LV14754B - Method for splicing of wood and wooden materials by use of plasto-elastic deformation of jointing elements - Google Patents

Description

Description of the Invention

The invention relates to the woodworking and construction industries.

Brief overview of known methods of joining wood parts and problems of their application

There is a wide variety of joints of wood elements known (see, e.g., a source by A. Vitckopf, Wood and its Processing. A Handbook for Carpenters, Carpenters and Self-taught; VAGA 1994, p. 416). options, including distortion, lugs, connection, etc. End coatings can be made, for example, with straight plugs, through or non-perforated longitudinal and transverse pins. The more pins, the larger the surface area of the joints and the tighter the joint. Matching options are: with single-gap pins, double-gap pins, and so on. Most often carpenters' work uses rectangular and inclined angles, such as cylindrical pivot bindings or flat inserts, which are usually created or embedded in one of the parts and then submerged in the respective sockets of the other.

The cuckoo or dovetail joint is a long-known and widely used type of joint in various wood products. It is very durable and is therefore widely used in furniture cabinets and drawers as well as in carpentry and joinery. This joining principle is also used in the form of cross-bars in furniture and doors. The cotyledon joint is also used for extensions. But during the 20th century, as a result of the industrialization of the manufacture of wood products, the use of this compound has been greatly reduced due to the high labor intensity. There are several technical solutions that use this ancient principle, but only the connecting element is made of plastic (see ntemeta site http://www.hoffmann-schwalbe.de/).

The development of design and manufacturing technologies offers opportunities to reduce the labor-intensive nature of complex structures and offers a variety of solutions to connect cornices with state-of-the-art digital technologies. But since machining is done with rotary cutting tools, the connecting elements have rounded corners, which significantly changes the way the connection works. However, most of these solutions involve the use of sophisticated and expensive equipment, while offering a very narrow scope. The solutions offered are either specific to the type of material or article.

DendroLight® (patent EP 1913211) is an innovative product with high added value. It is a lightweight cellular solid wood panel which, due to special technology, has lost about half the weight of solid wood as it is made of cellular material with many voids. An important feature of this material is its durability and other physically mechanical properties, which make it suitable for use in load-bearing structures, including beams and furniture, making them lighter and more durable, but the problem is with DendroLight® furniture component-free bolted joints loads do not break, as happens with chipboard. When using traditional DendroLight® component joining techniques, it is to be taken into account that the joining (bonding) surfaces of the parts are heterogeneous and have a significantly smaller contact area than in solid wood.

Many of the world's leading institutes have long been working on alternatives to the use of softwood, which comes mainly from felling forests, as currently the only alternative to its use is pulp or energy. The main challenge is the use of thin dimensions for the production of wood products. The small-scale assortment interconnection solutions offered so far are very energy and material intensive and therefore not implemented in practice. In order to glue light wood by traditional methods, it must first be sawn, dried, peeled and then glued and re-glued.

Because of the above, it is necessary to create a fundamentally new one. a method of joining structural elements such as DendroLight® and a thin assortment of joining wood and wood components in ways and conditions where known bonding and mechanical joining techniques do not provide economically and technically feasible solutions.

In the scientific literature and patent publications, no technical solution was found which suggested the idea of using elastic plastic deformation of joining elements (pins or flat elements) in joining wood materials, artificially reaching their joints by thermal or hydrothermal way before joining.

The technical object of the invention is to provide a fundamentally new method of joining wooden structures with artificially (thermally and / or hydrothermally) plasticized wooden pins and / or flat elements which provide the possibility of joining the wood and wood components under conditions (e.g. DendroLight®), in which known bonding and mechanical bonding techniques do not provide economically and technically feasible solutions. It has been experimentally proven that the use of such pins enables the connecting element to be deformed during formation of the joint and to form a structure similar to that of a clogged or swallow-tailed joint, whereby the strength of the joint is ensured by its strength after cooling and humidity equalization; the mutual positioning of the connecting elements makes the connection irreversible; both wet and dry wood can be bonded, as the compound retains its resilience even when the moisture content of the wood changes significantly; the bonding can be done with or without the use of adhesive, with additional adhesive welding being optional but not required.

The essence of the invention as defined in claims 1 and 6, in step-by-step form, is illustrated in the accompanying drawings, in which:

- Fig. 1 a connection with cylindrical pins is shown;

- Fig. 2 a connection with broken cylindrical pins is shown;

- Fig. 3 the connection with flat structured (profiled) pins is shown.

Possible variants of the connecting elements are: cylindrical wooden pin 1.1 (Fig. 1); cylindrical wooden pin (2.1), lengthwise divided into several parts (Fig. 2); flat wood pin (3.1) consisting of several parts, eg plywood and / or UPM Grada® (Fig. 3) glued together with thermoplastic glue.

