Automatically adjusting friction clutch with over adjustment protection and reset mechanism

An adjustment mechanism for a frictional clutch for a motor vehicle includes a pressure plate, a first annular cam member, a second annular cam member, a cam spring, a cam control finger, an anti-rotation feature, and a control finger drag spring. The pressure plate has an axis of rotation and an engagement surface substantially normal to the axis of rotation. The first annular cam member is concentric with the axis of rotation and has a plurality of first ramped cam surfaces. The first annular cam member is rotatively fixed with respect to the pressure plate. The second annular cam member is rotatable relative to the first annular cam member and has a plurality of second ramped cam surfaces in engagement with the first ramped cam surfaces. The second annular cam member, together with the first annular cam member, define an effective pressure plate thickness. The second annular cam member also has an engagement step at its outer periphery. The cam spring is functionally disposed between the cam members and rotatively biases the cam members toward an increased cam height. The cam control finger is slidably disposed within an aperture in the pressure plate. The cam control finger has a shank portion which is disposed in the aperture in the pressure plate and is axially oriented for axial slidable displacements relative to the pressure plate. The cam control finger also includes an engaging portion radially extending from the shank portion and in engagement with the second annular cam member. The anti-rotation feature engages the finger thereby preventing rotation of the finger relative to the pressure plate. The control finger drag spring biases the finger into engagement with the side of the aperture and induces a frictional drag force resisting axial displacement of the control finger.

FIELD OF THE INVENTION 
This invention relates to the field of friction clutches and more 
particularly to friction clutches having automatic adjustment mechanisms. 
BACKGROUND OF THE INVENTION 
Known friction clutches provide a releasable torsional connection between a 
motor vehicle engine flywheel and an associated transmission. Such 
clutches require adjustment of the clutch pressure plate's released 
position relative to the flywheel to ensure that complete engagement of 
the friction clutch can be achieved after the friction material of the 
clutch driven disc begins to wear. Some clutches are provided with 
automatic adjustment mechanisms which are disposed between the pressure 
plate and an associate biasing member such as a diaphragm spring. The 
clutch engagement force provided by the biasing member in the engaged 
condition prevents adjustment of the adjustment mechanism. However, when 
the clutch is released, excessive adjustment of the clutch may occur, 
particularly if the biasing member separates from the pressure plate. It 
is known to provide elements connected to the pressure plate which limits 
adjustment. However, adjusters which have such a limiting element 
typically also require complete disengagement of the biasing member from 
the pressure plate before adjustment occurs. This requirement of complete 
disengagement results in adjustment occurring only periodically, when the 
clutch pedal is fully depressed. 
It is therefore desired to provide an adjustment limiting device which 
allows for continuous automatic adjustment with each clutch pedal stroke 
while preventing over adjustment for automatic adjustment mechanisms. It 
is further desired to provide a limiting device comprising a minimal 
number of parts. 
Another concern is with the difficulty of resetting adjustment mechanisms. 
Some types of adjustment mechanisms may require disassembly of the 
pressure plate from the cover to reset the adjustment mechanism. When a 
worn driven disc is replaced, it is highly desirably to reset the 
adjustment mechanism to a new or unworn position from a worn position 
without disassembling the pressure plate from the cover. 
It is desired to provide a clutch having an easy-to-use reset mechanism 
which enables the adjustment mechanism to reset the adjustment mechanism 
from a worn position to a new or unworn position. 
SUMMARY OF THE INVENTION 
The disclosed automatically adjusting friction clutch includes a limiting 
device which allows for continuous automatic adjustment with each clutch 
pedal stroke while preventing over adjustment. Further, a limiting device 
for use with the automatic adjustment device comprises a minimal number of 
parts. Also disclosed is an easy-to-use reset mechanism which enables 
resetting the automatic adjustment device from a worn position to a new or 
unworn position without separating the clutch cover from the pressure 
plate. 
An adjustment mechanism for a frictional clutch for a motor vehicle 
includes a pressure plate, a first annular cam member, a second annular 
cam member, a cam spring, a cam control finger, an anti-rotation feature, 
and a control finger drag spring. The pressure plate has an axis of 
rotation and an engagement surface substantially normal to the axis of 
rotation. The first annular cam member is concentric with the axis of 
rotation and has a plurality of first ramped cam surfaces. The first 
annular cam member is rotatively fixed with respect to the pressure plate. 
The second annular cam member is rotatable relative to the first annular 
cam member and has a plurality of second ramped cam surfaces in engagement 
with the first ramped cam surfaces. The second annular cam member, 
together with the first annular cam member, define an effective pressure 
plate thickness. The second annular cam member also has an engagement step 
at its outer periphery. The cam spring is functionally disposed between 
the cam members and rotatively biases the cam members toward an increased 
cam height. The cam control finger is slidably disposed within an aperture 
in the pressure plate. The cam control finger has a shank portion which is 
disposed in the aperture in the pressure plate and is axially oriented for 
axial slidable displacements relative to the pressure plate. The cam 
control finger also includes an engaging portion radially extending from 
the shank portion and in engagement with the second annular cam member. 
