DESC: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
“TUNABLE SHOCK ABSORBER FOR A TWO-WHEELER”

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

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

Field of Invention

The present invention relates to a shock absorber for a two wheeler. More particularly, the present invention relates to a tunable shock absorber having a top cap capable to accommodate internal parts with varying damping characteristics and configured to vary the damping characteristics by dismantling and reassembling the internal parts in the said top cap as required to achieve a set of damping performance thus covering the wide range damping performance thereby.

Background of the Invention

The shock absorber is an essential component of a two wheeled vehicle. It provides a smooth ride and comfort to the user. The conventional shock absorbers has at least one main spring to absorb the energy transferred from the motor vehicle’s wheel when it encounters a road surface irregularity. It also has at least a damping assembly that dissipates the energy absorbed by the main spring during its compression and expansion. This damping assembly prevents excessive oscillations that would result from un-damped compression and expansion of the main spring. Given the difficulty in altering the characteristics of the main spring and the damping assembly after the inverted front fork is assembled, engineers and/or persons skilled in the art ordinarily have to decide and fix one general purpose setting for both the main spring’s preload and the damping assembly’s compression and rebound damping. The predefined general purpose setting decides the suitability of driving a vehicle in a given loading and driving surface condition.

During development of such conventional shock absorbers, multiple prototypes have to be built and tested in order to arrive at the ideal damping force settings. This need for building and testing multiple prototypes arises primarily because it is not possible to arrive at an accurate figure for damping force generated by an inverted front fork by using only theoretical methods. Ordinarily, a single set of shock absorber is therefore repeatedly disassembled and reassembled with new sub-components and tested again and again until the ideal value of pre-compression of the main spring and damping force is achieved.

The prototype shock absorber needs to be discarded if it does not meet the required damping criteria for a set of designed parameters since the shock absorbers are generally crimped at their top end and a washer / cap closes the said top end. Thus it is not possible to open the shock absorber due to the non-serviceable constructional characteristic of the shock absorbers and further a new prototype of the shock absorber with altered design needs to be generated from the scratch. Thus, the whole process accounts for a huge time elapse and cost incurred therein.

Hence, there exists is a need to develop a shock absorber which can be dismantled and reassembled easily in order to change the internal parts responsible for setting up the damping characteristic of the shock absorber with ease of operation and using the same shock absorber with changed set of damping characteristics for the subsequent trials with the cost effective solution.

Objectives of the Present Invention

The main objective of the present invention is to provide a tunable shock absorber for a two wheeler.

Another objective of the present invention is to provide a tunable shock absorber capable of being dismantled and reassembled to change the piston and damping valves as per the requirement of desired damping characteristics.

Another objective of the present invention is to provide a shock absorber configured to have the ease of reassembling so as to accommodate the main springs of different stiffness.

Still another objective of the present invention is to provide a shock absorber having the means to adjust the compression load of the spring.

Yet another objective of the present invention is to provide a shock absorber which is reusable, provides an ease of assembly and reassembly for different sets damping characteristics and is cost effective.

Brief Description of Drawings

This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein and advantages thereof will be better understood from the following description when read with reference to the following drawings, wherein
Figure 1 discloses an assembled perspective view of the tunable shock absorber of a two wheeler of the present invention.

Figure 2 describes an exploded perspective view of the tunable shock absorber of a two wheeler of the present invention.

Figure 3 discloses an assembled cut-sectional view of the tunable shock absorber in accordance with the present invention.

Figure 4 discloses a cut-sectional view of the outer tube assembly as per the present invention.

Figure 5 discloses the cut-sectional view of the piston rod assembly in accordance with the present invention.

Figures 6a and 6b disclose isometric and cut-sectional views, respectively of the top cap in accordance with the present invention.

Figures 7a, 7b and 7c show the cut-sectional views of the sleeve, rod guide and oil seal, respectively as per the present invention.

