The present invention relates to a method of folding over and pressing a fibrous sheet to produce a panel-shaped building element having two large faces.

It also relates to a device for folding over and pressing a fibrous sheet to produce a panel-shaped building element having two large faces. BACKGROUND ART

In furniture manufacturing, for example, low weight elements are widely used. Such elements usually consist of a hollow body enclosing a lightweight filling material. The hollow body is covered by a thin film for increasing the aesthetic impression as well as for providing a protective coating for the element.

Such low weight elements can be used as building elements, door panels, and a large amount of furniture elements. Especially in case of home interior applications, heavy demands are made on the thin film. Any damage or degeneration will deteriorate the quality of the low weight element. Consequently, pluralities of manufacturing methods for such low weight elements have been presented.

WO 2010/049418 Al discloses a laminated board, a furniture element including the laminated board, and a method of and a machine for manufacturing the laminated board. The laminated board comprises a board material having a foil laminated to one side and on the other side an elongate groove extending to the laminating foil. Upon folding the board material along the groove, a corner or an edge is formed. To ensure that the formed edge has an even surface, the groove is a groove with an x-shaped cross-section, whereby a normal corner/edge of 90 degrees is beveled to form two corners/edges of 135 degrees. If desired, it is also possible to give the innermost portion of the x-shaped cross-section such a shape that a single rounded corner is formed.

Furthermore, from KR-101126262 there is known a machine and a method for folding over and pressing a fibrous sheet to produce a panel-shaped building element having two large faces, namely a first half and a second half, wherein the first half carries spacing elements for providing a desired thickness of the building element, and the second half is divided into two parts to be folded on top of the first half from one side each by means of two reciprocating link arrangements each carrying a press roll to fold and attach the two parts by means of adhesive.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method of and a device for folding over and pressing a fibrous sheet to produce a panel-shaped building element, where one and the same member is used to fold a second half of the fibrous sheet on top of a first half and thereafter also put pressure on top of the assembly formed to safely attach the halves to each other.

This object is achieved in that the method comprises the steps of:

- providing a fibrous sheet having a width, a length, and a thickness and including a first and a second half adapted to form at least a part of the faces, of the building element, the first half carrying spacing elements for providing a desired thickness of the building element,

- providing an adhesive for adhering the second half to the spacing elements;

- providing a rotary press roll, and moving the press roll in a loop of 360° in the same direction around the fibrous sheet to carry out the following steps:

- folding the fibrous sheet such that the second half of the fibrous sheet is placed on top of the first half; and

- pressing the second half of the fibrous sheet against the spacing elements on the first half of the fibrous sheet to become adhered thereto and to produce the building element having two main faces interconnected by the spacing elements and the adhesive.

The fibrous sheet preferably has on one side a foil cladding and on the on opposite side two lengthwise extending parallel grooves of perpendicularly at least partly V-shaped cross-section that are spaced apart from each other a distance equal to an intended thickness of the building element reduced by the double thickness of the cladding forming between them an intermediate first elongate portion to permit the fibrous sheet to be folded 90 degrees two times to position the second half on top of the first half. Further, preferably the first elongate portion after those two times of 90 degrees folding forms at least a major portion of a first narrow face of the building element. In this context, the term "half is adapted to mean a fibrous sheet portion that is adapted to form at least a major portion of one of the two large faces of the finished building element. Thus, as an illustrative example, the fibrous sheet may include the following portions separated from one another by the grooves and in the following order:

1. A minor portion of the second half of the fibrous sheet,

2. a portion for forming a first narrow face of the building element,

3. the first half of the fibrous sheet,

4. a portion for forming a second narrow face of the building element and,

5. a major portion of the second half of the fibrous sheet

By such a method, the fibrous sheet can be folded over swiftly and carefully in a very effective manner to produce the panel-shaped building element. The fact that the press roll is moved in a loop of 360° in the same direction around the fibrous sheet makes it possible to start making preparations for forming a subsequent building element already during the time the press roll is moved, in the loop, back to a starting position. To speed up production, it is preferable to feed a sequence of fibrous sheets

continuously through said loop, and at the same time move the press roll back and forth in the feed direction of the fibrous sheets so as to move together with each of the fibrous sheets while carrying out said folding and pressing, wherein said loop is in the form of a non-circular closed path movement, enabling the press roll to move along a desired path.

To accomplish this, it is suitable to provide a conveyor for feeding the fibrous sheets, a carriage for carrying the press roll, and at each end of the press roll a link system having two link arms for controlling the movement of the press roll in said loop.

The fibrous sheet to be folded over and pressed to form the, preferably low weight, panel-shaped building element may be of various types known to the skilled art worker. However, preferably, the folding includes folding the fibrous sheet in the groove closest to the first half of the fibrous sheet to form a first 90 degree fold, and then folding the fibrous sheet in a second groove to form a second 90 degree fold, whereby the second half of the fibrous sheet is placed on top of the first one.

