FIELD OF THE INVENTION

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 OF THE INVENTION

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, e.g. a foil, 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 2017/007406 A1 discloses a method of and a device for folding over and pressing a fibrous sheet to produce a panel-shaped building element having two large faces. The device comprises a pressing member that moves in a closed loop around the fibrous sheet to first fold one half of the fibrous sheet over the other half and then press the combined two halves to form the building element.

KR 10-1126262 B1 discloses a method of and a device for folding over a fibrous sheet to produce a panel-shaped building element having two large faces. The fibrous sheet includes a central portion, and on each side of the central portion a narrow first lateral portion separated from the central portion by a first groove, and a wider second lateral portion separated from the narrow first lateral portion by a second groove. The device comprises a support for receiving the fibrous sheet. The support has a central portion for receiving the central portion of the fibrous sheet and on both sides thereof an opening located under the lateral sheet potions and the grooves. Further, under each opening the device has a first pivotal link that is pivotal between a horizontal position under the support and a vertical position, where it projects through the opening and has made a first 90 degree fold in the first groove to place the narrow first lateral sheet portion against a narrow

longitudinal side of the central sheet portion. Thereby it also lifts the wider second lateral sheet portion to a horizontal position above the support. Further, under each opening the device also has a second pivotal link. This second link is L-shaped and pivotal to swing the wider second lateral sheet portion around the second groove from the horizontal position and past a vertical position to let the wider second lateral sheet portion fall down onto the central sheet portion and the sheet be folded by gravity. In doing so, the L-shaped link passes over the upper ends of the first links. No pressing is disclosed, and the outer free end of the L-shaped link presses the wider second lateral sheet portion against the central sheet portion at one point only.

To a great extent, the present invention starts out from the teachings of

WO 2017/007406 A1 having an international filing date of June 30, 2016, and claiming convention priority from Swedish patent application No. 1550962-3 filed on July 3, 2015, the disclosure of which hereby is incorporated in its entirety in the present application.

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 the production rate can be increased while maintaining a firm attachment of the components of the building element to one another.

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 central portion and two lateral portions parallel thereto and adapted to form at least a part of the large faces of the building element, all three portions extending the full length of the sheet, the central portion carrying spacing elements for providing a desired thickness of the building element; - providing an adhesive for adhering the two lateral portions to the spacing elements;

- providing a folding mechanism and operating it to fold the two lateral portions of the fibrous sheet upward such that they are in their entirety upturned, preferably at a right angle, relative to the central portion;

- providing a pressing mechanism having two pressing members and operating it to carry out the following steps:

i) first folding down an outer part of each of the two upturned lateral portions to place said outer parts of the lateral portions on top of the central portion; and

ii) then making the two pressing members move on top of said outer parts of the lateral portions to press them against the spacing elements on the central portion 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 opposite side there are on both sides of a central portion 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 narrow elongate first lateral portion to permit the fibrous sheet to be folded 90 degrees two times to position the wider second lateral portion on top of the central portion. 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.

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 pressing member is moved mainly in a horizontal plane and to a minor extent a short vertical distance instead of describing a loop around the fibrous sheet makes it possible to reduce the time necessary for carrying out the steps and thus makes it possible to increase the production rate. Preferably, the method further comprises providing a table for receiving the fibrous sheet, said table including a central table portion and two lateral table portions parallel thereto and adapted to receive the central portion and two lateral portions, respectively, of the fibrous sheet, a plurality of fingers included in each one of said two lateral table portions, said fingers being included in said folding mechanism and preferably spaced apart from one another and being pivotal between a lying position in plane with the central table portion and an upright position; and pivoting the fingers between the lying position and the upright position to fold two lateral portions of the fibrous sheet upward such that they are upturned relative to the central portion. Preferably, the fingers constitute said two lateral table portions. By folding up the entire lateral sheet portion from a horizontal position to a vertical position instead of folding up just the narrow first lateral sheet portion, the upright wider lateral sheet portion will be in position to be folded down over the central sheet portion by the approaching pressing member.

