Abstract
The invention relates to a material board, in particular an engineered wood board (1) comprising at least one core layer (2) made of strands (3), and outer layers (4, 5) made of chips (6), characterised in that one or both of the outer layers (4, 5) is/are designed as partial-coverage outer layers such that individual strands (3) extend at least partly through the outer layer (4, 5) up to the board surface, thereby forming interruptions in the outer layer (4, 5).
Claims
1. A construction board comprising: at least one core layer made of wood strands and cover layers made of chips, one or both cover layers being non-full-surface cover layers in which individual strands extend at least partially through the cover layers to form interruptions in the cover layer on the board surface.
2. The construction board according to claim 1, wherein parts of the strands projecting through the respective cover layer onto the surface or visible on the surface constitute at least 20% of the total surface of the board.
3. The construction board according to claim 1, wherein the core layer made of strands is between the cover layers and consists of a plurality of sublayers, and the strands are oriented in the respective individual sublayers of the core layer in different directions in the respective sublayers of the core layer.
4. The construction board according to claim 1, wherein the cover layers have a weight per unit area of less than 1.5 kg/m.sup.2.
5. The construction board according to claim 1, wherein the cover layers constitute less than 10% of the weight per unit area of the board.
6. The construction board according to claim 1, wherein the two cover layers of chips have a different basis weight per unit area of one of the cover layers at least 10% greater than the weight per unit area of the other cover layer.
7. A method of making a flat construction board, the method comprising the steps of: making a multilayer pressed material mat having at least one core pressed-material layer of strands and a lower and an upper covering pressed-material layer of chips, and pressing the multilayer pressed material mat with the core layer and the cover layers to form the material board.
8. The method according to claim 7, wherein the lower cover pressed-material layer and the upper cover pressed-material layer are made such that, during pressing, the non-full-area cover layers are formed and individual strands extend at least partially through the cover layers to form interruptions in the cover layer out to the board surface and thus become visible.
9. The method according to claim 7, wherein the lower cover pressed-material layer and the upper cover pressed-material layer are made such that, during pressing, first complete cover layers with closed surfaces made of cover layer chips are formed, the method further comprising the step of subsequently: surface treating the cover layers such that individual strands extend at least partially through the cover layers to form interruptions in the cover layers up to the surface of the board and thus become visible.
10. The method according to claim 7, wherein the core pressed-material layer is made from strands by strewing.
11. The method according to claim 7, wherein the cover pressed-material layers are made from chips by strewing.
12. The method according to claim 7, wherein the cover pressed-material layers are made from a fluent chip/liquid mixture.
13. The method according to claim 12, wherein the upper pressed-material layers are made from the fluent chip-liquid mixture by extrusion or by roller application.
Description
[0034] The invention is explained in more detail below on the basis of drawings showing a single embodiment. Therein:
[0035] FIG. 1 is a simplified vertical section through a wood construction board according to the invention,
[0036] FIG. 2 is a large-scale plan view of a detail of the surface of a wood construction board according to the invention,
[0037] FIG. 3 is a vertical section through a pressed material mat for making a boards as shown in FIG. 1,
[0038] FIG. 4 is a highly simplified side view of a possible apparatus for making a wood construction board according to the invention.
[0039] FIG. 1 is a simplified transverse section through a wood construction board 1 according to the invention that has on the one hand a core layer 2 made of strands 3 and on the other hand an upper cover layer 4 and a lower cover layer 5 made of chips 6. In the illustrated embodiment, the core layer 2 consists of a plurality of sublayers 2a, 2b, and 2c each consisting of the strands 3, with the strands 3 oriented in each of the individual sublayers 2a, 2b, and 2c. The drawing shows a possible embodiment in which the strands 3 extend in the middle layer 2b transversely to the longitudinal direction of the board or production direction P. The strands 3 of the upper layer 2a and of the lower layer 2c are longitudinally oriented, that is to say they extend with their longitudinal direction generally parallel the longitudinal direction P of the board. Such wood construction boards with multilayer core layers and in each case upper and lower cover layers are known in principle from the prior art. According to the invention, the strands 3 extend at least partially through the cover layer 4, 5 to form interruptions of the respective cover layer 4, 5 at the board surface and are thus visible. This results from a comparative consideration of FIGS. 1 and 2. The cover layers 4, 5 do not cover the entire surface, but individual strands 3 project as far as the surface, so that they are directly visible, for example, in the top view according to FIG. 2 on the cover layer 4. Although an upper cover layer 4 made of (fine) chips 6 is provided in the board according to the invention, it is so thin according to the invention that individual strands 3 extend as far as the surface and consequently through the cover layers 4 and are thus visible. Consequently, only very small amounts of cover layer chips 6 are used and these serve (only) for leveling the relatively coarse surfaces of the OSB board, so that a wood construction board 1 with perfect surface quality is created This is shown in FIG. 2. It should be noted that here in most cases only parts of the strands 3 are seen, since these strands lie partly below the surface and only their ends or sections project as far as the surface and are visible on the surface.
