METHOD OF EXTRUDING A THERMOPLASTICS TUBULAR FILM HAVING PERFORATIONS, AND APPARATUS FOR PERFORMING THIS METHOD

摘要

1. Process embodying the extrusion of a sheath of thermo-plastic material (17) in the form of a tubular film containing perforated sectors, type in which the film from extrusion and still in the plastic state is applied to a skirting (18) crossed through by ducts distributed over its circumference and communicating with an inner chamber (32) containing a pressurized gas, a part of the ducts (30) intermittently blowing initial jets of gas such as hot air with physical characteristics so that the pressure of flow rate cause perforation of the sectors of the film designed to be perforated, process characterized in that another sector of the ducts (30') is designed to intermittently blow second jets of gas or air with lower physical characteristics so that these jets leave unperforated the sectors of the film designed to remain unperforated, the second jets blowing the air occupying the interface between the film and the outer wall of the skirting.This air cushion avoiding contact between the film and the said walls, thus enabling the film to flow continously along this wall.