Screw-on container cap with perforating prong - has flexible flange between threaded cap and surrounding skirt

摘要

The screw-on cap for a container has a perforating spike to burst a sealing disc (16) across the container opening at the time of first opening. The perforating element (22) is mounted in the centre of the screw-on cap (20, 21) which is attached to a surrounding skirt (24) by a thin flexible flange (26). This flexible flange is deformed to a conical shape (26') when the skirt and cap are rotated. The flexible element can be of a conical shape before deformation, the surface sloping upwards towards the centre. Alternatively the flexible element can be between the cap and a liner inside the skirt the screw cap and perforator moving on a short shaft.