Abstract: An internal combustion engine comprises a cylinder having a horizontal axis, one end of the cylinder being formed as a combustion chamber and the other end opening into a crankcase receiving a lubricating atmosphere. A piston slidable in the cylinder has a space therein communicating with the crankcase. The piston is formed with grooves of rectangular cross-section with a base and a pair of transverse surfaces. A scraper groove furthest from the combustion chamber receives a scraper ring and has orifices in its base communicating with the piston space, the other sealing grooves receiving piston rings, annular gaps between the piston and cylinder being left on each side of the piston and scraper rings. The annular gaps are placed in continuous communication with the groove bases by at least one recess on each transverse surface of a sealing groove and by at least one recess on that transverse surface of the scraper groove which is nearest the combustion chamber.

Abstract: A reciprocating piston assembly for a compressor is disclosed in that a piston with at least one groove formed in its outer surface is slidably mounted in a cylinder bore and at least one piston ring made of polymers of fluorine-containing olefin monomers, the outer diameter of said piston ring being smaller than the diameter of said cylinder bore prior to operation of the compressor but said piston ring being in contact with the inner wall defining said cylinder bore during operation of the compressor.

Abstract: A fluid operated reciprocating piston rock drill wherein the piston has a stem portion closely slidably received in a guide bushing and the cylinder of the rock drill provides clearance space around the head of the piston.

Abstract: An impact motor has a reciprocating piston that has its piston rod guided in bushings in the housing. The bushings are lubricated by oil-loaded compressed air but the piston is forced to reciprocate by oil-free compressed air.

Abstract: The invention provides a bypass around virtually the entire periphery of a piston in a two cycle engine without substantially increasing costs or obsoleting production tooling. This is done by reshaping a cavity formed inside an engine casting to enlarge the crank case opening and to provide three oppositely displaced bypasses. The fourth side of the piston is open to the exhaust port. Therefore, virtually the entire perimeter of the piston is bypassed to greatly increase power by improved breathing.