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 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 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 suspension system of a two wheeled motor vehicle. More particularly, the invention is related front fork having a mechanism for reducing and eliminating instances of occurrence of cavitation in the oil lock mechanism of a front fork suspension.

Background of the Invention

[002] The front fork for two wheeled motor vehicle are conventionally provided with an oil lock mechanism to prevent metal to metal between the inner and outer tubes in case of full compression of the front fork. This complete compression of a front fork is generally identified as bottoming of a front fork. The conventional oil lock mechanisms as provided, function by creating a hydraulic lock thereby taking advantage of the known fact that liquids are barely compressible.

[003] The oil lock mechanism provided conventionally in a front fork have at least a collar which is constructionaly a part of the inner tube and a locking piece that is constructionaly a part of the outer tube. These components together form a defined space in the front fork generally limited by the profile of the collar, the locking piece and the outer tube. They function together to gather and confine some volume of the damping fluid in the defined space when inner and outer tube are just about to bottom out. This defined space/chamber which facilitates creation of a hydraulic lock is normally not provided with any feature that can relieve a vacuum.

[004] During reexpansion of the front fork under the influence of the expanding main spring of the front fork, a momentary vacuum is created in the defined space/chamber. Ordinarily this vacuum is released when damping fluid rushes in form the limited clearance provided between the collar, the locking piece and the outer tube. In extreme conditions when full compression and expansion is happening in quick succession the clearance provided may not allow sufficient quantity of damping fluid to flow in quickly. This creates an extreme vacuum condition in which the damping fluid boils off under localized low pressure condition created in the defined space/chamber. These damping fluid vapor bubbles so formed, collapse immediately when the pressure rises again to the normal value as the damping fluid flows into the defined space/chamber. This phenomenon is identified as called cavitation. This leads not only to creation of noise but also to deformation the surfaces within the defined space/chamber as the damping fluid vapor bubbles collapse over them.

[005] The front forks of high end two wheeled motor vehicles include a valve mechanism to deal with cavitation in the defined space/chamber of the oil lock mechanism. One such valve mechanism is disclosed in the Indian patent number 255274. In the front fork disclosed by the patent, the component identified as a spindle taper (oil lock piece) has a groove that has orifices located within it. The groove is located along the base of the spindle taper which is attached to the front fork outer tube by a fork bolt. An O-ring mounted in this groove functions to open and close the orifices when pressure difference creates exerts sufficient force over the O-ring to cause it to expand. The problem with this mechanism is that the O-ring which is normally made up of some form of flexible polymer can disintegrate under the action of the high pressure damping fluid flowing out of the orifices. This leads to loss of functionality of the oil lock mechanism and contamination of the damping fluid with O-ring debris. The functionality of this valve mechanism is also affected if the O-ring expands after prolonged exposure to the damping fluid considering that a flexible polymeric material is normally selected for making this O-ring. The O-ring in its expanded state does not function as an effective seal for the orifices given in the groove of the spindle taper.

[006] Another such valve mechanism for a front fork suspension is disclosed by the Indian patent number 329504. In the front fork disclosed in this patent, the spindle taper having a groove with orifices is covered by a flexible check valve. This flexible check valve deforms to allow the damping fluid to flow out of the orifices when a pressure difference is created across it. This flexible check valve can get damaged under the force exerted by the high pressure damping fluid flowing out of the orifices. Here again, the damaged check valve can cause the oil lock mechanism to lose its functionality besides also causing contamination of the damping fluid with its debris.

[007] These prior art valve mechanisms are therefore not only costly but are also not very durable considering the construction of their sub-components and the materials essentially required to be used for manufacturing them. In order to overcome these limitations of the prior art and to resolve the problem of cavitation occurring in the defined space of the oil lock mechanism of conventional front fork, there exists a need for a front fork that has a more durable valve mechanism to ensure proper functioning of its oil lock mechanism.

Objectives of the Invention

[008] The main object of the present invention is to provide a front fork that has a durable valve mechanism which ensures proper functioning of the oil lock mechanism while also resolving the problem of cavitation that occurs in the defined space/chamber of the oil lock mechanism.

[009] Another object of the present invention is to provide, a front fork with a durable valve mechanism ensuring proper functioning of its oil lock mechanism that does not contaminate the damping fluid with its debris as it wears down or is damaged during operation.

[0010] Still another object of the present invention is to provide, a front fork with increased durability.

[0011] It is yet another objective of the invention to provide, a front fork which reduces and eliminates noise associated with cavitation occurring in the oil lock mechanism.

Brief Description of the 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 with reference to the following drawings, wherein

[0013] Figure 1 illustrates a horizontal cut section view of the first preferred embodiment of the front fork in accordance with the current invention.

[0014] Figure 2 illustrates a magnified horizontal cut section view of the oil lock mechanism provided in the first embodiment of the front fork in accordance with the current invention.

[0015] Figures 3a and 3b illustrate a seat pipe as provided in the second preferred embodiment of the front fork in accordance with the current invention.
[0016] Figure 4 illustrates a horizontal cut section view of the third preferred embodiment of the front fork in accordance with the current invention.

[0017] Figure 5 illustrates a magnified horizontal cut section view of the oil lock mechanism provided in the first embodiment of the front fork in accordance with the current invention.

