Machine and process for capping and sealing containers

Abstract

A machine for applying lids to containers and for further heat sealing a metal foil membrane to each container beneath its lid includes a main conveyor and a timing screw at the feed end of the conveyor for releasing open top containers onto the conveyor at equally spaced intervals. As the containers move along the main conveyor, captivator blocks, which are carried on synchronized chains located at each side of the main conveyor, converge toward and close upon the side walls of the containers so as to confine the containers in the horizontal direction while they move along the main conveyor. Lids are applied to the containers at a lid applicator while the containers are gripped by the captivator blocks. Thereafter the containers pass beneath an overhead belt and the lower pass of this belt is backed by a pair of skid plates and a plurality of rollers, with the rollers being interposed between the two skid plates. An induction coil creates a magnetic field beneath the rollers, and this field is of sufficient intensity to elevate the temperature of each foil membrane to above the point at which the membrane will bond to the rim of its container. As each container passes beneath the first skid plate, the force applied to the lid squeezes the membrane against the container rim with a constant force and excludes foreign particles from the interface. Thereafter the membrane is heated and as it is heated, the rollers apply an undulating force to the membrane, causing the heated membrane to seal snugly against the rim of the container. Finally the second skid plate applies a constant force to the membrane and holds it down against the container rim, allowing the membrane to bond to the rim as the membrane cools.