DESC: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
“UPSIDE DOWN FRONT FORK SUSPENSION FOR TWO AND THREE WHEELED VEHICLES”

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

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

Field of Invention

The present invention relates to a front fork suspension for a two wheeler. More particularly, the present invention relates to an upside down front fork suspension having a functional leg and a follower leg wherein the said upside down front fork suspension is capable of adjusting the preload of the said suspension system.

Background of the Invention

The front fork suspension systems of a two wheeled vehicle plays a vital role of absorbing the undulations from road surface irregularities as well imparting the better steering maneuverability and braking control. The front suspension systems are generally classified as upright conventional front fork suspension and inverted / upside down front fork suspension based upon the constructional characteristics of the same. The telescopic suspension derives its name from the word telescope as both works in a similar manner wherein the fork pipe slides within the outer tube and the said fork pipe is attached to the handle bar of the vehicle with the help of a triple clamp whereas the outer tube is attached to the axle of the wheel through the axle clamp in case of upright conventional front fork suspension. The inverted or upside down front forks on the other hand are exactly opposite in the construction to the upright conventional front forks wherein the outer tube is attached to the handlebar of the vehicle with the help of triple clamp and the fork pipe is attached to the axle of the wheel through the axle clamps. The upright conventional front forks lacks in steering feedback / rider comfort as compared to the upside down forks since it experience the flexion near the triple clamp when a motorcycle is subjected to heavy braking or cornering at high speeds. Whereas the upside down front forks impart better structural strength / rider feel during cornering as the stresses are beard by the outer tube instead of the fork pipes which have less torsional stiffness in comparison to the outer tube.

The upside down front forks thus imparts improved rigidity, enhancing stability and rider feedback. Apart from enhanced ride feeling, the suspension system needs to be adjusted as per the different riding conditions. Depending on the variation in rider as well as ride condition, the riders need to adjust the preload of the suspension. The required preload adjustment is not easy in upside down front suspension due its constructional limitations wherein the main spring is placed in at the bottom and not easily accessible from the top end. Thus these changes can be performed at the manufacturer’s / service provider’s end wherein the said exercise require an excessive amount of time and money to ensure safe operation.

Thus, there exists a long pending unmet requirement of providing the preload adjustment in the upside down front fork suspension system.

Objectives of the Present Invention

The main object of the present invention is to provide an upside down front fork suspension for a two wheeled vehicle.

Another object of the present invention is to provide an upside down front fork suspension unit having a functional leg and a follower leg for two wheeled vehicles.

Another objective of the present invention is to provide an upside down front fork suspension with the means to adjust the compression load of the spring of the suspension system.

Still another objective of the present invention is to provide an upside down front fork suspension which is configured to employ a hydraulic lock in the follower leg of the suspension system.

Yet, another objective of the present invention is to provide an upside down front fork which reduces the un-sprung mass of the vehicle and is cost effective.

Brief Description of Drawings

This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The disclosure herein and advantages thereof will be better understood from the following description when read with reference to the following drawings, wherein

Figure 1 discloses an assembled perspective view of the upside down front fork suspension for a two and three wheelers as per the present invention.

Figure 2 presents an assembled cut-sectional view of the upside down front fork suspension in accordance with the present invention.

Figure 3 discloses cut-sectional view of the functional leg of the upside down front fork suspension in accordance with the present invention.
Figure 4 discloses cut-sectional view of the follower leg of the upside down front fork suspension in accordance with the present invention.

Figures 4a discloses enlarged view of the H portion in the Fig. 4 of the present invention.

Figure 5 shows the exploded view of the fork bolt assembly of the upside down front fork suspension of the present invention.

Figures 6 and 7 show the isometric view and cut sectional view, respectively of the fork bolt assembly of the upside down front fork suspension of the present invention.

Figures 8 and 9 show the cut sectional view respectively of the fork bolt and the adjuster bolt of the adjuster fork bolt assembly of the upside down front fork suspension of the present invention.

Detailed Description of the Present Invention

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 Fig. 1, the upside down front fork suspension (500) of the present invention comprises of a functional leg (100), a follower leg (200), a steering shaft (10) and a triple clamp (20) wherein the said functional leg (100) is fixedly connected to the said follower leg (200) with the help of the triple clamp (20). The said steering shaft (10) is fixedly connected to the said triple clamp (20) at its lower end and mounted to the handlebar of the vehicle at its upper end.
Referring to Fig. 2, the functional leg (100) of the upside down front fork suspension (500) of the present invention has an adjuster fork bolt assembly (300), an outer tube (30), a fork pipe assembly (40A), a dust seal (60), an oil seal (70), a piston rod assembly (170A), a main spring (120), a bump stop (140) and an adaptor bush (190).

