Method and Device for the Control of a Feed Mechanism

Abstract

A method for the control of a feed mechanism of a web-fed printing press, i.e., for the control of tensile stress and/or web tension of a printing material web to be taken into the printing unit by the feed mechanism, wherein thereby an actual value is compared with a desired value. According to the discrepancy between the actual value and the desired value, a control device for the tensile stress and/or the web tension produces a correcting variable for the feed mechanism. The actual value of the tensile stress and/or the web tension is determined by calculation based on a model.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a method for automatically controlling a feed mechanism of a web-fed printing press. The invention also concerns a device for automatically controlling a feed mechanism of a web-fed printing press.

2. Prior Art

It is already well known from practice that webs of printing material can be drawn into printing units of a web-fed printing press by feed mechanisms. A feed mechanism, the purpose of which is to draw a web of printing material into a printing unit of a web-fed printing press, has at least one roll driven by a drive unit of the feed mechanism. The driven roll of the feed mechanism is operated at a lower speed of revolution or peripheral speed than the rolls or cylinders of the printing unit that serve to convey the web of printing material, so that a well-defined web tensile stress is produced between the feed mechanism and the printing unit for the web of printing material that is to be drawn in. The web tensile stress is a force, and the web tension is calculated from the web tensile stress by dividing the web tensile stress by the width of the web of printing material that is to be drawn in.

It is known from EP 0 976 674 B2 that the web tension can be automatically controlled by comparing an actual value of the web tension with a corresponding setpoint value, where a control unit generates a correcting variable for the feed mechanism, depending on the difference between the actual value and the set point or the deviation of the actual value from the set point. According to EP 0 976 674 B2, a measured actual value of the web tension is used, from which it follows that a suitable measuring device is necessary for measuring the web tension. The use of a measuring device for the web tension necessitates a complex design of the feed mechanism and of the web-fed printing press which increases the feed mechanism's costs.

SUMMARY OF THE INVENTION

An object of the present invention is to create a novel method and device for automatically controlling a feed mechanism of a web-fed printing press.

In accordance with one embodiment of the invention, the actual value of the web tensile stress and/or the web tension is determined mathematically based on a model.

Accordingly, there is no need for a measuring device or a sensor for determining an actual value of the web tensile stress and/or the web tension. This results in a simpler design of the feed mechanism and the web-fed printing press with less complexity and thus lower costs.

The automatic control of the web tensile stress and/or the web tension is preferably superimposed on the automatic control of a speed of the drive of the feed mechanism or on the automatic control of a state of the drive of the feed mechanism.

The invention is described in greater detail below with reference to specific embodiments, but it is not limited to these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic section of a web-fed printing press to illustrate one embodiment the invention;

FIG. 2 is a schematic drawing of a preferred automatic control design for a drive of a feed mechanism of the web-fed printing press;

FIG. 3 is a signal-flow diagram of a model for mathematically determining an actual value of the web tensile stress and/or the web tension; and

FIG. 4 is a signal-flow diagram of another model for mathematically determining an actual value of the web tensile stress and/or the web tension.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic section of a web-fed printing press in the area of two printing units 10, 11 arranged one above the other and a reel changer 12 located upstream of the two printing units 10, 11. In the vicinity of the reel changer 12, a web printing material is kept ready in the form of a roll of printing material 13 and is unwound from the roll of printing material 13 as a web of printing material 14. The web of printing material 14 is drawn into the printing unit 10 by means of a feed mechanism 15 assigned to the printing unit 10. The feed mechanism 15 has a roll 17, which is driven by a drive 16 and serves the purpose of drawing the web of printing material 14 into the printing unit.

The printing units 10, 11 are preferably 8-cylinder printing units. Accordingly, each of the printing units 10, 11 has four printing couples, and each printing couple has a form cylinder 18 and a transfer cylinder 19. The transfer cylinders 19 of each pair of printing couples roll against each other to form a nip for the web of printing material 14. The transfer cylinders 19 also take on the function of further conveyance of the web of printing material 14 through the printing units 10, 11. The roll 17 of the feed mechanism 15 is driven at a different speed of rotation or peripheral speed from the transfer cylinders 19 of the printing units 10, 11 in order to produce a well-defined web tensile stress and/or a well-defined web tension for the web of printing material 14.

