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

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

TITLE OF THE INVENTION

“AN INVERTED FRONT FORK FOR SUSPENSION SYSTEM OF A MOTOR VEHICLE”

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

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

Field of Invention

[001] The present invention is related to suspension system of a motor vehicle. More particularly, the present invention relates to an inverted front fork with preload adjustment and damping control system for suspension unit of two and three wheeled vehicles.

Background of the Invention

[002] The conventional inverted front fork has at least one main spring to absorb the energy transferred from the motor vehicle’s wheel when it encounters a road surface irregularity. It also has at least a damping assembly that dissipates the energy absorbed by the main spring during its compression and expansion. This damping assembly prevents excessive oscillations that would result from un-damped compression and expansion of the main spring. Given the difficulty in altering the characteristics of the main spring and the damping assembly after the inverted front fork is assembled, engineers and/or persons skilled in the art ordinarily have to decide and fix one general purpose setting for both the main spring’s preload and the damping assembly’s compression and rebound damping. The predefined general purpose setting decide the suitability of driving a vehicle in a given loading and driving surface condition. Hence, it tends to affect the vehicle’s classification as well viz. off-road vehicles, racing vehicles, etc.

[003] During development of such conventional inverted front fork, multiple prototypes have to be built and tested in order to arrive at the ideal damping force settings. This needs for building and testing multiple prototypes arises primarily because it is not possible to arrive at an accurate figure for damping force generated by an inverted front fork by using only theoretical methods. Ordinarily, a single set of inverted front fork is therefore repeatedly disassembled and reassembled with new sub-components and tested again and again until the ideal value of pre-compression of the main spring and damping force is achieved. This manner of developing an inverted front fork to arrive at the pre-compression load of the main spring and ideal damping force setting consumes both time and money before a version of an inverted front fork is finalized. Even after extensive prototyping and testing the finalized inverted front fork cannot be said to be ideally suited for driving in any condition other than the driving condition in which it was tested.

[004] While the inverted front fork pre-compression and damping settings get fixed after the development phase, the requirement of a motor vehicle user doesn’t always remain the same. Expert riders, depending upon their determined requirement for a particular trip, may want to adjust pre-compression of the main spring and damping settings of their suspensions as per the different requirement viz. weight of the rider or road irregularity conditions. These changes may be carried out in coordination with engineers at well-equipped garages. In order to ensure safety of operation, such post manufacturing changes require excessive expenditure of both time and money. As such, even though the change may be required for a trip, the required expenditure of time and money makes the same unjustifiable for most of the riders. The conventional solutions to this problem require provision of complex mechanisms that make the inverted front fork difficult and harder to manufacture and quite costlier to provide in low end motor vehicles.

[005] Hence, there exists a long pending unmet requirement of providing an inverted front fork wherein the pre-load of the main spring and damping settings can be adjusted safely and conveniently with ease of operation by the rider and is economic in nature.
Objectives of the Present Invention

[006] The main objective of the present invention is to provide an inverted front fork with pre-load adjustment and damping control for suspension system of a two wheeled motor vehicle.

[007] Another objective of the present invention is to provide an inverted front fork having separate mechanisms for adjusting the pre-load of the main spring and damping of the suspension system of a two wheeled vehicle.

[008] Another objective of the present invention is to provide an inverted front fork with preload adjustment and damping control wherein the preload of the main spring can be adjusted without disturbing the damping setting of the suspension system of the two wheeled vehicles and vice-versa.

[009] Still another objective of the present invention is to provide an inverted front fork with damping control wherein the preload and damping settings can be adjusted safely, conveniently and at ease of the motor vehicle users/riders and also is an economical solution.

[0010] Further objective of the present invention is to provide superior ride comfort to the user / rider of the vehicle at low cost.

Brief Description of Drawings

[0011] 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

[0012] Figure 1a discloses the front break view of the inverted front fork suspension as per the first embodiment of the present invention.

[0013] Figure 1b presents the cut-sectional view of the inverted front fork suspension as disclosed in Fig. 1a in accordance with the first embodiment of the present invention.

[0014] Figures 2a, 2b and 2c describes the isometric view, front view and sectional view, respectively of the pre-load adjustment assembly of the first embodiment of the present invention.

