| 摘要 |
<p>A web of synthetic plastics film, having a series of panels separated by longitudinally spaced transverse zones of weakness extending across the width of the web. The zones of weakness are constituted by a series of heat-produced perforations along the lengths of the zones. Adjacent perforations are separated by unperforated portions of the web. When the web is a double layer then the panels are in the form of bags, the layers being sealed at the sides of the bags at the perforations in the zones of weakness. A machine for making the web, causes a web of synthetic plastics material to pass longitudinally past a transverse hot cutting and welding edge which cyclicly intersects the web at longitudinally spaced intervals. The hot cutting and welding edge has a series of interruptions along its length.</p> |