[0018] Figures 5a and 5b illustrate the oil lock piece as provided in the third preferred embodiment of the front fork in accordance with the current invention.

[0019] Figures 6a, 6b, 6c and 6d illustrate the oil lock piece as provided in the fourth preferred embodiment of the front fork in accordance with the current invention.

[0020] Figures 7a, 7b and 7c illustrate the seat pipe as provided in the fifth preferred embodiment of the front fork in accordance with the current invention.

[0021] Figure 8 illustrates a horizontal cut section view of the sixth preferred embodiment of the front fork in accordance with the current invention.

[0022] Figure 9 illustrates a magnified horizontal cut section view of the oil lock mechanism provided in the sixth embodiment of the front fork in accordance with the present invention.

[0023] Figures 10a and 10b illustrate the oil lock piece as provided in the sixth embodiment of the front fork in accordance with the current invention.

[0024] Figure 11 illustrates a magnified horizontal cut section view of the oil lock mechanism provided in the seventh embodiment of the front fork in accordance with the current invention.

[0025] Figure 12 illustrates a magnified horizontal cut section view of the oil lock mechanism provided in the seventh embodiment of the front fork in accordance with the current invention.

[0026] Figure 13 illustrates the oil lock piece as provided in the seventh embodiment of the front fork in accordance with the current invention.

Detailed Description of the Present Invention

[0027] 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.

[0028] The preferred embodiments of the front fork as per the current invention are commonly provided with a main spring (30) that rests on its one end on a spacer tube (20) and on the piston (51) of the seat pipe on its other end. The space tube (20) itself rests on a fork bolt (10) which closes off an open end of the inner tube (100). The seat pipe itself is attached to the outer tube (200) by a fork bolt (80). The outer tube (200) at its closed end is generally provided with a wheel axil mounting hole (120) and a bolt accommodating hole (130). The bolt accommodating hole (130) which is located below the wheel axil mounting hole (120) on the outer tube (200) functions to accommodate a bolt that can be tightened to reduce the clearance given between the two holding teeth of the wheel axil mounting hole (120). The outer tube (200) is also commonly provided with mounting points (140 and 150) at a location adjacent to the open end of the outer tube (200).

[0029] The front fork also has a rebound spring (40) which is accommodated concentrically with the seat pipe between a valve (110)’s accommodating structure and the lower surface of the piston (51). The valve (110) is supported on a stepped surface within the inner tube (100) on its one side and the oil lock collar (90) on its second side such that the oil lock collar (90) is positioned and locked in its place at the open end of the inner tube (100). The valve (110) closes when the front fork rebounds and allows only a minimal amount of damping fluid to leak past it as the front fork re-expands. During rebound, the flow of damping fluid through the orifices (OB1, OB2 and OA, OA1) on the seat pipe creates the required damping force to dissipate the energy absorbed by the main spring (30) during its compression. The rebound spring (40) as the name suggests absorbs the energy that is exerted by the lower surface of the piston (51) and the inner tube (100) (via the valve (110)’s accommodating structure) by getting compressed when front fork rebounds.

[0030] The front fork as per the preferred embodiments of the current invention is also provided with a sealing assembly (300). The sealing assembly (300) includes a guide element (305), an oil seal (304), a washer (303), a circlip (302), and a dust seal (301) that are positioned and mounted in that order in the outer tube (200) over a stepped surface given inside the outer tube (200) such that the dust seal (301) is located and locked in its position at the open end of the outer tube (200).

[0031] Referring to Figs. 1 and 2, the first preferred embodiment of a front fork (1000) for a two wheeled motor vehicle is stated to comprise of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (50), an oil lock collar (90), a valve (110), a sealing assembly (300), an oil lock piece assembly (500), wherein, the inner tube (100) telescopically slides within the outer tube (200); the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (50); the oil lock piece assembly (500) comprises of an oil lock piece (60), a spring (70) and a washer (160); the seat pipe (50) and the oil lock piece (60) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that oil lock piece (60) forms a chamber (II) with the seat pipe (50); the washer (160) is positioned concentrically on the seat pipe (50) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (50) such that it is located between the washer (160) and the base of the oil lock piece (60).

[0032] In the front fork (1000) (refer fig. 2), the frusto-conical curved surface of the seat pipe (50) forming the chamber (II) with the inside surfaces of the oil lock piece (60) has at least one orifice on its frusto-conical curved surface such that the orifice(s) (indicated by OC1, OC2, OC3) provided are on the same plane above the base of the oil lock piece (60). The orifice(s) (indicated by OC1, OC2, OC3) on the frusto-conical curved surface of the seat pipe (50) fluidly connect the chamber (II) with a chamber (I) that is formed by the inner curved surface of the seat pipe (50). The oil lock piece (60) has at least one orifice (indicated by OD1, OD2) on its curved side surface that are compulsorily below the plane on which the orifice(s) (indicated by OC1, OC2, OC3) provided on the frusto-conical curved surface of the seat pipe (50) are located, and the orifice(s) (indicated by OD1, OD2) on its curved side surface of the oil lock piece (60) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (50) and the oil lock piece (60), and the inner curved surface of the outer tube (200).

