Patent ID: 6423261
Filing Date: 2002-07-23
Classification: B29C

Abstract:
A method of producing blown film in a blown film extrusion apparatus, which includes:(i) an annular die for extruding a film tube; (ii) at least one sensor located adjacent said extruded film tube for transmitting interrogating pulses to said extruded film tube and for producing a position signal corresponding to a detected position of said extruded film tube; (iii) a bubble position control system for receiving and processing said position signal; (iv) means for varying a quantity of air within said extruded film tube in response to said bubble position control system for urging said extruded film tube to a desired position, including a controllable valve, a supply blower, and an exhaust blower; the method comprising the steps of: (a) providing a collapsing frame assembly for receiving said extruded film tube and collapsing said extruded film tube; (b) said collapsing frame assembly including: (1) a plurality of frame boards; (2) at least one board position transducer for detecting the position of at least one of said plurality of frame boards; (3) at least one board position actuator for adjusting the position of at least one of said plurality of frame boards; (4) a board control system for receiving board position information from said at least one board position transducer and for providing control signals to said at least one board position actuator to maintain at least one of said plurality of frame boards in a predetermined position; (c) concurrently operating said bubble position control system and said board control system during blown film extrusion operations in order to produce blown film product of uniform diameter by utilization of said board control system of said collapsing frame assembly to receive position signals from said at least one board position actuator and to actuate said at least one board position actuator to position said plurality of frame boards in order to track a specific diameter of the extruded film tube which is being produced.