Hot knife for slitting and welding tubular thermoplastic film - where the curved blade profile can be set to suit various materials

摘要

A cutting device for simultaneously slitting and welding >=2 superimposed layers of thermoplastic film, where the film is led over a convex curved sheet which is slotted to allow a heated knife to project through a slot in the sheet. The knife has a radiused edge and can pivot about a locus which is not co-incident with te focus of the radius of the curved surface. The degree to which the knife can project through the curved sheet is adjustable. Esp. used for conversion of tubular thermoplastic tubing into subsidiary tubing of reduced width and having parallel welded seams. The knife cuts and welds in a single pass. The sheet paths progressively diverge from the leading edge of the cutter and disengage smoothly from the trailing edge. The effective blade root can be adjusted to suit the elasticity and haul-off tension of different film materials. The curved film path maintains film/blade contact.