Description:FORM 2
The Patent Act 1970
(39 of 1970)
and
The Patent Rules, 2005

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

TITLE OF THE INVENTION
“SHOCK ABSORBER FOR A VEHICLE”

Endurance Technologies Limited
E-92, M.I.D.C. Industrial Area, Waluj,
Chh. Sambhajinagar – 431136 (formerly Aurangabad)
Maharashtra, India

The following specification describes the nature of the invention and the manner in which it is to be performed.
 
Field of Invention

[001] The present invention is related to a shock absorber for a motorbike. More particularly, the present invention is related to a shock absorber for two and three wheeled vehicles wherein said shock absorber has a uniquely profiled guide sleeve having intelligently optimized damping fluid flow paths thereby not only enhancing the damping performance of the shock absorber but makes it compact and economic in nature.

Background of the Invention

[002] In vehicles, the suspension unit is one of the important systems of a vehicle imparting ride comfort to the user of the vehicle during driving. The level of ride comfort offered by the suspension system, particularly in two-wheelers such as bikes and scooters, is directly related to the damping performance of the suspension system in response to varying road conditions.

[003] Shock absorbers are integral components of automotive suspension systems, designed to absorb unwanted vibrations that occur during driving in response to the irregularity of the road surface. Among the various types of shock absorbers, mono-tube and twin-tube shock absorbers are the most common particularly in two and three wheeled vehicles.

[004] In a mono-tube shock absorber, the piston is housed inside a single pressure tube, dividing the tube into an upper and a lower chamber. The piston with communicating passages therein controls the flow of damping fluid between these two chambers, producing a damping force that resists vibrations and thereby impart superior ride and comfort to the vehicle rider. In twin-tube shock absorbers, a reservoir chamber is situated between the concentric outer and inner tubes, with a base valve assembly positioned between the lower working chamber of the inner tube and the reservoir chamber. Both the base valve assembly and the fluid flow passages given in the piston jointly control the flow of damping fluid to produce a damping force.

[005] A check valve is located above the piston passages in both dual-tube and mono-tube shock absorbers, restricting the flow of damping fluid and thus the damping force is generated. In case of both types of shock absorbers, the damping performance relies on the action of check valves positioned above the piston orifices. The design of these check valves, often being normally closed or opened, is critical to have desired functioning of the shock absorber. These check valves open and close in response to the pressure exerted by the damping fluid, thus regulating the fluids flow and modulating the damping force.

[006] However, during the high-velocity movement of the piston, significant pressure variations are generated within the shock absorber. These fluctuations in pressure can subject the check valves to substantial forces, especially during rapid compression and extension phases. In many cases, these forces exceed the design limits of the check valves, leading to failure or post-breakage of the valve components. Once the check valve is damaged, the shock absorber loses its ability to maintain the desired damping force, resulting in diminished suspension performance and compromised ride quality. This issue is particularly problematic in vehicles used in regions with rough road conditions and/or terrains, where the shock absorbers are subjected to more extreme loads and pressure variations.

[007] Therefore, to address these limitations of the existing solutions, there has been a long pending need to provide an intelligent and cost effective solution that moderates the pressure acting on the check valves without compromising the overall damping performance of the shock absorber wherein said solution not only improves the durability of the check valves but also enhance the damping forces without changing the design characteristic of the shock absorber.

Objectives of the Present Invention

[008] The main objective of the present invention it to provide an intelligent and cost effective shock absorber for two and three wheeled vehicles.

[009] Another objective of the present invention is to provide a shock absorber for two and three wheeled vehicles wherein said shock absorber is configured to have a uniquely profiled guide sleeve therein having an intelligently optimized damping fluid flow paths.

[0010] Still, further objective of the present invention is to provide a shock absorber which is configured to reduce the high variable pressures acting on the check valves of the shock absorber, particularly during high-velocity jounce movements, to prevent the failure of the check valves.

[0011] Yet, the objective of the present invention is to provide a shock absorber that is simple in construction, easy to manufacture, and provides an economic solution to achieve desired damping performance in two and three wheeled vehicles.

[0012] Yet, another objective of the present invention is to provide a shock absorber having damping control system therein thereby enhancing the rider comfort while ensuring safety.

[0013] Still, the objective of the present invention is to enhance the damping performance of the shock absorber under a variety of operating conditions, without affecting and/or altering design characteristics of the shock absorber.

[0014] Further objective of the present invention is to provide a simple and effective solution to improve the damping performance and durability of existing shock absorber designs without significant modifications to the core structure of the shock absorber.

Brief Description of Drawings

[0015] This invention is illustrated in the accompanying drawings, throughout which like reference letters / numerals indicate the corresponding parts in the various figures. The embodiment herein and the advantages thereof will be better understood from the following description when read in conjunction with the following drawings, wherein

[0016] Figure 1 discloses an isometric view of the mono tube shock absorber in accordance with the first embodiment of the present invention.

[0017] Figure 2A discloses a sectional view of the shock absorber shown in Fig. l in accordance with the first embodiment of the present invention wherein said shock absorber has oil only as the working fluid.
[0018] Figure 2B discloses a sectional view of the shock absorber shown in Fig. l in accordance with the first embodiment of the present invention wherein said shock absorber has oil and gas as the working fluid and said oil chamber and gas chambers separated by the floating piston.

[0019] Figure 3 discloses a sectional view of the piston rod assembly of the shock absorber shown in Fig. l in accordance with the first embodiment of the present invention.

[0020] Figure 4A discloses a sectional view of the outer tube assembly of the shock absorber shown in Fig. 2A in accordance with the present invention.

[0021] Figure 4B discloses a sectional view of the outer tube assembly of the shock absorber shown in Fig. 2B in accordance with the present invention.

[0022] Figure 5A discloses an isometric view of a twin tube shock absorber without canister in accordance with a second embodiment of the present invention.

[0023] Figure 5B discloses an isometric view of a twin tube shock absorber gas canister in accordance with the second embodiment of the present invention.

[0024] Figures 6A and 6B show a sectional view of the shock absorber shown in Figs. 5A and 5B, respectively in accordance with the second embodiment of the present invention.

[0025] Figure 7 presents a sectional view of the piston rod assembly of the shock absorber shown in Figs. 6A and 6B in accordance with the second embodiment of the present invention.

[0026] Figures 8A and 8B present enlarged sectional views of the outer tube assembly of the shock absorbers shown in Figs. 6A and 6B, respectively in accordance with the second embodiment of the present invention.

[0027] Figure 9A shows an isometric view of the uniquely profiled guide sleeve of shock absorber of the invention in accordance with the first and second embodiment.
[0028] Figures 9B to 9E show a sectional view of the guide sleeve along the Y-Y plane, a sectional view of the guide sleeve along the X-X plane, top view and bottom view, respectively of the guide sleeve shown in Fig. 9A in accordance with the first and second embodiment of the present invention.

Detailed Description of the Present Invention

[0029] The invention will now be described in detail with reference to the accompanying drawings which must not be viewed as restricting the scope and ambit of the invention. Referring to Figs. 1, 2A and 2B, the shock absorber (500) according to the first embodiment of the present invention for a vehicle, particularly for two and three wheeled vehicles, comprises of a piston rod assembly (50), an outer tube assembly (100A, 100B), a main spring (20), a spring locator (15), a spring seat (35), a spring adjuster (25), and a pair of mounting brackets (1 and 5). The mounting brackets (1 and 5) are employed to mount the shock absorber (500) on the vehicle wherein the mounting bracket (1) is fixedly attached to the frame of the vehicle and the mounting bracket (5) is fitted at the wheel axle of the vehicle.

