Electrophotography – Image formation – Development
Reexamination Certificate
2000-04-27
2001-10-23
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06308037
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a developing apparatus which develops an electrostatic image by feeding a toner as a visualizing material in an image forming apparatus represented by, for example, a copying machine of electrophotographic system or a laser beam printer.
Known developing apparatuses which are incorporated in image forming apparatuses using electrophotographic process are of a two-component system which uses a carrier and a toner for a developer, and a one-component system which uses only a toner for a developer. In addition, a proposal has been recently made for a developing apparatus which is of the one-component system and also uses a small amount of magnetic carrier.
Developing apparatuses which are of the one-component system and also use a small amount of magnetic carrier is known from Japanese Patent Application KOKOKU Publication No. 7-40156 and Japanese Patent Application KOKOKU Publication No. 7-43554. These publications disclose an example in which a carrier container area for preventing a toner, which has fallen from a developing sleeve, from being mixed into a toner holding section is positioned below a developing sleeve.
Japanese Patent Appplication KOKAI Publication No. 9-6106 will be cited as an example in which an area for holding a developer is provided under the developing sleeve. According to this publication, a developer is fed by a rotation arm rotated about a rotation center which is positioned lower than the rotation center of the developing sleeve, and a part of a developing housing which holds the developer such that the developer can be fed to the developing sleeve is formed under the developing sleeve.
Each of the developing apparatuses described above has a common feature that the toner is magnetized and a toner layer is formed on the surface of the developing sleeve by a magnetic roller in which N and S poles are provided alternately.
However, in the developing apparatus disclosed in each publication, there is a limitation to the layout of the developing sleeve and the magnetic roller for feeding the toner onto the developing sleeve with predetermined thickness, due to influences from the layout of magnetic poles and the like. Therefore, a problem arises in that all the toner contained in the toner container section of the developing apparatus can not be fed to the developing sleeve.
Hence, in the developing apparatus disclosed in each publication, a toner holding section which is a part of a container area and a developing housing is provided between the magnetic roller and the toner container section.
However, every of the developing apparatuses disclosed in the above described publications has a problem that a large amount of toner remains in the toner holding section in the developing apparatus and a next charge of toner is requested regardless of the remaining toner.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an image forming apparatus which is capable of maintaining a stable image density for a long time period without causing any unevenness of density due to short toner feed.
Another object of the present invention is to provide a developing apparatus which is capable of reducing the amount of toner which may remain in a toner hopper.
A further another object of the present invention is to provide a developing apparatus which is capable of feeding toner stably toward a developing roller.
The present invention has been made on the basis of the problem described above and provides an image forming apparatus comprising an image forming section for forming a latent image on an image carrier, and a developing apparatus for supplying a visualizing agent to the latent image formed on the image carrier, thereby to develop the latent image, said developing apparatus including: a housing for holding a toner fed to a latent image formed on a image carrier; a developing roller provided to be rotatable about a rotation center positioned below a rotation shaft of the image carrier in a vertical direction; a supporting member as a part of the housing, for positioning the toner close to the developing roller; and an agitation member provided to be rotatable in the housing and having sheet-like member having a free length which is defined to be longer than a distance between a rotation center of the sheet-like member and a wall surface of the housing, for feeding the toner in the housing to the supporting member and for agitating the toner in the housing, as the agitation member is rotated along an inner wall of the housing.
Also, the present invention provides a method for forming an image with use of an image forming apparatus, comprising steps of: forming a latent image on an image carrier; and feeding a visualizing agent to the image formed on the image carrier, thereby to develop the image, wherein the step of feeding the visualizing agent includes a housing for holding a toner fed to a latent image formed on a image carrier, a developing roller provided to be rotatable about a rotation center positioned below a rotation shaft of the image carrier in a vertical direction, a supporting member as a part of the housing, for positioning the toner close to the developing roller, and an agitation member provided to be rotatable in the housing and having sheet-like member having a free length which is defined to be longer than a distance between a rotation center of the sheet-like member and a wall surface of the housing, for feeding the toner in the housing to the supporting member and for agitating the toner in the housing, as the agitation member is rotated along an inner wall of the housing.
Further, the present invention provides an image forming apparatus comprising: a developing apparatus including a photosensitive member on which a latent image corresponding to image information to be outputted is formed, for supplying selectively a toner to the latent image formed on the photosensitive member, thereby to develop the latent image, said photosensitive member including a developing magnet internally provided with N and S poles arranged alternately, a sleeve formed to be rotatable on an outer circumference of the developing magnet, for supplying an image carrier with a toner to be supplied onto the latent image formed on the image carrier, a toner hopper as a part of the housing, provided below a rotation center of the sleeve in a vertical direction at a predetermined distance therefrom, and having a table for holding temporarily the toner which should be supplied to the sleeve, thereby to contain the toner, a developer agitating member formed to be rotatable in the toner hopper, as an elastic member having a longer free length than a inner diameter of the toner hopper, for feeding the toner in the toner hopper toward the sleeve and for agitating the toner, as the developer agitating member is rotated later in comparison with vicinity of a rotation center when the developing agitating member is rotated in the toner hopper, and a supporting member defined at a predetermined position in the housing, for temporally supporting the developer which is moved by the developer agitating member; and a transfer device for transferring a toner image formed on the photosensitive member by the developing apparatus, to a transfer target object.
REFERENCES:
patent: 4947211 (1990-08-01), Ono et al.
patent: 5461465 (1995-10-01), Sunaga et al.
patent: 5809386 (1998-09-01), Iwata
patent: 5943537 (1999-08-01), Ahn
patent: 5995791 (1999-11-01), Kawasaki
patent: 7-43554 (1995-05-01), None
patent: 7-40156 (1995-05-01), None
Foley & Lardner
Royer William J.
Toshiba Tec Kabushiki Kaisha
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