Detailed Description of the Present Invention

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 and 2, the tunable shock absorber (500) of the present invention comprises of a bracket (10), bushing (10B), a spring guide (20), a top cap (50), a rod guide (60), an oil seal (70), an outer tube assembly (100), a piston rod assembly (150), an outer spring (80), a threaded tube (160), a pair of adjusters (170A and 170B), a bump stop (180) an extension bracket (190) and an extension bushing (190B).

Referring to Fig. 4, the outer tube assembly (100) includes an outer tube (30) and a sleeve (40). The outer tube (30) is a hollow cylindrical tube having a proximal end (30E1) and a distal end (30E2). The sleeve (40) is joined with the outer tube (30) at its distal end (30E2) with the help of brazing wherein the sleeve (40) is a hollow cylindrical body having male threads (T) on its outer peripheral surface. The sleeve (40) is configured to have an annular thickness (t) so as to ease the manufacturing of the threads over the outer peripheral surface of the sleeve (40). Further, the sleeve (40) and the outer tube (30) are made of ferrous / aluminum alloys with suitable content of metal/non-metal alloying components and the joining process could be selected from well-known joining methods. The outer diameter (Ds) of the sleeve is calculated from the below mention well-known correlation:
s= ?(4F/(p?(Ds?^2- ?Dt?^2)))
Where,
s is the ultimate tensile stress (MPa)
F is the force acting on the sleeve
Ds is the outer diameter of the sleeve
Dt is the outer diameter of the outer tube

Referring to Fig. 5, the piston rod assembly (150) includes a piston rod (110), a rebound spring (120), a rod bush (130), a piston (140), a valve stack (140V) and a piston nut (145). The piston rod (110) is a cylindrical rod having a tube fixing portion (110T) and a piston seating portion (110P) wherein the diameter of the piston seating portion (110P) is less than the diameter of the piston rod (110) thus forming a step (140S) there. The rod bush (130) rests over the step (140S) of the piston seating portion (110P) and the valve stack (140V) is positioned over the said rod bush (130). The piston (140) is sleeved to the piston rod (110) at the piston seating portion (110P) and locked there with the help of the nut (145). The piston (140) is positioned over the valve stack (140V) in a manner such that the said valve stack (140V) is sandwiched in between the piston (140) and the rod bush (130). The said piston (140) of the piston rod assembly (150) is telescopically disposed with the outer tube (30) of the outer tube assembly (100) from the distal end (30E2) of the outer tube (30), thus forming a plurality of fluid chambers viz. (C1 and C2). The piston (140) has a piston ring (140R) positioned in an annular groove formed over the outer periphery of the said piston (140) wherein the said piston ring (140R) facilitates the separation of the chambers (C1) and (C2) formed above and below the piston (140) respectively.

Referring to Fig. 6a, the top cap (50) is configured to have an annular L-shaped lower portion (50L), a cylindrical upper portion (50U) and a cavity (50CV) forming a cup shaped stepped cylindrical body in conjunction with each other. The lower portion (50L) of the top cap (50) has an outer diameter lesser than the outer diameter of the upper portion (50U) thus forming a step (50S1) at the outer peripheral surface of the top cap (50) thereby. The said lower portion (50L) has a flat circular base (50B) configured to have an opening (50BH) formed there to allow the passage of the piston rod (110) of the piston rod assembly (150). Further, the lower portion (50L) has two across flat surfaces (50AF) formed over its outer peripheral surface in a diametrically opposite manner to each other. The said across flat surfaces (50AF) are formed by removing the material from its outer peripheral surface and facilitates the torqueing and de-torqueing of the top cap (50) during the assembly and dismantling of the shock absorber (500). The cavity (50CV) includes a first portion (50A), a second portion (50B) and a third portion (50C) wherein the first portion (50A) and the second portion (50B) are separated by an undercut (50UC). The said first portion (50A) is configured to have female threads (Th) formed over its inner peripheral surface and the undercut (50UC) facilitates the formation of the starting point for the first thread. Further, the undercut (50UC) is configured to house an O-Ring (50R) to avoid the leakage of oil from the suspension unit.

