Technical Field

[0001] The present invention relates to a damper, such as a shock absorber. The present invention relates in particular to a hydraulic damper, such as a damper of the twin tube cross-over type.

Background Art

[0002] Dampers, such as shock absorbers, are used in many applications requiring the absorption of shocks or damping in general. A damper comprises a tube, such as a cylinder, in which a piston is provided. The piston divides the tube in two damping chambers, often referred to as the compression chamber and the rebound chamber. In particular, hydraulic dampers are used, said dampers comprising a liquid damping medium. Hydraulic dampers comprise the damping medium in both damping chambers. A damper can comprise valves to regulate the compression and the rebound.

[0003] One particular type of dampers uses a positive pressure build-up. This type of dampers has a pressure greater than zero on both sides of the piston, regardless whether the damper is in compression mode or rebound mode. Pressurization on both sides of the piston is achieved by means of a pressurized member arranged in a pressurization reservoir, which pressurizes a damping medium-filled chamber fluidly connected to both damping chambers to a predetermined pressure.

[0004] US 9,091 ,319 discloses a damper of the twin tube cross-over type with a positive pressure build-up. This damper comprises an inner tube with a piston positioned therein, an outer tube around the inner tube, a pressurization chamber, two adjustable valve assemblies for generating a damping force acting in opposition to the stroke movement by restricting a damping medium flow between the damping chambers and the pressurization chamber via separate flow paths. The two adjustable valve assemblies are arranged in separated chambers. Equally, JP2011012806 discloses a damper of the twin tube cross-over type.

[0005] A limitation of the above-mentioned twin tube cross-over damper is that its reaction time, in particular the hydraulic reaction time, is considered too high for certain applications. In particular, a short reaction time of the damper in motorbikes, in particular sportive motorbikes, such as motorbikes used in racing competition, allows a better control of the wheels, such as the rear wheel, and a more stable driving, leading to safer riding conditions. [0006] Another limitation is that damper systems aiming to reduce the reaction time are often very complex and/or large. However, in particular with motorbikes, the place for implementing and providing the damper system is limited.

Summary of the Invention

[0007] It is an object of the present invention to overcome one or more of the above drawbacks. It is an aim of the invention to provide a damper with a faster reaction time.

[0008] For the above purpose, the invention is directed to a damper filled with a damping medium in use comprising:

- an inner tube;

- a piston slidably disposed within the inner tube, the piston defining a first working chamber and a second working chamber within the inner tube;

- an outer tube being arranged around the inner tube, the outer tube defining an outer chamber between the inner tube and the outer tube, the outer chamber being in fluid communication with the second working chamber;

- an end member disposed at an end of the inner tube, the end member having an inner surface facing towards the first working chamber;

- two valve assemblies, namely a first and a second valve assembly disposed, respectively, in a first and a second valve assembly chamber, the two valve assemblies each comprising a bleed valve, namely a first and a second bleed valve with an upstream side in fluid communication with the first working chamber and the outer chamber, respectively;

- two check valves, namely a first and a second check valve, the first check valve being configured to allow flow from the first chamber to the second chamber via the first bleed valve, the second check valve being configured to allow flow from the second chamber to the first chamber via the second bleed valve;

- a pressurization reservoir divided by a separating member to define a third chamber filled with the damping medium, in use, and pressurized by a force acting on the separating member, the third chamber being in fluid communication with a downstream side of the first bleed valve and a downstream side of the second bleed valve; wherein the end member is provided with a first pressure regulation valve, for regulating flow between the first chamber and the second chamber, the first pressure regulation valve having an upstream side in fluid communication with the first working chamber, the first pressure regulation valve being a biased check valve, in particular a shim valve or a poppet valve.

[0009] According to specific embodiments of the invention, the damper comprises one or more of the following technical features:

- a downstream side of the first pressure regulation valve is in fluid communication with the third chamber;

- the end member comprises at least one through-passage extending between the end member inner surface and an end member outer surface, the first pressure regulation valve being mounted on the end member outer surface;

- the first pressure regulation valve comprises one or more shims positioned downstream from the at least one through-passage;

- the first and the second check valve being in fluid communication with the first and the second bleed valve, respectively;

- an upstream side of the first and the second check valve is in fluid communication with the downstream side of the first and the second bleed valve, respectively;

- a downstream side of the first and the second check valve are in fluid communication with the outer chamber and the first working chamber, respectively;

- the third chamber is in fluid communication with the upstream side of the first check valve and the upstream side of the second check valve ;

- the end member comprises at least one further passage with an upstream end opening in the at least one through-passage and a downstream end in fluid communication with the upstream side of the first bleed valve;

