Abstract: The present invention comprises a double acting actuator having a piston movable within a cylinder, a main poppet control valve connected to a fluid pressure source, and first and second poppet valves connected in series to a rod side chamber of the cylinder. The piston is extended upon actuation of both first and second poppet valves, while allowing retraction of the piston upon release of either the first or the second poppet valves.

Abstract: The infinitely positionable coupling system of the present invention includes a hollow outer race, a hollow inner race, and a locking assembly which permits locking of the hollow inner race to the hollow outer race in an infinite number of positions. The hollow outer race engages a nose piece and the hollow inner race threadably engages the drill housing. Accordingly, the nose piece is infinitely positionable with respect to the drill housing by positioning the hollow inner race with respect to the hollow outer race and allowing the locking assembly to hold them in position one with respect to the other.