[0015] Figures 3a and 3b discloses the isometric view and cut-section view, respectively of the fork bolt of the pre-load adjustment assembly respectively as per the first embodiment of the present invention.

[0016] Figures 4a and 4b discloses the isometric view and cut-section view, respectively of the cam adjuster of the pre-load adjustment assembly in accordance with the first embodiment of the present invention.

[0017] Figure 5 discloses the cut-sectional break view of the second embodiment of the inverted front fork suspension of the present invention.

[0018] Figures 6a, 6b and 6c describes the isometric view, front view and the cut-sectional view, respectively of the pre-load adjustment assembly of the second embodiment of the present invention.

[0019] Figures 7a and 7b discloses the isometric view and cut-section view, respectively of the fork bolt of the pre-load adjustment assembly as per the second embodiment of the present invention.

[0020] Figures 7c and 7d discloses the isometric view and cut-sectional view, respectively of the sleeve of the pre-load adjustment assembly as per the second embodiment of the present invention.

Description of the Present Invention

[0021] The invention will now be described in detail with reference to the accompanying drawings which must not be viewed as restricting the scope and ambit of the invention. Referring to Figs. 1 and 2, in accordance with the present invention, an inverted front fork (500) for suspension system of a motor vehicle comprises of an outer tube (15), an inner tube (25), an axle mounting bracket (40), a main spring (30), a pre-load adjustment assembly (50), a damping assembly (DA), a piston rod assembly (60) and a cartridge tube assembly (120).

[0022] The inverted front fork (500) has the inner tube (25) positioned so as to have the same central axis as that of the outer tube (15) and is free to reciprocate telescopically within the outer tube (15). The lower end of the inner tube (25) is fixedly connected to the axle mounting bracket (40) and the upper end of the said inner tube (25) is free to slide in a telescopic manner within the outer tube (15). The said outer tube (15) is configured to have a pair of diametrically opposite longitudinal slots (15S) formed over its top inner peripheral surface. The cartridge tube assembly (120) is positioned in the inner tube (25) wherein the said cartridge tube assembly (120) includes a cartridge tube (35), an adapter bush (45), a base valve (55), a base tap (65) and a socket headed bolt (75). The cartridge tube (35) of the cartridge tube assembly (120) is a hollow cylindrical tube having a lower open end (E1) and an upper open end (E2) and is fixed concentrically within the inner tube (25). The cartridge tube (35) is fixed within the inner tube (25) in a manner such that the outer peripheral surface of the cartridge tube (35) forms an annulus chamber (C) with the inner peripheral surface of the inner tube (25).

[0023] The base tap (65) is fixed within the cartridge tube (35) at its lower end and locked there with the help of the socket headed bolt (75). The base valve (55) is concentrically placed over a stem portion of the base tap (65) and locked there with the help of a locking nut (76) wherein the locking nut is screwed with the stem portion of the base tap (65). The adapter bush (45) is fitted to the upper open end (E2) of the cartridge tube and is positively locked there with the help of spinning process. The adaptor bush (45) is configured to have a cylindrical body (45B) at its lower end wherein a circular flange (45F) extends radially around the top end of the cylindrical body (45B). An annular collar (45C) projects out from the circular flange (45F) in a manner such that a fluid reservoir (45R) is formed within the inner peripheral surface of the annular collar (45C). The cylindrical body (45B) has a central opening to facilitate the passage of a piston rod (80) of the damping adjustment assembly (DA).

[0024] The damping adjustment assembly (DA) comprises of an adjuster knob (5), an adjuster screw (7), a locking bush (9), a set of spherical balls (B), a tube retainer (11), a detent spring (not shown) and an adjuster tube (13). The adjuster knob (5) is connected to the top portion of an adjuster screw (7) as shown in Fig. 1b. The adjuster screw (7) accommodates within its central opening, the set of spherical balls (B) and the detent spring given in between them. The spherical balls (B) lock with matching notches given within the locking bush (9). The locking bush (9) is mounted concentrically with the lower portion of the adjuster screw (7) within a cavity of the fork bolt (10). The said adjuster screw (7) is threadedly connected with the tube retainer (11) at its lower end. The tube retainer (11) is fixedly connected with the adjuster tube (13) so as to form a positive lock in D-shaped interlock between the outer profile of the tube retainer (11) and an inner profile of the adjuster tube (13). This feature prevents any slippage between the tube retainer (11) and the adjustment tube (13) when the adjuster screw (7) is rotated with the help of adjustment knob (5).

