DE102020006637A1 - Process for monitoring a steel strip in a continuous press for material build-up and continuous press - Google Patents

Abstract

The invention relates to a method for monitoring at least one circulating steel strip (5a, 5b) in a continuous press (1) for material panels, in particular wood-based panels, for material build-up, with the steel strip (5a, 5b) being used to apply pressure to a press mat at a preselected strip speed is exercised to create the material panel, and wherein the circulating steel strip (5a, 5b) is monitored via at least one optoelectronic detector (2) at least on one side of the steel strip (5a, 5b) for material buildup, in that a light transmitter (14) generates a light pattern ( 16) onto the steel strip (5a, 5b) and a light receiver (15) records the light pattern (16) using the reflection method and forwards it to an evaluation unit (3), which detects changes. In order to keep the maintenance effort to find a harmful material adhesion low, it is proposed that material adhesions detected on the steel strip (5a, 5b) after the start of the detector measurement (27) with an absolute or relative time or distance distance value to each other to the Evaluation unit (3) are passed on.

Description

The invention relates to a method for monitoring a circulating steel strip in a continuous press for material panels, in particular wood-based panels, for material build-up, with the steel strip being used to exert pressure on a press mat to produce the material panel at a preselected strip speed.
and wherein the circulating steel bath is monitored for material buildup at least on one side of the steel strip via at least one optoelectronic detector,
a light transmitter sends a light pattern onto the steel strip and a light receiver records the light pattern using the reflection method and forwards it to an evaluation unit that detects changes.

The invention also relates to a continuous press with an optoelectronic monitoring device for carrying out the method.

A camera is usually used as the light receiver.

In this invention, material adhesions are to be understood as meaning deposits from detached parts of the press mat, which due to their properties adhere to the steel strip. In the following, these material adhesions are sometimes also referred to as caking.

Typically, material panels, for example made of wood fibers or chips, are produced in a continuous pressing process in which material mixed with binding agent and scattered to form a press mat is formed between two rotating steel belts and hardened. In principle, however, fibers made of other materials, e.g. B. plastics, (co-) be used.

If parts that still contain adhesive or binding agent come loose from the press mat, it can easily happen that chips, for example, get stuck on the steel strip, which leads to undesirable elevations on the steel strip. The surface of the material panels is particularly influenced by the surface structure or surface quality of the steel strips. With the pressure applied, the local elevations caused by material adhesions on the steel strip are pressed into the press mat with each revolution, causing local damage to the subsequent plate. An even and uniform product surface is desirable, particularly with ultra-thin panels, and material buildup on the steel strip can have such a negative impact on the product that it can even lead to rejected panels.

Furthermore, the steel strip is the most expensive individual component of a continuous press. Due to the design and sometimes high belt speeds of > 2 m/s, manual monitoring for typical damage patterns during operation is hardly possible. Harmful operating behavior is only recognizable when the steel strip is at a standstill and inspected, and this is only possible to an insufficient extent due to the installed condition. However, a continuously acting cleaning device, for example by using a (rotating) cleaning brush with or without the addition of solvents, can only keep the surface of the steel strip clean to a limited extent. If this cleaning device constantly acts on the steel strip, it can even have the unpleasant consequences of increased wear.

In addition, material deposits on the steel strip at these points cause greater pressure on the steel strip as soon as it enters the press nip. This can have a negative impact on the steel strip and permanently damage it, which can result in plastic deformation that is reflected in the material panels produced.

The inspection of such a steel strip for material adhesions when it is stationary is very time-consuming, because such a strip can be up to 200 m long. When checking the steel strip, any material adhesion must be manually searched for and removed.

It is known to use optoelectronic detectors to monitor steel strips in the paper industry, where steel strips that apply pressure to the paper web must be monitored during calendering. An example of such a procedure is EP 2304105 B1 described. In the paper industry, however, one has less to do with sticky buildup, so that in the EP 2304105 B1 described detector is used only for the detection of cracks or deformation in the steel strip.

It is the object of the invention to obtain automated information about any buildup of material on the steel strip and to make detected material buildup easily accessible for cleaning work.

