EP1347878B1 - Method for controlling a circumferential register in a web-fed rotary press - Google Patents

Abstract

The invention relates to a method for controlling a circumferential register in a web-fed rotary press, according to which an actual value pertaining to a tension (51-55) of a web (03) passing through the printing units (04, 06, 07, 08) is determined, and an angular position and/or an angular velocity of a cylinder (12, 16) of a first printing unit (04) with regard to a cylinder of a second printing unit (06) is changed according to this determined tension. The correction of a register offset ensues without controlling the tension (51-55) and without the use of an optical recognition system by determining the value of the necessary change for the angular position (deltaphi) and/or the angular velocity (deltaphi) as a function of the measured tension (51-55) of the web (03).

Description

The invention relates to methods for controlling a circumferential register according to claims 1 or 8.

By EP 09 51 993 A1 a regulation of the transverse and longitudinal register is known, wherein the correction of the transverse register is effected by means of a tension roller. A change in longitudinal strain is determined by web speeds and other parameters, such as stress-strain and tension setpoints, and fed back to cylinder pressure regulators and / or an actuator for adjustment and correction of the cut register.

WO 00/34042 discloses a method for controlling a register, wherein a deviation of a web tension from a desired value changes a rotational speed and / or angular position of a first pressure point relative to a second pressure point.

EP 0 950 519 A1 discloses a method for controlling the cut and color register of a plurality of webs to each other and between the individual printing units. Strains are determined on the basis of the operating points of the drives for transport rollers, the employed cylinders and draw rollers and calculated therefrom calculated correction variables as position offset the reference variables for the cutting register or the color register.

The invention has for its object to provide methods for controlling a circumferential register in web-fed rotary printing presses.

The object is achieved by the features of claims 1 or 8 solved.

The achievable with the present invention consist in particular that an error in the circumferential register due to voltage fluctuations or fluctuations in the extent of printing cylinders, z. B. caused by short-term changes in a thickness of the web is counteracted without much measurement and control effort. The error to be corrected may be a registration error (error in the so-called color register) or a registration error between the two sides of the printed web. A difference in the transport speed of the web between two pressure points is corrected with a change in the relative rotational position of the pressure points relative to one another.

Of great advantage is that can be dispensed with elaborate measurement and regulations by means applied on the web color marks. It must be done for the purpose of correction of the circumferential register neither a direct measurement of strain nor a voltage regulation or torque control means of the operating points of the drives after the printing unit.

Particularly advantageously, the method and a corresponding device can be used for register offset in printing units with several successive or stacked double printing in rubber-against-rubber operation such. B. in a two so-called. H-pressure units put together eight-high pressure tower, wherein at least two of the pressure points successively print on the same side of a web.

For four-high towers consisting of two H-printing units, it is particularly advantageous to evaluate the change in the tension of the web (eg before and after passing through a splice of the web) behind the last printing unit or the last printing unit and only one change Angular position of make in the direction of the web first H-pressure unit relative to the second H-pressure unit. Generally this is Control of the circumferential register, in particular the color register, advantageous for several, z. B. at least three consecutive traversed by a web printing units, wherein a distance between the two first terminal points is significantly smaller than a subsequent distance to a third terminal point. The four-high tower consisting of two H-pressure units is an example of this.

In printing machines having satellite printing units, the method is advantageously usable to control the register between the two sides of the web.

In one embodiment, it is of particular advantage that a temporal change of the voltage after the last printing unit, i. H. a difference in the voltage at a first and a second time, directly and linearly used to correct the registration offset of the second H-pressure unit relative to the first. This requires a very low measurement and control effort with sufficient accuracy.

Advantageously, can be applied to a voltage control, for. B. be dispensed by means of a torque-controlled draw roller behind the printing tower. An unregulated pull roll with controlled speed is sufficient here. A z. B. caused by a splice register offset is corrected in an advantageous embodiment exclusively on the circumferential register of the cylinder, in particular the cylinder of the first printing unit or the first two printing units. In particular, the two first printing units, for example as an H printing unit, can be controlled jointly, so that only a single correction quantity is determined, and a single correction must be made.

An embodiment of the invention is illustrated in drawings and will be described in more detail below.

Fig. 1

eine schematische Darstellung einer Druckeinheit mit Rollenwechsler;

Fig. 2

eine schematische Darstellung der Spannung in Abhängigkeit von der Zeit beim Durchgang einer Klebestelle;

Fig. 3

eine schematische Darstellung einer Korrekturgröße bzw. Änderung im Drehwinkel in Abhängigkeit von der Zeit.

Show it:

Fig. 1

a schematic representation of a printing unit with reel changer;

Fig. 2

a schematic representation of the voltage as a function of time during the passage of a splice;

Fig. 3

a schematic representation of a correction variable or change in the rotation angle as a function of time.

For example, a web-fed rotary printing press has a four-high tower 01 and a roll changer 02. From the roll changer 02 runs during printing a web 03, z. B. a paper web 03, for example via an unillustrated Einzugwerk, through the four-tower 01 therethrough.

The four-high tower 01 has a total of four printing units 04; 06; 07; 08, equivalent to four terminal points 04; 06; 07; 08, up. In the example, these printing units 04; 06; 07; 08 as double printing units 04; 06; 07; 08 and work during printing in rubber-against-rubber operation. Two of the printing units 04; 06 are within a first, in the example lower H-pressure unit 09, and the other two pressure units 07; 08 within a second, in the example upper H-pressure unit 11 is arranged. Each of the printing units 04; 06; 07; 08 has at least 3, four cylinders 12 in the example; 13; 14; 16, z. Example, a first forme cylinder 12, a cooperating with the first forme cylinder 12 transfer cylinder 13, one with the transfer cylinder 13 via the paper web 03 cooperating impression cylinder 14, and, if the impression cylinder 14 as here designed as a second transfer cylinder 14, one with this cooperating second forme cylinder 16.

Each of the printing units 04; 06; 07; 08 has in the example representative at least one drive motor 17; 18; 19; 21 on. However, it can also each cylinder 12; 13; 14; 16 of each printing unit 04; 06; 07; 08 or also each pair of transfer cylinders 13; 14 and forme cylinder 12; 16 together have a drive motor. However, it is also possible that the lower H-pressure unit 09 by means of a drive motor 17; 18 and the upper H-pressure unit 11 by means of a drive motor 19; 21 form driven drive network. After the last printing unit 08, a tension roller 22 is arranged. Between the reel changer 02 and the first printing unit 04, a retraction unit 23 (symbolized by a tension roller) is arranged. The printing units 04, 06; 07, 08 are not shown inking units and possibly associated with dampening units.

In the course of the paper web 03 from the roll changer 02 to behind the last printing unit 08 of the four-high tower 01, seen in the paper running direction, there are stresses S1; S2; S3; S4; S5 before. Before the eight-tower 01 is the voltage S1, z. B. S1 between 30 and 50 daN / m, between the printing units 04 and 06, the voltage S2, between the first H-pressure unit 09 and the second H-pressure unit 11, the voltage S3, between the pressure units 07 and 08, the voltage S2 and after the last printing unit 06, the voltage S5, z. B. S5 between 10 and 20 daN / m, in particular 12-15 daN / m. The exact levels and the exact differences, however, depend on the water sensitivity of the paper used. The significantly higher level of voltage S1 compared to S5 is essential. A regulation of the voltage S1 is z. B. by means of the infeed 23rd

During the passage through the four-high tower 01, the paper web 03 changes its stress-strain characteristic due to moisture (color, possibly dampening solution). Advantageously, the voltage levels before and after the four-tower 01 will be selected such that an elongation before and after the four-tower 01 is approximately the same. The voltage S1 is usually higher than the voltage S5.

If, during stationary production conditions, a change of a roll in the roll changer 02, in particular a flying change by means of gluing, then runs a splice with the paper web 03 from the roll changer 02 through the four-high tower 01. The splice has z. B. an area which two layers of the paper web 03 and an adhesive layer, for. As an adhesive strip includes. A so-called adhesive flag, i. a range of two-ply paper, can go well beyond the width of the bond. The paper web 03 thus has a region 24 with a greater thickness, which moves through the printing press.

Now the area 24 of greater thickness passes through a printing unit 04; 06; 07; 08, so due to the increased thickness and the fixed center distance of the cooperating cylinder 13; 14 an elastic support on the cylinders 13; 14, z. B. blankets, slightly compressed. At constant angular velocity, the peripheral speed of the cylinder 13 is reduced; 14. For example, the higher peripheral speed is still present in the printing unit 07, while at the same time the peripheral speed in the printing unit 06 is lowered when passing through the region 24. Between the printing units 04; 06; 07; 08 and after the four-tower 01 thus increases the level of the voltages S2 abruptly; S3; S4, S5 (Fig. 2 for the voltage S5).

