WOODEN BEAM OR STUD AND METHOD FOR PRODUCING SUCH A BEAM OR STUD

Abstract: A wooden beam or stud is made in one piece from wood shavings or chips, glued together under pressure and heat, and shaped as an elongate member (10), having a bent and/or curved profile and a material thickness which is small in relation to the total extent of said member (10) in every direction transversal to the longitudinal direction of said member.

Description: ocden beam or stud and method for producing such a beam or stud The present invention relates to a wooden beam or stud. In recent years, within the building industry, beams and studs of solid wood have been replaced to an increasing extent by profiled sheet-metal beams and studs. The main reason is that beams and studs of solid wood have an uneven quality and an imperfect shape performance and that such beams and studs also have a higher weight and fetch a higher price than sheet-metal beams and studs having a corresponding strength. However, the use of sheet-metal beams and studs has disadvantages following from the material properties of such beams and studs. Among other things, it is more difficult to effect machining operation on sheet-metal beams and studs than on beams and studs of wood. In addition, as a consequence of their high thermal conductivity, sheet-metal beams and studs pose a high risk of so-called thermal bridges while simultaneously giving rise to an impaired stability in the case of a fire. Moreover, the electrical conductivity results in a high risk of electrical accidents. In the light of these facts, the invention has for its purpose to provide a new kind cf wooden beams or studs which may constitute a competitive alternative to the mere and more common sheet-metal beams and studs and which makes it possible to avoid the abovementioned disadvantages of such beams and studs as well as the disadvantages of beams and studs consisting of solid wood. The wooden beam or stud, according to the invention proposed for said purpose, is primarily characterized in that it is made in one piece from wood shavings or chips, glued together under pressure and heat, and that it has the shape of an elongate member, having a bent and/or curved profile and a material thickness which is small in relation to the total extent of said member in every direction transversal to the longitudinal direction of said member. Although the beam or stud mainly consists of wood, the invention makes it possible to give it a strength corresponding to the strength of a sheet-metal beam or stud having the same weight and a similar profile. More- over, the manufacturing costs may be reduced to an amount corresponding tc or even falling below the costs for producing a corresponding sheet-metal beam or stud. Simultaneously, a good shape performacnce may be secured. A special advantage is that, in the production of the beam or stud according to the invention, it is possible to benefit from substantial portions of the extensive knowledge and experience previously obtained in connection with the production of the plane board- shaped products which consist of wood shavings or chips, glued together under pressure and heat, and which are known under the designation Oriented Strand Board (OSB). Thus, as is the case in connection with the production of said plane board-shaped products, one may for instance use cheap woods, not suited for the production of timber products, as a basic material for the wood shavings or chips. Furthermore, before glueing the wood shavings or chips together under pressure, one may prepare them in the same manner as in connection with the production of said board-shaped products. The wooden beam or stud may suitably have an approximately constant material thickness along at least the major portion of its cross-section .< In addition, it may well have an approximately constant density along at least the major portion of its cross-section. Here, the term approximately constant means that the variation in thickness or density, respectively, should not be higher than some few or possibly some ten percent. Moreover, at each transition between two adjoining cross-section portions, extending in mutually different directions, the beam or stud may have a curved or bevelled transition section. By shaping the transition section in this manner, it is possible to achieve an increased strength in said section. Additionally, in order to obtain a still further increased strength in the transition section, within the region of said section, the beam or stud may be given a material thickness which is increased in relation to the thickness of said two portions and/or a density which is increased in relation to the density of said two portions. According to a preferred embodiment of the invention, the beam or stud may suitably have the shape of a U-profile member. Profile members having such a shape may be used for a plurality of different purposes. Inter alia, they may be utilized as studs in stud walls or as supporting beams in various building structures. Moreover, it is also possible in an easy manner to join two profile members together in order to form an I-profile or H-pro- file beam or stud. However, if so desired, beams and studs having