Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-07-09
2004-05-04
Adams, Russell (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06729716
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid drop jet heads and ink jet recording apparatuses.
2. Description of the Related Art
An ink jet recording apparatus is used as a picture recording apparatus or picture forming apparatus such as a printer, facsimile, copy machine, or plotter. An ink jet head is used for the ink jet recording apparatus as a liquid drop jet head. The ink jet head includes a nozzle, a liquid room, and a driving means (pressure generating means). An ink drop is jetted out by the nozzle. The nozzle is connected to the liquid room. The liquid room is called a pressurized liquid room, pressure room, jet room, or ink channel. The ink in the liquid room is pressurized by the driving means (pressure generating means). The ink drop is jetted out from the nozzle due to the pressure in the liquid room generated by the pressure generating means. Although there are several types of liquid drop jet heads such as a liquid drop jet head jetting a liquid resist as a liquid drop or a liquid drop jet head jetting a test material of DNA as a liquid drop, the ink jet head will be described.
A piezo type ink jet head is known as an ink jet head. An electromechanical transducer element such as a piezoelectric element as a driving means generating pressure by which the ink in the liquid room is pressurized is used in the piezo type ink jet head. A vibration board that is capable of elastically deforming and forms a wall surface of the liquid room is deformed by a deformation of the driving means, so that the volume is decreased/pressure is increased in the liquid room and the ink drop is jetted, in the piezo type ink jet head. See Japanese Laid-Open Patent Application, No. 2-51734.
In the above mentioned ink jet head, the piezoelectric element is deformed by charging or discharging so that the vibration board coming in contact with the piezoelectric element is deformed. The pressure inside of the pressurized liquid room increases due to the vibration board deforming so as to contract the volume of the pressurized liquid room so that the ink drop is jetted from the nozzle. After the ink drop is jetted, the piezoelectric element is deformed so as to deform the vibration board and expand the volume of the pressurized liquid room.
One example of the above mentioned ink jet head is shown in
FIGS. 1 and 2
.
FIG. 1
is a cross sectional view along a long side direction of the liquid room of the ink jet head according to the conventional art.
FIG. 2
is a cross sectional view along a short side direction of the liquid room of the ink jet head according to the conventional art.
In this ink jet head, a pressurized liquid room
114
connecting to a nozzle
113
jetting an ink drop
122
and a common liquid room
119
supplying the ink through a connecting part
120
to the pressurized room
114
are formed by connecting the liquid room substrate
111
and the nozzle board
118
, and a piezoelectric element
117
provided on a base board
112
is connected to an outside surface of the vibration board
116
forming a part of a wall surface of the pressurized room
114
.
The vibration board
116
is elastically deformed based on a deformation of the piezoelectric element
117
. However, the vibration board
116
generally has a smaller rigidity (larger compliance) than other walls forming the pressurized room
114
. Furthermore, the common liquid room
119
is connected to an ink tank not shown in
FIGS. 1 and 2
. A support member
121
is provided between the liquid room board
111
and a base board
112
.
The piezoelectric element
117
is deformed by applying a voltage from a driving circuit not shown in
FIGS. 1 and 2
to the piezoelectric element
117
so that the vibration board
116
is deformed so as to increase or decrease the volume of the pressurized liquid room
114
. In a case where the volume of the pressurized room
114
is increased, the inside pressure of the pressurized liquid room
114
is reduced so that the ink is filled up through a connecting part
120
from the common liquid room
119
to the pressurized liquid room
114
.
After that a driving force is implemented so as to increase the inside pressure of the pressurized liquid room
114
. That is, in a case where the piezoelectric element
117
is driven so as to reduce the volume of the pressurized liquid room
114
, the inside pressure of the pressurized liquid room
114
is increased. Because of this, ink is pushed out from the nozzle
113
and sprayed as the ink drop
122
to adhere to a recording medium such as paper so that recording can be implemented.
Thus, the ink drop in the ink jet head using the vibration board is formed based on a deformation of the vibration board. A connection part with the piezoelectric element as a driving resource is an important factor as a capability for the ink jet head.
Because of this, as disclosed in Japanese Patent No. 3147132 or Japanese Patent No. 3070625, there is a technology wherein a convex part having an island shape for connecting with the piezoelectric element is formed on the vibration board.
A structure of the above mentioned conventional ink jet head is described with reference to FIG.
3
through FIG.
6
.
FIG. 3
is a perspective view of the conventional ink jet head.
FIG. 4
is a expanded view of a part shown in FIG.
3
.
FIG. 5
is a perspective view of the vibration board of another example of the conventional ink jet head.
FIG. 6
is a rough perspective view of the conventional ink jet head. In FIG.
3
through
FIG. 6
, parts that are the same as the parts shown in FIG.
1
and
FIG. 2
are given the same reference numerals, and explanation thereof will be simplified.
In this ink jet head, a concave part
123
is formed at the vibration board
116
forming one of the wall surfaces of the pressurized liquid room
114
so that a concave part
123
is formed. A convex part
124
having as island shape is formed as a thick part at a position where the piezoelectric element
117
comes in contact with the vibration board
116
. That is, the thin part
126
surrounds all of the convex part
124
having the island shape as a thick part with a substantially constant thickness.
The piezoelectric element
117
corresponds to the pressurized liquid room
114
. The concave part
123
, which surrounds the convex part
124
having the island shape that comes in contact with the piezoelectric element
117
, is divided by the thick part
125
. The thin part
126
is formed by the vibration board
116
shown in FIG.
5
. The convex part
124
having the island shape is formed on the thin part
126
as a thick part.
It is possible to reduce the amount of vibration of the piezoelectric element
117
that is transferred to other neighboring pressurized liquid rooms by making the piezoelectric element
117
come in contact with the convex part
124
having the island shape and driving the piezoelectric element. Furthermore, it is possible to convert the deformation of the piezoelectric element to the change of the volume of the pressurized liquid room efficiently, namely by a pressure change.
However, according to the above mentioned conventional ink jet head, it is necessary for the convex part
124
having the island shape formed on the vibration board
116
to be formed having a constant distance from the border of the division of the pressurized liquid rooms
114
. Accordingly, it is necessary to form the thin part
126
having a constant width surrounding the convex part
124
having the island shape. Hence, it is required to have higher measuring precision or positioning precision.
Furthermore, the long side of the convex part
124
having the island shape is a longer than the long side of the head end part of the piezoelectric element
117
In addition, it is necessary to provide space for the thin part
126
so that it is difficult to make the whole of the ink jet head small. Hence, there is a problem to correspond to an arrangement of pressurized liquid rooms
114
with a high density. Furthermore, since a change
Eguchi Hirotoshi
Hiyoshi Takayuki
Kusunoki Masanori
Matsumoto Shuzo
Ogata Kenichi
Adams Russell
Cooper & Dunham LLP
Do An H.
Ricoh & Company, Ltd.
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