BACKG ROUND TO THE INVENTION AND PRIOR ART

The present invention relates generally to production of inner walls in buildings and edifices . Particularly, the invention per- tains to a method of man ufacturing a bui lding board accordi ng to the preamble of claim 1 and a building board obtainable by such a method.

Today, there are many solutions for mounting cladding , for example in the form of wooden panels and similar on the walls of a house. Moreover, there are established methods for mounting other kinds of wal l coatings inside a room , such as boards of plaster, wood fiber or laminated wood. A common denominator for the latter methods is that they require particular measures to accomplish good looking joints between the different wall ele- ments of the coating. To combine an aesthetically appealing look with an uncomplicated and cost-efficient manufacturi ng has proven to be especially challenging .

One example of a relatively cost-efficient design is a system where plasterboards are pre-wallpapered with wallpaper exten- ding around the edges of the plasterboards. Further, the plaster- boards are provided with hidden attachment means on the backside or at the edges of the boards for fitting the boards onto a wall structure. This allows a room to be completed for occupancy in a very short time. PROBLEMS ASSOCIATED WITH THE PRIOR ART

However, since the dimensions of standard plasterboards always vary somewhat, both with respect to width and thickness, the completed walls will not have a perfect finish . For example any variations in width will result in triangular-shaped vertical gaps in the wall . Moreover, any thickness variations will lead to ugly shadowing occurring in trailing light. To reduce these phenomena, the plasterboards are often beveled, which results in clean-cut, however very visible joints. SUMMARY OF TH E I NVENTION

The object of the present invention is therefore to provide a solution through which bui lding boards can be manufactured i n a cost-efficient man ner, and where the fin ished buildi ng boards can be mounted quickly onto a building structure so as to result in aesthetically appealing inner walls.

According to one aspect of the invention , the object is ach ieved by the initially described method of manufacturing a buildi ng board , wherein a first groove is milled in a first edge side of said edge sides. The first groove is milled by forwarding the body element between a fixed roller and a flexible roller and past a cutting tool . More precisely, the body element is forwarded so that the cutting tool is introduced into the first edge side while the body element is forwarded, the fixed roller contacts the primary side and the flexible roller contacts a secondary side opposite to the pri mary side, such that during passage of the cutting tool, a first distance from the cutting tool to the primary side is maintained constant even if an overall measure between the primary and secondary sides varies along a length of the body element. The first groove is configured to receive one or more mounting clips to attach the building board to a wall structure.

This manufactu ring method is advantageous because the constant distance from the cutting tool to the primary side ensures that all the surfaces of the mounted building boards which face the interior of the room , i .e. the primary sides, are i n perfect level with one another despite any thickness variations in the bui l ding boards. Natu rally, this vouches for an aesthetical ly appealing look of the finished walls. According to embodiments of this aspect of the invention , the reinforcement layer is applied to the primary side either prior to or after that the first groove has been milled in the first edge side. However, according to one embodiment of the invention, the reinforcement layer is applied such that the reinforcement layer also covers the entire first edge side in order to enhance the durability of the first edge. In such a case, the reinforcement layer must be applied prior to milling the first groove. Otherwise the reinforcement layer will obstruct the first groove.

According to another embodiment of this aspect of the invention , after having applied the reinforcement layer to the primary side, the method involves cutting the reinforcement layer along the first edge side flush with an intersection line between the first edge si de and the primary side. This is advantageous because it both results in minimum joint distances between adjoining building boards, and avoids rounding of the intersection l ine between the pri mary side and the first edge side . In other words, an almost unbroken wall surface can be obtained.

According to one embodiment of this aspect of the invention , prior to milling the first groove in the first edge side, the method involves precision cutting the first edge side and a second edge side opposite thereto so as to attain a high degree of parallelism between the first and second edge sides. Namely, standard plas- terboards have relatively large dimensional tolerances in the width measure, and as discussed above, this may lead to triangular-shaped joint gaps. However, if the vertical edge sides of all building boards are as parallel as possible to one another, the risk of having such undesired joint gaps is minimized.

According to one alternative embodiment of this aspect of the invention , the milling of the first groove in the first edge side also involves precision cutting the first edge side so as to attain a high degree of parallelism between the first and second edge sides. In other words, the milling of the first groove and the precision cutting is executed in a joint action . Naturally, for efficiency reasons this is beneficial .

