GB1103768A - Improvements relating to braking systems - Google Patents

Abstract

1,103,768. Fluid-pressure brakes. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. 15 Sept., 1965 [21 Sept., 1964], No. 38370/64. Heading F2F. A fluid-pressure braking system for tractor/ trailer vehicles, particularly a compressed-air system employing diaphragm type actuators, has a dual driver's valve 8 which feeds service and auxiliary chambers of tractor brake actuators (not shown) via lines 11, 12 from separate reservoirs 3, 6 and also supplies at least one set of chambers of brake actuators 27, 28 on the trailer, via service connections 20, 20a, and a pair of linked valves 14, 15 which are operated manually by a hand-brake lever 13 to supply air from a further reservoir 7 to further chambers of the rear wheel tractor brake actuators, and are also adapted to connect emergency lines 19, 19a of the tractor and trailer to exhaust, via the driver's valve 8 and a check valve 16, to cause either a spring application of the trailer brakes (in the embodiment shown) or alternatively a fluid-pressure application of the trailer brakes adapted to be held by a locking device, followed by release of fluid pressure (Figs. 3 and 4, not shown). In the embodiment shown, the trailer brakeapplying springs are normally held inoperative by pressure in the emergency line 19, 19a which communicates with emergency chambers of the actuators opposing the spring pressure. The actuators also have service chambers which act in opposition to the emergency chambers to apply the trailer brakes when driver's valve 8 is operated, through a service line connection including a double-check valve 17 and connections 20, 20A leading to a relay valve 24 on the trailer whch causes air from a reservoir 23 to pass via line 25 to the service chambers of trailer brake actuators 27, 28. The reservoir 23 is maintained charged from the service line via check valve 22. A second relay valve 26 is inserted in the line 25 and controlled by the pressure in the emergency line such that line 25 is blocked when the emergency line is exhausted, thus preventing both a service and a spring application taking place together. However, when valve 15 is operated to exhaust the emergency line it also connects the reservoir 7 to the double-check valve 17 to ensure that the trailer reservoir 23 is charged. In the modification of Fig. 2 (not shown), the relay valve (26) is rendered unnecessary by connecting the emergency chambers of the actuators (27), (28) to a separate auxiliary line (21), (21A) and using a valve (29) in place of valve 15 which when operated by the hand brake lever exhausts the auxiliary line, to cause a spring application, but does not exhaust the emergency line, which in this embodiment acts to maintain the reservoir (23) charged. Since exhausting of the auxiliary line is via the driver's valve a double actuation of the trailer brakes is again prevented. In the off position of the hand brake lever the auxiliary line is connected by the valve (29) to the emergency line so that the springs are held off. In the embodiment of Fig. 3 (not shown), tractor brake actuators (31)-(34) of double or treble diaphragm type providing two front wheel brake chambers and three rear wheel brake chambers are shown and these are supplied by a dual driver's valve (8) and by a valve (14) operated by a dual driver's valve (8) and by a valve (14) operated by the hand brake lever in the manner described above in connection with Fig. 1. The trailer actuators (35), (36) however are of the type having two brake-applying chambers and a mechanical lock which is releasable by fluid pressure. The two brake-applying chambers are supplied by respective service and auxiliary connections (20), (20A) and (21), (21A) with the tractor service and auxiliary circuits, the latter being via double-check valve (17), which is also supplied by the valve (15) operated by the hand brake lever, and the former being via the usual relay valve (24) which also charges reservoir (23) from the emergency line (19), (19A). Reservoir (23) can also be charged from the auxiliary line as shown. Operation of valve (15) by the hand brake lever also exhausts the emergency line via the driver's valve (8), as in the previous embodiment, and since this is connected with the lock-release chambers of the trailer brake actuators (35), (36) the brake application via double-check valve (17) and the auxiliary line is locked. In the modification of Fig. 4 (not shown), operation of the valve (15) by the hand brake lever acts to pressurize the service line instead of the auxiliary line and, since this acts via the relay valve (24) on the trailer, a relay valve (40) is provided on the trailer between relay valve (24) and the service chambers of the actuators (35), (36) and is controlled by pressure in the emergency line, so as to isolate the service chambers from the reservoir (23) when the emergency line is exhausted, and to exhaust them via a restriction providing a delay to ensure that the trailer brakes are first locked in the applied position.