Developing apparatus of electric photographic printer

Electrophotography – Internal machine environment – Particle or contaminant control

Reexamination Certificate

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C399S267000, C399S277000

Reexamination Certificate

active

06801732

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2001-74157, filed Nov. 27, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus of an electric photographic printer, and more particularly, to a developing apparatus of an electric photographic printer capable of preventing a developing agent from being scattered in a developing area.
2. Description of the Related Art
An electric photographic printer is an apparatus to print an image by transferring an electrostatic latent image formed at a photosensitive medium to a printing medium after developing the electrostatic latent image to a visible image using a developing agent. In this case, the developing agent is normally a magnetic one-element developing agent or a nonmagnetic two-element developing agent.
The two-element developing agent includes toner and a carrier mixed at a predetermined rate. The carrier adheres as a brush shape to a surface of a developing roller by a magnetic force of the developing roller, and the toner adheres to the carrier by an electrostatic force.
FIG. 1
is a sectional view schematically showing a structure of a developing apparatus
10
of the electric photographic printer using the two-element developing agent.
Referring to
FIG. 1
, the developing apparatus
10
includes a developing roller
13
, a developing agent mixing roller
17
, a developing agent supplying roller
18
, a magnetic bar
19
and a housing
11
.
The developing roller
13
includes a developing sleeve
14
and a fixing magnet
15
. The developing sleeve
14
is a hollow cylindrical shape and rotatably installed at the housing
11
. The developing roller
13
transfers a developing agent
1
to a developing area A facing a photosensitive medium
20
disposed at opposite to the developing roller
13
with respect to the developing area A. The fixing magnet
15
is installed inside the developing sleeve
14
and is a cylindrical shape having a plurality of fragments. The fixing magnetic
15
has a magnetic pole N
1
disposed to face the developing area A, and magnetic poles, S
1
, N
2
, N
3
, and S
2
disposed in a counterclockwise in order from the magnetic pole N
1
with respect to a center of the developing roller
13
. Moreover, a developing blade
16
is disposed in a predetermined space at one upper side of the developing sleeve
14
, thus a thickness of the developing agent attached to the developing sleeve
14
can be adjusted to be thinner by a predetermined degree.
The developing agent mixing roller
17
is installed at a rear of the developing sleeve
14
. The developing agent mixing roller
17
mixes two elements, such as the toner and the carrier, and allows the developing agent
1
to be electrically charged to have an electrostatic force.
The developing agent supplying roller
18
is disposed at a rear portion of the developing agent mixing roller
17
and supplies the developing agent
1
to the developing agent mixing roller
17
.
The housing
11
has the developing sleeve
14
, the developing agent mixing roller
17
, and the developing agent supplying roller
18
. An area of the developing sleeve
11
a
faces the photosensitive medium
20
through an housing opening portion
11
a
of the housing
11
.
The magnetic bar
19
is disposed at an outside of upper and lower ends of the hosing open portion
11
a
and adsorbs the developing agent
1
scattered at the developing area A.
An operation of the developing apparatus
10
having the above structure will be described hereinbelow.
The developing agent
1
in the housing
11
is supplied to the developing agent mixing roller
17
by the developing agent supplying roller
18
, and thus the toner and the carrier are mixed. The mixed developing agent
1
adheres to the developing sleeve
14
by a magnetic force of the fixing magnet
15
installed inside the developing sleeve
14
and forms a magnetic brush shape. When the developing sleeve
14
is rotated, the developing agent
1
attached to a portion of the developing sleeve
14
passes through the developing agent blade
16
and becomes thinner to a predetermined thickness.
When the portion of the developing sleeve
14
rotates continuously and is disposed at the developing area A, the developing agent
1
, which has become thinner, moves to the photosensitive medium
20
by an operation of an electrostatic force of the electrostatic latent image of the photosensitive medium
20
.
At this time, when the developing agent
1
has little electrostatic force due to an insufficient electric charge, the developing agent
1
is scattered. Yet, the scattered developing agent
1
adheres to the magnetic bar
19
disposed at an outside portion of upper and lower ends of the hosing open portion
11
a
of the developing apparatus
10
and is prevented from being discharged to the outside portion of the developing apparatus
10
.
However, in the developing apparatus
10
described so far, since the magnetic bar
19
is disposed at the outside portion of the housing open portion
11
a
, the developing agent leaking out to the outside portion of the housing
11
of the developing apparatus
10
is adsorbed to the magnetic bar
19
. Therefore, a problem occurs that the developing agent
1
scattered at the developing area A cannot be completely prevented from leaking out to the outside portion of the housing
11
.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above and other problems of the prior art. Accordingly, it is the object of the present invention to provide a developing apparatus of an electric photographic printer capable of effectively preventing a developing agent scattered in the developing area from leaking out to an outside portion of the developing apparatus by forming a magnetic force brush between a developing roller and a magnetic bar disposed on an inside portion of the housing.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to achieve the above and other objects, a developing apparatus of an electric photographic printer to supply a two-element developing agent to develop an electrostatic latent image formed on a photosensitive medium includes a housing, a developing agent supplying roller disposed at a lower part of the housing to transfer the developing agent, a developing agent mixing roller disposed at one side of the developing agent supplying roller to mix the developing agent so that two elements of the developing agent can be mixed equally, a developing sleeve rotatably disposed at one upper part of the developing agent mixing roller to transfer the mixed developing agent to a developing area facing the photosensitive medium by rotating in a counterclockwise direction, a fixing magnet disposed inside the developing sleeve to have magnetic poles N
1
, S
1
, N
2
, N
3
, and S
2
arranged from the developing area in the counterclockwise direction with respect to a center of the developing roller to allow the developing agent attached to the developing sleeve to be transferred to the developing area, and a magnetic bar disposed inside the housing to face the magnetic pole S
1
of the fixing magnet through the developing sleeve, to form a magnetic force brush preventing the developing agent from being scattered as the developing agent passes through the developing area.
It is possible that the fixing magnet has the magnetic pole N
1
disposed to face the photosensitive medium, and a sectional rotation sleeve area of the magnetic pole S
1
is almost equal to a total sectional rotation sleeve area of the magnetic poles S
2
, N
3
and N
2
.
In addition, the magnetic bar includes a magnetic pole with a magnetic polarity, which is opposite to that of the magnetic pole S
1
of the fixing m

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