A drive controller 20 is assigned to the drive 16 of the feed mechanism 15. FIG. 2 shows the preferred configuration of the drive controller 20. The drive controller 20 illustrated in FIG. 2 automatically controls not only the web tensile stress and/or the web tension of the web of printing material but also the speed of the drive 16. Accordingly, the drive controller 20 of FIG. 2 comprises a control system 21 for automatically controlling the speed of the drive 16. This speed controller 21 outputs a correcting variable Y_MOT for the drive 16 based on the deviation of a measured actual value N_IST of the speed of the drive 16 from a setpoint value N_SOLL for the speed of the drive 16. A speed sensor 22 is assigned to the drive 16 to make the measurement of the actual value N_IST of the drive 16.

Automatic control of the web tensile stress and/or the web tension is superimposed on the automatic speed control. The drive controller 20 comprises, in addition to the speed controller 21, a control system 23 for automatically controlling the web tensile stress and/or the web tension. On the basis of the deviation between a setpoint value X_SOLL for the web tensile stress and/or the web tension and a corresponding actual value X_IST, the control system 23 for automatically controlling the web tensile stress and/or the web tension determines a correcting variable Y_N for the feed mechanism 15. In the specific embodiment of FIG. 2, this set point Y_N for the feed mechanism 15 is an offset for the set point N_SOLL of the speed of the drive 16.

In accordance with one embodiment of the present invention, the actual value X_IST of the web tensile stress and/or the web tension is not determined by measurement but rather mathematically based on a model. The output variable of the model 24 is the actual value X_IST for the web tensile stress and/or the web tension. In the specific embodiment of FIG. 2, the following input variables are supplied to the model 24: a motor torque M_MOT of the drive 16, which is measured by a torque sensor 25, the actual value N_IST of the speed of the drive 16, which is measured by the speed sensor 22, a web tensile stress value and/or web tension value X_RW of the reel changer 12, and a friction torque M_REIB of the feed mechanism 15. The friction torque M_REIB of the feed mechanism 15 is a speed-dependent quantity, where the friction torque is preferably linearized M_REIB=m*N_IST+c.

The model 24 according to FIG. 4 then determines the actual value X_IST of the web tensile stress and/or the web tension as follows:)

X _IST =G2(X_RW)+a*[G1(M_MOT)+m*N_IST+c]

where:

X_IST is the computed actual value of the web tensile stress and/or the web tension,

X_RW is the value of the web tensile stress and/or the value of the web tension of the reel changer,

M_MOT is the motor torque of the drive,

N_IST is the speed of the drive,

G1 and G2 are smoothing functions,

and a, m, and c are constants.

In one embodiment, instead of the motor torque M_MOT of the drive 16, an electric current that creates the motor torque is determined by measurement and used as the input quantity for the model 24. Likewise, instead of the web tensile stress value and/or the web tension value of the reel changer, it is possible to use a quantity that creates the web tensile stress value and/or the web tension value.

The smoothing functions G1 and G2, which smooth the motor torque M_MOT or the web tensile stress value and/or the web tension value X_RW of the reel changer, are filter functions. The smoothing functions G1 and G2 are preferably dispensed with if quantities that are already suitably smoothed are being supplied by the torque sensor 25 and/or reel changer.

As has already been noted, the quantities c, m, and a are constants. The quantities c and m are the constants of the speed-dependent, linearized friction torque M_REIB.

The constant a is a conversion factor, which is dependent on a speed ratio i between the drive 16 and roll 17 of the feed mechanism 15 and on the radius r of the roll 17. The conversion factor is defined as follows:

$a=\frac{i}{r}$

Instead of the model 24 illustrated in FIG. 4 for computing the actual value X_IST for the web tensile stress and/or the web tension, the simplified model 24′ shown in FIG. 3 can also be used. In the model 24′, a constant friction torque M_REIB=c is used for computing the actual value X_IST of the web tensile stress and/or the web tension, so that the speed N_IST of the drive 16 is not needed as an input variable for the model 24′. The model 24′ according to FIG. 3 then determines the actual value X_IST of the web tensile stress and/or the web tension as follows:

X _IST =G2 X_RW+a*[G1(M_MOT)+c]

where

X_IST is the computed actual value of the web tensile stress and/or the web tension,

X_RW is the value of the web tensile stress and/or the value of the web tension of the reel changer,

M_MOT is the motor torque of the drive,

G1 and G2 are a smoothing functions, (which can be equal to 1 when the smoothing function is not required) and

a and c are constants.