The object is achieved in terms of the method with the features of claim 1 and in particular in that material adhesions detected on the steel strip after the start of the detector measurement with an absolute or relative time or the distance between them can be forwarded to the evaluation unit.

The continuity of the reflection pattern is monitored to detect material adhesion. If the reflective steel strip surface is covered with a material adhesion (mostly wood, non-reflective), the reflection pattern is interrupted at this point. The deviation from the original sample is evaluated by the camera and the corresponding evaluation software of the evaluation unit.

In this way, however, the distances of the individual material adhesions on the steel strip determined by the detector measurement are also known. After one revolution of the belt, the same material build-up is detected again and again, so that the coordinates between the material build-ups are determined during operation, for example by calculating the time distance using the preselected belt speed. This clearly defines the exact location of the material adhesion on the belt. The size of the material adhesion is determined from the reflection measurement, so that a limit value can be set from which intervention is required.

It is particularly advantageous if the steel strip is provided with a reference marking that is used by the optoelectronic detector as the starting point for the detector measurement.

Such a starting point can be, for example, the point in time or space at which the camera is pointed when the tape starts. With the help of the known increase in speed and the known length of the steel strip, the instantaneous location of the point can be calculated at any time.

A reference marking can be a marking that is either detected by the optoelectronic detector itself or a marking detection by another sensor that forwards this point to the evaluation unit.

In the first case, for example, a punctiform or linear color marking high in contrast to the steel strip can be defined as a reference marking or, in a particularly simple manner, the connecting weld seam of the steel strip, which is easily recognizable for an optoelectronic detector system, can be used. With each rotation of the steel belt, the reference marking is re-recorded by the detector system in a trigger-like manner and the time or distance value to a material adhesion is continuously and precisely determined in just one belt revolution.

If the reference marking is not detected by the optoelectronic detector, it can also be recorded by another sensor and transmitted to the optoelectronic detector as a start signal. For example, an inductive sensor that reacts to one or more notches in the steel strip can be used here. However, the drive signal from the motors driving the steel belt - for example via a belt deflection drum - can also be used to precisely trigger the starting point or reference point.

This eliminates slip-dependent displacements that can occur compared to the starting point of the measurement, which is only determined once when the continuous press is started. The starting point of the detector measurement is thus set anew with each revolution by the reference mark.

It is preferred that a time specification is also stored with each passage of a material adhesion through the optoelectronic detector.

In addition, it is advantageous if the image size of the material adhesion is compared with one of the previous runs during at least one further run of a material adhesion through the optoelectronic detector.

In this way, the size development of the material adhesion over time can be traced. If a previously defined limit value is exceeded or approached, a warning signal can also be generated automatically. The real-time data are provided with a time specification and stored in a database. This means that the local changes in the steel strip over time can also be traced. If, for example, the steel strip experiences increased material buildup within a short period of time, this circumstance can be compared with process parameters in order to detect possible causes and avoid further material buildup. The general condition and quality of the steel strip can also be easily monitored.
It should be pointed out that the evaluation unit can also be programmed to be self-learning, so that after a learning phase it can independently and automatically emit a warning signal when the material buildup develops in a certain way.

In a particularly preferred manner, the evaluation unit generates a preferably two-dimensional developed image of the steel strip with the representations of material adhesion on a monitor.

In this rectangular representation of the steel strip, the coordinates of each material adhesion can be entered through the known position. The development of each material adhesion is quickly recognizable via a planned possibility of scrolling over time. By recognizing the point in time at which a material buildup occurred, determining the cause is significantly simplified.

It is preferred to move a harmful material adhesion to a suitable cleaning position and to stop there, taking into account the stored time or distance distance value in relation to the starting point of the detector measurement in the evaluation unit. There the material adhesion is at least partially removed manually or with a cleaning device. The cleaning device can be implemented, for example, by an adjustable rotating brush, which does not have to extend over the entire width of the steel strip, but can be designed to traverse if necessary. In addition or as an alternative, cleaning agents or solvents can be sprayed onto the steel strip.

