Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-05-20
2001-12-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06328399
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to printing apparatus and methods and more particularly relates to a printer and print head capable of printing in a plurality of dynamic ranges of ink droplet volumes, and method of assembling same.
An ink jet printer produces images on a receiver medium by ejecting ink droplets onto the receiver medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
Thus, ink jet printers are used in a variety of applications. For example, an ink jet printer may be required to print an image having a single density level at 180 dpi (
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nch) for outdoor signage. This density level for outdoor signage is aesthetically acceptable because such images are typically viewed from a relatively long distance (e.g., 30 feet or 9.14 meters) away from the image. Ink jet printers are also called upon to print relatively high quality images having 16 density levels at 1440 dpi, such as in the case of 8 by 10 inch (20.32 by 25.4 centimeters) photographs. This density level for photographs is aesthetically desirable because photographs are typically viewed from a relatively short distance (e.g., 6 inches or 15.24 centimeters) away from the viewer.
However, available ink jet printers are not capable of printing both low density and high density ranges. The terminology “dynamic range” is commonly defined in the art to mean the range of minimum ink droplet volume to the maximum ink droplet volume which is provided by one ink nozzle. That is, each individual ink jet printer possesses a density range particularly suited for its intended use. For example, an ink jet printer used for signage typically has a density range different from the density range of an ink jet printer used for photographs. Clearly, for purposes of economy, it is desirable to have the same ink jet printer print in both low density and high density ranges.
Ink jet printers having continuous tone to high resolution printing performance are known. One such printer is disclosed in U.S. Pat. No. 5,412,410 titled “Ink Jet Printhead For continuous Tone And Text Printing” issued May 2, 1995, in the name of Ivan Rezanka. The Rezanka device provides a thermal ink jet print head both for continuous tone printing and high resolution printing by controlling the area covered by the ink at each pixel location of the printed image. The print head includes at least two different groups of differently sized nozzles from which ink droplets of different ink volumes are selectively ejected. Thus, according to the Rezanka patent, nozzles of one group, or both groups, may be selectively used to print continuous tone and/or high resolution text.
However, certain printing applications require a range of 16 to 256 different ink droplet volumes and it does not appear that the Rezanka device is capable of ejecting 16 to 256 different ink droplet volumes in a suitable manner. That is, it appears that the Rezanka device requires 16 to 256 nozzle groups to print 16 to 256 ink droplet volumes for a pixel in an image. Manufacturing such a great number of nozzles increases manufacturing and assembly costs of the printer and associated print head. Also, the Rezanka device appears to permit only a relatively small number of nozzles of a given nozzle diameter within each nozzle group. That is, it appears from the Rezanka disclosure that if a total of 256 nozzles having 256 nozzle sizes are present in a print head, there is only one nozzle for each nozzle diameter.
Moreover, it is known that the nozzle diameter may only be varied in a limited range to permit effective ink droplet ejection. In this regard, if the nozzle diameter is tool large, ink tends to inadvertently seep-out the nozzle. On the other hand, if the nozzle diameter is too small, viscosity forces acting at the nozzle wall will be too high for ink ejection. This limitation in variation of nozzle diameter further reduces the range of ink drop volumes that can be provided by prior art devices, such as the Rezanka device. Therefore, a problem in the art is limited range of ink drop volumes produced by ink jet printers.
Therefore, there has been a long-felt need to provide a printer and print head capable of printing in a plurality of dynamic ranges of ink droplet volumes, and method of assembling the printer and print head.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a printer and print head capable of printing in a plurality of dynamic ranges of ink droplet volumes, so that the number of ink ejection nozzles are minimized, and method of assembling the printer and print head.
With this object in view, the present invention resides in a printer, comprising a print head body; a first nozzle connected to said print head body, said first nozzle having a first nozzle orifice of a first size for ejecting fluid therethrough having a first volume selected from a first dynamic range of volumes associated with said first nozzle; and a second nozzle connected to said print head body, said second nozzle having a second nozzle orifice of a second size different from the first size of the first orifice for ejecting fluid therethrough having a second volume different from the first volume, the second volume being selected from a second dynamic range of volumes associated with said second nozzle, the second dynamic range of volumes being substantially different from the first dynamic range of volumes.
In one embodiment of the invention, a plurality of first nozzles are connected to a print head body, each first nozzle having a first orifice of a first size for ejecting an ink droplet having a first volume. The ink droplet volume is selected from a first dynamic range of volumes. The terminology “dynamic range” is defined herein to mean the range of minimum ink droplet volume to the maximum ink droplet volume which is provided by one ink nozzle. The first dynamic range of volumes is uniquely associated with each first nozzle. A plurality of second nozzles are also connected to the print head body, each second nozzle having a second orifice of a second size larger than the first size of the first nozzles for ejecting an ink droplet therethrough having a second volume larger than the first volume. The second volume is selected from a second dynamic range of volumes. The second dynamic range of volumes is uniquely associated with each second nozzle. Moreover, the second dynamic range of volumes is substantially different from the first dynamic range of volumes. For example, the second dynamic range of volumes may be greater than the first dynamic range of volumes.
In addition, the first nozzles are arranged to define a first nozzle row and the second nozzles are arranged to define a second nozzle row adjacent the first nozzle row, so that the first nozzles defining the first row are co-linearly aligned with respective ones of the second nozzles defining the second row. Alternatively, the first nozzles can be arranged to define the first nozzle row and the second nozzles can be arranged to define the second nozzle row adjacent the first nozzle row, such that the first nozzles defining the first row are off-set relative to respective ones of the second nozzles defining the second row.
A feature of the present invention is the provision of a nozzle plate comprising nozzles having nozzle orifices arranged in rows according to orifice size, so that orifices of the same size are assigned to the same row of orifices.
Another feature of the present invention is the provision of a nozzle plate, wherein one nozzle orifice from each row of nozzles define a pixel group, the nozzle orifices defining the pixel group are adjacent to each other.
An advantage of the present invention is that dynamic range in ink droplet volume provided by each pixel group is significantly larger than what is provided by prior art thermal ink jet print
Barlow John
Eastman Kodak Company
Stevens Walter S.
Stewart Jr. Charles W.
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