Spreading device and method for spreading

Abstract

The invention relates to a spreading device (1) for spreading free-flowing particles, in particular for producing a mat-shaped product or pre-product (2), e.g., for the manufacture of material sheets or material mats, with a multi-level spreading head (3) having at least two superimposed spreading levels (4a, 4b, 4c), each comprising one or more spreading tools (7a, 7b, 7c). The device is characterized in that particles of a first particle type (5a) can be supplied as at least a first component to a first spreading level (4a) of the spreading head (3), and particles of a second particle type (5b) can be supplied as at least a second component to a second spreading level (4b) of the spreading head (3) arranged below the first spreading level (4a).

Description

The invention relates to a spreading device for the (continuous) spreading of free-flowing particles, in particular for the production of a mat-shaped product or semi-finished product, e.g., for the manufacture of material boards or mats, with a multi-level spreading head having at least two superimposed spreading levels (i.e., spreading levels), each comprising one or more spreading tools. Preferably, the spreading device is for the continuous production of spreading mats during the manufacture of material boards or mats, e.g., boards made of plant particles (e.g., wood-based panels), insulating boards, rubber boards or mats, or composite boards or mats. Alternatively, the invention also includes the production of other board- or mat-like products or semi-finished products, e.g., the production of nonwovens such as technical nonwovens made of fibers. The spreading device with the spreading head is used in particular to create a mat of material or the like on a conveyor, e.g., a forming belt, so that a mat-shaped product is formed from the spread particles through a progressive spreading process on the spreading belt conveyor or forming belt. For this purpose, the spreading head or the individual spreading levels can each have several rotating spreading tools, e.g., several rotating spreading rollers arranged one behind the other in a transport direction. The spreading rollers can be, for example, structured rollers, disc rollers, or rollers with tools arranged on the circumference of the roller, e.g., dissolving tools such as spiked rollers. In practice, the spreading material, i.e., the particles, is fed from, for example, a spreading material hopper onto the spreading head, specifically, in the prior art, onto the uppermost spreading level. From there, the spreading material passes onto the spreading level below and finally onto the forming belt, on which the spread mat is built up. The spreading levels can have a classifying or separating effect. For example, in the wood-based materials industry, it is often desirable for the spreading machine to separate the particles according to size or shape in order to influence the product properties of the subsequently manufactured panels as desired. Thus, for example, with particleboard, the geometrically smallest particles are spread towards the respective surface of the spread mat, while with OSB, the largest particles are spread towards the surface of the mat.Rotating discs or structured rollers, arranged at varying distances from one another, are used as spreading tools. At closer intervals, the smaller particles are initially removed from the spreading mixture, while the larger particles are carried further above the spreading device until the spacing between the tools is large enough for them to also fall through. The chosen arrangement and separation effect of the spreading heads are determined by the material being produced or the desired plate structure. In practice, several such spreading heads are usually used, typically arranged one behind the other and oriented in opposite directions along the transport path. This allows the particles to be built up layer by layer into a mat. The mat is then spread onto the conveyor belt running underneath. The mat is usually multi-layered, as several spreading heads can be used in succession to create, for example, outer top layers and one or more intermediate middle layers. The top layers and the middle layer(s) generally differ at least in particle size. During the production process, the mat produced in this way is then pressed into a material, such as a sheet, for example, in a hydraulic press where the mat is compressed into the sheet using pressure and / or heat. The press can be a batch press or a continuous press, for example.be designed as a double belt press. In the prior art, for example, glued particles are generally used for the production of wood-based panels or panels made from other plant particles. For this purpose, the particles, e.g., chips, fibers, or strands, are coated with a binder, e.g., a liquid glue, so that the liquid glue adheres to the surface of the particles as small droplets. Such glued particles are produced, for example, in suitable mixers. The glued particles produced in this way are temporarily stored in a hopper and then dispensed, for example, onto a spreading head of the type described. The known spreading devices of the type described have proven themselves well in practice, especially when the spreading material consists of a single type of particle, e.g. (glued) chips for chipboard, fibers for fiberboard or strands for OSB boards. However, there is also a need to add additional solid components, such as powdered fire retardants. These often only partially adhere to the liquid droplets, while another portion is separated from the mixture by mechanical influences such as vibrations during transport, but also, and especially, in the spreading devices known to date. Overall, handling and, in particular, spreading mixtures of different (solid) components or several (solid) particle types with conventional spreading equipment can lead to problems. Due to physical effects, loose spreading materials separate their particles in a variety of ways during pouring, spreading, and transport, primarily based on their size, shape, and density. With particles of approximately the same density and shape, the smaller ones settle downwards. Particles of approximately the same density and size separate according to their shape. Possible shapes include, for example, spherical, cubic, flat, needle-shaped, or fiber-like. This order is based on the surface area of ​​the particles, from smallest to largest, assuming the same volume. In these cases, the particles with the smallest surface