Patent GB-134294-A (GB)
Title: Improvements relating to Fluid Pressure Braking Apparatus.
Inventor: CROSS JAMES WILLIAM
IPC: B60T15/18
Filed: 1918-10-28
Abstract: 134,294. Cross, J. W. Oct. 28, 1918. Fluid-pressure.-In a triple valve adapted to give a graduated release of the brakes, the triplevalva piston opens a separate brake-cylinder exhaust valve when the train-pipe pressure is raised, and, when this pressure has equalized with the auxiliary-reservoir pressure, the exhaust valve closes, under the influence of the brakecylinder air, and also returns the triple-valve piston sufficiently to close the feed-passages between the train-pipe and the auxiliary reservoir. Means are provided for permitting a rapid feed to the auxiliary reservoir until the train-pipe pressure reaches a predetermined value, when it is restricted to ensure the complete release of the brakes. The train-pipe is connected by passages 7, 8 to the piston chamber 2, from which a feedgroove 10 leads to the chamber 12 connected at 13 to the auxiliary reservoir. An additional feedpassage to the reservoir extends from a port 44 in the chamber 2 by a pipe 46 to the chamber 47, Fig. 2, of a feed-valve device 48 secured to the main-valve casing. The feed-valve 51 is adapted to open, under the influence of a spring 58, when the train-pipe pressure is below a determined value, so as to connect the chamber 47 to the chamber 12 through the passage 45. The brake-cylinder supply valve comprises a fixed tubular valve seat 21 with two sets of ports 24, 25, within and over which respectively slide a plug valve 26 and a tube 20. The tube 20 is attached directly to the piston 3, and the plug 26 is secured by a pin 28 to the tube 20. A rod 43 extends between the plug 26 and the brake-cylinder exhaust valve 30, which seats on an exhaust passage 37 leading to atmosphere or to an exhaust receptacle at 41. The brake cylinder is connected at 14, and passages 15, 16 lead from it to the supply and exhaust valves respectively. The parts are shown in the running position, in which the train-pipe feeds into the auxiliary reservoir through the groove 10 and the exhaust valve 30 is held open, it may be against the action of a light spring 42, by reason of the difference in area of the two sides of the piston 3 subject to pressure. When the train-pipe pressure is partly reduced to make a service application of the brakes, the piston moves as far as the stop 5. During the first part of this movement, the exhaust valve 30 closes, and the plug-valve 26 is then withdrawn from contact with the stem 43 sufficiently to uncover the ports 24, permitting air to pass from the chamber 12 through the passage 15 to the brake cylinder. Upon equalization of the auxiliary-reservoir pressure with the train-pipe pressure, the piston 3 moves back until the valve 26 again abuts against the stem 43, as shown in broken lines in Fig. 1, and covers the supply ports 24. In an emergency application, the piston 3 overcomes the stop 5, and the ports 25 are uncovered in addition to the ports 24. If, after an application, the train-pipe pressure is raised a small amount above the auxiliary-reservoir pressure, the parts return to the position shown in full lines in Fig. 1, and the brake-cylinder commences to exhaust. But as the feedvalve 51 is open at this stage, the train-pipe pressure rapidly equalizes with that in the auxiliary reservoir sufficiently to permit the brake-cylinder pressure to close the exhaust valve 30 and, in so doing, to return the piston 3 to close also the feed-port and groove 44, 10. The exhaust passages 37, 41 are relatively larger in cross-section than the ports 36, to prevent pressure from building up on the inner side of the exhaust valve 30 when the air is exhausting from the brake cylinder. The release operation may be continued until the brake cylinder is completely exhausted. When the train-pipe pressure has been raised to within, say, 10 lb. of the running pressure, the feed-valve 51 closes, and, as equalization can then take place only through the groove 10, it is ensured that, in the last stage of the release operation, the exhaust valve 30 is held open sufficiently long to allow the brake cylinder to exhaust completely. According to the Provisional Specification, a valve may be arranged to establish communication between opposite sides of the piston 3, for example when a predetermined difference of pressure is produced upon oposite sides of the piston, or means may be provided for varying the effective area of the feed-groove.