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 THREE WHEELED AND LIGHT COMMERCIAL VEHICLES”

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 relates to a twin tube shock absorber for three-wheeled and light commercial vehicles (LCVs). More particularly, the present invention relates to a shock absorber having an improved piston rod assembly therein wherein a uniquely profiled hydraulic lock load assembly is configured to provide hydraulic lock load during the rebound stroke of the shock absorber thereby completely eliminating the topping up effect leading to enhanced durability and service life of the shock absorber.

Background of the Invention

[002] Shock absorbers are one of the critical sub-systems of automotive vehicles and are specifically configured to absorb and dissipate unwanted vibrations generated during running of the vehicle in response to surface irregularities. Among the different types of shock absorbers, mono-tube and twin-tube shock absorbers are the most commonly used, especially in three-wheeled vehicles.

[003] In a mono-tube shock absorber, the piston of the piston rod assembly is positioned within a single pressure tube, dividing the tube into an upper chamber (generally called as rebound chamber) and a lower chamber (generally called as compression chamber). The piston, with internal fluid passages, regulates the flow of damping fluid between these two chambers, generating a damping force that counteracts vibrations and improves ride comfort for the vehicle operator. In twin-tube shock absorbers, an oil reservoir chamber is formed in the annular space between the concentrically positioned outer tube and inner tube, with a base valve assembly hydraulically communicating 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 leading to smoother and comfortable ride.

[004] Conventionally, in shock absorber systems, a rubber guard is positioned above the piston plate of the piston rod assembly to prevent metal-to-metal contact during the rebound stroke. This rubber guard acts as cushioning element and is designed to absorb the impact when the shock absorber reaches to its maximum extension, thereby protecting the internal components from metal to metal contact and potential damage. However, over the period of time, this rubber guard degrades due to repeated stress and environmental factors leading to a loss of its effectiveness as a cushioning member. When this rubber guard degrades, the shock absorber is susceptible to damage from topping effect (i.e. the metal to metal contact of the components), where the piston plate makes direct contact with the end cap, completely defeating the intent of the shock absorber and thereby potentially leading to failure of the shock absorber.

[005] To address the limitations of this solution, some shock absorber designs incorporate a rebound spring. The rebound spring serves to control the extension of the shock absorber, preventing topping by providing resistance during the rebound stroke. While this solution offers improved performance, it introduces new challenges viz. metal-to-metal contact between the rebound spring and piston plate that generates noise, leading to undesirable noise during operation; and more importantly its implementation feasibility particularly in three wheeled vehicles and LCVs.

[006] Thus, there are a variety of solutions in the public domain with varying degree of success. But each of these solutions suffers from one or the other drawbacks. Hence, to overcome the drawbacks associated with conventional solutions available in the public domain, there is a long pending unmet need to provide a shock absorber, particularly for three wheeled vehicles and LCVs, having an improved piston rod assembly with its uniquely profiled sub-components and strategic orientation of the same so as to create a controlled hydraulic load force on the rebound side which consequently leads to enhanced damping performance, eliminates topping effect and lengthens the life of the shock absorber.

Objectives of the Present Invention

[007] The main objective of the present invention is to provide a shock absorber for three wheeled and light commercial vehicles (LCVs).

[008] Another objective of the present invention is to provide a shock absorber having an improved piston rod assembly with its uniquely profiled sub-components leading to provide a hydraulic lock load.

[009] Further, the objective of the present invention is to provide a shock absorber with strategically positioned internal components that create a controlled hydraulic load force on the rebound side, effectively preventing topping without the need for direct mechanical contact.

[0010] Yet, the objective of the present invention is to provide the shock absorber aimed to enhance durability, performance, working life of the suspension and completely eliminates metal to metal contact offering a more reliable and longer-lasting solution.
[0011] Still, the objective of the present invention is to create hydraulic lock / hydraulic retention that ensures superior and consistent damping characteristics under varying conditions, offering smoother and more reliable performance.

[0012] Still, the objective of the present invention is to eliminate the noise caused by metal-to-metal contact and thereby the wear and tear of the sub-components of the shock absorber.

