DE10322098B4 - Method and device for controlling the web speed on a transport device for webs - Google Patents

Abstract

Method for controlling the web speed on a transport device for webs, wherein the web passes through at least one web section with a first conveying nip and a subsequent discharging nip, and at least one nip is equipped with an electrically controllable drive,
characterized in that
The web tension (σ _1ist ) is measured before the conveying nip (K1),
- the web speed (v ₁ ) is detected at the conveying nip (K1),
- the web tension (σ _2soll ) between the two clamping points (K1, K2) is specified as a setpoint value,
The modulus of elasticity (E) of the material web (WB) is recorded as an auxiliary control variable by measurements on the running web or provided externally,
- Then the values of the measured web tension (σ _1ist ), the predetermined web tension (σ _2soll ) and the modulus of elasticity (E) are processed in a stage for setpoint generation, which constantly controls the drive of the abfördernden nip (K2) so that the web speed (v ₂ ) at the discharging clamping point (K2) after the ...

Description

The The invention relates to a method and a device for controlling the web speed at a transport device for webs, wherein the web has at least one web section with a first feeding-in Run through clamping point and a subsequent promotional clamping point, and at least one nip with an electrically controllable drive Is provided.

at the webs are, for example, continuous webs made of paper, foil or fabric. To ensure trouble-free operation of the Transport device and a good quality of the produced web, e.g. To ensure a printed paper web, are the voltage and the speed of the web within a given one Range relatively constant.

to Achieving good print or image quality must be multicolored when printing Images in printing presses the partial images of multicolor printing, the in successive printing units of the respective printing form transferred to the running track be, in terms of image size and position on each other fit. On her way through the printing press goes through the to be printed web so-called clamping points, for example are designed as driven rollers or cylinders. At this Locations act on the moving web friction forces and / or adhesion forces as a result a wrap of the rollers through the web. This can help before and behind the terminal point different web tension and Set web speeds.

It are state-of-the-art solutions known who have made the task by means of rule or Control devices one possible uniform web tension and to achieve web speed.

So will in the DE 198 34 725 A1 a control device and a method for regulating the tension of a paper web of a printing press described, in which within the controlled system (web tension section), the measured web tension actual value is detected. A speed reference setpoint and a web tension setpoint are specified. About difference a size for the speed control of the drive motor is determined. With this web tension control, the deviation of the individual web tension at different points of the paper path can be kept within certain limits.

From the DE 102 01 993 A1 For example, an apparatus and a method for dynamically controlling a drive for transport rollers in a web-fed printing press are known. The task was to ensure a desired web tension and a required print quality at different stages of machine operation. The web tension to be controlled lies between two transport roller pairs (clamping points). The controller operates in a web tension control mode during a first phase of the printing press operation to maintain the web tension at a first desired web tension value. The control of the speed is based here on a voltage in one of the terminal point upstream track section. In a second phase of the printing press operation, the drive speed ratio based control of the speed of the drive occurs in a speed control mode.

In the DE 42 21 395 C2 is a method for determining the breaking strength as a failure characteristic for the paper used on a printing machine described. The web speed and the web tension are recorded in front of and behind a web clamping point. However, the method is exhausted in the determination of the modulus of elasticity, without performing further steps to control the web speed or the drive speed.

The DE 36 05 168 C2 discloses an arrangement for low-vibration transport of an elastic, under tension fabric, in which to adapt to different moduli of elasticity and cross sections of the fabric both in the speed as in the band adjustment, an adjustment of the controller parameters is made by the fact that the controller parameters in Depending on the geometric mean of modulus of elasticity and cross section to be changed.

In the EP 0951993 A1 In a method for a register-driven drive of a cylinder or a registration roller of a rotary printing machine, a change in a longitudinal extent of a section of a printing web is determined from measured variables such as speed and web tension and by register translation ment of the cylinder and / or the register roller balanced.

These solutions The prior art are either associated with a high cost or do not compensate the detected disturbances.

In the DE 69114302 T2 For example, there is provided an apparatus and method for calculating and controlling elongation of a traveling belt wherein the change in length of a reference length of the belt material is measured in conjunction with at least one increase or decrease in belt tension. The voltage change is performed by means of an acceleration and deceleration means which accelerates or decelerates a portion of the band to a voltage higher or lower than the original voltage. It is assumed that a voltage equality in adjacent sections of the tape. If that does not apply, it can lead to incorrect controls or a large residual error. Thus, this device can not be used for example in a printing machine with multi-color printing, because the condition of approximately equal voltage between all printing units is not met.

The cyclic acceleration or deceleration also causes a cyclic Working method, which is also not for all processing machines suitable is.

