Screw cap

Claim 1

IN COMBINATION WITH A CONTAINER HAVING AN EXTERIORLY THREADED NECK WITH A MOUTH THERETHROUGH, A UNITARY, INTERNALLY THREADED CAP CONSISTING ESSENTIALLY OF A SYNTHETIC PLASTIC MATERIAL HAVING A STIFFNESS WITH THE RANGE FROM ABOUT 50,000 TO 150,000 POUNDS PER SQUARE INCH AND ADAPTED TO FIT OVER SAID NECK AND CLOSE SAID MOUTH, THE CAP HAVING A SIDE WALL, A TOP WALL COMPRISING AN ANNULAR WALL PORTION EXTENDING INWARDLY FROM THE SIDE WALL, SAID ANNULAR WALL PORTION HAVING A LOWER ANNULAR SURFACE PORTION, AND AN INTERNAL SEALING RING INTEGRALLY FORMED WITH AND PROTRUDING FROM THE INNER SURFACE OF THE TOP WALL AT THE INNER PORTION OF THE ANNULAR WALL PORTION THEREOF, SAID RING PROTRUDING FROM SAID INNER SURFACE A DISTANCE WHICH IS A MINOR FRACTION OF THE INTERNAL DEPTH OF THE CAP AND BEING RELATIVELY MORE FLEXIBLE THAN SAID ANNULAR WALL PORTION, SAID RING BEING THINNER THROUGHOUT ITS HEIGHT THAN SAID ANNULAR WALL PORTION, SAID RING HAVING DOWNWARDLY CONVERGING FRUSTRO-CONICAL INNER AND OUTER SURFACES, SAID RING LOWER ANNULAR SURFACE PORTION HAVING A SIZE AND CONFIGURATION RELATIVE TO THE SIZE AND CONFIGURATION OF THE NECK OF THE CONTAINER SO THAT, AS THE CAP IS POSITIONED ON THE NECK OF THE CONTAINER BY ROTATION AND THE THREADS OF THE CAP ENGAGE WITH THE THREADS OF THE CONTAINER, THE CONTAINER NECK IS IN CONTACT AT ITS TOP INNER EDGE WITH THE OUTER SURFACE OF THE RING BEFORE THE CAP IS FULLY SEATED AND WHEN THE CAP IS FULLY SEATED THE RING IS SLIGHTLY COMPRESSED, THE TOP INNER EDGE OF THE CONTAINER NECK IS SEATED FIRMLY AGAINST THE BASE PORTION OF THE RING, AND THE TOP OF THE NECK IS SEATED FIRMLY AGAINST SAID LOWER ANNULAR SURFACE PORTION.