EP0744289B1 - Method for regulating the quantity of damp - Google Patents

Description

The invention relates to a method for controlling a Quantity of dampening solution on a printing plate Web-fed rotary printing press according to the preamble of Claim 1.

EP 03 88 697 A2 describes a method for Determination of a measuring location for the determination of a Quantity of dampening solution on a printing plate. Here scans a measuring head the surface of the printing plate and places the Measurement site so firm that the measurement site in a zone with medium area coverage is as low as possible.

The disadvantage of this method is that with each Change of pressure plates the measuring location is redefined.

DE 43 28 864 A1 shows a device for detection the smear limit in offset printing of a printing press, with one outside of a subject of a printing form color-free surface zone on the printing form is trained. This surface zone is by means of of an optical sensor monitored for color guidance.

A disadvantage of this device is that the most Plate cylinder arranged a device Accessibility to a printing unit is restricted and each plate cylinder has its own device is. In addition, there is no clear reference surface set so that changes in Reflective properties of the printing form, e.g. B. by Oxidation of an aluminum printing plate, for incorrect measurements being able to lead.

EP 03 57 987 B1 describes a method for Monitoring and control of dampening solution management in an offset printing machine described in which a Measuring range scanned by an optical sensor becomes. This measuring range includes a higher measuring field Area coverage and one - seen in the printing direction - immediately following, in itself color-free Area.

The disadvantage here is that there is no reference value is the change in the reflective properties of a sheet to be evaluated. A big disadvantage is that either an additional pressure control element what limits the usable area of a cylinder circumference, must also be printed or with each new one Print job in the printing form of the measuring range new must be determined.

The invention has for its object a method to regulate the amount of dampening solution on a Printing plate of a web-fed rotary printing press create with which, regardless of a subject Pressure plate and without the pressure plate by means of detectors to scan and without a usable pressure range Cylinder circumference through pressure control elements restrict the regulation of the amount of dampening solution he follows.

This object is achieved by the features of the characterizing part of claim 1 solved.

The advantages that can be achieved with the invention are, in particular, that the measuring location for determining a tone boundary is fixed in relation to the cylinder and is independent of a subject of a printing plate. Complex devices and methods for determining this measuring location are not necessary. By evaluating a strip located on a web, a measuring bar can largely be arranged anywhere in the region of a web guide according to the printing units to be controlled and is therefore freely accessible. This measuring bar is less exposed to dirt than pressure plate-scanning measuring heads and the accessibility to the cylinders is preserved. No pressure control elements are necessary, since the evaluation takes place in an image-free strip, which means that the web can be optimally used for the finished product, ie there are no unusable areas as a result of the additionally printed pressure control elements.
Changes in the properties of the web (e.g. color, dirt, reflection) can be compensated for by reference measurements on the web. It is advantageous that by means of monitoring the entire width of the web with a large number of detectors, only narrow toning areas are recognized. Such toning zones, which run in the circumferential direction of the plate cylinder, occur in particular in spray dampening systems when individual spray nozzles fail. A uniform regulation of the amount of dampening solution over the width of the web can also be achieved by changing the spray quantity of the individual spray nozzles.

The inventive method is based on the drawing and described in more detail below.

Fig. 1

eine schematische Darstellung einer Rollenrotationsdruckmaschine zur Durchführung eines erfindungsgemäßen Verfahrens;

Fig. 2

eine schematische Darstellung eines Meßbalkens gemäß Fig. 1;

Fig. 3

einen vergrößerten Ausschnitt des Meßbalkens gemäß Fig. 2;

Fig. 4

einen schematischen Ausschnitt einer zu messenden Bahn.

Show it

Fig. 1

a schematic representation of a web-fed rotary printing press for carrying out a method according to the invention;

Fig. 2

a schematic representation of a measuring bar according to FIG. 1;

Fig. 3

an enlarged section of the measuring bar according to FIG. 2;

Fig. 4

a schematic section of a web to be measured.

A web 1 is by means of printing units 2, in example shown four printing units 2, in the Schön and Back printing in a web-fed rotary printing press, especially a newspaper printing press. Each this printing units 2 is in bridge construction symmetrical to lane 1. In side frames of these printing units 2 are two rubber cylinders 4, two plate cylinders 6 and the associated color or Dampening units 7, 8 stored. The inking units 7 are in present example as anilox short inking units, each consisting of an ink transfer roller 9, one Anilox roller 11 and a doctor blade device 12, executed. The dampening units 8 are, for example, as Spray dampers trained and exist in essentially of three dampening solution transfer rollers 13, 14, 16 and one cooperating with them Spray device 17. On the plate cylinders 6 are Pressure plates attached, which by means of the dampening units 8 a certain amount of dampening solution is supplied. The amount of dampening solution applied to the printing plates e.g. B. from a frequency of the spray pulses Spray device 17 dependent. Instead of with Plate cylinders 6 provided with printing plates are also Forme cylinders with other printing forms, e.g. B. sleeves, possible. On at least one rubber or plate cylinder 4, 6 is a rotary encoder 18, z. B. a resolver, coupled to the angular position of the plate or Determine rubber cylinder 6.4. After the pressure units 2 is seen in the running direction of the web 1 to both Sides of web 1 each have a measuring bar 19 transverse to web 1 arranged.

