EP2516120A1

EP2516120A1 - Joined veneer strip

Info

Publication number: EP2516120A1
Application number: EP10800933A
Authority: EP
Inventors: Achim Möller; Andreas Wagner
Original assignee: Padana AG
Current assignee: Padana AG
Priority date: 2009-12-23
Filing date: 2010-12-22
Publication date: 2012-10-31
Also published as: WO2011076855A4; CA2784266A1; DE102009055282A1; BR112012017143A2; US20120282423A1; DE102009055282B4; JP2013515626A; WO2011076855A1

Abstract

The invention relates to veneer strips made of individual veneer layers (1), wherein adjacent veneer layers overlap (7) and comprise a joint (4) having a wedge-shaped cross-section in the region of the overlapping. The veneer layers are connected to each other by means of adhesive. The invention further relates to a method, to a device for performing the method, and to a use of the veneer strips.

Description

Made veneer sheet

The invention relates to a joined veneer sheet, a method for joining or assembling veneers for the production of closed, single or multilayer veneer sheets, their use and a device for carrying out the method.

Veneers are usually cut straight on the longitudinal edges by means of veneer paring scissors, provided on these cut surfaces with an adhesive, then fanned out to avoid sticking together of the veneer edges provided with adhesive and finally glued together in a veneer veneer at the longitudinal edges to a veneer sheet, such. B. in G 90 11 185.0 described. Such veneer sheets may be used to coat a support member such as a wood-based panel.

This method requires a high number of steps at high mechanical complexity. The problem is the processing of heavily wavy, bulky veneers. The specific structural features of the wood waves or bumps are pressed flat when trimming, after relaxing from the holder of the veneer package scissors, the waves spring back again and distort the originally straight cut edge. As a result, proper bonding in the veneer molding machine is difficult or impossible. By prior ironing of the veneers such waves or bumps can be smoothed, but this is only successful to some degree against the waviness and represents a high overhead.

For joining veneers, other bonding methods are also customary, such as the zigzag-shaped sticking of a hot melt-coated stitching thread onto the joint area or the sticking on of a paper adhesive tape. Again, the ripple is very detrimental.

DE 00 0000948357 B describes a method which circumvents the mentioned disadvantages. There are very thin, 0.1mm thick veneer sheets, which need not necessarily be cut straight, glued and then superimposed scale on the support member. The carrier component must be so compressible that the areas of the scale-like overlap are pressed into the carrier component in order to obtain a flat surface. The disadvantage here is the required compressibility of the support member, which is not sufficiently given in conventional wood-based panels and the existing on the visible veneer edges, in cross-section wedge-shaped joint at higher quality, veneered surfaces is not acceptable. Furthermore, the required, complex gluing of the individual veneer sheets is disadvantageous. In addition, veneers with a thickness of <0.45 mm have a significantly different appearance than veneers with larger thicknesses. The depth effect of the wood disappears and the Habtik corresponds to that of Holzsubstitutprodukten. The processing of thicker veneers is not conceivable by this method, since the already existing disadvantages would increase even more.

For pressing laminated materials as well as the pressing of veneer sheets on support components, such as wood-based panels, various press pads have been proposed, whose task is to keep the pressing pressure as constant as possible regardless of thickness tolerances of the material to be pressed and inaccuracies of the press over the entire pressing surface. In A 274334 a press pad made of a fabric is described, which near the edge of the support member has a gradually increasing edge reinforcement to compensate for the pressure drop at the edge. In this case, however, any differences in thickness of the support member outside the edge area are not taken into account. Furthermore, the locally occurring pressing pressure is dependent on the size of the respective thickness deviation. The fabric also has a poor thermal conductivity, so that pressing at higher temperatures is difficult to achieve.

In DD 264 189, as well as in DD 255 130 press pads are described from various compressible textile fabrics, but also act only in the limits described in A 274334 pressure equalizing and can conduct the heat bad.