such a profile may also be produced directly in one single piece. The invention also relates to a method for producing a wooden beam or stud. This method is primarily characterized by subjecting an elongate string of previously glue-coated wood shavings or chips, while heating it, to a pressing operation, during which said string is formed into an elongate member, having a bent and/or curved profile and a material thickness which is small in relation to the total extent of said member in every direction transversal to the longitudinal direction of said member. According to a preferred manner of carrying out said method, during the pressing operation, said string of wood shavings or chips may suitably be subjected to a controlled simultaneous pressing in two at least substantially perpendicular transversal directions. Futher- more, the pressing operation may preferably be carried out under the control from a process computer. The method, proposed according to the invention, makes it possible, if so desired, to give the member a material thickness and/or density, varying between different portions of its cross-sectional area. However, during the pressing operation, said string of wood shavings or chips is preferably formed into an elongate member having an approximately constant material thickness and/or density along at least the major portion of its cross-section. The method according to the invention also makes it possible, if so desired, to give the produced member a cross-section, varying at least to some degree along the length of said member. Thus, contrary to what is the case when producing different kinds of profile members through an extrusion or rolling process, according to the invention it is for instance possible to give the member a material thickness varying along its length. In addition, the method according to the invention also makes it possible, if so desired, to give the member, instead of a strictly straight shape, a slightly curved or bent shape along its entire length or portions thereof. However, during the pressing operation, the material string is preferably formed into a straight profile member having an at least approximately constant cross-section along its length. After the pressing operation, the member formed through said operation may suitably be subjected to a trimming operation which preferably may comprise clean- cutting said member at both ends thereof as well as at the longitudinal edges thereof. Below the invention is further described with reference to the accompanying drawings, in which :- Figures 1 , 2 and 3 show perspective views of three different wooden beams or studs according to embodiments of the invention, selected by way of example only, Figure 4 shows a diagrammatic partial view, in cross-section, of a press, intended to be used for the production of a beam or stud according to Figure 1 , illustrating different parts of said press in their initial positions before the production of a beam or stud in the press, and Figure 5 shows a partial view of said press, corresponding to Figure 4 but illustrating the parts of the press in their final positions after the completion of a pressing operation. Each one of the beams or studs shown in Figures 1 - 3 has the shape of an elongate profile member 10 of generally U-shaped cross-section which comprises a plane central web portion 11 and two plane mutually parallel side flanges 12 which project from web portion 11 at right angles thereto and which are connected to said portion each by means of a transition section 13. Within all portions thereof, member 10 has a material thickness which is small in relation to the total extent of said member in every direction transversal to the longitudinal direction of said member. As a consequence, member 10 has a slender profile highly similar to that of the sheet- metal beams and studs of U-shaped cross-section nowadays commonly used within the building industry. The beams or studs shown in Figures 1 - 3 differ from each other only in respect of the shape of transition sections 13. In all three embodiments, member 10 consists of wood shavings or chips, glued together under pressure and heat, and it has been made by subjecting a string of previously glue-coated wood shavings or chips, while heating it, to a pressing operation during which said string is formed into a member having the desired profile. The wood shavings or chips used for the production of member 10 may suitably consist of thin elongate shavings of the kind utilized in connection with the production of plane boards of OΞB-type. Hereby, to a great extent, the finished profile member will consist of comparatively long wood fibres which, as a consequence of the pressing operation effected on said string, within web portion 11 as well as within each flange 12 are oriented in planes extending at least approximately parallel to the mutually parallel main surfaces of the portion of member 10 in question. In the embodiment according to Figure 1, transition sections 13 are shaped as bevelled plane sections having a material thickness equal to the uniform material thickness of web portion 11 and flanges 12, while, in the embodiment according to Figure 2, they do instead consist of