[0040] A wood construction board of this type according to FIGS. 1 and 2 is made by first making a multilayer pressed material mat 1′ that has a core pressed-material layer T made of strands and an upper cover pressed-material layer 4′ made of chips and a lower cover pressed-material layer 5′ made of chips 6. Such a pressed material mat T that made on a forming belt 7 is shown in FIG. 3. This pressed material mat T can be made, for example, in a press 8 using pressure and heat to form the wood construction board according to FIG. 1. The drawing shows an embodiment in which the layers are made during manufacture of the pressed material mat T such that, during pressing in the press 8, the wood construction board 1 is made directly with the strands of the core layer 2 extending through the cover layers 4, 5 to the surface and thus being visible. In FIG. 3 by way of example, a pressed material mat T is shown, in which all layers are made from spreadable, free-flowing pressed material, that is to say both the cover pressed-material layers 4′, 5′ and the core pressed-material layer 2′ are made of strewn chips or strands in free-flowing form with conventional strewing devices one after the other on the forming belt 7. In principle, these are particles 3, 6 that are provided with a binding agent.
[0041] It has already been explained with reference to FIG. 1 that the core layer 2 consists of a plurality of sublayers 2a, 2b, and 2c with different strand orientations. For this purpose, according to FIG. 3, a pressed material mat 1′ is made in which the core pressed-material layer 2′ is again made from a plurality of sublayers 2a′, 2b′, 2c′ with the corresponding orientations of the strands 3. This is also indicated in FIG. 3 by the different representation of the strands 6 in the individual sublayers 2a′, 2b′, 2c′.
[0042] In this embodiment, it is also expedient if chips or layers with a different weight per unit area are used for the two cover layers 4, 5. FIG. 3 shows that slightly fewer chips 6 can be used for the lower cover pressed-material layer 5′ than for the upper cover pressed-material layer 4′. The consideration is that the lower cover pressed-material layer 5′ is initially substantially closed and applied flat to the forming belt 7, while the upper cover pressed-material layer 4′ applied to the core layer 2′ partially flows into the upper surface. As a result, unequal tensile stresses of the cover layers are formed after the pressing. As a result of the unequal area weights of the two fine-particle cover layers, they are made the same by the pressing process, so that a wood-based construction board 1 with satisfactory properties is produced.
[0043] Optionally, it is also possible to produce the upper pressed-material layers 4′, 5′ not from conventional free-flowing chips, but from a fluent chip-liquid mixture 9. Such a production is illustrated by way of example in FIG. 4. The installation for making a construction board 1, which is only illustrated in a simplified manner, has the already mentioned press 8 and the belt 7 on which the pressed material mat 1′ is made, so that this pressed material mat 1′ is pressed in the press 8 using pressure and heat to form the wood construction board 1. In order to produce the pressed material mat 1′, the system has a forming station 10 that, on the one hand, has feeders 11 for the core layer and, on the other hand, feeders 12 for the cover layers. While the feeders 11 for the core layer are in the form of conventional spreading machines or strewing heads for the application of the strands 3, the feeders 12 for the two cover layers in this embodiment are adapted for the already mentioned liquid application of the cover layers or for making the chip-liquid mixture 9. They can be, for example, extruders that emit the chip-liquid mixture 9 to form the respective cover pressed-material layers 4′ and 5′. Thus, first of all, the lower cover pressed-material layer 5′ is extruded onto the shaping belt 7 as a chip/liquid mixture. The individual sublayers 2a, 2b, and 2c of the core-pressed-material layer 2′ are conventionally strewed thereon, specifically by the feeders 11, and a strewing head 11 for the lower core layer and a strewing head 11 for the upper core layer and two intermediate strewing heads 11 for the central core layer are shown between them. The upper cover pressed-material layer 4′ is in turn extruded as a chip/liquid mixture to the core pressed-material layer 2′, specifically in turn with the extruder 12.
[0044] Moreover, the system indicated schematically in FIG. 4 can, of course, have further conventional components that are not shown in FIG. 4. Thus, for example, devices for processing the pressed material mat 1′, a pre-press and/or preheater, devices for detecting foreign bodies and/or a faulty bed can be provided between the molding station 10 and the press 8.
