Piston ring assembly

Claim 1

IN A PISTON RING ASSEMBLY ADAPTED TO BE INSTALLED IN AN ANNULAR GROOVE FORMED IN A PISTON OF OF AN INTERNAL COMBUSTION ENGINE AND INCLUDING A PAIR OF ANNULAR RAILS, AN ANNULAR SPACER-EXPANDER FOR FORCING THE RAILS OUTWARDLY, SAID SPACER-EXPANDER COMPRISING A PLURALITY OF CIRCUMFERENTIALLY SPACED AXIALLY EXTENDING SUPPORT MEMBERS, AND A PLURALITY OF U-SHAPED SPRING MEMBERS CONNECTING SAID SUPPORT MEMBERS FOR CIRCUMFERENTIALLY EXPANDING SAID SPACER-EXPANDER, EACH OF SAID SPRING MEMBERS INCLUDING A PAIR OF ARMS CONNECTED AT THEIR OUTER ENDS BY AN INTERMEDIATE PORTION WHICH EXTENDS AXIALLY TO SUPPORT SAID RAILS ADJACENT THEIR OUTER PERIPHERIES, THE INNER ENDS OF SAID ARMS BEING CONNECTED TO ADJACENT SUPPORT MEMBERS, AND SAID SPRING MEMBERS EXTENDING RADIALLY OUTWARD FROM SAID SUPPORT MEMBERS, EACH ARM OF EACH OF THE SAID SPRING MEMBERS INCLUDING AN INNER PORTION WHICH DECREASES ION CROSS SECTION FROM SAID SUPPORT MEMBERS TO SUBSTANTIALLY THE MIDPOINT OF SAID ARM, AND AN OUTER PORTION WHICH INCREASES IN CROSS SECTION FROM SUBSTANTIALLY SAID MIDPOINT TO SAID INTERMEDIATE PORTIONS, BOTH OF SAID ARM PORTIONS HAVING A SUBSTANTIALLY UNIFORM STRESS CONDITION THROUGHOUT THE LENGTH THEREOF UNDER LOAD, AND THE AREA AT EACH SECTION OF EACH OF SAID ARM PORTIONS CORRESPONDING SUBSTANTIALLY TO THE MOMENT IMPOSED ON THAT SECTION, SAID INNER AND SAID OUTER PORTIONS OF EACH ARM WHEN TAKEN TOGETHER APPROXIMATELY A PAIR OF TRIANGLES, WITH THEIR APEXES JOINED IN SAID MIDPOINT REGION, THE MIDPOINT REGION OF EACH OF SAID ARMS HAVING A SHAPE AND SIZE JUST SUFFICIENT TO MAINTAIN THE