Field of the invention;
The present invention relates to automobile clutches in general and more particularly to pull type angle spring clutches.
Background of the invention;
Friction Clutches are well known mechanisms in automobiles. They are used to connect a driven means and a rotational power source which is usually the crankshaft of an automobile engine. The clutch works as a flexural member between the engine and transmission of a vehicle. Typically a plurality of springs is used provide clamping load to the pressure plate of the clutch. The clutch pedal is used to move the clutch from an engaged position to a disengaged position. The plurality of springs requires a high magnitude of force to be exerted on the clutch pedal for arriving at the disengaged position. Consequently the operator of an automobile vehicle is required to exert a high amount of pressure on the clutch pedal frequently at the time of changing gears resulting in discomfort and fatigue after continuous driving for long durations.
To overcome the above mentioned problems US Patent No. 6,619,458 disclosed a clutch having pivot point release load adjuster assembly for use in a pull type angle spring clutch pressure plate assembly. The clutch assembly disclosed in US 6,619,458 provided greater flexibility in varying the axial load and in turn the release load to any desired configuration. A pin means and a cradle means have been disclosed so as to enable a swiveling movement of the cradle means on which the housing end of the pressure springs were mounted. The pin means is connected to the housing of the clutch assembly and the swiveling end of the pin means is having a pivoted contact surface on the cradle on which the springs are swivelingly mounted. This swiveling mechanism helps in obtaining the desired pivot point at a desired distance away from the spring seat on the swiveling end. The possibility of achieving the pivot point at such desired point away from the spring seat results in an increase in the lever ratio, consequently the release load is decreased and the pedal pressure is lowered.
Friction surface of the clutch disc as disclosed in US 6,619,458 wears as the clutch is used in service. The clutch assembly internal mechanism has to adjust to compensate for the wear on the friction surface in order to work effectively. The clutch internal parts more particularly the load providing member and the parts that conies into contact with the vehicle clutch release mechanism rearrange themselves. If clutch does not adjust properly, either the clutch will become inoperable resulting in downtime or the clutch would work at a reduced performance.
To compensate wear, a manual adjuster is generally provided in a heavy duty clutch. But this will need a continuous monitoring and manpower to perform manual adjustment. There are various designs of automatic wear adjustment mechanism used in the past. Most of them includes some cumbersome mechanisms and are placed outside the clutch thereby prone to damage. They also suffer from their inability of correct and timely adjustment.
Hence their remains a need for pull type clutches having pivot point release load adjuster assembly that can have a comfortable pedal pressure throughout the life of the clutch and that can have an effective adjustment mechanism with minimum additional parts to automatically adjust the wear throughout the life of the clutch and not prone to damage.
Summary of the Invention;
According to principal embodiment of the present invention a pull type angle spring clutch assembly having a pivot point release load adjuster is disclosed. The pull type angle spring pressure plate clutch assembly have a cover, one or more clutch discs, a pressure plate, a release sleeve retainer, plurality of release levers, an adjusting ring, plurality of pressure springs spaced between the cover and the release sleeve retainer, a plurality of pivot point release load adjuster assemblies. The clutch assembly has an auto adjustment mechanism, provided between the adjusting ring and the cover. The adjustment mechanism comprises a left circular ring, a right circular ring, a bush, a constant force flat spring and a hook. The left circular ring is attached to the adjustment
ring and is rotatably fixed with respect to the clutch assembly. The right circular ring is rotatable relative to the left circular ring. Both left and right rings having a plurality of mutually engaged cam surfaces such that rotation of the right ring relative to the left ring in a direction increases a height of the adjustment mechanism. The bush is fixed to the cover in such a manner that the constant force flat spring whirls around the bush. The other end of the constant force flat spring is riveted to a hook. The hook being configured to attach the constant force flat spring, with the right circular ring. The constant force flat spring rotatively biases the rings opposite to each other resulting in automatically adjustment of the clutches on wear.
Other details and advantages of the invention will become apparent by reference to the following description and illustrative drawings of certain present embodiments thereof and certain present preferred methods of practicing the same proceeds.
