Method for producing a scattered particle mat, a device for carrying out said method and material plate

Abstract

The invention relates to a method and a device for producing a scattered particle mat (1) from particles (2, 3), for example from lignocellulose-containing material such as fibres or chips or mineral particles, on a running forming belt (23), comprising the following steps: a) providing a bunker (4) having mixed fine and coarse particles (2, 3) which are at least partially provided with a binder, b) dividing the particles (2, 3) emerging from the bunker (4) via at least one size-dividing device (5) into at least one first partial quantity (6) of fine particles (2) and at least one second partial quantity (7) of coarse particles (3), c) further fractionating the at least first partial quantity (6) and the at least second partial quantity (7) again according to particle size, and d) scattering the particles of each partial quantity (6, 7) as a layer having an increasing or decreasing size onto the forming belt (23) in order to form the scattered particle mat (1). In order to reduce the required energy consumption of the scattering device and / or to reduce the overall size, the invention proposes that the first partial quantity (6) of the entire particulate material is fractioned by means of an air classifier (17).

Description

[0001] Method for producing a spreading mat, apparatus for carrying out the method, and material plate

[0002] The invention relates to a method for producing a spreading mat from particles, for example from lignocellulose-containing material such as fibers or chips or mineral particles, on a moving conveyor belt, comprising the following steps: a) providing a hopper with mixed fine and coarse particles, which are at least partially provided with a binder, b) dividing the particles exiting the hopper by means of at least one size-separating device into at least a first subset with fine particles and at least a second subset with coarse particles, c) further fractionating the at least first subset as well as the at least second subset again according to particle size, and d) spreading the particles of each subset as a layer of increasing or decreasing size onto the conveyor belt to form a spreading mat.

[0003] The invention further relates to a device for carrying out the method with

[0004] - at least one bunker containing fine and coarse particles, for example made of lignocellulose-containing material such as fibers or shavings, or mineral particles that are at least partially coated with a binder,

[0005] - at least one size-separating device for dividing the particles exiting the bunker into at least a first subset of fine particles and at least a second subset of coarse particles,

[0006] - one fractionation device each for the fine particles of the first subset and for the coarse particles of the second subset, - at least one first spreading device for the fine particles onto a forming belt to form a first spreading mat layer,

[0007] - at least a second spreading device for the coarse particles onto the forming belt immediately before or after the first spreading device to form a second layer of spreading material mats.

[0008] Finally, the invention comprises a material plate produced using the method and the device.

[0009] To realize the invention, the method and the apparatus incorporate different particle sizes for scattering the various layers. Particleboard, OSB, and MDF panels, as well as hybrid panels constructed from individual layers of such composites, are particularly widespread. This also applies to all other particles consisting of lignocellulose-containing material or mineral components. The scattering mat is compacted under pressure and heat to produce the material panel.

[0010] These material panels are typically made from wood particles of different shapes and sizes, with the particles being joined together by stimulating their own adhesion mechanisms and adding binders (usually a glue).

[0011] The production of sheet materials takes place either in cycles or continuously. Since significant pressures are generally applied in the compression units, or the combined joining and compression units, during sheet material production, these units are usually referred to by those skilled in the art as press components when referring to the entire system. In the production of sheet materials as described in this document, the operating pressures here, depending on the material and size of the sheet being produced, are usually in the range of approximately 50 N / cm². 2 and approximately 500 N / cm 2 and advantageously between 100 N / cm 2 and 400 N / cm 2The operating principle of the joining and / or compaction unit determines whether the overall process is described as a cycle-based or continuous process. In cycle-based production, the material sheets are pressed as flat objects with finite dimensions in all three spatial directions, whereas the material sheets produced in a continuous process represent lengths of a continuously pressed web material.

[0012] To produce all of these material sheets, the aggregate, i.e., the particles, must first be spread in layers onto a forming belt. This aggregate, spread in layers and different positions, forms the basis for the production of the material sheet.

[0013] Both economically and in terms of their technical applicability, wood-based panels occupy a special position among engineered wood products. Wood-based panels are manufactured in a wide variety of designs for diverse applications.

