Patent GB-1311621-A (GB)
Title: Electro-magnetically controlled fluid-pressure braking systems
IPC: B60T13/66
Filed: 1971-01-14
Abstract: 1311621 Fluid-pressure brakes WESTING- HOUSE BRAKE & SIGNAL CO Ltd 25 Nov 1971 [14 Jan 1971] 1865/71 Heading F2F An electromagnetically controlled fluid-pressure braking system has a plurality of electromagnetically opened valves 2, 3, 4 whose outlet ports 9 are connected to multiple pressureresponsive diaphragms 16, 17, 18 of different areas and controlling a self-lapping second valve 25 feeding a brake cylinder over line 34, and in addition, there is a third, emergency valve 55 which serves to close the exhaust ports 10 of the electromagnetic valves to atmosphere and supply them with fluid pressure to directly feed the fluid inlet port of the second valve. High pressure from the Main Reservoir is fed over line 42 to a self-lapping load-responsive regulating valve 40 of known type, and over line 30, through a choke 80 (a by-pass valve 70 being closed) to the self-lapping valve 25. The load-varied. pressure from valve 40 is fed over line 55 to the emergency valve 55 and also over lines 53 and 95 to the inlet ports 8 of the valves 2, 3 and 4. Normally, the coils 11 are energized to close inlet ports 7 so that no pressure is fed to chambers 13, 14 and 15 under the diaphragms 16, 17, 18. To apply the brake, one or more of the coils 11 are de-energized to open 8 and close 10 so that pressure from variable-load valve 40 at ports 8 passes over one or more of conduits 12 to lift the stem 19 of the diaphragms. This opens valve 26, 28 to allow load-varied pressure at 30 to pass to duct 34 and so to the brake cylinder. Pressure also builds up in space 29 and this passes by duct 31, through choke 32, to space 33 above a further diaphragm 20 to balance the upward force on the stem 19. This reseats valve 26, 28 to lock the pressure into the brake cylinder. Re-energization of the coil or coils 11 vents the chambers 13, 14, 15 through ducts 10 and 96 to a manually-controlled isolating valve 90, conduits 97 and 67 to the hollow stem 61 of the piston valve 56 in the emergency valve 55 to vent at 60. This reopens valve 26, 28 to vent this valve to atmosphere at 22 to vent the brake cylinder. The underside of piston 56 of the emergency valve 55 is normally subject to main pressure over conduit 100. This compresses spring 58 and holds the piston up to vent chambers 13, 14, 15 through valve 64, 65. When this pressure at duct 100 is reduced in an emergency, the piston 56 descends to close valve 64, 65 and open valve 63, 65, this connecting the load-varied pressure from 48 to over duct 67 to push down diaphragm 69 to open valve 74, 76. This by-passes the choke 80 to rapidly present full pressure to the valve 25. The pressure in duct 67 is also fed over line 97 to the isolating valve 90 and conduit 96 to the exhaust ports 10 of the valves 2, 3 and 4. This will pass over ducts 12 to the chambers 13, 14 and 15 to operate the brake as before except of the maximum magnitude. The isolating units 90 are used when the electromagnetic control fails, and this acts to seal the ports 8 and cuts off the outlet ports 10 and conduits 67 through which the chambers 13, 14 15 are normally depressurized, also fluid pressure in conduit 67 passes to conduits 98, 95 to the inlet ports 8. Hence the pressure at ports 8 now passes directly to ports 6 to effect operation of the diaphragm to give emergency braking.