Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-11-30
2003-04-29
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06554409
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording head provided with pressure generators that produce pressure in pressure chambers, respectively to jet ink.
2. Description of the Related Art
A conventional ink-jet recording head (hereinafter, referred to simply as “recording head”) provided with piezoelectric vibrators of a flexural vibration mode will be described by way of example with reference to
FIGS. 7
to
9
. As shown in
FIGS. 7
to
9
, the recording head has actuator units
100
and a passage unit
105
superposed on the actuator units
100
.
Each actuator unit
100
includes a pressure chamber forming plate
10
provided with a plurality pressure chambers
2
, a vibrating plate
11
superposed on the pressure chamber plate
10
so as to cover the open upper ends of the pressure chambers
2
, and a plurality of piezoelectric vibrators
6
placed at positions respectively corresponding to the plurality of pressure chambers
2
on the vibrating plate
11
.
The passage unit
105
includes a nozzle plate
17
provided with nozzle apertures
3
, a storage chamber forming plate
16
provided with ink storage chambers
4
, and an ink supply port forming plate
18
superposed on the storage chamber forming plate
16
. The passage unit
105
is attached to the lower surface of the actuator units
100
. Each pressure chamber
2
is an elongated slot having one end communicating with the ink storage chamber
4
and the other end communicating the nozzle aperture
3
.
The ink storage chamber forming plate
16
is provided with connecting holes
9
communicating with the nozzle apertures
3
. The ink supply port forming plate
18
is provided with ink supply ports
15
through which the ink is supplied from the ink storage chambers
4
into the pressure chambers
2
, and connecting holes
8
connecting the pressure chambers
2
and the connecting holes
9
communicating with the nozzle apertures
3
, respectively. The ink supply port forming plate
18
is provided also with ink supply ports
24
through which the ink is supplied from an ink cartridge, not shown, into the ink storage chambers
4
.
The recording head shown in
FIG. 7
is a six-color recording head that prints in six color inks. The recording head is provided with the three actuator units
100
. Each actuator unit
100
is provided with two rows of the pressure chambers
2
arranged in a feed direction in which a recording sheet is fed. The three actuator units
100
are arranged in a scanning direction along the width of the recording sheet in which the recording head is moved for printing. The six ink storage chambers
4
of the passage unit
105
are arranged along the width of the recording sheet so as to correspond to the rows of the pressure chambers
2
, respectively. The color inks of the different colors are jetted through the nozzle apertures
3
of the six rows respectively corresponding to the rows of the pressure chambers
2
.
Lower electrodes
19
are formed on the upper surfaces of portions of the vibrating plate
11
of each actuator unit
100
corresponding to the pressure chambers
2
, respectively. Flat piezoelectric vibrators
6
are formed on the upper surfaces of the lower electrodes
19
and an upper electrode
20
is formed on the upper surfaces of the piezoelectric vibrators
6
, respectively.
As shown in
FIG. 8
, terminals
21
are formed on the opposite ends of the upper surface of each actuator unit
100
so as to be connected electrically to the upper electrodes
20
on the piezoelectric electric vibrators
6
, respectively. A flexible wiring board
22
is placed on the terminals
21
. Driving signals are applied through the terminals
21
and the upper electrodes
20
to the piezoelectric vibrators
6
.
The ink drops are jetted through the nozzle apertures
3
by producing pressure in the pressure chambers
2
by the flexural vibration of the piezoelectric vibrators
6
. As shown in
FIG. 10
, the piezoelectric vibrator
6
contracts laterally when a driving signal is applied to the piezoelectric vibrator
6
. A lower portion of the piezoelectric vibrator
6
fixed to the vibrating plate
11
does not contract and only an upper portion of the same contracts. Consequently, a portion of the vibrating plate
11
corresponding to the piezoelectric vibrator
6
and the piezoelectric vibrator
6
bend in a downward convex shape to compress the pressure chamber
2
, so that the pressure in the pressure chamber
2
is increased and the ink contained in the pressure chamber
2
is jetted through the nozzle aperture
3
in the form of an ink drop
23
. The ink drop
23
forms a dot on the recording sheet for printing. When the driving signal is removed from the piezoelectric vibrator
6
to allow the piezoelectric vibrator
6
to return to its original shape, the ink is supplied from the ink storage chamber
4
through the ink supply port
15
into the pressure chamber
2
.
In the conventional recording head, the six ink storage chambers
4
are formed in the single storage chamber forming plate
16
to supply the inks from the six ink storage chambers
4
to the six rows of the pressure chambers
2
and the inks are jetted through the six rows of the nozzle apertures
3
. Since the six ink storage chambers
4
are arranged laterally in a plane, the recording head necessarily has a large lateral size.
Studies have been made in recent years to use more than six color inks for the further improvement of print quality. The use of more than six color inks inevitably entails increase in the size of the recording head, affects adversely to accuracy and hence has not been realized.
In another known recording head, one row of pressure chambers
2
is divided into a plurality of sections, and a plurality of ink storage chambers
4
are formed for the sections of the row of the pressure chambers
2
, respectively, to use a plurality of color inks. This known recording head, similarly to the foregoing conventional recording head, needs one storage chamber forming plate provided with many ink storage chambers
4
and there is a limit to the reduction of the size of the recording head.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide an ink-jet recording head of a small size and capable of using an increased number of kinds of inks without increasing the size.
According to the present invention, an ink-jet recording head has: an actuator unit including a pressure chamber forming plate provided with a plurality of pressure chambers, and a plurality of pressure generators that produce pressure in the pressure chambers, respectively, to jet ink, the pressure chambers being grouped into two or more pressure chamber groups that correspond to two or more kinds of inks, respectively; and a passage unit stacked on the actuator unit and including two or more ink storage chamber forming plates that are stacked on each other, each of the two or more ink storage chamber forming plates being provided with at least one ink storage chamber, the ink storage chambers storing inks to be supplied to the pressure chamber groups, respectively.
Preferably, the pressure chambers are arranged in a row. The passage unit may have two or more ink inlet openings through which inks are supplied into the two or more ink storage chambers, respectively. The two or more ink inlet openings may be arranged in a direction perpendicular to a direction in which the pressure chambers are arranged.
Preferably, the ink-jet recording head further has at least one partition plate interposed between the storage chamber forming plates. The two or more ink storage chambers may overlap at least partly each other with respect to a direction in which the two or more storage chamber forming plates are stacked. Portions of the two or more ink storage chambers overlapping each other may be isolated from each other by the partition plate.
Preferably, the partition plate is a flexible plate
Nguyen Thinh
Seiko Epson Corporation
Sughrue & Mion, PLLC
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