A recent trend has been to promote the use of wood in various con- structions, interior decorations, coatings, furniture, etc., in view of the special properties of wood and also with increasing environmental awareness. In many such objects, metal or plastic has been previously used, e.g. because of their easy workability, durability and light weight.

However, one disadvantage with the use of metals and plastic is the fact that their manufacture uses irrenewable resources of natural raw materials and energy, wherein the manufacturing processes pollute the environment to a considerable extent.

Further, surfaces made of metal laths have the problem of poor acous- tics, being manifested in sonority of the room to be decorated. For avoiding this, sound insulating materials must be used either behind the metal laths or in other surfaces of the room to be decorated.

However, in many projects, the aim is to give the impression that a wood material has been used instead of metal or plastic. For this pur- pose, coating methods have been developed, by which the metal or plastic is coated, and a pattern resembling the fibre construction of wood is provided in the coating. Further, the coatings are aimed at giv- ing other exterior features, such as colour, of a desired wood species.

However, coatings of this kind do not fully correspond to real wood be- ing used as the material. For example, acoustic factors, as well as fac- tors affecting the quality of inside air are not the same as with real wood.

Also, cladding surfaces manufactured of wood laths, have been re- cently used for coating buildings, particularly in wall and ceiling sur- faces. Surfaces of this kind are made of solid wood laths having usually

a rectangular cross-section. The aim has been to accomplish surfaces which are aesthetically more decorative and acoustically better than what has been possible to achieve with said metal and plastic laths.

Such surfaces made of wood laths according to prior art have the problem of relatively high weight of wood laths compared with e.g.

plastic laths, setting high demands for the fastening of the wood laths.

The use of wood in constructions has, however, been limited e.g. by the problem that untreated wood stands poorly attacks by weather, such as changes in humidity and temperature, wherein wood, particularly when used outdoors, must be treated with wood preservatives for increasing durability. Also indoors, wood does not necessarily withstand stresses caused by changes in indoor air, but different slits, warpings and bends may occur in the wood. Particularly in winter time, wherein heaters must be used in rooms under cold conditions, indoor air becomes dry and causes above-mentioned deformations also in wooden structures, even increasingly due to changes in humidity conditions. For example, in constructions where elongated wood pieces, or wood laths, are placed close to each other, even a small warping of wood is visible, and the appearance of the surface does no longer correspond to the original.

Thus, a surface made of wood laths is no longer aesthetically pleasant, whereby the surface may need to be replaced. It has not been possible with present methods for fixing solid wood pieces to eliminate totally the disadvantages caused by stretching and contracting of elongated wood pieces. Stretching and contracting have been affected by selection of the wood material and by fixing the wood pieces densely, but this is an expensive solution, particularly when a so-called hidden joints are re- quired as the fixing method.

Consequently, the weatherproof properties of wood can be promoted by preservatives, but these are usually environmentally polluting. One must be particularly careful and wear respirator filters or the like when handling preservatives. Moreover, preservatives may cause allergic re- actions to more sensitive persons. The work can be made less harmful to the environment by arranging the preservative treatments at a fac- tory.

Still another factor limiting the use of wood is the fact that fixing pieces made of wood e.g. in buildings has required either gluing or fixing with attachments, such as screws. Gluing is not a useful solution in objects where the piece to be fixed must also be detachable e.g. in connection with cleaning or another maintenance operation. In such a case, screw fastening is more useful but rather laborious. Further, with time, the fix- ing of a screw fastening becomes poorer in objects where the fixing must be opened relatively often.

The above-mentioned disadvantages of surfaces made of wood laths are primarily caused particularly by the basic properties of wood mate- rial. Wood is an organic material, whose behaviour is affected by its own individual factors and properties ascribed to its growing time, pri- mary treatment, use environment, and embodiment environment. Due to its structure, i.e. internal tensions are generated in wood because of changes in the environment, such as changes in humidity and temperature. Tensions generated during the growing time and primary treatment of wood can also relax. Said external changes caused by stretching and contracting of wood, as well as their way of manifestation and intensity depend particularly on the factors of growth and treatment of the wood.