- each valve assembly comprises a tube having one or more openings and a needle slidably disposed inside the tube for controlling a damping medium flow entering inwardly through the one or more openings, in operation;

- the needle is actuated by a solenoid, a stepper motor or biased by an adjustable spring;

- the second valve assembly comprises the first check valve;

- the first check valve comprises at least one shim disposed about the tube of the second valve assembly and being biased against a first valve seat, an outside diameter of the first valve seat coinciding with an inside diameter of the second valve assembly chamber, the first valve seat comprising openings facing the at least one shim of the first check valve;

- the at least one shim of the first check valve, in particular one shim, is slidingly disposed about the tube and biased by a first helical spring, an end of the first helical spring resting against the at least one shim of the first check valve and an opposite end of the first helical spring being arranged in a first spring receiver disposed about the tube of the second valve assembly;

- the at least one shim of the first check valve comprises one or more shims fixed about the tube of the second valve assembly;

- the one or more shims of the first check valve are sandwiched between the first valve seat and a flange formed on the tube of the second valve assembly;

- the end member comprises the second check valve;

- the second check valve comprises one or more shims mounted on the end member inner surface and positioned downstream from at least one additional passage formed in the end member, the at least one additional passage being in fluid communication with the downstream side of the second bleed valve;

- the piston comprises a second pressure regulation valve with an upstream side in fluid communication with the second working chamber and a downstream side in fluid communication with the first working chamber;

- a third pressure regulation valve with an upstream side in fluid communication with the outer chamber and a downstream side in fluid communication with the first working chamber;

- the third pressure regulation valve comprises one or more shims disposed about a shaft;

- the one or more shims of the pressure regulation valve are sandwiched between a third valve seat disposed about the shaft and a flange formed on the shaft;

- the first valve assembly comprises the second check valve;

- the second check valve comprises at least one shim disposed about the tube of the first valve assembly and being biased against a second valve seat, an outside diameter of the second valve seat coinciding with an inside diameter of the first valve assembly chamber, the second valve seat comprising openings facing the at least one shim of the second check valve;

- the at least one shim of the second check valve, in particular one shim, is biased by a second helical spring, an end of the second helical spring resting against the at least one shim of the second check valve and an opposite end of the second helical spring being arranged in a second spring receiver disposed about the tube of the first valve assembly;

- the at least one shim comprises one or more shims fixed about the tube of the first valve assembly;

- the one or more shims of the second check valve are sandwiched between the second valve seat and a flange formed on the tube of the first valve assembly; - the first valve assembly comprises a fourth pressure regulation valve with an upstream side in fluid communication with the first chamber and a downstream side in fluid communication with the third chamber;

- the fourth pressure regulation valve is arranged upstream or downstream of the first bleed valve;

- the fourth pressure regulation valve is arranged upstream of the first bleed valve, the fourth pressure regulation valve comprising one or more shims disposed about the tube of the first valve assembly, the one or more shims being sandwiched between a fourth valve seat disposed about the tube of the first valve assembly and a flange formed on the tube of the first valve assembly;

- a cylinder head arranged at an end of the outer tube, the cylinder head being adjacent to the end of the inner tube and connected to the end member, wherein the first valve assembly chamber, the second valve assembly chamber and the third chamber and optionally a further chamber for housing the third regulation valve are formed in the cylinder head;

- the piston comprises a fifth pressure regulation valve with an upstream side in fluid communication with the first chamber and a downstream side in fluid communication with the second working chamber;

- the piston comprises a rod disposed in the second working chamber. [0010] Advantageously, the measures according to the invention allow a larger adjustment range and a simpler design.

Brief Description of Drawings

[0011] Aspects of the invention will now be described in more detail with reference to the appended drawings, wherein same reference numerals illustrate same features. [0012] Figure 1 represents a damper flow circuit according to a first embodiment of the present invention. The first embodiment comprises the following options:

- a bypass pressure regulation valve for the rebound flow, see dashed lines, being complementary to or serving as an alternative to the rebound valve in the piston, and/or

- a bypass pressure regulation valve for the compression flow, see dashed lines, being complementary to the pressure regulation valve in the end member, said valve being positioned upstream or downstream of the bleed valve for the compression flow.

[0013] Figure 2 schematically represents a damper according to a second embodiment of the present invention (without the above-mentioned bypass pressure regulation valves). [0014] Figure 3 represents a cross-sectional view of a damper according to either:

- the second embodiment (without the above-mentioned bypass pressure regulation valves),

- the third embodiment (with the bypass pressure regulation valve for the rebound flow and without the bypass pressure regulation valve for the compression flow), or

- the fourth embodiment (without the bypass pressure regulation valve for the rebound flow and with the bypass pressure regulation valve in the compression flow) of the present invention.

