{HEAD ~ A mechanism} for controlling {TAIL ~ 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 the displacement device to control flow of liquid to or from the device 
{ HEAD ~ A mechanism } for controlling { TAIL ~ 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 the displacement device to control flow of liquid to or from the device
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH