DE102007000679A1 - Method and device for detecting a crack and / or a modulus of elasticity of a material web - Google Patents

Abstract

The invention relates to a method for detecting a crack and / or for determining a modulus of elasticity (E) of a material web (2), in particular fibrous web, in a machine for producing the same between two fixed points (3.1, 3.2), in which the material web (2) at the first of the fixed points (3.1) by means of a drive device (5.1) with a desired speed (v_ref (i)) is driven and a measure corresponding to the modulus of elasticity (E) of the material web (2) is determined. The invention is characterized in that a torque curve of an actual torque (M (i)) of the drive device (5.1) is detected and evaluated in order to determine the measure in accordance with the modulus of elasticity (E).

Description

The The invention relates to a method for detecting a crack and / or a modulus of elasticity of a material web, in particular Fibrous web in a machine for making the same between two fixed points at which the material web at the first of the fixed points by means of a drive device with a desired speed is driven and a measure according to the modulus of elasticity the web is determined and a device for performing of such a procedure.

Usually be for detecting a crack of a material web, in particular a paper tear between two in the direction of passage of the web predefined fixed points or areas in a machine used for producing such material webs device arrangements, which by means of a separate sensor a crack to capture. The material webs are fibrous webs, especially in the form of paper, board or tissue webs.

US 2006 0070713 A1 discloses a transfer system for paper webs in a dryer section, in which inter alia an optical detection arrangement is arranged in the region of the paper web in order to detect a paper tear.

US 5,289,007 describes a web break detection device for detecting a crack in a web, the web running between an infrared light emitter and an infrared light receiver and, with the web intact, preventing passage of the infrared light between emitter and detector.

EP 0 660 898 A1 describes a device in which a negative pressure applied to a passing path, in order to be able to detect a sudden change in pressure in the event of a crack can. DE 101 57 915 A1 describes a method for web tear monitoring and a machine for carrying out the method, in which a material web is monitored by means of at least one web train detecting and attached to the measuring device sensor on a web break, so that when detected web tear at least one tee device can be activated.

DE 101 57 914 A1 describes a method for web break monitoring and a machine for carrying out such a method in which a sensor arranged adjacent to the web detects the web speed of the web in order to be able to determine a web break. As a further aspect, it is stated that a power consumption of a drive unit for driving a roller can be monitored with regard to its power consumption, in order to be able to activate a tee device, in particular a knock-off meter, during a change in power consumption during normal operation. Advantageously, it is stated that essentially existing components of a corresponding paper machine can be accessed.

EP 1 066 515 B1 describes a method for determining an irreversible stretch and a dynamic modulus of elasticity of a paper web. In the production line, a pressure sensor for measuring a transversely measured tension profile of the paper web is tensioned against the paper web between two fixed points, that is to say between two roller assemblies which tension the paper web. A stress profile results here as the product of a basic weight profile, a dynamic modulus of elasticity and a power, in particular the power 1, of the subtraction result of an irreversible elasticity constant subtracted from a relative elasticity value. A disadvantage of such an arrangement that it is constructed very expensive and the paper web is acted upon by the sensor arrangement for measuring voltage. In addition, a variety of different sizes must be specified and calculated and processed accordingly in a control device.

Of the Invention is therefore the object of a method and a Device for detecting a paper tear and / or a modulus of elasticity to propose, which a lower structural complexity and a preferably allow easier data processing.

These Task is solved by a method for detecting a Paper tear and / or a modulus of elasticity with the Features according to claim 1 respectively by a device for detecting a paper tear and / or a modulus of elasticity with the features according to claim 9. Advantageous embodiments are in the subclaims described.

Accordingly, a method for detecting a crack and / or for determining a modulus of elasticity of a material web or of a size at least indirectly characterizing it, in particular a paper tear, between two fixed points, in which the material web at the first of the fixed points by means of a drive device with a desired speed is driven and in which a measure corresponding to the modulus of elasticity or this at least indirectly characterizing size of the material web is determined, wherein for determining the measure according to the modulus of elasticity be As a torque characterizing this at least indirectly characterizing a torque curve of an actual torque of the drive device is detected and evaluated. In this case, an already for the operation of the machine, in particular their control to be determined size is detected, so that the cost of the inventive method keeps relatively low. In particular, this size can be accessed, for example, via the control of the machine for producing such material webs and thus of the individual drive units.