Finnish patent application Fl-945494 discloses an arrangement for the manufacture of wood lath ceilings. The arrangement comprises wood laths placed at predetermined intervals and braces placed transversely to the wood laths, wherein each wood lath is fixed to a brace. The braces are metal supporting battens having guide brackets extending to the wood laths, the wood laths being placed between the guide brack- ets. The wood laths are provided with fixing grooves, and the arrange- ment comprises fixing means extending to the fixing grooves and over them onto the supporting battens so that they press the wood laths against the mounting batten. The wood laths constitute the actual vis- ible surface. A problem with this arrangement is, however, that the construction becomes very heavy, because the wood laths are primarily solid in cross-section. Further, this arrangement has the above-men- tioned disadvantages caused by stretching and contracting of wood, such as warping, bending and split forming, particularly due to changes in the environmental conditions.

The purpose of the present invention is to eliminate the above-men- tioned disadvantages to a major extent and to provide a method for supporting wood in a way that its use in various constructions is possi- ble and stretching and contracting of wood is reduced to a minimum.

The invention relates also to a fixing piece for supporting the wood piece or the like according to the method. Further, the invention relates to a wood piece that maintains its original shape as long as possible, ir- respective of the effect of environmental conditions. The method of the invention is based on the idea that the wood piece is supported at least on one wall on an area of three fourths of the height of its inner volume, located closest to its bottom part in its cross-sectional profile form, ad- vantageously on the area between halfway and the bottom of the height of the inner volume, located closest to its bottom part in its cross-sec- tional profile form. The support is arranged advantageously inside the profile form. The method of the invention is characterised in what will be presented in the characterising part of the appended claim 1. The wood piece of the invention is characterised in what will be presented in the characterising part of the appended claim 6. Further, the fixing piece of the invention is characterised in what will be presented in the characterising part of the appended claim 15.

The present invention gives considerable advantages to methods, fix- ing pieces and wood pieces of prior art. When making the wood piece a construction with thin walls and supporting the wood piece according to the invention, it has been surprisingly found that it is thus possible to reduce substantially deformations caused by internal tensions which are due to stretching and contracting of wood and possibly left in the wood piece at the stage of its manufacturing, as well as their effect on the appearance of the wood piece. With a fixing piece according to the invention, the wood piece can be fixed in its object by a simple force effect directed to the wood piece substantially in the direction of open- ing of the profile form, i.e. upwards, for example by pressing the wood piece in the direction from its bottom part. Thus, mounting the wood piece involves no tools which might leave scars in the wood piece at the fixing stage, such as knocking scars by a hammer or scars left by a screw driver. Further, laborious inserting of fixing means into fixing grooves is eliminated, because preferably the walls of the wood piece

bend at the mounting stage and return when the wood piece is in place, thus securing the attachment of the wood piece in the fixing piece. It is also easy to detach the wood piece, when necessary, without a need to open fixing means e.g. with a screw driver. Because a wood piece fixed with a fixing means according to the invention is also easily detachable, it is possible to use wood pieces of this kind also in objects which need to be opened e.g. for maintenance. Thanks to its lighter construction, the fixing of the wood pieces can be implemented with lower strength requirements than before, which makes the fixing less expensive than when using wood pieces of prior art. The fixing can also be easily im- plemented as hidden fixing, and the inner surface of the profile form can be designed more freely.

Moreover, the wood piece provided by the invention makes it possible that it can be treated economically to become better resistant to weather with environmentally safe treating methods, such as thermal treatment or the like. This reduces the need for protecting the wood piece with other wood preservatives or paints. If necessary, wood pieces of the invention can be exposed to surface treatment in a pro- duction plant and cut-to-size wood pieces can be delivered to the site of installing, thereby reducing the work at the site of installing.

In a wood piece according to the invention, dimensional stability is bet- ter than in elongated wood pieces of prior art, due to e.g. the fact that the wood piece is dried evenly and the tensions possibly existing in the wood piece are smaller.