[0014] More recently, efforts have been made to utilize annual plants, particularly grasses, for the production of engineered wood panels, in addition to wood-based materials which require many years to regenerate. Thus, multi-layered engineered wood panels, whose individual layers consist of annual plants, are already known from the prior art.

[0015] However, processing annual plants is significantly more complicated than processing wood particle-based panels. The high precipitation of silicates during the manufacturing process, which are abrasive to the plant structure, presents a major obstacle, and new methods and devices for separating specific particle sizes must be implemented.

[0016] In the field of engineered wood panels made from multi-year timber, there are numerous state-of-the-art technologies regarding layer structure. Examples include MDF panels made from chopped and washed wood chips, some of which are thermodynamically refined into fibers and spread into a fleece that is then pressed. MDF panels offer the advantages of high strength, smooth and uniform surfaces, and good milling properties.

[0017] OSB boards with the typical OSB strand separation (coarse on the outside, fine in the core) are also well-known. They are characterized by high flexural strength and low product density.

[0018] Pure particleboard (for example with a fine top layer and a coarser middle layer) has the advantage of high material yield and offers the possibility of using lower-quality wood assortments inside, while on the outside they have smooth and uniform product surfaces.

[0019] Similar procedures are used for mineral fiber panels.

[0020] To create a multi-layered structure in spreading mats, the particles of the spreading material are currently fractionated according to their size in various ways and then sequentially scattered in spreading devices. This allows for the scattering of larger particles onto a moving conveyor belt in layers near the top or core layer, or conversely, the scattering of smaller particles.

[0021] For fractionation, sieves, so-called roller scattering heads or, for example, air classifiers are often available.

[0022] The latter are often found in conjunction with sieves, especially chip screens. EP 1 889 702 A2 serves as an illustrative example of the prior art. The particle stream exiting the hopper or metering device for the spreading material is only cleaned of excessively large particles, including clumps. The spreading material intended for use is then passed through the airflow of the air classifier and, due to its weight or the mesh size of the sieves, is distributed along its length in such a way that a spreading material mat with layers of different particle sizes is formed on the circulating conveyor belt. Roller spreading heads with roller beds, arranged so that, for example, the spreading material is carried from roller to roller in the direction of rotation, allowing increasingly larger particles to fall through the gaps, are also a long-standing example of the prior art.As an example of such a fractionation device, DE 2026 113 014 B4 may be mentioned. As shown in the figures in this document, an air classifier can also be installed upstream of these roller spreading heads.

[0023] It should also be noted that the rollers of the roller spreading heads can have different designs, which allow, for example, longer chips or fibers to be oriented as they are spread onto the forming belt, for instance, perpendicular or longitudinal to the direction of travel of the forming belt. This makes it possible to create layers with different orientations of chips or other elongated particles in the spreading mat. A descriptive prior art, DE 10 2007 049 947 A1, should also be mentioned here.

[0024] The use of air classifiers, as cited in EP 1 889 702 A2 or DE 2026 113014 B4, has proven to be a very effective means of fractionating spreading material. Innovations, such as those described in DE 10 2021 124 789 B3, achieve the necessary airflow in the air classifier chamber via a sophisticated fan array. While this method is effective, the energy consumption, particularly regarding airflow, is quite high. Furthermore, the air classifier chamber in conventional air classifiers is relatively large.

[0025] Therefore, the object of the invention is to reduce the energy required by the spreading device and / or to reduce its size.

[0026] The problem is solved with respect to the method by the features of claim 1, and in particular by the fact that the fractionation of the first subset of the total spreading material is carried out by an air classifier. The problem is solved with respect to the apparatus by the features of claim 11, and in particular by the fact that an air classifier is provided as the fractionation device for the fine particles of the first subset.

[0027] The inventors recognized that the high energy consumption of the air classifier is due to the fractionation of the entire intended spreading material, including both coarse and fine particles. They therefore implemented a size-division device to divide the entire quantity of spreading material into at least two subsets with different particle sizes. Finally, the first subset, containing the fine particles, is fractionated using the air classifier. Significantly less airflow is required to fractionate the fine particles than if the same air classifier were also used for the coarse particles. Previously, the area near the air outlet always had to be overcome when sorting out the fine particles, as the coarser particles in this area would fall, for example, onto the forming belt. With this invention, the range of particle sizes for the air classifier is much smaller and much easier to regulate.Furthermore, the fine particle spreading chamber is significantly smaller than in conventional air classifiers, which fractionate coarse and fine spreading particles. This results in two distinct spreading zones: one for fine spreading material and one primarily for coarse spreading material.

