GB790657A - Improvements relating to vacuum brake apparatus for railway vehicles - Google Patents

Abstract

790,657. Vacuum brakes. GRESHAM & CRAVEN, Ltd. July 25, 1956 [Aug. 19, 1955], No. 23927/55. Class 103 (1). In vacuum brake apparatus for railway vehicles, an automatic isolating valve is con-. nected between the high vacuun chamber and the exhauster and automatic feed valve and acts to close the connection during a brake release operation when the vacuum in the high vacuum chamber is below a predetermined value, but opens the connection when the vacuum in the train pipe of the brake system exceeds the predetermined maximum at which the automatic feed valve closes. In the embodiment illustrated, wherein Fig. 1 shows the " running position, Fig. 2 the " brake applied" position, and Fig. 3 the " brake release "position, the brake system comprises an exhauster a, a non-return valve b, an automatic feed valve c which closes to cut exhauster a off from train pipe d when the vacuum in the train pipe is higher than a predetermined amount (e.g. 21 inches of mercury), a high vacuum chamber e, and an automatic isolating valve f which cuts off communication with the high vacuum chamber e under certain conditions. In the " running " position shown in Fig. 1, the control valve i allows the exhauster to exhaust train pipe d and maintain the brake pistons in their " brake off " position and when the vacuum at the driver's control valve side of valve c is sufficiently high (21 inches of-mercury) the valve will be closed and the exhauster will be concentrated on the isolating valve f and the high vacuum chamber e; the valve element p of the isolating valve being held open by the vacuum in chamber e acting on diaphragm rand by vacuum at s acting on valve element p. When the brakes are applied, as shown in Fig. 2, by movement of driver's brake control valve i to allow air to pass into train pipe d the feed valve c still remains closed and the isolating valve f remains open. In the quick brake release position shown in Fig. 3 the driver's brake control valve i puts feed valve c in communication with the train pipe d to open valve c and allow air to pass to the exhauster and also to chamber e. The combined action of the exhauster a and high vacuum chamber e gives quick release. Should the valve in the high vacuum chamber be reduced below a predetermined level (e.g. 19 inches of mercury) the valve element p is allowed to close, thus preventing the vacuum in the chamber e from falling below a useful value (for example 19 inches of mercury) particularly when several brake applications and releases are made in quick succession without allowing time for the necessary re-charging of the high vacuum chamber e to give quick brake releases.