Droplet ejector and liquid supply tube

Incremental printing of symbolic information – Ink jet – Ejector mechanism

Reexamination Certificate

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Details

C347S050000

Reexamination Certificate

active

06692106

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique of ejecting droplets, and is applicable to a technique of ejecting droplets from the forward end of a unidirectionally extending instrument, for example.
2. Description of the Background Art
A technique of vibrating a liquid having an exposed liquid surface with ultrasonic waves from a portion other than the liquid surface for converging acoustic energy in the vicinity of the liquid surface and ejecting droplets from the liquid surface is generally proposed.
FIG. 15
is a sectional view showing the structure of a head
200
for an inkjet printer employed as an example of a conventional droplet ejector. The head
200
comprises an ink tank
201
and a piezoelectric transducer
204
provided on the bottom surface of the ink tank
201
.
The ink tank
201
has a cavity for storing ink
203
therein, and a reflecting wall
202
forms the inner wall of this cavity. The cavity is provided on its upper surface, i.e., the side isolated from the bottom surface provided with the piezoelectric transducer
204
, with an opening
213
for spraying the ink
203
.
The piezoelectric transducer
204
is formed by an electrode
205
and a piezoelectric vibrator
206
connected with wires
208
and
209
respectively. The wires
208
and
209
are connected to an ac power source
207
. The electrode
205
is electrically connected with the piezoelectric vibrator
206
and backs the cavity from the bottom surface thereby preventing leakage of the ink
203
. An ink inlet
210
is provided on a position of the cavity closest to the electrode
205
.
The piezoelectric transducer
204
substantially planarly introduces acoustic waves
211
to the ink
203
and the acoustic waves
211
are reflected by the reflecting wall
202
. The reflecting wall
202
presents a parabola on the section shown in FIG.
15
and the opening
213
is arranged in the vicinity of the focus
212
of this parabola, whereby the acoustic waves
211
are converged on the opening
213
for increasing the concentration of acoustic energy of the ink
203
on this portion so that ink droplets DP are sprayed from the opening
213
.
For example, Japanese Patent Application Laid-Open No. 10-278253 (1998) discloses such a technique.
On the other hand, the technique of ejecting a liquid is not exclusively required to a printer ejecting ink. For example, it is preferable to eject a desired quantity of liquid from the forward end of a tube having a diameter of several mm in consideration of liquid supply to a narrow portion.
While the aforementioned technique is excellent in the point that the ink inlet
210
is arranged on a position hardly damaging the function of the reflecting wall
202
, the direction for introducing the ink
203
into the cavity is along the electrode
205
and substantially perpendicular to the direction for ejecting the droplets DP. Therefore, the dimension along the direction perpendicular to that for ejecting the droplets DP is hard to reduce.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a droplet ejector comprises a vibration excitor, a nozzle plate opening a nozzle ejecting a liquid to be ejected and a reflector having an inlet opening toward the vibration excitor, an outlet opening toward the nozzle plate and a reflecting wall storing the liquid, reflecting acoustic waves from the vibration excitor and converging the same in the vicinity of the nozzle, while the vibration excitor is provided with a through hole for supplying the liquid to the reflector.
In the droplet ejector according to the first aspect, the liquid can be directly supplied into the reflector through the through hole of the vibration excitor, whereby the dimension along a direction perpendicular to that for ejecting droplets can be suppressed for providing a droplet ejector having a compact structure. When the outer diameters are equal, therefore, an opening on the inlet side of the reflector can be enlarged for widening the effective reflecting wall. Further, the reflecting wall may not be provided with a hole for liquid supply, whereby stronger ultrasonic waves can be converged for improving efficiency of the apparatus.
According to a second aspect of the present invention, the droplet ejector further comprises a hollow needle engaging with the through hole for supplying the liquid to the reflector.
In the droplet ejector according to the second aspect, the vibration excitor drives no liquid but that stored in the reflector, whereby loss of ultrasonic waves converged in the vicinity of the nozzle can be avoided.
According to a third aspect of the present invention, a forward end of the hollow needle closer to the reflector has an opening whose edge is arranged on a surface of the vibration excitor closer to the reflector.
In the droplet ejector according to the third aspect, the liquid supplied to the reflector spreads on the surface of the vibration excitor to be stored in the reflector from the side separate from the outlet. Therefore, it is possible to inhibit bubbles from remaining around the inlet of the reflector and hindering transmission or convergence of ultrasonic waves.
According to a fourth aspect of the present invention, the hollow needle opens in a plurality of portions toward a plurality of different directions.
In the droplet ejector according to the fourth aspect, the liquid is stored in the reflector without remarkably moving on the surface of the vibration excitor, whereby residual of bubbles can be further suppressed.
According to a fifth aspect of the present invention, the droplet ejector further comprises a liquid storage tank provided on an end of the hollow needle opposite to the reflector.
In the droplet ejector according to the fifth aspect, the liquid storage tank is provided on the back surface of the vibration excitor, whereby liquid supply is simplified and the overall apparatus can be effectively miniaturized.
According to a sixth aspect of the present invention, the through hole has a smaller diameter than the outlet and is provided on a position opposed to the outlet.
In the droplet ejector according to the sixth aspect, ultrasonic waves generated from the position provided with the through hole are not reflected by the reflecting wall but have a small possibility of contributing to convergence of acoustic energy around the nozzle. Therefore, the efficiency for converging the acoustic energy around the nozzle is not remarkably hindered.
According to a seventh aspect of the present invention, the vibration excitor is formed by a plurality of components divided on a boundary including the through hole.
In the droplet ejector according to the seventh aspect, a step of forming the through hole in the vibration excitor can be omitted and the vibration excitor can be prevented from cracking in working.
According to an eighth aspect of the present invention, the droplet ejector further comprises a plurality of conductive members provided on the opposite side of the reflector for supplying a signal to the vibration excitor.
According to a ninth aspect of the present invention, at least one of the plurality of conductive members has a projecting spring member.
According to a tenth aspect of the present invention, all conductive members have projecting spring members.
According to an eleventh aspect of the present invention, at least one of the plurality of conductive members has an extension part extending oppositely to the reflector.
In the droplet ejector according to the eighth to eleventh aspects, both the liquid and a signal to the vibration excitor are supplied from the same side, whereby the liquid and the signal can be supplied to the droplet ejector through a compact structure.
According to a twelfth aspect of the present invention, a liquid supply tube comprises a hollow body supplying a liquid and a plurality of conductors, insulated from each other, provided on the outer side surface of the body.
According to a thirteenth aspect of the present invention, the hollow body i

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