| 摘要 |
Control apparatus for automatically maintaining the desired blown tube diameter in the blown plastic film process where the blown tube is internally cooled by a gas flow into and out of the interior of the tube. A by-pass duct having a by-pass damper is provided on either the inlet or exhaust duct by-passing the inlet or exhaust duct damper respectively and this by-pass damper is controlled by tube diameter sensors. By thus controlling only a small percentage of the inlet or exhaust flow a very fine and stable control is achieved. Control apparatus is also provided to maintain the by-pass damper in its optimum operating range.
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