EP4446264A1 - Method for scattering material and scattering installation - Google Patents

Abstract

The invention relates to a method and a device for spreading wood chips or wood fibers to form a spreading material mat during the production of material panels, wherein a first and a second spreading material from at least a first and a second bunker with a dosing unit is fed into a first and a second spreading device arranged above the spreading belt conveyor, and wherein a first layer of spreading material is spread from the first spreading device onto the spreading belt conveyor. In order to improve the density distribution of the spreading material in a mat in terms of its uniformity and to detect errors early and, if necessary, in a way that can be corrected, it is provided that in a first step, a profile measurement is carried out by means of a radiometric or photometric measurement across the width of the first spreading material layer behind the at least first spreading device in the conveying direction, and a profile measurement is carried out by means of a radiometric and/or photometric measurement across the width of the second spreading material layer behind the second spreading device in the conveying direction; the determined profile measurement values are fed to an evaluation and control device and with these determined profile measurement values the spreading quantity over the width of the first or second spreading material layer is at least partially adjusted with at least one first actuator so that the profile measurement values are adapted to a target density profile.

Description

The invention relates to a method for spreading spreading material, in particular wood chips or wood fibers, onto a spreading belt conveyor to form spreading material mats during the production of material panels, wherein a first spreading material is fed from at least one first bunker with a dosing unit into a first spreading device arranged above the spreading belt conveyor, and wherein a first layer of spreading material is spread from the first spreading device onto the spreading belt conveyor, and wherein a second spreading material, which is physically or chemically different from the first spreading material, is fed from at least one second bunker with a dosing unit into a second spreading device arranged above the spreading belt conveyor, a second layer of spreading material from at least the second spreading device is spread onto the spreading belt conveyor onto the first layer of spreading material to form a spreading material mat.

The invention further relates to a spreading system for spreading spreading material, in particular wood chips or wood fibres, onto a spreading belt conveyor to form a spreading material mat, in the course of material plate production, in particular for carrying out the method, wherein a first spreading material is fed from at least one first bunker with a dosing unit into at least one first spreading device, and wherein a first layer of spreading material can be spread from the first spreading device onto the spreading belt conveyor to form a spreading material mat, and wherein a second spreading material, which is physically or chemically different from the first spreading material, can be fed from at least one second bunker with a dosing unit into at least one second spreading device arranged above the spreading belt conveyor, and wherein at least a second layer of spreading material can be spread from the second spreading device onto the spreading belt conveyor onto the first layer of spreading material to form a spreading material mat.

There are numerous different spreading systems for producing material boards, in particular those consisting at least partially of wood chips or wood fibers. These spreading systems can have one or preferably several spreading devices from which layers (hereinafter referred to as layers) of grit are spread onto a spreading belt conveyor, usually a conveyor belt. The resulting grit mats are then pressed into material boards under pressure and heat. By connecting several spreading devices in series, material boards with several different layers can be produced. For example, grit is often used for the top layers of a material board that differs from that of a middle layer in terms of size, glue content or material.

The term spreading device here refers to so-called spreading heads, with or without alignment rollers for chips or fibers, as well as wind spreading devices. Examples of such spreading devices are shown in the DE 20 2016 102 898 U1 and the DE 10 2015 112 013 A1 .

Regardless of whether only one layer is spread from a spreading device or many layers from several layers on top of each other, the aim is to make the height profile as uniform as possible across the width of the spread layer. This is important during commissioning in order to obtain a height profile that is so straight that the later pressed board has as few density fluctuations as possible. But even during later operation, turbulence in the spreading and sticking of the glued spreading material to walls often leads to irregularities in the height cross-section, which are only detected much too late.

From the EP 4 082 764 A1 It is known to record a height profile of the spread mat using a distance measuring device at the end of a spreading station and, if necessary, to influence the previous spreading using actuators so that the height profile is evened out. Spreading head slides in one or more spreading heads have already been mentioned for this purpose. However, in such a process it is not possible to specifically influence each spread layer. Only the end result of the height profile can be corrected. Since the profiles of the individual layers are not recorded, a forecast for the density distribution of the chipboard mentioned there is also not possible.