[0030] Referring to Fig. 3, the piston rod assembly (50) of the first embodiment of the present invention comprises of a piston rod (45), an oil seal (70), a rod guide (75), a rod guide bush (72), a support plate (85), a pair of pistons (90A, 90B), a plurality of shims (90SH1, 90SH2, 90SH3), a guide sleeve (110) and a nut (45N). The piston rod (45) of the piston rod assembly (50) is configured to have a cylindrical stepped profile at its upper end and the lower end forming three portions viz. a proximal portion (45P1), a central portion (45P2) and a distal portion (45P3). The proximal portion (45P1) of the piston rod (45) is connected with the mounting bracket (1) by suitable fastening means preferably a threaded engagement. The central portion (45P2) of the piston rod has a diameter greater than the diameter of the proximal portion (45P1). The distal portion (45P3) has a diameter smaller than the diameter of the proximal portion (45P1). Thus, the diameter of the stepped portions of the piston rod (45) is in the order 45P2 > 45P1> 45P3 and the axial length of the stepped portions of the piston rod (45) is in the order 45P2 > 45P3 > 45P1.

[0031] The rod guide (75) and the seal member (70) are sleeved over the piston rod (45) and positioned on the central portion (45P2). The rod guide (75) guides the movement of the piston rod (45) by supporting the piston rod (45) to be movable in the axial direction while restricting its movement in a radial direction. The seal member (70) is in close contact with an outer circumferential surface of the piston rod (45) moving in the axial direction in the inner circumferential portion of the seal member (70). The seal member (70) prevents the damping fluid in the outer tube (38) from leaking to the outside.

[0032] The pair of pistons (90A and 90B) as disclosed in Fig. 3, has a cylindrical body and said cylindrical body is configured to have at least two longitudinal orifices (90AO1, 90AO2, and 90BO1, 90BO2) passing through it in the axial direction of the piston rod (45). Further, the piston (90A) is configured to have a groove (g) on the outer peripheral surface of the cylindrical body and an O-ring (90AO3) is fitted in the said groove (g) of the piston (90A) to avoid the leakage of damping fluid from the peripheral surface of the piston (90A) and thereby maintain the pressure in the oil chamber. The longitudinal orifices (90AO1, 90AO2, 90BO1 and 90BO2) on the said pair of pistons (90A, 90B) are provided for the restricted flow of damping fluid during the operation of the shock absorber. Said pistons (90A, 90B) are sleeved over the piston rod (45) and positioned on the distal end (45P3) in such a way that they are separated by a uniquely profiled guide sleeve (110) and said guide sleeve (110) is sandwiched between these pistons (90A and 90B). The said pair of pistons (90A, 90B) and said guide sleeve (110) are fitted on the piston rod (45) on the interference fitting. The positioning of the piston (90A), the guide sleeve (110) and the piston (90B) on the distal portion (45P3) of the piston rod (45) is configured to create hydraulic / oil chambers (113, 114, 115) inside the outer tube (38) in assembled condition of the shock absorber (500). The hydraulic chamber (113) is formed in between the piston (90B) and the guide sleeve (110), the hydraulic chamber (114) is formed in between the guide sleeve (110) and the piston (90A), and the hydraulic chamber (115) is formed in between the piston (90A) and the rod guide (75).

[0033] Referring to Figs 3, 7 and 9, the guide sleeve (110) is fitted between the pair of piston (90A and 90B) on the piston rod (45) of the piston rod assembly (50). The guide sleeve (110) is configured to have a hollow cylindrical body (125) and an annular skirt (126) whereas the said annular skirt (126) is projecting outward in the radial direction from the cylindrical body (125). The upper end and lower end of the cylindrical body (125) of the guide sleeve (110) is configured to have flat resting surfaces (128A, 128B) and the said annular skirt (126) is formed between the upper and lower resting surfaces on the outer peripheral surface of the cylindrical body (125). The guide sleeve (110) with the cylindrical body (125), annular skirt (126) and flat resting surface (128A, 128B) is a single unitary structure. The cylindrical body (125) at its portion (125A) above the annualr skirt (126) is configured to have a plurality of thorough holes / oil passages (128H1, 128H2) in the radial direction from its center. The annular skirt portion (126) is configured to have a plurality of thorough holes / oil passages (126H1, 126H2, 126H3) and said oil passages (126H1 to 126H3) are configured to communicate between the oil chamber (113) and the oil chamber (114). The annular skirt portion (126) of the guide sleeve is configured to have an annular groove (G) on its outer peripheral surface and said groove (G) is coated with Polytetrafluoroethylene (PTFE) coating to reduce the friction between the guide sleeve (110) and the inner surface of the outer tube (38) while the working of the shock absorber. The flat resting surfaces (128A, 128B) of the guide sleeve (110) are configured to provide the resting surface for the shims (90SH1, 90SH2) during working of shock absorber.

[0034] Referring to Fig. 3, the distal end (45P3) of the piston rod (45) is configured to have an oil passage (45H1) bored therein in the axial direction of the piston rod (45) and said oil passage (45H1) is concentric with the said piston rod (45). At the end of the oil passage (45H1), said piston rod (45) is configured to have an oil passage (45H2) throughout its diameter in such a way that the oil passage (45H1) and the oil passage (45H2) are orthogonal with each other and jointly forms a T-profiled seamless oil passage and said T-profiled seamless oil passage is configured to hydraulically communicate with the hydraulic chamber (112, 112’) in the outer tube (38) and the hydraulic chamber (114) formed in between the piston (90A) and the guide sleeve (110) through the thorough holes (128H1, 128H2) of the guide sleeve (110). A first set of shims (90SH1) is concentrically placed between the lower side of the guide sleeve (110) and the upper side of piston (90B) and said first set of shims (90SH1) partially covers the orifices (90BO1 and 90BO2) of the piston (90B). Another set of shims (90SH2) is concentrically positioned between the flat resting surface (128A) of the guide sleeve (110) and the lower surface of the piston (90A), whereas, the third set of shims (90SH3) is concentrically positioned above the piston (90A) and said third set of shims (90SH3) located above the piston (90A) partially covers the orifices (90AO1 and 90AO2). The washer (85), a set of shims (90SH3), piston (90A), a set of shims (90SH2), the guide sleeve (110), the set of shims (90SH1), and the piston (90B) are sleeved on the distal end (45P3) of the piston rod (45) in the given order and positioned and locked there in the same order with the help of a nut (45N).

[0035] Referring to Fig. 4a, the first embodiment of the outer tube assembly (100A) of the shock absorber (500) comprises of an outer tube (38), a bottom cap (36), a pair of lugs (37) and an outer sleeve (39). The outer tube (38) of the outer tube assembly (100A) is a hollow cylindrical tube having an upper end (38T) and a lower end (38B). The upper end (38T) of the outer tube (38) is configured to have annular recess (38AR) on its inner peripheral surface to position a circlip (75C) which restricts the upward movement of the rod guide (75) of the piston rod assembly (50). The lower end (38B) of the outer tube (38) is fitted with the bottom cap (36) with the help of fastening means preferably selected from threaded joinery by having threads on the inner surface of the bottom end (38B) of the outer tube (38) and the matching threads on the outer surface of the bottom cap (36) thereby making the lower end (38B) of the outer tube (38) is hermetically closed. However, the outer tube (38) can be joined to the bottom cap (36) using any known method such as welding, press-fitting, fastening, etc. The mounting bracket (5) is fixed at the lower end of a bottom cap (36) by welding or the like any other fastening means.