In a first slightly modified embodiment, the fibrous sheet in addition to said first and second halves and an intermediate first elongate portion, which is adapted to form a first narrow face of the building element, includes a second elongate portion bounded from said first half by a third identical groove and adapted to form at least a major portion of a second narrow face of the building element. Then, the method further comprises folding the fibrous sheet in the third groove to form a third 90 degree fold. Thereby, a possible joint between neighboring edges of the fibrous sheet enclosing forming the exterior surface of the building element may be located on the second narrow face of the building element, if desired.

In a second slightly modified embodiment, the second elongate portion has a width adapted to cover the second narrow face of the building element, so as to place the joint in the comer between the second narrow face and the second large face of the building element.

In a third slightly modified embodiment, the fibrous sheet in addition includes a third elongate portion bounded from the second elongate portion by a fourth identical groove and adapted to form a minor portion of the second large face of the building element, and a width of said second half is reduced by at least a width of the third elongate portion to make the second half and the third elongate portion either meet or form a narrow gap (e.g. to enable support for a sheet formed rear side piece of a furniture) of at most a few millimeters width between them. Then, the method further comprises folding the fibrous sheet in the fourth groove to form a fourth 90 degree fold. Thereby the possible joint will be located on the second large face of the building element.

The grooves may or may not expose the cladding foil but are of form and/or a depth sufficient to permit the forming of the 90 degree folds. By saving a thin layer of fiber material at the bottom of the groove, the handling of the fibrous sheets may be facilitated, as the connection between the first and second halves is more stable than if the cladding foil provides the entire connection.

Another object of the invention is achieved in that a device for the folding and pressing comprises:

- a drive arrangement including at least a pair of annular members for actuating a looping movement of at least a pair of arm members pivotally and controllably connected thereto,

- a rotary press roll extending between said arm members,

- a table for receiving the fibrous sheet located between the arm members,

- a control arrangement arranged to move the press roll in a loop of 360° around the table from a position below the table to firstly fold over a second half of the sheet onto a first half of the sheet, secondly to press onto the second half in counter action with the table towards the first half and finally to return the press roll to a position below the table.

By such a device, the fibrous sheet can be folded over swiftly and carefully in a very effective manner to produce the panel-shaped building element.

According to further aspect of the device, it may be suitable that:

- each arm member comprise a link system having a first and a second link arm, the first link arm having a first end pivotally attached to one of the annular members and a second end rotary attached to the press roll, and the second link arm having a first end pivotally attached to the same annular member and a second end pivotally attached to a middle portion of the first link arm, providing a structure that in a flexible manner may fold and press along a variety of desired loops.

- the annular members comprise a first and a second ring pulley in a first pair of rotary ring pulleys, and a first and a second ring pulley in a second of rotary ring pulleys, said ring pulleys being coaxial, providing a structure that in an extra reliable and/or cost effective manner may fold and press along a variety of desired loops;

- peripherally arranged bearing assemblies are arranged to support the annular

members radially and axially, providing a structure that in an extra reliable and/or cost efficient manner may fold and press along a variety of desired loops.

- the control arrangement (18, 19) comprises:

- a first drive for rotating the two first ring pulleys

- a second drive for rotating the two second ring pulleys,

- wherein one of the first and second drives is arranged to rotate the pulleys rotated thereby at a speed that varies relatively to the speed at which the other of the first and second drives rotates the pulleys rotated thereby during a completion of a full turn of the ring pulleys, providing a structure that in an extra reliable and/or cost efficient manner may fold and press along a variety of desired loops, wherein preferably the first drive includes two first drive pulleys, each first drive pulley driving an associated one of the two first ring pulleys over a first timing belt, and said two first drive pulleys being interconnected by a synchronizing roll shaft, and wherein more preferred also the second drive includes two second drive pulleys, each second drive pulley driving an associated one of the two second ring pulleys over a second timing belt, and said two second drive pulley being interconnected by a synchronizing roll shaft.

- the second drive is arranged to provide a first speed, preferably constant, and the first drive includes a gear train operatively connected to the second drive and arranged to provide a second speed which varies in relation to the first speed, providing a control arrangement that in an extra reliable and/or cost efficient manner may fold and press along a variety of desired loops, wherein preferably the varying speed is arranged to cause a distance between the pivotal end of the first link arm and the first pivotal end of the second link arm to vary during a turn so as to move the press roll in the loop around the table, and more wherein during the full turn the pivotal end of the first link arm lies ahead of the first pivotal end of the second link arm and an angle between these two pivotal ends varies within an interval of 20° to 120°.

