This application claims the priority of German Patent Document No. 10 2006 049 619.1, filed Oct. 20, 2006, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method for operating an inking system of a printing press.
Inking systems of printers have an ink fountain in which printing ink is kept in readiness; the printing ink that is kept in readiness in the ink fountain is scooped out of the ink fountain by a doctor roller. The amount of ink required for a print substrate may vary zonally, which is why the amount of ink to be transferred out of the ink fountain onto the doctor roller per ink zone is adjustable via so-called ink sliders or ink blades. A film roller or a siphon roller is arranged downstream from the doctor roller, removing the printing ink from the doctor roller and transferring it to at least one of the inking system rollers downstream from the film roller or siphon roller. The printing ink ultimately goes to a printing plate on a plate cylinder via the/each inking system roller downstream from the film roller or siphon roller.
With inking systems that have a film roller downstream from the doctor roller, the transfer of ink from the doctor roller to the film roller is problematical when small quantities of ink are needed and thus the ink layer thickness on the doctor roller corresponds approximately to the gap width of the gap between the doctor roller and the film roller. If the ink layer thickness turns out to be somewhat too small, it may lead to an interruption in the ink transfer between the doctor roller and the film roller; if the ink layer thickness is too great, this results in a percentage change in the quantity of ink on the print substrate in the two-digit percentage range. Accurate metering of the amount of ink is thus difficult with inking systems using film rollers under the operating condition that the ink layer thickness on the doctor roller corresponds approximately to the gap width of the gap between the doctor roller and the film roller.
In the case of an inking system in which the doctor roller is downstream from a siphon roller, accurate metering of ink is possible in this regard, but the oscillating motion of the siphon roller leads to vibration of the printer, which is unacceptable in the case of high-speed web-fed printing presses in particular. Therefore, inking systems with film rollers are used with web-fed printing presses.
Against this background, the present invention is based on the problem of creating a novel inking system for a printing press using a film roller such that the system allows accurate metering of the amount of ink under all operating conditions. According to the invention, at least one ink slider or ink blade is controlled in such a way that the amount of ink transferred to the doctor roller zonally is varied over the circumference of the doctor roller.
The present invention provides an inking system having a print roller and a film roller in which ink sliders or ink blades of the inking system are controlled in such a way that the amount of ink transferred to the doctor roller varies over the circumference of the doctor roller. The amount of ink applied to the doctor roller per revolution is obtained from the average amount of ink, which varies over the circumference of the doctor roller. This permits a highly accurate metering of the amount of ink with film inking systems.
According to an advantageous embodiment of the present invention, the ink sliders and/or ink blades are controlled in such a way that, depending on the desired zonal area coverage or ink layer thickness, a frequency and/or an amplitude of the zonal ink quantity transferred to the doctor roller and/or zonal change in the gap between the doctor roller and the ink sliders and/or ink blades is/are adjusted.
Preferred embodiments of the invention are derived from the following description. Exemplary embodiments of the invention are explained in greater detail below, without being limited to these embodiments, on the basis of the drawings.
The present invention is explained in greater detail below with reference to
The inking system 13 of the print mechanism 10 has an ink fountain 16, in which printing ink 17 is kept in readiness. A doctor roller 18 scoops printing ink 17 out of the inking system 13 with the intermediate arrangement of an immersion roller 19, whereby the amount of ink transferred per ink zone out of the ink fountain 16 onto the doctor roller 18 is adjusted via the ink sliders and/or ink blades 20.
A film roller 21, which is operated at a relatively high rotational speed, is downstream from the doctor roller 18, which is operated at a relatively low rotational speed, the printing ink being transferred from the doctor roller 18 via the film roller 21 to the inking system rollers 22 and/or 23 downstream from the film roller 21. The inking system rollers 23 roll over the plate cylinder 11 and are also known as ink applicator rollers.
To take this problem into account, a film inking system is operated in the sense of the present invention (see
To do so, the ink blades 20 are constantly moved back and forth in the direction of the double arrow 27 according to
The back-and-forth movement of the ink blades 20 of the inking system 13 as mentioned above is performed in particular when small quantities of ink are to be applied to the doctor roller 18 and to the film roller 21. The thickness of the ink layer 24′ on the doctor roller 18, which develops downstream from the ink blades 20 and upstream from the gap 25, is preferably alternately smaller and larger than the dimension of the gap 25. However, the ink blades 20 may also be controlled in such a way that the thickness of the ink film 24′ on the doctor roller 18 is always greater than the width 25 between the doctor roller 18 and the film roller 21.
Thus in the sense of the present invention, the ink blades 20 of the inking system 13 are controlled in such a way that a zonal gap width of the gap between the doctor roller 18 and the ink blades 20 is constantly varied to provide a varying thickness of the ink film 24′ over the circumference of the doctor roller 18. The amount of ink applied per ink zone to the doctor roller 18 is obtained from the average of the respective zonal amount of ink over the relevant, i.e., effective, circumference of the doctor roller 18.
The ink blades 20 are controlled so that the frequency and/or amplitude of the amount of ink transferred zonally to the doctor roller and/or a zonal change in the gap between the doctor roller 18 and the ink blades 20 is adjusted, depending on the desired ink layer thickness and/or the desired zonal coverage. It is possible here to adapt either exclusively the frequency or exclusively the amplitude of the change in the ink layer thickness of the ink film 24′ and/or the change in the gap between the doctor roller and the ink blades 20. In addition, it is also possible to change the frequency and amplitude jointly.
In particular, electromechanical drives, electric motors, e.g., linear motors or stepping motors, electromagnetic drives and pneumatic or hydraulic actuator devices may be used as the drives 28 for adjusting the ink blades 20 in the sense of the present invention.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
Number | Date | Country | Kind |
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10 2006 049 619.1 | Oct 2006 | DE | national |