GB1321619A - Actuators for use in vehicle braking apparatus - Google Patents

Abstract

1321619 Spring applied; fluid pressure released brakes CLAYTON DEWANDRE CO Ltd 3 Dec 1970 [23 Dec 1969] 62607/69 Heading F2F A brake actuator comprises a fluid pressure motor A with two spaced diaphragms 1a, 1b the outer diaphragm 1a being movable therein under the action of pressure fluid supplied to the space between the diaphragms la, 1b through a port 13 to move on output rod 5 to apply the brakes: the actuator also comprises a spring actuated unit S including a port 14 whereby fluid may be vented from the unit S to cause a spring 10 to move a piston 8 to thereby move the diaphragms 1a, 1b and the rod 5 to apply the brakes. Thus as seen in the Figure, when fluid pressure enters the unit A through the port 13 the diaphragm 1a is moved to operate the rod 5 but the diaphragm 1b will tend to move in the opposite direction: hence if the units A and J are actuated simultaneously the force on the diaphragm 1b will oppose the action of the unit S and the effort of only one unit will be transmitted to the rod 5. The fluid pressure may be hydraulic or pneumatic, but the embodiment of the Figure is specifically for compressed air systems. A spacer 3 is located between the diaphragms 1a, 1b and presser plates 4, 9 are in operative connection with the other sides of the diaphragms la, 1b respectively. The piston 8 has a hollow hub structure 11 extending through a transverse wall 12 separating the units A and S into engagement with the plate 9. An axial bolt 15 extends through the hub structure 11 and the bolt 15 has an enlargement 16 on one end slidable within the structure 11: at the other end an elongated nut 17 is in screwthreaded engagement with the bolt 15 and the nut 17 is in engagement with a bushing 19 whereby after displacement of the piston 8 by the spring 10, rotation of the nut 17 will withdraw the bolt 15 and by engagement of the enlargement 16 with a shoulder 20 on the hub structure, simultaneously withdraw the piston 8.