- a carriage for carrying said annular members press roll, arm members, table and control arrangement, said carriage being adapted to be supported by an elongate support structure and be movable back and forth thereon, the carriage being arranged to move together with each of the fibrous sheets while carrying out said folding and pressing, providing a structure that in an extra reliable and/or cost efficient manner may achieve an automated line for producing building elements by folding and pressing.

- a belt conveyor having a pervious belt is provided for continuously feeding a

sequence of fibrous sheets through the device, providing a structure that in an extra reliable and/or cost efficient manner may achieve an automated line for producing building elements by folding and pressing, wherein preferably the device including a suction member arranged to fix a portion of each fibrous sheet to the table.

- said table has an inner end parallel to and adjacent the axis of the annular members, said device further comprising a first pushing apparatus acting at said end and arranged to fold an intermediate first elongate portion of the fibrous sheet, providing a structure that in an extra reliable and/or cost efficient manner may achieve an automated line for producing building elements by folding and pressing.

According to one embodiment the device may comprise;

- a first and a second ring pulley in a first pair of rotary ring pulleys, and a first and a second ring pulley in a second pair of rotary ring pulleys, said ring pulleys being coaxial and said pairs being spaced from each other;

- bearing assemblies for supporting the ring pulleys radially and axially;

- a rotary press roll extending from the first pair of ring pulleys to the second pair;

- at each pair of ring pulleys a link system having a first and a second link arm, the first link arm having one end pivotally attached to one of the ring pulleys and the other end rotary attached to the press roll, and the second link arm having a first end pivotally attached to the second ring pulley and a second end pivotally attached to a middle portion of the first link arm;

- a table for receiving the fibrous sheet located between the two link systems;

- a first drive for rotating the two first ring pulleys;

- a second drive for rotating the two second ring pulleys;

- wherein one of the drives is arranged to rotate either the first ring pulleys or the second ring pulleys at a varying speed during a completion of a full turn of the ring pulleys so as to move the press roll in a closed loop around the table for folding over and pressing the fibrous sheet to produce the panel-shaped building element having two large faces.

The drive providing variable speed may be of various types known to the skilled art worker, e.g. a driving motor may be controlled electronically by a CPU. However, preferably, one of the drives is arranged to provide a constant speed, and the other drive that is arranged to provide varying speed comprises a gear train incorporated in the first drive, said gear train also being operatively connected to the second drive, the gear train preferably being such that the varying speed causes a distance between the pivotal end of the first link arm and the first pivotal end of the second link arm to vary during a turn of 360° so as to move the press roll in a closed loop around the table to first fold over the fibrous sheet, then roll the press roll over the folded fibrous sheet to produce the building element, and finally return the press roll under the table to a start position to close the loop, i.e. by moving the press roll in one and the same direction in a 360° loop around the table. A mechanical drive generally is more reliable than an electronic one. To provide the desired loop movement of the press roll, it is suitable that during the full turn of the ring pulleys the pivotal end of the first link arm lies ahead of the first pivotal end of the second link arm and an angle between these two pivotal ends may vary within an interval of 30° to 90°. It is preferred that the first drive includes two first drive pulleys, each first drive pulley driving an associated one of the two first ring pulleys over a first timing belt, and said two first drive pulleys being interconnected by a synchronizing roll shaft. Thereby, the two first drive pulleys are synchronized to each other. Likewise it is preferred that the second drive includes two second drive pulleys, each second drive pulley driving an associated one of the two second ring pulleys over a second timing belt, and said two second drive pulleys being interconnected by a synchronizing roll shaft. Thereby, the two second drive pulleys are synchronized to each other.

To improve the ability to include the device in a production line, the device suitably comprises a carriage for carrying said ring pulleys, press roll, link systems, table and drives, said carriage being adapted to be supported by an elongate support structure and movable back and forth thereon.

Further the device suitably comprises a belt conveyor having a pervious belt for continuously feeding a sequence of fibrous sheets through the device, a suction member for fixing a portion of each fibrous sheet to the table, and the device is continuously reciprocating along the support structure to move together with each of the fibrous sheets while carrying out said folding and pressing. Hereby the rate of production can be increased.

It is suitable that the table has a longitudinal slot parallel to the axis of the ring pulleys, and that the device further comprises a first pushing apparatus acting through said slot for assisting in an initial portion of the folding of the fibrous sheet and contributing to the high production rate.

