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Thermal ink-transfer printer capable of preventing off-registration of colors at color printing

  • US 5,026,180 A
  • Filed: 12/22/1988
  • Issued: 06/25/1991
  • Est. Priority Date: 12/22/1987
  • Status: Expired due to Fees
First Claim
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1. A thermal ink-transfer printer for printing a color image on a printing paper wound along an outer surface of a platen roller by pressing a thermal head against the paper and an ink film interposed therebetween and by melting an ink on the ink film caused by the thermal head, said paper being moved by rotation of the platen roller, said printer comprising:

  • driving means for causing controlled rotation of the platen roller;

    clamp means provided rotatably at both ends of said platen roller for clamping and holding an end of the paper fed to the outer surface of said platen roller, said clamp means being rotatable independently from the platen roller and comprising supporting rings rotatably provided at both ends of a shaft of said platen roller for supporting a holding member parallel to said platen roller along a longitudinal direction, and clamp levers mounted respectively on inner surfaces of both said supporting rings for clamping corners of said end of the paper in conjunction with said holding member;

    clutch means for coupling and decoupling said clamp means to and from said platen roller so that said clamp means rotate together with said platen roller when coupled thereto by said clutch means, said clutch means comprising clutch levers arranged respectively at inner surfaces of said supporting rings and arranged to engage with said clamp levers for causing said clamp levers to separate from said holding member, and clutch rings mounted on both ends of the shaft of the platen roller between the platen and inner sides of the clamp and clutch levers for rotation with said platen, each of said clutch rings having a recess with which a projection provided on each of said clutch levers engages;

    a pinch roller for pressing the paper against said platen roller, when the paper is clamped by said clamp means and is moved by said platen roller in a printing mode;

    encoder means mounted on said platen roller for generating a control signal for controlling a print starting time for each color; and

    control means for controlling said clutch means to couple said platen roller to said clamp means so that said platen roller and said clamp means holding the end of the paper rotate together for a predetermined angular range thereof and to decouple said platen roller from said clamp means to allow said platen roller to rotate beyond said predetermined angular range independent from the clamp means so that the paper continues to move for full printing range thereof in the printing mode, for controlling operations of said pinch roller and said driving means and for controlling said print starting timing for each color on the basis of said control signal from said encoder means.

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