area settle downwards.Particles of approximately the same size and shape separate in such a way that those with higher density geometrically align themselves at the bottom. In summary, this means that during spreading or pouring, fines are always separated downwards. This behavior is also known as segregation. Consequently, during the processing of an initially homogeneous mixture of particles of different types, a more or less pronounced segregation always occurs. This effect, which is used for classification in a known air classification process, is generally undesirable in other processing of bulk materials, and especially in spreading with spreader heads of the type described above. This is where the invention comes in. Spreading devices or spreading heads with several superimposed spreading levels for producing pressed material mats are known, for example, from EP 2 008 783 B1, EP 0 800 901 A1 and DE 10 2007 049 947 A1. The spreading material is always fed from, for example, a spreading material hopper onto the uppermost spreading level, so that from there it finally reaches the forming belt via the lower spreading level arranged below it. This also applies, for example, to a spreading head known from DE 10 2023 000 028 A1, with several spreading planes arranged one above the other. The first and second planes each have coaxial rollers for manipulating the material, with a preferably classifying roller arrangement with attached discs for orienting the material in the production direction being arranged in the second plane above the forming belt. In the first plane, a classifying roller bed with rollers for classifying according to the thickness of the material is arranged. Another embodiment of a spreading device with a multi-level spreading head is described, for example, in DE 10 2018 107 354. The spreading head has at least two spreading zones arranged one behind the other with different roller geometries and / or different roller operating modes. A switching device is arranged between the spreading material hopper and the spreading head, with which the flow of spreading material from the hopper can be selectively directed to either only the first spreading zone or only the second spreading zone of the spreading head. This switching device can be designed as a roller assembly with several switching rollers whose direction of rotation can be reversed. Furthermore, WO 2009 / 048859 A1 describes a method or apparatus for the production of mats, in particular for catalytic converters of motor vehicles, wherein inorganic fibers are applied to an upper roller level via an inlet of a spreading box. From there, the fibers pass to a lower roller level. If oversized fibers reach the lower roller level, they are conveyed back to the upper level via a conveyor belt for another pass and further comminution. Based on the prior art, the invention aims to create a spreading device for improved scattering, which in particular avoids the problems encountered in the prior art when scattering mixtures of several components or different particle types. Furthermore, an improved scattering method is to be developed. To solve this problem, the invention teaches a spreading device with the features of claim 1. In a spreading device of the generic type described above, it is provided that particles of a first particle type can be supplied to, or are supplied to, a first (upper) spreading plane as at least a first component, and particles of a second particle type can be supplied to, or are supplied to, a second (lower) spreading plane as at least a second component, wherein the second spreading plane is arranged below the first spreading plane. For this purpose, at least one first feeding device is provided, comprising a first hopper for the particles of the first particle type, and at least one second feeding device, comprising a second hopper for the particles of the second particle type. The particles of the first particle type are supplied to the first spreading plane by the first feeding device, i.e., fed from the first hopper onto the first plane.The second feeder supplies the particles of the second particle type to the second spreading level, i.e., it feeds them from the second hopper onto the second level. Optionally, the spreading head can have a third level or further levels in addition to the first and second levels. In that case, it may be advantageous to add a third component via the third level, or possibly even a further level, in addition to the first and second components. The numbering of the components and spreading levels preferably refers to the order of addition from top to bottom. This does not preclude, for example, the possibility that the second component is the main component with the largest proportion in terms of quantity and / or weight of the resulting mixture, while the first component added is an additional component with a smaller proportion. According to the invention, not all components traverse all levels of the spray head. At least one component traverses at least one fewer level than another component. Preferably, at least one component traverses all levels (including the top level), while at least one other component traverses at least one fewer level and in any case not the top level. The invention is based on the understanding that the problems encountered in practice when using a pre-prepared mixture of different components can be avoided if, instead of applying a pre-prepared mixture to the dispensing head, the individual components are added through spatially stacked and separated dispensing levels and thus selectively dosed. The desired mixture therefore builds up first in the multi-level dispensing head and finally in the mat formed below. The uncontrolled separation of a previously prepared mixture of different components is reliably prevented in a structurally simple manner. According to the invention, therefore, it is not a mixture of several components that is applied to the uppermost dispensing level, but rather the individual components, i.e.,The particles of different types are selectively dosed onto different spreading levels of the multi-level spreading head. This allows for the targeted dosing and precise delivery of materials consisting of multiple solid components or particles that may differ in size, shape, and / or density to the individual levels of the spreading head. This enables control over the distribution of each component and thus influences the position of its particles within a bulk or scattered material across the geometric height of the mat. In a