[0036] The outer sleeve (39) of the outer tube assembly (100A) is a hollow cylindrical tube having an upper end (39T) and lower end (39B). The upper end (39T) of the outer sleeve (39) is configured to have an inward tapered surface (39TT) and the lower end (39B) has a step profile (39SB). The said outer sleeve (39) is fixed at the lower end of the outer tube (38) by welding or like other fastening means. A pair of lugs (37) are fitted on the outer surface of the outer sleeve (39) by welding or the like and said lugs (37) facilitate a seating for mounting the spring adjuster (25) of the outer tube assembly (100A). The piston rod (45) along with the piston rod assembly (50) passes through the top open end (38T) of the outer tube (38) of the outer tube assembly (100A) creating the hydraulic chamber (112) in between the piston (90B) and the bottom cap (36) of the outer tube assembly (100A). The cap seal washer (W) of the piston rod assembly (50) closes the top open end (38T) of the outer tube (38).

[0037] Referring to Fig. 4b, the second embodiment of the outer tube assembly (100B) of the shock absorber (500) comprises of an outer tube (38), a bottom cap (36), a separation piston (40), a pair of lugs (37) and an outer sleeve (39). Said separation piston (40) is positioned inside the outer tube (38) in such a way that it forms two chambers namely an oil chamber (112’) above it and a gas chamber (106) in between the separation piston (40) and the bottom cap (36) of the outer tube assembly (100B). The said separation piston (40) acts as a wall between the hydraulic chamber (112’) and the gas chamber (106). The outer peripheral surface of the separation piston (40) is configured to have a groove (G’) to accommodate an O-Ring (40O1) therein and said O-ring interfaces with the inner surface of the outer tube (38) so as to seal the leakage of damping fluid, if any, from the oil chamber (112’) to the gas chamber (106). The gas chamber (106) contains pressurized gas therein for maintaining pressure over the damping fluid in the hydraulic chamber (112’). This unique arrangement of outer tube assembly (100B) facilitate to maintain the consistent damping performance during long periods of rapid compression and expansion of the shock absorber (500A). The piston rod (45) along with the piston rod assembly (50) passes through the top open end (38T) of the outer tube (38) of the outer tube assembly (100B) creating the hydraulic chamber (112’) in between the piston (90B) and the separation piston (40) of the outer tube assembly (100B). The cap seal washer (W) of the piston rod assembly (50) closes the top open end (38T) of the outer tube (38).

[0038] The adjuster (25) is rotatably placed over the lugs (37) of the bottom cap (36) and the spring locator (15) is fitted over the bump stop washer (224) of the mono-tube type shock absorber (500). The main spring (20) is positioned between the spring locator (15) and the adjuster (25). The shock absorber (500) of the present invention assembled in this fashion is then mounted on the vehicle by fixing the mounting bracket (5) with the swing arm of the vehicle and the mounting bracket (1) with the vehicle frame. The mounting of this shock absorber (500) is at an angle ranging from 15 to 20 degrees with the horizontal. The spring locator (15) is fitted at the mounting bracket (1) and spring seat (35) is positioned on the outer peripheral surface of the outer tube (38). The main spring (20) is located between the spring locator (15) given on the bracket (1) and the spring seat (35) given on the outer tube (38) of the outer tube assembly (100A, 100B) so as to be concentric with the piston rod (45) and the outer tube (38). The spring seat (35) itself is positioned on the upper surface of the spring preload adjuster (25) of the outer tube (38) of the outer tube assembly (100A, 100B). A hollow cylindrical shaped dust cover (51) having a collar (51C) at its top end is positioned on a support washer (15c) located on the spring locator (15) such that they are concentric with the piston rod (45).

[0039] Referring to Figs. 5A to 6B, the shock absorber (600) as per the second embodiment of the present invention for a vehicle particularly for two wheeled vehicles comprises of a piston rod assembly (300), an outer tube assembly (310A, 310B), an inner tube (320), main spring (330), spring locator (15’), spring seat (35’), a spring adjuster (25’), a base valve assembly (340) and a pair of mounting brackets (1 and 5). The mounting brackets (1 and 5) are employed to mount the shock absorber (600) on the vehicle wherein the mounting bracket (1) is fixedly attached to the frame of the vehicle and the mounting bracket (5) is fitted at the wheel axle of the vehicle.

[0040] Referring to Fig. 7, the piston rod assembly (300) of the second embodiment of the present invention comprises of a piston rod (45), an oil seal (70’), a rod guide (75’), a rod guide bush (72), a support plate (85’), a rebound spring (RS), a pair of pistons (90A’, 90B’), a plurality of shims (90S1, 90S2, 90S3), a guide sleeve (110), a support washer (90SW) and a nut (45N). The piston rod (45) of the piston rod assembly (300) is configured to have a cylindrical stepped profile at its upper end and the lower end forming three portions viz. a proximal portion (45P1), a central portion (45P2) and a distal portion (45P3). The proximal portion (45P1) of the piston rod (45) is connected with the mounting bracket (1) by suitable fastening means preferably a threaded engagement. The central portion (45P2) of the piston rod has a diameter greater than the diameter of the proximal portion (45P1). The distal portion (45P3) has a diameter smaller than the diameter of the proximal portion (45P1). Thus, the diameter of the stepped portions of the piston rod (45) is in the order 45P2 > 45P1> 45P3 and the axial length of the stepped portions of the piston rod (45) is in the order 45P2 > 45P3 > 45P1.

[0041] The rod guide (75’) and the seal member (70’) are sleeved over the piston rod (45) and positioned on the central portion (45P2). The rod guide (75’) guides the movement of the piston rod (45) by supporting the piston rod (45) to be movable in the axial direction while restricting its movement in a radial direction. The seal member (70’) is in close contact with an outer circumferential surface of the piston rod (45) moving in the axial direction in the inner circumferential portion of the seal member (70’). The seal member (70’) prevents the damping fluid in the inner tube (320) from leaking to the outside.

[0042] The pair of pistons (90A’ and 90B’) as disclosed in Fig. 7, has a cylindrical body and said cylindrical body is configured to have at least two longitudinal orifices (90AO1, 90AO2, and 90BO1, 90BO2) passing through it in the axial direction of the piston rod (45). The longitudinal orifices (90AO1, 90AO2, 90BO1 and 90BO2) on the said pair of pistons (90A’, 90B’) are provided for the restricted flow of damping fluid during the operation of the shock absorber (600). Said pistons (90A’, 90B’) are sleeved over the piston rod (45) and positioned on the distal end (45P3) in such a way that they are separated by a uniquely profiled guide sleeve (110) and said guide sleeve (110) is sandwiched between these pistons (90A’ and 90B’). The said pair of pistons (90A’, 90B’) and said guide sleeve (110) are fitted on the piston rod (45) by the interference fitting. The positioning of the piston (90A’), the guide sleeve (110) and the piston (90B’) on the distal portion (45P3) of the piston rod (45) is configured to create hydraulic / oil chambers (113’, 114’, 115’) inside the inner tube (320) in assembled condition of the shock absorber (600). The hydraulic chamber (113’) is formed in between the piston (90B’) and the guide sleeve (110), the hydraulic chamber (114’) is formed in between the guide sleeve (110) and the piston (90A’), and the hydraulic chamber (115’) is formed in between the piston (90A’) and the rod guide (75’).