[0015] Figure 4a or 4b represents a cross-sectional view of a rebound (second) valve assembly according to any of the embodiments of the present invention.

[0016] Figure 5 represents a cross-sectional view of a compression (first) valve assembly according to the second or third embodiment of the present invention.

[0017] Figure 6 represents a cross-sectional view of a (separate) bypass rebound regulation valve for the rebound flow as a complementary valve to the rebound valve in the piston, according to the third embodiment.

[0018] Figure 7 represents a cross-sectional view of a compression (first) valve assembly according to the fourth embodiment of the present invention.

[0019] Figure 8 schematically represents a damper according to a fifth embodiment of the present invention (without the above-mentioned bypass pressure regulation valves)

[0020] Figure 9 represents a cross-sectional view of a compression (first) valve assembly according to the fifth embodiment of the present invention.

[0021] Figure 10 shows a perspective view of a damper according to the invention.

Detailed description

[0022] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness.

[0023] The dampers of the present invention are filled with a damping medium. Preferably, the damping medium is a liquid damping medium, for example oil. Other damping media known in the field of dampers can be used as well.

[0024] Fig. 1 discloses a schematic view of a damper according to a first embodiment of the invention. The damper comprises an inner tube 101. A piston 110 is slidably disposed within the inner tube 101 and defines a compression working chamber 121 and a rebound working chamber 122 within the inner tube 101. The piston 110 comprises a rod 119 disposed in the rebound working chamber 122. An outer tube 103 is provided around the inner tube 101 and defines an outer chamber 124 between the inner tube 101 and the outer tube 103. The outer chamber 124 is in fluid communication with the rebound working chamber 122.

[0025] The damper further comprises a compression bleed valve 181 , with an upstream side in fluid communication with the compression working chamber 121. In parallel with the compression bleed valve 181 , there is provided a first pressure regulation valve 136, being a pressure regulation compression valve. The pressure regulation compression valve 136 has an upstream side in fluid communication with the compression working chamber 121. The damper further comprises a rebound bleed valve 191 , with an upstream side in fluid communication with the outer chamber 124.

[0026] The damper further comprises a compression check valve 195 and a rebound check valve 135, 185. The compression check valve 195 has an upstream side in fluid communication with a downstream side of the compression bleed valve 181 and a downstream side in fluid communication with the outer chamber 124. The rebound check valve 135, 185 has an upstream side in fluid communication with a downstream side of the rebound bleed valve 191 and a downstream side in fluid communication with the compression working chamber 121.

[0027] The damper further comprises a pressurization reservoir divided by a separating member, thereby defining a third chamber 123. The third chamber 123 is filled with the damping medium pressurized by a force acting on the separating member. The force acting on the separating member can be provided by means of a spring and/or a gas provided in the pressurization reservoir. When a gas is used, the gas preferably comprises an inert gas, such as argon, helium or nitrogen, or a combination of two or more thereof. The third chamber 123 is in fluid communication with the downstream side of the compression bleed valve 181 and the rebound bleed valve 191 , and the upstream side of the compression check valve 195 and the rebound check valve 135, 185.

[0028] The piston 110 of the damper of Fig. 1 preferably comprises a second pressure regulation valve 115. The valve 115 has an upstream side in fluid communication with the rebound working chamber 122 and a downstream side in fluid communication with the compression working chamber 121.

[0029] Additionally to the first pressure regulation valve 136, a fourth pressure regulation valve 146 for the compression flow, can be provided.

[0030] Additionally or alternatively to the second pressure regulation valve 115, a third pressure regulation valve 175, namely a bypass pressure regulation valve, can be provided. Preferably, the third pressure regulation valve 175 is provided in parallel with the rebound bleed valve 191 in a dedicated chamber 127. The valve 175 has an upstream side in fluid communication with the outer chamber 124 and a downstream side in fluid communication with the compression working chamber 121. The third pressure regulation valve 175 is not disposed in series with the rebound check valve 185, thereby improving the response time.

[0031] In Fig. 1 the second and/or third pressure regulation valve 115, 175 are also named pressure regulation rebound valve.

[0032] The piston 110 of the damper of Fig. 1 may further comprise a fifth pressure regulation valve 116. The valve 116 has an upstream side in fluid communication with the compression chamber 121 and a downstream side in fluid communication with the rebound working chamber 122.