It is preferred that the pressing members are segmented and preferably include a plurality of pressing member devices, which preferably have the form of rotary wheels, spaced apart from one another. Each pressing member device, such as each rotary wheel, is preferably carried by a dedicated lever. Then it is also preferred that the spaces between the fingers are sufficiently large to let the pressing member devices, e.g. the rotary wheels, pass between the fingers, so as to make it possible to maintain the fingers in an upright position during at least a part of, or even the entire, pressing step. Thereby, the narrow first lateral sheet portion and the upright wider lateral sheet portion will be attached to their intended exact positions on the central sheet portion.

In addition, it is preferred that the spaces between the pressing member devices, e.g. between the rotary wheels, are sufficiently large to let the rotary wheels of one pressing member pass between the rotary wheels of the other pressing member when they meet adjacent to the central portion of the fibrous sheet, said method further including, during the pressing step, moving the pressing member devices, e.g. the rotary wheels, of the pressing members on the folded fibrous sheet from a side edge of the central portion to at least the middle of the central portion. Suitably, to increase the production rate, the method further includes providing a carriage for carrying the table, the folding mechanism, and the pressing mechanism; and continuously feeding a sequence of fibrous sheets through said carriage, and at the same time moving the pressing members back and forth so as to move together with each of the fibrous sheets while carrying out said folding and pressing. Then, it is also suitable to provide a conveyor for feeding the fibrous sheets.

Preferably, the fibrous sheet on one side has a foil cladding and on the opposite side on each side of the central portion has 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, and said grooves forming between them an inner part of each of the two lateral portions to permit the fibrous sheet to be folded 90 degrees two times to position an outer part of each of the two lateral portions on top of the central portion, preferably the first elongate portion after those two times of 90 degree folding forms at least a major portion of a first narrow face of the building element.

The folding step suitably includes folding the fibrous sheet in the groove that is closest to the central portion of the fibrous sheet to form a first 90 degree fold; and folding the fibrous sheet in the other groove to form a second 90 degree fold, whereby the outer part of the lateral portion of the fibrous sheet is placed on top of the first half, and preferably said first 90 degree fold is completed before the completion of said second 90 degree fold.

In another aspect, the object of the invention is achieved in that a device for producing a panel-shaped building element having two large faces by folding over and pressing a fibrous sheet including a central portion and two lateral portions parallel thereto and adapted to form at least a part of the large faces of the building element, all three portions extending the full length of the sheet, comprises:

- a table for receiving the fibrous sheet, said table including a central table portion and two lateral table portions parallel thereto and adapted to receive the central portion and two lateral portions, respectively, of the fibrous sheet, - a plurality of fingers included in each of the two lateral table portions, each plurality of said fingers being movable as a single unit between a position no higher than in plane with the central table portion and a position where a main part of each finger is located above said plane;

- a first control arrangement arranged to move the fingers so as to fold the fibrous sheet such that each of the two lateral sheet portions forms a first 90 degree fold relative to the central portion;

- a pressing mechanism having two pressing members arranged on opposite sides of the central portion; and

- a second control arrangement arranged to move the pressing members to firstly fold down an outer part of the respective lateral sheet portions onto the central sheet portion, secondly to move on top of said outer parts of the lateral sheet portions and press onto the lateral sheet portions, in counter action with the table, towards the central sheet portion.

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. The fact that the pressing member is moved mainly in a horizontal plane and to a minor extent a short vertical distance instead of describing a loop around the fibrous sheet makes it possible to reduce the time necessary for carrying out the steps and thus makes it possible to increase the production rate.

Suitably, the fingers are pivotal, so that they can constitute the two lateral table portions and give the lateral portions of the fibrous sheet a maximum support during the folding from a lying position to an upright one.

