EP3509832A1

EP3509832A1 - Wood material panel hot press and method for operating a wood material panel hot press

Info

Publication number: EP3509832A1
Application number: EP17758202.0A
Authority: EP
Inventors: Peter Dröge
Original assignee: Swiss Krono Tec AG
Current assignee: Swiss Krono Tec AG
Priority date: 2016-09-07
Filing date: 2017-08-31
Publication date: 2019-07-17
Also published as: CN109789658A; RU2019103149A3; UA123712C2; US20190176425A1; KR20190043612A; JP2019529114A; DE202017007606U1; AU2017324217A1; US12059861B2; CA3033692A1; JP2022176941A; CN109789658B; RU2019103149A; MX2019001873A; AU2022215296B2; WO2018046390A1; BR112019004443A2; AU2022215296A1; ZA201900983B; CA3033692C

Abstract

The invention relates to a wood material panel hot press for producing a wood material panel (32), wherein the wood material panel hot press (12) has an inlet side (30) and an outlet side (34) and is designed to press a blank (18) supplied on the inlet side (30) in order to form a wood material panel (32). According to the invention, a temperature measurement device (36) is provided, which is designed to automatically measure the temperature (T) of the wood material panel (32) on the outlet side (34) in a spatially resolved manner.

Description

Wood-based panel hot press and method for operating a wood-based panel hot press

The invention relates to a wood-based panel hot press for producing a wood-based panel according to the preamble of claim 1. According to a second aspect, the invention relates to a method for operating such a wood-based panel hot press.

Such wood-based panel hot presses are used, for example in the production of HDF panels, to press a fiber cake to the wood-based panel. Such hot presses work continuously, but are stopped when, for example, a damage is to be repaired or when a wood-based material board with a different plate thickness is to be produced.

It is desirable to be able to operate such a hot press at the highest possible speed. However, if the feed rate is too high, errors occur in the wood-based panel produced. For example, near-surface material defects, so-called splitters, can arise, which are caused by vapor bubbles forming in the resulting wood-based panel and causing material to break away. The optimum process parameters for operating such a wood-based panel hot press are selected by the machine operators on the basis of experience. It is not known whether the optimum feed rate can be achieved in this way.

It has been proposed to reduce scrap during start-up by not regulating the temperature of a press belt of the wood-based panel hot press but controlling the heat output from the hot press. While this approach reduces the level of the committee, further reduction of the committee is desirable.

From EP 1 526 377 A1 a generic wood-based panel hot press is known. The thermal camera is used to identify and discard defective wood-based panels or the speed with which the hot press works, monitor. For this purpose, thermograms recorded with the infrared camera are compared with reference thermograms. In this way, it is indeed possible to prevent faulty wood-based panels from being processed further and that rejects due to an incorrect flow velocity can be avoided. It helps to further reduce the reject rate. From WO 01/35086 A2 a device for the non-contact examination of test specimens is known, in which a thermographic camera for detecting surface imperfections is used. In the paper by P. Meinlschmidt "Thermographical detection of defects in wood and wood-based materials", 14th international symposium of nondestructive testing of wood, Hannover, Germany, May 2 to 4, 2005, it is described that thermography for the detection of It is described in US 2001/0042834 A1 how defects can be detected by creating a computer-generated model after taking a first image, the differences between a second recorded image and the results obtained on the basis of an image of the model are compared.

From EP 2 927 003 A1 it is known to detect the spatial temperature distribution in order to obtain a printed image in a subsequent printing, which changes as little as possible over time. Such a method is suitable to compensate for any inhomogeneities in the temperature distribution subsequently, but not to avoid them.

The invention has for its object to improve the production of wood-based panels. The invention solves the problem by a generic wood-based panel hot press with the features of claim 1. According to a second aspect, the invention solves the problem by a method having the features of claim 7. The invention is based on the finding that the surface temperature of the wood-based panel at the outlet side so accurately characterizes the thermal and mechanical processes within the wood-based panel hot press that it is sufficient for controlling the process parameters of the wood-based panel hot press. This is surprising insofar as it has long been known from the prior art to detect the temperature within the wood-based panel hot press. However, it has been found that the temperature sensors used so far are not able to provide a usable signal for the control. Thus, known temperature sensors are located at a relatively large distance from the surface of the resulting wood-based panel. In other words, in the prior art, the temperature is not measured on the surface of the wood-based panel, but a temperature of the press itself. If the heat transfer from the press into the wood-based panel changes, this will change the properties of the panel, even if the temperature of the wood-based panel - Plate hot press remains constant.

It has also surprisingly been found that the surface of the wood-based panel at the outlet side can have locally strongly differing temperatures. It is therefore possible in wood-based panel hot presses from the prior art that the temperature measured in the interior at a location does not change, but the distribution of the temperature in the wood-based panel and thus the (local) error rate.