Since the distance of each material adhesion is recorded and stored, for example, from the reference marking, a material adhesion recognized as critical and requiring maintenance can be easily moved to a specific position at a defined (slower) feed speed of the steel strip, where this point can be easily reached and cleaned can. This makes it particularly easy for the maintenance staff to find and remove material build-up. For this purpose, it can be provided in terms of software to simply click on the material adhesion on the monitor in the two-dimensional representation of the steel strip using a pointing device (mouse). If the user decides to remove a material adhesion on the steel strip, he can select the caking in the visual output, whereby the system control moves the damaged area to a previously selected cleaning position. There, the site can be cleaned manually or by means of the cleaning device specified as an example. The cleaning device should then be activated or can only be activated when the material adhesion is in the cleaning position so that the steel strip is not constantly stressed. Due to the material contact between the cleaning device and the steel strip, natural wear occurs due to abrasion on the steel strip surface. It is therefore desirable to keep the intervention time as short as possible. The invention makes this possible without the plant operator having to do anything.

The color and/or brightness of the light transmitter is preferably adjusted with the aid of a calibration device in the field of view of the light receiver.

This leads to the minimization of disturbing environmental influences on the camera system, such as changed hall lighting, lateral incidence of light, changed color temperature of the environment, and different properties of the steel strip present. For this purpose, the light transmitter is suitable, for example, for emitting any desired wavelengths (for example by using an RGB LED). Corresponding environmental effects can be compensated for by adjusting the light intensity and hue. For example, in the case of reddish ambient light, a blue light pattern should be selected in order to achieve maximum contrast with the surroundings. To determine the ambient conditions, for example, there is a specially printed calibration disc as a calibration device in the camera's field of view. Since the color tone of the light pattern of this pane is known, the environmental conditions can be determined using the software.

• - wenigstens einem umlaufenden Stahlband zur Verdichtung einer bewegten Pressmatte mittels aufgebrachtem Druck durch Druckgeber,
• - mit einer Steuerung zur Regelung der Stahlbandgeschwindigkeit und
• - mit einer optoelektronischen Überwachungsvorrichtung, die einen Lichtsender umfasst, der ein Lichtmuster auf das Stahlband sendet, und einen Lichtempfänger, der geeignet ist, im Reflexionsverfahren das Lichtmuster aufzunehmen und an eine Auswerteeinheit weiterzugeben, die Veränderungen feststellt,

zur Durchführung des Verfahrens gemäß einem der Ansprüche 1 bis 7 gelöst und insbesondere dadurch,
dass das Stahlband einen Anfangspunkt der Detektormessung aufweist, der von dem fixierten optoelektronischen Detektor erfassbar ist, und dass alle weiteren erkannten Materialanhaftungen mit einem Zeit- oder Abstands-Entfernungswert von diesem Anfangspunkt der Detektormessung an die Auswerteeinheit weitergebbar und dort abspeicherbar sind. In terms of device, the task is carried out by a continuous press

• - at least one circulating steel belt for compacting a moving press mat by means of pressure applied by pressure transmitters,
• - with a controller for regulating the speed of the steel belt and
• - with an optoelectronic monitoring device, which includes a light transmitter that sends a light pattern onto the steel strip, and a light receiver that is suitable for recording the light pattern in the reflection process and forwarding it to an evaluation unit that detects changes,

for carrying out the method according to one of claims 1 to 7 and in particular by
that the steel strip has a starting point of the detector measurement, which can be detected by the fixed optoelectronic detector, and that all other detected material adhesions with a time or distance value from this starting point of the detector measurement can be passed on to the evaluation unit and can be stored there.

• - wenigstens eine erfasste Materialanhaftung bei jedem Durchlauf durch den optoelektronischen Detektor in der Auswerteeinheit mit einer Zeitangabe versehbar sein, und/oder
• - eine zweidimensionale Abbildung des Stahlbandes auf einem Monitor, der mit der Auswerteeinheit gekoppelt ist, mit Materialanhaftungen darstellbar sein, und/oder
• - der Antrieb des Stahlbandes mit Hilfe der Steuerung zur Regelung der Stahlbandgeschwindigkeit geeignet sein, aufgrund von aufgezeichneten Abständen zwischen dem Anfangspunkt der Detektormessung und der Materialanhaftung, kritische Materialanhaftungen an eine Wartungsstation zu fahren.

