FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
An operating mechanism for retarding the speed of a driving shaft of an off-road vehicle
APPLICANTS
Mahindra & Mahindra Ltd, Gateway Building, Apollo Bunder, Mumbai 400 001, Maharashtra, India, an Indian company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
[0001] This invention relates to an operating mechanism for retarding the speed of a
driving shaft of an off-road vehicle. The operating mechanism minimizes clashing noise between a driving shaft and gears when engine power is transferred from an engine to a wheel axle assembly.
DESCRIPTION OF THE BACKGROUND ART
[0002] In off road vehicles or work vehicles such as tractors, earth movers or mowers,
engine power generated from an engine is transmitted to a clutch housing and further to a speed section positioned adjacent to the clutch housing. The speed section houses various gears that are operably arranged with one another in multiple gear ratios. From the engine section, the desired engine power is further transferred to a rear wheel-axle assembly so as to drive the off-road vehicle at multiple ground speeds. Typically, an engine crank case includes an engine crank shaft arranged therein and operating in accordance with the engine power obtained from the engine. The crank shaft is also operably connected to a flywheel that converts and stores the engine power of the crank shaft in rotational energy form. The flywheel is further coupled to a clutch plate of the clutch system. Both the flywheel any the clutch system, including the clutch plate, are suitably positioned inside the clutch housing. within the clutch housing a driving shaft (or clutch shaft) is also positioned and rotatably connected with the clutch plate splines formed on one end of the driving shaft. Opposite end of the driving shaft is rotatably connected, directly or via couplings, to the gear box having gear various; arrangements with the help of splines provided at the opposite end like constant mesh or sliding mesh arrangements. The clutch system is

connected to a clutch pedal, accessible by the operator (driver), with the help of mechanical linkages, or through hydraulic or electrical mechanisms.
[0003] When the engine is in running condition, the clutch plate along with the driving
shaft is continuously engaged with the flywheel resulting in continuous rotation of the driving shaft. Appropriate selection of gears from the speed section allows the engine power obtained at the driving shaft end to be transmitted to the rear wheel axle assembly and the rear wheels. In running condition of the off-road vehicle, the clutch system basically acts as a mechanical device that when engaged with the flywheel allows the engine power to be transmitted to the speed section. Similarly, when the clutch plate is disengaged from the flywheel, the engine power is not transmitted to the speed section. Engagement and disengagement of the clutch plate with the flywheel is controlled by the clutch pedal, wherein actuation of the clutch pedal results in disengagement of the clutch plate from the flywheel.
[0004] During operating condition of the off-road vehicle, there are instances when it is
desired that the off-road vehicle runs at variable ground speeds. Such demands are met by gear change by sequentially actuating the clutch pedal and a gear shifting lever. Upon actuation of the clutch pedal, the fixedly connected driving shaft and the clutch plate are disengaged from the flywheel and as a result the rotational speed of the driving shaft starts to gradually decrease. Further, upon actuating the gear shifting lever appropriate gears are selected and coupled with the opposite end of the rotating driving shaft. Finally, the desired engine power generated from the speed housing is transmitted to the rear wheel-axle assembly resulting in the off-road vehicle running at the desired running speeds.
[0005] Though the above mechanical arrangements between the driving shaft and the
gears fulfil the requirement of variable running ground speed, there are certain drawbacks with