An ideal pressure equalization over the surface to be pressed is achieved in known membrane presses, which achieve the pressing pressure via a membrane subjected to compressed air. The membrane clings to strongly profiled parts, but can transfer only very limited heat, so that correspondingly long pressing times are necessary. This technique is suitable for veneering highly shaped off-plan moldings, but does not allow productive coating of plate-shaped parts.

To extend shorter pieces of veneer, the so-called finger jointing is generally known, in which the veneers to be joined are finger-jointed and subsequently assembled and glued to fit. Also is the repair of wood defects customary, wherein the error range is usually elliptical punched and then filled with an equally shaped, faultless veneer piece. These techniques are complex and often allow only a lower quality of the finished product, since the optical effect is very impaired.

The object of the invention is to eliminate the disadvantages of the known prior art and a joined, single or multi-layer veneer sheet, which is inexpensive to produce and to propose a method for their preparation and further processing, their advantageous use and an apparatus for performing the method.

The object is solved by the features of the invention essential to claims 1, 5, 6, 8 and 9.

The veneer sheet consists of a layer of veneer sheets with an average thickness of 0.2 mm to 2.5 mm, wherein each adjacent veneer sheets overlap in the contact area of the veneer sheets to form a joint scaly and are joined together in the joint area by an adhesive.

In this case, the joint cross-section in the upper part of a dense joint and in the lower part of a wedge-shaped, filled with adhesive joint, such. B. shown in Fig. 02a.

Preferably veneer sheets are used with a thickness of 0.2 mm to 2.0 mm, particularly preferably with a thickness of 0.3 mm to 0.8 mm.

As the adhesive is preferably a thermosetting glue, z. As a urea-Formaldehydharzleim, a melamine glue, a PVAc glue or a PUR glue used.

The innovative veneer sheet is picked up on a rigid or limited elastically deformable carrier, such as a chipboard, an OSB, MDF, plywood, aluminum or plastic plate. By eliminating the usual trimming the otherwise blunt contiguous veneer strips on the longitudinal edges and the complex bonding of the butt joints, the cost of veneer sheet are significantly reduced.

To adapt the veneer sheet to the support, a preferably heated press pad is made of a soft, stretchable mat and a layer of a plastic mass behind it, which achieves its plasticity at the press temperature which can be set in each case. When the pressure builds up, the plastic mass flows proportionally from the protruding overlap areas into the adjoining area of the carrier, thereby maintaining the pressing pressure both at the overlapping areas and at the remaining areas the carrier component constant. The stretchable mat is also pressed against the edges of the overlap so that the overlapping veneer with a very small radius lays around the edge of the underlying veneer sheet. This results in the top of the veneer cross-section a dense joint, in the lower area remains a wedge-shaped, filled with adhesive joint, but always hidden. The mat, preferably made of silicone with a low Shore hardness and the plastic material conduct the heat from the press well to the component.

After curing of the preferably heat-acting adhesive, the veneered component is removed from the press. Subsequently, the overlying the component surface overlap areas z. B. removed by grinding or milling, so that the component receives a continuous surface with dense veneer joints. At the former overlapping areas, the veneer is compacted by the pressing as well as at the flat areas, thus ensuring a uniform surface texture of the veneer coating.

Such a veneered component is used for the production of furniture, interior fittings, vehicle bodies or housings.

Inventively coated parts may be planar boards made of wood-based material such as chipboard, medium-density fiberboard or plywood. However, it is also possible to coat planar or curved components with profiled edges including the profiled edge according to the invention. For this, the press pad follows the profile of the component.

The veneer sheets according to the invention can be overlapped on both the longitudinal and the transverse edges, wherein the transverse edges of each underlying veneer sheet are preferably zigzag cut in the manner of so-called, known finger joints to obtain an oblique course of the transverse overlap. It is also possible, from a veneer sheet an opening with z. B. known punching tools or cut by means of water jet cutting technology and occupy the peripheral edge overlapping with a suitably formatted veneer piece. In this way, partially undesirable characteristics such as branches can be repaired.

