Patent GB-616569-A (GB)
Title: Improvements in electro-pneumatic braking systems
IPC: B60T15/30
Filed: 1946-09-03
Abstract: 616,569. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO., Ltd. Sept. 3, 1946, No. 26469. Convention date, Dec. 30, 1944. [Class 103 (i)] An electro-pneumatic braking system comprises a triple valve operable electro-pneumatically or wholly pneumatically which has associated therewith (1) a release relay valve which repeats the operation of a release magnet valve and, when closed, cut off a first communication between the brake cylinder and a main exhaust outlet, and (2) a pneumatic device operated, when the triple valve slide valve moves to the full " application " position, from its normal position to a position wherein an alternative connection between the brake cylinder and the main exhaust outlet is prepared, this connection being completed when the slide valve returns to the " release " position in response to a wholly pneumatic operation of the triple valve. The triple valve shown comprises main and graduation slide valves 50 and 61 operated by a piston 30 in a chamber 29 connected to the train pipe 54, the auxiliary reservoir being connected to pipe 58; an accelerating bulb 7 connected to atmosphere through a restricted orifice 8; a " stabilizing " bulb 9; a piston-operated quick-inshot " valve 92; application and release valves 21 and 22 operating through pneumatic relays 13 and 14 and actuated by an armature 68 and electro-magnets 11 and 12 arranged and energized in a similar manner to those described in Specification 616,145; and a constant delivery exhaust plug 19, the connections to which are controlled bv a distributor valve 15 comprising a slide valve 18 operated by pistons 16, 17 of different diameters. The chamber 28 of the valve 21 is permanently connected to the chamber 29 through a passage 31, chamber 32, passage 23 in the piston of relay 13, and passage 33; the chamber 41 to the left of piston 17 is connected to the chamber 42 of the valve 22 through a passage 43; the central chamber 44 of the valve 15 is permanently connected to the auxiliary reservoir through a passage 45 and communicates with the chamber 41 through a passage 102 in the piston 17; and the chamber 46 to the right of piston 16 is connected to the face of the slide valve 50 through passages 47, 48. The brake cylinder is connected to a pipe 88 fitted with a safety valve 20. Charging. Air from the train pipe passes to the auxiliary reservoir through feed grooves 55, 56, to the piston chamber of valve 92 through passage 59, thus raising piston 85 to unseat valve 92, and to the chamber 46 and the seat of an auxiliary reservoir venting valve 4 through passages 49, 48 and 47. Air also passes through passages 33 to charge the chamber 28, through passages 62, 63 to the face of the slide valve 61, and through passages 65 to charge the chamber 64 above the diaphragm 98 actuating the valve 4, the chamber below this diaphragm being charged to auxiliary reservoir pressure through a passage 60. Electro-pneumatic application. Magnet 11 is energized to unseat valve 21, thus venting chamber 28 and causing the piston of relay 13 to move downwards and place passage 33 in communication with atmospheric port 69. The depression produced in chamber 29 causes the piston 30 to move to the position of Fig. 3 (not shown), spring 71 being compressed, and the slide valve 61 then connects the passage 62 to passage 74 so that the train pipe is also vented through the bulb 7. Air from the train pipe also passes through passage 76 to seat a final release valve 2. Further movement of the piston 30 to the right (see Fig. 4, not shown) moves the slide valve 50 to isolate passage 62 from passage 74 and connect it to passage 75 so that the train pipe is placed in communication with the brake cylinder through passage 80, orifice 81, valve 82, valve 83, which is held open by a projection 84 on the piston 85, and passages 86, 87. At the same time, slide valve 61 has been moved to uncover a passage 90 so that air from the auxiliary reservoir is admitted to the brake cylinder through a passage 91 and the valve 92 which remains open until the brake cylinder pressure acting on the piston 85 rises to a predetermined value, this piston then being moved downwardly to allow seating of the valve 92 so that the subsequent supply to the brake cylinder is through a restricted passage 93. The valve 83 is also seated when the piston 85 moves downwardly and air from the train pipe then passes to the bulb 9 through a restricted orifice 89, the pressure in the train pipe being thus stabilized. Pneumatic application. If the pressure in chamber 29 is reduced by operation of the driver's valve, the sequence of operation is the same except that the train pipe is not vented through the port 69. It is stated that with electro-pneumatic application, the flow of air through the port 69 is such that the bulb 7 receives little or no air from the train pipe. Pneumatic release. During pneumatic or electro-pneumatic application, the chamber 46 is connected to atmosphere through passages 47, 48, port 51, passages 94 and 95, and port 96. The slide valve 18 is thus displaced to the right (see Fig. 4, not shown) and connects a passage 37 leading to the exhaust plug 19 with a passage 52. If the train pipe pressure and hence the pressure in chamber 29 is increased by operation of the driver's valve, the piston 30 moves to the left to the position shown, and the slide valve 50 connects the passage 52 to passage 86 so that the brake cylinder exhausts through the plug 19. Prior to movement of the slide valve, the passage 48 is connected to exhaust through passage 52 so that a slight increase in train pipe pressure causes downward movement of the diaphragm 98 to unseat the valve 4 and vent the auxiliary reservoir. Electro-pneumatic release. With the valves in the position of Fig. 4 (not shown), the chamber 100 above the piston of relay 14 is in communication with the auxiliary reservoir through passages 38, 39 and 49, and the chamber 101 below this piston is also in communication with the auxiliary reservoir through passages 103, 43 and 102, chamber 44 and passage 45. If the valve 22 is unseated by energizing magnet 12, the piston 14 moves downwardly and places passages 37 and 38 in communication so that the auxiliary reservoir chamber of the main slide valve 50 is vented through the port 19. The piston 30 then moves the slide valve to the position shown in which it connects the chamber 100 to the bulb 9 through passages 38, 40, 94 and 75, and to the brake cylinder through passages 38, 40, port 51 and passages 86, 87. Air from the bulb and brake cylinder then escapes through the plug 19. At the same time, the slide valve 18 moves to the left, due to the charging of the chamber 46 through the passages 49, 48, 47 and the venting of the chamber 41, and cuts off communication between the passages 52 and 37. When the magnet 12 is de-energized, the piston of relay 14 moves upwardly under the action of a spring 35 and the auxiliary reservoir pressure re-established below it to isolate passage 38 from passage 37. If, due to the spring 35, a small residual pressure exists in the brake cylinder at the end of brake release, the brake cylinder is finally vented through the valve 2. This valve, which was seated during the first stage of brake application, is unseated by its spring when the bulb 7 has exhausted through the orifice 8, the piston 85, by this time, having returned to its lower position to allow seating of the valves 83 and 92, and cutting off communication between the passage 78 and exhaust port 105. During the first stage of brake release, the piston remains in the lower position, but at the end of brake release it moves upwardly to allow the residual air in the brake cylinder to escape through the port 105.