[0033] When the damper of Fig. 1 is subjected to a compression damping cycle, the piston 110 moves in a direction that reduces the volume of the compression working chamber 121. The piston 110 drives the damping medium to flow from the compression working chamber 121 to the rebound working chamber 122 via one or more external loops and/or one or more passages in the piston 110. The resulting flow resistance generates a pressure difference across the piston 110 that opposes the piston 110 motion.

[0034] When the compression damping is performed, a first portion of the damping medium will follow a flow path via optionally the fourth regulation valve 146, 156, the compression bleed valve 181 and the compression check valve 195 and a second portion of the damping medium will reach the rebound working chamber 122 via the first pressure regulation valve 136, the compression check valve 195 and the outer chamber 124. Preferably, a third portion of the damping medium will reach the rebound working chamber 122 via the fifth pressure regulation valve 116 in the piston. [0035] When the damper of Fig. 1 is subjected to a rebound damping cycle, the piston 110 moves in a direction that reduces the volume of the rebound working chamber 121. The piston 110 drives the damping medium to flow from the rebound working chamber 121 to the compression working chamber 122 via one or more external loops and/or one or more passages in the piston 110. The resulting flow resistance generates a pressure difference across the piston 110 that opposes the piston 110 motion. [0036] When the rebound damping is performed, a first portion of the damping medium will follow a flow path via the rebound bleed valve 191 and the rebound check valve 135, 185. A second portion of the damping medium will reach the compression working chamber 121 via the second pressure regulation valve 115 in the piston. In an alternative or in addition to the second pressure regulation valve 115, a further portion of the damping medium will reach the compression working chamber 121 via the third pressure regulation (rebound) valve 175.

[0037] The advantage of the embodiment of Fig. 1 of the present invention is that a large flow of damping medium can be handled during the compression and/or rebound cycle. The provision of at least one of the first pressure regulation valve 136 in the end member 134, the second pressure regulation (rebound) valve 115 and/or the fifth pressure regulation (compression) valve 116 in the piston 110, instead of being arranged in the valve assembly chambers as it is the case in US 9,091 ,319, not only frees some space in the valve assembly chambers 128, 129 that would be advantageously utilized but also allows the selection of larger valve(s) fitting with the larger diameter of the piston 110 and/or the end member 134, compared to the diameter of the valve assembly chambers 128, 129. This leads to an increased flow port surface area in the valve(s), in particular the at least one of the pressure regulation valve 136, the second pressure regulation (rebound) valve 115 and/or the fifth pressure regulation (compression) valve 116, thereby allowing a higher flow rate that can be handled by the valve(s). Increasing the size of the valve aperture(s) improves the hydraulic response time, and therefore the damper 100 response time.

[0038] As the effective area(s) of the above-mentioned valve port(s) are larger than those of the compression and rebound valves disclosed in US 9,091 ,319, the forces exerted on the spring of the valve are also greater. A spring with a higher spring rate is needed to guarantee a stroke compatible with the space available. Advantageously, thanks to a larger orifice size, the stroke of the movable element of the valves can be even reduced compared to the state of the art. Moreover, as the spring rate is higher, the mechanical natural frequency of the valves is increased, thereby preventing valve resonance.

[0039] Furthermore, as the valve assembly chambers 128, 129 are freed from the presence of pressure regulation (compression) valve and the pressure regulation (rebound) valve in comparison to the design of US 9,091 ,319 (in which, in each valve assembly chamber, a bleed, a regulation and check valves are arranged in a stack), more space is available in the valve assembly chambers 128, 129 for the bleed valves 181 , 191 and the check valve(s) 135, 185, 195, thereby enhancing their flow characteristics because of an increased available space, in particular in the longitudinal direction, namely the stroke direction. An increased stroke and the optimization of the space in the valve assembly chamber, as for instance shown in the embodiments of the invention, allow to handle a higher flow effective cross section and thereby higher flow rate, resulting in an improved dynamic response of the damper. Furthermore, springs with a higher spring rate can be provided in the valve assembly chambers 128, 129, thereby improving control and advantageously shifting the natural frequencies to higher range.

[0040] The rebound check valve 185, when disposed in its valve assembly chamber 128 (see Fig. 9 for the fifth embodiment), is, in general, sufficiently large enough. Indeed, it handles, in general, a lower flow rate than the compression check valve 195. The flow is reduced since the rebound check valve 185 sees only a part of the rebound flow as the other parts can flow through the piston 110 via the second pressure regulation valve 115 and/or the third pressure regulation valve 175.

