CA1250536A

CA1250536A - Drive strap system

Info

Publication number: CA1250536A
Application number: CA000469932A
Authority: CA
Inventors: Ronald E. Heymann; Martin E. Kummer
Original assignee: Dana Inc
Current assignee: Dana Inc
Priority date: 1983-12-13
Filing date: 1984-12-12
Publication date: 1989-02-28
Also published as: ZA849253B; IT1178286B; ES8602217A1; IT8449293A1; GB2151315B; SE8406297L; IT8449293A0; AU3639684A; FR2556430B1; BR8406330A; FR2556430A1; GB8430276D0; SE8406297D0; ES538512A0; KR850004520A; IN163362B; DE3442611A1; GB2151315A; AU576803B2; JPS60139918A

Abstract

Title Drive Strap System Abstract of the Disclosure A friction clutch of the type including a pressure plate and cover includes a drive strap oriented along a cord at the mean radius of the pressure plate. The strap is affixed to the pressure plate by a rivet which extends through a bore entirely through the pressure plate at the mean radius thereof. In a preferred form, the bore defines small and large diameter portions interconnected by a flared step. The flared step defines an angle which opens in a direction toward the disc-engaging surface of the pressure plate.

Description

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Title Drlve Strap System Background of the Invention This invention relates to vehicular clutches of the type wherein a drive strap system is employed to connect the cover and pressure plate members. More particularly, the invention relates to a drive strap system wherein the straps are oriented along a cord at the mean radius of the pressure plate.
Prior art clutches of the friction disc type have employed drive strap systems of less than satisfactory construction. Many of such systems have located the drive strap apparatus along areas other than at the mean radius, resulting in less than optimal load-carrying performance. ~or example, where riveted connections between drive strap and pressure plate members have been utilized, such connections have been located radially outwardly of the mean radius of the pressure plate. Such clutch constructions have required placement of cast ears on the edges of the pressure plate members, or cast recesses at the edges of such members. In systems wherein drive strap apparatus has been located on the mean radius of the pressure plate, such systems have utilized bosses on the back sides of the pressure plates which have included drilled and tapped holes for securement of drive straps t~ the pressure plates by bolts. The latter constructions have resulted in heavier pressure plates and thicke{ clutch profiles.

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-2- ~Z~5053 Summar~_of the In_ention ~ he drive strap system of the present invention provides an apparatus wherein a drive strap may be oriented along a cord at the mean radius of the pressure plate, and wherein both connections of the drive straps, viz. to both cover and pressure plate members, are riveted. Such a construction does not require special bosses on the back sides of the pressure plate, nor drilled and tapped holes for securement of the straps thereto.
In the present invention, the drive strap system utilizes a pressure plate having a bore extending entirely through the pressure plate at the mean radius thereof, and disposed for receiving a rivet for connecting the strap at the mean radius location. In a preferred form, the bore is stepped, and comprises large and small diameter portions having a flared step between the portions. The flared step defines an angle which opens in a direction toward the disc-engaging side of the pressure plate.
Brief Descriptlon of the Drawings Fig. 1 is a view, partly in section, of the rear of a friction clutch which incorporates a preferred embodiment of the drive strap system of the present invention;
Fig. 2 is a view along lines 2-2 of Fig. 1.
Detailed Description of a Preferred Embodiment _______________ ___________________________ _ Referring initially to Fig. 1, a friction clutch 10 incorporates the drive strap system 12 of the present invention. The drive strap system 12 includes a chordally oriented drive strap 14 connected at its respective ends to a clutch cover 16 ~fixed to a flywheel, not shown) and a pressure plate 18. The strap 14 is positioned optimally on the mean radius of the pressure plate 18, as will be appreciated by those skilled in the art.

