1. Field of the Invention
The present invention is generally concerned with clutch cover assemblies, that is to say the assembly of parts which in order to make up a clutch, in particular for an automotive vehicle, is fastened as a unit to a reaction plate or flywheel with a friction disk disposed between them.
2. Description of the Prior Art
As is known, a clutch cover assembly generally comprises a first generally annular member called the cover through which it is adapted to be attached to the associated reaction plate, a second generally annular member called the pressure plate, which is constrained to rotate with said cover whilst being mounted so as to be movable axially relative to the latter and which is adapted to clamp the friction disk axially against said reaction plate, and elastic means which, for the purposes of this clamping or engagement, urge said pressure plate in the direction towards said reaction plate, said elastic means bearing for this purpose on the cover so as to exert a force in the axial direction on the pressure plate.
Elastic means of this kind may, for example, form part of a third generally annular member called the diaphragm spring which is inserted axially between the pressure plate and the cover and comprises, on the one hand, a circumferentially continuous peripheral part forming a Belleville washer and constituting said elastic means and, on the other hand, a central part subdivided into radial fingers by slots, said central part forming levers by means of which the assembly may be operated to disengage it.
In practice, a diaphragm spring of this kind usually and at present bears directly on the pressure plate, the pressure plate having for this purpose an annular bead projecting in the axial direction, possibly circumferentially subdivided into separate bosses.
Be this as it may, in service the internal volume of a clutch cover assembly of this kind is inevitably subjected to an increase in temperature, in particular due to friction forces which are developed between the friction disk on the one hand and, on the other hand, the pressure and reaction plates, each time the clutch is disengaged and each time it is engaged.
To ventilate this internal volume so as to maintain the temperature within acceptable limits, it has already been proposed to provide the pressure plate with cooling fins which project axially from the side opposite that through which it is adapted to act on the friction disk and which delimit between them air circulation grooves which are oblique relative to a radial plane passing through their median area.
Arrangements of this kind are described inter alia in U.S. Pat. Nos. 1,767,309, 2,770,341, 2,885,047 and 2,205,629.
In U.S. Pat. No. 1,767,309, the cooling fins employed extend substantially from the inside perimeter of the pressure plate to its outside perimeter.
However, the elastic means disposed between the cover and the pressure plate are helical coil springs in this instance, arranged axially, and thus the cooling fins alternate circumferentially with these springs, which are relatively bulky.
Apart from the fact that their numbers are correspondingly reduced, the circulation of air between the grooves delimited by the fins is inevitably disturbed by these springs, which is prejudicial to the effectiveness of the ventilation required.
In U.S. Pat. Nos. 2,770,341 and 2,885,047, the elastic means disposed axially between the cover and the pressure plate consist of the circumferentially continuous peripheral part of a diaphragm spring and, as indicated hereinabove, this bears axially on circumferentially disposed bosses provided for this purpose on said pressure plate.
The cooling fins conjointly employed are of only limited extent, these fins extending from said bosses either in the direction towards the inside perimeter of the pressure plate, as is the case in U.S. Pat. No. 2,770,341, or in the direction towards the outside perimeter of the latter, as is the case in U.S. Pat. No. 2,885,047.
The required ventilation is correspondingly reduced.
Moreover, in these U.S. Pat. Nos. 1,767,309, 2,770,341 and 2,885,047 the air circulation grooves defined by the cooling fins which may be employed are open in the axial direction on the side opposite the pressure plate, extending freely in the axial direction from the latter.
As a result, these cooling fins operate more through agitating the air than by forced circulation thereof.
Their effectiveness with regard to the required ventilation is then less than certain.
In U.S. Pat. No. 2,205,629 the air circulation grooves are closed off in the axial direction, on the side opposite the pressure plate, by a member referred to hereinafter for convenience as the confinement member.
However, in this U.S. Pat. No. 2,205,629 this confinement member is an integral part of the pressure plate, the air circulation grooves being formed in its thickness.
As a result, the pressure plate is complex and costly to manufacture.
A general objective of the present invention is an arrangement with which this disadvantage may be circumvented and further providing additional advantages.