[0013] Further, the objective of the present invention is to improve overall user experience, ride, comfort by providing a quieter and efficient shock absorber and thereby ensure the safety of the three wheeler / LCV user.

Brief Description of Drawings

[0014] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiment/s herein and advantages thereof will be better understood from the following description when read with reference to the following drawings, wherein

[0015] Figure 1 discloses an isometric view of the twin tube shock absorber in accordance with the present invention.

[0016] Figures 2A, 2B and 2C presents sectional view of the shock absorber of the present invention in normal state, partially compressed state, and fully compressed state, respectively in accordance with the present invention.
[0017] Figures 3A and 3B show an isometric view and cut sectional view, respectively of the piston rod assembly of the shock absorber as per the present invention.

[0018] Figures 4 discloses exploded view of the piston rod assembly of the shock absorber in accordance with the present invention.

[0019] Figures 5A and 5B disclose an isometric view and sectional view, respectively of a uniquely profiled rod guide of piston rod assembly of the shock absorber in accordance with the present invention.

[0020] Figures 6A, 6B and 6C disclose an isometric view, cut-sectional view and front view, respectively of a profiled washer of the piston rod assembly of the shock absorber in accordance with the present invention.

[0021] Figures 7A and 7B disclose an isometric view and the cut sectional view, respectively of the elastomeric cap of the piston rod assembly of the shock absorber in accordance with the present invention.

[0022] Figures 8A and 8B shows an isometric view and sectional view, respectively of a uniquely profiled rod guide of the piston rod assembly fitted with the elastomeric cap in accordance with the present invention.

Detailed Description of the Present Invention

[0023] 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 Figures 1, 2A, 2B, and 2C, the shock absorber (10) according to the present invention, intended for use in vehicles particularly three-wheeled vehicles and LCVs comprises a piston rod assembly (50), outer tube (100), inner tube (110), eyelet (600), dust cover (200), rubber cushion (300), rebound lock washer (400), hex nut (500), and tube ring (550).

[0024] The outer tube (100) is configured to have a cylindrical profile with an upper end (102) and a lower end (104). The said lower end (104) of the outer tube (100) is closed with the help of the bottom cap (15) in such a way the bottom cap (15) is sleeved inside the lower end (104) of the outer tube (100) followed by welding. The said bottom cap (15) is configured to have a bowl-shape. The base (301) of the bowl-shape bottom cap (15) is fitted with an eyelet (600) by the fixing means viz. welding, threading, etc. The said eyelet (600) is used to connect the twin tube shock absorber (10) with the wheel axle of the vehicle.

[0025] The said inner tube (110) is configured to have a cylindrical profile with an upper end (111) and a bottom end (112). The said bottom end (112) of the inner tube is closed by press fitting a base valve assembly (70) therein. The inner peripheral surface of the inner tube (110) forms an inner working chamber (IC). The base valve assembly (70) is configured to restrict the oil from escaping when the piston and valve assembly is moves in downward direction during the compression stroke. The outer diameter of the inner tube (110) is less than the inner diameter of the outer tube (100). Further, the length of the inner tube (110) is also less than the length of the outer tube (100). The inner tube (110) having base valve assembly (70) in the bottom end (112) is concentrically sleeved inside the outer tube (100) from the upper end (102) and abuts over the bowl-shape bottom cap (15). The annular space between the inner peripheral surface of the outer tube (100) and the outer peripheral surface of the inner tube (110) form an outer working chamber (OC).

[0026] Referring to Figures 3A, 3B, and 4, the piston rod assembly (50) of the present invention comprises of a piston rod (45), a shell cap (46), an oil seal (70), an oil seal support plate (71), a hydraulic lock load assembly (60), a piston assembly (P), and a bump stopper (35). The piston rod (45) of the piston rod assembly (50) is configured to have a cylindrical stepped profile throughout its length forming three portions viz. a proximal portion (45P1), a central portion (45P2) and a distal portion (45P3). The said central portion (45P2) is divided into two portions viz. first portion (45P4) and second portion (45P5) through a step (S). The piston assembly (P) comprises of a piston support plate (85), a piston (90), a piston ring (95), a plurality of shims (90S1, 90S2, 90S3), a piston nut (PN). The piston support plate (85) followed by piston (90) followed by the piston ring (95) and a plurality of shims (90S1, 90S2, 90S3) are mounted in a given sequential order on the distal portion (45P3) of the piston rod (45) and locked there with the help of the piston nut (PN) to form the piston assembly (P). During working of the shock absorber, when it is subjected to the compression stroke, the piston rod (45) travels in downward direction and the piston assembly (P) mounted on the distal portion (45P3) of the piston rod (45) divides inner working chamber (IC) of the inner tube (110) into two working chambers namely compression chamber (CC) and the rebound chamber (RC). The chamber formed above the piston assembly (P) is the rebound chamber (RC) and the chamber formed in between the piston assembly (P) and the base valve assembly (70) is the compression chamber.

