Printing – Rolling contact machines – Rotary
Reexamination Certificate
2000-09-26
2003-04-22
Eickholt, Eugene (Department: 2854)
Printing
Rolling contact machines
Rotary
C226S001000, C226S088000, C226S093000
Reexamination Certificate
active
06550384
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a rotational body configuration and a method for a web width correction between two printing positions of a rotary printing machine. The printing machine concerned is preferably a wet-on-wet printing machine, in particular an offset printing machine, particularly preferred being a reel-fed rotary printing machine.
BACKGROUND OF THE INVENTION
In wet-on-wet print rotary printing machines, transverse strain changes occur due to the moistness of the web. This phenomenon, known as fan-out effect, has the undesirable effect that the width of the web, measured transversely to its running direction, varies between two printing nips where the web is printed in sequence. The web, moistened in the one printing nip, swells in its path and becomes wider by the time it reaches the next printing nip. If measures to correct this are not taken, misprints arise in the transverse direction of the web in the printing cylinders forming the printing nips.
One possibility of correcting this, as disclosed, for example, in DE 195 16 368 C2, is to axially adjust the position of the print plates of the plate cylinders which transfer the respective print images on the printing cylinders of the printing nips.
As an alternative to shifting the position of the print plates, it is known to correct the web width. Thus, a device for correcting the fan-out effect on reel-fed rotary printing machines is known from the generic patent specification EP 0 838 420 A2, with which the web is deformed in a wave-like manner transversely to its running direction before entering the subsequent printing nip. The web is guided through two arrays of rolls in the device. The rolls of the one array are arranged staggered to the rolls of the other array transversely to the running direction. As at least one of the two roll arrays is movable into the path of the web, a wave-like profile is imposed on the web, and thus the web width for the print in the subsequent printing nip is reduced.
Comparable devices are known from DE 43 27 646 A1. This document discloses correcting devices comprising rotational body configurations arranged on both sides of the web, and also devices having rotational body configurations arranged only on one side of the web, with which the web is deformed in a wave-like manner transversely to its running direction.
In this device, the web is guided linearly through a number of printing sections, between which a web width correction device is arranged, respectively. This device comprises a number of peripheral projections, laterally spaced away from each other, in the form of rings or brush bodies. Due to the linear web guidance, the web only comes into contact with the peripheral projections, between which the web is freely guided.
WO 99/40006 A1 discloses a guide roll for correcting the side location of webs or also of longitudinal folds. These guide rolls are employed subsequent to the web being printed, whereby the web may also partially wind around the guide roll. The guide roll comprises at least two outer (i.e. near journal of a shaft) expanding elements, which vary in diameter and are located in the region of the ends, the elements being pressurized with pressure means in order to expand. However, guide rolls are not known to be employed for correcting the fan-out effect.
A further device with only local applying of pressure to the web is disclosed in US patent specification U.S. Pat. No. 5,553,542. A number of distanced rolls or compressed air nozzles, the latter being located in the direct vicinity of the web, are provided for applying pressure to the web in order to correct the fan-out effect. Due to the web being guided linearly and vertically, the web partially winds around the pressure application locations only, while otherwise being guided linearly and vertically, however.
Further guide roll means are disclosed in the book of Walewski, Wolfgang: Der Rollenoffsetdruck, Fachschriften-Verlag, 1995, page 94, in German patent specifications DE 33 10 450 C1 and DE 87 03 732 U1, as well as in the European patent specification EP 0 253 981 B1.
In these known devices, the web is guided past the deforming rotational body configurations, decisive web contact only being necessary as a result of web width correction. For this purpose, the rotational body configurations are advanced into the path of the web. Correcting the web width in this way automatically results in the length of the web being changed between the printing nips. Upon printing in the subsequent printing nip, circumferential register errors arise, or circumferential register corrections are required matching the web width correction.
SUMMARY AND OBJECTS OF THE INVENTION
It is an objective of the invention to enable a web width correction which does not require matching circumferential register corrections.
The invention relates to a rotational body configuration for a web width correction between an upstream printing nip and a downstream printing nip of a rotary printing machine, which is preferably a reel-fed newspaper offset rotary printing press. In the two printing nips, in printing production, a web, passing through, is printed in sequence. The rotational body configuration is arranged on one of the two sides of the web and is rotatable in the running direction of the web. In axial direction, it comprises alternatingly juxtaposed radially protruding shell portions and radially retracting shell portions in order to deform the web in a wave-like manner transversely to its running direction.
In accordance with the invention, the rotational body configuration is arranged in a path of the web between the upstream printing nip and the downstream printing nip such that, or the web is guided on its way between the printing nips such that, the web, in the protruding shell portions and in the retracting shell portions, permanently winds around in part the rotational body configuration, i.e. the web permanently contacts not only the protruding shell portions, but also the retracting shell portions throughout the entire printing production. This thus assures neat linear guidance of the web at all times.
In accordance with the invention, for web width correction, a web is not guided past a rotational body configuration, provided for this purpose, which would need to be moved into the path of the web for the purpose of web width correction. In accordance with the invention, the web permanently winds around in part the rotational body configuration. The rotational body configuration in accordance with the invention permanently redirects the web. The web partially winds around the rotational body configuration by at least 3°, i.e. it is permanently redirected by at least 3° by the rotational body configuration. A higher wrap angle of approx. 5° or more is preferred. Advantageously, the rotational body configuration is wound around in part by 10° or more. The wrap angle may be as much as 180°.
Due to the invention, one such rotational body configuration may be formed by a single rotational body comprising the protruding shell portions and the retracting shell portions as a non-variable surface shape. The fixed arrangement of such a rotational body, rotatable as a whole, has surprisingly proved to already be sufficient to significantly reverse an expansion of the web such that further web width corrections to achieve a sufficiently good register transversely are not necessary. Adjustments for the width correction, for example, depending on the type of paper and/or web speed is achievable by slightly modifying the longitudinal tension of the web specifically. Preferably, such a rotational body is configured in a wave-like manner at its surface in longitudinal direction. It is particularly preferred that it has concave and convex, or protruding and retracting shell portions continuously merging into the other. The web is in contact with such a rotational body at all times over its full width. The amplitude of the wavy shell surface area, and preferably also the radial distance between the protruding and ret
Eickholt Eugene
Maschinenfabrik Wifag
McGlew and Tuttle , P.C.
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