[0028] As a size-division device upstream of the air classifier, this preferably includes a roller spreading head.

[0029] If a roller spreading head is used for this process, the screening of the finer material can be influenced by the structure of the rollers, their spacing, and by rotational or differential speeds. The finer material then falls through the roller spreading head, while the coarser particles of the spreading material are transported to the side above, i.e., in or against the direction of production. By producing smaller subsets, significantly fewer particles (only a subset) need to be fractionated by the air classifier. At least the spreading material containing the finer particles is taken into account. For this purpose, a blower unit is provided laterally below the roller spreading head, which blows the fine spreading material to the side within a fines spreading chamber, in such a way that the fine spreading material is further fractionated by size before being spread, for example, onto the spreading mat on the forming belt.In contrast, the coarse spreading material particles are transported to an adjacent coarse spreading chamber, where they are further fractionated and spread. This system advantageously ensures that the first subset, containing fine particles, is directed to a fine spreading chamber, and the second subset, containing coarse particles, is directed to a coarse spreading chamber.

[0030] It is preferred to provide and use fans in at least a single-row fan array as the blower unit of the air classifier.

[0031] Since space constraints often necessitate supplying air between the coarse and fine material spreading chambers from the side of the system, cross-flow fans are particularly well-suited. These are preferably individually controllable to allow for varying air volumes and flow velocities perpendicular to the production direction. The fraction of finer particles falling between the rollers is guided by the supply air into the more horizontal or slightly angled airflow, thus further separating them. This ensures that the finer particles are deposited in the outer mat layers on the forming belt. The fan array should have at least two fans, but ideally at least six, spanning the width of the fine material spreading chamber. These should be individually controllable to ensure uniform distribution across the spreading width.

[0032] For simplification, the second subset of material, containing the coarser particles and conveyed laterally on the roller spreader head, can simply be fractionated again using a second roller spreader head in a coarse material spreading chamber and then spread onto the forming belt in the direction of travel, either in front of or behind the fine material. In the simplest case, this results in a layer of fine material particles, which are graduated in size layer by layer, and a layer of coarse material particles, which are also graduated in size layer by layer. Of course, the invention is also intended to apply to spreading mats composed of multiple layers. In this case, the spreading process, with the formation of the subsets, is carried out several times.

[0033] It is advantageous if undesirably large clumps are also separated from the second subset containing the coarser particles.

[0034] This is achieved, for example, via a discharge device at the end of the roller bed of the second roller spreading head, whereby oversized particles fall into a trough and are transported away. This protects the pressing mechanisms of the continuous press.

[0035] It is advantageous that a cross-profiling device for the coarse particles is provided and can be activated in the coarse material spreading chamber.

[0036] In a preferred embodiment, the coarse particles of the spreading material derived from the size-division device are guided across the width of the coarse material spreading chamber via openings with several adjustable openings controlled by actuators and partially discharged section by section. This allows for a uniform spreading distribution transverse to the production direction. The transverse distribution of the coarse particles can be checked on the forming belt or on the finished pressed plate using known transverse profile measuring devices and readjusted by means of a control device.

[0037] As a further option, at least one additional blower, which blows air into the coarse material spreading chamber above the second roller spreading head, can separate the coarser fraction. The vertical position of the air injection is height-adjustable and can be adapted to the material properties, such as the dimensions and composition of the material, or to the throughput rates. When the supply air is used to separate the coarser particles, larger chips are captured by means of one or more vertically or diagonally installed sieves, preventing them from reaching the near-surface areas of the spreading mat. The inventors have also recognized that the machinability of a material sheet, particularly with regard to surface treatment, depends to a very high degree on the design of the outermost layers of the spreading mat, especially the respective top layer(s).Producing the top layer from the finest particles is therefore approached by using wind separation of the finer grit particles to facilitate the creation of a particularly smooth surface. For this reason, it is especially advantageous to use the first batch of material after the size-division device to spread the top layers of the grit mat, which also form the top layers of the finished material panel after pressing.