As already explained in more detail in the method claims, it should also be preferred

• - at least one detected material adhesion can be provided with a time indication in the evaluation unit during each passage through the optoelectronic detector, and/or
• - A two-dimensional image of the steel strip can be displayed on a monitor, which is coupled to the evaluation unit, with material adhesions, and/or
• - the drive of the steel strip with the help of the controller for regulating the speed of the steel strip should be suitable for driving critical material buildup to a maintenance station based on recorded distances between the starting point of the detector measurement and the material buildup.

It is also advantageous if at least one line of light extending across the width of the steel strip is used as the light pattern.

• 1 den Einlauf einer kontinuierlichen Presse und schematisch den Detektor und die Auswerteeinheit,
• 2 einen Lichtsender,
• 3 ein Lichtmuster auf dem Stahlband
• 4a bis 4c die Veränderung des reflektierten Lichtmusters bei Bewegung des Stahlbandes mit einer Materialanhaftung und
• 5 die Darstellung des Stahlbandes auf einem Monitor.

The invention is explained in more detail below with the aid of the figures. show it

• 1 the inlet of a continuous press and schematically the detector and the evaluation unit,
• 2 a light transmitter,
• 3 a light pattern on the steel strip
• 4a until 4c the change in the reflected light pattern when the steel strip moves with material adhesion and
• 5 the display of the steel strip on a monitor.

In 1 one can see the inlet area of a continuous double belt press 1, as is used for the production of material boards, in particular material boards made of wood-based materials. It is shown that the continuous press 1 in its basic structure has an upper press part 1a with an upper heatable pressure plate 7a and a lower press part 1b with a lower heatable pressure plate 7b. Frame 12, in which pressure transmitters 8 are also supported for pressure generation, connect the press upper part 1a and the press lower part 1b. In the press upper part 1a and in the press lower part 1b, endlessly circulating steel belts 5a, 5b are guided to form a press gap for the press mat, not shown, the steel belts 5a, 5b being supported against the pressure plates 7a, 7b with the interposition of rolling rods 10. The roller bars 10 are guided by means of roller bar bearing bolts on endlessly revolving roller bar chains, which, however, are not shown. The chains are guided over the chain deflection rollers 11 indicated by dot-dash lines.

The steel bands 5a, 5b are guided in a circumferential manner over upper and lower band deflection drums 9a, 9b. Of course, such belt deflection drums are also provided analogously at the end of the press, which is not shown. For reasons of clarity, the continuous double belt press 1 is not shown as a whole, because the steel belt 5a, 5b can be up to two hundred meters long.

In the inlet area of the continuous press 1 shown, the upper steel strip 5a and the lower steel strip 5b form an inlet gusset for the press mat (not shown), which is also referred to as the inlet mouth 6 .

In the exemplary embodiment, an optoelectronic detector 2 is installed in front of each tail pulley 9a, 9b. This optoelectronic detector 2 consists of a light transmitter 14, for example an LED strip, and a light receiver 15, for example a camera system. Depending on the width of the press, the images from multiple cameras can be combined across the width into one image. The light emitter 14 consists of at least one light source, which projects a light pattern 16 directly or indirectly onto the reflective steel strip surface. In the exemplary embodiment, the light pattern 16 is projected onto the circumference of the rollers of the deflection drums 9a, 9b and hits the steel strip surface of the upper or lower steel strip 5a, 5b here. There is high belt tension on the deflection drums 9a, 9b, as a result of which the steel belt 5a, 5b rests directly on the circumference of the drum. The camera system 15 captures both the projected light pattern 16 and the surrounding steel strip surface in a camera detail. Due to the uniform reflection properties of an undamaged and cleaned steel strip 5a, 5b, the projected light pattern 16 is reflected unaltered and captured by the camera system 15. The light pattern 16 can be embodied in various forms. Checkerboard patterns, grid lines, colored image projections, etc. can be used. In this exemplary embodiment, at least one horizontal line should be shown across the width of the steel strip. In principle, however, the light pattern can also be projected onto other points on the steel strip 5a, 5b which are not running around a deflection drum 9a, 9b.

