Abstract: This positive displacement device features relative rotation and translation of a piston and a cylinder where the rotation accomplishes a rotary valve function and the translation accomplishes a change in chamber volume function. The preferred embodiment is a ported, single-piston, four-stroke internal combustion engine with one moving part and low emissions, a sinusoidal cam on the cylinder is confined between two fixed cams relative to the generally fixed piston. The cam creates a four-stroke translational movement of the cylinder about the piston for each revolution of the cylinder. A transfer port on the cylinder facilitates movement of the intake charge from an intake port on the piston into the combustion chamber where it is compressed, ignited, and then removed by means of the transfer port and an exhaust port on the piston.

Abstract: An improved sealing means for internal combustion engines comprising a combination of a metal primary sealing ring positioned substantially within a groove on the piston, and a compliant secondary sealing ring positioned in the groove behind the primary compression ring so that the compressed combustion gases force the compliant secondary sealing ring to form a seal between the groove and the primary sealing ring. In the preferred embodiment, the gapped ring is non-planar in order to provide effective sealing in a ported fixed-piston, rotating and translating cylinder engine such as the Deckard engine. Alternate embodiments include gapless rings with only a primary compression ring, and gapless rings with a compliant secondary sealing ring. An alternate embodiment is a single piece metal-capped compliant secondary sealing ring.