| 摘要 |
863,827. Fluid pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. May 29, 1959 [May 30, 1958], No. 17301/58. Class 103 (1). An automatic control valve device, for variable load fluid pressure braking apparatus, particularly vacuum systems having empty and load brake cylinders, comprises a check valve 11 separating train pipe chamber 14 from a chamber 15 connected to the lower chamber of the load brake cylinder, and a diaphragm 16 separating chamber 19 connected to the upper chamber of the load brake cylinder, and an atmospheric chamber 20. The diaphragm 16 carries a sleeve 24 slidable on a post 25 fixed to a partition 22. A stem 28 is slidable in post 25 and partition 22 and abuts an adjustable bolt 31 of a piston 32 movable against spring 36 to an upper position by the vehicle load (partially acting on the piston) approximating to a predetermined value. The diaphragm 16, stem 28 and valve 11 are biased to the shown positions by springs 26, 33, 12 respectively. Balls 34, interposed between the outwardly flared end of sleeve 24 and stem 28, are biased downwardly by spring 35 on to the post 25. On charging of the braking apparatus, the lower chambers of the load brake cylinder is exhaused to the train pipe via valve 11 as is the upper chamber via the hollow end 29 of stem 28 and valve 11. When vacuum in the upper chamber reaches 6 inches of mercury, diaphragm 16 and sleeve 24 are moved up, the balls 34 wedging between sleeve 24 and stem 28 after the sleeve has moved a predetermined distance, to also raise stem 28. If the vehicle load is below the predetermined value, then when upward movement of diaphragm 16 is halted (by engagement with the valve casing) the end 28 is short of valve 11 so isolating the load brake cylinder from flow of air from the train pipe, the brake cylinder chambers remain connected via the hollow stem end 29. When the load is above the predetermined value, the stem 28 is raised by piston 32 before charging and when diaphragm 16 rises, the stem is moved further to open valve 11 to connect the train pipe to the lower chamber of the load brake cylinder. In a modification, the train pipe is connected to chamber 19 and hollow end 29 is modified to be connected to the upper chamber, a choke and small reservoir, arranged between the train pipe and chamber 19, preventing the device being changed from load to empty condition on emergency brake application when the train pipe is connected to atmosphere. |