As an alternative to adhering the overlapped veneer sheets to the carrier component and the simultaneous pressing of the joint area, the veneer sheets can also be glued together and ground in a first step using the press pad according to the invention alone and glued in a second step on the support member. For this, the edge of the overlapping veneer sheet must be coated with adhesive. For bonding are particularly suitable thermosetting adhesives such. As urea-Formaldehydharzleim or polyurethane adhesive. Particularly advantageous is the oblique gate of this edge by means of a router or saw or other tool, so that the overlap can nestle at a smaller angle to the veneer plane, the wedge-shaped, filled with adhesive joint area is much smaller and the adhesive surface larger. This results in an even better adhesion of the joined veneer sheets to each other.

According to an advantageous variant, such an oblique edge can already be produced during the veneer production, in which the knife block clamped in the veneer knife machine has an outer surface running obliquely to the knife movement direction. The adhesive application can be made before the knife on the oblique outer surface of the knife block, so that when veneers already provided with adhesive veneer sheets.

The abrading of the overlap after pressing can be done in a calibrating veneer grinding machine, possibly as an endless belt transversely to the joint direction. Subsequently, the endless veneer sheet is cut to fixed dimensions.

The format-cut veneer sheets produced in this way can be glued onto a carrier component in a conventional veneer press, wherein no press pad is required. Sticking can be done with the wedge-shaped joint area upwards, this area being removed during the subsequent grinding of the veneered component, so that the underlying joint is closed to the support plate. However, it is also possible to position the wedge-shaped area towards the carrier component. The surface does not need to be cut so deeply that the wedge-shaped joint area, which lies flat, remains covered. For light wood species this joint area could possibly show through dark. In this case, as is generally known in veneering, the glue may be added with a light dye which corresponds to the color of the wood and which makes the joint area invisible.

The bevels and separate Beieimen the overlapping veneer edge is also possible when directly adhering the overlapped veneer sheets on the support member and the simultaneous pressing of the joint area. The advantage here is the dense bond line to a greater depth, whereby the risk of the translucency of adhesive is also reduced here. Instead of sticking the veneer sheet according to the invention onto a carrier component, it is also possible for a plurality of veneer sheets to be glued to one another, so that a layered or plywood is produced.

The sole bonding of the veneer sheets together has the advantage that the veneer sheet joining processes and adhering to a support component can be made temporally and / or spatially separated from each other, and veneering presses with rigid press plates common for veneering can be used.

The veneer can with a usual in veneer processing, low wood moisture (about 12% moisture content), but also with high wood moisture (up to 100% moisture content), as occurs directly after veneer production by knives or peeling or with moisture, the lie in between, be processed according to the invention.

If dry veneer is pressed, certain types of wood may cause heavy waves and bumps during drying due to the wood structure, which can not be leveled during pressing and can lead to cracks. Likewise, the sanding of single, wavy veneers causes great problems. Such waves and bumps are not yet formed at higher wood moisture, so you can fix this deficiency by processing the veneers according to the invention at higher wood moisture.

During simultaneous pressing of the overlaps and the total area on a carrier component, the high moisture content of the veneer is partially absorbed by the carrier component, in part discharged to the outside after opening the press, so that the veneered component finally reaches a leveling humidity which is customary in use.

In this case, the adhesive suitable for wet bonding must be selected and the pressing time adjusted accordingly. Particularly suitable for this purpose is a polyurethane adhesive specially adjusted for the bonding of damp wood.

If moist veneer according to the invention added alone and the veneer is then calibrated in a grinding machine, a proportion of veneer moisture after leaving the press must be maintained by appropriate covers, by humidified air and / or by immediate Nachbefeuchtung. After grinding, it is possible to dry to the desired final moisture content, whereby a short pressing time is achieved when the veneer sheet is pressed onto the carrier component. When processing wet veneers, the expensive and energy-intensive process of today's customary individual drying of the veneer sheets becomes superfluous.