these arrangements. The primary drawback being generation of 'Clashing Noise' from the off-road vehicle whenever the clutch pedal and the gear shifting lever are sequentially actuated for variable speed selection needs. As noted above, though upon actuation of the clutch pedal, the driving shaft is disengaged from the flywheel but the rotational speed of the driving shaft does not decrease fast enough because of the inertia. As such, whenever the gear shifting lever is actuated, the inertia-driven rotating driving shaft tries to engage with the gears but sometimes proper engagement between the coupling at the opposite end of the driving shaft and the gears does not take place as the gears do not mesh with the coupling, thereby leading to unpleasant 'Clashing Noise'. Furthermore, the gears themselves may be subject to rotation due to their own inertia, which may further aggravate the noise problem when the inertia-driven rotating driving shaft couples with the gears. Each time the operator tries to actuate the gear shifting lever after actuating the clutch pedal, noise is generated. Such noise is very unpleasant to the operator and does not provide a good driving experience to the operator. Additionally, wear and tear between the driving shaft and gears, and their related components will also take place over a period of time. Wear and tear will also lead to delay in shifting of gears.
[0006] The above problems have been partially addressed by providing synchronised
gear arrangement within the speed housing. Nowadays some of the off-road vehicles come with a combination of constant mesh, sliding mesh and synchronised gears. It has been observed that the synchronised gear arrangement reduces the noise level to certain extent. Due to the presence of the constant mesh and sliding mesh gears in such off road vehicles, the drawbacks of noise and wear and tear still remain and need to be addressed. Further, providing synchronised gears for all the running speed requirements is quite costly resulting in enhanced overall price of the off-road vehicles.

[0007] As such there is need to develop an operating mechanism that substantially
reduces the noise levels during variable running speed needs of off-road vehicles.
SUMMARY OF THE INVENTION
[0008] The invention provides an operating mechanism for retarding the speed of a
driving shaft of an off-road vehicle, the driving shaft being disposed within a clutch housing and arranged within a driving shaft retainer in spaced apart relationship, the driving shaft retainer having a flange attached to its one end that is stably held within the clutch housing, the clutch housing including a clutch rail operatively connected to a clutch pedal and angularly rotatable in a first direction when the clutch pedal is depressed by an operator and in a second direction when the clutch pedal is released, the operating mechanism including a rotatable disc insertable over the driving shaft and positioned at a distance from the flange, the rotatable disc being rigidly attached to the driving shaft and rotatable at the driving shaft speed when the driving shaft is driven by an engine power, a sleeve member inserted over the driving shaft in spaced apart relationship and fastened to the clutch housing, a stopper having a planar body extending between a disc facing surface and a flange facing surface and including a central opening, the stopper engageably insertable over the sleeve member through the central opening and slidable over the sleeve member from a deactuating position to an actuating position, the stopper engaging an opposing surface of the rotatable disc to exert a retarding force thereupon in the actuating position and the stopper disengaging from the opposing surface of the rotatable disc in the deactuating position, and an actuating assembly operatively connected between the flange facing surface of the rotatable disc and the clutch rail, the actuating assembly allowing the stopper to be disposed in the actuating position when the clutch rail is rotated in the first

direction and allowing the stopper to be disposed in the deactuating position when the clutch rail is rotated in the second direction.
[0009] In some embodiments, the disc facing surface of the stopper includes a friction
material attached thereto for exerting a retarding force on the opposing surface of the rotatable disc in the actuating position, and wherein the flange facing surface of the stopper includes a protruding portion formed on a substantial portion of the flange facing surface, a peripheral edge of the protruding portion has a plurality of grooves formed thereon that runs along entire periphery.
[0010] In some embodiments, the actuating assembly includes a shaft supported below
the sleeve member and arranged parallely to the clutch rail, and wherein a corresponding fork is inserted over the shaft from its opposite end and fixedly connected to the shaft in such a manner that free ends of the forks abut with the flange facing surface of the friction divider, the free ends of the forks are fastened to the peripheral grooves.
[0011] In some embodiments, the shaft and the clutch rail are operatively connected to
each other through an interconnecting rod-clevis assembly, the rod-clevis assembly allowing the shaft to be angularly rotated by an equal amount in the second and first directions when the clutch rail is angularly rotated in the first and second directions, respectively.
[0012] In some embodiments, the sleeve member and the flange includes a partition wall
of the clutch housing positioned therebetween, and wherein the sleeve member, the flange member, and the partition wall includes a matching hole through which a fastening member passes for fastening the sleeve member, the flange member, and the partition wall together.

A BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The above-mentioned and other features and advantages of the various
embodiments of the invention, and the manner of attaining them, will become more apparent and better understood by reference to the accompanying drawings, wherein:
[0014] FIG. 1 is a sectional perspective view of a clutch housing of a typical off-road
vehicle illustrating a securely mounted driving shaft and an internally disposed mechanical components that are operably connected to the driving shaft according to an embodiment of the present invention;
[0015] FIG. 2 is an elevation of the driving shaft and the operably connected mechanical
components isolated from the clutch housing;
[0016] FIG. 3 is a perspective view of a rotatable disc that is connectable to the driving
shaft of FIG. 2 according to an embodiment of the present invention;
[0017] FIG. 4 is a perspective view of a driving shaft retainer within which the driving
shaft of FIG. 2 is inserted and held in spaced apart relationship;
[0018] FIG. 5 is a perspective view of a sleeve member that is inserted over the driving
shaft of FIG. 2 according to an embodiment of the present invention;
[0019] FIG. 6 is a perspective view of a stopper that is slidably insertable over the sleeve
member according to an embodiment of the present invention;
[0020] FIG. 7 is a perspective view of an actuating assembly operably connectable to the
driving shaft of FIG. 2 according to an embodiment of the present invention;
[0021] FIG. 8 is a perspective view of a fork insertable over a shaft of the actuating
assembly of FIG. 7;

[0022] FIG. 9 is an elevation of the driving shaft of FIG. 2 and the actuating assembly
that is operatively connectable to a clutch pedal; and
[0023] FIG. 10 is a sectional elevation of the clutch housing of FIG. 1 showing a speed
housing section disposed adjacent thereto.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] FIG. 1 shows a sectional perspective view of a clutch housing 100 of an off-road
vehicle and includes a driving shaft 102 centrally mounted therein in known manner and operably connected to an operating mechanism 104 for retarding speed of the driving shaft 102, according to an embodiment of the present invention. The clutch housing 100 extends between a first end 106 of the clutch housing 100 connectable to a crank case (not shown) and a second end 108 connectable to a speed housing section 110 (See FIG. 10). Although not shown but it would be understood by a skilled person in the art that the first end 106 and second end 108 are connected to the crank case and the speed housing section 110, respectively, with the help of fasteners or other fastening means.
[0025] In FIG. 2 the driving shaft 102 and the operably connected operating mechanism
104 is shown to be isolated from the clutch housing 100. The driving shaft 102 extends between a first end 112 and a second end 114 with both the first and second ends 112, 114 having splines 116 formed thereon. When centrally mounted within the clutch housing 100, as noted from FIG. 1, the driving shaft 102 passes through central openings of at least two of the partition walls. As seen in FIG. 2 and understood in view of FIG. 1, the splines 116 formed on the first end 112 of the driving shaft 102 is capable of being coupled to a clutch plate of the clutch system through. The splines 116 ensure that the first end 112 of the driving shaft 102 is rigidly connected to the clutch plate and to avoid any relative play therebetween. Further, the clutch system is mounted

over a flywheel (not shown), which is also positioned within the clutch housing 100. The flywheel is operably connected to a crank shaft that is positioned within the crank case. The crank shaft operates in accordance with the engine power generated from the engine and transmits the same to the flywheel that stores the engine power in the form of rotational energy. The clutch system, and particularly the clutch plate when engaged with the flywheel, allows the rotational energy of the flywheel to be transmitted to the driving shaft 102, which rotates along its central axis, and finally towards a rear wheel-axle assembly.
[0026] The second end 114 of the driving shaft 102, as seen in FIG. 2 and understood
from FIG. 1, may be connected to a plurality of gears 118 that are positioned within the speed housing section 110 (FIG. 10) with the help of a coupling (not shown). The gears 118'may be chosen from constant mesh, sliding mesh, etc., arrangements depending on the needs of manufacturers. The splines 116 formed on the second end 114 are generally connected with an end of the coupling that is further connected to the plurality of gears 118 through an opposite end of the coupling. Alternatively, the second end 114 of the driving shaft 102 may also be directly engaged with the plurality of gears 118 of the speed housing section 110 with the help of splines 116. The engine power obtained at the second end 114 of the driving shaft 102 is further transmitted to the speed housing section 110 and upon appropriate selection of the gears 118, by actuating a gear shifting lever (not shown), the desired engine power is further transmitted to a rear wheel-axle assembly for allowing the rear wheels to run variable ground speeds.
[0027] FIGS. 1 and 2 also show the clutch housing 100 to include a portion of a clutch
plate actuating mechanism 120. The clutch plate actuating mechanism 120 includes a pair of U-shaped forks 122 having a central passage formed at a bottom portion of the U-shaped forks 122 (FIG. 2). A clutch rail 124 is inserted within the central passage and bolted therewith with the

