GB927688A - Fluid pressure control valves - Google Patents

Abstract

927,688. Fluid-pressure brakes. BENDIX CORPORATION. Sept. 14, 1961 [Oct. 3, 1960], No. 33038/61. Class 103 (1). [Also in Group XXIX] Apparatus controlling vehicle brakes consists of an hydraulic intensifier piston B connected with lost-motion to the rod 16 of a vacuumsuspended spring-loaded diaphragm C; the piston B slides in a bore 14 and its rearward position is defined by a shoulder 26 having a washer 24 positioned by a further washer 30 and a perforated bushing 32. Fluid-pressure from a master cylinder is admitted to the rear of the piston B via a port 46; the forward end of the piston B has a compensating bore 52 opening to the bore 14 by a port 54, the inner end of the bore 52 being controlled by a ball 56 on the end of the rod 16. The operation of the diaphragm C is controlled by a self-lapping valve arrangement E embodying a vacuum chamber 64 always open to the diaphragm chamber 60, a control 68 leading to the diaphragm chamber 58 and an atmospheric chamber 72. A spring-loaded elastomeric diaphragm 76 attached to the intensifier housing defines chambers 64, 68, whilst the diaphragm periphery is extended to form the chamber 72 which is separated from chamber 68 by a partition 78 with an opening 82 therethrough controlled by a poppet valve 86 which is aligned with a tube 84 in the diaphragm 76 providing communication between chambers 64, 68. The poppet valve 86, which is spring closed, has a closure portion 90 and an inner flange 92. The diaphragm 76 is retained upon the tube 84 by plates 100, 104, the latter of which is curved, and a groove 106 in the tube; a hub part 94 of the diaphragm extends over and beyond the end of the tube and is rounded away from the latter to ensure a good seal with the flange 92. The inner end of the tube 84 is solid and is housed in a bore 110 which opens to the chamber at the rear of the intensifier piston B and hence to the port 46. When pressure from the master cylinder is applied to the port 46 the tube 84 is lowered so that the hub 94 abuts flange 92 and closes off the vacuum connection to diaphragm chamber 58, the hub end subsequently deforming until the end of the tube 84 abuts the flange 92; continued movement of the tube 84 unseats the poppet valve 86 to admit air from chamber 72 and diaphragm chamber 58 via control chamber 68, the pressure build-up in the latter causing the hub 94 to be biased radially on to the tube 84. The resulting motion of the diaphragm C causes the ball 56 to close the compensating bore 52 and move the piston B into the bore 14, the displaced fluid operating the braking system. The pressure continues to build up in control chamber 68 until the diaphragm 76 is urged upwardly a sufficient amount to enable the poppet valve 86 to reseat. The pressure in the port 46 is reduced to release the braking effort so that the diaphragm 76 moves further upwards to open the passage through the tube 84 the piston B travels leftwardly and displaces fluid against the tube 84 which again seats on the flange 92. Complete removal of pressure from the port 46 causes the parts to return to the inoperative position shown.