As described above with reference to FIG. 2, in the preferred embodiment, automatic control of the web tensile stress and/or the web tension is superimposed on the automatic speed control of the drive 16. In one embodiment, the automatic control of the web tensile stress and/or the web tension is superimposed on automatic control of a state of the drive 16 of the feed mechanism 15, in which case the control system 23 for the web tensile stress and/or the web tension then outputs an offset for the setpoint value of the state of the drive 16 as a correcting variable. In this embodiment, the control system 23 can also adjust a transmission or scaling factor.

In one embodiment of models 24 and 24′ according to FIG. 4 and FIG. 3, respectively, a moment of inertia of the feed mechanism is considered as a further input variable in order to improve the computation of the actual value X_IST of the web tensile stress and/or the web tension when changes in the speed occur.

According to FIG. 2, in the preferred embodiment, the control system 23 for the web tensile stress and/or the web tension and the model 24 for mathematically determining the actual value X_IST of the web tensile stress and/or the web tension are integrated in the drive controller 20. However, it is also possible to realize these units as a separate system outside the drive controller 20.

The constants a, c, and possibly m of the models 24 and 24′ are determined manually or by automated means. In the case of automated determination of the parameters, a device for measuring the web tension is installed between the feed mechanism 15 and the printing unit 10 for determining the parameters, and in this case, the drive controller 20 is operated with different setpoint values for the web tensile stress at different speeds. In this connection, the torque of the drive or the current of the drive that creates the torque, the speed of the drive, and the web tension are determined by measurement, and the parameters c, m, and a are computed from these measured determinations by numerical optimization. The parameters determined in this way are then used in the model in order to mathematically determine the actual value X_IST for the web tensile stress and/or the web tension later in the operation without a measuring device for the web tensile stress.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1.-10. (canceled)

11. A method for automatically controlling at least one of a web tensile stress and a web tension of a web of printing material drawn into a printing unit by a feed mechanism, the method comprising: comparing an actual value of at least one of a web tensile stress and a web tension of a web of printing material of a drive of the feed mechanism with a setpoint value of the drive of the feed mechanism;generating a correction variable for the feed mechanism based at least in part on the deviation of the actual value of the drive of the feed mechanism from the setpoint value of the drive of the feed mechanism; andcomputing the actual value of the at least one of the web tensile stress and the web tension based on a model.

12. The method in accordance with claim 10, wherein an input to the model comprises at least one of: a motor torque of a drive of the feed mechanisman electric current that creates the motor torque,a friction torque of the feed mechanism,a web tensile stress value,a web tension value supplied by a reel changer located upstream of the feed mechanism,a quantity that forms the web tensile stress value, anda quantity that forms the web tension value.

13. The method in accordance with claim 12, wherein the friction torque of the feed mechanism is a constant friction torque.

14. The method in accordance with claim 13, wherein the model determines the actual value of at least one of the web tensile stress and the web tension as follows: XIST=G2XRWa*[G1(MMOT)+c]

15. The method in accordance with claim 12, wherein the friction torque of the feed mechanism is a speed-dependent friction torque and, the input to the model further comprises the speed of the drive of the feed mechanism.

16. The method in accordance with claim 15, wherein the model determines the actual value of the at least one of the web tensile stress and the web tension as follows: XIST=G2(XRW)+a*[G1(MMOT)+m*NIST+c]

17. The method in accordance with claim 11, wherein the method further comprises: superimposing the automatic control of the at least one of the web tensile stress and the web tension on an automatic control of a speed of the drive of the feed mechanism; andoutputting an offset for a setpoint value of the speed of the drive of the feed mechanism as a correcting variable.

18. The method in accordance with claim 11, wherein the method further comprises: superimposing the automatic control of the at least one of the web tensile stress and the web tension on an automatic control of a state of the drive of the feed mechanism; andoutputting an offset for a setpoint value of the state of the drive of the feed mechanism as a correcting variable.

19. A device for automatically controlling the at least one of a web tensile stress and a web tension of a web of printing material to be drawn into a printing unit by a feed mechanism, the device comprising: a control system for the at least one of the web tensile stress and the web tension configured to generate a correcting variable for the feed mechanism as a function of a deviation of an actual value of the at least one of the web tensile stress and the web tension from a setpoint value of the at least one of the web tensile stress and the web tension,wherein the device is further configured to determine the actual value the at least one of the web tensile stress and the web tension based on a model.

20. A device in accordance with claim 19, wherein the device for automatic controlling the at least one of a web tensile stress and a web tension is integrated in a drive controller of a drive of the feed mechanism.

21. The method in accordance with claim 15, wherein the speed-dependent friction torque is linearized.