[0027] The rebound lock washer (400), the rubber cushion (300) and the tube ring (550) are sleeved over the proximal portion (45P1) of the piston rod (45) and locked there with the help of the hex nut (500). The dust cover (200) followed by the bump stopper (35) are mounted on the upper end of the central portion (45P2) of the piston rod (45). The dust cover (200) is the cylindrical body made preferably of plastic that covers the sealing are of the shock absorber from the dust and environmental contaminations. The proximal portion (45P1) of the piston rod (45) is configured to get connected with the vehicle body and the eye portion (600) gets connected with the axle of the wheel of the vehicles.

[0028] The hydraulic lock load assembly (60) comprises a uniquely profiled rod guide (75), a rod guide bush (47), a washer (150) and an elastomeric cap (250). The rod guide (75) is made from a metal preferably selected from aluminum and configured to have a stepped cylindrical body having a first cylindrical body portion (75S1), a second cylindrical body portion (75S2) and a third cylindrical body portion (75S3) and these body portions (75S1, 75S2, 75S3) are configured to seamlessly merged with each other in a given order to form the rod guide (75) in such a way that a three stepped cavity (75C) is formed inside the rod guide (75) (refer Figs. 5A and 5B). The first cylindrical body portion (75S1) has a through oil passage (75H) formed in the downward inclined direction so as to hydraulically communicate between the inner working chamber (IC), more particularly the rebound chamber (RC) of the inner working chamber (IC) and the outer working chamber (OC) of the shock absorber during its operation.

[0029] The stepped cavity (75C) of the rod guide (75) is divided into three steps (75C1, 75C2, 75C3) on its inner peripheral surface. The inner diameter of the first stepped cavity (75C1) is equal to the outer diameter of the piston rod (45) thereby allowing axial guidance of the said piston rod (45) with minimal radial clearance and said stepped cavity (75C1) is housed in the first cylindrical body portion (75S1) of the rod guide (75). The second stepped cavity (75C2) is formed with a greater inner diameter relative to the first stepped cavity (75C1) and said cavity (75C2) is partially housed in the first cylindrical body portion (75S1) and partially in the second cylindrical body portion (75S2). The delta annular space (δ) being created in the second stepped cavity (75C2) due the difference between the inner diameter of the first stepped cavity (75C1) and the inner diameter of the second stepped cavity (75C2) is configured to house the rod guide bush (47) while mounting the said rod guide (75) on the piston rod (45). The third stepped cavity (75C3) is formed in the third cylindrical body portion (75S3) and it do have inner diameter greater than the inner diameter of the second stepped cavity (75C2). Thus, the inner diameters of the stepped cavities (75C1, 75C2, 75C3) are in the order of Ø 75C1 < Ø 75C2 < Ø 75C3. The annular space (75CV) between the inner diameter of the third stepped cavity (75C3) and the outer diameter of the piston rod (45) is operatively configured to act as a hydraulic lock chamber during the rebound stroke of the shock absorber, wherein damping fluid becomes momentarily trapped to generate increased hydraulic resistance.

