Ricoh Company, Ltd.

Kazuhiro Nishido

Naoki Iwata

Ichiro Komuro

Koji Suzuki

Takeshi Saito

Hiroshi Tanabe

Noriyoshi Tarumi

Hidetoshi Yano

Akira Sawada

Hiromitsu Takagaki

Takaya Muraishi

Yasuo Hirano

Kazunori Karasawa

Fuchio Takeda

Nobuhiro Shima

Takeo Wada

Shigeki Sawa

Jun'ichi Murano

A paper guide device for guiding a sheet of paper to an image transfer device includes an upper guide plate and a lower guide plate, and an elastic transfer guide plate which is attached to the upper paper guide plate. A free end of the elastic transfer guide plate faces the transfer device and is bent downward such that a bend or crease line is perpendicular to a paper feed direction. The free end of the elastic transfer guide plate is parallel to paper feed direction at a transfer position to better orient/direct the paper as it approaches a photosensitive member or image transfer location. The arrangement allows for a compact paper feed design, while avoiding adverse effects which can occur where paper (particularly thicker paper) springs as it exits a paper guide.

Paper guide device for image forming apparatus

In a developing device for an image forming apparatus, a developing roller has dielectric portions and conductive portions distributed regularly or irregularly over the surface thereof. The surfaces of the dielectric portions are smaller in height than the surfaces of the conductive portions. The difference in height is greater than one-half of the volumetric mean particle size of a toner. A charge opposite in polarity to a charge to be deposited on the toner is deposited on the dielectric portions. The dielectric portions, or recesses, each has a width more than three times as great as the volumetric mean particle size of the toner and a depth less than five times the volumetric particle size. The dielectric portions may be greater in height than the conductive portions and may be implemented as spiral grooves inclined more than 30 degrees relative to the axis of rotation of the developing roller. The developing roller may be moved at a higher linear velocity than a photoconductive drum.

Developing device for an image forming apparatus

A color copier capable of producing, without disturbing a toner image formed in the first color, an image in the second color and preventing the first color from being mixed with the second color. In the event of development in the second color, a bias voltage is applied to a developing roller at a repetition frequency shorter than 5 kHz. One period of the bias voltage consists of a pulse voltage VPULS having a duration TA (shorter than 100 .mu.sec), and a DC bias voltage VDC having a duration TB. The pulse voltage VPULS is higher than the potential VD of a non-image area in order to enhance a developing potential. The DC voltage VDC is lower than the potential VD and a potential VT of a toner layer of first color and higher than the potential VL of an image area in order to set up a sufficient developing potential. The DC voltage VDC and the potential VT has a potential difference smaller than 500 V. A gap for development ranges from 100 .mu.m to 300 .mu.m. The pulse voltage VPULS may include an overshoot portion at the negative-going edge thereof or may be replaced with a voltage having a triangular waveform. The adhesion of the toner of first color to an image carrier is not susceptible to electric fields formed for development in the second color. For development in the second color, a toner exhibiting a particular moving characteristic in the gap is used.

Nondestructive multicolor image forming apparatus

A developing device for use in an image forming apparatus and having a developing roller, developing sleeve or similar developer carrier for supplying a one-component developer, or toner, to a latent image which is electrostatically formed on an image carrier such as a photoconductive element. A dielectric layer forming part of the developer carrier and closely related to the fluctuation of developing characteristic has a frequency characteristic which is confined in a predetermined range. Hence, the device is operable in a desirable manner by confining the fluctuation of developing characteristic ascribable to that of developing linear speed in a predetermined range without resorting to the actual measurement of a response characteristic of a developer carrier.

Developer carrier with a dielectric layer having a frequency

A toner carrier in a mono-ingredient nonmagnetic developing device for an electrostatic printing machine which is a roller rotating in contact with a latent image carrier to carry toner on a surface of the latent image carrier, and to develop an electrostatic latent image formed on the latent image carrier with the toner. A toner carrier according to the first invention comprises a rotating shaft, an elastic layer surrounding the shaft, and a thin resin layer built up around the elastic layer or a thin resin cylinder provided with conductivity. A toner carrier according to the second invention comprises a conductive rotating shaft, an elastic layer surrounding the shaft, a thin cylinder surrounding the elastic layer and a toner carrying layer surrounding the cylinder, where the thin cylinder is conductive and the elastic layer is conductive or semi-conductive. And a toner carrier according to the third invention comprises a rotating shaft, an elastic layer surrounding the shaft, and a base consisting of a thin cylinder surrounding the elastic layer, where the elastic layer is made of compression molded soft urethane foam.

Toner carrier for developing device for electrostatic printing apparatus

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Tokyo, Japan

Kazuhiro Nishido