Compressor employing piston-ring check valves

A compressor that forms a compressor inlet and compressor outlet, draws fluid in through the compressor inlet, compresses fluid thereby drawn thereinto, drives the fluid thus compressed from the compressor outlet, and includes:

• A) a piston-chamber wall that extends axially to define a piston chamber with which the compressor inlet and outlet communicate;
• B) at least one piston disposed within the piston chamber and axially slidable with respect to the piston-chamber walls;
• C) a piston driver that causes each piston to travel alternately in upstream and downstream directions;
• and
• D) a piston ring associated with each piston, forming a sliding seal with the piston-chamber wall, and retained on that piston for limited axial movement with respect thereto between an upstream position, in which it so seals against the downstream face of the piston with which it is associated as to cooperate therewith to prevent fluid flow between the portions of the piston chamber upstream and downstream of the piston, and a downstream position, in which it is so spaced from the downstream face of the piston with which it is associated as to leave a fluid-flow path by which the portions of the piston upstream and downstream of the piston communicate, whereby the piston tends to move through the fluid in the piston chamber when the piston is moving upstream but tends to compress fluid in the portion of the piston chamber downstream thereof when the piston is moving downstream.