EP0085750A1 - Ink feed adjusting device in a rotary printing press - Google Patents

Abstract

The adjusting device (26) generates a readjustment signal for the ink zone adjusting screws (18, 19) in dependence on the individual requirement of ink in the individual ink zones, which signal is to be of different sizes for the same ink difference. The actual values of the ink density determined by means of ink measurement probes (23, 24) are compared to reference values for the ink density and the readjustment signal ( DELTA t) determined therefrom is adjusted in respect of its size or duration in such a way that a greater readjustment is effected for a high ink requirement in a certain ink zone than in ink zones with a low ink requirement. For determining the signal required for the readjustment of the ink zone adjusting screws (18, 19), the information stored in a scanning device (21) can be used which was derived from a film assembly or from the printing plate and served for the preliminary adjustment of the ink zone adjusting screws. <IMAGE>

Description

The invention relates to a device for regulating the ink supply in a rotary printing machine, with remotely adjustable ink zone actuators on an inking unit, a measuring device for detecting the zone-by-zone ink requirement corresponding to the area to be printed for the purpose of presetting ink zone actuators and an evaluation circuit for zone-by-zone determination of the manipulated variable for readjusting the ink zone actuators from one Target-actual comparison.

From DE-AS 22 29 500 a method for predetermining the setting of the ink fountain keys of an inking unit of a rotary printing press is known, in which a template is measured photoelectrically to determine the density distribution of the printing form. The stored results of the photoelectric measurements are used by the operator of the printing machine as a guide for the adjustment of the ink zone screws on the ink fountain for the various zones of the printing form. As is known, the ink zone screws control the amount of ink supplied to the individual zones of the inking roller by changing the space between an ink knife or slide and the ink fountain roller determine. It is also known (DE-AS 27 28 738) to readjust the color guidance, the printed image being scanned by means of color density measuring devices in order to process the measurement results in a target-actual comparison circuit, so that an adjustment value for the individual is obtained from the target-actual comparison Color metering elements can be generated.

In the known control systems for color guidance, it is disadvantageous that the control algorithm is the same for all color zones, i. This means that a manipulated variable for the ink fountain keys is only generated as a function of the target / actual value difference. Inevitably, the control behavior had to be determined in such a way that sufficient and exact adjustment of the ink zone screws was still possible in color zones with minimal color requirements in the event of color deviations, so that unstable control was avoided. As a result, however, the readjustment in zones with high color requirements reacted very sluggishly (poor control dynamics), since with a certain target / actual value difference in these color zones with high color requirements, the assigned color zone adjusting screws were only adjusted by the same amount as with the same difference in the Color zones with low color requirements is the case. With such a sluggish regulation, a disproportionate amount of waste with color deviations was inevitable.

The object of the invention is to develop a device of the type described in the introduction in such a way that the control dynamics and thus the accuracy of the color guidance are equally good both for color zones with low color requirements and for color zones with high color requirements.

This object is achieved by using the features in the characterizing part of patent claim 1. Further developments result from the subclaims and from the description in conjunction with the drawings.

The invention is based on the recognition that the zonal color density is inversely proportional to the printed area, i. that is, the larger the area to be printed, the greater the amount of ink required to achieve the same color density. As already mentioned, the knife position in the individual color zones is in turn set proportionally to the amount of color required. In the device according to the invention, an additional value proportional to the printing area is input to the controller for each color zone. The controller uses this to determine a correction value for each ink zone, which is taken into account when readjusting the ink zone adjustment screws. This value, which is proportional to the color area, can be taken from the film / plate scanner in printing presses with presetting systems. In the case of printing presses without a presetting system, the position of the ink metering elements (ink knife, ink slide) can be used as an alternative, whereby the time of takeover must be after the press has been set up. The control behavior is significantly improved by the device according to the invention in comparison with the known devices, since at a certain color density difference value the color metering element is adjusted to a much lesser extent in zones with low color requirements than in color zones with high color requirements. The readjustment is therefore carried out equally quickly for all ink zones, which significantly reduces the production of waste.

