Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-10-24
2003-03-25
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06536880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric ink jet printer head and a method for manufacturing the same.
2. Description of the Related Art
FIG. 1
shows a conventional ink jet printer head
100
used in an ink jet printer. The ink jet printer head
100
includes a cavity plate
130
and a piezoelectric actuator
110
. The cavity plate
130
is formed with a plurality of ink chambers
131
. The piezoelectric actuator
110
is adhered onto the cavity plate
130
so as to cover the ink chambers
131
. When a voltage is applied to the piezoelectric actuator
110
, the piezoelectric actuator
110
deforms into the ink chambers
131
, whereupon the volume of the ink chambers
131
decreases. As a result, the pressure in the ink chambers
131
increases so that an ink droplet is ejected from the orifices
132
of the ink chambers
131
.
The piezoelectric actuator
110
includes active layers
120
and inactive binding layers
150
. The active layers
120
include piezoelectric ceramic layers
140
that are formed with an internal negative electrode layer
142
, laminated in alternation with piezoelectric ceramic layers
140
that are formed with internal positive electrode layers
144
a
,
144
b
, and
144
c
. The internal positive electrode layers
144
a
,
144
b
, and
144
c
are aligned with the ink chambers
131
of the cavity plate
130
. The binding layers
150
includes a plurality of layers of piezoelectric ceramic layers
171
that are unrelated to drive of the ink jet printer head
100
.
When a drive voltage is applied between the internal positive electrode layers
144
a
to
144
c
and the corresponding internal negative electrode layer
142
, the lowermost piezoelectric ceramic layer
140
, that is, the piezoelectric ceramic layer
140
adhered to the cavity place
130
, is actually inactive and does not add to the drive force of the ink jet printer head
100
.
SUMMARY OF THE INVENTION
However, because the lowermost piezoelectric ceramic layer
140
is inactive in this way, a sufficiently high positive pressure is not generated in the ink chambers
131
. It is conceivable to screen print another electrode for driving the lowermost piezoelectric ceramic layers
140
onto the surface where the lowermost ceramic layer
140
attaches to the cavity plate
130
. However, a separate insulation film would need to be formed on this electrode to protect it from the ink in the ink chambers
131
. This extra film would increase production costs.
It is an objective of the present invention to overcome the above-described problems and provide a piezoelectric type ink jet printer head and a method of manufacturing a piezoelectric type ink jet printer head that enables the lowermost piezoelectric ceramic layer that is adhered to the cavity plate to be driven as an active layer.
In order to achieve the above and other objectives, there is provided an ink jet head including a cavity plate and a piezoelectric actuator. The cavity plate is formed with a plurality of nozzles and a plurality of pressure chambers in one-to-one correspondence with the nozzles. The piezoelectric actuator includes a plurality of first piezoelectric sheets and a plurality of second piezoelectric sheets laminated in alternation. Each of the first piezoelectric sheets being provided with a first electrode, and each of the second piezoelectric sheets is provided with a second electrode. One of the first piezoelectric sheets has a first surface on which the first electrode is provided and a second surface opposite from the first surface and provided with no electrode, the second surface being attached to the cavity plate while covering over the pressure chambers. The cavity plate and the second electrodes are all connected to a same potential.
There is also provided a manufacturing method for an ink jet head. The method includes the steps of forming a laminated structure of a plurality of first piezoelectric sheets and a plurality of second piezoelectric sheets laminated in alternation, each of the first piezoelectric sheets being provided with a first electrode on a first surface, each of the second piezoelectric sheets being provided with a second electrode, attaching a second surface of a lower most one of the first piezoelectric sheets to a cavity plate, the second surface being opposite from the first surface, and polarizing the first piezoelectric sheets and the second piezoelectric sheets by applying a voltage between the first electrodes and corresponding ones of second electrodes and between the first electrode on the lower most one of the first piezoelectric sheets and the cavity plate.
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patent: 5266964 (1993-11-01), Takahashi et al.
patent: 5402159 (1995-03-01), Takahashi et al.
patent: 5639508 (1997-06-01), Okawa et al.
patent: 5912526 (1999-06-01), Okawa et al.
patent: 6142614 (2000-11-01), Hashizume et al.
patent: 6142615 (2000-11-01), Qiu et al.
patent: 6443566 (2002-09-01), Watanabe et al.
patent: 6450626 (2002-09-01), Ikeda et al.
Brother Kogyo Kabushiki Kaisha
Nguyen Judy
Oliff & Berridg,e PLC
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