In the following, the invention will be described in more detail with ref- erence to the appended drawings, in which Fig. 1 is a cross-sectional view on a wood piece according to the invention, fixed in a fixing piece according to the invention, Fig. 2a shows a wood lattice of a ventilation window fixed by the method of the invention and installed in its place, seen from the front,

Fig. 2b is a cross-sectional view at point A-A of the wood lattice of a ventilation window shown in Fig. 2a, and Figs. 3a to 3k show some alternative cross-sectional profiles for the wood piece, and shapes of fixing pieces corresponding to them.

Wood pieces 1 are manufactured preferably by working with conven- tional wood working methods, for example with a cornice plane or by milling on one side of the wood piece 1 so that the wood piece 1 is shaped advantageously into a U-form or the like, wherein a structure with two or more walls is formed in the longitudinal direction of the wood piece 1. At least part of the walls, preferably the outermost walls, are advantageously thin, whereby their thickness is primarily smaller than their height, preferably primarily less than half of the height of the walls.

In the working, a great part of the wood material is removed from the wood piece, even more than a half, i.e. the area of the cross-sectional profile of the worked wood piece 1 is less than a half of the area of the surface formed by the imaginary smallest circumferential measurement around the cross-section of the worked wood piece 1, or a so-cailed reference area. In a case that the wood piece 1 is worked of a planed wood piece so that its outer dimensions remain unchanged, the refer- ence area can be the cross-sectional area of this wood piece before working. The wood piece 1 of the invention can also be made directly of saw timber, wherein thicker wood is cut into blanks of wood pieces which are planed, if necessary, at least on the surfaces that will be vis- ible. Thus, the reference area is the area of the smallest peripheral measurement of the worked wood piece 1, as described above. In practical solutions, the maximum value for the ratio between the sur- face area of the cross-sectional profile of the wood piece according to the invention and the reference area is approximately 0.8, advanta- geously less than 0.6, preferably less than 0.4. The quantity to be worked depends particularly on the wood species used and on the shape of the cross-sectional profile to be worked on the wood piece.

This surface area formed by the imaginary minimum peripheral meas- urement around the cross-section of the wood piece 1 can be regarded as the reference area also for wood pieces 1 made by other methods than by working.

If a cornice plane is used in working, the width of the working part of the cornice plane is set slightly narrower than the width of that side of the wood piece 1 in the transverse direction of the wood piece, to which measurement the wood piece of the invention is to be worked. After planing, the wood piece 1 comprises side walls 1a, 1b and bottom part 1c in the embodiments of Figs. 1, 3a3k. The side walls la, 1b and the bottom part 1c constitute an inner volume 2 from which the wood material is worked out. The wood piece of Fig. 3f comprises also a partition wall 1d, wherein it is possible to increase the rigidity of the wood piece, which is advantageous particularly in the manufacture of panel walls and ceilings. Furthermore, the partition wall 1d facilitates the unbending of possible warpings and lateral distortions, because the force effects caused by unbending are distributed not only to the first 1 a or second side wall 1b but also primarily to the partition wall 1d which can be made thicker than the side walls 1 a, 1 b.

A structure with thin walls is advantageous e.g. in the respect that in- ternal tensions of the wood piece are smaller and cause fewer exter- naily visible defects, such as bends, slits and warpings.

Wood pieces 1 can be made more flexible e.g. by means of flexible grooves 6a, 6b formed at the joint of the side walls and the bottom part (Fig. 3c). This additional flexibility gives the advantage that the installa- tion of the wood pieces 1 is easier.

Under working, also other moulding methods are understood, known as such, whereby the wood material is brought to a workable or mouldable state by vaporising, radio-frequency irradiation, microwave irradiation, or the like. Further, the COMPWOODTNl method can be used for moulding wood. The choice of the method to be used in moulding de- pends e.g. on the desired shape of the cross-sectional profile for the wood piece, the quality of wood, as well as the desired appearance of the wood piece. However, it is not essential in this invention in what way the wood piece is moulded or how the wood piece is brought into a mouldable state.

