A mechanism for controlling the position of a movable member and for locking it in any desired position comprising a hydraulic displacement device movable with the member and a slide valve hydraulically connected to {HEAD ~ the displacement device} to control {TAIL ~ flow} of liquid to or from the device 
to control
A mechanism for controlling the position of a movable member and for locking it in any desired position comprising a hydraulic displacement device movable with the member and a slide valve hydraulically connected to { HEAD ~ the displacement device } to control { TAIL ~ flow } of liquid to or from the device
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