The fibrous sheet to be folded over and pressed to form the, preferably low weight, panel-shaped building element may be of various types known to the skilled art worker. However, preferably, the fibrous sheet has a width, a length, and a thickness and on one side a foil cladding and on the on opposite side two lengthwise extending parallel grooves of perpendicularly V-shaped cross-section that are spaced apart from each other a distance equal to an intended thickness of the building element reduced by the double thickness of the fibrous sheet to form a first and a second half adapted to form the two large faces of the building element and permit the fibrous sheet to be bent 90 degrees two times to position the second half on top of the first one. The first one of the halves carries spacing elements for providing a desired thickness of the building element, and the spacing elements and/or the second half carry an adhesive for fixing the second half to the spacing elements in a finished building element. The adhesive may be applied at any time before the folding over of the second half, outside or inside of the device. Further, the pairs of ring pulleys are spaced from each other a longer distance than the length of the fibrous sheet, and the ring pulleys are of a single size and have a diameter that is larger than the width of the fibrous sheet. The spacing elements preferably include solid pad members of sufficient size to permit attachment screws to penetrate and be firmly anchored therein. Thereby the strength and stability of the produced building elements can be increased and the mounting of them in installations by means of screws be more secure.

Further, the spacing elements preferably include board strips standing on their edge and extending parallel to the grooves. Thereby the pad members can be placed in a space between two parallel neighboring board strips. In a first slightly modified embodiment, the fibrous sheet in addition to said first and second halves and an intermediate first elongate portion, which is adapted to form a first narrow face of the building element, includes a second elongate portion bounded from said first half by a third identical groove and adapted to form at least a major portion of a second narrow face of the building element. Then, the device further comprises a second pushing apparatus for folding the fibrous sheet in the third groove to form a third 90 degree fold. Thereby, a possible joint between neighboring edges of the fibrous sheet enclosing forming the exterior surface of the building element may be located on the second narrow face of the building element, if desired. If desired, the second elongate portion has a width adapted to cover the second narrow face of the building element, so as to place the joint in the comer between the second narrow face and the second large face of the building element.

In a second slightly modified embodiment, the fibrous sheet in addition includes a third elongate portion bounded from the second elongate portion by a fourth identical groove and adapted to form a minor portion of the second large face of the building element, and a width of said second half is reduced by at least a width of the third elongate portion to make the second half and the third elongate portion either meet or form a narrow gap of at most a few millimeters width between them. Then, said second pushing apparatus also folds the fibrous sheet in the fourth groove to form a fourth 90 degree fold. Thereby the possible joint will be located on the second large face of the building element.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail with reference to preferred embodiments and the appended drawings. Fig. 1 is a perspective view of part of a machine for producing panel-shaped building elements from fibrous sheets and including a folding over and pressing device of the invention with one finished building element leaving the machine. Fig. 2 is a perspective view of the machine of Fig. 1 viewed from the side.

Fig. 3 is a perspective view of the machine of Figs. 1 and 2 viewed from an opposite direction at an intake end of the machine and showing one stage in the folding of the fibrous sheet.

Fig. 4 is a perspective view of the machine of Fig. 3 viewed from an intake end of the machine and showing the same stage in the folding as Fig. 3.

Fig. 5 is a perspective view of an interior end of the folding over and pressing device in the machine of Figs. 1-4 and showing the folding and pressing mechanism of the device.

Fig. 6 is a perspective view of part of two ring pulleys included in the folding and pressing mechanism, and a bearing assembly for supporting the ring pulleys radially and axially.

Fig. 7 is a perspective view similar to Fig. 6 but from another direction.

Fig. 8 is a perspective view of a drive assembly for driving the ring pulleys.

Figs. 9a-9f are cross-sectional views of the machine and show different stages in the folding and pressing of the fibrous sheet to form the building element.

Fig. 10 is an enlargement of part of Fig. 4 and showing in detail the fibrous sheet with spacing elements and pads and one half of the sheet being bent by a press roll assisted by a pusher.

Fig. 1 la is a perspective view of one end of one embodiment of a produced building element. Figs. 1 lb and 1 lc are end views of part of a fibrous sheet with grooves, which part can be folded and pressed to form the right hand side of the building element of Fig. 1 1a. Fig. 12a and 12b are end views of part of a fibrous sheet with grooves, which part can be folded and pressed to form the left hand side of the building element of Fig. 1 1a.

Fig. 13 is a plan view of one end of another embodiment of a produced building element with the top side made invisible for better clarity.

Fig. 14 is an end view of the building element of Fig. 13.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The machine shown in the drawings includes a folding and pressing device 1 for folding over and pressing a fibrous sheet 2 to form a low weight panel-shaped building element 3 having two large faces 30, one of which is shown facing upwards in Fig. l .The pressing device 1 has an inlet end 10 and an outlet end 1 1 , and a conveyor assembly, not shown in the drawings, transports the fibrous sheet 2 in a feeding direction F through the inlet end 10 into the pressing device 1, where the fibrous sheet 2 is being folded over and pressed, and discharges the produced building element 3 through the outlet end 11.

