Patent ID: 7559361

Claim:
A well tool for applying a pulling or a pushing force to an object in an interior of a well bore, comprising: a) a drive mandrel; b) an engaging mandrel; c) an actuator; d) a housing sealing a portion of the drive mandrel and a portion of the engaging mandrel within an interior space, the drive mandrel and the engaging mandrel extending from opposite ends of the housing; e) a drive mandrel piston area defined at a drive mandrel end portion of the housing between an outside diameter of the housing and an outside diameter of the drive mandrel sealed at the housing; and f) an engaging mandrel piston area defined at an engaging mandrel end portion of the housing between the outside diameter of the housing and an outside diameter of the engaging mandrel sealed at the housing; wherein the actuator is adapted to reversibly move the housing longitudinally relative to the drive mandrel and the engaging mandrel, and wherein the drive mandrel piston area and the engaging mandrel piston area are substantially equal so that external pressure acting on the two piston areas, generates two opposing forces that are substantially balanced during relative movement.