Abstract: A hydraulic head clamp assembly is integral with a drill head mounted on a mobile drill rig. A side-shift carriage is provided for shifting the drill head from side-to-side relative to a centerline of a drill rod string. The clamp assembly includes a rigid jaw mounted on the side of the drill head, and a movable jaw mounted adjacent to said rigid jaw with a space between the jaws for receiving the drill rod string. The movable jaw is connected to a pair of hydraulic cylinder actuators that are actuated via a hydraulic circuit to control the clamp action between the rigid jaw and the movable jaw. The clamp assembly can be used to retract a drill rod string from the ground without limiting access to the inner diameter of the drill rod, and can also be used to advance the drill rod into the ground via a static push.

Abstract: A hydraulic head clamp assembly is integral with a drill head mounted on a mobile drill rig. A side-shift carriage is provided for shifting the drill head from side-to-side relative to a centerline of a drill rod string. The clamp assembly includes a rigid jaw mounted on the side of the drill head, and a movable jaw mounted adjacent to said rigid jaw with a space between the jaws for receiving the drill rod string. The movable jaw is connected to a pair of hydraulic cylinder actuators that are actuated via a hydraulic circuit to control the clamp action between the rigid jaw and the movable jaw. The clamp assembly can be used to retract a drill rod string from the ground without limiting access to the inner diameter of the drill rod, and can also be used to advance the drill rod into the ground via a static push.