Patent ID: 7730866

Claim:
A sealing device for a piston for an alternating internal combustion engine or alternating compressor, designed to move in alternating linear movement parallel to an axis of a circular cylindrical sliding surface of a chamber divided by the piston into a high pressure volume and a low pressure volume, the sealing device comprising: a sliding surface partly bounding the chamber, and defining a perimeter, an annular groove provided in the piston which is coaxial with the sliding surface and opened towards the sliding surface, a closed resilient metallic sealing ring having a uniform cross section and a sealing bearing surface, the ring being housed within the groove in leak tight fashion, and being in sealing contact with the sliding surface, through said sealing bearing surface, said sealing bearing surface having a perimeter, said perimeter of said sealing bearing surface in the free state being slightly greater than the perimeter of the sliding surface so that the sliding surface imparts permanent resilient compression deformation on the ring which brings about a substantially uniform bearing pressure between the bearing surface and the sliding surface when the ring is resiliently held tightly against the latter, and a lubricating oil film between the ring and the sliding surface which is sized by the ring to a limit lubricating thickness of 0.1 μm to 1 μm when the ring moves from the high pressure volume to the low pressure volume.