Abstract: The described air compressor has an annular piston received within a cylinder for reciprocal movement to drive pressurized air on both piston strokes to an outlet which is arranged in line with the air inlet and driving power source. A shuttle valve alternately opens and closes ports at opposite ends of the pump cylinder to accomplish valving for the pressurized air. Rotative drive applied to an axially located rotor within the compressor housing via a planetary gear assembly alternately drives the rotor in opposite directions. A gear on the rotor is drivingly related to gears located on two threaded shafts which pass through threaded openings in the piston. Accordingly, rotation of the rotor drives the annular piston from one extremity to another in the pump cylinder.

Abstract: An annular piston is received within a suitably dimensioned cylinder and reciprocally driven to pump fluid on both piston strokes to a fluid carrying line with which the pump is arranged in an in-line relationship. A centrally located shuttle-valve alternately opens and closes ports at opposite ends of the pump cylinder to accomplish the required in-line valving for the pump.

Abstract: The present invention relates generally to an improved fluid compressor and, more particularly, to such a compressor driven by a hydraulic motor, the working liquid of which serves as a coolant for the compressed fluid.