first embodiment, it is possible to deliberately dose the components of different particle types, which always separate due to natural effects, asymmetrically on several levels of a multi-level spreading device in order to achieve a spreading mat with a homogeneous distribution. Alternatively, in the second embodiment, it is possible to create a deliberately asymmetrical distribution of the components or particle types across the height of, for example, a spreading mat, if this is advantageous for the desired properties of, for example, the plate to be produced. Examples of this will be explained later. The design of the spreading head, and in particular the design of the individual spreading levels, can draw upon generally known principles. Preferably, each spreading level has several rotating spreading tools. For example, the spreading head can be designed as a roller spreading head, with each spreading level having several rotating spreading rollers arranged one behind the other in a transport direction. The spreading rollers can be, for example, cylindrical rollers, which can optionally be provided with tools on their circumference, such as structured rollers or spiked rollers. Such spreading rollers with circumferentially arranged tools, e.g., spiked rollers, can also have a dissolving function and are therefore designed as dissolving rollers.Alternatively, the term "spreading rollers" also includes so-called disc rollers, which consist of a large number of discs distributed across the roller's width. Such disc rollers can, for example, have an additional orientation function, meaning they are suitable for the oriented scattering of particles, e.g., in the production of OSB boards. Optionally, the spacing of several or all spreading tools or rollers within a spreading plane of the spreading head, or possibly in all spreading planes, and / or the rotational speeds of several or all spreading tools or rollers of the spreading head can be adjusted, so that individual, several, or all rollers can be operated with different spacing and / or different rotational speed and / or different direction of rotation. In a preferred embodiment, one, several, or all of the spreading heads are designed as classification levels with a classification function, such that particles of a particle type with, for example, varying sizes are classified and consequently scattered inhomogeneously over the length of the spreading level. Such spreading heads with classifying levels are known from the prior art. Below the spreading head, as already described, a transport device, e.g. a forming belt or other conveyor belt, is preferably arranged, on which the particles are spread, e.g., forming a mat that builds up on the transport device. Optionally, a conveyor, i.e., an intermediate conveyor, can be arranged between two spreading planes of the spreading head, e.g., between the first and second spreading planes. This intermediate conveyor can, for example, be an endlessly circulating intermediate belt. Such an intermediate conveyor can optionally be driven in reverse, allowing for a change of direction. Of particular importance – as explained – is the selective dosing of the spreading material or individual particle types across the different levels of the spreading head. For this purpose, at least one of the feed devices or a hopper, e.g., the second hopper (or alternatively or additionally, the third hopper), can have an outlet for the respective component, which is positioned vertically between two spreading material levels, e.g., between the first and second levels and / or between the second and third levels. It is within the scope of the invention that several or all spreading planes of the spreading head have the same length and are arranged in alignment with one another, so that they overlap over their entire length. Alternatively, it can also be advantageous to arrange several spreading planes, e.g., two spreading planes arranged directly one above the other, offset from one another in a side view and / or to provide spreading planes of different lengths. In this case, however, it is expedient if the two spreading planes arranged one above the other have an overlap of at least 20%, preferably at least 40%, e.g., at least 50%, or alternatively at least 60%. It is particularly advantageous if the overlap is at least 70% or at least 80%. A limited overlap of less than 100% is, for example,This can be achieved by arranging two superimposed spreading planes offset from each other along the longitudinal direction and / or having different lengths. The degree of overlap can refer to the total length of the spreading head or to the length of the longer spreading plane. In one possible embodiment of the invention, it is provided that at least two spreading planes of the spreading head, e.g. all spreading planes of the spreading head, are oriented parallel to each other and optionally one, several or all spreading planes are (also) oriented parallel to the forming strip arranged under the spreading head. However, it can also be advantageous to arrange one or more scattering planes of the spreader head at an angle (≠ 0°) relative to another scattering plane of the spreader head, so that, for example, one or more scattering planes are oriented rising or falling relative to another scattering plane. Alternatively or additionally, it is possible that one, several or all scattering planes are oriented at an angle (≠ 0°) relative to the shape band, i.e., one, several or all scattering planes can be arranged rising or falling relative to the shape band. It is possible that all scattering planes are horizontally oriented. Alternatively, one, several, or all scattering planes can also be oriented upwards or downwards with respect to the horizontal. The behavior of the spreading head or the individual spreading levels can be varied by adjusting its orientation. For example, if the material metered onto a level is transported upwards, this effect prevents (undesirable) over-piling of the particles moving over the transport rollers, thus preventing unwanted inhomogeneities in the material mats forming on the spreading levels. A downward-sloping transport can support the effort of carrying the finer material all the way to the end of the roller arrangement. In an embodiment with more than two scattering planes, e.g., with three scattering planes, it is possible to set the vertical distances between the scattering planes uniformly, so that the distance (in the vertical direction) between the first and second scattering planes is identical or