GB141785A - Improvements relating to fluid pressure braking apparatus - Google Patents

Abstract

141,785. Cloud, J. W. Jan. 16, 1919. Fluid-pressure. - Relates to valve mechanism of the kind described in Specification 120,652 for effecting the graduated release of the brakes and comprising a brake-cylinder exhaust valve controlled by train-pipe and brake-cylinder pressure in opposition to constant reservoir pressure. According to the invention, two separate diaphragms, subject respectively to the constant reservoir pressure and to the train-pipe pressure, together with a spring, are provided, these diaphragms being coupled by a lever to the combined abutment and valve controlling the brake-cylinder pressures. As shown in Fig. 1, a pair of diaphragms 10, 12 are connected by a stem 11 pivoted at 17 to a lever 16 turning about a fixed pivot 16<1>. The diaphragm 12 is constantly subject to train-pipe pressure admitted at 5 and to the pressure of a spring 13. The diaphragm 10 is subject to the pressure in a reservoir 1 also connected to the train-pipe or to the auxiliary reservoir at 8, but through a non-return valve 9. The space between the diaphragms is open to atmosphere. The lever 16 is also connected to a plunger 19 sliding in a chamber 6 connected at 7 to the brake-cylinder exhaust port of the triple valve. Ports 22 in the chamber 6, leading to a passage 21 open to atmosphere, are normally uncovered by the plunger 19. When the brakes are applied, the pressure in the reservoir 1 is unaffected and therefore moves the diaphragms 10, 12 against the reduced train-pipe pressure in the chamber 4, the ports 22 being thereby covered by the plunger 19. When the train-pipe pressure is raised to effect the partial release of the brakes, the brake-cylinder pressure, admitted to the chamber 6 by the triple valve, acting on the plunger 19, together with the train-pipe and spring pressure acting on the diaphragm 13, overcomes the constant pressure in the reservoir 1, and the exhaust ports 22 are uncovered until the brake-cylinder pressure has fallen sufficiently for the pressure in reservoir 1 again to return the plunger 19. The ball valve 9 may be arranged in a spring-pressed valve 27, Fig. 2, adapted to permit a limited return of air from the reservoir 1, and so prevent the pressure in this reservoir from exceeding by more than 20 to 30 lb., the pressure in the train-pipe or auxiliary reservoir when it has been reduced in applying the brakes.