In the DE 10 2005 020 297 A1 A radiometric measuring method has already been described that can be used to directly determine the density of a material plate. However, this document only deals with the finished, pressed plate material, which is scanned with a radiation detector. A grit mat, let alone its individual layers, are not examined.

It is therefore the object of the invention to improve the density distribution of the grit in a grit mat with regard to its uniformity and to detect errors at an early stage and, if necessary, in a way that can be corrected.

The term material boards refers in particular to chipboards made from wood chips. In principle, however, the invention also includes fibreboards made from wood fibres or annual plants and sometimes also artificial products. The grit mats spread on the spreading belt conveyor are pressed into wood-based panels in a press, for example a continuously operating press or a cycle press, using pressure and heat. The quality of the wood-based panels produced depends largely on the quality and properties of the grit mats produced using the spreading station, which comprises several spreading devices. The grit is usually glued grit, e.g. glued chips or fibers, which are fed to the spreading devices from a grit bunker or dosing bunker.

The spreading station should have several spreading devices or spreading heads, especially if multi-layered spreading material mats are to be produced from two cover layers (for example made of fine material) and one or more middle layers (for example made of coarse material). The individual layers are therefore made from different spreading material, whereby the difference can be caused not only by the size of the spreading material, but also, for example, by the material or the amount of glue added. The individual spreading devices are then arranged one behind the other along the conveying direction above the spreading belt conveyor, so that first a first cover layer is spread onto the spreading belt conveyor, then the middle layer(s) onto the first cover layer and then again the second cover layer onto the middle layer. The spreading system according to the invention is used in particular to produce layers with a good spreading profile across the width, i.e. a spreading profile that can be pressed to a uniform density profile across the width.

• in Förderrichtung hinter einer ersten Streuvorrichtung eine Profilmessung mittels einer radio- oder photometrischen Messung über die Breite hinweg einer ersten Streugutschicht vorgenommen wird,
• in Förderrichtung hinter einer zweiten Streuvorrichtung eine Profilmessung mittels einer radio- und/oder photometrischen Messung über die Breite hinweg einer zweiten Streugutschicht vorgenommen wird;
• die ermittelten Profilmesswerte einer Auswerte- und Steuereinrichtung zugeleitet werden und
• mit diesen ermittelten Profilmesswerten die Streumenge über die Breite der ersten oder zweiten Streugutschicht mit mindestens einem ersten Stellglied zumindest teilweise so eingestellt wird, dass die Profilmesswerte einem Dichtesollprofil angepasst werden.

Thus, the problem with regard to the method is solved by the features of claim 1 and in particular by the fact that in a first step

• in the conveying direction behind a first spreading device, a profile measurement is carried out by means of a radiometric or photometric measurement across the width of a first layer of spreading material,
• in the conveying direction behind a second spreading device a profile measurement by means of a radiometric and/or photometric measurement across the width of a second layer of grit;
• the determined profile measurement values are fed to an evaluation and control device and
• Using these determined profile measurement values, the spreading quantity across the width of the first or second spreading material layer is at least partially adjusted using at least one first actuator in such a way that the profile measurement values are adapted to a target density profile.

In the following, the term profile measurement is to be understood as the measurement of the height profile (preferably photometric) or the density profile (preferably radiometric) on a scattered layer. For example, after the first layer of the grit mat has been spread, a measurement is taken that provides information about what the density distribution of the first layer of the grit mat alone would be and this measurement is compared with that behind the scattering of a second layer. The first layer is usually a relatively thin cover layer compared to the middle layers. But even with such a cover layer, a density distribution error is largely excluded. This means that errors cannot be summed up with the second layer. If the profile measurements of the first layer already show a lack of uniformity across the width of the grit mat, a correction to a target density profile is possible for the first layer using a first actuator, which is controlled by the evaluation and control device so that the profile is evened out. Possible actuators that can be used are explained below with the description of subclaims.

