Description

Self-Adjusting Clutch Arrangement

Technical Field

This invention relates to a friction clutch arrangement which is self-a justing and which is spring loaded to normally disengaged position. Such a clutch arrangement is particularly useful as a power takeoff clutch.

Background Art

Clutches are well known for connecting together a rotating driving member to drive a rotatingly driven member. For example, the engine- driven flywheel of a vehicle may be connected to a driving ring which is meshed with a friction plate structure, generally one or more friction plates. In such an arrangement a pressure plate extends radially from a driven member, such as a shaft, to one side of .the friction plate structure. An additional pressure plate extends from the driven shaft to the other side of the friction plate structure. Generally, one, but not both, of the pressure plates is axially slidable on the driven shaf , so that the friction plate structure can be compressed between the two pressure plates, thus providing a driving relationship between the driving ring and the driven shaft.

It is also known to provide an annular load ring surrounding the driven shaft and movable towards or away from the pressure plates and which operates,

in opposition to a spring force which normally biases the pressure plates together, to move the two pressure plates apart from each other and out of frictional engagement with the friction plate structure. A typical prior art structure which operates in this manner is disclosed in U.S. Patent - 2,439,611 issued on April 13, 1948 to A.T. Nabstedt.

A problem with such arrangements is the fact that the spring structure causes the clutch to be normally engaged. Thus, should any of the components fail which enable the load ring to be moved to a position wherein the clutch will disengage, then the apparatus or vehicle using the clutch arrangement will remain in, or, shift into, the driven mode. The same result occurs should any of the parts fail -between the load ring and the movable pressure plate. Depending upon what component has failed, it may be quite difficult to disengage the driven shaf from being driven by the driving ring.

Certain prior art clutch arrangements exist wherein the clutch is spring biased so that the pressure plate members thereof are normally disengaged. For example, one such structure is taught in U.S. Patent 3,724,620 issued on April 3, 1973 to Carl I. Benson, Jr. The structure taught by this patent is, however, relatively complex in nature, and does not allow the engagement of the clutch responsive to the sliding of a load ring which fits about the driven shaft. Accordingly, relative complex linkages must be utilized to engage and disengage the clutch arrangement.

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Another problem with such prior art structures as have just been discussed is that it is generally necessary to mount them, more or less one part at a time, about the driven sha t. This is quite time consuming, particularly because of the relatively cramped quarters in which the mechanic must work to accomplish it. Still another problem with some such arrangements has been that torque transmitting capability has varied considerably as the clutch plates have worn.

Disclosure of Invention

The present invention is directed to overcoming one or more of the problems as set forth above.

In one aspect of the invention this is accomplished by providing a self-adjusting clutch- including a pressure plate engageable with a friction plate structure, a load ring movable between first and second positions, a load spring means for concurrently pressing the pressure plate against the friction plate structure and biasing the load ring away from its first position when the load ring is in its first position, a coupling means for allowing a limited degree of movement of the pressure plate relative to the load ring so that when the load ring is in its first position the load spring means will maintain the pressure plate in engagement with the friction plate structure in spite of wear of the friction plate structure, the coupling means also functioning to move the pressure plate away from the friction plate structure during movement of the load ring from its first to its second position, and actuating means for forcing the load ring from

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lts second to its first position.

In another aspect of the invention, a pressure plate assembly is provided, the assembly including a pressure plate, a load ring and load spring means, the pressure plate and load ring being coupled together for limited movement relative to each other and the load spring means being confined between the pressure plate and load ring to yieldably bias the pressure plate and load ring apart with a predetermined force.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

Brief Description of Drawings

Figure 1 is a longitudinal cross section view illustrating a clutch embodiment of the present invention in the engaged mode]

Figure 2 is an enlarged portion of Fig. 1 illustrating the coupling between the second pressure plate and load ring.

Figure 3 is a view similar to Figure 1, but with the clutch in the disengaged mode of operation.

Best Mode for Carrying Out the Invention

The figures of the drawings illustrate a clutch arrangement 10 mounted within a housing 12. The clutch arrangement 10 includes a rotatable friction plate structure 14, in the embodiment illustrated a single clutch disc, driven by a rotating driving member 16 which may itself be driven by an engine flywheel (not illustrated).