[0043] The hydraulic chamber (115’) houses the rebound spring (RS) in such a way that the said rebound spring (RS) is concentrically sleeved over the central portion (45P2) of the piston rod (45) and abuts against the support plate (85’) mounted on the distal portion (45P3) at its one end and the rod guide (75’) mounted on the central portion (45P2) at its other end. The oil passages (126H1 to 126H3) on the annular skirt portion (126) of the guide sleeve (110) are configured to communicate between the oil chamber (113’) and the oil chamber (114’). The flat resting surfaces (128A, 128B) of the guide sleeve (110) are configured to provide the resting surface for the shims (90S1 and 90S2) during working of shock absorber. The T-profiled seamless oil passage in the distal portion (45P3) of the piston rod (45) is configured to hydraulically communicate with the hydraulic chamber (HC) in the inner tube (320) and the hydraulic chamber (114’) formed in between the piston (90A’) and the guide sleeve (110) through the thorough orifices (128H1, 128H2) of the guide sleeve (110). A first set of shims (90S1) is concentrically placed between the lower side of the guide sleeve (110) and the upper side of piston (90B’) and said first set of shims (90S1) partially covers the orifices (90BO1 and 90BO2) of the piston (90B’). Another set of shims (90S2) is concentrically positioned between the flat resting surface (128A) of the guide sleeve (110) and the lower surface of the piston (90A’), whereas, the third set of shims (90S3) is concentrically positioned in between the piston (90A’) and the support plate (85’) and said third set of shims (90S3) located above the piston (90A’) partially covers the orifices (90AO1 and 90AO2). The support plate (85’), a set of shims (90S3), piston (90A’), a set of shims (90S2), the guide sleeve (110), the set of shims (90S1), the piston (90B’) and the support washer (90SW) are sleeved on the distal end (45P3) of the piston rod (45) in the given order and positioned and locked there in the same order with the help of a nut (45N).

[0044] The inner tube (320) is a hollow cylindrical tube having its diameter lesser than that of the outer tube (38’) of the outer tube assembly (310A, 310B). The bottom end (320B) of the said inner tube (320) is fitted with the base valve (340). The piston rod (45) along with the piston rod assembly (300) passes through the top open end (320T) of the inner tube (320) creating the hydraulic chamber (HC) in between the support washer (90SW) of the piston rod assembly (300) and the base valve (340) fitted at lower open end of the said inner tube (320).

[0045] Referring to Fig. 8a, the first embodiment of the outer tube assembly (310A) of the shock absorber (600) comprises of an outer tube (38’), a bottom cap (36’), a pair of lugs (37’) and the mouting bracket (5). The outer tube (38’) of the outer tube assembly (310A) is a hollow cylindrical tube having an upper end (38T’) and a lower end (38B’). The lower end (38B’) of the outer tube (38’) is fitted with the bottom cap (36’) with the help of fastening means preferably threaded joinery by having threads provided on the inner surface of the bottom end (38B’) of the outer tube (38’) and the matching threads provided on the outer surface of the bottom cap (36’) thereby making the lower end (38B’) of the outer tube (38’) is hermetically closed. However, the outer tube (38’) can be joined to the bottom cap (36’) using any known method such as welding, press-fitting, fastening, etc. The mounting bracket (5) is fixed at the lower end of a bottom cap (36’) by welding or the like any other fastening means.

[0046] A pair of lugs (37’) are fitted on the outer surface of the outer tube (38’) by welding or the like and said lugs (37’) facilitate a seating for mounting the spring adjuster (25’) of the outer tube assembly (310A). The inner tube (320) fitted with the piston rod (45) along with the piston rod assembly (300) therein concentrically passes through the top open end (38T’) of the outer tube (38’) of the outer tube assembly (310A) creating the reservoir chamber (58) in between the annual space between the outer peripheral surface of the inner tube (320) and the inner peripheral surface of the outer tube (38’) of the outer tube assembly (310A). The base valve (340) fitted at the lower end of the inner tube (320) is configured to hydraulically communicate between the hydraulic chamber (HC) and the reservoir chamber (58).

[0047] Referring to Fig. 8b, the second embodiment of the outer tube assembly (310B) of the shock absorber (600) comprises of an outer tube (38’), a uniquely profiled mounting bracket (5’) with a canister assembly (6) integrated to it, a pair of lugs (37’) and an adjuster (25’). The mounting bracket (5’) is configured to have cylindrical wall portion (5W) which is integrated with the axle portion (5E) of the mounting bracket (5’). The canister assembly (6) is fixedly connected with the axle eye portion (5E) of the mounting bracket (5’) through the neck (6N). Thus, the cylindrical wall portion (5W), axle eye portion (5E), canister assembly (6) with its neck (6N) forms a single piece unitary structure of the mounting bracket (5’). The lower end (38B’) of the outer tube (38’) is threadedly fitted with the inner peripheral surface of the cylindrical wall portion (5W) of the mounting bracket (5’) wherein the threads on the outer surface of the bottom end (38B’) of the outer tube (38’) and the matching threads provided on the inner surface of the cylindrical wall (5W) of the mounting bracket (5’) thereby making the lower end (38B’) of the outer tube (38’) is hermetically closed.

[0048] A pair of lugs (37’) are fitted on the outer surface of the outer tube (38’) by welding or the like and said lugs (37’) facilitate a seating for mounting the spring adjuster (25’) of the outer tube assembly (310A). The inner tube (320) fitted with the piston rod (45) along with the piston rod assembly (300) therein concentrically passes through the top open end (38T’) of the outer tube (38’) of the outer tube assembly (310B) creating the reservoir chamber (58) in between the annual space between the outer peripheral surface of the inner tube (320) and the inner peripheral surface of the outer tube (38’) of the outer tube assembly (310B). The base valve (340) fitted at the lower end of the inner tube (320) is configured to hydraulically communicate between the hydraulic chamber (HC) and the reservoir chamber (58). The gas filled canister assembly (6) is hydraulically linked with the reservoir chamber (58) through a passage formed through canister neck portion (6N) of the mounting bracket (5’). The gas canister (6) so connected performs the function of keeping the damping fluid under sufficient pressure at all times thereby avoiding foaming of damping fluid/cavitation during operation of said shock absorber (600).

[0049] The adjuster (25’) is rotatably placed over the lugs (37’) of the outer tube (38’) and the spring locator (15’) is fitted over the bump stop washer (224’) of the twin-tube type shock absorber (600). The main spring (330) is positioned between the spring locator (15’) and the adjuster (25’). The shock absorber (600) of the present invention assembled in this fashion is then mounted on the vehicle by fixing the mounting bracket (5, 5’) with the swing arm of the vehicle and the mounting bracket (1) with the vehicle frame. The mounting of this shock absorber (600) is at an angle ranging from 15 to 20 degrees with the horizontal. The spring locator (15’) is fitted at the mounting bracket (1) and spring seat (35’) is positioned on the outer peripheral surface of the outer tube (38’) of the outer tube assembly (310A, 310B). The main spring (330) is located between the spring locator (15’) given on the bracket (1) and the spring seat (35’) given on the outer tube (38’) of the outer tube assembly (310A, 310B) so as to be concentric with the piston rod (45) and the outer tube (38’). The spring seat (35’) itself is positioned on the upper surface of the spring preload adjuster (25’) of the outer tube (38’) of the outer tube assembly (310A, 310B). A hollow cylindrical shaped dust cover (51) having a collar (51C) at its top end is positioned on a support washer (15c) located on the spring locator (15’) such that they are concentric with the piston rod (45).