To the Detecting a paper tear is z. B. an increase of the actual torque the drive device used as a decision criterion. To the Determining the measure according to the elastic modulus or a characterizing this at least indirectly Size is preferably an actual torque of a used second drive means, which at the second fixed point is used to drive the web. To capture a Cracking of the web can be a drop in an actual torque the second drive means can be used.

A Decision of detecting a crack of the material web becomes preferably made dependent on a not or only within a limit value changed target speed at least a drive device. The detection of a crack of the material web can also be dependent on a comparison of the actual torques at different times and outside one of one Threshold dependent tolerance range can be determined.

To the Determine the modulus of elasticity or a measure according to the modulus of elasticity, an acting Moment on the material web and / or an actual torque to one Time before a demolition of the web over a Speed ratio are applied.

By the method included and / or certain parameters including the modulus of elasticity or one on the elastic modulus Measured measure are preferred for later Processing or use for controlling the paper machine in stored in a memory.

Prefers Also, an apparatus for detecting a crack and / or for determining a modulus of elasticity or a size that at least indirectly characterizes this a material web, in particular a paper web, with at least two fixed points, between which the material web in tensioned Condition runs, with at least one drive device at the first fixed point for driving the material web in the direction of second fixed point and with a control device for controlling the drive device and / or for evaluating detected parameters, wherein the control device is an actual torque of at least the drive device detected at the first fixed point and for determining an increase of the actual torque is designed and / or programmed to provide the thereof calculated modulus of elasticity of the web before a Demolition of the web behind the first fixed point and / or to Determining a measure according to this modulus of elasticity.

The Control device is preferred for detecting an actual torque a second drive means designed at the second fixed point and trained or programmed, the actual torque of the second drive means in addition to the actual torque of the drive device of the first fixed point for determining the elastic modulus and / or the measure corresponding thereto.

The Control device can be designed and / or programmed for Analyzing a target speed of at least the drive device at the first fixed point for detecting a crack of the material web on change the actual torque just in case of during the change is equal to or within a tolerance threshold remained desired speed.

Preferably is the device with a memory device for storing at least in the case of a detected crack of the Material web determined modulus of elasticity and / or a equipped with this appropriate measure.

One Embodiment will be described below with reference to FIGS explained in more detail. Show it:

1 schematically an exemplary arrangement of a run between fixed points paper web and a control device for controlling drives and for evaluating detected parameters;

2 exemplary diagrams for illustrating a drive behavior during a paper break on the basis of speed and torque data, which act in the region of a roller drive;

3 exemplary components of a circuit arrangement for detecting a band break, wherein such components can also be implemented in the form of a software algorithm;

4 a diagram of a demolition torque over a speed ratio for two different web materials; and

5 Components of a circuit arrangement or method steps of an algorithm for determining a paper elastic modulus.

1 illustrated in a schematic simplified representation based on a section of a machine 1 for producing a material web 2 , in particular fibrous web, two in the direction of passage of the web 2 successively arranged drive groups 4.1 . 4.2 how they can be used for example in a press section. Preferably, the system is always used where a minimum tensile strength prevails, for example in a press section. The drive groups 4.1 and 4.2 are here as press facilities 12 . 13 formed, each comprising two, a press nip forming rollers between which the material web 2 supported by at least one felt belt 14 is passed. However, it is also conceivable use in other areas, such as a drying group.

The material web 2 is between two fixed points 3.1 . 3.2 guided, which is to be understood by a fixed point a path point in which the material web is clamped, in particular guided without slip. Between two such fixed points 3.1 . 3.2 can instead of a linear guide the web 2 also deflections of the material web 2 done by rollers, guide rollers or the web processing components. Within the scope of a particularly preferred embodiment, it is even conceivable to implement a corresponding arrangement with only a single fixed point at which parameter monitoring takes place.

The drive groups 4.1 . 4.2 Here, at least in each case comprise a drive roller, on which the material web 2 with a felt tape 19 by a rotation of the rollers of the drive groups 4.1 . 4.2 in the machine direction, ie passage direction L of the material web 2 is advanced.