The reflected line recorded by the camera system is sent to an evaluation unit 3 and can be examined there for changes. The reflected line can also be displayed on a monitor 17. If material buildup affects the area of the light pattern 16 applied to the surface of the steel strip by the light transmitter 14, in this example a line, the reflection recorded by the camera system 15 will change or even disappear completely.

show as an example 2 a light transmitter 14 and 3 a light pattern 16 on a steel strip. The light emitter here includes, for example, a light source 19 in the form of a steel strip-wide LED bar, a screen 21 and a diffuser 20. The arrows indicate that two lines of light are emitted. These form in the form of two lines as a light pattern 16 on the steel strip 5, 5a, 5b. The camera section 23 is also indicated as an example tet, who observes this reflected light pattern as it were when the steel strip 5, 5a, 5b runs.

Different principles of action can be used to detect the material adhesions mentioned. Geometric deformations in the surface of the steel strip change the angle of emergence of the reflection of the light pattern 16 and thus optically lead to a curvature of the projected light pattern. But as a rule, the light pattern is no longer reflected when it runs over a material adhesion. The deviation from the original pattern is detected by the light receiver 15 and the corresponding evaluation software in the evaluation unit 3 .

Due to the fixed position of the light transmitter 14 and light receiver 15 (camera system), the position of the light pattern 16 relative to the camera section 23 is initially constant. Due to the continuous circulation of the steel strip, the light pattern iteratively scans every surface point of the steel strip. If an adhesion of material passes through the light pattern 16, the effect just explained arises.

The position of the material adhesion in relation to the width of the steel strip results from the conversion of the strip or surface section that is not reflected in the image to the real width of the steel strip. The position in the running direction can also be determined by software. For this purpose, the path of the steel strip can be followed, for example, via a reference mark or simply from the starting point of the steel strip. Furthermore, existing features such as the weld seam can be used as a trigger-like synchronization feature. Since the speed of the steel strip 5 is constantly measured by a sensor 13 and the length of the steel strip is known anyway, the exact determination of the location of a material adhesion based on the strip length from a starting point of the detector measurement or a reference point is not a problem.

For a better understanding of the reflection phenomenon, the 4a until 4c as a chronological sequence, i.e. quasi as individual images of a film, how a material adhesion 25 can be recognized and assessed. In 4a a possible camera section 23 can be seen with a line as a light pattern 16 on a steel strip 5, the light pattern 16 just not sweeping over any material adhesion 25. The arrow indicates the direction of the steel strip circulation. Above the line, ie approaching the light pattern, there is a geometric material adhesion 25 on the steel strip surface, which later touches the light pattern, ie the line 16, with its edge region as the strip rotates. As a result, a failure of the reflection can be determined (cf. 4b) until the center of material adhesion is on the light pattern line. the Figure 12 shows the material attachment leaving the light pattern 16 and the light pattern going solid again.

When material adhesion is detected, the position and size are stored in a database of the evaluation unit 3 . If desired, a message can then be sent to the plant manager according to predefined rules. The plant operator can use an optional monitor 17 to manually assess the condition of the steel strip and determine whether partial repairs are necessary.

5 shows a schematic representation of the tape 5 in the unwound state 24 with its material adhesions on a monitor 17. The left edge of the tape 27 corresponds to the starting point of the detection. After a system standstill, the software can output the exact coordinates 29 by clicking on a corresponding material adhesion 25 (see cursor 26 indicated) in relation to the starting point of the detection 27. Furthermore, the steel strip 5 can be moved to a previously defined Move to cleaning position 18. In 1 indicates that the cleaning position 18 can be provided with a cleaning brush 18a that can be set against the steel strip 5, 5a, 5b. Alternatively, any other form of cleaning agent, including the spraying of liquid solvents, is also included here. This saves the operator from having to manually search for the location of material adhesion.

Not only are the exact coordinates 29 displayed on the development 24 for the clicked material adhesion, but also a time indication 30 is assigned, for example on the right side of the monitor, in which the material adhesion 25 had the size shown, with the development of the size being recorded via the time selection button 28 can be traced.

