| 摘要 |
There is disclosed a combined servo control and jack unit which comprises a casing, an actuated piston slidably disposed in a piston chamber and having a piston rod extending outwardly of the casing. A servo valve chamber, axially parallel to the piston chamber, has slidably mounted therein a spool and also a sleeve member which is mechanically connected to the piston rod. Shifting the spool in either axial direction directs hydraulic fluid to one or the other side of the piston, thus moving the latter until spool stopping, at which time the sleeve automatically, almost instantly, blocks off the flow in the new position. A variable speed, gradual action of the piston is obtained without hydraulic shock or cavitation.
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