[0030] Referring to Figs. 5A and 5B, the base portion (B) of the third cylindrical body portion (75S3) of the rod guide (75) is configured to have a plurality of oil passages (75P) cut in semi-circular profile and said oil passages runs over the outer peripheral surface of the third cylindrical body portion (75S3) in axial direction upto the height (h’) and said height (h’) of the oil passage (75P) is 0.8 times the height (H) of the third cylindrical body portion (75S3) of the rod guide. The said oil passages (75P) are at equal angular distance from each other and the sectional profile of said oil passages is not limited to semi-circular but varies from square, rectangular, triangular, and like. However, the preferred sectional profile of these oil passages (75P) is semi-circular so as to avoid drag to the fluid flow during the rebound stroke of the shock absorber and the most optimized number of said oil passages (75P) is four each positioned at 90 degree angular distance from its subsequent oil passage (75P) so as to have desired resistance to the oil flow to create an effective and efficient hydraulic lock.

[0031] Referring to Figs. 6A to 6C, the washer (150) is configured to have a cylindrical body (150B) with a thorough opening (150C) at its center. The body portion (150B) of the washer (150) is divided into two halves viz. upper half (H1) and the lower half (H2). The outer diameter of the lower half (H2) is uniform throughout its length whereas the outer diameter of the upper half (H1) decreases gradually throughout its length thereby forming an inward tapered profile (150T) with the lower half (H2) making a taper angle (α) with the vertical and/or the lower half (H2) of the washer (150). The said taper angle (α) varies in the range of 5 to 10 degrees depending on the hydraulic lock requirement of said washer (150) with the rod guide (75). The said washer (150) is made from any metal but preferably selected from aluminum. However, it can be made from plastic or plastic plus metal with the metal reinforcement overmoulded with plastic. Thus, the washer (150) is made from the material selected from metal, plastic, metal inserted with overmoulded plastic and like.

[0032] Referring to the Figs. 7A and 7B, elastomeric cap (250) is configured to have a cylindrical body (251) with a thorough opening at the center (250C). The wall portion (251w) of the cylindrical body extend axially in the downward direction and gets radially inward forming the flange portion (252). Thus, cross section of the wall portion (251w) and the flange portion (252) of the cylindrical body (251) of the elastomeric cap (250) forms L-shaped sectional profile. Said elastomeric cap (250) is intelligently press fitted over the third cylindrical body portion (75S3) in such a way that it defines seamless oil passage (75P) that opens through its mouth (75P’) so as to hydraulically communicate in between the third stepped cavity (75C3) of the rod guide (75) and the rebound chamber (RC) inside the inner tube (110) (refer Figs. 8A and 8B).

[0033] The rod guide (75) is sleeved over the central portion (45P2) of the piston rod (45) and positioned over the lower end of the portion (45P4). The annular space (δ) houses the rod guide bush (47) through interference fitting so that the piston rod (45) is easily slideable through the rod guide (75). The elastomeric cap (250) is press fitted over the third cylindrical body portion (75S3) to define seamless oil passage (75P). The washer (150) is fitted over the portion (45P5) of the piston rod (45) in such a way that the top portion of the washer (150) is locked with the step (S) and the bottom portion of said washer (150) is locked there with the locking ring (R). This novel arrangement of the uniquely profiled rod guide (75), rod guide bush (47), elastomeric cap (250) over the portion (45P4) of the piston rod (45) in conjunction with the washer (150) mounted over the portion (45P5) forms an inventive hydraulic lock load assembly (60) of the present invention.

[0034] The piston rod assembly (50) is inserted into the inner tube (110) for its mounting in such a way that the outer peripheral surface of the first cylindrical body portion (75S1) of the rod guide (75) is fitted in the outer tube (100) and the base portion of said first cylindrical body portion (75S1) abuts against the mouth of the inner tube (110) in such a way that the outer peripheral surface of the second body portion (75S2) of the rod guide (75) completely closes the mouth of the inner tube (110). In this arrangement, the thorough oil passage (75H) in the first cylindrical body portion (75S1) is in hydraulic communication with the outer working chamber (OC) and the seamless oil passage (75P), formed in the third body portion (75S3) with the help elastomeric cap (250), is in hydraulic communication with the rebound chamber (RC) through its mouth (75P’) third stepped cavity (75C3) of the rod guide (75).