The third portion (50C) of the cavity (50CV) is configured to have a smaller inner diameter than the inner diameter of the second portion (50B) thus forming a step (50BS) thereby. The first portion (50A), second portion (50B) and the third portion (50C) of the top cap (50) jointly houses the rod guide (60) in such a manner that a seal portion (60OS) of the rod guide (60) is housed in the third portion (50C) and a sleeve portion (60SS) of the rod guide (60) is housed in the first portion (50A) of the top cap (50). The third portion (50C) of the cavity (50CV) is configured to house the oil seal (70. Further, the first portion (50A), second portion (50B) and the third portion (50C) of the top cap (50) are formed so as to maintain the below mentioned empirical relations:
?(l/((2Dco - Dci) ))= C1 …..1
y=b-a1-a2 …..2
?(x/((y + z) ))= (h - s)/((b + c) ) …..3
dc/dos =C2 …..4
Where,
l is the total length of the top cap;
Dco is the outer diameter of the outer body B1 of the top cap;
Dci is the inner diameter of the outer body B1 of the top cap;
C1 is shape factor ratio ranging from 0.75 to 1.50;
dc is the diameter of the outer body B2 of the top cap;
dos is the diameter of oil seal;
C2 is the diameter ratio ranging from 0.8 to1.5;
x is the length of the first portion of the top cap;
y is the length of the second portion of the top cap;
z is length of the third portion of the top cap;
h is the length of the sleeve;
s is the free length of the sleeve;
b is the total height of the rod guide;
a1 is the height of the sleeve portion 60SS of the rod guide;
a2 is the height of the seal portion 60OS of the rod guide;
c is the total height of the oil seal.

The threaded tube (160) is a hollow cylindrical tube having a proximal end (160P) and a distal end (160D). The said tube (160) is configured to have male threads (T”) formed over its outer peripheral surface wherein the said threads starts from a vertical distance td from the bottom edge of the proximal end (160P) of the threaded tube (160). The td is 0.1 to 0.5 times the outer diameter of the threaded tube. The proximal end (160P) of the threaded tube (160) has two across flat surfaces (160AF) formed diametrically opposite to each other. The said across flat surfaces (160AF) are formed by removing the material from its outer peripheral surface. The across flat surfaces (160AF) facilitates the torqueing and de-torqueing of the threaded tube (160) during the assembly and dis-assembly of the shock absorber (500).

During the assembly of the shock absorber (500), the outer tube (30) of the outer tube assembly (100) is fixed with the spring guide (20) with the help of interference fitting and is joined with the bracket (10) with the help of the joining methods selected from interference fitting, threaded joinery, welding or a combination thereof. The piston rod assembly (150) is then positioned within the outer tube assembly (100) wherein the damping oil is filled in the outer tube assembly (100) prior to fitment of the piston rod assembly (150) in the outer tube assembly (100). The rod guide (60) is positioned within the outer tube (30) and is sleeved over the piston rod (110) of the piston rod assembly (150) in a manner such that the guide bush (60B) is positioned in between the outer peripheral surface of the piston rod (110) and the inner peripheral surface of a central opening (60H) of the rod guide (60). The guide bush (60B) facilitates to reduce the sliding friction between the said the piston rod (110) and the rod guide (60). The rod guide (60) is positioned within the outer tube (30) in a manner such that the lower face of the sleeve portion (60SS) of the rod guide (60) abuts with the top end of the rebound spring (120) of the piston of assembly (150) and the upper face (60U) of the sleeve portion (60SS) of the rod guide (60) rests over the top edge of the distal end (30E2) of the outer tube (30), thus closing the open of the outer assembly (100) thereby. Post fixing of the rod guide (60), the oil seal (70) is snuggly fitted over the outer peripheral surface of the piston rod (110) in a manner such that the said oil seal (70) abuts with the seal portion (60OS) of the rod guide (60). The top cap (50) is screwed over the sleeve (40) of the outer tube assembly (100) by sliding the top cap (50) over the piston rod (110) from the opening (50BH) of the said top cap (50) to close the outer tube assembly (100). The top cap (50) is fixed with the outer tube assembly (100) in a manner such that the seal portion (60OS) of the rod guide (60) is housed in the third portion (50C) of the cavity (50CV) of the top cap (50), the sleeve portion (60SS) of the rod guide (60) is housed in the first portion (50A) of the cavity (50CV) of top cap (50) and the oil seal (70) is housed in the third portion (50C) of the cavity (50CV) of the top cap (50). This configuration of the joining of the top cap (50) with the outer tube assembly (100) facilitates the easy assembly and dis-assembly of the shock absorber since the oil seal (70) is positioned completely outside of the outer tube (30) of the outer tube assembly (100).

