TECHNICAL FIELD
[0001] The present subject matter described herein in general relates to a suspension system for a vehicle and in particular relates to a telescopic front fork assembly for a two-wheeJed vehicle.
BACKGROUND [0002] A telescopic front fork assembly is employed in a two-wheeled vehicle to act as a shock absorbing means or suspension means, and to facilitate effective braking and handling of the vehicle. Shock absorbers are necessary to keep a rider isolated from the road jerks and vibrations, thereby.making the ride comfortable. In addition, effective braking and handling of the vehicle is important for safety reasons. Typically, the telescopic front fork assembly connects the front wheel of the two-wheeled vehicle with the handlebar and in this way shares the load of the vehicle. [0003] The telescopic front fork assembly includes two parallel placed fork tubes, each of which has an identical construction. These tubes, in particular, dampen the vibrations felt by a rider. The telescopic front fork assembly facilitates upward and downward displacements of the front wheel to absorb jerks and vibrations caused due to a rough and uneven road while the vehicle is in motion. In addition, the telescopic front fork assembly ensures a firm ground contact of the front wheel for better control and steerabilily.
[0004] Generally, variable dampening characteristics are required to be exhibited by the telescopic front fork on the basis of varying road conditions. As an example, the amount of dampening required when the vehicle is driven on a smooth road surface is very low. Contrary to this, the amount of dampening required on a rough and uneven road is very high. To suit different kinds of road surfaces, the dampening characteristics of the telescopic front fork need to be varied. However, conventional telescopic front fork assemblies provide a constant dampening characteristic. The constant dampening characteristic is mainly due to the non-variable size and the

number of the compression and extension orifices located on the circumference of the pistons provided inside the front forks of the telescopic front fork. [0005] These orifices are of a circular cross-section and are identical in shape and diameter. This provides a constant, non-variable dampening characteristic to the
j conventional telescopic front fork assembly, since the flow of a dampening fluid through these orifices during the compression and the extension cycles takes place in a predetermined way.
[0006] More recently, telescopic front fork assemblies, such as cartridge type dampening systems, which provide adjustable dampening, have been developed to
) achieve the variable dampening characteristics. However, these telescopic front fork assemblies with adjustable dampening design employ substantially higher number of additional components as compared to the conventional assemblies. The additional components, which include pneumatic valves, adjustment rods, spring discs, elastomeric pads etc., make the design complex and the structure considerably heavy.
5 [0007] The presence of the large number of components requires additional serviceability. Moreover, the manufacturing and the maintenance costs associated with such telescopic front fork assemblies are high.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The above and other features, aspects and advantages "of the subject matter will be better understood with regard to the following description, appended claims, and accompanying drawings, where:
[0009] FIG. 1 shows a perspective view of a telescopic front fork assembly for a 5 two-wheeled vehicle, according to one embodiment of the present subject matter.
[00010] FIG. 2 shows a sectional view of a telescopic strut of the telescopic front
fork assembly of FIG. 1.
[00011] Fig. 3 illustrates a perspective view of the piston and the sleeve.

[00012] Fig. 4 illustrates the dampening mechanism connected to a brake fluid hose according to an embodiment of the present invention.
[00013] Fig. 5 illustrates an assembly of the dampening mechanism attached to the secondary brake force transmission member.
[00014] Fig. 6 illustrates a flow diagram illustrating a method to actuate and de-actuate the adjustable dampening mechanism.
[00015] Fig. 7 illustrates a detailed view of the adjustable dampening mechanism for adjusting the dampening characteristics of the front suspension assembly.
DETAILED DESCRIPTION
[00016] Generally, in a conventional motorcycle, the vehicle body pitch varies due to effect on longitudinal accelerations. During braking of the motorcycles, load transfers to the front wheel and to improve the handling stability and rider safety, it is required to avoid more pitching of the vehicle when brake is applied. If the motorcycle is equipped with telescopic forks, the added load on the front wheel is transmitted through the forks, which compresses the front suspension. This shortening of the forks causes the front end of the vehicle to move lower, and this is called as dive behaviour of the vehicle. Telescopic forks are particularly prone to the diving. Brake dive can cause discomfort to the rider and leads to reduced vehicle stability creating unsafe conditions. Brake dive with telescopic forks can be reduced by either increasing the spring rate of the fork springs, or increasing the compression damping of the forks. However, all of these changes make the vehicle less pleasant to ride on rough roads.
[00017] It is known in the art wherein, a user controlled adjustment of the dampening characteristics of the telescopic front fork assembly exists, depending upon the varied road conditions. However, manual control of the dampening characteristics as desired by the user makes it impossible to get higher compression settings. Further, with available configuration of the front forks for cartridge type