[0041] Fig. 2 in combination with Fig. 3 shows a second embodiment for the damper 100 of the present invention. The second embodiment is more specific than the first embodiment. The second embodiment is characterized in that the rebound check valve 135 is arranged in the end member 134 of the compression chamber 121. Furthermore, the second embodiment does not comprise a compression bypass pressure regulation valve 146 positioned in parallel with the first regulation valve 136 that is arranged in the end member 134. The second embodiment comprises a second regulation rebound valve 115 in the piston 110 instead of a third pressure regulation valve 175 (see Figure 6) in a dedicated chamber 127 arranged in the cylinder head 130.

[0042] In the second embodiment, the compression valve assembly 180 comprises a compression bleed valve 181 , with an upstream side in fluid communication with the compression working chamber 121 as shown in Fig. 2.

[0043] Fig. 5 shows a realization of the compression valve assembly 180 according the second embodiment. The compression valve assembly 180 comprises a tube 182 having one or more openings and a needle 188. The needle 188 is advantageously slidably disposed inside the tube 182. Advantageously, the needle 188 controls the damping medium entering the tube 182 via the one or more openings, when in operation, i.e. when a compression damping cycle is performed. Preferably, the needle is actuated by a solenoid, a stepper motor (not shown) or biased by an adjustable spring (not shown).

[0044] As shown in Fig. 2, the rebound valve assembly 190 comprises a rebound bleed valve 191 , with an upstream side in fluid communication with the outer chamber 124. The rebound valve assembly 190 further comprises a compression check valve 195. The compression check valve 195 has an upstream side in fluid communication with a downstream side of the compression bleed valve 181 and a downstream side in fluid communication with the outer chamber 124.

[0045] In Fig. 4a, the rebound valve assembly 190 of the second embodiment comprises a tube 192 having one or more openings and a needle 198. The needle 198 is advantageously slidably disposed inside the tube 192. Advantageously, the needle 198 controls the damping medium entering the tube 192 via the one or more openings, when in operation, i.e. when a rebound damping cycle is performed. Preferably, the needle 198 is actuated by a solenoid, a stepper motor (not shown) or biased by an adjustable spring (not shown).

[0046] The rebound valve assembly 190 further comprises the compression check valve 195. Advantageously, the compression check valve 195 comprises a shim 193 slidably disposed about the tube 192. The shim 193 is biased against a valve seat 194. An outside diameter of the valve seat 194 coincides with an inside diameter of the rebound valve assembly chamber 129. Advantageously, the valve seat 194 comprises openings facing the shim 193. Advantageously, the compression check valve 195 is biased by a helical spring 196. Preferably, an end of the helical spring 196 rests against the shim 193. Preferably, an opposite end of the helical spring 196 is arranged in a spring receiver 197. Preferably, the spring receiver 197 is disposed about the tube 192.

[0047] Alternatively to a shim 193 slidably disposed about the tube 192, a shim or a stack of shims can be fixed about the tube 192 as shown in Fig. 4b. The compression check valve 195 can comprise one or more shims fixed about the tube 192 of the rebound valve assembly 190 and preferably sandwiched between the valve seat 194 and a flange formed on the tube 192.

[0048] Referring back to Fig. 2, the damper 100 comprises an end member 134 disposed at an end of the inner tube 101. The end member 134 has an inner surface facing towards the compression working chamber 121. The end member 134 comprises a pressure regulation compression valve 136 and a rebound check valve 135.

[0049] In Fig. 3, the end member 134 comprises at least one through-passage 200 extending between the end member inner surface and an end member outer surface.

[0050] In Fig. 3, the end member 134 comprises at least one further passage 201 with an upstream end opening in the at least one through-passage 200 and a downstream end in fluid communication with the upstream side of the compression bleed valve 181.

[0051] In Fig. 3, the pressure regulation compression valve 136 is mounted on an outer surface of the end member 134. The pressure regulation compression valve 136 has an upstream side in fluid communication with the compression working chamber 121 and a downstream side in fluid communication with the third chamber 123. Preferably, the pressure regulation compression valve 136 comprises one or more shims positioned downstream from the at least one through-passage 200. The shim valve is the preferred design for the pressure regulation compression valve 136. As an alternative to the shim valve, a poppet valve can be foreseen.

[0052] In Fig. 3, the rebound check valve 135 has an upstream side in fluid communication with a downstream side of the rebound bleed valve 191 and a downstream side in fluid communication with the compression working chamber 121. [0053] As shown in Fig. 3, the rebound check valve 135 comprises one or more shims. Preferably, the shim(s) are mounted on the inner surface of the end member 134. Preferably, the shim(s) are positioned downstream from at least one additional passage 202 formed in the end member 134. Advantageously, the at least one additional passage 202 is in fluid communication with the downstream side of the rebound bleed valve 191.