Further, the threaded tube (160) at its proximal end (160P) is fitted with the extension bracket (190) wherein the fitting method can be selected from interference fitting, threaded fitting, welding or other known convention fitting methods. The said extension bracket (190) includes an extension bushing (190B) press fitted within an opening formed in the extension bracket (190). The bump stop (180) is positioned over the inside bottom surface of the threaded tube (160) and the piston rod (110) of the piston rod assembly (150) at its tube fixing portion (140T) is fixed to the extension bracket (190). The piston rod (110) of the piston rod assembly (150) passes from an opening provided in the bump stop (180) thus locking the bump stop in its place. In this condition, the distal end (160D) of the threaded tube (160) covers the entire periphery of the top cap (50) while the proximal end (160P) of the threaded tube (160) is fixed to the extension bracket (190). The adjusters (170A and 170B) are sleeved over the threaded tube (160) and the spring (80) is positioned in between the spring guide (20) and the adjuster (170B) in a manner such that the end (E1) of the spring (80) abuts with the spring guide (20) and the end (E2) of the outer spring (80) rests over the top surface of the adjuster (170B) to form the shock absorber (500). The adjuster (170A) acts as a lock nut to prevent the loosening of the adjuster (170B) from the vibrations imparted to the adjuster (170B) during the working condition of the shock absorber (500). Further, the adjusters (170A and 170B) can be rotated in clockwise / anti-clockwise direction with the help of tool in order to adjust the pre-compression load of the outer spring (80). The threaded tube (160) thus telescopically houses the outer tube assembly (100) along with the top cap (50) and acts as a dust cover for the shock absorber (500).

Similarly, the shock absorber (500) can be dismantled in order to change the outer spring (80), piston (140) and the valve stack (140V) during the requirement of altered damping characteristics of the shock absorber (500). During the dismantling, the adjusters (170A and 170B) can be removed by rotating the adjusters (170A and 170B) over the threaded tube in anti-clockwise direction. The removal of the adjusters (170A and 170B) can be followed by removing the outer spring (80) and changing the same with other spring of different stiffness. The threaded tube (160) can be opened with the help of a tool by de-torqueing it along the across flat surfaces (160AF) with respect to the extension assembly (190). At this, stage the top cap (50) can be de-screwed with the sleeve (40) of the outer tube assembly (100) followed by the removal of oil seal (70) and the rod guide (60) from the piston rod (110) of the piston rod assembly (150). The piston (140) and the valve stack (140V) thus now can be accessed by pulling out the rebound spring (120) and the rod bush (130). Further, the said piston (140) and the valve stack (140V) can be replaced with the modified pistons and valve stacks and the shock absorber (500) can be assembled to have the modified damping characteristics.

The shock absorber (500) of the present invention eliminates the challenge of tuning the damping characteristics of the shocker without scrapping the said shock absorber. Thus, the shock absorber can be tested for a number of iterations in order to fine tune the required damping characteristics. Also the shock absorber can be serviced at the end of the user in case of failure of any component viz. outer spring, piston ring, valve stack, rebound spring, rod guide and oil seal.

