Electrophotography – Image formation – Combined or plural functions by single component
Reexamination Certificate
2002-09-30
2004-10-26
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Combined or plural functions by single component
C399S252000, C399S285000
Reexamination Certificate
active
06810223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for forming an image and a method therefor, and more particularly, to a developing apparatus adapted for use in an image forming apparatus using electrophotography, and a method of forming an image using the developing apparatus.
2. Description of the Related Art
In an image forming apparatus using electrophotography, a photosensitive object is exposed to light, and then, a latent electrostatic image invisible to the naked eye is formed on a portion of the photosensitive object according to image information obtained from an original copy or a predetermined source. Next, a developing solution (toner) is applied onto the portion of the photosensitive object to visualize the latent electrostatic image. Then, the visualized image is transferred to and fixed onto paper.
The image forming apparatus using electrophotography is classified into a wet-type image forming apparatus and a dry-type image forming apparatus according to the type of toner used. The wet-type image forming apparatus uses a mixture of powdered toner and a volatile liquid carrier as a developing solution, whereas the dry-type image forming apparatus uses only powdered toner.
In the image forming apparatus using electrophotography, the developing solution is supplied to the photosensitive object to visualize the latent electrostatic image formed thereon. Specifically,
FIGS. 1 and 2
are cross-sectional views of conventional developing apparatuses in the dry-type image forming apparatus using electrophotography.
Referring to
FIG. 1
, a charging roller
12
charges the circumference of a photosensitive drum
10
with an electric charge. When a laser beam containing image information is scanned on a portion of the charged circumference of the photosensitive drum
10
by a laser scanning unit
14
, a static electric charge of the portion is removed, and then, a latent electrostatic image corresponding to the image information is formed on the circumference of the photosensitive drum
10
. The latent-electrostatic image can be visualized by a developing roller
16
supplying toner charged with the same or opposite electric charge to the circumference of the photosensitive drum
10
. The developing roller
16
is supplied with toner by a supply roller
20
. A portion of the supply roller
20
is in contact with the circumference of the developing roller
16
, and another portion of the supply roller
20
is in contact with toner
18
.
Above the developing roller
16
, a toner layer control unit
22
is installed adjacent to the circumference of the developing roller
16
so as to control a toner layer formed on the circumference of the developing roller
16
. Also, below the developing roller
16
, first and second seal members
24
and
28
are installed to seal a first case
20
containing the toner
18
and the supply roller
20
, and a bottom of the first case
26
is connected to the toner layer control unit
22
. In an opposite side of the developing roller
16
, a waste toner storage member
32
, which stores waste toner collected from the circumference of the photosensitive drum
10
after the latent electrostatic image has been transferred onto paper (not shown), is disposed in a second case
34
having the charging roller
12
.
Also, to prevent the leakage of the waste toner, a third seal member
30
is connected to a bottom of the second case
34
while being in contact with the circumference of the photosensitive drum
10
. A cleaning blade
36
, which is used to remove the waste toner remaining on the circumference of the photosensitive drum
10
, is installed adjacent to the charging roller
12
in the waste toner storage member
32
and between the charging roller
12
and the third seal member
30
. Here, reference numeral
38
denotes a lid of a toner storage member
40
of the first case
26
.
FIG. 2
is a cross-sectional view of another conventional developing apparatus in an image forming apparatus. Referring to
FIG. 2
, a charging apparatus
52
, which has the same operations as the charging roller
12
of
FIG. 1
, is installed adjacent to a photosensitive drum
50
. In the front of the charging apparatus
52
is installed a discharging lamp
54
removing an electric charge from the circumference of the photosensitive drum
50
prior to charging the photosensitive drum
50
. When an exposure apparatus
21
emits light on the circumference of the photosensitive drum
50
charged by the charging apparatus
52
, a latent electrostatic image is formed on the circumference of the photosensitive drum
50
. The formed latent electrostatic image can be visualized by a developing apparatus
56
installed adjacent to the photosensitive drum
50
.
A toner hopper
60
containing toner
58
is installed in an upper portion of a case
56
a
. A developing roller
62
, which supplies the toner
58
to the photosensitive drum
50
so as to visualize the latent electrostatic image, is installed at an aperture at a lower portion of the case
56
a
. Between the developing roller
62
and a toner outlet of the toner hopper
60
is installed a supply roller
64
supplying the toner
58
to the developing roller
62
. An upper side of the circumference of the developing roller
62
is in contact with a toner layer control unit
66
controlling an amount of the toner
58
and toner layers formed on the developing roller
62
, and a lower side of the developing roller
62
is in contact with a sealing blade
68
preventing the leakage of the toner
58
out of the case
56
a.
A cleaning roller
70
is installed at an upper aperture of the case
56
a
and is separated from a lower aperture of the case
56
a
by a predetermined distance. The cleaning roller
70
is spaced-apart from the photosensitive drum
50
by about 200 &mgr;m and is used to remove the toner
58
remaining on the circumference of the photosensitive drum
50
. The upper and lower sides of the circumference of the cleaning roller
70
are in contact with a toner layer control unit
66
, which controls the amount of the toner
58
and the toner layers, and a sealing blade
74
, which prevents the leakage of the toner
58
, respectively. The developing roller
62
and the cleaning roller
70
are connected to a power source
76
supplying a predetermined cleaning and developing voltage thereto so as to remove the toner
58
remaining on the circumference of the photosensitive drum
50
, supply the toner
58
to the circumference of the photosensitive drum
50
, and visualize the latent electrostatic image formed on the circumference of the photosensitive drum
50
.
The conventional developing apparatus of
FIG. 1
may perform an excellent cleaning operation since the toner remaining on the circumference of a photosensitive drum is mechanically removed by a blade when a latent electrostatic image is transferred on paper and then cleaned. However, the conventional developing apparatus of
FIG. 1
is disadvantageous in that it is difficult to minimize the conventional developing apparatus in size since a region for additionally storing waste toner is required, there is a limitation in reducing at toner consumption due to the waste toner, and additional devices are further needed to collect and store the waste toner when the image forming apparatus is manufactured. These disadvantages would cause an inconvenience of a user and contamination of an image.
On the other hand, the conventional developing apparatus of
FIG. 2
may perform less excellent cleaning operations than that of the developing apparatus of
FIG. 1
, but is advantageous in that it does not require an additional space for storing the waste toner. However, the developing apparatus of
FIG. 2
has a low efficiency in collecting the waste toner from a photosensitive drum, thereby still causing the contamination of an image, such as a ghost image, due to a poor cleaning operation.
SUMMARY OF THE INVENTION
To solve the above and other problems, it is an object of the present invention to provide a d
Eun Jong-moon
Lee Duck-hee
Chen Sophia S.
Staas & Halsey , LLP
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