GB218994A - Improvements relating to fluid pressure braking apparatus - Google Patents

Abstract

218,994. Duchatel, E. E. H. July 9, 1923, [Convention date]. Fluid - pressure. - A graduated release valve operating in conjunction with the triple valve or other distributing valve of fluid-pressure brakes is so arranged that gradual variations in the train pipe, pressure produce a graduated release of the brakes, whilst sudden pressure variations result in full release. The valve comprises a pair of pistons P<1>, P<2> connected respectively to a valve t subject to the pressure of a spring r<1> and to a slide valve i subject to the pressure of a spring r<3> and having a projection q engaging with the curved portion of a spring r<2>, stops u being provided to limit the upward movement of the piston P<2>. The chambers b, a, e communicate respectively with the exhaust part of the triple valve, the train pipe, and the auxiliary reservoir, whilst a pipe g connects the chamber b with a cavity in the slide valve l, and a passage f leads to exhaust. When train pipe pressure is reduced to apply the brakes, the pressures in the chamber b, e keep the ports in the position shown and the movement of the triple valve isolates the chamber b from the brake cylinder, but when fluid is again supplied to the train pipe to release the brakes, the chamber b communicates with the brake cylinder through the pipe c and the exhaust port of the triple valve. If the supply is gradual, the train pipe and auxiliary reservoir pressures remain substantially equal and the piston P<2> will remain in position, and the pipe g will be cut off from the exhaust f by the slide valve l. The valve t will, however, open to vent the brake cylinder as soon as the resistance of the spring r<1> is overcome by the combined upward pressures in the chambers a, b, and will remain open until these forces equalize, thus effecting a partial release of the brakes. If, however, the train pipe is rapidly charged, so that train pipe pressure increases more rapidly than auxiliary reservoir pressure, the piston P<2> will be moved downwards and the slide valve l will connect the pipe g to the exhaust f to effect complete release of the brakes. The piston will remain in its lower position until train pipe pressure is again reduced, when excess pressure in the chamber e, assisted by the spring r<3>, will move it back to normal position. A cock may be provided in the pipe c to cut out the graduated release valve, and the latter may comprise an upper and a lower valve each containing a chamber a, the cavity in the slide valve l then being connected directly to the pipe c. The lower valve may also be used alone in conjunction with the brake cylinder, or it may be interposed between the triple valve and the brake cylinder. In the latter case, the slide valve l would control ports leading respectively to the triple valve, the brake cylinder, and the atmosphere.