The connecting parts (2, 3), for example, may be made of solid wood, glued wood, DendroLight® wood cellular material, as well as the aforementioned thin assortments, whereby the parts may be made of different materials or combinations thereof. Other embodiments of the invention emerge from the following information:

Connecting pins according to any one of claims 1 to 10 may be implemented using connecting pins made from the following materials: wood, plywood and / or UPM Grada® plywood glued together with thermoplastic adhesive, or combinations thereof, wherein each step of the joint assembly process the pairs of pins are crossed and / or (Fig. 1 and 2) or joined to each other (Fig. 3), whereby:

- the connecting elements (2, 3) can be selected from the group of wood materials: solid wood, including hardwood, glued wood materials, woody cellular material DendroLight®, and a combination thereof;

- the joints are additionally treated with adhesive prior to the joining of the joint, but the formation of the adhesive seam is optional but not obligatory;

- the possible use of wood structural elements containing component joints obtained according to any one of claims 1 to 10, not only in furniture components, but also in load-bearing structures of buildings (various types of beams, beams, edges, etc.) element joints: welds, grafting, extensions, including with distortion and gussets, etc., whereby the ends of the workpiece ends can be formed not only with non-permeable longitudinal pins as described in the examples but also with cross pins, including perforated pins .

Examples of realization of the invention

The connecting elements mentioned in the examples may be:

- round (cylindrical) wooden pins made of solid hardwood (oak, ash, beech) or birch; their diameter depends on the thickness of the joints and the strength calculations are analogous to conventional round-joint joints; one-piece pins are recommended to be no larger than 12 to 14 mm thick;

- round wooden pins, longitudinally split into two (four or four) and made of hardwood (oak, ash, beech) or birch; splitting pins is recommended, starting with a diameter of 14 mm, and their diameter depends on the thickness of the fittings, whereby the strength calculations are analogous to traditional round pins;

- flat wood elements made of plywood, preferably not more than 4-6 mm thick; their strength calculations are analogous to conventional flat-pin joints;

- flat wood elements consisting of several parts made of plywood with a thickness of 4 mm; after joining, the individual parts are glued together and form a seamless connecting member; the number of individual parts depends on the thickness of the parts to be joined and their strength calculations are analogous to traditional flat-pin connections;

- both the round pins and the flat fittings are plasticized by heating up to about 70 degrees, which can be done by contact heating or convection heating in hot steam, or by microwave heating; Hydrothermal heating can be used where the humidity of the pin is not important and can be done in hot water or hot steam;

- the plywood glued with UPM Grada® thermoplastic adhesive is heated by contact heating;

- the inclination of the bores and sockets to the perpendicular axis is preferably 7 to 30 degrees, or 14 to 60 degrees between the holes or sockets, with the slope depending on the type, thickness and intended use of the material to be joined;

- since the joints described in the examples can be made independently of the moisture content of the parts to be connected, this results in significant energy savings and does not require several energy intensive preparation operations (drying and planing) of the parts to be compared with prior art.

Example 1 - Connecting to a Round Pin (Fig. 1)

Inclined holes (1.4) are inserted symmetrically in relation to the longitudinal joint (Fig. 1a) of the connecting parts (1.2 and 1.3). The bore axes intersect at the point of detail matching. The pins (1.1) are thermally or hydrothermally plasticized prior to insertion into the joint. Apply glue to the holes and insert the plasticized pins (1.1) The elastic plastic deformation of the pins occurs during the connection of the parts (Fig. 1b) and slides into the oblique bores (1.4) The plastic deformations allow the pins to bend during connection. close. As the pins cool down and the moisture levels out, the wood stiffeners are restored and the adhesive hardens to form a permanent bond (Fig.lc). You can also connect without glue.

Example 2 - Connection with broken cylindrical pins (Fig. 2)

In the fittings (2.22 and 2.3), oblique holes (2.4) are inserted analogously to Example 1. The bore axes (Fig.2a) intersect at the parts matching. The pins (2.1) are thermally or hydrothermally plasticized prior to insertion into the joint. Larger diameter pins are split into longitudinal sections before plasticization. Apply glue to the joining surfaces in the holes (2.4) and split pins (2.1). The pins shall be placed perpendicular to the surfaces to be joined before the coupling assembly. During the connection the elastic plastic deformation (Fig.2b) is carried out by inserting the pins into the holes and they bend. Plastic deformations provide the ability for the pins to bend during alignment, while the force created by the elastic deformation of the pins keeps the joint closed. As the pins cool down and the moisture levels out, the wood stiffeners are restored and the adhesive hardens to form a permanent bond (Fig.2c). You can also connect without glue.

