GB547736A - Improvements in or relating to braking systems - Google Patents

Abstract

547,736. Valves. BENDIX-WESTINGHOUSE AUTOMATIC AIR BRAKE CO. Feb. 4, 1941, No. 1499. Convention date, Jan. 18, 1940. [Class 135] [Also in Group XXXIV] In a fluid-pressure brake system, particularly for motor vehicles, in which a brake actuator is supplied with pressure fluid by a relay valve controlled by fluid supplied by the driver's valve from a main reservoir, the relay valve is adapted also to be automatically operated by a spring to supply the brake actuator when the main reservoir pressure falls below a predetermined value. The system comprises front and rear brake actuators 7, 8, a driver's self-lapping valve 9 and a main reservoir 5 connected by pipe 67, a non-return valve 25 and an air-strainer 28 to the relay-valve chamber 24 to which an auxiliary reservoir 16 is connected. The relay valve comprises chambers 47, 48, 49 separated by diaphragms 45, 46, the chambers 48, 49 being connected by pipes 66, 12 respectively to atmosphere and the valve 9, while chamber 47 is connected by a restricted passage 51 to a chamber 32 to which the actuators 8 are connected by pipe 69. The front brake actuators 7 as shown are directly connected by pipe 13 to the valve 9 but may be connected like the actuators 8 for supply by the relay valve. The diaphragm 45 comprises upper and lower metal plates 56, 57 riveted to a diaphragm and through which passes loosely a tubular valve member 39 secured to a member 42, a rubber sealing ring 61 being compressed within a depression formed in the lower plate and the upper plate resting against the member 42. The diaphragm 46 is similarly constructed and surrounds a stem 64 also secured to member 42. The stem 64 fits loosely in and normally abuts on a stem 74 that is secured by a plate 79 to a further diaphragm 71 upon which acts a spring 78 adjustable by a screw 81 and plate 80. Pressure of the spring on the stem 64 is normally prevented by the main reservoir pressure acting through the pipe 81a and chamber 73 on the diaphragm 71. Supply and exhaust valves 35, 38 connected by a stem 36 are normally held by a spring 37 so as to seat the valve 35 as shown, while the valve 38 is separated from the member 39 so that the actuators 8 are connected to the exhaust pipe 66 through chambers 32, 48. Upon operation of the driver's valve 9, pressure fluid is supplied from the main reservoir 5 directly to the actuators 7 and to chamber 49, depressing diaphragms 46, 45 and member 39 to seat valve 38 and unseat valve 35 thus supplying the actuators 8 from the main and auxiliary reservoirs through chambers 24, 32. When the pressure in the actuators 8 and chambers 32, 47 acting on diaphragm 45 is sufficient to overcome the pressure established in chamber 49 acting on diaphragm 46 the diaphragms move downwards to seat the valve 38. A graduated application of the brakes determined by the setting of the valve 9 may thus be obtained and in a similar manner by operation of the valve 9 to release pressure fluid from chamber 49 a graduated release of the brakes may be effected. If the pressure in the main reservoir and thus in chamber 73 should fall below the value determined by the spring 78 the relay valve is operated to supply the actuators. 8 and to an extent dependent upon the fall of main reservoir pressure since the pressure in the actuator acts in chamber 47 in opposition to the spring. The checkvalve 25 prevents return of pressure fluid from the auxiliary to the main reservoir. Brakes on a following vehicle may be controlled by the same or additional relay valves. The self-lapping valve 9 may be as described in U.S.A. Specification 2,133,275.