• _Fig. 1 eine Offsetrotationsdruckmaschine für Schön- und Widerdruck mit der erfindungsgemäßen Vorrichtung zur Regelung der Farbzuführung;
• Fig. 2 eine detailliertere Darstellung der in Fig. 1 verwendeten Vorrichtung zur Regelung der Farbzuführung als Funktionsblockschaltbild;
• Fig. 3 ein Kennlinienfeld zur Erläuterung des Regelverhaltens;
• Fig. 4 einen Auszug aus dem Funktionsblockschaltbild gemäß Fig. 2;
• Fig. 5 einen in dem Funktionsblockschaltbild gemäß Fig. 2 verwendbaren Verstärker und
• Fig. 6 eine alternativ zu dem Verstärker gemäß Fig. 5 verwendbare Speichertabelle.

The invention is described below with reference to exemplary embodiments, reference being made to the accompanying drawings. In these show:

• _F ig. 1 shows an offset rotary printing machine for face and back printing with the device according to the invention for regulating the ink supply;
• FIG. 2 shows a more detailed illustration of the device for controlling the ink supply used in FIG. 1 as a functional block diagram;
• 3 shows a characteristic field to explain the control behavior;
• FIG. 4 shows an extract from the functional block diagram according to FIG. 2;
• FIG. 5 shows an amplifier that can be used in the functional block diagram according to FIG. 2 and
• FIG. 6 shows a memory table that can be used as an alternative to the amplifier according to FIG. 5.

1 shows two printing units 1, 2 arranged one behind the other, in which a paper web 4 coming from a supply roll 3 can be printed on both sides. The printing units 1, 2 can have the same structure, which is why the same reference numerals are used in the following for the same components. The printed paper web 4 can be shown schematically in a subordinate one indicated folder 5 are processed.

Each of the printing units 1, 2 comprises in a conventional manner two plate cylinders 6, 7 and two blanket cylinders 8, 9. The upper plate / blanket pair 6, 8 is assigned an inking unit 10 and the bottom plate / blanket pair 7, 9 an inking unit 11. The dampening systems have been omitted for the sake of simplicity. In each of the inking units 10, 11, an ink fountain 12, 13 is provided, on each of which an ink fountain roller 14, 15 is arranged. The ink metering takes place by means of an ink knife or slide 16, 17, which can be adjusted in a conventional manner with regard to their distance from the ink fountain rollers 14, 15 by means of motor-operated ink fountain screws 18, 19.

The ink zone adjusting screws 18, 19 can be adjusted from a color control panel 20 and their position can be queried. The presetting of the ink zone adjustment screws takes place via the control panel 20 from a scanning device 21, in which a memory 22, for example a magnetic tape cassette, is present, in which the individual adjustment values for the ink zone adjustment screws are stored. These values were generated in a known manner by a previous zone-wise scanning of the film assembly or the plate, the print image of which is subsequently to be transferred to the paper web 4 in the printing units 1, 2.

After presetting the ink zone adjusting screws in printing units 1, 2, these can be put into operation, so that the color intensity in the various ink zones on the printed images can be scanned by ink density measuring heads 23, 24, which can be arranged above and below the paper web 4. The of the _F arbdichtemeßköpfen 23, 24 signals D produced accessed through a signal conditioner 25 to a controller 26. This controller 26 is preferably a microprocessor or a part of such.

The signals generated by the measuring heads 23, 24 are subjected to a setpoint / actual value comparison in the controller 26 and from this comparison a signal At for the readjustment of the color zone adjusting screws 18, 19 is derived via the color control panel 20 if color deviations ΔD are found . This signal At for readjustment of the ink zone adjusting screws 18, 19 is, however, generated in the controller 26 according to the invention either taking into account the signals applied to the controller via line 27 indicating the position of the ink meter or slider in the individual ink zones, or that when presetting the ink zone adjusting screws 18, 19 relevant values in the memory 22 of the scanning device 21, which can be applied to the controller 26 via the line 28. The setpoint can be entered via a line 29.

