Apparatus for producing a reciprocating oscillation of a power output shaft comprises a plurality of peripherally spaced cylinders disposed in generally tangential relationship to the periphery of a cylindrical fluid pressure chamber and connected at their inner ends to such fluid pressure chamber. The gas pressure in such chamber is regulated to maintain a selected value above ambient. Cooperating pistons in each of the cylinders are interconnected by connecting rods to a spoke-like rocker element which is freely oscillatable about the output shaft to which the housing defining the cylindrical fluid pressure chamber is secured for co-rotation. A flywheel mass is connected to the spokes of the rocker element. Inlet and exhaust valves are provided in a cylinder head mounted in the outer end of each cylinder and are operable by contact with the outer face of the respective piston. A radial exhaust port is uncovered by each piston as it nears the end of its power stroke, thus reducing the fluid pressure on the outer piston face to ambient and permitting the regulated fluid pressure chamber to effect the return of the pistons to their outermost pistons relative to the cylinder.
Edwin W. Dibrell; Glenn B. O'Neal; Wilbur A. Schaich