Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-12-10
2004-05-18
Feggins, K. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06736492
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-377865, filed Dec. 12, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for ejecting liquid droplets, particularly, to a share mode type ink jet head.
2. Description of the Related Art
An apparatus for ejecting liquid droplets, e.g., a share mode type apparatus for ejecting liquid droplets, is widely known to the art. The apparatus is widely used as an ink jet head for ejecting an ink droplet.
An example of a conventional share mode type ink jet head (prior art 1) will now be described with reference to
FIGS. 1 and 2
.
FIG. 1
is an exploded perspective view schematically showing an ink jet head as an apparatus of prior art 1.
FIG. 2
is a vertical cross sectional view schematically showing the ink jet head shown in FIG.
1
.
As shown in the drawings, the ink jet head of prior art 1 includes a rectangular piezoelectric body
10
, which is thin and flat. A plurality of parallel grooves
12
, which are arranged a predetermined distance P apart from each other in a predetermined arranging direction, are formed on a flat plane
10
a
of the piezoelectric body
10
. These grooves
12
are equal to each other in size. Each of grooves
12
has a pair of ends. One end
12
a
of each groove
12
is open at one end surface
10
b
perpendicular to the plane
10
a
so as to form a nozzle-side opening. Also, the other end
12
b
of each groove
12
is formed such that the depth of the groove
12
is gradually decreased from the midway of the groove
12
. As a result, the other end
12
b
does not extend to reach the other end surface
10
c
perpendicular to the plane
10
a.
Electrodes, which are not shown in the drawings for simplicity of the drawings, are formed on inner surfaces, i.e., a side wall and a bottom surface, of each of the plural grooves
12
. A conductive pattern
14
is a conductive means formed together with the electrode and electrically connected to the electrode. The conductive pattern
14
is formed to extend in a region between the other end
12
b
of the groove
12
and the other end surface
10
c
on the plane
10
a.
A terminal flange
16
a
of a liquid supply section
16
is fixed to cover the entire open portion of the plane
10
a
in the region where the plural grooves
12
are open on the plane
10
a
. The terminal flange
16
a
has an ink outlet port
16
c
. The ink outlet port
16
c
communicates with a region in the vicinity of the other end of the opening of each groove
12
on the plane
10
a
. The liquid supply section
16
also includes a small ink container
16
e
equipped with a connection plug
16
d
. A flexible ink supply pipe (not shown) extending from an ink supply source such as an ink tank (not shown) is connected to the connection plug
16
d
. The small ink container
16
e
includes an ink reservoir
16
f
into which the ink from the ink supply pipe flows through the connection plug
16
d
. The ink reservoir
16
f
is fixed to cover the ink outlet port
16
c
on the surface opposite the surface facing the plane
10
a
of the piezoelectric body
10
in the terminal flange
16
a
. An ink filter
16
g
is arranged within the ink reservoir
16
f.
One end portion of a flexible substrate
18
is fixed to the region to which the plural conductive patterns
14
extend on the plane
10
a
. A plurality of conductive patterns
18
a
is formed on the flexible substrate
18
. The conductive patterns
18
a
is electrically connected respectively to the conductive patterns
14
of the piezoelectric body
10
. Also, a driving circuit
18
b
is fixed to the flexible substrate
18
. The driving circuit
18
b
selectively transmits the voltage supplied from an outer power source (not shown) to the conductive pattern
14
as a driving signal.
A nozzle plate
20
covering the end
12
a
of each of the grooves
12
is fixed to the end surface
10
b
of the piezoelectric body
10
. A plurality of nozzles
20
a
is formed in the nozzle plate
20
. Each of the nozzles
20
a
is arranged substantially in the center of one end
12
a
of each groove
12
. An ink repelling treatment is applied to the outer surface of the nozzle plate
20
on the side opposite the surface facing the end surface
10
b
of the piezoelectric body
10
.
First, The ink jet head of prior art 1 pressurizes the ink in the ink supply source, and supplies the ink to the ink reservoir
16
f
through the ink supply pipe and the connection plug
16
d
. The ink thus supplied into the ink reservoir
16
f
flows into all the grooves
12
of the piezoelectric body
10
through the ink filter
16
g
and the ink outlet port
16
c
. It is possible for the ink filling the plural grooves
12
to leak to the outside through the plural nozzles
20
a
of the nozzle plate
20
. However, the ink is repelled by the outer surface of the nozzle plate
20
and, thus, is not attached to the outer surface of the nozzle plate
20
.
A pressure of the ink within the groove
12
is reduced to negative pressure relative to the atmospheric pressure when the pressurization is released. As a result, the ink forms a meniscus because of the surface tension within each nozzle
20
a.
While the ink is held under this state, the driving circuit
18
b
selectively impresses a driving signal (driving voltage) to the electrode within the groove
12
in accordance with the control signal generated from a control circuit (not shown), e.g., a control circuit of a personal computer connected to the ink jet printer using a conventional ink jet head. As a result, the side wall of the groove
12
corresponding to the electrode to which the driving signal is impressed is deformed so as to reduce the lateral cross section. When area of the lateral cross section is reduced in the groove
12
, the ink in each groove
12
receives a shock wave. A predetermined amount of the ink is ejected outward from the corresponding nozzle
20
a
in the form of ink droplets.
The grooves
12
are formed by applying a rotary cutter blade to the plane
10
a
of the piezoelectric body
10
. In each of the grooves
12
, the side wall between the adjacent grooves
12
are formed deformable and have sufficient durability. Such being the situation, it is necessary for the side wall between the adjacent grooves
12
to have a reasonable thickness. Because of the particular requirement, the highest groove density achieved nowadays is about 200 grooves/inch (25.4 mm). In general, 180 grooves are formed per inch. In other words, the nozzle density (density of the ejected ink droplets) of the ink jet head using a piezoelectric body thus manufactured is 180 dpi.
The construction of a share mode type ink jet heat of prior art 2 will now be described with reference to
FIGS. 3 and 4
.
FIG. 3
is an exploded perspective view schematically showing the ink jet head of prior art 2, and
FIG. 4
is a vertical cross sectional view schematically showing the ink jet head shown in FIG.
3
.
The ink jet head of prior art 2 is constructed such that the density of the ejected ink droplets is set at 360 dpi, which is twice the density for the ink jet head of prior art 1.
As shown in
FIGS. 3 and 4
, the ink jet head of prior art 2 includes two ink jet heads of prior art 1. The two ink jet head is joined to each other such that other surfaces (on the back side of the plane
10
a
) of the piezoelectric bodies
10
stand opposite to each other. It should be noted that, in the ink jet head of prior art 2, the piezoelectric bodies
10
are joined to each other such that a plurality of nozzles side openings (i.e., opening of one end
12
a
of each of the grooves
12
) on one end
10
b
of one of the piezoelectric bodies
10
are deviated by half the pitch P, i.e., ½P, from the nozzles side openings of the other piezoelectric body
10
in the arranging direction of the nozzle-side openings, as apparent from FIG
Matsuyama Takashi
Shimizu Masanobu
Yamada Takahisa
Feggins K.
Olympus Optical Co,. Ltd.
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