GB1423160A - Vehicle wheel brake actuators - Google Patents

Abstract

1423160 Brake actuators GIRLING Ltd 18 Dec 1973 [19 Dec 1972 5 Jan 1973 4 Sept 1973] 58647/72 853/73 and 41451/73 Heading F2F In a wheel brake actuator comprising a first piston assembly 5 for service braking and a second piston 2 urged by a spring 3 to apply the brakes for parking or in emergency and released by fluid pressure, force transferring means 13 extending axially and outwardly and release means 12 the parts 12, 13 extend through piston 2 with clearance, part 13 being engageable with piston 2 upon release of the opposing fluid pressure. A bush 14 is screw-threadedly connected at or near the outer end of part 13 and is a loosefit within an outer bush 15 screwthreadedly attached to piston 2, the bushes having complementary shoulders which are normally spaced apart and permit relative movement of the bushes in one axial direction but prevent it in the reverse sense. In the event of pressure failure the brake can be released manually by unscrewing member 13 from the bush 14 which is frictionally held against rotation by bush 15, member 13 being thus moved axially to release the brake. In a modification the force transferring member carries a part having diametrically opposed slots and a bush carries pins or pegs, release of the brake being achieved by aligning pins and slots to allow longitudinal movement. In another modification Fig. 5, a push rod 25 has a counterbore 26 within which is located a release plunger 27 with a wedge portion 28 and balls 29 are retained in circumferentially spaced apertures in the wall of the counterbore, to engage the part 28, by a cylindrical member 31 held in position by an end cap 32. The brake is released in the event of fluid pressure failure by pressing plunger 27 against a spring 33 to allow the balls to move inwardly and allow movement of the rod 25.