With the increased level in the voltages S2; S3; S4; S5 is accompanied by an increased level for the stretching of the paper web 03 and thus causes between the individual printing units 04; 06; 07; 08 an offset ΔP in the circumferential direction, a so-called. Passer offset ΔP in the circumferential register.

The sudden increase of the voltages S2; S3; S4; S5, and thus also the strain, is dependent on the original levels of the stresses S1; S2; S3; S4; S5, in particular a difference between S1 and S5, and the length of the adhesive tail, ie the length of the region 24 of greater thickness. The latter, in particular with staggered cylinders, ie several channels on a lateral surface of the cylinder are juxtaposed in the axial direction, but offset from each other in the circumferential direction. In this case, the length of the adhesive tail is greater than or equal to the distance of the channels in the circumferential direction, so a partial relief can take place.

By means of a measuring 26 and a control device 27, the sudden increase of the voltage S2; S3; S4; S5, in particular the voltage S5 of a target value S-soll behind the four-tower 01 z. B. determined by a difference .DELTA.S (FIG. 2) before and after passing through the area 24 and further processed.

On the basis of this difference ΔS, a correction quantity K is formed, and the occurred register offset ΔP between two printing units 04; 06; 07; 08 or between two H-pressure units 09; 11 corrected. This compensation is made i. d. R by a relative change Δφ an angular position φ, z. B. the angular position φ, the considered H-pressure units 09; 11 or the cylinder 12; 13, 14; 16 of the considered printing units 04; 06; 07; 08 to each other.

In the example, the voltage S5 by means of a measuring device 26, z. B. a sensor 26 such. B. a measuring roller 26, after the four-tower 01, here following a catch roller 28, determined and given to the controller 27, a computer 27 or to the control computer 27. From the difference .DELTA.S determines the controller 27 or the calculator 27, the average correction quantity K between the lower H-pressure unit 09 and the upper H-pressure unit 11. The angular position φ of the lower H-pressure unit 09, in particular that of the forme cylinder 12; 16 of the printing units 04 and 06, is now by a corresponding change Δφ in the rotation angle φ relative to the lower H-pressure unit 09, in particular the forme cylinder 12; 16, twisted and thus the occurred Passerversatz ΔP corrected. As in the example, no voltage control means of the draw roller 22 and another device such. B. a dancer roller, takes place behind the last printing unit 08 up to and including the tension roller 22, the voltage S5 falls with further transport of the paper web 03 by the printing units 04; 06; 07; 08 slowly. During the fall, the circumferential register is now readjusted in the opposite direction by means of the correction quantity K in accordance with the changing difference ΔS between S5 and S-soll (FIG. 3). This is done advantageously not continuously but at suitable intervals.

In the present embodiment for the four-high tower 01 is no correction between the two adjacent, the same H-pressure unit 09; 11 associated printing units 04; 06 or 07; 08 made, but only a relative angular position φ between the lower and upper H-pressure unit 09; 11 considered as a change Δφ the rotational angle position φ. Here, each printing unit 04; 06, at least one each, with double printing units 04; 06 at least two, cylinder 12; 13; 14; 16, advantageously each of the forme cylinder 12; 16 changed in their relative angular position φ. The deviation between the one H-pressure unit 09; 11 associated printing units 04; 06 or 07; 08 is, in particular for the newspaper printing, within the permissible tolerances for the deviation in the register.

In general, the described regulation of the circumferential register is advantageous for at least three successively arranged printing units 04; 06; 07; 08, wherein a distance a1 (eg 0.4 m to 1 m) between the two first clamping points 04; 06 is significantly smaller than a subsequent distance a2 (eg> 1 m) to a third nip 07. The four-high tower 01 from two H-pressure units 09; 11 is an example for this. In particular, on the way between the short distance a1 successive first two printing units 04; 06 is a moisture influence, and thus a voltage-induced register offset ΔP low, so that the control for the first two pressure units 04; 06 in the same way relative to the upper pressure units 07; 08, and not in addition to each other, can be done. Between the two printing units 07; 08 of the upper H-printing unit 11 is again followed by a shorter distance a3 (eg 0.4 m to 1 m). A relative change takes place only on printing units 04; 06 with a long distance a2 to one subsequent printing unit 07.