[0033] When the oil lock collar (90) starts moving back up with the inner tube (100) after full compression of the front fork, the washer (160) that is supported on the spring (70) compresses the spring (70) and moves down within the chamber (II). This allows the damping fluid to flow out of the chamber (II) through the orifice(s) provided on its curved side surface and into the chamber (III) that surrounds the chamber (II). The damping fluid flowing out of the orifice(s) (OD1, OD2) on the curved side surface of the oil lock piece (60) and into the chamber (III) is compensated by flow of equal volume of damping fluid from the chamber (I) in case of the front fork (1000). This volume of flow of damping fluid from the orifice(s) (OD1, OD2) on the curved side surface of the oil lock piece (60) and into the chamber (III) is in addition to that which flows into the defined space of the oil lock mechanism from the clearances given between the oil lock collar (90), the oil lock piece and the outer tube (200) in each of embodiments of the front fork as per the disclosed embodiments of the current invention.

[0034] In the second embodiment of the front fork for a two wheeled motor vehicle in accordance with the current invention, the arrangement as disclosed for the first embodiment is retained with the exception of inclusion of a new seat pipe (2050). The seat pipe (2050) (refer figs. 3a and 3b) has one stepped surface in place of the frusto-conical surface as provided in the seat pipe (50) of the first preferred embodiment. The seat pipe (2050) is provided with at least one orifice (indicated by OC1, OC2, OC3) on its stepped surface for establishing a fluid connection between a chamber (I) (defined by the inside curved surface of the seat pipe (2050)) and a chamber (II) (defined by inside surface of the oil lock collar (60) and the seat pipe (2050)). The seat pipe (2050), like the seat pipe (50) is otherwise also provided with the orifice(s) (indicated by OA, OA1) at a location below the piston (51) at one end of the seat pipe but above the plane in which orifice(s) (indicated by OB1, OB2) are located. The orifice(s) (indicated by OB1, OB2) are in turn located above the stepped portion having the orifice(s) (indicated by OC1, OC2, OC3). The front fork (2000) hence can be stated to be comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (2050), an oil lock collar (90), a valve (110), a sealing assembly (300), an oil lock piece assembly (500), wherein, the inner tube (100) can telescopically slide within the outer tube (200), the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (2050), the oil lock piece assembly (500) comprises of an oil lock piece (60), a spring (70) and a washer (160); the seat pipe (2050) and the oil lock piece (60) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (60) forms a chamber (II) with the seat pipe (2050).

[0035] In the front fork (2000), the washer (160) is positioned concentrically on the seat pipe (2050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (2050) such that it is located between the washer (160) and the base of the oil lock piece (60). The stepped surface of the seat pipe (2050) forming the chamber (II) with the inside surfaces of the oil lock piece (60) has at least one orifice on its stepped surface such that the orifices (indicated by OC1, OC2, OC3) provided are on the same plane above the base of the oil lock piece (60). The orifice(s) (indicated by OC1, OC2, OC3) on the stepped surface of the seat pipe (2050) fluidly connect the chamber (II) with a chamber (I) that is formed by the inner curved surface of the seat pipe (2050). The oil lock piece (60) has at least one orifice (indicated by OD1, OD2) on its curved side surface that are compulsorily below the plane on which the orifice(s) (indicated by OC1, OC2, OC3) provided on the stepped surface of the seat pipe (2050) are located, and the orifice(s) (indicated by OD1, OD2) on the curved side surface of the oil lock piece (60) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (2050) and the oil lock piece (60), and the inner curved surface of the outer tube (200).

[0036] The seat pipe (2050) of the front fork (2000) has its orifice(s) (indicated by OC1, OC2, OC3) on its stepped portion. In this orientation of the orifice(s) (indicated by OC1, OC2, OC3), the damping fluid can flow between the chamber (II) and the chamber (I) more freely. During operation of the front fork (2000), when the oil lock collar (90) starts moving back up with the inner tube (100) after full compression of the front fork, the washer (160) that is supported on the spring (70) compresses the spring (70) and moves down within the chamber (II). This allows the damping fluid to flow out of the chamber (II) through the orifice(s) (OD1, OD2) provided on its curved side surface and into the chamber (III) that surrounds the chamber (II). The damping fluid flowing out of the orifice(s) (OD1, OD2) on the curved side surface of the oil lock piece (2060) and into the chamber (III) is compensated by flow of equal volume of damping fluid from the chamber (I) in case of the front fork (2000). This flow happens via the orifices indicated by OC1, OC2, and OC3, as provided on the stepped surface of the seat pipe (2050). This volume of flow of damping fluid from the orifice(s) (OD1, OD2) on the curved side surface of the oil lock piece (2060) and into the chamber (III) is in addition to that which flows into the defined space of the oil lock mechanism from the clearances given between the oil lock collar (90), the oil lock piece and the outer tube (200) in each of embodiments of the front fork as per the disclosed embodiments of the current invention.
[0037] Referring Figs 4, 5, 5a and 5b, a front fork (3000) which is the third embodiment of the front fork for a two wheeled motor vehicle in accordance with the current invention can be stated to be comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (3050), an oil lock collar (90), a valve (110), a sealing assembly (300), an oil lock piece assembly (3500), wherein, the inner tube (100) telescopically slide within the outer tube (200); the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (3050); the oil lock piece assembly (3500) comprises of an oil lock piece (3060), a spring (70) and a washer (160); the seat pipe (3050) and the oil lock piece (3060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that there is a clearance (C) between the seat pipe (3050) and the open end of the oil lock piece (3060); the inside surface of the oil lock piece (3060) forms a chamber (II) with the seat pipe (3050).