The anti-rotation feature engages the finger thereby preventing rotation 
of the finger relative to the pressure plate. The control finger drag 
spring biases the finger into engagement with the side of the aperture and 
induces a frictional drag force resisting axial displacement of the 
control finger. 
A frictional clutch for a motor vehicle includes a cover, a pressure plate, 
a first biasing member, a second biasing member, a first annular cam 
member, a second annular cam member, a cam spring, a cam control finger, 
an anti-rotation feature and a control finger drag spring. The pressure 
plate is coupled to the cover for rotation therewith about an axis and has 
a frictional engagement surface substantially normal to the axis. The 
first biasing member is interposed between the cover and the pressure 
plate and is selectively moveable between engaged and disengaged 
positions. In the engaged position, the first biasing member biases the 
pressure plate to an engaged pressure plate position. The second biasing 
member rotatably couples the pressure plate with the cover. The second 
biasing member biases the pressure plate toward the cover. The first 
annular cam member is centered about the axis and is rotatably fixed 
relative to the pressure plate. The first annular cam member has a 
plurality of first ramped cam surfaces. The second annular cam member is 
centered about the axis and is rotatable relative to the first annular cam 
member. The second annular cam member has a plurality of second ramped cam 
surfaces engaging the first ramped cam surfaces. The engaged cam members 
are axially disposed between the pressure plate and the first biasing 
member. The engaged cam members define an effective thickness of the 
pressure plate from the frictional engagement surface to an engagement 
feature of the second annular cam with the thickness increasing with 
relative rotation of the cams in a first direction. The second annular cam 
member also has an engagement step at an outer periphery thereof, the step 
having an included angle at least as great as the anticipated rotation of 
the second annular cam member. The cam spring is disposed between the cam 
members and induces relative rotation therebetween in the first direction. 
The cam control finger is slidably disposed within an aperture in the 
pressure plate and has a shank portion and an engaging portion. The shank 
portion is disposed in the aperture in the pressure plate and is axially 
oriented for axial displacement relative to the pressure plate. The 
engaging portion extends radially from the shank portion and engages the 
second annular cam member. The anti-rotation feature engages the finger 
and comprises part of the pressure plate. The anti-rotation feature 
prevents rotation of the finger relative to the pressure plate. The 
control finger drag spring is disposed substantially within the aperture 
and biases the finger into engagement with a side of the aperture. The 
control finger drag spring induces a frictional drag force resisting axial 
displacement of the control finger. The drag force is sufficient to resist 
axially biasing forces attributable to the cam spring, but is not 
sufficient to withstand a force attributable to the first biasing member.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A frictional clutch 20 for a motor vehicle is shown in FIG. 1. A more 
detailed perspective view of clutch 20 is shown in FIG. 11. Clutch 20 
rotates about axis 22. A flywheel 24, shown in FIG. 2, is rotatably fixed 
to an output shaft of a motor vehicle engine (not shown). A driven disc 26 
centered with respect to axis 22, has a hub (not shown) which engages an 
input shaft of the motor vehicle transmission (not shown). A friction 
element 28 of driven disc 26 is engaged by an engagement surface 30 of 
pressure plate 32 on one side and by an engagement surface 34 of flywheel 
24 on the other side. 
A cover 36, shown partially broken away in FIG. 1, is disposed over 
pressure plate 32 and is fixed to flywheel 24 as is best shown in FIGS. 
2-5. A diaphragm spring 38 with a plurality of radially inwardly extending 
fingers serves as a biasing member, and is disposed between cover 36 and 
pressure plate 32. Spring 38 forces pressure plate 32 against driven disc 
26 which in turn is pressed against flywheel engagement surface 34 in an 
engaged condition. Fingers 37 of diaphragm spring 38 have their inner tips 
axially engaged by a release bearing (not shown). Clutch 20 is selectively 
moved between engaged and released conditions by axially displacing the 
release bearing which resultantly deflects diaphragm spring 38. A 
potential alternative to diaphragm spring 38 is a plurality of clutch 
levers disposed between cover 36 and pressure plate 32, with either a 
diaphragm spring without fingers, or a plurality of coil springs, acting 
against the levers to bias pressure plate 32 toward flywheel 24. A leaf 
spring 39 connecting pressure plate 32 and cover 36, shown schematically 
in FIGS. 2-5 and in section in FIG. 13, biases pressure plate 32 toward 
cover 36. An automatic adjustment mechanism 40 is disposed between 
pressure plate 32 and diaphragm spring 38. 
Diaphragm spring 38 engages both cover 36 and adjustment mechanism 40 
indirectly by contact with a first or outer diameter pivot ring 42 and a 
second or inner diameter pivot ring 44 respectively. First pivot ring 42 
is disposed inside cover 36 and a second pivot ring 44 is centered over 
automatic adjustment mechanism 40. 
