Expandable ring closure device

Abstract From the Canadian patent

A closure device for severing the frangible section between the cap and body of a blow-fill-seal plastic container comprising an expandable ring constructed and arranged to encircle the container cap an outer ring having at one end internal threads compatible with the external threads located on the neck of the container body and a tamper proof overcap. Counterclockwise rotation of the outer ring transmits uniform upward pressure to the expandable ring which causes tension between the container cap and container body, rupturing the frangible line of weakness on the container, to permit opening of the container. Conversely clockwise rotation of the outer ring causes compression to rupture …