For example, the wood piece of Fig. 1 can be formed also in a way that the wood piece 1 is brought into a mouldable state, after which the wood piece is compressed in a mould or the like to accomplish the de- sired cross-sectional profile in the wood piece 1. In moulding, it is also possible to use the roll forming technique known as such, whereby the wood piece in a mouldable state is conveyed by rolls and the edge parts of the wood piece 1 are simultaneously bent by successive roll frames, wherein the cross-sectional profile is gradually changed to the desired profile form of the wood piece 1.

The wood piece 1 of the invention can also be made of two or more parts, such as laths, by gluing, to achieve the desired cross-sectional profile. Further, the wood piece can also be extended in the longitudinal direction by gluing shorter lath blanks or already glued wood pieces to- gether. The profiles can be worked on the gluing surfaces to facilitate the alignment of the surfaces to be glued together and to increase the gluing surface area. The gluing seams of the laths to be glued can be placed, for example, advantageously either at the joints of the walls and the bottom part or e.g. advantageously in the middle of the bottom part.

The laths to be glued can be worked more roughly, wherein the final working is conducted first after gluing, or they can be worked to finish, wherein no finishing working will be needed after gluing. Further, the thickness of one or several walls and/or the bottom part of the wood piece can be accomplished by gluing them of two or several parts (overlaying). Thus, the boundary lines between the walls and the bot- tom part can be formed at the gluing stage advantageously by bending or gluing.

Wood pieces produced by the above-mentioned moulding and gluing methods may cause higher manufacturing costs, but they may come into question in some cases.

The wood piece of the invention can be manufactured of a thermally treated wood blank, or it can be subjected to thermal treatment e.g. af- ter working. In thermal treatment, wood is treated under different tem- perature and humidity conditions, resulting in a wood material resisting well the conditions of the environment. Heat-treated wood suits well to objects to be used outdoors, because its rot-preventing property is

better and deformations caused by humidity are smaller because of less water being absorbed in the wood material and fewer changes in the cellular structure of the wood. If necessary, it is possible to use known preservative treatments. Deformations caused by changes in humidity can also be reduced by surface treatment of the wood piece 1 on its outer as well as inner surfaces.

For securing the attachment of the wood piece 1, it is possible to pro- vide the wood piece 1 also with attachment means 3a, 3b e.g. by mill- ing. The attachment means can be made either at the same stage when the wood piece 1 is provided with the desired cross-sectional profile form, or in another suitable connection.

Figures 3a to 3k show some advantageous cross-sectional profile forms as well as corresponding forms for fixing means 4, whereby the support according to the invention can be arranged in the wood piece 1.

Within the scope of the idea of the invention, the cross-sectional profile comprises advantageously two or more walls 1a, 1b, 1d. Further, the wood piece 1 may contain a bottom part 1c, to which the walls 1a, 1b, 1d are connected at the lower edges of the walls 1a, 1b, 1d. In this de- scription, the lower edge of the walls refers to that part of the walls which in the wood pieces shown in Figs. 1, 3a--3k is located in the lower part of the wood piece 1, i.e. close to the edge on the side of the bottom part 1c. When the wood part 1 is in its operational position, the lower edge is not necessarily facing downwards, but it can be also fac- ing to the side or even upwards, but this is not significant for the appli- cation of the invention. As a result from the definition of the lower edge presented above, the upper edge of the walls 1a, 1b, 1d is placed at the edge opposite to the lower edge, i.e. in the upper parts of the wood pieces 1 in the embodiments shown in Figs. 1, 3a3k.

