Screw-type bottle cap having improved sealing properties

Claim 1

In a screw-type bottle cap molded in one piece from plastic material and comprising an internal sealing skirt depending from the top of said cap and adapted to be force-fitted into the externally threaded neck of a bottle, a first sealing lip concentric with said skirt and positioned to engage the upper end of the neck of said bottle when said cap has been screwed home, and a second sealing lip adapted to cooperate with the upper outer surface of said bottle neck, the improvement according to which said sealing skirt comprises a short upper portion having a slight outward conicity when unstressed, and the external diameter of which, at its connection to the top of said cap, is greater than the maximum internal diameter of said neck, allowing for manufacturing tolerances, said upper portion merging into a central portion having an inward conicity, and terminating in a substantially radial collar, the periphery of which is adapted to bend upwardly as the cap is screwed down to form an additional seal with the inner surface of said bottle neck, and said second sealing lip is circular, circumferentially continuous, and adapted to cooperate with a smooth portion of said bottle neck above the threads thereon.