According to a further embodiment of this aspect of the inven- tion , prior to applying the reinforcement layer to the pri mary side, the method involves infusing a hardening liquid into the first edge side. The hardening liquid (e.g . containing polymer concrete?) is configured to, after harden ing , instill a durabi lity of the first edge side which is improved relative to an original du rability of the first edge prior to infusing the hardening liquid. This is desirable because such a reinforced edge side is less prone to breakage in connection with handling and mounting of the building board. According to yet another embodiment of this aspect of the invention , prior to applying the reinforcement layer to the pri mary side, the method involves applying a laminating layer on the primary side and the first edge side, such that the laminating layer covers at least a part of the primary side and the laminating layer covers the entire first edge side. Optionally the laminating layer covers also a part of the secondary side. Thereby, the breakage risk of edge side reduced during handling and mounting of the building board.

According to still another embodi ment of this aspect of the i n- vention , the method further involves milling a second groove in a second edge side of the body element. The second edge side is opposite to the first edge side , and analogous to first edge side, the second groove is milled by forwarding the body element between fixed and flexible rollers, and past a cutting tool such that the cutting tool is introduced into the second edge side while the body element is forwarded. The fixed roller contacts the primary side and the flexible roller contacts the secondary side , such that during passage of the cutting tool , the cutting tool is maintained at the first distance from the primary side constant even if the overall measure between the primary and secondary sides varies along the length of the body element. The second groove is configured to receive one or more mounting clips to attach the bu ilding board to the wall structure. Since, typically, all bui lding boards are con nected to a wall structure along both thei r vertical edge sides, it is high ly desired to have grooves i n both the first and the second edge side, in other words the vertical edge sides.

According to yet a further embodiment of this aspect of the invention , after having applied the reinforcement layer to the pri- mary side, the method also involves cutting the reinforcement layer along the second edge side flush with an intersection line between the second edge side and the primary side. As mentioned above, this is advantageous because it results in minimum joint distances between adjoining building boards, and thus also minimal joint visibility.

According to another embodiment of this aspect of the invention , prior to milling the second groove in the second edge side, the method involves precision cutting the first and second edge sides so as to attain a high degree of parallelism between the first and second edge sides.

According to a further embodiment of this aspect of the invention , prior to applying the reinforcement layer to the primary side, the method involves infusing a hardening liquid i nto the second edge side. The hardening liquid is configured to, after hardening , instill a durabi lity of the second edge side which is im proved relative to an original durability of the second edge prior to infusing the hardening liquid. Of course, analogous to the first edge side, it is desirable to improve the durability of the second edge side.

According to another embodiment of this aspect of the invention , prior to applying the reinforcement layer to the primary side, the method further involves applying a laminating layer on the primary side and the second edge side, such that the laminating layer covers at least a part of the primary side and the laminating layer covers the entire second edge side. Optionally the laminating la- yer covers also a part of the secondary side. Hence, the breakage risk of edge side reduced du ring handling and mounting of the building board.

According to one embodi ment of this aspect of the invention , the method further involves milling a straight cut in the secondary si de. The straight cut extends along the full length of the body element from a third edge side of said four edge sides to a fourth edge side opposite to the third edge side . The straight cut is pa- rallel to the first and second edge sides. The straight cut has a bottom angle of 90 degrees, and each side of the straight cut shows an angle of 225 degrees to the secondary side. The straight cut has a depth that is slightly smaller than the overall measure between the primary and secondary sides. For example, the straight cut may reach down to an outer layer on the primary side of the body element. Nevertheless, after having cut the straight cut, a reinforcement sheet is inserted into the straight cut such that a first side of the reinforcement sheet adjoins a first cut side of the straight cut. Subsequently, the body element is folded along the straight cut, so that a second cut side of the straight cut adjoins a second side of the reinforcement sheet, and the reinforcement sheet is thus clamped in the straight cut. This results in a highly durable wall corner.

According to one embodiment of this aspect of the invention , method involves introducing at least one mounting clip into the first groove. The at least one mounting clip has at least one attachment member, a base member and at least one engagement member. The at least one attachment member is configured to be attached to a wall structure. The at least one engagement mem- ber and the at least one attachment member protrude from the base member in such respective directions that the at least one engagement member can be introduced into the first groove when the at least one attachment member is attached to the wal l structure. Such i ntegration of mounting clips i nto the building board further reduces the overall mounting time for an i nner wall .

According to another aspect of the i nvention , the object is achieved by a building board having been obtai ned via the above-described method. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained more closely by means of embodiments, which are described as examples, and with reference to the attached drawings.

