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Method and apparatus for controlling the position of a transported web

  • US 4,692,819 A
  • Filed: 04/16/1986
  • Issued: 09/08/1987
  • Est. Priority Date: 08/31/1984
  • Status: Expired due to Term
First Claim
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1. Apparatus for controlling the position of a web relative to a path along which it is transported, the web having a number of markers thereon from which positions on the web relative to the path can be determined, comprising:

  • first means for transporting the web along the path;

    second means for detecting markers on the web as the web is transported along the path;

    third means independent of the markers responsive to the transport of the web along the path for generating first signals indicative of lengths of displacement of the transported web along the path, the third means generating a number of first signals for a selected length of displacement of the transported web greater than the number of markers detected during such displacement;

    fourth means responsive to the detection of markers and to first signals for generating a second signal indicative of the position of the web along the path corresponding to the length of displacement of the transported web indicated by said first signals following detection of a marker;

    fifth means for generating a reference signal representative of a selected position along the web relative to the a marker;

    sixth means responsive to the reference signal and the second signal for generating an error signal representative of a difference between the position of the web and the selected position; and

    ,seventh means responsive to the error signal for controlling the first means to eliminate the difference between the position of the web and the selected position.

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