GB883894A - Hydraulic automatic adjusting mechanism - Google Patents

Abstract

883,894. Fluid pressure brakes. GOODRICH CO., B. F. Oct. 27, 1958 [Oct. 28, 1957], No. 34344/58. Class 103 (1). An hydraulic adjusting mechanism, particularly for brakes, comprises an actuator 31 dividing a casing 13 into chambers 13a, 53 having entry and exit openings and being connected by a port 38 controlled by valve member 44 urged by a spring 50 against fluid pressure in chamber 53 into engagement with a seat 39, the member 44 reciprocating in a housing 41 closed at one end to seal off its interior from fluid in the chambers, a passage 54 being provided to permit fluid in chamber 13a to act on the annular surface 52 of valve member 43 to open the valve. On braking, fluid from master cylinder 12 moves actuator 31 to displace fluid from chamber 53 to apply the brake 17-20. If wear has taken place, the actuator 31 will seat on wall 37 of housing 13 and pressure, built up in chamber 13a acts, through passage 54 and groove 40 in the actuator, on surface 52 to raise valve member 43 to permit fluid to flow into chamber 53 and the brake cylinder 16, Fig. 2. On brake release, spring 50 closes valve member 44 on to seat 39 and the fluid in chamber 53, pressurized by the brake return springs 22, returns actuator 31 against spring 55 to the release position, Fig. 1; the volume of chamber 53 corresponds to the volume required to apply the brakes when there is the normal predetermined brake clearance. Should the normal clearance be decreased, e.g. by shrinkage of the brake drum, the brake will be applied before the actuator 31 engages wall 37, the valve member 43 is raised by pressure on surface 52 and since the pressure on either side of the actuator balances the spring 55 moves the actuator against wall 37, fluid flowing through port 38. Should the drum shrink to exert a pressure on the brake shoes an increase in pressure in chamber 53 results to open valve 43 and bleed off some of the fluid, the brake shoes then being in light rubbing contact with the drum, normal brake clearance being attained by a pedal depression creating brake application before actuator 31 engages wall 37, as above. In Fig. 3 (not shown), the valve member is replaced by a synthetic plastic body, e.g. nylon, sliding in a bell-shaped housing fixed to the actuator. Specification 833,857 is referred to.