substantially identical to the distance between the second and third scattering planes, in each case with respect to the vertical direction. In an alternative embodiment, however, different distances can also be achieved, for example, by making the distance between the first and second scattering planes differ from the distance between the second and third scattering planes, e.g., by being larger or smaller. This allows for optimal adaptation to the flow conditions between the scattering planes. The invention relates not only to the described device, but also to a method according to claim 14 for the (continuous) scattering of scatterable (solid) particles, in particular for the production of a mat-shaped product or precursor, e.g., for the manufacture of material sheets or material mats. The method is preferably carried out with a device of the type described. According to the invention, it is provided that, as at least a first component, particles of a first particle type are supplied to or placed onto a first (upper) scattering plane, and as at least a second component, particles of a second particle type are supplied to or placed onto a second (lower) scattering plane, wherein the second scattering plane is arranged below the first scattering plane. Different particle types are used for the various components. The particles of the first type can differ from those of the second type in terms of material, material composition, shape, density, mass, and / or size. One possible application is the scattering of particles for the production of composite panels or mats, e.g., wood-based panels or panels made from other plant particles. For this purpose, wood particles or plant particles from perennial or annual plants, e.g., chips, fibers, or strands, can be used as one (first or second) particle type. A binder, e.g., a powdered or fibrous binder, is particularly suitable as another (first or second) particle type. According to the invention, the scattering of these two particle types does not occur as a pre-mixed mixture, but rather the mixing of the particles takes place during the scattering process within the scattering head according to the invention. It is particularly advantageous to add the binder as the first component of the first (upper) scattering layer, while the plant particles or...While wood particles form the "base particles," they are added as a second component only to the second spreading layer located below. In this case, the first, spatially uppermost spreading layer distributes the binder or the first component, which, due to separating behavior, trickles through and tends towards the bottom, across the surface of at least one spreading layer below it. The second spreading layer below primarily distributes the material component, e.g., the wood-based material particles, and consequently, a component that, due to separating behavior, tends towards the top. Depending on factors such as the gap spacing and the tool geometry, the material can again be separated or scattered almost unseparated. The additional particles introduced by the first spreading layer above, e.g.,...The binder passes through the second level almost unaffected by the tools of the second level because they tend to "trickle through" as described. Uncontrolled segregation does not occur in this case, since a pre-prepared mixture of different components is not dispensed via a spreader head. Instead, the individual components are metered through spatially stacked and separated spreader levels and only build up into a mixture in the multi-level spreader head and finally in the mat formed below. Alternatively or additionally, at least one additive can be used as a component, e.g., a fire retardant, an insecticide, an agent to improve wear resistance or mechanical properties, e.g., powdered glass, glass fibers, mineral fibers, or plastic fibers, or the like. It is always advantageous not to add such components to the mixture beforehand, but rather to dose them selectively via one of the spreading levels in order to create the desired properties of the mat and thus the panel. In one embodiment, it is possible to design an upper spreading layer for solid or powdered binders such that this layer selectively doses different proportions of the binder as a gradient to the building layer of binder material. An example is the production of particleboard, where the binder content of the face layers is usually higher than in the core layer. This is due to the specific surface area of ​​the differently sized chips. Less adhesive is sufficient for bonding in the core layer. In fact, according to the prior art, the adhesive content is limited to a single value per layer, e.g., 12% adhesive in the face layer material and 6% in the core layer material, since the adhesive is added to the chips before spreading. In contrast, the present invention allows a gradient of the binder to be introduced into the mat, for example...25% glue is applied to the outermost layer of the surface layer (in the case of particleboard, this is also the area with the smallest geometric wood particles, and therefore the largest specific surface area), with decreasing glue content towards the center (as the particle size increases and the surface area decreases), for example, to only 8%. This gradient improves the mechanical properties, particularly the bending strength, compared to conventionally glued surface layer material, assuming the same average glue content. If only comparable strengths are desired, this gradient allows for glue savings compared to the conventional distribution of the binder (homogeneous surface layer material). Such a gradient in the degree of gluing can also be advantageous in the core layer. Furthermore, the invention enables the addition of specific additives, e.g., selectively only in the outer cover layers or the outer areas of the cover layers. For example, reinforcing materials and glass fibers for mechanical stiffening can be added (gradually) to the cover layers, while fire retardants are to be distributed evenly throughout the entire mat. Alternatively, the invention also enables the optimized spreading of spreading mats or individual layers of spreading mats, or even multi-layered spreading mats made of several components of different spreading materials, e.g., different plant particles. These can be, for example, mats or layers of chip material and / or fiber material and / or strands (long chips) for OSB production. In this way, the different particle types, e.g., chips on the one hand and OSB material on the other, can be