Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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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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
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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.
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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.
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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
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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.
