Printing – Processes – Condition responsive
Reexamination Certificate
2002-01-24
2004-03-16
Nolan, Jr., Charles H. (Department: 2854)
Printing
Processes
Condition responsive
C400S076000
Reexamination Certificate
active
06705229
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method and device for setting printing-technology and other job-dependent parameters of a printing machine. The visual impression of a printed image, which can also contain text, is influenced by many factors. These include the state and type of paper used, the types of inks and dampening solution used and the admixtures thereof, the ink density required by the subject, the ink distribution, the sequence of inks printed over one another and the ambient conditions, such as atmospheric humidity and atmospheric temperature. In the case of planographic printing, particularly rotary offset printing, the ink supply and the water supply additionally play a part, having a great mutual influence on one another. The aforementioned influencing variables will be referred to hereinbelow as input values.
Some of the values listed (input variables) are associated with the material used or can be read via labeling and taken into account in the settings of a printing machine. These include, for example, the ink or paper that is used. Other predefined input variables are, for example, the ink distribution based upon the predefined subject, the sequence of inks printed above one another or the preselected printing speed. Input variables of this type are taken into account at the start of proof printing or production printing in the machine settings of the printing machine (such as ink zone openings, dampening solution setting, sheet-guiding blown air, dryer output).
Result parameters, such as the printed shade and the ink density achieved, can certainly be measured with some effort and can be reset on the printing machine. Here, however, the subjective impression of the operator on the printing machine is often more important than the measured result. One reason for this resides in the fact that all of the aforementioned parameters are subject to specific tolerances, so that the trained eye of the operator is more important for producing an optimum printed result than the results of predefined machine settings.
Settings on the printing machine do not have to be made just once but many times. A setting is necessary, for example, in order to produce a proof on a printing machine, which is most often specifically used for this purpose, the proof then being presented to the customer for assessment and to define the desired printed result. The measured values resulting from measurements on the proof (original) approved by the customer are then used as the basis for the setting up for continuous printing or production printing. Although, when setting up a printing machine in this way, a number of measured input variables are made available, the setting-up of a printing machine for continuous printing is still very complicated. Firstly, the tolerances of the measured input variables can add up in the direction of an unfavorable printed result, so that the operator (pressman) has to intervene simply for this reason. Furthermore, it may occur that the pressman would like to print at a speed which differs from the graduated characteristic values provided. Here, too, the set machine settings have to be modified appropriately in order to achieve an optimum printed result.
In planographic printing and, in particular, in rotary offset printing, finally, it is additionally necessary for the water feed and the ink distribution to be set until the printed result is satisfactory to the pressman. In order to achieve a good printed result, a stable equilibrium between ink and water must be reached (ink-water balance). While, as already outlined further hereinabove, the imprinting of the ink and the way it rests on the printed sheet can be measured by the pressman in the form of measuring the ink density, the optimum dampness cannot currently be measured directly with tolerable effort and adequate accuracy, but can only be assessed indirectly by the printed result. If too little water is transferred to the surface of the printing plate, the half-tone dots are then printed more fully (smearing), or the half-tone dots become filled in. The surface of the plate therefore picks up more ink than desired, because no adequate wetting has been carried out by the dampening unit. Conversely, in the event of excessive water feed, a pale printed result may occur, and therefore, from time to time, a high level of displacement of the printing ink results.
With regard to the ink distribution, care must be taken that the ink is distributed appropriately, depending upon the requirements of the subject, over the entire width of the printed product, i.e., transversely with respect to the direction of movement, in the case of rotary printing. For this purpose, the transfer of ink from the individual ink fountains or ducts to the ductor roller can be set in stripes, so that the ink is distributed on the ductor roller in accordance with the subject.
It therefore transpires that the procedure of setting up a machine is very time-consuming and, therefore, expensive. In order to shorten the set-up times, tables (or characteristic curves) are assigned to the individual printing machines, on the basis of which the ink distribution in a specific machine can be set as a function of the printing speed. Furthermore, in the case of some printing machines, paper data (format, thickness), the ink filling of the printing units and the ink distribution can be input or read in from the plate reader or the preprinting stage. For the purpose of controlling ink and dampening solution at different speeds, characteristic curves are used, although these have been determined for average values of ink zone openings.
The problem of the long times for setting up a printing machine is made even more critical by the fact that a setting, once selected, has to be adapted many times, for example, if the printing machine is stopped for a relatively long time, if the plates have to be changed or the rubber blanket has been washed. In order to provide a remedy here, the German Utility Model (DE-GM) 29612159 discloses the practice of recording individual set values in suitable memories, from which they can be output as required in order to set up the printing machine again. In this case, individual procedures, such as the washing of a rubber blanket or the printing of register marks, can have specific programs assigned thereto, which start up when the relevant program is to be performed. Appropriate programs can be provided to refresh the ink profile after a machine stoppage or after the setting of the dampening unit. The individual memories can be programmed freely and can, therefore, be adapted to the respective state or condition previously set.
Further times are needed in order to set the individual machine parameters if, during printing, in particular, production printing, there is a change in the required machine parameters to be set. This can occur, for example, as a result of the fact that the quantity of ink in the ink fountains decreases, and therefore the quantity of ink discharged at the set ink zone opening changes, or that the ambient temperature in the surroundings of the printing machine changes or other set values of the printing machine change, so that resetting is necessary. Because some of the described printed result parameters can be measured automatically with appropriate measuring instruments, in the interim, a series of printing machines have been equipped with control installations which, on a control strip on the printed sheet, compare measured actual values with prescribed desired or nominal values, and readjust the printing machine accordingly. Because control procedures of this type run relatively slower, compared with the machine speeds which can be reached presently, attempts have been made to shorten the control procedure. For example, the European Published Non-prosecuted Patent Application (EP-B) 922 581 describes control methods wherein, based upon prescribed starting conditions, a new condition in the printing machine is set in the manner of a step change.
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Nolan, Jr. Charles H.
Stemer Werner H.
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