It has been found that the temperature, in particular the surface temperature, of the wood-based panel at the exit side allows such an extensive insight into the pressure and temperature conditions in the wood-based panel hot press that further parameters for the regulation of the wood-based panel hot press are dispensable , Although it is possible to use other parameters for control, but this is not necessary. Thus, it is advantageously possible to compensate for temperature differences on the surface of the wood-based panel by controlling at least one process parameter. As a result, the homogeneity of the wood-based panel along its width direction is increased, so improved. Thus, the wood-based panel hot press can be driven at a higher feed rate, until it comes to errors in the wood-based panel. In addition, since the temperature of the wood-based panel is measured directly, it can be determined, as provided in accordance with a preferred embodiment, by comparing these temperatures with a desired temperature, whether the heat transfer from the wood-based panel hot press to the resulting wood-based panel in a predetermined destination Interval is. For example, if the actual temperature of the wood-based panel averaged over the width deviates by more than a predetermined threshold value from the press belt temperature of a press belt of the wood-material panel hot press measured by means of a preferably existing press belt temperature measuring device, a warning signal can be output. This indicates that the heat transfer from the hot press into the resulting wood-based panel is disturbed. This can for example be counteracted by the fact that the feed rate is reduced. Alternatively or additionally, moisture of the fiber cake can be reduced, for example by reducing or suppressing spraying with a liquid.

When the temperature is measured without contact, contact conditions between a temperature sensor and the wood-based panel play no role. The measurement is therefore particularly accurate. It has also been found that the

Surface properties of the wood-based panel so little change that a non-contact measurement, for example, with an infrared camera, has only a low systematic uncertainty. In the context of the present description, the wood-based panel is understood in particular to be a fibreboard, an HDF board, an OSB board or a chipboard. It is particularly favorable if the fiber cake is fed continuously. In other words, it is favorable if the wood-based panel hot press is a continuous press.

The temperature measuring device is understood to mean, in particular, a device by means of which a measured value can be generated which correlates to the temperature, in particular the surface temperature, of the wood-based material panel in such a way that it can be used to determine the temperature. It is possible, but not necessary, in that the temperature measuring device is designed to measure the temperature with respect to a temperature scale. Although it is particularly advantageous if the temperature measuring device indicates the temperature in Kelvin, degrees Celsius or with respect to another temperature scale. But it is also possible that only a temperature change is measured to a predetermined reference temperature, for example, the temperature of the fiber cake on the inlet side or any, but firmly selected reference temperature. It is also sufficient that there is an example electrically or coded present temperature signal. For example, the temperature may be represented by an electrical voltage, a resistance or a wavelength of the highest spectral power density.

Non-contact measurement is understood to mean that no physical contact between the wood-based panel and the meter is necessary to determine the temperature.

By spatially resolved measurement is meant, in which at least three, preferably at least five, in particular at least ten measured values are recorded along a width dimension of the wood-based material board. It is expedient and represents a preferred embodiment that at least one point exists at which two or more temperature measured values are recorded in succession with respect to a material flow direction of the wood-based panel by the wood-based panel hot press. It is possible and preferred to mittein over at least two, preferably more, in this way consecutively measured temperatures in order to obtain a temporally less fluctuating measured value for the temperature.

Preferably, the temperature measuring device is designed for spatially resolved measuring the temperature over at least 80%, in particular at least 90%, preferably 100% of the full width of the wood-based material board. The process parameter, which can also be called process parameters, is understood to mean, in particular, a variable machine parameter which influences the temperature and / or the temperature distribution of the wood-based material board on the outlet side. For example, the process parameter is the feedrate speed of the fiber cake, the heating capacity of at least one heating circuit o- of the pressing pressure. The process parameter can be a vector, that is to say an ordered n-tuple, for example the vector which (i) the pressing pressure at different points of the hot press and / or (ii) the heating power of the heating circuits and / or (iii) at least one Position of a frame to which the press belt or a press belt force transmitting device is attached, and / or (iv) a position of a pressing force on the press belt transmitting component relative to the frame. The process parameters are in particular one, two or more variables selected from the list comprising: the pressing pressure at a first position, the pressing pressure at a second position different from the first position, the pressing pressure at one of the first and the second second position different, third position, the temperature at a first position, the temperature at a different from the first position second position, the temperature of a different from the first and the second position, third position, the heating power of a first heating line, the heating power a second heating line different from the first heating line, the total heating power, the moisture content of the fiber cake, the temperature of the fiber cake, the ambient temperature and a feed rate at which the wood-based material board moves in the material flow direction. The feed rate is changed in particular by controlling at least one drive with which a conveyor belt is driven, on which the fiber cake and / or the wood-based material board rests. According to a preferred embodiment, the temperature measuring device is designed for continuously measuring the temperature. This is understood in particular to mean that the temperature is measured repeatedly. In particular, the temperature measuring device is set up for automatic recording of temperature measured values at least every ten seconds, preferably every five seconds, in particular at least once per second. It has proven to be particularly favorable if temperature measured values are recorded at least five times per second. This allows a quick response to any changes in temperature. According to a preferred embodiment, the temperature measuring device is designed for low-delay measurement of the temperature. A low-delay measurement of the temperature means that between the beginning of the measuring process and the presence of the measurement result, half the time required for a volume element to travel through the wood-based panel hot press, in particular at most ten seconds, preferably at most one second passes. In other words, the measured temperature gives a very good approximation of the instantaneous temperature of the wood-based panel and not a temperature that the panelboard had a long time ago. In other words, the temperature measuring device for measuring the temperature is designed so that the temperature measurement can be considered in a sufficiently good approximation as instantaneous.