The said fork pipe assembly (40A) comprises a fork pipe (40), an axle clamp (50), a cartridge tube (150), a base tap (55), a socket headed bolt (95) and a base valve (195). The said fork pipe (40) is threadedly engaged with the axle clamp (50) at its lower end with the help of external threads provided on the lower end (40L) of the outer peripheral surface of the fork pipe (40) and matching internal threads provided on the inner circumferential surface of the axle clamp (50). A grub screw (90) tightly holds the lower circumferential end (40L) of the fork pipe (40) passing through a thorough hole formed in axle clamp (50). The said grub screw (90) imparts high structural rigidity to the fork pipe (40) during its functioning. The base tap (55) is fixedly positioned at the inner bottom surface of the axle clamp (50) with the help of the socket headed bolt (95). The base valve (195) is configured to have a plurality of orifices (195O), and is fixedly mounted over the said base tap (55) in a manner such that a base tap spindle (55T) guides the base valve (195) annularly and a nut (195N) is screwed over the spindle (55T) so as to arrest the longitudinal movement of the said base valve (195). The cartridge tube (150) of the fork pipe assembly (40A) is configured to have two orifices (150P) at its lower end (150L) and is fixed to the outer circumferential surface of the base tap (55) with the help of a circlip (not shown) at its lower end (150L). The said base valve (195) allows the passage of damping fluid from the interior of the cartridge tube (150) to the annular space formed in between the said cartridge tube (150) and the fork pipe (40).

The piston rod assembly (170A) includes a hollow piston rod (130), a spring guide (110), a tap rebound slit (160), a piston (170) and a rebound spring (180). The said hollow piston rod (130) at its top end is inserted into the threaded bore (310BT) and threadedly connected with the adjuster bolt (310) by the virtue of the external threads provided on the outer surface of the top end (130T) of the said piston rod (130) and matching internal threads provided on the inner peripheral surface of the threaded bore (310BT) of the adjuster bolt (310). The spring guide (110) is sleeved over the piston rod (130) and fitted over the piston rod below the fork bolt assembly (300) through the threaded joinery. The tap rebound slit (160) is screwed to the lower end of the said hollow piston rod (130) closing the said end of the hollow piston rod (130) thereby. Further, the piston (170) is mounted over the said tap rebound slit (160) and fixed there with the help of a hex nut (170N) wherein the said piston (170) has a plurality of damping orifices (170D). The rebound spring (180) is placed annularly around the piston rod (130) in a manner such that the lower end of the said rebound spring (180) rests over the said tap rebound slit (160).

The fork pipe (40) of the fork pipe assembly (40A) of functional leg (100) is telescopically disposed within the outer tube (30) in a manner such that the upper end of the said fork pipe (40) is free to slide within the said outer tube (30) and the axle clamp (50) of the fork pipe assembly (40A) is fixed with the axle wheel (not shown) of a motor vehicle. The top end of the outer tube (30) of the said functional leg (100) is closed with the help of the adjuster fork bolt assembly (300) and the annular space in between the fork pipe (40) of the fork pipe assembly (40A) and the outer tube (30) is closed with the oil seal (70) and the dust seal (60) at the mouth portion of the outer tube (30). Further, the top end of the cartridge tube (150) of the said fork pipe assembly (40A) is configured to receive the piston (170) of the piston assembly (170A) such that the piston is free to slide within the cartridge tube (150) of the fork pipe assembly (40A). The top open end of the said cartridge tube (150) is configured to receive the adaptor bush (190) in a manner such that a flange portion (190F) of the adaptor bush (190) rests over the top circumferential edge of the said cartridge tube (150) and a lower end of the said adaptor bush (190) abuts against the top end of the rebound spring (180) of the piston rod assembly (170A). Further, the cartridge tube (150) is locked with the adapter bush (190) by deforming the outer peripheral surface of the said cartridge tube (150) over a preformed groove (190G) of the said adaptor bush (190). The bump stop (140) is positioned within a flange cup profile (190FC) of the adaptor bush (190). The main spring (120) is placed annularly around the spring guide (110) of the piston rod assembly (170A) in a manner such that the lower end of the said main spring (120) rests against the flange portion (190F) of the adaptor bush (190) and top end of the said main spring (120) abuts against the lower end of the adjuster fork bolt assembly (300). The said spring guide (110) guides the main spring (120) so as to prevent the buckling of the spring (120) during its functioning. Also, the spring guide (110) in combination with the bump stop (140) prevents the metal to metal contact during the extreme compression stroke of the suspension. Further, the piston rod (130) of the piston rod assembly (170A) is secured with the adjuster fork bolt assembly (300) with the help of threaded connection in between the top end of the said piston rod (130) and an adjuster bolt (310) of the adjuster fork bolt assembly (300) as would be described in detail in subsequent disclosure of the present invention.