[0038] For example, with two of the spreading devices according to the invention, a dispersed mat or pressed plate, which generally has two cover layers, is produced with a core layer, or simply core, consisting of at least two layers of coarse particles, and at least the layers adjacent to the cover layers consisting of fine particles, each as a mixture with binders. All layers can change layer by layer from larger to smaller particle sizes or vice versa.

[0039] This allows coarser particles, pre-sorted by size, to be scattered into a core. While very coarse chips are scattered in the center of the core, separate layers of finer chips are scattered towards the outer layers. This simplifies the formation of the spreading heads.

[0040] It is advantageous that the particles of the core layer and the particles of the surface layers comprise binders from the same binder group, preferably the same binder, because they all originate from the same hopper and are only allocated as subsets for either the core layer or the surface layer of the grit mat after passing through a size-division device. This increases the load-bearing capacity of the resulting material panel.

[0041] With regard to the method and the apparatus, the object of the invention is achieved procedurally by the features of claims 1 to 10 and 11 to 18. In this respect, the resulting and described advantages apply analogously to the method and the apparatus.

[0042] Using such a process and device, a material sheet can be produced that offers significant advantages, as the distribution of the individual layers is much more effective and, above all, more precise. The distributed mat is preferably pressed in a continuous press between two pressurized, rotating belts under heat treatment until the adhesive, cross-linked with the particles, has hardened and a stable sheet has formed. This sheet consists of several layers containing either the fine or the coarse particles.

[0043] As described, just two spreading devices are capable of creating a spreading mat with outer layers of fine spreading particles and a thick core layer of coarse spreading particles, even though all particles come from a common hopper. This results in a spreading mat where the subsequent wood-based panel has a smooth and closed surface, allowing for direct and easy finishing, e.g., by applying a coating (paper or thin veneer) or by varnishing or painting.

[0044] A particularly advantageous feature is that the flexural stiffness of the material panel, even in its internal transition areas, is only minimally affected, as the surface layers and the core layer form very homogeneous transitions. Understandably, mats with surface layers containing coarse particles and core layers containing fine particles are equally conceivable.

[0045] The invention is explained in more detail below with reference to two exemplary embodiments illustrated in the drawings. These show:

[0046] Figure 1: a schematic representation of a first apparatus according to the invention

[0047] Spreading device

[0048] Figure 2: a schematically represented second invention

[0049] Spreading device. The figures are intended to illustrate, by way of example, the inventive method for producing a spreading mat and a suitable system for its production.

[0050] It should be noted at the outset that the spreading material located in the hopper or resting on the rollers of the roller spreading head or a conveyor belt is not shown for the sake of clarity. The operation of the air separator and the fractionation of the spreading material are also only indicated or described, as a graphic representation does not appear feasible.

[0051] Figure 1 shows a hopper 4 at the top, containing both coarse and fine particles to be spread. The particles referred to here are primarily shavings or fibers, and possibly also mineral particles. Ultimately, a spreading mat 1 is to be formed on a forming belt 23 circulating around deflection rollers 24. This mat has at least two layers: one with fine particles and one with coarse particles, in which the particle size decreases or increases as much as possible in successive layers. The resulting layers and strata are not shown in the figures.

[0052] A bunker discharge dosing unit 15 continuously delivers approximately the same quantity of spreading material per unit of time from bunker 4, consisting of fine particles 2 and coarse particles 3. The terms "coarse" and "fine" are, understandably, relative. For a particleboard being manufactured, "coarse" and "fine" describe different dimensions than, for example, for an MDF or OSB board being manufactured.

[0053] From the hopper discharge dosing unit 15, the spreading material falls onto a size-separating device 5, which is implemented here by way of example by a roller spreading head 11 and a conveyor belt 14. Between the individual rollers of the roller spreading head 11, there can be gaps both axially and towards the adjacent roller, through which the spreading material, in this case the fine particles 2 of a first subset 6, can fall into the fine material spreading chamber 8. The coarser particles 3 remain on the roller spreading head 11, which, by rotation (in the illustrated case, all rollers rotate counterclockwise), guides them towards the conveyor belt 14. Passed along by the conveyor belt 14, the coarse particles 3 fall at the end of the conveyor belt 14 as a second subset 7 into the coarse material spreading chamber.

