Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
1999-10-26
2001-03-20
Chen, Sophia S. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S273000, C399S283000
Reexamination Certificate
active
06205304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus that develops an electrostatic image on an image bearing member, and more particularly to a developing apparatus preferably applied to an image forming apparatus such as a copier or a printer of the electrophotographic system, or a process cartridge detachably attachable to the image forming apparatus.
2. Related Background Art
Up to now, as a developing apparatus for use in an electrophotographic image forming apparatus such as a printer or a copier, as shown in
FIG. 9
, there has been proposed a developing apparatus having a process cartridge B detachably attachable to a main body of the electrophotographic image forming apparatus. Referring to
FIG. 9
, in the developing apparatus of this type, a magnet Mg is disposed within a hollow cylindrical developing roller
60
c
that functions as a developer bearing member, and its magnetic force allows a developer (hereinafter referred to as “toner”) to be attracted onto the developing roller
60
c
. Then, with the rotation of the developing roller
60
c
(or the magnet Mg), the toner is carried to a developing section that allows a latent image to be visualized.
As a manner of preventing the toner from being leaked outward from a developing container
60
b
, there has been known a method in which a sealing member such as a felt is brought into contact with the developing roller outside of an image region, or as shown in
FIG. 9
, a ferromagnetic member
71
that functions as a sealing member is disposed out of contact with the developing roller
60
c
so that its magnetic force allows the toner to be held.
In addition, in order that the toner carried on the downstream side of the sealing member with the rotation of the developing roller
60
c
or the magnet Mg as described above is again returned within the developing region so as to be prevented from being leaked outwardly, a scraping member
72
is disposed on the downstream side of the above-described sealing member (the ferromagnetic member
71
in
FIG. 9
) in a direction along which the developing roller
60
c
rotates, and a part of the scraping member
72
is brought into contact with the developing roller
60
c.
Also, in order to hold a distance between a photosensitive drum
57
and the developing roller
60
c
constant, there is applied a method in which both end portions of the developing roller
60
c
are covered with cap rollers (not shown) the thickness of which is severely managed.
However, in the above-described conventional example, there was a case in which when the toner scraped off by the scraping member
72
is over-deposited on the scraping member
72
, the toner comes off from the developing roller
60
c
and flies up with the result that the toner is temporarily or permanently dispersed and exists in the form of a lump on a portion where the photosensitive drum
57
and the cap rollers are abutted against each other. In this case, when the rotation of the photosensitive drum
57
or the developing roller
60
c
permits a lump of the toner to come to a position where the photosensitive drum
57
and the cap rollers are in contact with each other, a distance between the photosensitive drum
57
and the developing roller
60
c
becomes rapidly larger than a given distance (the thickness of the cap rollers), thereby causing a case in which the distance made larger returns to the given distance after the lump of toner has passed between the photosensitive drum
57
and the developing roller
60
c
. This leads to a phenomenon (hereinafter referred to as “white banding”) in which an image on a portion corresponding to the lump of toner is thinned.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a developing apparatus that regulates the amount of developer which is deposited on a developer scraping member.
Another object of the present invention is to provide a developing apparatus that restrains the developer scraped off by the developer scraping member from coming off from a developer bearing member and flying up.
Still another object of the present invention is to provide a developing apparatus that prevents the above white banding from occurring or delays the occurrence of the white banding for a long period of time.
Yet still another object of the present invention is to provide a developing apparatus that reduces the amount of developer leaked from the developer scraping member.
Other objects and features of the present invention will become apparent by reading the following detailed description with reference to the accompanying drawings.
REFERENCES:
patent: 5084733 (1992-01-01), Katoh et al.
patent: 5655178 (1997-08-01), Ishikawa et al.
patent: 5895144 (1999-04-01), Nishimura
patent: 6-011958 (1994-01-01), None
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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