Under the feature that the temperature measuring device is designed for measuring the temperature at the outlet side, is in particular understood that a distance between the point at which the heat transfer from the hot press to the wood material panel ends, and the first point in the material flow direction on the temperature is measured, not more than 2 m, preferably at most 1 m. The greater the distance between the hot press and the location at which the temperature is measured, the greater the influence, for example, of convection on the measurement result, so that the significance of a measurement result obtained at a large distance is lower, which is undesirable.

The temperature measuring device comprises an infrared camera. This infrared camera is, for example, a video camera which is designed to take several pictures per second. The advantage of an infrared camera is that a large number of individual temperature measuring points can be recorded with one measuring process. Preferably, the infrared camera is a CCD camera having a corresponding CCD chip. This CCD chip preferably has at least 200 × 50 pixels. With an infrared camera, the temperature of the wood-based panel can be determined quickly and reliably with high accuracy. The wood-based panel hot press has a control unit configured to automatically perform a method comprising the steps of (a) detecting a first side temperature at a first location in a left side region of the wood-based panel; (b) detecting a second side temperature of one of (c) changing at least one process parameter of the hot press so that the first side temperature approaches the second side temperature and in particular a difference in the two temperatures decreases in magnitude. It has been found that local temperature differences can lead to material defects, for example to vapor bubbles.

Changing the process parameter is increasing a pressing pressure on the low temperature side. Namely, if the pressing pressure is increased, the heat transfer from the wood-based panel hot press, in particular from a revolving press belt, to the wood-based panel improves so that the temperature of the panelstock increases. The fact that changing the pressing pressure significantly influences the temperature of the wood-based panel is surprising since it was initially assumed that the compacting pressure during normal operation is so great that a change in the compacting pressure does not lead to any significant change in the heat transfer.

Alternatively, or in addition to increasing the press pressure on the low temperature side, changing the process parameter may include decreasing the press pressure on the higher temperature side.

Preferably, the wood-based panel hot press has a heating device by means of which a circulating press belt of the wood-based panel hot press in the width direction is locally heated differently. In particular, the heating device has at least two, preferably three juxtaposed heating zones, which can be controlled or regulated to different temperatures.

In other words, changing the process parameter may increase the pressing pressure on the low temperature side relative to the pressing pressure on the low pressure side Include side of higher temperature. In addition, changing the process parameter may be or include locally increasing the heating power P and / or the temperature T on the low temperature side compared to the higher temperature side. Of course, it is possible for two or more process parameters to be changed so that the first side temperature approaches the second side temperature.

The left-hand side region is understood in particular to be the region which extends from the left-hand side of the wood-based material panel in the material flow direction to 0.4 times, in particular 0.33 times, the width of the wood-based panel. Accordingly, the right side region is in particular the region of the wood-based panel which extends from the right edge to 0.4 times, in particular 0.33 times, the side width. According to a preferred embodiment, the method comprises the steps of comparing an actual temperature measured by means of the temperature measuring device with a predetermined setpoint temperature and increasing a feed rate of the fiber cake if the actual temperature is above the setpoint temperature by a predetermined difference temperature and / or a lowering of the feed rate when the actual temperature is a predetermined second differential temperature below the target temperature. If the actual temperature is neither at least the predetermined difference temperature above the setpoint temperature nor the predetermined second differential temperature below the setpoint temperature, then the feed rate preferably remains unchanged.

Alternatively or additionally, the heating power and / or the temperature of the hot press, in particular of the press belt, is reduced when the actual temperature is above the predetermined differential temperature above the desired temperature, wherein the heating power and / or the temperature is preferably increased, if the actual temperature is below the setpoint temperature by the predetermined second differential temperature. It is favorable if the feed rate is regulated at least also by means of the temperature averaged over the width of the wood-based panel. Of course, it is possible that different differential temperatures are used for controlling the feed rate and the regulation of the heating power or the temperature of the hot press before a control intervention takes place.

It is favorable if the first differential temperature and / or the second differential temperature is at most 5 Kelvin. It is particularly favorable if the sum of the amounts of the difference temperature is at most 5 Kelvin, in particular at most 3 Kelvin. It is therefore possible to keep the temperature of the wood-based panel in a narrow temperature range. There is therefore less rejects.

Preferably, the target temperature is between 100 ° C and 1 10 ° C, in particular 102 ° C and 108 ° C, when the plate thickness is between 5 and 6 mm. If the plate thickness is between 7 and 8 mm, the target temperature is preferably between 121 ° C and 131 ° C, preferably between 123 ° C and 129 ° C. It has been found that such high quality wood-based panels can be produced. The wood-based panel hot press is preferably designed to produce a wood-based panel having a panel thickness of at least 2.5 millimeters, in particular at least 3.0 millimeters, preferably at least 5 millimeters. In particular, the wood-based panel hot press is designed for producing a wood-based panel having a panel thickness of at most 8 mm, in particular at most 12 mm, preferably at most 38 mm. With thin wood-based panels, in particular with a panel thickness between 5 and 8 millimeters, which is preferably an HDF panel, rejection of the process parameters is particularly fast. The invention is therefore particularly advantageous in the production of this type of wood-based panels.