[0054] These spreading chambers then create the spreading zones. Spreading zone 26 symbolizes the section in which fine particles are spread, i.e., the spreading zone for fine spreading material. Spreading zone 27 symbolizes the section in which primarily coarse particles are spread, i.e., the spreading zone for coarse spreading material.

[0055] Crucially, the invention requires that only the first subset 6, i.e., the fine particles 2, be further fractionated in the fines spreading chamber 8 by an air classifier 17. This typically allows for the use of a single-row fan array 16. The energy and space requirements are therefore significantly lower than with conventional air classifiers. The small installation space of the air classifier 17 is simply covered by the conveyor belt 14 and protected from contamination. A series of cross-flow fans is used as the fan array 16 to supply the intake air from the side of the spreading device 10.The airflow exiting the air outlet 18 collides with the first subset 6 that has fallen through the roller spreading head 11 and deposits particularly light particles furthest from the air outlet 18 at the beginning of the forming spreading mat 1, and somewhat heavier particles somewhat closer to the air outlet 18 onto the particularly light and fine particles already lying on the forming belt. This creates, for example, a lower top layer of the spreading mat that contains only fine particles 2. In this top layer, particularly fine and light particles then lie on the lower surface of the spreading mat 1, and also on the subsequent material panel.

[0056] A potentially core layer of coarse particles 3 from the second subset is subsequently spread onto this lower top layer containing fine particles 2 from the first subset 6. For this purpose, the coarse particles 3 are conveyed from the size-separating device 5 via the conveyor belt 14 to the coarse material spreading chamber 9. Here, the second subset 7 is also fractionated by means of a second roller spreading head 1T. This ensures that the coarse particles are also spread in increasing size. In the second roller spreading head 1T, the rollers in the illustrations also rotate counterclockwise and pass the spreading material to the rear (left in the figure) through increasingly larger slots between the rollers. This also makes it possible to transport lumps of glue or similarly large rejects to a discharge device 12, where they can be transported away, for example, in a trough via a spindle.

[0057] Should the coarse particles 3 be unevenly distributed across the width during spreading, it is possible to pre-adjust the coarse particles 3 to be fed section by section via a transverse profiling device 20. For this purpose, a pivoting guide plate 21 is used as an example, which directs the coarse particles 3 to one of several adjustable openings 22, where, considering the spreading width, a portion of the coarse particles can be separated and transported away in a further discharge device 12'.

[0058] In Fig. 2, the direction of travel of the forming belt is rotated by way of example, so that in the case where this embodiment of Fig. 2 is positioned behind that of Fig. 1, coarse particles 3 are again sprinkled onto the coarse particles 3 of a second subset 7, thus doubling the core layer thickness, for example, while subsequently fine particles 2 of a first subset 6 are again sprinkled on as the upper cover layer.

[0059] In addition, there are two helpful accessories in the spreading device 10'. A small modification shows an additional blower 19 and a sieve 25. This allows fine particles that were accidentally carried along by the second sub-quantity 7 in the size-division device 5 to be blown from the coarse material spreading chamber 9 into the fine material spreading chamber 8. The sieve 25 has a mesh size that corresponds to the through-slots of the roller spreading head 11. Reference numeral list

[0060] grit mat

[0061] fine particles

[0062] Coarse particles

[0063] bunker

[0064] Size division device

[0065] First subset

[0066] Second subset

[0067] Fine material spreading chamber

[0068] Coarse material spreading chamber, 10' Spreading device, spreading head, 1 T Roller spreading head, 12' Discharge device a Fractionation device fine material b Fractionation device coarse material

