DESC: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 TWO WHEELER”

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

The following specification particularly describes and ascertains the nature of this 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 guide sleeve positioned therein for connecting a seat pipe of 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, the fork leg assembly of the suspension system of two and three-wheeled vehicles comprises of an inner tube assembly 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 a 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 manufacturing of the outer tube and axle mounting clamp separately followed by the assembly of the same create issues of misalignment of the seat pipe within the outer tube particularly made of steel. 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 jamming 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 to provide the axle mounting clamp configured to have a stepped profiled opening on its top surface with threads from its inner side and the seat pipe 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, manufacturing of such variable section in the tube with solid projection at its lower end requires heavy machinery that accounts for expensive tooling investment. Also, there is 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 guide sleeve therein for connecting the seat pipe of 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 guide sleeve placed therein for connecting the seat pipe of 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 increase 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 reinforce the 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 facilitates easy replacement of the 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

[0013] 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.

[0014] Figure 2 presents cut view of a fork leg of the front fork suspension assembly in accordance with the present invention.

[0015] Figure 3a shows a cut sectional view of the leg assembly of the front fork suspension assembly as per the present invention.

[0016] Figure 3b discloses the placement of guide sleeve in the leg assembly at the joinery of the seat pipe with the axle mounting clamp as per the present invention.

[0017] Figure 4 depicts the cut view of the seat pipe of the front fork suspension assembly as per the present invention.
[0018] Figure 5 shows the cut view of the axle mounting bracket of the front fork suspension assembly per the present invention.

[0019] Figures 6 and 7 shows the top view and the cut sectional view, respectively of the guide sleeve of the front fork suspension assembly per the present invention.

Detailed Description of the Present Invention

[0020] 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 (200) that are interconnected with each other with the help of a triple clamp assembly (15) to form the said fork assembly (1000). When the suspension unit (1000) is fitted on the vehicle, each of the fork legs (200) is positioned on either side of the front wheel. Each of the leg assemblies (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 (22) to avoid entry of foreign particles into the leg assemblies (200) and leakage of hydraulic fluid therefrom.

[0021] Referring to Fig. 2, each of the leg assemblies (200) comprises of an inner tube assembly (10AS), an outer tube assembly (20) and a seal assembly (10S). The inner tube assembly (10AS) further comprises of an inner tube (10), a main spring (S), a spacer tube (ST), a piston valve assembly (35), a rebound spring (16) and a fork bolt (10B). The outer tube assembly (20) comprises an outer tube (22), an axle mounting clamp (40), a seat pipe (30) and a guide sleeve (50).
[0022] The fork bolt (10B) closes the inner tube (10) from the top end. The spacer tube (10ST) is placed in the inner tube (10) in a manner such that the one end of the spacer tube (10ST) abuts against the lower face of the fork bolt (10B) and the other end of the spacer tube (10ST) arrests the top end of the main spring (S). The other end of the main spring (S) rests against the top surface of a piston (16P) of the seat pipe (30) of the outer tube assembly (20).

[0023] The outer tube assembly (20) is formed by assembling the outer tube (22) with the axle mounting clamp (40). The axel mounting clamp (40) is fitted at the bottom end (22b) of the outer tube (22) by the suitable fastening means viz. press fitting/interference fitting, threaded joints, and like followed by welding. The seat pipe (30) is fixed to the axle mounting clamp (40) with the help of internal threads provided on the seat pipe (30) and the external threads provided on a projected portion (40P) of the axle mounting clamp (40). The guide sleeve (50) is positioned in between the bottom face (32C) of the seat pipe and the top face (40TS) of the axle mounting clamp (40) so as to guide the seat pipe (30) orthogonally in relation to the axle mounting clamp (40). The annular space between the inner tube assembly and the outer tube assembly is filled with the help of a seal assembly (10S) such that the inner tube assembly (10) is slidably engaged in the outer tube assembly (20). The seal assembly (10S) includes a dust seal and an oil seal provided therein to avoid the entry of foreign particles into the leg assemblies (100, 200) and leakage of hydraulic fluid therefrom.

[0024] 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 a threaded opening (33A) to accommodate a projection (40P) of the axle mounting clamp (40); and said bottom face (32C) is configured to have a plain surface with the chamfered profile (32CA) at the inner periphery of said plain surface (32C). 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.

[0025] Referring to Figs. 2 and 3b, the axel mounting 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) and an axle eye portion (40B). The axle eye portion (40B) has an axle eye opening (40C) for accommodating the axle of the vehicle. The cylindrical upper portion (42) is having a flat top surface (40TS) and said top surface (42TS) is configured to have an orthogonal projection (40P) with threads on its outer peripheral surface. The projection (40P) having threads (40PT) of the axle clamp (40) is fitted inside the threaded opening (33A) in the bottom face (32C) of the bottom end (32B) of the seat pipe (30). The orthogonal projection (40P) of the axle clamp (40) houses the uniquely profiled guide sleeve (50) in such way that the said guide sleeve (50) positions the seat pipe (30) in orthogonal direction with respect to the top surface (42TS) of the axle clamp (40).

[0026] The guide sleeve (50) is configured to have an upper face (54), a lower face (55), a stepped opening (50S) at the center and at least a pair of D-profiled cuts (56D) on its outer peripheral surface wherein each of the cuts (56D) is positioned exactly opposite to each other on the outer peripheral surface of the guide sleeve (50). These D-profiled cuts (56D) facilitate sound and orthogonal engagement of the seat pipe (30) with the threaded projection (40P) of the axle clamp (40). The stepped opening (50S) has an annular guiding and resting portion (G) with a step (R) wherein the diameter of the guiding and resting portion (G) is equal to the outer diameter of the seat pipe with a tolerance so that the said seat pipe is orthogonally press fitted inside the guiding and resting portion (G) with the lower face (32C) of the seat pipe resting on the step (R) of the guide sleeve (50). The stepped opening (50S) of the guide sleeve (50) houses the lower end (32B) of the seat pipe (30) inside it in such way that it eliminates the chances of misalignment of the seat pipe (30) from its required position while assembling it with the threaded orthogonal projection (40P) of the axle clamp (40). During assembly of the seat pipe (30) with the axle clamp (40), the threaded projection (40P) of the axle clamp (40) is fitted inside the threaded opening (33A) in the bottom face (32C) of the bottom end (32B) of the seat pipe (30). The guide sleeve (50) is designed in a manner so as to have the below mentioned empirical relations in order to guide the seat pipe (30) in an orthogonal manner with respect to the axle mounting clamp (40):

d / a ~ 2.5 – 4.0 …1
a / b ~ 2.0 – 3.5 …2
where,
a is the length of the guiding portion of the guide sleeve.
b is the length of the resting portion of the guide sleeve.
d is the diameter of the lower end of the seat pipe.

[0027] The axle eye portion (40B) has an axle eye opening (40C) for accommodating the axle of the vehicle. The axle eye portion (40B) of the axle mounting bracket (40) is made flat (not shown) 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 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.

[0028] The front fork assembly of the present invention in accordance with an embodiment 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 ensures the desired alignment of the seat pipe in orthogonal direction w.r.t. the top cylindrical surface of the axle mounting clamp and thereby eliminate the chances of jamming the leg assembly.
- Eliminates the requirement of costly heavy manufacturing machinery and tools and provides the very simple assembly.
- 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 in case of the leg assembly wherein the outer tube is made of steel.

[0029] The foregoing description of the specific embodiment of the invention will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiment/s herein have been described in terms of preferred embodiment, those skilled in the art will recognize that the embodiment/s 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 suspension system of a vehicle having a pair of leg assemblies (200) interconnected with each other with the help of a triple clamp assembly (15); each of the leg assemblies (200) configured to comprise an inner tube assembly (10AS), an outer tube assembly (20) and a seal assembly (10S); and said outer tube assembly (20) comprising an outer tube (22), an axle mounting bracket (40), a seat pipe (30), and a guide sleeve (50);
wherein,
- the guide sleeve (50) is configured to have an upper face (54), a lower face (55), a stepped opening (50S) at the center and at least a pair of D-profiled cuts (56D) on its outer peripheral surface;
- 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); said bottom face (32C) of the bottom end (32B) of the seat pipe (30) is configured to have a threaded opening (33A);
- the guide sleeve (50) is positioned in between the bottom face (32C) of the seat pipe and the top face (40TS) of the axle mounting clamp (40) so as to guide the seat pipe (30) orthogonally in relation to the axle mounting clamp (40);
- the seat pipe (30) is fixed to the axle mounting clamp (40) with the help of internal threads provided on the seat pipe (30) and the external threads provided on a projected portion (40P) of the axle mounting clamp (40); and
- the axel mounting clamp (40) is fitted at the bottom end (22b) of the outer tube (22) by the fastening means selected from press fitting/interference fitting, threaded joints, followed by welding.

