GB683350A - Improvements in or relating to fluid-pressure braking systems for vehicles - Google Patents

Abstract

683,350. Compressed air brakes. BENDIX-WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. Jan. 2, 1951, No. 174/51. Class 103 (i). In a compressed air brake system for tractor-trailer units comprising the usual compressor 10, main reservoirs 16, 18, control valve 40, front and rear brake cylinders 21 and 23 on the tractor, and auxiliary reservoir 68, relay valve 70 and brake cylinders 62 on the trailer, a special valve device 76 fitted on the tractor is connected into the service brake lines 56, 54 and emergency brake lines 46, 44 and operates to prevent flow through these lines in the event of the pressure at the main reservoirs 16, 18 falling below a certain value, e.g. 50 pounds per square inch, this arrangement thus pre. venting the exhaustion of the main reservoir, in the event of a break in the service or emergency lines, to an extent that would prevent the effective operation of the tractor brakes. The valve device 76 is shown in the position in which it would be if there were no air in the system on the tractor, the brakes on the trailer then being applied from the auxiliary reservoir 68 through the relay valve 70. Under these conditions the passage between service lines 56 and 54 and emergency lines 46 and 44 is cut-off by valves 80 and 78 respectively under the action of springs 84 and 82. As pressure is built up by the compressor 10 in the reservoirs 16 and 18, this is transmitted by pipes 22 and 126 to a governor valve 124, which, for the condition of valve device 76 shown, would connect the chamber 111 at the top, above diaphragm 108 to atmosphere. When the reservoir pressure reaches, say, 75 pounds per square inch, the valve 124 operates to connect pipes 126 and 123. The resulting pressure in chamber 111 thus causes a downward deflection of diaphragm 108. Valve member 112, which is moved downwardly, first engages valve element 122 and thus cuts off chamber 90 and the trailer emergency lines 44, 64 from exhaust outlet 120 and then opens valves 78 and 80 to connect up service and emergency lines 56, 54 and 46, 44 on the tractor, the valve device 76 then being set for normal running of the vehicles. In the event, however, of breakage or serious leakage from the service or emergency lines to an extent sufficient to reduce the pressure in reservoirs 16, 18 below, say, 50 pounds per square inch, the governor valve will operate to cut off pipe 126 from pipe 123 and connect the latter to atmosphere. The diaphragm 108 will thus be returned to the position shown closing valves 78 and 80 and preventing further loss of pressure. The tractor reservoir pressure will thus be conserved between 50 and 75 pounds per square inch. In order to release the trailer brakes, after an undesired emergency application a handactuated valve 134 may be used to supply pressure from a reservoir 130 by pipe 136 and double check valve 140 to pipe 126 and the governor valve 124. The reservoir 130 is charged with the reservoirs 16 and 18 through a non-return valve 132. The control valve 140 may be such as described in Specification 488,208, [Group XXIX].