In this case, there would be no summation of profile errors with the profile of the second layer, but a great advantage arises if it is also ensured with regard to the second layer that, in a second step, a profile measurement is also carried out in the conveying direction behind the second scattering device by means of a radio- and/or photometric measurement across the width of the second layer of spreading material, the determined profile measurement values are fed to a control device and with these determined profile measurement values the spreading quantity over the width of the second layer of spreading material is at least partially adjusted with at least one second actuator so that the profile measurement values are adapted to a desired density profile.

With a second control loop, the scattering of a second layer can also be influenced with regard to a constant height profile and, taking into account the different scattering quantities and scattering weights, the density of the subsequent material plate can be better predicted.

It is advantageous to also carry out a profile measurement on additional spreading devices, but at least three. In the best case, there is even a profile measuring device behind all spreading devices. This increases the possibility of being able to influence the desired height or density profile by means of actuators that can be assigned to the individual spreading devices.

If the photometric measurement method is chosen, electro-optical distance measurement is the preferred method. Laser or infrared light can be used. The reflected light beam must be picked up by a corresponding laser or infrared sensor. The method using laser triangulation is particularly suitable.

Such a method is not associated with high radiation requirements, such as the radiometric alternative measurement. At the same time, the speed of the measurement still allows for a high resolution. In each layer of scattered material, the topography can be measured across the width and thus a profile of the thickness or a density to be predicted can be determined.

Alternatively, it may also be useful to carry out a radiometric measurement using gamma or X-ray beams, because then the density profile can be determined directly, albeit with a certain degree of safety.

It is preferred if the first measurement profile determined behind the first spreading device and the second measurement profile determined behind the second spreading device are fed to the control device and the control device compares the first measurement profile with a first target profile and influences at least one actuator of the first spreading device in such a way that deviations of the first measurement profile are at least partially compensated when considering the second measurement profile.

Alternatively, it is preferred if the first measurement profile determined behind the first spreading device and the second measurement profile determined behind the second spreading device are fed to the control device and the control device compares the first measurement profile with a first target profile and influences at least one actuator of the second spreading device in such a way that deviations of the first measurement profile are at least partially compensated when considering the second measurement profile.

By using at least two measurement profile determinations, you have two effective procedures in which, by comparing the first and second measurement profiles, you adjust actuators in either the first or the second spreading device in such a way that you get an optimized second measurement profile. If there are large deviations across the width in the second measurement profile, you can of course also adjust actuators in both spreading devices.

This method can be extended to any number of spreaders with ever-improving results if a profile measurement is carried out behind each spreader.

Care should be taken to ensure that the profile measurement values in at least the first layer of spreading material vary by a maximum of ± 5% across the width. This is detected by the profile measurement after the spreading device. Only if the deviations are greater should the actuators of the first spreading device be acted upon retroactively. If the deviations are smaller, the control device should be used in such a way that it makes the profile more balanced by adjusting the actuators of the second and possibly further spreading devices.

In a particularly preferred manner, the grit mat consisting of an upper and a lower cover layer and at least one middle layer is spread with at least three spreading devices.

The cover layers can be sprinkled with different grit than that used in the middle layer or layers. For example, the cover layers are often sprinkled with finer material to make coating easier, or particularly long chips are used to achieve greater bending strength in the subsequent material plate.

Thus, it is preferred if, in the event of a change in production, a changed height of only at least one middle layer is spread on a new material plate thickness.

This means that the target values of the profile measurement of the outer layers are not changed and can be retained in the control system. The profile measurement of the middle layer(s) with the changed thickness can easily be integrated into the control system with new values.

In particular, if the resulting profile of the profile measurement behind the last spreading device is sufficiently straight, a continuous Pressing of a grit mat strand in a continuous belt press is made possible in an effective manner.

In a continuous process, a material plate with a uniform density across the width and length can be produced, which can then be sawn into rectangular plates of the desired size. Subsequent grinding processes are largely avoided with such a uniform density profile resulting from several measurement profiles.

Such a density profile or density distribution over the length and width of a finished material plate can be predicted in a much more reliable manner than before by taking a profile measurement of the height after each layer spreading of a spreading device, which gives the invention a significant added value.

