The present invention relates to a method for the manufacture of a curved wood fibre board which is coated with veneer on the front side. The invention also relates to a furniture board of wood fibre and coated with veneer.
Wood fibre boards, such as chipboards, MDF boards and the like, are extensively used in the manufacture of furniture, as such boards are easy to machine and inexpensive as starting products. They are moreover strong and have some advantageous properties with respect to massive or laminated wooden boards with respect to e.g. stability of shape under various temperature and moisture conditions, which makes wood fibre boards suitable for the manufacture of furniture. The board material is coated with a wooden veneer and/or other surface coating and cut to shape, following which the board sections are built together to a bookcase, a loudspeaker cabinet or the like. This manufacturing procedure can be carried out in an automatic process, which makes it simple and not very costly, just as it provides a good protection for the furniture boards against ingress of moisture. The surface finishing and the cutting of the boards can thus be performed on the same process equipment, in which a plane board may be subjected to surface finishing as well as cutting.
When machining wood, including particularly wood fibre boards for the manufacture of furniture, the manufacturers moreover sometimes have to manufacture curved boards for furniture panels, e.g. for cabinet ends, cabinet doors and side panels in loudspeaker cabinets. Such panels are particularly used in connection with more exclusive furniture design, but the curved shape has been found to involve an extremely costly process which is much more difficult to handle. Various methods for the bending of wooden boards are known, comprising e.g. subjecting a board, such as a wood fibre board, which may initially have been provided with grooves or the like, to liquid or steam treatments and/or thermal treatments. In connection with these treatments or immediately after them, the board is bent in a moulding tool, is provided with a binder and is fixed for a given period of time until the board has hardened in its new shape. These known manufacturing methods require extensive process equipment, which makes them costly and time-consuming processes.
Further, DE 28 15 714 Al and DE 43 40 049 Al among others disclose methods corresponding to the introductory portion of claim 1 for bending wood fibre boards by cutting slits in one side of the board. The boards are then bent upwards and moulded, following which they may be given a surface finishing in their final convex shape. This surface finishing may consist of sanding with subsequent lacquering, spray-painting or the like.
When the board has been moulded by one of these bending methods, a surface finishing, such as coating with veneer, may be applied. However, the surface finishing, such as wiping, lacquering and polishing of the surface of the bent board, is difficult to perform in an automated process because of the curved face or faces which have been applied to the surface. The finishing of the curved surface on such a board is therefore performed manually, which is time-consuming and the quality of it depends on the craftsmanship available.
It is characteristic of the various known methods for the manufacture of curved wooden panels that they involve low technology processes, which are labour-intensive and have a very low degree of automization.
Accordingly, the object of the invention is to provide a method for the manufacture of curved furniture boards which makes the manufacture simpler and less expensive, and which lends itself for implementation in automated process equipment, and to a furniture board manufactured using such a method.
The invention comprises a method of the type mentioned in the opening paragraph in which the veneer layer is given a surface finishing in a plane state either before or after the slits are made in the rear side of the board, and the board is bent to a concavely and/or convexly curved configuration.
A method according to the invention allows the surface to be finished in the plane state of the board, and ensures that the surface coating is not damaged in the subsequent bending. Also, an extremely uniform and smooth bending of the surface of the board is obtained by the method according to the invention. This means that boards for curved furniture panels may be manufactured in the same process system as is used for the manufacture of plane boards for furniture. This provides the same advantages in terms of automization, including both saving of time and low production costs, in the manufacture of boards with curved panels as are obtained in the manufacture of plane panels.
Moreover, a method according to the invention allows boards to be bent independently of their thickness, which makes the method extremely flexible in relation to the production of furniture in which various board thicknesses are frequently used. Further, it has been found that i is possible to manufacture both convexly and concavely curved boards by a method according to the invention.
The invention also relates to a wood fibre furniture board coated with veneer, wherein at least part of the rear side to be bent is formed with groove-shaped slits of such a shape as to allow the board to be bent.
