Abstract: A sealing apparatus for a square piston used for compressing and feeding a fluid is applied to equipment used for compressing or feeding the fluid on the basis of a new concept, and maintains a perfectly sealed state to thus guarantee stable operation of the equipment. The sealing apparatus includes a first sealing member having upper, lower, left-hand and right-hand sides and a first square hole in contact with the square piston, a second sealing member having upper, lower, left-hand and right-hand sides and a second square hole in contact with the square piston, first and second elastic means disposed on the upper and right-hand sides of the first sealing member and installed in a cylinder housing, and third and fourth elastic means disposed on the lower and left-hand sides of the second sealing member and installed in the cylinder housing.

Abstract: A two ring piston and piston ring assembly has an upper thin steel compression ring and a lower ring which is thicker than the compression ring and which acts both as a compression ring and an oil control ring. The lower piston ring is made of a material which is more conformable than steel, for example a plastics material, which may be reinforced. In this way, effective sealing is provided using only two piston rings, while the frictional forces between the piston and an associated cylinder are reduced.