Printing – Rolling contact machines – Rotary
Reexamination Certificate
2003-06-05
2004-05-04
Yan, Ren (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S216000, C101S232000
Reexamination Certificate
active
06729232
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the compensation of the fanout for affecting the width of a web, which is printed on in the printing press. The present invention pertains to both a fanout compensator and to a process for compensating the fanout. The fanout compensator may already be installed in the printing press or it may also be provided outside the printing press for installation for the purpose of fanout compensation. The printing press is a machine that prints according to the wet method, preferably with the use of a moistening agent. Offset printing shall be mentioned here as an example, in particular. The printing press may be a newspaper printing press for printing large newspaper runs. The web is preferably guided as an endless web through the machine and is wound off from a roll, i.e., the printing press is a web-fed printing press and especially preferably a web-fed rotary printing press in such an embodiment.
BACKGROUND OF THE INVENTION
Changes occur in lateral expansion in printing presses because of the liquid having penetrated the web. This phenomenon, known as fanout, has the undesired consequence that the width of the web measured at right angles to the direction of conveying of the web changes between two printing gaps in which the web is printed on one after another. Even though the fanout phenomenon may be caused, in principle, by the ink that alone has penetrated, the fanout is significant in practice especially in the case of printing operating with moistening agent because of the moistening of the web which is associated with it. The web moistened in the upstream printing gap along the web swells on its path and becomes wider in the next printing gap of the two printing gaps, which is located downstream along the web. This leads to printer's errors in the transverse direction of the web unless measures are taken to compensate the change in width.
EP 1 101 721 A1 shows devices for compensating the fanout for the web-fed rotary printing, with which the web is deformed in a wave-shaped pattern at right angles to its direction of conveying before it runs into a next printing gap, in which it is printed on. The width of the web is corrected, i.e., compensated in such a way that it is adapted in advance to the change in width that is to be expected based on the fanout. The present invention also pertains, in particular, to fanout compensators as they are known from EP 1 102 721 A1 and pertains, furthermore, especially also to the fanout compensation processes that can be embodied therewith.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the fanout compensation; in particular, the fanout compensation shall not adversely affect the printing process.
The present invention pertains to the fanout compensation in a printing press by means of a fanout compensator, which comprises a rotary body formation, which is wrapped around by a web to be printed on. The wrapping angle should be at least 3°. A wrapping angle of 5° or more, e.g., 10°, is, however, preferred. The wrapping angle may reach up to 180°. A wave profile is imposed on the web by the rotary body formation at right angles to the direction of conveying because of the wrapping and the longitudinal tension of the web, which acts in the direction of conveying. The width of the web is reduced by the imposition of the wave profile corresponding to the amplitude of the wave profile in order to compensate the increase in width caused by the fanout. In the best possible approximation, the web should have the same width in the two printing gaps located closest to the fanout compensator in the path of the web, i.e., in the printing gaps between which the fanout compensator is arranged.
According to the present invention, a fluid gap is generated between the surface of the rotary body formation and the web, so that the web has the smallest possible contact area and preferably no direct contact with the rotary body formation at all, but is located at a spaced location from the surface of the rotary body formation corresponding to the thickness of the fluid gap. Frictional forces acting on the web are thus minimized by the fanout compensation, and the longitudinal tension of the web between the printing gaps is advantageously changed much less than in the fanout compensators according to the state of the art. If the underside of the web facing the rotary body formation is printed on with printing ink, the risk that printing ink may be transferred from the underside of the web to the rotary body formation is reduced and, in the ideal case, eliminated.
The fanout compensator according to the present invention comprises a rotary body formation, which has foot sections and head sections, which alternate next to each other along its longitudinal axis and form a wave-shaped surface in order to deform the web to be printed on in a wave-shaped pattern at right angles to the direction of conveying of the web. The foot sections form the wave valleys and the head sections the wave peaks of a wave profile. Fluid channels, which open on the surface of the rotary body formation, are formed in the rotary body formation. The rotary body formation has, furthermore, at least one fluid connection, which is connected to the fluid channels and via which the fluid channels can be supplied with a pressurized fluid. The pressurized fluid introduced via the fluid connection into the fluid channels is guided by the fluid channels to the wave-shaped surface of the rotary body formation and is discharged under pressure on the surface at the opening sites, so that a fluid cushion in the form of the fluid gap is formed between the surface and the underside of the web.
The pressurized fluid is preferably a pressurized gas. Compressed air is especially preferred.
The opening sites of the fluid channels may be arranged distributed uniformly over the surface of the rotary body and uniformly in the circumferential direction. The density of the opening sites per unit area of the surface may, however, vary periodically with the period of the head and foot sections in the axial direction in case of a preferably uniform distribution in the circumferential direction. Thus, the surface density of the opening sites may be greater in the surface sections formed by the head sections than in the surface sections formed by the foot sections in order to compensate axial flows from the head sections into the foot sections.
The fluid channels may be formed as holes and extend from their opening sites on the surface through the head sections and/or foot sections of the rotary body formation radially inwardly into one cavity or optionally into a plurality of cavities, through which they can be or are connected to a fluid source. Such holes may be especially straight and unbranched. Holes may be drilled in the direct sense of the word or they may be prepared by another manner of processing, e.g., by means of laser.
Each of the fluid channels may be separated from each of the other fluid channels and form a single opening site. However, the fluid channels or some of the fluid channels may also branch toward the surface of the rotary body formation and form a plurality of opening sites each there. There may also be cross connections between the fluid channels.
Providing the head sections and/or the foot sections of the rotary body formation with a porosity sufficient for the guiding of the fluid to obtain the fluid channels also corresponds to a preferred embodiment. The porosity is preferably an open porosity, so that the pores of the porous material, which are connected to one another, form the fluid channels. Especially original shaping by compression molding a powder, preferably a metal powder, with subsequent or simultaneous sintering of the molding, is especially suitable for forming porous head sections and/or foot sections. If the foot sections and/or the head sections form fluid channels due to material porosity, holes may also be prepared subsequently, so that the fluid channels are in their entirety part
Evans Andrea H.
Maschinenfabrik Wifag
McGlew and Tuttle , P.C.
Yan Ren
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