The said functional leg (100) of the upside down front fork suspension (500) is filled damping fluid wherein the said damping fluid travels from the outer tube (30) to the annular space in between the cartridge tube (130) and the fork pipe (40) followed by entering into the interior of cartridge tube (130) through the passages (130P) of the cartridge tube (130) during compression stroke of the said upside down front fork suspension (500) of the present invention. The reverse path is followed by damping fluid during the rebound stroke of the upside down front fork suspension (500).

Referring to Fig. 2, the follower leg (200) of the present invention includes an adjuster fork bolt assembly (300), an outer tube (30), a dust seal (60), an oil seal (70), a main spring (220), a fork pipe (40), an axle clamp (50), a spring seat (240), a hydraulic lock chamber (H) and a piston rod assembly (230A). The said fork pipe (40) is telescopically disposed within the outer tube (30) at its upper end and is threadedly engaged with the axle clamp (50) at its lower end (40L) with the help of external threads provided on the lower end of the outer peripheral surface of the fork pipe (40) and matching internal threads provided on the inner circumferential surface of the axle clamp (50). Also, a grub screw (90) tightly holds the lower circumferential end (40L) of the fork pipe (40) passing through a thorough hole in axle clamp (50). The said grub screw (90) imparts high structural rigidity to the fork pipe (40) during its functioning. The spring seat (240) is positioned at the top end of the fork pipe (40) and fixed there with the help of a threaded connection in between said spring seat (240) and the said fork pipe (40). The said spring seat (240) is configured to have an annular collar (240C) projecting away from a flat surface (240F) wherein the said annular collar (240C) is integral to the flat face thus forming an L-shaped cross-sectional ring shaped profile thereby.

The piston rod assembly (230A) includes a piston rod spindle (230), a spring guide (210), a spring support ring (260) and a rebound spring (250). The said spring guide (210) is configured to have a cylindrical portion (P1) and a converging tapered portion (P2). The said cylindrical portions (P1) and the tapered portion (P2) are formed in a manner such that a horizontal plane (X-X) divides the total vertical length (l) of the spring guide (210) in the ratio of l1:l2 in the longitudinal direction of the said spring guide (210) wherein the said cylindrical portion (P1) extends up to the length (l1) in the longitudinal direction and the tapered portion (P2) converges gradually up to the length l2 in the longitudinal direction. The tapered portion (P2) of the spring guide (210) is configured to form a taper angle (a) with the vertical geometric axis of the spring guide (210).

The piston rod spindle (230) is threadedly connected with the threaded bore (310BT) of the adjuster bolt (310) through the spring guide (210) at its top end by the virtue of the external threads provided on the outer surface of the top end of the said piston rod spindle (230) and matching internal threads provided on the threaded bore (310BT) of the adjuster bolt (310) and the top inner surface of the spring guide (210). The spring support ring (260) is screwed to the lower end of the said piston rod spindle (260) wherein the spring support ring (260) is configured to have a plurality of damping orifices (260D). The rebound spring (250) is placed annularly around the lower end of the piston rod spindle (230) in a manner such that the lower end of the said rebound spring (250) rests over the said spring support ring (260) and the upper end of the said rebound spring (250) abuts against the lower surface of the spring seat (240).

The fork pipe (40) of the follower leg (200) is telescopically disposed within the outer tube (30) in a manner such that the upper end of the said fork pipe (40) is free to slide within the said outer tube (30) and the axle clamp (50) of the fork pipe (40) is fixed with the axle wheel of a motor vehicle. The top end of the outer tube (30) of the said follower leg (200) is closed with the help of the adjuster fork bolt assembly (300) and the annular space in between the said fork pipe (40) and the said outer tube (30) is closed with the oil seal (70) and the dust seal (60) at the mouth of the outer tube (30). The main spring (220) is placed annularly around the spring guide (210) of the piston rod assembly (230A) in a manner such that the lower end of the said main spring (220) rests against the flat surface (240F) of the spring seat (240) and top end of the said main spring (220) abuts against the lower surface of the adjuster fork bolt assembly (300). The hydraulic lock chamber (H) is a fluid chamber formed in between the lower end of the fork bolt (320) of the adjuster fork bolt assembly (300) and the spring seat (240) of the piston rod assembly (230A). Further, the piston rod spindle (230) of the piston rod assembly (230A) is secured with the adjuster fork bolt assembly (300) with the help of threaded connection in between the top end of the said piston rod spindle and an adjuster bolt of the adjuster fork bolt assembly (300) as would be described in detail in subsequent disclosure of the present invention.