For driving one of the rollers of the drive groups 4.1 or 4.2 of the fixed points 3.1 respectively 3.2 serve drive devices 5.1 respectively 5.2 ,

For controlling the drive devices 5.1 . 5.2 serves a control device 7 , The control device 7 may for example be formed by a circuit arrangement which consists of a plurality of individual components, the control device 7 but can also be configured from a processor with correspondingly suitable external interfaces and a control algorithm for controlling the process. From the controller 7 are control signals, in particular control variables for the drive means 5.1 . 5.2 issued to the drive equipment 5.1 . 5.2 for realizing a desired setpoint speed v_ref (i), v_ref (i + 1) with i = 1 to n drive. The index i always refers to the specification of the corresponding drive group 4.i , The desired speed v_ref (i) or v_ref (i + 1) corresponds to the speed at which the material web 2 at the successively arranged drive groups 4.1 . 4.2 should be led. In order to achieve this, appropriate manipulated variables Yv_ref (i) and Yv_ref (i + 1) are to be formed, which are then used to control the adjusting devices of the rollers of the drive groups 4.1 . 4.2 be used. For example, hard-wired cables are used for transmission 8.1 . 8.2 , However, other mechanisms for the transmission of control signals are possible, that is in addition to line-bound signals or currents and wireless systems, for example by radio or infrared interface provide transmitted signals. In addition to the specification and the transmission of the manipulated variables to obtain a setpoint speed v_ref (i), v_ref (i + 1) can by the control device 7 also other control variables to the drive devices 5.1 respectively 5.2 are transmitted, such as a manipulated variable Y for setting a target torque Ms (i) or Ms (i + 1), wherein in this exemplary case, the drive means 5.1 respectively 5.2 corresponding control devices for adjusting the corresponding desired torques Ms (i) or Ms (i + 1) have.

In addition, by the controller 7 from the drive devices 5.1 . 5.2 Receive parameter. For the method for detecting a paper tear, an actual value, in particular an actual speed v (i), v (i + 1) and an actual torque M (i), M (i + 1) from the drive devices 5.1 respectively 5.2 receive. The control device 7 is configured and / or programmed to detect a paper tear by comparing the received actual parameters with the desired parameters and also to determine at least one, a modulus of elasticity E at least indirectly, ie directly or via further parameters. Via an appropriate line 9 In this way, certain parameters can be determined together with desired parameters and actual parameters as well as further parameters in a memory device 10 be stored in order to access such stored values for analysis and control purposes at a later date. The storage device 9 can also be in the controller 7 be integrated.

Optionally, such a machine 1 also with a tee 6 equipped, which is a discount knife 6.1 and before the first of the fixed points 3.1 is arranged. When detecting a paper tear behind the first of the fix Points 3.1 can the controller 7 via an appropriate line 6.2 the tee device 6 to control, by means of the blunt knife 6.1 the material web 2 to separate. As a result, a material web jam can be avoided. And in the area of the press section of the machine 1 If necessary, the pickup roller can be lifted.

The control device 7 is corresponding to detecting a paper tear between, for example, two different pressing means 12 . 13 which through the fixed points 3.1 . 3.2 be formed, and in the case of such a paper tear for determining the modulus of elasticity of the paper of the web 2 designed, actual torques M (i), M (i + 1) at least one of the drive means 5.1 . 5.2 and actual velocities v (i), v (i + 1) of the material web 2 between through the drive means 5.1 . 5.2 driven rollers 4.1 . 4.2 evaluate. It may be equivalent to the drive speed of the material web 2 as the actual speed v (i), v (i + 1) also a drive speed or rotational speed of the drive means 5.1 . 5.2 itself be recognized, which in particular in the case of transmission transmission between the drive device 5.1 . 5.2 and the correspondingly driven rollers 4.1 . 4.2 may be appropriate.

