The present invention concerns a method for joining longitudinal wooden elements cut from board material one after another and one above another to a construction piece, and a joint for longitudinal wooden elements cut from board material attachable to each other one above another and one after another in a construction piece.

Arrangements are known in which structural parts are formed from longitudinal planar wooden elements placed one on top of another and one after another, which wooden elements are joined together only by means of adhesive without any mechanical joint ar- rangement locking the elements together immediately when assembled.

The object of the present invention is to provide a solution with which elements of a construction piece are firmly attached to each other as soon as another layer of elements are assembled to the construction part, regardless of whether or not adhesive is used. This ob- ject is achieved with a method being characterized in that a vertical drilling is made to both ends of elements, which are to be assembled one after another in the same layer of the construction piece, at a first distance of the element's end in question, and still another vertical drilling is made to one end of the element at a distance from the first drilling in the element's longitudinal direction being twice as long as the first distance. The elements to be assembled one after another in the next layer fit on top of the elements in the previous layer, but the two vertical drillings will be made at the end opposite to that of the elements in the previous layer, so that three vertical drillings with uniform distances from each other will always be formed in connection with a joint of two successive elements in each layer. Wooden pegs, having a length corresponding to the height of a construction piece to be built, or to a part of it, are pushed into all vertical drillings in the first layer, after which the elements of the next layer are placed so that the element's end equipped with two vertical drillings is pushed onto the wooden peg pushed into the vertical drilling of the end below equipped with one vertical drilling and onto the wooden peg pushed into the outer vertical drilling of the adjacent end equipped with two vertical drillings, whereby the vertical drill- ing of the end equipped with one vertical drilling of a next element in the upper layer is pushed onto a wooden peg pushed into the inner vertical drilling of the element in the lower layer, and the elements of the next layer are pushed onto the same wooden pegs as the elements of the first layer so that the ends of the elements on top of each other form a zigzag pattern. Additional vertical drillings maybe made evenly distributed along the length of long elements, so that the additional drillings of elements on top of each other are aligned, and a wooden peg is also pushed into them.

A joint according to the invention is characterized in that both ends of elements positioned one after another in the same layer of a construction piece have a vertical drilling at a first distance from the end in question, and one end of the element has still another vertical drilling located at a distance in the longitudinal direction of the element from the first ver- tical drilling being twice as long as the first distance, and the end of the elements placed one after another in the next layer being equipped with two vertical drillings is the end opposite to that of the elements in the previous layer, whereby in the joint the elements of two successive layers fit together when displaced so that the outer vertical drilling of the end equipped with two vertical drillings of elements on top of each other is aligned with an outer vertical drilling of an end equipped with two vertical drillings of an element in the other layer, so that in each joint there are always three adjacent vertical drillings at an uniform distance from each other, to which vertical drillings wooden pegs extending through the elements on top of each other are fitted. Advantageously elements in the same layer are of a common shape and the elements of two successive layers follow each other's shape from the end equipped with one vertical drilling halfway between the two vertical drillings at the opposite end, and an extension comprising the outer vertical drilling follows the shape of an extension comprising the outer vertical drilling at the opposite end of an element in the adjacent layer.

According to an embodiment of the invention the elements of an joint have a shape of a 90° arch so that every other element in each layer archs towards one direction and every other element towards the opposite direction, so that each element is bounded both on top and/or on bottom and on adjacent sides by elements of different type.

According to a preferred embodiment, the elements in a same layer have an outer tongue at one end and inner tongue at the other end, which tongues are shaped so that they supplement each other and form a sealing coupling at the joint between two adjacent elements. The element ends equipped with tongues and grooves are located on the same side of elements in all layers.

Elements joinable together can be straight pieces, arch shaped or of an wave-like shape, in which case long elements are arranged with additional vertical drillings at the element's mid-section for further stabilization a construction part assembled from the elements.

In the following the invention is described in more detail with reference to the enclosed drawings, where

fig. 1 illustrates a perspective view of a first embodsiment of the present invention; fig. la illustrates a top view of the two types of elements used in a joint according to l;

fig. lb illustrates a top view of a joint according to fig. 1;

fig. 2 illustrates a perspective view of a second embodiment of the present invention; fig. 2a illustrates a top view of the elements used in a joint according to fig. 2;

fig. 2b illustartes a top view of a joint according to fig. 2;

fig. 3 illustrates a perspective view of a third embodiment of a joint according to the present invention;

fig. 3 a illustrates a top view of the elements used in a joint according to fig. 3; and fig 3b. illustrates a top view of a joint according to fig. 3;

