GB1397122A - Internal shoe drum brakes - Google Patents

Abstract

1397122 Shoe drum brake slack adjusters AUTOMOTIVE PRODUCTS Ltd 2 May 1973 [12 May 1972] 22378/72 Heading F2E In an internal shoe drum brake, a strut 23 is coupled to one shoe 10 substantially at the shoe centre for movement thereby, and can move freely inwardly with respect to a second shoe 11, the strut being positioned substantially at that shoe centre, but is connected thereto by a one-way locking device for preventing inward movement of the shoe 11 with respect to the strut a lost motion connection allowing limited such movement. The brake which has a double leading shoe for anti-clockwise rotation and provides a double trailing shoe for opposite rotation, is operated by piston-cylinder actuators 12, 13 each providing a fixed anchorage for the shoe operated by the other actuator. The strut 23 of square section, has a projection 32 engaging a hole 33 in the shoe 10, the hole being larger in the axial direction of the strut to provide the lost-motion connection for brake clearance. A pivoted locking member 42, forming the device, on the shoe 11 has a flat surface 43, as shown, or a curved surface, offset from the perpendicular from the pivot to the strut 23 to allow inward strut movement with respect to the shoe, but, by means of a spring 44, increases frictional grip on the strut during opposite movement. The surface 43 may be plane or serrated, wherein the locking member comprises a series of abutting plates whose serrations are staggered to reduce the effective pitch thereof. The member 42 has a tail 45 to allow a tool to be inserted for strut release when the shoes are replaced. The lostmotion connection may be within the strut or at the locking member pivot. The brake may be of the leading-trailing shoe type.