[0025] The piston rod (80) of the piston rod assembly (60) is configured to house the adjuster tube (13) of the damping assembly (DA). The piston rod assembly (60) includes the piston rod (80), a tap slit (17), a piston (85), a needle (19), a rebound spring (86) and a needle spring (87). The piston rod (80) of piston rod assembly (60) is locked with the fork bolt (200) at its top end with the help of a circlip (80C) and the adjuster tube (13) is housed within the piston rod (80) in a manner such that top end of said adjuster tube (13) is locked with the tube retainer (11) and the bottom end is configured to house the needle (19). Further, the bottom end of the piston rod (80) is fitted with the tap slit (17) wherein the piston (85) is concentrically fitted over the tap slit (17) and locked there with the help of a locking nut (85N).

[0026] The tap slit (17) is configured to have a longitudinal groove and a transverse groove wherein the longitudinal groove houses the needle (19). The said needle (19) is fitted with the adjuster tube (13) at its upper end and is configured to move telescopically within the longitudinal groove of the tap slit (17). The needle (19) and the tap slit (17) are jointly housed within the piston rod (80) in a manner such that the needle spring (87) is positioned in between the tap slit (17) and an annular collar of the needle (19). The needle spring (87) helps the needle (19) to regain its position during the damping adjustment. The piston (85) of the piston rod assembly (60) is telescopically disposed within the cartridge tube (35) of the cartridge tube assembly (120).

[0027] The main spring (30) of the inverted front fork (500) is positioned between the adapter bush (45) and the cam adjuster (300) in a manner such that the top end (S1) of the main spring (30) abuts against the lower surface of the cam adjuster (300) and the bottom end (S2) of the said main spring (30) rests over the circular flange (45F) of the adapter bush (45). A spring guide (36) is concentrically placed in between the outer peripheral surface of the piston rod (80) and the inner diameter of the main spring (30) in a manner such that the said spring guide (36) is fixed with the piston rod (80) at its top end. A guiding and sealing assembly (110) comprising of a guide bush (106), an oil seal (107), a dust seal (108) and a holding cover (109) is positioned in that order in the recessed portion formed at the annular opening in between the outer tube (15) and inner tube (25).

[0028] The pre-load adjustment assembly (50) of the present invention has a fork bolt (200) and a cam adjuster (300). The fork bolt (200) of the pre-load adjustment assembly (50) is fitted to the top end of the outer tube (15) with the help of a circlip (25C) thus preventing the ejection of the fork bolt (200) from the outer tube (15) thereby. The said fork bolt (200) is configured to have a hex profiled boss (210) formed over an annular body portion (220) and an annular stem portion (230) protruding out from the annular body portion (220). The hex profiled boss (210) and the annular stem portion (230) are formed as an integral unit to the annular body portion (220). The annular body portion (220) is configured to have a plurality of O-Ring projections (220P) wherein the said O-Ring projections (220P) facilitates in evenly distributing the oil pressure around the fork bolt (200). The O-Ring projections (220P) may range from two projections to three projections separated from each other by an O-Ring groove (220G) wherein the said O-Ring groove (220G) accommodates an O-Ring (R). The O-Ring (R) helps preventing the leakage of the damping fluid from the fork bolt (200). The stem portion (230) is configured to have a plurality of lugs (240), preferably two lugs formed diametrically opposite to each other on the outer peripheral surface of the said stem portion (230).