metered via different spreading levels of the spreading head. In principle, adhesive-coated spreading material can be used. However, preferably, even with this spreading of several plant particle types, the binder, e.g., the adhesive, is added separately, e.g., via the first, upper spreading level. This is explained by way of example in the figure description. With the solution according to the invention, it is possible to arrange each individual solid component in a targeted manner in the different height levels of a mat and, depending on the requirements, to distribute it either in different proportions and gradients or uniformly. As already described, it is possible to supply only one specific particle type via each of the individual spreading levels. Alternatively, it is also within the scope of the invention to supply not a single, pure particle type, but a mixture of several particle types via at least one of the spreading levels. For example, it is possible to supply adhesive material, i.e., plant particles or other particles already coated with a binder, e.g., glue, via one spreading level. The invention enables a particularly diverse and individual distribution of mixtures with individual properties, so that homogeneous or specifically inhomogeneous mixtures or layer structures can be produced in the described manner. In inhomogeneous mixtures, the proportion of one of the components can, for example, have at least one, preferably at least one first and one second inflection point, over the height profile of a fill / mat (e.g. relating to a single layer). Alternatively or additionally, at least one component's proportion gradient can differ from the density gradient along the height profile. For example, a binder or adhesive content can be higher in a less dense area (e.g., the core of the mat) than in other (denser) areas, and possibly also very high in particularly dense edge areas, i.e., potentially similar to the density gradient there. The invention is preferably used for the production of mats for manufacturing wood-based panels or other panels made from renewable raw materials. However, the invention is not limited to this application; it can also be used for the production of sheet-like materials made from minerals (e.g., glass or rock wool) or plastics (thermosets, thermoplastics, both as granules, in powder form, or as fibers, e.g., aramid fibers or rubber) as well as other solid components (e.g., graphite powder, carbon fibers, or metal filaments) and combinations thereof. Alternatively, the invention is also applicable to nonwovens, i.e., technical nonwovens made of fibers. In the course of the production process, the mat produced according to the invention is subsequently pressed into a material, e.g., a sheet-shaped material, for example, in a hydraulic press, in which the mat is pressed into the sheet under pressure and / or heat. The press can be designed as an intermittent press or, preferably, as a continuous press, e.g., a double-belt press. The invention will now be explained in more detail with reference to drawings which merely represent exemplary embodiments. Fig. 1a shows an embodiment of a spreading device according to the invention in a simplified side view, Fig. 1b shows a modified variant of the embodiment according to Fig. 1a in a simplified side view, and Fig. 2 shows a further embodiment of a spreading device according to the invention in a side view. The figures each depict a spreading device 1 for spreading free-flowing particles to produce a mat-shaped product or pre-product 2, particularly for the manufacture of material sheets or mats. The spreading device 1 has a multi-level spreading head 3, which has at least two superimposed spreading levels 4a, 4b, 4c, each comprising one or more spreading tools 7a, 7b, 7c. According to the invention, different types of particles 5a, 5b, 5c are fed in via the different spreading levels 4a, 4b, 4c; that is, preferably, a prepared mixture of the different types of particles is not sprinkled onto the uppermost level 4a of the spreading head, but rather the particles are added via the individual levels 4a, 4b, 4c, so that the desired, finished mixture of the spreading material is only formed within the spreading head 3 and preferably only after exiting the lowest spreading level 4b or 4c. Figures 1a and 1b show exemplary embodiments of a spreading device 1 with a multi-level spreading head 2, which has two superimposed spreading levels 4a, 4b, each comprising a plurality of spreading tools 7a, 7b. A first, upper spreading level 4a is provided, and below it a second, lower spreading level 4b. Particles of the first particle type 5a are fed as the first component via the first spreading level 4a, and particles of a second particle type 5b are fed as the second component via the second spreading level 4b. For this purpose, a first hopper 6a is provided as the first feeding device for the particles of the first particle type 5a, and a second hopper 6b is provided as the second feeding device for the particles of the second particle type 5b.From the first hopper 6a, particles of the first particle type 5a are fed onto the first spreading level 4a via its opening 10, and from the second hopper 6b, particles of the second particle type 5b are fed onto the second spreading level 4b via its opening 10. The upper spreading level 4a has a plurality of rotating spreading tools 7a, which are rotating spreading rollers or roller-like spreading elements, preferably arranged one behind the other in a transport direction T in each spreading level. In the illustrated embodiment, the spreading tools 7a of the first spreading level 4a are designed as cylindrical bodies, e.g., as structured rollers. The spreading tools 7b of the second spreading level 4b arranged below are designed as spiked rollers in the embodiment.The spacing and / or rotational speeds of the individual rollers 7a, 7b within a spreading plane 4a, 4b can optionally be variably adjustable. The direction of rotation can also be selected in individual cases, groups, or for the entire system. Details are not shown in Fig. 1a and Fig. 1b. Below the spreading head 3, a transport device, in this embodiment a forming belt 8, is provided, which moves in a transport direction T. The material exiting the spreading head 3 at the bottom falls onto the continuous transport belt 8, so that the desired spreading mat 2 is built up on the forming belt 8 from the two components or from the two particle types 5a, 5b. Figure 1a indicates that the particles of the first component, supplied via the