The following terms will still be defined for the wood piece 1 according to the invention: The outer surface of the wood piece 1 refers to the surface formed in the cross-sectional profile by the surface of the out- ermost walls 1 a, 1 b and possibly of the bottom part 1 c facing away from the wood piece 1. In a corresponding manner, the inner surface refers to the surface formed by the surface opposite to the outer surface of the outermost walls la, 1b and of the possible bottom wall 1c, as well

as the surface of possible partition walls 1d. Inner volume 2 refers pri- marily to the minimum volume limited by the inner surface of the wood piece 1 as defined above. For example, in Fig. 3,2a broken like 2' is drawn to illustrate an imaginary plane limiting the inner volume in the upper part of the wood piece 1 in this direction. This broken line 2' is also part of the minimum peripheral measurement by means of which the reference area was determined above in this description.

At least some of the walls 1 a, 1 b, 1 d, preferably the outermost walls 1 a, 1b, are advantageously thin, wherein their thickness is smaller than their height, preferably less than a half of their height. On the other hand, the invention can also be applied in a construction with thick walls, wherein the flexibility of the wood piece 1 is accomplished pref- erably by forming thinner portions with better flexibility in part of the cross-sectional profile. It is also possible to provide the thinner portions in only part of the wood piece, wherein the cross-sectional profile can vary on the length of the wood piece 1. The structure with thin walls and/or the varying cross-sectional profile of the wood piece 1 according to the invention has e.g. the advantage that the internal tensions of the wood piece 1 are smaller and cause fewer externally visible defects, such as bends, slits and warpings.

Further, the structure with thin walls has the advantage that the wood piece can be treated with different additives, such as various preserva- tives, which can be effectively absorbed even to the whole wood mate- rial, from disadvantageous factors, such as rotting, burning, colour changes, etc. With effective absorption of the preservative, the resis- tance of the wood piece 1 against different changes in the conditions can also be improved, thus increasing the uses of wood pieces 1 ac- cording to the invention. Wood pieces 1 of the invention, treated with a preservative, can be used even in objects where it is not possible to use wood pieces of prior art.

When installing the wood piece 1, its flexibility allows that the distance between the walls 1a, 1b is slightly changed, at least at the upper edge, wherein the piece accomplishing the support functions of the fixing means 4 can be placed in the U profile form, or the like, in the wood piece 1. The wood piece being set in its place, the flexibility of the wood

4a, 4b in the fixing means are placed against each other according to the desired arrangement, accomplishing the fixing of the wood piece 1 in its place.

The fixing means 4 is advantageously designed so that it supports the cross-sectional profile of the wood piece 1 in its inner volume. The wood piece is supported on at least one wall la, 1b, Id on the area of three quarters of its height, located closer to its bottom part in the cross-sectional profile form, i.e. in the height direction at least partly in the range from 0 to 75 %, advantageously underneath the midpoint of the height of the inner volume, i.e. in the height direction at least partly in the range from 0 to 50 %, preferably on the lowermost quarter of the height of the inner volume, i.e. at least partly in the range from 0 to 25 % of the height of the inner volume. For clarity, said percentage values are given e.g. in Figs. 3a and 3b. This supporting at the bottom section gives, inter alia, the advantage that deformations possibly tak- ing place in the wood piece 1, particularly visible warpings at the bottom part, can be eliminated almost totally and the shape of the wood piece 1 will not be changed to a significant degree.

For keeping the wood piece 1 of the invention in place, it is possible to provide the wood piece 1 with attachment means 3a, 3b and the fixing means 4 with counterparts 4a, 4b. The attachment means 3a, 3b are placed advantageously in the area between the midpoint and the lower edge of the walls, but, according to the use in question, also elsewhere at the wall, e.g. close to the upper edge, as shown in the embodiment of Fig. 3e. The most advantageous location of the attachment means 3a, 3b is affected e.g. by the cross-sectional profile form of the wood piece 1 as well as by the wood material used in the wood piece 1. With the position and design of the attachment means 3a, 3b and the coun- terparts 4a, 4b, it is possible to affect e.g. the suspension strength and the force required upon installing. One possibility is to place the fixing means also on the outer surface of the wood piece 1. The attachment means 3a, 3b used are advantageously grooves, indents, crowns, pro- jections, or the like. Thus, the fixing means 4 is advantageously pro- vided with a counterpart 4a, 4b, such as a crown, projection, groove, indent, or the like, to receive the fixing means. Particularly in cases where the attachment means are provided on the outer surface of the

wood piece 1 the counterparts 4a, 4b can be separate from the fixing means 4 for accomplishing the actual support. An example of this is shown in Fig. 3g. Counterparts 4a, 4b are used to improve the fixing of the wood pieces primarily in a direction perpendicular to the profile form of the wood piece, i.e. in the vertical direction in Figs. 3a to 3k. The fix- ing means 4 is used e.g. to accomplish the support of the wood pieces 1 in the lateral direction and thus their fixing in position.

