Electrophotography – Document handling – Copy
Reexamination Certificate
2000-11-22
2002-07-30
Chen, Sophia S. (Department: 2852)
Electrophotography
Document handling
Copy
C399S049000, C399S072000, C399S302000
Reexamination Certificate
active
06427062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic method, and more particularly to an image forming apparatus such as a copying machine, a printer or a facsimile machine.
2. Related Background Art
FIG. 8
shows a schematic structure of an example of a process station (image forming station) in a conventional image forming apparatus using the electrophotographic method.
A process station
2
shown in
FIG. 8
includes a photosensitive drum
21
that rotates in a direction indicated by an arrow R
2
as an image bearing member. After the surface of the photosensitive drum
21
is uniformly charged by a primary charger
22
, the surface receives an exposure
23
′ based on image information by an exposure device
23
such as an LED or a laser, to thereby form an electrostatic latent image thereon. Toner is stuck onto the latent image by a developing sleeve
27
of a developing device
24
which rotates in a direction indicated by an arrow R
3
, to thereby develop the latent image as a toner image. The toner image thus obtained is electrostatically transferred by a transfer charging blade
103
onto a transfer material P which is born on a conveying belt
1
and conveyed in a direction indicated by an arrow R
1
.
After the toner image has been transferred onto the transfer material P, non-transferred toner which has remained on the surface of the photosensitive drum
21
without being transferred onto the transfer material P is removed by a cleaning blade
25
and then collected within a waste toner container
26
. The photosensitive drum
21
the surface of which has been thus cleaned is ready for succeeding image formation.
FIG. 9
shows a four-color full color image forming apparatus of a so-called in-line system in which four process stations having the same structure as that of the above-described process station
2
are arranged.
As shown in
FIG. 9
, in the image forming apparatus, a conveying belt
1
is disposed as transfer material conveying means, and the conveying belt
1
is put around four rollers consisting of an attractive opposite roller
6
, a driving roller
7
and tension rollers
8
and
9
, and rotated in a direction indicated by an arrow R
1
by the drive of the driving roller
7
. Four process stations
2
a,
2
b,
2
c
and
2
d
for yellow (Y), magenta (M), cyan (C) and black (K) are disposed tandem in the stated order from the upstream side along the moving direction of the conveying belt
1
as indicated by the arrow R
1
.
Transfer blades
103
a,
103
b,
103
c
and
103
d
are abutted against the conveying belt
1
in order to make the conveying belt
1
push with predetermined pressure toward photosensitive drums
21
a,
21
b,
21
c
and
21
d
within the respective process stations
2
a,
2
b,
2
c
and
2
d.
The respective transfer blades
103
a,
103
b,
103
c
and
103
d
are connected with transfer bias power supplies
104
a,
104
b,
104
c
and
104
d
each of which applies a transfer bias.
Up to now, the photosensitive drum
21
(
21
a,
21
b,
21
c
and
21
d
) is made of negative organic photoconductor (OPC), and in the case where an exposed portion of the surface of the photosensitive drum
21
where negative electric charges are decayed by the exposure of the exposing device
23
is developed, a developer containing negative toner therein is employed. Accordingly, during transferring operation, a positive transfer bias is applied to the transfer blade
103
(
103
a,
103
b,
103
c
and
103
d
) by the transfer bias power supplies
104
(
104
a,
104
b,
104
c
and
104
d
). The transfer blade
103
is generally formed of a low-resistance resin film.
The transfer material P is conveyed from a sheet feed cassette
15
toward the conveying belt
1
by a feed roller
14
. In order to make the transfer material P in synchronism with the toner image formed on the photosensitive drum, after the transfer material P thus conveyed is nipped by a pair of registration rollers
10
and
11
once, the transfer material P is conveyed in predetermined timing to an attractive portion N of the conveying belt
1
where an attractive roller
5
and an attractive opposite roller
6
are opposite to each other, and the transfer material P is attracted to the conveying belt
1
by the attractive roller
5
and the attractive opposite roller
6
.
A given voltage is applied to the attractive roller
5
from an attractive bias power supply
12
which is a high voltage power supply, as a result of which electric charges are induced to the transfer material P, and the conveying belt
1
is dielectrically polarized, thereby allowing the transfer material P to be electrostatically attracted onto the surface of the conveying belt
1
so as to be firmly born by the surface of the conveying belt
1
.
The transfer material P born on the conveying belt
1
sequentially passes through the respective transfer portions of the four process stations
2
, and the toner images of the respective colors on the respective photosensitive drums
21
a,
21
b,
21
c
and
21
d
are sequentially superimposed and transferred on the transfer material P by the action of the transfer blade
103
, to thus obtain a full color image of four colors on the transfer material P.
The transfer material P onto which the toner image of four colors has been thus transferred is separated from the conveying belt
1
and is then conveyed to a fixing device
16
where the transfer material P is heated and pressurized so that the toner image is fixed on the surface of the transfer material P, to thereby form a permanent image of the full color. Thereafter, the transfer material P is discharged to the external of the image forming apparatus. After electric charges are eliminated by a charge eliminating charger
13
from the surface of the conveying belt
1
, from which the transfer material P has been separated, the conveying belt
1
is ready for a succeeding image forming process.
Up to now, the conveying belt
1
is formed of a resin film such as PVdF (polyvinylidene fluoride), ETFE (tetrafluoroethylene—ethylene copolymer), polyimide, PET (polyethylene terephthalate) or polycarbonate which is 50 to 200 &mgr;m in thickness and about 10
9
to 10
16
&OHgr;cm in volume resistivity, or an urethane rubber in which fluorine resin such as PTFE is dispersed coated on a base layer made of rubber such as EPDM which is about 0.5 to 2 mm in thickness.
There is no case in which the conveying belt
1
is contaminated by the toner since the toner image is not directly transferred onto the surface of the conveying belt
1
during the normal image forming operation. However, in the case where the transfer material P is jammed or fogging toner on background is stuck onto a non-image portion of the photosensitive drum, the conveying belt
1
is contaminated by the toner. Also, in the case of executing a density control mode that controls the density of a toner image formed on the photosensitive drum or a registration control mode that controls a timing at which the toner images of the respective colors are formed on the respective photosensitive drums so as to appropriately superimpose the toner images of the respective colors on the transfer material P on each other, since a density patch or a register patch is transferred onto the conveying belt
1
as a detection toner image and then detected by a photosensor
31
, the conveying belt
1
is contaminated by the toner by the density patch or the register patch.
The contamination toner on the conveying belt
1
is cleaned and removed by the cleaning blade
32
which is disposed opposite to a backup member
33
through the conveying belt
1
. The removed toner is collected into a waste toner container
34
.
Since the waste toner container
34
needs to be replaced by a fresh container when the container
34
is filled with the collected toner, this replacing work is troublesome for a user, as a result of which the useability may be lowered. Also, since the waste toner container
34
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
Tran Hoan
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