Electrophotography – Image formation – Development
Reexamination Certificate
2001-05-15
2003-08-19
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06608982
ABSTRACT:
This application is a complete application filed under 35 U.S.C. §1.111(
a
) and claims pursuant to 35 U.S.C. §119(a), the date of Korean Patent Nos. 2000-522007 and 2001-35005 filed on Sep. 4, 2000 and Jan. 22, 2001, respectively. The Korean Patent Nos. 2000-52207 and 2001-3585 are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drying unit for a liquid electrophotographic printing apparatus that is used in printing on printing paper an image developed on a photosensitive medium using a liquid carrier as a mediator. Specifically, the drying unit of the present invention dries the carrier remaining in the photosensitive medium. Additionally, the present invention relates to a liquid carrier drying method using the same, and more particularly, to a drying unit for a liquid electrophotographic printing apparatus having the structure where a liquid carrier on the photosensitive medium can be dried in a non-contacting way.
2. Description of the Related Art
Generally, a liquid electrophotographic printing apparatus forms an electrostatic latent image on a photosensitive medium such as a photosensitive drum or a photosensitive belt and operates as an image forming unit that can obtain a desired image by developing the electrostatic latent image with a toner of certain colors and transferring it onto a printing paper.
With reference to
FIG. 1
, a general liquid electrophotographic printing apparatus scans laser beams using laser scanning units
21
,
23
,
25
and
27
and forms an electrostatic latent image on a photosensitive belt
11
circulating along a predetermined path, and develops the electrostatic latent image using developing units
30
,
40
,
50
and
60
. Then, after a drying unit
70
dries the liquid carrier remaining on the photosensitive belt
11
, a dried image is transferred from a transfer unit
80
onto a printing paper P, and is thus printed. The photosensitive belt
11
rotates by being wound around a driving roller
13
, a transfer backup roller
15
and a steering roller
17
.
Each of the developing units
30
,
40
,
50
and
60
on which a predetermined voltage is applied comprise developing rollers
31
,
41
,
51
and
61
that are positioned face to face while maintaining a developing gap G when developing the electrostatic latent image; injectors
33
,
43
,
53
and
63
that provide ink inside the developing gap G; and squeegee rollers
35
,
45
,
55
and
65
that are positioned on the photosensitive belt
11
in such a way that the belt is pressured. The developing units
30
,
40
,
50
and
60
make a film of an image developed on the photosensitive belt
11
. The ink provided through the injectors
33
,
43
,
53
and
63
consists of a toner that forms a color image transferred on the printing paper and a liquid carrier that transfers the toner to a region where an electrostatic latent image of the photosensitive belt
11
is formed.
The drying unit
70
absorbs and evaporates the liquid carrier containing the image developed on the photosensitive belt
11
, and the liquid carrier is then recycled by condensation and filtration. For this purpose, the drying unit
70
comprises a manifold
71
, a drying roller
72
, a regeneration roller
73
, a heater
74
, a ventilation channel
75
, a condenser
76
, a ventilation pump
77
and a filter
78
. Also, the drying unit
70
comprises a pressing device (not shown) such that, according to various modes, i.e., a home mode, a printing mode and a standby mode, the drying roller
72
is selectively in or out of contact with the photosensitive belt at a predetermined pressure and the regeneration roller
73
is selectively in or out of contact with the drying roller
72
.
The drying roller
72
is equipped in the manifold
71
and installed such that the drying roller can be in contact with the face where the image of the photosensitive belt
11
is formed by the pressing device. An absorbing layer
72
a
is equipped outside the perimeter of the drying roller
72
and the carrier remaining on the surface of the photosensitive belt
11
is absorbed through the absorbing layer
72
a.
The regeneration roller
73
is equipped in the manifold
71
in such a way that it can be in contact with the drying roller
72
, and inside is equipped with a heater
74
that heats the regeneration roller
73
. The carrier absorbed in the absorbing layer
72
a
of the drying roller
72
is evaporated at the regeneration roller
73
heated by the heater
74
. This evaporated carrier is discharged through the ventilation channel
75
connected to the manifold
71
by the pumping action of the ventilation pump
77
. The condenser
76
is equipped on the ventilation channel
75
and condenses the carrier moving through the ventilation channel
75
. Here, the condensed carrier is separated from the water that is condensed with the carrier and re-supplied to the developing units
30
,
40
,
50
and
60
through another supply channel (not shown). The carrier that is not condensed is discharged after being filtered by the filter
78
.
Meanwhile, a discharging device
91
that irradiates lights and removes charges remaining in the photosensitive belt
11
; a charging device
93
that charges up to a predetermined voltage after removing charges; and a plurality of topping chargers
94
,
95
and
96
that elevate the surface voltage of the photosensitive belt
11
after developing each color are installed proximate to the photosensitive belt
11
of the liquid electrophotographic printing apparatus.
The transfer unit
80
is positioned, at an interval of the photosensitive belt
11
, facing the transfer backup roller
15
, and comprises a transfer roller
81
where an image I developed at the photosensitive belt
11
is transcribed and a fuser roller
83
that is positioned at an interval for the printing paper P facing the transfer roller
81
, thus immobilizing the printing paper P. Here, the image transcribed on the transfer roller
81
is transcribed on the printing paper P supplied between the transfer roller
81
and the fuser roller
83
.
In the prior liquid electrophotographic printing apparatus comprising as described above, the drying unit is structured such that the drying roller contacts with the photosensitive belt and absorbs the liquid carrier. Thus the contacting time at the work point of the photosensitive belt is short and this contacting time is not enough for absorbing the liquid carrier. Therefore the prior printing apparatus has a disadvantage of a low drying efficiency. In particular, since drying is not sufficient enough in continuous printing, it causes a bad transfer of the image on the printing paper. At the same time, due to the bad drying, the liquid carrier is absorbed in the transfer roller, which in turn cause wrinkles in the printing paper, which induces a jam in the printing paper.
Also, since the drying roller contacts with the region where the image on the photosensitive belt is formed, the quality of the image is badly affected by picking the image on the photosensitive belt. In addition, since the picked image remains in the drying roller and the regeneration roller and is transmitted back to the photosensitive belt, it thereby contaminates other images on the photosensitive belt.
Furthermore, since the drying unit is of the contact-type, abrasion and contamination make the drying unit have a limited lifetime after printing several ten thousands times. Therefore, since it should be replaced after this limited lifetime, the maintenance cost is excessively high.
SUMMARY OF THE INVENTION
The present invention is contrived after considering the problems described above, and it is an object of the present invention to provide a drying unit for a liquid electrophotographic printing apparatus such that a liquid carrier on a photosensitive belt is dried in a non-contacting way, and a liquid carrier drying method using the drying unit.
To achieve the above objective, a drying unit for a liquid electrophotographic printing app
Choi Jae-myoung
Lee Won-seok
Shin Seong-soo
Woo Hyun-goo
Grainger Quana M.
Samsung Electronics Co,. Ltd.
Sughrue & Mion, PLLC
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