~;2S~536 The drive strap system 12 is shown in greater detail in Fig. 2. A bore 20 through the cover 16 receives a rivet 22 having a head 28 for securement of the strap 14 to the cover 160 The rivet is secured by a peening process which forms a peened end 24 at the rear face 48 of the clutch cover.
As per conventional practice, the drive strap 14 comprises a flexible spring steel member by which the strap 14 not only rotatably drives the pressure plate with respect to the cover, but also provides relative axial movement under its spring force to enable the pressure plate to be pulled toward the cover 16 and thus away from an engaging friction disc (not shown).
A bore 30 extends entirely through the pressure plate 18 at the mean radius location of the pressure plate. A rivet 32 extends through the bore 30 to retain the strap 14 against the rear surface 50 of the pressure plate 18. The rivet includes a shank 34 having a head 36 in direct contact with the strap 14 to hold same against the surface 50. The free end of the shank 34 is peened to form a peened end 44 to permanently secure the rivet 32 in the bore 30.
The bore 30 includes small and large diameter portions 38 and 40, respectively. ~ flared step 42, positioned at the interface of the small and large diameter portions 38 and 40, defines an angle which opens in a direction toward the disc-engaging surface 46 of the pressure plate 18. It will be appreciated by those skilled in the art that the flared step 42 defines an angled annular surface against which the peening of a rivet end may be more successfully controlled, whereby plastic deformation of the end is less likely to be non-uniformly distributed about the shank axis "a-an. Thus, the flared step assures a more consistently uniform radial distribution of the plastically distorted peened end 44 in an assembly line environment.

-4~ 0536 Although the angle of the flared step 42, as measured with respect to the shank axis na-a", is 45 degrees in the embodiment herein described, the preferred angle may fall within a range of 30 to 60 degrees. The large diameter portion 40 of the bore 30 will enable a dependable visual inspection of the quality of the peened rivet end 44, to the extent that a satisfactorily peened end 44 has been formed whenever the flared step 42 is rendered entirely invisible.
It will also be appreciated by those skilled in the art that the use of rivets in the mean radius location of the pressure plate will enable the employment of a lesser relative profile of the overall clutch system.
As was mentioned previously, prior art systems incorporating mean radius connections of drive straps have utilized bosses on the back sides of pressure plates. The bosses have included drilled and tapped holes for securement of the drive straps. The addition of bosses to the relatively otherwise thin pressure plate areas at the mean radius has added to both thickness and weight of the pressure plate. The drive strap system 12 of the present invention thus enables the achievement of a relatively thin clutch profile, as well as a more efficient, lighter construction.
Finally, it will be seen that the clutch drive strap embodiment of Fig. 2 has a peened end 44 which does not fully fill the large diameter portion 40 of the bore 30. If desirable, the resulting recess or void may be filled with metal or other material to provide a smooth friction surface without such voids on the disc-engaging side 46 of the pressure plate.
However, the existence of such voids will not generally pose a problem with respect to use of most modern clutch facings, and particularly where friction discs are employed which have ceramic facings. Thus, those - ( l ~ZSOS~6 skilled in the art will appreciate that the embodiment of Fig. 2 is particularly suitable for use with friction discs having ceramic facings.
Although not described or shown herein, there are many variations of the present invention which will fall within the scope of ~he appended claims.

Claims

Title Drive Strap System THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a friction clutch including a pressure plate and a cover, a drive strap connecting said pressure plate to said cover, said drive strap oriented along a cord at the mean radius of the pressure plate; an improvement comprising said pressure plate having a bore positioned at one end of said cord, said bore extending entirely through said pressure plate from the rear thereof to the disc-engaging surface thereon, said bore disposed for receiving a rivet therethrough for connecting said strap to said pressure plate at said mean radius.

2. The clutch of Claim 1 wherein said bore comprises a small diameter portion at said rear of said pressure plate, and a large diameter portion at said disc-engaging surface of said pressure plate, said bore further comprising a flared step between said small and large diameter portions, said flared step defining an angle which opens in a direction toward said disc-engaging surface of said plate.

3. The clutch of Claim 2 wherein said flared step defines an angled annular surface whereby the peening of a rivet end may be controlled, and wherein said large diameter portion of said bore provides a means for visual inspection of the quality of said rivet end after said peening.