The object of the invention is achieved with regard to a spreading system for spreading grit, in particular according to the method claims, with the features according to claim 14 and in particular in that a profile measuring device with a radiometric or photometric measuring method is provided across the width in the conveying direction behind a first spreading device and behind a second spreading device, which enables radiation exposure across the width and at least one sensor is arranged above and/or below the grit mat, which can continuously detect the light, X-ray or gamma radiation.

The inventors have recognized that a significantly higher accuracy in the density distribution of the material plate can be achieved with a profile measuring device for determining a height or density profile both behind a first and behind a second spreading device on the spreading belt conveyor.

As already described, a radiometric or photometric measurement, in particular laser triangulation, is a suitable method to To determine profile measurements. Laser triangulation preferably involves a light beam in the form of a laser beam hitting the grit layer at an angle of between 20 and 70° to the surface of the grit layer, where it is reflected and captured by a suitable light sensor that records the distance very precisely so that a height measurement profile can be created across the width of the grit layer.

Preferably, the spreading system for producing multiple layers has more than two spreading devices and a profile measuring device is provided behind more than two spreading devices.

Advantageously, it is ensured that an evaluation unit and control device are provided by which the height profile over the width of the spreading material layer can be determined from the profile measurements and adjustment commands can be passed on to at least one actuator of the first or second or a further spreading device.

This creates a variety of possibilities for correcting the determined height profile in the sense that after a pressing process, a density distribution that is as uniform as possible is obtained in the material plate produced.

The spreading devices can have different actuators. In this application, three essential actuators are listed, but this should not exclude other alternatives from the invention. It is advantageous if the actuator is a) a distribution device across the width when feeding the bunker, b) a distribution device across the width in the spreading device and/or c) a material removal device acting on the layer of spreading material.

All of these actuators allow the spreading to be varied and adjusted across the width of the spreading mat. This allows thinner areas of the More grit is added to the grit mat and less grit is added to thicker areas of the grit mat.

In a particularly preferred variant of the actuators within the spreading device, the distribution device is a zone-controlled discharge device. Here, a greater or lesser part of the spreading material can be directed out of the spreading device in zones across the width, for example via several flaps, and removed for recycling. This means that areas of the spreading material mat that have been covered in excess are provided with less new spreading material, which serves to even out the width.

Last but not least, it is advantageous if a visualization device for the profile measurements and/or a predicted density distribution is available.

Here, the operator of the system can always check what his material plate will look like in terms of thickness or density distribution. Depending on how automated the spreading control is, he can intervene in emergencies and adjust actuators manually. This option is particularly useful when the spreading material sticks to the walls of the spreading device.

• Fig. 1 eine schematisierte Streuanlage in der Seitenansicht,
• Fig. 2 eine schematisierte Streuvorrichtung,
• Fig. 3a und 3b eine Ausschleusungsvorrichtung innerhalb einer Streuvorrichtung im Längs- und Querschnitt (2. Beispiel für Stellglied),
• Fig. 4 eine sektionale Abtragungsvorrichtung auf dem Streubandförderer (3.
• Beispiel für Stellglied),
• Fig. 5 eine teilweise vergrößerte Darstellung von Fig. 1 mit Verteileinrichtung über die Breite bei der Bunkerbeschickung (1. Beispiel für Stellglied),
• Fig. 6 eine schematische Profilmesseinrichtung

In the following, the invention is explained in more detail with reference to drawings which merely represent exemplary embodiments.

• Fig. 1 a schematic spreading system in side view,
• Fig. 2 a schematic spreading device,
• Fig. 3a and 3b a discharge device within a spreading device in longitudinal and cross-section (2nd example of actuator),
• Fig. 4 a sectional removal device on the spreading belt conveyor (3rd
• example of actuator),
• Fig. 5 a partially enlarged view of Fig. 1 with distribution device across the width when feeding the bunker (1st example for actuator),
• Fig. 6 a schematic profile measuring device