The shock absorber (500) of the present invention provides the following technical advantages that contributes to the technical advancement of shock absorbers technology:
It provides freedom to mount the shock absorber at any mounting condition and dismantle and assemble shock absorber at multiple times to get desired suspension configuration.
It provides a compact shock absorber adapted to be used with two wheelers having seat height limitations.
It provides means for adjusting the spring pre-load.
It reduces the assembly cycle time thus reducing the overall effective cost of the system.
It provides freedom to exchange / replace diffident shim/ valve stacks to get desired damping result according to the ride and handling requirement.
It ensures the consistent relative engagement of an oil seal with piston rod as an oil seal has been kept out of damper tube as a part of extraordinary design approach.
This is because oil seal is significantly critical when it comes to suspension performance as the oil seal lips are significant and delegate in nature.
As well as, the rod guide kept out of the damper to arrest its movement to ensure relative engagement with respect to the suspension configuration.
Further, it imparts freedom to exchange different bump stops to address the vehicle sag height and rider comfort in order to enhance ride and handling.
It allows to exchange or change rebound springs to vary the Sprung and un-sprung mass of the vehicle with the scope for the appropriate design of rebound spring to enhance ride control and ride handling.
In totality, it allows to form different combination to make the suspension suitable with respect to vehicle configuration and requirement.

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:

A tunable shock absorber (500) for a two wheeler comprising of a bracket (10), bushing (10B), a spring guide (20), a top cap (50), a rod guide (60), an oil seal (70), an outer tube assembly (100), a piston rod assembly (150), an outer spring (80), a threaded tube (160), a pair of adjusters (170A and 170B), a bump stop (180) an extension bracket (190) and an extension bushing (190B)
wherein,
the top cap (50) is configured to have an annular L-shaped lower portion (50L), a cylindrical upper portion (50U) and a cavity (50CV) forming a cup shaped stepped cylindrical body; and said cavity (50CV) is formed by a first portion (50A), a second portion (50B) and a third portion (50C) wherein said first portion (50A) and the second portion (50B) are separated by an undercut (50UC);
the outer tube assembly (100) comprises of an outer tube (30) and a sleeve (40) wherein said sleeve (40) is joined with the outer tube (30) at its distal end (30E2) with the help of brazing;
the piston rod assembly (150) is telescopically disposed within the outer tube (30) of the outer tube assembly (100) to form a plurality of fluid chambers (C1 and C2);
the said top cap (50) is screwed over the sleeve (40) of the outer tube assembly (100) and is configured to house seal portion (60OS) and sleeve portion (60SS) of the rod guide (60) and the oil seal (70);
the said outer tube (30) of the outer tube assembly (100) is fixed with the spring guide (20) with the help of interference fitting and is joined with the bracket (10) with the help of the joining means selected from interference fitting, threaded joinery, welding and combination thereof;
the threaded tube (160) is fitted with the extension bracket (190) and the bump stop (180) is positioned over the inside bottom surface of said threaded tube (160); and the piston rod (110) of the piston rod assembly (150) is fixed to the extension bracket (190) at its tube fixing portion (140T); and
the adjusters (170A and 170B) are sleeved over the threaded tube (160) and the spring (80) is positioned in between the spring guide (20) and the adjuster (170B).

The tunable shock absorber (500) for a two wheeler as claimed in claim 1, wherein
the seal portion (60OS) of the rod guide (60) is housed in the third portion (50C) of the cavity (50CV) of the top cap (50), the sleeve portion (60SS) of the rod guide (60) is housed in the first portion (50A) of the cavity (50CV) of top cap (50) and the oil seal (70) is housed in the third portion (50C) of the cavity (50CV) of the top cap (50); and
the end (E1) of the spring (80) is configured to abut with the spring guide (20) and the end (E2) of said spring (80) rests over the top surface of the adjuster (170B) to form the shock absorber (500).

