Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-02-27
2001-07-24
Fuller, Benjamin R. (Department: 2855)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C310S326000
Reexamination Certificate
active
06264310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an on-demand ink jet head utilizing piezoelectric elements, and more particularly to such a head wherein a plurality of the nozzles are tightly arranged in confrontation with the piezoelectric elements.
2. Description of the Prior Art
An example of conventional ink jet head is illustrated in FIG.
1
. As shown therein, piezoelectric elements
4
are in alignment with one another in a columnar direction orthogonal to a main scanning direction. The piezoelectric elements
4
have one end secured to a head substrate
6
and another end attached to a diaphragm
3
by an adhesive material
11
. Pressurizing chambers
1
are formed in association with the piezoelectric elements
4
, which chambers are defined by a nozzle plate
14
formed with nozzles
1
and a chamber plate
13
. Ink is supplied from a common ink channel (not shown) into the pressurizing chambers
1
through individual ink channels defined by the restricting plate
12
and the diaphragm
3
.
Referring again to
FIG. 1
, bonding of the piezoelectric elements
4
and the diaphragm
3
is performed in such a manner that the piezoelectric elements
4
with a predetermined amount of adhesive material
11
coated on the end surfaces thereof are pressed against the diaphragm
3
. An excess amount of the adhesive material
11
is then expelled out of the space between the end surface of the piezoelectric element and the diaphragm
3
. The flowed out adhesive material
11
is confined in a space between the adjacent two piezoelectric elements
4
. Hence, when the adhesive material
11
is solidified, the intervened piezoelectric elements are supported by the solidified adhesive material layers of substantially the same shape. However, with respect to the two endmost piezoelectric elements, the solidified adhesive material layer in the outer side is different in shape from that in the inner side. The solidified adhesive material
11
has elasticity and serves as dampers of the piezoelectric elements
4
.
When printing is performed with the ink jet head thus constructed, a secondary droplet is occasionally ejected following ejection of a primary droplet. The two droplets do not overlap when they impinge on a recording medium.
SUMMARY OF THE INVENTION
In order to improve the print quality, the present inventors investigated the reasons for the production of the secondary droplet and have found that the secondary droplets result from the distribution of the adhesive material
11
through extensive experiment. The inventors have also found through experimentation that all of the piezoelectric elements
4
of
FIG. 1
need to be supported by the dampers of the same shape in order to attain uniform operability of the piezoelectric elements
4
.
In view of the foregoing, an object of the present invention is to provide a multi-nozzle ink jet head using a plurality of piezoelectric elements in which uniform operation of those piezoelectric elements is ensured.
In order to achieve the above and other objects, the present invention provides a multi-nozzle ink jet head including a nozzle plate formed with a plurality of nozzles from which ink droplets are ejected; a diaphragm supported to be substantially in parallel with the nozzle plate; a chamber plate; a restricting plate; a plurality of piezoelectric elements; a plurality of input terminal pairs provided corresponding to respective ones of the plurality of piezoelectric elements individually; and two dummy elements, each disposed in a position outside each of two endmost piezoelectric elements of the plurality of piezoelectric elements. The piezoelectric elements and the two dummy elements are spaced at a substantially constant interval.
The chamber plate, the nozzle plate, and the diaphragm form a plurality of pressurizing chambers corresponding to respective ones of the plurality of nozzles individually. The restricting plate, the chamber plate, and the diaphragm form a plurality of ink channels connecting each of the plurality of pressurizing chambers with a common ink channel. The restricting plate is provided for controlling an inflow amount of ink into each of the pressurizing chambers from the common ink channel. The piezoelectric elements are provided corresponding to respective ones of the pressuring chambers individually. Those piezoelectric elements are in alignment with one another so that one end of each of the plurality of piezoelectric elements face the diaphragm. During assembly of the above-described components, an adhesive material is used for bonding one end of each piezoelectric element to the diaphragm. The adhesive material is in a fluid state at a time of bonding and in a solid state when dried. In the present invention, two dummy elements prevent the fluid state adhesive material from flowing out during assembly. When the adhesive material is dried, it has elasticity and serves as a damper of the piezoelectric element for damping unwanted vibrations of the piezoelectric elements. Such an adhesive material is made from a silicon resin, an acrylic resin, or a nitrile resin.
With the head thus constructed, when the input terminal pairs selectively apply a voltage to the corresponding piezoelectric elements to cause them to deform, for example, against the diaphragm, ink filled in the corresponding pressurizing chambers is pressurized and ink droplets are ejected from the corresponding nozzles. By the provision of the dummy elements, the distribution of the adhesive material serving as the damper is substantially even between the piezoelectric elements. Therefore, with the same voltage applied to the piezoelectric elements, ink droplets are ejected from the nozzles substantially at the same speed. Further, generation of a secondary droplet following a primary droplet can be prevented and thus print quality is improved.
Preferably, the two dummy elements are piezoelectric elements.
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Akimoto Kazuaki
Akiyama Yoshitaka
Kugai Kenichi
Kurosawa Nobuhiro
Matsuoka Takao
Dickens C.
Fuller Benjamin R.
Hitachi Koki Co,. Ltd.
McGuireWoods LLP
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