Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-07-02
2002-01-08
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S071000
Reexamination Certificate
active
06336715
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an ink jet recording head which jets ink in the form of a droplet from an ink nozzle by utilization of a piezoelectric effect.
(2) Description of the Related Art
An ink jet recording head for jetting ink in the form of a droplet from an ink nozzle by utilization of a piezoelectric effect has been well known in the art. Examples of such ink recording heads are disclosed in U.S. patent application Nos. 4,819,614 and 4,752,788.
FIG. 1
is a sectional view of a conventional ink jet recording head. As shown in
FIG. 1
, a plurality of concave-shaped ink cavities
52
are formed on one surface of a piezoelectric plate
51
; the piezoelectric plate
51
made of piezoelectric materials is disposed between adjacent concave-shaped ink cavities; and a convex portion
53
made of piezoelectric materials is formed to conform the concave shape of the concave-shaped ink cavity
52
. The top of the concave-shaped ink cavities is covered with a cover plate
54
.
Each of the concave-shaped ink cavities
52
matching with the convex portion
53
comprises two deep grooves (b) for spacing the piezoelectric plate
51
and the convex portion
53
from each other and a shallow groove (a) between the deep grooves (b). An electrode
55
is provided on the bottom of the piezoelectric plate
51
; and an electrode
56
is provided on the convex-portion
53
. Also, a nozzle
57
is formed on the same surface of the piezo-electric plate
51
as the ink cavity to have the nozzle be coupled with the corresponding ink cavity.
When a voltage is applied across a selected pair of electrodes
55
and
56
in the ink jet recording head thus constructed, the convex portion
53
is deformed to change the volume of the ink cavity
51
; as a result, ink in the ink cavity is jetted from the nozzle. The ink jet recording head, however, has the following drawbacks.
As was described with referring to
FIG. 1
, two deep grooves and one shallow groove are constructed in the piezoelectric plate
51
; and the manufacturing cost of this piezoelectric plate
51
is relatively expensive. Particularly in the case when it is required to arrange ink cavities at a high density, the width of each groove (b) becomes as narrow as some &mgr;m, and it is considerably difficult for the present manufacturing technique to form such ink cavities in a piezoelectric plate.
Further, between adjacent ink cavities is provided a bulkhead made of piezoelectric materials, accordingly, an electric field formed across the electrodes
55
and
56
may vibrate the bulkhead between the ink cavities. As a result, the volume of the adjacent ink cavity is changed due to cross-talk between the ink cavities. As a result, around a nozzle is stained with leakage of ink from the adjacent ink cavity, whereby the ink jetting direction is fluctuated.
The cross-talk between ink cavities may be prevented; however, since the convex-portion
53
and the bulkhead are provided as an integral unit, deformation of the convex portion
53
may cause deformation of the bulkhead. Consequently, effective ink jetting is hindered; otherwise, a high-speed response ability is retarded.
Further, the vibration of the convex portion
53
moves ink into the groove (b), the groove (b) for spacing the convex portion
56
and the bulkhead
51
; therefore, ink jetting effect is degraded; or ink penetrates the convex portion
53
from its side walls, as a result of which a bulk resistance is lowered. Accordingly, a drop of voltage or an electrolysis of ink occurs. Also, a cavitation of ink occurs at the groove (b) due to the vibration of the piezoelectric plate, as a result of which effective jetting by utilization of pressure is hindered.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an ink jet recording head which can be readily manufactured at a low manufacturing cost, and to achieve effective ink jetting by preventing cross-talk between ink cavities.
Also it is another object of the present invention to provide an ink jet recording head which enables effective jetting of ink which is pressured due to vibration of an piezoelectric member by preventing a drop of an effective voltage and a cavitation.
The above objects may be fulfilled by a multi-nozzle ink jet head comprising a first member including a plurality of first convex parts disposed in line on a part of its surface, in which at least a part of the first convex part is a piezoelectric element, a second member made of non-piezoelectric materials, including a plurality of concave parts which correspond to the first convex parts, and a second convex part disposed between every two adjacent concave parts, in which the second member is engaged with the first member by inserting each second convex part between a couple of adjacent first convex parts and forming an ink cavity between a bottom of each concave part and a top of the respective first convex part, and a plurality of electrodes being applied to the piezoelectric element included in the first convex part, in which each electrode deforms the respective piezoelectric element by applying a voltage to the same and jets ink in the ink cavity from an ink nozzle.
The first convex part may be inserted into the non-piezoelectric concave part in such a manner that either of them can be movable to the other.
A first gap may be formed between a side surface of the first convex part and a side surface of the non-piezoelectric concave part.
The second filling member for filling the second gap may include a filling and adhesive member, the surface of the first member including the convex part may be covered with a protection film and the protection film may be adhered to the convex part with the filling and adhesive member, and the second filling member may include a part of the protection film besides the filling and adhesive member.
The first member may include a base member and a piezoelectric chip which is disposed on the base member, the piezoelectric chip being equivalent to the piezoelectric element.
The electrodes may be disposed on surfaces of the corresponding piezoelectric chip, the surfaces opposing to each other.
Any one of the piezoelectric chips may be a lamination of piezoelectric layers.
The piezoelectric element may be made of piezoelectric materials and the first member is an integral unit.
Conductive treatment may be applied to the first member except the first convex part.
The piezoelectric element included in the first convex part may be polarized in the same direction as an electric field formed by applying a voltage across the electrodes, and the polarization direction may be substantially perpendicular to an ink jetting direction.
A front end of each ink cavity along with the ink jetting direction may be covered with a front member in which the ink nozzles are formed, a back end of each ink cavity along with the ink jetting direction may be blocked with a block member, and a ink supplying slit communicating with the ink cavity may be formed in the second member.
A non-return valve may be constructed to the ink supplying slit.
According to this construction and manufacturing method, the first member can be readily formed; accordingly the manufacturing cost is reduced by large.
Since the bulkhead between the adjacent ink cavities is made of non-piezoelectric materials, it is not vibrated by the electric field generated by application of a voltage across a selected pair of electrodes. Also, since the bulkhead and the first convex part in the first member are formed independently from each other, a cross-talk can be highly suppressed.
The second object may be fulfilled by the multi-nozzle ink jet head further including a first filling member for filling the first gap.
One surface of the first member which includes the convex part may be covered with a protection film, and the first filling member may consist of a part of the protection film.
A second gap may be formed between a top surface of the non-piezoelectric second convex and the firs
Ebisu Osamu
Higashino Kusunoki
Hotomi Hideo
Masaki Kenji
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
Nguyen Thinh
LandOfFree
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