Figure 1 illustrates how a body element of a building board is cut to obtain highly parallel edge sides according to one embodiment of the invention;

Figure 2 illustrates how a groove is milled in the body element according to the invention;

Figure 3 illustrates how a hardening liquid is infused into the body element according to one embodiment of the invention;

Figures 4a-b illustrate how the body element is provided with a laminating layer according to embodiments of the invention;

Figures 5a-b illustrate how a reinforcement layer is applied to the body element according to one embodiment of the invention;

Figure 6 illustrates how building boards are attached to a wall structure according to one embodiment of the invention;

Figures 7a-c illustrate how an outer corner is formed in a building board according to one embodiment of the invention; and

Figure 8 shows a flow chart over the general method

cording to the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 schematically illustrates how a body element 100 that will serve as a basis for a building board is precision cut according to one embodiment of the invention. The body element 100 is preferably made of plaster. However, other materials are also conceivable according to the invention, such as wood fiber or laminated wood. The body element 100 has the essential shape of a rectangular cuboid including two opposite main sides 110 and 120 respectively having relatively large delimitation surfaces, and four edge sides with relatively small delimitation surfaces.

The purpose of the cutting is to obtain a high degree of parallelism between two opposing edge sides, here first and second edge sides 101 and 102 delimiting the long sides of the body element 100. A typical building board is substantially longer than it is wide, and the support structure onto which the building board is to be mounted normally contains support studs arranged in such a manner that the building board should be mounted with its long side vertically to match the support studs. Therefore, to minimize the risk of having vertical gaps between the mounted building boards, it is most important that the long sides, i.e. the first and second edge sides 101 and 102, are parallel to one another. However, according to the invention, alternatively, or additionally, third and second edge sides delimiting the short sides of the body element 100 may also be cut according to the below procedure.

The proposed precision cutting is effected by forwarding the body element 100 on a flat surface between two sawblades 151 and 152, e.g. of circular type, which are perfectly parallel to one another and located at a well-defined distance from one another that is shorter than an original width of the body element 100. Thus, after that the full length of the body element 100 has passed the sawblades 151 and 152, the width dimension of the body element 100 equals said well-defined distance, and the first and second edge sides 101 and 102 are parallel to one another. Alternatively, given that one of the edge sides, say 102, is already highly flat and has well-defined 90 degree angles to the main sides 110 and 120, it is sufficient to precision cut only the other edge side 101. In such a case, the body element 100 is forwarded on a flat surface between a fixed support and the saw- blade 151, where the second edge side 102 is pushed against the fixed support while the body element 100 is forwarded pass the sawblade 151. Further, of course, if both the first and second edge sides 101 and 102 have well-defined 90 degree ang- les to the main sides 110 and 120, and are parallel to one another already when the body element is received, the cutting step can be omitted.

Figure 2 illustrates how a groove is milled in the body element 101 according to one second embodiment of the invention. Spe- cifically, after any precision cutting of the body element 100 as described above, a first groove 101G is milled in the first edge side 101.

The first groove 101G is milled by forwarding the body element 100 between a fixed roller 211 and a flexible roller 212, and past a cutting tool 230, such that the cutting tool 230 is introduced into the first edge side 101 while the body element 100 is forwarded. The fixed roller 211 contacts the primary side 110 and the flexible roller 212 contacts the secondary side 120. We now refer briefly to Figure 6, which illustrates how building boards may be atta- ched to a wall structure 610.

Due to the arrangement of the rollers 211 and 212, during passage of the cutting tool 230, a first distance D1 from the cutting tool 230 to the primary side 110 is maintained constant even if an overall measure D2 between the primary and secondary sides 110 and 120 varies along a length of the body element 100. The first groove 101G is configured to receive one or more mounting clips 620 to attach the building board to a wall structure 610. This means that, since the first distance D1 is reliably constant, it is possible to mount a number of building boards that all have been manufactured through the proposed method, such that the respective primary sides 110 of the building boards are in perfect level with one another. Of course, this is desirable because it vouches for an aesthetically appealing end result. As an alternative to precision cutting the first and second edge sides 101 and 102 in an initial step, as described referring to Figure 1, and subsequently milling the first groove 101G in the first edge side 101, as described referring to Figure 2; given an ade- quate design of the cutting tool 230, these two steps can be combined into a joint action wherein the milling of the first groove 101G in the first edge side 101 also involves precision cutting the first edge side 101 so as to attain a high degree of parallelism between the first and second edge sides 101 and 102 respecti- vely.

