SK592007A3 - Process of bending of natural veneers by method of post forming - Google Patents

Abstract

Process of bending of natural veneers by method of post forming is based on the fact that on a basic structural board by means of a contact waterproof adhesive is fixed a thick natural veneer overlapping edges of the structural board, which is before the bending at the desired point of the bending saturated in a short time within 3 minutes by pre-treated fluid enters to the machinery, where in the interaction of a heat, of a feed speed and of a humidity cancels the original boundary between the free and the bound water, then is bended into the desired shape, while it is glued and it is simultaneously dried within 1 minute to prior values of the humidity of the veneer. The bended thick natural veneer has a thickness ranging from 0.8 to 3.0 mm, preferably a thickness of 1.5 to 3.0 mm.

Description

Defects of natural veneers by postforming method

Technical field

The invention falls within the field of wood production, in particular building-joinery and furniture production.

BACKGROUND OF THE INVENTION

Veneered surfaces are used in the construction and joinery industry on various components, such as stairs, wall claddings, thresholds and other products, and in furniture production, for example, in the manufacture of doors, table tops or other elements in interior production. Profile edges are standardly made with a massive button. The individual parts usually consist of DTD or MDF construction boards on which the plywood (solid wood) is glued. After pressing the top veneer onto the board, the leading edge is milled to the desired radius. This known process, however, has some drawbacks which are manifested in structural joints, in particular with changes in temperature and relative humidity. They cause destruction or deterioration of the product, such as dropping of the napkin or cracking of the veneer over the joint of the construction board with the napkin.

Another less known method for bending veneers is the use of the postforming method. Postforming processes are used in specialized production, so far only rarely for bending veneers, even only to a thickness of 0.6 mm. It is mainly used for HPL laminate surfaces. In particular, it is the cladding of cores (centers, foundations) of wooden boards or the like whose edges are preferably curved (rounded). Traditional postforming involves cutting the core-base of said woodboard or board to dimensions prescribed by the client, then cutting the core lining in parallel or not and proceeding to milling the core edges and then lining the core surface with a heat and pressure fixation operation are placed in the desired position under simultaneous pressure on the free edge of the lining, by joining it to the rounded edge of the core that has been preformed on the milling cutter.

There are serious deficiencies in these postforming processes where postforming has to be done over a wide range of core sizes and thicknesses, requiring the preparation and adjustment of all of the equipment used in the core cutting, tiling cutting, core edge milling, correct positioning with glue, adding thermal energy and finally postforming.

The main drawback of traditional postforming processes is the need to start the core process without lining due to a core milling operation if it is facing on one side, which may be top or both, an extremely complex operation requiring the use of a milling cutter (setting) (and size or use) makes the process laborious and energy intensive, moreover, milling a core lined on one or two sides is not feasible, a milling line is not suitable for such materials and would result in jagged edges.

The improved postforming process protects EP 389400. According to the present invention, a core lined on one or two sides is directly subjected to postforming, eliminating the above drawbacks. This means alignment (linear alignment) and adjustment of the entire production line to allow cutting of the core, cutting of the lining, milling of the core, positioning of the core with the lining and fixed by heat. The line does not need to be adjusted when processing different thicknesses of cores and linings to be processed. The process can be serial or parallel, continuous without interruption.

The process starts with a core lining (also called sandwich), the core is lined on one or two sides that is cut into multiple layers according to the selected distance program, followed by direct milling of the core edges and one of the lining, leaving the other overlapping without modification so that it later forms a curved profile, the height of which corresponds exactly to the thickness of the core, and finally, by means of adhesive, heat and pressure, the curved profile is lined with the overhang. The improvement of the previous processes consists in particular in the manner of positioning the profiles parallel to the direct gate of the core, in addition these profiles may be suitable for spraying the polymer through a nozzle placed on the machine. The polymer may be one or more component, sprayed continuously so that the profile formation rate is the same as that of the lined core being fed.

This procedure is also applicable to arbitrary curvature profiles, the profile being fed to a straight edge will be made separately, designed according to different decorative requirements.

So far, this method has only been used in connection with a decorative HPL laminate on which wood is imitated, or rarely with a natural veneer thickness of 0.6 µm, not larger.

In order to take advantage of existing machinery allowing postforming even for veneers of greater thickness, the development has focused primarily on removing veneer cracking and pore opening, final post-drying cracking, selecting the appropriate postdforming temperature and feed rate, selecting water-resistant and waterproof adhesive. dyeing in some species such as oak and determination of sufficient wetting of wood fibers. The wood bending technology used up to now has been time-consuming and time-consuming, so that the development was also aimed at reducing the bending time.

SUMMARY OF THE INVENTION

The essence of the invention is the bending of natural veneers by the postforming method, in which a thick natural veneer overlaps the edges of the construction board is pressed onto the base board by means of a water-resistant contact glue, which is saturated in a short time within 3 min. pre-treated liquid, enters the machinery where, in cooperation with heat, feed rate and humidity, the boundary in the wood species between the original water free and bound is removed, followed by bending to the desired shape, sealing and drying itself within 1 min. to the original veneer moisture values. The bent thick natural veneer has a thickness of 0.8 to 3.0 mm, preferably a thickness of 1.5 to 3.0 mm.

