| 摘要 |
<p>976,657. Valves. FMC CORPORATION. Oct. 1, 1962 [Oct. 18, 1961], No. 37030/62. Heading F2V. A valve comprises a housing 12, Fig. 1, having an inlet 14 and an outlet 16. A valve assembly 30 is mounted in the housing and comprises a cylindrical body 32 forming a chamber 44 which is in communication with the inlet through passages 40, 42 controlled by a throttle valve 48. A piston member 57 is slidable in the chamber and carries a seating ring 62 which co-operates with a valve seat 86, surrounding the outlet. The seating ring also forms a seat for a pressurerelieving valve member 81 which is loaded by a spring 82 and controls a bleed port 98 leading to the outlet by ports 100. The stem 78 of the valve 81 carries a collar 106 and a slot 110 which receives an actuating lever 114. To open the valve, the lever is actuated to open the pressure-relieving valve to allow escape of fluid from the chamber 44 and the collar 106 then abuts a cap 64 of the piston and the lever then opens the main valve. When the lever is released, the pressure-relieving valve closes and the flow of fluid through the restricted passage 40, 42 allows slow closing of the main valve. The valve may be closed quickly by hand, by rotating the lever to engage a pin 124, such movement of the piston 57 creates a suction effect in the chamber 44 and the valve must be held closed until the chamber is filled through the restricted passage. The cap member 64, Fig. 5, is formed with three equally spaced concave surfaces 104 separated by cavities 102. The cavities have holes 68 for attaching the cap by bolts to the piston member 57 and ports 100 leading from the bleed port 98. When the valve is being opened, flow past the surfaces 104 creates a suction effect in the cavities 102 which assists the bleed from the chamber 44. When the valve is closing, the flow past the valve seat is changed in direction by the concavities 104 and the reaction forces act against the valve closure movement to prevent chatter and the valve slamming to the closed position. The surfaces 104 may be formed as surface of a cylinder having a radius equal to that of the piston 57 and axis tangential to the piston 57.</p> |