According to the invention is also a wood-based panel manufacturing device with a wood-based panel hot press according to the invention and arranged in the material flow direction behind the wood-based panel hot press saw and / or Besäumanlage. Preferably, the wood-based panel hot press on a control unit. The control unit is preferably set up to automatically carry out a method according to the invention.

It is advantageous if the method steps mentioned in this description are carried out at a press standstill after a standstill and / or after a product change from one wood-based panel format to another. Such a method according to the invention preferably comprises the steps of calculating an inequality parameter, in particular a difference between a maximum temperature and a minimum temperature of the wood-based panel. The inequality parameter is a measure of the inhomogeneity of the temperature of the wood-based panel at the outlet side. For example, the inequality parameter is determined from the spatially resolved measured temperature T (y), the y-coordinate being measured transversely to the material flow direction.

The inequality parameter may be, for example, the variance or the standard deviation of the temperature distribution in the width direction. The inequality parameter can also be, for example, the difference between a maximum and a minimum temperature of the wood-based material board. The data used to calculate the inequality parameter may have been obtained from the measured raw temperature data by temporal and / or spatial notification over a predetermined range.

The inequality parameter is understood in particular to mean a value which describes how much the spatially resolved measured temperature deviates from the desired temperature distribution. Preferably, the method comprises the step of outputting a warning signal when the difference in amount exceeds a predetermined warning threshold. It is possible, but not necessary, for this warning signal to be perceptible by a human being. In particular, it is also possible for the warning signal to be purely electrical. Again, it is possible, but not necessary, to change at least one process parameter of the wood-based panel hot press due to the warning signal so as to reduce the inequality parameter. This may be, for example, a local change in the press pressure and / or a local change in the heating power and / or the temperature of the hot press.

Preferably, the method comprises the steps of (i) detecting an inhomogeneity of the press belt and (ii) suppressing the issuing of the warning signal when the warning threshold is exceeded due to the inhomogeneity. Such inhomogeneity arises, for example, from repairing the press belt by separating and replacing a faulty area. In the area of the joint between the exchanged area and the remainder of the press belt, there is a change in the heat transfer from the press belt to the fiber cake, which manifests itself in the local temperature of the wood-based panel. The result is a characteristic temperature pattern that appears once per revolution of the press belt. If, due to this temperature pattern, the warning threshold is exceeded, no warning signal is output, as there is no process fault.

The temperature pattern can be recognized, for example, by the fact that it occurs exactly once per press belt circulation and / or has the shape of the replaced area. The temperature pattern is recognized, for example, by image recognition or identified once by hand as inhomogeneity and its position calculated from the rotational speed of the press belt and the elapsed since the last occurrence of the temperature pattern time.

The step of detecting the inhomogeneity preferably comprises (i) measuring the temperature of the wood-based panel at the outlet side of the wood-based panel hot press for a period of at least twice, preferably at least four times a cycle time of the press belt, and (ii) eliminating Deviations from an average temperature that is periodic in the orbital period are. In this way, such variations in the temperature of the wood-based panel can be identified.

The elimination of deviations from an average temperature, which are periodic in the circulation time, can take place, for example, by first carrying out a, for example temporal, Fourier transformation of the temperature data which depends on the time. This is how the spectrum of temperature data is obtained. In this spectrum, the components which belong to the rotational frequency of the press belt are filtered out and the spectrum obtained is inversely Fourier transformed. Thus, the temperature data obtained solely from the press belt is obtained.

The suppression of the issuing of the warning signal can be effected, for example, by correcting the temperature measured values for the temperature by a differential temperature which is caused by the press belt. The spectrum of the corrected temperature measured values thus obtained has no components belonging to the rotational frequency.

The fact that the temperature measured values for the temperature are corrected by a differential temperature may mean that the - optionally negative - differential temperature is added to the respective temperature measured value. The differential temperature is usually time-dependent (and periodically with the rotational frequency) and location-dependent with respect to the widths coordinate perpendicular to the material flow direction of the wood-based panel.

It should be noted that it is possible, but not necessary, for the detection of inhomogeneity to be automatic. In particular, it is possible that the inhomogeneity is marked and the position of the differential temperature resulting from the inhomogeneity is automatically calculated and the temperature measured values are automatically corrected by the difference temperature.

According to a preferred embodiment, the regulation of the at least one process parameter based on the temperature comprises the following steps: (i) inputting the time- and location-dependent temperature measured values as input variables in a neural network, wherein the neural network outputs as output variables process parameters and adjusting these process parameters in the wood-based panel manufacturing device, wherein the neural network is trained to minimize a deviation between them preferably by means of a Infrared camera measured temperature readings and a predetermined target temperature distribution.

The target temperature distribution is, for example, the uniform temperature distribution that has the same value at each point with respect to a position along the material flow direction regardless of time. The temperature can become smaller as the path along the material flow direction increases, since the wood-based panel cools.

