Printing – Processes
Reexamination Certificate
2000-12-05
2003-04-15
Colilla, Daniel J. (Department: 2854)
Printing
Processes
C101S365000
Reexamination Certificate
active
06546870
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for controlling a quantity of ink located on an ink roller of a printing machine during the processing of a printing job. The larger this ink quantity is, the more intense the tinting or coloration thereof is. It is therefore important to keep this ink quantity constant as long as the print result is satisfactory with respect to the tinting or color thereof, and to be able to adjust the ink quantity to a new value as quickly as possible, if color deviations are discovered, it being expected that the new value would be able to deliver a satisfactory inked printing result.
The inking unit of a printing machine typically includes an ink source, potentially in the form of an ink fountain or duct having a metering device, and a transport device, which includes a greater or lesser number of ink rollers and which feeds the ink quantity flow that is apportioned by the ink source to the printing form. Printing machines for high-quality ink printing allow an independent control of such an ink roller, respectively, zonally. Printing machines with this characteristic are described in the published German Patent Documents DE 40 04 056 A1, DE 37 07 685 A1 and DE 197 27 387 C1, for example. In this way, zones of the ink roller that serve for inking zones of the printing form having a high ink consumption are inked more intensely than those zones having a low consumption. In order to set the ink quantity on a zone of the ink roller to a new value, it is necessary to vary the ink quantity flow that is released for this zone from the ink source. Because this ink quantity flow is distributed to a large number of rollers before reaching the printing form, a fairly long time passes between a modification of the desired or nominal value of the ink quantity and a corresponding resetting of the metering device, on one hand, and the time at which the modified proportion influences the quantity of ink on the roller and thus the ink supply to the printing form. During this time, spoilage is produced.
It is therefore highly desirable to keep this time as short as possible. To this end, applicants have developed a method by which, when the desired or nominal value of the ink quantity for a zone of the roller is changed from a first value to a second value, a first correction ink quantity flow is prescribed, and during a transition interval, the ink quantity flow for this zone is set to the sum of the correction ink quantity flow and the ink quantity flow corresponding to the second desired or nominal value. When the second desired or nominal value is greater than the first, the correction ink quantity flow is positive, and when the second desired or nominal value is less than the first, the correction ink quantity flow is negative. This means that ink which is sufficient for a time, i.e., too little ink, is fed from the ink source, in order to obtain the desired or nominal quantity of ink on the ink roller as rapidly as possible, and after the expiration of a time-span after which this second ink quantity should have been approximately attained, there is a changeover to the ink quantity flow corresponding to the second ink value, which is dimensioned so that the second ink quantity is maintained on the roller in continuous operation.
This method has been used in the inking units of Heidelberger Druckmaschinen A.G. of Heidelberg, Germany since 1986. A corresponding method is also described in the published German Patent Document DE 43 37 343 A1. The application of similar methods for dampener control in an offset printing machine has become known heretofore from the published German Patent Documents DE 39 07 584 A1 and DE 197 01 219 A1.
A problem arises in the control of the ink quantity zonally in that when the desired or nominal value of the ink quantity flow that is released by the ink source for one zone is changed, not only the ink supply of the corresponding zone of the printing form is changed, but also that of neighboring zones. The reason for this is that the ink in the inking unit of the printing machine is distributed, so that an exchange of ink takes place between different zones.
The ink exchange between the zones prolongs the time until a steady state sets in again in the affected zone and the neighboring zone subsequent to modification of a desired or nominal value.
Another problem of the conventional ink quantity regulation by a correction ink quantity flow is that, for a sharp reduction of the desired or nominal value of the ink quantity, the correction ink quantity flow is so intensely negative that the sum of the correction ink quantity flow and the ink quantity flow corresponding to the second desired or nominal value, a sum which must be set during the transition time interval, is less than zero. Such a negative ink quantity flow would correspond to the uptake of ink from the inking unit by the ink source and cannot be realized using conventional ink sources. It therefore takes a particularly long time before a new desired or nominal value for the ink quantity of a zone actually to be attained in this case.
A similar problem arises when the desired or nominal value of the ink quantity is increased. The greatest possible ink quantity flow that the ink source can apportion in one zone is limited, and it is conceivable that when the desired or nominal value of the ink quantity flow is increased, the sum of the correction ink quantity flow and the ink quantity flow corresponding to the second desired or nominal value, a sum which is set during the transition interval, is greater than the maximum quantity of ink that can be apportioned. In this case, as well, the new desired or nominal ink quantity is attained only with a considerable delay.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for controlling ink quantity in different zones of an ink roller which allows a rapid setting of a new desired or nominal value of the ink quantity even in the foregoing cases; is i.e., a method by which a zone for which the desired or nominal value of the ink quantity has been changed and the neighboring zones thereof attain stationary ink quantities as rapidly as possible.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for controlling an ink quantity in different zones of an ink roller in a printing machine, nominal values of the ink quantity for each zone being prescribed in a time-dependent manner, and a value of the ink quantity flow released for the zone by an ink source corresponding to each nominal value of the ink quantity, whereby, when the nominal value for the zone remains constant, a constant ink quantity is maintained in the respective zone by a release from the ink source of an ink quantity flow corresponding to the nominal value, and in the event the nominal value for a given zone is changed from a first value to a second value, the ink quantity in the given zone is changed in that a first correction ink quantity flow is prescribed in accordance with a given rule dependent upon the first and the second nominal values and, during a transition interval, the ink quantity flow for the given zone is set to the sum of the first correction ink quantity flow and the ink quantity flow corresponding to the second nominal value, which comprises prescribing additional correction ink quantity flows for the zones situated adjacent the given zone and, during the transition interval, setting the ink quantity flow for each of the zones situated adjacent the given zone to the sum of the correction ink quantity flow and the ink quantity flow corresponding to the nominal value of the given zone.
In accordance with another mode, the method includes imposing a condition for prescribing the additional correction ink quantity flows that the difference between the first and the second nominal values exceeds a limit value.
In accordance with a further mode, the method includes imposing a condition for prescribing the additional co
Mayer Martin
Pfeiffer Nikolaus
Colilla Daniel J.
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Stemer Werner H.
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