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Vacuum sizing apparatus with controlled vacuum

  • US 5,340,295 A
  • Filed: 07/19/1993
  • Issued: 08/23/1994
  • Est. Priority Date: 07/19/1993
  • Status: Expired due to Fees
First Claim
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1. Apparatus for cooling and sizing a molten plastic extrudate comprising:

  • a vacuum chamber containing water;

    an entry passage into said vacuum chamber for said plastic extrudate;

    an exit passage from said vacuum chamber for said plastic extrudate;

    seal means sealing said entry passage and said exit passage while said plastic extrudate is passing through said passages;

    a variable speed motor driven vacuum pump to reduce the atmospheric pressure within said vacuum chamber;

    an adjustable vent valve to admit atmospheric pressure to said vacuum chamber in varying amounts depending upon the amount said vent valve is open;

    a pressure transducer to sense the level of pressure within said vacuum chamber; and

    an electrical circuit that controls the speed of said vacuum pump motor and the position of said adjustable vent valve to control the level of pressure within said vacuum chamber in response to signals from said pressure transducer.

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