[0029] The fork bolt (200) is configured to have a thorough cavity (200C) formed at its center and extending vertically across its length. The cavity (200C) is divided into a first cavity (C1), a second cavity (C2) and a third cavity (C3) wherein the first cavity (C1) extends from the center of the hex profiled boss (210) and partially into the annular body portion (220) of the fork bolt (200). The second cavity (C2) is formed in the annular body portion (220) wherein it starts from the ending point of the first cavity (C1) and extends up to the interfacial point of the annular body portion (220) and the stem portion (230). The third cavity (C3) is formed in the stem portion (230) wherein the said cavity (C3) has a groove (230G) to accommodate the circlip (80C) therein. The said circlip (80C) may have a cross-sectional profile selected from a circular profile, rectangular profile or a square shaped profile. The first cavity (C1) is configured to house the adjuster screw (7), the second cavity (C2) is configured to house the locking bush (9) and third cavity (C3) houses the piston rod (80) of the piston rod assembly (60). Further, the said cavities (C1-C3) are formed in a manner such that the diameter of the said cavities (C1-C3) are in the order of ØC1 < ØC2 < ØC3. The said fork bolt (200) is preferably made from an Aluminium alloy.
[0030] The cam adjuster (300) of the pre-load adjustment assembly (50) is configured to have a cylindrical body (310) and an annular flange (320) wherein the cylindrical body (310) protrudes out from the annular flange (320). The annular flange (320) is configured to have two guiding tabs (330) formed over the outer peripheral surface of the annular flange (320) in a diametrically opposite relation to each other. The guiding tabs (330) are configured to slide in the slots (15S) of the outer tube (15) and thus have a confirming matching geometry as that of the slots (15S) of the outer tube (15). The cylindrical body (310) of the cam adjuster (300) is configured to have a plurality of cam profiled grooves (310A, 310B, ….., ….., …., 310n) at its upper peripheral edge with a depth difference in a stepwise manner. The cam profiled grooves (310A, 310B, ….., ….., …., 310n) are configured to receive lugs (240) of the fork bolt (200) wherein the pre-compression of the main spring (30) depends on the engagement of the lugs (240) with the selected groove (310A, 310B, ….., ….., …., 310n) having the desired depth. The cam adjuster (300) is made from hardened steel, preferably selected from E34 steel Grade.

[0031] Referring to Fig. 5, the inverted front fork (500’) as per the second embodiment of the present invention comprises of a an outer tube (15), an inner tube (25), an axle mounting bracket (40), a main spring (30), a pre-load adjustment assembly (50’), a damping assembly (DA), a piston rod assembly (60) and a cartridge tube assembly (120). The pre-load adjustment assembly (50’) has the same configuration as the pre-load adjustment assembly (50) (refer Figs. 6a-7d) as provided in the inverted front fork (500) except for the fact that pre-load adjustment assembly (50’) is provided with an extra sleeve (350) and the fork bolt (200’) with the modified profiled cavity (200C’).

[0032] The sleeve (350) of the pre-load adjustment assembly (50’) is configured to have a flat base (360) and an annular projection (370) projecting out from the flat base (360). The annular projection (370) is configured to have male threads over its outer peripheral surface wherein the said male threads threadingly engages with the female threads provided on the inner peripheral surface of the stem portion (230’) of the fork bolt (200’). The flat base (360) of the sleeve (350) is configured have its outer peripheral surface having two D-profiled surface and two across flat surfaces. The unique profile of the flat base (360) thus helps to prevent the slip in between the sleeve (350) and the fork bolt (200’) during its fitment and provides positive locking thereby.

[0033] The fork bolt (200’) is configured to have a thorough cavity (200C’) formed at its center and extending vertically across its length. The cavity (200C’) is divided into a first cavity (C1’), a second cavity (C2’), a third cavity (C3’) and a fourth cavity (C4’) wherein the first cavity (C1’) extends from the center of the hex profiled boss (210’) and partially into the annular body portion (220’) of the fork bolt (200’). The second cavity (C2’) is formed in the annular body portion (220’) wherein it starts from the ending point of the first cavity (C1’) and extends up to the interfacial point of the annular body portion (220’) and the stem portion (230’). The third cavity (C3’) is formed in the stem portion (230’) and extends up to an imaginary plain x-x within the stem portion (230)’. The fourth cavity (C4’) is configured to house a circlip (80C) wherein the said circlip (80C) may have a cross-sectional profile selected from a circular profile, rectangular profile or a square shaped profile. The length of the said cavity depends on the thickness of the said circlip (80C). The fourth cavity (C4’) is formed in the stem portion (230’) wherein the said cavity (C4’) starts from the ending point of the cavity (C3’).

