Sealing device for engine piston

Claim 1

A sealing device for reciprocating type pistons of engines in which the piston has a piston ring installed into the piston-ring groove and is slidably fitted in the cylinder bore of the cylinder block, said sealing device comprising: a piston-ring groove cut in the outer periphery of the piston, having an outwardly expanding nearly V-shaped cross section and consisting of first and second annular inclined surfaces; a piston ring consisting of an annular inclined surface that abuts tightly against said first annular inclined surface of the piston-ring groove and an external sealing surface that abuts tightly against the cylinder wall; and an auxiliary ring having an annular inclined surface that bears against said second annular inclined surface of the piston-ring groove and also having a flat surface that bears against the piston ring, said auxiliary ring having a tendency to contract inwardly; whereby the auxiliary ring slides downwardly along the second annular inclined surface to cause the annular inclined surface of the piston ring to bear tightly against and slide outwardly along the first annular inclined surface of the piston-ring groove so that the external sealing surface of the piston ring is forced tightly against the cylinder wall.