GB850052A - Distributor valve means for a vacuum braking system - Google Patents

Abstract

850,052. Fluid pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd., and SIMMONS, A. W. July 25, 1958 [July 26, 1957], No. 23718/57. Class 103 (1). A distributer valve means for a railway vacuum brake system comprises a relay inlet valve 25 for admitting atmospheric air locally, check valve means 73 in a communication between the lower chamber of a brake cylinder and a train pipe 95 and permitting evacuation of the lower chamber from the train pipe, and an inshot valve 63 controlling, in dependence upon the differences between the degrees of vacuum in the upper and lower chamber of the brake cylinder, the rate of flow of the locally admitted atmospheric air to the lower chamber such that the rate of flow is reduced when the lower chamber vacuum is reduced in excess of a predetermined reduction sufficient to bring brake shoes, operated by the brake cylinder, to an engaged position. The distributer valve means comprises a housing 1 having chambers 19, 21 separated by a diaphragm 11 and chambers 49, 51 separated by diaphragm 15 carrying a head 53 of a push rod 55 held against the in-shot valve 63 by a spring 57, the chambers 49 and 19 being connected to the brake cylinder lower chamber, chamber 51 to the upper chamber and chamber 21 to the train pipe 95. On the evacuation of the system, vacuum in the train pipe acts through port 95 to evacuate the lower brake cylinder chamber via port 85 and valve 73, and chambers 49 and 19 via passages 89 and 87. The train pipe vacuum in chamber 21 raises diaphragm 11 from the head 27 of a push rod 23 to evacuate the valve means and brake system more quickly through diaphragm aperture 17. On completion of charging, valve 73 is reseated and the valve means is as shown. On brake application, air admitted to the train pipe acts in chamber 21 to seal diaphragm 11 against the head 27 and then move the push rod 23 against springs 39, 33 to open inlet valve 25 and connect chamber 43 to atmosphere. Since in-shot valve 63 is raised by the combined action of springs 57, 61, 77, 79 and service valve 73 is closed by spring 77, the air in chamber 43 flows past restricted ducts 81, 83 to the lower brake cylinder chamber. Air in chamber 43 opens valve 73 permitting air to flow to the train pipe via port 95. When vacuum has been reduced to a first predetermined value in the brake cylinder lower chamber the pressure in chamber 49 lowers diaphragm 15 and spring 71 moves a collar 69 to close quick service valve 73; air continues to flow to the brake cylinder until at a second predetermined pressure diaphragm 15 is lowered sufficiently to allow spring 79 to close valve 63, air then flowing to the brake cylinder via the smaller restricted duct 81 until the brake cylinder pressure, acting through passages 87 and 89 to chamber 19, corresponds to the degree of vacuum in train pipe and closes valve 25. A further decrease of vacuum in the train pipe causes reopening of the valve 25 and stronger braking. Should the train pipe vacuum increase slightly then diaphragm 11 is drawn away from the head 27 permitting exhausting of the lower brake cylinder chamber via passages 87, chamber 49, passage 89, chamber 19 and aperture 17. As exhausting proceeds decrease in pressure in the chamber 49 raises the diaphragm 15 to open valve 63, compresses spring 71 to allow valve 73 to open to increase the rate of exhausting of a brake cylinder. On complete exhausting the valve 73 recloses. In an embodiment, Fig. 2, the distributing valve means is connected to the lower chambers of a no-load brake cylinder via passages 85 and .full-load brake cylinder via passage 107, both brakes being operated when the vehicle is loaded, and the full load cylinder disconnected when not required. On brake application a decrease in vacuum in train pipe 95 causes diaphragm 11 to open passage 103 and admit atmospheric pressure to chamber 21, the increase in pressure in chamber 21 causes push rod 23 to open valve 25 to admit atmospheric pressure via filter 129, passages 45, 47 to the chamber 43, air passing through restricted ducts 81, 83 and passage 85 to the lower chamber of the no-load brake cylinder and through further restricted ducts 111, 108 to the lower chamber of the fullload brake cylinder. The increased pressure in these chambers acts at a first predetermined pressure in chamber 49 to move a push rod 55 to allow ball valve 125 to reseat and close the connection 127 between atmosphere and chamber 21, further flow of atmospheric pressure being supplied to chamber 21, from train pipe 95. Further downward movement of the push rod 55 effects at a second predetermined increase of pressure in the lower chamber, closure of the in-shot valve 63, air flow continuing to lower chambers through the restricted ducts 81 and 111 until the pressure in the chamber 19 rises sufficiently to balance the pressure in chamber 21 and close the inlet valve 25. A further rise in the train pipe pressure and in chamber 21 effects reopening of valve 25 to cause further flow of air to the lower chambers of the brake cylinder and cause an increase in brake application. If it is required to release the brake shoes, an increase in the train pipe vacuum causes air to flow from the chamber 21 and from the lower chamber of the no-load brake cylinder via ducts 83 and 113 causing the opening of check valve 133 to permit air flow past restriction 109 and check valve 135 to train pipe 95, and from the lower chamber of the full load cylinder past restrictions 108, 109 and check valve 135.