[0035] As far as the working of the present invention is concerned, when the shock absorber (10) is subjected to compression stroke (refer Fig. 2C), the piston rod (45) along with the washer (150) and the piston assembly (P) travels in downward direction towards the base valve assembly (70) thereby compressing the oil in compression chamber (CC). In this case, some oil in the compression chamber (CC) passes through the base valve assembly (70) into the outer working chamber (OC) and some oil passes through the orifices of the piston (90) into the rebound chamber (RC). When the shock absorber undergoes rebound stroke (refer Figs. 2B and 2A), the piston rod (45) along with the washer (150) and the piston assembly (P) travels in upward direction towards the rod guide (75) thereby compressing the oil in the rebound chamber (RC). In this case, some oil in the rebound chamber (RC) passes through the oil passage (75H) into the outer working chamber (OC) and some oil passes through the orifices of the piston (90) into the compression chamber (CC). When the shock absorber (10) approaches to the extreme of the rebound stroke, the uniquely profiled washer (150) mounted over the portion (45P5) of the piston rod (45) through its tapered profile of upper portion (H1) gets accommodated within the third stepped cavity (75C3) of the rod guide (75). This tapered profile of the washer (150) and the seamless oil passage (75P) mandatorily maintains the oil in the third stepped cavity (75C3) creating a significant increase in hydraulic resistance and provides hydraulic lock thereby preventing metal-to-metal contact between the rod guide (75) and the washer (150). Further, the uniquely profiled elastomeric cap (250) and its intelligent positioning over the third cylindrical body portion (75S3) of the rod guide (75) completely avoids metal-to-metal contact between the base portion (B) of the third cylindrical body portion (75S3) and the piston support plate (85) of the piston assembly (P). Thus, the invention completely eliminates the topping effect in the shock absorber during rebound stroke by intelligently avoiding metal to metal contact wherever possible.

[0036] The shock absorber of the present invention having improved piston rod assembly configured to create an efficient hydraulic retention / lock in accordance with the present invention provides the following technical advantages that contributes to the advancement of technology leading to establish the inventive step:
- The hydraulic lock load assembly eliminates the topping effect during the rebound stroke in the shock absorber.
- It completely eliminates the metal to metal connect during the rebound stroke that help to reduce the noise in the in shock absorber.
- It enhances the durability and longer operational life of the shock absorber.
- It precisely controls the topping behavior without mechanical stops and any hindrance in its working leading to enhanced ride comfort and vehicle stability.
- It provides increased reliability and reduced failure rate, especially in harsh or high-load environments while navigating with the irregularity of the different road surfaces.

The foregoing description of the specific embodiment of the invention will so fully reveal 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 embodiment. 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 embodiment herein has been described in terms of preferred embodiment, those skilled in the art will recognize that the embodiment herein can be practiced with modification within the spirit and scope of the embodiment as described herein.
, Claims:We Claim:

1. A shock absorber (10) for three wheeled and light commercial vehicles comprising of a piston rod assembly (50), outer tube (100), inner tube (110), eyelet (600), dust cover (200), rubber cushion (300), rebound lock washer (400), hex nut (500), and tube ring (550),
wherein
- the piston rod assembly (50) is configured to comprise of a piston rod (45), a shell cap (46), an oil seal (70), an oil seal support plate (71), a hydraulic lock load assembly (60), a piston assembly (P), and a bump stopper (35);
- the piston rod (45) of said piston rod assembly (50) has a cylindrical stepped profile throughout its length forming a proximal portion (45P1), a central portion (45P2) and a distal portion (45P3); and said central portion (45P2) is divided into first portion (45P4) and second portion (45P5) through a step (S);
- the hydraulic lock load assembly (60) is configured to comprise of a uniquely profiled rod guide (75), a rod guide bush (47), a washer (150) and an elastomeric cap (250) wherein said rod guide (75) has a stepped cylindrical body having a first cylindrical body portion (75S1), a second cylindrical body portion (75S2) and a third cylindrical body portion (75S3) and these body portions (75S1, 75S2, 75S3) are configured to seamlessly merged with each other in a given order thereby forming a three stepped cavity (75C) inside the rod guide (75);
- the washer (150) is configured to have a cylindrical body (150B) with a thorough opening (150C) at its center and said body portion (150B) of the washer (150) is divided into upper half (H1) and the lower half (H2);
- said rod guide (75) is sleeved over the central portion (45P2) of the piston rod (45) and positioned over the lower end of the portion (45P4); and the elastomeric cap (250) is press fitted over the third cylindrical body portion (75S3); and
- said washer (150) is fitted over the portion (45P5) of the piston rod (45) in such a way that the top portion of the washer (150) is locked with the step (S) and the bottom portion of said washer (150) is locked there with the locking ring (R).

