GB1514755A - Pressure-fluid actuator for the brakes of a road vehicle with service emergency and parking braking actions - Google Patents

Abstract

1514755 Actuators R POINTOUT 30 June 1975 [8 Oct 1974] 27532/75 Heading F1D To prevent the simultaneous application of both the service braking and the parking/emergency braking to an output rod 5 of an actuator comprising a service brake 1 with a movable wall 2 acting on the rod 5 and a spring applied fluidpressure released parking/emergency brake with a movable wall 16 acting through a push-rod 20 which extends through a seal 21 into the service brake and acts through the movable wall 2, the push-rod 20 has means to close the fluid supply to the actuation chamber 3 of the service brake and to vent it to atmosphere when it is extended. In Fig. 1 compressed air is supplied to the chamber 3 from a port 14, through an annular passage 11 within a tube 10, ports 13 and past a seal 23 on an abutment head 22 of the push-rod. Should the pressure in the chamber 17 be released allowing the springs 18, 19 to move the piston 16 and the push-rod to the left, the seal 23 closes the inlet to the chamber 3 which is vented through the gap appearing between the abutment 22 and the end-wall 1a, ports 24 and a resilient annular one-way valve-member 25 to the chamber 17. In Fig. 3 the push-rod 120 carries a valvemember 132 which is urged by a spring 133 against a shoulder 134 at the end of the push-rod. On advancing of the push-rod the valve-member 132 first closes a feed passage 113 for the service brake and is then displaced from the shoulder allowing air from the chamber 103 to escape though external grooves of the members 132 and the hollow push-rod to an outlet 135. The push-rod 20 carries a pin 26 which is releasable from hooked recesses 27 Fig. 2 (not shown) of a hub 28 of the piston 16 by rotation of push-rod.