A method of manufacturing hollow furniture parts, such as table legs, as well as an apparatus for carrying out said method

Abstract: A method of manufacturing hollow furniture parts, such as table legs comprises conveying wooden laminae to a work station (2) to form the furniture parts. The number of wooden laminae (6 a ′, 6 b ′, 6 c ′, 6 d ′) conveyed to a modelling unit provided with polygonally, preferably squarely arranged guide surfaces (2 a ′, 2 b ′, 2 c ′, 2 d ′) corresponds to the number of said guide surfaces (2 a ′, 2 b ′, 2 c ′, 2 d ′). The wooden laminae slide across the guide surfaces (2 a ′, 2 b ′, 2 c ′, 2 d ′) while abutting said surfaces. The longitudinal edges of the individual lamina are undercut so that the laminae form a prismatic, hollow tube (7) subsequent to being assembled. The side surfaces of said tube (7) are mitred along the longitudinal edges of the tube, and the wooden laminae (6 a ′-6 d ′) are glued together in pairs by means of a fast-drying glue applied shortly before the laminae reach the modelling unit (2). Support and/or end blocks (18, 19) are then optionally inserted in and glued to the inside of the prismatic tube (7). Finally the tube (7) is cut into small pieces corresponding to the furniture parts. This method enables the manufacture of furniture parts with prismatic shape in a simple manner while avoiding such steps in the pocess resulting in considerable inner stresses in the wood.

Description: The invention relates to a method of manufacturing hollow furniture parts, such as table legs, said method being optionally continuous, and comprising conveying a plurality of wooden webs to a modelling station having polygonally arranged guide surfaces, each wooden web being fed to its guide surface and sliding thereon while abutting said surface and gluing the wooden webs together in pairs by means of a fast-drying glue applied shortly before the webs reach the modelling station. It has been known for a long time to manufacture tubes of circular cross-section by helically wrapping strips of veneer. This method is, however, unsuitable for the manufacture of a large number of pieces of furniture, where the furniture parts are to be prismatic or possibly rectangular. Moreover, there is a risk of considerable stresses being developed in the wood due to the strong bending of the wood. US-A-2 631 956 discloses a method and an apparatus for the manufacture of box girders said method comprising feeding four wooden web strips to the apparatus and gluing the strips together. The apparatus has several sets of outer and inner rollers to support the web strips. The strips are not mitred together and no sanding devices are provided. The disclosed method and apparatus are not satisfactory because they are too complicated. US-A-3 477 485 describes a method of assembling wooden T and I beams. These beams have no hollow cross-section and there is no disclosure concerning miter-shaping of the edges of the wooden webs used. Glue is applied to the webs by glue spreading rollers. The webs are sanded before the glue is applied and not after, a further difference with respect to the present invention as will be made clear hereinafter. The object of the invention is to provide a method enabling the manufacture of furniture parts with prismatic shape in a simple manner while avoiding steps in the process that result in considerable inner stresses in the wood. The object is solved in accordance with the invention by a method having the features of claim 1. This results in a simple method of manufacturing the desired prismatic furniture parts without running the risk of serious inner stresses in the wood, as the wooden webs are conveyed to the modelling station substantially without being deformed. At the modelling station the wooden webs are glued together in pairs at the undercut longitudinal edges so that a prismatic tube is formed. The glue is of the fast-drying type to ensure that the tube does not collapse right after the modelling station. The support and/or end blocks are inserted to reinforce the prismatic tube. The sanding of the tube after glue has been applied will ensure removal of superfluous glue. Finally the prismatic tube is cut into small pieces corresponding to the furniture parts. The end blocks close the openings at the end of the furniture parts so that the hollowness of the furniture parts is not noticed. In an aspecially suitable embodiment of the invention the webs used are wooden veneers or fiber-boards. The inventive end blocks used may be provided with recesses for fastening the furniture part to other furniture parts, thus facilitating the attachment of said furniture part to another part of the furniture. The inventive support block may be arranged in the middle of the inside of the furniture part, such as a table leg, giving the furniture part mechanical