Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-13
2001-05-01
Yockey, David F. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06224188
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink-jet recording apparatus having an ink-jet recording head capable of jetting ink from nozzles to form dots on a recording medium according to printing data. In particular, this invention is related to an ink-jet apparatus which can recover the ability of a nozzle to jet ink by discharging ink with no relation to a printing operation from the nozzles.
BACKGROUND OF THE INVENTION
FIG. 10
is a partly sectional view of a general recording head. The recording head has: a base plate
46
, piezoelectric vibrating members
42
vibratably contained and mounted in a containing space
53
formed in the base plate
46
, and a passage unit
47
fixed to an under surface of the base plate
46
.
The passage unit
47
has: a nozzle plate
50
having openings such as nozzles
40
, a thin vibrating plate
43
which can deform elastically, and a passage forming plate
49
sealingly fixed between the nozzle plate
50
and the vibrating plate
43
. In the passage forming plate
49
, pressure chambers
41
respectively communicating with the nozzles
40
, an ink saving chamber
48
for temporarily saving ink supplied into the pressure chambers
41
, and ink supplying passages
51
respectively connecting the pressure chambers
41
and the ink saving chamber
48
are formed. On the other hand, the base plate
46
has an ink way
55
connecting to the ink saving chamber
48
through an ink supplying hole
52
. Thus, new ink is supplied into the ink saving chamber
48
through the ink supplying hole
52
.
The arrangement of the ink supplying hole
52
, the ink saving chamber
48
and the pressure chambers
41
is explained with reference to FIG.
11
. As shown in
FIG. 11
, the ink saving chamber
48
has a flat trapezoidal shape. The ink supplying hole
52
is connected to a substantially middle portion of the ink saving chamber
48
. The pressure chambers
41
and the ink supplying passages
51
are arranged in parallel with each other in one side of the ink saving chamber
48
. Each of the pressure chambers
41
and each of the ink supplying passages
51
are perpendicular to the longitudinal direction of the ink saving chamber
48
. The pressure chambers
41
are respectively communicated to the nozzles
40
.
Each of the piezoelectric vibrating members
42
is fixed to a supporting plate
54
fixed in the containing space
53
of the base plate
46
in such a manner that the piezoelectric member
42
can vibrate in the containing space
53
. A lower end of the piezoelectric vibrating member
42
adheres to an island portion
43
a
of the vibrating plate
43
of a passage unit
47
.
The recording head operates as below. At first, electric power is supplied to a piezoelectric vibrating member
42
. Then, as shown in
FIGS. 12
a
and
12
b,
the piezoelectric vibrating member
42
contracts with respect to a normal original state thereof, a pressure chamber
41
expands with respect to a normal original state thereof, and the pressure therein is reduced. Thus, a meniscus
46
of ink in a nozzle
40
is dented toward the pressure chamber
41
, and ink in an ink saving chamber
48
is supplied into the pressure chamber
41
through an ink supplying passage
51
.
When electric charges are discharged from the piezoelectric vibrating member
42
after a predetermined time, the piezoelectric vibrating member
42
returns to the original state thereof, as shown in
FIG. 12
c.
Then, the pressure chamber
41
contracts and the pressure therein is increased.
Thus, the ink in the pressure chamber
41
is pressed to jet from the nozzle
40
as ink drops, which form images or characters on the recording paper.
In the above recording head, the ink
44
in the nozzles
40
may dry up and clog the nozzles
40
while the recording head remains stopped after a printing operation. Then, the nozzles are sealed by a capping unit except while the recording head is in the printing operation. However, a solvent of the ink
44
in the nozzles
40
may gradually evaporate to increase a viscosity of the ink
44
if the nozzles are sealed for a long time. In that case, it may be difficult to start a printing operation immediately. In addition, there may be some troubles, including that the quality of printed images may deteriorate.
During the printing operation, the nozzles
40
frequently jetting inkdrops
45
are scarcely clogged with the ink
44
because new ink
44
is supplied thereinto in succession. However, even during the printing operation, the nozzles
40
rarely jetting inkdrops
45
(for example, the nozzles arranged at an upper end portion or a lower end portion) are liable to be clogged with the ink
44
because the ink
44
in such nozzles
40
is liable to dry to increase the viscosity thereof.
To solve the above problems, a “flushing operation” or a “cleaning operation” is carried out by forcibly discharging the clogging ink
44
from the nozzles
40
in no relation to the printing operation, to recover the ability of the nozzles
45
to jet inkdrops. The above flushing or cleaning operation may be carried out when power supply starts to be given to the recording apparatus or when a first printing signal is inputted to the recording apparatus, as a preparatory step before the printing operation.
In the flushing operation, a driving signal in no relation to the printing data is supplied to the piezoelectric vibrating members
42
to jet the clogging ink
44
having a relatively increased viscosity from the nozzles
40
. The cleaning operation is carried out when the ability of the nozzles to jet inkdrops is not sufficiently recovered by the flushing operation. In the cleaning operation, a suction pump applies a negative pressure to the nozzles
40
to forcibly absorb the clogging ink
44
having a relatively increased viscosity from the nozzles
40
.
The degree of the increasing viscosity of the ink
44
in the nozzles
40
, i.e., the degree of clogging the nozzles
40
, becomes worse depending on the length of the capping time for which the recording head remains sealed by the capping unit or on the length of the total printing time until, the recording head is sealed by the capping unit.
Therefore, as shown in
FIG. 13
, whether the flushing operation or the cleaning operation should be carried out is determined by the combination of the capping time and the total printing time. The flushing operation is carried out when the capping time or the total printing time is relatively short (see a flushing area in FIG.
13
). The cleaning operation is carried out when the capping time or the total printing time is relatively long (see a cleaning area in FIG.
13
).
In the above apparatus, when ink in the pressure chambers
41
is consumed for a flushing, cleaning or printing operation, new ink is supplied from the ink supplying hole
52
into the pressure chambers
41
through the ink saving chamber
48
. Then, the new ink supplied from the ink supplying hole
52
flows easily into the pressure chambers
41
disposed near to the ink supplying hole
52
. However, on the contrary, it is difficult for the new ink supplied from the ink supplying hole
52
to flow into the pressure chambers
41
disposed far from the ink supplying hole
52
. Thus, there may be a difference in viscosity of the ink in the different portions of the ink saving chamber
48
. That is, the viscosity of the ink at a portion near to the ink supplying hole
52
may be different from the viscosity of the ink at a portion far from the ink supplying hole
52
.
For example, as shown in
FIG. 11
, the viscosity of the ink in the ink saving chamber
48
may be highest to lowest in the order of D area, C area, B area and A area. In that case, volumes of ink jetted from the nozzles
40
far from the ink supplying hole
52
in the flushing operations may be small when the same driving signal is used for all of the pressure chambers
41
. Thus, ink having an increased viscosity might remain in the pressure chambers
41
far from the ink supplying hole
52
. That is, the ability of the nozzles
40
fa
Seiko Epson Corporation
Wenderoth , Lind & Ponack, L.L.P.
Yockey David F.
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