arcuately curved sections having a corresponding material thickness. As a consequence, in these two embodiments, member 10 has a constant material thickness along its entire cross-section. Member 10 of Figure 3 is similar to the profile member according to Figure 2 but differs from the latter in that the curved transition sections 13 have a material thickness which is increased in relation to the thickness of web portion 11 and flanges 12. The reason why members 10 are provided with transi- tion sections 13 which, as above described, have the shape of plane bevelled sections or arcuately curved sections and which in addition may have an increased material thickness and/or density, is that member 10 will hereby have an increased strength in the transi- tions between web portion 11 and flanges 12. Below, a method for producing a wooden beam or stud according to the invention will be described with reference to Figures 4 and 5 which show diagrammatic partial views in cross-section of a press intended for the production of a beam or stud according to Figure 1 and illustrate said press in two different states. Said press comprises an elongate press table 14, having a plane upper surface 15 and, centrally in said surface, a longitudinally extending cavity which has the shape of a groove 16 of generally rectangular cross- section, containing a vertically movable elongate plunger 17. On each side of groove 16, there is provided an elongate press jaw 18 which rests upon press table surface 15 and is arranged horizontally movable in a direc- tion transverse to the longitudinal direction of the press table. Moreover, the press also comprises a plane horizontal cover plate 19, located above the press table and vertically movable between a lifted position shown in Figure 4 and a lowered position shown in Figure 5 and in which said plate rests on fixed supports 20, projecting in an upward direction from press table 14 and located outside the motion region of press jaws 18. In the illustrated case, said supports have been assumed to consist of two parallel rows of cylindrical pins mounted on the press table. In order to facilitate a rectilinear movement of plunger 17, press jaws 18 and cover plate 19 in the directions indicated by double arrows A, B and C in Figure 4, the press is provided with guide means and operating means not shown in the drawings. The operating means may preferably consist of hydraulic cylinders or other pressure-fluid-driven operating means. In Figure 4, the various parts of the press have been shown in their initial positions which they assume before the production of a profile member 10 in the press, In this situation, plunger 17 has its plane upper surface 21 located flush with the upper surface 15 of press table 14, while the two press jaws 18 are located at maximum horizontal distance from each other and uncover respec- tive longitudinally extending portions of press table surface 15 adjacent to groove 16. Furthermore, cover plate 19 is in a position in which it is lifted from supports 20 and located at a substantial distance above press jaws 18. The production of a member 10 takes place in the following manner. hile the press remains in the state shown in Figure 4, a string 22 of previously glue-coated wood shavings or chips is introduced into the space 23 located between press jaws 18 and above press table sur- face 15 and plunger surface 21. Said introduction of glue-coated wood material into space 23 may be effected in any suitable manner. For instance, it may be effected with the aid of a horizontally movable sheet which, after the deposition of the required amount of wood material thereupon, may be inserted under cover plate 19 and from which said material then may be brought to drop down into space 23 through openings in the bottom of the sheet provided with retractable shutters. Upon the introduction of the material string into said space, it is possible, if so desired, in a separate step to adjust the profile of the string so as to adapt its shape well to the subsequent pressing operation. Hereupon, cover plate 19 is lowered to the position shown in Figure 5 and secured in said position in which it rests upon supports 20 and is located at a neglectable distance above the upper ends of press jaws 18. Space 23 is hereby closed in an upward direction and brought to form an elongate press chamber which, in cross-section, is closed in all directions. Within said closed chamber, material string 22 is then subjected to a simultaneous pressing in two mutually perpendicular directions and formed into a profile member 10 having the shape shown in Figure 1. During this pressing operation, which is carried out while simultaneously heating the material string, for instance by electric heating means mounted within various parts of the press or by feeding a gaseous or liquid heating medium through ducts provided in various parts of the press, the two press jaws 18 are moved horizontally towards each other from the positions shown in Figure 4 to the positions shown in Figure 5, while simultaneously plunger 17 is moved in an upward direction from the position shown in Figure 4 to the position shown in Figure 5. During said pressing operation, material string 