strength despite it being hollow and of comparatively light weight. The guide surfaces of the modelling station may be placed so as to form the sides of a square; as a result a product is obtained which may be used in many fields of use. The inventive guide surfaces of the modelling station may be placed so as to form the sides of a triangle, preferably an equilateral triangle, resulting in a triangular cross-section of the furniture part. A table leg of such a cross-section is especially suitable for a low coffee table. Furthermore, the inventive support and/or end blocks may be inserted into the hollow tube by being previously, fastened to one of the wooden webs. As a result the manufacture of the prismatic tube and thus the furniture part is especially simple. According to the invention long pieces of wooden web may be used instead of an "endless" web, the length of said pieces corresponding to once, twice or several times the length of a furniture part, such as the length of a table leg. As a result the risk of undesired stresses in the prismatic tube is very low, as it is almost unnecessary to bend the wooden webs during their way to the modelling station. The invention also relates to an apparatus for carrying out the inventive method, which apparatus is defined in claim 9. This ensures an especially simple and inexpensive manufacture of the inventive furniture part. In one embodiment of the inventive apparatus the guide bodies may be arranged in such a way that their guide surfaces form a square aperture of the size correscponding to the cross-section of the furniture part, such as a table leg. This renders the apparatus especially suitable for the manufacture of all types of table legs. According to the invention the guide bodies may be slightly staggered with respect to each other seen in the forward direction of the prismatic tube, resulting in more space for the shafts of the guide bodies. Finally, the inventive guide bodies may be rigid and form a large block with an aperture in which the prismatic tube is formed. This is an especially suitable embodiment when the wooden webs are to be conveyed at a low velocity. The guide surfaces are stationary, since there is no risk of extensive friction between the guide surfaces of the modelling station and the wooden webs. The invention is described in greater detail below and with reference to the accompanying drawings, in which Figure 1 is a diagrammatic, lateral view of an apparatus for carrying out the inventive method, Figure 2 illustrates an embodiment of the modelling station of the apparatus, where the guide bodies with corresponding guide surfaces form substantially a square, Figure 3 is a perspective view of a table leg manufactured according to the inventive method, the parts of said table leg being separate, Figure 4 is a perspective view of a modelling station, where the three guide bodies are arranged to form substantially an equilateral triangle, Figure 5 illustrates a modelling station in form of a solid block with an aperture, where the defining surfaces of the aperture form the guide surfaces for the wooden webs, Figure 6 illustrates a table leg during its manufacture, where pieces of wooden web with a predetermined length are used instead of an endless web, and Figure 7 is a cross-sectional view of a square table leg with mitred corners. The apparatus of Figure 1 comprises a bottom plate 1 above which there is mounted a modelling station 2 carrying a number of guide bodies with corresponding guide surfaces 2'. Figure 2 illustrates how the guide bodies comprise the rollers 5 a , 5 b , 5 c , 5 d being of circular cross-section. In this case the guide surfaces are the curved surfaces 2 a ', 2 b ', 2 c ', 2 d ' of the rollers 5 a , 5 b , 5 c , 5 d . In Figure 2 the guide bodies are arranged such that they substantially form the sides of a square. On the other hand, the use of more guide bodies than four, i.e. a guide body for each side of a polygon, is also possible. The guide bodies can be slightly staggered with respect to each other, seen in the longitudinal direction of the apparatus, so that the shafts of the rollers do not impede each other. The apparatus of Figure 1 comprises furthermore four holders 6 a , 6 b , 6 c , for rolls of wooden webs (actually fiberboard) (the fourth holder is hidden behind the holder 6 c and thus not provided with a reference numeral). The rolls of wooden web have cores (not shown) with large diameters to ensure that the wooden webs reeled off the rolls have a comparatively slight curvature when they are on the rolls. Instead of said rolls of wooden web long pieces of wooden web (bands) of a predetermined length, see below, can also be used. On the right-hand side of Figure 1 the apparatus is provided with a cutting means 45 for cutting off finished furniture parts, such as table legs, from a prismatic