The regulation of the correction of the register offset .DELTA.P by means of the correction quantity K as a function of the difference .DELTA.S from the initially spontaneously increasing and subsequently decreasing change of the voltage S5 by a difference .DELTA.S is preferably carried out as a proportional control, wherein between the difference .DELTA.S of the voltage S5 and the Correction K advantageously a linear relationship is established. The control device 27 is designed as a proportional controller 27 in an advantageous embodiment.

The correction quantity K satisfies (in the range of the voltages S56ΔS to be considered here) in an advantageous embodiment approximately the equation K = a * ΔS, where a represents the slope and no constant element has to be taken into account. The pitch a is for the regulation of the lower H-pressure unit 09 relative to the upper H-pressure unit 09 for the considered four-tower 01 between 1 / (35 daN / m / mm) and 1 / (45 daN / m / mm), in particular at about 1 / (40 daN / m / mm) when the difference ΔS of the voltage S5 in daN / m and the correction amount K of the registration error ΔP on the circumference of the cylinder 12; 13; 14, 16 are measured in mm.

For example, if for a cylinder diameter of about 230 mm, a measured difference .DELTA.S of the voltage S5 10 daN / m, the rotational angular position φ for the lower H-pressure unit 09 is corrected relative to the upper H-pressure unit 11 such that an offset on the circumference of modified cylinder 12; 13; 14; 16 by about 0.25 mm. The change Δφ in the rotational angle position is proportional to the correction value K and the register offset ΔP. Thus, the change Δφ of the rotational angle position over a circumference of the respective cylinder (12; 13; 14; 16) is also linearly related to the difference ΔS, that is to say the value of the change in the relative angular position Δφ = a ^* c ^* .DELTA.S. The relative change Δφ is thus for example for the above cylinder in about 0.12 ° - 0.13 °. Instead of the change Δφ of the angular position can for a certain time, a change in the angular velocity Δφ done.

For different qualities of the paper web 03, there is a different dependency of the correction to be taken into account, so that preferably a quality variable Q or a quality function Q for taking into account the present grade of the paper web 03 (moisture behavior and / or stress-strain characteristic, etc.) of said dependence to be superimposed. The desired correction by the correction quantity K or the change Δφ in the rotational angle position φ or the angular velocity Δφ is thus a function of the voltage S5 or the difference ΔS of the circumference of the cylinder 12 to be corrected; 13; 14; 16 and the quality size Q.

The correction of the register offset .DELTA.P is carried out in a preferred embodiment only by means of register adjustment. A voltage regulation in the range of the voltage S5 behind the last printing unit 08 does not take place in this context. In a preferred embodiment, the tension roller 22 is designed as a tension roller 22 which is controlled with respect to its rotational speed and to which neither tension values nor torque values have to be traced. The measured voltage S5 is advantageously used to control the voltage S1 (shown by dashed lines in FIG. 1) in order to meet the requirement of the above-mentioned. Condition of a larger voltage S1 compared to S5 meet.

Particularly suitable is the method and a corresponding device for controlling the circumferential register for the correction of the registration offset ΔP, which occur during the stationary printing operation as short-term disturbances, for example due to the flying change of paper rolls of the same quality. After this disorder, stationary conditions and the same paper quality are usually present again.

In an advantageous embodiment, each of the cylinders 12; 13; 14; 16 each printing unit a separate drive motor 17; 18; 19; 20 on. For the said correction of the registration offset ΔP, however, all the drive motors 17; 18 one of the two printing unit 04; 06 or all drive motors 17; 18 of the two lower pressure units 04; 06 corrected by the same value at the same time. For a pairwise drive each of a form cylinder 12; 16 with the associated transfer cylinder 13; 14, the same applies mutatis mutandis.

The method for controlling the circumferential register is also for other configuration of the printing press than the four-high tower 01 with at least two printing units 04; 06; 07; 08 suitable if these several spaced apart in the direction of the web 03 from each other clamping points 04; 06; 07; 08 or printing units 04; 06; 07; 08 or also pressure points 04; 06; 07; 08 has.