front fork, implementing the control adjustment during braking becomes complex and uneconomical.
[00018] The subject matter described herein is directed to a telescopic front fork assembly for a two-wheeled vehicle. In accordance with one embodiment of the present subject matter, the telescopic front fork assembly includes a pair of telescopic front forks. The telescopic front forks include an outer tube and an inner tube, and each tube has a first end and a second end. The second end of the inner tube is capable of axialiy sliding through the first end of the outer lube, towards the second end of the outer tube. Furthermore, a piston having a first end and a second end is concentrically disposed inside the inner tube. A number of extension dampening holes are disposed circumferentially towards the first end of the piston. Likewise, a number of compression dampening holes are disposed circumferentially towards the second end of the piston. An annular space between the second end of piston and outer tube acts as an area of storage of dampening fluid.
[00019] Further, the telescopic front forks include an adjustable dampening mechanism for adjusting the dampening characteristics of the front suspension assembly. The- adjustable dampening mechanism includes a sleeve that is concentrically disposed between the inner tube and the piston. The adjustable dampening mechanism also includes a rotating mechanism for rotating the sleeve. The sleeve is rotated such that the sleeve is enabled to selectively cover the compression dampening holes and the extension dampening holes, located on the piston. Thus, the hole opening size or number of holes or both are selectively controlled depending upon the portion or number of the holes covered by the sleeve. Furthermore,, the hole opening size or the number of holes is directly proportional to the volume of the dampening fluid flowing across the holes. Accordingly, the selective control of the hole opening size or the number of holes increases the resistance towards the flow of the dampening fluid across the holes, thereby increasing the dampening characteristics.

[00020] The front suspension assembly includes a pair of telescopic front forks. Each of the telescopic front- forks includes an outer tube and an inner tube, and each tube has a first end and a second end. The inner tube is operably connected with the outer tube in a manner such that the inner tube axially slides through the first end of the outer tube towards the second end of the outer tube.
[00021] A spring is operably arid axially disposed between the first end of the inner tube and a first end of a piston. The piston is concentrically disposed inside the inner tube. A number of extension dampening holes and the compression dampening holes are disposed circumferentially towards two different ends of the piston. An annular space between the piston and outer tube acts as a storage-area of damping fluid. When the front fork assembly is at rest, the fluid lies in the annular space over the second end of the piston.
[00022] As and when the vehicle encounters a jolt due to the uneven road, the wheel either displaces upwards or downwards. In case of the upward displacement, the telescopic strut also moves upwards along with the wheel. Similarly, the telescopic strut moves downwards during the downward displacement. In both scenarios there is a relative motion between the inner tube and the outer tube. This relative motion enables axial slide of inner tube along the outer tube, thereby compressing or extending the spring lying there between.
[00023] The inward sliding of the inner tube pressurizes the dampening fluid in the annular space over the second end of the piston. Accordingly, the inward sliding of the inner tube forces the pressurized dampening fluid to flow into a chamber of the piston through the compression dampening holes. The inward flow of the dampening fluid opposes the compression forces exerted on the spring, thus dissipating the compression'forces. Consequently, the dampening fluid absorbs the impact of the jerk.
[00024] Immediately after the jerk is overcome, the compressed spring lends to extend so as to release a potential energy that gets stored by virtue of compression.

