GB222351A - Improvements in or relating to vacuum brake apparatus for railway vehicles - Google Patents

Abstract

222,351. Peters & Co., Ltd., G. D., and Rawlings, V. P. Dec. 10, 1923. Fluid-pressure.-The diaphragm lift valve of a guard's application valve for vacuum brakes is manually operated by means permitting the admission of air at the valve to be regulated as desired and such that, with the parts in the normal position, the lift valve may function as usual as an accelerating valve for emergency applications of the brakes. The valve comprises as usual a lower portion 1, connected to the train pipe at 2, and separated from a vacuum chamber 3 by a diaphragm 4 to which is connected a lift valve 5 normally seating at 6, the space between the members 4, 5 being open to atmosphere through ports 7. An equalizing passage 8 in the valve stem 9, terminating in a cross port 35, connects the chamber 3 to the train pipe. Manual control of the valve is effected by a handle 13 moving between stops and mounted on a shaft 14 which carries cams 25, 26 adapted to engage surfaces 27, 28 formed in a recess or hole 29 in the stem 9. When the handle 13 is rotated from the normal position the cam 25 effects a gradual opening of the valve, whilst the cam 26 engages the surface 28 to prevent movement of the valve by other means, and also serves to close the valve positively when the handle is returned. The admission of air is further graduated by means of a coned plate 10 mounted on the underside of the valve, and adapted, on its initial movement, to afford only a small passage for the air entering the train pipe. As shown in Fig. 3, when the valve is in its closed position, the cam 26 is located over a recess 30, so that the valve is then free to lift to function as an accelerating valve in an emergency application of the brakes. Premature closing of the valve, when it is so actuated, is prevented by a sleeve 31 which is held by a spring 33 normally clear of the ports 35, but which covers these ports as the valve rises, so that equalization between the train pipe and the chamber 3 can be effected only through a leakage groove 36. Alternatively the passage 8 may extend to the end of the spindle and the sleeve be so arranged that it closes the passage when the valve rises, in which case a leakage groove would be provided either in the spindle head or in the sleeve. The usual vacuum gauge 38 is provided and it may be secured in place by a screw plug 43 located inside the casing and engaging the socket 40, so as to minimize the liability of theft. Alternatively, the stem 41 of the gauge may pass through the casing and be secured by a nut screwed from within.