Adjustment mechanism 40 includes a first or stationary annular cam 46 
disposed within a cam groove 48 in pressure plate 32. Stationary annular 
cam 46 is concentric with axis 22. Cam 46 has a plurality of first ramped 
cam surfaces 50 on a side opposite cam groove 48. Alternatively, 
stationary annular cam 46 and first ramped cam surfaces 50 are formed 
integral with pressure plate 32 such that cam surfaces 50 are formed as a 
singular unit with pressure plate 32 as shown in FIGS. 12 and 19. The 
stationary annular cam 46 of FIG. 2 is prevented from rotating by a 
plurality of anti-rotation pins 52 extending from a bottom surface of 
groove 48 into receiving apertures of cam 46. A second or rotating annular 
cam 54 is disposed over stationary annular cam 46, and has a plurality of 
second ramped cam surfaces 56 in engagement with first cam surfaces 50 as 
best seen in FIGS. 3 and 6. Second pivot ring 44 is disposed in a groove 
in rotating annular cam 54 on a side opposite cam surfaces 56. An 
effective pressure plate thickness H from engagement surface 30 to a top 
of cam 54 is controlled by adjustment mechanism 40 as shown in FIGS. 3 and 
6. Alternatively, rotating annular cam 54 can be formed with a peak 
defining a constant diameter circle on the side of cam 54 opposite cam 
surfaces 56 for engagement with diaphragm spring 38 as shown in FIG. 12. 
The provision of the peak eliminates the need for second pivot ring 44. 
A plurality of cam alignment pins 57 are disposed radially within rotating 
annular cam 54 for engagement therewith to maintain cam 54 in concentric 
alignment with axis 22. Alternatively, cam 54 can be provided with a pilot 
shoulder 58 as shown in FIGS. 12 and 14 which maintains cam 54 concentric 
with respect to pressure plate 30. 
A cam spring 60 formed of round wire, best shown in FIGS. 7 and 8, is 
disposed between stationary annular cam 46 and rotating annular cam 54, 
biasing the cams in the direction tending to increase effective pressure 
plate thickness 11 from engagement surface 30 to second pivot ring 44 as 
shown in FIG. 6. Cam spring 60 is shown in a "new" clutch position in 
phantom lines and in a "worn" clutch position in solid lines. Cam spring 
60 has a first end 59 which is disposed in a hole in rotating annular cam 
54 for movement therewith. A second end 61 of spring 60 is preferably 
received by a slot in either stationary annular cam 46 or pressure plate 
32. Alternatively, as shown in FIGS. 16-18, cam spring 60 can be formed of 
flat wire like that used for clock springs. As shown in FIG. 22, first end 
59 of flat wire spring 60 has an included angle .alpha. of approximately 
74.degree. that engages a spring hook 62 on rotating annular cam 54 having 
an included angle .beta. of approximately 72.degree.. Having angles of 
less than 90.degree. significantly reduces any tendency of first end 59 to 
slip off hook 62. A triangular web portion extending between hook 62 and 
shoulder 58 axially traps first end 59 on one side of cam member 54 while 
pressure plate 32 traps it on the other. Second end 61 of spring 60 is 
disposed in a notch 63 in a ring portion of pressure plate 32, best shown 
in FIG. 19. FIGS. 16, 17 and 18 show flat wire spring 60 in a free 
position, a worn clutch position and a new clutch or fully wound position 
respectively. As driven disc 26 wears, spring 60 unwinds, biasing cam 54 
to a position of increased thickness H. 
A mechanism for limiting adjustment of adjustment mechanism 40 includes a 
plurality of pressure plate extensions 65, best shown in FIG. 9 and FIG. 
19, which extend radially from an outer diameter of pressure plate 32. 
Extensions 65 each have an aperture 66 slidably retaining a cam control 
finger 64 for axial movement therein parallel to axis 22. Fingers 64, a 
first embodiment of which is best shown in FIG. 10, are substantially 
square in cross section along their entire length. Fingers 64 have an 
axially extending shank portion 68 disposed in apertures 66, and an arm 
portion 70 extending radially inwardly to engage rotating annular cam 54. 