The extension of the spring makes the inner tube to slide back to its initial position, thereby causing the fluid present inside the chamber of the piston to flow back towards the annular space, over the second end of the piston, through the extension dampening holes. The outward flow of the dampening fluid opposes the extension of the spring, thus dissipating the extension forces. Consequently, the oscillations of the spring, are damped by the flow of the dampening fluid through the aforementioned dampening holes.
[00025] Thus, the dampening characteristic of the assembly, i.e., the extent of absorption of the impact of a jerk, is determined by various factors such as the spring constant of the spring and the amount of dissipation provided by the flow of' dampening fluid. In order to allow variation in the dampening characteristics, the assembly includes a mechanism to adjust the dampening characteristics of the front fork assembly. Such mechanism may be referred as an adjustable dampening mechanism. The adjustable dampening mechanism includes a sleeve, which is concentrically disposed between the inner tube and the piston. In addition, a rotating mechanism is provided within the adjustable dampening mechanism for rotating the sleeve. In case a variation in the dampening characteristics is required, the sleeve circumscribing the piston is rotated. A user controlled rotation of the sleeve facilitates ' selective control the hole opening size or number of the extension and the compression dampening holes. Accordingly, the flow of the dampening fluid through aforementioned dampening holes is controlled. Conclusively, the dampening characteristics of the vehicle may be adjusted or varied.
[U0026] The present subject matter proposes a solution to provide user friendly and quicker adjustment of the dampening characteristics of the front suspension assembly whenever brakes are applied, thereby enhancing the rider comfort. Further, the adjustable dampening system as proposed herein is carried out automatically without manual intervention.

[00027] According to an embodiment of the present invention, the adjustment of the dampening characteristics is carried out by actuating the adjustment of dampening characteristics through a plunger mechanism acting under directions given by one or more brake fluid hoses.
[00028]' According to an embodiment of the present invention, a portion of the main brake force transmission member configured to control the braking performance of the motorcycle is deviated to form a secondary brake force transmission member. The secondary brake force transmission member is capable of modulating the brake actuation signal that is received from the main brake force transmission member. The secondary brake force transmission member is configured to actuate the plunger mechanism after the modulating brake actuation signal is applied to the adjustable dampening mechanism. In particular, the brake fluid pressure in the brake fluid hose is converted into the rotational movement of the gear mechanism through the plunger. The dampening characteristics include suitable plunger mechanism capable of converting the brake fluid pressure to the rotational movement of the gear mechanism.
[00029] According to an embodiment of the present invention, whenever front brakes in the vehicle are applied, hydraulic pressure in the brake fluid hose is diverted into the secondary brake force transmission member that is configured to operate the gear mechanism of the adjustment of dampening characteristics. Further upon increment of the braking pressure, the sleeve rotates and is capable of blocking the compression damping hose and the flow of damping fluid is restricted accordingly. The restriction of the flow of damping fluid makes the suspension stiffer as desired and prevents excessive compression of the pair of front forks. This provides better stability and control of the vehicle.
[00030] Furthermore, according to another embodiment of the present invention, the adjusted dampening characteristics can be released or brought back to normal settings by providing a reverse mechanism, which includes a return spring and with use of

rotatable gear mechanism which brings the sleeve back to its normal position once the applied brake is released.
[00031] Therefore, the adjustment of the dampening characteristics of the front suspension assembly is not carried out manually by the user/ the rider. Whenever, the rider feels the necessity of adjusting the dampening characteristics, the rider need not stop riding, or get off the vehicle and perform the adjustment of the dampening characteristics according to the conditions of the road. The manual adjustment which is cumbersome and not user friendly under all circumstances is prevented. The manual performing of adjustment of the dampening characteristics is also undesirable by the user.
[00032] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary.is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[00033] FIG. 1 shows a perspective view of a telescopic front fork assembly 100 for a two-wheeled vehicle. In one embodiment of the present subject matter, the telescopic front fork assembly 100 comprises a pair of telescopic struts (not shown). Each of the struts of a pair of strut 102 includes an outer tube 104 having a first end 106 and a second end 108. Further, an inner tube 110 is slidably and operably disposed within the outer tube 104. The inner tube 110 also includes a first end 112 and a second end 114.
[00034] The second end.114 of the inner tube 110 is operable to axially slide into the outer tube 104, through the second end 108 of the outer tube 104 towards the first end 106 of the outer tube 104. Specifically, the inner tube 110 is operable to slide back and forth inside the outer tube 104.