In view of keeping the wood piece 1 in its place, it should be considered that the minimum distance W1 between the walls comprising the at- tachment means 3a, 3b of the wood piece (Fig. 3a) above the attach- ment means 3a, 3b is smaller than the maximum width W2 of the fixing means 4 at the counterparts 4a, 4b in the case that the attachment is arranged inside the profile form of the wood piece 1. Fixing the wood piece 1 on the outside, in turn, requires that the distance between the walls comprising the attachment means 3a, 3b of the wood piece above the attachment means 3a, 3b, indicated by W3 in Fig. 3g, is smaller than the minimum distance W4 between the counterparts 4a, 4b of the fixing means 4.

In addition to the fact that the wood piece 1 is supported at the lower part of the height of the inner volume, it is possible to arrange also other supports to the wood piece 1.

The fixing means can be provided with supporting indents 9a, 9b to re- ceive the upper parts of the walls 1a, Ib of the wood pieces. Thus, the walls la, Ib of the wood pieces are also supported at the edges of the supporting indents 9a, 9b, which prevents the walls of the wood profile from drawing away from the counterparts 4a, 4b and thus secures the fixing of the wood piece 1 in its attachment. By the design and place- ment of the supporting indents 9a, 9b, it is possible to effect that, upon installing or detaching the wood piece 1, at least one wall 1 a, I b of the wood piece 1 bends in relation to the counterparts 4a, 4b, and that, the wood piece being fixed in the fixing means 4, the bent walls la, Ib are straightened substantially to their initial shape. Thus, it is secured that the wood piece 1 is fixed in its place.

Figure 3g shows an example of a wood piece 1, where the support is arranged on the inside, close to the lower part of the wood piece 1, and the attachment means 3a, 3b are placed outside the wood piece 1.

Thus, the counterparts 4a, 4b are arranged outside the wood piece I accordingly. The attachment means 3a, 3b are placed preferably higher in the profile than that part of the fixing means 4 which accomplishes the support functions.

In the embodiment of Fig. 3h, the fixing means 4 supports wood pieces 1, 1' on the outside. In this embodiment, one fixing means 4 is arranged to support two adjacent wood laths 1, 1' The attachment means 3a, 3b and the counterparts 4a, 4b are placed inside the profile form of the wood piece 1, 1' It is obvious that the fixing means 4, 4' can be divided into two fixing means next to each other, wherein one fixing means supports one wood piece 1 and the other fixing means supports the adjacent wood piece 1' Figure 3i shows a further example of supporting the wood piece 1 from outside. That part of the fixing means 4, 4' which accomplishes the support functions, is thus placed outside the wood piece 1, at least partly on the height dimension of the inner volume, within its range of three quarters located closest to its bottom part in the cross-sectional profile form, advantageously in the range between the midpoint of the height of the inner volume and the bottom part. Also the attachment means 3a, 3b and the counterparts 4a, 4b are placed outside the wood piece 1. In this embodiment, the upper edge of the wood piece 1 is fur- ther supported by support indents 9a, 9b, preventing e.g. the bending of the walls 1 a, I b inwards in a self-acting manner.

Figure 3j shows still another advantageous embodiment of the inven- tion. Wood pieces 1 are placed close to each other so that one wall Ib of the wood pieces 1 is provided with a protruding part intended to be placed at least partly underneath the first wall la of the next wood piece. Thus, adjacent wood pieces provide each other with additional support and, on the other hand, a substantially solid surface is ob- tained, to be used e.g. as a wall panel.

