GB885467A - Improvements relating to railway vehicle vacuum braking apparatus - Google Patents

Abstract

885,467. Fluid pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. June 30, 1959 [July 1, 1958], No. 21001/58. Class 103 (1). A control mechanism for a railway vehicle vacuum braking apparatus including empty and load brake cylinders 13, 17 respectively, having upper and lower chambers with means by which the upper chambers can be evacuated by train pipe 11, comprises a valve 14 to establish or interrupt communication between the load brake cylinder lower chamber and pipe 11, means 18 actuated by vehicle load and by which a displaceable member 37 of the valve causes the valve to establish said communication for so long as the load exceeds a predetermined value, and a locking device 41, 42 responsive to a decrease in train pipe vacuum to prevent displacement of member 37 from its prevailing position to prevent a change from empty to load braking or vice versa during brake application. Train pipe 11 is connected via application valve 12 to " empty " brake cylinder 13 and valve 14 which comprises a diaphragm 23, Fig. 2, separating a chamber 21, connected to an empty-load valve 18, from an atmospheric chamber 22, and carrying member 37 slidable in a fixed sleeve 27, the train pipe, upper and lower chambers of "load" brake cylinder 17 being connected to ports 35, 31, 30, respectively, of valve 14 via valve 12 and pipes 15, 16. A lever 42, rotated by operation of the "empty" brake cylinder 13, engages a plunger 41 with aperture 39 or 40 in stem valve 37. Initially, the upper and lower chambers of the load brake cylinder are evacuated to the train pipe through ports 28, 29 in sleeve 27 and past a check valve 33 lightly biased by spring 34 against sleeve 27. When the load is less than a predetermined value, valve 18, operated from a vehicle spring 20 through linkage 19, supplies vacuum from pipe 16 to chamber 21, diaphragm 23 and stem valve 37 moving against spring 26 to the shown position, the upper and lower chambers of the load brake cylinder being connected and the load cylinder isolated from the train pipe by valve 33. On braking empty cylinder 13 only is operated and plunger 41 engages aperture 39 to prevent valve 14 changing from empty to load braking during brake application. When the load exceeds the predetermined value, valve 18 supplies atmospheric pressure to chamber 21, spring 26 then moving stem valve 37 to raise valve 33, to cut off connection between the upper and lower load cylinder chambers and connecting the lower chamber to the train pipe. On braking the load and empty cylinders are operative and plunger 41 engages aperture 40 to prevent change to empty braking during brake application. In alternative arrangements, the plunger is replaced by a ball moved into notches in stem valve 37 by a plunger controlled by a diaphragm and vacuum in the train pipe or empty brake cylinder; or the plunger has a serrated end to engage serrations on the stem valve which is pivoted to the load and empty positions by a spring which is compressed by a linkage system connected to a vehicle spring, the valve 18 and diaphragm 23 of valve 14 being omitted.