tube 7 formed by wooden webs 6 a ', 6 b ', 6 c ', 6 d ' at the modelling station 2. The apparatus of Figure 1 is furthermore provided with several glue application means 10 at the corners of the square formed by the guide bodies 5 a , 5 b , 5 c , 5 d . When the guide bodies form an n -sided polygon instead of a rectangle, the apparatus is provided with n glue application nozzles each at a corner of the polygon, and with n guide bodies. Figure 3 illustrates a table leg manufactured by means of the inventive method, the parts of said table leg being separate. There are four pieces of wooden web 16 a , 16 b , 16 c , 16 d , each of their ends being provided with end blocks 18. Inside the table leg a support block 19 is inserted, preferably in the middle of the leg. The end blocks are optionally provided with recesses 20 (depicted with a dotted line) to ensure an easy mounting of the table leg to a table leaf. Instead of a modelling station with four guide surfaces (one on each rotating guide body) the modelling station may have only three guide surfaces 32 a , 32 b , 32 c , cf. Figure 4, in which there are only three rotating guide bodies. The latter are arranged such that they substantially form the sides of a triangle, preferably an equilateral triangle. The modelling station can also comprise a solid plate 40 with an aperture 41 in its middle, said aperture being provided with a number of guide surfaces 12 a , 12 b , 12 c , 12 d . Such a modelling station is used when the friction between the conveyed wooden web and the guide surfaces is negligible during conveyance. The inventive method is carried out on an inventive apparatus in the following way: The rolls of wooden web are placed in their respective holders 6 a , 6 b , 6 c , 6 d , whereupon the wooden webs 6 a ', 6 b ', 6 c ', 6 d ' are pulled or pushed through the modelling station 2, said wooden webs abutting the guide surfaces 2 a ', 2 b ', 2 c ', 2 d ' of the guide bodies 5 a , 5 b , 5 c , 5 d , cf. Figure 1. The individual wooden web is mitred along its longitudinal edges, i.e. it is undercut, so that it forms an even joint with its neighbouring webs. The undercutting on a wooden web is performed either in advance or by conveying the wooden web through an undercutting means (not shown) of the apparatus, where the undercutting is performed by e.g. planing or sanding. Simultaneous with the webs 6 a ', 6 b ', 6 c ', 6 d ' being conveyed through the modelling station (and abutting the guide surfaces) glue is applied to the longitudinal edges of the wooden webs from the application nozzles 10. The nozzles are supplied with glue by means of a common tubing system (not shown). The glue is preferably of the fast-drying type. Subsequent to passing the modelling station 2 the wooden webs are glued together to form a prismatic tube 7, cf. Figure 7. The prismatic tube can be provided with support and/or end blocks 18, 19, cf. Figures 2 and 3. The blocks are in advance attached to the wooden web 2 d ' on the side facing the inside of the prismatic tube 7. The blocks are usually of such a cross-section that they fill out the entire cross-section of the prismatic tube 7. Subsequent to the wooden webs having passed the modelling station and the glue having dried the prismatic tube is cut into lengths corresponding to the individual furniture parts, typically table legs. The cutting is performed by the cutting means 45. The wooden webs used are e.g. wooden veneer or fiberboard. Optionally the outside of the prismatic tube 7 is sanded down along the mitred edges by a sanding means 25, diagrammatically shown in Figure 1. The sanding occurs after the wooden webs have been assembled but be fore the cutting into suitable parts. If it is desired that the prismatic tube 7 has the cross-section of an equilateral triangle instead of a square, the wooden webs pass through the modelling station of Figure 4. The longitudinal edges of each web are in this case undercut by 30°. The longitudinal edges of the wooden webs of Figure 2 are undercut by 45°. When the wooden webs are very smooth the modelling station 2 of Figure 5 is most suitable. Instead of an endless web (rolled-up wooden web) comparatively long pieces of wooden web can be used for the inventive method. Such pieces can have a length corresponding to twice or several times the length of the furniture part, such as a table leg. In this case the individual piece of wooden web 30 b is conveyed to the modelling station 2 by means of a holding means 32 operating with vacuum, the outer ends of said holding means being provided with suction cups 33 ensuring a secure hold of the piece of wooden web 30 b . In the present application the term "wooden web" refers to a web made of wood. The term is, however, to be understood in a much broader sense, since it covers many other materials, such as plastics or press-wood.

