Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-09-03
2002-06-18
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06406123
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a capping unit for an ink jet recording head incorporated in an ink jet recording apparatus, and a method of manufacturing the same. In particular, the ink jet recording apparatus comprises: an ink jet recording head installed on a carriage moved in the widthwise direction of recording paper, for jetting ink droplets from nozzle orifices by pressurizing ink from an ink tank supplied into associated pressure generating chamber by a pressure generating member such as piezoelectric vibrators, heating elements or the like; and a capping unit provided with a capping member for sealing a surface of the recording head on which the nozzle orifices are formed (hereinafter, the nozzle-formed surface), and receiving negative pressure generated by a negative pressure generating member, wherein vaporization of an ink solvent from the capping member is inhibited during the halt of recording operation in order to prevent from clogging of the nozzle orifices.
As for an ink jet recording apparatus, noise in printing is relatively small and in addition, small dots can be formed in high density, such an ink jet recording apparatus is currently used for many types of printing including color printing.
The ink jet recording apparatus described above provided with an ink jet recording head to which ink from an ink cartridge is supplied, and a paper feeding mechanism for relatively moving recording paper under the recording head. The recording is performed by jetting ink droplets onto the recording paper, moving the recording head on a carriage in the widthwise direction of the recording paper.
Recording heads for jetting black ink and each color ink of yellow, cyan and magenta are mounted on the carriage, and full color printing is enabled by changing the ratio of the jetting of each ink in addition to text printing by black ink.
The above ink jet recording head has a problem that printing failure is caused by the increase of ink viscosity caused by the vaporization of a solvent from nozzle orifices, the solidification of ink, the adhesion of dust, further the mixture of bubbles or the like, because the printing is performed by jetting ink pressurized in the pressure generating chambers onto recording paper from nozzle orifices as an ink droplet.
Therefore, the above ink jet recording apparatus is provided with: a capping member normally composed of a plastic cap holder (cap case) and a cap made of elastic material such as rubber for sealing the nozzle orifices of the recording head while the printing is halted; and a cleaning member for cleaning a nozzle plate if necessary.
The above capping member not only functions as a cap for preventing ink at nozzle orifices from drying while printing is halted but is provided with functions for sealing the nozzle plate by the cap in case the nozzle orifices are clogged, sucking ink from the nozzle orifices by negative pressure generated by a suction pump as a negative pressure generating member, and solving the clogging caused by the solidification of ink at the nozzle orifices and a failure in the jetting of ink caused by bubbles mixed in an ink passage.
FIG. 23
schematically shows a state in which the nozzle-formed surface of the recording head is sealed by the capping member.
As shown in
FIG. 23
, the capping member
10
is provided with a rectangular cap case
10
a
the upper face of which is opened and a cap
10
b
housed in the cap case
10
a
and made of flexible material such as rubber material, and the cap
10
b
is formed so that the upper edge thereof is slightly protruded from the top face of the cap case
10
a.
An ink absorber
10
c
made of porous material is housed at the inner bottom of the cap
10
b
and is held by a holder
10
d
integrally formed with the cap
10
b.
A suction hole
10
e
and an air hole
10
f
are formed at the bottom of the cap case
10
a
and penetrate the cap case
10
a
and the cap
10
b.
A suction pump
11
as a negative pressure generating member is connected to the suction hole
10
e
of the cap case
10
a
via a tube T
1
and discharge side of the suction pump
11
is connected to a waste ink tank
13
.
Further, an air valve
14
is connected to the air hole
10
f
of the cap case
10
a
via a tube T
2
.
In the meantime, a reference number
7
in
FIG. 23
denotes a recording head. As the capping member
10
is moved upwards when the recording head
7
is moved toward above the capping member
10
, the nozzle-formed surface, that is, a nozzle plate
7
a
is sealed (capped) by the above cap
10
b.
Plural nozzle orifices
7
b
are formed on the nozzle plate
7
a
, and black ink and each color ink such as yellow, cyan and magenta are jetted by the action of a piezoelectric vibrator
7
c
arranged corresponding to each nozzle orifices
7
b.
Owing to the above structure, ink is sucked from the recording head in a state in which the cap
10
b
is adhesively contacted to the nozzle plate
7
a
of the recording head
7
and the air valve
14
is closed as shown in FIG.
23
.
That is, negative pressure is applied to the internal space of the cap
10
b
by operating the suction pump
11
in this state and ink is discharged from the nozzle orifices
7
b.
When the above air valve
14
is opened while the suction pump is halted in a predetermined time and the negative pressure inside the cap decreases to some extent because ink is discharged, the air is introduced inside the cap and inside negative pressure is released.
When the suction pump
11
is operated again in a state in which the air valve
14
is opened, operation for sending ink discharged inside the cap to a waste ink tank
13
via the tube T
1
is executed.
In the meantime, while the printing is halted, the nozzle-formed surface of the recording head, that is, the nozzle plate
7
a
is sealed by the cap
10
b
as shown in
FIG. 23
, the above air valve
14
is closed and the internal space of the cap
10
b
is kept moist by an ink solvent. Hereby, the nozzle orifices of the recording head is prevented from being clogged by drying, and the reliability of printing operation when printing is restarted can be secured.
However, there is a problem that the ink solvent is vaporized in a passage communicating from the internal space of the cap to the suction hole or the air hole and further, in a path which leads to the suction pump connected to the suction hole and the air hole and the air valve.
FIG. 24
shows an example which is a sectional view showing a passage making the internal space of a cap and a suction hole communicate in an example of a cap case in capping member currently used.
The same reference number is allocated to a part shown in
FIG. 24
equivalent to the part already described and shown in FIG.
23
and therefore, the description is omitted.
As shown in
FIG. 24
, the passage
10
g
for making the internal space of the cap and the suction hole
10
e
communicate is formed so that the inner diameter is relatively large and the length is relatively short. A reference number
10
n
denotes a fitting member for fitting the cap.
As described above, in a state in which the passage
10
g
is formed so that the inner diameter is large and the length is short, there is a problem that flow resistance on the side of a suction pump is small and therefore, the vaporization to the outside of an ink solvent is caused in a tube connected to the suction pump.
Particularly, for the suction pump, a low-cost tube pump which is securely operated is used and for a tube composing the tube pump, elastic and restorable silicon rubber is used.
However, silicon rubber has a problem that it is relatively inferior in gas-barrier characteristic, and thereby an ink solvent would be vaporized from the tube to the outside.
Therefore, as an ink solvent is gradually vaporized from the internal space of the cap via the above passage and a moist state in the cap is deteriorated in case a recording apparatus is halted for a long term, clogging in the nozzle orifices of the recording head is caused.
After the recording ap
Fukasawa Shigenori
Hara Kazuhiko
Hayakawa Hitoshi
Komatsu Katsuhiro
Usui Minoru
Hsieh Shih-wen
Sughrue & Mion, PLLC
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