Arm portion 70 extends at an angle, as shown in FIGS. 2-5, from shank 
portion 68 to a tip portion 73. Tip portion 73 is of reduced thickness 
compared to arm portion 70 and shank portion 68. Shank portions 68 each 
have a drag spring 72 disposed in a finger spring pocket 74 in a lateral 
side of shank portion 68. Drag springs 72 are leaf springs which bow 
outward from pockets 74 to produce a drag or retention load within 
aperture 66 resisting axial movement therein. Leaf springs advantageously 
present a significant amount of surface area for even distribution of the 
spring load against the facing wall of aperture 66 and also introduce a 
minimal number of additional parts. The drag spring 72 preload and spring 
rate are selected to induce sufficient axial resistance to finger movement 
to prevent movement of fingers 64 due to axial loading induced by cam 
spring 60, while slipping responsive to the force of diaphragm spring 38 
forcing pressure plate 32 against driven disc 26. A first end of cam 
control fingers 64 contacts engagement surface 34 of flywheel 24 when 
clutch 20 is engaged. Fingers 64 are forced to slide in apertures 66 when 
the ends of shank portions 68 come into contact with engagement surface 34 
and the pressure plate diaphragm spring 38 or an equivalent biasing member 
forces pressure plate 32 against driven disc 26. An alternative embodiment 
of fingers 64 and drag springs 72 is shown in FIG. 20 and FIG. 12 with 
drag spring 72 being disposed on a radially inner side of shank portion 
68. Yet alternatively, drag springs 72 could be disposed on more than one 
side of shank portion 68. The alternative finger 64 of FIGS. 12 and 20 has 
its arm portion 70 bent, first extending parallel to pressure plate 32 
from shank portion 68 and then angling up to tip portion 73. 
Determining the optimal combination or balance of spring rates and preloads 
for leaf spring 39, cam spring 60 and finger pre-load springs 72 may 
require some experimentation for a particular clutch. As noted above, the 
drag springs 72 must enable fingers 64 to resist the biasing force of cam 
spring 60 and give way to the force exerted by diaphragm spring 38. This 
balance is relatively easy to achieve because of the large difference in 
force between that attributable to cam spring 60 and diaphragm spring 38. 
Also, cam spring 60 should not be so strong that it, by itself, could 
overcome the resistance to rotation of rotating cam 54 imposed by leaf 
spring 39, thus rendering the fingers 64 ineffective in limiting 
adjustment of cam 54. 
Cam control fingers 64 are prevented from rotating relative to pressure 
plate 32, not only by the substantially square shape of the shank portion 
and the apertures, but also by a pair of opposed anti-pivot shoulders or 
positioning lugs 76 disposed on opposite sides of arm portion 70. While a 
rectangular shape, and in particular a substantially square shape is 
preferred for the cross section of fingers 64, other cross sectional 
shapes may alternatively be employed, especially when positioning lugs 76 
are provided, as the shape of the cross section is made less critical in 
the prevention of the rotation of fingers 64 by lugs 76. It should be 
appreciated that the bent arm portion 70 shown in FIG. 12 and FIG. 20 
advantageously enables the use of lower profile lugs 76. 
Tip portion 73 engages an engagement step 80 formed at an outside diameter 
arc portion of rotating annular cam 54. Both step 80 and tip portion 73 
with its reduced thickness contribute to providing a low profile cam 
travel limit which avoids interference with the operation of diaphragm 
spring 38. A first end 82 and a second end 84 of engagement step 80 define 
rotary stops separated by an included angle .gamma. of approximately 
34.degree.. The included angle .gamma. is approximately equal to the 
amount of rotation that cam 54 is expected to rotate which varies with the 
anticipated wear driven disc 26 and the slope of cam surfaces 50 and 56. 
Of course, alternative structures could provide this rotation limiting 
function. For example, step 80 could completely circumscribe cam 54, with 
rotation being limited by engagement between a radially extending feature 
of cam 54 and an axially extending projection from pressure plate 32. 
FIG. 21 shows a section of clutch 20 with a reset mechanism 86. Reset 
mechanism 86 includes a reset driver or driving tool 88 selectively 
slidably disposed over pilot pin 90. Driver 88 has a pilot bore 92 
enabling driving tool 88 to rotate about pilot axis 94 of pilot pin 90. A 
driver head 96 of driving tool 88 has five driver teeth 98 which drivingly 
engage cam teeth 100 of rotating annular cam 54. Of course there could be 
a different number of teeth 98 on head 96. Hex flats 102 define a driving 
feature of driving tool 88 on an end opposite driver head 96, and enable 
engagement of driving tool 88 by a conventional wrench. Diaphragm spring 
fingers 37 terminate in arcuate shaped openings 10 with one of openings 
110 being aligned with a cover notch 106 on the inside diameter of cover 
36, both of which are in alignment with pilot pin 90. The alignment of 
diaphragm spring opening 104, cover notch 106 and pilot pin 90 enable 
driving tool 88 to be selectively slipped over pilot pin 90 for driving 
engagement of driver teeth 98 with cam teeth 100, and for driving tool 88 
to be selectively removed from clutch 20. 
A finger access opening 105 is aligned with each of cam control fingers 64 
in alignment with shank portions 68. Opening 105 is sufficient large to 
enable a pin or a punch to be engaged against fingers 64 for the purpose 
of returning them to a new or unworn position after rotating annular cam 
54 has been returned to a new or unworn position. 