[0038] In the front fork (3000) (refer fig. 5), the washer (160) is positioned concentrically on the seat pipe (3050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (3050) such that it is located between the washer (160) and the base of the oil lock piece (3060). The clearance (C) between the frusto-conical curved surface of the seat pipe (3050) and the oil lock piece (3060) fluidly connects the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (3050) and the oil lock piece (3060), and the inner curved surface of the outer tube (200). The clearance (C) between the frusto-conical curved surface of the seat pipe (3050) and the oil lock piece (3060) is ideally in the range of 0.5 mm to 2.5 mm. The oil lock piece (3060) has at least one orifice (OD1, OD2) on its curved side surface and the orifices on the curved side surface of the oil lock piece (3060) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (3050) and the oil lock piece (3060), and the inner curved surface of the outer tube (200).

[0039] The spring (70), the washer (160), the seat pipe (3050) and the oil lock piece (3060) once assembled in the front fork (3000) form a single unit that permits damping fluid flow from a higher level in the chamber (III) (via clearance (C)) to a lower level in chamber (III) (via orifice(s) OD1, OD2). This damping fluid flow happens when value of difference in pressure below the washer (160) than that above it, attains a certain threshold value, allowing the spring (70) to be compressed by the washer (160) till the washer (160) achieves the level of the orifice(s) (OD1, OD2). The condition of pressure below the washer (160) being lower than that above it arises when the lower end of the inner tube (100) moves past the level plane of the orifice(s) (OD1, OD2) while the main spring (30) is decompressing. This condition is maintained till the lower end of the inner tube (100) has crossed the clearance indicated by (C). The front fork (3000) has a seat pipe (3050) that is comparably easy to manufacture as it has no orifices on its frusto-conical curved surface. The volume of material removed from the oil lock piece (3060) for creating the clearance (C) also makes the oil lock piece (3060) comparatively lighter in weight.

[0040] In the fourth embodiment of the front fork for a two wheeled motor vehicle in accordance with the current invention, the arrangement as disclosed for the first embodiment is retained with the exception of inclusion of a seat pipe (4050) and an oil lock piece (4060) which forms a sub-component of a new oil lock piece assembly (4500). The seat pipe (4050) does not have any orifices on its frusto-conical surface. The oil lock piece (4060) (refer figs. 6a and 6b) of the new oil lock piece assembly (4500) is stated to have at least one orifice (OD1, OD2) on its curved side surface that is compulsorily below the plane of the frusto-conical curved surface of a seat pipe (4050). The oil lock piece (4060) further has longitudinal recess(s) on its curved surface that extend from one end of its inner curved surface to a plane above the orifice(s) (OD1, OD2) provided of the oil lock piece (4060). The front fork (4000) hence can be stated to be comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (4050), an oil lock collar (90), a valve (110), a sealing assembly (300), an oil lock piece assembly (4500), wherein, the inner tube (100) telescopically slide within the outer tube (200); the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (4050); the oil lock piece assembly (4500) comprises of an oil lock piece (4060), a spring (70) and a washer (160).

[0041] In the front fork (4000), the seat pipe (4050) and the oil lock piece (4060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (4060) forms a chamber (II) with the seat pipe (4050). The washer (160) is positioned concentrically on the seat pipe (4050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (4050) such that it is located between the washer (160) and the base of the oil lock piece (4060). The oil lock piece (4060) has at least one orifice (indicated by OD1, OD2, OD3) on its curved side surface that is compulsorily below the plane of the frusto-conical curved surface of the seat pipe (4050). The orifice(s) on the curved side surface of the oil lock piece (4060) connect the chamber (II) with the chamber (III). The oil lock piece (4060) has longitudinal recess(es) on its curved surface that proceed from one end of its inner curved surface to a plane above the orifice(s) (indicated by OD1, OD2, OD3) provided of the oil lock piece (4060). The longitudinal recesses in the oil lock piece (4060) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (4050) and the oil lock piece (4060), and the inner curved surface of the outer tube (200). The longitudinal recess(es) (R1, R2, R3) in the oil lock piece (4060) connecting the chamber (II) with chamber (III) may be provided with a helical shape (refer Figs. 6c and 6d).