Reference List

1

continuous double belt press

1a

Upper part of the press

1b

Lower part of the press

2

optoelectronic detector

3

evaluation unit

4

Steel belt speed control

5a

Upper steel band

5b

Lower steel band

6

inlet mouth

7a

Upper pressure plate

7b

Lower pressure plate

8th

pressure transmitter

9a

Upper idler pulley

9b

Lower idler pulley

10

roller bars

11

chain pulleys

12

frame

13

Steel belt speed sensor

14

light transmitter

15

Light receiver, camera system

16

Light pattern, here line

17

monitor

18

cleaning position

18a

Attachable cleaning brush

19

light source

20

diffuser

21

cover

22

calibration device

23

camera cutout

24

Developed representation of the steel strip 5

25

material adhesion

26

cursor

27

Starting point of detection

28

timer button

29

coordinates

30

time indication

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2304105 B1 [0010]

Claims (12)

Method for monitoring at least one circulating steel belt (5a, 5b) in a continuous press (1) for material boards, in particular wood-based material boards, for material build-up, with the steel belt (5a, 5b) applying pressure at a preselected belt speed to a press mat to produce the material board is exerted, and wherein the circulating steel strip (5a, 5b) is monitored via at least one optoelectronic detector (2) for material adhesions at least on one side of the steel strip (5a, 5b), in that a light transmitter (14) projects a light pattern (16) onto the steel strip (5a, 5b) and a light receiver (15) picks up the light pattern (16) in the reflection process and forwards it to an evaluation unit (3) which detects changes, characterized in that on the steel strip (5a, 5b) after the start of the Detector measurement (27) detected material build-up with an absolute or relative time or distance distance value to each other at the off value unit (3) are passed on. procedure according to claim 1 , characterized in that the steel strip (5a, 5b) has a reference mark which is used by the optoelectronic detector as the starting point of the detector measurement (27). procedure according to claim 1 or 2 , characterized in that with each passage of a material adhesion (25) through the optoelectronic detector (2), a time specification (30) is also stored. Method according to one of Claims 1 until 3 , characterized in that during at least one further run of a material adhesion (25) through the optoelectronic detector (2), the image size of the material adhesion (25) is compared with one of the previous runs. Method according to one of Claims 1 until 4 , characterized in that the evaluation unit (3) generates a preferably two-dimensional developed representation (24) of the steel strip (5a, 5b) with the material adhesion representations on a monitor (17). Method according to one of claims 3 until 5 , characterized in that a harmful material adhesion (25), taking into account the stored time or distance distance value in relation to the starting point of the detector measurement (27) in the evaluation unit (3) to a suitable cleaning position (18) and there manually or with a cleaning device is at least partially removed. Method according to one of Claims 1 until 6 , characterized in that the color and/or brightness of the light transmitter (14) is set in the field of view of the light receiver (15) with the aid of a calibration device (22). Continuous press with - at least one circulating steel belt (5a, 5b) for compacting a moving press mat by means of pressure applied by pressure transducers (8), - with a controller (4) for regulating the speed of the steel belt and - with an optoelectronic monitoring device (2), which Includes a light emitter (14) which sends a light pattern (16) onto the steel strip (5a, 5b), and a light receiver (15) which is suitable for recording the light pattern (16) using the reflection method and forwarding it to an evaluation unit (3), determines the changes to carry out the method according to one of Claims 1 until 7 , characterized in that the steel strip (5a, 5b) has a starting point for the detector measurement (27) and in that all other detected material build-ups with a time or distance value from this starting point for the detector measurement can be passed on to the evaluation unit (3) and can be stored there . Continuous press according to claim 8 , characterized in that at least one detected material adhesion (25) can be provided with a time indication (30) in the evaluation unit (3) during each passage through the optoelectronic detector (2). Continuous press according to claim 8 or 9 , characterized in that a two-dimensional image of the steel strip (5a, 5b) as a development 24 can be displayed on a monitor 17, which is coupled to the evaluation unit 3, with material adhesions. Continuous press according to any of Claims 8 until 10 , characterized in that the drive of the steel strip (5a, 5b) with the help of the controller (4) is suitable for regulating the speed of the steel strip, based on recorded distances between the starting point of the detector measurement (27) and the material adhesion, critical material adhesions to a cleaning position ride. Continuous press according to any of Claims 8 until 11 , characterized in that at least one light line extending across the width of the steel strip is used as the light pattern (16).

Images