Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-10-05
2002-10-22
Barlow, John (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06467877
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to acoustic ink printing. It finds particular application in conjunction with producing higher pixel resolutions from an acoustic ink printhead and will be described with particular reference thereto. It will be appreciated, however, that the invention will also find application in correcting directionality errors for droplets produced by acoustic ink printers, and the like.
Various fluid application technologies, such as printing technologies, are being developed. One such technology uses focused acoustic energy to eject droplets of marking material from a printhead onto a recording medium.
Acoustic ink printheads typically include a plurality of droplet ejectors, each of which launches a converging acoustic beam into a pool of fluid (e.g., liquid ink). The angular convergence of this beam is selected so that the beam focuses at or near the free surface of the ink (i.e., at the liquid-air interface). Printing is performed by modulating the radiation pressure that the beam of each ejector exerts against the free surface of ink to selectively eject droplets of ink from the free surface.
FIG. 1
illustrates a schematic of a conventional ejector of a printhead
10
for use in an acoustic ink printer. A transducer
12
and a lens
14
are disposed on opposite sides of a wafer
16
. The wafer
16
is preferably formed of a glass. A thin metal plate
18
is spaced vertically from the wafer
16
. The metal plate
18
defines an aperture
22
. The aperture
22
is disposed adjacent the lens
14
and the transducer
12
. A fluid
24
, preferably selected from a group including water and aqueous inks, is disposed between the metal plate
18
and the wafer
16
. An air space is disposed on the side of the metal plate
18
opposite the fluid
24
. An air-fluid interface
26
is disposed at the aperture
22
of the metal plate
18
. The fluid
24
wets the edges of the aperture
22
. The air-fluid interface
26
is curved (e.g., crescent-shaped) and is commonly referred to as a meniscus.
In the operation of the ejector, the transducer
12
generates an acoustic wave, which propagates through the fluid
24
. Dotted lines in
FIG. 1
indicate the boundaries of the acoustic wave. The direction in which the acoustic wave propagates is indicated by the arrows
28
,
32
. The lens
14
focuses the acoustic wave to a spot
34
on the meniscus
26
. A droplet
36
is ejected from the aperture
22
. The aperture
22
surrounds a region of the droplet formation and helps to constrain the location of the fluid surface. Ideally, as shown in
FIG. 1
, the droplet
36
is ejected in the direction indicated by arrow
38
.
Conventional methods for ejecting a droplet from the meniscus have primarily been directed to insuring the consistent directionality of the ejected droplet. More specifically, it has typically been desirable to eject the droplet along the line defined by the propagating acoustic wave. The propagation direction is illustrated as line
38
in FIG.
1
.
A first method for ejecting a droplet along the propagation direction focuses the acoustic wave to a spot on the meniscus that has a tangential plane perpendicular to the propagation direction (see spot
34
in FIG.
1
). If acoustic waves of an arbitrary shape are generated, focusing the acoustic wave to such a spot is critical for producing droplets which eject in the propagation direction.
A second method for ejecting a droplet along the propagation direction is disclosed in U.S. Pat. No. 5,808,636 (“the '636 patent”), which is incorporated herein by reference. The '636 patent discloses that an ideally shaped acoustic wave produces a droplet that is ejected in the desired direction, regardless of the angle between the acoustic wave and the meniscus. The ideally shaped acoustic wave disclosed in the '636 patent is about 2 &mgr;s.
While the conventional methods for ejecting droplets from the printhead achieve a desired directionality, they also result in at least one drawback. More specifically, because the conventional methods of ejecting droplets from the printhead strive to project the droplets in a single direction, the resolution of the printed output is limited by the spacing of apertures in the printhead.
The present invention provides a new and improved apparatus and method which overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
An apparatus ejects a droplet of a fluid from a surface of the fluid. An acoustic wave is generated to eject the droplet from an ejection spot on the surface of the fluid. A propagation direction of the acoustic wave is not perpendicular to a plane tangent to the ejection spot. The acoustic wave is shaped into a plurality of tonebursts. An ejection direction of the droplet is a function of the shape of the toneburst.
In accordance with one aspect of the invention, the fluid includes an aqueous ink.
In accordance with another aspect of the invention, a first toneburst causes a first droplet of the fluid to be ejected from the surface in a first ejection direction. The first ejection direction is substantially along the propagation direction of the acoustic wave and is independent of disturbances to the surface of the fluid caused by capillary waves generated by high-speed printing.
In accordance with a more limited aspect of the invention, a second toneburst, having a shape different from the first toneburst, causes a second droplet of the fluid to be ejected from the surface in a second ejection direction. A third toneburst, having a shape different from the first and second tonebursts, causes a third droplet of the fluid to be ejected from the surface in a third ejection direction.
In accordance with another aspect of the invention, the fluid is ejected from an ejector of a printhead of a printer.
In accordance with another aspect of the invention, the fluid is ejected from an ejector of a printhead during high-speed printing.
In accordance with another aspect of the invention, the means for generating the acoustic sound wave includes a piezo-electric element.
In accordance with a more limited aspect of the invention, the acoustic wave is shaped by a Fresnel lens.
One advantage of the present invention is that the resolution of an acoustic ink printhead is increased.
Another advantage of the present invention is that the directionality of droplets ejected from an acoustic ink printhead is controlled by the shape of the acoustic sound wave.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
REFERENCES:
patent: 4386358 (1983-05-01), Fischbeck
patent: 4602852 (1986-07-01), Moroz
patent: 4748461 (1988-05-01), Elrod
patent: 5122818 (1992-06-01), Elrod et al.
patent: 5191354 (1993-03-01), Quate
patent: 5565113 (1996-10-01), Hadimioglu et al.
patent: 5808636 (1998-09-01), Stearns
patent: 5912679 (1999-06-01), Takayama et al.
patent: 6045208 (2000-04-01), Hirahara et al.
patent: 6155671 (2000-12-01), Fukumoto et al.
patent: 6364454 (2002-04-01), Hadimioglu
Hamimioglu et al., “Acoustic Ink Printing”, IEEE 1992. Ultrasonics Symposium (Cat. No. 92CH3118-7), NY, NY, 1992, p. 929-35, vol. 2.
Imaino et al., “Acoustic Dispersion and Attenuation in Toners”, Photographic Science and Engineering, vol. 28, No. 6, Nov./Dec. 1984.
Fay Sharpe Fagan Minnich & McKee LLP
Feggins K.
Xerox Corporation
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