The The object of the invention is a method and a device to control the web speed of a web, the at large Field of application and relatively little effort or web tension changes strong disturbances occur minimize or completely avoid and allow a uniform conveying of the web.

According to the invention Task solved in each case by the features of the main claims. Further embodiments emerge from the dependent claims.

Proceeding according to will the facilitator Clamp the web tension and at the zufördernden nip the web speed measured. The web tension between the two clamping points is called Setpoint specified. The modulus of elasticity of the web is a Auxiliary control variable and will recorded by measurements on the moving web or provided externally. The values of the measured web tension, the given web tension and the modulus of elasticity finally become processed in a stage for setpoint generation, the drive the encouraging Nip constantly with the under consideration the web tension and the modulus of elasticity at the conveying off Terminal point controls certain web speed.

As well is the consideration the web elongation possible. It is also before the zufördernden nip the web tension and at the zufördernden Nip detects the web speed. The web stretch between the two clamping points is specified as a setpoint. The modulus of elasticity the web is an auxiliary control variable and is determined by measurements recorded on the running track or provided externally. Then the values of the measured web tension, the given Web elongation and elastic modulus processed in a stage for setpoint generation, the drive the abfördernden nip with constantly the under consideration the web elongation and the modulus of elasticity at the conveying off Terminal point controls certain web speed.

Further Embodiments of the invention see the determination of the modulus of elasticity with change the web tension or the web elongation before.

at Presence of several, traversed by the web, track sections each with a zufördernden Nip and a promotional Nip will reduce the web speed at each Clamping point according to the cited Calculation rules determined.

Is possible also, instead of the web speed, the speed at the zufördernden Determine nip and instead of the web speed the encouraging Clamp the speed under consideration of the web tension and the modulus of elasticity and / or the web elongation and the modulus of elasticity.

Furthermore, means for detecting signals for the web tension may advance before the first be arranged the nip. According to a further embodiment of the invention, means for detecting signals of the web tension after the first zufördernden nip are additionally arranged.

The Invention is based on an embodiment be explained in more detail.

It demonstrate:

1 : The schematic representation of the arrangement for controlling the web speed on a web, taking into account the web tension

2 : The schematic representation of the arrangement for controlling the web speed on a web, taking into account the web elongation

3 : the schematic representation of the arrangement according to 1 with E-modulus determination

4 : the schematic representation of the arrangement according to 2 with E-modulus determination

The Transport device for Webs with the inventive method and device is preferably a printing press. But it can also be a machine for slides or textile webs.

The web WB with a web tension σ and a web elongation ε passes according to the 1 to 4 in the direction of the arrow first a first upstream path section A1, which is bounded by a first, zufördernden, nip K1. At the end of the adjoining second path section A2 is a second, abfördernde, nip K2. These clamping points K1 and K2 are preferably as pairs of cylinders, consisting of impression cylinder 11 . 12 and powered cylinders 21 . 22 , trained and are with speed-controlled drives M1 and M2, each consisting of a motor, a control for current, speed and angle control, a power controller, preferably a frequency converter, and a measuring device, preferably designed as a rotary encoder, but not here are described in more detail. A control device RE is assigned to the drives M1, M2. On the in the 1 to 4 shown speeds N _conduct , N _1soll and N _2soll will be discussed in more detail below. Before the zufördernden nip K1 is a transmitter 3 , via which the measurement of the web tension σ _{1 is carried out} in the web section A1 and the web speed v _{1 is} detected at the forwarding nip K1.

In 3 and 4 is another transmitter 4 for detecting the value of the web tension σ _{2istis provided} in the second web section A2.

To carry out the method for controlling the web speed of a web, the web tension σ _{1 is measured in} front of the conveying nip K1 and the web speed v _{1 of} the web WB is _measured at the nip K1. The web tension σ _2soll between the two nips K1 and K2 in the web section A2 is specified as the desired value. Likewise, instead of the web tension σ _2soll, the web elongation ε _{2soll can be} specified. The modulus of elasticity E of the material web is detected either by measurements of the running web or made available as an auxiliary control variable. The values thus determined are processed in the control device RE as set out in the following statements.

