Force transmission device

Abstract

A force transmission device for a disc brake operable to move a friction element of the brake into engagement with a rotary brake disc along a first axis in response to a loading from an actuating member, the device comprising: a guide member having a generally cylindrical guide form; a piston comprising a complementary generally cylindrical outer sliding surface slideable within the guide member, wherein; an anti-rotation formation is provided between the guide member and the piston, the formation comprising a recess extending generally parallel to the first axis and a complementary projection.

1 . A force transmission device for a disc brake operable to move a friction element of the brake into engagement with a rotary brake disc along a first axis in response to a loading from an actuating member, the device comprising:
 a guide member having a generally cylindrical guide form; and   a piston comprising a complementary generally cylindrical outer sliding surface slideable within the guide member;   wherein an anti-rotation formation is provided between the guide member and the piston, the formation comprising a recess extending generally parallel to the first axis and a complementary projection.   
     
     
         2 . A force transmission device according to  claim 1  wherein the recess is provided on the guide member and the projection provided on the piston. 
     
     
         3 . A force transmission device according to  claim 2  wherein the projection is arranged proximate an end of the piston remote from the friction element. 
     
     
         4 . A force transmission device according to  claim 1  further comprising at least one inner tappet located at least partially within the piston. 
     
     
         5 . A force transmission device according to  claim 4  wherein the inner tappet is arranged to cause the piston to extend to maintain a substantially constant running clearance in response to wear of the friction element, wherein extension of the piston is achieved by virtue of relative rotation of the tappet with respect to the piston. 
     
     
         6 . A force transmission device according to  claim 1  wherein the guide member comprises a yoke. 
     
     
         7 . A force transmission device according to  claim 6  wherein the yoke is movable together with the piston during loading from the thrust member to apply the brake, wherein the yoke is further configured to transmit a return force to the piston to restore a running clearance between the rotor and friction element after a brake application. 
     
     
         8 . A force transmission device according to  claim 6  wherein the yoke comprises two guide forms to guide two pistons. 
     
     
         9 . A force transmission device according to  claim 8  wherein the yoke is further arranged to receive an adjuster assembly, wherein the adjuster assembly is located intermediate to the guide forms. 
     
     
         10 . A force transmission device according to  claim 6  wherein the yoke is a die cast component, and/or the yoke is an extruded component, or the yoke is an assembly comprising multiple components. 
     
     
         11 . A tappet comprising a shaft portion for transmission of a thrust loading from an actuating member to a piston of a disc brake, the tappet further comprising a gear portion for transmission of rotary motion to the shaft, wherein the gear portion is formed as a separate piece from the shaft portion. 
     
     
         12 . A tappet according to  claim 11  wherein the gear portion is formed from lower strength material than the shaft, for example the gear portion is formed from a selected one of the following materials: sintered metal, die cast metal, injection moulded metal, cast metal, injection moulded plastics, and/or the shaft is formed from a selected one of the following materials: forged metal, cast metal. 
     
     
         13 . A tappet according to  claim 11  wherein the shaft portion defines an axis, and the shaft portion and the gear portion comprise complementary abutting surfaces in a direction transverse the axis. 
     
     
         14 . A tappet according to  claim 13  wherein the complementary abutting surfaces restrain movement of the gear portion toward an inboard end of the actuating member at which the actuating member is located. 
     
     
         15 . A tappet according to  claim 11  wherein the shaft defines an axis, and the shaft and the gear comprise complementary abutting surfaces in a circumferential direction so as to restrict relative rotation of the gear with respect to the shaft. 
     
     
         16 . A cover plate for mounting over a rotor side opening in a housing in a disc brake caliper, and having at least one aperture therein through which a piston may extend and move a friction element into contact with a brake rotor. 
     
     
         17 . A cover plate according to  claim 16  which is a pressed sheet metal component, preferably sheet steel. 
     
     
         18 . A cover plate according to  claim 17  further comprising at least one journal bearing form pressed therein, preferably wherein the bearing form is a plain bearing, or wherein the bearing form further comprises a bushing. 
     
     
         19 . A cover plate according to  claim 16  wherein the bearing form comprises a substantially circular wall extending away from a major plane of the cover plate and a second wall extending back towards the major plane to form a blind substantially cylindrical bore. 
     
     
         20 . A cover plate according to  claim 16  further comprising a seal for connection to a piston overmoulded directly thereon, and/or further comprising a peripheral seal overmoulded directly thereon.