This can be, for example, a printing machine which is a plurality of bridge printing units arranged on top of each other or a plurality of juxtaposed standing rubber-against-rubber printing units with horizontal guidance of the paper web 03. Likewise, for each of the examples mentioned, the respective first transfer cylinder 13 can also interact with a counter-pressure cylinder 14 designed as a steel cylinder 14. Again, after the last printing unit 08, the voltage S5 is measured, and arranged before the last printing unit 08 printing units 04; 06; 07 regulated by the difference .DELTA.S and the voltage S5. This can again in groups with several consecutive printing units 04; 06 or also each with individual printing units 04; 06; 07 happened. The printing units 04; 06; 07 are in principle regulated against the unmodified last printing unit 08. Between the first and second printing units 04; As a rule, no relative change has to be made because of the not yet complete moisture penetration.

In addition to the register or color register, ie the exact relative position of two successively printed on the same side of the web 03 printed images, usually different colors, the method in an embodiment not shown in the same way also suitable to control the register between the two successive printed pages of the web 03. This is for example for the arrangement of two, each one or more pressure points having satellite printing units 09; 11 of advantage. The satellite printing units 09; 11, z. B. run as a so-called. Nine-cylinder satellite or ten-cylinder satellite, are traversed by the train 03 successively, wherein in one of the printing units 09; 11 the one side of the web 03, and then in the other printing unit 11; 09 the other side of the web 03 is printed one or more colors.

A measurement and evaluation of the difference ΔS in the voltage S2; S3; S4; S5 can for separate requirements between the individual terminal points 04; 06; 07; 08 and a change in the rotational position of the preceding terminal points 04; 06; 07; 08 be effected.

In the case of larger differences ΔS within a larger voltage range for the voltages S2; S3; S4; S5 may u. U. also a non-linear relationship between the difference .DELTA.S and the required correction of the registration offset .DELTA.P be applied to the correction quantity K. However, a corresponding functional relationship is also in this case in a simple manner in the control device 27 considered.

LIST OF REFERENCE NUMBERS

01

high tower

02

reelstands

03

Railway, paper web

04

Printing unit, nip, double printing unit, printing unit;

05

-

06

Printing unit, nip, double printing unit, printing unit;

07

Printing unit, nip, double printing units, printing unit;

08

Printing unit, nip, double printing units, printing unit;

09

H-pressure unit, lower, first

10

-

11

H-pressure unit, upper, second

12

Cylinder, forme cylinder

13

Cylinder, transfer cylinder

14

Cylinder, impression cylinder, transfer cylinder, steel cylinder

15

-

16

Cylinder, forme cylinder

17

Drive motor (04)

18

Drive motor (06)

19

Drive motor (07)

20

-

21

Drive motor (08)

22

Traction element, draw roller

23

infeed

24

Greater Thickness Area (03)

25

-

26

Measuring device, sensors, measuring roller

27

Control device, computer, control computer, proportional controller

28

catcher roll

a1

Distance (04; 06)

a2

Distance (06; 07)

a3

Distance (07; 08)

K

correction variable

Δφ

Change of the angular position

Δφ

Change of angular velocity

.DELTA.P

pass offset

S1

tension

S2

tension

S3

tension

S4

tension

S5

tension

S-target

setpoint

.DELTA.S

difference

Claims (17)

