AU427115B2 - Clutch pack - Google Patents

Description

lit Il 2p/m Conventional clutch packs encounter two problems. Vhen W the clutch pack is free spinning, i.e.

not transmitting poweri the discs tend to drag on each other and build up heat. To some extent this can be compensated by flooding the pack with cooling oil. The second problem is one termed "flutter failure". The drum which supports one set of plates or discs tends to wobble relative to the shaft which supports the other set of discs. While the exact ciuse of the wobble is not definitely established, it is believed that the tolerances in the bearings rotatably mounting the drum is the significant factor. Whatever the reason, It is known that for a given geometry clutch pack, tbo discs will become excited and tend to flutter at certain speeds when the clutch is free spinning*-, When the discs fluttar, they do not remain parallel to each other and hence come into spot or point contact with adjacent discs. Such small areas of contact concentrates the heat build-up and often flooding with cooling oil is insu fficient to prevent burning of the discs in these areas. Severe cases of flutter can elevate the temperature-in the areas of contact sufficiently high to actually weld the plates together.

-2- 2 7.'115 a1,112 Many attempts have been made to provide a means for separating the plates during free spinning. All of the prior art clutch pack separators, however, have suffered from at least one of the following deficiencies: restricting or sac- rificing frictional area; requiring moving contact between the separator and the discs during free spinning; imposing a fric- tional load on the lining material from the separator during free spinning; or have utilized a separator having a physical arrangement and located such that it is capable of damaging the lining material on the discs.

It is therefore an object of this invention to pro- vide a separator for a clutch pack which does not sacrifice frictional area, which does not require moving contact between the separator and the disc, which does not come into contact with the frictional lining material, and which is incapable of damaging the discs in the event of failure of the separator. It is also an object of this invention to provide a method for installing a separator in a disc of a clutch pack. It is a further object of this invention to provide a separator which is easy to insta-il and which will provide a long service life.

SFIGURE 1 is a cross-sectional view of a portion of a clutch pack incorporating the present invention, FIGURE 2 is a plan view of a single disc, with a portion broken away, showing the spacer of the present invention secured thereto, and

FIGURE 3 is a cross-sectional view, to a larger scale, taken on lines 3-3 of FIGURE 2.

427,1

11, 11 2 PREFERRED EMBODIMENT OF THE INVENTION

Since it is intended that the present invention may be incorporated into conventional clutch packs already in production, FIGURE 1 illustrates a portion of such a conven- tional clutch pack, indicated generally at 10. An outer member or drum 12 is mounted in bearings, (not shown), for rotation about the axis 14. An inner sleeve or shaft 16 is also jour- nalled for rotation about the axis 14. One of the members 12 and 16 is the driving member and the other is the driven member. The shaft member 16 is provided with an external spline 18 which permits the mounting of a plurality of plates 20. The plates 20 are provided with internal diameters having a shape complementary with the spline 18 and mount on the spline 18 so that the plates are axially shiftable, but non-rotatable rela- tive to the member 16. Frictional material 22 is secured to each face of the plates 20. Typically, the plate 20 is formed of a steel material and the facing of frictional material 22 is formed of sintered bronze. Interleaved between the plates are a plurality of discs 24. Each disc is provided with a plurality of tangs 26, as shown in FIGURE 2, which tangs are engageable with complementary slots 28 formed on the interior of the drum 12. The engagement of the tangs 26 with the slots 28 permit the axial shifting of the discs 24 relative to the drum 12 while prohibiting relative rotation between the two. An actuator means 30, which customarily takes the form of a hy- draulically actuated piston means, is moveable between the dis- engaged position, such as shown in FIGURE 1, wherein the discs are free to rotate relative to the plates, and an engaged position wherein the plates and discs are forced into friction- al engagement. In the engaged position power will be trans- mitted between the two members 12 and 16, whereas in the

4271 15 disengaged position pow-er flow betwen the two members will be interrupted._ A separator or spacer 32 is provided on every other one of the discs. 'These spacers are made -of an elastomeric material capable of withstanding high temperature levels, such as fluorocarbon rubber, which is sold by DuPont under the trademark Vj ton. In order to preclude cocking-or side tilting of the discs, it is desirable to install a plurality of such spac- ers on each one of the alternate discs equipped with spacers and to locate the spacers so that-they are equi-angularly arranged around the periphery of the discs, as shown in FIGURE 2. The tang 26 of each disc does not make any contribution toward the friction engagement between the discs 26 and the plates 24, and hence it is highly advantageous to position the spacers 24 on the tang 26.

