Patent GB-1501844-A (GB)
Title: Brake system having alternative electropneumatic or purely pneumatic control
IPC: B60T13/66
Filed: 1976-04-27
Abstract: 1501844 Electropneumatic brake systems WERKZEUGMASCHINENFABRIK OERLIKON-BUHRLE AG 27 April 1976 [20 June 1975] 17137/76 Heading F2F  A rail brake system which may operate electropneumatically or purely pneumatically comprises a control valve system (Fig. 1), a driver's brake valve (Fig. 2) incorporating electrical switching 108 to operate the electromagnetic part of the control valve system, a pressure controller 91 and a transmission valve 96 for operating the purely pneumatic part of the control valve system and a quick application valve 102, the transmission valve 96 being closed during electropneumatic braking to immobilize the purely pneumatic part but being opened in the absence of current for electropneumatic operation by means of solenoid valve 94. In the control valve system a common shutoff valve 15 opens or closes feed-pipe 10, brake pipe 11 and load control pipe 14 and the system comprises an electropneumatic control valve assembly 24 incorporating three electromagnetic valves 26, 27 and 28 operated by switches 108 controlling entry of air to chambers 29, 30 and 31, respectively, pressure regulator 23, load control valve 25, purely pneumatic control valves 39, 40, the piston-rod 37 of the latter being contiguous with rod 35 of the electropneumatic control valve assembly 24 unless dissociated by actuation of a coupling rod 36 by valve 52. Piston-rod 37 bears on one end of a balance beam 38 the position of whose fulcrum 75 is load dependent according to the pressure in load control pipe 14, a piston-rod 53 of load control valve 25 bearing on the other end of the balance beam 38. The flow of pressure from auxiliary reservoir 12 to brake cylinder 13 is controlled by valve 22 dependent on the pressure particularly in chamber 56. Sequence of operation.-On setting of handle 81 to a non-braking driving position switches 108 remain open and thus valve 94 remains open to allow air from control reservoir 109 to open transmission valve 96 permitting pressure increase in brake pipe 11 deriving from feed pipe 10 via the open stop valve 101. The setting of handle 81 to a braking position causes closing of switches 108 to open one or more of valves 26, 27 or 28 allowing air from auxiliary reservoir 12 to chambers 29, 30 or 31 of the electropneumatic valve assembly via regulator 23 in turn causing a thrust from piston-rod 37 on balance beam 38, a corresponding thrust on piston-rod 53 opening load control valve 25. Air now passes from regulator 23 via valve 25 to chamber 56 opening valve 22 to allow air to pass directly from auxiliary reservoir 12 to brake cylinder 13 via chamber 61 of valve 22. In all electropneumatic braking positions valve 94 is energized to close so that transmission valve 96 is in a correspondingly closed position. On electric power failure valve 94 opens to cause a brake pipe pressure reduction allowing spring 47 to open the purely pneumatic control valve 39 so pressurizing chambers 48 and 50 of valve assembly 40 to the effect that piston 51 actuates coupling-rod 36 to dissociate piston-rod 37 from piston-rod 35, pressure in chamber 48 providing the necessary thrust on the balance beam 38 to operate the brakes. Quick application valve 102 is operated by an extreme position of handle 81 to vent brake pipe 11 and thus to allow rapid purely pneumatic application of the brakes as distinct from stop valve 101 which incorporates a flow restricting cylinder 110 to limit the rate of recharging of brake pipe 11 after an emergency application. In order to obviate a situation where the handle 81 is turned quickly beyond the electropneumatic braking positions to operate valve 102 in error resulting in de-activation of both electropneumatic and purely pneumatic valve systems a switch 70 connected to coupling-rod 36 automatically opens transmission valve 96 by energizing valve 94 whenever purely pneumatic operation is initiated.