The said follower leg (200) of the upside down front fork suspension (500) is filled damping fluid wherein the said damping fluid travels from the outer tube (30) to the fork pipe (40) passing through the annular collar (240C) of the spring seat (240) followed by passing through the damping orifices (260D) of the spring support (260) during the compression stroke of the upside down front fork suspension (500). During the extreme compression stroke of the upside down front fork suspension (500), the tapered portion (P2) of the spring guide (210) enters in an overlapping manner within the annular collar (240C) of the spring seat (240) (refer Fig. 3) due to the compression of the main spring (220) in the hydraulic lock chamber (H). This overlapping of the tapered portion (P2) within the annular collar (240C) of the spring seat (240) leads to accumulation of the fluid therein thus leading to the formation of the hydraulic lock thereby. This hydraulic lock prevents the abutment of the fork pipe (40) and the adjuster fork bolt assembly (300) thus eliminating the metal to metal contact and the unwanted noise coming therefrom. The spring guide (210) is designed in to have the optimum ratio of the tapered portion (P2) and the cylindrical portion (P1) to form the hydraulic lock in accordance with the below mentioned design calculations:
l1/l2= k1 ((l1+l2))/(ds/tan?(a))

dc/ds= k2
where,
l1 is the length of the cylindrical portion P1 of the spring guide;
l2 is the length of the tapered portion P2 of the spring guide;
dc is the diameter of the annular collar of the spring seat;
ds is the diameter of the tapered end of the spring guide;
a is taper angle of the spring guide;
k1 is the form constant of the spring guide wherein k1 = 3.0 to 4.0;
k2 is the hydraulic lock constant wherein k2 = 1.15 to 1.25;

This unique construction of the spring guide (210) and the spring seat (240) eliminates the need of a separate bump stop as the equivalent function is performed by the hydraulic lock formed thereof. Further, the follower leg (200) does not require the socket headed bolt (95), the base tap (55), the cartridge tube (150), piston (170), tap rebound slit (160), adaptor bush (190) and the bump stop (140). As these components are totally eliminated from the follower leg, the suspension system of the invention leads to drastic reduction in weight and cost as well.
The adjuster fork bolt assembly (300) (refer Figs. 5 -7) of the present invention includes an adjuster bolt (310), a fork bolt (320), a threaded washer (330), a lock nut (340) and a spacer (350). The said fork bolt (320) is configured to have an annular skirt portion (320S) projecting away in a longitudinal downward direction from an annular disk portion (320D) and a hex profiled boss (320H) projecting away in a longitudinal upward direction from the annular disk portion (320D). The said hex profiled boss (320H) and the annular skirt portion (320S) are integral to the annular disk portion (320D) forming a unitary structure of the fork bolt (320). The annular skirt portion (320S) of the fork bolt (320) is configured to have an O-ring groove (320G) and threads (320T) formed over its outer peripheral surface. Further, the said fork bolt (320) is configured to have a first cavity (C1), a second cavity (C2) and a third cavity (C3) wherein the diameter of the said cavities (C1 to C3) are in the order of ØC1 < ØC2 < ØC3. An annular step (320AS) is formed at the interface of the first cavity (C1) and the second cavity (C2) wherein the said step (320AS) provides the seat for the adjuster bolt (310) of the adjuster fork bolt assembly (300). The third cavity (C3) is configured to have a pair of arcuate slots (300ST) formed on its inner peripheral surface wherein the said slots (300ST) extends over the entire length of the said cavity (C3) in axial direction of the adjuster bolt (310).

The adjuster bolt (310) is a cylindrical body configured to have a head portion (310H) and a body portion (310B) wherein an annular step (310AS) is formed at the interface of the said head portion (310H) and the said body portion (310B). The said body portion (310B) is configured to have external threads (310T) formed over its outer peripheral surface and a threaded bore (310BT) formed so as to receive the threaded shank of the hollow piston rod (130) / piston rod spindle (230). Further, the head portion (310H) is configured to have a hex shaped profile so as to ease the torqueing and de-torqueing of the said adjuster bolt (310). The said adjuster bolt (310) has been provided with the indication means (310IM) carved on the top surface of the head portion (310H) of the adjuster bolt which indicates the direction of torqueing or de-torqueing of the adjuster bolt (310). The threaded washer (330) is a stepped profiled hollow cylindrical body having female threads formed over its inner peripheral surface. The lock nut (340) is a hollow disk shaped body configured to have two arcuate profiled bosses (340B) formed over its outer peripheral surface and internal threads formed over its inner peripheral surface.