The fibrous sheet 2 to be folded over and pressed to form the low weight panel-shaped building element 3 may be of various types known to the skilled art worker. However, preferably, the fibrous sheet 2 preferably has a width W, a length L (best shown in Fig. 1), and as shown in Figs, l ib and 12a, a thickness t. The sheet 2 may preferably originate from a rolled up store of sheet material, e.g. made of board, having the desired width W, wherein the length L preferably is cut prior to the pressing device, or alternately merely one half 24 of the board 2 is cut prior to the pressing device, as illustrated in Fig. 3.

The fibrous sheet 2 suitably comprises, as best shown in figs 1 lb and 12a, a board sheet 20 having on one side a foil cladding 21 and on the on opposite side two lengthwise extending parallel grooves 22 ^' , 22 ^{' '} of perpendicularly V-shaped cross-section that are spaced apart from each other a distance D equal to an intended thickness T _to t (Fig. 1 1c) of the building element reduced by the double thickness of the cladding 21 to form a first 23 and a second 24 half adapted to form the two large faces of the building element 3. The grooves 22 ^' , 22 ^" (Fig. l ib) permit the fibrous sheet 2 to be bent 90 degrees two times to position the second half 24 on top of the first half 23. Thus, in addition to said first and second halves 23 and 24, the fibrous sheet 2 has an intermediate first elongate portion 23 ^' (Figs. 1 lb, 1 1c) and a second elongate portion 23 ^" (Figs. 12a, b), which are bounded by grooves 22 ^' , 22 ^" and adapted to form a first narrow face 31 (Figs. 1 1a, 11 c) and a second narrow face 32 (Figs. 1 1a, 12b) of the building element 3. Further, the first one 23 of the halves carries spacing elements 25, 26, 27 (Figs. l l a,b,c, 12a,b) for providing a desired thickness of the building element 3, and said spacing elements 25, 26, 27 carry an adhesive 28 for fixing the second half 24 to the spacing elements 25, 26, 27 in a finished building element 3. As alternative to, or in combination with being applied on the spacing elements 25, 26, 27, adhesive may also be applied on the second half 24. Hence, adhesive 28 may be applied to the spacing elements 25, 26, 27 and/or on the second half 24. The adhesive 28 may be applied at any time before the folding over of the second half 24, outside or inside of the folding and pressing device 1 and at any or both of the parts 24, 25, 26, 27 that are to be joined by adhesive.

In a preferred embodiment, the board sheet 20 has a thickness of about 1 -3 mm, the spacing elements are board strips 25 of the same thickness and a height of about 10 to about 30 mm standing on their longitudinal edges parallel to the grooves 22, laths 26 forming the longitudinal side edges of the building element 3, and in spaces between the other spacing elements, solid pad or block members 27 of sufficient size are arranged to permit attachment members, e.g. screws 29 (Fig. 13) to penetrate and be firmly anchored therein. Thereby the strength and stability of the produced building elements 3 can be increased and the mounting of them in installations by means of screws be more secure. If desired, it is of course possible to provide more laths 26 and/or pads/blocks 27 and place them at other locations than shown in the drawings.

In the shown preferred embodiment, the spacing board strips 25 are straight, but as is evident for the skilled person they may be of varying shape/form to fulfill its purpose, e.g. alternatively have a zigzag or wave shape or an interconnected structure, e.g. honey comb structure. The described preferred fibrous sheet may contribute to a high production rate. The grooves 22', 22" may, for example, be formed in accordance with principles previously known and described in WO 2010/049418, see for example Figs. 2a-2b of that document. Hence, for example, as illustrated in Fig. l ib of the current application first groove portions GP1 are first formed in a first face Fl of the fibrous sheet 2. Then the foil cladding 21 is applied to the first face Fl . Then second groove portions GP2 are formed in a second face F2, being opposite to the first face Fl, of the fibrous board 2. By the forming of the second groove portions GP2 the final appearance of the grooves 22', 22" is obtained, as illustrated in Fig. 1 lb, and the halves 23, 24 and the intermediate first elongate portion 23 ' become separated from each other, but are still held together by the foil cladding 21. When performing the folding the edge will obtain the appearance of Fig. 11 c. It will be appreciated that the opposite edge, illustrated in Fig. 12b, may also be designed according to the general principles described in Figs. l lb-c.

Returning to Fig. 1 the folding and pressing device 1 comprises a cage-like frame 12 having a first open bracket member 121 at the inlet end 10 of the press device 1 and a second open bracket member 120 at the outlet end 1 1 to permit the fibrous sheet 2 to enter through the opening in the first bracket member 121 and after folding and pressing be discharged as a finished building element 3 through the opening in the second bracket 120. These two bracket members 120 and 121 are fixed to a base member 123.