[0050] As far as the working of first embodiment of the shock absorbers (500) is concerned, when the shock absorber (500) is subjected to the road surface irregularity, the main spring (20) positioned between the spring locator (15) and the spring adjuster (25) is compressed and pushing the piston rod (45) to travel downward inside the tube (38). At this time the damping fluid from the oil chamber (112, 112’) starts to flow through the orifices (90BO1 and 90BO2) on the piston (90B) to the oil chamber (113) being formed above the piston (90B). The first set of shims (90SH1) deflects during this stage to allow the passage for damping fluid present in the oil chamber (112). Simultaneously, the damping fluid from the oil chamber (112) starts to flow through the T-profiled oil passage to the oil chamber (114) via the plurality through holes (128H1, 128H2) on the annular hollow resting portion (128) of guide sleeve (110). When the piston rod moves further inside the outer tube (38), the damping fluid from the oil chamber (113) starts to flow through the plurality of holes (126H1, 126H2, 126H3) on the guide sleeve (110) to the oil chamber (114).

[0051] When the main spring (20) is about to get fully compressed, the bump stop (225) comes into contact with the cap seal washer (W) fitted at the top end (38T) of the outer tube (38) and absorbs the residual energy through its own compression so as to avoid the bottoming effect in the fully compressed condition of the spring (20). When the vehicle has moved past the irregularity of the road surface and runs on the smooth road surface, the main spring (20) starts getting decompressed and releases its stored energy making the piston (90) move up at its original position. At this point, the damping fluid in the oil chamber (115) starts flowing through the orifices (90AO1 and 90AO2) to chamber (114) below the piston (90A). During this, the damping fluid in the chamber (115) within the outer tube (40) deflects the second set of shims (90SH2) and flows back into the oil chamber (114). Further, the damping fluid present in the oil chamber (114) flows back to the oil chamber (113) via the plurality of through holes (126H1, 126H2, 126H3) on the guide sleeve (110) and further retraction of the piston causes the damping fluid present in the oil chamber (113) flows back to oil chamber (112) via the orifices (90BO1 and 90BO2).

[0052] As far as the working of second embodiment of the shock absorber (600) is concerned, when the vehicle fitted with twin-tube shock absorber (600) is subjected to the road surface irregularity, the spring (330) is compressed and pushing the piston rod (45) to travel downward inside the inner tube (320) towards base valve (340). At this time the damping fluid from the oil chamber (HC) starts to flow through the orifices (90BO1 and 90BO2) on the piston (90B’) to the oil chamber (113’). The first set of shims (90S1) deflects during this stage to allow the passage of damping fluid present in the oil chamber (HC). Also, the damping fluid from the oil chamber (HC) starts to flow through the T-profiled oil passage in the distal portion (45P3) of the piston rod (45) to the oil chamber (114’) via the plurality of thorough holes (128H1, 128H2) on the annular hollow resting portion (128) of guide sleeve (110). And when the piston rod moves further inside the inner tube (320), the damping fluid from the oil chamber (113’) starts to flow through a plurality of holes (126H1, 126H2, 126H3) on the guide sleeve (110) to the oil chamber (114’).

[0053] When the vehicle has moved past the irregularity of the road surface and runs on the smooth road surface, the spring (330) starts getting decompressed and releases its stored energy making the piston (90A’) to move up at its original position. At this point, the damping fluid in the oil chamber (115’) starts flowing through the orifices (90AO1 and 90AO2) to chamber (114’). During this, the damping fluid in the chamber (115’) deflects the second set of shims (90S2) and flows back into the oil chamber (114’). Further, the damping fluid present in the oil chamber (114’) flows back to oil chamber (113’) via the plurality of through holes (126H1, 126H2, 126H3) on the guide sleeve (110) and further retraction of piston causes the damping fluid present in the oil chamber (113’) flows back to oil chamber (HC) via the orifices (90BO1 and 90BO2) by deflecting the support washer (90SW).

[0054] The base valve assembly (340) has its own set of damping holes and shims that deflect to permit damping fluid to flow from within the inner tube (320) to the reservoir chamber (58) formed between the inner tube (320) and the outer tube (38’) when the main spring (330) are compressing. The set of damping holes and shims given on the base valve assembly (340) also deflect to permit damping fluid is flow back into the inner tube (320) from the reservoir chamber (58) formed between the inner tube (320) and the outer tube (38’) when the main spring (330) is decompressing. Thus, the base valve assembly (340) offers resistance to the flow of damping fluid during compression of the main spring (330), thereby providing some of the required damping force in these instances.

[0055] The guide sleeve (110) in the shock absorber (500, 600) as per the present invention eliminates the use side support washer/s for the shims in comparison to a conventional shock absorber. Further, the unique arrangement of the guide sleeve (110) helps in removing the breakage of shims due to the extra forces generated while working. Thus, the shock absorber (500, 600) of the present invention as disclosed above overcome the technical limitations of the conventional shock absorbers enhancing the damping performance and therefore are more technologically advanced to provide ideal damping performance.

[0056] This novel and inventive construction of the shock absorber (500, 600) having the uniquely profiled guide sleeve (110) intelligently positioned in the piston rod assembly (50, 300) as disclosed above provides the following technical advantages contributing to technical advancement of the technology domain of damping control systems.
- It is simple and compact in construction and hence is easy to manufacture and install motor vehicles, particularly in two wheeled vehicles.
- It generates a 30-50% more damping force without the need of a higher bore size.
- It passively moderates the equal distribution of internal pressure with the combination of double piston design and provided shims.
- Prevents the breakage of shims by reducing the higher pressure acting on shims when the vehicle is experiencing vertical movement velocities of higher magnitude.
- It reduces the friction force generated inside the damper by providing then low friction PTFE band.
- It provides a balanced oil flow through the holes and orifices provided when the vehicle is experiencing vertical movement velocities of higher magnitude.
- It enhances rider comfort and safety in a motor vehicle, particularly two wheeled vehicles, in a wide variety of operating conditions.
- It provides consistent performance in a variety of operating conditions.

