Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-04-16
2004-01-13
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06676247
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a head chip that is mounted on an ink jet recording device applied to, for example, a printer or a facsimile.
2. Description of the Related Art
Conventionally, there is known an ink jet recording device that records characters and images on a medium to be recorded using an ink jet head having a plurality of nozzles for discharging ink. In such an ink jet recording device, the nozzles of the ink jet head are provided in a head holder so as to oppose the medium to be recorded, and this head holder is mounted on a carriage to be scanned in a direction perpendicular to a conveying direction of the medium to be recorded.
A schematic exploded view of an example of a head chip of such an ink jet head is shown in
FIG. 12 and a
sectional view of main parts of the same is shown in FIG.
13
. As shown in
FIGS. 12 and 13
, a plurality of grooves
102
are provided in parallel with each other in a piezoelectric ceramic plate
101
, and each groove
102
is separated by sidewalls
103
. An end portion in the longitudinal direction of each groove
102
is extended to an end surface of the piezoelectric ceramic plate
101
and the other end portion is not extended to the other end surface, making the groove
102
to be gradually shallow. In addition, electrodes
105
for applying a driving electric field are formed on surfaces on opening side of both sidewalls
103
in each groove
102
throughout its longitudinal direction.
In addition, a cover plate
107
is joined on the opening side of the grooves
102
of the piezoelectric ceramic plate
101
via adhesive
109
. The cover plate
107
includes a common ink chamber
111
to be a recessed portion communicating with the other end portion where each groove
102
is shallow and an ink supply port
112
that is bored from the bottom portion of this common ink chamber
111
in the direction opposite to the grooves
102
.
In addition, a nozzle plate
115
is joined to an end surface of the joined body of the piezoelectric ceramic plate
101
and the cover plate
107
in which the grooves
102
are opened, and nozzle openings
117
are formed in the nozzleplate
115
at positions opposing the respective grooves
102
.
Further, a wiring substrate
120
is fixed to the surface of the piezoelectric ceramic plate
101
on the other side of the nozzle plate
115
and on the other side of the cover plate
107
. Wiring
122
connected to each electrode
105
via bonding wires
121
or the like is formed on the wiring substrate
120
, and a driving voltage can be applied to the electrodes
105
via this wiring
122
.
In a head chip configured in this way, when each groove
102
is filled with ink from the ink supply port
112
and a predetermined driving electric field is caused to act on the sidewalls
103
on both sides of the predetermined groove
102
via the electrode
105
, the sidewalls
103
are deformed to change the capacity inside the predetermined groove
102
, whereby the ink in the groove
102
is discharged from the nozzle opening
117
.
For example, as shown in
FIG. 14
, if ink is discharged from the nozzle opening
117
corresponding to a groove
102
a
, a positive driving voltage is applied to electrodes
105
a
and
105
b
in the groove
102
a
and, at the same time, opposing electrodes
105
c
and
105
d
to the respective electrodes are grounded. Consequently, a driving electric field in the direction toward the groove
102
a
acts on sidewalls
103
a
and
103
b
and, if the driving electric field is perpendicular to a direction of polarization of the piezoelectric ceramic plate
101
, the sidewalls
103
a
and
103
b
are deformed in the direction of the groove
102
a
by a piezoelectric thickness slip effect and the capacity inside the groove
102
a
decreases to increase pressure, whereby the ink is discharged from the nozzle opening
117
.
In such a head chip, sound pressure is repeatedly reflected and takes a long time to completely attenuate because a degree of sealing a groove is low, although time to be consumed since vibration of sidewalls due to ink discharge is stopped until pressure of ink inside a groove declines to zero to enable discharge of the next ink depends on a length of a groove, a form of a nozzle opening, and the like. Thus, there is a problem in that it is difficult to achieve high speed consecutive discharge, that is, to achieve high speed printing.
In addition, particularly, since time to be consumed until sound pressure attenuates fluctuates significantly due to a form of a nozzle opening, there is a problem in that it is very difficult to control a discharge amount according to the form of a nozzle opening.
Moreover, a chamber consists of a boundary portion communicating with a common ink chamber and a pump portion from a nozzle opening to the boundary portion which is driven for discharging ink, and converging time during which pressure in the chamber attenuates is determined depending on a length of the pump portion, that is, a distance from the nozzle opening to the boundary portion. Thus, there is a problem in that, if the length of the pump is shortened in order to reduce converging time, the ink discharge property is deteriorated and printing is not performed normally.
SUMMARY OF THE INVENTION
In view of such circumstances, it is an object of the present invention to provide a head chip which reduces converging time, during which pressure in a chamber attenuates, to achieve high speed printing without deteriorating the ink discharge property and, at the same time, does not cause converging time to fluctuate even if a discharge amount is controlled according to a shape of a nozzle opening.
According to a first aspect of the present invention for solving the above-mentioned object, there is provided a head chip comprising: chambers defined on a substrate, having one-end portions in a longitudinal direction thereof, which communicate with nozzle openings; and electrodes provided on sidewalls of the chambers, in which a driving voltage is applied to the electrodes so that a capacity within the chambers is changed to discharge ink filled in the inside from the nozzle openings,
characterized in that: an ink chamber plate defining a common ink chamber communicating with the chambers is joined on the substrate; the common ink chamber is provided with a partitioning portion for partitioning the chambers and the common ink chamber; and that communicating holes defining a pump length according to a distance from the nozzle openings are provided in the partitioning portion.
According to a second aspect of the present invention, in the first aspect of the invention, a head chip is characterized in that a plurality of the communicating holes are provided at an interval equivalent to the pump length.
According to a third aspect of the present invention, in the first or second aspect of the invention, a head chip is characterized in that the partitioning portion is formed of a separate member.
According to a fourth aspect of the present invention, in any one of the first to third aspects of the invention, a head chip is characterized in that the substrate is formed of a piezoelectric ceramic plate, and the chamber is defined by forming grooves in the piezoelectric ceramic plate and, at the same time, communicates with the common ink chamber at openings on the opposite side of the substrate at one end portion in the longitudinal direction of the chamber.
According to a fifth aspect of the present invention, in any one of the first to third aspects of the invention, a head chip is characterized in that the sidewalls made of piezoelectric ceramic are arranged on the substrate at a predetermined interval to define the chambers between the sidewalls and, at the same time, the common ink chamber is defined on the substrate, and the chambers and the common ink chamber communicate with each other at one end in the longitudinal direction of the chambers.
In the present invention described above, a communicating hole for defining a le
Adams & Wilks
Do An H.
Meier Stephen D.
SII Printek Inc.
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