Patent GB-190504880-A (GB)
Title: Improvements in Air-brake Systems and Automatic Valves therefor.
Filed: 1905-03-08
Granted: 1906-03-01
Abstract: 4880. British Thomson-Houston Co., [General Electric Co.]. March 8. Brakes.-The pneumatic-pressure braking-systems of the several cars of a train are independent of one another, and are controlled by means of a train-pipe which only carries sufficient air to operate the automatic valves on the cars. In one arrangement, Fig. 1, the train-pipe t can be connected, by means of the motorman's valve V, either to atmosphere or to a reservoir R. A second reservoir R', connected to the reservoir R through a one-way valve and charged by the same compressor C, is connected to the brake cylinder B through the automatic valve A. This valve is shown in Fig. 2. The pipe t<1> from the train-pipe opens between two diaphragms d, d<1>, which are of different areas and are rigidly connected together ; the reservoir R<1> is connected to the valve through a pipe r<1>, and the brake cylinder through a pipe b<1>. The parts are shown in " lap " position. To apply the brakes, the pressure in the train-pipe is reduced ; the reduction of pressure between the diaphragms d, d<1> allows a spring 9 to move them towards the left, whereby valve 1 is unseated and the chamber 2 connected to the brake cylinder, which is at atmospheric pressure, through a passage 15. Reservoir pressure, acting on a piston 3, then moves a slide valve 6 towards the right and connects the reservoir to the brake cylinder through the pipes r<1>, b<1>. The brake-cylinder pressure acts upon the outer side of the diaphragm d, and, when it has reached a value depending upon the reduction of train-pipe pressure, the outside area of the diaphragm d, and the difference between the inside areas of the two diaphragms, the diaphragms are returned to their normal position, closing the valve 1. The pressures on the two sides of the piston 3 are then equalized through a small passage in the piston, and the slide valve returned to top position by a spring. To release the brakes, the train-pipe pressure is increased, moving the diaphragms d, d' towards the right and unseating a valve 8. The lefthand side of a piston 13 is thereby connected to atmosphere through a port 12, and brake-cylinder pressure, acting upon the piston 13, moves a slide valve 17 towards the left and vents the brake cylinder through a port 18 and passage 15. When the brake-cylinder pressure has fallen to a certain value, the spring 9 returns the diaphragms d, d<1> to their normal position, seating the valve 8. The pressures on the two sides of the piston 13 are then equalized through a small passage therein, and the port 18 closed by the slide valve. Other arrangements of diaphragms may be employed, so long as train - pipe pressure multiplied by a constant, plus brake-cylinder pressure multiplied by a constant, is opposed by a constant force, such as the pressure of a spring. In a modified arrangement, an additional motorman's valve is provided at each end of a vehicle to connect the reservoir to the brake cylinder independently of the automatic valve. A gauge may be fitted to indicate the pressures in the train-pipe and reservoir. A simplified form of automatic valve is shown in Fig. 4 in its " release position. When train-pipe pressure is reduced, the piston P is moved towards the left by a spring S, and the slide valve a closes the pipe b<1> leading to the brake cylinder or connects it to the reservoir through the pipe r<1>.