| 摘要 |
1427042 Valves GRESEN MFG CO 2 March 1973 [2 March 1972] 10313/73 Heading F2V In a valve assembly for controlling two independent loads by means of spool valves 70, 130, additional spool valves 51, 111 are provided to control the distribution of the available operating fluid between the two loads in accordance with the demands of the loads and the pressures developed thereby and to bypass surplus fluid. The overall assembly comprises an inlet unit 11, two valve units 12, 13 and an outlet or exhaust unit 14. Included in each valve unit 12, 13 are relief and anti-cavitation valves 43, 44 and 103, 104. In Fig. 2, both spools 70, 130 are in the neutral position. On operating either of these spools an appropriate land on the operated spool blocks an open-centre pilot passageway 28 to close it from exhaust. This causes valve 25 to close, cutting off the inlet port 20 from an exhaust passageway 21. Valve 22 then opens to supply fluid to the valve units 12, 13. Fig. 7 shows spool 130 in a position to supply fluid to a load port 102, spool 70 being still in the neutral position shown in Fig. 3. With fluid now flowing into valve unit 12, pressure is fed via passageway 56 in spool 51 to the top of the spool which is forced fully downwards against the action of spring 52, a dump passage 54 being open to exhaust via the spool valve 70. All the fluid now flows into the valve unit 13 and via duct 150 to load port 102 to operate the load. If the fluid supply to the load exceeds the demand, pressure at the outlet and thus at passageway 107 will build up until a situation is reached where this pressure, fed via passageway 116 in spool 111, will move the spool downwards against the force of spring 112 and the pressure fed, via the axial and radial passageways 137 and 139 in the spool 130, to the bottom of the spool. Under these conditions some or all of the fluid is fed direct to exhaust, the control land of spool 111 being provided with metering grooves 117 to control this flow. Should pressure at the load rise to that at which a relief valve 160 is set to operate, the pressure fed to the bottom of the spool 111 is released and the spool moves even further downwards by-passing more or all of the fluid to exhaust. If spool 70 is positioned to supply fluid also to a load connected to load port 41 or 42, spool 51 will take up a position determined by the relative demands of the two loads which determine the pressures operating on the upper and lower ends of the spool. |
