Clamped-wave lid seal structure

Abstract

An article is disclosed comprising a lid engaged to a container by the formation of interlocking waves of lid material and container material at the junction of the lid and container. The interlocking waves are geometrically aligned relative to the interior of the container so as to maximize the burst strength of the container, and also to minimize the force required to peel the lid from the container. An unheated clamp head is used to clamp the lid structure immediately adjacent a heated seal head, the heated seal head being used to form the interlocking wave structure around the inside rim of the container. The clamp head prevents any melted portions of the container or lid from flowing to or towards the outside rim of the container, and thereby prevents the formation of similar interlocking waves about the outside rim of the container. Elimination of the interlocking waves about the outside rim of the container yields a clamped-wave seal structure having reduced peel initiation forces and reduced average peel forces, without affecting the resistance of the container/lid system to high burst pressures typically encountered under retort conditions.