Further, and as illustrated in Figure 6, a second groove 101Gb is preferably milled in the second edge side 102. Analogous to the first groove 101G, the second groove 101Gb is milled by forwarding the body element 100 between the fixed roller 211 and the flexible roller 212, and past the cutting tool 230 such that the cutting tool 230 is introduced into the second edge side 101Gb while the body element 100 is forwarded. Again, the fixed roller 211 contacts the primary side 110 and the flexible roller 212 contacts the secondary side 120, such that during passage of the cutting tool 230, the cutting tool 230 is maintained at the first distance D1 from the primary side 120 even if the overall measure D2 between the primary and secondary sides 110 and 120 varies along the length of the body element 100.

Similar to the first groove 101G, the second groove 101Gb is configured to receive one or more mounting clips 620 to attach the building board to the wall structure 610.

Figure 3 illustrates how a hardening liquid 300 is infused into the body element 100 according to one embodiment of the invention. Preferably prior to applying a reinforcement layer to the primary side 110, the hardening liquid 300 is infused into the first edge side 101. Namely, the reinforcement layer is typically represented by a wallpaper, and the hardening liquid 300 may cause unwel- come stains thereon if the reinforcement layer is already in place when the hardening liquid 300 is infused. The hardening liquid 300 is configured to, after hardening, instill a durabi lity of the first edge side 1 01 , which durability is improved relative to an original durability of the first edge 101 prior to infusing the hardening li quid 300.

Naturally, likewise preferably prior to applying the reinforcement layer to the primary side, the hardening liquid 300 may be infused into the second edge side 102 to accomplish the same improve- ment of the durability there.

Figures 4a and b illustrate how the body element 1 00 is provided with a laminating layer 400 according to embodiments of the invention .

Figure 4a shows an example where the laminating layer 400 is applied on the primary side 1 10 and the first edge side 101 (e.g. by gluing) , such that the laminating layer 400 covers at least a part of 410 the primary side 1 1 0, and the laminating layer also covers 401 a the entire first edge side 1 01 . Consequently, the laminating layer 400 shall be applied prior to mil ling the first groove 1 01 G , such the laminating layer 400 does not risk to obstruct the first groove 1 01 G .

In any case, in addition to, or as a complement to the hardening liquid 300, the laminating layer 400 reinforces the first edge side 1 01 , and thereby reduces the breakage risk of the first edge side 1 01 during handling and mounting of the building board.

Alternatively, to further enhance the durability, the laminating layer 400 may be applied , such that the laminating layer 400 also covers at least a part of 401 b the secondary side 120 , for example as illustrated in Figure 4b. Naturally, analogous to the hardening liquid 300, the lami nating layer 400 may be applied on the second edge side 1 02 (e.g . by gluing) . More precisely, in such a case, the laminating layer 400 is applied on the primary side 110 and the second edge side 102, so that the laminating layer 400 covers at least a part of the primary side 110 and the laminating layer 400 covers the entire second edge side 102. Alternatively, the laminating layer 400 is applied such that the laminating layer 400 also covers at least a part of the secondary side 120.

As an alternative to the above, the reinforcement layer 510 can instead be applied such that the reinforcement layer 510 also covers the entire first edge side 101, and possibly also a part of the secondary side 120. Thus, there is no need for a separate laminating layer 400. Here, the reinforcement layer 510 has the function of the laminating layer 400.

Figures 5a and b illustrate how a reinforcement layer 510 is applied to the body element 100 according to one embodiment of the invention.

The reinforcement layer 510 is applied (e.g. by gluing) to the primary side 110 such that the reinforcement layer 510 covers the entire primary side 110 and preferably also extends somewhat over the first edge side 101, as illustrated in Figure 5a. The rein- forcement layer 510, e.g. represented by a wallpaper, is configured to be shown to an interior of a room the inner wall of which the building board forms a part when being mounted in the building.

As mentioned above, if the building board includes a laminating layer 400, the reinforcement layer 510 must be applied after that the laminating layer 400 has been applied. Preferably, as mentioned above, the reinforcement layer 510 should also be applied after infusing any hardening liquid 300. However, it is basically irrelevant if the reinforcement layer 510 is applied prior to, or af- ter that the first or second grooves 101G and 101Gb are milled in the first and second edge sides 101 and 102 respectively.

