Fremgangsmåte og anordning for helisk skjæring av en fleksibel, rörformet folie av polymermateriale

摘要

PCT No. PCT/GB89/00712 Sec. 371 Date Jan. 11, 1991 Sec. 102(e) Date Jan. 11, 1991 PCT Filed Jun. 26, 1989 PCT Pub. No. WO89/12533 PCT Pub. Date Dec. 28, 1989.Flexible tubular film is helically cut into a flat strip by feeding the tubular film in flattened form from a supply source to a film feeding means advancing the flat film tube at a predetermined velocity to a tube expansion zone in which the flat tube is expanded into a generally cylindrical tube and passed axially over a hollow mandrel slightly less in external diameter than the diameter of the expanded tube to be cut helically while on the mandrel into a flat strop that is removed at an angle to the mandrel axis. The tube is expanded in the zone by inflation with air fed through the mandrel in a direction countercurrent to the direction of tube movement and under a pressure sufficient to render the expanded tube stiff as it slides over the mandrel and resistant to deformation while being helically cut. The advance and expansion of the flat tube in the expansion zone is positively controlled by moving surfaces contacting the film, which surfaces define a diverging expansion zone and are driven at a velocity substantially at least as great as the predetermined velocity of advance of the flat film tube to the expansion zone.