US Patent 7757892 Closure device for closed receptacles of plastic film

A closure device attachable above a location of a closed receptacle, comprising a stopper portion with a cylindrical pour-out spout connected or connectable to the receptacle, and a screw cap screwed onto the lower part, and a cylindrical piercing element that in the axial direction is open at both sides and is displaceably mounted in the lower part, wherein catch portions move the piercing element helically downwards when screwing off the cap for the first time, wherein the piercing element is equipped with at least one cutting element.