GB843230A - Automatic adjuster for vehicle brakes - Google Patents

Abstract

843,230. Disc brake adjustment. GIRLING Ltd. March 11, 1959 [March 12, 1958], No. 7905/58. Class 103 (1). In an automatic adjuster for power-operated disc brakes for railway vehicles of the kind in which friction pads 31 adapted to be applied to opposite faces of a rotating disc 30 are mounted on the inner ends of interconnected caliper levers 33, 34 of which one (33) is pivoted at its outer end to the piston or diaphragm of a fluid-pressure cylinder 38 (e.g. vacuum), the pivot 39 for the non-actuated caliper lever 34 is carried or located by a piston-rod 40 associated with a piston 41 working in a cylinder 42 into which liquid is forced through a non- return valve 45 by a sensing piston 48 working in another cylinder 47 and coupled through a lost-motion device 53, 50 to the piston-rod or like of the fluid-pressure cylinder 38. In operation, should the stroke of the fluid pressure actuator exceed a predetermined value, as determined by the free movement of fork 53 between shoulder 54 and abutment 51, through wear of the friction pads or other parts of the brake mechanism, the sensing piston 48 forces liquid into the first cylinder 42 via non-return valve 45 and moves piston 41 outwardly so that the pivot of the non-actuated caliper lever 34 is displaced through a distance sufficient to compensate for the wear and to restore the stroke of the power actuator to its normal value. A diagrammatic representation is illustrated in Fig. 1 wherein when fork or collar 18 attached to the piston-rod of a fluid pressure actuator engages the outer shoulder 19 of reduced diameter part 17 of sensing piston 16 the latter piston is moved outwardly through a small distance dependent on the amount of wear of the friction pads. This outward movement of piston 16 causes liquid to be drawn into the inner end of the bore 12 through valve 21 from reservoir 10. On release of the brake, the collar 18 on its return movement engages the shoulder 20 and moves piston 16 inwardly so that surplus liquid which has been drawn into the bore 12 is forced through a valve 22 into the inner end of a bore 11 and moves a piston 13 outwardly to engage the non-actuated or anchored caliper lever of the disc brake. When the friction pads are worn and have to be replaced, opening of a valve 23 allows liquid to return from the bore 11 to the reservoir to restore the parts to their original positions.