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