Piston,especially for compression ignition engines

Claim 1

A piston, especially for an internal combustion engine of automatic ignition type, piston ring grooves formed in said piston, and piston rings mounted in said grooves and slidably engaging the wall of the cylinder in which the piston slides, one of said rings comprising an oil control ring having at least one scraper edge moving along the cylinder wall, spring means biasing said oil control ring radially outwardly on said piston, an annular space between the radially inner side of said oil control ring and the bottom of the groove in which said oil control ring is disposed, aperture means extending radially through said oil control ring for the flow of oil into said annular space, and means forming an oil return flow system for said piston comprising passage means inclined downwardly and leading from said annular space toward the periphery of said piston at the end thereof remote from the end of the piston facing the combustion chamber, said passage means at the end remote from said annular space terminating in an annular recess formed in said means forming the oil return flow system and opening radially outwardly, and a conical skirt portion forming the end of said piston and having a downwardly extending circumferential outer conical surface defining a wall of said annular recess and a downwardly extending inner conical surface, said inner and outer conical surfaces terminating in an edge defining a restricted clearance with the cylinder wall.