3, Example - Connection with flat pins (Fig. 3)

Slanted elongated sockets (3.4) are inserted symmetrically to the longitudinal axis of the joint in the connecting parts (3.2 and 3.3). The longitudinal socket of the sockets overlaps the parts. The flat pins (3.1) are thermally or hydrothermally plasticized prior to insertion into the joint. Higher thickness pins are made of several lamellae. Apply glue to the elongated sockets (3.4) and place the plasticized pins initially perpendicularly to the surfaces to be joined (Fig.3a). The elastic plastic deformation of the pins occurs during the connection of the parts and the pins slide into the elongated sockets (Fig.3b). Plastic deformations provide the ability for the pins to bend during alignment, while the force caused by the elastic deformation of the pins keeps the joint closed. As the pins cool down and the moisture levels out, the wood's firmness is restored and the adhesive hardens to form a permanent bond (Fig.3c). You can also connect without glue.

Example 4 - Connection with flat pins for cellular material

DendroLight®

This compound can be made analogously to Example 3, but it should be taken into account that the joining (adhesive) surfaces are heterogeneous with a significantly smaller contact area than in solid wood, as DendroLight® is cellular. Therefore, the strength and durability of the joint in this case is ensured not only by the area of the surfaces to be bonded, but by the greatest possible mass of joining and joining parts. By inserting the plasticized flat elements into the slanting grooves embedded in the fittings, we obtain a joint whose durability is ensured not only by the bonded surfaces of the joint, but mainly by the construction of the cross-linked material. This ensures that the load is distributed over a much larger portion of the cellular material in the joint and thus solves the problem of combining cellular material with conventional joints. In addition, it solves the problem of the formation of a gluteal joint, which is practically unavailable due to the very fragile nature of the cells. Plasticizing the connecting elements significantly reduces its shear resistance during slanting during insertion. This reduces the risk of disrupting cellular structure by pinching the parts together in the connecting elements.

Example 5 - Connecting thin assortments with round or broken pins

This connection can be made analogously to Example 1 or 2. Using the joining method of the invention, the thin assortment is only cut in half and calibrated to the same thickness, then at 60 degrees, sawed off, drilled, and in this case without dry putty, wet wood, forcing the resulting trapezoidal cross sections against one another. a plate that can already be put together in the dryer. Outstanding excellent construction material, which can be widely used in place of traditional lumber. For larger diameter logs, the edges at an angle of inclination can be reduced to 45 degrees and joined in the form of square beams. Attempts have been made in recent years to develop wet wood gluing, but this method has also failed to commercialize, and in many places construction gluing is not required.

It should be noted that the embodiments of the invention in no way limit its applicability in terms of the choice of materials for the joining and joining elements, in the shape and dimensions of the joining members, and in the associated holes and / or cuts, shapes, angles and dimensions. to some of the most relevant applications today.

Claims (10)

Claims 1. Method of joining wood materials, characterized in that at least one pair of oblique bores (1.4) are formed in each of the joining members (1.2 and 1.3) symmetrically to the longitudinal axis of the part (Fig. 1) and inserting joints of suitable length L and diameter d. pins, also made of wood material and thermally and / or hydrothermally plasticized prior to joining, thereby subjecting them to plastic deformations due to temperature and humidity, which, during operation, change from viscous elastic deformations to viscous elastic deformations in the joint area deformations and form a practically irreversible connection. The method of claim 1, wherein the bore inlets are spaced apart and not more than 3d to 5d apart. The method of claim 1, wherein said bore angle is selected from 7 to 30 degrees, preferably about 20 degrees, and the bore inputs are adjacent or even coincident, but said bore diameter d is not less than a pin. diameter d plus 5% of d. The method of claim 2, wherein, if the bore inlets coincide, the inlet diameter is not less than 2d plus 5% of d. A method according to any one of claims 1 to 4, wherein the pins having a diameter greater than 12 to 14 mm are divided into longitudinal axes prior to plasticization to form split pins (Fig. 2). 6. Method of joining wood materials, characterized in that at least one pair of oblique cut-outs (3.4) are formed symmetrically in relation to the longitudinal axis of the part (Fig. 3) in the joining parts (3.2 and 3.3) and inserted therein (L2) and thickness d flat connecting pins (Fig. 3), also made of wood and thermally and / or hydrothermally plasticized before forming the joint, thereby subjecting them to plastic deformation under the influence of temperature and humidity, the temperature and humidity of these components, from viscous elastic deformations to permanent deformations and form a practically irreversible connection. The method of claim 6, wherein the inputs of the plugs are spaced apart and not more than 3d to 5d apart. The method according to claim 6 or 7, wherein the angle of said plots is selected from 7 to 30 degrees, preferably about 20 degrees, and the plugs' inputs are adjacent or even overlapping, but said plots are not smaller in size. for the corresponding size of the flat connecting pin plus 5% of it. The method of claim 2, wherein, when the inlets of the plugs coincide, the width of the inlet is at least twice the thickness of the flat connecting pin plus 5% of d, and the plugs of greater thickness are formed from a plurality of lamellae. The method according to any one of claims 6 to 9, wherein the flat connecting pins along the entire width of the template are provided with figurative cut-outs prior to plasticization to form a structured (profiled) pin surface (Fig. 3).