first hopper 6a, have a smaller dimension than the particles of the second component. The design according to the invention ensures that the mixture of the first and second particles only forms below the second layer 4b, and thus during the formation of the mat 2 on the forming belt 8. The first particle type 5a can therefore be a binder, and the second particle type 5b can be the base particles, e.g., plant particles such as fibers or shavings.This ensures that the binder and the fibers or chips are only mixed within the spreading head 3 (and outside the hopper), thus avoiding the segregation observed in the prior art, since the particles are only homogeneously mixed within or below the spreading head (and possibly only within the mat). This results in a homogeneously formed spreading mat 2, built up on the forming belt 8 in the exemplary embodiment, which can consist, for example, of binder (glue) and wood-based material particles (e.g., fibers, chips, or OSB). In each of the spreading levels 4a, 4b, a collection device 9 is connected to the respective conveying direction F1, F2 of the respective spreading level 4a, 4b, which can collect excess material at the end of the respective spreading level. In any case, this is illustrated by the figure.1a shows by way of example how a homogeneously designed mat 2 or a homogeneously designed layer of a multi-layered spreading mat can be produced with the spreading device 1 according to the invention. Figure 1a illustrates that the desired homogeneous distribution of the various components in the spreading mat is achieved primarily because the spreading material is mixed only within the spreading head. Figure 1a also indicates that the individual spreading levels result in essentially homogeneous spreading. By way of example, Figure 1a shows an embodiment in which the conveying direction F1 of the upper spreading level 4A is oriented opposite to the conveying direction F2 of the lower spreading level 4B. Starting with Fig. 1a, Fig. 1b shows a modified embodiment with two spreading planes 4a, 4b. In this example, the two hoppers 6a, 6b are arranged on the same side, so that the conveying direction F1 of the first spreading plane 4a and the conveying direction F2 of the second spreading plane 4b are oriented in the same direction, namely from left to right. The spreading materials or particle types 5a and 5b each pass over the spreading plane or its spreading tools 7a, 7b. Fig. 1b illustrates the possibility that the spreading materials decrease in height along the conveying direction F1 or F2 over the spreading planes, so that the spreading material on the spreading plane decreases in a wedge shape from left to right. In this embodiment, this results in the fine particle type 5a being discharged asymmetrically under the first spreading plane 4a, with more fine material 5a being discharged in the front or left area of ​​the spreading plane 4a than in the rear right area.The fine material 5a therefore falls asymmetrically onto the second spreading level 4b below it. The same or a similar pattern applies to the coarser material 5b on the second spreading level 4b, which also decreases in a wedge shape from left to right and falls slightly inhomogeneously below the spreading level 4b. In the "mixing zone" below the second spreading level 4b, the distribution of the fine material 5a, which comes from the first level 4a, is approximately homogeneous, although slightly more material falls in the left area than in the right area. In any case, the coarser material 5b from the second level 4b is distributed in a very slightly higher quantity on the left than on the right. In this case, a truly homogeneous distribution of the two particle types 5a and 5b only occurs within the developing mat 2. Upon impact, and the resulting local movement of the chips, the fine material 5a continues to trickle downwards, so that the desired homogeneous distribution in the mat 2 is achieved.Figure 1b illustrates, by way of example, the production of a particularly homogeneous spreading mat 2 by (at least slightly) asymmetrical dosing. This is shown in a simplified manner in the drawing. This is to be distinguished from the deliberately asymmetrical spreading used to create an inhomogeneous layer structure, as shown, for example, in Figure 2. Another embodiment of a spreading direction 1 according to the invention is shown in Fig. 2. This has three spreading planes 4a, 4b, 4c and three corresponding feeding devices or hoppers 6a, 6b, 6c. A first, upper spreading plane 4a is provided with a plurality of spreading tools 7a arranged side by side and one behind the other along the transport direction (in the side view). Below this is a second spreading plane 4b with also a plurality of spreading tools 7b arranged side by side or one behind the other, and finally a third spreading plane 4c with also a plurality of spreading tools 7c arranged one behind the other. Particles of a first particle type 5a are fed in as the first component via the first hopper 6a.Particles of a second particle type 5b are fed via the second hopper 6b as at least the second component onto the second spreading level 4a, and finally, particles of a third particle type 5c are fed via the third hopper 6c as the third component onto the lowest, third spreading level 4c. Here, too, it is provided that each pair of spreading levels arranged one below the other has an opposite conveying direction F1, F2, F3 for the material fed onto it. In the illustrated embodiment, the spreading tools 7a of the first spreading level are designed as rollers, in particular as structured rollers. The spreading tools 7b in the second spreading level arranged below are designed as spiked rollers in the embodiment. Alternatively, they can also be designed as star-shaped discs. In the third spreading level 4c arranged below, the spreading tools 7c are designed as spreading discs or disc rollers in the manner of a disc spreading head.In the uppermost spreading plane 4a, the spreading tools rotate such that the particles on the spreading plane are transported in a conveying direction F1 (e.g., from right to left). In the second spreading plane 4b located below, the spreading tools 7b rotate such that the particles are transported in a conveying direction F2 (e.g., from left to right), opposite to F1, and consequently in the opposite direction to the first spreading plane. In the third spreading plane 4c located below, the spreading tools 7v rotate such that the introduced particles of the third particle type 5c are transported in a conveying direction