Printing – Processes – Position or alignment
Reexamination Certificate
2002-10-03
2004-08-24
Eickholt, Eugene H. (Department: 2854)
Printing
Processes
Position or alignment
C101S486000, C101S211000, C101S228000
Reexamination Certificate
active
06779454
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a process and a device for determining the position of at least one printed web, preferably a paper web in a printing press, especially for determining the cutting position of a printed paper web in a rotary printing press for printing newspapers.
BACKGROUND OF THE INVENTION
Newspapers are produced predominantly according to the offset printing process. A plurality of paper webs are wound off from rolls in such a process, printed on in the printing units, and are finally folded and cut in the folder. While a paper web is running through the press, it is always in a tensioned state.
The paper comes into contact with water and printing ink during wet offset printing, as a result of which the stretching properties of the paper change. The addition of water and printing ink is not the same for all printing mechanisms. The paths traveled by the individual paper webs have different lengths. The stretching properties vary from one paper grade to the next, and there is a difference in the stretching behavior of the paper even within the same paper grade.
Double-width paper webs are divided into two or more strands in the direction of run after printing. The individual strands of a paper web may travel over different paths via turning bars before they are brought together into multilayer bundles.
The different strands are brought together into multilayer bundles before entering the folder and are folded in the direction of run of the webs. The bundles are subsequently cut in the folder at right angles to the direction of run in such a way that the cut is located outside the printing area of the pages. Errors in the cutting position cause the printed newspapers to become unable to be sold.
The cutting position can be adjusted by the printer by adjusting the web length between the printing mechanism and the cutting knife or the cutting cylinder by means of compensator rollers. It is also possible to set the cutting position by an equal adjustment of the angular position of the printing cylinders printing on the web and thus to do away with a compensator roller, which is also called a virtual main register. The cutting positions of the individual strands of a paper web can be set independently from one another by means of the compensator rollers of the secondary registers.
Difficulties arise concerning the correct cutting of the bundled webs in the folder from the different paths of the individual webs and strands and the different degrees of stretching, which the individual paper webs and strands undergo during their run through the printing press.
If similar productions are repeated, the suitable positions of the main registers and secondary registers are known and can be preset more or less accurately at the start of the production run. However, the printer usually must adjust the cutting positions manually at the beginning of the production run. This results in an amount of spoiled copies and a loss of time in the production.
Processes that make possible the automatic regulation of the cutting position have been known. Special markings, so-called marks, are printed along, which are detected by suitable optoelectronic sensors before the individual strands converge into multilayer bundles at the formers and thus yield measured values that can be used for the automatic measurement and regulation of the cutting position.
A large measuring mark on the printed paper web can be detected, e.g., by a simple optoelectronic sensor, e.g., a contrast scanner. However, large marks compromise the appearance of the printed product, e.g., the newspaper. Smaller marks, which are less disturbing, require more complicated optoelectronic sensors, e.g., CCD cameras, in conjunction with digital pattern recognition or image data processing. The technical effort for recognizing the marks increases, in general, with the decrease in the size of the marks.
Furthermore, processes have been known that can automatically measure and regulate the cutting position without the use of print marks. The crop mark is first set by the printer manually from the control panel. A reference signal is then formed by scanning the printing style on the paper web by optoelectronic sensors. The cutting position is subsequently determined automatically by comparing the current measured signal with the reference signal. The drawback of this process is that the printer must first set the cutting position manually. This means that the cutting position cannot be immediately regulated automatically at the start of a new production run. Moreover, it is also impossible to regulate the cutting position during a flying change from one edition to another without manual intervention. The manual interventions cause spoiled copies and loss of time in the production.
Another possibility of recognizing errors in the cutting position has been known from DE 199 10 835 C1 and it comprises the scanning of the printing style at two points. The first scanning at the outlet of the printing mechanism forms a reference, which can be compared with the scanning in front of the inlet of the former. The position error between the two measurement points can be determined from the correlation of the signals, and this error can then be corrected automatically by a corresponding regulation. The drawback of this process is that only the position error between the two measurement points is corrected and that a plurality of sensors must be used.
In another process known from DE 195 06 774 A1, a magnetic field of a mark is detected with a sensor. This process requires the printing of magnetizable marks, e.g., with colorless printing ink containing metal particles and has the drawback that these marks must be applied by means of an additional printing mechanism.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process and a device which can determine the position of a printed paper web in the direction of run of the paper web automatically without the use of printed marks in any state of the press. A preferred application is the automatic measurement and regulation of the cutting position of printed paper webs in rotary printing presses for printing newspapers.
In the process for determining the position of a printed paper web in a printing press, especially in a rotary printing press for printing newspapers, reference values are obtained according to the present invention for the position determination or position calculation from the image data of the preliminary printing stage, which are, e.g., digital or analog image data or the print originals.
The printing style or part of the printing style on the paper web in the printing press is detected with one or more sensors, e.g., optoelectronic sensors. The signals measured by the sensors are advantageously processed into suitable digital measured values.
The reference values of the preliminary printing stage or of the print originals are then compared with the measured values, e.g., the correlation of these values is examined and calculated. The position of the printed paper web in the direction of run can be calculated from the comparison of the reference values with the measured values. The position of a printed paper web can thus be determined accurately in a simple manner without applying an additional mark in the printing style.
The digital or analog image data from the publisher or from the preliminary printing stage may be, e.g., in the form of image contents of multicolor newspaper pages and delivered, e.g., in the form of files in the Postscript format or PDF format.
The digital image data from the publisher or from the preliminary printing stage may also be, e.g., in the form of image contents of the printing plates. The image data of a multicolor newspaper page are usually converted into half-tones by Raster Image Processing (RIP) and separated into the image data of the printing plates for the primary colors cyan, magenta, yellow, black. The digital image data of the corresponding printing plates are thus formed from the di
Mengisen Jean-Claude
Munz Curt
Eickholt Eugene H.
Maschinenfabrik Wifag
McGlew and Tuttle , P.C.
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