2. The front fork assembly (1000) for suspension system as claimed in claim 1, wherein
- each of the cuts (56D) of the guide sleeve (50) is positioned exactly opposite to each other on the outer peripheral surface of said guide sleeve (50); and
- said D-profiled cuts (56D) are configured to have an orthogonal engagement of the seat pipe (30) with the threaded projection (40P) of the axle clamp (40).

3. The front fork assembly (1000) for suspension system as claimed in claim 2, wherein
- the guide sleeve (50) is configured to have a stepped opening (50S) and said opening (50S) has an annular guiding and resting portion (G) with a step (R); and
- said stepped opening (50S) of the guide sleeve (50) is configured to house the lower end (32B) of the seat pipe (30) inside it eliminating the chances of misalignment of the seat pipe (30) when said seat pipe (30) is threaded with the orthogonal projection (40P) of the axle clamp (40).

4. The front fork assembly (1000) for suspension system as claimed in claim 3, wherein
- the top end (32T) of the seat pipe (30) has a sliding piston (16P) integrated to it 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 a threaded opening (33A) to accommodate a projection (40P) of the axle mounting clamp (40); and
- said bottom face (32C) is configured to have a plain surface with the chamfered profile (32CA) at the inner periphery of said plain surface (32C).

5. The front fork assembly (1000) for suspension system as claimed in claim 4, wherein the sliding piston (16P) is detachably attached to the seat pipe (30) at its top end (32T) by the fastening means.

6. The front fork assembly (1000) for suspension system as claimed in claim 4, wherein
- the axel mounting clamp (40) is configured to have a cylindrical upper portion (42) at its top end (40T), a stem portion (44) and an axle eye portion (40B);
- the axle eye portion (40B) has an axle eye opening (40C) for accommodating the axle of the vehicle;
- the cylindrical upper portion (42) has a flat top surface (40TS) and said top surface (42TS) is configured to have an orthogonal projection (40P) with threads on its outer peripheral surface;
- the projection (40P) having threads (40PT) of the axle clamp (40) is configured to get fitted inside the threaded opening (33A) in the bottom face (32C) of the bottom end (32B) of the seat pipe (30); and
- said orthogonal projection (40P) of the axle clamp (40) holds the uniquely profiled guide sleeve (50) in such way that the said guide sleeve (50) positions the seat pipe (30) in orthogonal direction with respect to the top surface (42TS) of the axle clamp (40).

7. The front fork assembly (1000) for suspension system as claimed in claim 6, wherein
- the ratio of the length (a) of the guiding portion (G) of the guide sleeve (50) to the length (b) of the step (R) of the resting portion of the guide sleeve is in the range of 2.0 to 3.5; and
- the ratio of the outer diameter (d) of the lower end of the seat pipe to the length (a) of the guiding portion (G) of the guide sleeve (50) is in the range of 2.5 to 4.0.

8. The front fork assembly (1000) for suspension system as claimed in claim 1, wherein
- the inner tube assembly (10AS) is configured to comprise of an inner tube (10), a main spring (S), a spacer tube (ST), a piston valve assembly (35), a rebound spring (16) and a fork bolt (10B);
- the annular space between the inner tube assembly and the outer tube assembly is filled with the help of a seal assembly (10S) such that the inner tube assembly (10) is slidably engaged in the outer tube assembly (20);
- and said seal assembly (10S) comprieses a dust seal and an oil seal to avoid the entry of foreign particles into the leg assemblies (200) and leakage of hydraulic fluid therefrom.

9. The front fork assembly (1000) for suspension system as claimed in claim 8, wherein
- the fork bolt (10B) closes the inner tube (10) from the top end;
- the spacer tube (10ST) is placed in the inner tube (10) in a manner such that the one end of the spacer tube (10ST) abuts against the lower face of the fork bolt (10B) and the other end of the spacer tube (10ST) arrests the top end of the main spring (S); and
- the other end of the main spring (S) rests against the top surface of a piston (16P) of the seat pipe (30) of the outer tube assembly (20).

Dated this 30th day of Mar. 2023

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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