Cap for containers

Claim 1

A CONTAINER CAP STRUCTURE, EMBODYING THE COMBINATION, WITH A CONTAINER HAVING A CIRCULAR TOP PORTION WITH AN EXTERNAL DOWNWARDLY FACING SHOULDER, OF A HOLLOW LID MEMBER HAVING A DOME-SHAPED TOP WALL AND A DEPENDING OUTER CIRCULAR WALL ADAPTED TO FIT OVER THE UPPER PORTION OF THE CONTAINER, SAID LID MEMBER BEING COMPOSED OF AN ELASTICALLY FLEXIBLE MATERIAL AND HAVING AN INTERNAL FLANGE ON THE OUTER CIRCULAR WALL BELOW THE DOME TOP ADAPTED TO FORCIBLY CONTRACT UNDER THE CONTAINER SHOULDER, AN INTERNAL HOLLOW FORMATION RIGIDLY ATTACHED TO AND DEPENDING FROM THE LID DOME WALL, SPACED INWARDLY OF THE LID OUTER WALL, AND SPACEDLY ENTERING THE TOP PORTION OF THE CONTAINER, MEANS CAUSING RADIAL EXPANSION OF THE LOWER PORTION OF SAID DEPENDING FORMATION UPON FORCIBLE FLATTENING OF THE LID TOP WALL, INTER-ENGAGEABLE FORMATIONS INTERNALLY ON THE TOP PORTION OF THE CONTAINER AND EXTERNALLY ON THE LOWER PORTION OF SAID DEPENDING FORMATION, ADAPTED TO BE INTER-ENGAGED BY EXPANSION OF SAID LOWER PORTION, AND AT LEAST ONE OF SAID INTER-ENGAGEABLE FORMATIONS BEING OF THE NATURE OF A HELICAL SCREW THREAD, WHEREBY, WITH SAID INTER-ENGAGEABLE FORMATIONS HELD IN INTER-ENGAGEMENT, RELATIVE ROTATION OF THE LID WILL FORCE THE LID UP AND FORCIBLY PULL THE INTERNAL FLANGE OF ITS OUTER WALL FREE OF ITS CONTRACTIVE ENGAGEMENT UNDER THE CONTAINER SHOULDER.