FORM 2
THE Patent Act, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
Front fork of a two wheeler
Endurance Technologies Pvt Ltd
R&D, E 93, MIDC Industrial Area, Waluj, Aurangabad, Maharashtra—431136
The following specification describes the invention
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Field of the invention
The present invention [relates to “Front fork of a two wheeler” and more particularly to
preload adjustment for use in front fork of two wheelers with separate spring leg and
damping leg.
Description of the prior art
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A conventional prior art hydraulic damper or front fork shock absorber comprises a
cylinder which is adapted at one end for attachment to the sprung or un—sprung mass
of a vehicle. A piston is slideably disposed within the cylinder with the piston
separating the interior of the cylinder into two fluid chambers.-A piston rod is
connected to the piston and extends out ofvone end of the cylinder where it is
adapted for attachment to the other of the sprung or unsprung ‘mass of the vehicle.
Various conventional motorcycles employ, as a means for supporting a front wheel,
a telescopic front fork including two sets of axially slidable inner and outer tubular
members, each set of the tubular members including a fork pipe and a bottom case,
respectively, and a hydraulic system interposed between the two tubular members
for providing a shock absorbing action. Upon braking of such conventional
motorcycles, displacement of the centre of gravity, a force of inertia, etc., act in a
direction to contract the front fork. Particularly, upon sudden braking, the front fork
will come to assume the fully contracted position thereof.
A front wheel suspension system for a motorcycle is already known which includes a
contraction restraining mechanism for intercepting, upon braking of a front wheel of
the motorcycle, a main oil communicating passage between a fork pipe and a bottom
case to restrain axially contracting motion between the fork pipe and the bottom case
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in order to prevent a front part of the motorcycle from diving or moving down by
sudden braking operation of the front wheel.
In such a conventional front wheel suspension system for a motorcycle, a spring is
pre—loaded to support the sprung mass of the vehicle. In such systems, an optional
_ preload adjustment system improves the rider comfort under variable driving
conditions. With preloading higher forces can be obtained within the same stroke of
fork by giving initial deflection to the spring with same fork length and provides a
good handling or a good road grip. For high speed travel on smooth roads, preload
on the spring is required to be higher than the pre—set preload. Higher pre—|oading of
the spring is required to keep the tire always in Contact with the road surface and to
achieve high speed cornering or turning. For rough road conditions with a lot of
undulation and slow travel speeds, thelspring is required to absorb higher jerks;
hence the suspension spring should be soft to give a driver a comfortable ride.
Accordingly, the preload is required to be lower than the pre—set preload.
Generally such a preload adjustment is not provided’ in telescopic front forks.
Accordingly, the US Patent 5947498 illustrates a modular telescopic front_ fork
assembly having a removable se|f—contained damper cartridge which includes
housing, a cover forcovering a portion of the housing of said removable self-
contained damper and a reciprocating piston rod axially extending from the housing.
A suspension spring is positioned about and concentric with the reciprocating piston
rod. The modular te|escopic_front fork is provided with an adjustable spring seat.
assembly which operates to permit multiple spring preload adjustments. The rotation
of the cover enables an upper and lower spring seats of the adjustable spring seat
assembly to rotate with respect to one another and hence providing'a preload
adjustment. The concerned patent (US 5947498) in addition to other solutions are
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complicated in construction and cannot be easily be operated by the user of the two
wheeler depending on the road conditions to provide the required pre—load. Further
in another example, preload adjustment is provided in shock absorbers in the form of
cam—profile arrangement also as mentioned in the application no. 2354/MUM/2009.
But this adjustment of preload in shock absorbers requires the rider to stop the
vehicle, get down and do the adjustment. Further, the adjustment of preload also
requires lot of effort in to compensate for the cam to turn.
Additionally, to reduce weight and improve functionality, front forks with separate
damping leg and metal ‘spring leg have been incorporated in the prior art. As
mentioned in Japanese patent application no JP O6—230808 and Japanese utility
modelnpublication 849-1162 published in 1974 discloses a" pair of front forks one of
which is served as an oil pressure shock absorber provided with a damping force
generating mechanism and the other of which is served as a guide cylinder provided
with a suspension spring. However, there doesn’t exist any‘ provision in the prior art
to adjust preload in the above mentioned types of front forks.