FIGS. 23 and 24 show a reset mechanism 107 slightly different from that of 
reset mechanism 86. Reset mechanism 107 is substantially the same as reset 
mechanism 86, except that reset mechanism 107 includes a driving tool 108 
which is not removed from clutch 20. Driving tool 108 is biased along 
pilot pin 90 to a disengaged or non-driving position by a coil type driver 
return spring 109. Retaining washer I 10, having an outside diameter 
larger than that of diaphragm spring opening 104 is disposed on driver 108 
between driver head 96 and diaphragm spring 38. A shank portion of driver 
108 has an internal hex or Allen type socket. As shown in FIG. 23, cam 54 
is in a worn position. In FIG. 24, the same reset mechanism 107 is shown, 
but with the clutch assembly 20 in a released condition, and with cam 54 
having been reset to a new or unworn position. 
FIGS. 25-40 are all directed to yet other alternative reset mechanism 
embodiments. 
The reset mechanism 114 of FIG. 25 includes an L-shaped driving tool 116 
having star-shaped driver heads 118 on each end thereof. The star-shaped 
driver heads 118 have six points but could have more or fewer points. Cam 
54 has a driving slot 120 which receives one of drivers 118 of driving 
tool 116. Slot 120 has a series of undulations on at least one side which 
cause cam 54 to be reset with rotation of driving tool 116. 
The reset mechanism 122 shown in FIG. 26 is substantially the same as reset 
mechanism 114 of FIG. 25, except that a removable drill chuck key 124 is 
used as the driving tool. A slot 126 in cam 54 receives a tip of chuck key 
124. Teeth of rotating cam 54, engaged by the teeth of chuck key 124, are 
disposed on cam 54 adjacent slot 126. 
Reset mechanism 128 of FIG. 27 is substantially similar to reset mechanism 
122 except that driving tool 130 of mechanism 128 remains constantly 
engaged with cam 54. Driving tool 130 has a tip disposed in a slot 126. 
Tool 130 is retained by a plastic bushing 132 slidably disposed over a 
shank of driving tool 130, and having locking tabs 134 extending from 
bushing 132 preventing removal of bushing 132 and driving tool 130 from 
clutch cover 36. Driving tool 130 has an Allen head drive socket (not 
shown). 
The reset mechanism 136 of FIG. 28 is substantially the same as reset 
mechanism 128, except that driving tool 138 is provided with a large 
diameter shank 140 and a small diameter end 142 with driving tool 138 
being trapped between cover 36 and cam 54. 
The reset mechanism 144 of FIG. 29 is substantially the same as reset 
mechanism 107 of FIGS. 23 and 24. Driving tool 146 is retained within 
clutch 20 by an oversized flange 148 between cover 36 and diaphragm spring 
38. Also, driver head 96 remains in constant engagement with cam teeth 
100. 
The reset mechanism 150 of FIG. 30 is substantially similar to reset 
mechanism 114 except that the driving tool 152 of reset mechanism 150 
remains with clutch 20. While driving tool 152 is shown with the same 
driving head 118 as used in reset mechanism 114, it does not have an 
L-shaped handle but instead has a hex head driving feature for engagement 
by a box wrench, an open end wrench or a rachet. Driving tool 152 is 
retained in clutch 20 by a pair of snap rings 156, one placed on either 
side of cover 36 as shown in FIG. 30. Alternatively, push lock rings may 
be used in place of snap rings 156. 
The reset mechanism 158 of FIG. 31 has a driving tool 160 biased to a 
disengaged or non-drive position by biasing spring 162. A snap ring 164 
engaging driving tool 160 and oversized hex head 166 axially retain 
driving tool 160 within clutch 20. A force directed against hex head 166 
in thc direction of spring 162 forces driving tool 160 into engagement 
with cam teeth 100. Disengagement of driver head 96 from cam teeth 100 
eliminates fretting corrosion between the gear teeth which would otherwise 
result from engagement between the parts when the engine is operating. 
The reset mechanism 168 of FIG. 32 is substantially similar to reset 
mechanism 138 of FIG. 28. A driving tool 170 has a tip disposed in slot 
126. Teeth of driving tool 170 are in engagement with teeth of cam 54. 
Driving tool 170 has a large diameter shank portion 172 and a small 
diameter shank portion 174 opposite large diameter shank portion 172 from 
the tip of driving tool 170. A push-on belville spring 176 is disposed 
over small diameter shank portion 174 outside cover 36 to bias driving 
tool 170 to a disengaged position. FIG. 32 shows driving tool 170 in an 
engaged position as if it were being pressed towards cam 54 overcoming the 
spring load of belville spring 176. As with reset mechanism 158 of FIG. 
1., driving tool 170 is biased out of an engagement position when clutch 
20 is in operation, thereby eliminating fretting corrosion. 
