Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-07-19
2001-04-10
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S063000, C347S065000
Reexamination Certificate
active
06213587
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ink jet printhead with improved transducer life, and, more specifically, to an ink jet printhead having a reduced nozzle plate thickness, a reduced barrier height, and a reduced power density applied to the heaters of the printhead.
BACKGROUND OF THE INVENTION
Ink jet printers typically include recording heads, referred to hereinafter as printheads, that employ transducers which utilize kinetic energy to eject ink droplets. For example, thermal printheads rapidly heat thin film resistors (or heaters) to boil ink, thereby ejecting an ink droplet onto a print receiving medium, such as paper. According to this ink jet method, upon firing a resistor, a current is passed through the resistor to rapidly generate heat. The heat generated by the resistor rapidly boils or nucleates a layer of ink in contact with or in proximity to a surface of the resistor.
The nucleation causes a rapid vaporization of the ink vehicle, creating a vapor bubble in the layer of ink. The expanding vapor bubble pushes a portion of the remaining ink through an aperture or orifice in a plate, so as to deposit one or more drops of the ink on a print receiving medium, such as a sheet of paper. The properly sequenced ejection of ink from each orifice causes characters or other images to be printed upon the print receiving medium as the printhead is moved relative to the print receiving medium.
Typically, the orifices provided on such a plate are arranged in one or more linear arrays. Moreover, the paper is typically shifted each time the printhead moves across the paper. The thermal ink jet printer is generally fast and quiet, as only the ink droplet is in contact with the paper. Such printers produce high quality printing and can be made both compact and economical.
In general, the reliability of a printhead can be dependent on the reliability of the energy-generating elements or transducers it utilizes. Accordingly, and as can be understood, increasing the expected lifespan of the transducers would improve the reliability of the printheads in which they are used. Thus, it would be advantageous to have a printhead that has increased transducer life.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to improve the reliability of inkjet printheads.
It is another object of the present invention to provide an inkjet printhead including a transducer having an increased life span.
According to one embodiment of the present invention, an inkjet printhead comprises a transducer (such as a heater resistor), a chamber, and a plate. At least a portion of the transducer is arranged within the chamber, and the plate is provided with at least one aperture capable of cooperating with the chamber to allow ink to be ejected therefrom. The plate has a thickness of less than 62 microns and the transducer can be selectively energized with a power density less than 2.159 GW/m
2
to cause droplets of the ink to be ejected.
Preferably, the plate is separated from the transducer by a distance of less than 28 microns. More preferably, the plate is so separated by about 8 to about 27 microns. In preferred inkjet printheads according to this embodiment, the transducer comprises a heater having a heater area of less than about 2800 microns
2
, and/or the inkjet printhead comprises a mono ink.
According to another preferred embodiment of the present invention, the plate thickness is less than about 60 microns and, more preferably, is about 35 to about 55 microns. In a further preferred embodiment, the transducer is capable of being selectively energized with a power density less than about 2 GW/m
2
to cause droplets of ink to be ejected from the chamber. With mono-ink printheads, this transducer is capable of being selectively energized with a power density preferably less than about 1.3 GW/m
2
to cause droplets of ink to be ejected from the chamber and, more preferably, from about 0.7 to about 1 GW/m
2
. Meanwhile, with multi-color ink printheads, this transducer is capable of being selectively energized with a power density preferably from about 0.7 to about 1.5 GW/m
2
.
In a preferred embodiment, the printhead comprises a mono ink. This embodiment can be particularly preferred when utilizing a transducer capable of being selectively energized with a power density greater than 1 GW/M
2
to cause droplets of ink to be ejected from the chamber or when the plate is separated from the transducer by a distance of less than 28 microns. When using mono ink and a heater as a transducer, the heater area is preferably greater than about 1900 microns
2
.
According to an alternative embodiment, the printhead comprises a multi-color non-phosphate ink. This alternative can be particularly preferred when utilizing a transducer capable of being selectively energized with a power density less than 2 GW/r
2
to cause droplets of ink to be ejected from the chamber or when the plate thickness is greater than 40 microns. As with mono ink, when using a multi-color non-phosphate ink and a heater as a transducer, the heater area is preferably greater than about 1900 microns
2
. By comparison, when using an ink containing phosphates and a heater as a transducer, the heater area is preferably less than about 2800 microns
2
.
In another embodiment of the present invention, an inkjet printhead comprises a plurality of transducers and chambers, with at least a portion of each transducer being arranged within a respective chamber. A plate having a plurality of apertures is also provided. Each aperture cooperates with a respective chamber to allow ink to be ejected therefrom.
According to this embodiment of the present invention, the plate has a thickness of less than 62 microns. Moreover, each transducer can be selectively energized with a power density less than 2.159 GW/m
2
to cause the ejection of the ink. Preferably, the plate is separated from the transducer by a distance of less than 28 microns.
In yet another embodiment of the present invention, an inkjet printer comprises a printhead and power source. The printhead includes a transducer, a chamber, and a plate. At least a portion of the transducer is arranged within the chamber.
The plate is provided with at least one aperture capable of cooperating with the chamber to allow ink to be ejected therefrom. The plate also has a thickness of less than 62 microns. In addition, the power source is capable of selectively energizing the transducer with a power density less than 2.159 GW/m
2
to cause the ejection of the ink from the chamber. In a preferred form, the plate can be separated from the transducer by a distance of less than 28 microns.
Still other aspects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described various embodiments of this invention, simply by way of illustration. As will be realized, the invention is capable of other different aspects and embodiments without departing from the scope of the invention. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not as restrictive in nature.
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pat
Barlow John
Brady John A.
Lexmark International Inc.
Stephens Juanita
LandOfFree
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