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A shaft 18, extending axially to the friction plate structure 14 and supported by bearings 20, is drivable by the rotating driving member lβ when the first pressure plate 22 and a second pressure plate 24 are compressed against the first and second sides 26 and 28, respectively of the friction plate structure 14, as will be noted, the first pressure plate-22 is rigidly mounted to and held against axial movement relative to shaft 18 while the second pressure plate 24 is positioned about sha t 18 for axial movement thereon. A load ring 30, mounted for axial movement relative to the second pressure plate 24 is biased away therefrom by load spring means 32, which comprises a load spring 34, or more usually a plurality of equally spaced load springs around the second pressure plate 24, each positioned about a pin 36 and confined between the second pressure plate 24 and load ring 30.

In accordance with the present invention means 42 are provided for mounting the second pressure plate 24 for axial and non-rotative movement relative to shaft 18. In the present embodiment, the second pressure plate 24 is mounted by longi udinally extending splines 44 on a sleeve 46 which is rigidly attached at 48 to shaft 18, so that the second pressure plate 24 can move axially relative to sha 18 while being held against rotation relative thereto.

Also in accordance with the present invention, a clutch actuating means 50 is provided for positively moving the load ring from its second, or disengaged, position illustrated in Fig. 3 to

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its first, or clutch-engaged, position of Fig. 1. When the load ring is in its first position load spring means 32 will concurrently press the second pressure plate 24 against the friction plate structure 14 and bias the load ring 30 away from its clutch-engaged position. This is to be contrasted to prior art structures wherein the load springs bias the load ring to, and hold it at, a clutch-engaged position. The particular clutch actuating means 50 illustrated herein includes a crank 52 pivotally mounted by pin 54 to ear 56 extending from sleeve 46, the crank 52 having a first arm 58 positioned to contact cam surface 60 formed on load ring 30. Generally at least three cranks 52 will be mounted on sleeve 46 and spaced equally apart around the circumference thereof.

The clutch actuating means 50 also includes means 64 which serve to move crank 52 so that it will force load ring 30 to its clutch-engaged position or will allow the load ring 30 to move to its clutch- disengaged position. The particular means 64 illustrated herein includes sleeve 66 mounted for axial movement on shaft 18, the second arm 68 of crank 52 being received in annular groove 70 on sleeve 66. Sleeve 66 has an annular ridge 72 therearound engaged by the bifurcated arm of collar 74 which is pivoted at 76 to drive arm 78, the latter being fixed to control shaft 80 which is connected to an operator-controlled clutch demand mechanism (not shown). Collar 74 is annular. As is apparent, movement of control shaft 80 about the axis thereof will move sleeve 66 axially on shaft 18.

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As will be noted in Fig. 1, when crank 52 is holding load ring 30 in its clutch-engaged, position, crank 52 is in a first, slightly over- center position so that minimal force is required to hold the clutch engaged. Reference to Fig. 3 will show the crank 52 in a second over-center, position allowing the clutch arrangement 10 to disengage.

In accordance with the present invention, an auxiliary spring 84, confined between the first and second pressure plates 22 and 24, constitutes means for biasing the two pressure plates axially away from each other. For purposes of balance, a plurality of auxiliary springs 84 are preferably used, such springs being spaced equally from each other around shaft 18. When crank 52 is rotated to its Fig. 3 position, auxiliary spring 84 will move the second pressure plate 24 rightwardly so that the pressure plates separate -out of driving frictional engagement with the friction plate structure 14. As will be noted in Fig. 1, when the clutch is engaged, load springs 34 are pressing the second pressure plate 24 to the left and into frictional engagement with the friction plate structure 14, while auxiliary springs 84 are biasing the second pressure plate 24 to the right. Accordingly, the total spring force of the auxiliary springs 84 must be sufficiently less than the total spring force of load springs 34 so that the desired clutch pressure is provided.

In further accordance with the invention, a coupling means 88 is provided for interconnecting the second pressure plate 24 and load ring 30 so as to

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allow a limited degree of axial movement of the second pressure plate 24 in a direction towards the friction plate structure 14 under the force of the load spring means 32 when the load ring 30 is in its first, clutch-engaged, position (Fig. 1), and for moving the second pressure plate 24 away from the friction plate structure 14 upon partial movement of the load ring 30 from its first to its second (Fig. 3) position. As particularly illustrated herein, coupling means 88 includes a pair of radially- extending, opposed stop members 9 and 94, stop members surface 92 being a radially inturned lip on load ring 30 and stop member 94 being a snap ring which is removably carried at the end of hub 9 and extends radially outwardly therefrom. Hub 96 is integral with the second pressure plate 24 and forms an annular, axial extension therefrom, hub 96 extending through the central opening 98 of load ring 30. As will be noted in Fig. 3, when the load ring 30 is in its second, or clutch-disengaged, position, the load spring means 32 will bias the second pressure plate 24 and load ring apart so that the stop members and 9 will be in engagement with each other. As the load ring 30 is moved towards the left, second pressure plate 24 will be moved unitarily therewith until such time as the second pressure plate 24 comes into engagement with the friction plate structure 14. Further lef ward movement of the load ring to its first position will cause the interengaged stop members 92 and 94

