Patent GB-1050072-A (GB)
IPC: B60T13/36
Abstract: 1,050,072. Fluid-pressure brakes. BENDIX WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. March 31, 1965 [April 3, 1964]. No. 13699/65. Headings F2F and F2V. In a compressed air braking system for road vehicles of the kind employing an actuator 68 which is provided with service and emergency diaphragms 74, 76 acting on a common brakeapplying shaft 81, air being supplied to the service chamber 73 via a driver's valve 60 and to the emergency chamber 86 via a normallyopen valve, the normally-open valve is a relay valve 100 which is controlled by a control pressure provided by a separate manuallyoperated valve 32, the control pressure also controlling a normally-closed relay valve 44 in the supply line from the brake valve 60 to the service chamber 73 so that, when control pressure is fed to the control chambers of valves 100, 44, via connections 40, 84, 108, valve 100 is closed and valve 44 is simultaneously opened, permitting service operation of the brake only, while removal of control pressure similarly permits an emergency brake application but prevents service application, whereby only one at a time of the two diaphragms 74, 76 can act on the brakes. As shown, the system also includes the provision in the actuator of spring-applied, fluid-pressure released, locking means 82 of the kind in which in the absence of pressure at a port 72 a oneway locking action is applied to the shaft 81 to allow movement in the braking direction but prevent release of the brake. This port 72 is fed from the control pressure line 40 via a line 84, so that the lock is released whenever valve 44 is open to allow service application and valve 100 is shut. In addition, to prevent the emergency chamber 86 being continuously pressurized when control pressure in line 40 is vented, by manually pulling the handle 34 of valve 32, an additional valve 92 is provided in the emergency feed which both determines a maximum pressure in chamber 86, which is less than that in the main reservoir 10, and vents the emergency chamber 86 when this pressure has been reached, the brakes remaining applied due to the lock 82. This valve (Fig. 2, not shown) consists of a double valve assembly comprising a valve member 136 carried by a spring-loaded piston 132 and co-operating with a seat 142, and a spring-loaded valve actuating member 146 the upper end 160 of which constitutes a second valve member sealing against the member 136 inwardly of the portion engaging the seat 142. Chamber 158 is arranged at all times to be in communication with inlet 94 via a restricted passage 159, bore 148 in member 146, aperture 138 in valve member 136 and bore 134 in piston 132. When pressure is fed to the inlet by the valve 100 it passes via bore 134, aperture 138 and around the valve actuating member 146 to outlet 90, to charge the emergency chamber 86, and at the same time passes via restriction 159 to chamber 158 to build up pressure in the latter. When pressure in chamber 158 rises sufficiently, piston 150 moves upwardly, cutting off the supply to the outlet 90 and exhausting the emergency chamber 86 via exhaust outlet 93. Since the end 160 of member 146 is now sealed against member 136 pressure continues to build up in chamber 158 so that outlet 90 remains connected to exhaust 93 until control pressure is removed from the inlet 94. The system further includes, in addition to the main reservoir 10, a reserve reservoir 12, and a manually operable change-over valve 24 is provided to enable control pressure and pressure for an emergency application to be obtained from the reservoir 12, should reservoir 10 be exhausted.