Patent ID: 8056640

Claim:
A hydraulic head clamp assembly for retracting a drill rod string, comprising: a drill head adapted to be mounted on a mobile drill rig with a means for shifting the drill head from side-to-side in a horizontal direction and for raising and lowering the drill head in a vertical direction relative to the mobile drill rig; a rigid jaw mounted on a side of the drill head; a movable jaw mounted adjacent to said rigid jaw with a space between the jaws for receiving a drill rod string; and at least one hydraulic actuator for moving said movable jaw toward said rigid jaw to clamp the drill rod string between the rigid and movable jaws; wherein said hydraulic actuator comprises first and second hydraulic cylinder actuators with respective rod ends connected to said movable jaw; wherein said first and second hydraulic cylinder actuators each comprises a cylinder and piston assembly arranged for linear movement of the piston assembly relative to said cylinder in a horizontal direction; and wherein each of said piston assemblies comprises a rod that extends horizontally through the drill head on opposite sides of a centerline of a drive mechanism for driving the drill rod string into the ground, and said movable jaw is pin connected to the respective rod ends protruding from the side of the drill head.