help of roll pins 126 so as provide a tight fitting therebetween, Both ends of the clutch rail 124, as understood from FIG. 1, are supported to opposite walls 128 of the clutch housing 100. The clutch rail 124 allows the U-shaped forks 122 to be securely positioned at the centre of the clutch housing 100. As seen in FIG. 2 and understood from FIG. 1, the driving shaft 102 is disposed substantially in the middle of the U-shaped forks 122. One of the ends of the clutch rail 124 is exposed outside the clutch housing 100 and understood to be connectable to a clutch linkage assembly (not shown) that is further operably coupled to a clutch pedal 130 (See FIG. 9). The clutch plate actuating mechanism 120 may also include a clutch release bearing mechanism that is suitably connected between free ends 132 of the U-shaped forks 122 and the clutch plate of the clutch system.
[0028] It is a common general knowledge that when the engine is in running condition,
the clutch plate is continuously engaged with the flywheel so as to allow the engine power to be transferred from the crank shaft to the speed housing section 110 and finally to the rear wheel axle assembly. However, in cases where different ground running speeds are required, the clutch plate is required to be disengaged from the flywheel. Upon disengaging the clutch plate from the flywheel, the rotational speed of the driving shaft 102 reduces and then the gear shifting lever is actuated for appropriately selecting the gears 118 and its coupling to the second end 114 of the driving shaft 102. The clutch plate actuating mechanism 120, as noted above, allows the clutch plate to be disengaged and engaged from the flywheel.
[0029] Upon actuating the clutch pedal 130, the clutch linkage assembly exerts a pre-
calculated and predetermined counter-clockwise rotational force on the clutch rail 124 due to which the clutch rail 124 is angularly rotated in a first direction. The first direction, when seen in FIG. 2 from the front, resembles a counter-clockwise rotational direction. The angular rotation of

the clutch rail 124 allows the U-shaped forks 122 to be pivotally displaced thereby exerting a pushing force on the clutch release bearing mechanism. The clutch release bearing mechanism, when pushed, results in disengaging the clutch plate from the flywheel. Similarly, in order to engage the clutch plate with the flywheel after the gear selection has been made, the clutch pedal 130 is released by the operator resulting in the clutch rail 124 to be angularly rotated by an equal amount in a second direction (clockwise direction) allowing the clutch rail 124 to be returned return back to its original position. This further result in the U-shaped forks 122 returning back to the normal position for allowing the clutch plate to be again engaged with the flywheel.
[0030] Reference is now given to the constructional components of the operating
mechanism 104 that when operably coupled with the driving shaft 102 and operated allows retarding the rotational speed of the driving shaft 102.
[0031] FIG. 3 shows a circular rotatable disc 134 having a central hole and formed to
have a thickness that extends between an engine side surface 136 and a gear side surface 138 according to an embodiment of the present invention. Both the engine and the gear side surfaces 136, 138 are planar in construction and a connecting member 140 attached on the gear side surface 138. The connecting member 140 also has a central opening 142 and when attached on the gear side surface 138 of the rotatable disc 134 matches the central hole thereof. The connecting member 140 also has a pair of opposite holes 144 formed on its outer periphery. The rotatable disc 134 is inserted over the driving shaft 102 and rigidly attached to the driving shaft 102 through the pair of opposite holes 144 (See FIG. 2) with the help of any of the known fastening members. Thus, the rotatable disc 134 rotates at the same speed as that of the driving shaft 102 when the driving shaft 102 is in rotating condition. Although the shape of the rotatable disc 134 is chosen to circular for the purpose of explaining the working of the invention however