The invention also relates to the bending of thick natural veneer, which is possible on the front or two opposite edges of the base board and for natural veneer thicknesses up to 0.9 mm, bending is possible on all 4 edges.

It is also an object of the present invention to bend coarse natural veneer by the postforming method at the leading edge of the baseboard with the alignment of the veneer wood fibers.

Moisture in wood mass is the proportion of free water and the proportion of bound water. In preparation it is necessary to reach the saturation point of the fibers of the surface layer of the woody species in the bent place. The bending phase must be carried out fast enough to prevent destruction during the bend itself.

The advantage of the new production process over the so-called “slag system” technology is:

- total elimination of the napkin from production, which saves material and eliminates some of the operations associated with manufacturing, gluing and milling the napkin, thereby shortening the manufacturing process.

Significantly reduced bending time compared to previously used production methods, significant savings in wood mass. To produce an average natural wood staircase, 3 to 3.5 m ^{3 of} wood is needed, which is about 2 medium-sized trees. About 12 m ^{2 of} veneer, which is about 0.3 m ^{3 of} wood mass, is required for the same staircase according to the invention.

shortening the production process, since some operations related to the production, gluing and milling of the veneer are eliminated.

Examples of bsM’C'W’t

Example 1

The part that serves as a lining for stairs consists of an MDF construction board with a water resistant nose (or no nose) and a CPL counterpressure. The surface of the cladding is formed by a pressed natural veneer of 2.5 mm thickness, extending beyond the front. It bends to the desired shape on the leading edge. The part enters the postforming machine at a speed of 20 m / min and at a temperature of 290 ° C by automatic feed. Then the panel passes through a series of wheels that bend the veneer to the desired shape. In this short time, free water evaporates from the wood and "glue". The part with bent veneer comes out of the machine.

The boiling of the wood mass in the postforming machine takes a short time (as compared to previous technologies) and causes the boundary between free and bound water in the wood mass to be removed in this short time (up to 4 min) for bending. fiber flexibility.

The pressed natural veneer, bent at the front edge of the panel, gives the impression of an all-wood board with a beautiful drawing created by a veneer splinter.

The possibility to bend the thick veneer is provided by a new product, namely the lining system for stairs, which is tested by the relevant testing room with better results than the solid wood used so far.

The advantage of the product obtained by this method is

- dimensional stability, even when used in new buildings or when changing the heating period

- shortness of the production process (compared to previous)

- the appearance of real wood. As the scale made of solid wood is glued from French fries in classical technology, the drawing of the wood breaks and scatters the color. Bending of veneers by the postforming method uses a design in the form of a furniture splinter, which creates a more beautiful and full drawing of wood.

- the availability of exotic tree species, as the exotic tree species of costly species is replaced by veneer of these tree species

Example 2

The postforming production process according to Example 1 proceeds in the production of a staircase with a changed orientation of the wood drawing in such a way that it proceeds from the upper step to the bottom uninterrupted, resulting in a visual waterfall from the wood drawing.

Example 3

A similar procedure to that described in Example 1 was followed for the manufacture of furniture parts. The thickness of the used veneers was 0.9 - 1.5 mm. The temperature, the feed rate in the postforming machine as well as the dampening intensity in the pre-bending phase were determined according to the veneer thickness.

Example 4

A procedure similar to that described in Example 2 was followed to produce the top of the table top. The thickness of the veneers used was 0.9 mm. The manufacturing process was similar to that of Example 1, but the veneer bending in the first phase took place on two longer opposite sides and in the second phase the exact profile of the bent table edge was cut and subsequently the cross-fiber veneer was bent on the two shorter opposite sides. Thus, all 4 sides were bent without the use of a napkin. The napkin was necessary for the technologies used so far.

Industrial usability

Postformig bending of natural thick veneers can be used in the construction industry to produce various components such as stairs, wall claddings, sills, handrails, window sills, doorframes and other products, as well as in furniture production, for example, in door construction, table tops or other elements in the interior production, where aesthetic and purposeful rounding is required.

Claims (5)

PATENT CLAIMS 1. Bending of natural veneers by the postforming method, characterized in that a thick natural veneer extending beyond the edges of the construction board is pressed onto the base board by means of a water-resistant contact glue, which is saturated in a short time into the required bending point 3 min pre-treated liquid, enters the machine where, in cooperation with heat, feed rate and moisture, the boundary between the original water free and bound is removed, followed by bending to the desired shape, sticking and at the same time drying itself within 1 min. to the original veneer moisture values. Postforming bending of natural veneers according to claim 1, characterized in that the bent rough natural veneer has a thickness of 0.8 to 3.0 mm, preferably a thickness of 1.5 to 3.0 mm. 3. Bending of natural veneers according to the postforming method according to claims 1 and 2, characterized in that bending of the rough natural veneer is possible on the front or two opposite edges of the base board. Post-forming bending of natural veneers according to claim 1, characterized in that bending of natural veneer to a thickness of 0.9 mm is possible on all four edges of the base board. The bending of natural veneers by the postforming method according to claims 1 and 2, characterized in that bending of the natural veneer is possible at the leading edge of the base board with a changed orientation of the wood fibers of the veneer.