Importance

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Abstract

An apparatus for compressing a gas includes a preferably substantially vertically oriented cylinder body, having a longitudinally extending bore with a wall, and a preferably substantially vertically oriented piston adapted for reciprocating movement in the cylinder bore. The piston includes a piston head preferably having a substantially horizontally oriented top face and a seal groove extending around the periphery of the piston head and spaced from the piston head top face. At least one fluid passage extends in the piston head from the top face thereof to the seal groove. A seal member is positioned in the groove and has an outer face adapted to contact the cylinder inner wall. A layer of a lubricant is provided on the piston head top face. An inlet aperture is provided for allowing a gas to enter the cylinder above the piston head. A movement member is provided to urge the piston upwardly and compress the gas. This pressurizes the lubricant, a portion of which flows through the fluid passage and into the seal groove to urge the seal member against the cylinder bore wall.

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First Claim