Fig. 1 shows a spreading system in a schematic side view. Below a spreading material feed system (not shown) there are various bunkers 3a, 3b, 3c, 3d that can receive and store spreading material 4a, 4b, 4c, 4d. The different lowercase letters after the reference symbol are intended to indicate that the spreading material 4 can be different in all bunkers 3. For example, chips of different lengths can be in the bunkers or plant fibers or plastics can be stored in a bunker. The spreading material 4a, 4b, 4c, 4d is fed into a spreading device 2a, 2b, 2c, 2d via dosing units 13. Here too, and further on in the spreading material layers 6, the lowercase letters after them indicate the possibility of differences. The invention is understandably not limited to four bunkers and spreading devices as in this embodiment. However, at least two spreading devices must be present to implement the invention.

From there, spreading takes place in one or more layers as required, whereby there may be special differentiated requirements between the middle layer and the top layers. In this embodiment, wind spreading is considered for the top layers from the spreading devices 2a and 2d and so-called indirect spreading via spreading roller systems is considered for the two middle layers from the spreading devices 2b and 2c. In indirect spreading, the spreading material discharged from the spreading material bunker falls onto so-called spreading rollers 19, which can divide the spreading material and, if necessary, also align it (see also Fig. 2 ). Here, the spreading of a layer by a spreading device often makes a decisive difference for the strength and usability of the finished material plate, depending on whether the chips or fibers are in the running direction of the spreading mat 7 or across it or simply randomly.

The grit layers 6a, 6b, 6c, 6d - in Fig. 1 only referred to as 6, since the individual layers are not recognizable - each lie on a Spreading device 2a, 2b, 2c, 2d scattered one above the other on a spreading belt conveyor 5. The spreading material layers 6a and 6d can, for example, be cover layers of the later material plate and 6b and 6c a middle layer.

Behind each spreading device in the exemplary spreading system 1, a profile measuring device 8 is arranged near the spreading belt conveyor 5. Such a profile measuring device can, for example, record the height profile of the spreading material layer 6 or the entire spreading material mat 7 as part of a photometric measurement using a laser triangulation method. Or the method of a radiometric measurement is used, which can provide direct information about the density distribution in the spreading material mat. In both variants, the measurement is carried out across the entire width of the spreading material mat 7, for which corresponding sensors 16 are provided to implement the results. The measurement results are passed on to an electronic evaluation unit and control device 9, which can influence actuators 10 to correct the measured profile (more details in Fig. 3 to 6 ).

The evaluation is based on at least two measurement profiles. The first and second measurements are compared and used to operate the existing actuators 10 in such a way that at least the second measurement profile has a uniform height distribution. Together with the first measurement profile of a spreading material layer 6, 6a, 6b, 6c, 6d, a density profile for the finished material plate can be predicted based on the known spreading materials in the associated spreading devices 2a, 2b, 2c, 2d.

In this configuration with at least two layers of spreading material and two associated profile measuring devices 8, 8.1, 8.2, various correction methods are possible. An alternative is to regulate the first measuring profile via actuators 10 in and around the first spreading device. A profile deviation across the width of a maximum of ± 5%. A further or additional alternative is to measure at least two profiles and then equalize the first measurement profile using scattering actuators in the vicinity of the second scattering device.

The evaluation unit and control device 9 is therefore able to indicate the actual profile values, for example from height or density measurements across the width. With a suitable correlation matrix, which is made available to the evaluation unit and control device from empirical values or calculated values, it is also able to display a probable density profile of a finished material plate. It makes sense to make these profiles available to the operator on a visualization device 17, for example a screen or his mobile phone display, with current values (see also Fig. 6 ).

The invention allows for increasingly more precise corrections with an increasing number of spreading material layers 6 if a profile measuring device is provided behind each spreading material layer 6a, 6b, 6c, 6d and the profile measurement values are used for actuators 10, which in turn correct these or other profile measurement values in the control loop.

The actuators essentially include three alternative or shared facilities.

