GB616131A - Improvements relating to fluid pressure braking systems for railway vehicles and the like - Google Patents

Abstract

616,131. Fluid-pressure operated brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Aug. 28, 1946, No. 25828. Convention date, Sept. 18, 1944. [Class 103 (i)] In charging automatic compressed air brake systems after an application, the supply pressure for the brake pipe is initially substantially the normal main reservoir pressure and falls automatically after a predetermined period to the normal operating pressure. This is effected by temporarily subjecting the diaphragm of the feed valve to a fluid pressure in addition to the usual spring pressure. According to one arrangement, Fig. 1, the usual accelerating bulb of the triple valve 3 is dispensed with and in the application position the brake pipe passage 15 is connected by the triple valve passage 17 and passages 18, 30-32 to the spring chamber 13 of the feed valve 2. Passage 18 leads to the chamber 29 of a piston valve 26 which is thus held seated as shown so as to close a branch 32<SP>1</SP> from the passage 32. When the drivers valve 1 and thus the triple valve are returned to the release position shown, the passage 18 and chamber 29 are cut off by the triple valve from the brake pipe passage 15 and are connected to passage 19 and thus to a restricted exhaust port 5. Air at the pressure existing in the brake pipe at the end of the application is however locked in the feed valve chamber 13 by a non-return valve 31 and acts on the diaphragm 14 to increase the supply pressure for the brake pipe until the falling pressure in piston chamber 29 is overcome by the pressure in chamber 13 acting through passage 32<SP>1</SP> on the upper face of the piston 26 which then moves down and connects the chamber 13 to atmosphere by passage 35. The feed valve then acts to supply the system at the normal operating pressure determined by the spring 8. The main reservoir, brake pipe and brake cylinder are connected respectively to passages 6, 10, 23. The auxiliary reservoir is shown at 20. A modification is shown in which the connection of the passage 18 to the brake pipe and then to the exhaust passage 19 is effected by the drivers valve instead of by the triple valve. In this arrangement the chambers 13, 29 are connected to the main reservoir in the emergency position of the drivers valve to allow for the possibility that the brake pipe pressure may in an emergency application be reduced to a low value. In another arrangement the chambers 13, 29 are connected to the main reservoir in both the service and emergency position of the drivers valve and the chamber 13 is isolated from the chamber 29 and the chamber 29 is connected to the exhaust passage 19 by the drivers valve when this is returned to the release position; the non- return valve 31 being dispensed with. In a further arrangement, Fig. 8, the feed valve 21 is provided with an additional diaphragm 43, the chamber 42 of which in the application positions of the drivers valve is connected by a passage 12<SP>1</SP>, a passage in the rotary valve 1<SP>1</SP> of the drivers valve and passage 23, to the brake cylinder. In the application positions also the piston chamber 29 is connected to the main reservoir by passage 18<SP>1</SP>, a passage in the valve 11, chamber 1<SP>11</SP> and passage 6 so that the piston 26 is seated to close passage 32<SP>1</SP>. When the drivers valve is returned to the release position shown, the piston chamber 29 is connected to the exhaust port 5 by passages 18<SP>1</SP>, 36, 19 and air at brake cylinder pressure locked in the feed valve chamber 42 acts with the spring 8 on the diaphragm 14 to increase the supply pressure for the brake pipe until the piston 26 is moved to the lower position shown by the pressure in chamber 42 acting in passage 32<SP>1</SP> to connect this chamber to atmosphere by passage 35. The area of the diaphragm 42 is such that even with the minimum brake cylinder pressure the brake pipe will be supplied at substantially full main reservoir pressure. A further arrangement is shown in which the drivers valve in application positions connects the piston chamber 29 to the brake cylinder and the feed valve chamber 13, Fig. 1, to the main reservoir and in release position connects chamber 29 to exhaust port 5, air at main reservoir pressure being thus locked in chamber 13 until released by movement of the pistons 26.