In particular, the method comprises the steps of automatically changing at least one process parameter, in particular at least two process parameters, particularly preferably at least three process parameters, by means of the control unit as a function of the time-dependent measured temperature measured values, wherein the at least one process parameter is calculated by means of the neural network becomes. Preferably, the neural network has at least one intermediate layer (hidden layer), preferably at least three intermediate layers.

Preferably, the neural network has been trained by means of deep learning. For this purpose, the time-dependent process parameters and the time-dependent measured temperature measured values are used as input variables (inputs). The output sizes are process parameters and are set on the wood-based panel hot press. The size to be minimized is the deviation of the temperature measured values from the target temperature distribution. In the following the invention will be explained in more detail with reference to the accompanying drawings. It shows

FIG. 1 shows a schematic view of a wood-based panel hot press according to the invention,

Figure 2 shows a measurement result of the temperature measurement with the temperature measuring device, and Figure 3 is a schematic horizontal section through a wood-based panel hot press whose structure substantially corresponds to that of Figure 1, but in which heating circuits are arranged side by side.

FIG. 4 shows schematically how an inhomogeneity of the press belt of a wood-based panel hot press according to FIG. 1 is reflected in the temperature measured values.

FIG. 1 schematically shows a wood-based panel manufacturing apparatus 10 according to the invention which has a wood-based panel hot press 12 and a spreader 14 arranged in a material flow direction M in front of the wood-based panel hot press 12 and a sawing unit 16 arranged behind it. The spreading machine 14 is designed for spreading an endless fiber cake 18 made of glued wood fibers on a revolving conveyor belt. The wood-based panel hot press 12 has a circumferential first press belt 20.1, which, for example by means of rods 22.1, 22.2, ... with a pressing force F _{p is} applied. The press belt 20.1 is formed from a metal sheet, for example made of stainless steel. The wood-based panel hot press 12 is drawn interrupted in the middle, since a plurality of rods exists. The fiber cake 18 lies on a second circulating press belt 20.2, which rotates at the same speed as the first press belt 20.1. The wood-based panel hot press 12 has a heating device 24, by means of which the press belt 20 by means of tubes 26.1, 26.2, ... is heated. A heat transfer fluid 28 is circulated in the tubes 26, which is heated by a non-illustrated heat generator, for example a boiler, which is part of the heating device 24. The heat transfer fluid 28 releases the heat via heating plates and / or roller rods to the respective press belt 20.1, 20.2, from where it is transferred to the fiber cake 18.

In the present embodiment, the heating device 24 has a plurality of heating circuits 29.1, 29. n, where for example n = 3, 4, 5, 6, 7, 8, or 9. More heating circuits are possible. The heating circuits 29 i are designed to heat the fiber cake 18, in the present case over its full width, and are arranged one behind the other in the material flow direction M. Alternatively or additionally, however, it is also possible that two heating circuits are arranged next to one another, as shown in FIG.

The wood-based panel hot press 12 has at least one temperature sensor 27 i (i = 1, n) for each of the heating circuits 29. 1, 29. In the present case, each heating circuit 29.i has three temperature sensors, one each for determining the flow temperature (temperature when entering the heating circuit), the return temperature (temperature when leaving the heating circuit) and the temperature of the press plate.

The fiber cake 18 runs continuously on an inlet side 30 into the continuously operating wood-based panel hot press 12 and is pressed there to the wood-based panel 32, which leaves the wood-based panel hot press 12 at an outlet side 34.

The wood-based panel hot press 12 has a plurality of frames 35.1, 35.2, 35. M, wherein for m, for example M = 35 applies. By means of the frame 35. m is the press nip in the respective region of the frame 35. m at least two, preferably three or more, locations in the width direction of the wood-based panel, so in the height direction of the wood-based panel hot press 12, adjustable. For example, in the material flow direction M on the left, a larger or smaller pressing force and / or a smaller press nip can be set than on the right. In particular, the rods 22. I themselves or on the rods 22. I can be fastened to individual frames 35. M by means of components which transmit a pressing force. By a change in position of a frame 35. m or by changing the position of the component relative to the frame 35. m so the pressing force can be changed, which exerts the press belt 20 on the fiber cake or the resulting wood-based panel.

On the outlet side 34, a temperature measuring device 36 is arranged in the form of an infrared camera. Their field of view 38 detects the wood-based panel 32 on the outlet side 34 of the wood-based panel hot press 12.

Alternatively, the temperature measuring device 36 can also be formed by a plurality of contact-free temperature sensors, which are each arranged at a distance from one another with respect to a width direction B.

The temperature measuring device 36 is connected to a control unit 40, which evaluates the temperature measurement data of the temperature measuring device 36. In the present case, the control unit 40 is also connected via not shown lines to the temperature sensors 27. i.

FIG. 2 shows an image 42 taken with the temperature measuring device 36. It can be seen that the temperature T = T (x, y) is measured in two spatial directions x, y. The temperature T is recorded at a plurality of points (Xj, yj) (j = 1, 2, ..., N) of the widthwise direction B of the wood material board 32. In this case, preferably N> 2, in particular N> 5, preferably N <1000 applies. In addition, a plurality of measured values for the temperature T in a longitudinal direction L are recorded in succession. The type of temperature measurement by means of an infrared camera shown in FIG. 2 is particularly advantageous because, as shown in FIG. 2, a detailed image of the temperature T (x, y) of the wood-based panel 32 is obtained. The control unit 40 (see Fig. 1) detects, for example, a first side temperature Ti, which in the present case results as an arithmetic mean over a range A1. The side temperature Ti is assigned to a first location S1. The point S1 in the present case is the center of the area A1. The point S1 is located in a left side region of the wood-based panel 32, as can be seen in the lower partial image, which shows the same location on the wood-based panel 32 and has been added for clarity.

