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Electrostatic image transfer device having a two level transfer voltage for improving image quality at leading and trailing edge regions

  • US 5,541,718 A
  • Filed: 08/03/1994
  • Issued: 07/30/1996
  • Est. Priority Date: 09/21/1993
  • Status: Expired due to Term
First Claim
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1. An image-transfer device for transferring an image-bearing member to a sheet-like material, comprising:

  • means, responsive to a transfer voltage and spacedly positioned from the image-bearing member, for charging the sheet-like material in a predetermined polarity so that the image on the image-bearing member is transferred onto the sheet-like material;

    means for transporting the sheet-like material through a transfer region between the charging means and the image-bearing member, the transporting means including a guide member for guiding the sheet-like material, the guide member having a first edge portion arranged at an upstream side of the transfer region and a second edge portion arranged at a downstream side of the transfer region so as to form an opening at the transfer region;

    means for applying a first transfer voltage and a second transfer voltage to the charging means, the second transfer voltage having a lower absolute value than the first transfer voltage;

    means for detecting the size of the sheet-like material; and

    means for setting the applying means to apply the first transfer voltage when the sheet-like material is guided by both the first edge portion and the second edge portion, and setting the applying means to apply the second transfer voltage when at least one of the first edge portion and the second edge portion does not guide the sheet-like material,wherein the setting means includes means for determining the timing at which the first transfer voltage and the second transfer voltage are set, corresponding to the detected size of the sheet-like material.

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