Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2003-05-14
2004-07-27
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S007000
Reexamination Certificate
active
06767073
ABSTRACT:
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
TECHNICAL FIELD
This invention relates to dot matrix printers, and more particularly to dot matrix printers including stationary arrays of printing heads for printing at high-speed and high-resolution.
BACKGROUND OF THE INVENTION
Dot matrix printers typically include at least one print head with a plurality of individual printing elements arranged within the print head. A dot matrix printer typically actuates individual printing elements in the print head in a pattern of operation that is controlled by a stream of data in successive steps as the print head traverses a printing surface of a printing medium such as paper. During each step, the print head prints an area of dots and then move horizontally to a new position to print a succeeding area of dots. This process is repeated to produce a horizontal line of characters or other such image across the printing medium. After one horizontal line is printed, the print medium is typically incrementally moved in the vertical direction to permit another horizontal line of the image, such as a row of characters.
Therefore, dot matrix printers require successive actuation of one or more print heads typically including multiple printing elements arranged across a relative path of movement between the printing medium and the print head. One technique to progressively increase printing speed employs printing while moving in opposite directions back and forth in a rectangular path. Another technique employs multiple printing heads arranged side-by-side along a rectangular path. Another technique for increasing speed, employs double or multiple height print heads arranged across the rectangular path to simultaneously print two or more rows of characters during each traverse of the printing medium.
There are many examples of previous rearrangements of dot matrix print heads or their printing elements for increasing printing speeds and/or image resolution. For example, U.S. Pat. No.4,462,706 for STACKABLE DOT MATRIX PRINTING CARTRIDGE MODULES describes a stacked array of print heads that are stacked horizontally or vertically; U.S. Pat. No. 4,552,064 for DOT MATRIX PRINTERS AND PRINT HEADS THEREFOR describes a print head having the dimensions of a 34 pin head being 2.0 inches wide, 1.5 inches thick, and 14.2 inches in length; and U.S. Pat. No. 4,236,836 for DOT IMPACT PRINTER AND ACTUATOR THEREFOR describes a dot matrix printer in which 44 to 132 print heads are employed to print one line at a time.
U.S. Pat. No. 5,793,392 for PRINTING APPARATUS AND METHOD, which is assigned to the assignee of this application, describes a printing system for printing an image having a width on a printing medium. The printing system includes a print head array having multiple columns of print heads. Each column includes a plurality of print heads having varying positions in a first dimension in the print head array for printing in a corresponding printable column area of the printing medium and having a corresponding printable column width. The multiple columns of print heads are arranged for printing throughout the image width. A first mechanism moves the printing medium relative to the print head array in the first dimension to cause selected non-contiguous portions of a printable segment along a second dimension substantially perpendicular to the first dimension to be printed in each printable column area by the print heads. Further movement in the first dimension causes selected non-contiguous portions of multiple defined printable segments to be printed to fill the corresponding image portions of each column area. A second mechanism moves the print head array relative to the printing medium in the second dimension. A movement in the second dimension not more than the widest distance between any two non-contiguous portions of any printable segment in combination with the movement in the first dimension is sufficient to print all printable segments contained in the image.
Just as many types of dot matrix printers are available, a corresponding variety of print head types exist. For example, in electro-mechanical actuator impact print heads, a plurality of print wires are selectively driven by corresponding solenoids to impact a printing surface directly with or through a transfer ribbon. A commercially popular type of print head is an ink-jet print head which uses a number of individual ink-jets to pulse droplets of ink in spatial combinations to print characters as a sequence of dots. Another type of dot matrix print head is the thermal printer in which printing is carried out by contact of multiple heated printing elements to heat sensitive paper or to an intervening thermal transfer ribbon to print data on ordinary paper.
The ink-jet print head is typically mounted on a carriage that moves substantially perpendicular to a media motion direction, to enable an ink-jet type dot matrix printer to produce a line of characters or type. An advantage of the ink-jet print head is that other than the movement of the carriage and the drops of ink moving through the ink-jet print head, there are no moving parts such as in the electro-mechanical actuator impact print head. Another advantages of the ink-jet print head are its relatively high image quality, color purity, and low cost. Unfortunately, ink-jet printers print relatively slowly.
To increase printing speed, U.S. Pat. No. 5,907,338 describes a media-width ink jet print head having four rows of nozzles for ejecting four colors of ink. Unfortunately this print head is very expensive and still requires at least two printing passes to produce a high-resolution image.
As described above, skilled workers have approached the problem of increasing the printing speed of ink-jet printers in various ways including developing faster print heads, increasing the number of print heads per printer. These approaches have achieved printing speeds several orders of magnitude greater than those achievable twenty years ago. There are, however, significant design and manufacturing problems associated with further increasing the throughput of individual print heads or the number of print heads per printer.
Increasing the number of ink-jet nozzles per print head as well as increasing the frequency at which each nozzle is able to place dots on the print page increases the printing speed of individual ink-jet print heads. Currently, individual high-resolution print heads have ink-jet nozzle arrays for one, three, four, and six colors. It has been either infeasible or prohibitively expensive to manufacture high-density ink-jet nozzle arrays wider than one inch.
Increasing the number of print heads in a printer also increases the printing speed of a printer. Many color ink-jet printers employ a linear array of four or six single-color print heads or a linear array comprising a single-color and a multicolor print head. Some color ink-jet printers, such as ones described in the afore-mentioned U.S. Pat. No. 5,793,392, employ a linear or a two-dimensional array of twelve single-color print heads.
There are several significant problems encountered when trying to increase the number of print heads in a printer. A first problem is dot placement precision, and a second problem is the cost of manufacturing a precisely aligned array of print heads.
As a print head array scans bilaterally across the width of the page, significant error accumulates in the accuracy of placing the dots of the printed image. This dot placement error also accumulates due to reversing the direction of the print head array and the incremental movement of the print medium through the printer.
Suppose that the columns of print heads in the print head array evenly partition the entire width of the printable image area and the rows of print heads evenly partition a small segment of the length of the printable image area. Then, the dot placement error E
i
is represented mathematically as follows:
Let w and l be the width and length of the printable image area, respectively. Let h
w
and h
l
be the width and leng
Gordon Raquel Yvette
Marger & Johnson & McCollom, P.C.
Wellspring Trust
LandOfFree
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