Patent ID: 7140865
Filing Date: 2006-11-28
Classification: B29C,B29K

Abstract:
1. An apparatus for extruding a polymeric foam from an extrudate comprising a polymeric resin and a blowing agent for providing the extrudate with a cellular structure upon extrusion, the apparatus comprising: an extruder having an inlet adapted to receive the extrudate; an extrusion die having an annular die opening forming an outlet for the extruder through which the extrudate is adapted to be pulled at a predetermined line speed, the extrusion die defining a longitudinal axis, and the annular die opening being concentrically oriented relative thereto and positioned therefrom at a first radial distance; a choke ring having an opening defined by an annular choke ring surface, the choke ring being positioned relative to the extruder such that the annular die opening is received within the choke ring opening, the choke ring opening being concentric about the longitudinal axis and positioned therefrom a second radial distance; and wherein the difference between the second radial distance and the first radial distance comprises a gap, the size of the gap being determined by the ratio of the gap (in units of millimeters) to the line speed (in units of millimeters per second) and the ratio ranges from 0.001 to 0.020 second.