such shapes should not be construed to be limiting as the rotatable disc 134 may have other shapes as well such as oval, square, rectangular, etc. All such shapes should be considered to be within the scope of the present invention.
[0032] FIG. 4 shows an embodiment of a driving shaft retainer 146 that is mounted over
the driving shaft 102 in spaced apart relationship as seen in FIG. 2. The driving shaft retainer 146 includes a flange 148 attached on it one end and when the driving shaft retainer 146 is mounted over the driving shaft 102 the flange 148 faces the engine side surface 136 of the rotatable disc 134. The flange 148 includes a plurality of equally spaced apart connecting holes 150. At least two of the oppositely placed holes of the flange 148 match the corresponding holes of one of the partition wall. Through these oppositely placed holes, the flange 148 is securely held against the driving shaft 102 in spaced apart relationship. Thus, the driving shaft retainer 146 remains relatively stationary when the driving shaft 102 is in rotating condition.
[0033] FIG. 5 shows an embodiment of a sleeve member 152 that is mounted over the
driving shaft 102 also in spaced apart relationship (See FIG. 2) according to an embodiment of the present invention. As seen in FIG. 5, the sleeve member 152 is formed to have a small cylindrical body 154 having a pair of opposing ears 156 attached to an end thereof. Each of the ears 156 has a hole formed therein whereas the diametrically opposite surfaces of the cylindrical body 154 have a corresponding elongated groove 160 formed therein. Within the elongated grooves 160 a thin plate (not sown) may be fitted within the elongated grooves 160 in such a manner that the thin plate protrudes to a predetermined height from the elongated grooves 160. When the sleeve member 152 is assembled over the driving shaft 102, holes of the sleeve member 152 are concentric to the holes of the flange 148 as well as the holes of the partition wall. Preferably, a fastening member passes through all these concentric holes to attach the

sleeve member 152 and the flange 148 with the partition wall (See FIG. 1). Such an arrangement results in the driving shaft 102 rotating at variable speeds within the relatively stationary sleeve member 152 and the driving shaft retainer 146.
[0034] A friction slider 162 is shown in FIG. 6 according to an embodiment of the
present invention. The friction slider 162, which acts as a stopper member, has a planar body that extends between a disc facing surface 164 and a flange facing surface 166 and includes a central opening 168 having a pair of oppositely formed keyways 170. The depth of the keyways 170 is defined by the height of the thin plate fitted on the elongated grooves 160 of the sleeve member 152 so that when the friction slider 162 is insertable over the sleeve member 152 through the central opening, the friction slider 162 is positively fitted thereon (See FIG. 2). As seen in FIG. 2, the disc facing surface 164 includes a friction material 175 attached thereto on at least a substantial portion thereof, whereas as seen in FIG. 6 the flange facing surface 166 includes a protruding portion 174 formed on a substantial portion of the flange facing surface 166. A peripheral edge of the protruding portion 174 has a plurality of grooves 176 formed thereon that runs along an entire periphery of the protruding portion 174. The friction slider 162 when mounted over the sleeve member 152 is capable of sliding there over from a deactuating position to an actuating position.
[0035] A skilled person in the art, having reference of FIGS. 2 and 9, would easily
understand that when the friction slider 162 is disposed in the actuating position, the disc facing surface 164 thereof engages an opposing surface of the rotatable disc 134 to exert a retarding force thereupon (FIG. 9). This results in retarding the rotational speed of the driving shaft 102. Similarly, when the friction slider 162 is disposed in the deactuating position, the disc facing surface 164 thereof looses contact with the opposing surface of the rotatable disc 134 (FIG. 2).