2 shows in the upper part of the diagram the time course of the states at the first pressing device 12 and in the lower part the conditions at the pressing device 13 , In the upper part are over time t a time course of a moment, in particular actual torque M (i) of the material web 2 at the drive group 4.1 at the first fixed point 3.1 outlined. In the diagram below, the velocity profile of the actual velocity v (i) of the material web is correspondingly 2 in the first fixed point 3.1 applied. In the second diagram below, a moment, in particular an actual torque M (i + 1) of the material web, is over a time course 2 at the drive group 4.2 at the second fixed point 3.2 outlined. In the diagram below, the actual velocity v (i + 1) of the material web 2 is correspondingly in the region of the second fixed point 3.2 illustrated. Recognizable is in a first lateral section up to the time tx with a continuous and undisturbed operation that the parameter values, that is, the actual torques M (i), M (i + 1) and the actual speeds v (i), v (i + 1) remain at an approximately continuously constant value. It is shown by way of example that during a course over the time t at a point in time tx last regular parameters can be detected, while immediately following a paper tear occurs, so that at a subsequent time tx + 1 already a fault condition of the paper machine 1 occured. In this case, the discrete points in time for the detection of the parameters are chosen such that in particular depends on the actual speed v (i) of the material web 2 a sufficiently fast and sufficiently accurate detection of a fault condition is ensured. The corresponding sampling interval can easily be determined by simple experimental investigations.

In the area of the paper rip preceding group, that is at the first fixed point 3.1 , a speed drop of the actual speed v (i) and an increase in torque of the actual torque M (i) can be detected. This is due to the fact that due to the applied paper train or train of the material web 2 it during production to pull the upstream pressing device 12 through the downstream pressing device 13 or, for example, a downstream aggregate comes. Once the paper breaks, this connection is no longer given. Therefore, the speed immediately drops at the first fixed point at the crack 3.1 and the drive device 5.1 at the first fixed point 3.1 must increase the torque to bring the actual speed v (i) back to the setpoint, that is the setpoint speed v_ref (i). Accordingly, results for the downstream group, that is, the drive device 5.2 at the second fixed point 3.2 , which pulls, when paper ripped an acceleration due to the excess moment. Therefore, the second drive means 5.2 at the second fixed point 3.2 take the moment back to set the local target speed v_ref (i + 1) again. Accordingly takes after the paper tear at the second fixed point 3.2 abruptly the actual speed v (i + 1) to, while the actual torque M (i + 1) decreases abruptly.

Mathematically, the following applies before the demolition: M (i) = M_ required (i) + M_paper-pull (i-1, i) -m_paper-pull (i, i + 1) with i as index for the drive group, here i = 1, M_ required (i) as the required torque at the i-th drive group and M_Paper pull the acting torque of the paper train between two consecutive drive groups.

After the demolition applies: M (i) = M_ required (i) + M_paper train (i-1, i), with i as index for the drive group, here i = 1, M_ required (i) as the required torque at the ith drive group and M_paper pull the acting torque of the paper train between two consecutive drive groups, here the upstream working group and the ith working group.

From the difference of the moments before the Ab Cracked and after the demolition you get the tensile moment.

Thus, during the course of the paper machine, the drive torques and the speeds of adjacent dryer groups are permanently adjusted by means of an algorithm and / or a circuit arrangement in the form of the control device 7 observed. If, at the same time, there is a variation of the actual parameters, as described above, then the algorithm or the control device detects 7 a band break of the web 2 , In this case, threshold values or certain limitations are taken into account, which must be exceeded in order to prevent tripping due to noise and system-related signal fluctuations. In addition, a comparison with the corresponding desired parameters, in particular the desired speeds v_ref (1), v_ref (i + 1), is carried out in order to rule out that the detected changes in the actual parameters are due to a variation of the paper tension between the adjacent drive groups have arisen.

While in principle a conversion to a single group, that is at a single fixed point 3.1 or 3.2 is possible due to the local parameters, preferably the temporal behavior of the moments, that is, in particular actual torques M (i), M (i + 1) of the two adjacent groups relationship as their drive means 5.1 or 5.2 analyzed. In addition, it is verified that no change in the desired speeds v_ref (i), v_ref (i + 1) is specified during the measurement. Optionally, in addition, the actual speed behavior of the drive devices 5.1 . 5.2 by comparing their actual velocities v (i) and v (i + 1), respectively, to make band-crack detection even safer.

3 exemplifies the basic principle of the method according to the invention with reference to a block diagram, wherein was dispensed with the presentation of a concrete circuit arrangement for detecting band breaks. These method steps can, via appropriate circuits or optionally also software-technologically, by a corresponding control algorithm for controlling a suitably designed processor in the control device 7 be implemented.