In a preferred embodiment, the groove-shaped slits are formed with a certain width in the bottom and with a uniform depth, thereby leaving an outer board layer below the veneer whose thickness substantially corresponds to the width of the grooves. This results in an extremely uniform and smooth bend, and any "edges" because of cracks in the veneer are avoided.
A further aspect of the invention is a furniture board manufactured in the performance of the method according to the invention, in which the bent board is held in the curved shape in that a rear support has been applied to the board. In a preferred embodiment, the rear support applied to the rear side of the board may be a flexible sheet, such as melamine paper, applied by gluing. This also provides a uniform inner face of the furniture board. When a furniture board according to the invention is used for loudspeaker cabinets, this embodiment of the rear support may also be used to compensate for any unacceptable sound reflections which might otherwise have occurred because of slits of the rear side. Further, a rear support according to this embodiment may serve as a moisture barrier, thereby preventing moisture from penetrating into the board. This is extremely advantageous in the production of furniture or furniture panels which are to be exported from a tempered climate region to regions of other climatic conditions, such as subtropical or tropical climate conditions.
In another embodiment, the rear support may comprise a matrix or a similar framework having ribs whose shape corresponds to the desired curve shape of the furniture board or boards. It is hereby possible to bend the board directly in connection with the construction on the basis of a matrix or similar framework for the furniture, which simplifies the mounting of a furniture board according to the invention in a furniture panel. This form of rear support may moreover be used as a supplement to the application of a sheet.
Alternatively, the rear support of a furniture board according to the invention may be formed by joining the furniture board with another board, said boards being secured to each other at their rear sides so that the slats in the first furniture board produced between the groove-shaped slits engage groove-shaped slits in the second board, whereby the two boards serve as a rear support for each other.
A curved furniture panel coated with veneer on both sides can be obtained hereby, as both boards may be manufactured substantially identically. This may be attractive in connection with furniture panels which are visible from both sides as well as in case of free-standing panels or articles of furniture. Further, this embodiment may also be used as a reinforcement of the furniture panel.
Another aspect of the invention is a furniture board, which, provided with groove-shaped slits in one or more sections and formed with one or more cut-outs or openings for subsequent mounting of fittings of various types, such as loudspeaker units, is erected to a tubular shape so that the slitted section or sections form curved panel sides of the cabinet.
As a result, several different sides forming part of the furniture, including the incorporated curved portion or portions, may be provided in the same furniture board, thereby avoiding numerous changes in production equipment. It is also ensured that even furniture of circular, oval or similar cross-sections can be manufactured without a significant increase in the production costs.
Moreover, the rear side of the furniture board may be provided with V-tracks in parallel with the grooves to form corner edges when erecting the furniture board to said tubular shape. This moreover ensures that the furniture board may be folded along the V-tracks, thereby making it possible to manufacture furniture of polygonal cross-sectional shapes where one or more of the sides are curved.
The invention will be described more fully below with reference to the drawings, in which:
Fig. 1 shows a furniture board according to the invention which comprises a wood fibre board 1 coated with veneer 2 on the front side. The rear side of the board 1 is formed with groove-shaped slits 3 of a depth slightly smaller than the thickness t of the board, so that the outer layer of the front side of the board 1 is intact, but of a suitably small thickness t for it be pliable and flexible so that it can assume a uniform curved shape on the outer side.
The grooves 3 are formed with a flat bottom and two parallel sides in the embodiment shown. The width b of the groove bottom is of the same size as the thickness t of the outer layer, thereby providing a satisfactory uniformity in the curvature of the veneer side. It is realized by the invention that for a smooth and even curvature to be obtained it is important that the grooves 3 have the same depth so that the thickness t is the same along the entire board.
Tests have thus shown that inter alia a satisfactorily smooth and uniform curvature of a veneer coated MDF board having a board thickness T of 19 mm may be obtained. In this case, the grooves in the rear side are formed with a width b of 2 mm and with a depth such that the thickness of the outer layer on the veneer side is 2.5 mm as well as with a spacing (slat width) of about 7 mm between one another.