2. The shock absorber (10) as claimed in claim 1, wherein
- the first cylindrical body portion (75S1) of the rod guide (75) has a through oil passage (75H) formed in the downward inclined direction so as to hydraulically communicate between the inner working chamber (IC) and the outer working chamber (OC) of the shock absorber during its operation;
- the stepped cavity (75C) of the rod guide (75) is configured to have three stepped portions namely the first stepped cavity (75C1), the second stepped cavity (75C2) and the third stepped cavity (75C3) on its inner peripheral surface;
- said stepped cavity (75C1) is housed in the first cylindrical body portion (75S1) of the rod guide (75), the second stepped cavity (75C2) is partially housed in the first cylindrical body portion (75S1) and partially in the second cylindrical body portion (75S2);
- the third stepped cavity (75C3) is formed in the third cylindrical body portion (75S3); and
- the inner diameters of the stepped cavities (75C1, 75C2, 75C3) are in the order of Ø 75C1 < Ø 75C2 < Ø 75C3.
3. The shock absorber (10) as claimed in claim 2, wherein
- the difference between the inner diameter of the first stepped cavity (75C1) and the inner diameter of the second stepped cavity (75C2) is configured to form an annular space (δ) in the second stepped cavity (75C2); and said annular space (δ) is configured to house the rod guide bush (47) while mounting the said rod guide (75) on the piston rod (45); and
- the annular space (75CV) between the inner diameter of the third stepped cavity (75C3) and the outer diameter of the piston rod (45) is operatively configured to act as a hydraulic lock chamber during the rebound stroke of the shock absorber.

4. The shock absorber (10) as claimed in claim 2, wherein
- the third cylindrical body portion (75S3) of the rod guide (75) has a base portion (B) and said base portion (B) is configured to have a plurality of oil passages (75P);
- said oil passages (75P) runs over the outer peripheral surface of the third cylindrical body portion (75S3) in axial direction upto the height (h’);
- said height (h’) of the oil passage (75P) is 0.8 times the height (H) of the third cylindrical body portion (75S3) of the rod guide; and
- said oil passages (75P) are at equal angular distance from each other.

5. The shock absorber (10) as claimed in claim 4, wherein
- the cross sectional profile of the oil passages (75P) is selected from the profiles of semi-circular, square, rectangular, triangular, and combination thereof; and
- and the optimized number of said oil passages (75P) is four each positioned at 90 degree angular distance from its subsequent oil passage (75P) so as to have desired resistance to the oil flow to create an effective and efficient hydraulic lock.

6. The shock absorber (10) as claimed in claim 1, wherein
- the lower half (H2) of the washer (150) has uniform outer diameter throughout its length whereas the outer diameter of the upper half (H1) decreases gradually throughout its length thereby forming an inward tapered profile (150T) with the lower half (H2) making a taper angle (α) with the vertical and/or the lower half (H2) of the washer (150);
- said taper angle (α) varies in the range of 5 to 10 degrees; and
- said washer (150) is made from the material selected from metal, plastic, metal insert with overmoulded plastic and combination thereof.

7. The shock absorber (10) as claimed in claim 1, wherein
- the elastomeric cap (250) is configured to have a cylindrical body (251) with a thorough opening at the center (250C), and the wall portion (251w) of said cylindrical body (251) extend axially in the downward direction and gets radially inward forming the flange portion (252);
- the cross section of the wall portion (251w) and the flange portion (252) of the cylindrical body (251) of the elastomeric cap (250) forms L-shaped sectional profile; and
- said elastomeric cap (250) is press fitted over the third cylindrical body portion (75S3) of the rod guide so as to define seamless oil passage (75P) that opens through its mouth (75P’) which hydraulically communicates in between the third stepped cavity (75C3) of the rod guide (75) and the rebound chamber (RC) inside the inner tube (110).