[0042] The spring (70), the washer (160), the seat pipe (4050) and the oil lock piece (4060) once assembled in the front fork (4000) form a single unit that permits damping fluid flow from a higher level in the chamber (III) (via recess(es) indicated by R1, R2, R3, R4) to a lower level in chamber (III) (via orifice(s)indicated by OD1, OD2, OD3). This damping fluid flow happens when value of difference in pressure below the washer (160) than that above it, attains a certain threshold value, allowing the spring (70) to be compressed by the washer (160) till the washer (160) achieves the level of the orifice(s) (OD1, OD2, OD3). The condition of pressure below the washer (160) being lower than that above it arises when the lower end of the inner tube (100) moves past the level plane of the orifice(s) (OD1, OD2, OD3) while the main spring (30) is decompressing. This condition is maintained till the lower end of the inner tube (100) has crossed the recess (es) indicated by R1, R2, R3, R4. The front fork (4000) has a seat pipe (4050) that is comparably easy to manufacture as it has no orifices on its frusto-conical curved surface. The volume of material removed from the oil lock piece (4060) for creating the recess (es) indicated by R1, R2, R3, R4 also makes the oil lock piece (4060) comparatively lighter in weight. The reduction in rigidity of the oil lock piece (4060) is comparatively lower given that the amount of material removed for creating the recess (es) indicated by R1, R2, R3, R4 is lower.

[0043] In the fifth embodiment of the front fork for a two wheeled motor vehicle in accordance with the current invention, the arrangement as disclosed for the first embodiment is retained with the exception of inclusion of a seat pipe (5050). The seat pipe (5050) (refer figs. 7a, 7b and 7c) has a cylindrical curved surface with at least one longitudinal recess(es) that starts below the plane on which damping orifices (OB1, OB2) are provided on the seat pipe (5050) and end at a stepped portion of the seat pipe (5050). The front fork (5000) hence can be stated to be comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (5050), an oil lock collar (90), a valve (110), a sealing assembly (300), an oil lock piece assembly (500), wherein, the inner tube (100) telescopically slide within the outer tube (200); the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (5050); the oil lock piece assembly (500) comprises of an oil lock piece (60), a spring (70) and a washer (160); the seat pipe (5050) and the oil lock piece (60) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (60) forms a chamber (II) with the seat pipe (5050); the washer (160) is positioned concentrically on the seat pipe (5050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (5050) such that it is located between the washer (160) and the base of the oil lock piece (60).

[0044] In the front fork (5000), the cylindrical curved surface of the seat pipe (5050) has at least one longitudinal recess (C1, C2, C3, C4) that starts below the plane on which damping orifices (OB1, OB2) are provided on the seat pipe (5050) and end at the stepped portion of the seat pipe (5050). The longitudinal recesses (C1, C2, C3, C4) on the seat pipe (5050) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (5050) and the oil lock piece (60), and the inner curved surface of the outer tube (200). The oil lock piece (60) has at least one orifice(s) (OD1, OD2) on its curved side surface that is compulsorily below the plane of the stepped portion of the seat pipe (5050).

[0045] The spring (70), the washer (160), the seat pipe (5050) and the oil lock piece (5060) once assembled in the front fork (5000) form a single unit that permits damping fluid flow from a higher level in the chamber (III) (via longitudinal recess(es) indicated by C1, C2, C3, C4) to a lower level in chamber (III) (via orifice(s)indicated by OD1, OD2). This damping fluid flow happens when value of difference in pressure below the washer (160) than that above it, attains a certain threshold value, allowing the spring (70) to be compressed by the washer (160) till the washer (160) achieves the level of the orifice(s) (OD1, OD2). The condition of pressure below the washer (160) being lower than that above it arises when the lower end of the inner tube (100) moves past the level plane of the orifice(s) (OD1, OD2) while the main spring (30) is decompressing. This condition is maintained till the lower end of the inner tube (100) has moved past the recess(es) indicated by C1, C2, C3, C4. The volume of material removed from the seat pipe (5050) for creating the recess(es) indicated by C1, C2, C3, C4 makes the seat pipe (5050) comparatively lighter in weight. The reduction in rigidity of the seat pipe (5050) is minimal given that the amount of material removed for creating the recess(es) indicated by C1, C2, C3, C4 is very less. The seat pipe (5050) can therefore continue to function as a load bearing component.

[0046] Referring Figs 8, 9, 10a and 10b, a front fork (6000) which is the sixth embodiment of the front fork for a two wheeled motor vehicle in accordance with the current invention can be stated to be comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (6050), an oil lock collar (6090), a valve (110), a sealing assembly (300), an oil lock piece assembly (6500), wherein, the inner tube (100) telescopically slide within the outer tube (200); the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (6050); the oil lock piece assembly (6500) comprises of an oil lock piece (6060), a spring (70) and a washer (160); the seat pipe (6050) and the oil lock piece (6060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (6060) forms a chamber (II) with the seat pipe (6050); the washer (160) is positioned concentrically on the seat pipe (6050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (6050) such that it is located between the washer (160) and the base of the oil lock piece (6060).

[0047] In the front fork (6000) (refer fig. 8), the oil lock piece (6060) has at least one orifice(s) (OD1, OD2) on its curved side surface that is compulsorily below the plane on which an annular groove is provided on the inside surface of the oil lock piece (6060); and the oil lock piece (6060) is provided with inclined holes (IH1, IH2, IH3) that open into the annular groove thereby connecting a chamber (III) that is formed between the outer curved surface of the seat pipe (6050) and the oil lock piece (6060), and the inner curved surface of the outer tube (200) with the chamber (II).