In any case, after having applied the reinforcement layer 510, the reinforcement layer 510 is cut along the first edge side 101 flush with an intersection line between the first edge side 1 01 and the primary side 1 1 0 , as illustrated in Figure 5b.

Figures 7a, 7b and 7c illustrate how an outer corner 700 is formed in a bui lding board according to one embodiment of the in- vention .

First, a straight cut 720 is milled in the secondary side 1 20 , as illustrated in Figure 7a. The straight cut 720 extends along the full length of the body element 1 00 from a third edge side 1 03 thereof to a fourth edge side 1 04 thereof. Further, the straig ht cut 720 is parallel to the first and second edge sides 1 01 and 102, and has a depth that is slightly smaller than the overall measure between the primary and secondary sides 1 1 0 and 1 20. For instance, the straight cut 720 may extend all through down to the reinforcement layer 51 0 on the primary side 1 1 0. The straight cut 720 has a bottom angle of 90 degrees, and each side of the straight cut 720 shows an angle of 225 degrees to the secondary side 1 20.

Then , after completing the straight cut 720, a reinforcement sheet 725 is inserted into the straight cut 720 , such that a first side of the reinforcement sheet 725 adjoins a first cut side of the straight cut, as illustrated in Figure 7b. To avoid damaging the reinforcement layer 510, the reinforcement sheet 725 is preferably rounded on an edge side that is placed towards the bottom of the straight cut 720. Finally, as illustrated in Figure 7c, the body element 1 00 is folded along the straight cut 720 such that a second cut side of the straight cut 720 adjoins a second side of the reinforcement sheet 725, which second side is opposite to the first side of the reinforcement sheet 725, thus causing the reinforcement sheet 725 to be clamped in the straight cut 720. To ensure fixation of the reinforcement sheet 725, glue may be applied to at least one of the first or second sides of the reinforcement sheet 725 before folding the body element 1 00. Consequently, when the outer corner 700 has been completed as described above, a first section 1 20-i of the secondary side 1 20 shows a90 degree angle to a second section 1 20-ii of the secondary side 1 20, which is located on an opposite side of the reinforcement sheet 725 relative to the first section 1 20-i .

Returning now to Figure 6, we wi ll explain h ow the proposed buildi ng boards can be mounted onto a wall structure 61 0.

The mounting procedure involves introducing at least one mounting clip 620 into the first g roove 1 01 G . Before introducing any mounting clip 620 into the first groove 1 01 G , the mou nting clip 620 has been attached to the wall structure 61 0 , for example by means of one or more screws th rough at least one attachment member 623 of the mounting cl ip 620. The mounti ng clip 620 further includes a base member 625 and at least on e engage- ment member 627. The at least one engagement member 627 and the at least one attach ment member 623 protrude from the base member 625 in such respective directions that the at least one engagement member 627 can be introduced i nto the first groove 1 01 G when the at least one attach ment member 623 is attached to the wall structure 61 0 , e.g . as shown in Figure 6.

To sum up, the general method accordi ng to the invention for manufacturing the proposed building boards wi ll now be described with reference to the flow chart in Figure 8.

In a first step 81 0 , a body element is received. The body ele- ment has the essential shape of a rectangular cuboid including two opposite main sides with relatively large delimitation surfaces and four edge sides with relatively small delimitation surfaces.

Then , in a step 820, a first groove is milled in a first edge side of the edge sides. The first groove is milled by forwarding the body element between a fixed roller and a flexible roller, and past a cutting tool, such that the cutting tool is introduced into the first edge side while the body element is forwarded . The fixed roller contacts the primary side and the flexible roller contacts the secondary side, such that during passage of the cutting tool a distance from the cutting tool to the primary side is maintained constant even if an overall measure between the pri mary and secondary sides varies along a length of the body element. The first groove is configured to receive one or more mounting clips to attach the building board to a wall structu re .

Subsequently, in a step 830, a reinforcement layer is applied to the primary side. The reinforcement layer covers the entire primary side, and the reinforcement layer is configured to be shown to an interior of a room the inner wall of which the building board forms a part when mounted i n the buildi ng .

Thereafter, the procedure may end. However, as discussed above referri ng to Figure 5b, the reinforcement layer is also preferably cut flush with an intersection line between the primary side and the first edge side.

The invention is not restricted to the embodiments, which have been described above with reference to the drawings, however it may be varied freely within the scope of the subsequent claims.