Figure 3k shows an embodiment in which a separate cover piece 12 can be installed in the interspace between wood pieces 1, or the inter- space is covered either by the flange part of the wood piece 1, the flange part of the wood piece 1', or the flange parts of both wood pieces 1, 1'. Thus, the walls 1a, 1b are supported indirectly from the outside either by the flange part of one of the wood parts or by the cover piece 12.

Further, it is obvious that the invention is not limited solely to the profile forms of Figs. 1 to 3k, but the profile forms can vary. For example, the thickness of the walls and the bottom part can be changed also in the longitudinal direction of the wood piece 1, wherein the profile form is not necessarily identical throughout the wood piece 1. The wood piece 1, particularly its outer surface, can be provided with patterns affecting its appearance, such as grooves, bulges, or even holes penetrating the walls and the bottom part. By these operations, it is possible also to im- prove the acoustic and other functional properties of the wood piece, to affect the flexibility, tensions, stretching and contracting of the wood piece 1.

The wood lattice 1 of a ventilation window arranged in connection with a window 5, as shown in Fig. 2a, is made, according to the invention, of shaped wood laths 6, 7, 8, 9 connected at their ends to each other to form a rectangular shape. Preferably between the substantially parallel vertical laths 6, 7, there are also transverse laths 11, spaced substan- tially equidistantly, fixed to cover the opening of the ventilation window and to give a finished appearance to the wood lattice 1. The window frame 10 is provided with a sufficient number of fixing means 4 which are fixed e.g. by screws and whose design corresponds to the shape of the cross-sectional profile of the inner volume of the wood laths 9.

The wood lattice is installed advantageously by pressing. This kind of a wood lattice can also be easily detached e.g. for cleaning.

Because deformations may occur also in the wood pieces 1 of the in- vention to some extent, the wood piece 1 is advantageously fixed at one or several points by means of designed, advantageously rigid fixing means 4. The distance between the fixing means and their number must be determined on the basis of the shape, size, wood species,

wood quality and other factors of the wood piece 1 to be used, consid- ering also the effect of the use conditions and loading factors. By fixing one or several spaced fixing means 4, it is possible to straighten warp- ings possibly existing or caused at the use situation in the wood piece 1. With a single fixing means 4, it is possible to straighten e.g. lo- cal forces effective on the cross-sectional form of the profile.

Those parts and shapes of the fixing means 4 which accomplish the support functions are placed primarily within the range of three quarters of the height of the inner volume located closest to the bottom in the cross-sectional profile form of the inner volume, advantageously under- neath the midpoint of the height of the inner volume. The fixing means 4 support the wood piece 1 advantageously on the inside on a sufficient portion, depending on the profile, and keep the wood piece 1 in its profile form. The supporting can be continuous or discontinuous.

Further, the fixing means 4 can be designed in a way that it is sup- ported by the profile form, at least its one wall, on at least the portion either directly or at a distance from the upper edge of the wall 1 a, 1 b, or substantially on the entire length from the upper edge of the wall advan- tageously to the lower edge of the fixing means, and further on the at- tachment means 3a, 3b by means of the counterparts 4a, 4b. The sup- porting can also be discontinuous. Moreover, the fixing means 4 can be supported to the profile form also in the bottom part 1c either on its whole length, discontinuously, or not at all.

By the supporting functions of the walls 1a, 1b, 1d and the bottom part 1c inside the profile, it is also accomplished that the profile will not collapse inside.

Furthermore, the fixing means 4 can support the profile either directly or indirectly advantageously at least at or close to the upper edge of one wall la, 1b, thus preventing the walls of the profile form of the wood piece from drawing away from the counterparts, if this occurred.

In the main embodiment, the fixing means 4 is rigid, wherein the sur- faces of the fixing means corresponding to or limiting the profile remain fully in their shape during fixing and detaching of the wood piece 1.

Thus, during fixing and detaching, the flexible part is the profile, i.e. the wood piece 1.