[0048] The spring (70), the washer (160), the seat pipe (6050) and the oil lock piece (6060) once assembled in the front fork (6000) form a single unit that permits damping fluid flow from a higher level in the chamber (III) (via inclined holes indicated by IH1, IH2, IH3) to a lower level in chamber (III) (via orifice(s) indicated by OD1, OD2). This damping fluid flow happens when value of difference in pressure below the washer (160) than that above it, attains a certain threshold value, allowing the spring (70) to be compressed by the washer (160) till the washer (160) achieves the level of the orifice(s) (OD1, OD2). The condition of pressure below the washer (160) being lower than that above it arises when the lower end of the inner tube (100) moves past the level plane of the orifice(s) (OD1, OD2) while the main spring (30) is decompressing. This condition is maintained till the lower end of the inner tube (100) has moved past the inclined holes indicated by IH1, IH2, IH3. The volume of material removed from the oil lock piece (6060) for creating the inclined holes indicated by IH1, IH2, IH3 makes the oil lock piece (6060) comparatively lighter in weight. The reduction in rigidity of the oil lock piece (6060) is minimal given that the amount of material removed for creating the inclined holes indicated by IH1, IH2, IH3 is very less.

[0049] Referring Figs 11, 12 and 13, a front fork (7000) which is the seventh embodiment of the front fork for a two wheeled motor vehicle in accordance with the current invention can be stated to be comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (50), an oil lock collar (90), a valve (110), a sealing assembly (300), an oil lock piece assembly (7500), wherein, the inner tube (100) telescopically slide within the outer tube (200); the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (50); the oil lock piece assembly (7500) comprises of an oil lock piece (7060), a spring (70) and a washer (160); the seat pipe (50) and the oil lock piece (7060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (7060) forms a chamber (II) with the seat pipe (50); the washer (160) is positioned concentrically on the seat pipe (50) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (50) such that it is located between the washer (160) and the base of the oil lock piece (7060).

[0050] In the front fork (7000) (refer fig. 12), the frusto-conical curved surface of the seat pipe (50) forming the chamber (II) with the inside surfaces of the oil lock piece (7060) has at least one and a maximum of four evenly distributed orifices (OC1, OC2, OC3, OC4) on its frusto-conical curved surface such that the orifices provided are on the same plane above the base of the oil lock piece (7060). The orifices (OC1, OC2, OC3, OC4) on the frusto-conical curved surface of the seat pipe (50) fluidly connect the chamber (II) with a chamber (I) that is formed by the inner curved surface of the seat pipe (50). The oil lock piece (7060) has a plurality of orifices (OD1, OD2 and more) on its curved side surface that are evenly distributed in a spiral/helical form spread across different planes and are compulsorily below the plane on which the orifices provided on the frusto-conical curved surface of the seat pipe (50) are located. The orifices (OD1, OD2 and more) on its curved side surface of the oil lock piece (7060) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (50) and the oil lock piece (7060), and the inner curved surface of the outer tube (200).

[0051] The spring (70), the washer (160), the seat pipe (50) and the oil lock piece (7060) once assembled in the front fork (7000) form a single unit that permits damping fluid flow from the chamber (I) into the chamber (II) (via orifice(s) indicated by OC1, OC2, OC3, OC4) and then to a lower level in chamber (III) (via orifice(s) OD1, OD2 and more). This damping fluid flow happens when value of difference in pressure below the washer (160) than that above it, attains a certain threshold value, allowing the spring (70) to be compressed by the washer (160) till the washer (160) achieves the level of the orifice(s) (OD1, OD2 and more). The condition of pressure below the washer (160) being lower than that above it arises when the lower end of the inner tube (100) moves past the level plane of the orifice(s) (OD1, OD2 and more) while the main spring (30) is decompressing. This condition is maintained till pressure imbalance is removed by fluid flowing in from the chamber (I). Given the spiral distribution of orifices (OD1, OD2 and more) on the oil lock piece (7060), the rate of damping fluid flow achieved varies directly in accordance with the number of orifices uncovered by washer (160) during its compression of the spring (70). A higher pressure difference between the chamber (I) will allow for greater number of orifices to be uncovered on the oil lock piece (7060). The spiral distribution of orifices on the oil lock piece (7060) ensures that no single portion of the oil lock piece (7060) becomes excessively weak due to material removal. The presence of multiple orifices on the oil lock piece (7060) helps in faster movement of damping fluid from the chamber (I) to chamber (III) via chamber (II).

[0052] For all the embodiments of the front fork for a two wheeled motor vehicle the washer (160) has to have an inside and outside cylindrical curved surface with surface smoothness (Ra) value greater than or equal to 25 µm. This is necessary so as to allow the washer to freely up and down within the chamber (II).

[0053] The technical advantages obtained from the disclosed invention are:-
- The front fork for suspension system of a vehicle can prevent the occurrence of cavitation in the oil lock mechanism.
- The front fork for suspension system of a vehicle has an oil lock mechanism with a very high durability.
- The front fork for suspension system of a vehicle has an oil lock mechanism which does not contaminate the damping fluid with debris as it wears down or gets damaged during its operation.
- The front fork suspension system of a vehicle operates smoothly without emitting noise resulting from occurrence of cavitation in the oil lock mechanism.

