Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-11-12
2004-08-24
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06779860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording apparatus provided with a recording head having nozzles capable of jetting ink particles through the nozzle.
2. Description of the Related Art
An ink-jet recording apparatus generates relatively low noise during a printing operation and is capable of forming small dots with a high density. Accordingly, the ink-jet recording apparatus has been used prevalently in recent years for printing images, including full-color images.
The ink-jet recording apparatus comprises an ink-jet recording head supplied with ink from an ink cartridge, and a sheet feed mechanism for moving a recording sheet relative to the recording head. A carriage mounted with the ink-jet recording head is moved in a direction along the width of the recording sheet and ink particles are jetted onto the recording sheet by the ink-jet recording head for recording (printing). A full-color ink-jet recording apparatus is provided with black, yellow, cyan and magenta ink-jet recording heads mounted on a carriage and capable of jetting black, yellow, cyan and magenta ink particles, respectively. The full-color ink-jet recording apparatus is capable of full-color printing by jetting those color inks at appropriate ratios, as well as text printing by forming black letters.
The ink-jet recording head jets ink particles by pressure produced in a pressure chamber through nozzles onto a recording sheet for printing. Therefore, it is possible that operation of the ink-jet recording head results in faulty printing due to the increase of the viscosity of the ink or the solidification of the ink, resulting from the evaporation of the solvent of the ink through the nozzles. Faulty printing will also be caused by the adhesion of dust to the nozzles or the formation of bubbles in the ink.
The ink-jet recording apparatus is provided with a capping means for sealing up the openings of the nozzles of the recording head when the recording head is not in printing operation, and a cleaning device for cleaning a nozzle plate when necessary.
The capping means functions as a cover for preventing the ink from drying in the nozzles while the ink-jet recording apparatus is not in printing operation. The capping means further functions to remove the ink solidified in the nozzles which clogs the nozzles and to remove bubbles formed in ink passages and causes a faulty ink jetting operation, in cooperation with a suction pump, by bringing the capping means in close contact with the nozzle plate and by applying a negative pressure to the nozzles to suck out the ink clogging the nozzles, when the nozzles are clogged.
The suction cleaning operation for forcibly sucking out the ink from the clogged nozzles of the recording head and for removing bubbles from the ink passages is generally called a cleaning operation. The cleaning operation is carried out before resuming the printing operation after a long interruption of the printing operation. The cleaning operation is also carried out when an operator operates a cleaning switch to clean the nozzles when the print quality of printed images deteriorates. A wiping operation is carried out to wipe the surface of the recording head with a wiping member consisting of elastic plates such as rubber plates, after removing the ink from the nozzles by the cleaning (suction) operation.
The recording head can forcibly jet ink particles when a driving signal unrelated with printing operation is applied. This jetting operation is generally called a flushing operation. The flushing operation is performed to regulate menisci of the ink at the outlet openings of the nozzles of the recording head when the menisci are disturbed by the wiping operation after the cleaning operation. The flushing operation is also performed to discharge the mixed ink forced to flow in reverse into the nozzles by the wiping operation, from the nozzles. The flushing operation is performed periodically to prevent the nozzles through which only a small amount of the ink is jetted during the printing operation from being clogged with the ink due to an increase in the viscosity of the ink.
The ink-jet recording apparatus is provided with, for example, a recording head as shown in
5
c
FIG.
10
.
FIG. 10
is a sectional view showing one of the ink passages of a recording head
5
. As shown in
FIG. 10
, a practical multinozzle recording head
5
has ink jetting nozzles arranged in rows, each of the rows is formed by combining an ink passage and a nozzle.
A lower electrode
5
b
is formed on a surface of a vibrating plate
5
a
. A piezoelectric member
5
c
, such as a PZT, is placed on the surface of the lower electrode
5
b
. An upper electrode
5
d
is formed on a surface of the piezoelectric member
5
c
. The piezoelectric member
5
c
expands or contracts by a driving signal applied thereto through the lower electrode
5
b
and the upper electrode
5
d
, and then the vibrating plate
5
a
is driven (distorted) for vertical movement in FIG.
10
.
A spacer
5
e
underlies the vibrating plate
5
g
. The spacer Se is provided with a recess in its surface facing the vibrating plate
5
a
to form a cavity (pressure chamber)
5
f
under the vibrating plate
5
a.
An ink supply port forming plate
5
g
underlies the spacer
5
e
. The plate
5
g
is provided with an ink supply port
5
h
opening into the cavity
5
f.
A spacer
5
i
underlies the ink supply port forming plate
5
g
. The spacer
5
i
is provided with a hollow for forming a reservoir (common ink chamber)
5
j.
A nozzle plate
5
m
provided with a nozzle
5
k
underlies the spacer
5
i
. The ink supply port forming plate
5
g
and the spacer
5
i
are provided with openings forming a straight ink passage
5
n extending between the cavity
5
f
and the nozzle
5
k
. The spacer
5
e
, the ink supply port forming plate
5
g
and the spacer
5
i
are bonded together with adhesive layers.
As mentioned above, the vibrating plate
5
a
vibrates vertically, as shown in
FIG. 10
, by the expansion and contraction of the piezoelectric member
5
c
. When electric power is supplied to the piezoelectric member
5
c
, the vibrating plate
5
a
moves vertically downward. Consequently, pressure is applied to the ink contained in the cavity
5
f
to force the ink to flow through the ink passage
5
n
and the ink is jetted through the nozzle
5
k
as ink particles. When electric charges are discharged from the piezoelectric member
5
c
, the vibrating plate Sa returns to an original state thereof Consequently, the cavity
5
f
expands, the ink is supplied from the ink reservoir
5
j
(the common ink chamber) through the ink supply port
5
h
into the cavity
5
f
to replenish the cavity
5
f
with the ink for the next printing cycle.
Thus, the volume of the cavity
5
f
is changed by the piezoelectric member
5
c
to replenish the cavity
5
f
with the ink supplied from the ink reservoir
5
j
and to jet the ink supplied from the cavity
5
f through the ink passage
5
n
through the nozzle.
5
k
as ink particles.
FIGS.
11
(
a
) and
11
(
b
) are sectional views of the recording head for explaining the behavior of ink particles jetted in the flushing operation.
As shown in FIG.
11
(
a
), a main ink particle M and an ink string following the main ink particle M are spewed out from the nozzle
5
k
when the volume oft he cavity
5
f
is reduced. A part of the ink string changes into a plurality of small ink particles S because of the surface tension of the ink as shown in FIG.
11
(
b
). Those small ink particles S are referred to also as satellite particles.
Generally, the small ink particles S fly at low speed, have very small weight and are liable to float in air as ink mist. The ink mist may contaminate the interior of the recording apparatus, and may be discharged outside through an opening of the recording apparatus, such as an exhaust opening for a cooling fan, to contaminate the peripheral equipment.
When the recording apparatus has a second flushing region on the opposite side of the cappi
Fukasawa Shigenori
Hara Kazuhiko
Maruyama Norihiro
Takahashi Nobuhito
Feggins K.
Nguyen Lamson
Seiko Epson Corporation
Wenderoth , Lind & Ponack, L.L.P.
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