Embodiment 1 (Figures Ol, 02 and 02a):

A 19mm thick, provided with a light colored urea-Formaldehydharzleim or similar acting glue chipboard as a carrier (6) is coated with 0.55 mm thick, about 150 mm wide and 2400 mm long mahogany sliced veneer wood moisture of 8% on both sides, wherein each veneer sheet (1) overlaps the adjacent one at the longitudinal edge (1) by 10 mm - 20 mm. The prepared plate is placed in a hydraulic press, heated to 180 ° C pressure plates (9), each with a press pad, consisting of a 2 mm thick plastic mass (11) made of polypropylene and about a soft, 2 mm thick mat (10 ) made of silicone rubber, are occupied. When closing the press with a specific pressing pressure of 0.6 N / mm ² , this press pad follows the surface contour with the overlapping points and transmits the set pressing pressure uniformly over all areas. The longitudinal edge (II) of the veneer sheet (1) located below in the overlapping area (7) is enclosed and compacted by the overlying veneer (1).

Thus, in the upper region of the veneer cross-section, a dense joint (5) is formed, in the lower region remains a wedge-shaped, adhesive-filled joint (4).

The overlapping veneer area (7) protruding beyond the veneered wide area by approx. 0.5 mm is sanded in a special grinding machine. This machine scans the wide surface of the plate and sanding only the overlaps flush with the wide surface. After a further, generally usual smoothing of the entire plate surface a veneered plate (Fig. 02a) with closed veneer joints was created according to a productive production process, as is commercially produced today with considerably higher production costs.

Exemplary embodiment 2 (FIGS. 03 and 04):

A 25 mm thick medium density fiberboard with the dimensions 500 x 650 mm has a circumferential profile of FIG. 3, as it is in z. B. furniture door panels is common. This plate is coated as a carrier (6) with a known in the manufacture of furniture urea Formaldehydharzleim or similar acting glue and then with 0.55 mm thick, approx. 70 mm wide, 10% wet oak veneer sheets, each veneer sheet (1) overlapping the adjacent one by 5 - 15 mm. The veneer sheets (1) are arranged such that each overlapping area is located in the vicinity of a three-dimensionally formed profiled corner (12). The plate thus prepared is placed in a hydraulic press whose heated to 190 ° C upper pressure plate to the profile of the fiberboard (10) and with a press pad, consisting of a 3 mm thick layer of polyethylene and about a soft, 3 mm thick silicone rubber mat analog Example 1 is occupied. The corner areas are reinforced with a metal sheet following the contour, which guarantees a safe squeezing out of the sharp-edged corners. When closing the press with a specific pressing pressure of 1.2 N / mm ² , this press pad follows the surface contour with the overlapping points and transmits the set pressing pressure uniformly to all areas. The veneer edge located in the overlapping area below is enclosed and compacted by the overlying veneer, as shown in Example 1. In the corner region (12) of the profile, the veneers move in a wedge shape over one another during the closing of the press (13) and can thus largely avoid the extreme stresses in a three-dimensional deformation, whereby the risk of cracks is minimized. The plate is finally profiled so that the overlaps are removed and the entire surface is smoothed.

The result is a productively produced door panel whose tread depth is greater than conventionally veneered parts of this type.

Embodiment 3 (Figures 05 and 06):

Dried birch peeling veneer, 0.53 mm thick, 2.5 m long and 400 mm wide, is cut straight in a 25 mm high veneer package (14) on a longitudinal edge by means of a veneer package shears, by bending the package in a bending device (15) obliquely fanned (16) on the inclined surface milled (17) and provided by a Beleimwalze (18) with a urea-Formaldehydharzleim or similar acting glue and then brought by bending back into the starting position (19). Thus veneer sheets (1) each have a bevelled, glued, now dried and distanced from the adjacent glued edges, beveled edges (8).

These veneer sheets are placed overlapping after an eventual short-term storage to an endless veneer sheet, wherein the glued edges (8) are each arranged below the approximately 10 - 30 mm wide overlap region (7). This veneer path now arrives by means of a conveyor belt in a cyclically operating, in the working direction 1.5 m long press, the lower, heated to 120 ° C pressure plate (9u) rigid and the upper pressure plate (9o) with a press pad (10, 11) gem. Embodiment 1 is equipped. When pressing with parameters analogous to Example 1 follows the overlapping veneer area (7) for the most part of the glued slope (8) and connects both veneer sheets (1) each other.

