GB1457434A - - Google Patents

Abstract

1457434 Tractor-trailer braking WABCO WESTINGHOUSE 7 Dec 1973 [8 Dec 1972] 56964/73 Heading F2F A fluid pressure operable tractor braking system, for tractor braking and for supplying pressure signals for trailer braking, has a direct brake pipe 11 supplied by a source 56 via a relay valve 38 for providing a pressure signal for trailer brake actuation in response to a pressure signal at a first input of the valve, and an automatic pipe 10, normally supplied with fluid pressure and connected to a second valve input, providing a connection to a trailer emergency line 13 and affording the sole path for charging the source so that heavy demands on the source drop the pressure in the automatic line to cause trailer brake actuation by means of the emergency line. An air compressor 1 feeds front brake and rear brake reservoirs 66, 67 respectively via protection valves, controlled by a pedal 6; brake lines to the brakes also feed chambers 51, 64 (see Fig. 2) of the relay valve 38 whereby pressure increase in either chamber causes the source 56 e.g. a reservoir to be connected via a chamber 55 and a chamber 52 to an output 53 to feed the direct pipe 11. This pipe operates a trailer relay valve 15 to feed trailer brake lines from a reservoir 27 at a higher pressure than those of the tractor brake lines to avoid jack-knifing. The reservoirs 66, 67 provide the pressure for the automatic pipe 10 via one-way valves 69, 70, a common chamber 68, a braking valve 71, which has a predetermined difference between opening and closing pressures, and a regulator 72, and to supply the reservoir 56 and a chamber 55 of the valve 38 such that a decrease therein feeds the direct line 11. A pre-set relief valve 12 controls trailer emergency line pressure. As well as the provision against heavy demand on the source 56, if the pipe 11 ruptures, the source is exhausted to drop the automatic pressure, likewise caused if a rupture occurs in the pipe 10. The trailer emergency braking occurs by operation of the valve 15 when the input via the emergency line drops.