E

Elastizitätsmodul in den Bahnabschnitten A1 und A2

E*

Näherung für E-Modul in den Bahnabschnitten A1 und A2

v₁

Bahngeschwindigkeit an der Klemmstelle K1

v₂

Bahngeschwindigkeit an der Klemmstelle K2

σ_1ist

Bahnspannung im Bahnabschnitt A1

σ_2ist

Bahnspannung im Bahnabschnitt A2

σ_2soll

Bahnspannungssollwert für Bahnabschnitt A2

ε_2soll

Bahndehnungssollwert für Bahnabschnitt A2

k_gl

Glättungsfaktor

S

Drehzahlschlupf

k_pl

plastischer Dehnungsanteil an Gesamtdehnung

R₁

Radius des Gegendruckzylinders 21 an Klemmstelle K1

R₂

Radius des Gegendruckzylinders 22 an Klemmstelle K2

N_leit

Leitdrehzahl

N_1soll

Drehzahlsollwert der zufördernden Klemmstelle K1

N_2soll

Drehzahlsollwert der abfördernden Klemmstelle K2

A list of the formula symbols used is prefixed:

e

Young's modulus in the web sections A1 and A2

e *

Approximation for modulus of elasticity in sections A1 and A2

v ₁

Web speed at the nip K1

v ₂

Web speed at the nip K2

σ _{1 ist}

Web tension in the web section A1

σ _2ist

Web tension in web section A2

σ _2soll

Web tension setpoint for web section A2

ε _2soll

Web expansion setpoint for path section A2

k _gl

smoothing factor

S

Speed slip

k _pl

plastic strain proportion of total strain

R ₁

Radius of the impression cylinder 21 at terminal point K1

R ₂

Radius of the impression cylinder 22 at nip K2

N _leit

Leitdrehzahl

N _1soll

Speed setpoint of the forwarding clamping point K1

N _2soll

Speed setpoint of the discharging clamping point K2

starting point for the considerations leading to the invention are the transport behavior of an elastic web in one System driven, embraced rolls underlying, from the Mechanics known basic laws: equation of motion, equation of continuity, Coulomb's law of friction and Hooke's elasticity approach. Using some simplifications (relative speed v is approximately equal 0; there is dry coulomb friction between web and driving surface) can be a stationary Web run through the press as in fluid mechanics by means of the continuity condition to be discribed.

By an arbitrarily selected cross-section A _x is the mass flow m = с x · v x · A x = constant.

ist durch den Dehnungszustand ε gegeben, weil der tragende Bahnquerschnitt (die Geschwindigkeit v ist annähernd 0) praktisch konstant bleibt.The concentration

is given by the strain state ε, because the supporting web cross-section (the velocity v is approximately 0) remains practically constant.

This produces the following form as a continuity equation:

The Hooke's approach σ i = ε i · e links the strains to the stresses. Since, on the one hand, the track lengths considered (eg, between the terminal points K1 and K2) are relatively short and, on the other hand, the changes in the modulus of elasticity E are generally slow along the material web, the instantaneous value of the modulus of elasticity E may be set constant. This is from above equation

These Linked equation the strain or tension and the web speed of any location (1) the web with the elongation or tension and the web speed at another point (2) of the fabric under the practically permissible, simplifying assumption that the transverse strains and the cross-sectional changes the fabric virtually disappear.

The speed v ₁ here is understood to mean the web speed v _{1 of} the first, conveying center K1 and, as v _2, the web speed v _{2 of} the subsequent, discharging nip K2. Instead of σ ₁ , the web tension σ _{1ist is} used, and instead of σ ₂ a setpoint σ _2soll for the web tension between the two clamping points K1 and K2 in the web section A2 is specified in accordance with the technical requirements. Now we get for the web speed v ₂ at the discharging nip K2 according to 1 the following calculation rule:

The web tension σ _1ist here corresponds to the web tension which is measured in the upstream web section A1 in front of the conveying nip K1. E is the modulus of elasticity of the web WB.

Accordingly, the calculation rule for the web speed v ₂ according to the web elongation according to 2 out:

Here, the web elongation ε _{2soll is entered} as a setpoint value for the web section A2 between the two terminal points K1 and K2.

The specified as setpoint value web tension σ _2soll is correctable. By changing them, the elastic modulus E can be identified at σ _2soll = σ ₂ ( 3 ). Taking into account the smoothing factor k _gl , the following formula results:

These Determination of Young's modulus E is especially important for Goods webs consisting of films or fabrics.

For the in Printing machines used printable paper webs, the web elongation ε is a priority Size.

The determination of the modulus of elasticity E taking into account the web elongation ε _2soll ( 4 ) shows the following formula:

The modulus of elasticity E can be determined while the machine is running. It can be constantly monitored and tracked and thus adjusted exactly. This has the advantage that no transition process of the web tension σ _{2 is} more recognizable in speed _changes .

zu ermitteln sowie den plastischen Dehnungsanteil an der Gesamtdehnung nach der Formel

festzustellen.By means of the condition of continuity stated above, it is also possible to determine the rotational speed slip S of the material web WB according to the formula

to determine as well as the plastic strain on the total elongation according to the formula

determine.