These are detection devices 16.1 to 16.4 provided by means of which at least one of an actual torques M (i), M (i + 1) and additionally the actual velocities v (i), v (i + 1) are determined. In a comparison device 15 comprising four comparison modules 11.1 - 11.4 For analysis, in each case one of the actual torques M (i), M (i + 1) at a first discrete time t and at a subsequent discrete time t + 1 or the corresponding desired speeds v_ref (i) and v_ref (i + 1). In this case, the values of the values entered later are set, for example, instead of the values first entered, and in each case a new later value is entered into the arrangement, so that a continuous monitoring is carried out on the basis of two values between two points in time.

The Acquisition of the values or parameters is preferably carried out continuously or at predefined time intervals, for example, in a common clock with a clock phase in the size of 0.05 to 3 seconds. Thus there There is only one time delay that is used (FiFo Buffer). Furthermore a torque limit M_Lim is input, which serves as a threshold value. For example, set a threshold with a deviation of 3% a continuously detected value of the actual torque M (i) allowed become.

The comparison modules 11.1 . 11.2 For comparing the torques, in each case both the values of the actual torque M (i) of the first drive device are obtained 5.1 as well as the actual torque M (i + 1) of the second drive means 5.2 fed. The same applies accordingly for the comparison modules 11.3 . 11.4 for comparing the desired velocities v_ref (i) and v_ref (i + 1), respectively, to the corresponding values of the desired velocities v_ref and v_ref2 of the two drive devices 5.1 respectively 5.2 be created. From the comparison modules, corresponding comparison values are output in the form of comparison or difference values M_Diff (i), M_Diff (i + 1), v_Diff (i) and v_Diff (i + 1).

The difference values M_Diff (i), M_Diff (i + 1) and v_Diff (i), v_Diff (i + 1) of the comparison device 15 become an evaluation device 17 supplied in which in the sub-evaluation facilities 18.1 to 18.3 the values are subjected to an evaluation and an output signal A is output, which indicates a band break bd or not. For this purpose, a signal or a value A is output due to the applied values in the event of a deviation of the torques within a period of time while the setpoint speed remains unchanged, which signal indicates a torque change and thus a possible belt break bd.

Based 4 is a principle for determining a demolition torque over a speed ratio v_rel (i) shown. For two different materials of exemplary material webs, two corresponding strip breakage torque values are sketched.

The function of the E-module detection is based on the duration of the speed stabilization after a paper tear in the range of typically one minute. Depending on the speeds and material of the material web 2 however, it is also possible to consider periods of time that deviate significantly from this. During the duration of the speed stabilization, it can be assumed that the environmental conditions, for example the effects of applied scrapers or of friction, do not change significantly. The demolition is at a tee position and is in previous groups the paper or the web 2 after the demolition cut off not in upstream groups, so the paper train or train, which remains on the web 2 acts, up to the tearing group, that is, with the actual torque M (i) present, for example, up to the first fixed point 3.1 receive. Thus, the tensile torque applied before the demolition can be determined by the variation in the applied moment.

Before the demolition applies accordingly: M (i) = M_ required (i) + M_Paper train (i-1, i) -M_Paper train (i, i + 1).

After the demolition applies accordingly: M (i) = M_ required (i) + M_paper train (i-1, i).

If now the actual torque M (i) is deducted before the demolition of that actual torque M (i) after the demolition, we obtain the tensile torque. Plotting these moments of tension or the paper draw above the speed ratio, which is also referred to as Draw, leads to the diagram according to FIG 4 , which is the modulus of elasticity of the material web 2 , that is in particular related to the elastic modulus of paper.

Cracks in the material web 2 , in particular cracks in a paper web, are more likely to occur at higher speeds or acting moments. Causes are usually lateral tears, holes or wrinkles. By a consistent recording of the paper tears can be good statements about the course of the upper range of the modulus of elasticity curve of the corresponding paper or the corresponding material web 2 be won. Before given are therefore appropriate parameters and parameters derived therefrom in the memory device 10 stored for direct and / or later analysis and use.

5 shows an example of a method for determining the modulus of elasticity of the material web 2 or a variable which at least indirectly describes it or a dimension corresponding to such a modulus of elasticity.

In some cases, it is possible to fall back on components or components issued values, which are already based on 3 are described. So it is back to the target speed v_ref (i), which the third comparison module 11.3 is fed, resorted to. The third comparison module 11.3 a time difference value t_diff of, for example, 30 s is applied as an additional input variable. A corresponding comparison relationship or difference value v_Diff (i), which of the third comparison module 11.3 is output, is again corresponding to an evaluation device 18.2 fed. Further input variables are a path test value t_FIFO * dependent on the clock rate t_FIFO and a trigger value t_trig.