[0054] Fig. 6 shows the third pressure regulation valve 175 according to the third embodiment. The third embodiment differs from the second embodiment in that the damper 100 comprises the third pressure regulation valve 175 positioned in a dedicated (further) chamber 127 arranged in the cylinder head 130. Therefore, the third embodiment comprises two pressure regulation valves 115, 175 for the rebound flow. In an alternative, the damper 100 does not comprise a second pressure regulation valve 115 to ease the manufacturing of the piston 110. In this case, the third pressure regulation valve 115 is adapted to control a larger rebound flow.

[0055] The (third) pressure regulation (rebound) valve 175 has an upstream side in fluid communication with the outer chamber 124 and a downstream side in fluid communication with the compression working chamber 121. The (third) pressure regulation (rebound) valve 175 comprises one or a plurality of shims disposed about a shaft 179. The shim(s) are advantageously sandwiched between a third valve seat 177 disposed about the shaft 179 and a flange formed on the shaft 179. Alternatively to the one or more shims, alone or in combination with helical springs. Even though the shim valve is the preferred design, other type of biased check valves such as a poppet valve can be used.

[0056] Fig. 7 shows the compression valve assembly 180 according to the fourth embodiment. The fourth embodiment differs from the second embodiment in that the damper 100 comprises the fourth pressure regulation valve 146 arranged in a compression valve chamber 128. Furthermore, an upstream side of the compression bleed valve 181 is in fluid communication with the compression working chamber 121 via the fourth pressure regulation rebound valve 146. In an alternative, the fourth pressure regulation valve 156 can be arranged downstream for the compression bleed valve 181.

[0057] Preferably, and as shown in Fig. 7, the fourth pressure regulation valve 146, namely a bypass pressure regulation valve for the compression flow, comprises one or a plurality of shims disposed about the tube 182. The shim(s) are advantageously being sandwiched between a fourth valve seat 147 disposed about the tube 182 and a flange formed on the tube 182.

[0058] Fig. 8 shows a fifth embodiment for the damper 100 of the present invention. The fifth embodiment is more specific than the first embodiment. This embodiment differs from the second embodiment in that the rebound check valve 185 is positioned in the compression valve assembly chamber 128 instead of being mounted on the inner surface of the end member 134.

[0059] A compression valve assembly 180 adapted for the fourth embodiment is shown in Fig. 9. The compression valve assembly 180 comprises a compression bleed valve 181 with an upstream side in fluid communication with the compression working chamber 121. The compression valve assembly 180 further comprises a rebound check valve 185. The rebound check valve 185 has an upstream side in fluid communication with a downstream side of the rebound bleed valve 191 and a downstream side in fluid communication with the compression working chamber 121. [0060] Advantageously, the compression valve assembly 180 comprises a tube 182 having one or more openings and a needle 188. The needle 188 is advantageously slidably disposed inside the tube 182. Advantageously, the needle 188 controls the damping medium entering the tube via the one or more openings, when in operation, i.e. when a compression damping cycle is performed. Preferably, the needle 188 is actuated by a solenoid, a stepper motor (not shown) or biased by an adjustable spring (not shown).

[0061] The rebound valve assembly 190 suitable for the fourth embodiment is presented in Fig. 4a, 5b and comprises the compression check valve 195. The general layouts of the valve assemblies of Fig. 4a, 4b and Fig. 9 share several commonalities, in particular the stack design with a check valve, a bleed valve and a solenoid (or equivalent(s)).

[0062] Advantageously, in Fig. 9, the rebound check valve 185 comprises a shim 183 slidably disposed about the tube 182. The shim 183 is biased against a (second) valve seat 184. An outside diameter of the valve seat 184 coincides with an inside diameter of the compression valve assembly chamber 128. Advantageously, the valve seat 184 comprises openings facing the shim 183. Advantageously, the rebound check valve 185 is biased by a helical spring 186. Preferably, an end of the helical spring 186 rests against the shim 183. Preferably, an opposite end of the helical spring 186 is arranged in a spring receiver 187. Preferably, the spring receiver 187 is disposed about the tube 182.

[0063] In an alternative or in addition to shim design, the rebound check valve can comprise one or more shims fixed about the tube about the tube 182 of the compression valve assembly 180.

[0064] The rebound valve assembly 190 of the fifth embodiment is presented in Fig. 4a, 5b. Thus, the details are not repeated for brevity.