The reset mechanism 178 of FIG. 33 is substantially the same as reset 
mechanism 128 of FIG. 27. Plastic bushing 132 of reset mechanism 178 is 
slightly shorter, enabling biasing spring 180 to be disposed between 
bushing 132 and the head of driving tool 160 which bears the engagement 
teeth. Spring 180 biases driving tool 130 to an engaged position so that 
it remains engaged with the teeth of cam 54 even when clutch 20 is being 
operated. Biasing driving tool 130 in this direction introduces additional 
friction in the system which damps the cam movement caused by torsional 
pulses from the vehicle drive train. The spring load also reduces the 
amount of fretting corrosion between the gear teeth when compared with the 
unbiased system of FIG. 27. 
Reset mechanism 182 as shown in FIG. 34 is substantially similar to reset 
mechanism 150 of FIG. 30. However, a driving tool 184 of reset mechanism 
182 has slots for snap rings 156 spaced slightly further apart then does 
driven 152. Additionally, a belville spring 186 disposed between cover 36 
and the outermost of snap rings 156 biases driving tool 184 to a 
disengaged position, even through driving tool 184 is shown in an engaged 
position in FIG. 34. As noted in the discussion of reset mechanism 158 and 
168, when driving tool 184 is disengaged from cam 54 and its teeth, 
fretting corrosion is eliminated. 
The reset mechanism 188 of FIG. 35 is somewhat similar to reset mechanism 
144 in that driving tool 190 pilots on pin 90. Driver head 96 remains 
engaged with cam teeth 100. A threaded bushing 192 is fixed in cover 36. A 
threaded shank portion 194 of driving tool 190 is threadably engaged with 
and disposed within bushing 192. A biasing spring 190 is disposed between 
driver head 96 and threaded bushing 192. The spring biasing load, as noted 
earlier, helps damp torsional impulses which tend to cause the cam 54 to 
adjust. It should be appreciated that the exposed end of driving tool 190 
extending beyond cover 36 can be used as an indicator of clutch wear, as 
the amount of driving tool 190 extending beyond cover 36 will vary with 
the amount of wear. For example, reset mechanism 188 could be configured 
so that when the clutch is worn, the end of driving tool 190 in which the 
allen head driving feature 112 is disposed will be flush with an outer 
surface of bushing 192 when the clutch is worn. 
The reset mechanism 198 shown in FIGS. 36 and 37 employs a driving tool 200 
having a toothed drum 202 affixed thereto. Toothed drum 202 driveably 
engages cam teeth 204. Driving tool 200 is maintained in its operating 
position by having a first end piloting in an aperture 205 in pressure 
plate 32 and having a second end piloting in an aperture in bushing 206 
which is in turn disposed in cover 36. Driving tool 200 has a 
handle/indicator portion 208 which extends at 90.degree. to axis 94 on 
which driving tool 200 is piloted. Toothed drum 202 drives rotating 
annular cam 210, which is disposed between pressure plate 32 and a 
non-rotating but axially displaceable annular cam 212. A retaining member 
214 is fixed to non-rotating annual cam 212 and slidably engages pressure 
plate 32. As driven disc 26 wears, handle/indicator portion 208 pivots 
from the "New" position, shown in solid lines in FIG. 37, to the "Replace" 
position, shown in phantom lines in FIG. 37. It should be appreciated that 
precise dimensions of these parts, and the angle shown in FIG. 37 will 
vary depending upon the specific application. 
The reset mechanism 216 of FIG. 38 is shown only in part. A rotating cam 
ring 218 moves with respect to the associated non-rotating cam ring and 
pressure plate (note shown). Rotational travel of cam ring 218 occurs when 
driven disc 26 wears. A screw driver 220 or other prying tool is used to 
pry ring 218 as required to reset the clutch. Screwdriver 220 engages 
notches 222 in cam ring 218. Rotation of cam ring 218 is limited by pins 
224 which are fixed to a non-rotating part of the clutch, such as the 
pressure plate. 
Reset mechanism 226 of FIGS. 39 and 40 includes a return lever 228 which 
toggles within a lever slot 230 in cover 36 between a new or unworn 
position shown in solid lines and a used or worn position shown in phantom 
lines. Lever 228 pivots about lever pivot 232 on fixed cam 234. A link 
member 236 extends from rotating cam 238 to a lower slot in lever 228. 
The invention operates in the following manner. In a new or no-wear 
condition, as shown in FIGS. 2 and 3, cam control fingers 64 are at their 
original position relative to pressure plate 32. With clutch assembly 20 
engaged, the first ends of cam control fingers 64 are in contact with 
flywheel engagement surface 34. The effective thickness H of pressure 
plate 32 is at its minimum when the thickness of driven disc 26 is at its 
maximum. The contact surface of tip portion 73 is in contact with the 
surface of engagement step 80. The load applied in the engaged condition 
by diaphragm spring 38 against adjustment mechanism 40 maintains the 
relative rotative position of cams 46 and 54. Cam control fingers 64 do 
not come into contact with cover 36 at any time during the travel of 
pressure plate 32 when the clutch is released as shown in FIG. 3. As 
clutch assembly 20 is released by displacing diaphragm spring 38 as shown 
in FIG. 3, leaf spring anti-rotation strap 39 biases pressure plate 32 
away from flywheel 24 and toward cover 36. When the clutch is fully 
released, the axial force of rotating cam 54 against diaphragm spring 38 
drops to equal the force attributable to leaf spring 39 biasing pressure 
plate 32 toward cover 36. Cam control fingers 64 move axially with 
pressure plate 32 as a unit, thereby preventing rotation of rotating 
annular cam 54. 
