Heat-shrinkable film tube with an internally ribbed closed end, and a method of making it

Abstract

A method for forming a closed end on a tube of heat-shrinkable film wherein the tube is placed over a cylindrical mold with one end of the tube extending beyond top end of the mold, includes forming a pattern of grooves in the mold's top end, and then heating the tube so that it shrinks and tightly contacts and covers the grooved end of the mold. Excess film protruding from the end of the tube which has shrunk against the grooved end of the mold is cut off or folded down and then this end of the tube is pressed with a heated smooth plate against the grooved end of the mold. Excess film material remaining on this end portion of the tube is squeezed into the grooves, whereby the end of the film tube is formed with a uniform thickness and with low thermal stresses thereby reducing any tendency for distortion of the closed end and providing a surface that can be more easily printed on.

Dependencies are inferred from the claim text.