Studded drum for hot perforation of thermoplastic film - to produce holes with thickened, smooth tear resistant borders

摘要

Appts. for continuously perforating thermoplastic film comprises a rotating drum provided with heated studs and partially enclosed by a shroud which controls the film/drum clearance. The shroud is slightly eccentric relative to the drum axis and is evacuated so that the film path makes tangential contact with the stud crowns so as to be softened before being perforated as the shroud/drum clearance progressively reduces. Suitable for producing holes with slightly thickened and smooth fused borders. Produces holes more quickly than hot air jet drills and with higher tear resistance than cold puncture borders.