In addition, a second side temperature T2 at a second point S2 is determined, which lies in a right-hand side region of the wood-based material panel 32. The second temperature T2 is also determined by averaging over a pixel range of the temperature measuring device 36.

The controller 40 determines an inequality parameter U, which may be formed for example by the temperature U = ΔΤ = I Ti - T2. If the inequality parameter U exceeds a predetermined warning threshold value Uwam, the control unit 40 changes a process parameter P. This process parameter P may be, for example, the local compacting pressure p = p (y) with which the rods 22 i = 1, 2, ... (see Fig. 1) locally press on the press belt 20. The process parameter P can also be a heating power ΡΗΘ _ΙΖ , which the heating device 24 transmits to the press belt 20.

By averaging over the full width B at a predetermined location along the material flow direction M, for example at the height Mo, an (averaged) actual temperature Ti _s t can be determined. If this actual temperature Ti _s t deviates from a predefined desired temperature Tsoii by more than ΔΤ ₀ upward or AT _U downward, then the control unit 40 can output a corresponding warning signal. An operator may then increase or decrease a feed rate v. Alternatively, this is done automatically. The feed rate v denotes the speed at which the wood-based panel 32 (see Fig. 1) moves in the material flow direction M in the region of the outlet side 34.

Figure 3 shows schematically a horizontal part-section AA through a wood-based panel hot press 12 according to the invention, which except for the arrangement of Heating circuits as the wood-based panel hot press 12 is constructed according to Figure 1. It can be seen that the heating device can heat a first heating line with which a first heating area Hi can be heated, a second heating line with which a second heating area H2 can be heated, and a third heating line with a third heating area H3. having. Alternatively, two or four or more heating areas H, may be present. It is also possible that more than one heating element is present per heating area. The number of heating strands may differ or be the same for different heating ranges. The heating areas are arranged side by side in the material flow direction M and jointly heat the - press belt 24 at full width. The temperature T, or the heating area H, and / or the heating power P, are independently adjustable.

A method according to the invention is carried out, for example, by resting the wood-base plate hot press 12 for at least 15 minutes, for example for maintenance work or for a product change. It is then initially supplied less heating power than average in the retracted operation. At the beginning of the wood-based panel has a higher temperature on the outlet side than average in retracted operation. For example, the averaged over the full width temperature is 1 18 ± 1 ° C, for example, a 7.6 mm thick wood-based panel. The feed rate is in the example

v = 510 mm / sec.

Due to the lack of heat, the temperature of the wood-based panel decreases again - in the example to 1 14 ° C - and it can come without temperature control to critical temperature falls, resulting in splitters - and thus broke -. The feed rate in the example is therefore preferably automatically lowered to v = 445 mm / sec. The flow temperature of the press and the temperature of the hotplate are increasing but the plate surface temperature is not yet high.

As the plate temperature rises, the feed rate is increased, particularly automatically, so that the full-width averaged temperature exceeds the setpoint temperature. Temperature Tsoii 124 ± 1 ° C assumes and the feed rate has reached its maximum achievable value or a target value of, for example v = 530 mm / sec. This often takes up to 30 minutes. An inventive method is also carried out by first changing the plate thickness of the wood-based panel. Different plate thicknesses require different pressing temperatures and different surface temperatures. For example, the full-width averaged temperature is 126 ± 1 ° C for a 12 mm plate thickness and 1 10 + 1 ° C for a 5.5 mm plate thickness. Thus, the heating capacity of the press must be adapted to the new production. Depending on the situation, however, the necessary heat output can only be roughly estimated.

Therefore, during production of the wood-based panel with smaller or larger panel thicknesses, the heating power and / or the forward shear rate are initially changed during ongoing production in such a way that the temperature averaged over the full width is lowered successively by 5 to 7 ° C. Thereafter, the plate thickness is changed. By means of the averaged over the full width temperature, the feed rate v is preselected and then regulated on the basis of the temperature, the feed rate v and the heating power P of the individual heating circuits.

In the context of a method according to the invention, an inequality parameter U in the form of a maximum difference ΔΤΒ is preferably automatically calculated by the control unit 40, which may consist of a plurality of spatially separated units. For this purpose, the temperature measured values T (y) are first grouped into at least five, in particular at least ten, preferably equidistant, evaluation ranges Aj. An evaluation area is, for example, a two-dimensional interval.

In the mathematical sense, the evaluation areas Aj preferably form a partition of the measured values of at least 80%, in particular at least 90%, of the full width of the wood-based panel. But it is also possible that the totality of all evaluation ranges does not cover the entire width of the wood-based panel, but for example at least 50%, at least 60%, at least 70% or at least 80%. Subsequently, the mean value of the temperature within each evaluation area Aj is calculated. From the evaluation range temperatures thus obtained, the maximum difference ΔΤΒ is calculated as the inequality parameter U.