[0054] The foregoing description of the specific embodiments 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 also 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 (1000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (50), an oil lock collar (90), a valve (110), a sealing assembly (300) and an oil lock piece assembly (500); wherein,
- the inner tube (100) telescopically slides within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (50);
- the oil lock piece assembly (500) comprises of an oil lock piece (60), a spring (70) and a washer (160);
- the seat pipe (50) and the oil lock piece (60) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that oil lock piece (60) forms a chamber (II) with the seat pipe (50);
- the washer (160) is positioned concentrically on the seat pipe (50) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (50) such that it is located between the washer (160) and the base of the oil lock piece (60);
- the frusto-conical curved surface of the seat pipe (50) forming the chamber (II) with the inside surfaces of the oil lock piece (60) has at least one orifice on its frusto-conical curved surface such that the orifices provided are on the same plane above the base of the oil lock piece (60);
- the orifices on the frusto-conical curved surface of the seat pipe (50) fluidly connect the chamber (II) with a chamber (I) that is formed by the inner curved surface of the seat pipe (50);
- the oil lock piece (60) has at least an orifice on its curved side surface that are compulsorily below the plane on which the orifices provided on the frusto-conical curved surface of the seat pipe (50) are located, and
- the orifice(s) on its curved side surface of the oil lock piece (60) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (50) and the oil lock piece (60), and the inner curved surface of the outer tube (200).

2. A front fork (2000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (2050), an oil lock collar (90), a valve (110), a sealing assembly (300) and an oil lock piece assembly (500); wherein,
- the inner tube (100) telescopically slide within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (2050);
- the oil lock piece assembly (500) comprises of an oil lock piece (60), a spring (70) and a washer (160);
- the seat pipe (2050) and the oil lock piece (60) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (60) forms a chamber (II) with the seat pipe (2050);
- the washer (160) is positioned concentrically on the seat pipe (2050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (2050) such that it is located between the washer (160) and the base of the oil lock piece (60);
- the stepped surface of the seat pipe (2050) forming the chamber (II) with the inside surfaces of the oil lock piece (60) has at least an orifice on its stepped surface such that the orifices provided are on the same plane above the base of the oil lock piece (60);
- the orifices on the stepped surface of the seat pipe (2050) fluidly connect the chamber (II) with a chamber (I) that is formed by the inner curved surface of the seat pipe (2050);
- the oil lock piece (60) has at least an orifice on its curved side surface that are compulsorily below the plane on which the orifices provided on the stepped surface of the seat pipe (2050) are located; and
- the orifices on the curved side surface of the oil lock piece (60) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (2050) and the oil lock piece (60), and the inner curved surface of the outer tube (200).

3. A front fork (3000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (3050), an oil lock collar (90), a valve (110), a sealing assembly (300) and an oil lock piece assembly (3500); wherein,
- the inner tube (100) telescopically slide within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (3050);
- the oil lock piece assembly (3500) comprises of an oil lock piece (3060), a spring (70) and a washer (160);
- the seat pipe (3050) and the oil lock piece (3060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that there is a clearance (C) between the seat pipe (3050) and the open end of the oil lock piece (3060);
- the inside surface of the oil lock piece (3060) forms a chamber (II) with the seat pipe (3050);
- the washer (160) is positioned concentrically on the seat pipe (3050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (3050) such that it is located between the washer (160) and the base of the oil lock piece (3060);
- the clearance (C) between the frusto-conical curved surface of the seat pipe (3050) and the oil lock piece (3060) fluidly connects the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (3050) and the oil lock piece (3060), and the inner curved surface of the outer tube (200);
- the oil lock piece (3060) has at least an orifice on its curved side surface, and
- the orifices on the curved side surface of the oil lock piece (3060) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (3050) and the oil lock piece (3060), and the inner curved surface of the outer tube (200).

4. A front fork (4000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (4050), an oil lock collar (90), a valve (110), a sealing assembly (300) and an oil lock piece assembly (4500); wherein,
- the inner tube (100) telescopically slide within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (4050);
- the oil lock piece assembly (4500) comprises of an oil lock piece (4060), a spring (70) and a washer (160);
- the seat pipe (4050) and the oil lock piece (4060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (4060) forms a chamber (II) with the seat pipe (4050);
- the washer (160) is positioned concentrically on the seat pipe (4050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (4050) such that it is located between the washer (160) and the base of the oil lock piece (4060);
- the oil lock piece (4060) has at least an orifice on its curved side surface that is compulsorily below the plane of the frusto-conical curved surface of the seat pipe (4050),
- the orifices on the curved side surface of the oil lock piece (4060) connect the chamber (II) with the chamber (III),
- the oil lock piece (4060) has at least a longitudinal recess on its inner curved surface that proceed from one end of its inner curved surface to a plane above the orifices provided of the oil lock piece (4060), and
- the longitudinal recesses in the oil lock piece (4060) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (4050) and the oil lock piece (4060), and the inner curved surface of the outer tube (200).

