Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-11-08
2002-03-05
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S065000, C347S067000
Reexamination Certificate
active
06352337
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a drop-on-demand inkjet printer having a droplet separator that includes a mechanism for assisting the selective generation of micro droplets of ink.
BACKGROUND OF THE INVENTION
Inkjet printing is a prominent contender in the digitally controlled electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper, and its avoidance of toner transfers and fixing. Inkjet printing mechanisms can be categorized as either continuous inkjet or drop-on-demand inkjet. Drop-on-demand inkjet printers selectively eject droplets of ink toward a printing media to create an image. Such printers typically include a print head having an array of nozzles, each of which is supplied with ink. Each of the nozzles communicates with a chamber which can be pressurized in response to an electrical impulse to induce the generation of an ink droplet from the outlet of the nozzle. Many such printers use piezoelectric transducers to create the momentary pressure necessary to generate an ink droplet. Examples of such printers are present in U.S. Pat. Nos. 4,646,106 and 5,739,832.
While such piezoelectric transducers are capable of generating the momentary pressures necessary for useful drop-on-demand printing, they are relatively difficult and expensive to manufacture since the piezoelectric crystals (which are formed from a brittle, ceramic material) must be micro-machined and precision installed behind the very small ink chambers connected to each of the inkjet nozzles of the printer. Additionally, piezoelectric transducers require relatively high voltage, high power electrical pulses to effectively drive them in such printers.
To overcome these shortcomings, drop-on-demand printers utilizing thermally-actuated paddles have been suggested. Each paddle would include two dissimilar metals and a heating element connected thereto. When an electrical pulse is conducted to the heating element, the difference in the coefficient of expansion between the two dissimilar metals causes them to momentarily curl in much the same action as a bimetallic thermometer, only much quicker. A paddle is attached to the dissimilar metals to convert momentary curling action of these metals into a compressive wave which effectively ejects a droplet of ink out of the nozzle outlet.
Unfortunately, while such thermal paddle transducers overcome the major disadvantages associated with piezoelectric transducers in that they are easier to manufacture and require less electrical power, they do not have the longevity of piezoelectric transducers. Additionally, thermal paddle transducers are prone to attracting dye deposit due to heat used in actuation. The dynamic response characteristics of the paddle will alter as dye deposit builds making the paddle unreliable for reproducible ink drop generation. Thermal paddle transducers therefore are preferably used with specially formulated inks that have additives to minimize heat-induced deposition and/or have lower dye content.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an improved drop-on-demand type printer which utilizes paddles, but which is capable of ejecting ink droplets at higher speeds and with greater power to enhance printing accuracy and reliable drop ejection, and to render the printer compatible with inks of greater viscosity and dye content.
According to a feature of the present invention, a drop-on-demand inkjet print head includes a nozzle with an ink outlet, an ink supply channel through which a body of ink is supplied to the nozzle, and a member movable in the ink supply channel toward the nozzle outlet for causing a droplet to separate from the body of ink. A micro-actuator applies a mechanical force to the member. The micro-actuator includes a body of elastomer material having opposed first and second surfaces spaced apart in a first direction by a predetermined at-rest dimension. A charge mechanism is coupled to the first opposed surface of the elastomer material so as to apply an electrical charge in the first direction. The charge is spatially varied in a second direction substantially normal to the first direction so as to create spatially varied mechanical forces across the elastomer material such that the elastomer material exhibits spatially varied growth in the first direction. The member is associated with the second opposed surface of the elastomer material so as to move in the first direction in response to growth of the elastomer material.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiments presented below.
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patent: WO 99/17083 (1999-04-01), None
USSN 09/671,438 entitled Deformable Micro-Actuator, by Ravi Sharma et al., filed Sep. 27, 2000.
Barlow John
Eastman Kodak Company
Sales Milton S.
Stephens Juanita
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