Preferably, the fingers are spaced apart from one another and are of a length corresponding to at least 1/3, more preferably at least 40% , of the width of the lateral portion of the fibrous sheet, and the pressing member is segmented and includes pressing member devices, preferably in the form of a plurality of rotary wheels spaced apart from one another, each wheel preferably being carried by a dedicated lever. Then, it is suitable that the spaces between the fingers are sufficiently large to let the pressing member devices, e.g. the rotary wheels, pass between them. Thereby, the fingers can be maintained in an upright position during a part of, or even the entire, pressing step. Consequently, the narrow first lateral sheet portion and the upright sheet portions will be attached exactly to their intended positions on the central sheet portion.

Then, to ensure that the entire surface of the wider lateral sheet portions will be pressed against the central sheet portion with a desired uniform pressure, it is preferred that the spaces between the pressing member devices, e.g. the rotary wheels, are sufficiently large to let the pressing member devices of one pressing member pass between the pressing member devices of the other pressing member when they meet substantially in the middle of the central portion of the fibrous sheet, thereby enabling an overlapping meeting between the two pressing members.

A drive arrangement for moving the pressing members preferably includes one, or preferably at least two, parallel beams extending over the table, and trolley assemblies are carried by and travelling along said beams. Suitably, each trolley assembly includes a rotary shaft interconnecting each pair of two trolleys on the same side of the table, and said pressing member is mounted in a plurality of levers fixed to the shaft, so that a rotation of the shaft in one direction moves the pressing member downward to press against the fibrous sheet, and a rotation in the opposite direction lifts the pressing member up from the fibrous sheet. The rotation of the shaft is effected by the second control arrangement.

To use the invention in a production line, the device further suitably comprises a carriage for carrying said table, trolley assemblies with pressing members, and control arrangement. The carriage is adapted to be supported by an elongate support structure and be movable back and forth thereon, and it is also arranged to move together with each of the fibrous sheets while the folding and pressing is being carried out.

For continuously feeding a sequence of fibrous sheets through the device, a belt conveyor having a pervious belt is preferably provided, and the device preferably includes a suction member arranged to fix a portion of each fibrous sheet to the table.

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 central portion of the fibrous sheet carries spacing elements for providing a desired thickness of the building element, and the spacing elements and/or the lateral portions carry an adhesive for fixing the lateral portions 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 pressing members have a length that is at least as long as the length of the fibrous sheet.

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 an isometric 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 an end view of the machine of Fig. 1 at the start of the folding step and with spaced apart folding fingers and segmented pressing members in their starting positions.

Fig. 3 is an end view similar to Fig. 2 but showing the two lateral portions of the fibrous sheet folded upward to an upright position by means of the pivotal fingers.

Fig. 4 is an isometric view of what is shown in Fig. 3.

Fig. 5 is an isometric view similar to Fig. 4, but showing the pressing members, which are segmented and include a plurality of spaced apart rotary wheels, moved to a position where they are ready to start folding down the upright lateral sheet portions onto the top of the central sheet portion. Fig. 6 is an end view of what is shown in Fig. 5.

Fig. 7 is an isometric view similar to Fig. 5, but showing the pressing members after they have folded down the lateral sheet portions onto the top of the central sheet portion and have passed through the spaces between the fingers and started to roll on the building element toward its middle while pressing the lateral sheet portions against the central sheet portion,

Fig. 8 is an end view of what is shown in Fig. 7.

Fig. 9 is an end view similar to Fig. 6 but showing the end of the pressing step where the two pressing members have met at the middle of the central sheet portion and the wheels of one pressing member are passing through the spaces between the wheels of the other one.

Fig.10 is an end view similar to Fig. 9 but showing the two pressing members lifted from the produced building element and ready to return to their starting positions.

Fig.1 1 is an end view similar to Fig. 10 but showing the two pressing members returned to their starting positions while the fingers still have to be returned to their starting positions, and,

Figs. 12a, 12b show exemplary embodiments of building elements produced

according to the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

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. 1. The folding and pressing device 1 has an inlet end 10 and an outlet end 1 1 . 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 1 1 .

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, the fibrous sheet 2 has a width, a length, and a thickness. The sheet 2 may preferably originate from a rolled up store of sheet material or from a stack of flat sheets of material, e.g. made of board, having the desired width, wherein the length preferably is cut prior to the pressing device.