The adjuster bolt (310) of the adjuster fork bolt assembly (300) is in threaded connection with the threaded washer (330) and the lock nut (340) wherein the head portion (310H) of the adjuster bolt (310) is positioned in the first cavity (C1) and the body portion (310B) is jointly housed by the second cavity (C2) and the third cavity (C3). The threaded washer (330) is positioned within the second cavity (C2) such that the top surface of the threaded washer (330) abuts against the lower surface of the annular step (320S). The lock nut (340) is positioned within the third cavity (C3) in a manner such that the top surface of the said lock nut (340) rests over the step (320AS) formed at the interface of the second cavity (C2) and the third cavity (C3) and the arcuate profiled bosses (340B) of the said lock nut (340) are free to slide within the arcuate slots (300ST) of the third cavity (C3). The said arcuate profiled bosses (340B) of the lock nut (340) in combination with the arcuate slots (310ST) of the fork bolt (320) prevents the rotational movement of the lock nut (340) with respect to the fork bolt (320). Further, the spacer (350) is placed in the third cavity (C3) in a manner such that the top surface of the said spacer (350) abuts against the bottom surface of the lock nut (340).

The second cavity (C2) and the third cavity (C3) of the fork bolt (320) of the adjuster fork bolt assembly (300) are profiled in a manner so as to jointly house the threaded washer (330), the lock nut (340) and the spacer (350) working in combination with each other to adjust the preload of the main spring (120, 220). The said profiles are worked out in a manner so as to maintain the below mentioned empirical relations obtained by various iterations performed in the proto lab:
?((a+b+c)/(x+y))= k3 s/(r.?) …..1
?((x+y)/c)= q …..2
where,
a is the width of the threaded washer;
b is the width of the lock nut;
c is the width of the spacer;
x is depth of the second cavity;
y is depth of the third cavity;
s is the pre-compression of the main spring at the time of assembly and said pre-compression (s) of the spring varies from 5.0 to 10.0 mm;
r is the radius of the body portion of the adjuster bolt;
? is the measure of the angular displacement of the adjuster bolt in radians
k3 is the correction constant wherein k3 = 0.0 to 0.5
q is equivalence constant wherein q = 2.0 to 2.5

As per intent of the present invention the user rotates the adjuster bolt (310) in a clockwise / anti-clockwise direction to adjust the preload of main spring (120, 220) of the said upside down front fork suspension (500). The rotation of the said adjuster bolt (310) leads to the translational movement of the threaded washer (330) and the lock nut (340) wherein the clockwise rotation leads to the downward motion of the threaded washer (330) and the lock nut (340) which in turn leads to the downward movement of the spacer (350) thus compressing the main spring (120, 220) thereby. Similarly, the anti-clockwise rotation of the said adjuster bolt (310) leads to an upward movement of the threaded washer (330) and the lock nut (340) which in turn causes the vertical displacement of the spacer (350) in upward direction causing the main spring (120, 220) to expand thus reducing the pre-compression thereby.

The upside down front fork suspension (500) of the present invention enables an easy adjustment of the pre-load of main spring which is not possible in the conventional upside down front fork suspension. Further, the upside down front fork suspension (500) of the present invention provides the following technical advantages that contributes to the advancement of preload adjustment technology in upside down front fork suspension having a functional leg and a follower leg:
Easy adjustment of the preload of the suspension system.
Eliminating the metal to metal contact in the follower leg with the help of the hydraulic lock.
Reduces the un-sprung weight of the vehicle
It provides a light weight, compact and durable suspension system for a two-wheeler with reduced number of parts yet same operational performance.
It provides system a cost effective solution to the two-wheeler suspension without compromising the efficiency of the system.
The socket headed bolt, the base tap, the base valve, the cartridge tube, piston, tap rebound slit, adaptor bush and the bump stop are completely eliminated from the follower leg which consequently leads to drastic reduction in weight and cost as well of the suspension unit.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:We Claim:

An upside down front fork suspension (500) for two and three wheeled vehicles comprising of a functional leg (100), a follower leg (200), a steering shaft (10) and a triple clamp (20);
wherein,
the functional leg (100) is configured to comprise of an adjuster fork bolt assembly (300), an outer tube (30), a fork pipe assembly (40A), a dust seal (60), an oil seal (70), a piston rod assembly (170A), a main spring (120), a bump stop (140) and an adaptor bush (190);
the follower leg (200) is configured to comprise of an adjuster fork bolt assembly (300), a fork pipe (40), an axle clamp (50), a spring seat (240), a hydraulic lock chamber (H) and a piston rod assembly (230A);
said functional leg (100) is fixedly connected to the said follower leg (200) with the help of the triple clamp (20); and
said triple clamp (20) is fixedly connected to the handlebar of the vehicle through the steering shaft (10) wherein the lower end of the steering shaft (10) is fitted to the triple clamp (20) and the upper end of said steering shaft (10) is connected to the handle bar of the vehicle.