FIG. 4 shows clutch 20 in an engaged position after it has experienced some 
wear of friction element 28, but without any adjustment of effective 
thickness H by adjustment mechanism 40. Because of the continuous 
adjusting characteristic of adjustment mechanism 40, the size of a gap D 
between the surface of tip portion 73 and engagement step 80 is always 
very small when there is one, as it would in most cases be limited to the 
amount of wear attributable to a single clutch re-engagement. The size of 
gap D has been exaggerated in FIG. 4 for this illustration. 
When the clutch pedal (not shown) is depressed, a release bearing (not 
shown) axially displaces the tips of diaphragm spring 38's finger portions 
proximate to axis 22 away from flywheel 24 to unload pressure plate 32. 
Clutch 20, when disengaged or released, continuously adjusts the rotative 
position of rotating annular cam 54 relative to stationary annular cam 46 
by using the torsional vibrations induced by the firing pulses of the 
engine. The torsional vibrations are alternatively identified as torsional 
firing pulses. The firing pulses help cam spring 60 overcome the 
resistance to adjustment imposed by leaf spring 39 which biases rotating 
cam 54 against diaphragm spring 38. The desired adjustability is made 
possible by selecting diaphragm spring, leaf spring 39 and cam spring 60 
having spring characteristics which enable the torsional firing pulses to 
induce rotation of rotating cam 54 relative to stationary cam 46 when 
clutch 20 is in a released condition and leaf spring 39 biases rotating 
cam 54 against spring 38. The resultant continuous adjustment for wear, or 
adjustment with each disengagement of the clutch assembly 20, represents 
an advantage over known automatic adjustors. Known automatic adjustors 
typically adjust only when the diaphragm spring is deflected sufficiently 
far to separate the diaphragm spring from the adjustor. Mechanisms 
requiring such full disengagement may require a conscious effort by the 
vehicle operator to extend the clutch pedal to a full travel position to 
obtain the desired adjustment, making the adjustment less than fully 
automatic. 
A first departure gap E, shown in FIG. 5, is present between flywheel 
engagement 25 surface 34 and the first end of finger 64. A second 
departure gap F between pressure plate engagement surface 30 and driven 
disc 26. Departure gap E exceeds departure gap F by the amount, if any, 
that driven disc 26 deflects when it is unloaded. The amount of deflection 
will, of course, be greater if driven disc 26 is a cushioned driven disc. 
FIG. 5 reflects the adjustment of the rotating annular cam 54 that occurs 
with the engine firing pulses. Annular cam 54 appears to have increased in 
sectional thickness because of its rotation relative to the sectional 
plane. The axial position of finger 64 in pressure plate extensions 65 
relative to pressure plate engagement surface 30 does not change while the 
clutch remains disengaged. But, when the clutch pedal is released and 
pressure plate 32 reengages driven disc 26, the resultant small amount of 
wear of friction element 28 will cause finger 64 to shift relative to 
pressure plate engagement surface 30. When the clutch is later released, 
cam 54 will adjust to the amount permitted by fingers 64, thereby 
increasing thickness H an amount equal to the wear of friction element 28. 
It is such small incremental shifts in the position of fingers 64, in 
combination with the responsiveness of rotating annular cam 54 to engine 
firing pulses, which enables the advantageous continuous adjustment 
characteristic of the present invention. 
The reset mechanism 86 of FIG. 21 is used after it has been determined that 
driven disc 26 has reached the end of its useful life and clutch assembly 
20 is removed from the motor vehicle to enable replacement of driven disc 
26. Clutch 20 is mounted to a loading fixture and diaphragm spring 38 is 
subsequently deflected to relieve pressure plate 32 and adjustment 
mechanism 40 of the associated load. When adjustment mechanism 40 is 
unloaded, driving tool 88 of reset mechanism 86 is passed through 
diaphragm spring opening 104 and cover notch 106 and slipped over pilot 
pin 90. Driver teeth 98 of driver head 96 mesh with cam teeth 100. Reset 
driving tool 88 is engaged by a ratchet wrench or the like, and rotated to 
return rotating annular cam 54 back to its new or unworn position. 
Sufficient torque must be exerted on driving tool 88 to overcome cam 
spring 60. Before the torque is released from driving tool 88, the 
relative rotative position of rotating annular cam 54 must be set relative 
to stationary annular cam 46. This can be accomplished by releasing the 
diaphragm spring to re-engage adjustment mechanism 40 or by resetting one 
or more of fingers 64. 
