Ricoh Company, Ltd.

Tosio Nakahara

Nobuo Kasahara

Hidetoshi Yano

Tadahide Sawamura

Masayosi Watanuki

A control system for a color copier which sets up an adequate color copying time for any particular size of paper sheets. A color document is repeatedly scanned to sequentially expose a single photoconductive drum, which is rotated at a constant speed, to a plurality of separated color components. Each of the latent images is developed by toner complementary in color to the color component associated with the latent image, and sequentially transferred to a paper sheet. The control system includes a paper size setting circuit, a scanning sensor for sensing the start of a scanning, and a home sensor for sensing an instantaneous angular position of the transfer drum. A control circuit is constructed to determine a transfer start and a transfer end time in response to a paper size signal, an output signal of the scanning sensor, and an output signal of the home sensor, and to variably control the rotation speed of the transfer drum during the interval between the transfer start and transfer end times so as to register the leading end of a paper sheet loaded on the transfer drum and that of each of the toner images.

Image forming apparatus and control system therefor

A device applicable to a color copier or the like for transferring an image to a paper sheet which includes a hollow drumlike frame the peripheral wall of which is removed except for opposite circumferential edge portions and a connecting portion which links the edge portions to each other. A conductive sheet is wrapped around the frame to cover the removed portion of the frame. An intermediate portion of the conductive sheet is bulged radially outward beyond the outer periphery of the frame.

Image transferring device for a copier

In an arrangement of a photoconductive drum and a transfer drum which are installed in a color image forming apparatus, the rotation speed of the transfer drum is increased during the interval between consecutive image transfers so as to increase the recording speed. The photoconductive and transfer drums are each rotatable about a shaft driven independently of the other. A photoconductive drum and a dielectric sheet are wrapped around the photoconductive drum and the transfer drum, respectively. The transfer drum is constituted by a hollow cylindrical frame which is made up of two rotatable rings and a connecting portion which interconnects the two rings. The rings and connecting portion cooperate to define an intermediate opening, and the dielectric sheet is positioned to close the intermediate opening. The axial width of the photoconductive drum is smaller than that of the intermediate opening. In opposite end portions of the photoconductive drum where the photoconductive material is absent, positioning disks are provided each making direct rolling contact with a portion of a respective one of the rotatable rings where the dielectric sheet is absent.

Image forming apparatus

A single magnetic brush developing unit is disposed adjacent to a photoconductive drum for applying toner thereto. Three applicator units are selectively actuatable to apply three toners of respective primary colors to the developing unit.

Color electrostatographic apparatus

A magnetic brush development apparatus comprises a developer application roller and a development roller. When development is stopped, the developer application roller is stopped so that the supply of developer to the development roller is stopped. Normally, the development roller is continuously rotated or when development is stopped, the developer application roller is stopped first and after a while the rotation of the development roller is stopped.

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Yokohama, Japan

Tosio Nakahara