| 摘要 |
977,541. Valves. BRAKESHOE INTERNATIONAL S.A. Aug. 15, 1962 [Oct. 5, 1961], No. 31358/62. Heading F2V. A spring-loaded pistonvalve 44 controls ports 41-43, each of different area, between an inlet 17 and an outlet 18, the latter being open to the space 39 behind the piston through passages 19 and 93, a restricted orifice 73 in a piston 72, and a passage 59. Flow through the restricted passage 93 is controlled by a needle valve 86 supported by a member 78 urged by a spring 83 against a sleeve 64 in which the piston 72 is slidable; the valve 86 is loaded by a spring 87 in the member 78. The position of the element 89 incorporating the passage 93 is adjustable. The piston valve 44 remains closed whilst the outlet pressure is greater than or equal to the inlet pressure. When the inlet pressure gradually rises above the outlet pressure the piston valve 44 uncovers ports 41-43 as rapidly as the fluid is displaced from space 39 to the outlet 18 via the restricted orifice 73 and valve 80. Should a surge of pressure appear at the inlet, the resulting pressure-drop across the orifice 73 causes rightward motion of the piston 72 and member 78 so sealing the valve 80 against the adjacent end of passage 93, which movement is cushioned by the spring 87. Any further translation of the piston valve 44 is thereby prevented. When the pressures across the piston 72 equalize, since flow through the orifice 73 is prevented, the spring 83 reacts to slightly open the valve 86 and permit a slow release of fluid from the space 39; piston 72 then resumes control of the valve 86 and movement of the piston valve 44. When the inlet pressure drops the piston valve 44 is urged downwardly by its spring 47 and space 39 is filled with fluid from the outlet 18. Orifice 73 is smaller than restricted passage 93. |