Further, the folding and pressing device 1 comprises a first 131 and a second 132 ring pulley (Fig. 3) in a first pair 13 (Fig. 1) of rotary ring pulleys, and a first 141 and a second 142 ring pulley (Fig. 3) in a second pair 14 (Fig. l) of rotary ring pulleys. The four ring pulleys are coaxial and the pairs 13 and 14 are spaced from each other a distance that is larger than the length L of the fibrous sheet 2. The inner diameter of the four ring pulleys 131 , 132, 141 , 142 is larger than the width W of the fibrous sheet 2 to permit its passage through the ring pulleys.

As is best shown in Figs. 6, 7, and 9a-9f, bearing assemblies 15 are arranged for supporting the ring pulleys 131 , 132, 141 , 142 radially and axially. In the shown preferred embodiment each ring pulley is supported by four bearing assemblies 15 spaced around, preferably equidistantly, the periphery of each ring pulley. Each bearing assembly 15 is attached to the frame 12 and includes a housing 151 with a plurality of wheels 152, e.g. three wheels for each ring pulley, in the shown preferred embodiment a single housing 151 with six wheels 152, three for each ring pulley in the pair. One of the wheels 152 gives radial support to a ring pulley and the two other wheels 152 support the ring pulley axially in opposed directions. Further, the folding and pressing device 1 comprises a rotary press roll 16 (Fig. 5) extending from the first pair 13 of ring pulleys to the second pair 14. The press roll 16 has a length that is larger than the length L of the fibrous sheet 2. Still further, as is best shown in Figs. 5 and 9a-9f, the folding and pressing device 1 comprises at each pair 13 and 14 of ring pulleys a set of arm members in the form of a link system 17 having a first 171 and a second 172 link arm. As the two link systems are identical but mirror symmetrical, only the link system at pair 13 is described. The first link arm 171 has one pivotal end 171 1 pivotally attached to one 131 of the ring pulleys and the other end 1712 (Figs. 9a-9f) rotary attached to the press roll 16, and the second link arm 172 has a first end 1721 pivotally attached to the other ring pulley 132 in the pair and a second end 1722 pivotally attached to a middle portion of the first link arm 171. A table 124 for receiving and supporting the fibrous sheet 2 is located between the two link systems 17 and the table 124 is at its ends carried by the two brackets 120 and 121.

As shown in Fig. 4, the folding and pressing device 1 further comprises a first drive 18 for rotating the two first ring pulleys 131, 141 and a second drive 19 for rotating the two second ring pulleys 132, 142. One of the drives 18 and 19 is arranged to rotate either the first ring pulleys 131, 141 or the second ring pulleys 132, 142 at a varying speed, compared to the other drive 19, 18, during a completion of a full turn of the ring pulleys. Thereby, the first and second link arms 171, 172 will move in relation to each other and will move the press roll 16 in a closed loop, i.e. rotating the ring pulleys 131, 132, 141 , 142 360° in one and the same direction makes the press roll 16 follow a closed loop of 360°, following one and the same direction, around the table 124 for folding over and pressing the fibrous sheet 2 to produce the low weight panel-shaped building element 3 having two large faces, as will be described in more detail hereinafter. The drive providing variable speed may be of various types known to the skilled art worker, e.g. a driving motor may be controlled electronically by a CPU. However, in the preferred embodiment shown in Fig. 8, the second drive 19 is arranged to provide a constant speed, and the first drive 18 includes a gear train 181 arranged to provide varying speed. The gear train 181 is also operatively connected to the second drive 19, as explained in more detail below. The second drive 19 includes a shaft 199 having an intermediate 195 and an outer 192 drive pulley, here called the second drive pulley. The first drive 18 has an inner drive pulley 185 that drives a first gear drive belt 186, which in turn drives a first gear train pulley 1810 of the gear train 181 on its input side. On the output side of the gear train 181 there is second 181 1 and third 1812 gear train pulley. The second gear train pulley 181 1 is via a second gear drive belt 196 connected to the intermediate drive pulley 195 on the shaft 199 of the second drive 19. The third gear train pulley 1812 is via a third gear drive belt 187 connected to an input pulley 188 for a shaft 189 driving a first drive pulley 182. The gear train 181 comprises a planetary gear (not shown) providing a desired gear ratio between input and output shafts, preferably in the interval of 1 : 1 ,5 to 1 :5. By means of this arrangement the driving of the first and second drive pulleys 182, 192 is interconnected such that their speed may be controlled by varying the speed of the first drive 18 in relation to the speed of the second drive 19, e.g. by keeping a constant speed of the first drive 19 and periodically increase and decrease the speed of the first drive 18, respectively. Accordingly, the gear train 181 is such that the varying speed causes a distance between the pivotal end 1711 of the first link arm 171 and the first pivotal end 1721 of the second link arm 172 to vary during a turn so as to move the press roll 16 in a closed loop around the table 124.

