a friction clutch wherein the diaphragm spring has two sets of inwardly extending prongs which are axially spread apart by the marginal portion of an axially movable release plate serving to disengage the clutch by pivoting the diaphragm spring relative to a plate - like carrier on the crankshaft of the engine in a motor vehicle to thereby relax the bias upon a pressure plate which normally presses a clutch disc against a counterpressure plate connected to the carrier . the coupling between the marginal portion of the release plate and one set of the prongs is a bayonet lock type connection which can be disengaged by turning the release plate relative to the diaphragm spring against the opposition of male and female detent members to thereby move each prong of the one set into register with a discrete opening in the marginal portion of the release plate . the release plate stresses the two sets of prongs and is clamped between them when it is turned in a direction to move the prongs of the one set out of register with the corresponding openings . at such time , the prongs of the one set move along sloping ramps which guide them into engagement with convex abutments at one side of the release plate . the other side of the release plate has convex abutments for the prongs of the other set .