Piston and fire ring construction

Claim 1

IN COMBINATION: A PISTON ADAPTED FOR RECIPROCATION IN AN INTERNAL COMBUSTION ENGINE CYLINDER, SAID PISTON HAVING A TRANSVERSE END SURFACE ADAPTED TO FROM A MOVABLE WALL OF THE CYLINDER COMBUSTION CHAMBER, A CYLINDRICAL PERIPHERAL SURFACE HAVING A PLURALITY OF CIRCUMFERENTIAL GROOVES THEREIN SPACED AXIALLY FROM ONE ANOTHER AND FROM SAID END SURFACE INCLUDING FIRST AND SECOND GROOVES RESPECTIVELY CONSTITUTING THE CLOSEST AND NEXT CLOSEST GROOVES TO SAID END SURFACE OF SAID PLURALITY OF GROOVES, AND A HEAD LAND BOUNDED BY SAID END SURFACE AND SAID SECOND GROOVE; A SET OF PISTON RINGS INDIVIDUALLY DISPOSED IN ALL BUT SAID FIRST GROOVE OF SAID PLURALITY OF GROOVES INCLUDING A PARTED FIRST COMPRESSION RING DISPOSED IN SAID SECOND GROOVE HAVING A FREE STATE OUTSIDE DIAMETER GREATER THAN THE DIAMETER OF THE CYLINDER WHEREBY SAID COMPRESSION RING IS ADAPTED TO BE RADIALLY COMPRESSED BY THE CYLINDER WALL TO DEVELOP COMPRESSION SEALING CONTACT THEREWITH; AND A PARTED FINE RING DISPOSED IN SAID FIRST GROOVE AND CONSITUTING THE SOLE RING ELEMENT DISPOSED IN FIRST GROOVE, SAID FIRE RING BEING DIMENSIONED AXIALLY RELATIVE TO SAID FIRST GROOVE TO PROVIED A PREDETERMINED AXIAL CLEARANCE THEREBETWEEN SUFFICIENT TO PERMIT SAID FIRE RING TO DISH AND MOVE AXIALLY IN SAID FIRST GROOVE IN RESPONSE TO PISTON RECIPROCATION IN THE CYLINDER, SAID FIRE RING HAVING A FREE STATE INSIDE DIAMETER GREATER THAN THE ROOT DIAMETER OF SAID FIRST GROOVE TO PERMIT ROTATION OF SAID FIRE RING RELATIVE TO THE PISTON IN RESPONSE TO PISTON RECIPROCATION AND SAID FIRE RING HAVING A FREE STATE OUTSIDE DIAMETER SUBSTANTIALLY EQUAL TO THE DIAMETER OF THE CYLINDER SUCH THAT SAID FIRE RING HAS A RELATIVELY LOW UNIT PRESSURE CONTACT WITH THE CYLINDER WALL COMPARED TO THAT OF SAID FIRST COMPRESSION RING WHEREBY SAID FIRE RING HAS A MERE WIPING RATHER THAN SEALING CONTACT WITH THE CYLINDER WALL.