As also disclosed in WO 2017/007406 A1 , see for example Figs. 12a and 12b of that document, and the description connected thereto, the fibrous sheet 2 suitably comprises a board sheet having on one side a foil cladding and on the opposite side two pairs of 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 cladding (if any) to form a central portion 23 and two lateral portions 24.

The central sheet portion 23 is defined between the two innermost grooves of each pair and is adapted to form one of the two large faces of the building element 3, while the two outer lateral sheet portions 24a located outside the outermost grooves of each pair together form the other large face. Thus, the width of the central portion 23 is about half the width of the fibrous sheet 2, while the width of each one of the two lateral sheet portions 24 is about a quarter of the width of the fibrous sheet 2. The outermost groove of each pair divides each lateral sheet portion 24 into an inner narrow lateral sheet portion 24b and an outer wider lateral sheet portion 24a. The grooves permit the lateral portions 24 of the fibrous sheet 2 to be bent 90 degrees two times to make each inner narrow lateral sheet portion 24b form a longitudinal narrow side face of the building element 3 while each outer wider lateral sheet portion 24a covers a half of the top of the central portion 23.

Further, the fibrous sheet 2 carries spacing elements 25, 26 for providing a desired thickness of the building element 3 that is produced by folding and pressing the fibrous sheet 2. In the preferred embodiment shown in the drawings, the spacing elements are carried by the central sheet portion 23, but alternatively they can be carried by the two lateral sheet portions 24 or be provided on all or some of the sheet portions 23, 24. The spacing elements 25, 26 suitably carry an adhesive for fixing the sheet portions 23, 24 to one another in a finished building element 3. As alternative to, or in combination with being applied on the spacing elements 25, 26, adhesive may also be applied on the sheet portion 24 to be attached to them. Hence, adhesive may be applied to the spacing elements 25, 26, and/or on the lateral sheet portions 24. The adhesive may be applied at any time before the folding over of the lateral sheet portions 24, outside or inside of the folding and pressing device 1 and at any or all of the parts 23, 24, 25, 26 that are to be joined by adhesive.

In a preferred embodiment, the fibrous board sheet has a thickness of about 1 -3 mm, the spacing elements are board strips 25 which may be of the same thickness and have a height of about 10 to about 30 mm standing on their longitudinal edges parallel to the grooves, and laths 26 may be arranged for forming the longitudinal side edges of the building element 3. Furthermore (as also disclosed in WO

2017/007406 A1 , see Fig. 13), in spaces between the other spacing elements, solid pad or block members of sufficient size may be arranged to permit

attachment members, e.g. screws, to penetrate and be firmly anchored therein. In the present description, the term "spacing elements" is intended to include not only strips 25 and laths 26 but also such solid pads or block members although not shown in the drawings. By providing such solid pads or block members, 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 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 to fulfill their purpose, e.g. alternatively have a zigzag or wave shape or may be an

interconnected structure, e.g. honeycomb structure. The described preferred fibrous sheet may contribute to a high production rate.

As disclosed in WO 2017/007406 A1 , the grooves 22 ^' , 22 ^" (see Fig. 12a of that document) may have a cross sectional shape of a "V" having a bottom angle of 90 degrees or alternatively in the general shape of an "X" (see Fig. 1 1 b of

WO 2017/007406 A1 ) having the same angle between the groove sides.