The principle of action on which the invention is based is explained in detail below with reference to FIG. 2.

In Fig. 2, a print template 30 is indicated schematically, which is divided into eight color zones a to h. The geometric figures displayed in the printing template 30 are intended to interpret the printing areas which are also to be correspondingly generated on the paper web 4.

A comparison of the printing areas in the individual zones a to h of the printing template 30 shows the different ink requirements in these individual zones, which are 3arfskurve 31 is shown below the template 30 and is decisive for the presetting of the ink zone adjustment screws 18, 19. The values representing the adjustment of the ink zone adjustment screws 18, 19 are sent to an analog / digital converter 32, which can be controlled by a multiplexer 33 LED display 34 and via this to the controller 26.

Manual adjustment of the ink zone adjustment screws 18, 19 is possible via a control panel 35, indicated schematically, in which a number of ink zone actuator switches 36 are present.

The values determined in the controller 26 for the adjustment of the ink zone adjusting screws 18, 19 at a determined color difference AD, which, as already mentioned, were further processed taking into account the preset values or the actual values, are supplied to an electronic switch 38 via lines 39. This actuates the associated contacts 37, whereby a suitable voltage, for. B. of 24 volts, to the individual color zone adjusting screws 17, 18 associated motors can be applied.

As indicated in dashed lines in FIG. 2, instead of querying the individual ink zone adjusting screws 18, 19, which, as already mentioned, was further processed via the analog / digital converter 32, the controller 26 can also serve as a reference basis for the readjustment value from the scanning device 21 or the values relevant for the presetting of the ink zone adjusting screw are fed to the memory 22 (shown in dashed lines).

Fig. 3 shows a simplified representation of characteristic curves for individual color zones, for the sake of simplicity only the color zones a, c, e and f are considered. As the color demand curve 31 shown in FIG. 2 and the characteristic curves shown in FIG. 3 show, the color requirement is the smallest for the color zone e and the greatest for the color zone f. If, for example, a determined target / actual difference value ΔD is determined on the abscissa in the illustration according to FIG. 3, the individual correction value Δt for the change or change can be taken into account from this, taking into account the inclination of the respective characteristic curve which indicates the color requirement in the respective zone Readjustment of the ink zone adjusting screw can be derived, as is indicated by dashed lines for ink zone c. Fig. 3 shows that the inclination of the lines for ink zones with the greatest color requirement is greatest, whereby a significantly larger adjustment value .DELTA.t is determined for the ink zone adjusting screws 18, 19 when a setpoint-actual difference value AD is found than is the case with characteristics with a lower inclination , ie ink zones with smaller ink requirements, is the case.

The conversion of the target / actual value difference 6D into a time signal .DELTA.t in the controller 26 can be carried out, for example, with the aid of the amplifier 43 indicated in FIG. 5, which has a variable gain factor P. The individual amplification factor for each color zone is determined by the area-proportional zone value according to the color demand curve 31, so that, according to the characteristic curve in FIG. The voltage U generated at the output of the amplifier 43 taking into account the set amplification factor P for a specific color density difference is fed to a timing element 44. which generates a time signal Ät at its output, which is used to control the motors assigned to the ink zone adjusting screws 18, 19. Depending on the amount to be adjusted, the respective motor is operated either for a longer time or for a shorter time. By connecting the amplifier appropriately, non-linear characteristics can also be achieved.

FIG. 4 shows in simplified form the electrical signal curve of the device according to FIGS. 1 and 2. The values D determined by the color density measuring heads 23, 24 reach an comparator 42 in the controller 26 via an amplifier 39 and an analog / digital converter 40 the comparator 42 is entered here by a setpoint memory 41 for the respective color zone, the corresponding setpoint. Taking into account the respective color requirement or the corresponding presetting of the ink zone adjusting screws, which is indicated by the characteristic curves 31 according to FIG. 2, the after-control signal Δt is then generated, which actuates the electronic switch 38 for a specific time.