The veneer endless web thus formed is wound up and stored at the press outlet with a total length of 400 m, then ground as a continuous web in a known Kalibrierschleifmaschine at the overlapping points transverse to the wood fiber direction to the uniform thickness of 0.5 mm and finally by means of a veneer clipper cut a format of 1.25 m. The resulting so-called veneer fixings are glued to chipboard according to known technology by means of a brightly colored adhesive and then ground again over the entire surface. These veneered chipboards are universally applicable.

Embodiment 4 (Figs. 07 and 08):

A knife block (22) made of beech is smoothly milled on an inclined surface (23), at which the veneer knife (26) later immersed in the block, briefly heated by means of heat radiators (24) and immediately coated with a Melaminharzleim (25). By heating, the surface of the 80% wet block dries, so that the application of the adhesive and immediate drying is possible. Subsequently, veneer is cut from the knife block (22) whose longitudinal edge (II) now already has an oblique, glued edge (8). These veneer sheets, as described in Example 3, glued together, wherein the rigid pressure plate (9) is covered with a close-meshed, customary in chipboard production, so-called. Flexoplansieb (29). This sieve allows the partial escape of water vapor (30) produced during the pressing of the wet veneer to the outside. As a result, the veneer is dried during pressing to a wood moisture content of 20%.

The further processing of the pressed veneer sheet corresponds except the changed wood moisture Example 3. The particular occurring in the type of wood beech ripple after drying is not pronounced at the wood moisture 20%, so that the passage through the grinder without damage from cracks is possible. During sanding and further transport, the veneer still gives off approx. 4% moisture and is glued to the chipboard with approx. 16% on both sides. The increased wood moisture prevents Any cracks in the veneer sheet during the pressing on the chipboard, also results in a slightly increased yield due to reduced shrinkage of the veneer.

Embodiment 5:

Analogously to Example 1, a veneered panel is produced, but undried beech veneer is used for a wood moisture content of about 80%. For the bonding of the fired floor, a two-component polyurethane adhesive is used at a pressing temperature of 80 ° C. The moisture in the wood is partially directed into the plate during pressing, sometimes it escapes after opening the press from the hot veneer directly to the outside. An advantage over Example 1 is the elimination of the separate step of drying and the prevention of cracks due to waviness.

Embodiment 6:

A 1.5 mm thick oak veneer sheet is prepared as described in Example 4 and glued on one side to a 10 mm thick medium-density fiberboard and finished, on the other side conventionally joined, 1.5 mm thick beech peeling veneer is applied with known press plates. The veneered panel is used to produce prefabricated parquet elements.

Embodiment 7 (Fig. 09):

A veneered panel according to Example 1 is produced, wherein the veneers are overlapped not only on the 2400 mm long longitudinal edges (II), but also, depending on the attack of shorter veneer pieces, on the 150 mm wide transverse edges (lq). The lower transverse edges (lq) are zigzag-shaped with a known finger joint punching tool (31). When the veneer is pressed in, the press pad follows the zigzag contour as well as the longitudinal edges (II), so that all the joints are densely pressed. Wood defects, such as branches, are punched out with a peripheral punching tool, which runs off sharply at the edges, and then covered with a veneer piece (33) covering the punched-out portion (32). During pressing, this contour is also pressed tightly. The further processing of the plate corresponds to Example 1. Advantageous is the possibility of recovery of otherwise unusable remnants. By punching out localized wood defects, large-format veneer sheets can be processed as a whole, without having to be cut into smaller formats because of the occasional occurrence of wood characteristics.

