Abstract: The annular expander of a piston ring assembly with vertically extending notches each of which is formed on either side of a plurality of circumferentially spaced upstanding tabs projecting from the top and bottom edges of the expander. The tabs, which form the abutments for the inner peripheral edges of upper and lower annular side rails, the outer peripheral edges of which are in sliding contact with a cylinder wall, undergo elastic deformation made possible by the notches when the corresponding side rails are subjected to a strong force received from the cylinder wall owing to piston wobble during reciprocation. The elastic deformation of the tabs assures that the side rails will remain in contact with the cylinder wall at all times during the reciprocation of the piston.

Abstract: A piston ring assembly including a pair of rails engageable with a cylinder wall and a spacer and expander member for holding and expanding the rails. The spacer and expander member has a corrugated base and arms extending alternately upwardly and downwardly from lower and upper crowns of the corrugated base, which arms are inclined radially outwardly to provide an improved resilient spring-like action to the rails supported on the crowns.

Abstract: A rotary piston internal combustion engine has a rotor journalled on an eccentric portion of an engine shaft. A sealing arrangement comprises a first radially extending annular face connected to the engine shaft, a disc connected to the rotor and having a second radially extending annular face, and a sealing ring disposed between the first and second faces. A spring biases the sealing ring to maintain sealing contact of the sealing ring with one of the first and second faces. An O-ring is disposed between the sealing ring and that one of the rotor and engine shaft which is in rotatable unison with the other one of the first and second faces.