Patent GB-190325856-A (GB)
Title: Improvements in Automatic Air-brake Systems
Filed: 1903-11-26
Granted: 1904-10-13
Abstract: 25,856. British Thomson-Houston Co., [General Electric Co.]. Nov. 26. Brakes, pneumatic-pressure. A variation of the pressure in the train-pipe operates slide valves which cause a greater variation in the pressure in the brake cylinders. Fig. 1 shows a simple form of the invention, which comprises a slide valve operated by a differential piston 23 in a casing 3 open at 32 to the atmosphere and connected to the train-pipe 1 and the brake cylinder 5. Compressed air is admitted to the train-pipe and the chamber 26 until it forces the slide valve to the left, thus opening the port 30 and enabling the compressed air to flow through the chamber 24, the pipes 4, 8, 6, the non-return valve 9, and past the packing of the brake-cylinder piston 10 to the auxiliary reservoir 7. If the train-pipe pressure is reduced, the spring 27 forces the valve to the right, closes the port 30, and opens the port 31 to the atmosphere, so that the brakes are applied by the total or partial evacuation only of the brake cylinder 5, the chamber 24, and the pipe 4 connecting them. The port 31 remains open, and the air continues to escape, until the train-pipe pressure, acting on the larger end of the double piston 23, overcomes the pressure of the spring 27 and of the brakecylinder pressure acting on the smaller end of the piston 23, and, the larger end of the piston being, say, twice as large as the smaller end, the fall of the pressure in the brake cylinder is therefore twice as large as the fall of pressure in the trainpipe. Fig. 2 shows a valve which enables the engineer to apply the brakes if he fails to obtain a proper action after moving his valve to the usual service position. The valve is attached to the brake cylinder 5, and is connected by the pipe 83 to the right-hand end of the cylinder. The double piston 43 operates two slide valves 50, 51 and their graduating-valves 52, 53. In charging the system, the compressed air flows through the train-pipe 1 and the strainer 71 to the chamber 47, and moves the double piston to the right. The air then flows through the ports 56, 62, lifts the valve 61, and passes through the port 60 to the chamber 49 and the right-hand end of the brake cylinder 5, and thence past the piston 10 and through the passage 76 to the auxiliary reservoir, and also through the passages 74, 75 to the intermediate chamber 48. The compressed air also passes by the valve 78 and the passage 77 to the chamber 48, and performs there the same functions as the spring 27, Fig. 1. In making a service application, a reduction of the train-pipe pressure causes the double piston 43 to move to the left, closing the ports 56, 62, and opening the graduating-valve port 57, thus exhausting the chamber 49 and applying the brakes. This exhaustion continues until the fall of pressure enables the train-pipe pressure to move the piston 43 to the right and to close the graduating-port 57. In this application, the reduction in the train-pipe pressure is not sufficient to open the valve 80 against the pressure of the spring 81. If it is found that the service operation of the engineer's valve has not applied the brakes, the engineer's valve is moved so as to effect a greater reduction in the train-pipe pressure, which then opens the valve 80 and allows the air in the right-hand end of the brake cylinder 5 to pass through the pipe 83, chamber 49, and the passage 60, 79 to the trainpipe. An emergency application is effected by a sudden and large reduction in the train-pipe pressure; the piston 43 is then forced to the extreme left, compressing the spring 65 and opening the port 63 and valve 80 completely. The spring 65 afterwards moves back the piston, first closing the graduating-port 57 and then the port 63.