As a first exemplary device, an actuator 10 can be provided which fills the bunker for spreading material 3, 3a, 3b, 3c, 3d in such a way that more spreading material is delivered to the spreading device across the width, where it throws too little material onto the spreading belt conveyor. For this purpose, a distribution device 12 in or in front of the bunker, for example a chute 18 which can be pivoted across the width of the bunker, can be used as the actuator 10. This chute is in the Fig 5 schematically indicated. The bunker is then in certain places filled to a higher level and can also deliver more spreading material to the indirect spreading device 2b, 2c due to the higher material pressure at these points

Fig. 2 shows schematically an exemplary spreading device 2, 2b, 2c. It contains various spreading rollers 19, which can often distribute and separate the spreading material according to size and, if necessary, also align the spreading material, i.e. chips or fibers, in their spreading position before they fall onto the spreading material mat 7. In Fig. 2 The quantity and direction of movement of the spreading material 4 is shown by thick black arrows as it is distributed from the bunker 3 within the spreading device. The white arrows with a black outline symbolize only an example direction of rotation of the spreading rollers 19. In this sorting process, several adjustable discharge devices 11 arranged across the width can be present as a second possible actuator. These separate an adjustable part of the spreading material 4 in one or more selected width ranges in such a way that it does not fall onto the spreading material mat but is transported away to the side. In the embodiment according to Fig. 2 , but more clearly shown in the Figures 3a and 3b , there are several flaps 23 next to each other which can take in a certain amount of grit depending on how far they are swung out. The picked up material is then guided to a conveyor screw 24 and transported away to the side. It can then be fed back into the bunker. The flaps 23 are adjusted and swung using small servo motors which can be electrically or pneumatically operated. They are adjusted by the evaluation unit and control device on the basis of the determined measurement profiles, resulting in a control loop for a grit mat which is as homogeneous and evenly high as possible and which, after pressing, produces a material plate with the smallest density deviations. This discharge device is a second example possibility for an actuator 1o.

As a third exemplary possibility of using an actuator 10, reference is made to an old document of the applicant, which DE 3938681 A1 . It is considered Fig. 4 once again the one listed therein Fig. 2 used. Depending on the result of the at least two measurement protocols, motor-driven rams 21 are pressed against the conveyor belt 20 of the spreading belt conveyor 5 with different pressure across the width, so that high-density sections are pressed more strongly and lower-density sections are pressed less strongly against a cylindrical leveling roller. The leveling roller removes the spreading material at the lifted points, so that a new distribution of the spreading material is created with the aim of achieving a more uniform result across the width in the second profile measuring device.

In an alternative design not shown here, the leveling roller can also be segmented and the individual segments can be arranged at different heights around the axis of the roller. The conveyor belt can then run on a flat, horizontal surface. However, this has the disadvantage that the roller has a complicated structure with eccentric adjustment for each roller segment.

Fig. 5 clarifies the location of the at least two profile measuring devices 8.1, 8.2 in connection with the invention. In the embodiment, a height profile measurement with a photometric measuring method, the laser triangulation device, is desired and I Fig. 6 shown. A laser light beam is directed, for example, at an angle of 20 to 70° from a laser emitter 15 onto the top scattered layer 6a, 6b and recorded by a camera sensor 16. With this method, the height profile of the layer can be determined precisely. The arrow indicates the direction of travel of the grit mat. After the lower cover layer 6a has been scattered, the height profile is determined using the first profile measuring device 8.1. For this purpose, a laser emitter 15 sends at least one laser beam across the entire width of the grit layer 6a, which is indicated by the dashed lines. The camera sensor 16 can easily record the height profile. The same process takes place on the second scattered layer 6b using the profile measuring device 8.2. The increasing height of the second layer 6b during the scattering was taken into account. omitted from the illustration and only the final height after the second spreading device is shown.

