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
“UNITARY FORK BOLT ASSEMBLY FOR FRONT FORK SUSPENSION SYSTEM OF 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 front fork suspension of a vehicle. More particularly, the present invention is related to a unitary fork bolt assembly of front fork suspension system of two and three wheeled vehicles.

Background of the Invention

[002] The front fork suspension system of a two-wheeled vehicle plays a crucial role in absorbing road surface irregularities as well as imparting the better steering maneuverability and braking control. These suspension systems are typically classified into two main types, viz. telescopic front fork suspension and inverted (upside-down) front fork suspension, which differ based on their constructional characteristics.

[003] In telescopic suspension systems, the fork pipe slides within the outer tube. The fork pipe is connected to the handlebar of a vehicle via a triple clamp assembly, while the outer tube is connected to the wheel axle. On the other hand, the inverted front fork suspension features a construction where the outer tube is connected to the handlebar of a vehicle through a triple clamp assembly and the fork pipe is attached to the wheel axle.

[004] In the front fork suspension system, the fork leg assembly is filled with the damping fluid, particularly the oil, and is secured from leakages by sealing assembly and fork bolt. Conventionally, the cylindrical spacer tube, commonly made of steel, is employed and sandwiched between the fork bolt and the main spring which acts as a space filler and helps to reducing the required spring length within the fork leg assembly. But this conventional construction does not make any impact on the oil requirement therein the leg assembly. However, the volume of the oil required in the leg assembly of the suspension varies with the length of the leg assembly of the suspension system which is dependent on the vehicle architecture and specification. Larger quantity of oil in the legs of the front suspension of a vehicle directly impacts the overall weight, cost, maintenance and complexity of the system. At the time of servicing of the suspension system (at the intervals of 2 to 3 years), it becomes very troublesome to handle the larger quantity of oil while emptying and refilling the leg assembly with oil leading to increased maintenance costs over time.

[005] Therefore, there is a long pending unmet need of providing an intelligent solution that facilitates to maintain the optimum quantity of oil in the leg assembly so as to achieve the at par damping performance irrespective of the length of the fork leg assembly and the vehicle architecture. The present invention is aimed at providing a unitary fork bolt assembly that addresses the drawbacks of the conventional practices followed, facilitates to maintain the optimum quantity (variable volume) of oil in the leg assembly required for its at par performance, improves the ease of assembly and minimizes the overall maintenance costs.

Objectives of the Invention

[006] The main objective of the present invention is to provide a unitary fork bolt assembly for front fork suspension system of two and three-wheeled vehicles.

[007] Another objective of the present invention is to provide a unitary fork bolt assembly that simplifies the assembly process of the leg assembly and reduces the overall complexity of the suspension system.
[008] Still the objective of the present invention is to provide a unitary fork bolt assembly for front fork suspension of a vehicle which is configured to drastically reduce requirement of damping oil in the leg assembly leading to substantial reduction in weight and cost of the front fork suspension.

[009] Yet, the objective of the present invention is to provide a unitary fork bolt assembly for front fork suspension of a vehicle which is configured to eliminate the requirement of dedicated metal spacer tube in the leg assembly leading to significant reduction in weight and cost of the front fork suspension.

[0010] Further objective of the present invention is to provide a unitary fork bolt assembly for front fork suspension of a vehicle which significantly reduces the manufacturing and assembly cycle time and does not require any expensive machinery and/or tool for its assembly.

[0011] Yet, the objective of the present invention is to provide a unitary fork bolt assembly configured to maintain the variable volume of the oil in the leg assembly of the suspension system.

[0012] Further, the objective of the present invention is to provide a unitary fork bolt assembly for front fork suspension of a vehicle which eliminates noise and prevents leakage of the oil in the leg assembly thereby enhancing the overall performance of front fork suspension system.

Brief Description of Drawings

[0013] 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

[0014] Figure 1 discloses the front view of the front fork suspension system for two and three wheeled vehicles in accordance with the present invention.

[0015] Figure 2 presents isometric view of a fork leg of front fork suspension system in accordance with the present invention.

[0016] Figure 3 presents sectional view of the fork leg of front fork suspension system in accordance with first embodiment of the present invention.

[0017] Figure 4A discloses the enlarged sectional view of the unitary fork bolt assembly as per the first embodiment of the present invention as marked in Fig. 3.

[0018] Figure 4B shows the sectional view of the extended body portion of the unitary fork bolt assembly of the present invention.

[0019] Figure 4C discloses the sectional view of the fork bolt body along with the metal inserts therein of the unitary fork bolt assembly of the present invention as marked in Fig. 4b.

[0020] Figure 4D discloses the sectional view of the nut of t the unitary fork bolt assembly in accordance with first embodiment of the present invention.

[0021] Figure 5 presents enlarged sectional view of the unitary fork bolt assembly in accordance with second embodiment of the present invention.

[0022] Figure 6 presents sectional view of the fork leg of the front fork suspension having incorporated third embodiment of the unitary fork bolt assembly of the present invention.

[0023] Figure 7 discloses the enlarged sectional view of the unitary fork bolt assembly in accordance with the third embodiment of the present invention.

[0024] Figure 8 discloses the enlarged sectional view of the extended body portion of the unitary fork bolt assembly in accordance with the fourth embodiment of the present invention.

Detailed Description of the Present Invention

[0025] 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 to 2, the present invention provides a front fork suspension system (1000) for two and three-wheeled vehicles. The front fork suspension system (1000) comprises of a pair of leg assemblies (100, 100’) and a triple clamp assembly (15) wherein said leg assemblies (100, 100’) are connected with each other with the help of a triple clamp assembly (15) to form the said front fork suspension system (1000).

[0026] Referring to Figs. 3 and 5, each of the leg assembly (100, 100’) of the front fork suspension system comprises of an inner tube (12), an outer tube (22), a main spring (14), a unitary fork bolt assembly (200, 200*, 200’, 200”), an axle mounting bracket (40), a rebound spring (16), a seat pipe (30), a sealing assembly (10S), and a valve assembly (18). The inner tube (12) of the leg assembly (100, 100’) is configured to have an open upper end (12UE) and a lower end (12LE). The lower end (12LE) of the inner tube is (12) is fitted with the valve assembly (18) and the upper open end (12UE) of the inner tube (12) is closed with the unitary fork bolt assembly (200, 200*, 200’, 200”). The inner tube (12) is concentrically positioned inside the outer tube (22) and is telescopically slideable therein. The annular space between the inner tube (12) and the outer tube (22) at the mouth of the said outer tube (22) is closed by the sealing assembly (10S). The said sealing assembly (10S) includes a pair of dust seal and an oil seal to avoid entry of foreign particles into the leg assemblies (100, 100’) and leakage of hydraulic fluid therefrom. The main spring (14) is housed in the inner tube (12) in a manner such that top end of the main spring (14) abuts against the lower face of the extended body portion (20E, 20E*, 20E’, 20E”) of the unitary fork bolt assembly (200, 200*, 200’, 200”) and the other end (lower end) rests on a top surface (32U) of a piston (32P) of the seat pipe (30).

[0027] Referring to Figs. 4A to 8, the unitary fork bolt assembly (200, 200*, 200’, 200”) is configured to comprise of a fork bolt body (20B), a metal sleeve (20S) and an extended body portion (20E, 20E*, 20E’, 20E”). The fork bolt body (20B) of the unitary fork bolt assembly (200, 200*, 200’, 200”) is made in plastic having a metallic washer (20W) insert moulded therein. The said fork bolt body (20B) is over moulded by the insert molding process on the uniquely profiled metal sleeve (20S) forming a cylindrical cup-shaped profile around the said metal sleeve (20S). The said cup shaped profiled fork bolt body (20B) is configured to have an annular skirt (20BS) projecting in downward axial direction forming a frustum shaped cavity (20BC) therein. The metal sleeve (20S) is configured to have cylindrical body (20Sb) with a head portion (20Sh) at its top portion. The inner peripheral surface of the metal sleeve (20S) is provided with the threads (Th) and said threads (Th) are configured to lock the upper bracket (15U) of the triple clamp assembly (15).
[0028] The extended body portion (20E) of the unitary fork bolt assembly (200) is configured to have a cylindrical profile with two ends (20Ea, 20Eb). The upper end (20Ea) of the extended body portion (20E) is configured to have an annular skirt portion (20Es) projecting out in upward axial direction forming a cavity (20Ec) therein and the lower end (20Eb) of the unitary fork bolt assembly (200) is open forming the resting face for the main spring (14). The inner diameter of the skirt portion (20Es) of the extended body portion (20E) is equal to the outer diameter of the annular skirt portion (20BS) of the fork bolt body (20B). This unique configuration of annular skirt portions (20BS and 20Es) makes the extended body portion (20E) to get tightly fitted over the annular skirt portion (20BS) of the fork bolt body (20B) through the press fitting or interference fitting making the unitary structure of the fork bolt assembly (200). However, the extended body portion (20E) can be fitted to the annular skirt portion (20BS) of the fork bolt body (20B) by any of fastening means selected from threaded joints, adhesive bonding, welding and combination thereof. In case of threaded joint of extended body portion (20E) with the fork bolt body (20B), the outer peripheral surface of the annular skirt portion (20BS) has a plurality of threads matching with the threads provided on the inner peripheral surface of the annular skirt portion (20Es) of the extended body portion (20E). In case of welding of extended body portion (20E) with the fork bolt body (20B), said welding is selected from laser welding, fusion welding, ultrasonic welding and friction welding.

[0029] Referring to Fig. 5, another embodiment of the invention, the extended body portion (20E*) of the unitary fork bolt assembly (200*) is configured to have a cylindrical profile with two ends (20Ea*, 20Eb*). The upper end (20Ea*) of the extended body portion (20E*) is configured to have an annular skirt portion (20Es*) projecting out in upward axial direction and merging with the fork bolt body (20B) thereby forming a cavity (20Ec*) therein and the lower end (20Eb*) of the unitary fork bolt assembly (200) is open forming the abutting face for the main spring (14). This unique configuration of annular skirt portion (20Es*) of the extended body portion (20E*) seamlessly merging with the fork bolt body (20B) makes the unitary structure of the fork bolt assembly (200*).

[0030] The inner peripheral surface of the extended body portion (20E, 20E*) is configured to have a plurality of threads (20Et, 20Et*) throughout its length till the start of the annular skirt portion (20Es, 20Es*). The extended body portion (20E, 20E*) of the unitary fork bolt assembly (200, 200*) is configured to moveably house a nut (20N) and said nut (20N) is configured to have a plurality of threads (20Nt) on its outer peripheral surface and a key-slot (20Ng) coaxially grooved at its bottom surface. The threads (20Nt) on the nut (20N) are configured to mesh with the threads (20Et, 20Et*) of the extended body portion (20E, 20E*) and the key-slot (20Ng) is configured to hold the allen-key or any other suitable tool so as to rotate the nut (20N) in clockwise or anti-clockwise direction as per the requirement.

[0031] When the nut (20N) is rotated in clockwise direction with the help of allen-key or any other suitable torqueing means, the threads (20Et, 20Et*) of the extended body portion (20E, 20E*) and the threads (20Nt) of the nut (20N) meshes with each other and makes the said nut (20N) to move upward inside the extended body portion (20E, 20E*) thereby increasing the volume for the damping fluid (oil) in the inner tube (12). When the nut (20N) is rotated in anti-clockwise direction with the help of allen-key or any other suitable torqueing means, the threads (20Et, 20Et*) of the extended body portion (20E, 20E*) meshes with the threads (20Nt) of the nut (20N) and makes the said nut (20N) to move downward inside the extended body portion (20E, 20E*) thereby decreasing the volume for the damping fluid (oil) in the inner tube (12). The movement of the nut (20N) within the extended body portion (20E, 20E*) facilitates to vary the volume within the inner tube (12) for the damping fluid (oil). Thus, the unitary fork bolt assembly (200, 200*) of the front fork suspension (1000) very efficiently caters the variable volume for the damping oil as per the requirement to have at par performance of the suspension system (1000).

[0032] Referring to Fig. 7, another embodiment of the unitary fork bolt assembly (200’), the extended body portion (20E’) of the unitary fork bolt assembly (200’) is configured to have a solid bar profile with two ends (20Ea’, 20Eb’). The upper end (20Ea’) of the extended body portion (20E’) is configured to have an annular skirt portion (20Es’) projecting out in upward axial direction forming a cavity (20Ec’) therein and the lower end (20Eb’) of the unitary fork bolt assembly (200’) is closed being a solid bar forming the face for the main spring (14). The inner diameter of the skirt portion (20Es’) of the extended body portion (20E’) is equal to the outer diameter of the annular skirt portion (20BS) of the fork bolt body (20B). This unique configuration of annular skirt portions (20BS and 20Es’) makes the extended body portion (20E’) to get tightly fitted over the skirt portion (20BS) of the fork bolt body (20B) through the press fitting or interference fitting making the unitary structure of the fork bolt assembly (200’). However, the extended body portion (20E’) can be fitted to the annular skirt portion (20BS) of the fork bolt body (20B) by any of fastening means selected from threaded joints, adhesive bonding, welding and combination thereof. In case of threaded joint of extended body portion (20E’) with the fork bolt body (20B), the outer peripheral surface of the annular skirt portion (20BS) has a plurality of threads matching with the threads provided on the inner peripheral surface of the annular skirt portion (20Es’) of the extended body portion (20E’). In case of welding of extended body portion (20E) with the fork bolt body (20B), said welding is selected from laser welding, fusion welding, ultrasonic welding and friction welding.
[0033] Referring to Fig. 8, still another embodiment of the unitary fork bolt assembly (200”), the extended body portion (20E”) of the unitary fork bolt assembly (200”) is configured to have a hollow cylindrical profile with two ends (20Ea”, 20Eb”). The upper end (20Ea”) of the extended body portion (20E”) is configured to have an annular skirt portion (20Es”) projecting out in upward axial direction forming a cavity (20Ec”) therein and the lower end (20Eb”) of the unitary fork bolt assembly (200”) is permanently closed forming the hollow cavity (HC) in the extended body portion (20E”). The lower end (20Eb”) acts as the resting face for the main spring (14). The inner diameter of the skirt portion (20Es”) of the extended body portion (20E”) is equal to the outer diameter of the annular skirt portion (20BS) of the fork bolt body (20B). This unique configuration of annular skirt portions (20BS and 20Es”) makes the extended body portion (20E”) to get tightly fitted over the skirt portion (20BS) of the fork bolt body (20B) through the press fitting or interference fitting making the unitary structure of the fork bolt assembly (200”). However, the extended body portion (20E”) can be fitted to the annular skirt portion (20BS) of the fork bolt body (20B) by any of fastening means selected from threaded joints, adhesive bonding, welding and combination thereof. In case of threaded joint of extended body portion (20E”) with the fork bolt body (20B), the outer peripheral surface of the annular skirt portion (20BS) has a plurality of threads matching with the threads provided on the inner peripheral surface of the annular skirt portion (20Es”) of the extended body portion (20E”).

[0034] The fork bolt body (20B) and the extended body portion (20E, 20E*, 20E’, 20E”) of the unitary fork bolt assembly (200, 200’, 200”) is made by injection moulding any of the suitable engineering plastic fulfilling the desired mechanical properties selected from Polycarbonate, Polystyrene, Polyvinyl chloride, Polyamide, High-density Polyethylene, Polyphenylene sulfide, Thermoplastic polyurethane, Polyoxymethylene, Polyethylene terephthalate (PET), Polybutylene terephthalate (PBT), Polycaprolactam (Nylon 6), Polyethylene, Polymethylmethacrylate (PMMA), Polyphenylene oxide (ΡΡΟ), Polysulphone (PSU), etc.

[0035] Referring to Figs. 3 and 5, the seat pipe (30) of the leg assembly (100, 100’) of the front fork assembly (1000) is configured to have a cylindrical body and said cylindrical body is having a plurality of orifices (30O) thereon forming the oil passage from inside of the seat pipe (30) to the outer tube (22). The top end of the seat pipe (30) is fitted with a sliding piston (32P) wherein the said piston (32P) can be detachably attached to the seat pipe (30) at its top end (30T) by suitable fastening means. The seat pipe (30) along with the sliding piston (32P) is jointly housed in the inner tube (12) and the outer tube (22) in a manner such that the piston (32P) of the seat pipe (30) is positioned in the inner tube (12). The inner tube valve assembly (18) is positioned at the lower crimped end of the inner tube (12) and the rebound spring (16) is placed in between the piston (32P) of the seat pipe (30) and the top end of the inner tube valve assembly (18). This rebound spring (16) prevents the metal to metal contact in between the lower crimped end (12LE) of the inner tube (12) and the lower surface of the piston (32P) of the seat pipe (30) during the rebound stroke, thus preventing the unwanted noise thereby.

[0036] The inner tube valve assembly (18) includes an oil lock collar (189), a valve seat (186), a valve retainer (188) and a leaf spring (187). The oil lock collar (189) is sandwiched in between the valve seat (186) and the valve retainer (188). The leaf spring (187) is positioned in between the oil lock collar (189) and the valve retainer (188). The valve seat (186) functionally coupled to the oil lock collar (189) such that the inner tube valve assembly (18) is positioned in its place at the open end of the inner tube (12) and the said valve assembly (18) is adapted to facilitate flow of the hydraulic fluid in the fork assembly.

[0037] The axle mounting bracket (40) is assembled with outer tube (22) in such a manner that the said axle mounting bracket (40) is press fitted and welded to the lower end of the outer tube (22). However, the axle mounting bracket (40) may be fitted to the bottom end of the outer tube (22) by any of fastening means selected from press fitting / interference fitting, threaded joints, and like followed by welding. The seat pipe (30) is fixedly attached to the inner top surface of the outer tube (22) with the help of the socket headed bolt (92) in a manner such that the oil cap lock (50) is concentrically positioned in between the lower end of the seat pipe (30) and the top inner surface of the outer tube (22). This oil cap lock (50) creates the hydraulic lock during the extreme compression stroke of the leg assembly (100, 100’) and eliminates the bottoming of the inner tube (12) with the bottom inner surface of the outer tube (22).

[0038] The inner tube (12) and the outer tube (22) of the leg assembly (100, 100’) of the present invention as described above is filled with a suitable damping fluid preferably the damping oil, in order to achieve the damping performance. The said damping fluid also helps in dissipating the heat energy generated as a result of the damping of the shock loads and vibrations. The fork leg assembly (100, 100’) having unitary fork bolt assembly (200, 200*, 200’, 200”) fitted therein imparts following technical advantages contributing to the advancement of technology.
- The present invention very easily maintains the variable volume for the working fluid (oil) in the leg assembly of the suspension system suiting to different architecture and configuration of the two wheeled vehicles;
- It drastically reduces the weight and cost of the fork leg assembly without compromising performance;
- It facilitates easier and more efficient assembly of the front fork suspension;
- The unitary fork bolt assembly simplifies the assembly process of the leg assembly and reduces the overall complexity of the suspension system;
- It drastically reduces the requirement of damping oil in the leg assembly leading to substantial reduction in weight and cost of the front fork suspension;
- This construction of the unitary fork bolt assembly of the invention completely eliminates the requirement of dedicated metal spacer tube in the leg assembly leading to significant reduction in weight and cost of the front fork suspension;
- It significantly reduces the manufacturing and assembly cycle time and does not require any expensive machinery and/or tool for its assembly; and
- It eliminates noise and prevents leakage of the oil in the leg assembly thereby enhancing the overall performance of front fork suspension system.

[0039] It is understood that the invention is not limited to the embodiments described and illustrated herein, which are to be considered as implementing examples of the unitary fork bolt assembly. Rather, the invention is likely to be modified as to its shape and parts, functional and constructional details and materials being used. For example, the invention can be either applied also to USD (Up Side Down) front fork suspension units. 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 invention herein has been described in terms of a generalized form, those skilled in the art will recognize that the invention herein can be practiced with modification within the spirit and scope of the invention as described herein.
, Claims:We Claim:

1. A unitary fork bolt assembly (200, 200*, 200’, 200”) for front fork suspension system (1000) of a vehicle comprising of a fork bolt body (20B), a metal sleeve (20S) and an extended body portion (20E, 20E*, 20E’, 20E”), wherein
- the fork bolt body (20B) is made in plastic having a metallic washer (20W) insert moulded therein and said fork bolt body (20B) is over moulded by the insert molding process on the uniquely profiled metal sleeve (20S) forming a cylindrical cup-shaped profile around the said metal sleeve (20S);
- said cup shaped profiled fork bolt body (20B) is configured to have an annular skirt (20BS) projecting in downward axial direction forming a frustum shaped cavity (20BC) therein;
- the metal sleeve (20S) is configured to have cylindrical body (20Sb) with a head portion (20Sh) at its top portion; the inner peripheral surface of said metal sleeve (20S) is provided with the threads (Th) and said threads (Th) are configured to lock the upper bracket (15U) of the triple clamp assembly (15);
- the extended body portion (20E, 20E*, 20E’, 20E”) is configured to have an upper end (20Ea, 20Ea*, 20Ea’, 20Ea”) and a lower end (20Eb, 20Eb*, 20Eb’, 20Eb”), said upper end (20Ea, 20Ea*, 20Ea’, 20Ea”) of the extended body portion (20E, 20E*, 20E’, 20E”) is configured to have an annular skirt portion (20Es, 20Es*, 20Es’, 20Es”) projecting out in upward axial direction forming a cavity (20Ec, 20Ec*, 20Ec’, 20Ec”); and
- said extended body portion (20E, 20E*, 20E’, 20E”) at its annular skirt portion (20Es, 20Es*, 20Es’, 20Es”) is configured to get tightly fitted with the annular skirt portion (20BS) of the fork bolt body (20B) thereby making the unitary structure of the fork bolt assembly (200).

2. The unitary fork bolt assembly (200) for front fork suspension system (1000) of a vehicle as claimed in claim 1, wherein
- the extended body portion (20E) of the unitary fork bolt assembly (200) is configured to have a cylindrical profile with two ends (20Ea, 20Eb) and the lower end (20Eb) of the unitary fork bolt assembly (200) is open forming the resting face for a main spring (14);
- the inner diameter of the skirt portion (20Es) of the extended body portion (20E) is equal to the outer diameter of the annular skirt portion (20BS) of the fork bolt body (20B); and
- the configuration of annular skirt portions (20BS and 20Es) is configured to get the extended body portion (20E) tightly fitted over the annular skirt portion (20BS) of the fork bolt body (20B) through the fastening means selected from the press fitting, interference fitting, adhesive bonding, threaded joints, welding and combination thereof.

3. The unitary fork bolt assembly (200*) for front fork suspension system (1000) of a vehicle as claimed in claim 1, wherein
- the extended body portion (20E*) of the unitary fork bolt assembly (200*) is configured to have a cylindrical profile with two ends (20Ea*, 20Eb*);
- the upper end (20Ea*) of the extended body portion (20E*) is configured to have an annular skirt portion (20Es*) projecting out in upward axial direction and merging with the fork bolt body (20B) thereby forming a cavity (20Ec*) therein and the lower end (20Eb*) of the unitary fork bolt assembly (200) is open forming the abutting face for the main spring (14); and
- said annular skirt portion (20Es*) of the extended body portion (20E*) is configured to seamlessly merge with the fork bolt body (20B) thereby making the unitary structure of the fork bolt assembly (200*).

4. The unitary fork bolt assembly (200, 200*) for front fork suspension system (1000) as claimed in any of the claims 2 and 3, wherein
- the inner peripheral surface of the extended body portion (20E, 20E*) is configured to have a plurality of threads (20Et, 20Et*) throughout its length till the start of the annular skirt portion (20Es, 20Es*);
- said extended body portion (20E, 20E*) is configured to moveably house a nut (20N) and said nut (20N) is configured to have a plurality of threads (20Nt) on its outer peripheral surface and a key-slot (20Ng) coaxially grooved at its bottom surface; and
- the threads (20Nt) on the nut (20N) are configured to mesh with the threads (20Et, 20Et*) of the extended body portion (20E, 20E*) and the key-slot (20Ng) is configured to hold the allen-key or any other suitable tool so as to rotate the nut (20N) in clockwise or anti-clockwise direction as per the requirement.

5. The unitary fork bolt assembly (200, 200*) for front fork suspension system (1000) as claimed in claim 4, wherein the movement of the nut (20N) within the extended body portion (20E, 20E*) is configured to vary the volume within the inner tube (12) for the damping fluid (oil) thereby catering variable volume for the working fluid (oil) in the leg assembly (100, 100’) of the suspension system (1000) suiting to different architecture and configuration of the two wheeled vehicles.

6. The unitary fork bolt assembly (200’) for front fork suspension system (1000) of a vehicle as claimed in claim 1, wherein
- the extended body portion (20E’) of the unitary fork bolt assembly (200’) is configured to have a solid bar profile with two ends (20Ea’, 20Eb’);
- The upper end (20Ea’) of the extended body portion (20E’) is configured to have an annular skirt portion (20Es’) projecting out in upward axial direction forming a cavity (20Ec’) therein and the lower end (20Eb’) of the unitary fork bolt assembly (200’) is closed being a solid bar forming the face for the main spring (14);
- the inner diameter of the skirt portion (20Es’) of the extended body portion (20E’) is equal to the outer diameter of the annular skirt portion (20BS) of the fork bolt body (20B); and
- the configuration of annular skirt portions (20BS and 20Es’) is configured to get the extended body portion (20E’) tightly fitted over the annular skirt portion (20BS) of the fork bolt body (20B) through the fastening means selected from the press fitting, interference fitting, adhesive bonding, threaded joints, welding and combination thereof.

7. The unitary fork bolt assembly (200”) for front fork suspension system (1000) of a vehicle as claimed in claim 1, wherein
- the extended body portion (20E”) of the unitary fork bolt assembly (200”) is configured to have a hollow cylindrical profile with two ends (20Ea”, 20Eb”);
- the upper end (20Ea”) of the extended body portion (20E”) is configured to have an annular skirt portion (20Es”) projecting out in upward axial direction forming a cavity (20Ec”) therein and the lower end (20Eb”) of the unitary fork bolt assembly (200”) is permanently closed forming the hollow cavity (HC) in the extended body portion (20E”);
- the inner diameter of the skirt portion (20Es”) of the extended body portion (20E”) is equal to the outer diameter of the annular skirt portion (20BS) of the fork bolt body (20B); and
- the configuration of annular skirt portions (20BS and 20Es”) is configured to get the extended body portion (20E”) tightly fitted over the annular skirt portion (20BS) of the fork bolt body (20B) through the fastening means selected from the press fitting, interference fitting, adhesive bonding, threaded joints, welding and combination thereof.

8. The unitary fork bolt assembly (200, 200’, 200”) as claimed in any of the claims 2, 6 and 7, wherein
- in case of threaded joint of extended body portion (20E, 20E’, 20E”) with the fork bolt body (20B), the outer peripheral surface of the annular skirt portion (20BS) has a plurality of threads matching with the threads provided on the inner peripheral surface of the annular skirt portion (20Es, 20Es’, 20Es”) of the extended body portion (20E, 20E’, 20E”); and
- in case of welding of extended body portion (20E, 20E’, 20E”) with the fork bolt body (20B), said welding is selected from laser welding, fusion welding, ultrasonic welding and friction welding.

9. The unitary fork bolt assembly (200, 200*, 200’, 200”) for front fork suspension system (1000) of a vehicle as claimed in any of the claims 5, 6 and 7, wherein the fork bolt body (20B) and the extended body portion (20E, 20E*, 20E’, 20E”) of the unitary fork bolt assembly (200, 200*, 200’, 200”) are made by injection moulding any of the suitable engineering plastic fulfilling the desired mechanical properties; and said plastic is selected from Polycarbonate, Polystyrene, Polyvinyl chloride, Polyamide, High-density Polyethylene, Polyphenylene sulfide, Thermoplastic polyurethane, Polyoxymethylene, Polyethylene terephthalate (PET), Polybutylene terephthalate (PBT), Polycaprolactam (Nylon 6), Polyethylene, Polymethylmethacrylate (PMMA), Polyphenylene oxide (ΡΡΟ), and Polysulphone (PSU).

