Kabushiki Kaisha Toshiba

Toshiba Tec Kabushiki Kaisha

Yoshiya Hashimoto

Osamu Takagi

Hiroshi Murata

Masashi Hiroki

Takao Izumi

Toshihiro Kasai

Kazuhisa Kimura

Shoko Seto

The developing device has four developing units arranged along a photosensitive belt stretched across endlessly. These developing units contain toners of different colors, and each has a developing roller at its leading end which faces the photosensitive belt. The developing device has a contact-enabling mechanism for selectively bringing one of the four developing units into contact with the photosensitive belt. The contact-enabling mechanism has four cams provided such an arrangement that they are out of phase with each other by an angle of 72 degrees, thereby brining each of the developing units into contact with the photosensitive belt, one driving source for rotating the four cams and one clutch for transmitting a driving force from the driving source to the four cams so as to rotate them at the same time. With this structure, the four cams are each rotated by an angle of 72 degrees each time the clutch is set on, and one of the four developing units is selectively brought into contact with the photosensitive belt.

Developing device with a contact-enabling mechanism

As an image forming apparatus of this invention, a color copying machine in which four image forming units are juxtaposed along the convey direction of a paper sheet is known. Each image forming unit has a photosensitive drum which is in rolling contact with a conveyor belt. Around the photosensitive drum, a charging device, exposure device, developing device, transfer device, cleaning device, and charge removing device are placed in turn along the rotation direction of the drum. An image unit is interposed between the photosensitive drum in the predetermined image forming unit, and the photosensitive drum in the image forming unit, which neighbors that image forming unit on its upstream side. The image unit integrally holds the developing device for developing an electrostatic latent image formed on the downstream photosensitive drum, and the cleaning device for cleaning the upstream photosensitive drum. Also, the image unit is detachably inserted between the two neighboring photosensitive drums.

Image forming apparatus with integrally holding image unit

A developing roller is opposed to a photosensitive drum on which a latent image is carried, and developer supplied to the latent image is held and fed by the developing roller. Developer is supplied from a feeding roller to the developing roller. A thickness defining blade is pressed against the feeding roller to press the feeding roller against the developing roller and form a developer layer of certain thickness on the feeding roller. A developing device thus arranged enables developer to be electrically charged without adding any stress to the developer, and a developer layer of certain thickness to be formed.

Developing device including device for selecting varying the thickness

Growing community of inventors

Yokohama, Japan

Yoshiya Hashimoto