METHOD FOR FORMING STRAIGHT HEAT SEAL PART IN PLASTIC FILM MADE BAG WITH ZIPPER

摘要

PURPOSE: To prevent an ugly appearance of the formation of a contracted seal line in the manufacture of a plastic-made product such as a zipped bag of thermoplastic film by heat-sealing a film with a zipper. CONSTITUTION: This is a method and a device to recover the initial length of the contracted seal line S by undulating and extending it between the teeth 21a and 22a of the corresponding gears, and further to re-extend the seal part without undulations.