutment surfaces. However, between the respective abutment surfaces, each piston plate 330A and 330B (or 530A, 530B) is able to move axially independent of the inner member 310 (510).

[0068] A relatively large or rapid axial displacement of the inner member 1 10 in response to a sufficiently strong force will cause the piston 130 to abut against one the flanges 1 12, 1 14, thereby blocking the auxiliary fluid passage 170. Axial displacement with sufficient amplitude/velocity will also increase the pressure of the damper fluid on one side of the piston relative to the other side. It will be understood that a similar effect causing blocking of the auxiliary fluid passages can be observed in a multi-piston embodiment such as the two-piston embodiment of Figs. 4 to 6, as a large axial displacement of the inner member 310 or 510, respectively, will cause both piston plates 330A and 330B, or 530A, 530B, to abut against their respective abutment surfaces. In practice, it can be that one piston shuts off before the other, depending on the direction and magnitude of the force, and depending on rebound effects.

[0069] As long as the one or more pistons 130, 330A, 330B, 530A, 530B abut against a flange 1 12, 1 14, 312, 313, 314, 512, 513, 514, the respective auxiliary fluid passage 170, 370A, 370B remains blocked. As a consequence of the blocking, the damper fluid can only pass through the permanent fluid passage 160 but cannot pass via the auxiliary fluid passage 170, 370A, or 370B, respectively. Because the auxiliary fluid passage 170, 370A, or 370B, respectively makes up a significant proportion of the total area available for passage of the damper fluid, the blocking of the auxiliary fluid passage 170 means that the equilibration of pressure between the upper and lower compartment, or between the series of compartments 352, 354, 356, or 552, 554, 556, is delayed while the damper fluid is forced through the permanent fluid passage 160. This provides a damping effect that is a function of the velocity (or frequency).

[0070] To give an illustration of the above, an example is provided assuming that the inner member is mounted to a driver cabin and that the outer member is mounted to a chassis of an off-road vehicle. It will be appreciated that the weight put onto a chassis by a driver cabin will cause the inner member to move down, axially relative to the outer member. The weight of the cabin slightly increases as a driver mounts the vehicle, and the inner member may lower a bit further. During such relatively slow changes of the axial position, the piston will travel axially with the inner member, keeping the auxiliary fluid path or fluid paths open and self-centralizing between the abutment surfaces. As the vehicle moves, the weight distribution of the cabin may change. For instance, the angle of incline may change as the vehicle drives uphill and the local load on a damper may be temporarily reduced (or temporarily increased). This might cause the inner member to move up (or down as the load further increases), and as long as such a change in load distribution is sufficiently slow, the one or more pistons will move along axially with the inner member and remain self-centralized. However, as there is a sudden impact, the axial displacement is abrupt and the piston, being more inert in the fluid than the inner member, abuts against the abutments surfaces. This applies the damping effect, as described above.

[0071 ] The above-described embodiments comprise flanges 1 12, 1 14, 312, 313, 314, or 512, 513, 514 which provide, in the form of axial ly-facing surfaces, the abutment surfaces that limit the travel of the one or more pistons. In an embodiment, one or more circumferential grooves may be provided in one of the inner or outer members in each of which a piston is axially slidably disposed and wherein the travel is limited by the abutments surfaces formed by the sidewalls of the one or more grooves.

[0072] In an embodiment, the permanent fluid passage 160 comprises a groove or apertures in the abutment surfaces, allowing permanent fluid communication independent of the axial position of the one or more pistons.

[0073] The outer circumference 132 of the one or more pistons 130, 330A, 330B, 530A, 530B may comprise a resilient surface. The resilient surface allows the fluid-tight seal between the outer circumference 132, 332A, 333B and the inner surface of the outer member 200, 400, 600 to be improved. [0074] The auxiliary fluid passage 170, 370A, 370B may be provided across the outer circumference of at least one of the one or more pistons. In that case, the outer circumference of the at least one of the one or more pistons may be smaller than the circumference of the inner surface of the outer member. The abutment surfaces may, correspondingly, be provided on the inner surface of the outer member 200, 400, 600. In that case, the inner circumference 134, 334A, 334B of at least one of the one or more pistons 130, 330A, 330B, 530A, 530B may provide a fluid-tight seal with the chamber-facing surface of inner member 1 10, 310, 510. The inner circumference of at least one of the one or more pistons 130, 330A, 330B530A, 530B may comprise a resilient surface to improve the fluid-tight seal.

[0075] A surface of at least one of the one or more pistons 130, 330A, 330B, 530A, 530B may comprise a resilient surface for improved blocking of the auxiliary fluid passage.

[0076] One or each of the abutment surfaces may comprise a resilient surface for improved blocking of at least one of the auxiliary fluid passages.

[0077] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated as incorporated by reference and were set forth in its entirety herein.

[0078] For the purposes of promoting an understanding of the principles of the invention, reference has been made to the preferred embodiments illustrated in the drawings, and specific language has been used to describe these embodiments.

However, no limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art.

[0079] The embodiments may be described in terms of functional block

components and various processing steps. Such functional blocks may be realized by any number of components that perform the specified functions.

[0080] The particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way. For the sake of brevity, conventional aspects of the systems (and components of the individual operating components of the systems) may not be described in detail. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical device. Moreover, no item or component is essential to the practice of the invention unless the element is specifically described as "essential" or "critical". [0081] The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted,"

"connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings. Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. [0082] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) should be construed to cover both the singular and the plural. Furthermore, recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Finally, the steps of all methods described herein are performable in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.

[0083] The words "mechanism" and "element" are used herein generally and are not limited solely to mechanical embodiments. Numerous modifications and

adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention.