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

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

TITLE OF THE INVENTION
“FRONT FORK ASSEMBLY FOR SUSPENSION SYSTEM OF A VEHICLE”

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

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

Field of Invention

[001] The present invention is related to a suspension system of two and three-wheeled motor vehicles. More particularly, the invention is related to a front fork assembly with a stud adaptor therein for connecting the front fork assembly with an axle mounting clamp of the suspension system of two and three-wheeled vehicle.

Background of the Invention

[002] Conventionally, in fork leg assembly of the suspension system of two and three-wheeled vehicles, an inner tube assembly is telescopically arranged inside the outer tube. The outer tube assembly is formed by joining together two separate parts namely an outer tube and an axel clamp. Manufacturing the tube and its axle mounting clamp separately and then assembling them together to form a finished outer tube assembly for a front fork suspension assembly is a known solution for creating structurally stronger fork leg for suspension systems of vehicles. In the leg assembly of a front fork, a seat pipe must be aligned orthogonal to an inner top surface of the axle mounting clamp so that the seat pipe does not foul with the inner surface of the inner tube leading to scratches thereon.

[003] The outer tube and an axle mounting clamp are manufactured separately and then assembling them to form an outer tube assembly does create issues of misalignment of the seat pipe within the outer tube. In one of the conventional solutions wherein the axle mounting clamp has a projected portion with threads on which the seat pipe having matching internal threads is mounted, the misalignment of parts during their assembly is a very common problem, and such misalignment generally creates issues with regards jam or sticky fork movement, rubbing noise, wear and tear of parts which consequently affect the damping performance of the suspension system and causes a reduction in life of the front fork. To solve the aforementioned problems, another conventional solution is that the axle mounting clamp is configured to have a step profiled opening on its top surface with threads from its inner side and the seat pipe is having a profiled threaded projection at its lower end. This structure makes the seat pipe to get fitted in the axle mounting clamp through a specially designed insert addressing the problem of misalignment to some extent. However, the manufacturing of such variable section in the tube with solid projection at its lower end requires heavy machinery that causes expensive tooling investment. There is also a problem of high-stress concentration at a variable section in the tube (where the diameter of the pipe is reduced) which causes less tensile strength.

[004] Hence, in order to overcome the problems prevalent in the prior art and/or conventional solutions, there is prolonged unmet need to provide a solution which will not lead the problem of high stress concentration at variable section of the tube and/or axle clamp, eliminates the expensive tooling investment, imparts easiness in assembling the front fork assembly and also provides an economical solution. The present invention clearly addresses the drawbacks of the prior art and/or conventional solutions by providing a unique design of front fork assembly wherein the front fork assembly is provided with a uniquely profiled stud adaptor therein for connecting the front fork assembly with an axle mounting clamp of the suspension system of two and three-wheeled vehicle.

Objectives of the Invention

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

[006] Another objective of the present invention is to provide a front fork assembly with a uniquely profiled stud adaptor therein for connecting the front fork assembly with an axle mounting clamp of the suspension system of two and three-wheeled vehicle.

[007] Further, the objective of the present invention is to provide a front fork assembly for suspension system that enhances the life of the front fork suspension as the damage which can result from imperfect alignment of the seat pipe and high-stress concentration at the variable cross-section of the pipe/axle clamp are eliminated.

[008] Yet, the objective of the present invention is to provide a front fork assembly that does not deteriorate the manufacturing and assembly cycle time and does not require any expensive machinery and/or tool for its assembly.

[009] Another objective of the present invention is to provide a front fork assembly for suspension system that ensures the perfect alignment of the seat pipe with its relevant components and eliminates the chance of any misalignment of any of the components of the front fork assembly.

[0010] Yet, the objective of the present invention is to provide a front fork assembly for suspension system that improves the tensile strength at the joint portion of the seat pipe and axle clamp and imparts easiness in assembling the front fork assembly and that also by providing an economical solution.

[0011] Still, the objective of the present invention is to provide a front fork assembly for a suspension system that is simple in construction, easy to manufacture, and facilities easy replacement of the stud adaptor in case of damage to its threads instead of replacing the whole seat pipe.

Brief Description of Drawings

[0012] 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 in conjunction with the drawings enclosed herewith, wherein

Figure 1 discloses an isometric view of the front fork assembly for suspension system of the two-wheeled vehicle in accordance with the present invention.
Figure 2 presents an exploded view of an outer tube assembly with a seat pipe and axle mounting clamp in accordance with the present invention.
Figures 3a and 3b present a seat pipe and a stud adaptor of the present invention in dismantled and assembled condition, respectively.
Figure 4 discloses second embodiment of the stud adaptor in accordance with the present invention.
Figures 5a and 5b present a seat pipe and second embodiment of stud adaptor (as shown in Fig. 4) of the present invention in dismantled and assembled condition, respectively.
Figure 6 discloses an exploded view of the axle mounting clamp of front fork suspension unit as per the present invention.

Detailed Description of the Present Invention

[0013] Referring to Fig. 1, the present invention provides a front fork assembly (1000) for a suspension system for two and three-wheeled vehicles. The front fork assembly (1000) comprises a pair of leg assemblies (100, 200) that are interconnected with each other with the help of a triple clamp assembly to form the said fork assembly. When the suspension unit is fitted on the vehicle, each of the fork legs is positioned on either side of the front wheel. Each of the leg assemblies (100, 200) is filled with a fluid, preferably oil, in order to achieve damping performance and also for lubricating the various child parts of the assembly. It also helps in dissipating the heat energy generated as a result of the damping of the shock loads and vibrations. A pair of dust seals and oil seal is provided in the top portion of the outer tube to avoid entry of foreign particles into the leg assemblies (100, 200) and leakage of hydraulic fluid therefrom.

[0014] Each of the leg assemblies (100, 200) comprises an inner tube (10), an outer tube (22), a seat pipe (30), a stud adaptor (50), and an axle clamp (40). The outer tube (22) and axel clamp (40) together form an outer tube assembly (20). The axel clamp (40) is fitted into the bottom end (22b) of an outer tube (22) by the suitable fastening means viz. press fitting/interference fitting, threaded joints, and like followed by welding. The inner tube (10) is telescopically moveable within the outer tube (22). The inner tube assembly (10) further comprises an inner tube, a main spring, a piston valve assembly, and a seat pipe (30), etc. The main spring is arranged inside the inner tube (10) and is supported by the spring guide at its one end. The spring guide rests over a top surface of the piston (16P) attached to top end of the seat pipe (30). The seat pipe (30) is detachably fitted to the axel clamp (40) by using a uniquely profiled stud adaptor (50).

[0015] Referring to Figs. 2 to 3b, the seat pipe (30) is configured to have a cylindrical body (32) having a top end (32T), a bottom end (32B) and a bottom face (32C), where the top end (32T) is fitted with the sliding piston (16P) and said top end (32T) of the seat pipe (30) along with the piston (16P) is slideably moveable within the inner tube (10). The bottom face (32C) of the bottom end (32B) of the seat pipe (30) is configured to have threaded opening (33A) to accommodate the upper projection (53) of the stud adaptor (50); and said face (32C) is configured to have a plain surface with the chamfered profile (32Ca) at the outer periphery of said plain surface. The seat pipe (30) has a piston (16P) integrated at its top end (32T). However, the said piston (16P) can be detachably attached to the seat pipe (30) at its top end (32T) by suitable fastening means.

[0016] The stud adaptor (50) has an upper projection (53), a lower projection (52), and a body portion (56) in between the said upper and lower projections (53 and 52). The length of the upper projection (53) of the stud adaptor (50) is at least 0.30 times the length (y) of the lower projection (52) of the stud adaptor (50). The upper projection (53) and the lower projection (52) of the stud adaptor (50) is configured to have threads (53A) and (52A), respectively on its outer surface. The upper projection (53) having threads (53A) of the stud adaptor (50) is fitted inside the threaded opening (33A) in the bottom face (32C) of the bottom end (32B) of the seat pipe (30) and the lower projection (52) having threads (52A) of the stud adaptor (50) is fitted inside the threaded opening (42HT) provided in the top face (40TS) of the axle clamp (40) as shown in Fig. 6. The body portion (56) of the stud adaptor (50) has an upper face (54), a lower face (55) and at least a pair of D-profiled cuts (56d) wherein each of the cuts (56d) is positioned exactly opposite to each other on the outer surface of the body portion (56). These D-profiled cuts (56d) facilitate better and positive engagement during the torqueing of the stud adaptor (50).

[0017] Referring to Figs. 2 and 6, the axel clamp (40) according to the present invention is configured to have a cylindrical upper portion (42) at its top end (40T), a stem portion (44), an axle eye portion (40B) and a metal insert (45). The cylindrical upper portion (42) is having a flat top surface (40TS) and it has an opening (42H) through its top surface (42TS) that opens into a slot (44S) made inside the stem portion (44) of the axle mounting clamp (40). The opening (42H) has a stepped profile (42HS) on its inner surface and said stepped profile (42HS) houses a washer inside it and also eliminates the chances of misalignment of the stud adaptor (50) fitted with the seat pipe (30) from its required position while assembling it with the axle clamp by using the stud adaptor (50).

[0018] During assembly of the seat pipe (30) with the axle clamp (40), the upper projection (53) having threads (53A) of the stud adaptor (50) is fitted inside the threaded opening (33A) in the bottom face (32C) of the bottom end (32B) of the seat pipe (30) and the lower projection (52) having threads (52A) of the stud adaptor (50) is fitted inside the opening (42HS) provided through the top face (40TS) of the axle clamp (40) by means of the washer (70) and a threaded engagement. The washer arrangement at both joint section helps to prevent the leakage of oil (not shown).

[0019] Referring to Fig. 6, the stem portion (44) of the axle clamp (40) is configured to have a slot (44S) and an axel eye portion (40B) and said axle eye portion (40B) has an axle eye opening (40C) for accommodating the axle of the vehicle. The slot (44S) is having a predefined depth up to its backside surface in order to comfortably house the metal insert (45) therein. The slot (44S) is made in any suitable profile selected from quadrilateral cross-section viz. rectangular, square, and like or circular shaped cross-section. The most preferred profile of the slot (44S) is with circular shaped cross-section as shown in Fig. 6. The said slot (44S) is made using any known metal removing process, preferably milling. The backside surface of the slot (44S) in the in the stem portion (44) has a hole that opens in the slot (44S) and said hole is provided for removing the metal insert (45) fitted in the slot (44S) of the stem portion (44). The inside top surface of the said slot (44S) is configured to have a circular relieve opening communicating with the opening (42HS) that receives the lower projection (52) of the stud adaptor (50).

[0020] The axel clamp (40) is adapted to have a metal insert (45) that gets fitted inside the slot (44S) by means of press fitting. The metal insert (45) is made in any suitable profile selected from quadrilateral cross-section viz. rectangular, square, and like or circular shaped cross-section matching with the profile of the slot (44S). The most preferred profile of the metal insert (45) is with circular shaped cross-section as shown in Fig. 6. The metallic insert (45) has a threaded hole (45H) at its top surface and said hole (45H) opens at the bottom surface of the metal insert (45). The opening (42H) of the cylindrical upper portion (42), the threaded hole (45H) of the insert (45), and the relieve opening in the slot (44S) are concentric and have the same diameter. The lower projection (52) having threads (52A) of the stud adaptor (50) passes through the hole (42H) of the cylindrical upper portion (42) and gets meshed inside the threaded hole (45H) of the insert (45) through the relieve opening in the slot (44S). For removing or replacing the metal insert (45) in case of any damage, the metal insert (45) needs to be hit using a pin through the hole provided in the backside surface of the slot (44S).

[0021] In another embodiment, Referring to Figs. 4 to 5b, the seat pipe (30) is configured to have a cylindrical body (32) having a top end (32T), a bottom end (32B) and a bottom face (32A). Further, the face (32A) of the bottom end (32B) of the seat pipe (30) is configured to have a tapered profile (32AT) and an opening (33B) thereon to accommodate the upper projection (53) of the stud adaptor (50). The body portion (56) of the stud adaptor (50) has a tapered upper face (54A), a lower face (55) and a cylindrical outer surface (56c). The upper projection (53) of the stud adaptor (50) is configured to have plain outer surface and the lower projection (52) of the stud adaptor (50) is configured to have threads (52A) on its outer surface. The upper projection (53) of the stud adaptor (50) is press fitted inside the opening (33B) in the face (32A) of the bottom end (32B) of the seat pipe (30) followed by the welding in the conical space (S) formed by the joining of tapered profile (32AT) of the seat pipe (30) and the tapered upper face (54A) of the stud adaptor (50). Said welding is selected from friction welding, CO2 welding, brazing and seam welding in the conical space (S) formed by joining the tapered profile (32AT) of the face (32A) of the bottom end (32B) of the seat pipe (30) and the upper tapered face (54A) of the body portion (56) of the stud adaptor (50) to form the rigid joint of the stud adaptor (50) with the seat pipe (30). The lower projection (52) having threads (52A) of the stud adaptor (50) is fitted inside the opening (42H) provided in the top face (40TS) of the axle clamp (40). The angle of the tapered upper face (54A) of the body portion (56) and tapered bottom face (32AT) of the seat pipe (30) with the horizontal is in the range of 30 to 50 degree to have better weld penetration and tensile strength of the joint.

[0022] Referring to Fig. 6, the axle eye portion (40B) of the axle mounting bracket (40) is made flat at its bottom end surface. The flattening is done by machining or it can be done by forging while manufacturing the axle mounting bracket followed by machining. This flat profile (40BF) of the axle mounting bracket (40) facilitates the easiness in fitting the said bracket with the outer tube. Further, this flat surface lead to require less efforts and less time while fitting the axle mounting bracket (40) with the outer tube (22) leading the reduction in cycle time of assembling the outer tube assembly.

[0023] The front fork assembly of the present invention in accordance with the embodiments as discussed above provides the following technical advantages that contribute to the technical advancement of the front fork assembly of the suspension system of two-wheeled and three-wheeled vehicles.
- The front fork assembly of the present invention improves the tensile strength at joint section by deterring the stress concentration at variable cross section of the seat pipe and axle clamp.
- Eliminates the requirement of costly heavy manufacturing machinery and tools and provides the very simple assembly.
- Ensures the desired alignment of the seat pipe in orthogonal direction w.r.t. the top cylindrical surface of the axle mounting clamp.
- Facilities easy replacement of the stud adaptor in case of any damage / failure instead of replacing the whole seat pipe.
- Enhances the life of the front fork suspension as the damage which can result from misalignment of the seat pipe is totally eliminated.
- It is simple construction, easy to manufacture and provide an economic solution for eliminating the misalignment of the seat pipe with the axle mounting bracket.

[0024] The disclosed invention thus overcomes the limitation of the known solutions of the front fork assembly. It provides an axle mounting clamp that is easy to provide within all front fork suspensions where the outer tube and axle mounting clamp are manufactured separately and then joined together to form an outer tube assembly. Altering the components forming the suspension unit does not directly affect the performance of the front fork assembly in accordance with the disclosed invention. Such alterations must therefore not be considered to be out of the scope of the present invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. , Claims:We Claim

1. A front fork assembly (1000) for two wheeled and three wheeled vehicles having a pair of leg assemblies (100, 200), said leg of the pair of leg assemblies comprises of :
• an outer tube (22),
• an inner tube (10)
• a seat pipe (30),
• an axle clamp (40), and
• a stud adaptor (50)
wherein,
- the inner tube (10) is telescopically moveable within the outer tube (22) and said outer tube (22) is configured to have a main cylindrical body;
- the axle clamp (40) has an axel eye portion (40B) and said eye portion (40B) is configured to have an opening (40C) for accommodating the axle of the vehicle; and said axle clamp (40) is press fitted with the outer tube (22) at its bottom end (22b);
- the seat pipe (30) is configured to have a cylindrical body (32) having a top end (32T) and a bottom end (32B), where the top end (32T) is fitted with the sliding piston (16P) and said sliding piston (16P) along with the top end (32T) of the seat pipe (30) is slideably moveable within the inner tube (10);
- the stud adaptor (50) is configured to have a body portion (56), an upper projection (53) and a lower projection (52); and
- said stud adaptor (50) rigidly connects the bottom end (32B) of the seat pipe (30) with the axle mounting clamp (40) through its projections (53 and 52); wherein the upper projection (53) of the stud adaptor (50) is fitted in the bottom end (32B) of the seat pipe (30) and the lower projection (52) of said stud adaptor (50) is fitted with the axle clamp (40).

