Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
1999-09-17
2001-11-20
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C347S105000, C347S101000, C347S102000
Reexamination Certificate
active
06318853
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an image forming apparatus including an intermediate medium, wherein an image is first formed on the intermediate medium by ink jet heads using phase-changeable ink, and then transferred onto a recording medium, more particularly, release oil is applied on the intermediate medium before the phase-changeable ink is ejected.
2. Description of Related Art
An ink jet printer, shown in
FIG. 7
, is known as the image forming apparatus described above, for example.
FIG. 7
shows a schematic diagram of the main structure of the ink jet printer
80
.
The ink jet printer
80
forms images using hot melt inks of yellow, magenta, cyan, and black. The ink jet printer
80
includes a drive roller
11
, a following roller
12
, an intermediate transfer belt
13
, and a pair of sheet feed rollers
15
.
The drive roller
11
is driven by a motor (not shown). The following roller
12
is provided opposite to and separate from the drive roller
11
. The intermediate transfer belt
13
is wound around and spans between the drive roller
11
and the following roller
12
. The sheet feed rollers
15
are disposed below the intermediate transfer belt
13
to feed a sheet P.
The ink jet head unit
20
is provided above the intermediate transfer belt
13
and includes an yellow head
21
, a magenta head
22
, a cyan head
23
, and a black head
24
, which eject yellow, magenta, cyan, and black colored inks respectively. The yellow head
21
, the magenta head
22
, the cyan head
23
, and the black head
24
are provided above the intermediate transfer belt
13
such that their nozzle surfaces face to the intermediate transfer belt
13
, and have nozzles which are oriented in the direction of the width of the intermediate transfer belt
13
, that is they are line heads. Hot melt ink is ejected from each head onto the intermediate transfer belt
13
so that the color image is formed on the intermediate transfer belt
13
.
A transfer roller
16
is disposed under the intermediate transfer belt
13
and, above the transfer roller
16
, a heat roller
17
is provided opposite to the transfer roller
16
with the intermediate transfer belt
13
passing therebetween. The transfer roller
16
is movable in a direction indicated by an arrow F
3
as the transfer roller
16
has a movement mechanism (not shown). On the left side of the transfer roller
16
is a separation pawl
18
provided for peeling the sheet S from the intermediate transfer belt
13
. The separation pawl
18
is movable in a direction indicated by an arrow F
4
as the separation pawl has a movement mechanism (not shown). A belt marker sensor
14
is provided on the left side of the ink jet head unit
20
in order to detect that the intermediate transfer belt
13
has reached a start position where an image is formed.
A silicon oil applying unit
90
is provided substantially below the following roller
12
and includes an oil tank
92
storing silicon oil
91
in which a felt
93
is soaked. The felt
13
is provided such that one end extends from an open mouth provided in the upper area of the oil tank
92
so as to contact the intermediate transfer belt
13
. The upper end of the felt
93
, contacting the intermediate transfer belt
13
, has a width corresponding to the width of the intermediate transfer belt
13
. A bracket
94
for a bolt is provided in the upper area of the oil tank
92
and a plate
95
is attached to the bracket
94
so as to be able to pivot. The upper end of the felt
93
is attached to a fore end of the plate
95
and an upper end of a coil spring
96
is attached to a rear end of the plate
95
. A lower end of the coil spring
96
is connected to a plunger
98
of a solenoid
97
.
When the ink jet printer
80
described above is turned on, the intermediate transfer belt
13
is transported by rotation of the drive roller
11
. Then the solenoid
97
of the silicon oil applying unit
90
is driven so that the plunger
98
is pulled downward. As a result, the plate
95
pivots in the counterclockwise direction, as shown in
FIG. 7
, so that the end of the felt
93
is pushed against the intermediate transfer belt
13
. In this way, silicon oil that soaks into the felt
93
is applied to the surface of the intermediate transfer belt
13
. Because the width of the upper end of the felt
93
corresponds to the width of the intermediate transfer belt
13
as described above, silicon oil
91
is applied to the entire area of the intermediate transfer belt
13
.
When the belt marker sensor
14
detects that the intermediate transfer belt
13
has reached a start position where an image is formed, the ink jet head unit
20
is driven and hot melt ink is ejected from the yellow head
21
, the magenta head
22
, cyan head
23
, and black head
24
, as appropriate, onto the intermediate transfer belt
13
. In this way, a color image using hot melt inks is formed on the silicon oil applied to the intermediate transfer belt
13
.
Then a sheet P is fed from a cassette (not shown) included in the ink jet printer
10
toward the sheet feed rollers
15
, and further transported toward the transfer roller
16
by the sheet feed rollers
15
. The time when the sheet P reaches an image forming position at the transfer roller
16
and the time when an edge of the image formed on the intermediate transfer belt
13
reaches the transfer roller
16
are controlled so as to be synchronized. The transfer roller
16
moves in a direction indicated by the arrow F
3
to press the sheet P against the intermediate transfer belt
13
. At that time, hot melt ink comprising the image on the intermediate transfer belt
13
is heated by the heat roller
17
and becomes soft. At the same time the softened hot melt ink is transferred onto the sheet P by the pressure of the transfer roller
16
.
Then the sheet P is peeled from the intermediate transfer belt
13
by the separation pawl
18
, which moves in the direction indicated by the arrow F
4
, and is discharged onto a tray (not shown).
However, as described above, because the silicon oil
91
applying unit
90
, provided with the ink jet printer
10
, must apply the silicon oil
91
to the entire area of the intermediate transfer belt
13
, it can not apply the silicon oil
91
to only a specific area of the intermediate transfer belt
13
.
Moreover, the thickness of the silicon oil film can not be controlled because the pressure with which the end of the felt
93
presses the intermediate transfer belt
13
is determined by the force of the coil spring
96
so that the pressure is not constant.
Furthermore, the felt
93
gets dirty ink as a result of remaining in contact with the surface of the intermediate transfer belt
13
. In particular, the felt
93
gets stopped up with the ink leftover with intermediate transfer belt
13
so that silicon oil
91
can not be applied onto the intermediate transfer belt
13
evenly. Therefore, some parts of the hot melt ink do not come off completely and transfer precision declines.
As described above, the previous ink jet printer
10
is not capable of controlling the area to which silicon oil
91
is applied, the thickness of the silicon oil film, and the application of the silicon oil
91
evenly.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an image forming apparatus which is capable of controlling the area where silicon oil is applied and the thickness of the silicon oil film as well as being capable of applying the silicon oil evenly.
In order to achieve the above and the other objects, an image forming apparatus comprises ink jet heads that eject hot melt inks; an intermediate medium on which is formed an ink image composed of hot melt ink ejected from the ink jet heads onto the surface thereof; and a transfer unit that transfers the image formed on the intermediate medium onto a recording medium, wherein a release oil jet head that ejects release oil on the intermediate medium where an image is to be formed is provided without contacting with the surfac
Asano Takeshi
Katayama Naoki
Barlow John
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
Shah Manish S.
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