Typewriting machines – Platen or platen-moving mechanism
Reexamination Certificate
1999-04-08
2001-11-27
Funk, Stephen R. (Department: 2854)
Typewriting machines
Platen or platen-moving mechanism
C400S659000, C101S474000, C248S363000, C269S021000, C271S194000, C271S276000
Reexamination Certificate
active
06322265
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 vacuum workbed for supporting a sheet material to be worked upon. The vacuum workbed includes the following: a workbed having a worksurface for supporting the sheet material, the worksurface including a plurality of apertures for applying suction to the sheet material, the apertures separated into first and second zones for accommodating sheet material of different sizes and orientations; a suction source for applying suction to the apertures; a manifold for providing fluid communication between the suction source and the apertures for applying the suction thereto; and a sensor in fluid communication with the suction source for providing a signal responsive to the degree of vacuum drawn by the suction source on the apertures. The flow rate through one of the zones of apertures is restricted for producing a greater than nominal degree of vacuum when the one zone includes unblocked apertures.
In another aspect, the invention provides a vacuum workbed for supporting a sheet material to be worked upon. The vacuum workbed includes the following: a workbed having a worksurface for supporting the sheet material, where the worksurface includes a plurality of apertures separated into a plurality of zones; a suction source for applying suction to the apertures; a first manifold for providing fluid communication between the suction source and a first group of zones; and a second manifold for providing fluid communication between the suction source and a second group of zones. The first and second groups include at least one zone each. The vacuum workbed of the invention also includes a sensor in fluid communication with the suction source for providing a signal responsive to the degree of vacuum drawn by the suction source on the apertures, a first flow control valve fluidly interposed between the first group and the suction source, and a second flow control valve fluidly interposed between the second group and the suction source. The first flow control valve is fluidly interposed between the second flow control valve and the suction source.
The first group can include first and second zones and the second group can include third, fourth and fifth zones. The workbed can include first and second flow restriction elements interposed between the first and second zones, respectively, and the suction source, and third, fourth and fifth flow restriction elements, interposed, respectively, between the third, fourth and fifth zones and the suction source. The flow restriction elements are for providing a selected flow rate through the zones of apertures when unblocked.
In yet a further aspect, the invention provides a method of automatically determining the size or orientation of a sheet material supported by a workbed having suction apertures therein. The method includes the following steps: a) grouping the apertures into N groups of apertures; b) applying suction to one of the groups of apertures; c) incrementing the number of groups to which suction is applied by applying suction to an additional group and sensing the difference in the degree of vacuum attained between the application of suction prior to and subsequent to incrementing the number of groups;
Binnall Daniel G.
Loos William A.
MacQueen Raymond J.
Mindek David M.
Wood Kenneth O.
Funk Stephen R.
Gerber Scientific Products, Inc.
McCormick Paulding & Huber LLP
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