[0034] The first cavity (C1’) of the fork bolt (200’) is configured to house the adjuster screw (7), the second cavity (C2’) is configured to house the locking bush (9), the third cavity (C3’) is configured to house the circlip (80C) and the fourth cavity (C4’) house the sleeve (350) wherein the sleeve (350) is threadedly fixed with the piston rod (80) of the piston rod assembly (60). Further, the said cavities (C1’-C4’) are formed in a manner such that the diameter of the said cavities (C1’-C4’) are in the order of ØC1’ < ØC2’ < ØC3’< ØC4’. The said fork bolt (200’) is preferably made from an Aluminium alloy.

[0035] As far as the working of this invention is concerned, when the adjustment knob (5) of the inverted front fork (500) is operated/rotated, the adjuster screw (7) connected with the adjustment knob (5) is also rotated. This causes the detent spring to be compressed by the spherical balls (B) as said balls (B) climb and then descend into an adjacent internal notch of the locking bush (9). The movement of the spherical balls (B) into the adjacent notch of the locking bush (9) fixes the adjuster screw (7) in the newly achieved orientation until the adjustment knob (5) is operated/rotated again. The rotation of the adjuster screw (7) also causes rotation of the adjustment tube (13) leading to the vertical movement of the needle (19). The movement of the needle (19) causes the uncovering of the latitudinal groove of the tap slit (17) causing an alteration in the flow of the damping fluid, thus changing the damping force thereby.

[0036] During the adjustment of the pre-compression of the main spring (30), the fork bolt (200, 200’) of the pre-load adjustment assembly (50, 50’) is rotated. The rotation of the said fork bolt (200, 200’) leads to the movement of the lugs (240, 240’) from the cam profiled groove (310A) to another cam profiled groove (310B) wherein the inverted front fork (500) is presumed to have the initial engagement of the cam profiled groove (310A) and the lugs (240). The movement of the lugs (240, 240’) from a respective cam profiled groove to another cam profiled groove causes the vertical displacement of the cam adjuster (300) wherein the locking tabs (330) of the cam adjuster (300) slides within the vertical slots (15S) of the outer tube (15). This vertical movement of the cam adjuster (300) causes the compression / expansion of the main spring (30) of the inverted front fork (500) thus changing the pre-compression of the main spring (30) thereby.

[0037] It is to be noted that the rotation of the fork bolt (200) of the pre-load adjustment assembly (50, 50’) does not affect the working of the damping assembly (DA) and vice-versa since the fork bolt (200, 200’) rotates with slipping over the outer peripheral surface of the piston rod (80) without disturbing the needle (19) of the piston rod assembly (80). Similarly, the adjuster tube (13) rotates within the piston rod (80) without disturbing the cam adjuster (300) of the pre-load adjustment assembly (50, 50’) of the inverted front fork (500) during the damping adjustment. This unique combination of the damping assembly (DA) and the pre-load adjustment assembly (50, 50’) allows altering the damping requirements as well as altering the pre-load of the inverted front fork (500). Thus, the combination of the damping assembly (DA) and the pre-load adjustment assembly (50, 50’) is configured to alter the damping requirements and the pre-load of the main spring (30) independent of each other.

[0038] The inverted front fork (500) in accordance with the present invention provides the following technical advantages that contributes to the technical advancement of technology:
- It reduces the need for repeated disassembling and reassembling of the inverted front fork with new sub components during its development phase.
- It gives the user the option of safely changing the damping settings without having to open and alter sub-components of the inverted front fork.
- It reduces/eliminates the chances of leakage of damping fluid from in between the relatively moving/stationary sub-components of the suspension unit.
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 embodiment. 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 herein has been described in terms of preferred embodiment, those skilled in the art will recognize that the embodiment herein can be practiced with modification within the spirit and scope of the embodiment as described herein. , Claims:We Claim:

1. An inverted front fork (500, 500’) for suspension system of motor vehicle comprising of an outer tube (15), an inner tube (25), an axle mounting bracket (40), a main spring (30), a pre-load adjustment assembly (50, 50’), a damping assembly (DA), a piston rod assembly (60), and a cartridge tube assembly (120)
wherein,
- the outer tube (15) is configured to have a pair of diametrically opposite longitudinal slots (15S) formed over its top inner peripheral surface;
- the main spring (30) is positioned in between an adapter bush (45) of the cartridge tube assembly (120) and a cam adjuster (300) of the pre-load adjustment assembly (50, 50’);
- the top end (S1) of the main spring (30) is configured to abut against the lower surface of the cam adjuster (300) of the preload adjustment assembly (50, 50’) and the bottom end (S2) of said main spring (30) rests over the circular flange (45F) of the adapter bush (45) of the cartridge tube assembly (120);
- the cam adjuster (300) is configured to have two guiding tabs (330) and said guiding tabs (300) are configured to slide in the slots (15S) of the outer tube (15);
- the fork bolt (200, 200’) of the preload adjustment assembly (50, 50’) is configured to have a hex profiled boss (210, 210’) formed over an annular body portion (220, 220’) and an annular stem portion (230, 230’) is configured to protrude out from said annular body portion (220, 220’); and said hex profiled boss (210, 210’) and the annular stem portion (230, 230’) are configured to form an integral unit to the annular body portion (220, 220’) of the fork bolt (200, 200’);
- said stem portion (230, 230’) is configured to have at least two lugs (240, 240’) formed diametrically opposite to each other on the outer peripheral surface of the said stem portion (230, 230’); and
- said fork bolt (200, 200’) of the pre-load adjustment assembly (50, 50’) is fitted to the top end of the outer tube (15) with the help of a circlip (25C) and said circlip (25C) is configured to prevent the ejection of the fork bolt (200, 200’) from the outer tube (15).

2. The inverted front fork (500) for suspension system of motor vehicle as claimed in claim 1, wherein
- the pre-load adjustment assembly (50) comprises of a fork bolt (200) and a cam adjuster (300);
- said fork bolt (200) is configured to have a thorough cavity (200C) formed at its center and extending vertically across its length and said cavity (200C) is divided into a first cavity (C1), a second cavity (C2) and a third cavity (C3), wherein
• the first cavity (C1) is configured to extend from the center of the hex profiled boss (210) and partially into the annular body portion (220) of the fork bolt (200);
• the second cavity (C2) is formed in the annular body portion (220) and is configured to start from the end point of the first cavity (C1) and extends up to the interfacial point of the annular body portion (220) and the stem portion (230); and
• the third cavity (C3) is configured to form in the stem portion (230) and said cavity (C3) has a groove (230G) to accommodate the circlip (80C) therein; and
- said cam adjuster (300) of the pre-load adjustment assembly (50) is configured to have a cylindrical body (310) and an annular flange (320);
- said cylindrical body (310) of the cam adjuster (300) is configured to protrude out from the annular flange (320); and
- said annular flange (320) is configured to have two guiding tabs (330) formed over the outer peripheral surface of the annular flange (320) in a diametrically opposite direction to each other.

3. The inverted front fork (500) for suspension system of motor vehicle as claimed in claim 2, wherein
- the first cavity (C1) is configured to house an adjuster screw (7), the second cavity (C2) is configured to house a locking bush (9) and third cavity (C3) houses the piston rod (80) of the piston rod assembly (60);
- said cavities (C1-C3) are formed in a manner so that the diameter of the said cavities (C1 to C3) are in the order of ØC1 < ØC2 < ØC3;
- the annular body portion (220) of the fork bolt (200) is configured to have a plurality of O-Ring projections (220P) wherein the said O-Ring projections (220P) facilitates in evenly distributing the oil pressure around the fork bolt (200);
- said O-Ring projections (220P) ranges from two projections to three projections separated from each other by an O-Ring groove (220G) and said O-Ring groove (220G) is configured to accommodate an O-Ring (R) threin so as to prevent the leakage of the damping fluid from the fork bolt (200);
- said fork bolt (200) is made from an Aluminium alloy; and
- the circlip (80C) of said fork bolt (200) is configured to have a cross-sectional profile selected from a circular profile, rectangular profile and a square shaped profile.