[0057] The foregone description of the specific embodiments reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. , Claims:We Claim:

1. A shock absorber (500) for a vehicle comprising of a piston rod assembly (50), an outer tube assembly (100A, 100B), a main spring (20), a spring locator (15), a spring seat (35), a spring adjuster (25), and a pair of mounting brackets (1 and 5)
wherein,
- the piston rod assembly (50) is configured to comprise of a piston rod (45), an oil seal (70), a rod guide (75), a rod guide bush (72), a support plate (85), a pair of pistons (90A, 90B), a plurality of shims (90SH1, 90SH2, 90SH3), a guide sleeve (110) and a nut (45N), wherein
 the guide sleeve (110) is configured to have a hollow cylindrical body (125) and an annular skirt (126) projecting outward in the radial direction from the cylindrical body (125); and
 said guide sleeve (110) is fitted between the pair of pistons (90A and 90B) on the piston rod (45) of the piston rod assembly (50);
- the outer tube assembly (100A) has a cylindrical outer tube (38) having an upper end (38T) and a lower end (38B), and said upper end (38T) of the outer tube (38) is configured to have annular recess (38AR) on its inner peripheral surface to position a circlip (75C) to restrict the upward movement of the rod guide bush (75) of the piston rod assembly (50);
- the spring locator (15) is fitted at the mounting bracket (1), the spring seat (35) is positioned on the outer peripheral surface of the outer tube (38) of the outer tube assembly (100A, 100B), and the main spring (20) is located between said spring locator (15) and the spring seat (35) concentric with the piston rod (45) and the outer tube (38); and
- the piston rod (45) along with the piston rod assembly (50) passes through the top open end (38T) of the outer tube (38) of the outer tube assembly (100A, 100B) creating the hydraulic chamber (112, 112’) therein, and the cap seal washer (W) of the piston rod assembly (50) closes the top open end (38T) of the outer tube (38).

2. The shock absorber (500) for a vehicle as claimed in claim 1, wherein
- the guide sleeve (110) is configured to have flat resting surfaces (128A, 128B) at its upper end and lower end of the cylindrical body (125) and the annular skirt (126) is formed between the upper resting surface (128A) and the lower resting surface (128B) on the outer peripheral surface of the cylindrical body (125);
- said guide sleeve (110) with the cylindrical body (125), annular skirt (126) and flat resting surfaces (128A, 128B) is a single unitary structure;
- the cylindrical body (125) at its portion (125A) above the annular skirt (126) is configured to have a plurality of thorough holes / oil passages (128H1, 128H2) in the radial direction from its center; and
- the annular skirt portion (126) is configured to have a plurality of thorough holes / oil passages (126H1, 126H2, 126H3) and said oil passages (126H1 to 126H3) are configured to communicate between the oil chamber (113) and the oil chamber (114).

3. The shock absorber (500) for a vehicle as claimed in claim 2, wherein
- the annular skirt portion (126) of the guide sleeve (110) is configured to have an annular groove (G) on its outer peripheral surface and said groove (G) is coated with Polytetrafluoroethylene (PTFE) coating to reduce the friction between the guide sleeve (110) and the inner surface of the outer tube (38) of the outer tube assembly (100A, 100B); and
- the flat resting surfaces (128A, 128B) of the guide sleeve (110) are configured to provide the resting surface for the shims (90SH1, 90SH2).

4. The shock absorber (500) for a vehicle as claimed in claim 3, wherein
- the outer tube assembly (100A) of the shock absorber (500) is configured to comprise of an outer tube (38), a bottom cap (36), a pair of lugs (37) and an outer sleeve (39);
- the lower end (38B) of the outer tube (38) is fitted with the bottom cap (36) by a fastening means selected from threaded joinery, welding, press-fitting and combination thereof making the lower end (38B) of the outer tube (38) is hermetically closed;
- the mounting bracket (5) is fixed at the lower end of a bottom cap (36) by welding;
- the outer sleeve (39) of the outer tube assembly (100A) is a hollow cylindrical tube having an upper end (39T) and lower end (39B); the upper end (39T) of the outer sleeve (39) is configured to have an inward tapered surface (39TT) and the lower end (39B) has a step profile (39SB); and said outer sleeve (39) is fixed at the lower end of the outer tube (38) by welding;
- the lugs (37) are fitted on the outer surface of the outer sleeve (39) by welding and said lugs (37) are configured to facilitate a seating for mounting the spring adjuster (25) of the outer tube assembly (100A);
- the piston rod assembly (50) is configured to create the hydraulic chamber (112) in between the piston (90B) and the bottom cap (36) of the outer tube assembly (100A); and
- a hollow cylindrical shaped dust cover (51) having a collar (51C) at its top end is positioned on a support washer (15c) located on the spring locator (15) so as to be concentric with the piston rod (45).

5. The shock absorber (500) for a vehicle as claimed in claim 3, wherein
- the outer tube assembly (100B) of the shock absorber (500) is configured to comprise of an outer tube (38), a bottom cap (36), a separation piston (40), a pair of lugs (37) and an outer sleeve (39);
- the lower end (38B) of the outer tube (38) is fitted with the bottom cap (36) by a fastening means selected from threaded joinery, welding, press-fitting and combination thereof making the lower end (38B) of the outer tube (38) is hermetically closed;
- the separation piston (40) is positioned inside the outer tube (38) so as to form two chambers namely an oil chamber (112’) above it and a gas chamber (106) in between the separation piston (40) and the bottom cap (36) of the outer tube assembly (100B);
- the outer peripheral surface of the separation piston (40) is configured to have a groove (G’) to accommodate an O-Ring (40O1) therein and said O-ring interfaces with the inner surface of the outer tube (38) so as to seal the leakage of damping fluid from the oil chamber (112’) to the gas chamber (106);
- the piston rod assembly (50) is configured to create the hydraulic chamber (112’) in between the piston (90B) and the separation piston (40) of the outer tube assembly (100B);
- the adjuster (25) is rotatably positioned over the lugs (37) of the bottom cap (36); and
- a hollow cylindrical shaped dust cover (51) having a collar (51C) at its top end is positioned on a support washer (15c) located on the spring locator (15) so as to be concentric with the piston rod (45).

6. The shock absorber (500) for a vehicle as claimed in any of the claims 4 and 5, wherein
- the piston rod (45) of the piston rod assembly (50) is configured to have a cylindrical stepped profile at its upper end and the lower end forming three portions namely a proximal portion (45P1), a central portion (45P2) and a distal portion (45P3);
- the proximal portion (45P1) of the piston rod (45) is connected with the mounting bracket (1) by a fastening means selected from a threaded engagement;
- the central portion (45P2) of the piston rod has a diameter greater than the diameter of the proximal portion (45P1) and the distal portion (45P3) has a diameter smaller than the diameter of the proximal portion (45P1); and
- the diameter of the stepped portions of the piston rod (45) is in the order 45P2 > 45P1> 45P3 and the axial length of the stepped portions of the piston rod (45) is in the order 45P2 > 45P3 > 45P1.

7. The shock absorber (500) for a vehicle as claimed in claim 6, wherein
- the distal end (45P3) of the piston rod (45) is configured to have a concentric oil passage (45H1) bored therein in the axial direction of the piston rod (45) and an oil passage (45H2) bored throughout its diameter at the end of the oil passage (45H1);
- said oil passage (45H1) and the oil passage (45H2) are orthogonal with each other thereby jointly forming a T-profiled seamless oil passage;
- said T-profiled seamless oil passage is configured to hydraulically communicate with the hydraulic chamber (112, 112’) in the outer tube (38) and the hydraulic chamber (114) formed in between the piston (90A) and the guide sleeve (110) through the oil passages (128H1, 128H2) of the guide sleeve (110);
- a first set of shims (90SH1) is concentrically placed between the lower side of the guide sleeve (110) and the upper side of piston (90B) and said first set of shims (90SH1) partially covers the orifices (90BO1 and 90BO2) of the piston (90B);
- another set of shims (90SH2) is concentrically positioned between the flat resting surface (128A) of the guide sleeve (110) and the lower surface of the piston (90A)
- a third set of shims (90SH3) is concentrically positioned above the piston (90A) and said third set of shims (90SH3) located above the piston (90A) partially covers the orifices (90AO1 and 90AO2); and
- the washer (85), a set of shims (90SH3), piston (90A), a set of shims (90SH2), the guide sleeve (110), the set of shims (90SH1), and the piston (90B) are sleeved on the distal end (45P3) of the piston rod (45) in the given order and positioned and locked there in the same order with the help of a nut (45N).