2. The front fork assembly as claimed in claims 1, wherein the face (32C) of the bottom end (32B) of the seat pipe (30) is configured to have threaded opening (33A) to accommodate the projection (53) of the stud adaptor (50); and said face (32C) is configured to have a plain surface with the chamfered profile (32Ca) at the outer periphery of said plain surface.

3. The front fork assembly as claimed in claim 2, wherein
- the body portion (56) of the stud adaptor (50) has an upper face (54), a lower face (55) and a pair of D-profiled cuts (56d) wherein said cuts (56d) are positioned opposite to each other on its outer cylindrical surface;
- the upper projection (53) and the lower projection (52) of the stud adaptor (50) is configured to have threads (53A) and (52A), respectively on its outer surface;
- the upper projection (53) having threads (53A) of the stud adaptor (50) is fitted inside the threaded opening (33A) in the face (32C) of the bottom end (32B) of the seat pipe (30); and
- the lower projection (52) having threads (52A) of the stud adaptor (50) is fitted inside the opening (42H) provided in the top face (40TS) of the axle clamp (40).

4. The front fork assembly as claimed in claims 1, wherein the face (32A) of the bottom end (32B) of the seat pipe (30) is configured to have a tapered profile (32AT) and an opening (33B) thereon to accommodate the projection (53) of the stud adaptor (50).

5. The front fork assembly as claimed in claim 4, wherein
- the body portion (56) of the stud adaptor (50) has a tapered upper face (54A), a lower face (55) and a cylindrical outer surface (56c);
- the upper projection (53) of the stud adaptor (50) is configured to have plain outer surface and the lower projection (52) of the stud adaptor (50) is configured to have threads (52A) on its outer surface;
- the upper projection (53) of the stud adaptor (50) is press fitted inside the opening (33B) in the face (32A) of the bottom end (32B) of the seat pipe (30) followed by the welding in the conical space (S) formed by joining the tapered profiles of the face (32A) of the bottom end (32B) of the seat pipe (30) and the upper face (54A) of the body portion (56) of the stud adaptor (50) to form the rigid joint of the stud adaptor (50) with the seat pipe (30); and
- the lower projection (52) having threads (52A) of the stud adaptor (50) is fitted inside the opening (40H) provided in the top face (40TS) of the axle clamp (40).

6. The front fork assembly as claimed in claim 5, wherein the welding is selected from friction welding, CO2 welding, brazing and seam welding.

7. The front fork assembly as claimed in claim 6, wherein the angle of the tapered upper face (54A) of the body portion (56) with the horizontal is in the range of 30 to 50 degree to have better weld penetration and tensile strength of the joint.

8. The front fork assembly as claimed in any of the claims 3 and 7, wherein the length of the upper projection (53) of the stud adaptor (50) is 0.30 times the length (y) of the lower projection (52) of the stud adaptor (50).

9. The front assembly as claimed in claim 8, wherein
- the axle clamp (40) is configured to have a cylindrical upper portion (42), a stem portion (44) and an axle eye portion (40B);
- the cylindrical upper portion (42) of the axle clamp (40) has an opening (42H) in its top surface (40TS) that opens into a slot (44S) made inside the stem portion (44);
- said opening (42H) in cylindrical portion (42) of the axle clamp (40) has a stepped profile (42HS) at its upper end to accommodate the body portion (56) of the stud adaptor (50) wherein the lower face (55) of the stud adaptor (50) rests on the stepped portion of the stepped profile (42HS) and rest of the opening (42H) is configured to plain inner surface;
- the stem portion (44) has a slot (44S), said slot (44S) is configured to be fitted with a metal insert (45), said metal insert (45) has an opening (45H) through it, and said opening (45H) securely accommodates the lower projection (52) of the stud adaptor (50); and
- said stem portion (44) has an integrated axel eye portion (40B) for accommodating the axle of the vehicle wheel.

10. The front fork assembly as claimed in claim 9, wherein,
- the lower projection (52) having threaded portion (52A) of the stud adaptor (50) passes through the opening (42H) in the cylindrical upper portion (42) of the axle clamp (40) and gets rigidly engaged inside the threaded hole (45H) of the metal insert (45) thereby joining the axle clamp (40) with seat pipe (30); and
- said seat pipe (30) has a piston (16P) detachably attached at its top end (32T) and said piston (16P) is configured to slideably move inside the inner tube (10) of the front fork assembly.

Dated this 8th day of Feb. 2023

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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