GB638686A - Improvements relating to compressed air braking systems - Google Patents

Abstract

638,686. Fluid-pressure brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Dec. 23, 1947, No. 33909. Convention date, Dec. 4, 1946. [Class 103 (i)] In an automatic compressed air braking system for railway vehicles and the like, there is provided in combination with the usual triple valve on each vehicle a regulating device comprising an exhaust control device controlling the exhaust from the brake cylinder and a supply control device controlling the supply to the auxiliary reservoir, both these devices being so constructed as to allow a constant flow of air therethrough, independently of the pressures existing in the brake cylinder or the auxiliary reservoir. The triple valve assembly shown has, in addition to the usual slide valve piston 31 in a cylinder 94 open at one end to the auxiliary reservoir 2, further units as follows. A relay valve 4, from which two passages 83 and 84 lead respectively to the brake cylinder and a supplementary reservoir (both not shown), the latter being charged independently from the train pipe through a check valve, and which has two piston valves 80, 85 having between them a chamber 29, the pressure within which is automatically reproduced in the brake cylinder. An exhaust unit 6 having a diaphragm 87 subject on its upper face to the train pipe pressure from passage 17 and on its lower face to that of the control chamber 2 by passage 25 with a needle valve 89 controlling port 92 connecting passages 17 and 25 by way of a non-return valve 27 ; a control device 18 having a diaphragm 57 subjected on its right-hand face to the train pipe pressure via passages 15, 19 and 20 and on its left-hand face to the pressure of the auxiliary reservoir 2 via passages 60 and 25 and valve 58; a distribution device 21 having a piston 61, a spring 61<SP>1</SP>, and a slide valve 62 ; and a regulating device 23 comprising the brake cylinder exhaust control device 66 and the auxiliary reservoir supply control device 65, both these devices being arranged to give a constant flow at all times, which as shown is obtained by the use of pistons having central flow tubes 68 moved towards coned members 77 so that the area of flow is varied automatically with the compression of the springs 75. All the brake apparatus being at atmospheric pressure, charging is carried out as follows. Air is fed along the train pipe 11 from the compressor, through passages 12, 13 to chamber 14 and piston 31 is moved to the left to uncover port 16. Air then flows through passages 15, 19 to chambers 20 and 22. Air in chamber 20 deflects diaphragm 57 to open valve 58. Air in chamber 22 moves piston 61 and also slide valve 62 to the left. Air may then pass to the auxiliary reservoir 2, (a) by port 96, chamber 59, valve 58, and passages 60 and 25 and (b) by passage 64, uncovered by slide valve 62, chamber 98, through constant flow device 65 and then by passage 24. When the pressure in auxiliary reservoir 2 equals that of the train pipe diaphragm 57 of device 18 shuts valve 58, the piston 61 then being pressed to the right by spring 61<SP>1</SP> to also close slide valve 62 over passage 64. After a brake application, during which the triple valve 3 has built up a certain pressure in chamber 29 of the relay valve 4, which pressure is reflected in the brake cylinder, the brake is released by increasing the pressure in train pipe 11. This pressure is transmitted to chambers 20 and 22 so that the slide valve 62 is again moved to the left opening up passage 64 and also connecting passage 73 with the passages 28 and 30. Air is then discharged to atmosphere through port 100 from the chamber 29 of the relay valve 4, the pressure within which corresponds to that in the brake cylinder, at the same constant rate at which it passes into the auxiliary reservoir 2 by passage 64, constant flow device 65 and passage 24. The purpose of the exhaust unit 6 is to prevent a higher pressure being maintained in the auxiliary reservoir 2 than exists in the train pipe 11. It is stated that the constant flow units 65 and 66 may take other forms such as a flow tube having a longitudinal groove of varying depth.