Claims: A method of manufacturing hollow wooden parts (16), said method being continuous, and comprising conveying a plurality of wooden webs (6a', 6b', 6c', 6d') to a modelling station (2) having polygonally arranged guide surfaces (2a', 2b', 2c', 2d'), each wooden web being fed to its guide surface and sliding thereon while abutting said surface, and gluing the wooden webs (6a' to 6d') together in pairs by means of fast-drying glue applied shortly before the webs reach the modelling station (2); characterized in that before gluing the wooden webs together the longitudinal edges of each wooden web are undercut and adapted to be mitred with the adjacent wooden webs so as to form a prismatic, hollow tube (7) subsequent to being assembled, that the assembling is carried out by means of the guide surfaces (2a', 2b', 2c', 2d') arranged exclusively circumferentially around the outer surface of the prismatic, hollow, tube (7) being formed, that support and/or end blocks (18, 19) are inserted into the hollow tube (7) and glued to the inside of the latter during the continuing assembling procedure, and that the prismatic tube (7) is sanded down (at 25) along the mitred edges whereafter said tube is cut into pieces corresponding to the furniture parts (16). A method as claimed in Claim 1, characterized in that the webs (6 a ', 6 b ', 6 c ', 6 d ') used are made of wooden veneers or fiberboards. A method as claimed in Claim 1 or 2, characterized in that the end blocks (18) used are provided with recesses (20) for fastening the furniture part to other furniture parts. A method as claimed in Claim 1, 2 or 3 characterized in that the support block (19) is arranged in the middle of the inside of the furniture part, such as a table leg. A method as claimed in one or more of the preceeding Claims 1 to 4 characterized in that the guide surfaces of the modelling station are placed so as to form the sides of a square. A method as claimed in one or more of the preceding Claims 1 to 4 characterized in that the guide surfaces (3 a , 3 b , 3 c ) of the modelling station (2) are placed so as to form the sides of a triangle, preferably an equilateral triangle. A method as claimed in one or more of the preceding Claims 1 to 6 characterized in that the support and/or end blocks (18, 19) are inserted into the hollow tube by being previously fastened to one of the wooden webs (6 d '). A method as claimed in one or more of the preceding Claims 1 to 7 characterized in that long pieces of wooden web are used instead of "endless" webs, the length of said pieces corresponding to once, twice or several times the length of a furniture part, such as the length of a table leg. An apparatus for carrying out the method as claimed in any one of Claims 1 to 8, which apparatus comprises a number of holders (6a, 6b, 6c, 6d) for wooden webs (6 a ', 6 b ', 6 c ', 6 d ') to form a prismatic, hollow tube (7), a modelling station (2) having guide bodies (5 a , 5 b , 5 c , 5 d ) provided with corresponding guide surfaces (2 a ', 2 b ', 2 c ', 2 d ') polygonally arranged along the sides of the modelling station (2) for assembling the wooden webs and for conveying the resulting prismatic tube (7), and a number of glue application means (10) for applying glue to the longitudinal edges of the wooden webs (6 a ', 6 b ', 6 c ', 6 d ') characterized in that the guide surfaces (2a', 2b', 2c', 2d') are arranged exclusively circumferentially around the outer surface of the hollow, prismatic tube (7) for assembling the webs, which have previously been mitered along their longitudinal edges, into a miter-joined tube, in that sanding means (25) are arranged after the modelling station (2) and near the mitred edges of the prismatic tube, and in that a cutting means (45) is provided for cutting off furniture parts of a desired length from said tube (7). An apparatus as claimed in Claim 9, characterised in that the guide bodies (5 a , 5 b , 5 c , 5 d ) are arranged in such a way that their guide surfaces (2 a ', 2 b ', 2 c ', 2 d ) form a square aperture of a size corresponding to the cross-section of the furniture part, such as a table leg.. An apparatus as claimed in Claim 9 or 10, characterized in that the guide bodies (5 a , 5 b , 5 c , 5 d ) are slightly staggered with respect to each other seen in the forward direction of the prismatic tube (7). An apparatus as claimed in Claim 9 or 10 characterized in that the guide bodies (5 a , 5 b , 5 c , 5 d ) are rigid and form a large block (40) with an aperture (41) in which the prismatic tube (7) is formed.

Inventors: PETERSSON OLLE, PETERSSON, OLLE
Applicants: INTER IKEA AS, INTER-IKEA A/S
Application year: 1988
Main classification: B27D1
IPC codes: B27M3, B27D1