Printing – Inkers – Fountains
Reexamination Certificate
2000-06-21
2004-06-01
Yan, Ren (Department: 2854)
Printing
Inkers
Fountains
C101S484000
Reexamination Certificate
active
06742451
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method of controlling a supply of ink in a printing machine, more particularly, wherein the ink is differently guided zonally on an ink-fountain roller transversely to the printing direction, and is transferred by a vibrator roller to a distributor roller, and to a printing machine for performing the method, including an electronic control device, an ink metering device and a distributor roller having a starting time that is adjustable relative to a rotational-angle setting of a printing-form cylinder.
In modern printing machines, the instant of reversal, referred to hereinafter as the application time or starting time, is adjustable relative to the phase angle of the printing-form or plate cylinder, with the distributor roller located in a dead center position beginning to oscillate in a direction towards the dead center position opposite thereto at that instant of time. Consequently, it is possible for the pressman to compensate for the fall-off in ink layer thickness over the format length, a phenomenon known as ink fading, in the printing direction. The causes for the ink fading can be a nonuniform division of subjects on the printing form and the print-free space on the printing form cylinder caused by the cylinder gap. The not as yet compensated-for ink fading can, for example, have a maximum of the ink layer thickness thereof at the printing start, and a minimum of the ink layer thickness thereof at the printing end on the printing form. In this case, by adjusting the starting time, the maximum of the ink layer thickness can be displaced from the printing start in the printing direction as far as the center of the format, so that the ink fading on the printed product is no longer perceptible with the naked eye.
In this regard, the German Published Non-prosecuted Application (DE-OS) 23 36 061 describes a device by which the beginning of the distribution of ink on distributor rollers is adjustable relative to the rotational movement of a plate cylinder.
The published German Patent Document DE 36 14 555 C2 describes a method of setting the starting time of the lateral distribution, by which the optimum starting or application time is determined directly by the computer of a measuring device.
The published German Patent Document DE 40 04 056 A1 describes a device for performing a method for controlling ink and for zonally presetting ink metering elements, wherein an oscillation phase angle of an oscillating distributor is controlled by a ghosting computer in accordance with a subject-specific inking profile that is to be expected from an original.
In all of the devices and methods described in the aforementioned published documents, the oscillatory movement of the distributor roller is controlled.
As is generally known, many printing machines include an ink metering device by which the quantity of ink supplied into the inking unit is zonally adjustable, so that the quantity of ink that is supplied can be metered differently over the format width in accordance with an inking profile suitable for the subject.
In this regard, the published German Patent Document DE 43 41 011 A1 describes a method of controlling ink by which ink is not supplied in specific zones on the ink-fountain roller. Although in this method the lateral ink flow due to the transverse distribution is taken into consideration in adjusting the ink density of individual zones, the method has no relationship whatsoever to the starting or inception time for an operating range of a distributor roller.
A drawback in this method is that, in the course of the conceivable performance thereof by a printing machine with a distributor roller having an adjustable starting time, during the adjustment of the starting time by the pressman, the zonal ink adjustment must be reset manually every time, because the ink fading and the zonal ink adjustment are actuating values which compete with one another. Especially great problems arise therefrom in label printing and in other multiple-copy work, because there is a requirement therein for all the blanks arranged on the sheet of printing material to be printed in absolutely the same hue. For example, the green hue of labels to be printed on the sheet of printing material is produced by autotypical or half-tone ink mixing of the cyan and yellow inks printed after one another. In this regard, the slightest deviations from one another of the ink layer thickness of the yellow ink on two labels are noticeable in a conspicuously disturbing manner when the hues of the two labels are compared.
The foregoing also applies to a printing device described in the Japanese Published Non-prosecuted Patent Application (JP-OS) 59-71 863, and to a method described in the published German Patent Document DE 197 11 918 A1.
In practice, the zonal ink metering device is preset initially in accordance with an inking profile suitable for a subject, for which purpose data determining the inking profile are fed to the ink metering device from a plate scanner. It is then an obligation of the pressman to adjust the starting or inception time and to correct the preset inking profile so that the hue of all the labels located within the format area is the same to the greatest possible extent. These manual adjustments are very time-consuming and laborious. If the pressman adjusts the starting time in order to balance the hue of labels located at the start of printing with the hue of labels located at the end of printing, the hue balance or equalization of labels located beside one another transverse to the printing direction is lost. In order to balance the hue on labels located at the side edges of the format to the hue of labels located at the center of the format, the printer has to correct the zonal metering again, due to which the hue balance in the printing direction is, in turn, influenced detrimentally. Balancing or equalizing the hue is particularly difficult in the case of an even-numbered, for example half-turn, vibrator cycle, in conjunction with an even-numbered, for example likewise half-turn, distributor cycle, because in this case it is additionally necessary to balance the hue of labels located on the right-hand side edge of the format with the hue of labels located on the left-hand side edge. A half-turn cycle means that the printing plate cylinder executes two revolutions for each vibrator or distributor oscillation. The pressman must adjust the starting time and the zonal ink metering in ever finer actuating steps and alternately until the pressman has found the optimum color balance of all the labels over the entire format area.
SUMMARY OF THE INVENTION
With a view to these problems, which have heretofore been unsolved in practice, it is an object of the invention to provide a method of controlling the supply of printing ink in a printing machine, wherein the pressman is relieved of lengthy setting-up operations, and to provide a printing machine for performing the method effectively.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of controlling the supply of ink in a printing machine wherein the ink is differently guided zonally on an ink-fountain roller transversely to the printing direction, and is transferred by a vibrator roller to a distributor roller, which comprises metering the ink zonally for counteracting ink transfer disturbances caused by a stroke movement of the distributor roller, so as to minimize the disturbances automatically to at least an effective extent.
In accordance with another mode, the ink transfer disturbances are at least one of ink deficiency and ink excess disturbances resulting from a change in a periodically repeating edge offset of the distributor roller with respect to the vibrator roller as ink is transferred from the vibrator roller to the distributor roller, the disturbances being located in the vicinity of the edge offset, and the method includes compensatingly adjusting the supply of ink in at least
Heidelberger Druckmaschinen AG
Mayback Gregory L.
Yan Ren
LandOfFree
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