METHOD OF PRODUCING A BUILDING ELEMENT DESTINED FOR THE MAKING OF A LAMINATED WOODEN FLOOR

Abstract: In a method of producing a building element, which consists of glued-together layers of wood (15-17) and which is destined for the making of a laminated wooden floor, such as a parquet floor, at least two layers of wood (15-17) are placed one above the other with an intermediate layer of glue so as to form a base unit (14). The base unit (14) is compressed between two press plates (10, 11) extending in parallel with the layers of wood (15-17). During compression, an electromagnetic high-frequency alternating field is applied across the base unit (14) in order to harden the glue in the layer of glue. The electromagnetic high-frequency alternating field is applied across two electrode plates (12, 13) which extend perpendicular to the press plates (10, 11) and which, during the compression of the base unit (14), are placed on both sides of the base unit in the vicinity of two opposite side edges thereof.

Description: METHOD OF PRODUCING A BUILDING ELEMENT DESTINED FOR THE MAKING OF A LAMINATED WOODEN FLOOR The present invention relates to a method of pro¬ ducing a building element, which consists of glued- together layers of wood and which is destined for the making of a laminated wooden floor, such as a parquet floor, in which method at least two layers of wood are placed one above the other with an intermediate layer of glue so as to form a base unit, which is compressed between two press plates extending in parallel with the layers of wood, an electromagnetic high-frequency alter- nating field being applied across the base unit in order to harden the glue in the layer of glue. A known method of this kind will now be described in more detail with reference to Fig. 1, which schematically illustrates the known method. A base unit in the form of a rectangular board 1, which is of a width of about 1 m and a length of about 2 m, is made up of five layers of wood 2-6 with inter¬ mediate layers of heat-hardenable glue. The board 1 con¬ sists of a lower, about 2-mm- hick bottom veneer layer 2, an about 10-mm-thick intermediate veneer layer 3 ar¬ ranged thereon, an about 10-mm-thick intermediate layer 4 arranged on the layer 3 and consisting of a plurality of wood bars laid in a predetermined pattern, an about 10-mm-thick intermediate veneer layer 5 placed on the intermediate layer 4 and being of the same kind as the intermediate veneer layer 3, and an upper, about 2-mm- thick bottom veneer layer 6, which is of the same kind as the bottom veneer layer 2. The board 1 is placed in a press between an upper press plate 7 and a lower press plate 8, between which it is compressed. During compression, an electromagnetic high-frequency (10-30 MHz) alternating field is applied across the board 1 to harden the glue in the glue layers. This high-frequency alternating field is applied by means of an oscillator system 9, which is connected to the two press plates 7 and 8 as shown in Fig. 1. After hardening of the glue (after about 1 min), the board 1 is removed from the press to be divided into two boards by sawing in the centre of the intermediate layer 4. The divided layer 4 of each board should form an upper wearing coat of the wooden floor that is to be produced of the boards. When the board 1 is removed from the press, it has a temperature of up to 100 C C. However, the board 1 has an uneven temperature distribution and is warmest in its intermediate portion. The uneven temperature distribution results in an uneven moisture distribution in the board 1, which in turn causes unfavourable stress conditions in the board. Before the board 1 is divided and then used as building element, it must therefore be reconditioned under predetermined climatic conditions. Such recondi¬ tioning lasts 2-5 days. The object of the present invention is to provide a method of producing a building element, the method being of the type described by way of introduction and permit¬ ting a reduction of the working time in the press and not requiring any subsequent reconditioning step. The object is achieved by a method which is of the type described by way of introduction and characterised in that the electromagnetic high-frequency alternating field is applied across two electrode plates which are substantially perpendicular to the press plates and which, during the compression of the base unit, are placed on both sides of the base unit in the vicinity of two opposite side edges thereof. The invention will now be described in more detail with reference to the accompanying drawing. Fig. 1 illustrates schematically the above described known method. Fig. 2 illustrates schematically the inventive method. Fig. 2 shows a press, which comprises a horizontal upper press plate 10 and a horizontal lower press plate 11. The press also comprises two vertical plates 12 and 13 which are parallel with each other. A plurality of board-shaped base units 14 being of a length of about 2 m and a width of about 20 cm, are made up of three layers of wood 15-17 with intermediate layers of heat-hardenable glue. Each base unit 14 con¬ sists of an about 2-mm-thick bottom veneer layer 15, an about 6-mm-thick intermediate veneer layer 16 arranged thereon, and an about 2-mm-thick upper layer 17 arranged on the intermediate veneer layer 16 and consisting of a plurality of wood bars laid in a predetermined pattern. The upper layer 17 should form an upper wearing coat of the wooden floor that is to be produced of building ele¬ ments made of the base units 14. A stack of 20-30 superposed base units 14 are placed in the press between the two press plates 10 and 11 and vertical plates 12 and 13 thereof to be compressed verti¬ cally. The stack is arranged in the press, such that the long sides of the board-shaped base units 14 included therein extend in parallel with the vertical plates 12 and 13. The vertical plates 12 and 13 are laterally dis- placeable to be able to be moved towards the stack and orient the base units 14 included therein in relation to each other and in relation to the press plates 10 and 11. During compression, the vertical plates 12 and 13 are held slightly spaced from the stack. The vertical plates 12 and 13 constitute electrode plates and are connected to an oscillator system (not shown) in order to apply, during compression, an electro¬ magnetic high-frequency (10-30 MHz) alternating field across the stack and, thus, cause hardening of the glue in the glue layers between the layers of wood 15-17 in each base unit 14. The upper press plate 10 and the lower press plate 11 each consist of a metal plate, which on its underside and its upper side, respectively, supports a plastic plate 10', 11' preventing flashover between the vertical plates 12, 13 on the one hand and the respective press plates on the other hand. By applying the electromagnetic high-frequency alternating field by means of the two vertical plates 12 and 13, it reaches all glue layers directly without first passing through one or more layers of wood. For this reason, the glue is hardened in a very short time (10-30 sec) and heated between the layers of wood 15-17 but to a small extent, which makes it unnecessary to per¬ form any subsequent reconditioning of the building ele- ments produced in the press.

Claims: CLAIMS 1. A method of producing a building element, which consists of glued-together layers of wood (15-17) and which is destined for the making of a laminated wooden floor, such as a parquet floor, in which method at least two layers of wood (15-17) are placed one above the other with an intermediate layer of glue so as to form a base unit (14), which is compressed between two press plates (10, 11) extending in parallel with the layers of wood, an electromagnetic high-frequency alternating field being applied across the base unit (14) in order to harden the glue in the layer of glue, c h a r a c t e r i s e d in that the electromagnetic high-frequency alternating field is applied across two electrode plates (12, 13) which are substantially perpendicular to the press plates (10, 11) and which, during the compression of the base unit (14), are placed on both sides of the base unit in the vicinity of two opposite side edges thereof. 2. The method as claimed in claim 1, c h a r a c ¬ t e r i s e d in that, before the compression of the base unit (14), the electrode plates (12, 13) are used to orient the layers of wood (15-17) relative to each other.

Inventors: LINDER JOHNNY, LINDER, JOHNNY
Applicants: LINDER JOHNNY, TARKETT AB, LINDER, JOHNNY
Application year: 1996
Main classification: B27M3
IPC codes: B27M3, B32B21, F26B3, F26B7, H05B6