4. The inverted front fork (500’) for suspension system of motor vehicle as claimed in claim 1, wherein
- the pre-load adjustment assembly (50’) is configured to comprise of a fork bolt (200’), a uniquely profiled sleeve (350) and a cam adjuster (300);
- said fork bolt (200’) is configured to have a thorough cavity (200C’) formed at its center and extending vertically across its length and said cavity (200C’) is divided into a first cavity (C1’), a second cavity (C2’), a third cavity (C3’) and a fourth cavity (C4’), wherein
• the first cavity (C1’) is configured to extend from the center of the hex profiled boss (210’) and partially into the annular body portion (220’) of the fork bolt (200’);
• the second cavity (C2’) is formed in the annular body portion (220’) and it starts from the end point of the first cavity (C1’) and is configured to extend up to the interfacial point of the annular body portion (220’) and the stem portion (230’);
• the third cavity (C3’) is formed in the stem portion (230’) and extends up to an imaginary plane x-x within the stem portion (230’);
• the fourth cavity (C4’) is formed in the stem portion (230’) and said cavity (C4’) starts from the end point of the cavity (C3’) and is configured to house a circlip (80C) wherein the said circlip (80C) has a cross-sectional profile selected from a circular profile, rectangular profile and a square shaped profile;
- said cam adjuster (300) of the pre-load adjustment assembly (50) is configured to have a cylindrical body (310) and an annular flange (320);
- said cylindrical body (310) of the cam adjuster (300) is configured to protrude out from the annular flange (320); and
- said annular flange (320) is configured to have two guiding tabs (330) formed over the outer peripheral surface of the annular flange (320) in a diametrically opposite direction to each other.

5. The inverted front fork (500’) for suspension system of motor vehicle as claimed in claim 4, wherein
- the first cavity (C1’) of the fork bolt (200’) is configured to house the adjuster screw (7);
- the second cavity (C2’) is configured to house the locking bush (9);
- the third cavity (C3’) is configured to house the circlip (80C);
- the fourth cavity (C4’) house the sleeve (350) wherein said sleeve (350) is threadedly fixed with the piston rod (80) of the piston rod assembly (60);
- said cavities (C1’to C4’) are formed in a manner so that the diameter of the said cavities (C1’to C4’) are in the order of ØC1’ < ØC2’ < ØC3’< ØC4’; and
- said fork bolt (200’) is made from an Aluminium alloy.
6. The inverted front fork (500’) for suspension system of motor vehicle as claimed in claim 5, wherein
- the sleeve (350) of the pre-load adjustment assembly (50’) is configured to have a flat base (360) and an annular projection (370) projecting out from the flat base (360);
- said annular projection (370) is configured to have male threads over its outer peripheral surface wherein the said male threads threadingly engages with the female threads provided on the inner peripheral surface of the stem portion (230’) of the fork bolt (200’);
- the flat base (360) of the sleeve (350) is configured have its outer peripheral surface having two D-profiled surface and two across flat surfaces; and
- said unique profile of the flat base (360) of the sleeve (350) is configured to prevent the slip in between the sleeve (350) and the fork bolt (200’) during its fitment and provides positive locking thereby.

7. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in any of the claims 3 and 6, wherein
- the cylindrical body (310) of the cam adjuster (300) is configured to have a plurality of cam profiled grooves (310A, 310B, ….., ….., …., 310n) at its upper peripheral edge with a depth difference in a stepwise manner;
- said cam profiled grooves (310A, 310B, ….., ….., …., 310n) are configured to receive lugs (240) of the fork bolt (200, 200’), and engagement of said lugs (240) with the selected groove (310A, 310B, ….., ….., …., 310n) defines the preload of the main spring (30); and
- said cam adjuster (300) is made from hardened steel selected from E34 steel Grade.

8. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in claim 7, wherein
- the rotation of the fork bolt (200, 200’) of the pre-load adjustment assembly (50, 50’) is configured not affect the adjustment of the damping assembly (DA);
- an adjuster tube (13) is configured to rotate within the piston rod (80) without disturbing the cam adjuster (300) of the pre-load adjustment assembly (50, 50’); and
- the combination of the damping assembly (DA) and the pre-load adjustment assembly (50, 50’) is configured to alter the damping requirements and the pre-load of the main spring (30) independent of each other.

9. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in claim 8, wherein
- said inverted front fork (500) has the inner tube (25) telescopically and concentrically positioned in the outer tube (15) and is free to reciprocate within the outer tube (15);
- the lower end of the inner tube (25) is fixedly connected to the axle mounting bracket (40) and the upper end of the said inner tube (25) is free to slide in a telescopic manner within the outer tube (15);
- the cartridge tube assembly (120) is positioned in the inner tube (25) and said cartridge tube assembly (120) is configured to have a cartridge tube (35), an adapter bush (45), a base valve (55), a base tap (65) and a socket headed bolt (75); and
- said cartridge tube (35) of the cartridge tube assembly (120) is a hollow cylindrical tube having a lower open end (E1) and an upper open end (E2) and is fixed concentrically within the inner tube (25) in a manner so that the outer peripheral surface of the cartridge tube (35) is configured to form an annulus chamber (C) with the inner peripheral surface of the inner tube (25).

10. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in claim 9, wherein
- the base tap (65) is fixed within the cartridge tube (35) at its lower end and locked there with the help of the socket headed bolt (75);
- the base valve (55) is concentrically placed over a stem portion of the base tap (65) and locked there with the help of a locking nut (76) and the locking nut is screwed with the stem portion of the base tap (65);
- the adapter bush (45) is fitted to the upper open end (E2) of the cartridge tube and is positively locked there with the help of spinning process;
- said adaptor bush (45) is configured to have a cylindrical body (45B) at its lower end and the circular flange (45F) extends radially around the top end of the cylindrical body (45B);
- an annular collar (45C) projects out from the circular flange (45F) forming a fluid reservoir (45R) within the inner peripheral surface of the annular collar (45C); and
- the cylindrical body (45B) has a central opening to facilitate the passage of a piston rod (80) of the damping adjustment assembly (DA).
11. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in claim 10, wherein
- the damping adjustment assembly (DA) comprises of an adjuster knob (5), an adjuster screw (7), a locking bush (9), a set of spherical balls (B), a tube retainer (11), a detent spring (not shown) and an adjuster tube (13);
- said adjuster knob (5) is connected to the top portion of an adjuster screw (7) and said adjuster screw (7) is configured to house the set of spherical balls (B) and the detent spring within its central opening;
- said spherical balls (B) are configured to get locked with the matching notches given within the locking bush (9) which is mounted concentrically with the lower portion of the adjuster screw (7) within a cavity of the fork bolt (10); and
- the adjuster screw (7) is threadedly connected with the tube retainer (11) at its lower end and said tube retainer (11) is fixedly connected with the adjuster tube (13) so as to form a positive lock in D-shaped interlock between the outer profile of the tube retainer (11) and an inner profile of the adjuster tube (13).

12. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in claim 10, wherein
- the piston rod (80) of the piston rod assembly (60) is configured to house the adjuster tube (13) of the damping assembly (DA) and said piston rod assembly (60) is configured to comprise of the piston rod (80), a tap slit (17), a piston (85), a needle (19), a rebound spring (86) and a needle spring (87);
- said piston rod (80) of piston rod assembly (60) is locked with the fork bolt (200, 200’) at its top end with the help of a circlip (80C) and the adjuster tube (13) is housed within the piston rod (80) in a manner so that the top end of said adjuster tube (13) is locked with the tube retainer (11) and the bottom end is configured to house the needle (19); and
- the bottom end of the piston rod (80) is fitted with the tap slit (17) and the piston (85) is concentrically fitted over said tap slit (17) and locked there with the help of a locking nut (85N).

13. The inverted front fork (500, 500’) for suspension system of motor vehicle as claimed in claim 12, wherein
- the tap slit (17) is configured to have a longitudinal groove and a transverse groove and said longitudinal groove houses the needle (19);
- said needle (19) is fitted with the adjuster tube (13) at its upper end and is configured to move telescopically within the longitudinal groove of the tap slit (17);
- the needle (19) and the tap slit (17) are jointly housed within the piston rod (80) in a manner so that the needle spring (87) is positioned in between the tap slit (17) and an annular collar of the needle (19); said needle spring (87) is configured to regain the needle (19) its position during the damping adjustment;
- the piston (85) of the piston rod assembly (60) is telescopically disposed within the cartridge tube (35) of the cartridge tube assembly (120);
- the spring guide (36) is concentrically placed in between the outer peripheral surface of the piston rod (80) and the inner diameter of the main spring (30) in a manner so that the said spring guide (36) is fixed with the piston rod (80) at its top end; and
- a guiding and sealing assembly (110) comprising of a guide bush (106), an oil seal (107), a dust seal (108) and a holding cover (109) is positioned in that order in the recessed portion formed at the annular opening in between the outer tube (15) and inner tube (25).

Dated 24th day of Jan. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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