GB587916A - Improvement in valve mechanism - Google Patents

Abstract

587,916. Fluid-pressure brakes. BENDIXWESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. Nov. 27, 1944, No. 23652. Convention date, Feb. 17. [Class 103 (i)] [Also in Group XXIX] The flow and exhaust of pressure fluid to a brake cylinder 16 is controlled by self-lapping inlet and exhaust valves 12, 14, respectively, the latter including a graduating spring 22 acted upon by a pedal 29a, and when the latter is depressed, its initial movement actuates an auxiliary valve 38 to put the source of pressure fluid, e.g., a reservoir 32, in communication with inlet valve 12, the latter being held open by the graduating spring when the pedal is in its released position. The pedal carries a cam 50 which, on the initial movement of the pedal, first closes an exhaust valve 44 and then opens the inlet valve 38 against its loading spring 39. Pressure fluid then flows from chamber 34, through chamber 36, passage 42, chamber 5, past valve 12, into chamber 6, and so to the actuator 16. The pressure built up in chamber 6 is communicated through a restricted passage 24 to the underside of a diaphragm 21 which supports the lower end of the graduating spring, the upper end of the latter being acted on by an abutment 25 in contact with the pedal. When the pressure on the underside of the diaphragm overcomes the tension in spring 22, the diaphragm will rise sufficiently to allow spring 13 to close valve 12. When the pedal is released, the diaphragm will rise and open exhaust valve 14 so that the pressure fluid in the actuator can flow along passage 53, past a non-return valve 55, past exhaust valve 40 which will have been released by the cam and opened by the exhaust fluid pressure, through ports 46, and so to atmosphere at 47. Auxiliary valve 40 ensures a complete exhaust of pressure fluid from the actuator when the pedal is released. Non-return valve 55 prevents the entering pressure fluid in chamber 36 from flowing to chamber 6 through passage 53. A stop 28 limits the downward movement of the diaphragm. The apparatus is adjusted initially by means of shims 56, 57. A screw 52 engaging a keyway 51 in the exhaust valve plunger keeps the follower 49 in engagement with the cam 50.