Electrophotography – Image formation – Development
Reexamination Certificate
2000-08-23
2002-04-09
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06370347
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid electrophotographic color printer using a developer composed of a powder toner and a liquid carrier, i.e. a solvent, and more particularly, to a squeezing apparatus of a liquid electrophotographic color printer for removing both the carrier of the developer and the residual developer left after a developing operation.
2. Description of the Prior Art
Generally, a liquid electrophotographic color printer includes a belt type photosensitive medium
1
, as shown in FIG.
1
. The photosensitive medium
1
is wound around rolls
2
,
3
,
4
and travels in a certain path in a body of the printer (not shown). Around the photosensitive medium
1
, an electric charging unit
10
, exposure unit (not shown), developing units
20
a
,
20
b
,
20
c
,
20
d
, drying unit
30
, and transfer/fixing unit
40
are disposed. Further, developer feeding devices (not shown) adjacent to the developing units
20
a
,
20
b
,
20
c
,
20
d
are disposed to feed the developer of a certain density to the developing units
20
a
,
20
b
,
20
c
,
20
d.
An electrostatic latent image is formed on the photosensitive medium
1
by the exposure unit (not shown), and is developed by the developing units
20
a
,
20
b
,
20
c
,
20
d
which jet the developer on to the photosensitive medium
1
, separate most of the carrier from the developer to retain the toner of the developer at the electrostatic latent image area of the photosensitive medium
1
. The carrier is removed during the developing operation since excess carrier at the image formed on the photosensitive medium
1
by the toner, hinders an image transfer of the transfer/fixing unit
40
. The residual carrier which is not removed by the developing units
20
is removed while the photosensitive medium
1
passes through the drying unit
30
.
Accordingly, as shown in
FIG. 2
, each one of developing units (e.g., developing unit
20
a
) includes a developer jetting nozzle
22
, developing roll
24
, developing backup roll
26
, developer recovery tank
28
, and a squeezing device
60
for removing the carrier. Here, the squeezing device
60
includes a squeezing roll
62
and a squeezing backup roll
64
.
The squeezing device
60
is described below in greater detail with reference to FIG.
3
.
As shown in
FIG. 3
, the squeezing roll
62
is disposed to be selectively forced against a surface of the photosensitive medium
1
, while the squeezing backup roll
64
is disposed to be selectively forced against the opposite surface of the photosensitive medium
1
. Further, a pair of forcing blocks
66
b
,
66
c
are disposed on a shaft
61
of the squeezing roll
62
to force the squeezing roll
62
against the squeezing backup roll
64
with a certain force, and each one of a pair of the airjet nozzles
68
b
,
68
c
are disposed at both sides of the squeezing roll
62
. The air jet nozzles
68
b
,
68
c
jet air toward both ends of the squeezing roll
62
, thereby preventing the developer from undesirably attaching to the ends of the squeezing roll
62
and transferring to a next color.
Further, the squeezing device
60
includes a driving section
70
for reverse-rotating the squeezing roll
62
in a drip line removing mode, and a squeezing blade
72
for removing ink on the squeezing roll
62
.
The squeezing device
60
, constructed as above, squeezes the carrier out of the developer applied on the surface of the photosensitive medium
1
by its passive-rotation while forcing against the surface of the photosensitive medium
1
with a certain force. Here, the squeezing roll
62
is forced by the force approximately of 20 kgf.
After the printing operation finishes, the drip line removing mode starts. During the drip line removing mode, less force is applied to the squeezing roll
62
than during the printing mode. Here, the driving section
70
rotates the squeezing roll
62
in contact with the squeezing blade
72
, in the reverse direction, attracting unnecessary ink from the photosensitive medium
1
. The unnecessary ink on the reverse-rotating squeezing roll
62
is removed by the squeezing blade
72
forced against the outer circumference of the squeezing roll
62
.
Meanwhile, in the squeezing apparatus
60
of a liquid electrophotographic color printer having the above operation, slipping should not occur when the squeezing roll
62
is passive-rotated while being forced against the photosensitive medium
1
. If slipping occurs, a smeared image is formed on the image area of the photosensitive medium
1
, resulting in a deterioration of print quality. Accordingly, in order to increase a frictional force between the squeezing roll
62
and the photosensitive medium
1
, the squeezing roll
62
is usually made of a material having a high friction coefficient.
While the squeezing roll
62
, made of a material having a high friction coefficient, has an advantage of preventing slippage, it also has a disadvantage, i.e., a high peel force. A certain amount of toner is attached to the squeezing roll
62
with the high peel force, when the carrier is squeezed out from the developer on the photosensitive medium
1
, causing squeezing offset error. Further, with the high friction coefficient of the squeezing roll
62
, the image area of the photosensitive medium
1
is considerably damaged during the reverse-rotation of the squeezing roll
62
for removing the drip line.
Accordingly, slipping should be prevented and the proper peel force should be maintained when the squeezing roll
62
is driven by the photosensitive medium
1
.
Conventionally, the squeezing roll
62
has a reduced peel force while having a certain degree of friction force from a TEFLON or silicon coating on the surface of the squeezing roll
62
. That is, in order to prevent image smearing or squeezing offset error, a material having a certain amount of friction force which can maintain a low peel force, is employed.
In the conventional squeezing apparatus described as above, however, the squeezing is performed while the toner is left on the entire contact area between the photosensitive medium
1
and the squeezing roll
62
. Even though the force of 20 kgf is applied to the photosensitive medium
1
and the squeezing roll
62
, there are problems caused by the load produced by a roll deformation during a nip formation, load between a supporting structure and a roll shaft caused by the pushing force, and load of the driving elements of the driving section
70
for the drip line removing mode. The problems result in a small, but an unignorable relative speed difference between the photosensitive medium
1
and squeezing roll
62
. There is a maximum 150 gm/sec relative speed difference, slightly varying depending on the colors used. Consequently, there are problems such as image smearing.
Further, the structure of the conventional squeezing roll
62
, made of a material having a low peel force and a certain amount of friction coefficient, has limitations, and accordingly, a printing environment can increase the peel force of the squeezing roll
62
, or the squeezing roll
62
may still slip. As a result, the problems such as the squeezing offset error caused by the increasing peel force of the squeezing roll
62
, and the image smearing caused by the slip of the squeezing roll
62
can not be prevented.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above problems of the prior art, and accordingly, it is an object of the present invention to provide a squeezing apparatus of a liquid electrophotographic color printer for removing the carrier from a developer without causing any damage to a developed image on a photosensitive medium by maintaining a proper (e.g., small) amount of peel force and preventing any slips.
Another object of the present invention is to provide a squeezing apparatus of a liquid electrophotographic color printer for minimizing any possible damage to a photosensitive medium due to a squeezing roll during a drip line removing mode by decreasing
Byun Seung-young
Shin Hyun-seong
Lee Susan S. Y.
Samsung Electronics Co,. Ltd.
LandOfFree
Squeezing apparatus of a liquid electrophotographic color... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Squeezing apparatus of a liquid electrophotographic color..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Squeezing apparatus of a liquid electrophotographic color... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2851613