US 4,545,325 AGranted

Developing apparatus

AssigneesHitachi, Ltd., Hitachi Koki Co., Ltd.

InventorsIsamu Komatsu, Masayasu Anzai, Nobuyoshi Hoshi, Susumu Akimaru

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Abstract

Disclosed is a second toner developing apparatus for use in a two color electro-photographic recording apparatus in which a photosensitive drum is uniformly charged, subject to a first exposure, developed with a first toner, subject to a second exposure, and then developed with a second toner. The second developing apparatus is provided with a rotary sleeve for performing magnetic brush development and a fixed magnet disposed within the rotary sleeve. The fixed magnet includes a plurality of magnetic poles of the same polarity provided close to each other, so as to temporarily separate the second developer from the surface of the rotary sleeve at the position of these same polarity magnetic poles. An electrostatic attraction electrode attracts the first toner mixed in the thus separated second developer to thereby remove the first toner from the second developer.

Claims10

Dependent claims

A developing apparatus for developing, by a second toner of a second developer, a second electrostatic latent image formed on a recording medium carrying a first toner image formed by a first toner attracted to a first electrostatic latent image on said recording medium, said apparatus comprising second developing means for developing with said second toner of said second developer said second electrostatic latent image formed on said recording medium, said second developing means including a developer container for accommodating said second developer and means for carrying said second developer in said developer container to said recording medium to develop said second electrostatic latent image on said recording medium;

and mixed toner removal means for removing first toner, which is mixed in the second developer including the second toner and which is charged in the polarity different from the second toner, said removal means including an electrostatic attraction electrode which is supplied with a voltage of the same polarity as the second toner, to thereby remove the first toner from the second developer, and a non-magnetic rotary sleeve disposed in opposition to said electrostatic attraction electrode, magnet means being provided at the inside of said rotary sleeve so as to attract the second developer to the outer periphery of said rotary sleeve, said magnet means being provided with a plurality of magnetic poles of the same polarity formed closely to each other at a position opposed to said electrostatic attraction electrode.

Dependencies are inferred from the claim text.