Both height profile measurement results can be fed to the evaluation unit and control device 9, which creates the corresponding conversions and forecasts for the density of the finished material plate and makes them available to the operator of the system on the visualization device 17, for example a screen. Limit values can also be clearly displayed on the screen in the manner indicated. However, a radiometric measurement method is also to be covered by the invention. Such measuring devices, also in connection with the production of material plates, are known for example - as already described in the introduction - from the EP 4 082 764 A1 and the DE 10 2005 020 297 A1 known.

list of reference symbols

1 spreading system 2, 2a, 2b, 2c, 2d spreading device 3, 3a, 3b, 3c, 3d bunker for grit 4, 4a, 4b, 4c, 4d grit 5 spreading belt conveyor 6, 6a, 6b, 6c, 6d grit layer(s) 7 grit mat 8, 8.1 , 8.2 profile measuring device 9 evaluation unit and control device 10 actuator 11 discharge device in spreading device 12 distribution facility bunker 13 dosing unit 14 removal device 15 laser emitters 16 sensor 17 visualization device 18 Pivoting chute 19 spreader roller 20 conveyor belt 21 Motor-driven ram 22 leveling roller 23 flap 24 screw conveyor 25 actuator

Claims (22)

Method for spreading grit (4, 4a, 4b, 4c, 4d), in particular wood chips or wood fibres, onto a spreading belt conveyor (5) to form a grit mat (7), in the course of material plate production, wherein a first spreading material (4, 4a, 4b, 4c, 4d) is fed from at least one first bunker (3, 3a, 3b, 3c, 3d) with a dosing unit (13) into a first spreading device (2, 2a, 2b, 2c, 2d) arranged above the spreading belt conveyor (5), and wherein a first layer of spreading material (6, 6a, 6b, 6c, 6d) is spread from the first spreading device (2, 2a, 2b, 2c, 2d) onto the spreading belt conveyor (5) and wherein a second spreading material (4, 4a, 4b, 4c, 4d), which differs physically or chemically from the first spreading material, is fed from at least one second bunker (3, 3a, 3b, 3c, 3d) with a dosing unit (13) into a second spreading device (2, 2a, 2b, 2c, 2d) arranged above the spreading belt conveyor (5), and a second spreading material layer (6, 6a, 6b, 6c, 6d) from at least the second (2, 2a, 2b, 2c, 2d) spreading device onto the spreading belt conveyor (5) onto the first spreading material layer (6, 6a, 6b, 6c, 6d) to form a spreading material mat (7), characterized in that in a first step - in the conveying direction behind the first spreading device (2, 2a, 2b, 2c, 2d) a profile measurement is carried out by means of a radiometric or photometric measurement across the width of the first spreading material layer (6, 6a, 6b, 6c, 6d), and - in the conveying direction behind the second spreading device (2, 2a, 2b, 2c, 2d) a profile measurement is carried out by means of a radiometric and/or photometric measurement across the width of the second spreading material layer (6, 6a, 6b, 6c, 6d); - the determined profile measurement values are fed to an evaluation and control device (9) and - using these determined profile measurement values, the spreading quantity over the width of the first or second spreading material layer (6, 6a, 6b, 6c, 6d) is at least partially adjusted with at least one first actuator (10) such that the profile measurement values are adapted to a desired density profile. Method according to claim 1, characterized in that in a second step the spreading quantity over the width of the second spreading material layer is at least partially adjusted with at least one second actuator (10) such that the profile measurement values are adapted to a density target profile. Method according to claim 1 or 2, characterized in that scattering is carried out via further, but at least three scattering devices (2, 2a, 2b, 2c, 2d) and radiometric or photometric profile measurements are also carried out across the width downstream in the conveying direction. Method according to one of claims 1 to 3, characterized in that a photometric profile measurement is carried out via an electro-optical distance measurement. Method according to claim 4, characterized in that the electro-optical distance measurement is carried out via laser triangulation. Method according to one of claims 1 to 5, characterized in that a radiometric measurement is carried out by means of gamma or X-ray beams. Method according to one of claims 1 to 6, characterized in that the measured value behind the first scattering device (2, 2a, 2b, 2c, 2d) first measurement profile and the second measurement profile determined behind the second spreading device (2, 2a, 2b, 2c, 2d) are fed to the control device and the evaluation unit and control device (9) compares the first measurement profile with a first target profile and influences at least one actuator of the first spreading device in such a way that deviations of the first measurement profile are at least partially compensated when considering the second measurement