Hence, there exists a need to obviate the lacunae in the prior art and to provide a
simple solution for preload adjustment. Therefore the’ objective of the present
invention is to provide a preload adjustment system in motorcycles having separate
damping leg and spring leg that facilitates adjustment of preload in either inverted or
telescopic front fork on the go while riding the vehicle.
The second objective of the present invention is to provide easy preload adjustment
requiring less effort.
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Brief description of the invention
A preload adjustment ‘for front fork with separate main spring leg and a damping leg
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of a two wheeler comprising an actuation mechanism, a preload adjuster, a non
return valve wherein said non-return valve is mounted on said main spring of the
front fork through saidvpreload adjuster and a spacer. The actuation mechanism
comprises an actuation lever, a reservoir having a main hole, a microhole, a return
spring, a piston, hydraulic lines and a banjo bolt. When pressure from hydraulic
mechanism is transmitted to said preload adjuster through said non—return'valve
where said non-return valves acts as a hydraulic lock and said preload adjuster
pushesmain spring of said front fork via said spacer. The stroke of the" grooved
preload adjuster is restricted by the fork bolt on top and a washer mounted on circlip
on bottom. A lip seal is placed in the groove to prevent leakage across the piston.
Brief description of the drawings
Figure 1 illustrates a motorcycle with a front fork assembly according to the prior art
Figure 2 illustrates a pair of front fork with separate spring leg and damping leg
according tothe prior art
Figure 3 illustrates preload adjustment in the spring leg according to the present
invenfion
Figure 4 illustrates the actuation mechanism according to the present invention
, Figure 5 illustrates the enlarged view of the preload adjuster
Figure 6 illustrates mechanical lock and its subsequent release mechanism
according to the present invention
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Figure 7 illustrates pre.load adjuster according to the present invention
Figure 8 illustrates a multi—stage preload adjustment according to the present
invenflon
Figure 9 illustrates .pre|oad adjustment through a hydraulic line according to the
present invention
Detailed description of the invention
As illustrated in Figure 1 and Figure 2, a front suspension 101 is made up of a pair of
front forks, left and right. One of the front forks 101 comprises a spring leg 102
having a metal spring 104 for supporting motorcycle body, and theother front fork
comprises a damper leg 103 having a damping mechanism that dampens vibration
arising from the operation of the spring leg 102. The right and left legs are therefore
configured to have dissimilar functions. The spring leg 102 and damper leg 103 are
fixed in such a manner that the spring leg 102 and damper leg 103 are parallel to
each other.
Accordingto the present invention, the spring leg 102 of a telescopic front fork 101,
along with a cut section illustrating the actuation mechanism is depicted in figure 3.
The actuation mechanism 105 may be mounted on to the handle bar below the
clutch lever/brake lever for easy operation on adjustment of the preload. The
encircled portion in figure 3 illustrates a preload adjuster, which also functions
additionally as a fork bolt. Figure 4 shows the enlarged view of the actuation
mechanism. It consists of an actuation lever .106, which when pressed, pushes the
piston 107, closing micro-holes 108 present in the actuation mechanism and causing
hydraulic pressure build—up. This pressure is transmitted through a banjo bolt 109
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and a hydraulic line 110 to the preload adjuster. The reservoir 111 on top is
_ maintained at atmospheric pressure. It may have a viewfinder 112 on it for knowing
oil level. The main-hole 113 opens into the chamber formed between the piston 107
and low pressure seal to replenish any leaked oil through the high pressure seal into
the reservoir 111. It also maintains the oil in that chamber at atmospheric pressure.
The spring 114 ensures that the piston returns back on removal of the actuation
force_.