1. A method of regulating a circumferential register in a web-fed rotary printing press with at least two printing units (04; 06; 07; 08) through which a web (03) runs in succession, wherein an actual value of a tensioning (S5) of the web (03) is determined and an angle position (Δφ) or/and an angular speed (Δφ•) of at least one cylinder (12; 13; 14; 16) of a first printing unit (04; 06; 07; 08) is regulated relative to the angle position (Δφ) or/and the angular speed (Δφ•) of at least one cylinder (12; 13; 14; 16) of a second printing unit (04; 06; 07; 08) in a manner dependent upon the said tensioning (S5), characterized in that the tensioning (S5) is determined downstream of a last one of the printing units (08) in the production direction, and the regulation of the angle position (Δφ) or/and the angular speed (Δφ•) is carried out on the first printing unit (04; 06; 07) as viewed in the production direction in a manner dependent upon the said tensioning (S5) measured downstream of the last printing unit (08).
2. A method according to Claim 1, characterized in that a difference (ΔS) is formed from the measured tensioning (S5) with a nominal value (S-Soll), and the angle position (Δφ) or/and the angular speed (Δφ•) is altered in a manner dependent upon the said difference (ΔS).
3. A method according to Claim 2, characterized in that the value for the necessary change in the angle position (Δφ) or/and the angular speed (Δφ•) is formed in a manner dependent upon a quality variable (Q) or quality function (Q) which characterizes the quality of the web (03).
4. A method according to Claim 1, characterized in that the angle position (Δφ) or/and the angular speed (Δφ•) of at least one cylinder (12; 13; 14; 16) of the first printing unit (04) in the production direction is altered in a manner dependent upon the tensioning (S5).
5. A method according to Claim 1 or 3, characterized in that angle positions (Δφ) or/ and angular speeds (Δφ•) of cylinders (12; 13; 14; 16) of the first two printing units (04; 06) are altered in a manner dependent upon the tensioning (S5).
6. A method according to Claim 5, characterized in that the change in the angle position (Δφ) or/and the angular speed (Δφ•) is carried out by the same amount for the two printing units (04; 06).
7. A method according to Claim 2 or 3, characterized in that angle positions (Δφ) or/ and angular speeds (Δφ•) of cylinders (12; 13; 14; 16) of the two printing units (04; 06), which are first in the production direction of the web and which are constructed in the form of a first H-type printing unit (09), are altered at the same time and by the same amount in a manner dependent upon the difference (ΔS) in the tensioning (S5) downstream of the printing units (07; 08) which are constructed in the form of a second H-type printing unit (11).
8. A method of regulating a circumferential register in a web-fed rotary printing press with a first printing unit (09) comprising a plurality of printing points (04, 06; 07, 08) for at least one side of the web (03), and a second printing unit (11) comprising a plurality of printing points (07, 08; 04, 06) for the same or/and the other side of the web (03), wherein an actual value of a tensioning (S5) of a web (03) which runs through the printing units (09; 11) is determined downstream of the last printing point in the production direction, a difference (ΔS) is formed between the tensioning (S5) determined and a nominal value (S-Soll), and an angle position (Δφ) of at least two cylinders (12; 13; 14; 16) of the first printing unit (09) arranged upstream of the last printing unit (11) is regulated relative to the angle position (Δφ) of at least one cylinder (12; 13; 14; 16) of the second printing unit (11) in a manner dependent upon the said difference (ΔS), wherein the angle positions (Δφ) of the cylinders (12; 13; 14; 16) of the first printing unit (09) which are to be regulated are all changed by the same value.
9. A method according to Claim 1 or 8, characterized in that the circumferential register of a web-fed printing press comprising two H-type printing units (09; 11) is regulated by means of the method.
10. A method according to Claim 8, characterized in that the circumferential register of a web-fed printing press comprising two satellite printing units (09; 11) is regulated by means of the method.
11. A method according to Claim 2 or 8, characterized in that the value of the necessary change for the angle position (Δφ) or/and the angular speed (Δφ•) is determined as a function of the difference (ΔS) in the tensioning (S5) and a quality of the web (03).
12. A method according to Claim 2, 3 or 8, characterized in that the value for the change in the angle position (Δφ) or/and the angular speed (Δφ•) is formed by means of a linear relationship between the difference (ΔS) in the tensioning (S5) and the change in the angle position (Δφ) or/and in the angular speed (Δφ•).
13. A method according to Claim 1, 3 or 8, characterized in that a tensioning (S1; S2; S3; S4; S5) on the path from a roll changer (02) to the draw member (22) is regulated only between the roll changer (02) and the first printing unit (04).
14. A method according to Claim 1, 3 or 8, characterized in that the tensioning (S1) upstream of the first printing unit (04) is set higher than the tensioning (S5) downstream of the last printing unit (08) by at least 10 daN/m.
15. A method according to Claim 1, 3 or 8, characterized in that a correction of a register-mark offset (ΔP) during the stationary production operation takes place without a regulation of the tensioning (S2; S3; S4; S5) and without an optical detection system only over the functional interrelationship with the tensioning (S5) downstream of the last printing unit (08) and optionally a quality of a web (03).
16. A method according to Claim 1, 3 or 8, characterized in that a draw roller (22) arranged downstream of the last printing unit (08) is regulated to a constant rotational speed.
17. A method according to Claim 2, 3 or 8, characterized in that, after a spontaneous increase in the tensioning (S5), a change of the angle position (Δφ) or/and the angular speed (Δφ•) first takes place in a first direction in accordance with the difference (ΔS), and after that a change takes place in the opposite direction with a decrease in the difference (ΔS).

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