Abstract: A compact lightweight engine or pump is constructed having a H-shaped piston, usually double acting. Each end of the piston has extending surfaces which form two moving sidewalls which act with two case sidewalls and a block-shaped head protrusion to define a working chamber with the appropriate top surface of the piston which moves to extract or add energy to the working chamber. Energy is transferred between the piston and a crankshaft by means of a slide block on the crankshaft and the inner surfaces of a pair of parallel walls forming the center of the "H" of the piston, whose opposite surfaces form the piston top surfaces. Through the use of suitable cams and valves, 4-cycle, 2-cylinder equivalent engines can be produced. With suitable porting, baffles, and/or auxillary compression means, 2-cycle engines can also be produced as well as air pumps.

Abstract: An improved combustion chamber and piston therefor, for an internal combustion engine of the type having a cylinder block and a cylinder head positioned thereabove and having pistons slideably mounted in suitable hollow cylinders in the cylinder block. The piston has a concave piston head defining a combustion cavity therein and the cylinder head extends downwardly into the piston head cavity so that combustion takes places solely within the piston head cavity. During the piston power stroke, the expanding combusted fuel exerts force on the piston head but not on the cylinder walls.