Patent GB-889581-A (GB)
Title: Improvements relating to compressed fluid braking apparatus
IPC: B60T15/48
Filed: 1960-04-21
Abstract: 889,581. Fluid-pressure braking systems. WESTINGHOUSE AIR BRAKE CO. April 21, 1960 [April 27, 1959], No. 13950/60. Class 103 (1). A compressed-fluid braking apparatus includes a combined service and inshot valve device 2 comprising pistons 3, 4 defining a chamber 5 connected to an emergency reservoir 7, a chamber 9 connected to brake pipe 10, a chamber 20 connected via chamber 22 to brake cylinder 24, and an atmospheric chamber 17. The follower 25 of piston 4 forms a vent valve 27 adjacent a supply valve 32 having a stem 45 adjacent an inshot valve 40, the valves 32, 40 controlling the communication of auxiliary reservoir 38 with brake cylinder 24 via small and large chokes 36, 42, respectively. A plunger 47 is biased to one limit of a lostmotion connection with piston. 4 by springs 48, 49 bearing respectively on piston 4 and on a washer 55, and both bearing on a collar 50 of plunger 47. On charging, pressure in pipe 10 and chamber 9 holds piston 3 on rim 57 to open a valve 11 to charge reservoir 7 via choke 13 and chamber 5, the auxiliary reservoir and chamber 33, 41 being charged via check valve 58. The spring 49 biases piston 4 via collar 50, plunger 47 and nut 52, against washer 55 to keep valves 40, 32 closed. On completion of charging all components are as shown. For service braking, a pressure decrease in pipe 10 and chamber 9 raises piston 3 to close valve 11 and move plunger 47, collar 50 and piston 4 in unison against spring 49 to engage valve 27 with valve 32 to cut off the brake cylinder venting passage 28, 29, 30, 31 and then open valve 32 to charge the brake cylinder via small choke 36, inshot valve 40 then being opened to permit large capacity flow to the brake cylinder via choke 42. When the brake cylinder pressure exceeds a preselected value (10 p.s.i.) i.e. when brake slack has been taken up, the forces on piston 3, 4 overcome spring 48 to move piston 4 down relative to plunger 47 until plunger 47 engages the base of recess 54, the valve 40 being then closed. When the brake cylinder pressure reaches the required value, the pressure in chamber 20 with spring 49 moves pistons 3, 4 to a lap position wherein valves 40, 32 and 27 are closed. For complete brake release, the recharging of pipe 10 and chamber 9 moves pistons 3, 4 down to permit venting of the brake cylinder via passages 28, 29, 30, 31. When brake cylinder pressure drops below 10 p.s.i., spring 48 moves piston 4 and plunger 47 apart and when it reaches its normal value, the weight of piston 3 opens valve 11 to recharge reservoir 7 if necessary. For partial release to a pressure above 10 p.s.i., piston 4 moves down until the brake cylinder pressure reaches the required value when the stack assumes a lap position and since plunger 47 still engages the base of recess 54 a re-application of the brakes to a greater degree does not result in the opening of inshot valve 40. Emergency application.-When the brake pipe pressure reduces at an emergency rate, emergency valve 60 connects reservoir 7 to -brake cylinder 24 and vent valve 62 locally vents brake pipe 10, the device 2 operating to open valves 32, 40 as before and due to the venting of brake pipe 10 the pistons 3, 4 maintain valve 32 open. The combined volumes of reservoirs 7, 38 produce a higher brake cylinder pressure than during service braking. In Fig. 2, not shown, the cylinder 38 is replaced by a cylinder of sufficient volume to produce emergency braking using device 2, and the emergency reservoir 7 is replaced by a control reservoir, the emergency valves being omitted.