Ricoh Company, Ltd.

Toyoji Ishikawa

Nobuyuki Yanagawa

Katsuo Sakai

Toshio Kaneko

Hideya Furuta

Tadao Koike

Yoshihiro Ogata

Toshihiko Takaya

Shuichi Endo

An image developing device for use in an electrophotographic copying apparatus or a printer includes a developing roller for supplying toner to a latent image formed on a latent image carrier to develop the latent image into a visible toner image. The image developing device also includes a toner supply roller independently rotatable in abutting engagement with the developing roller for supplying the toner onto the developing roller. Each of the toner supply roller and the developing roller is electrically conductive. An electric potential with its polarity dependent on whether the toner is positively or negatively chargeable is applied between the toner supply toner and the developing roller by a bias voltage distributing circuit.

Image developing device

A dual-color electrophotographic copier includes a first photosensitive drum having a first layer comprised of a photoconductive material sensitive to light of a first selected color and a second layer formed on the first layer from a photoconductive material sensitive to light of a second selected color and a second photosensitive drum having a third layer comprised of a photoconductive material sensitive at least to the first selected color. A light image from the same original may be applied to the first and second drums simultaneously to form electrostatic latent images on the first and second drums. These images may be developed by differently colored toner and the toner images may be transferred to the same transfer paper superposingly to obtain a dual-color copy image.

Dual-color copier

Growing community of inventors

Kawasaki, Japan

Toyoji Ishikawa