Self-energizing disc brakes

Claim 1

In a spreading disc brake of the type having pressure plates which are angularly movable within a brake housing to initiate application of the brakes and wherein the angular movement of the plates is effected by an annular fluid pressure actuator which acts on an abutment carried by a pull-rod passing through the actuator with substantial clearance to operate in tension on toggle links connected to said pressure plates; said actuator being a cylinder housing rigidly fixed to the brake housing with the cylinder axis substantially at right angles to the axis of the plates and a piston operating in said cylinder: the invention comprising improved means for transmitting the thrust of said piston to the abutment carried by the pull-rod comprising a thrust member co-axially aligned with the piston and slidable therewith in said cylinder housing to transmit the force exerted by the piston, spring means urging said thrust member against said piston and urging said piston into the retracted position, a trunnion member forming part of said thrust member, part cylindrical bearings in said thrust member for rockably receiving said trunnion member, a substantially annular member slidably received in said cylinder housing between said thrust member and said spring means, said annular member having part cylindrical bearings complementary to the bearings in said thrust member and also rockingly receiving said trunnion member, and key means cooperating with said cylinder housing and said thrust member for maintaining the pivotal axis of the coupling parallel to the axis of the brake while confining angular movement of said pull-rod to a plane normal to the axis of the brake, said key means comprising an apertured plate fixed to said cylinder housing and extending across the outer end of the cylinder, an axially extending slot in said thrust member, and a projection on said apertured plate extending into said slot.