Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-10-09
2004-03-30
Brase, Sandra (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S111000
Reexamination Certificate
active
06714745
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as a copier or a printer, and particularly to an image forming apparatus for forming a layered image like a color image on a recording material by the utilization of a plurality of image forming stations and a unit detachably mountable on such apparatus.
2. Related Background Art
Reference is had to
FIG. 5
of the accompanying drawings to describe an example of the construction of an image forming apparatus of the electrophotographic type for obtaining multicolored images, i.e., a so-called color image forming apparatus.
The color image forming apparatus shown in
FIG. 5
is a color image forming apparatus of the so-called four-drum type, and a rotary transferring member, i.e., an intermediate transferring belt
6
in the present example, is passed over a driving roller
7
and a driven roller
8
, and is rotated in the direction of arrow. Color image forming stations Y, M, C and Bk for yellow, magenta, cyan and black, respectively, are provided along the direction of movement of the intermediate transferring belt
6
, and accordingly, four photosensitive drums
1
(
1
a
to
1
d
) which are image bearing members are disposed in succession on the upper side of the moving intermediate transferring belt
6
.
Around the photosensitive drums
1
(
1
a
to
1
d
), there are installed image forming means such as charging means
2
(
2
a
to
2
d
), laser scanners
3
(
3
a
to
3
d
) as exposing means, and developing means
4
(
4
a
to
4
d
) provided with developing rollers and containing developers (toners) of the respective colors therein. The image forming means of the respective colors are similar in construction to one another with the exception that Y, M, C and Bk toners are contained in the developing containers of the developing means
4
a
to
4
d.
Also, the photosensitive drum
1
, the charging means
2
and the developing means
4
are made into a unit (cartridge) which is detachably mountable on the main body of the apparatus.
Toner images of the respective colors developed on the respective drums
1
a
to
1
d
by the developing means
4
a
to
4
d
are successively transferred onto the intermediate transferring belt
6
by the use of transferring means
5
(
5
a
to
5
d
), and a full color image is obtained by the toners of four colors, i.e., yellow, magenta, cyan and black.
In the color image forming apparatus in the present example, no cleaning mechanisms are disposed around the photosensitive drums
1
a
to
1
d,
and this is because this apparatus adopts a cleaner system for collecting untransferred toners by the developing means
4
a
to
4
d
simultaneously with developing, and thereby, the downsizing and reduced cost of the apparatus become possible and further, it becomes possible to extend the life of the photosensitive drums because no cleaning blades frictionally contact with the photosensitive drums.
Description will now be made of the image forming operation of the color image forming apparatus constructed as described above.
A laser beam modulated in conformity with image data from a host apparatus such as a personal computer is applied by the exposing means
3
a
to
3
d
to the surfaces of the photosensitive drums
1
a
to
1
d
uniformly charged by charging rollers which are the charging means
2
a
to
2
d
, whereby desired electrostatic latent images are formed for the respective colors. These latent images are reversal-developed and visualized as toner images in developing regions by the developing means
4
a
to
4
d
which are developing apparatuses disposed in opposed relationship with the photosensitive drums
1
a
to
1
d
and containing the toners of the respective colors therein. These toner images are successively transferred to the intermediate transferring belt
6
, and are further transferred to a recording medium P fed by sheet feeding means (not shown) and conveyed by conveying means. These color toner images are melted and fixed by a fixing apparatus (not shown), and are permanently fixed on the recording medium P, whereby a desired color print image is obtained.
In the color image forming apparatus shown in
FIG. 5
, the photosensitive drums
1
a
to
1
d
, charging means
2
a
to
2
d
and developing means
4
a
to
4
d
which are the image forming means are made integral with one another to assume the form of process cartridges
10
a
to
10
d
as shown in
FIG. 6
of the accompanying drawings. The process cartridges
10
a
to
10
d
are made detachably mountable on the main body of the apparatus by cartridge mounting means (not shown).
In the color image forming apparatus of the above-described construction, provision is made of means for detecting the amount of remaining toner in each of the cartridges
10
a
to
10
d
, and when the toner in a cartridge of a certain color has become null and that cartridge has come to the end of its life, it is made possible to continuedly use the apparatus by a user simply interchanging that cartridge, and the maintenance by a serviceman as done in a copier or the like becomes unnecessary.
Also, for example, the photosensitive drums
1
a
to
1
d,
charging means
2
a
to
2
d
and developing means
4
a
to
4
d
which are image forming means are made integral with one another to form cartridges, whereby there is born the merit that stable and good images free of inconvenience can always be obtained until the end of the life of the cartridges and moreover, the user can easily effect the interchange of any cartridge when it has come to the end of its life.
However, in the color image forming apparatus of the construction as described above, image formation using four colors is not always effected, but image formation of single black color is effected in the case of black-and-white images and besides, image formation by various modes such as a two-color mode using only yellow and magenta, and a three-color mode using yellow, magenta and cyan is effected.
That is, there are a four-color mode using four colors, a three-color mode using only three colors of four colors, a two-color mode using only any two colors of four colors, and a single color mode using any one of four colors.
Here, the single color mode will be described as an example. Usually, image formation (printing) is effected in a full color mode (four-color mode), and a speed difference is given between the photosensitive drums and the intermediate transferring belt to thereby secure a good transferring property and obtain a good image.
Next, when for example, a monochromatic image of a single black color is to be formed, the other image forming means than for black are not operated, and a similar image forming operation is performed with the intermediate transferring belt
6
and the photosensitive drums
1
a
to
1
c
spaced apart from one another by a mechanism, not shown. In this case, however, the construction of the apparatus becomes complicated and the cost thereof becomes very high or the apparatus becomes bulky.
So, in the case of the single black mode, it is practised that the intermediate transferring belt
6
is not spaced apart and the photosensitive drums
1
a,
1
b
and
1
c
of the other colors continue to be rotated. In this case, there is not the problem of the increased cost of the apparatus, but yet it is conceivable that not only the photosensitive drum id concerned in image formation but the drums
1
a
to
1
c
not concerned in image formation are worn by the intermediate transferring belt
6
and the end of the life of the photosensitive drums is hastened.
In such a case, the black cartridge is concerned in image formation and therefore, it has been relatively easy to control the life thereof and it can be precisely reported to the user, but the cartridges of the other colors are not concerned in image formation and therefore, an error has occurred to the time for controlling the life thereof and the end of the life could not be sometimes precisely reported to the user.
Also, there have been cases wh
Kakeshita Tomomi
Ogata Hiroaki
Sasame Hiroshi
Yamamoto Shinya
Brase Sandra
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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