Patent GB-817634-A (GB)
Title: Dual fluid pressure braking systems for front and rear vehicle wheels or tractor/trailer vehicles
IPC: B60T17/18
Filed: 1956-02-24
Abstract: 817,634. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd., KERSHAW, J. W. G., SIMMONS, A. W., and KIRK, W. A. Feb. 25, 1957 [Feb. 24, 1956; May 15, 1956], Nos. 5913/56 and 15049/56. Class 103 (1). [Also in Group XXIX] In a fluid-pressure braking system comprising two separate braking systems, each system comprising a reservoir and one or more brake cylinders connected to the reservoir through a control valve, the two separate braking systems are connected in parallel to a common source of supply of pressure fluid, a charging valve being provided in one of such parallel connections and either a charging valve or a check valve in the other parallel connection. Fig. 1 illustrates the case where an air compressor 2 supplies two reservoirs 5 and 6 mounted in parallel connections 3 and 4; lines 7 and 8 leading to respective brake cylinders to separate control valves and a charging valve 11 provided in connection 3 and a check valve 12 permitting flow in direction of arrow only in connection 4. Should pressure fail in reservoir 5, the reservoir 6 will remain fully charged to the upper limit of pressure, due to the check valve 12, until the pressure therein is utilized for braking, and subsequently it can be recharged to the lower limit of pressure as determined by the charging valve 11 so as to continue to afford some reduce degree of braking potential. Should pressure fail in the reservoir 6, the reservoir 5 will remain charged initially only to the lower limit of pressure, due to the charging valve 11, so that the reduced degree of braking potential remains available. In this event, neither of the reservoirs can be re-charged since the compressor delivery can escape freely through the check valve and reservoir 6. In the arrangement according to Fig. 2, a first charging valve 21 is provided in connection 3 and a second charging valve 22 in connection 4. Should pressure fail in either one of the reservoirs 5 and 6, the other reservoir will remain charged initially to the lower limit of pressure so that the reduced degree of braking potential is available. The two charging valves illustrated in Fig. 2 may be combined into a single valve unit shown in Fig. 6 in which valve closure members 119 and 120 of the two charging valves are slidably disposed in line and back to back, the stem 121 of closure member 119 being in telescopic relationship with solid stem 122 of other closure member 120. Air from compressor enters orifice 132 and communicates through passage 131 with chambers 123 of both charging valves and by the opening of valve closure members against the action of spring 133 air passes to both reservoirs 5, 6 via outlets 126 and 126a respectively. Loss of pressure in one of the systems relieves the associate valve closure member of the thrust produced by reservoir pressure acting thereon in the opening direction over an area equivalent to the area of the hollow space in boss 124. The other closure member can then be opened at a lower value of the supply pressure to enable re-charging of the system remaining intact in the manner already described, the additional compression of the spring 134 by the opening of this closure member assists in keeping the other closure member seated by increasing the biasing force acting thereon. Specifications 732,959, 751,578 and 752,058 are referred to.