Method and apparatus for automatically balancing a blower in any blown film extrusion line

Abstract

The present invention is directed to a method and apparatus for startup of extruded film tubes. A controller member is utilized to provide control signals to a supply blower which supplies air to the extruded film tube in an amount corresponding to a supply control signal, and an exhaust blower which exhausts air from the extruded film tube in an amount corresponding to an exhaust control signal. The controller member executes program instructions which define at least one control routine for automatic and coordinated control of the supply blower and the exhaust blower during starting of the extruded film tube, by directing a series of supply control signals to the supply blower and exhaust control signals to the exhaust blower. When a valve is utilized to control the flow of air from the supply blower to the extruded film tube, the controller is also utilized to adjust the supply blower and the exhaust blower in order to optimize operation of the valve by placing the valve in a substantially linear operating range. Additionally, the controller member may be utilized to execute program instructions in order to implement a bubble break detection routine which utilizes software timers in combination with monitoring of a position signal in order to determine collapse or break of the extruded film tube.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001] This patent application includes a disclosure which, in large portion, is similar to the disclosure in U.S. patent application Ser. No. 08 / 658,369, entitled "Method and Apparatus for Cooling Extruded Film Tubes", which was filed on Jun. 5, 1996. However, this application is not a continuation or continuation-in-part of this co-pending application.[0002] 1. Field of the Invention:[0003] This invention relates generally to blown film extrusion lines, and specifically to operations of the inlet and outlet blowers of blown file systems.[0004] 2. Description of the Prior Art:[0005] Blown film extrusion lines are used to manufacture plastic bags and plastic sheets. A molten tube of plastic is extruded from an annular die, and then stretched and expanded to a larger diameter and a reduced radial thickness by the action of overhead nip rollers and internal air pressure. Typically, air is entrained by one or more blowers to provide a cooling mediu...

AI Technical Summary

Benefits of technology

[0010] It is yet another objective of the present invention to provide an additional routine which can be utilized to detect bubble breaks during and after the startup operations.

Problems solved by technology

However, during startup of the extrusion process, in the prior art, a great deal of human intervention is required in order to establish the bubble.

The startup of an extruded film is a relatively difficult operation to perform, and generally requires a relatively highly-skilled employee to oversee or perform the startup operations.

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