Sealing arrangement for piston in compressor

A sealing arrangement for a piston in a compressor having a cylinder block with a cylinder bore having an inner surface, formed therein to axially displaceably accommodate said piston, and a cylinder head attached to said cylinder block for forming a compression chamber on one side of said piston, the sealing arrangement comprising:

• a ring groove on an outer surface of said piston and comprising opposite side surfaces and a bottom surface between the side surfaces having first and second adjacent cylindrical portions;
• and
• a discontinuous ring seal member made of a plastic material and fitted in said ring groove and comprising,
• a main sealing portion having a main sealing outer surface and a pair of flexible lip portions arranged on opposed sides of said main sealing portion and outwardly circumferentially projecting from said main sealing outer surface,
• an inner surface comprising an inner bearing portion adapted to contact said first cylindrical portion of said bottom surface of said ring groove whereby said flexible lip portions contact the inner surface of said cylinder bore and are prestressed inwardly when said inner bearing portion contacts said first cylindrical portion, and
• an inner pressure receiving portion contiguous with said inner bearing portion wherein said inner pressure receiving portion faces said second cylindrical portion and provides a clearance between said inner pressure receiving portion and said second cylindrical portion while said inner bearing portion contacts said first cylindrical portion to receive pressure from said compression chamber, to thereby allow said ring seal member to expand and said main sealing outer surface to contact the inner surface of the cylinder bore.