Sealing arrangement for a piston in a compressor

A sealing arrangement for a piston in a compressor having a cylinder block with a cylinder bore formed therein to axially displaceably accommodating 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:

• means for forming a ring groove on an outer surface of said piston, said ring groove comprising opposite side surfaces and a bottom surface between the side surfaces;
• a continuous seal ring member fitted in said ring groove, said seal ring member having an initial shape provided with an internal diameter smaller than an outer diameter of said outer surface of said piston, an inner peripheral portion, and an outer peripheral portion whereby at least said inner peripheral portion is expanded when said seal ring member is fitted in said ring groove beyond said outer surface of said piston and said outer peripheral portion is axially and inwardly collapsed relative to said inner peripheral portion so that one of said side surfaces of the initial seal ring member constitutes an outer sealing surface for engagement with an inner surface of said cylinder bore and said outer peripheral portion in the original shape is arranged on the side of said compression chamber;
• and
• a backup ring member fitted in said ring groove on the side of said continuous seal ring member remote from said compression chamber, said backup ring member having a surface area abutting against said side surface of said ring groove on the side remote from said compression chamber and sufficient to retain said continuous seal ring member in said ring groove.