Electrophotography – Image formation – Development
Reexamination Certificate
1998-12-11
2001-05-08
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Development
C399S284000
Reexamination Certificate
active
06229980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a developing apparatus for visualizing an electrostatic latent image formed on an image bearing member such as an electrophotographic photosensitive member or an electrostatic recording dielectric member.
2. Related Background Art
As the output means of an external apparatus such as a computer, or a copying apparatus, there is an image forming apparatus using the electrophotographic method as shown, for example, in
FIG. 6
of the accompanying drawings.
The image forming apparatus has an electrophotographic photosensitive member usually in the form of a drum as an image bearing member, i.e., a photosensitive drum
100
, and the surface of this photosensitive drum
100
is uniformly charged by a primary charger
117
. Next, a light
123
is applied by an exposure device correspondingly to image information inputted from an external apparatus, and an electrostatic latent image is formed on the surface of the photosensitive drum
100
. This latent image is reversely developed by a developing apparatus
140
by the use of a developer T having a frictional charging polarity of the same polarity as the applied voltage of the primary charger
117
, and is visualized as a toner image.
This toner image is transferred onto a transfer material P supplied to the photosensitive drum
100
by a transfer charger
114
. The transfer material P having the toner image transferred thereto is separated from the photosensitive drum
100
, and then is conveyed to a fixating device
126
, where the toner image is fixated as a permanent image on the transfer material P. On the other hand, the photosensitive drum
100
has any untransferred developer T remaining on its surface removed by a cleaning device
116
and is used for the next image forming process.
The developing apparatus
140
is a magnetic one-component developing apparatus and a typical example of the construction thereof is shown in
FIG. 7
of the accompanying drawings. This developing apparatus
140
contains in a developing container
140
A a negatively chargeable magnetic toner containing a magnetic material as the developer T.
The developing apparatus
140
has its inner lower portion compartmented into a first toner agitating chamber A and a second toner agitating chamber B by a partition plate
108
, and first and second toner agitating members
109
and
106
are installed in the first and second agitating chambers A and B, respectively. A developing sleeve
102
rotatable in the direction of arrow in
FIG. 7
is installed in an opening portion on the first agitating chamber A side of the developing apparatus
140
which faces the photosensitive drum
100
(FIG.
6
), and a magnet roller
110
is disposed in this developing sleeve
102
. An elastic blade (developing blade)
103
as a toner amount regulating member is fixed to that portion of the developing apparatus which is above the developing sleeve
102
, and depends onto and elastically bears against the developing sleeve
102
.
The magnetic toner T contained in the developing apparatus
140
is conveyed from the second agitating chamber B to the first agitating chamber A by the rotation of the second agitating member
106
in the direction of arrow in FIG.
7
. The first agitating member
109
is rotated in the same direction to thereby rotate the conveyed toner T near the developing sleeve
102
and create the circulation of the toner so that a constant amount of toner may always be supplied to the developing sleeve
102
.
The first and second agitating members
109
and
106
each are formed by one of various rotatable plate materials, screws, rollers or the like, and are rotated at an appropriate speed to efficiently convey the toner T. The partition plate
108
present between the first and second agitating members
109
and
106
has its height made proper to thereby make the amount of toner in the first agitating chamber A substantially constant thus contributing to creating the circulation of a constant amount of toner.
If the amount of toner in the first agitating chamber A is too small, the amount of toner circulated near the developing sleeve
102
will also become small and a sufficient amount of toner cannot be supplied to the developing sleeve
102
. If the amount of toner in the first agitating chamber A is too great, the toner will excessively fill up and the irregular coat or streaks or the like of the toner will become liable to occur on the developing sleeve
102
. Accordingly, the height of the partition plate
108
is made proper so as to provide a medium amount. A great amount of toner T is contained in the second agitating chamber B.
The developing sleeve
102
comprises a cylindrical member of a non-magnetic electrically conductive metal such as aluminum or stainless steel, and in the present example, it has a diameter of 16 mm.
The developing sleeve
102
is disposed with a predetermined gap kept between it and the photosensitive drum
100
by a gap regulating member, not shown.
The magnet roller
110
which is magnetic field producing means in the developing sleeve
102
is fixed to the side wall of the developing apparatus
140
and is disposed concentrically and nonrotatably in the developing sleeve
102
. The developing sleeve
102
is rotated around the magnet roller
110
.
The magnet roller
110
, as shown, is provided with four magnetic poles S
1
, S
2
, N
1
and N
2
, and the magnetic pole S
1
is a developing pole, the magnetic pole N
1
is a toner amount regulating pole, the magnetic pole S
2
is a toner introducing and conveying pole, and the magnetic pole N
2
is a toner blow-out preventing pole.
The magnetic toner T supplied by the first agitating member
109
is carried on the developing sleeve
102
by the magnetic force of the magnet roller
110
, and is conveyed toward a developing area opposed to the photosensitive drum
100
with the rotation of the developing sleeve
102
. In the course of the conveyance, the toner has its layer thickness regulated by the elastic blade
103
bearing against the developing sleeve
102
, and is formed into a thin toner layer
107
prescribed to an amount of toner to be conveyed to the developing area.
The toner T conveyed to the developing area flies and adheres to the electrostatic latent image on the photosensitive drum
100
by a developing electric field by a developing bias applied to between the developing sleeve
102
and the photosensitive drum
100
, and visualizes the latent image as a toner image.
Descretely from the magnetic one-component developing apparatus as described above, a non-magnetic one-component developing apparatus has recently been put into practical use as a simple color developing apparatus. This non-magnetic one-component developing apparatus, as shown, for example, in
FIG. 8
of the accompanying drawings, can assume a construction resembling that of the magnetic one-component developing apparatus. This non-magnetic one-component developing apparatus
240
contains therein a non-magnetic toner T which is an insulative one-component developer, and in the present example, the non-magnetic toner T is negatively chargeable and contains any one of yellow, magenta, cyan and black pigments.
In a non-magnetic one-component developing method, the supply of the toner T to a developing sleeve
202
by a magnetic force is impossible and therefore, instead of a magnet roller being provided in the developing sleeve
202
, a toner supply roller
205
made of urethane sponge which serves also to strip off the toner is installed so as to bear against the developing sleeve
202
.
The supply roller
205
bears against the developing sleeve
202
and is rotated in the same direction as the latter to thereby supply the non-magnetic toner T onto the developing sleeve
202
and at the same time, strips off any toner remaining after the development in the developing area off the developing sleeve
202
. The toner T supplied to the developing sleeve
202
adheres to and is carried on the developing sleeve
202
by
Ogawa Kenya
Ozeki Yukihiro
Sakaizawa Katsuhiro
Yamamoto Takeshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grimley Arthur T.
Tran Hoan
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