As shown In Figs. 9a-9f a preferred path of the press roll 16 includes one part where the press roll 16 first lifts the second half 24 (see fig 9a). The press roll 16 is then moved vertically, basically by means of the rotation of the pair of pulleys 13. Thereafter the distance between the end 1711 of the first link arm 171 and the first pivotal end 1721 of the second link arm 172 is increased to make the press roll 16 fold the second half 24 (see figs. 9b-9c) onto the first half 23 and the roll 16 ending up in a position (Fig. 9c) contacting and pressing on top of the second half 24 adjacent the centrally positioned end thereof. Thereafter the distance between the pivotal end 1711 of the first link arm 171 and the pivotal end 1721 of the second link arm 172 is continuously decreased to make the press roll 16 move along a horizontal path pressing the second half 24 on to the top of the first half 23 (see figs. 9d). Thereafter the press roll 16 is positioned in its outermost position by having the distance between the pivotal end 171 1 of the first link arm 171 and the first pivotal end 1721 of the second link arm 172 at a minimum distance, requiring a limited space within the loop for the passage downwards of the press roll 16 at the peripheral end of the table 124 (see figs. 9e). Finally the press roll 16 is returned in a curved path under the table 124, wherein the distance between the pivotal end 1711 of the first link arm 171 and the pivotal end 1721 of the second link arm 172 is again continuously decreased (see fig 9f), to be moved to a start position to close the loop and to be in position for forming a subsequent building element 3.

Preferably, the arrangement is such that during the full turn, the pivotal end 171 1 of the first link 171 arm lies ahead of the first pivotal end 1721 of the second link arm 172 and an angle between these two pivotal ends varies within an interval of 40° to 70°. Thereby the desired shape of the loop can be achieved.

Accordingly, in Figs. 9a-9f there is shown the first pair 13 of ring pulleys and sequentially how the first and second link arms 171, 172 move the press roll 16, in a desired path, including a lifting path and a horizontal pressing path to perform the folding and pressing, by means of the multilink arrangement of the link arms 171, 172 that facilitates a controlled movement of the press roll 16 in desired path. Hence, thanks to this arrangement the link arms 171 , 172 together with the pairs 13, 14 of ring pulleys will form a four link mechanism, whereby the movement of the end pivot point 1712 carrying the press roll 16 may be controlled to follow a variety of paths, by varying the speed at which the first drive 18 rotates the ring pulleys 131 , 141 driven thereby in relation to the speed at which the second drive 19 rotates the ring pulleys 132, 142. Accordingly, thanks to the design, it is possible to use one and the same member, i.e. the press roll 16, to fold and thereafter also to pressurize/integrate a sheets to form a panel-shaped building element 3. Furthermore, by controlling the manner in which the first drive 18 rotates the ring pulleys 131 , 141 , and how the speed of rotation is varied during a turn, it is also possible to adjust the path of the press roll 16 and adapt the specific path to forming building elements 3 of varying widths. Hence, as described with reference to Figs. 9a-9f, the press roll 16 is moved in a loop of 360° in the same direction around the fibrous sheet 2, and during such loop the press roll 16 folds the fibrous sheet 2 to place the second half 24 on top of the first half 23, then presses the second half 24 against the spacing elements 25, 26, 27 on the first half 23 to become adhered thereto and to produce the building element 3, and then the press roll 16 returns to its starting position, moving below the fibrous sheet 2, the press roll 16 thereby completing the loop of 360°.

As is best shown in Figs. 4 and 8, the first drive 18 includes two first drive pulleys 182, and each first drive pulley drives an associated one of the two first ring pulleys 131, 141 over a first timing belt 183, and said two first drive pulleys 182 are interconnected by a synchronizing roll shaft 184. Also the second drive 19 includes two second drive pulleys 192, each second drive pulley drives an associated one of the two second ring pulleys 132, 142 over a second timing belt 193, and said two second drive pulleys 192 are interconnected by a synchronizing roll shaft 194.

To make it more efficient to include the folding and pressing device 1 in a production line, the frame 12 is designed to form a carriage for carrying the ring pulleys 131 , 132, 141, 142, press roll 16, link systems 17, table 124 and drives 18, 19, and is adapted to be supported by an elongate support structure 4 and movable back and forth thereon. As best shown in Fig. 1 , the support structure 4 includes two parallel beams 41 , preferably identical, on which the carriage 12 is movable back and forth driven by a drive mechanism 42. The drive mechanism has a motor 421 with an output shaft (not shown) and a person skilled in the art knows many mechanisms that can convert a rotation of the motor shaft to a reciprocating movement of the carriage 12. Fig. 3 shows an embodiment where the drive mechanism 42 also includes a second motor 422 for reciprocating the carriage 12.