8. The shock absorber (10) as claimed in claim 7, wherein
- the inner tube (110) is configured to have a cylindrical profile with an upper end (111) and a bottom end (112), and said bottom end (112) of the inner tube is closed by press fitting a base valve assembly (70) therein;
- the inner peripheral surface of the inner tube (110) is configured to form an inner working chamber (IC);
- the base valve assembly (70) is configured to restrict the oil from escaping when the piston and valve assembly is moves in downward direction during the compression stroke;
- said inner tube (110) having base valve assembly (70) in the bottom end (112) is concentrically sleeved inside the outer tube (100) from the upper end (102) and abuts over the bowl-shape bottom cap (15) in such a way that the annular space between the inner peripheral surface of the outer tube (100) and the outer peripheral surface of the inner tube (110) is configured to form an outer working chamber (OC).

9. The shock absorber (10) as claimed in claim 8, wherein
- the outer tube (100) is configured to have a cylindrical profile with an upper end (102) and a lower end (104), and said lower end (104) of the outer tube (100) is closed with the help of the bottom cap (15) in such a way the bottom cap (15) is sleeved inside the lower end (104) of the outer tube (100) followed by welding; and
- the said bottom cap (15) is configured to have a bowl-shape and the base (301) of the bowl-shape bottom cap (15) is fitted with an eyelet (600) by the fixing means selected from welding and threading.

10. The shock absorber (10) as claimed in claim 9, wherein
- the inner tube (110) houses the piston rod assembly (50) along with the piston assembly (P) for its mounting in such a way that the outer peripheral surface of the first cylindrical body portion (75S1) of the rod guide (75) is fitted in the outer tube (100) and the base portion of said first cylindrical body portion (75S1) abuts against the mouth of the inner tube (110) in such a way that the outer peripheral surface of the second body portion (75S2) of the rod guide (75) completely closes the mouth of the inner tube (110); and
- the thorough oil passage (75H) in the first cylindrical body portion (75S1) is in hydraulic communication with the outer working chamber (OC) and the seamless oil passage (75P), formed in the third body portion (75S3) with the help elastomeric cap (250), is in hydraulic communication with the rebound chamber (RC) through its mouth (75P’) third stepped cavity (75C3) of the rod guide (75).

11. The shock absorber (10) as claimed in claim 10, wherein
- the piston assembly (P) is configured to comprise of a piston support plate (85), a piston (90), a piston ring (95), a plurality of shims (90S1, 90S2, 90S3), a piston nut (PN);
- the piston support plate (85) followed by piston (90) followed by the piston ring (95) and a plurality of shims (90S1, 90S2, 90S3) are mounted in a given sequential order on the distal portion (45P3) of the piston rod (45) and locked there with the help of the piston nut (PN) to form the piston assembly (P);
- when the shock absorber (10) is subjected to the compression stroke, the piston rod (45) travels in downward direction and the piston assembly (P) mounted on the distal portion (45P3) of the piston rod (45) divides inner working chamber (IC) of the inner tube (110) into two working chambers namely compression chamber (CC) and the rebound chamber (RC); and
- the chamber formed above the piston assembly (P) is the rebound chamber (RC) and the chamber formed in between the piston assembly (P) and the base valve assembly (70) is the compression chamber.

12. The shock absorber (10) as claimed in claim 11, wherein
- the shock absorber (10) when it approaches to the extreme of the rebound stroke, the uniquely profiled washer (150) mounted over the portion (45P5) of the piston rod (45) through its tapered profile of upper portion (H1) gets accommodated within the third stepped cavity (75C3) of the rod guide (75);
- the tapered profile of the washer (150) and the seamless oil passage (75P) are configured to maintain the oil in the third stepped cavity (75C3) creating a significant increase in hydraulic resistance and provides hydraulic lock thereby preventing metal-to-metal contact between the rod guide (75) and the washer (150); and
- the uniquely profiled elastomeric cap (250) and its intelligent positioning over the third cylindrical body portion (75S3) of the rod guide (75) is configured to completely avoid metal-to-metal contact between the base portion (B) of the third cylindrical body portion (75S3) and the piston support plate (85) of the piston assembly (P).

Dated this 14th day of Oct. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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