22 is subjected to the action of an external pressure at all sides thereof. Hereby, it is possible in the finished member 10, produced by compressing and heating the material string, to obtain an approximately constant density along at least the major portion thereof. In order to make sure that the pressing operation will be effected in the best possible manner, said operation should be carried out under the control from a process computer . In order to make it possible to obtain the shape of transition portions 13 of member 10 shown in Figure 1, at their upper ends, press jaws 18 are provided with projections 24 of wedge-shaped profile which extend from the sides of said jaws facing each other, while, at its upper longitudinal edges, plunger 17 has inclined edge surfaces 25 formed as plane bevels. Due to the fact that the member produced through the above-described pressing operation may have slightly uneven surfaces at its two ends as well as at its free longitudinal edges, said member may subsequent to the pressing operation be subjected to a trimming operation. This trimming operation may comprise clean-cutting the member at both ends thereof and at the free longitudinal edges thereof. Hereby, the finished member may be brought to have fully plane and smooth end surfaces and edge surfaces. The invention is not restricted to the embodiments above described and shown in the drawings. Instead, many other embodiments are feasible within the scope of the invention as defined in the following claims. Especially, it should be noted that member 10 may have many other cross-sectional shapes than those shown in the drawings. Furthermore, the production method above descirbed may be modified in various respects in order to adopt it to the shape of the produced members desired in each individual case.

Claims: Claims 1. Wooden beam or stud, characterized in that it is made in one piece from wood shavings or chips, glued together under pressure and heat, and that it has the shape of an elongate member (10), having a bent and/or curved profile and a material thickness which is small in relation to the total extent of said member in every direction transversal to the longitudinal direction of said member. 2. Wooden beam or stud according to claim 1, characte- rized in that it has an approximately constant material thickness along at least the major portion of its cross- section. 3. Wooden beam or stud according to claim 1 or 2 , characterized in that it has an approximately constant density along at least the major portion of its cross- section. 4. Wooden beam or stud according to any of the preceding claims, characterized in that it has a curved or bevelled transition section (13) at each transition between two adjoining cross-section portions (11, 12) thereof, extending in mutually different directions. 5. Wocden beam or stud according to claim 4, characterized in that, within the region of said transition section (13), it has a material thickness which is in- creased in relation to the thickness of said two portions (11, 12). 6. Wocden beam or stud according to claim 4 or 5 , characterized in that, within the region of said transition section (13), it has a density which is increased in relation to the density of said two portions (11, 12). 7. Wocden beam or stud according to any of the preceding claims, characterized in that it has the shape of a U-profile member (10). 8. Method for producing a wooden beam or stud, charac- teπzed by subjecting an elongate string (22) of previously glue-coated wood shavings or chips, while heating it, to a pressing operation, during which said string is formed into an elongate member (10), having a bent and/or curved profile and a material thickness which is small in relation to the total extent of said member in every direction transversal to the longitudinal direction of said member. 9. Method according to claim 8, characterized by sub- jecting said string (22), during said pressing operation, to a controlled simultaneous pressing in two at least substantially perpendicular transversal directions. 10. Method according to claim 8 or 9 , characterized by carrying out said pressing operation under the control from a process computer. 11. Method according to any of claims 8 - 10, characterized by forming said string (22) of wood shavings or chips into an elongate member (10), having an approximately constant material thickness along at least the major portion of its cross-section. 12. Method according to any of claims 8 - 11, characterized by forming said string (22) into an elongate member (10), having an approximately constant density along at least the major portion of its cross-section. 13. Method according to any of claims 8 - 12, characterized by subjecting the member, formed through said pressing operation, to a trimming operation after said pressing operation. 14. Method according to claim 13, characterized in that said trimming operation comprises clean-cutting said member at both ends thereof as well as at the longitudinal edges thereof .

Inventors: NYBERG ULF LENNART ERNFRID, NYBERG, ULF, LENNART, ERNFRID
Applicants: NYBERG U L E, NYBERG, ULF, LENNART, ERNFRID
Application year: 2000
Main classification: B27N5
IPC codes: B27N5