Incremental printing of symbolic information – Thermal marking apparatus or processes – Multicolor
Reexamination Certificate
2001-12-10
2004-01-20
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Multicolor
Reexamination Certificate
active
06680743
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatus for printing a graphic product on sheet material in accordance with a printing program and stored data representative of the graphic product, and more particularly to methods and apparatus for printing a wide format multicolor graphic product on a printing sheet, such as a vinyl sheet for use as signage.
Known in the art are thermal printing apparatus for generating signs, designs, characters and other graphic products on a printing sheet in accordance with a printing program and data representative of the graphic product. Typically, a thermal printer interposes a donor sheet that includes donor material and a backing between a thermal printhead and the printing sheet. The thermal printhead includes an array of thermal printing elements. The thermal printhead prints by pressing the donor sheet against the printing sheet and selectively energizing the thermal printing elements of the array, thereby selectively transferring pixels of donor medium from the donor sheet to the printing sheet. Movement of the printing sheet relative to the thermal printhead (or vice versa) while pressing the donor sheet against the printing sheet with the thermal printhead draws fresh donor sheet past the thermal printhead. The printing sheet typically includes a vinyl layer secured to a backing layer by a pressure sensitive adhesive so that after printing the vinyl bearing the graphic product can be cut and stripped from the backing material and affixed to an appropriate sign board or other material for display.
The proper printing of many graphic products, such as commercial artwork or signage, can require high quality print work. Often, it is desired that the final multicolor graphic product be physically large, such as several feet wide by tens of feet long. Typically, existing thermal printers are limited in the width of printing sheet that they can print upon. For example, one popular thermal printer prints on sheets that are one foot wide. Accordingly, the final graphic product is often assembled from separately printed strips of printing sheet that must be secured to the signboard in proper registration with one another. Often, the registration is less than perfect and the quality of the final graphic product suffers, especially when backlit.
Wide format thermal printers are known in the art. For example, one wide format thermal printer currently available can accommodate a printing sheet up to three feet wide and uses four full width (i.e., three feet wide) printheads, each interposing a different color donor sheet between the printhead and the printing sheet. Accordingly, far fewer seams, if any at all, require alignment when creating the sign or other product. Also, the use of four printheads allows faster printing of the multicolor graphic product.
Unfortunately, this type of machine can be expensive to manufacture and to operate. For example, each printhead, at a typical resolution of 300 dpi, includes literally thousands of thermal printing elements, all of which are typically required to have resistances that are within a narrow tolerance range. Such a thermal printhead is difficult and expensive to manufacture, and moreover, burnout of simply a few thermal printing elements can require replacement of the entire printhead. Furthermore, donor sheet is also expensive, and the full-width printing heads can be wasteful of donor sheet when printing certain types of, or certain sections of, graphic products. For example, consider that a single color stripe one inch wide and perhaps a foot long is to be printed in center of the printing sheet. Though the printed object occupies {fraction (1/12)} of a square foot, an area of donor sheet that is three feet wide by one foot long, or three square feet, is transferred past the print head when printing the above object, and hence consumed. The printing of a wide format graphic product that includes a narrow border about the periphery of the printing sheet is another example that typically can be wasteful of donor sheet when printing with the above wide format thermal printer.
Other wide format printers are known in the art, such as wide format ink-jet printers, which can also print in a single pass. However, inkjet printed multicolor graphic products are typically not stable when exposed to the elements (e.g., wind, sun, rain) or require special post-printing treatment to enhance their stability, adding to the cost and complexity of printing with such apparatus.
Accordingly, it is an object of the present invention to address one or more of the foregoing and other deficiencies and disadvantages of the prior art.
Other objects will in part appear hereinafter and in part be apparent to one of ordinary skill in light of the following disclosure, including the claims.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a method of thermally printing a color plane of a multicolor graphic product on a printing sheet responsive to machine readable data representative of the graphic product. The method includes the following steps:
selecting a donor sheet corresponding to the color plane to be printed and interposing the donor sheet between a thermal printhead and the printing sheet, the thermal printhead having an array of printing elements extending for a printing width along a printing sheet translation axis;
printing the color plane onto the printing sheet in successive print swaths by translating the thermal printhead along a print axis orthogonal to the printing sheet translation axis and selectively energizing the thermal printing elements while pressing the donor sheet against the printing sheet with the thermal printhead;
translating the printing sheet in the direction of the printing sheet translation axis between print swaths; and
wherein, for at least one print swath, when consecutive pixels to be printed are separated by more than a minimum distance in the direction of the print axis, printing that swath includes refraining from pressing the donor sheet against the printing sheet with the printhead when translating the printhead at least part of the distance between the consecutive pixels, whereby the refraining from pressing substantially prevents donor sheet from being drawn past the printhead, thereby conserving donor sheet.
In another aspect, the invention provides a method of printing with a thermal printer that prints a multicolor graphic product on a printing sheet in each of different color planes responsive to selected machine readable data representative of the graphic product. The method includes the following steps:
A) selecting a supply length of donor sheet corresponding to the color plane to be printed and interposing a section of the supply length between the thermal printhead and the printing sheet, the thermal printhead having an array of printing elements extending along a printing sheet translation axis;
B) printing the color plane on the printing sheet in print swaths extending along a print axis substantially orthogonal to printing sheet translation axis by repeating the following steps 1) and 2) alternately
1) translating the printhead in the direction of the print axis and selectively energizing the thermal printing elements while pressing the selected donor sheet against the printing sheet with the thermal printhead so as to draw the donor sheet past the printhead;
2) translating the printing sheet in the direction of the printing sheet translation axis between print swaths; and
C) performing steps A) and B) for each of the color planes to be printed to print the multicolor graphic product on the printing sheet, wherein when printing at least one of the color planes the printing sheet is translated in the opposite direction along the printing sheet translation axis between successive print swaths to that in which it is translated between successive swaths when printing a different color plane; and
wherein, for at least one print swath, when consecutive pixels to be printed are separated by more than a minimum distance in the
Hevenor Charles M.
Kapushinski Ronald A.
Plude Howard H.
Feggins K.
Gerber Scientific Products, Inc.
McCormick Paulding & Huber LLP
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