The disclosure provides an oscillatable body mounting a cylinder defining an elongated fluid pressure chamber having at least one end thereof remotely located with respect to the axis of oscillation. The elongated fluid pressure chamber accommodates a free piston which reciprocates along the length of the chamber according to fluid pressure applied thereto. Solenoid operated inlet and exhaust valves are provided at each end of the elongated fluid pressure chamber, and sensing devices, responsive to the passage of the free piston therethrough are disposed on opposite ends of the elongated fluid pressure chamber and adjacent the medial portions thereof to control the operation of the inlet and exhaust valves in accordance with the desired objective to either maximize the extraction of mechanical energy from a pressured gas in the form of oscillating movements of the body, or maximize the expansion of the pressured gas to derive the greatest possible cooling effect therefrom.
Edwin W. Dibrell; Charles D. Wood