Resetting the position of rotating annular cam 54 has no effect on the 
axial positions of fingers 64. After resetting the rotative position of 
rotating annular cam 54, there will be a gap between tip portion 73 of 
fingers 64 and engagement step 80. Fingers 64 are reset individually by 
passing a pin or punch through finger access opening 105 to contact finger 
64. Lightly tapping the pin or punch displaces finger 64 in the direction 
of force and restores contact between tip portion 73 and engagement step 
80. The preferred embodiment, as disclosed herein, has four fingers 64. 
Each of the four fingers may be reset while the clutch is mounted to the 
loading fixture. However, resetting only one pin is sufficient to 
adequately restrain rotating annular cam 54 from excessive rotation prior 
to its installation in a vehicle. Preferably, only one finger is reset on 
the resetting fixture with the other three fingers being reset after the 
clutch, in combination with a new driven disc, is installed in a vehicle. 
FIGS. 23 and 24 illustrate the use of an alternative reset mechanism 107. 
Reset mechanism 107 is substantially the same as reset mechanism 86, 
except that alternative driving tool 108 is permanently installed in 
clutch 20. Driving tool 108 is spring loaded so that, when no in use as 
shown in FIG. 23, its teeth 98 are not engaged with cam teeth 100. 
Retaining washer 110 limited the axial travel of driving tool 108 due to 
spring 109. As shown in FIG. 24, adjustment occurs when the clutch is in a 
released condition. Driving tool 108 is simultaneously pressed downward 
toward pressure plate 32 while being rotated to reset the position of 
rotating annular cam 54. The change in profile from FIG. 23 to FIG. 24 of 
rotating annular cam 54 reflects the resetting of cam 54 from a worn 
position to a new position. Certain details of the clutch have been 
eliminated from FIGS. 23 and 24, such as fingers 64, to eliminate 
potentially confusing detail not directly relating to the alternative 
embodiment of the reset mechanism. 
FIGS. 25 and 26 both illustrate alternative embodiments of reset mechanisms 
114 and 122 which employ removable driving tools 116 and 125 respectively. 
FIGS. 27, 28, 29 and 30 all show alternative embodiments of reset 
mechanisms 128, 136, 144 and 150 respectively in which the associated 
driving tools are permanently captured, but are not spring loaded. FIGS. 
31, 32, 33 and 34 all show spring biased driving tools which are 
permanently captured within clutch 20. FIG. 35 shows yet another 
alternative embodiment of reset mechanism 188 in which an exposed end of 
driving tool 190 may be used as a wear indicator as described above. 
The reset mechanism 198 of FIGS. 36 and 37 is shown in combination with 
rotating annular member 210 which is disposed between pressure plate 32 
and non-rotating annular cam 212, unlike the other adjustment mechanisms 
discussed herein which had the rotating annular cam disposed opposite the 
stationary annular cam from the pressure plate. When the clutch of FIG. 36 
is loaded into the reset fixture, and the diaphragm spring load is 
removed, handle/indicator position 208 is easily pivoted to the new 
position to reset the adjustment mechanism. 
A very simple reset mechanism is shown in FIG. 38. Once the clutch has been 
unloaded in the reset fixture, rotating annular cam 218 is simply pushed 
back to its new or unused position by using a screwdriver to pry or push 
it back into place. When prying or pushing on rotating cam ring 218, a 
force sufficient to overcome cam spring 60 must be applied. 
FIGS. 39 and 40 show yet another alternative embodiment for a reset 
mechanism. Reset mechanism 226 is disposed radially outboard of stationary 
annular 234 and rotating annular cam 238. As the clutch driven disc 26 
wears, pressure plate engagement surface 30, moves lower and lower, as 
does rotating annular cam 238. Lever 228 moves from its new position, 
shown in solid lines, to the worn or used position shown in phantom lines. 
To reset the clutch adjustment mechanism for use with a new driven disc, 
lever 228 need merely be pivoted back to its new position when the load of 
diaphragm spring 38 is released. 
It should be appreciated that there are readily apparent alternative 
embodiments to the above-described clutch components. For example, the 
pre-load spring 72 associated with each finger 64 could be retained within 
apertures 66 instead of on fingers 64. Also, springs 72 could be placed on 
more than one side of each finger 64. Further, rotating annular cam 54 and 
stationary annular cam 46 could be transposed so that stationary annular 
cam 46 is engaged by diaphragm spring 38. With regard to the reset 
mechanisms, any of the configurations for the driver head (five point, six 
point) could be used on driving tool having any of the disclosed driving 
features (hex head, Allen socket). 
The embodiments disclosed herein have been discussed for the purpose of 
familiarizing the reader with the novel aspects of the invention. Although 
preferred embodiments of the invention have been shown and disclosed, many 
changes, modifications and substitutions may be made one having ordinary 
skill in the art without necessarily departing from the spirit and scope 
of the invention as described in the following claims.