This measuring bar 19 is at least one Lighting device 21 and close to each other arranged detectors 22, z. B. photodiodes provided. In the present embodiment there is Lighting device 21 from outside the Measuring bar 19 arranged light source 23, which means a variety of light guides 24 light in a itself Cylindrical lens 26 extending parallel to the measuring beam 19 transmits. This cylindrical lens 26 focuses that of the Light guides 24 outgoing light to a cross to the web 1 running light line. It is also possible on the Measuring beam 19 to arrange additional light guides 24 and these with detectors 22 arranged at any point connect. The lighting device 21 illuminates the Lane 1 continuously and the detectors 22 received light remitted by path 1 to by one Trigger signal specified times. In the present Exemplary embodiments are four along the measuring bar 19 Lighting devices 21 and associated detectors 22 arranged to cover an entire width b1, e.g. B. b1 = 1270 mm, the web 1 almost completely without measurement to be able to record. Only certain is possible selected areas and therefore Lighting devices 21 and detectors 22 only to be arranged partially along the width b1 of the web 1. Each printing unit 2 can also have its own measuring bar 19 be assigned.

The detectors 22 are equipped with an evaluation circuit 27 connected, which in turn with a computer 28 in Connection is established. The computer 28 is on the input side the rotary encoder 18 and the output side with the Dampening units 8 connected. In addition, is on the computer 28 an input station 29 for manual input of Correction or control data and a display unit 31 connected.

The web 1 is transverse, for example, with four type areas 32, i.e. with four picture or text fields, printed. In the running direction of web 1 is between two on top of each other following type area 32 each transverse to web 1, unprinted parallel to the cylinders 4, 6 Strip 33. This unprinted strip 33 with a Width b33, e.g. B. b33 = 35 mm consists of one Strip 34 which due to a channel of the respective Plate cylinder 6 is created and two to both Unprinted strips adjoining the sides of the channel 36, 37 together. An unprinted strip 36 with one Width b36, e.g. B. b36 = 9 mm, is in the range the beginning of printing, the other unprinted strip 37 with a width b37, e.g. B. b37 = 9 mm, in the range of Printing end one attached to the plate cylinder 6 Printing plate. The channel of the plate cylinder 6 and the Type area 32 thus limit the pressure-free, narrow strips 36, 37. These unprinted strips 36, 37 lie in areas of one from lane 1 manufactured product, e.g. B. a newspaper in which a Fold runs or punctures are recorded. This Strips 36, 37 can be seen in the finished product and are for each product, for example, as Edges present.

The one to be applied to the corresponding pressure plate The amount of dampening solution is regulated as follows:

The angular position of the cylinders 4, 6 is determined in the computer 28 by means of the rotary pulse generator 18 and thus a reference is made to the pressure-free strip 33 between the successive type area 32. The computer 28 thus determines a first trigger signal and triggers a measurement in the pressure-free strip 34 as a result of the channel of the plate cylinder 6. This strip 34 is always free of printing ink, since no printing ink can be transferred here due to the channel. This strip 34 can thus be used to determine a reference measurement. This reference measurement enables reliable measurement results even in the event of color tolerances of a base color or contamination of the web 1. This reference measurement can be carried out at every cylinder revolution or at specific intervals. After the reference measurement, a second measurement is carried out in one of the two pressure-free strips 36, 37, preferably in the strip 36 at the beginning of the pressure, by means of a second trigger signal. However, both pressure-free strips 36, 37 can also be measured one after the other. For the measurement, the running web 1 is continuously illuminated by the lighting device 21 and the light radiation remitted by the strips 34, 36, 37 of the web 1 is detected by the detectors 22 at times determined by the trigger signals. This remitted light radiation is broken down into individual spectral ranges associated with certain printing inks used. This can be done by means of a filter, a filter with a detector 22 being assigned to each spectral region typical of a printing ink. A printing ink is then assigned to these spectral ranges, whereby the corresponding printing unit 2 to be readjusted is defined.
The measurement of the pressure-free strip 36 in front of the type area 32 is compared with the reference measurement in the computer 28. If there are traces of one or more printing inks in the strip 36 in front of the type area 32, the amount of dampening solution is increased in the printing units 2 corresponding to these. This can be done in discrete steps of equal size, but the amount of dampening solution can also be increased depending on the amount of printing ink present in the measuring range. This amount of the printing ink present on the web 1 in the measuring range influences an intensity of the light radiation remitted by the web 1. The so-called tone limit is used as a criterion for an optimal amount of dampening solution. The tone boundary is generally the state of a printing process in which first particles of printing ink are deposited in the non-image areas of the printing plate or web 1. This tonal limit can be measured by measuring that the remitted light radiation differs only slightly from the light radiation of the unprinted web 1, ie the reference measurement. Starting from this tone limit, the amount of dampening solution supplied is increased by a small defined amount, for example 5% to 10%, so that an optimal amount of dampening solution is achieved a little above the tone limit. After each change in the amount of dampening solution is only after a certain reaction time, for. B. 10 cylinder revolutions, performed a further change in the amount of dampening solution. As long as the optimal amount of dampening solution has not been reached, ie the web 1 tones in the non-printing strips 36, 37, and the amount of the deposited ink exceeds a selectable setpoint value, a waste gate is opened, a signal is displayed on the display unit 31 and the corresponding products are discarded. If only a slight toning occurs, ie if a selectable second setpoint is exceeded, the waste gate can also remain closed and only one signal can appear on the display unit 31.
To avoid an excessive amount of dampening solution, it is possible at certain time intervals, e.g. B. 15 minutes, slowly reduce the amount of dampening solution until printing ink is deposited in the strip 36, 37 during the production process. Then the amount of dampening solution is increased again to the tone limit and increased by a small defined amount starting from the tone limit in order to obtain an optimal amount of dampening solution.
When using a spray dampening system, it is also possible to detect individual toning zones running in the circumferential direction and to regulate the amount of dampening solution zone by zone. This can be done, for example, by changing the frequency of the spray pulses of a respective associated spray nozzle. For this purpose, each zone is assigned at least one separate detector and one spray nozzle.