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to separate so that the full force of the load spring means 34 is immediately available to press the second pressure plate 24 towards the first pressure plate 22 and cause the two pressure plates to frictionally 5 engage the friction plate structure 14 therebetween. When the load ring is thereaf er moved from its first to its second position, the load spring means 32 will maintain the second pressure plate 24 in engagement with the friction plate structure until

10 the stop members 92 and 94 come into engagement with each other. Continued movement of load ring 30 to its second position (resulting from the bias auxiliary spring 84) will then move the second pressure plate 24 unitarily therewith and out of

15 engagement with the friction plate structure 14.

As is apparent, when the load ring 30 is held by crank 52 in its first position, it is spaced a fixed distance away from the first pressure plate 22. As the friction plate structure 14 wears and

20 becomes thinner, the load spring means 32 will force the second pressure plate 24 leftwardly to maintain clutch engagement until such time as the friction plate structure 14 becomes so worn that the stop members 92 and 94 come into engagement with each

25 other. As a consequence, the clutch arrangement will automatically adjust for wear of the friction plate structure 14. The amount of allowable wear, of course, corresponds to the inital gap existing

_* between the second pressure plate and load ring stop 30 members 92 and 4 when the load ring 30 is in its first position and the friction plate structure 14 is unworn.

It should also be noted that the second pressure plate 24, load ring 30, pins 36 and load springs 34 can be preassembled to form a preloaded pressure plate assembly 102. With these parts assembled, the load ring 30 is forced towards the second pressure plate 24, exposing the groove 100 on the end of hub 96 so that snap ring 95 can be fitted thereinto. The load ring 30 can now be released and the Interengaged stop members 92 and 94 will hold the assembly together with the load springs 34 having the desired amount of preload.

This arrangement is quite desirable in that the pressure plate assembly 102 may be easily removed and reinstalled as a unit, without having to disassemble ihe individual load springs 34. This is particularly important in allowing quick and easy field replacement of any worn or failed parts.

Industrial Applicability The present invention is adapted for use in any type of dry clutch having a pair of pressure plates and a friction plate structure therebetween and is particularly useful for power takeoff clutches. In normal operation the clutch arrangement

10 is engaged by shifting sleeve 66 leftwardly from its Fig. 3 position so that the crank 52 will cam the load ring 30 leftwardly. Initial movement of the load ring 30 will move the second pressure plate 24 and load springs 34 leftwardly therewith until the second pressure plate comes into contact with the friction plate structure 14. Once contact Is

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made, and the friction plate structure 1. is trapped between the first and second pressure plates 22 and 24, further rotation of crank 52 and leftward movement of load ring 30 will unseat the stop members 92 and 94 so that the preloaded spring force of the load springs 34 will be immediately applied to the second pressure plate 24.

The applied load on the friction plate structure 14 Is the total preload forces on the load springs 34 plus the additional force of these springs resulting from the compression thereof when the load ring 30 is unseated from them and moves ^" leftwardly relative to the second pressure plate 24. From this, the force of the auxiliary springs 84 must be subtracted.

As is apparent, the maximum load will exist when the friction plate structure 14 is unworn and the preloaded load springs 34 have been further compressed by the maximum amount of movement of the load ring 30 towards the second pressure plate 24. The minimum load will exist when the friction plate structure 14 has worn to a point wherein the stop members and 94 have a minimal amount of separation therebetween, such minimum load being essentially equal to the preload of load springs 34 less the force of auxiliary springs 84.

As a consequence, with the present invention the minimum and maximum pressures can be established and controlled by a selection of the number of springs 34 and 84, the selection of their spring rates, the amount of preload of the springs

and the allowable amount of leftward movement of load ring 30 towards the second pressure plate 24 when the friction plate structure 14 Is unworn.

Since the amount of preload of load springs 34 and the amount of additional compression of these springs by relative movement of the load ring and second pressure plate 24 is established in the preassembly of the pressure plate assembly 102, field repair of the clutch is greatly faciliated since no field adjustment is needed to set the clutch pressure li its.

Should any type of failure occur in the actuating means 50, springs 34 will move the load ring 30 away from pressure plate 24, to the extent permitted by stop members 22 and 24, and springs 84 will then force the pressure plates 22 and 24 away from each other and to the position of Fig. 3, thus providing a significant safety feature.

Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.