GB1528442A - Self-adjusting drum brake - Google Patents

Abstract

1528442 Automatic adjustment in drum brakes SOC ANON DBA 1 April 1977 [13 April 1976] 13904/77 Heading F2E A drum brake comprises two brake shoes, 12, 14, actuating means 22 in the form of an hydraulic wheel cylinder situated between two first adjacent ends 24, 26 of the shoes 12, 14, a fixed fulcrum block 28 situated between the other two ends 30, 32 of the shoes 12, 14, and adjusting means designed to increase the distance between the first ends 24, 26 of the shoes automatically as a function of the wear on the linings 16, 18 of the shoes 12, 14, the adjusting means comprising a lever 38 pivoted at one end on a first of said shoes 12 in the vicinity of the actuating means 22, a pawl 42 pivoted on said first shoe 12 and biased by resilient means 46 into engagement with a toothed sector 48 formed on the other end of the lever 38, and an operating member 50 in the form of a rod which is responsive to an increase in said distance between the first ends 24, 26 of the shoes 12, 14 so as to pivot the lever 38 in the direction corresponding to adjustment of the brake, wherein the resilient means comprise a spring of which at least part co-operates with that surface of the lever remote in the axial direction of the brake from the web of the first shoe irrespective of the position of the adjusting means. This prevents sector 48 excaping from pawl 42. As shown, spring 46 is a wire hairpin spring with at least one turn around the pivot of the pawl 42 and with first and second arms 62, 64 bearing respectively on shoe 12 and on pawl 42 so as to bias the pawl 42 into engagement with toothed sector 48-the second arm 64 includes a curved part constituting the part co-operating with the surface of the lever 38.