Patent ID: 6264874
Filing Date: 2001-07-24
Classification: A22C,B29C

Abstract:
In a process of extruding a transparent molten tube of nonderivatized cellulose downwardly through an air gap and about a mandrel having a stem terminating in an enlarged lower portion for sizing the tube and the tube containing an internal bath of a clear liquid around the mandrel stem adjacent the enlarged lower portion, a method for controlling the diameter of the tube in the region of the air gap comprising:a) passing a refractable beam horizontally through the extruded tube at a selected level above the enlarged lower portion of the mandrel, the beam being in a plane offset from the mandrel stem to prevent blockage of the beam's passage and the beam passing in a straight line path through the extruded tube when the internal bath of clear liquid is below the level of the beam;b) refracting the beam from its straight line path when the internal bath of clear liquid rises to a level above the selected level of the beam responsive to a decrease in the diameter of the extruded tube wherein the extruded tube and clear liquid of the internal bath together define a cylindrical lens means that causes said refracting of the beam;c) introducing air under pressure into the interior of the extruded tube responsive to the refracting of the beam to increase the diameter of the extruded tube in the region of the air gap thereby lowering the level of the internal bath to a level below the selected level of the beam; andd) terminating the introduction of air into the extruded tube responsive to the straight line passage of the beam through the extruded tube.