Gas bearing piston assembly

Claim 1

A piston assembly for reciprocating movement within a cylinder to form a variable volume chamber containing fluid gas under varying pressure conditions comprising: (A) a piston body having a peripheral wall shaped to form a slight clearance space with an interior wall of the cylinder when said piston body is co-axially positioned for reciprocating movement within the cylinder, said piston body containing an annular recess formed in said peripheral wall and opening toward the interior wall of the cylinder; (B) a source of gas under pressure including a gas reservoir chamber contained in said piston body and gas trapping means for allowing gas to flow from the variable volume chamber into said gas reservoir chamber when the gas pressure in the variable volume chamber is above the gas pressure within said gas reservoir chamber and for impeding reverse flow when the gas pressure in the variable volume chamber is below the gas pressure within said gas reservoir chamber; and (C) bearing means for generating a gas layer within the clearance space between said piston body and the interior wall of the cylinder to hold said peripheral wall out of contact with the interior wall of the cylinder during reciprocating movement of said piston assembly, said bearing means including a radially expandable and compressible ring formed in equal arcuate segments extending end-to-end around said piston body positioned within said annular recess in contact with the gas layer, said bearing means further including gas flow restriction means in communication with said source of gas for establishing a controlled flow of gas into the gas layer to cause the gas layer to impart a radially inwardly directed force on said ring which varies circumferentially between limits in inverse proportion to the radial thickness of the corresponding circumferential portion of the gas layer, biasing means for imparting to said ring an outwardly directed radial force having a magnitude intermediate the magnitude limits of said radially inwardly directed force imparted to said ring by the gas layer to cause each circumferential portion of said ring to seek such a force balanced radial position, wherein said biasing means includes gas pressure means for subjecting a predetermined area of an interior surface of each said ring segment defined by a pair of annular resilient seals positioned between said piston body and each said ring segment to provide a predetermined radially outward bias to each said ring segment to gas pressure from said reserovir chamber, and joint sealing means for rendering the end-to-end joints between adjacent ring segments substantially impervious to radial gas flow, wherein each said joint sealing means includes an interior insert spanning circumferentially between said segments and extending axially between said resilient seals and further includes an exterior insert assembly spanning circumferentially between said segments and extending axially along the entire axial extent of said piston segments.