| 摘要 |
<p>A servo arrangement includes a valve having a chamber into which opens a pair of aligned ports and a third port. A stem is movable within the pair of ports and carries a pair of closure members for the ports. The closure members are biased apart against stops so that in a mid-position of the stem both of the pair of ports are open to the third ports. When the stem has moved to shut one port, continued movement in the same direction allows a large flow through the other port. The servo arrangement also includes an actuating piston and a valve operating device responsive to a signal pressure and to the piston position. The valve controls the pressure supplied to one side of the piston.</p> |
