| 摘要 |
1,64,228. Fluid-pressure servomotor systems. AVERY-HARDOLL Ltd. Sept. 10, 1965 [Dec. 7, 1964]. No. 49756/64. Heading G3P. A valve 12 located downstream of a displacement meter (not shown) is adapted to close when the flow through the meter falls below a predetermined value. In the embodiment shown, when the flow rate falls a flow-responsive member 22 approaches its seat 23 and, via rod 32, unseats a pilot valve 34, thereby allowing liquid to pass via ports 36 to act on a piston 39 to raise the latter to cause a relay valve 21 to move to prevent flow via ports 48 from a chamber 16 above a piston 15 carrying the valve 12. Since the chamber 15 communicates via port 17 with the upstream side of valve 12, closure of ports 48 causes a pressure build-up in the chamber thereby causing the valve 12 to close. After the valve 12 has closed the pressure across piston 39 is equalized via restricted port 42 and passage 41, thereby allowing spring 45 to lower the piston, open the relay valve and thus open the valve 12. A pilot valve 19 may be provided which is actuated by a counting mechanism driven by the meter, this valve being normally open but arranged to cause closure of valve 12 after a predetermined quantity of liquid has passed through the meter. |