8. The shock absorber (500) for a vehicle as claimed in claim 7, wherein
- the pistons (90A and 90B) have a cylindrical body and said cylindrical body is configured to have at least two longitudinal orifices (90AO1, 90AO2, and 90BO1, 90BO2) passing through it in the axial direction of the piston rod (45);
- the piston (90A) is configured to have a groove (g) on the outer peripheral surface of the cylindrical body and an O-ring (90AO3) is fitted in the said groove (g) of the piston (90A) to avoid the leakage of damping fluid from the peripheral surface of the piston (90A);
- the longitudinal orifices (90AO1, 90AO2, 90BO1 and 90BO2) on the pistons (90A, 90B) are configured to provide restricted flow of damping fluid during the operation of the shock absorber;
- said pistons (90A, 90B) are sleeved over the piston rod (45) and positioned on the distal portion (45P3) separated by the guide sleeve (110) and said guide sleeve (110) is sandwiched between said pistons (90A and 90B); and
- said pair of pistons (90A, 90B) and said guide sleeve (110) are fitted on distal portion (45P3) the piston rod (45) by the interference fitting.

9. The shock absorber (500) for a vehicle as claimed in claim 8, wherein
- the positioning of the piston (90A), the guide sleeve (110) and the piston (90B) on the distal portion (45P3) of the piston rod (45) is configured to create hydraulic / oil chambers (113, 114, 115) inside the outer tube (38) in assembled condition of the shock absorber (500);
- the hydraulic chamber (113) is formed in between the piston (90B) and the guide sleeve (110), the hydraulic chamber (114) is formed in between the guide sleeve (110) and the piston (90A), and the hydraulic chamber (115) is formed in between the piston (90A) and the rod guide (75); and
- the rod guide (75) and the seal member (70) are sleeved over the piston rod (45) and positioned on the central portion (45P2) of said piston rod (45).

10. A shock absorber (600) for a vehicle comprising of a piston rod assembly (300), an outer tube assembly (310A, 310B), an inner tube (320), main spring (330), spring locator (15’), spring seat (35’), a spring adjuster (25’), a base valve assembly (340) and a pair of mounting brackets (1 and 5, 5’)
wherein,
- the piston rod assembly (300) is configured to comprise of a piston rod (45), an oil seal (70’), a rod guide (75’), a rod guide bush (72), a support plate (85’), a rebound spring (RS), a pair of pistons (90A’, 90B’), a plurality of shims (90S1, 90S2, 90S3), a guide sleeve (110), a support washer (90SW) and a nut (45N), wherein
 the guide sleeve (110) is configured to have a hollow cylindrical body (125) and an annular skirt (126) projecting outward in the radial direction from the cylindrical body (125); and
 said guide sleeve (110) is fitted between the pair of pistons (90A’ and 90B’) on the piston rod (45) of the piston rod assembly (300);
- the outer tube (38’) of the outer tube assembly (310A, 310B) is a hollow cylindrical tube having an upper end (38T’) and a lower end (38B’);
- the spring locator (15’) is fitted at the mounting bracket (1), the spring seat (35’) is positioned on the outer peripheral surface of the outer tube (38’) of the outer tube assembly (310A, 310B), and the main spring (330) is located between said spring locator (15’) and the spring seat (35’) concentric with the piston rod (45) and the outer tube (38’); and
- the piston rod (45) along with the piston rod assembly (300) passes through the top open end (320T) of the inner tube (320) creating the hydraulic chamber (HC) therein, and the cap seal washer (W) of the piston rod assembly (300) closes the top open end (38T’) of the outer tube (38’) of the outer tube assembly (310A, 310B).

11. The shock absorber (600) for a vehicle as claimed in claim 10, wherein
- the guide sleeve (110) is configured to have flat resting surfaces (128A, 128B) at its upper end and lower end of the cylindrical body (125) and the annular skirt (126) is formed between the upper resting surface (128A) and the lower resting surface (128B) on the outer peripheral surface of the cylindrical body (125);
- said guide sleeve (110) with the cylindrical body (125), annular skirt (126) and flat resting surfaces (128A, 128B) is a single unitary structure;
- the cylindrical body (125) at its portion (125A) above the annular skirt (126) is configured to have a plurality of thorough holes / oil passages (128H1, 128H2) in the radial direction from its center; and
- the annular skirt portion (126) is configured to have a plurality of thorough holes / oil passages (126H1, 126H2, 126H3) and said oil passages (126H1 to 126H3) are configured to communicate between the oil chamber (113’) and the oil chamber (114’).

12. The shock absorber (600) for a vehicle as claimed in claim 11, wherein
- the annular skirt portion (126) of the guide sleeve (110) is configured to have an annular groove (G) on its outer peripheral surface and said groove (G) is coated with Polytetrafluoroethylene (PTFE) coating to reduce the friction between the guide sleeve (110) and the inner surface of the inner tube (320) of the outer tube assembly (310A, 310B); and
- the flat resting surfaces (128A, 128B) of the guide sleeve (110) are configured to provide the resting surface for the shims (90S1, 90S2).

13. The shock absorber (600) for a vehicle as claimed in claim 12, wherein
- the outer tube assembly (310A) of the shock absorber (600) is configured to comprise of an outer tube (38’), a bottom cap (36’), a pair of lugs (37’) and the mounting bracket (5);
- the lower end (38B’) of the outer tube (38’) is fitted with the bottom cap (36’) with the help of fastening means selected from threaded joinery, welding, press-fitting, and combination thereof making the lower end (38B’) of the outer tube (38’) is hermetically closed;
- the mounting bracket (5) is fixed at the lower end of a bottom cap (36’) by welding;
- a pair of lugs (37’) are fitted on the outer surface of the outer tube (38’) by welding and said lugs (37’) are configured to facilitate a seating for mounting the spring adjuster (25’) of the outer tube assembly (310A);
- the inner tube (320) fitted with the piston rod (45) along with the piston rod assembly (300) therein concentrically passes through the top open end (38T’) of the outer tube (38’) of the outer tube assembly (310A) creating the reservoir chamber (58) in between the annual space between the outer peripheral surface of the inner tube (320) and the inner peripheral surface of the outer tube (38’) of the outer tube assembly (310A); and
- the base valve (340) is fitted at the lower end of the inner tube (320) and said base valve (340) is configured to hydraulically communicate between the hydraulic chamber (HC) and the reservoir chamber (58).