Parts list

1

train

2nd

Printing unit

3rd

Side frame

4th

Rubber cylinder

5

-

6

Plate cylinder

7

Inking unit

8th

Dampening system

9

Ink transfer roller (7)

10th

-

11

Anilox roller (7)

12th

Doctor device (7)

13

Dampening solution transfer roller (8)

14

Dampening solution transfer roller (8)

15

-

16

Fountain solution transfer roller (8th)

17th

Spray device (8)

18th

Rotary encoder

19th

Measuring bar

20th

-

21

Lighting device (19)

22

Detector (19)

23

Light source (21)

24th

Light guide (21)

25th

-

26

Cylindrical lens (21)

27

Evaluation circuit

28

computer

29

Input station

30th

-

31

Display unit

32

Type area

33

Stripes

34

Stripes (33)

35

-

36

Stripes (33)

37

Stripes (33)

b1

Web width (1)

b33

Strip Width (33)

b36

Strip Width (36)

b37

Strip Width (37)

Claims (11)

1. Method of controlling an amount of damping solution on a printing plate of a web-fed rotary printing machine by means of an optoelectronic detector (22), an amount of deposited printing ink being measured on the running web (1) in at least one intrinsically print-free first strip (36; 37) that extends transversely with respect to a web (1), the measured signal determined from the first strip (36; 37) then being compared with a reference signal and the amount of damping solution being controlled on the basis of this comparison, this first strip (36; 37) being bounded on one side by a print-free, second strip (34) that exists because of a channel in a plate cylinder (6), and on the other side by a text area (32), and the reference signal being determined in the second strip (34) on the printed, running web (1).
2. Method according to Claim 1, characterized in that if there is printing ink in the strip (36; 37), the amount of damping solution is increased up to the shading limit, that is to say until there is just no longer any kind of printing ink present in the print-free strip (36; 37), and in that the amount of damping solution is increased slightly, starting from the shading limit.
3. Method according to Claim 1, characterized in that, at selectable time intervals during the continuous printing process, the amount of damping solution is reduced until printing ink is deposited in the strip (36; 37), in that the amount of damping solution is then increased up to the shading limit, that is to say until there is just no longer any kind of printing ink in the print-free strip (36; 37), and in that the amount of damping solution is increased slightly, starting from the shading limit.
4. Method according to Claims 1 to 3, characterized in that, starting from the shading limit, the amount of damping solution is increased by about 5% to 10%.
5. Method according to Claims 1 to 4, characterized in that the amount of damping solution is changed zone by zone, the zones running in the circumferential direction of the plate cylinder.
6. Method according to Claims 1 to 5, characterized in that each zone is assigned at least one detector (22).
7. Method according to Claims 1 to 6, characterized in that each zone is assigned at least one spray nozzle of a damping unit (8) that is designed as a spray-damping unit.
8. Method according to Claim 1, characterized in that for the purpose of measurement, the running web (1) is illuminated continuously by means of an illumination device (21), and the light radiation reflected from the web (1) is registered by means of detectors (22) at times that are defined by trigger signals.
9. Method according to Claims 1 to 8, characterized in that a single measuring bar (19) is used to measure deposits of printing ink from a number of printing units (2).
10. Method according to Claims 1 to 9, characterized in that the light radiation reflected from the web (1) is broken down by means of optical filters into individual spectral ranges that are typical of the printing inks, and these spectral ranges are fed to a detector (22).
11. Method according to Claims 1 to 10, characterized in that increasing the amount of damping solution up to the shading limit is carried out as a function of the amount of printing ink deposited.

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