Of course, the grooves may also have other shapes, e.g. with a rounded, semi-circular or concave bottom face. However, it is important that the opening rearwardly is sufficiently large in the plane state so that the slats 4 produced between the groove-shaped slits do not contact each other by a convex bending of the surface, see fig. 2, or at any rate that contact is not established between two adjacent slats until the desired convex curvature has been obtained. The veneer coating and the milling of the grooves 3 are performed in the plane state of the board, following which the board 1 is curved to the desired shape, which may e.g. be the shape which is shown in fig. 2.
A rear support 5, 7, 1' is applied to maintain the furniture board 1 in its curve shape.
Fig. 3 shows an embodiment in which the rear support is a flexible sheet 5, such as melamine paper, glued to the rear side of the board after the bending. This covers the interior and untreated surface of the board, which will otherwise to exposed to moisture, which may have extremely unfortunate consequences, as the dimensional stability and durability of the board may be impaired. The glue 6 used for the gluing of the sheet to the rear side of the board 1 binds the sheet 5 to the slats 4 and only penetrates a short distance down between the grooves 3. Thus, only a modest amount of glue 6 is to be used. If further fixing is desired, the grooves 3 may be filled completely with the glue, but, in this case, it is preferred to use a jointing substance for the filling, as this is a cheaper solution.
In fig. 4, the furniture board 1 is secured to a framework 7, such as a matrix having a plurality of ribs 7 exhibiting engagement faces of the same contour as the desired curve shape of the furniture panel. The furniture board 1 is bent over and glued to these ribs 7. Here, the glue 6 used will likewise give a certain reinforcement of the panel.
In a variant of this embodiment the furniture board 1 is fixed in the desired curvature with a flexible sheet 5, as shown in fig. 3, following which the resulting furniture panel is fixed to a matrix, as shown in fig. 4.
In a third embodiment, the rear support is formed by a board 1' corresponding to the furniture board 1, as shown in fig. 5. The two boards 1, 1' are curved to the desired curvature, one to a concave shape and the other to a convex shape, and then they are joined preferably by gluing at their rear sides, both of which are formed with grooves 3, 3' and slats 4, 4'. The slats 4' in the board 1' extend into and engage the grooves 3 in the furniture board 1, and vice versa. The grooves 3, 3' and thereby the slats 4, 4' are geometrically shaped so as to be capable of engaging each other. The grooves 3, 3' and the slats 4, 4' in the two boards 1, 1' have been provided with glue (not shown) prior to the joining, which, in addition to binding the boards 1, 1' together, can also serve as a filler - and thereby to stiffen - the cavities inside the grooves 3, 3', should such cavities be present.
In the example shown in fig. 5, both boards 1, 1' are coated with veneer 2, 2' on the outer sides. This provides a furniture panel according to this embodiment of the invention with an acceptable surface finish on both sides, which will be advantageous in some furniture structures, including non-sitting furniture structures. In a variant of the example shown in fig. 5, only one of the boards 1 is coated with veneer 2. The other board 1' thus serves partly as a rear support and partly as a reinforcement of the furniture panel.
Figs. 6 and 7 show a furrniture board 1 which has been prepared with four sections 9, 10, 11, 12 corresponding to the four sides of a loudspeaker cabinet, as shown in fig. 8. In the rear side of the furniture board, the first section 9 is formed with holes 13 in which loudspeaker units may be mounted, the second and fourth sections 10, 12 are formed with groove-shaped slits to provide curved panel sections, and the transition between the sections 9, 10, 11, 12 is formed with V-tracks 8 which correspond to the corner edges in the cabinet, and which have a depth almost corresponding to the thickness of the board. When the board 1 is erected to a tubular shape, as shown in fig. 8, the board sections are folded about the V-tracks 8 which thereby collapse.
The invention has been described in relation to a loudspeaker cabinet, but it is realized by the invention that both a method and a furniture board according to the invention may be used for the manufacture of other types of furniture, such as cupboards, tables, chairs and the like in which one or more curved panels are desired for reasons of design.