RU2311288C1 - Method for profiled wood veneer article production - Google Patents

Abstract

FIELD: joining wood veneer with any material and forming shaped articles thereby.

SUBSTANCE: method involves applying binding agent on surfaces to be adhered one to another, stacking article sheets; pressing the obtained stack in press having flat panels; removing article from the press and forming profile by self-bending thereof. Stack is formed with the use of veneer sheets having different moisture. Profile is created as moisture becomes equal over the full laminated article volume.

EFFECT: increased article quality and simplified production.

5 dwg, 5 ex

Description

The invention relates to the woodworking industry and can be used in the manufacture of shaped wood laminated materials.

Closest to the claimed is a method for the manufacture of shaped products based on wood veneer (RF Patent No. 2122942 from 12/10/1997).

According to the known method, shaped products are obtained by flat pressing in presses with heated plates. The package in the manufacture of shaped products is formed from veneer sheets previously cut to fit the size of the product or a multiple thereof with an allowance for trimming. A binder is applied to each sheet of veneer, including external. The assembly of the package is carried out according to an asymmetric scheme based on varying the ratio of the number of longitudinal and transverse veneer sheets. The packages are glued in a press at a temperature of 130 ° C and a pressure of 2 MPa. After unloading the glued products, they spontaneously take a profile shape in the form of a convex surface with a given radius of curvature. The product acquires this form due to internal stresses in the veneer and glue line, which cause their deformation.

With this method of manufacturing profile products, it is assumed and, moreover, the presence of internal stresses in the product, the imbalance of which deliberately causes deformation of the veneer layers and the entire product as a whole. The presence of internal stresses in the finished product under certain conditions, when their values exceed the corresponding limit values of the strength characteristics of wood, can lead to the appearance of internal and surface cracks, unpredictable deformations, weakening of adhesive layers and to partial or complete destruction of the product itself. In addition, the product profile is rigidly connected with the assembly scheme, i.e. number of sheets, thickness and order of laying veneer in a package. Therefore, it is impossible to manufacture a product of the same thickness and ply, with a different radius of curvature, which limits the application of the known method. The radius of curvature obtained by the known method of the product cannot be predicted in advance, i.e. for each assembly scheme, the radius of curvature is determined empirically and is assumed constant for this scheme.

According to another known method, shaped products (plywood pipes) are made of two-layer plywood, obtained by flat pressing of veneer sheets with a binder (see "Guide to the production of plywood" edited by N.V. Kachalina, M., "Forest industry", 1984 , p. 308-315). After that, the plywood sheets are moistened with water up to 12 ... 20% on moisturizing rollers, then they are aged in dense feet for at least 12 hours to even out the moisture. After preparing the blanks for gluing, which consists in the formation of a fold, slipping the edges, applying a binder, they are wound on special cylindrical metal mandrels. Bonding is carried out in autoclaves in a saturated steam medium under a pressure of 0.3 ... 0.4 MPa.

This production method involves a complex technological process, including technological operations of gluing plywood, its moistening, shaping and gluing the workpiece. The disadvantage of this method is the attraction of additional costs for creating the necessary conditions and the use of special equipment when gluing shaped products.

The problem solved by the invention is the manufacture of shaped products with different radii of curvature, performed with the use of flat pressing presses, without deliberate creation of internal stresses as a prerequisite for spontaneous acceptance of an arcuate shape by the product, which will reduce the likelihood of internal and surface cracks in the product and increase its reliability manufacture.

The solution to this problem is ensured by the fact that in the method for producing profile products based on wood veneer, including applying a binder to glued surfaces, assembling the package and pressing it, assembling the package is carried out using veneer sheets of different humidity, and the profile is formed after removing the product from the press by spontaneous bending when equalizing humidity throughout the entire volume of the glued product.

The goal is achieved due to the fact that after pressing in the product, which is in a free state, moisture is equalized throughout the volume (the product acquires equilibrium moisture), while in the veneer sheets that make up the layered structure of the product, the dimensions across the fibers change (in width) as a result of which the product spontaneously acquires a profile, for example arcuate or cylindrical shape. For this it is necessary to assemble the package using veneer sheets of different humidity, between which adhesive layers are formed, and pressing should be carried out in a press with flat plates.

