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TWIN SHEET THERMOFORMER

  • US 3,787,158 A
  • Filed: 07/03/1972
  • Issued: 01/22/1974
  • Est. Priority Date: 07/03/1972
  • Status: Expired due to Term
First Claim
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1. Apparatus for forming a hollow object in sheets of deformable thermoplastic material comprising:

  • a central forming station;

    a pair of sheet heating stations on opposite sides of said central forming station at which sheets of deformable thermoplastic material are heated;

    upper and lower carriage means for supporting upper and lower pairs of said sheets of thermoplastic material;

    means mounting said upper and lower carriage means for movement between said sheet heating and forming stations;

    means for concurrently moving said upper and lower sheet supporting carriage means in opposite directions to move said lower sheet supporting means in a to-and-fro path between a first position in which one of said lower sheets is at one of said heating stations and the other of said lower sheets is at said forming station and a second position in which said other lower sheet is at the other heating station and said one sheet is at said forming station and to concurrently move said upper sheet supporting means in an opposite to-and-fro path between a first position in which one of said upper sheets is at said other heating station and the other of said upper sheet is at said forming station superposed with said other lower sheet and a second position in which said other of said upper sheets is at said one heating station and said one upper sheet is at said forming station superposed with said one lower sheet;

    upper and lower molding means including differential pressure applying means at said forming station movable toward and away from each other between removed positions and adjacent positions for forming a shape in at least one of the upper and lower superposed sheets and fusing the sheets together;

    energizable and deenergizable upper and lower sheet heating means at each of said heating stations; and

    means for selectively, individually operating each of said heating means at each station including control means for operating one of the heating means at one station for a longer time than any of the other heating means are operated and for operating one of the heating means at the other heating station for a shorter time than any of the other heating means are operated when said upper and lower sheet supporting means are in said first positions and for operating said one heating means at said one station for a shorter time than any of the other heating means and for operating said one heating means at the other heating station for a longer time than any of the other heating means when said upper and lower sheet supporting means are in said second positions.

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