Patent ID: 6761675
Filing Date: 2004-07-13
Classification: B29C,B31C,B65D

Abstract:
A method of making multi-ply tubular containers for products, comprising the steps of:advancing a continuous unsupported polymer film liner strip toward a shaping mandrel, the liner strip including a layer of heat-activated sealing material covering at least a first edge portion of the liner strip and a layer of a compatible polymer material to which the sealing material is adherable covering at least an opposite second edge portion of the liner strip, the sealing material having a predetermined sealing temperature at which said material is activated to bond to the compatible polymer material, the compatible polymer material having a melting temperature higher than the sealing temperature of the sealing material; wrapping the liner strip around the mandrel with the sealing material on the first edge portion of the liner strip facing outward and the compatible polymer material on the second edge portion facing inward toward the mandrel, and overlapping the first edge portion by the second edge portion to form an overlap joint therebetween having the sealing material on the first edge portion in contact with the compatible polymer material on the second edge portion, the wrapped liner strip forming a tubular liner having an outer surface; preheating the liner strip at a first heating station such that while the edge portions are overlapped to form the overlap joint the sealing material reaches an elevated temperature below the predetermined sealing temperature, said preheating being accomplished by internally heating at least that portion of the mandrel onto which the liner is wrapped to a temperature below the predetermined sealing temperature of the sealing material; applying heat locally to the overlap joint of the tubular liner at a second heating station to further raise the temperature of the sealing material to at least the predetermined sealing temperature and cause the sealing material to bond to the compatible polymer material; and wrapping a continuous paperboard body strip around the tubular liner and adhering the body strip thereto so as to create a tubular container.