Patent ID: 6196827
Filing Date: 2001-03-06
Classification: B29C

Abstract:
An external stabilizer arrangement employed in a plastic film blowing apparatus in which a tubular die, fed with a supply of molten thermoplastic polymer, extrudes a tube of the molten polymer and which injects air into said extruded tube to inflate the tube and expand the tube into a film of a desired thickness; and wherein means are positioned above said die for drawing the tube vertically upward along a vertical axis and collapsing and flattening the film; the external stabilizer arrangement being positioned on a frame surrounding the extruded tube above said die to keep the tube aligned on a predetermined path as the tube is drawn upwards, and comprising a plurality of swing arms arranged on said frame to define an iris aperture, and means on said frame to swing said arms toward and away from said axis to reduce and increase the size of the aperture, such that said swing arms are pivoted only at ends thereof remote from the extruded tube; comprising the improvement wherein each said swing arm is formed as an elongated unitary extrusion of a light-weight material having a pivot end mounted pivotally on said frame and a free end remote from said pivot end, with a portion of the extrusion not axially offset from said pivot end and situated between said pivot end and said free end of said swing arm that contacts the extruded tube and defines said iris aperture, and said portion of the extrusion having a profile that is rounded on a side that faces the extruded tube so that said extrusion has a rounded front surface; and a wear resistant material disposed on said rounded front surface of said extrusion, such that said tube slides therepast.