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 1, wherein
the adjuster fork bolt assembly (300) of the functional leg (100) and the follower leg (200) is configured to comprise of an adjuster bolt (310), a fork bolt (320), a threaded washer (330), a lock nut (340) and a spacer (350);
said fork bolt (320) is configured to have a first cavity (C1), a second cavity (C2) and a third cavity (C3);
said cavities (C1 to C3) are configured to jointly house the adjuster bolt (310) therein; and
the threaded washer (330), the lock nut (340) and the spacer (350) are sleeved over the adjuster bolt (310) in a manner so that the second cavity (C2) and third cavity (C3) of the fork bolt (320) of the fork bolt assembly (300) jointly houses the threaded washer (330), the lock nut (340) and the spacer (350) in combination with each other to adjust the preload of the main spring (120, 220).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 2, wherein
the said fork bolt (320) is configured to have an annular skirt portion (320S) projecting away in a longitudinal downward direction from an annular disk portion (320D) and a hex profiled boss (320H) projecting away in a longitudinal upward direction from the annular disk portion (320D) forming a unitary structure of the fork bolt (320);
said annular skirt portion (320S) of the fork bolt (320) is configured to have an O-ring groove (320G) and threads (320T) formed over its outer peripheral surface;
the diameter of the cavities (C1 to C3) of the fork bolt (320) are in the order of ØC1 < ØC2 < ØC3, and an annular step (320AS) is formed at the interface of the first cavity (C1) and the second cavity (C2) wherein the said step (320AS) is configured to provide a seat for the adjuster bolt (310) of the adjuster fork bolt assembly (300); and
said third cavity (C3) is configured to have a pair of arcuate slots (300ST) formed on its inner peripheral surface wherein the said slots (300ST) extends over the entire length of the said cavity (C3) in axial direction of the adjuster bolt (310).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 3, wherein
the adjuster bolt (310) is configured to have a body portion (310B) and a head portion (310H) and an annular step (310AS) is formed at the interface of the said head portion (310H) and the said body portion (310B);
said body portion (310B) is configured to have external threads (310T) formed over its outer peripheral surface and a threaded bore (310BT) formed so as to receive the threaded shank of the hollow piston rod (130) / piston rod spindle (230);
said head portion (310H) has a hex shaped profile and said hex shaped profile is configured to torque de-torque said adjuster bolt (310); and said head portion has indication means (310IM) carved on its top surface which indicates the direction of torqueing or de-torqueing of the adjuster bolt (310);
the threaded washer (330) is a stepped profiled hollow cylindrical body having female threads formed over its inner peripheral surface; and
the lock nut (340) is a hollow disk shaped body configured to have two arcuate profiled bosses (340B) formed over its outer peripheral surface and internal threads formed over its inner peripheral surface.

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 4, wherein
the adjuster bolt (310) of the adjuster fork bolt assembly (300) is in threaded connection with the washer (330) and the lock nut (340) and the head portion (310H) of the adjuster bolt (310) is positioned in the first cavity (C1) of the fork bolt (320) and the body portion (310B) is jointly housed by the second cavity (C2) and the third cavity (C3);
the threaded washer (330) is positioned within the second cavity (C2) and the top surface of the threaded washer (330) is configured to abut against the lower surface of the annular step (320S) of the fork bolt (320);
the lock nut (340) is positioned within the third cavity (C3) in a manner so that the top surface of the said lock nut (340) is configured to rest over the step (320AS) of the fork bolt (320) formed at the interface of the second cavity (C2) and the third cavity (C3); and the arcuate profiled bosses (340B) of the said lock nut (340) are free to slide within the arcuate slots (300ST) of the third cavity (C3);
said arcuate profiled bosses (340B) of the lock nut (340) in combination with the arcuate slots (310ST) of the fork bolt (320) are configured to prevent the rotational movement of the lock nut (340) with respect to the fork bolt (320); and
the spacer (350) is positioned in the third cavity (C3) in a manner so that the top surface of the said spacer (350) is configured to abut against the bottom surface of the lock nut (340).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 5, wherein the second cavity (C2) and the third cavity (C3) of the fork bolt (320) of the adjuster fork bolt assembly (300) of the fork leg (100, 200) are profiled in a manner so as to maintain the empirical relations as
?((a+b+c)/(x+y))= k3 s/(r.?) ; and ?((x+y)/c)= q,
where, a is the width of the threaded washer; b is the width of the lock nut; c is the width of the spacer; x is depth of the second cavity; y is depth of the third cavity; s is the pre-compression length of the main spring wherein s is equal to 5 to 10 mm; r is the radius of the body portion of the adjuster bolt; ? is the measure of the angular displacement of the adjuster bolt in radians; k3 is the correction constant wherein k3 = 0 to 0.5; and q is equivalence constant wherein q is equal to 2.0 to 2.5.