[00035] The!, front fork assembly 100 also includes a dampening mechanism 200 actuated by a secondary brake force transmission member 301 comprising a portion of the brake fluid deviated from the main brake force transmission member 300 operably connected to a front brakes 115.
[00036] FIG. 2 depicts a sectional view of the telescopic strut 102 of the front fork assembly 100. In one embodiment, a piston 200 having a first end 202 and a second end 204 is concentrically and operably disposed inside the inner tube 110. The second end 204 of the piston 200 is fastened to the second end 108 of. the outer tube 104 through a bolt 206. A spring 207 is operably disposed between the first end (not . shown) of the inner lube 110 and the First end 202 of the piston 200. A sleeve 212 is also concentrically disposed between the inner tube 110 and the piston 200. The sleeve 212 is preferably made from a metallic or a polymeric material. [00037] Further, an annular space between the piston 200 and the outer tube 104 defines a continuous space for the storage of a dampening fluid therein. When the front fork assembly 100 is at rest, the annular space over the second end 204 of the piston 200 stores the dampening fluid. The dampening fluid may include any fluid including oil, gas or a mixture thereof. Further, a rotating mechanism including a first bevel gear 214, operably and rigidly engaged with the sleeve 212, and a second bevel gear 216 operably engaged with the first bevel gear 214, is provided for rotating the sleeve 212. The operation of the rotating mechanism has been elaborated later. ' [00038] Fig. 3 illustrates a perspective view of the piston and the sleeve. The piston includes a first end 202 and a second end 204. The piston includes a plurality of extension dampening holes 208 and a plurality of compression dampening holes 210 disposed towards the first end 202 and the second end 204 respectively. The sleeve 212 is capable of being disposed concentrically around the piston 200. The sleeve 212 includes plurality of extension dampening control slots 230 and a plurality of compression .dampening control slots 235 disposed circumferentially towards a first end 218 and a second end 220 of the sleeve 212. According to the desired adjustment

of the dampening characteristics, the plurality of extension dampening control slots 230 and a plurality of compression dampening control slots 235 on the sleeve 212 cover/uncover or partially cover the plurality of extension dampening holes 208 and the plurality of compression dampening holes 210.
[00039] Fig. 4 illustrates the dampening mechanism connected to a brake fluid hose according to an embodiment of the present invention, A portion of the brake fluid in the main brake force transmission member is diverted into the secondary brake force transmission member 301 connected to the plunger mechanism 302 of the dampening mechanism. The pressure of the brake fluid created due to application of the brakes is transferred into the diverted secondary brake force transmission member 301 as well. The pressure of the brake fluid in the secondary brake force transmission member 301 is converted into the rotational movement of the plunger mechanism 302, which indirectly rotates the sleeve (not shown). Accordingly, due to the rotation of the sleeve, the opening of the one or more holes is controlled and the flow of the damping fluid is restricted. Accordingly, the desired adjustment of the front suspension assembly whenever the brakes are applied is achieved. [00040] Fig. 5 illustrates an assembly of the dampening mechanism attached to the secondary brake force transmission member. According to an embodiment of the present invention, the dampening mechanism includes a plunger mechanism 302 attached to the secondary brake force transmission member 301 through an intermediary attachment 304, The plunger mechanism 302 provides a linear motion to the one or more geared members including the first bevel gear 214 and the second bevel gear 216. The linear motion is converted into the rotational movement by the one or more geared members 214, 216, which effectively transfers the rotational movement to the sleeve 212, Therefore, the adjustment of the dampening characteristics is achieved automatically as desired by the user without any manual intervention. The adjustment of the dampening characteristics is achieved instantly as

and when the rider feels the need for changes in the dampening characteristics of the
front suspension assembly.
[00041] In another embodiment, the adjustable mechanism of the present telescopic
front fork assembly does not require any human intervention and may be achieved by
employing an automated mechanism. Specifically, the value of dampening may be
altered with respect to a sensing mechanism installed within the automated
mechanism provided in a two-wheeled vehicle. The sensing mechanism may be any
electronic vibration sensing means that senses the condition of the road. Accordingly,
the adjustable mechanism may automatically adjust the dampening value with respect
to the encountered road conditions on the basis of the inputs from the sensing
mechanism.
[00042] In another embodiment, the shape and size of the holes on the piston and the
slots on the sleeve may be varied so as to enable either discreet or continuously
varying control of the fluid path. This type of control of the fluid path enables
discreet change or smooth continuous change in damping characteristics.
[00043] In yet another embodiment, the main brake force transmission member 300
and the secondary brake force transmission member 301 is a brake hose including
pressurized fluid capable of enabling linear motion of the plunger mechanism 302.
[00044] In another embodiment, the main brake force transmission member 300 and
the secondary brake force transmission member 301 is a brake cable configured to
mechanically enable linear motion of the plunger mechanism 302.
[00045] The previously described versions of the subject matter and its equivalent
thereof have many advantages, including those which are described below:
[00046] The telescopic front fork assembly 100 of the present subject matter
facilitates user-enabled adjustability of the underlying dampening mechanism. The
user can exercise his control over the adjustable dampening mechanism with the help
of a rotalable valve type switch. If the present dampening mechanism is electrically

