Electrophotography – Image formation – Development
Reexamination Certificate
2000-02-10
2001-07-24
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Development
C366S319000, C399S281000
Reexamination Certificate
active
06266504
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a developing apparatus to be installed in an electrophotographic copying machine, a developing method, and an image forming apparatus.
In the developing apparatus of this type, a two-component developing agent made of a carrier and a toner is fed to a developing roller while stirring and circulating it with the aid of rotation of the feed mixer. The developing agent fed to the developing roller is further supplied to an electrostatic latent image formed on a photosensitive drum by the aid of rotation of the developing roller. In this way, the latent image is developed.
The feed mixer of the developing apparatus has a shaft member which has a spiral-form blade body for feeding the developing agent in a shaft direction. To the shaft member of the feed mixer, a paddle is horizontally fitted for scraping the developing agent upwardly to the position at which the developing roller is located.
The developing apparatuses includes a face-side type and a face-up type. In the face-side type, a developing roller is placed at a side of the photosensitive drum so as to face a side surface portion of the photosensitive drum. In the face-up type, the developing roller is placed under the photosensitive drum so as to face a lower surface of the photosensitive drum.
In the case of the face-up type developing apparatus, since the photosensitive drum is placed above the developing apparatus, the fixing position of a doctor blade is lowered in such a manner that the doctor blade for regulating a thickness of a layer of the developing agent formed on the developing roller is not in contact with the photosensitive drum. With this arrangement, the fixing position of the feed mixer is lowered. As the result, the position of the developing roller is placed higher than a center shaft of the feed mixer. Therefore, in the case of the face-up developing apparatus, it is necessary to increase the function of the feed mixer for scraping the developing agent upward, compared to the face-side developing apparatus.
Then, in a conventional type, the area of the paddle is enlarged by increasing a width of the paddle to improve the scraping-up function of the paddle.
However, if the scraping-up function of the feed mixer is simply increased, the ability for feeding the developing agent in a shaft direction is lowered, with the result that a speed for circulating the developing agent decreases. If the circulation speed decreases, the image is formed non-uniformly in concentration particularly in the case where a copy speed is high or where a printing rate is high.
BRIEF SUMMARY OF THE INVENTION
The present invention was made in the aforementioned circumstances. An object of the present invention is to provide a developing apparatus, a developing method, and an image forming apparatus satisfying the requirements for a circulating speed and scraping ability of the developing agent.
The developing apparatus of the present invention comprises
developing means facing an image carrier for carrying an electrostatic latent image, for developing the electrostatic latent image by supplying a developing agent thereto;
feeding means for feeding the developing agent to the developing means while stirring;
the feeding means comprising
a rotatable shaft member
a blade body spirally formed on an outer peripheral surface of the shaft member, for stirring the developing agent in a shaft direction; and
a plurality of projections arranged at the outer peripheral surface of the shaft member between tilted blade portions of the blade body, for scraping the developing agent upwardly toward the developing means, the plurality of projections, each being placed at an interval from the tilted blade portions of the blade body and are arranged at predetermined intervals along circumference of the shaft member.
The developing method of the present invention comprises the steps of
developing an electrostatic latent image carried on an image carrier by supplying a developing argent by a developing member; and
feeding the developing argent by a feeding member to the developing member while stirring,
the feeding member comprising
a rotatable shaft member
a blade body spirally formed on an outer peripheral surface of the shaft member; and
a plurality of projections arranged at the outer peripheral surface of the shaft member between tilted blade portions of the blade body, the plurality of projections, each being placed at an interval from the tilted blade portions of the blade body and are arranged at predetermined intervals along circumference of the shaft member and scraping the developing agent upwardly toward the developing means, at the same time the developing agent is fed while stirring in a shaft direction by rotation of the blade body.
The image forming apparatus of the present invention comprises
image forming means for forming an electrostatic latent image corresponding to an image data on a image carrier;
developing means arranged under the image carrier for developing the electrostatic latent image formed by the image forming means by supplying a developing agent thereto; and
transfer means for transferring a developing agent image developed by the developing means to a medium,
the developing means comprising
supply means arranged so as to face the image carrier for supplying the developing agent to the electrostatic latent image, thereby developing the electrostatic latent image;
feeding means for feeding the developing agent to the supply means while stirring the developing agent;
the feeding means comprising
a rotatable shaft member
a blade body spirally formed on an outer peripheral surface of the shaft member, for stirring the developing agent in a shaft direction; and
a plurality of projections arranged at the outer peripheral surface of the shaft member between tilted blade portions of the blade body, for scraping the developing agent upwardly toward the developing means, the plurality of projections, each being placed at an interval from the tilted blade portions of the blade body and are arranged at predetermined intervals along circumference of the shaft member.
REFERENCES:
patent: 4202636 (1980-05-01), Vanderveen
patent: 4974023 (1990-11-01), Aimoto et al.
patent: 4980724 (1990-12-01), Tanaka
patent: 5204721 (1993-04-01), Sharpe
patent: 5249019 (1993-09-01), Ishida et al.
patent: 5603568 (1997-02-01), Mobley et al.
patent: 5842090 (1998-11-01), Mikawa
patent: 6099159 (2000-08-01), Yoshida et al.
patent: 54-30838 (1979-03-01), None
Brase Sandra
Foley & Lardner
Toshiba Tec Kabushiki Kaisha
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