The time difference value t_diff is also used as the control or clock quantity for the first comparison module 11.1 created or applied to its function corresponding further comparison module, which gets the first torque to the first time M (i) created as a comparison size. The moment difference, which as a comparison or difference value M_Diff (i) from the comparison module 11.1 is output directly for analysis and / or later use of the storage device 10 fed. In the storage device 10 Additional parameters and data are additionally stored, such as preferably the output value of the control device 7 , which corresponds to the modulus of elasticity E or a value corresponding to the modulus of elasticity E at cracking times or also to continuously recorded times. Reference parameters such as the speed ratio v_rel (i) assigned in each case in time are also preferably stored.

Advantageous Thus, by means of a novel procedure, a detection of band breaks with the sizes present in the drive system in a simple way. It can on a Application of separate bandrole sensors are dispensed with. Provided such separate tape tear sensors can be used, their Signal to be checked for plausibility. This is particularly interesting in single row dryer groups, in which reflection measurements by means of band-gap sensors only conditionally work reliably.

Particularly advantageous is the possibility of determining the absolute strip tension during a paper tear as well as an E-module-like size or in the ideal case of the modulus of elasticity E itself in the case of demolition. The modulus of elasticity provides an advantageously usable setting variable for a safe operation of the dryer section of a machine 1 This makes it possible, in particular, that the set speed difference can be correlated directly with the corresponding traction torque.

advantageous Areas of application are in particular press sections and dryer groups a paper machine and subordinate aggregates, such as coating units, Calender.

1

machine (Paper machine)

2

web

3.1

fixed point

3.2

fixed point

4.1

drive group (Roller)

4.2

drive group (Roller)

5.1

First driving means

5.2

Second driving means

6

cutting device

6.1

chopping knife

7

control device

8.1

management

8.2

management

9

management

10

memory device

11.1

first comparison module

11.2

second comparison module

11.3

third comparison module

11.4

fourth comparison module

12

First presser

13

Second presser

14

Filzband

15

comparator

16.1

detector

16.2

detector

16.3

detector

16.4

detector

17

evaluation

18.1

Unterauswerteinrichtung

18.2

Unterauswerteinrichtung

18.3

Unterauswerteinrichtung

18.4

evaluation

A

output

bd

Ligament signal

e

modulus of elasticity

i

index the drive group

L

Machine direction (direction of passage)

M

Actual torque

M (i)

Actual torque the i-th drive group

M (i + 1)

Actual torque the drive group following the i-th drive group

M_Diff (i)

comparison or difference value

M_Diff (i + 1)

comparison or difference value

M_erforderlich

Required torque

M_erforderlich (i)

Required torque

M_Lim

torque limitation

M_Papierzug

acting torque

M_Papierzug (i, i + 1)

acting torque

M_Paper train (i-1, i)

acting torque

Ms (i)

Target torque the i-th drive group

Ms (i + 1)

Target torque the drive group following the i-th drive group

t

Time

tx

time

tx + 1

time

t_diff

Time difference value

T_FIFO

clock speed (Common tact)

T_FIFO *

Bahnprüfwert

t_trig

trigger value

v (i)

Is speed the i-th drive group

v (i + 1)

Is speed the on the ith drive group

following

 drive group

v_diff (i)

 comparison or difference value

v_diff (i + 1)

comparison or difference value

v_ref (i)

 Target speed the i-th drive group

v_ref (i + 1)

Target speed the drive group following the i-th drive group

v_rel (i)

speed ratio

Yv_ref (i)

 manipulated variable the i-th drive group

Yv_ref (i + 1)

manipulated variable the drive group following the i-th drive group

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 20060070713 A1 [0003]
• - US 5289007 [0004]
• - EP 0660898 A1 [0005]
• - DE 10157915 A1 [0005]
• - DE 10157914 A1 [0006]
• - EP 1066515 B1 [0007]

Claims (12)