In addition, speed N and circumferential speed v _u of each roller and each driven cylinder 21 . 22 linked together via the radius R: v u = 2 π RN

Assuming that peripheral speed of a roller or cylinder and web speed of the web are the same, you can work in all calculations instead of the web speeds with speeds. Unless expressly stated otherwise, all formulas are based on the assumption that equally large rolls or cylinders will be used. It therefore always applies R ₁ = R ₂ = R.

If one sets in the above-mentioned calculation rule for the web speed v ₂ at the Abfördernden clamping point K2, the speed N _2soll , we obtain the following formula:

In the case of different radii at the terminal points K1 and K2, the calculation rule results:

When changing the Leitdrehzahl N _leit creates no disturbing transient web tension σ _{2 is.}

With the method according to the invention and the device according to the invention for controlling the web speed of webs is at relative low technical equipment Effort a uniform promotion scored the web. The influence of disturbance variables, for example at speed and web tension changes can be greatly minimized. There is a fast control without transient behavior. In case of disturbances like changes The machine speed does not have to interrupt the process become. The continuous operation of the device and the Procedure allows the application on all processing machines.

moreover the solution according to the invention is easy retrofitted, because it is not bound to any technology.

Claims (8)

Method for controlling the web speed on a transport device for webs, wherein the web passes through at least one web portion with a first zufördernden nip and a subsequent abfördernden nip, and at least one nip is equipped with an electrically controllable drive, characterized in that - before the zufördernden nip (K1) the web tension (σ _1ist ) is measured, - the web speed (v ₁ ) is detected at the conveying clamping point (K1), - the web tension (σ _2soll ) between the two clamping points (K1, K2) is specified as a setpoint value, The modulus of elasticity (E) of the material web (WB) is recorded as an auxiliary control variable by measurements on the running web or made available externally, then the values of the measured web tension (σ _1act ), the predetermined web tension (σ _2soll ) and the elastic modulus ( E) process in one stage for setpoint generation t, which constantly controls the drive of the discharging clamping point (K2) in such a way that the web speed (v ₂ ) at the discharging clamping point (K2) according to the calculation rule

results. Method for controlling the web speed on a transport device for webs, wherein the web passes through at least one web portion with a first zufördernden nip and a subsequent abfördernden nip, and at least one nip is equipped with an electrically controllable drive, characterized in that - before the zufördernden nip (K1) the web tension (σ _1ist ) is measured, - the web speed (v ₁ ) is detected at the conveying clamping point (K1), - the web elongation (ε _2soll ) between the two clamping points (K1, K2) is specified as a setpoint value, The modulus of elasticity (E) of the material web (WB) is recorded as an auxiliary control variable by measurements on the moving web or made available externally, then the values of the measured web tension (σ _1act ), the predetermined web elongation (ε _2soll ) and the elastic modulus ( E) is processed in a stage for generating the setpoint w ground, which controls the drive of the abfördernden nip (K2) constantly so that the web speed (v ₂ ) at the abfördernden nip (K2) according to the calculation rule

results. A method according to claim 1, characterized in that the determination of the modulus of elasticity (E) according to the calculation rule

where (σ _{2 is} ) the measured web tension in the web section (A2) between the first conveying nip (K1) and the second discharging nip (K2), (E *) approximates the elastic modulus and (k _gl ) Represents smoothing factor. A method according to claim 2, characterized in that the determination of the modulus of elasticity (E) according to the calculation rule

where (σ _{2 ist} ) represents the web tension measured between the conveying point (K1) and the second conveying point (K2) in the web section (A2) and (E *) is an approximation for the modulus of elasticity. Method according to one of claims 1 to 4, characterized in that in the presence of several, of the web (WB) traversed, track sections (A1, A2, ... An), each with a zufördernden Clamping point (K1) and each one abfördernden clamping point (K2), the web speed (v ₂ ) at each conveying terminal point (K2) is determined. Method according to one of claims 1 to 5, characterized in that instead of the web speed (v ₁ ) determines the speed (N _1soll ) at the zufördernden nip (K1) and at the conveying nip (K2) instead of the web speed (v ₂ ) the Speed (N _2soll ) according to the calculation _instructions

is determined, where R _{1 is} the radius of the driven cylinder 21 at the zufördernden nip K1 and R _2, the radius of the driven cylinder 22 at the discharging nip K2. Device for controlling the web speed on a transport device for webs according to the method of claim 1 or 2, wherein the web passes through at least one web portion with a first zufördernden nip and a subsequent abfördernden nip, and at least one nip is equipped with an electrically controllable drive, characterized in that means for detecting signals for the web tension (σ _1ist ) are arranged in front of the first conveying nip (K1). Device for controlling the web speed according to claim 7, characterized in that further means for detecting signals for the web tension (σ _2ist ) are arranged after the first conveying nip (K1).