[0065] Fig. 10 shows a damper 100 comprising a cylinder head 130 arranged at an end of the outer tube 103 according to any of the embodiments of the invention. The cylinder head 130 is adjacent to the end of the inner tube and connected to the end member 134 (not shown). Advantageously, the compression valve assembly chamber (not shown), the valve assembly chambers 128, 129 (not shown) and the third chamber 123 (not shown), and optionally a further chamber 127 (not shown) for the third regulation valve 175 are formed in the cylinder head 130.

[0066] The damper further comprises a pressurization reservoir as disclosed in Fig. 1-2 and 8. The third chamber 123 of the pressurization reservoir is in fluid communication with the downstream side of the compression bleed valve 181 and the rebound bleed valve 191 , and the upstream side of the compression check valve 195 and the rebound check valve 135, 185.

[0067] The piston 110 of the damper of Fig. 1-3 and 8 comprises a second pressure regulation valve 115, advantageously a pressure regulation rebound valve, and a sixth pressure regulation (rebound) valve 116 as described for Fig. 1-3 and 8.

[0068] Further examples of the present disclosure or invention can be described with reference to the following numbered clauses:

1. Damper (100) filled with a damping medium in use comprising: an inner tube (101); a piston (110) slidably disposed within the inner tube (101), the piston (110) defining a first working chamber (121) and a second working chamber (122) within the inner tube (101); an outer tube (103) being arranged around the inner tube (101), the outer tube (103) defining an outer chamber (124) between the inner tube (101) and the outer tube (103), the outer chamber (124) being in fluid communication with the second working chamber (122); an end member (134) disposed at an end of the inner tube (101), the end member having an inner surface facing towards the first working chamber (121); two valve assemblies (180, 190), namely a first (180) and a second (190) valve assembly disposed, respectively, in a first (128) and a second (129) valve assembly chamber, the two valve assemblies (180, 190) each comprising a bleed valve (181 , 191), namely a first (181) and a second (191) bleed valve with an upstream side in fluid communication with the first working chamber (121) and the outer chamber (124), respectively; two check valves (195, 135; 195, 185), namely a first (195) and a second (135, 185), the first check valve (195) being configured to allow flow from the first chamber (121) to the second chamber (122) via the first bleed valve (181), the second check valve (135, 185) being configured to allow flow from the second chamber (122) to the first chamber (121) via the second bleed valve (122); a pressurization reservoir divided by a separating member to define a third chamber (123) filled with the damping medium, in use, and pressurized by a force acting on the separating member, the third chamber (123) being in fluid communication with a downstream side of the first bleed valve (181) and a downstream side of the second bleed valve (191), wherein the end member (134) is provided with a first pressure regulation valve (136) for regulating flow between the first chamber (121) and the second chamber (122), the first pressure regulation valve (136) having an upstream side in fluid communication with the first working chamber (121), preferably the first pressure regulation valve (136) being a biased check valve, in particular a shim valve or a poppet valve.

2. Damper according to clause 1 , wherein a downstream side of the first pressure regulation valve is in fluid communication with the third chamber (123).

3. Damper according to clause 1 or 2, wherein the end member (134) comprises at least one through-passage (200) extending between the end member inner surface and an end member outer surface, the first pressure regulation valve (136) being mounted on the end member outer surface.

4. Damper according to the previous clause, wherein the first pressure regulation valve (136) comprises one or more shims positioned downstream from the at least one through-passage (200).

5. Damper according to any of the previous clauses, wherein the first (195) and the second (135, 185) check valve being in fluid communication with the first (181) and the second (191) bleed valve, respectively; an upstream side of the first (195) and the second check valve (135, 185) are in fluid communication with the downstream side of the first (181) and the second (191) bleed valve, respectively; a downstream side of the first (195) and the second check valve (135, 185) are in fluid communication with the outer chamber (124) and the first working chamber (121), respectively; and the third chamber (123) is in fluid communication with the upstream side of the first check valve (195) and the upstream side of the second check valve (135, 185).

6. Damper according to the previous clause, wherein the end member (134) comprises at least one further passage (201) with an upstream end opening in the at least one through-passage (200) and a downstream end in fluid communication with the upstream side of the first bleed valve (181).

7. Damper according to any of the previous clauses, wherein each valve assembly (180, 190) comprises a tube (182, 192) having one or more openings and a needle (188, 198) slidably disposed inside the tube (182, 192) for controlling a damping medium flow entering inwardly through the one or more openings, in operation.

8. Damper according to the previous clause, wherein the needle (188, 198) is actuated by a solenoid, a stepper motor or biased by an adjustable spring.