The tunable shock absorber (500) for a two wheeler as claimed in claim 2, wherein,
the first portion (50A) of the top cap (50) is configured to have female threads (Th) formed over its inner peripheral surface and the undercut (50UC) is configured to facilitate the formation of the starting point for the first thread (Th) and house an O-Ring (50R) to avoid the leakage of oil from the shock absorber;
the lower portion (50L) of the top cap (50) has an outer diameter lesser than the outer diameter of the upper portion (50U) thus forming a step (50S1) at the outer peripheral surface of the top cap (50) thereby;
the third portion (50C) of the cavity (50CV) is configured to have a smaller inner diameter than the inner diameter of the second portion (50B) thus forming a step (50BS) thereby;
said lower portion (50L) has a flat circular base (50B) and said base (50B) is configured to have an opening (50BH) formed there to allow the passage of the piston rod (110) of the piston rod assembly (150) and two across flat surfaces (50AF) formed over its outer peripheral surface in a diametrically opposite manner to each other; and
the said across flat surfaces (50AF) are formed by removing the material from its outer peripheral surface and are configured to facilitate the torqueing and de-torqueing of the top cap (50) during the assembly and dismantling of the shock absorber (500).

The tunable shock absorber (500) for a two wheeler as claimed in claim 3, wherein
the piston rod assembly (150) is telescopically disposed within the outer tube (30) of the outer tube assembly (100) from the distal end (30E2) of the outer tube (30); and said piston rod assembly (150) is configured to comprise a piston rod (110), a rebound spring (120), a rod bush (130), a piston (140), a valve stack (140V) and a piston nut (145);
said piston rod (110) is a cylindrical rod having a tube fixing portion (110T) and a piston seating portion (110P) wherein the diameter of the piston seating portion (110P) is less than the diameter of the piston rod (110) thus forming a step (140S) there;
said rod bush (130) is configured to rest over the step (140S) of the piston seating portion (110P) and the valve stack (140V) is positioned over the said rod bush (130); and
the piston (140) is sleeved over the piston rod (110) at the piston seating portion (110P) and is locked there with the help of the nut (145) in a manner such that the said valve stack (140V) is sandwiched in between the piston (140) and the rod bush (130) and a piston ring (140R) is positioned in an annular groove formed over the outer periphery of the said piston (140) which facilitates the separation of the chambers (C1) and (C2) formed above and below the piston (140) respectively.

The tunable shock absorber (500) for a two wheeler as claimed in claim 4, wherein,
the outer tube (30) is a hollow cylindrical tube having a proximal end (30E1) and a distal end (30E2) and the sleeve is a hollow cylindrical body having male threads (T) on its outer peripheral surface;
the sleeve (40) is configured to have an annular thickness (t) so as to ease the manufacturing of the threads over the outer peripheral surface of the sleeve (40); and
the said sleeve (40) and the outer tube (30) of the outer tube assembly (100) are made of metal alloys selected from ferrous and aluminum alloys with necessary content of metal/non-metal alloying components.

The tunable shock absorber (500) for a two wheeler as claimed in claim 5, wherein
the outer tube assembly (100) is configured to house the piston rod assembly (150) and is filled with the damping oil prior to fitment of the piston rod assembly (150) therein;
the rod guide (60) is positioned within the outer tube (30) and is sleeved over the piston rod (110) of the piston rod assembly (150) in a manner such that the guide bush (60B) is positioned in between the outer peripheral surface of the piston rod (110) and the inner peripheral surface of a central opening (60H) of the rod guide (60) and the said guide bush (60B) is configured to reduce the sliding friction between the said the piston rod (110) and the rod guide (60);
the lower face of the sleeve portion (60SS) of the rod guide (60) is configured to abut with the top end of the rebound spring (120) of the piston of assembly (150) and the upper face (60U) of the sleeve portion (60SS) of the rod guide (60) rests over the top edge of the distal end (30E2) of the outer tube (30) ensuring the closure of an open end of the outer tube assembly (100);
the oil seal (70) is snuggly fitted over the outer peripheral surface of the piston rod (110) wherein said oil seal (70) abuts with the seal portion (60OS) of the rod guide (60); and
the top cap (50) is screwed over the sleeve (40) of the outer tube assembly (100) making the oil seal (70) positioned completely outside of the outer tube (30) of the outer tube assembly (100) thereby facilitating the easy assembly and dis-assembly of the shock absorber (500).