Embodiment 8 (Fig. 10)

A veneer sheet made according to Embodiment 3 is adhered to a MDF support member coated with a PVAc adhesive by means of a press pad described in Example 1. This carrier component is provided with 1.5 mm deep, decorative milled cuts and in other areas with 1 mm thick, decorative pads made of plastic strands. The press pad follows the recesses (34) and elevations (35) of the support member and presses the veneer sheet (36) in all areas contour true and with uniform pressing pressure. This is how a decorative piece of furniture was created.

Embodiment 9

Analogously to embodiment 1, a 19 mm thick chipboard with overlapping laid, 0.6 mm thick Eichefurnierblättern with a length of 700 mm and a width of 100 mm covered, wherein the overlap width is uniformly 15 mm. The longitudinal edges of the veneer sheets are just cropped. In contrast to Example 1, the overlaps are not abraded, but only smoothed together with the other surface areas by means of height-adjustable grinding tools. The resulting surface profile serves as a decorative, directional surface for finishing elements.

Overview of used qualifiers

1 veneer sheet

II longitudinal edge of the veneer sheet

lq transverse edge of the veneer sheet

2 transition area

3 visible surface

4 wedge-shaped joint

5 tight joint

6 carriers

7 overlap

8 chamfer

9 press plate

9o upper press plate

9u lower press plate

10 mat

11 plastic mass

12 profile corners

13 wedge-shaped displacement

14 veneer package

15 bending device

16 obliquely fanned ends of the veneer sheets

17 milling tool

18 With a roller

19 Starting position of the veneer package

22 knife block

23 oblique surfaces of the knife block 23rd

24 heat radiators

25 melamine resin glue layer

26 knives

27 resulting veneer sheet with oblique, glued edge edge II

29 flexoplan screen

30 escaping water vapor

31 formation

32 punched out

33 covering veneer piece

Claims

Patent claims

1. veneer sheet, consisting of veneer sheets (1) with an average thickness of 0.2 mm to 2.5 mm, each adjacent veneer sheets (1) in the transition region (2) on the visible surface (3) overlapping and in the underlying Area forming a cross-sectionally wedge-shaped joint (4), are joined together by an adhesive.

2. veneer sheet according to claim 1,

characterized,

the adhesive is a hardening glue, preferably a urea-formaldehyde resin glue, a melamine glue, a PVAc glue or a PUR glue.

3. veneer sheet according to claim 1,

characterized,

that the transverse edges (lq) of the respectively underlying veneer sheet (1) incisions, preferably with a zigzag course or recesses.

4. veneer sheet according to one of claims 1 or 2,

characterized,

that the longitudinal and / or transverse edge (II, lq) of the Funierblattes (1) is chamfered or has a chamfer (8).

5. Method for producing closed veneer sheets,

at the individual, on the longitudinal and / or transverse edges (II, lq) glued veneer sheets (1) having a thickness of 0.2 mm to 2.5 mm, overlapping each other like scales, pressed under pressure and on the visible surface ( 3) are milled and / or ground.

6. A method for producing multilayer, closed veneer sheets according to claim 5, wherein a plurality of closed veneer sheets are interconnected by adhesive and under pressure.

7. Method of making closed veneer sheets

according to claim 5 or 6,

characterized,

in that the positioning and adaptation of the veneer web on the carrier (6) takes place under pressure and at a pressing temperature of 20 ° C to 150 ° C.

8. A process for producing closed, single-ply veneer sheets according to one of claims 5 or 7,

in which faulty areas of the veneer sheet are eliminated by forming the transverse edges (lq) or openings (32) with a punching tool and then covering and pressing with a covering veneer piece (33).

9. Apparatus for carrying out the method according to one of claims 5 to 8, characterized

in that the positioning and adaptation of the veneer web on the carrier (6) takes place by means of a press pad which consists of a soft, extensible mat (10) and a layer of a plastic mass (11) lying behind it, which achieves its plasticity at the respectively adjustable pressing temperature ,

10. Use of a veneer sheet according to one of the preceding claims for the production of veneered component for the production of furniture, doors, wall panels, interior finishing elements, parquet elements, vehicle bodies or housings of all kinds.