US Patent 7185582 Oilless reciprocating fluid machine

An oilless reciprocating fluid machine has a piston mounted to a connecting rod by inserting a piston pin in a pin bore of a cylinder. The piston is reciprocally moved up and down in the cylinder with reciprocating of the connecting rod. A reinforcement plate is embedded in the top wall of the piston or attached on the lower surface of the top wall to increase strength of the piston. The reinforcement plate may be formed in various shapes.