The tunable shock absorber (500) for a two wheeler as claimed in claim 3, wherein
the first portion (50A), second portion (50B) and the third portion (50C) of the top cap (50) are configured to maintain empirical relations as:
?(l/((2Dco - Dci) ))= C1; y=b-a1-a2 ; ?(x/((y + z) ))= (h - s)/((b + c) ) ; and dc/dos =C2
where, l is the total length of the top cap, Dco is the outer diameter of the outer body B1 of the top cap, Dci is the inner diameter of the outer body B1 of the top cap, C1 is shape factor ratio ranging from 0.75~1.5, dc is the diameter of the outer body B2 of the top cap, dos is the diameter of oil seal, C2 is the diameter ratio ranging from 0.8-1.5, x is the length of the first portion of the top cap, y is the length of the second portion of the top cap, z is length of the third portion of the top cap, h is the length of the sleeve, s is the free length of the sleeve, b is the total height of the rod guide, a1 is the height of the sleeve portion 60SS of the rod guide, a2 is the height of the seal portion 60OS of the rod guide, and c is the total height of the oil seal.

The tunable shock absorber (500) for a two wheeler as claimed in claim 1, wherein
the threaded tube (160) is a hollow cylindrical tube having a proximal end (160P) and a distal end (160D) and telescopically houses the outer tube assembly (100) along with the top cap (50) and is configured to act as a dust cover for the shock absorber (500);
the said tube (160) is configured to have male threads (T”) formed over its outer peripheral surface and said threads (T”) starts from a vertical distance td from the bottom edge of the proximal end (160P) of the threaded tube (160);
the said vertical distance td is 0.1-0.5 times the outer diameter of the threaded tube and the proximal end (160P) of the threaded tube (160) has two across flat surfaces (160AF) formed diametrically opposite to each other; and
the said across flat surfaces (160AF) are formed by removing the material from its outer peripheral surface and are configured to facilitate the torqueing and de-torqueing of the threaded tube (160) during the assembly and dis-assembly of the shock absorber (500).

The tunable shock absorber (500) for a two wheeler as claimed in claim 8, wherein
the threaded tube (160) is fitted with the extension bracket (190) at its proximal end (160P) and the fitting method is selected from interference fitting, threaded fitting, and welding;
the said extension bracket (190) has an extension bushing (190B) press fitted within an opening formed in the extension bracket (190); and
the adjusters (170A and 170B) are sleeved over the threaded surface of the threaded tube (160).

The tunable shock absorber (500) for a two wheeler as claimed in claim 9, wherein
the adjuster (170A) is configured to prevent the loosening of the adjuster (170B) due to the vibrations imparted to the adjuster (170B) during the working condition of the shock absorber (500); and
the adjusters (170A and 170B) are configured to adjust the pre-compression load of the outer spring (80) when rotated in clockwise / anti-clockwise direction.

The tunable shock absorber (500) for a two wheeler as claimed in any of the claims 6, 7 and 8, wherein
said shock absorber (500) is configured to be dismantled in order to change the outer spring (80), piston (140) and the valve stack (140V) in response to the altered damping characteristics by removing the adjusters (170A and 170B) rotating over the threaded tube in anti-clockwise direction;
the removal of the adjusters (170A and 170B) is followed by removing the outer spring (80) and changing the same with other spring of different stiffness and the threaded tube (160) is opened with the help of a tool by de-torqueing it along the across flat surfaces (160AF) with respect to the extension assembly (190);
the top cap (50) is configured to be de-screwed from the sleeve (40) of the outer tube assembly (100) followed by the removal of oil seal (70) and the rod guide (60) from the piston rod (110) of the piston rod assembly (150); and
the piston (140) and the valve stack (140V) is configured to be accessed by pulling out the rebound spring (120) and the rod bush (130) so as to replace the piston (140) and the valve stack (140V) with the modified pistons and valve stacks having the modified set of damping characteristics.

Dated this 20th day of Jan. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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