14. The shock absorber (600) for a vehicle as claimed in claim 12, wherein
- the outer tube assembly (310B) of the shock absorber (600) is configured to comprise of an outer tube (38’), a uniquely profiled mounting bracket (5’) with a canister assembly (6) integrated to it, a pair of lugs (37’) and an adjuster (25’);
- the mounting bracket (5’) is configured to have cylindrical wall portion (5W) which is integrated with the axle portion (5E) of the mounting bracket (5’) and a canister assembly (6) is fixedly connected with the axle eye portion (5E) of the mounting bracket (5’) through the neck (6N) thereby forming a single piece unitary structure of the mounting bracket (5’);
- the lower end (38B’) of the outer tube (38’) is threadedly fitted with the inner peripheral surface of the cylindrical wall portion (5W) of the mounting bracket (5’) wherein the threads on the outer surface of the bottom end (38B’) of the outer tube (38’) and the matching threads provided on the inner surface of the cylindrical wall (5W) of the mounting bracket (5’) thereby making the lower end (38B’) of the outer tube (38’) is hermetically closed;
- the inner tube (320) fitted with the piston rod (45) along with the piston rod assembly (300) therein concentrically passes through the top open end (38T’) of the outer tube (38’) of the outer tube assembly (310B) creating the reservoir chamber (58) in between the annual space between the outer peripheral surface of the inner tube (320) and the inner peripheral surface of the outer tube (38’) of the outer tube assembly (310B);
- the base valve (340) fitted at the lower end of the inner tube (320) is configured to hydraulically communicate between the hydraulic chamber (HC) and the reservoir chamber (58); and
- the canister assembly (6) filled with gas is hydraulically linked with the reservoir chamber (58) through a passage formed through canister neck portion (6N) of the mounting bracket (5’) and said gas canister (6) is configured to maintain the pressure on the damping fluid thereby avoiding foaming of damping fluid/cavitation during operation of said shock absorber (600).

15. The shock absorber (600) for a vehicle as claimed in claim 14, wherein
- the adjuster (25’) is rotatably placed over the lugs (37’) of the outer tube (38’) and the spring locator (15’) is fitted over the bump stop washer (224’) at the mounting bracket (1) of the shock absorber (600);
- the spring seat (35’) is positioned on the outer peripheral surface of the outer tube (38’) of the outer tube assembly (310A, 310B);
- the main spring (330) is located between the spring locator (15’) given on the bracket (1) and the spring seat (35’) given on the outer tube (38’) of the outer tube assembly (310A, 310B) so as to be concentric with the piston rod (45) and the outer tube (38’); and
- a hollow cylindrical shaped dust cover (51) having a collar (51C) at its top end is positioned on a support washer (15c) located on the spring locator (15’) such that they are concentric with the piston rod (45).
16. The shock absorber (600) for a vehicle as claimed in any of the claims 13 and 15, wherein
- the piston rod (45) of the piston rod assembly (300) is configured to have a cylindrical stepped profile at its upper end and the lower end forming three portions namely a proximal portion (45P1), a central portion (45P2) and a distal portion (45P3);
- the proximal portion (45P1) of the piston rod (45) is connected with the mounting bracket (1) by the fastening means selected from the threaded joinery;
- the central portion (45P2) of the piston rod has a diameter greater than the diameter of the proximal portion (45P1) and the distal portion (45P3) has a diameter smaller than the diameter of the proximal portion (45P1); and
- the diameter of the stepped portions of the piston rod (45) is in the order 45P2 > 45P1> 45P3 and the axial length of the stepped portions of the piston rod (45) is in the order 45P2 > 45P3 > 45P1.

17. The shock absorber (600) for a vehicle as claimed in claim 16, wherein
- the distal end (45P3) of the piston rod (45) is configured to have a concentric oil passage (45H1) bored therein in the axial direction of the piston rod (45) and an oil passage (45H2) bored throughout its diameter at the end of the oil passage (45H1);
- said oil passage (45H1) and the oil passage (45H2) are orthogonal with each other thereby jointly forming a T-profiled seamless oil passage;
- the T-profiled seamless oil passage in the distal portion (45P3) of the piston rod (45) is configured to hydraulically communicate with the hydraulic chamber (HC) in the inner tube (320) and the hydraulic chamber (114’) formed in between the piston (90A’) and the guide sleeve (110);
- a first set of shims (90S1) is concentrically placed between the lower side of the guide sleeve (110) and the upper side of piston (90B’) and said first set of shims (90S1) partially covers the orifices (90BO1 and 90BO2) of the piston (90B’);
- another set of shims (90S2) is concentrically positioned between the flat resting surface (128A) of the guide sleeve (110) and the lower surface of the piston (90A’);
- a third set of shims (90S3) is concentrically positioned in between the piston (90A’) and the support plate (85’) and said third set of shims (90S3) located above the piston (90A’) partially covers the orifices (90AO1 and 90AO2); and
- a support plate (85’), a set of shims (90S3), piston (90A’), a set of shims (90S2), the guide sleeve (110), the set of shims (90S1), the piston (90B’) and the support washer (90SW) are sleeved on the distal end (45P3) of the piston rod (45) in the given order and positioned and locked there in the same order with the help of a nut (45N).

18. The shock absorber (600) for a vehicle as claimed in claim 17, wherein
- pistons (90A’ and 90B’) have a cylindrical body and said cylindrical body is configured to have at least two longitudinal orifices (90AO1, 90AO2, and 90BO1, 90BO2) passing through it in the axial direction of the piston rod (45);
- the longitudinal orifices (90AO1, 90AO2, 90BO1 and 90BO2) on said pistons (90A’, 90B’) are configured to provide restricted flow of damping fluid during the operation of the shock absorber (600);
- said pistons (90A’, 90B’) are sleeved over the piston rod (45) and positioned on the distal end (45P3) separated by the guide sleeve (110) and said guide sleeve (110) is sandwiched between these pistons (90A’ and 90B’); and
- said pistons (90A’, 90B’) and said guide sleeve (110) are fitted on the piston rod (45) by the interference fitting.

19. The shock absorber (600) for a vehicle as claimed in claim 18, wherein
- the positioning of the piston (90A’), the guide sleeve (110) and the piston (90B’) on the distal portion (45P3) of the piston rod (45) is configured to create hydraulic / oil chambers (113’, 114’, 115’) inside the inner tube (320) in assembled condition of the shock absorber (600);
- the hydraulic chamber (113’) is formed in between the piston (90B’) and the guide sleeve (110), the hydraulic chamber (114’) is formed in between the guide sleeve (110) and the piston (90A’), and the hydraulic chamber (115’) is formed in between the piston (90A’) and the rod guide (75’); and
- said rod guide (75’) and the seal member (70’) are sleeved over the piston rod (45) and positioned on the central portion (45P2).

20. The shock absorber (600) for a vehicle as claimed in claim 19, wherein
- the hydraulic chamber (115’) is configured to house the rebound spring (RS) and said rebound spring (RS) is concentrically sleeved over the central portion (45P2) of the piston rod (45) and abuts against the support plate (85’) mounted on the distal portion (45P3) at its one end and the rod guide (75’) mounted on the central portion (45P2) at its other end;
- the oil passages (126H1 to 126H3) on the annular skirt portion (126) of the guide sleeve (110) are configured to communicate between the oil chamber (113’) and the oil chamber (114’);
- the inner tube (320) is a hollow cylindrical tube having its diameter less than that of the outer tube (38’) of the outer tube assembly (310A, 310B), and said inner tube (320) is fitted with the base valve (340) at its bottom end (320B); and
- the piston rod assembly (300) is configured to create the hydraulic chamber (HC) in between the support washer (90SW) of the piston rod assembly (300) and the base valve (340) fitted at lower open end (320B) of the inner tube (320).

Dated this 4th day of Feb. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

To,
The Controller of Patents,
The Patent Office, at Mumbai.