GB1459452A - Vehicle brake actuators - Google Patents

Abstract

1459452 Actuators GIRLING Ltd 18 July 1974 [4 Sept 1973] 41470/73 Heading F2F A vehicle brake actuator comprises a cylinder 2 within which a service brake actuating diaphragm 4 operates and a cylinder 1 within which an auxiliary or emergency brake actuating piston 7 operates; the piston 7 is normally held in its illustrated brake released position by fluid pressure opposing the force of a coil compression spring 8 which biases the piston 7 away from a cylinder end wall 9. An elongate hollow release member 14 is rotatably mounted in an opening 15 in the end wall 9 and includes an internally screw-threaded portion 14B co-operating with a screw-threaded abutment member 17 having a head 17A engageable by a flange 18 on the piston 7 to limit movement of the piston 7 away from end wall 9; the piston 7 is slidably guided on the release member 14 by means of hollow piston part 13 and is retractable from its brake applying position against spring 8 by rotation of the hollow member 14 relative to the abutment member 17. As shown, the piston 7 has a piston-rod 11 which extends through a wall 12 dividing the cylinders 1, 2. During service actuation pressure fluid acts on diaphragm 4 to move an actuating member 3 leftwardly. In response to a pressure loss via inlet 10 (e.g. by manual valve control for parking or by pressure failure) the piston 7 moves in the brake applying direction, and rod 11 abuts diaphragm 4 to move actuating member 3, until flange 18 abuts head 17A. To manually release the brake the member 14 is rotated by a spanner or key and the abutment member 17 is thereby screwed into member 14 to retract piston 7. Substantial axial movement of member 14 is prevented by co-operation of a circlip 16 and an enlarged head 14A with the periphery of opening 15. Removal of a circlip 19 retaining end wall 9 allows piston 7 to be removed from the cylinder 1. The walls 9, 12 may be apertured plates. The piston-rod 11 may be articulated to the piston 7.