If the inequality parameter U exceeds a predetermined warning threshold value of, for example, U _W = 3 ° C., differences in plate quality can occur more frequently transversely to the material flow direction. This is counteracted by increasing a pressing pressure p on on the colder side.

Thus, for example, by means of a pressure equalization of 20% - 50% of the existing specific compressive pressure in a material rear direction behind the high pressure area of the continuous press the inequality parameter U of 4 ° C to 1 ° C can be lowered.

If, for example, an inequality parameter of U = 4 ° C. is measured in the manufacture of a wood-based panel with a 5.5 mm panel thickness, the higher temperature is in the right-hand area of the wood-based panel in the material flow direction and the other evaluation panel temperatures differ by less than 1 ° C. , so in the right area, especially the right high pressure area, the hot press of the pressing pressure is increased by 35%. This reduces the inequality parameter U to below 1 ° C.

In the context of a method according to the invention, the process parameter is preferably increased in the form of the total heating power ΡΗΘΙΖ, total and / or a heating power of one, two or more heating circuits 29.j if the averaged temperature of the wood-based panel is higher than the predetermined target temperature deviates downwards. This is especially true when a feed rate has a predetermined maximum velocity Vmax.

For example, with a plate thickness of 7.6 ± 0.5 millimeter, the target temperature Tsoii = 123 ± 1 ° C and v = v _ma x = 540 mm / sec. If, for example, the temperature averaged over the full width of the wood-based panel is 1 18 ° C., then the total heat output ΡΗΘΙΖ, total, is increased, preferably by raising the flow temperature. In the present example, the flow temperature T i for at least one heating circuit is increased 29.j, but preferably for two or more heating circuits, for example, 2 ° C. Thereafter, the temperature approaches the target temperature such that the inequality parameter U falls below the warning threshold. The specified steps can be performed automatically without a person receiving a warning signal.

FIG. 1 shows that at least some of the frames 35, m, preferably a majority of the frames 35, m, can be subjected to a respective force Fp, m by means of a respective control element 44.1, 44.2,. The adjusting elements 44, m can be, for example, hydraulic cylinders which are pressurized with a schematically drawn hydraulic supply. The adjusting elements 44. m are designed so that the individual pressures F _p , j may be different for different control elements. Each one of the pressing pressures F _p , _m represents a process parameter P _m , which can be set separately by the control unit 40. In addition, the heating powers of each heating circuit 29.i or the flow temperature of the heating fluid are also further process parameters P ,. These can also be set by the control unit 40. The wood-based panel hot press 12 further includes a humidity sensor 46 for measuring moisture of the fiber cake 18 prior to entering the wood-based panel hot press 12. The humidity sensor 46 is also connected to the control unit 40.

In addition, it is favorable if the wood-based panel hot press 12 has a second infrared camera which determines the temperature of the fiber cake 18 before entering the wood-based panel hot press 12. The second infrared camera 48 is also connected to the control unit 40.

The control unit 40 has a neural network, into which the process parameters P, as an input are received. In addition, the spatially resolved and time-resolved measured values of the temperature T (x, y, t) enter the neural network N as an input variable. The neural network N is then taught that the inequality para- meter U becomes as small as possible. The calculated by the neural network process parameters Pi are continuously transmitted to the respective component of the wood-based panel hot press wired or wireless and set there. FIG. 4 shows a schematic image 42 of a temperature measurement. It is assumed that the temperature has a high value Thoch only in regions B1, B2, B3 and has a normal temperature T _n0 rmai in all other regions. The areas B1, B2, B3 of the higher temperature Thoch are caused by an inhomogeneity in the press belt 20.1 (see FIG. For example, the inhomogeneity may be caused by a part of the press plate being defective and being cut out. The resulting hole was closed again with a replacement element and the surface of the press plate was smoothed.

The thermal conductivity of the exchanged piece of press plate is greater in the present example, resulting in a higher temperature. The elevated temperature is not significant for the quality of the wood-based panel produced. However, if the temperature fluctuates, it can easily happen that in one of the areas B a predetermined setpoint temperature is briefly exceeded. This would lead to a warning message, although there is no danger to the quality of the wood-based panel produced.

To avoid this, the temperature increase in areas B is eliminated. For this purpose, a Fourier transformation is carried out for each y-position, for example the position yo. It should be noted that it is not important whether this Fourier transformation is performed with respect to the x-coordinates or the complementary time coordinate, since the feed rate at which the fiber cake moves forward is substantially constant. Since the temperature increase is caused by inhomogeneity of the press belt, it is repeated at regular intervals, which corresponds to the belt length LB of the press belt 20. Associated with this is a circulation time Tu, which requires the press belt for one revolution.

In the spectrum of the Fourier transforms thus calculated, the components belonging to the band length LB are deleted. Becomes a temporal Fourier transform performed, the frequency components belonging to the revolution frequency fu are canceled, the revolution frequency fu being the inverse of the revolution time Tu. Subsequently, the corrected spectrum thus obtained is inverse Fourier transformed. This temperature signal no longer contains any components which are caused by inhomogeneities of the press belt. On the basis of the thus calculated, corrected temperature data, the wood-based panel hot press is regulated.

