Patent GB-279395-A (GB)
Title: Improvements relating to fluid pressure braking apparatus
IPC: B60T17/02
Filed: 1927-08-10
Abstract: 279,395. Westinghouse Brake & Saxby Signal Co., Ltd., (Assignees of McCune, J. C.). Oct. 19, 1926, [Convention date]. Fluid-pressure.-Fall of the pressure in the main reservoir which supplies the train-pipe of a fluid-pressure brake system effects the opening of a train-pipe venting valve to apply the brakes. The valve mechanism shown is especially suitable for a system in which two or more vehicles of a train are each equipped with a main reservoir connected to a common supply pipe to prevent in certain conditions the escape of the pressure fluid from one reservoir through the valve device of another. In normal conditions with the system charged the several valves occupy the positions shown and the main reservoir 2 supplied from the compressor by pipe 3 is connected to the driver's valve through the cut-off valve 9, a check valve 7 and the pipe 15. The valve 9 is held open by the main reservoir pressure acting against a spring 18, and its under side as open to atmosphere by a port 17. The pressure in the train-pipe 36 normally holds open a valve 32 against the action of a spring 40, the under side of this valve being open to atmosphere by a port 39. The venting valve for the train-pipe comprises a piston valve 19 slidable against a spring 29 in an outer casing 30 secured to a second piston 21. A restricted area of the valve proper 24 is exposed to the train-pipe pressure but as the underside of the piston 21 is normally exposed to the main-reservoir pressure through the passages 8,23 the valve is held seated. If the pressure in the reservoir 2 should fall to a value that is insufficient to overcome the spring 18 the valve 9 closes thus cutting off the reservoir from the pipe 15 and the unseating of the lower edge 11 of the piston connects the chamber 22 of the piston 21 to atmosphere through the port 17 whereupon the train-pipe pressure unseats the valve 19 and the train-pipe vents to atmosphere through the passages 41 and 28 at an emergency rate until the spring 40 causes the valve 32 to seat. The upward movement of the valves 9 and 32 is assisted by the pressure fluid which has access to the under sides of these valves when the lower edges 11, 34 thereof are unseated prior to its escape by the ports 17 and 39 respectively and the opening movement of these valves and also that of the valve 24 is rendered prompt by reason of the fact that an increased area of the upper faces of the valves becomes exposed to pressure when these faces move away from their seatings. The valves 32 and 7 are necessary only when two or more vehicles of a train are each equipped with a main reservoir connected to a common supply pipe 15 to prevent in the initial charging operation the pressure fluid from one reservoir which has reached the value sufficient to open the valve 9 from escaping through the port 17 or the vent valve 19 associated with another reservoir the pressure in which has not reached this value. The provision of the valve 32 prevents access of the train-pipe pressure to the vent valve 19 until the valve 9 on the same vehicle has opened to permit the main reservoir pressure to hold the valve 19 in the closed position. The check valve 7 prevents the air supplied from one main reservoir to the pipe 15 from escaping to atmosphere through the port 17 of the valve mechanism on another vehicle the valve 9 of which is closed.