Printing – Processes
Reexamination Certificate
2002-03-28
2004-03-23
Funk, Stephen R. (Department: 2854)
Printing
Processes
C101S351100, C101S216000, C101S352010, C101S148000
Reexamination Certificate
active
06708616
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method of adjusting two rollers that can be placed on each other and transfer a substance such as moisture or ink, with the aid of a stripe which is formed on the roller that accepts the substance when the rollers contact each other and which is subsequently measured. The invention further pertains to a printing unit having a control system that can be programmed via a memory.
One important precondition for good inking and dampening of the printing plates is exact setting of the inking and dampening rollers. The inking rollers ensure satisfactory transport of the printing ink from the ink fountain via the ink applicator rollers to the printing plate. In the case of the dampening rollers, it is a matter of satisfactory dampening, which is ensured only when, by means of good adjustment of the dampening-solution applicator rollers in relation to the plate and in relation to the dampening-solution driver, the preconditions for this are provided. As a result of poor adjustment or setting of the inking rollers, it is possible for a deficient transfer of ink to the printing material to occur. If the dampening rollers are set poorly, nonuniform dampening occurs. To some extent, the printing plate receives too little water, to some extent too much water. As a result, the printing plate becomes dry or else so-called water smudges can be seen in the printed product.
The foregoing statements concerning the dampening rollers apply in particular to printing units with planographic printing, and specifically offset printing machines. With regard to inking rollers, the statements made above apply to all printing machines wherein the ink is distributed via rollers and applied to the printing plate. This applies both to ductor inking units and to film inking units.
The metering of the printing ink is carried out via different ink splitting openings in the various inking zones. Regulating the quantity of ink over the entire width is carried out by changing the rotational speed of the ductor. The further transport (ink flow) of the ink stripe metered accurately by the printing machine operator (pressman) is performed, from the ink ductor, by the transfer, distribution, intermediate and distributor rollers arranged subsequently in the inking unit. There, the layer of printing ink is repeatedly distributed and split by the alternating arrangement of hard and soft rollers with different diameters and is distributed by friction by rollers which reciprocate laterally (distributor rollers). In the process, current inking units are calculated in such a way that, as a rule, the main flow of printing ink takes place on to the first two ink applicator rollers. The two last applicator rollers have substantially the task of equalizing the ink film on the plate. In addition to the transport and the distribution, however, the arrangement of the various rollers simultaneously also fulfills the task of ink storage. Finally, during continuous printing, the same amount of ink must immediately be available for renewed inking when, as a result of transfer to the rubber blanket, a specific amount of ink has been used up. In addition to the ink distribution in the circumferential direction, there is lateral distribution by means of traversing rollers. As a result, the ink remains supple, it is not possible for any accumulations of ink to form, and the traversing rollers are, moreover, an aid in setting the inking zones.
It follows from the foregoing that the setting of the individual rollers in relation to each other is particularly important for the printed result. For setting and checking the position of the rollers in relation to one another, numerous proposals have therefore been made. Checking the ink applicator rollers in relation to the printing plate is carried out by firstly the correctly backed printing plate being gummed uniformly thinly and subsequently dried. The machine is then hinged forward to such an extent that the printing plate is under all four or five applicator rollers. Then, with the aid of the “rollers on” lever, the applicator rollers provided with printing ink are set against the printing plate and then lifted back into the off position again immediately. This procedure can be repeated in order that the ink stripe on the printing plates can also be seen easily. If the ink applicator rollers are well adjusted, a uniform ink stripe about three to four millimeters wide from each roller must manifest itself on the plate. If this is not the case, regulation must be carried out with the aid of the setting screws present on each offset printing machine.
U.S. Pat. No. 5,485,785 (European patent EP 0 662 046 B1) describes a method and an apparatus for setting the pressure of a roller provided with a plastic cover in rotary printing machines. This reference is based on the fact that the position of the rollers in relation to one another is in a normal position at the start. This reference is based on the problem that the rollers can heat up during the printing operation, so that the position of the rollers in relation to one another and therefore the pressure exerted on one another changes. Therefore, the pressure exerted on one another by the rollers depends on the temperature. The object of that prior art is therefore to readjust the rollers in such a way that they exert a constant pressure on one another irrespective of the temperature. The object is achieved in that one of the rollers can be varied in terms of its position with respect to the roller resting on it by a hydraulic actuator as a function of the temperature. There, it is assumed that the two rollers already have a prescribed setting at the start of the regulation operation, the setting then being maintained by the regulating device even during temperature changes. A proposal as to how the two rollers are to be aligned in relation to each other at the start and how such a measurement can be carried out is not made in the publication.
U.S. Pat. No. 5,142,977 (German published patent application DE 38 25 517) describes a device for setting inking unit and dampening unit rollers on and off and setting them in a printing machine. There, the individual rollers operating with one another in an offset printing machine are also described, so that such a printing machine does not have to be described again at this point. In that reference, too, the possibility is described of setting the rollers in relation to one another with the aid of electrically operated actuating devices. One proposal mentioned there discusses determining the action of force of two rollers on each other with the aid of a force measuring cell. Another proposal made there discusses placing the rollers against each other briefly and then measuring the stripe produced in this way. In the case of inking rollers, this is then the ink stripe to be measured. It is already known to produce an (ink) stripe by allowing two rollers (for example inking rollers) to run against each other and then stopping the rollers. In this way, too, a stripe along the line of contact with which the rollers rest on each other is formed by the adhesion of the moist ink (at the points resting on each other for a relatively long time). The stripe width thereby depends on the pressure of the two rollers resting on each other and the duration of contact or the duration of the stoppage of the rollers. Since the rollers are always stopped for a defined time, the stripe width in a printing machine then always depends only on the pressure of the rollers against each other. The ink stripes are generally measured manually. In this case, the procedure is such that a copy of the ink stripe is prepared, at least in some sections, by placing a paper on the roller provided with the ink stripe. This copy can then be measured by the printing machine operator. However, in order to be able to prepare the copy, the printing machine operator must be able to make access to the roller. It must therefore be within his range. In that case, various d
Faulhammer Holger
Wagensommer Bernhard
Funk Stephen R.
Heidelberger Druckmaschinen AG
Hinze Leo T.
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