Method for detecting a crack and / or for determining a modulus of elasticity (E) of a material web ( 2 ), in particular fibrous web in a machine for producing the same between two fixed points ( 3.1 . 3.2 ), in which the material web ( 2 ) at the first of the fixed points ( 3.1 ) by means of a drive device ( 5.1 ) is driven at a desired speed (v_ref) and a measure corresponding to the modulus of elasticity (E) or a size of the material web (at least indirectly characterizing this) ( 2 ) is determined, characterized in that for determining the measure according to the modulus of elasticity (E) or a size that at least indirectly characterizing a torque curve of an actual torque (M) of the drive device ( 5.1 ) is recorded and evaluated. A method according to claim 1, characterized in that for detecting a paper tear, an increase of the actual torque (M (i)) of the drive device ( 5.1 ) is used as a decision criterion. A method according to claim 1 or 2, characterized in that for determining the measure according to the modulus of elasticity (E) or an at least indirectly characterizing magnitude actual torque (M (i + 1)) of a second drive means ( 5.2 ), which at the second fixed point ( 3.2 ) for driving the material web ( 2 ) is used. A method according to claim 3, characterized in that for detecting a crack of the material web ( 2 ) a falling of an actual torque (M (i + 1)) of the second drive means ( 5.2 ) is used. Method according to one of claims 1 to 4, characterized in that a decision of detecting a crack of the material web ( 2 ) is made dependent on a target speed (v_ref (i), v_ref (i + 1)) of at least one of the drive devices (v_ref (i), v_ref (i + 1)) that is not changed or only within a limit value ( 5.1 . 5.2 ). Method according to one of claims 1 to 5, characterized in that the detection of a crack of the material web ( 2 ) is performed depending on a comparison of the actual torques at different times and outside of a threshold value dependent tolerance range. Method according to one of claims 1 to 6, characterized in that for determining the modulus of elasticity or a size or a measure of this at least indirectly characterizing or corresponding to the modulus of elasticity (E) an acting moment on the material web ( 2 ) and / or an actual torque (M (i), M (i + 1)) at a time prior to a tear of the web ( 2 ) is applied over a speed ratio (v_rel (i)). Method according to one of claims 1 to 7, characterized in that by the method detected and / or certain parameters including the modulus of elasticity (E) or on the elastic modulus (E) related measure or at least indirectly characterizing this size in a memory ( 10 ) get saved. Device for detecting a crack and / or for determining a modulus of elasticity (E) or a size of a material web which at least indirectly characterizes it ( 2 ), in particular a paper web, with at least two fixed points ( 3.1 . 3.2 ), between which the material web ( 2 ) in a tensioned state, with at least one drive device ( 5.1 ) at the first fixed point ( 3.1 ) for driving the material web ( 2 ) in the direction of the second fixed point ( 3.2 ) and with a control device ( 7 ) for controlling the drive device ( 5.1 ) and / or for evaluating detected parameters, characterized in that the control device ( 7 ) an actual torque (M (i)) of at least the drive device ( 5.1 ) at the first fixed point ( 3.1 ) and designed to determine an increase in the actual torque (M (i)) and / or programmed to provide the elasticity modulus (E) calculated therefrom or a size of the material web which at least indirectly characterizes it ( 2 ) before an outline of the material web ( 2 ) behind the first fixed point ( 3.1 ) and / or for determining a measure corresponding to this modulus of elasticity (E) or a variable which at least indirectly characterizes it. Apparatus according to claim 9, characterized in that the control device ( 7 ) for detecting an actual torque (M (i + 1)) of a second drive device ( 5.2 ) at the second fixed point ( 3.2 ) is designed and programmed, the actual torque (M (i + 1))) of the second drive device ( 5.2 ) in addition to the actual torque (M (i)) of the drive device ( 5.1 ) of the first fixed point ( 3.1 ) for determining the modulus of elasticity (E) and / or the measure corresponding thereto. Device according to one of claims 9 or 10, characterized in that the control device ( 7 ) is designed and / or programmed to analyze a desired speed (v_ref (i), v_ref (i + 1)) of at least the drive device ( 5.1 ) at the first fixed point ( 3.1 ) for detecting a crack of the material web ( 2 ) when changing the actual torque ments (M (i), M (i + 1)) only in the case of the desired speed (v_ref (i), v_ref (i + 1)) remaining during the change equal to or within a tolerance threshold value. Device according to one of claims 9 to 11, characterized in that a memory device ( 10 ) for storing at least in the event of a detected crack of the material web ( 2 ) certain elasticity modulus (E) and / or this at least indirectly descriptive size is provided.