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 6, wherein
the fork leg (200) has the fork pipe (40) telescopically disposed within the outer tube (30) at its upper end and is threadedly engaged with the axle clamp (50) at its lower end (40L) with the help of external threads provided on the lower end of the outer peripheral surface of the fork pipe (40) and matching internal threads provided on the inner circumferential surface of the axle clamp (50);
a grub screw (90) is configured to tightly hold the lower circumferential end (40L) of the fork pipe (40) passing through a thorough hole in axle clamp (50) and impart high structural rigidity to the fork pipe (40) during its functioning;
the spring seat (240) is positioned at the top end of the fork pipe (40) and fixed there with the help of a threaded connection in between said spring seat (240) and the said fork pipe (40); and
said spring seat (240) is configured to have an annular collar (240C) projecting away from a flat surface (240F) wherein the said annular collar (240C) is integral to the flat face forming an L-shaped cross-sectional ring shaped profile.

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 7, wherein
the fork leg (200) has the piston rod assembly (230A) having a piston rod spindle (230), a spring guide (210), a spring support ring (260) and a rebound spring (250);
said spring guide (210) is configured to have a cylindrical portion (P1) and a converging tapered portion (P2), and said cylindrical portions (P1) and the tapered portion (P2) are formed in a manner so that a horizontal plane (X-X) divides the total vertical length (l) of the spring guide (210) in the ratio of l1:l2 in the longitudinal direction of the said spring guide (210);
said cylindrical portion (P1) is configured to extend up to the length (l1) in the longitudinal direction and the tapered portion (P2) is configured to converge gradually up to the length l2 in the longitudinal direction; and
the tapered portion (P2) of the spring guide (210) is configured to form a taper angle (a) with the vertical geometric axis of the spring guide (210).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 8, wherein
The piston rod spindle (230) of the piston rod assembly (230A) in the fork leg (200) is threadedly connected with the threaded bore (310BT) of the adjuster bolt (310) through the spring guide (210) at its top end by the virtue of the external threads provided on the outer surface of the top end of the said piston rod spindle (230) and matching internal threads provided on the threaded bore (310BT) of the adjuster bolt (310) and the top inner surface of the spring guide (210);
the spring support ring (260) is screwed to the lower end of the said piston rod spindle (260) and said spring support ring (260) is configured to have a plurality of damping orifices (260D); and
the rebound spring (250) is positioned annularly around the lower end of the piston rod spindle (230) in a manner so that the lower end of the said rebound spring (250) is configured to rest over the spring support ring (260) and the upper end of the said rebound spring (250) abuts against the lower surface of the spring seat (240).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 9, wherein
the spring guide (210) of the piston rod assembly (230A) of the fork leg (200) is configured to guide the main spring (220) annularly around it in a manner so that the lower end of the said main spring (220) rests against the flat surface (240F) of the spring seat (240) and top end of the said main spring (220) abuts against the lower surface of the adjuster fork bolt assembly (300);
the spring seat (240) of the piston rod assembly (230A) is configured to form the hydraulic lock chamber (H) with the lower end of the fork bolt (320) of the adjuster fork bolt assembly (300);
the piston rod spindle (230) of the piston rod assembly (230A) is secured with the adjuster fork bolt assembly (300) with the help of threaded connection in between the top end of the said piston rod spindle and an adjuster bolt of the adjuster fork bolt assembly (300); and
said fork leg (200) is filled damping fluid which is configured to travel from the outer tube (30) to the fork pipe (40) passing through the annular collar (240C) of the spring seat (240) followed by passing through the damping orifices (260D) of the spring support (260) during the compression stroke of the upside down front fork suspension (500).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 10, wherein
the spring guide (210) at its the tapered portion (P2) is configured to enter in an overlapping manner within the annular collar (240C) of the spring seat (240) due to the compression of the main spring (220) in the hydraulic lock chamber (H);
said overlapping of the tapered portion (P2) of the spring guide (210) within the annular collar (240C) of the spring seat (240) is configured to accumulate the fluid therein leading to formation of the hydraulic lock;
said hydraulic lock is configured to prevent the abutment of the fork pipe (40) and the adjuster fork bolt assembly (300) of the fork leg (200) eliminating the metal to metal contact and the unwanted noise coming therefrom; and
said spring guide (210) is configured to have optimized ratio of the tapered portion (P2) and the cylindrical portion (P1) to form the hydraulic lock in accordance with the relation as
l1/l2= k1 ((l1+l2))/(ds/tan?(a))

dc/ds= k2
where, l1 is the length of the cylindrical portion P1 of the spring guide; l2 is the length of the tapered portion P2 of the spring guide; dc is the diameter of the annular collar of the spring seat; ds is the diameter of the tapered end of the spring guide; a is taper angle of the spring guide; k1 is the form constant of the spring guide ranging from 3.0 to 4.0; and k2 is the hydraulic lock constant ranging from 1.15 to 1.25.

