Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-11-14
2003-07-01
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06585357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet head mounted on an ink jet recording apparatus applied to, for example, a printer or a facsimile machine.
2. Description of the Related Art
Conventionally, an ink jet recording apparatus for recording letters or images on a recording medium using a recording head for expelling ink from a plurality of nozzles is known. In such an ink jet recording apparatus, the recording head opposed to the recording medium is provided in a head holder, and the head holder is mounted on a carriage to scan the recording medium in a direction orthogonal to the direction of conveyance of the recording medium.
FIG. 6
is an exploded perspective view showing the main part of an example of such conventional recording head.
FIG. 7A
is a side sectional view and
FIG. 7B
is a frontal sectional view taken along line
7
B—
7
B in
FIG. 7A
showing the main part of the conventional recording head. As shown in
FIGS. 6 and 7
, a plurality of channels
102
are provided side by side in an actuator plate
101
formed of piezoelectric ceramic in its width direction. The channels
102
are separated from one another by side walls
103
. One end portion of the channels
102
in the longitudinal direction extends to one end face of the actuator plate
101
, while the other end portion does not extend to the other end face, with the depth being gradually decreased. An electrode
105
for applying a drive voltage is formed on the surface of the opening side of both side walls
103
and
103
of each channel
102
over the longitudinal direction.
A cover plate
107
is joined by an adhesive
109
to the opening side of the channels
102
in the actuator plate
101
. The gap between the shallow portions of the rear end portion of the channels
102
in the actuator plate
101
and the cover plate
107
is sealed with sealant
110
. The cover plate
107
has a common ink chamber
111
which is a concave portion communicating with the shallow, other end portion of the channels
102
, and an ink supply port
112
piercing from the bottom portion of the common ink chamber
111
in the opposite direction from the channels
102
. An ink flow path
114
of a flow path block
113
communicates with and opens to the ink supply port
112
. Further, a filter
116
is attached to an end portion of the ink flow path
114
of the flow path block
113
on the side of the ink supply port
112
.
A nozzle plate
115
is affixed and joined by an adhesive to an end face where the channels
102
of the joined body of the actuator plate
101
and the cover plate
107
are open. The width of the nozzle plate
115
is larger than the width of the end face of the joined body and the length of the nozzle plate
115
is larger than the length of the end face of the joined body. Nozzle openings
117
are formed in the nozzle plate
115
at positions opposed to the channels
102
, respectively. Further, as shown in
FIGS. 7A
,
7
B, a nozzle plate cover
118
is fixed by the adhesive to the rear surface of the nozzle plate
115
so as to cover the outer peripheral surface of an end portion of the joined body of the actuator plate
101
and the cover plate
107
and to cover the rear surface of the nozzle plate
115
.
It is to be noted that a wiring board
120
is fixedly attached to a surface of the actuator plate
101
which is opposite to the side of the nozzle plate
115
and opposite to the side of the cover plate
107
. Wirings
122
connected to the electrodes
105
, respectively, using bonding wires
121
, a flexible substrate, or the like are formed on the wiring board
120
, such that drive voltage can be applied to the electrodes
105
via the wirings
122
.
In the recording head described above, the channels
102
are filled with ink from the ink flow path
113
via the ink supply port
112
and the common ink chamber
111
. By applying a predetermined drive voltage on side walls
103
on both sides of a predetermined channel
102
via the electrodes
105
, the side walls
103
are deformed to change the volume in the predetermined channel
102
, which leads to expulsion of ink in the channel
102
from the nozzle opening
117
.
For example, as shown in
FIG. 8
which is a frontal sectional view showing the main part, in the case where ink is expelled from a nozzle opening
117
corresponding to a channel
102
a
, positive drive voltage is applied to electrodes
105
a
and
105
b
in the channel
102
a
while electrodes
105
c
and
105
d
opposed to the electrodes
105
a
and
105
b
, respectively, are grounded. By this, drive electric field toward the channel
102
a
acts on the side walls
103
a
and
103
b
. When this is orthogonal to the direction of polarization of the actuator plate
101
formed of piezoelectric ceramic, due to a piezoelectric thickness sliding effect, the side walls
103
a
and
103
b
are deformed to be warped toward the channel
102
, the volume in the channel
102
is decreased to increase the pressure, and ink is expelled from the nozzle opening
117
.
Further, in such a recording head, a water-repellent film having water repellency is provided on the surface of the nozzle plate
115
which is opposed to a printed material for the purpose of preventing a head from getting dirty due to attachment of ink, preventing clogging of the nozzle openings
117
, and the like. Further, the head end face is cleaned at predetermined regular time intervals or at a desired time. The cleaning is typically carried out by wiping out the face of the nozzle plate
115
which is opposed to a printed material with a wiper formed of, for example, rubber which has a relatively high hardness (Hs 40-50) and does not swell.
However, in the structure of the recording head described in the above, the whole thickness of the nozzle plate
115
is exposed. Therefore, there is a problem that, when the nozzle plate
115
is wiped out with a wiper, or, when a printed material (printed paper) is not properly fed and is jammed to be crumpled, force in the direction of peeling the nozzle plate
115
off the wiper or the printed material acts on the exposed nozzle plate
115
, and thus, the nozzle plate
115
is peeled off the end face of the joined body of the actuator plate
101
and the cover plate
107
.
SUMMARY OF THE INVENTION
The present invention is made in view of these circumstances, and an object of the present invention is to provide an ink jet head in which a nozzle plate does not peel off the end face of a joined body of an actuator plate and a cover plate and the durability of which is expected to be improved.
In order to solve the above problem, according to a first aspect of the present invention, an ink jet head comprises: an actuator plate formed of piezoelectric ceramic with a plurality of channels formed therein, the channels opening to one surface and to one end face; a cover plate with a common ink chamber and an ink supply port formed therein, the common ink chamber being joined to the one surface of the actuator plate to seal a part of openings of the channels and to communicate with the channels, and the ink supply port piercing from the bottom portion of the common ink chamber in a direction opposite to the channels; a flow path block provided with a broad ink flow path, the inlet side thereof communicating with a narrow opening in proximity to an ink inflow port and the outlet side thereof communicating with the ink supply port; and a nozzle plate sealing the one end face of the actuator plate and having nozzle openings corresponding to the channels, respectively, the ink jet head expelling ink filled in the channels from the nozzle openings by applying drive voltage to electrodes provided on side walls of the channels and thereby changing the volume in the channels, and is characterized by comprising a nozzle plate cover joined to an outer side surface of the joined body of the actuator plate and the cover plate for surrounding the nozzle plate to protect the nozzle plate, and is characterized in that a surface of t
Adams & Wilks
Nguyen Judy
Seiko Instruments Inc.
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