Figures 1 - lb illustrate a first embodiment of a joint according to the present invention in which fully straight wooden elements 1 and 2 cut from sheet material are joined together one after another and one above another as a construction piece. In the illustrated embodi- ment, the first layer of the construction piece comprises elements 2 placed one after another, at both ends of which one vertical drilling 3 and 4 have been made at a first distance from the element's 2 respective end, and to the left end of the element still another vertical drilling 5 has been made at a distance from the first vertical drilling 3 in the length direction of the elements, said distance being twice as long as the first distance. Thus, there is always a row of three vertical drillings at the joint between two elements 2, which vertical drillings 4, 3 and 5 are at a uniform distance from each other. In the next layer there are elements 1 being otherwise of the same shape, but having one vertical drilling 4 at the left end and two vertical drillings 3 and 5 at the right end. Wooden pegs 6, having a length substantially corresponding to the height of the construction piece to be built, are pushed in to all vertical drillings of the elements 2 in the first layer. The elements 1 in the second layer are placed so that the single vertical drilling 4 in their left end is placed onto the wooden peg pushed into the inner vertical drilling 5 at the left end of the elements 2 in the first layer, and the vertical drillings 5 and 3 at their right end are placed onto the wooden peg 6 pushed into the single vertical drilling 4 in the right end of the elements in the first layer and onto the wooden peg pushed into the outer vertical drilling 3 at the left end of the next element 2, so that the formed joint joins the elements 1 and 2 together, one after another and one above another. Next, again a layer of elements 2 is mounted, the vertical drillings 3, 5 and 4 of which elements are pushed onto the same wooden pegs 6 which are pushed into corresponding vertical drillings 3, 5 and 4 in elements 2 of the first layer straight below them. After this, again a layer of elements 1 is mounted, the vertical drillings 4, 5 and 3 of which elements are pushed onto the same wooden pegs which are pushed into corresponding vertical drillings 4, 5 and 3 in elements 1 of the second layer straight below them. Thus, the ends of the overlapping elements 1 and 2 in the construction piece, form a zigzag pattern.

If all surfaces of the elements look alike, only one type of element is required for assembling a construction part, so that the elements are rotated 180° around a vertical axis in every other layer.

In figs 2 - 2b another embodiment of the invention is illustrated, wherein the elements 1 and 2 to be used are of an arch shape. In the presented embodiment each element forms a 90° arch. Depending on the surface of the elements 1 and 2, only one type of element have to be used, or two types of elements 1 and 2, wherein, as in the embodiment according to figure 1, the elements in the lowest layer have two vertical drillings 3, 5 at their left end and a single vertical drilling 4 at their right end. Because every other element 1 , 2 in both layers arch towards opposite directions, two types of elements 1 , 2 have been used in all layers so that in the lowest layer, after element 2, element 1 is placed while rotated in such a way that its end equipped with two vertical drillings 3, 5 is on the left in the figure. In the next layer, on top of element 2, element 1 has been assembled so that the single vertical drilling in its left end is pushed onto the wooden peg 6 pushed into the inner vertical drilling 5 at the left end of the element in the lowest layer, and the inner vertical drilling 5 at the right end of the element lin the upper layer is pushed onto the wooden peg 6 pushed into the single vertical drilling 4 at the right end of the element 2 in the lowest layer. The outer vertical drilling 3 of this element 1 is pushed onto the wooden peg 6 pushed into the outer vertical drilling 3 of the next element 1 in the lowest layer. After the element 1 in the second layer, an element 2 is assembled while rotated in such a way that its end equipped with the single vertical drilling 4 is in contact with the end equipped with two drillings 3, 5 of the element 1, and its vertical drilling 4 is pushed onto the wooden peg 6 pushed into the inner vertical drilling 5 of the element 1 in the lowest layer. Assembled in such a way, the construction part will have a wave-like shape. Alternatively, a construction piece according to fig. 2 may be implemented with elements of a single type, such as elements 2, in which case the first element is placed as presented in fig. 2, and the adjacent element 1 is replaced with another element 2 which is turned upside-down, and the element 1 in the second layer is replaced with an element 2, which has been turned upside-down and rotated 180° around a vertical axis.

A construction piece according to figs. 3 - 3b is also built up of two different types of elements 1 and 2, which are relatively long and have wave-like shape. The elements in the same layer are of an equal shape so that the lower level comprises elements 2 placed one after another, and the layer on top of it comprises elements 1 placed one after another. The elements 2 in the lower layer follow the shape of the elements in the next layer from the end equipped with one vertical drilling up to the halfway between the two vertical drillings 3, 5 at the opposite end of the element, and the extension comprising the outer vertical drilling 3 follows the shape of the extension comprising the outer vertical drilling 3 at the opposite end of elements 1 in said layer. At the left end of elements 1 and 2, respectively there is an outer tongue 7a, and at the right end there is an inner tongue 7b, which tongues have been shaped so that at the joint of two elements 1 or 2 assembled one after another the tongues 7a and 7b supplement each other and form a sealing coupling. Three additional evenly spaced vertical drillings 8 have been arranged to the mid-section of elements 1 and 2 so that in assembling elements 1 and 2, the additional vertical drillings 8 of elements 1 and 2 in layers on top of each other are in line so that they too can be pushed onto wooden pegs 6 of their own for further stabilizing the construction piece built up of elements 1 and 2.