actuated, the user can set the level of desired dampening by means of an electrical
control/switch.
[00047] Further, the present adjustable dampening mechanism involves a sleeve and
the bevel gears to adjust the hole opening size of the dampening holes located on the
> piston 200. In terms of overall weight and space occupation, the telescopic front fork
assembly 100 scores over various conventional adjustable front fork assemblies such
as conventional assemblies which have cartridge type of construction. Also, the
overall manufacturing cost of the telescopic front fork assembly 100 is considerably
less as it employs less number of components than usual. Moreover, due to a simpler
) design, the upkeep and the maintenance costs associated with the telescopic front fork assembly 100 is low.
[00048] Fig. 6 illustrates a flow diagram illustrating a method to actuate and de-actuate the adjustable dampening mechanism. The user actuates the one or more front brakes.115 whenever the vehicle encounters undulations on the surface of the road.
i Upon actuation a front brake lever, the brake actuation force is transmitted to the one
or more frorit brakes 115 through the main brake force transmission member 300.
After the main brake force actuation member 300 receives the brake actuation signal,
. the signal is further transmitted through a secondary brake force transmission
member 301. The secondary brake force actuation member 301 modulates the
) received brake actuation signal, which is further applied on to the adjustable dampening mechanism. The adjustable dampening mechanism (150) is capable of actuating linear motion in a particular direction of a plunger mechanism (302) after receiving brake actuation signal through said secondary brake force transmission member (301), transferring linear motion of said plunger mechanism (302) into a
> rotary motion in a particular direction of a sleeve (212) through one or more geared
members (214, 216), actuating linear motion of said plunger mechanism (302) in an
opposite direction to said particular direction by a return spring (401) upon disabling
of said main brake force transmission member (300); and transferring linear motion

of said plunger mechanism (302) into a rotary motion in an opposite direction to said particular direction of said sleeve (212).
[00049] Fig. 7 illustrates a detailed view of the adjustable dampening mechanism for adjusting the dampening characteristics of the front suspension assembly. After the adjustment of the dampening characteristics is carried out automatically by application of brakes in the vehicle, the dampening characteristics have to be brought back to its original state. This is achieved easily by releasing the brakes. The rider/the user do not have to make any effort in order to bring back the dampening characteristics to its previous state. Just by releasing the applied brakes, the dampening characteristics are restored to their original state and the vehicle is ready. . to traverse through the road under normal conditions. Further, whenever the brakes are applied to encounter a pot hole or a speed breaker, correspondingly the dampening characteristics are accordingly adjusted to traverse over the pothole or the speed breaker. Further, after encountering the pot hole or the speed breaker, the-brakes are released and the dampening characteristics are restored that enable the vehicle to traverse through the road under normal conditions.
[00050] According to an embodiment of the present invention, the dampening characteristics are restored to its original state by a return spring 401 disposed around the intermediary attachment 304. Whenever the brakes are applied, the intermediary attachment 304 moves forward by compressing the return spring 401, the forward movement 304 moves the plunger mechanism 302, that rotates the one or more geared members 214, 216 through the plunger mechanism 302. Further, whenever the brakes' are released, the already compressed return spring 401 is ready to retain its non-compressed state and hence, the return spring 401 instantly decompresses, which correspondingly pulls back the plunger mechanism 302, the plunger mechanism 302 now rotates the sleeve in an opposite direction and hence, the dampening characteristics are accordingly restored to its original stale.

[00051] According to another embodiment of the present invention, the speed of actuation of the adjustable dampening mechanism can be controlled by the number of rotations of the sleeve, which is further controlled by optimizing the length r of the plunger mechanism 302, which further affects the arc S traversed by the plunger mechanism 302. Furthermore, the angle of displacement 9 can also be optimized with optimization of the length r of the plunger mechanism 3.02. [00052] Therefore, just by application and release of brakes, the dampening characteristics are adjusted and restored through a return spring. [00053] Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.