GB252115A - Improvements in valve mechanism for pneumatic brakes - Google Patents

Abstract

252,115. Drolshammer, I. May 12, 1925, [Convention late]. Fluid-pressure.-An auxiliary valve for use in connection with the main control valve of an automatic compressed-air brake to give a relatively free initial flow of air to the brake cylinder followed by a restricted flow is controlled by the brake cylinder pressure opposed to the pressure in the usual auxiliary reservoir or in a separate reservoir. As shown in the Figure, the device comprises a piston valve 14 constantly exposed on its upper surface to auxiliary reservoir pressure by passage 6 and engaging at its lower end a piston 13 the upper side of which is constantly open to atmosphere by the passage 30 and the lower side to the brake cylinder by the passage 12. In the release position shown, the brake cylinder is open to atmosphere by a passage 39 past the piston 13 in addition to the usual exhaust passage whereby complete release of the brakes is ensured. The valve 14 comprises ports 37, 40, 15 and in the initial stage of an application, air from the auxiliary reservoir flows to the brake cylinder at first by the wide port 37 and passage 9 until the pressure on the underside of the piston is sufficient to raise this piston and the valve 14 to bring the restricted port 40 into register with the passage 9. At this stage a spring '22 becomes operative and is compressed during further rise in the brake cylinder pressure until a third relatively wide port 15 is brought into register with the passage 9. Packing 21 on the piston 13 makes a tight joint with the valve bush 20 in the upper position of the piston. In a modification, the valve is interposed in the passage from the main valve to the brake cylinder instead of in that between the auxiliary reservoir and the main valve, the air passing to and from the brake cylinder through the, ports 37, 40, 15 and a bore in the valve stem and piston 13. Specification '225,566 is referred to.