Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
1999-08-30
2003-04-15
Grainger, Quana M. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S274000, C399S284000
Reexamination Certificate
active
06549735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus which can be used with an image forming apparatus such as an electrophotographic copying machine, an electrophotographic printer and the like.
2. Related Background Art
In image forming apparatuses of electrophotographic type, an electrostatic latent image formed on an image bearing body is visualized by a developing apparatus as a developer image.
As an example of such developing apparatuses, various dry type one-component developing apparatuses have been proposed and put to a practical use.
Nowadays, since improvement in resolution and clearness of an image have been requested, investigation regarding method and apparatus for forming a thin layer of developer (one-component developer) on a developer bearing body is inevitable and some attempts for improvement have been proposed.
For example, as disclosed in Japanese Patent Application Laid-Open No. 54-43038, an elastic blade (regulating member) made of metal or rubber abuts against a developing sleeve (developer bearing body) so that, by passing developer through an abutment area between the elastic blade and the developing sleeve to regulate the developer, a thin developer layer is formed on the developing sleeve and adequate triboelectricity is applied to the developer in the abutment area.
In this case, when non-magnetic developer is regulated by the elastic blade, a developer supplying member for supplying the developer onto the developing sleeve must be provided additionally. The reason is that, although magnetic developer can be supplied onto the developing sleeve by a force of a magnet disposed within the developing sleeve, the non-magnetic developer cannot be supplied by such a magnetic force.
To this end, a developing apparatus
50
as shown in
FIGS. 7 and 8
has been proposed. In this conventional developing apparatus
50
, an elastic roller
55
utilizing a foam body made of polyurethane foam or sponge or a fur brush is disposed within a developing container
54
containing non-magnetic developer
53
as a one-component developer. The roller
55
abuts against a developing roller
52
upstream of an elastic blade
51
in a rotational direction of the developing roller. By rotating the elastic roller in a direction shown by the arrow D, the developer
53
is supplied onto the developing roller
52
.
As the developing roller
52
is rotated, the developer
53
supplied to the developing roller
52
is sent to an abutment area between the elastic blade
51
and the developing roller
52
to form a thin layer which is in turn used for development of an electrostatic latent image on a photosensitive body
1
.
Residual developer
53
(which was not used in the development) remaining on the developing roller
52
is scraped by the elastic roller
55
, and new developer is supplied to the developing roller
52
by the elastic roller
55
as mentioned above. Such operations are repeated.
In this case, when a developing roller
52
is formed from metallic material, an elastic blade
51
formed from a thin metal plate is not preferable because of wear of the developing roller. In order to provide a desired thin developer layer, rubber material such as urethane or silicone must be used.
Further, since the surface of the developing roller
52
was subjected to blasting or carbon coating treatment, good carrying of developer
53
can be achieved by moderate unevenness.
Regarding a longitudinal direction of the developing container
54
, i.e., an axial direction of the developing roller
52
, a roughness formed region
52
a
on the surface of the developing roller
52
has an area greater than an opening portion
57
a
of the developing container, and developing roller end seals
58
are disposed at ends of the opening portion
57
a
so that lateral,leakage of the developer along the longitudinal direction of the developing roller
52
is prevented while sliding the seals frictionally on the surface of the developing roller
52
.
With the arrangement as mentioned above, the thin layer of non-magnetic developer can be effectively formed on the developing roller
52
.
However, in comparison with a magnetic developing apparatus in which magnetic developer can easily be held on a surface of a developing roller by the action of a magnetic field, since the non-magnetic developer is used, a magnetic adsorbing force cannot be utilized. Thus, it is difficult to prevent leakage of the developer
53
out of the developing apparatus
50
shown in FIG.
8
. That is to say, since the developing roller
52
cannot hold any developer other than the frictionally charged developer and an abutment area (hatched area in
FIG. 8
) is left between the elastic blade
51
and the developing roller
52
. The developer can then easily leak outside through a lower part and ends of the developing roller
52
, thereby causing developer contamination within the image forming apparatus.
To avoid this, at a developer collecting area of a lower part of the developing container
54
, there is provided a flexible seal member
56
lightly abutting against the developing roller
52
and having one end secured to a frame
57
of the developing container
54
, thereby permitting passage of non-used developer and preventing the developer
53
within the developing container
54
from leaking through the lower part of the container
54
.
While such a developing apparatus is used with a compact copying machine or page printer, recently, in order to facilitate maintenance, a developing cartridge in which a developing apparatus is formed as a unit or a process cartridge in which a developing apparatus, a photosensitive drum, a cleaner and a charging device (not shown) are integrally incorporated has been put to practical use as an exchangeable device.
As mentioned above, the developing roller
52
has moderate unevenness obtained by surface blasting or carbon coating treatment. The developer
53
can be effectively carried by such unevenness on the surface of the developing roller
52
.
However, if the developing operations using the above-mentioned conventional developing apparatus are repeated multiple times, the roughness formed region
52
a
on the surface of the developing roller
52
shown in
FIG. 9
slides frictionally against the end peripheral seal members (leakage preventing members)
58
for preventing the developer from leaking outside. In this case, in an area corresponding to the opening portion
57
a
of the developing container, at both ends of a coated zone of the developing roller
52
coated by the developer, the developer is carried to the frictional sliding surfaces of the end peripheral seal members
58
, with the result that the developer is melted on and adhered to the end peripheral seal members
58
, thereby worsening sealing ability between the developing roller
52
and the end peripheral seal members
58
. As a result, developer leakage occurs to cause serious contamination within the image forming apparatus.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a developing apparatus which can prevent fusion and adhesion of developer on end leakage preventing members.
Another object of the present invention is to provide a developing apparatus in which developer born on a developer bearing body is prevented from entering into sliding surfaces of end leakage preventing members.
Yet another object of the present invention is to provide a developing apparatus which can prevent leakage of developer from end leakage preventing members.
REFERENCES:
patent: 4903634 (1990-02-01), Ono et al.
patent: 5073797 (1991-12-01), Ono et al.
patent: 5202729 (1993-04-01), Miyamoto et al.
patent: 5550619 (1996-08-01), Komakine et al.
patent: 5701558 (1997-12-01), Kojima
patent: 0 314 436 (1989-05-01), None
patent: 54-43038 (1979-04-01), None
patent: 61-28977 (1986-02-01), None
patent: 7-72734 (1995-03-01), None
patent: 9-274382 (1997-10-01), None
Fujita Akiyoshi
Horikawa Tadashi
Matsuda Kenji
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