As an alternative to the analog generation of the readjustment signals Δt for the ink zone adjusting screws 18, 19 according to FIG. 5, digital adjustment of the readjustment signals Δt for the individual ink zones can also be carried out, in which case a memory table according to FIG. 6 can be used. In Fig. 6, the determined color deviations (difference signals) ΔD in stages 0 to 7 are given, which are assigned different correction factors Pl to P3 etc. according to the respective color requirements in the individual color zones, which z for a specific color deviation. B. AD = 3 different reset values or different reset times. Processing this 6 preferably takes place in a controller 26, which is designed as a microprocessor or as part of a microprocessor. This considerably simplifies the application and, if necessary, subsequent optimization of non-linear characteristic curves.

Reference symbol list:

• 1 printing unit
• 2 printing unit
• 3 roll
• 4 paper web
• 5 folder
• 6.7 plate cylinders
• 8.9 rubber cylinder
• 10.11 inking unit
• 12.13 color box
• 14.15 ink fountain roller
• 16.17 color knife / slide
• 18.19 ink zone adjustment screw
• 20 color control panel
• 21 scanner (film / plate)
• 22 cassette
• 23.24 color density measuring head
• 25 processors
• 26 controllers (µ, ϕ)
• 27,28,29 control lines
• 30 print template
• 31 color demand curve (smeasurement)
• 32 analog / digital converter
• 33 multiplexers
• 34 LED display
• 35 switch bench
• 36 color zone actuator switch
• 37 relay contact
• 38 relays
• 39 control lines
• 40 A / D converter
• 41 setpoint memory
• 42 comparators
• 43 amplifiers
• 44 potentiometers
• 45 timer

Claims (7)

1.Device for regulating the ink supply in a rotary printing press, with remotely adjustable ink zone actuators on an inking unit, a measuring device for recording the zone-by-zone ink requirement corresponding to the area to be printed for the purpose of presetting ink zone actuators and an evaluation circuit for zone-by-zone determination of the manipulated variable for adjusting the ink zone actuators from a target Actual comparison, characterized in that the manipulated variables determined for each color zone (a to h) are changed in a controller (26) as a function of the area to be printed in the respective color zone (a to h), so that with the same color density deviation in In a color zone (e.g. g) with a high color requirement, the readjustment (opening) of the color zone actuator (18, 19) is larger than in color zones (e.g. e) with a low color requirement. 2. Device according to claim 1, characterized in that the measured values scanned in a scanning device (20, 21) from a film template or printing plate for presetting the ink zone actuators (18, 19) can be fed to the controller (26) and that the controller (26) from this, a value proportional to the area to be printed is determined for each ink zone (a to h), and an actuating variable proportional to the printing area for changing the respective ink zone actuator (18, 19) is determined from this and from the respective manipulated variable determined from the target actual value. 3. Apparatus according to claim 1, characterized in that a paper web to be printed (4) by measuring heads (23, 24) can be scanned such that the signals generated by the measuring heads (23, 24) can be fed to the controller (26) via a measured value processor (25) that the position of the ink zone actuators (18, 19) via a color control panel (20 ) can be fed to the controller (26) and that the controller (26) generates a time-proportional control signal (At) which adjusts the ink zone actuators (18, 19) via the color control panel (20). 4. Device according to one of claims 1 to 3, characterized in that the controller (26) comprises an amplifier (43), the gain factor for each color zone (a to h) can be changed proportional to the printing area. 5. The device according to claim 4, characterized in that the output signal (U) of the amplifier (43) can be supplied to a timing element (45) which a time signal corresponding to the size of the output signal (U) (Δt) for the color zone actuators (18, 19th ) generated. 6. Device according to one of claims 1 to 3, characterized in that the controller (26) has a comparator (42) and a memory table (Fig. 6). 7. Device according to one of the preceding claims, characterized in that a microprocessor is used to regulate the color guidance.

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