The conveyor assembly for transporting board material through the production line and referred to above but not shown in the drawings may be of various types known in the art, but preferably a belt conveyor having a pervious belt is provided for continuously feeding a sequence of fibrous sheets 2 through the folding and pressing device 1. Then, a suction member (not shown) is suitably provided for fixing a portion of each fibrous sheet 2 to the table 124 during the folding and pressing, and the folding and pressing device 1 is continuously reciprocating along the support structure to move together with each of the fibrous sheets 2 while carrying out said folding and pressing illustrated in Figs. 9a-9f. After such sequence of folding and pressing the carriage 12 returns to its upstream starting position and is ready to receive another fibrous sheet 2. Hereby the rate of production can be increased.

As shown in Fig. 9a, the main part 124 A of the table 124 may have an outer edge 1245 positioned to facilitate passage of the press roll 16 and an inner edge 1244 positioned adjacent the axis C of the loop, (e.g. the ring pulleys 131, 132, 141, 142), which edges 1244, 1245 extends in parallel to the axis C. Preferably, the table 124 includes a further part 124B, besides the main part 124 A, and a longitudinal slot 1241 parallel to the axis C. The further part 124B of the table 124 may support the second half 24 prior to the press roll 16 starting the folding thereof.

As illustrated in Fig. 10 the folding and pressing device 1 further comprises a first pushing apparatus 1242 acting adjacent the inner edge 1244, e.g. through said slot 1241 (Fig. 9a), for assisting in an initial phase of the folding of the fibrous sheet 2. The first pushing apparatus 1242 may have the form of an elongated guide that folds the intermediate first elongate portion 23 ' in relation to the first half 23, in the first groove 22' (Fig. l ib), as illustrated in Fig. 10. The first pushing apparatus 1242 could achieve folding of the intermediate first elongate portion 23' in conjunction with (as illustrated in Fig. 10), or before, the rotary press roll 16 folding the second half 24 onto the first half 23.

As shown in Fig. 12a and 12b, the fibrous sheet 2 in addition to said first and second halves 23 and 24 and an intermediate first elongate portion 23 ^' (Figs, l ib and 1 1 c), which is adapted to form a first narrow face 31 of the building element 3, includes a second elongate portion 23" bounded from said first half 23 by (at least) a third identical groove 22' and adapted to form at least a major portion, preferably all, of a second narrow face 32 of the building element 3. Then, the folding and pressing device 1 further comprises a second pushing apparatus (not shown) for folding the fibrous sheet 2 in the third groove 22' to form a third 90 degree fold. Thereby, a possible joint 33 (as indicated in Fig. 14) between neighboring edges of the fibrous sheet 2 forming the exterior surface of the building element 3 may be located on the second narrow face 32 of the building element 3, or at the comer between the second narrow face 32 and the second large face 30.

If desired, as shown in Fig 1 la and Figs. 12a and 12b, the second elongate portion 23" has an extension 23" ' connected to it via a fourth groove 22", having a width adapted to extend a distance into the second large face 30 of the building element 3, so as to place the joint 33 away from the comer between the second narrow face 32 and the second large face 30 of the building element 3. Hence, the extension 23" ' may be adapted to form a minor portion of the second large face 30 of the building element 3, and having the width of said second half 24 reduced by at least a width of the third elongate portion 23" ' . Preferably the width of said second half 24 is reduced by more than the width of the third elongate portion 23" ' to make the second half 24 and the third elongate portion 23" ' form a gap 33 (Fig. 12b) of a desired width between them, e.g. to provide fitting space for a building member to be interconnected in an assembled furniture. Then, said second pushing apparatus (not shown) also folds the fibrous sheet 2 in the fourth groove 22" to form a fourth 90 degree fold. Thereby the possible joint 33 will be located on the second large face 30 of the building element 3.

To summarize, a method of and a device for folding over and pressing a fibrous sheet (2) to produce a panel-shaped building element (3) having two large faces (30) are disclosed. The device (1) comprises a press roll (16) that moves in a closed loop around the fibrous sheet (2) to first fold one half (24) of the fibrous sheet (2) over the other half (23) and then press the combined two halves (23, 24) to form the building element (3). Preferably, a sequence of fibrous sheets (1) is continuously fed through the device (1), and the device (1) continuously reciprocates to move together with each of the sheets during the folding and pressing thereof.

INDUSTRIAL APPLICABILITY

The invention is applicable for producing panel-shaped building elements by folding and pressing fibrous sheets that are useful as walls and shelves in bookshelves, bookcases, storage compartments, and as table tops, for example.