| 摘要 |
<p>A softened unperforated film and a perforated die which is generally cylindrical in movement are brought into contact and exposed, in a predetermined region, to a pressure gradient oriented radially of the die. The pressure gradient causes the local penetration of the film into the holes of the die and the consequent perforation of the film itself. The movement of the die is supported in a rigid manner solely upstream and downstream of the predetermined region in the common direction of movement of the film and the die. The die itself is subjected to a pulling action, along its generatrices at least close to the predetermined region.</p> |
