Plastic sheet material useful for packaging and packaging made from such sheet material and related methods

摘要

A method of driving a film formed into a tube about a vertical forming tube (48) of a vertical form, fill and seal machine, along said vertical forming tube (48). The film carries, at regular bag length intervals, a reclosable zip (6) extending transversely about a semicircle of the tube (48) having distal end portions located substantially diametrically opposite each other. The driving means comprises two endless flexible members (49) positioned adjacent to the tube and diametrically opposite, wherein the film is engaged therebetween and driven downwards. The flexible members (49) have a recess to accommodate the different thickness of the film material provided by the reclosable zip.