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Thermoforming machine with linear recirculation of sheet holding frames

  • US 5,980,231 A
  • Filed: 12/08/1997
  • Issued: 11/09/1999
  • Est. Priority Date: 12/08/1997
  • Status: Expired due to Term
First Claim
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1. A thermoforming machine including a heating station for preheating a sheet of thermoplastic material and a forming station whereat said preheated sheet is formed into an article by being shaped by tooling in said forming station, the improvement comprising:

  • a plurality of clamping frames, each having clamps for gripping a sheet therein;

    a loading station ahead of said heating station for placing a sheet into a clamping frame moved into said loading station;

    a linear advance transfer system including means for successively advancing each clamping frame loaded with a sheet out of said loading station and through each of said heating and forming stations;

    a return station;

    a first elevator mechanism vertically moving each clamping frame to a different level after being advanced out of said forming station and into said return station;

    a linear return transfer system receiving each vertically moved clamping frame and transferring each vertically moved clamping frame back past said forming and heating stations to a position aligned with said loading station;

    a second elevator mechanism returning each clamping frame to the level of said loading station and advance transfer systems;

    said advance transfer system comprising a horizontally extending advance transfer structure and drive means for moving said advance transfer structure back and forth between fully retracted and advanced positions to carry clamping frames step by step through each of said stations; and

    a lift device moving each clamping frame out of engagement with said advance transfer structure in said heating station, and means causing movement of said transfer structure so as to produce seperate transfer movement of another clamping frame remaining in engagement with said advance transfer structure while another of said clamping frames is out of engagement with said advance transfer structure in said heating station, whereby said another clamping frame is transferred ahead while one clamping frame remains in said heating station.

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