Method for closing a heat-resistant carton

Abstract

A closing method for a multi-sided paperboard carton includes sealing a cover with side edge extensions to corresponding side flanges defined by fold lines on the paperboard carton during continuous feeding of the carton along the feed path. The side flanges of the carton body are bent downward during continuous feed movement with a force sufficient to cause the flanges to fold and remain free and below a plane passing through the fold line when released. The cover is placed on the carton to lie substantially in a plane and with the edge extensions overlying the flanges. A hot air stream is directed into the half-V gap presented between each flange and associated cover side edge extension to activate an adhesive coating and the flanges are pressed against the cover for sealing. The carton is carried through the bending stage in a die having an open bottom cavity and forming blades on its side edges that engage the fold line between the side flanges and the carton side panels from below. Platen members are presented for engagement with the blade edges of the die to bend and squeeze the flanges to create the downwardly bent orientation and facilitate sealing during continuous movement. The side flanges may be pre-broken and preheated to facilitate the bending and sealing operations downstream.