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 6, wherein
the fork leg (100) has the fork pipe assembly (40A) having a fork pipe (40), an axle clamp (50), a cartridge tube (150), a base tap (55), a socket headed bolt (95) and a base valve (195);
said fork pipe (40) of the fork leg (100) is threadedly engaged with the axle clamp (50) at its lower end with the help of external threads provided on the lower end (40L) of the outer peripheral surface of the fork pipe (40) and matching internal threads provided on the inner circumferential surface of the axle clamp (50);
the grub screw (90) is configured to tightly hold the lower circumferential end (40L) of the fork pipe (40) passing through a thorough hole formed in axle clamp (50) and impart high structural rigidity to the fork pipe (40) during its functioning;
the base tap (55) is fixedly positioned at the inner bottom surface of the axle clamp (50) with the help of the socket headed bolt (95);
the base valve (195) is configured to have a plurality of orifices (195O), and is fixedly mounted over the said base tap (55) in a manner so that a base tap spindle (55T) guides the base valve (195) annularly and a nut (195N) is screwed over the spindle (55T) so as to arrest the longitudinal movement of the said base valve (195);
the cartridge tube (150) of the fork pipe assembly (40A) is configured to have two orifices (150P) at its lower end (150L) and is fixed to the outer circumferential surface of the base tap (55) with the help of a circlip (not shown) at its lower end (150L); and
said base valve (195) is configured to pass the damping fluid from the interior of the cartridge tube (150) to the annular space formed in between the said cartridge tube (150) and the fork pipe (40).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 12, wherein
the fork leg (100) has the piston rod assembly (170A) having a hollow piston rod (130), a spring guide (110), a tap rebound slit (160), a piston (170) and a rebound spring (180);
said hollow piston rod (130) at its top end is inserted into the threaded bore (310BT) and threadedly connected with the adjuster bolt (310) by the virtue of the external threads provided on the outer surface of the top end (130T) of the said piston rod (130) and matching internal threads provided on the inner peripheral surface of the threaded bore (310BT) of the adjuster bolt (310);
the spring guide (110) is sleeved over the piston rod (130) and fitted over the piston rod below the fork bolt assembly (300) through the threaded joinery, and the tap rebound slit (160) is screwed to the lower end of the said hollow piston rod (130) closing the said end of the hollow piston rod (130) thereby;
the piston (170) having a plurality of damping orifices (170D) is mounted over the said tap rebound slit (160) and fixed there with the help of a hex nut (170N); and
the rebound spring (180) is positioned annularly around the piston rod (130) in a manner so that the lower end of the said rebound spring (180) rests over the said tap rebound slit (160).

The upside down front fork suspension (500) for two and three wheeled vehicles as claimed in claim 13, wherein
the functional leg (100) has the outer tube (30) having its top end closed with the help of the adjuster fork bolt assembly (300);
the top end of the cartridge tube (150) of the fork pipe assembly (40A) is configured to receive the piston (170) of the piston assembly (170A) making the piston free to slide within said cartridge tube (150) of the fork pipe assembly (40A);
the top open end of the said cartridge tube (150) is configured to receive the adaptor bush (190) making the flange portion (190F) of said adaptor bush (190) to rest over the top circumferential edge of the said cartridge tube (150) and a lower end of the said adaptor bush (190) abuts against the top end of the rebound spring (180) of the piston rod assembly (170A);
the cartridge tube (150) is locked with the adapter bush (190) by deforming the outer peripheral surface of the said cartridge tube (150) over a preformed groove (190G) of the said adaptor bush (190);
the bump stop (140) is positioned within a flange cup profile (190FC) of the adaptor bush (190);
the main spring (120) is positioned annularly around the spring guide (110) of the piston rod assembly (170A) making the lower end of the said main spring (120) to rest against the flange portion (190F) of the adaptor bush (190) and top end of the said main spring (120) abuts against the lower end of the adjuster fork bolt assembly (300) of the fork leg (100);
said spring guide (110) is configured to guide the main spring (120) against the buckling of the spring (120) during its functioning; and
said spring guide (110) in combination with the bump stop (140) is configured to prevent metal to metal contact during the extreme compression stroke of the suspension (500).

Dated this 28th day of Jan. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

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