By using the fixing means 4 of the invention, the wood piece 1 can be attached to its object simply by a force directed at the wood piece 1 substantially in the direction of opening of the profile form, i.e. upwards, for example by pressing the wood piece from the direction of the bottom part 1c. Thus, installing the wood piece involves no tools which might leave scars in the wood piece at the fixing stage, such as knocking scars by a hammer or scars left by a screw driver.

Figure 3f shows still another profile form of the wood piece 1 in which the application can be advantageously applied. The wood piece 1 com- prises three walls la, 1b, 1d, one purpose of the intermediate wall 1d being to give the wood piece 1 supplementary rigidity, which is useful particularly in the manufacture of panel walls and ceilings. Also, the in- termediate wall 1d facilitates also to straighten possible warpings and lateral bends, because force effects caused by the straightening are divided primarily in the intermediate wall 1d which can be made thicker than the walls 1a, 1b. Further, the force effects can be directed partly also to the first wall 1a or the second wall 1b, or to both. In the three- wall profile structure of Fig. 3f, the support can also be arranged in a way that those means of the fixing means 4 which accomplish the sup- port functions are supported at least partly on the intermediate wall 1 d, whose height may not be necessarily the same as the height of the walls 1a, 1b. Some examples of the variation in the height of the inter- mediate wall 1d are indicated by broken lines in Fig. 3f. Moreover, the support can be arranged in a way that the support is directed to the in- termediate wall 1d from one side and to either of the walls 1a, 1b. It is essential, however, that the support functions are positioned at least partly within the three quarters of the height of the inner volume of the profile form located closest to the bottom part of the cross-sectional profile form, as presented above in this description.

Also other solutions for the fixing part 4 can be used, where, according to the invention, it is essential that when the wood piece 1 is fixed in its place, the fixing piece 4 supports the wood piece sufficiently, advanta- geously at its bottom part. By using fixing means 4 spaced in a desired

alignment, it is possible to prevent undesirable deformations existing or possibly arising in the wood piece 1. By arranging the support accord- ing to the invention at least in the range of three quarters of the height of the inner volume of the wood piece 1, placed closest to the bottom part of the wood piece in the cross-sectional profile form, preferably in or close to the bottom part, it is achieved that possible lateral bendings and warpings of the wood piece 1 can be straightened. Further, a pro- file supported according to the invention cannot change its shape, and the fixing of the profile is secured.

The fixing means 4 can be of any sufficiently rigid or sturdy material, such as metal (Fe, Al, etc.), but also polymers, wood in its different forms (wood lath, plywood, etc.) are feasible. The fixing means can also be arranged partly flexible e.g. with a spring, as shown in connection with the embodiment of Fig. 3b, or by making the fixing means e.g. a two-piece construction, as shown in connection with the embodiment of Fig. 3d. In the embodiment of Fig. 3d, the elastic bending of the fixing means 4 requires a greater force than required for controlling bendings and warpings possibly existing or arising in the wood piece 1 as a result of stretching and contracting. Figure 3d shows still another design for the fixing means 4, combining the supporting function of the fixing means 4 and the counterpart 4a, 4b.

As the raw material for the wood pieces 1, it is possible to use any suit- able workable wood species, such as pine, birch, spruce, alder, aspen, oak, etc. Thus, in the selection of the wood species to be used, it is possible to consider the desirable properties relating to appearance etc.

that are desired to accomplish with the wood piece 1.

In addition to those presented above, there are a number of applica- tions for the wood piece 1 according to the invention. The wood piece 1 and fixing means 4 of the invention can be used e.g. in laths, such as skirting boards, and in various pieces of furniture, thus giving the ad- vantage that the fixing can be easily made without scars left on the vis- ible surface by a tool. Because the wood piece 1 of the invention can be detached when necessary, it is advantageous to apply the invention also in duct-works e.g. for placing electric cables, wherein it will be

possible to add electric cables to or remove them from the duct-work, if necessary.

The present invention is not limited solely to the embodiments pre- sented above, but it can be modified within the scope of the appended claims.