Patent ID: 6592786
Filing Date: 2003-07-15
Classification: B29C

Abstract:
An apparatus for producing an extruded film tube and supplying said tube to a collapsing and roller assembly, comprising:(a) a die for extruding a molten material in the form of a tube which is in a molten state below a frost line and which is in a solid state above said frost line; (b) a blower system for supplying and exhausting cooling air to and from an interior portion of said tube; (c) a flow control valve for regulating the at least a portion of said blower system to control the extrusion and cooling process, and which determines in part the circumference of said tube; (d) at least one sizing sensor located proximate said tube in a position below said frost line for sensing the position of said tube, comparing such position to an extrusion set point, and generating an extrusion feedback error signal which is corrective of any difference between said position and said set point; (e) at least one lay flat sensor located proximate said tube in a position above said frost line for sensing the position of said tube prior to the collapsing and flattening of said tube by said collapsing and roller assembly, comparing said position to a lay-flat set point, and generating a lay-flat feedback error signal which is corrective of any difference between said position and said lay-flat set point; (f) a programmable controller for executing program instructions including a negative feedback control system which receives said extrusion feedback error signal and said lay-flat feedback error signal as negative feedback injection signals and which provides a control signal to said valve.