The essence of the invention lies in the fact that when forming a package for the manufacture of profile products, veneer sheets of different humidity are used, the order of their laying, as well as the direction and magnitude of the change in moisture in the veneer layers depend on the required profile of the front (back) surface (convex or concave) and radius of curvature. In this case, the assembly scheme of the package can be either symmetric or asymmetric, including, in addition to veneer sheets, other materials, for example, rubber, fabric and other layers.

Profile products obtained by flat pressing according to the known method, assume an asymmetric scheme for assembling packages (Fig. 1), when the veneer sheets in the package are located asymmetrically with respect to its central plane of symmetry with a certain ratio of longitudinal (1) and transverse (2) veneer layers. Binder (3) is applied to the middle veneer sheet on both sides. At the end of the pressing cycle, the product is removed from the press and it independently takes a profile arcuate shape (figure 2).

According to the proposed method, a variant of which is shown in Fig. 3, a binder 3 is applied to one of the surfaces of the veneer sheets 1 and 2, and a rubber gasket is laid in the middle part of the package 4. The moisture content of the veneer sheet 2 is greater than the moisture content of the veneer sheet 1. The package is glued in the press with flat heated stoves. At the end of the pressing cycle, the product is removed from the press and it takes a profile shape with a certain radius of curvature by spontaneous bending while equalizing humidity throughout the entire volume of the glued product (figure 4).

Example 1

A package consisting of two sheets of birch veneer, whose length was 250 mm, width 490 mm and thickness 1.3 mm, and a rubber layer of the corresponding format with a thickness of 5 mm was glued. The humidity of one of the veneer sheets is 12%, the other 6%. A binder was applied to the surface of the veneer sheets facing the inside of the bag. Pressing was carried out in a flat press at a temperature of 90 ° C for 10 min. After the end of the pressing cycle and unloading of the product from the press, it spontaneously takes a profile shape in the form of a convex surface due to a change (decrease) in the size of the moistened veneer sheet when it dries. The measured radius of curvature of the product upon reaching equilibrium humidity was 528 mm.

Example 2

Similar to example 1, the difference lies in the fact that the humidity of one of the sheets of veneer is 19%, the other is 6%. The measured radius of curvature of the product at equilibrium humidity was 275 mm.

Example 3

A package consisting of four sheets of birch veneer 250 mm long, 490 mm wide and 1.3 mm thick was glued, stacked with the longitudinal direction of the fibers. The moisture content of sheets 1, 2, 3, and 4 was 5, 6, 12, and 14%, respectively (Fig. 5). The binder was applied so that there was one adhesive layer between adjacent veneer sheets. Pressing was carried out in a press with flat plates at a temperature of 95 ° C for 10 minutes After pressing, the product begins to acquire a profile shape, and the surface from the side of sheet 1 becomes convex, and from the side of sheet 4 - concave. After the product reaches equilibrium humidity, its radius of curvature is 102 mm.

Example 4

Similar to example 3, the difference is that sheet 1 has a transverse direction of the fibers relative to sheets 2, 3 and 4, i.e. sheet 1 was 490 mm long and 250 mm wide. The radius of curvature of the product upon reaching equilibrium humidity was 165 mm.

Example 5

Similar to example 3, the difference is that the moisture content of the veneer sheets 1 and 2 was 5%, and that of sheets 3 and 4 was 12 and 14%, respectively. In addition, sheet 2 in the bag had a fiber direction transverse to sheets 1, 3 and 4. The radius of curvature of the product upon reaching equilibrium humidity was 370 mm.

Thus, the invention allows the use of standard flat pressing equipment for the manufacture of shaped products with a predicted radius of curvature without deliberate creation of internal stresses as a prerequisite for spontaneous adoption of an arc-shaped product. The radius of curvature of the product depends on the package assembly scheme and on the initial humidity of the veneer sheets placed in the package.

Claims (1)

A method of obtaining shaped products based on wood veneer, including applying a binder to the surfaces to be glued, assembling the bag and pressing it in a press with flat plates, followed by forming a profile after removing the product from the press by spontaneous bending, characterized in that the bag is assembled using sheets veneers of different humidity, and the profile is formed in the process of equalizing humidity throughout the entire volume of the glued product.

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