[0069] conveyor belt

[0070] Bunker outlet dosing

[0071] Fan field, air classifier, fine grit

[0072] Air classifier fine grit

[0073] Air outlet

[0074] Additional blower

[0075] Cross-profiling device

[0076] Guide plate

[0077] Adjustable opening

[0078] Form band

[0079] pulley

[0080] Sieve

[0081] Spreading area fine spreading material

[0082] Spreading area coarse spreading material

Claims

AMENDED CLAIMS received by the International Bureau on 20 January 2026 (20.01.2026) 1. A method for producing a grit mat (1) from particles (2, 3) of lig nocellulose-containing material on a moving conveyor belt (23), comprising the following steps: a) providing a hopper (4) with mixed fine and coarse particles (2, 3) which are at least partially provided with a binder, b) dividing the particles (2, 3) exiting the hopper (4) by means of at least one size-separating device (5) into at least a first subset (6) with fine particles (2) and at least a second subset (7) with coarse particles (3), c) further fractionating the at least first subset (6) as well as the at least second subset (7) again according to particle size, and d) spreading the particles of each subset (6, 7) as a layer of increasing or decreasing size onto the conveyor belt (23) to form the grit mat (1), characterized in that the fractionation of only the first subset (6) of the total grit is carried out by a Air classifier (17) is used.

2. Method according to claim 1, characterized in that the size division device (5) upstream of the air classifier (17) comprises a roller spreading head (11).

3. Method according to claim 1 or 2, characterized in that the first subset (6) containing fine particles (2) is fed to a fine material spreading chamber (8) and the second subset (7) containing coarse particles (3) is fed to a coarse material spreading chamber (9).

4. Method according to one of claims 1 to 3, characterized in that for fractionating the first subset (6) in the air classifier (17) a Blower unit with fans in a fan array (16) with at least one row.

5. Method according to one of claims 1 to 4, characterized in that a second roller spreading head (11 ') is used for fractionating the second subset (7).

6. Method according to one of claims 1 to 5, characterized in that undesirably large clumps are also separated from the second subset (7) containing the coarser particles (3).

7. Method according to claims 3 to 6, characterized in that a cross-profiling device (20) for the coarse particles (3) is activated in the coarse material spreading chamber (9).

8. Method according to claims 5 to 7, characterized in that an additional blower (19) is switched on in the coarse material spreading chamber (9) above the second roller spreading head (11'), which supports the fractionation of the second subset (7).

9. Method according to one of the preceding claims, characterized in that the fine particles (2) of the first subset (6) are used to spread the top layers of the spreading mat (1).

10. Method according to one of the preceding claims, characterized in that the coarse particles (3) of the second subset (7) are used to spread core layers of the spreading mat (1).

11. Device for producing a spreading mat (1) from particles (2, 3) of lignocellulose-containing material, in particular by carrying out the method according to one of claims 1 to 10, with - at least one bunker (4) containing fine and coarse particles (2, 3) of lignocellulose-containing material, which are at least partially coated with a binder, - at least one size-dividing device (5) for dividing the portions from the bunker (4) emerging particles (2, 3) into at least a first subset (6) with fine particles (2) and at least a second subset (7) with coarse particles (3), - one fractionation device each for the fine particles (2) of the first subset (6) and for the coarse particles (3) of the second subset (7), - at least one first spreading area (26) for the fine particles (2) onto a forming belt (23) to form a first spreading mat layer and - at least a second spreading area (27) for the coarse particles (3) onto the forming belt (23) immediately before or after the first spreading area (26) to a second spreading mat layer, characterized in that an air classifier (17) is provided as a fractionation device for the fine particles only of the first subset (6).

12. Device according to claim 11, characterized in that a roller spreading head (11) is included as a size division device (5) upstream of the air classifier (17).

13. Device according to claim 11 or 12, characterized in that the first subset (6) containing fine particles (2) can be fed to a fine material spreading chamber (8) and the second subset (7) containing coarse particles (3) can be fed to a coarse material spreading chamber (9).

14. Device according to one of claims 11 to 13, characterized in that a blower unit with fans in an at least single-row fan array (16) is provided for fractionating the first subset in the air classifier (17).

15. Device according to one of claims 11 to 14, characterized in that a second roller spreading head (1 T) is provided for fractionating the second subset (7).

16. Device according to one of claims 11 to 15, characterized in that a discharge device (12) is provided to from the second subset (7) containing the coarser particles (3) also to separate out undesirably large clumps.

17. Device according to claims 13 to 16, characterized in that a cross-profiling device (20) for the coarse particles (3) is provided and can be activated in the coarse material spreading chamber (9).

18. Device according to claims 15 to 17, characterized in that an additional blower (1) can be switched on in the coarse material spreading chamber (9) above the second roller spreading head (11 '), which supports the fractionation of the second subset (7).

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