This allows the retarding force acting on the rotatable disc 134 to cease. Although the shape of the friction slider 162 is chosen to be circular for the purpose of maintaining proper contact with the rotatable disc 134 however such shapes should not be construed to be limiting as the rotatable disc 134 may have other shapes as well such as oval, square, rectangular, etc, compatible with the working relationship of the rotatable disc 134. All such shapes should be considered to be within the scope of the present invention.
[0036] The operating mechanism 104 also comprises of an actuating assembly 178 as
shown in FIG. 7 according to an embodiment of the present invention. The actuating assembly 178 is operatively connected between the flange facing surface 166 of the rotatable disc 134 and the clutch rail 124. The purpose of the actuating assembly 178 is to enable the friction slider 162 to be disposed in the actuating position when the clutch rail 124 is rotated in the first direction (clockwise direction when seen in FIG. 7, which is the rear side view of FIG. 2) and also to dispose the friction slider 162 in the deactuating position when the clutch rail 124 is rotated in the second direction (counter-clockwise direction when seen in FIG. 7).
[0037] As seen in FIG. 7, the actuating assembly 178 includes a shaft 180 supported
below the sleeve member 152 and arranged parallely to the clutch rail 124. Further, as seen in FIG. 8, a fork member 182 having a pair of forks is inserted over the shaft 180 and fixedly connected to the shaft 180 in such a manner that free ends 184 of the forks abut with the flange facing surface of the friction slider 162. Furthermore, the free ends 184 of the forks are provided with a through hole adapted to be fastened to the peripheral grooves 176 with the help of fasteners (See FIG. 9). Thus, it would be understood that the friction slider 162 that slides over the sleeve member 152 having the free ends 184 of the fork tied up at its rear.

[0038] FIG. 7 also shows an interconnecting shaft rod-clevis assembly 186 that
operatively connects the clutch rail 124 to the shaft 180. A skilled person in the art, having reference to FIG. 7, would understand that when the clutch rail 124 is angularly rotated in the first direction due to depression of the pedal by an operator, the rod-clevis assembly 186 allows the shaft 180 to be angularly rotated by an equal amount in the second direction (counterclockwise direction, when seen in FIG. 7). Counter-clockwise angular rotation of the shaft 180 allows the pair of forks to exert a pushing force on the friction slider 162 thereby enabling the friction slider 162 to be slidably disposed in the actuating position. As noted above, in the actuating position, the disc facing surface 164 of the friction slider 162 engages with an opposing surface of the rotatable disc 134 to exert a retarding force thereupon (FIG. 9).
[0039] Similarly, when the clutch pedal 130 is released the clutch rail 124 angularly
rotates in the second direction (counter-clockwise direction as seen in FIG. 7) and due to this the rod-clevis assembly 186 allows the shaft 180 to be angularly rotated by an equal amount in the first direction (clockwise direction, when seen in FIG. 7). Clockwise angular rotation of the shaft 180 allows the exerting force to be released from the pair of forks and subsequently on the friction slider 162. As such, the pair of forks pulls back the friction slider 162 back to its deactivating position. As noted above, in the deactuating position, the disc facing surface 164 of the friction slider 162 looses contact with the opposing surface of the rotatable disc 134 (FIG. 2). This allows the retarding force acting on the rotatable disc 134 to cease.
[0040] A skilled person would appreciate that upon actuating the clutch pedal 130 two
purposes are achieved. First, the clutch plate, as noted above, is disengaged from the flywheel; and second, the rotational motion of the driving shaft 102 is significantly reduced in quick turnaround time. Extent to which the rotational speed of the driving shaft 102 may be decreased,