10. The unitary fork bolt assembly (200, 200*, 200’, 200”) for front fork suspension system (1000) of a vehicle as claimed in any of the claims 5 and 9, wherein
- each of the leg assembly (100, 100’) of the front fork suspension system (1000) is configured to comprise of an inner tube (12), an outer tube (22), a main spring (14), a unitary fork bolt assembly (200, 200*, 200’, 200”), an axle mounting bracket (40), a rebound spring (16), a seat pipe (30), a sealing assembly (10S), and a valve assembly (18);
- the inner tube (12) of the leg assembly (100, 100’) is configured to have an open upper end (12UE) and a lower end (12LE); said lower end (12LE) of the inner tube is (12) is fitted with the valve assembly (18) and the upper open end (12UE) of the inner tube (12) is closed with the unitary fork bolt assembly (200, 200*, 200’, 200”);
- said inner tube (12) is concentrically positioned inside the outer tube (22) and is telescopically slideable therein and the annular space between the inner tube (12) and the outer tube (22) at the mouth of the said outer tube (22) is closed by the sealing assembly (10S); and
- the main spring (14) is housed in the inner tube (12) in a manner such that top end of the main spring (14) abuts against the lower face of the extended body portion (20E, 20E*, 20E’, 20E”) of the unitary fork bolt assembly (200, 200*, 200’, 200”) and the other end (lower end) rests on a top surface (32U) of a piston (32P) of the seat pipe (30).

11. The unitary fork bolt assembly (200, 200*, 200’, 200”) for front fork suspension system (1000) as claimed in claim 10, wherein
- the seat pipe (30) of the leg assembly (100, 100’) of the front fork assembly (1000) is configured to have a cylindrical body and said cylindrical body is having a plurality of orifices (30O) thereon forming the oil passage from inside of the seat pipe (30) to the outer tube (22);
- the top end of the seat pipe (30) is fitted with a sliding piston (32P) wherein the said piston (32P) is detachably attached to the seat pipe (30) at its top end (30T) by suitable fastening means;
- said seat pipe (30) along with the sliding piston (32P) is jointly housed in the inner tube (12) and the outer tube (22) in a manner such that the piston (32P) of the seat pipe (30) is positioned in the inner tube (12); and
- the inner tube valve assembly (18) is positioned at the lower crimped end of the inner tube (12) and the rebound spring (16) is placed in between the piston (32P) of the seat pipe (30) and the top end of the inner tube valve assembly (18).

12. The unitary fork bolt assembly (200, 200*, 200’, 200”) for front fork suspension system (1000) as claimed in claim 11, wherein
- the inner tube valve assembly (18) is configured to comprise of an oil lock collar (189), a valve seat (186), a valve retainer (188) and a leaf spring (187); said oil lock collar (189) is sandwiched in between the valve seat (186) and the valve retainer (188); and the leaf spring (187) is positioned in between the oil lock collar (189) and the valve retainer (188);
- the valve seat (186) functionally coupled to the oil lock collar (189) such that the inner tube valve assembly (18) is positioned in its place at the open end of the inner tube (12) and the said valve assembly (18) is adapted to facilitate flow of the hydraulic fluid in the fork assembly;
- an axle mounting bracket (40) is press fitted and welded to the lower end of the outer tube (22);
- the seat pipe (30) is fixedly attached to the inner top surface of the outer tube (22) with the help of the socket headed bolt (92) in a manner such that a oil cap lock (50) is concentrically positioned in between the lower end of the seat pipe (30) and the top inner surface of the outer tube (22); and
- said oil cap lock (50) is configured to create the hydraulic lock during the extreme compression stroke of the leg assembly (100, 100’) to eliminate the bottoming of the inner tube (12) with the bottom inner surface of the outer tube (22).

Dated this 4th day of Mar. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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