Patent ID: 8555849

Claim:
A piston for an internal combustion engine comprising: a piston crown; a cylindrical side wall; and an annular piston ring groove being formed in the cylindrical side wall which accommodates an annular spring, wherein the annular spring comprises a single annular radially extending portion, a first projection, and a second projection, wherein the annular radially extending portion divides the annular piston ring groove into only two chambers in an axial direction of the piston, wherein an upper chamber closest to the piston crown accommodates an annular compression ring, wherein a lower chamber furthest from the piston crown accommodates an annular oil scraper ring, wherein the first projection is arranged to contact an upper surface closest to the piston crown of the annular piston ring groove, wherein the second projection is arranged to contact an inner surface of the annular oil scraper ring to urge it outwardly, and wherein a clearance exists between the compression ring and the upper surface of the annular piston ring groove closest to the piston crown extending from an inner surface of the compression ring to an outer surface of the compression ring, and wherein a clearance exists between the first projection and the inner surface of the compression ring whereby the first projection does not contact the inner surface of the compression ring, whereby in use, a pressure acting on the piston crown will act also on the inner surface of the compression ring and urge it in an outward direction.