In this location, the spacers do not diminish the contact area available for frictional engagement. Eacb spacer 32 extends from the free surface of each alternating disc into contact with the adjacent disc. Since the discs 24 are all moveable in rotational unison with the drum 12, there is no relative movement between the discs 24, and hence, there is no relative rotational movement between the free end of the spacer- and the adjacent disc. Each spacer extends beyond the side of the disc to which it is attached by an amount at least equal to the thickness of the adjacent plate 2D and preferable to in- sure minimum drag during free spinning, should extend from the side of the supporting disc a distance between .014 -to .024 inch greater than the adjacent plate's thickness. When the actuator means 30 moves to the right. as viewed in FIGURE 1, to engage the clutch pack, the discs and plates will be forced into tight contact. This will cause thb,

11, 1 2 elastomeric material to be compressed. As this material is co

pressed, each spacer will be shortened in length and increased in diameter or "buttoned up". To make sure that the adjacent plates do not cut the spacers under this "buttoned up" con- dition, each spacer must be positioned radially on the tang a distance sufficient to preclude contact with the plates under the maximum increased diameter conditions. That is, allowing

for the maximum permissible wear on the plates and discs, whic] creates conditions for maximum increase in diameter of the spacer, the spacer should be positioned radially outward on the tang a distance sufficient to clear the pla'tes. While the spacers may take a variety of shapes and may be secured to the tang in a variety of ways, it is preferro

that the spacer have the shape of a cylinder of substantially constant diameter, in its relaxed state, and that it be securer

to the tang by trapping it -in an opening in the tang of smalle: diameter than the cylinder. As shown in FIGURE 3, the spacer

32 has the form of a cylinder with a diameter 34. The opening

36 formed in the tang 26 has a diameter 38 which is smaller

than the diameter 34. The difference in diameter need not be substantial because the "button up" effect resulting from compression of the plates, increases the diameter of the cylin. der even more and tends to hold the cylinder within-the- openin! -36. A bevel or chamfer 40 is formed on each end of the openin! 36 to minimize the possibility of the spacer being cut when it is "buttoned up" during compression. The placement of the cylindrical spacer 32 in the. opening 36 is achieved in the following manner. A taper is formed on one end of a cylindrical rod of elastomeric material; the'-taper being sufficiently'long to'

427,115 permit it to be inserted tro gh the opening 36 and grasped on the other side. Once the tapered portion is grasped, a tension force is applied to the rod, which force must be sufficient to elongate the rod and reduce its diameter to be substantially equal to the diameter of the opening 36. While the rod is so tensioned, it is moved axially of the opening 36 to a position in which a full diameter portion extends a substantial distance on either side of the disc 24. The tension force can then be relaxed and the rod cut to provide a full diameter cylinder por- tion extending from each side of the disc a distance at least equal to the thickness of the adjacent plate and preferably .014 to .024 inch greater than that plate's thickness. While applicant has shown and described one form the invention may take and has described one method for assembling it, it is to be understood that various modifications may.be made in either the structure or the method without departing from the spirit of the invention.

427.1

11,112 po The clajas Cefining .the invention are as folaozz:

1. In a clutch pac]: for t ransnitting_ and Interrumtipg powier flow~ betreen an outer dram -means .arZd a shafts means mounted for rotation about a coin on axisz, said dram means having a pplura2.ity of axially extending z~ots, and said shaft-means having an external splime, a Plarality of discs having tan,-s en~rpenable -vith the slots and a plurality of plates having tootbed Inner diameter engageable wi.th the spline, said discs and plates being altvrzately Inter- leaved, and actuating means :for selectively forcing said discs Dlates into frictional iengagrement and permittingS said discs and plates to rotate relative to each other; the improvement coqprising; *every other one of said discs having at least one opening extending Vheretbrougb; a-spacer positioned in each of said onenings and consisting of a cylindrical member or elastoneric material having a constant diameter In its relaxed state larger than the diameter of said onening; each of said sp~acers -being retained withim the open-ing

solely by the forced constriction of an intermediate portion of the cylindrical member -bytbe smaller Ziameter openingz.

2. In a clutch pack accordinE to Claima I whertin the outer ends of each opening are -provided-%itb a tcembe1), w~hereby compression of the cyl1indrical neieer mnaer povier transnittingc conditions id.ll preclude crttizS said memiber.

3.In a clutch pack accord-ing to Clain 2, =bercin each

a 427.115 spacer extends fro 1hside of -the disc in which it is retained a distance which is between .0114 and 0.24 inches greater than the thickness of the adjacent plate, wihereby viscous drag between plates and discs is minimized when the clutch pack is in a free running position.

DATED this 27th day of MT1E, 1972.

INTERATIOEAL HARVESTER COM.PANY

Edwd. 'aters Sons, Russell Street, Melbourne. 3000, Victoria. AUSTRALIA.

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