Piston ring assembly with improved bearing contact

Claim 1

IN A PISTON RING ASSEMBLY OF THE CHARACTER WHEREIN, (A) A PAIR OF RAILS WHOSE OUTER PERIPHERY MAKE EDGEWISE ENGAGEMENT WITH A CYLINDER WALL AND ARE AXIALLY SEPARATED BY A NON-BOTTOMING SPACER-EXPANDER, (B) SAID SPACEREXPANDER HAVING A SERIES OF OPPOSITELY ORIENTED HUMPS SOME OF WHOSE CRESTS DEFINE A MAJOR DIAMETER LESS THAN THE OUTER DIAMETER OF SAID RAILS AND OTHER OF WHOSE CRESTS DEFINE A MINOR DIAMETER LESS THAN THEDIAMETER OF AN INNER PERIPHERAL EDGE ON SAID RAILS, (C) SAID FIRST MENTIONED HUMPS EXTENDING BETWEEN SAID RAILS TO SEPARATE THE SAME, AND (D) AT LEAST SOME OF SAID LAST-MENTIONED HUMPS HAVING AN ARCUATE TAB EXTENDING RADIALLY INWARDLY OF SAID RAILS IN AXIALLY OVERLAPPING ENGAGEMENT WITH AN INNER PERIPHERY ON ONE OF SAID RAILS, THE IMPROVEMENT WHICH COMPRISES: (1) THE LOCUS OF ENGAGEMENT BETWEEN A TAB AND A RAIL BEING DEFINED BY A RE-ENTRANTLY ARCUATE SURFACE ON THE TAB ENGAGING THE RAIL, SAID RE-ENTRANTLY ARCUATE SURFACE BEING ON A RADIUS LESS THAN THE INTERNAL RADIUS OF THE RAIL FROM A CENTER LOCATED WITHIN THE INNER PERIPHERY OF THE RAIL.