Patent ID: 7108108

Claim:
A device for controlling movement between that device and a rod operatively engaged with that device, comprising a body member, a bushing carried by said body member and provided with a central bore defining an inner surface through which the rod is coaxially and slidingly received, and a center section radially deflective between an inner position engaging and clamping the rod to stop movement between the rod and the body member and an outer position releasing the rod to permit movement between the rod and said body member, a hydraulic system for moving said center section between its said outer and inner positions comprising a liquid receiving expandable cell contiguous with said center section, passage means extending from said cell, at least one cylinder bore communicating with said passage means, a piston pin movable in said cylinder bore, and a substantially incompressible hydraulic liquid filling said hydraulic system, said piston pin being movable in said cylinder bore toward an inner position generating and transmitting pressure through said hydraulic liquid to expand said cell to move said center section to its inner position to clamp the rod, and to an outer position relieving pressure from and permitting contraction of said cell and movement of said center section to its outer position to release the rod, an actuating piston engaging said piston pin and moving therewith between inner and outer positions, means biasing said actuating piston and said piston pin toward their inner position, and means for applying pressure against said actuating piston to move said actuating piston and said piston pin in contravention to said biasing means to their outward position to release the rod, said biasing means moving said actuating piston and said piston pin toward their inner position to move said center section to its inner position to clamp the rod and stop movement between the rod and the device in the event of a significant reduction of pressure against said actuating piston.