Electrophotography – Image formation – Development
Reexamination Certificate
2001-04-25
2002-10-08
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Development
C399S262000
Reexamination Certificate
active
06463241
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-133516, filed May 2, 2000; and No. 2001-003923, filed Jan. 11, 2001, the entire contents of both of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a developing apparatus having a toner container for storing toner and a developing roller incorporated in the toner container, and to an electronic photographing apparatus, such as a laser printer or a copying machine, incorporating the developing apparatus. More specifically, the present invention relates to a structure for preventing toner from spilling from the toner container, when the toner pressure in the toner container is increased.
An electronic photographing apparatus, such as a laser printer, comprises a photosensitive drum having a surface on which an electrostatic latent image is formed, a developing apparatus for developing the electrostatic latent image to a toner image, and a transferring apparatus for transferring the toner image to a recording paper sheet.
The developing apparatus for use in this type of electronic photographing apparatus has a toner container for storing toner. The toner container has an opening portion, which faces the photosensitive drum. A developing roller and a developing plate are located in the opening portion. The developing roller is arranged parallel to the photosensitive drum. The developing roller incorporates a magnet roller. Owing to the magnetic force of the magnet roller, toner is attracted to the peripheral surface of the developing roller. As the developing roller rotates, the toner adhered to the peripheral surface of the developing roller is guided to a developing position between the developing roller and the photosensitive drum.
The function of the developing plate is to make a toner layer adhered to the peripheral surface of the developing roller uniform in thickness. The developing plate is arranged at a position opposite from the developing position in the direction of rotation of the developing roller.
With the developing apparatus described above, the toner adhered to the peripheral surface of the developing roller is first guided to the developing plate as the developing roller rotates, and excess toner is scraped off by the plate. As a result, a thin uniform toner layer is formed on the peripheral surface of the developing roller. The toner layer is guided to the developing position by the rotation of the developing roller, and adhered to the surface of the photosensitive drum at this position. Consequently, the electrostatic latent image on the surface of the photosensitive drum is developed, so that a toner image is formed on the surface.
In the conventional developing apparatus, the toner container has a bottom wall for receiving toner. The bottom wall has an end portion facing the opening portion. The end portion of the bottom wall is located under the developing roller and faces the peripheral surface of the developing roller. A gap is provided between the end portion of the bottom wall and the peripheral surface of the developing roller for the following reason.
Even after the toner passes through the developing position, part of the toner is kept attracted to the peripheral surface of the developing roller and remains on the surface. The remaining toner is returned to the opening portion of the toner container as the developing roller rotates.
At this time, if there is no gap between the developing roller and the bottom wall of the toner container, the toner remaining on the developing roller is brought into contact with the bottom wall at the opening portion, and removed from the peripheral surface of the developing roller. The removed toner is accumulated in the end portion of the bottom wall and cannot be returned into the toner container. Therefore, the amount of toner accumulated in the end portion of the bottom wall is increased with the passage of time, resulting in the drawback that the toner is scattered out of the toner container through the opening portion.
For the reason described above, according to the conventional developing apparatus, a gap is positively provided between the bottom wall of the toner container and the developing roller to avoid contact between the toner remaining on the peripheral surface of the developing roller and the bottom wall, thereby preventing scattering of the toner.
In the case where there is a gap between the bottom wall of the toner container and the developing roller, it is inevitable that part of the toner contained in the toner container will enter the gap. The toner in the gap is influenced by the magnetic force of the magnet roller and attracted to the peripheral surface of the developing roller in a normal image forming operation. Therefore, the toner in the gap is never scattered or spilt out of the toner container.
However, if the developing apparatus receives shock, for example, when the developing apparatus is set to the electronic photographing apparatus, the pressure of the toner contained in the toner container may be temporarily increased. This pressure may be exerted on the gap. Further, when the toner container is replenished with new toner, the new toner put in the toner container drops on the existing toner. Therefore, this shock may increase the pressure of the toner in the toner container. This pressure may be exerted on the gap.
In this case, the toner attracted to the peripheral surface of the developing roller at the position of the gap or the toner located near the gap may be pushed out from the toner container. This results in the problems that the toner is scattered around the toner container, contaminates the interior of the electronic photographing apparatus or adheres to recording paper.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a developing apparatus and an electronic photographing apparatus, in which although there is a gap between a toner supplying body and a bottom wall of a toner container, toner is prevented from spilling out through the gap.
To achieve the above object, a developing apparatus according to a first aspect of the present invention comprises: a toner container for storing toner, the toner container having a bottom wall for receiving the toner and an opening formed at an end portion of the bottom wall and facing a photosensitive body on which an electrostatic latent image is formed; a toner supplying body located at the opening of the toner container, the toner supplying body having a peripheral surface which is exposed in the toner container and to which the toner is adhered, for supplying the toner adhered to the peripheral surface to the photosensitive body by rotation, a gap being formed between the peripheral surface and the bottom wall to return toner remaining on the peripheral surface of the toner supplying body to the toner container; and a toner restricting portion projected upward from the bottom wall of the toner container, the toner restricting portion facing the gap at a position a distance from the gap to be inside the toner container.
In the above structure, if the toner container receives a shock or is replenished with new toner, the pressure of the toner in the toner container is increased. Due to the increase in pressure, the toner near the gap is liable to be pressed out through the gap. However, since the toner restricting portion faces the gap in the toner container, it can receive, immediately upstream from the gap, the pressure of the toner which is exerted toward the gap.
Therefore, the toner held by the toner supplying body and facing the gap or the toner existing near the gap is not pressed out of the toner container. Thus, the toner can be prevented from scattering out of the toner container.
To achieve the above object, a developing apparatus according to a second aspect of the present invention comprises: a toner container for storing toner, the toner container having a bottom wall for rece
Frishauf Holtz Goodman & Chick P.C.
Toshiba Tec Kabushiki Kaisha
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