Brief Description of the Drawings
In order to have a more complete understanding of the nature and goal of the present invention, reference must be made to the following detailed description made in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a plan view of a pull type clutch assembly
FIG. 2 illustrates a cross sectional view of a pull type clutch assembly according to an embodiment of the present invention;
FIG 3 illustrates an exploded view of an adjustment mechanism according to an embodiment of the present invention;
FIG 4 illustrates a section of a circular ring according to an embodiment of the present invention;
FIG 5 illustrates a hook according to an embodiment of the present invention;
Detailed description of the invention
Referring to figure. 1 and figure 2 that illustrates a pull type clutch assembly 100 according to an embodiment of the present invention. The pull type clutches 100 includes a cover 103, one or more clutch discs 101, a pressure plate 104, a release sleeve retainer
107, plurality of release levers 106, an adjusting ring 105, plurality of pressure springs
108, plurality of pivot point release load adjuster assemblies 132 and an auto adjustment
mechanism 121.
The clutch assembly 100 is adapted to be mounted on a flywheel 110, which is mounted on the crankshaft 111 of the engine. The clutch discs 101 are mounted on a splined primary input shaft 112, which is connected to a gearbox on one side and guided in a pilot bearing 113 in center of the flywheel 110. The discs 101 are sandwiched between the pressure plate 104 of the clutch assembly 100 and the flywheel 110. The pressure plate 104 can move axially during the engagement and disengagement of the clutch.
The pressure springs 108 are placed between the clutch cover 103 and the release sleeve retainer 107 through pivot point release load adjuster assemblies 132 and provide thrust to the release sleeve retainer 107 so that it tend to be in engaged position. To disengage the clutch the bearing cage 109 is pulled away from the flywheel 110 and thus the levers 106 pivots about the point 116 and a gap is created between the pressure plate 104 and the levers 106 at point 120. The pressure plate 104 is rotatably fixed with the clutch cover 103 by a securing arrangement 137 and is under the action of a biasing members 128. The pressure plate 104 thus pulled away from flywheel 110, under the action of the biasing members 128, to fill the gap thus created at point 120. The release levers 106 have one end 114 adapted to fit in the adjusting ring 105 and other end 115 adapted to fit in the groove of release sleeve retainer 107.
As the clutch discs 101 wears, the pressure plate 104 tends to move towards the flywheel 110 causing the levers 106 to pivot about the point 116, in the adjusting ring 105. Thus the wear on the clutch discs 101 causes the release sleeve retainer 107 and the bearing cage 109 to move towards the flywheel 110 thereby decreasing the overall setup
height of the clutch 100. The release fork (not shown) contacts the clutch at 117. With the wear on the clutch disc 101, the position of the point 117 moves towards the flywheel 110. It becomes difficult for the release fork to operate in this condition. The auto adjustment mechanism 121 operates between the adjusting ring 105 and the clutch cover 103 so that the release sleeve retainer 107 and the bearing cage 109 are always at the same position even after the wear on clutch discs 101.
In one embodiment the securing arrangement 137 comprises a bolt 138, a washer 139 and an outer bush 140 and an inner bush 143. The outer bush 140 is rigidly attached to the cover 103. The bolt 138 has a head arranged outside the cover 103 and a shaft. The shaft of the bolt 138 has two sections 141, 142. The first section 141 of the shaft is freely moveable with respect to the outer bush 140 and passes through inner bush 143 along its length and rests against the washer 139. The second section 142 of the shaft has a diameter narrower then the diameter of the first section 141 and has threads on it. The second section 142 of the shaft passes through the washer 139 and is configured to rigidly secure to the pressure plate 104, inner bush 143 and biasing members 128. Further the first section 141 and the second section 142 are so configured to provide a suitable gap between the outer bush 140 and the washer 139. The gap allows a controlled lift of pressure plate 104 and helps in stopping the pressure plate 104 to lift after a definite release travel given to the clutch on bearing cage 109. The balance release travel given to the clutch on bearing cage 109 causes the lever to pivot about the point 120 thereby moving the point 116 on adjusting ring 105 towards flywheel. This further causes the two circular rings 118 and 119 to separate and thus the right circular ring 119 rotates with respect to left circular ring 118. This in turn causes their total height to increase and thus the clutch adjusts. In a new clutch, this balance release travel is small and thus does not causes auto adjustment. As the clutch wears, the bearing cage 109 moves towards flywheel 110 and thus the freeplay between clutch fork (not shown) tips and the contact at 117. This causes an extra release travel to the bearing cage 109. Because the gap between the outer bush 140 and the washer 139 is same, the extra release travel causes extra rotation of lever about the point 120 and moves the point 116 on adjusting ring 105 towards flywheel to a great extent which is sufficient for the two circular rings 118 and 119 to adjust.
Figure 3 illustrates the exploded view of the auto adjustment mechanism 121. The auto adjustment mechanism 121 includes a left circular ring 118, a right circular ring 119, a bush 123, a constant force flat spring 122 and a hook 125. The left circular ring 118 is positioned adjacent to the adjusting ring 105. A first face 133 of the left circular ring 118 that faces the adjusting ring 105 is substantially flat and has a plurality of axial pins 126 projecting along the circumference. The axial pins 126 are configured to fit in a plurality of holes 127 provided in the adjusting ring 105. The axial pins 126 are so configured such that the left circular ring 118 is rotatably fixed with respect to the adjusting ring 105. A second face 134 of the left circular ring 118 opposite to first face 133 have a plurality of cam surface configured thereon along the circumference of the left circular ring 118.
The right circular ring 119 is configured just below the left circular ring 118. A first face 135 of the right circular ring 119 has a plurality of cam surface configured thereon along the circumference. The second face 136 of the right circular ring 119 is substantially flat and has a wear tab 129 projecting perpendicularly. The wear tab 129 in the right adjustment ring 119 is long enough to protrude from the slot in the clutch cover 103 and provides a quick visual indication of the proportional wear that has taken place in the clutch disc 101. The second face 136 of the right circular ring 119 has a slot configured to adopt one end of the hook 125. Other end of the hook 125 is attached to one end of the constant force flat spring 122 as shown in figure 5. A rivet 131 is provided to securely fasten the hook 125 and the constant force flat spring 122. The other end of the constant force flat spring 122 is attached to the bush 123. The bush 123 being immovably fixed to the cover 103 by a screw 124. The constant force flat spring 122 being whirled around the bush 123.
The cam surfaces provided on the second face 134 of the left circular ring 118 and on the first face 135 of the right circular ring 119 are mutually engaged with each other and are so configured such that rotation of the right ring 119 relative to the left ring 118 in a direction increases a height of the adjustment mechanism 121. The right circular ring 119 is under the action of the constant force flat spring 122 that keeps it into tension. The constant force flat spring 122 rotatively biasing the right ring 119 against the left ring, resulting in automatically adjustment of the clutches on wear. The constant force flat spring 122 provides constant pulling load to the auto adjusting mechanism 121
throughout the clutch life. The constant force flat spring 122 also act as a shield against dust, debris water etc.
In yet another embodiment the second face 134 of the left circular ring 118 and the first face 135 of the right circular ring 119 have plurality of small projections 130 as shown in figure 4. The projections 130 were formed at equal distance. The projections 130 were so configured such that the automatic adjustment can only happen when there is substantial wear on the clutch disc. The projections 130 helps in avoiding unnecessary slip of the circular ring 118, 119 over each other and thereby avoiding over adjustment. The projections 130 also help in a periodic adjustment, which takes place after substantial wear on the clutch disc.
While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the disclosure is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims.

We claim:
1. A pull type angle spring clutch assembly, having a cover 103, one or
more clutch discs 101, a pressure plate 104, a release sleeve retainer 107, plurality of
release levers 106, an adjusting ring 105, plurality of pressure springs 108 spaced
between the cover 103 and the release sleeve retainer 107, a plurality of pivot point
release load adjuster assemblies 132, characterized in that the clutch assembly have an
auto adjustment mechanism, provided between the adjusting ring 105 and the cover 103,
the adjustment mechanism comprising:
a left circular ring 118 rotatably fixed with respect to the cover 103;
a right circular ring 119 rotatable relative to the left circular ring 118, both rings having a plurality of mutually engaged cam surfaces such that rotation of the right ring 119 relative to the left ring 118 in a direction increases a height of the adjustment mechanism;
a bush 123 fixed to the cover 103;
a constant force flat spring 122, the constant force flat spring 122 being whirled around and attached to the bush 123 at one end, and at the other end the constant force flat spring 122 being attached to a hook 125, such that the hook 125 connects the constant force flat spring 122 with the right circular ring 119; wherein the constant force flat spring 122 rotatively biases the right circular ring 119 with respect to the left circular ring 118 resulting in automatically adjustment of the clutches on wear.
2. The clutch assembly as claimed in claim 1, wherein said left circular ring 118
and said right circular ring 119 have a plurality of small projections 130.
3. The clutch assembly as claimed in claim 1, wherein said constant force flat
spring 122 also acts as a shield for dirt, dust and debris.
4. The clutch assembly as claimed in claim 2, wherein said projections 130 are
equally spaced.
5. The clutch assembly as claimed in claim 1, wherein said hook 125 is attached
to said constant force flat spring 122 by a rivet 131.
6. The clutch assembly as claimed in claim 1, wherein said right circular ring
have a slot configured to adopt the hook 125.