once the clutch pedal 130 is actuated may be controlled by suitably adjusting the various interconnections in the actuating assembly 178. It should also be noted that that actuation of the actuating assembly 178 and clutch plate actuating mechanism 120 do not occur simultaneously whenever the clutch pedal 130 is actuated by the operator. Rather, there is slight, very minimal time lag between the two occurrences with the retarding of the driving shaft 102 occurring after the clutch plate actuating mechanism 120. There could be various means through which the time lag provision may be introduced in the working and should be considered within the scope of the present invention.
[0041] Now, because the rotational motion of the driving shaft 102 decreases upon
actuation of the clutch pedal 130, the noise generated when the second end 114 of the driving shaft 102 couples with the plurality of gears 118 (understood to be shown in FIG. 10) during speed selection by gear change is reduced significantly. Reduced noise levels during gear change help in providing the operator a better and comfortable driving experience. Further, the possibility of wear and tear is reduced thereby ensuring smooth operation over a long period of time and improving reliability and reducing cost.
[0042] Further, the above embodiments are explained by considering the mechanical
components comprising the operating mechanism 104 however, mechanical construction should not be construed as limiting to the present invention. Rather, the operating mechanism 104 could also comprise of pneumatic, electrical, combination of mechanical, electrical, or electronics means and all such means should be considered to be within the scope of the present invention.
[0043] It will be apparent to those skilled in the art that various modifications and
variations can be made to the present invention without departing from the spirit and scope of the

invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

We Claim:
1. An operating mechanism for retarding the speed of a driving shaft of an off-road vehicle, the driving shaft being disposed within a clutch housing and arranged within a driving shaft retainer in spaced apart relationship, the driving shaft retainer having a flange attached to its one end that is stably held within the clutch housing, the clutch housing including a clutch rail operatively connected to a clutch pedal and angularly rotatable in a first direction when the clutch pedal is depressed by an operator and in a second direction when the clutch pedal is released, the operating mechanism comprising:
a rotatable disc insertable over the driving shaft and positioned at a distance from the flange, the rotatable disc being rigidly attached to the driving shaft and rotatable at the driving shaft speed when the driving shaft is driven by an engine power;
a sleeve member inserted over the driving shaft in spaced apart relationship and fastened to the clutch housing;
a stopper having a planar body extending between a disc facing surface and a flange facing surface and including a central opening, the stopper engageably insertable over the sleeve member through the central opening and slidable over the sleeve member from a deactuating position to an actuating position, the stopper engaging an opposing surface of the rotatable disc to exert a retarding force thereupon in the actuating position and the stopper disengaging from the opposing surface of the rotatable disc in the deactuating position; and
an actuating assembly operatively connected between the flange facing surface of the rotatable disc and the clutch rail, the actuating assembly allowing the stopper to be disposed in the actuating position when the clutch rail is rotated in the first direction and also allowing the

stopper to be disposed in the deactuating position when the clutch rail is rotated in the second direction.
2. The operating mechanism according to claim 1, wherein the disc facing surface of the stopper includes a friction material attached thereto for exerting a retarding force on the opposing surface of the rotatable disc in the actuating position, and wherein the flange facing surface of the stopper includes a protruding portion formed on a substantial portion of the flange facing surface, a peripheral edge of the protruding portion has a plurality of grooves formed thereon that runs along entire periphery.
3. The operating mechanism according to claim 2, wherein the actuating assembly includes a shaft supported below the sleeve member and arranged parallely to the clutch rail, and wherein a corresponding fork is inserted over the shaft from its opposite end and fixedly connected to the shaft in such a manner that free ends of the forks abut with the flange facing surface of the friction slider, the free ends of the forks are fastened to the peripheral grooves.
4. The operating mechanism according to claim 3, wherein the shaft and the clutch rail are operatively connected to each other through an interconnecting rod-clevis assembly, the rod-clevis assembly allowing the shaft to be angularly rotated by an equal amount in the second and first directions when the clutch rail is angularly rotated in the first and second directions, respectively.

5. The operating mechanism according to claim 3, wherein the fastened free ends exert a pushing force on the flange facing surface of the stopper so as to allow the stopper to be positioned in the actuating position when the shaft is angularly rotated in the second direction, and wherein the fastened free ends exert a pulling force on the flange facing surface for allowing the stopper to be positioned in the deactuating position when the shaft is angularly rotated in the first direction.
6. The operating mechanism according to claim 1, wherein the sleeve member and the flange includes a partition wall of the clutch housing positioned therebetween, and wherein the sleeve member, the flange member, and the partition wall includes a matching hole through which a fastening member passes for fastening the sleeve member, the flange member, and the partition wall together.