LIST OF REFERENCE NUMBERS

10 Wood-based panel manufacturerF _p Pressing force

device i, j, m counting indices

12 wood-based panels hot-L longitudinal direction

Press M material flow direction

14 scattering machine N neural network

16 sawing plant

p pressure

18 fiber cake

P process parameters

ΡΗ _ΘΙΖ heating power

20 press belt

S place

22 pole

t time delay

24 heating device

T temperature

26 pipe

27 temperature sensor

Ti first side temperature

28 heat transfer fluid

Tact actual temperature

29 heating circuit

Tsoii target temperature

ΔΤο first differential temperature

30 inlet side

temperature

32 wood-based panel

34 outlet side

U inequality parameters

35 frames

Uwam Wam threshold

36 temperature measuring device

v Feed Rate 38 Field of View

40 control unit

42 picture

44 control element

46 humidity sensor

48 infrared camera

A range

B width direction

d thickness

Claims

Claims:

Wood-based panel hot press for producing a wood-based panel (32), wherein the wood-based panel hot press (12)

- Has an inlet side (30) and an outlet side (34) and

- Is formed for pressing a feedable on the inlet side (30) blank (18) to the wood material board (32),

marked by

a temperature measuring device (36), which is designed for automatically spatially resolved measuring the temperature (T) of the wood-based panel (32) on the outlet side (34).

Wood-based panel hot press according to claim 1, characterized by a control unit (40) which is designed to automatically carry out a method comprising the steps:

(a) detecting a first side temperature (Ti) of a first location (Si) in a left side region of the wood material board (32),

(b) detecting a second side temperature (T2) of a second location (S2) in a right side region of the wood material board (32), and

(c) changing at least one process parameter (P) of the wood-based panel hot press (12) such that the first side temperature (T1) approaches the second side temperature (T2).

Wood-based panel hot press according to claim 2, characterized in that the changing of the process parameter (P)

- Increasing a pressing pressure (P) on the side of the lower temperature (T) and / or

- comprises lowering the pressing pressure (p) on the higher temperature side.

4. wood-based panel hot press according to claim 2 or 3, characterized in that the method comprises the following steps:

Comparing an actual temperature (Ti _s t) measured by means of the temperature measuring device (36) with a predetermined target temperature (Tsoii) and - Increasing a feed rate (v) of the blank (18) when the actual temperature (Tact) is a predetermined difference temperature AT _U above the target temperature (Tsoii) and / or

Lowering the feed rate (v) when the actual temperature (Tact) is a predetermined second differential temperature AT _U below the target temperature (Tsoii).

5. wood-based panel hot press according to one of the preceding claims, characterized in that it is designed for producing a wood-based panel (32) having a thickness (d) of at most 12 millimeters.

6. wood-based panel manufacturing device (10) with

- A wood-based panel hot press (12) according to any one of the preceding claims and

- A in the material flow direction (M) behind the wood-based panel hot press (12) arranged sawing and / or Besäumanlage (16).

7. A method of operating a wood-based panel hot press (12), the

- Has an inlet side (30) and an outlet side (34) and

- one of the inlet side (30) supplied blank (18) pressed to the wood material board (32),

with the steps:

- Automatic, non-contact, spatially resolved measuring the temperature (T) of the wood-based panel (32) on the outlet side (34) and

- Rules at least one process parameter (P) of the wood-based panel hot press (12) based on the temperature (T).

8. The method according to claim 7, characterized in that the at least one process parameter (P) the feed rate (v) of the blank and / or a heating power (ΡΗΘΙΖ) and / or a temperature (T) of at least a portion of the wood-based panel hot press (12 ).

9. The method according to claim 7 or 8, characterized by the steps:

(a) detecting a first side temperature (Ti) of a first location (S1) in a left side region of the wood material board (32),

(b) detecting a second side temperature (T2) at a second location (S2) in a right side region of the wood material panel (32), and

(c) changing the at least one process parameter (P) of the wood-based panel hot press (12) such that the first side temperature (T1) approaches the second side temperature (T2).

10. The method according to any one of claims 7 to 9, characterized by the

Steps:

- Calculating an inequality parameter (U), in particular a difference ΔΤ9 between a maximum temperature (T _ma x) and a minimum temperature (Tmin) of the wood material board (32), and

- Issuing a warning signal when the inequality parameter (U) exceeds a predetermined warning threshold (U _W am).

1 1. Method according to one of claims 7 to 10, characterized by the

Steps:

(i) detecting inhomogeneity of the press belt and

(ii) suppressing the issuing of the warning signal when the warning threshold is exceeded due to the inhomogeneity.

12. The method according to any one of claims 7 to 1 1, characterized in that the controlling of the at least one process parameter (P) based on the temperature comprises the following steps:

(I) inputting the time- and location-dependent temperature measured values as input variables into a neural network, wherein the neural network outputs as output variables process parameters and

(ii) setting these process parameters in the wood-based panel manufacturing apparatus,

(iii) wherein the neural network is trained to minimize the inequality parameter.