| 摘要 |
<p>A bidirectional flow control valve (10, 10', 110) has one port (30, 130) co-axial with a tubular spool (18, 118) and another port (32, 132) opening to the side of the spool (18, 118), with openings formed in the side wall of the spool (18, 118) to establish communication between the two ports (30, 130 and 32, 132). The end of the spool (18, 118) adjacent to the one port (30, 130) abuts an annular shield (24, 125) which has an inside diameter less than the inside diameter of the spool (18, 118) so as to react against flow forces from the one port (30, 130) to the other port (32, 132) and prevent them from impinging on the end of the spool (18, 118). The shield (24) in two embodiments (10, 10') is an annular flat disc (24), with the lumen of the spool (18) open at both ends and the spool axis unrestricted from end to end so that flow forces are directed down the axis of the spool (18) and reversed in direction to act in the same direction as a spring (22) which biases the spool (18) open. In another embodiment (110), the end of the spool (118) adjacent to the one port (130) abuts the brim (124) of a tubular hat-shaped insert (125) which extends inside the lumen of the spool (118) to a closed end (162) on the distal side of the other port (132). The insert (125) reacts against flow forces, helps equalize pressures from one end of the spool (118) to the other, and does not increase the pressure drop across the valve.</p> |