F3 (e.g., from right to left), and consequently in the opposite direction to the conveying direction F2 of the second spreading plane. Furthermore, it is indicated that the spreading tools of the individual spreading planes can optionally be arranged at different distances along the length of the spreading plane. In the first spreading plane 4a, the spreading rollers 7a are arranged in area A with a first distance that is greater than the distance of the spreading rollers in area B. The distance in area B is, in turn, greater than the distance in the depicted area C. In combination with the surface structure of the rollers and the rotational speed, this allows more material to be spread in area A than in area B, and in turn more material in area B than in area C. This is indicated in a simplified manner in the drawing. In the second spreading plane 4b, which here forms the middle spreading plane, the spreading tools 7b, e.g., spiked rollers, are arranged in area D with a first distance that is greater than the distance of the spreading rollers in area E, and this in turn is greater than the distance of the spreading rollers in area F.This results in more material being discharged in area D than in area E, and in turn more in area E than in area F. While in the first level, in the exemplary embodiment, material is metered onto the first spreading plane along the forming belt direction T, in the second spreading plane, material is metered in the opposite direction to the forming belt direction T. In the third spreading plane 4c, overlapping spreading head discs are shown as an example. The diagram illustrates an identical spacing between the individual disc rollers. The discharge rate along the length of the spreading plane can be influenced, in particular, by controlling the rotational speeds of the individual bodies, so that even in the area of ​​the third spreading plane, an inhomogeneous distribution along the length is possible. Here, the metering and thus the transport of the material across the third spreading plane along the direction of the forming belt takes place. Since the components shown, for example three components according to Fig. 2, are dosed asymmetrically, an asymmetrical distribution also results in the forming mat 2, both in terms of quantity and height. In the illustrated case, the quantity of the finest and geometrically smallest components from the first hopper 6a is greatest directly adjacent to the forming belt 8 and decreases with increasing height of the forming mat. This area directly adjacent to the forming belt 8 forms the lower outer surface of the future product or the forming mat. The particles of the somewhat larger second component 5b from the second hopper 6b are dosed in the opposite direction. The majority is dosed towards the surface of the mat and thus only a small portion reaches the outer surface of the future product. The largest particles of the third particle type 5c from the third hopper 6c are, in turn, primarily scattered towards the outer surface of the future product.A mat 2 or a structure with a gradient is created as planned. As shown in Fig. 2, the first component from the first hopper 6a can be a binder, e.g., glue. Therefore, in this embodiment as well, unglued particles are dispensed; the glue is added within the dispensing head. The second component from the second hopper 6b can be plant particles, e.g., wood particles. These could be fibers or chips, which are added without glue in this second level. The particles of the third component, which are the largest in this case, are supplied via the third level and are, for example, long chips, i.e., strands for OSB (oriented strand board) production. Thus, in this example, a wood-based material mixture is produced with a relatively high amount of glue in the first and third components, and increasingly also in the second component, with a decreasing glue content towards the center of the exemplary dispensed (half) mat.Typically, the spreading head shown in Fig. 2 is arranged in reverse orientation along the transport direction of the forming belt behind the first spreading head, so that the other half of the mat is built up on top of the (half) mat shown in Fig. 2 in reverse order. Figures 1a, 1b, and 2 show examples of possible combinations of different levels with various spreading tools. In principle, other combinations of spreading tools are also possible with regard to number, type, transport direction, spacing, overlap, rotational speed, etc. Alternatively, the three-level spreading head shown in Fig. 2 could also be used to produce a mat made of three other components, e.g. a medium, an additive (e.g., fire retardant) and plant particles (e.g., fibers, chips or strands). In the exemplary embodiments, the individual planes are shown directly (aligned) above one another. Alternatively, however, it is also possible to arrange them one above the other and simultaneously horizontally offset from each other, so that, for example, the second plane in Fig. 2 could be oriented slightly further to the left. This would prevent any particles of this component from reaching the outside of the product, as they would be deposited more towards the center. Furthermore, exemplary embodiments are shown in which the lengths of the individual spreading planes 4a, 4b, 4c of a spreading head 3 are essentially identical. However, embodiments are also included in which the lengths of the spreading planes differ, e.g., the lengths of two spreading planes arranged directly one above the other, such that, for example, one plane is longer or shorter than the plane arranged above or below it. This also results in an overlap of the spreading planes over only a portion of the length of the spreading head. Details are not shown. Finally, the figures show exemplary embodiments in which the scattering planes, e.g., all scattering planes, are arranged parallel to each other and preferably also parallel to the forming belt arranged below. In these exemplary embodiments, all scattering planes are (essentially) horizontally oriented and preferably parallel to the forming belt. Alternatively, embodiments are also shown in which one or more or all scattering planes are not arranged parallel to each other and / or not parallel to the forming belt and / or not arranged in a horizontal direction. It may be particularly advantageous to orient individual scattering planes upwards or downwards (relative to another scattering plane and / or relative to the forming belt and / or relative to the horizontal). Details of these are not shown.

Claims

A spreading device (1) for spreading free-flowing particles, in particular for producing a mat-shaped product or pre-product (2), e.g. for the production of material sheets or material mats, with a multi-level spreading head (3) having at least two superimposed spreading levels (4a, 4b, 4c), each comprising one or more spreading tools (7a, 7b, 7c), characterized in that particles of a first particle type (5a) can be supplied as at least a first component to a first spreading level (4a) of the spreading head (3) and particles of a second particle type (5b) can be supplied as at least a second component to a second spreading level (4b) of the spreading head (3) arranged below the first spreading level (4a), wherein the spreading device has at least a first feeding device comprising a first hopper (6a) for the particles of the first particle type (5a), and at least a second feeding device.which includes a second bunker (6b) for the particles of the second particle type (5b), wherein the particles of the first particle type (5a) can be fed from the first bunker (6a) onto the first spreading plane (4a) using the first feeding device, and wherein the particles of the second particle type (5b) can be fed from the second bunker (6b) onto the second spreading plane (4b) using the second feeding device. Spreading device according to claim 1, characterized in that the spreading planes (4a, 4b, 4c) each have several rotating driven spreading tools (7a, 7b, 7c). Spreading device according to claim 2, characterized in that the spreading head (3) is designed as a roller spreading head, wherein the spreading planes (4a, b, c) each have several rotating spreading rollers arranged one behind the other in a transport direction as spreading tools (7a, 7b, 7c), e.g. structured rollers (7a), disc rollers (7c), spiked rollers (7b) or the like. Spreading device according to claim 2 or 3, characterized in that the distances of several or all spreading tools (7a,b,c) or rollers of one or more spreading planes (4a,b,c) of the spreading head (3) and / or the rotational speeds of several or all spreading tools (7a, b, c) or rollers of one or more planes (4a, b, c) of the spreading head (3) are adjustable. A spreading device according to one of claims 1 to 4, characterized in that one, several or all spreading planes are designed as classifying planes with a classifying function, such that the particles of one particle type are scattered in a classifying manner over the length of the spreading plane, e.g. classifying according to size. Spreading device according to one of claims 1 to 5, characterized in that a transport device, e.g. a forming belt (8), is arranged below the spreading head (3), onto which the particles are spread, e.g. by forming a mat (2) that builds up on the transport device. Spreading device according to one of claims 1 to 6, characterized in that an intermediate conveyor, e.g. an intermediate belt, is arranged between two spreading planes, e.g. between the first spreading plane (4a) and the second spreading plane (4b), which is preferably driven reversibly. A spreading device according to one of claims 1 to 7, characterized in that one or more further spreading levels, e.g. a third spreading level (4c), are arranged below the second spreading level (4b), wherein particles of a third particle type (5c) can be supplied to the third spreading level as, e.g., a third component, e.g., with a third feeding device, e.g., a third hopper (6c), onto the third spreading level (4c). Spreading device according to one of claims 1 to 8, characterized in that at least one feeding device, e.g. a hopper (6a, 6b, 6c), e.g. the second feeding device or the second hopper (6b), has an outlet for dispensing the respective component or particle type, which is arranged in the vertical direction between two spreading material levels, e.g. between the first spreading level (4a) and the second spreading level (4b). Spreading device according to one of claims 1 to 9, characterized in that the spreading planes of the spreading head arranged one above the other have an overlap (along the transport direction (T)) of at least 20%, preferably at least 40%, e.g. more than 50% or more than 60%, particularly preferably more than 70%, e.g. more than 80%. Spreading device according to one of claims 1 to 10, characterized in that two spreading planes of the spreading head, e.g. all spreading planes of the spreading head are oriented parallel to each other or (in a side view) are arranged at an angle to each other, such that e.g. one spreading plane or several spreading planes are oriented rising or falling relative to a spreading plane arranged above or below. Spreading device according to one of claims 1 to 11, characterized in that one, several or all spreading planes of the spreading head are oriented horizontally and / or parallel to the forming belt or that one, several or all spreading planes are arranged at an angle to the horizontal and / or to the forming belt, e.g. oriented rising or falling relative to the forming belt. A spreading device according to one of claims 1 to 12, characterized in that in an embodiment with at least three spreading planes (4a, 4b, 4c) the distances between the first spreading plane and the second spreading plane on the one hand and between the second spreading plane and the third spreading plane on the other hand are identical or that the distances to each other vary, for example by making the distance between the first spreading plane and the second spreading plane greater or less than the distance between the second spreading plane and the third spreading plane. Method for the continuous scattering of scatterable particles, in particular for the production of a mat-shaped product or pre-product, especially for the production of material sheets or mats, e.g. with a device according to one of claims 1 to 13, characterized in that particles of a first particle type from a first hopper are fed onto the first scattering plane as at least a first component and particles of a second particle type from a second hopper are fed onto the second scattering plane as at least a second component, wherein the second scattering plane is arranged below the first scattering plane. The method according to claim 14, characterized in that the particles of the first particle type differ from the particles of the second particle type in material, material composition, shape, density, mass and / or size. Method according to claim 14 or 15, characterized in that material particles (or base particles) for the production of material sheets or material mats are used as a component, e.g. as a second component, e.g. plant particles, rubber particles, mineral particles or the like. Method according to one of claims 14 to 16, characterized in that binder particles are used as a component, e.g. as a first component. Method according to one of claims 14 to 17, characterized in that additives are used as a component, e.g. as a first component or as a second or a third component, e.g. a fire retardant, flame retardant, insect repellent, stabilizing agent or the like. Method according to one of claims 14 to 18, characterized in that plant particles of a first type, e.g. fibers, chips or strands, are used as a component and that plant particles of a second type of particle, e.g. fibers, chips or strands, are used as another component, wherein preferably a binder or the like is used as a further component. Method according to one of claims 14 to 19, characterized in that at least one particle type is used for the production of a nonwoven fabric or woven fabric. Method according to one of claims 14 to 20, characterized in that a material mixture is used as one component or one particle type, e.g. a mixture of at least two particle types, e.g. a mixture of plant particles on the one hand and a binder on the other.

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