profile. Method according to one of claims 1 to 6, characterized in that the first measurement profile determined behind the first spreading device and the second measurement profile determined behind the second spreading device are fed to the control device and the control device compares the first measurement profile with a first target profile and influences at least one actuator of the second spreading device in such a way that deviations of the first measurement profile are at least partially compensated when considering the second measurement profile. Method according to one of claims 1 to 8, characterized in that the profile measurement values are adjusted such that they vary by a maximum of ± 5% across the width at least in the first layer of spreading material. Method according to one of claims 1 to 9, characterized in that the grit mat (7) consisting of an upper and a lower cover layer and at least one middle layer is spread with at least three spreading devices (2, 2a, 2b, 2c, 2d). Method according to claim 10, characterized in that in the course of material plate production, at least different heights of the at least one middle layer are scattered for different end products. Method according to one of claims 1 to 11, characterized in that the grit mat (7) is pressed in a continuous belt press to form a finished material plate. Method according to one of claims 1 to 12, characterized in that a density distribution in the finished material plate is predicted from the determined profile measurement values. Spreading system for spreading spreading material, in particular wood chips or wood fibres, onto a spreading belt conveyor (5) to form a spreading material mat (7), in the course of material plate production, in particular for carrying out the method according to claims 1 to 13, wherein a first spreading material (4, 4a, 4b, 4c, 4d) can be guided from at least one first bunker (3, 3a, 3b, 3c, 3d) with a dosing unit (13) into at least one first spreading device (2, 2a, 2b, 2c, 2d) arranged above the spreading belt conveyor (5), and wherein a first layer of grit (6, 6a, 6b, 6c, 6d) can be spread from the first spreading device onto the spreading belt conveyor to form a grit mat, and wherein a second spreading material (4, 4a, 4b, 4c, 4d), which differs physically or chemically from the first spreading material, can be guided from at least one second bunker (3, 3a, 3b, 3c, 3d) with a dosing unit into at least one second spreading device (2, 2a, 2b, 2c, 2d) arranged above the spreading belt conveyor (5), and wherein at least a second layer of grit (6, 6a, 6b, 6c, 6d) can be spread from the second spreading device (2, 2a, 2b, 2c, 2d) onto the spreading belt conveyor (5) onto the first layer of grit (6, 6a, 6b, 6c, 6d) to form a grit mat (7), characterized in that in the conveying direction behind the first spreading device (2, 2a, 2b, 2c, 2d ) and behind the second spreading device (2, 2a, 2b, 2c, 2d ) a Profile measuring device (8, 8.1, 8.2) is provided with a radiometric or photometric measuring method across the width, which enables radiation exposure across the width and at least one sensor (16) is arranged above and/or below the grit mat (7), whereby the light, X-ray or gamma radiation can be continuously detected. Spreading system according to claim 14, characterized in that a light beam in the form of a laser beam strikes the spreading material layer at an angle of between 20 and 70° to the surface of the spreading material layer (6, 6a, 6b, 6c, 6d). Spreading system according to one of claims 14 to 15, characterized in that it has more than two spreading devices (2, 2a, 2b, 2c, 2d) and a profile measuring device (8, 8.1, 8.2) is provided behind a plurality of spreading devices (2, 2a, 2b, 2c, 2d). Spreading system according to one of claims 14 to 16, characterized in that an evaluation unit and control device (9) is provided, by means of which the height profile over the width of the spreading material layer can be determined from the profile measurements and adjustment commands can be passed on to at least one actuator (10) of the first or second or a further spreading device (2, 2a, 2b, 2c, 2d). Spreading system according to claim 17, characterized in that one actuator (10) is a distribution device (12) across the width during bunker charging. Spreading system according to claim 17, characterized in that one actuator is a distribution device across the width in the spreading device. Spreading system according to claim 19, characterized in that the distribution device is a zone-controlled discharge device (11). Spreading system according to claim 17, characterized in that one actuator (10) is a material removal device (14) acting on the spreading material layer (6, 6a, 6b, 6c, 6d). Spreading system according to one of claims 14 to 20, characterized in that a visualization device (17) for the profile measurement values and/or a predicted density distribution is present.

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