Typewriting machines – Sheet or web – Including friction-feed means
Reexamination Certificate
2000-09-06
2001-10-23
Hilten, John S. (Department: 2854)
Typewriting machines
Sheet or web
Including friction-feed means
C400S583000, C400S587000, C400S637000, C400S639000, C399S239000, C399S246000, C399S249000
Reexamination Certificate
active
06305860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid electrophotographic printer for performing a printing operation using an ink as a developer which is composed of a power toner and a liquid carrier, i.e. solvent, and more particularly, to a squeezing apparatus of a liquid electrophotographic printer capable of removing the developer left after the developing operation and the carrier of the developer.
2. Description of the Prior Art
Generally, an electrophotographic printer such as, for example, a laser printer, obtains a desired image by the processes of: forming an electrostatic latent image on a photosensitive medium such as a photosensitive drum or photosensitive belt; developing the electrostatic latent image with a toner of a certain color; and transferring the developed electrostatic latent image onto a printed medium. Electrophotographic printers are mainly divided into a wet type and a dry type, depending on the type of toner the printer uses. The wet type electrophotographic printer uses a developer which is composed of a volatile liquid carrier and a toner. The wet type electrophotographic printer is in demand, since it has a higher print quality than the dry type which uses a powder toner, and cannot be damaged by harmful toner dust such as is used in the dry type printer.
FIG. 1
schematically shows the main portions of a wet type electrophotographic printer, which is described below.
As shown in
FIG. 1
, the wet type electrophotographic printer includes a photosensitive belt
1
disposed on an endless track, and first 2, second 3, and third 4 rollers for rotatably moving the photosensitive belt
1
on its destined path. Here, the third roller
4
is driven by a driving motor (not shown) to rotate the photosensitive belt
1
, and the second roller
3
is in the form of a steering roller for preventing the photosensitive belt
1
from skewing by adjusting the tension.
Further, around the photosensitive belt
1
, a charging unit
10
, exposure unit (not shown), developer unit
20
, drying unit
30
, and transfer/fixing unit
40
are disposed. Here, the charging unit
10
uniformly charges the photosensitive belt
1
, and the exposure unit (not shown) forms an electrostatic latent image on the photosensitive belt
1
by projecting a laser beam onto the photosensitive belt
1
according to an image signal. Further, the developer unit
20
develops the electrostatic latent image on the photosensitive belt
1
by attaching the developer having a certain color toner on the image formative area of the photosensitive belt
1
. For a color printer, there are a plurality of exposure units (not shown) for mixing the respective colors, and a plurality of developer units
20
for holding respective colors of toner.
The image formed on the photosensitive belt
1
by the toner and the developer unit
20
is transferred to the printed matter by a transfer roller
41
which is disposed parallel to the first roller
2
, while having the photosensitive belt
1
therebetween. The desired image is obtained on the printed matter as the printed matter is fed between the transfer roller
41
and a fixing roller
42
, which is parallel from the transfer roller
41
and spaced at a certain interval.
As shown in
FIGS. 2 and 3
, the developer unit
20
is disposed adjacent to the lower portion of the photosensitive belt
1
, and includes a casing
50
, developing device
60
, and squeezing device
70
.
The developing device
60
includes a developing roller
61
which is driven-rotated to selectively come into tight contact with the photosensitive belt
1
, developing backup roller
62
, and developer jetting nozzle
63
for feeding the developer between the photosensitive belt
1
and the developing roller
61
.
The squeezing device
70
performs the first removal of a residual developer left after the developing operation of the developing device
60
, and also a liquid carrier from the developer. Here, the liquid carrier has to be removed from the developer during the developing operation, since an excess of liquid carrier on the image formed by the toner hinders the image transference of the transfer/fixing unit
40
. The carrier which is not removed by the developer unit
20
is removed to a certain degree by the dry unit
30
which is appropriate for image transference.
The squeezing device
70
is described in greater detail with reference to FIG.
4
.
As shown in
FIG. 4
, the squeezing device
70
includes a squeezing roller
71
, squeezing backup roller
72
, and a squeezing brush
73
.
The squeezing roller
71
and the squeezing backup roller
72
are pressed into tight contact with the photosensitive belt
1
by a certain pressure (approximately of 20 kg/f) by a pressing section which is not shown, to thus squeeze out unnecessary liquid carrier from the developer applied on the photosensitive belt
1
by passive-rotational movement thereof.
Further, during the squeezing operation, the squeezing brush
73
removes the carrier and/or ink toner attached on the squeezing roller
71
by its rotational movement in tight contact with the outer circumference of the squeezing roller
71
. The squeezing brush
73
is rotated by the driving force transmitted from a developer roll driving section which is not shown in the drawings.
Further, albeit not shown, the squeezing device
70
includes a driving section for reverse-rotating the squeezing roller
71
during a drip line removing mode, and a squeezing blade
74
(See
FIGS. 2 and 3
) for removing the ink toner attached on the reverse-rotating squeezing roller
71
in tight contact with the outer circumference of the squeezing roller
71
, which is reverse-rotated by the driving section.
As shown in
FIG. 2
, the squeezing device
70
constructed as defined above squeezes out and removes the carrier from the developer applied on the surface of the photosensitive belt
1
by its reverse-rotational movement while being pressed into tight contact with the surface of the photosensitive belt
1
at a certain pressure. Here, the squeezing brush
73
is in contact with the squeezing roller
71
, and accordingly, the squeezing brush
73
removes the carrier and ink toner attached on the squeezing roller
71
while being rotated faster than the squeezing roller
71
by the driving force transmitted from the developer roller driving section.
After completion of the printing mode, a drip line removing mode is performed in which the ink toner unnecessarily attached on the photosensitive belt
1
is removed. In this situation, as shown in
FIG. 3
, the squeezing roller
71
is pressed with less pressure than in the printing mode, and the squeezing blade
74
is rotated by the driving section in a reverse direction from the rotation direction of the printing operation in contact with the squeezing roller
71
, to thus attract unnecessary ink toner from the photosensitive belt
1
thereto during its reverse-rotation. The ink attached on the reverse-rotating squeezing roller
71
is then removed by the squeezing blade
74
which is in contact with the outer circumference of the squeezing roller
71
. In such a situation, the developer roller
61
is spaced from the photosensitive belt
1
at a certain interval, and the squeezing brush
73
is spaced from the squeezing roller
71
at a certain interval.
In the squeezing apparatus of the liquid electrophotographic printer operating as above, it is very important to rotate the squeezing roller
71
, which is passive-rotated in contact with the photosensitive belt
1
, at the same speed as the travel speed of the photosensitive belt
1
without causing a slip occurrence. In the event of slippage due to different relative speeds of the photosensitive belt
1
and the squeezing roller
71
, the image formed on the photosensitive belt
1
is smeared and blurred, causing print quality deterioration. Accordingly, the slippage must be prevented during the passive-rotation of the squeezing roller
71
.
In the conventional squeezing apparatus, however, since the squeez
Crenshaw Marvin P.
Hilten John S.
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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