Patent GB-1387479-A (GB)
Title: Mixed air and vacuum-brake control apparatus and a relay therefor
IPC: B60T13/26
Filed: 1972-08-08
Abstract: 1387479 Compressed-air and vacuum braking system on railway vehicles COMPAGNIE DES FREINS EI SIGNAUX WESTING- HOUSE 8 Aug 1972 [19 Aug 1971] 36945/72 Heading F2F An air and vacuum brake control device for a railway vehicle comprises an air-brake pipe 1 and vacuum brake pipe 2 and includes a pressure transforming relay 7 actuable to control vacuum variation in pipe 2 in proportion to air pressure variations in the pipe 1. The device as shown also includes an air brake electro-pneumatic control device 12, a three way compressed air spool valve 14 and a three-way vacuum spool valve 15, a vacuum reducing valve 22, which acts as a vacuum regulator, and a relay valve 5 used to change the suction area in a suction pipe 4 between the vacuum pipe 2 and one or more vacuum pumps 3. Transforming relay.-The relay 7 is placed on a by-pass 8 connected to the pipe 4 and comprises a vacuum release valve plate 9 under the control of an operating means 11. The means 11 comprises a rod 27 carrying a piston 28 separating a reaction vacuum chamber 31 and a vacuum or pressure reference chamber 32 and the means 11 also includes a piston 35 separating a pilot pressure chamber 36 and a reference pressure chamber 37. Fig. 1 shows one operative connection between rod 27 and piston 35; in Fig. 2 (not shown) rod (27) seats in a conical cavity in piston (35) and in Fig. 3 (not shown) rod (27) and a rod (96) of piston (35) are disposed adjacent each other. In each case the chamber 37 contains a spring-biased valve plate 1. By alteration of the pressures in the chambers 31, 32, 36, 37 the net forces acting on rod 27 may be caused to move a valve plate 9 to connect pipe 2 to atmosphere to bring about braking: rod 27 may also be moved downwardly to interconnect chambers 32, 36. The plate 9 may take the form of a slide. Spool valves.-The spool valves 14, 15 are identical in construction. Valve 14 has a spool 71 with four guides 73, 74, 75, 76, and guide 76 comes up against a shoulder 77 when a chamber 70 is pressurized to provide a connection between pipes 16 and 18: when the pressure in chamber 70 drops the connection between pipes 16, 18 is interrupted and pipes 17, 18 are connected. In Figure 2 (not shown) pipe (18) by-passes the spool valve (14). Vacuum regulator.-The valve 22 comprises a valve plate 63 which is operable to connect a pipe 21 to atmosphere to maintain a reference vacuum. Relay.-The relay 5 includes two magnetic valves 50, 51 with double valve plates to provide a connection with atmosphere or with the suction pipe 4 for two chambers 52 and 53 respectively. A differential piston 54 bounding chamber 52 is guided inside a bore in a piston 55: the piston 54 can close an aperture 58 in piston 55 and a passage 62 is closed by a shoulder 60 of piston 55 resting on a seat 61. Control device.-The control device 12 contains a three-way selector 80 (isolation, service, neutral), an application and release lever 81, a filling-shot button 82, an overload switch 83, an emergency button 84, a locking screw 85, and emergency application and release lever 86. Pipe 17 is connected to an equalizing reservoir of device 12 and pipe 16 is connected with a calibrated self-lapping valve supplying a normal operating pressure or a release overload pressure. The pressure in the equalizing reservoir acts as pilot pressure for a main self-lapping relay. Operation.-To apply the brakes gradually lever 81 is operated causing a pressure drop in pipe 1 to apply the compressed air brakes. Magnetic valves 50, 51 are ceased to be excited and pipe 2 is isolated from pump 3. Valve plate 9 is raised by excess of pressure in chamber 37 over chamber 36 to cause application of the vacuum brakes. Subsequent excess of pressure in chamber 31 over chamber 32 will cause closure of plate 9. By pressing shot button 84 total brake release is brought about-a main reservoir is connected to pipe 1 and valves 50, 51 are excited to cause opening of passage 62 and connection of pump 3 to pipe 2. An electric contact then sets the pump 3 to main flow at high speed. The operator can also produce an overpressure in pipe 1 and main-flow suction in pipe 2 by using the overpressure switch 83. Modifications.-The device 12 may be replaced by a brake valve.