5. A front fork (5000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (5050), an oil lock collar (90), a valve (110), a sealing assembly (300) and an oil lock piece assembly (500); wherein,
- the inner tube (100) telescopically slide within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (5050);
- the oil lock piece assembly (500) comprises of an oil lock piece (60), a spring (70) and a washer (160);
- the seat pipe (5050) and the oil lock piece (60) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (60) forms a chamber (II) with the seat pipe (5050);
- the washer (160) is positioned concentrically on the seat pipe (5050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (5050) such that it is located between the washer (160) and the base of the oil lock piece (60);
- the cylindrical curved surface of the seat pipe (5050) has at least a longitudinal recess that starts below the plane on which damping orifices (OB1, OB2) are provided on the seat pipe (5050) and end at the stepped portion of the seat pipe (5050);
- the longitudinal recesses on the seat pipe (5050) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (5050) and the oil lock piece (60), and the inner curved surface of the outer tube (200); and
- the oil lock piece (60) has at least one orifice(s) on its curved side surface that is compulsorily below the plane of the stepped portion of the seat pipe (5050).

6. A front fork (6000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (6050), an oil lock collar (6090), a valve (110), a sealing assembly (300) and an oil lock piece assembly (6500); wherein,
- the inner tube (100) telescopically slide within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (6050);
- the oil lock piece assembly (6500) comprises of an oil lock piece (6060), a spring (70) and a washer (160);
- the seat pipe (6050) and the oil lock piece (6060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (6060) forms a chamber (II) with the seat pipe (6050);
- the washer (160) is positioned concentrically on the seat pipe (6050) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (6050) such that it is located between the washer (160) and the base of the oil lock piece (6060);
- the oil lock piece (6060) has at least one orifice(s) on its curved side surface that is compulsorily below the plane on which an annular groove is provided on the inside surface of the oil lock piece (6060), and
- the oil lock piece (6060) is provided with inclined holes that open into the annular groove thereby connecting a chamber (III) that is formed between the outer curved surface of the seat pipe (6050) and the oil lock piece (6060), and the inner curved surface of the outer tube (200) with the chamber (II).

7. A front fork (7000) for suspension system of a vehicle comprising of an inner tube (100), an outer tube (200), a main spring (30), a seat pipe (50), an oil lock collar (90), a valve (110), a sealing assembly (300) and an oil lock piece assembly (7500); wherein,
- the inner tube (100) telescopically slide within the outer tube (200);
- the main spring (30) is supported on its one end by the inner tube (100) and on its second end by a piston (51) of the seat pipe (50);
- the oil lock piece assembly (7500) comprises of an oil lock piece (7060), a spring (70) and a washer (160);
- the seat pipe (50) and the oil lock piece (7060) are concentrically aligned and fixed to one closed end of the outer tube (200) by a fork bolt (80) such that the oil lock piece (7060) forms a chamber (II) with the seat pipe (50);
- the washer (160) is positioned concentrically on the seat pipe (50) within the chamber (II) and the spring (70) is located concentrically with the seat pipe (50) such that it is located between the washer (160) and the base of the oil lock piece (7060);
- the frusto-conical curved surface of the seat pipe (50) forming the chamber (II) with the inside surfaces of the oil lock piece (7060) has at least one and a maximum of four evenly distributed orifices on its frusto-conical curved surface such that the orifices provided are on the same plane above the base of the oil lock piece (7060);
- the orifices on the frusto-conical curved surface of the seat pipe (50) fluidly connect the chamber (II) with a chamber (I) that is formed by the inner curved surface of the seat pipe (50);
- the oil lock piece (7060) has a plurality of the orifice on its curved side surface that are evenly distributed in a spiral/helical form spread across different planes and are compulsorily below the plane on which the orifices provided on the frusto-conical curved surface of the seat pipe (50) are located, and
- the orifices on its curved side surface of the oil lock piece (7060) connect the chamber (II) with a chamber (III) that is formed between the outer curved surface of the seat pipe (50) and the oil lock piece (7060), and the inner curved surface of the outer tube (200).

8. The front fork suspension system of a vehicle as claimed in claim 4, wherein the longitudinal recess(es) on the inner curved surface of the oil lock piece (4060) which connect the chamber (II) with chamber (III) have a helical shape.

9. The front fork for suspension system of a vehicle as claimed in any of the above claims, wherein the washer (160) has inside and outside cylindrical curved surface with a smooth surface having roughness value (Ra) not more than 25 µm for its smooth movement.

10. The front fork for suspension system of a vehicle as claimed in claim 9; wherein,
- the valve (110) is supported on a stepped surface within the inner tube (100) on its one side and the oil lock collar (90) on its other side such that the oil lock collar (90) is placed and locked in its position at the open end of the inner tube (100); and
- the sealing assembly (300) includes a guide element (305), an oil seal (304), a washer (303), a circlip (302), and a dust seal (301) positioned in that order in the outer tube (200) over a stepped surface given inside the outer tube (200) such that the dust seal (301) is located and locked in its position at the open end of the outer tube (200).

11. The front fork (3000) for suspension system of a vehicle as claimed in claim 3, wherein the clearance (C) between the frusto-conical curved surface of the seat pipe (3050) and the oil lock piece (3060) is in the range of 0.5 mm to 2.5 mm.

Dated this 28th day of Dec. 2021

Sahastrarashmi Pund
Head - IPR
Endurance Technologies Ltd.

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