TREA

Image forming apparatus

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Information

  • Patent Application
  • 20070231013
  • Publication Number
    20070231013
  • Date Filed
    April 03, 2006
    18 years ago
  • Date Published
    October 04, 2007
    17 years ago
Information
Abstract
A toner development unit for an image forming apparatus including a roller and an electrode adjacent thereto, the electrode having an arcuate extent adjacent to a portion of a surface of the roller to define a toner application gap therebetween, the roller being adapted to rotate in a given direction wherein the gap diverges in the direction of rotation of the roller relative to the electrode.
Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings, of which:



FIG. 1 is a diagram of an image forming apparatus shown in section according to an embodiment of the present invention;



FIG. 2 is a diagram of a developer assembly shown in section according to an embodiment of the present invention;



FIG. 3 is a detail diagram of a diverging gap shown in FIG. 2;



FIG. 4 is a perspective diagram of the developer assembly shown in FIG. 2;



FIG. 5 is an exploded diagram of a developer assembly shown in perspective according to an embodiment of the present invention;



FIG. 6 is a schematic diagram of a part of the developer assembly shown in FIG. 5 according to an embodiment of the present invention; and



FIGS. 7 and 8 illustrate graphs showing a comparison of flow streaks grading.


Claims
  • 1. A toner development unit for an image forming apparatus including a roller and an electrode adjacent thereto, the electrode having an arcuate extent adjacent to a portion of a surface of the roller to define a toner application gap therebetween, the roller being adapted to rotate in a given direction wherein the gap diverges in the direction of rotation of the roller relative to the electrode.
  • 2. A toner development unit according to claim 1 wherein the arcuate extent of the electrode has a leading edge and a trailing edge defined relative to the direction of rotation of the developer roller, and wherein the leading edge is at a distance of approximately 400±40 μm from the surface of the roller
  • 3. A toner development unit according to claim 2 wherein the trailing edge is at a distance of approximately 550±40 μm from the surface of the roller.
  • 4. A toner development unit according to claim 1 wherein the gap has a leading edge and a trailing edge such that the gap diverges by about 150 μm±50 μm.
  • 5. A toner development unit according to claim 1 wherein the gap diverges by an amount that is about 1% of the length of the radius of the roller.
  • 6. A toner development unit according to claim 1 wherein the gap between the arcuate extent of the electrode and the surface of the roller diverges linearly.
  • 7. A toner development unit according to claim 1 wherein the gap between the arcuate extent of the electrode and the surface of the roller diverges non-linearly.
  • 8. A toner development unit according to claim 1 wherein the electrode is pivotally mounted relative to the roller.
  • 9. A toner development unit according to claim 1 further comprising spaced end walls having the roller and the electrode mounted therebetween, the unit having at least one locating device for engaging at least one end wall for setting the dimensions of the diverging gap.
  • 10. A toner development unit according to claim 1 and further including spaced end walls having the roller and the electrode mounted therebetween, the development unit also comprising a connecting member between the end walls, the connecting member having at least one locating device for engaging at least one end wall for setting the dimensions of the diverging gap.
  • 11. An image forming apparatus including a toner development unit according to claim 1.
  • 12. A method of printing including applying toner to a developer drum using a toner development unit having an electrode and a rotatable roller with a divergent gap therebetween, the gap being divergent in the direction of rotation of the roller relative to the electrode.
  • 13. A method according to claim 12 further comprising adjusting the divergent gap to reduce flow streaks on a printed substrate.
  • 14. A method of reducing flow streaks on a substrate using a toner development unit having an electrode and a rotatable roller with a divergent gap therebetween in the direction of rotation of the roller relative to the electrode, the method including; supplying toner to the divergent gap;transferring toner from the gap to the rotatable roller;transferring the toner from the rotatable roller to a developer drum; andtransferring the toner from the developer drum to the substrate.
  • 15. A method according to claim 14 and further including adjusting the divergent gap to obtain an optimum diverging gap which minimises flow streaks on the substrate.
  • 16. Use of a divergent gap between an electrode and a rotatable toner transfer roller of a xerographic printer development unit in order to ameliorate flow streaks on printed products printed using the printer development unit.