Self-adjusting drum brake

Claim 1

A one-piece adjusting lever and mounting member for an internal shoe drum brake system which includes a pair of webbed brake shoes mounted in a conventional manner with a first pair of end portions supported for pivotal movement, one of the brake shoes having an aperture through the web, an axially extendable and contractable strut assembly between a pair of shoe second end portions with a rotatable member as part of the strut assembly so as to produce extension and contraction thereof, the one-piece adjusting lever and mounting member comprising: a sheet metal member having a first arm portion extending so that a free end thereof engages an end of the strut assembly to produce pivotal movements of the adjusting lever in response to relative movement between the strut assembly and the brake shoes; a second arm of the adjusting lever extending substantially normal to the first arm and through the aperture in the brake shoe web to provide a mounting fulcrum to pivot the adjusting lever in response to the actuating force on the first arm by the strut assembly, a third arm extending from the second arm in substantial parallelism with the web of the one brake shoe and on an opposite side thereof than the first arm; the adjusting lever further including a pawl arm for engaging the rotatable portion of the strut assembly at its free end so that pivotal movements of the adjusting lever about the point of engagement between the brake web and second arm produce circumferentially oriented movements of the pawl arm's free end relative to the struts rotatable member; means between the free end of the pawl arm and the rotatable member promoting mutual movement therebetween in one direction thus effecting rotation and resultant extension of the strut assembly and restraining mutual movement and rotation of the strut member so as to effect contraction thereof; biasing means on the adjusting lever including a first yieldable member between the third arm and the brake shoe for exerting a force between the movement promoting means as permitted by the interaction between the first arm and the strut assembly, a second yieldable member between the brake shoe and the pawl arm exerting a lateral force on and relative to the pawl arm to maintain engagement with the strut's rotatable member.