9. Damper according to any of the previous clauses, wherein the second valve assembly (190) comprises the first check valve (195).

10. Damper according to the previous clause in combination with clause 7, wherein the first check valve (195) comprises at least one shim (193) disposed about the tube (192) of the second valve assembly (190) and being biased against a first valve seat (194), an outside diameter of the first valve seat (194) coinciding with an inside diameter of the second valve assembly chamber (129), the first valve seat (194) comprising openings facing the at least one shim (193) of the first check valve (195).

11 . Damper according to the previous clause, wherein the at least one shim (193) of the first check valve (195), in particular one shim, being slidingly disposed about the tube (192) and biased by a first helical spring (196), an end of the first helical spring (196) resting against the at least one shim (193) of the first check valve (195) and an opposite end of the first helical spring (196) being arranged in a first spring receiver

(197) disposed about the tube (192) of the second valve assembly (190).

12. Damper according to clause 10 or 11 , wherein the one or more shims (193) of the first check valve (195) are sandwiched between the first valve seat (194) and a flange formed on the tube (192) of the second valve assembly (190).

13. Damper according to any of the previous clauses, wherein the end member (134) comprises the second check valve (135).

14. Damper according to the previous clause, wherein the second check (135) valve comprises one or more shims mounted on the end member inner surface and positioned downstream from at least one additional passage (202) formed in the end member (134), the at least one additional passage (202) being in fluid communication with the downstream side of the second bleed valve (191).

15. Damper according to any of the previous clauses, wherein the piston (110) comprises a second pressure regulation valve (115) with an upstream side in fluid communication with the second working chamber (122) and a downstream side in fluid communication with the first working chamber (121).

16. Damper according to any of the previous clauses, comprising a third pressure regulation valve (175) with an upstream side in fluid communication with the outer chamber (124) and a downstream side in fluid communication with the first working chamber (121), wherein the third pressure regulation valve (175) comprises one or more shims disposed about a shaft (179), preferably the one or more shims being sandwiched between a third valve seat (177) disposed about the shaft (179) and a flange formed on the shaft (179).

17. Damper according to any of the previous clauses 1 to 12, wherein the first valve assembly (180) comprises the second check valve (185).

18. Damper according to the previous clause in combination with clause 7, wherein the second check valve (185) comprises at least one shim (183) disposed about the tube (182) of the first valve assembly (180), the at least one shim (183) being biased against a second valve seat (184), an outside diameter of the second valve seat (184) coinciding with an inside diameter of the first valve assembly chamber (128), the second valve seat (184) comprising openings facing the at least one shim (183) of the second check valve (185).

19. Damper according to the previous clause, wherein the at least one shim (183) of the second check valve (185), in particular one shim, is biased by a second helical spring (186), an end of the second helical spring (186) resting against the at least one shim (183) of the second check valve (185) and an opposite end of the second helical spring (186) being arranged in a second spring receiver (187) disposed about the tube (182) of the first valve assembly (180).

20. Damper according to clause 18 or 19, wherein the one or more shims (183) of the second check valve (185) are sandwiched between the second valve seat (184) and a flange formed on the tube (182) of the first valve assembly (180).

21. Damper according to any of the previous clauses, wherein the first valve assembly (180) comprises a fourth pressure regulation valve (146, 156) with an upstream side in fluid communication with the first chamber (121) and a downstream side in fluid communication with the third chamber (123).

22. Damper according to the preceding clause in combination with clause 7, wherein the fourth pressure regulation valve (146) is arranged upstream of the first bleed valve (181), the fourth pressure regulation valve (146) comprising one or more shims disposed about the tube (182) of the first valve assembly (180), the one or more shims being sandwiched between a fourth valve seat (147) disposed about the tube (182) of the first valve assembly (180) and a flange formed on the tube (182) of the first valve assembly (180).

23. Damper according to any of the previous clauses, comprising a cylinder head (130) arranged at an end of the outer tube (103), the cylinder head (130) being adjacent to the end of the inner tube (101) and connected to the end member (134), wherein the first valve assembly chamber (128), the second valve assembly chamber (129) and the third chamber (123), and optionally a further chamber (127) for housing the third regulation valve (175) are formed in the cylinder head (130).

24. Damper according to any of the previous clauses, wherein the piston (110) comprises a fifth pressure regulation valve (116) with an upstream side in fluid communication with the first chamber (121) and a downstream side in fluid communication with the second working chamber (122).

25. Damper according to any of the previous clauses, wherein the piston (110) comprises a rod (119) disposed in the second working chamber (122).

[0069] Although the present invention has been described and illustrated in detail, it is understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.