Patent ID: 7922470
Filing Date: 2011-04-12
Classification: B29C

Abstract:
1. An apparatus for positioning an adjustable sizing cage in a blown film extrusion apparatus in which film is extruded as a tube from an annular die and then pulled along a predetermined path and located within the adjustable sizing cage, the apparatus comprising: a supply blower which supplies air to said extruded film tube in an amount corresponding to a supply control signal; an exhaust blower which exhausts air from said extruded film tube in an amount corresponding to an exhaust control signal; a controller member including executable program instructions which define at least one control routine for automatic and coordinated control of said at least one of the exhaust or supply blowers during extrusion of said extruded film tube by directing a series of supply control signals to said supply blower and/or exhaust control signals to said exhaust blower; a sizing cage subsystem surrounding said extruded film tube and including an electrically actuable and controllable actuator configured for moving said sizing cage inward and outward relative to said extruded film tube; at least one first non-contact sensor for measuring a distance between said cage subsystem and said extruded tube; at least one additional non-contact sensor for measuring a diameter of said extruded tube; and wherein said executable program instructions include a cage position control routine which utilizes said sizing cage subsystem-to-tube distance to control a location of said sizing cage subsystem when moving said sizing cage subsystem from a first position to a second position during startup and resizing of said extruded film tube.