Development station for an electrophotographic printing or copying station having a means for preventing the discharge of the mixture

US5307125A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventor

• Josef Knott · Schierling, DE

Key dates

• Filing date: Sep 30, 1992
• Grant date: Apr 26, 1994
• Expiry date: Sep 30, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G03G15/0921
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

In an electrophotographic printer or copier, a hollow, rotatable development drum carries a carpet mixture including toner from a toner delivery region through a conveying region to a charge image carrier such as a photoconductive drum, through the action of elongated magnets mounted within the development drum which attract the toner mixture to the outer surface of the drum. The development drum is separated from the charge image carrier by a development gap at which the toner mixture is transferred to the charge image carrier to develop the electrostatic image thereon. Non-uniform, stray magnetic fields are present at the ends of the magnets, which attracts a non-uniform layer of the toner mixture, resulting in poor print quality. The non-uniform distribution of toner mix in the non-uniform magnetic fields at the ends of the magnets is prevented, in one embodiment, by limiting elements that prevent the toner from reaching the non-uniform fields ends of the development drum at the toner conveying region but which widen from the conveying region to the development gap. Another embodiment includes a shorter magnet at the conveying region and a longer magnet at the development gap.