Figure 5 shows thefenlarged view of the preload adjuster. The hydraulic pressure
generated in the actuation mechanism is transmitted into the chamber above the
Non Return Valve (NRV) 115. The NRV 115 mounted on the spring 116 ensures that
flow occurs only in one direction preferably from top to bottom, thereby functioning
as a hydraulic lock. The other end of the spring rests on a washer mounted on a
circlip. The pressure in the chamber below the NRV 115 pushes down the grooved
preload adjuster 117, which in turn pushes the spacer 118, thereby increasing the
preload in the main spring 104. The stroke of the grooved preload adjuster 117 is
restricted by the fork bolt 119 on top and a washer 120 mounted on circlip on bottom.
A lip seal 121 is placed in the groove to prevent leakage across the piston.
A preload release mechanism, to get the preload back to the original setting, is also
incorporated into the main design in the form of a push rod 123 mounted on a spring
122, that extends from above the banjo bolt 124 to the NRV 115. On pushing the
preload release rod 123, the NRV 115 is also pushed down thereby releasing the
pressure locked below the NRV 115. This enables the spacer 118 to return back to
its original position, thereby releasing the preload.

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In one of the other embodiment of the present invention, a mechanical lock 125 is
provided to maintain the preload (Figure 6). The said mechanical lock 125 and its
subsequent release mechanism are mounted next to the actuation lever 106 as
.5 shown in figure 6. On application of force on the actuation lever 106, the rotation of
lever pushes the lock rod 126 mounted on spring. Beyond a predetermined angle,
once the lever 106 loses contact with lock rod 126, the mounted spring 116 pushes-
back the lock rod 126 to its original position, therebyflocking the lever _and
subsequently the piston, and maintaining the pressure built on the preload adjuster
depicted in figure 7. In order to release the preload, the user will have to push the
lock rod release 127 for releasing the actuation lever. This enables the piston to
move toits original position thereby releasing the pressure built up.
Further in another embodiment of the present invention a ratchet type mechanical
lock 128, isprovided to have a multistage preload adjustment. The ratchet 128 is '
mounted on to the actuation lever 106 and the locking pawl cum release mechanism
is mounted on reservoir 111 as depicted in figure 8.
Further in another embodiment of the present invention, -the non return valve 129 -
can be mounted separately connected through hydraulic lines 110 as illustrated in
figure 9. The separate unit is mounted in the vicinity of the head pipe of said two-
wheeler. The actuation mechanism 105, separate non—return valve 129 and the
preload adjuster 117 assembly can be mounted separately in various suitable
locations of a two wheeler.
While considerable emphasis has been placed herein on the particular features of
this invention, it will be appreciated that various modifications can be made, and that
many changes can be made in the preferred embodiments without departing from
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the principles of the invention. These and other modifications in the nature of the
invention or the preferred embodiments will be apparent to those skilled in the art
from the disclosure herein, whereby it is to be distinctly understood that the foregoing
descriptive matter is to be interpreted merely as illustrative of the invention and not
as a limitation.
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Claims
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We claim:
1. A preload adjustment system for front fork with separate main spring leg and
a damping leg of a two wheeler comprising an actuation mechanism, a
preload adjuster, a non return valve wherein said non—return valve is mounted
on said main spring of the front fork through said preload adjuster and a
spacer
2. The preloaduadjustment for front fork of a two wheeler as claimed in claim 1,
wherein said actuation mechanism comprises an actuation lever, a reservoir
having a main hole, a microhole, a return spring, a piston, hydraulic lines and
a banjo bolt. I
3. The preload ‘adjustment for front fork of a two wheeler as claimed in claim 1,
wherein when pressure from hydraulic mechanism is transmitted to said
preload adjuster through said non—retur‘n_valve where said non-return valves
acts as a hydraulic lock and said preload adjuster pushes main spring of said
front fork via saidspacer. I
4. The preload adjustment for front fork of a two wheeler as claimed in claim 1,
wherein a preload release mechanism is provided above said banjo bolt
comprising a push rod mounted over a spring that extends above said banjo
bolt to the non—return valve. I
5. The preload adjustment for front fork of a two wheeler as claimed in claim 1,
wherein said non-return valve is mounted separately from said.front fork, in
vicinity of head pipe of said two wheeler, connected through either hydraulic
or mechanical lines.
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_ 6. A two wheeler with said preload adjustment for front fork as claimed in claim
1 .