Image fusing unit of liquid electrophotographic printer

Electrophotography – Image formation – Development

Reexamination Certificate

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Details

C399S328000, C399S397000

Reexamination Certificate

active

06618568

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
An apparatus consistent with the present invention relates to an image fusing unit of a liquid electrophotographic printer.
2. Description of the Related Art
In a typical liquid electrophotographic printer such as a color laser printer, a desired image is developed on a photosensitive medium with a developer liquid mixture of charged toner particles and solvent, and then, the developed image is transferred to a sheet of print paper.
However, since the image transferred onto the print paper includes a large amount of solvent, an image fusing unit is needed to dry the image after transfer and completely fuse it on the print paper.
FIG. 1
shows a conventional image fusing unit for drying and fusing which is disclosed in U.S. Pat. No. 5,465,146. As shown in the drawing, the image fusing unit includes a drying portion
1
for drying a sheet of paper C where an image C
1
is transferred in a non-contact manner, and a fusing portion
2
for fusing the image C
1
by heating and pressing the paper C. The drying portion
1
includes a first roller R
1
where a heater H
1
is built in, a drying belt B circulating between the first roller R
1
and a second roller R
2
. The fusing portion
2
includes the second roller R
2
and a third roller R
3
where a heater H
2
is built in and rotating in contact with the second roller R
2
.
In the above structure, the paper C transferred to the image fusing unit through a transfer belt T is heated and dried while passing through the drying portion
1
. That is, heat generated from the heater H
1
of the first roller R
1
heats the drying belt B and the paper C passing under the drying belt B receives radiant heat of the heated drying belt B. This heat dries the image C
1
on the paper C and the solvent included in the image C
1
is vaporized and thus removed. Then, the paper C is heated and pressed as it passes between the second roller R
2
and third roller R
3
of the fusing portion
2
, so that the image C
1
which is previously dried is completely fused on the paper C.
However, in the image fusing unit having the above structure, since the drying portion
1
is configured in a non-contact heating manner, the efficiency of heat in the drying work is low. That is, since the paper C is heated in a non-contact manner through the radiant heat of the drying belt B heated by the heater H
1
, even when the temperature of the surface of the drying belt B is high, the temperature of the surface of the paper C heated thereby is quite low as compared to that of the drying belt B. Thus, in order to obtain a desired degree of dryness by increasing the temperature of the paper C to a predetermined level, since the temperature of the heater H
1
must be much higher than the predetermined level, much energy is consumed accordingly. To solve the problem, the paper C is preferably dried in a contact manner. In this case, however, since an image which is not sufficiently dried needs to be contacted, the image may be damaged during a drying step. Therefore, an image fusing unit having an improved structure to solve the above problem is required.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is an aspect of the present invention to provide an improved image fusing unit of a liquid electrophotographic printer which can restrict damage to an image while increasing the efficiency of heat during image drying.
To achieve the above aspect, there is provided an image fusing unit of a liquid electrophotographic unit for fusing an image developed by a developer, which is a mixture of a toner and a liquid solvent, and transferred onto a sheet of paper, the image fusing unit comprises a charging portion installed on a transfer path of the paper and which applies electric potential in a direction in which the toner is in close contact with the paper, a drying portion which dries the image by directly contacting and heating the paper, and a fusing portion which fixes the image to the paper by heating and pressing the paper.


REFERENCES:
patent: 4780742 (1988-10-01), Takahashi et al.
patent: 4903082 (1990-02-01), Dyer et al.
patent: 5025292 (1991-06-01), Steele
patent: 5150161 (1992-09-01), Bujese
patent: 5164782 (1992-11-01), Nagayama et al.
patent: 5495324 (1996-02-01), Kopp
patent: 5983048 (1999-11-01), Moser
patent: 6418289 (2002-07-01), Kleckner et al.
patent: 2001/0043821 (2001-11-01), Okamoto

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