Returning to Fig. 1 , the folding and pressing device 1 comprises a cage-like frame 12 carrying a table 13 for receiving the fibrous sheet 2. The table 13 includes a central table portion 131 and two lateral table portions, including (or in the form of) two folding units 14, parallel thereto, wherein the central table portion 131 is adapted to receive the central portion 23 of the fibrous sheet 2 and the two lateral table portions are adapted to receive the two lateral portions 24 of the fibrous sheet 2. Further, the folding units 14 preferably are segmented to provide passages, as will be explained further below. The passages are formed by providing each folding unit 14 with a plurality of fingers 140, i.e. included in each one of the two lateral table portions, wherein the fingers 140 are spaced apart from each other. The fingers 140 of each folding unit 14 are movable (preferably pivotable) as a single unit, around a pivot axis 142, between a position substantially in plane with the central table portion 131 and a position where a main part of each finger 140 is located above, and at an angle to, said plane. The fingers 140 may be spaced apart from one another like the teeth of a comb, thereby forming passages between adjacent fingers 140. Preferably the two folding units 14 are positioned off-set in relation to each other, to position their respective passages in an off-set relation to each other, as will be explained more in detail below. A first control arrangement 141 , which may include electric, pneumatic or hydraulic actuators, is arranged to pivot the fingers 140 to fold the fibrous sheet 2 such that each of the two lateral sheet portions 24 forms a first 90-degree fold relative to the central portion 23. In the preferred embodiment shown in the drawings, the fingers 140 may constitute the two lateral table portions, without any further support surfaces, but it is evident for the skilled person that supplementing fixed support surface may be easily provided for between the fingers, in the same plane as the central table portion 131 .

Further, the folding and pressing device 1 comprises a drive arrangement 15 including two trolley assemblies 151 movable towards and away from each other in a direction across the table 13. Each trolley assembly 151 includes two trolleys 152 located on the same side of the table 13, and further a pressing member 16a, 16b, preferably comprising rotary pressing member devices 161 . Each pressing member 16a, 16b is supported by and extends between the two trolleys 152 of each trolley assembly 151 . A second control arrangement 164 is arranged to move the pressing member 16a, 16b from a starting position outside of the table 13 to firstly contact and fold down the upright lateral sheet portions 24 onto the central sheet portion 23 to form a sandwich, secondly to press onto the lateral sheet portions 24 in counter action with the table 13 towards the central sheet portion 23 to convert the formed sandwich into the desired panel-shaped building element 3, and finally to return the pressing members 16a, 16b to the starting position.

By such a device, the fibrous sheet 2 can be folded over swiftly and carefully in an effective manner to produce the panel-shaped building element 3. The fact that the pressing member 16a, 16b is moved mainly in a horizontal plane and to a minor extent a short vertical distance makes it possible to reduce the time necessary for carrying out the steps of folding and pressing and thus makes it possible to increase the production rate.

Suitably, the fingers 140 are pivotal, so that they can be incorporated in the two lateral table portions and give the lateral portions 24 of the fibrous sheet 2 a maximum support during the folding from a lying position to an upright one. Thus, the fingers 140 when lying down suitably form part of the sheet carrying surface of the lateral table portions.

Preferably, the fingers 140 are spaced apart from one another and are preferably of a length that is less than the width of the lateral portion 24 of the fibrous sheet 2, preferably the length of the fingers 140 corresponds to at least 1/3 the width of the lateral portion 24 of the fibrous sheet 2, more preferred to at least 40% of the width of the lateral portion 24 of the fibrous sheet 2. The respective pressing member 16a, 16b is preferably segmented and includes a plurality of pressing member devices 161 , preferably in the form of rotary wheels 161 spaced apart from one another. The wheels 161 are adapted for rolling over the lateral portion 24 as the pressing member 16a, 16b moves on top of the outer part 24a of the respective lateral sheet portion 24. Each wheel is carried by a dedicated lever 163. Then, it is suitable that the spaces between the fingers 140 are sufficiently wide to let the pressing member devices 161 , e.g. the rotary wheels, pass through them. Thereby, the fingers 140 can be maintained in an upright position during the entire pressing step. Consequently, the inner narrow lateral sheet portions and the upright outer wider sheet portions will be attached exactly to their intended positions on the building element 3.

Then, to ensure that the entire surface of the outer lateral sheet portions will be pressed against the central sheet portion 23 with a desired pressure, it is preferred that the spaces between the pressing member devices 161 are sufficiently large to let the pressing member devices 161 of one pressing member 16a pass between the pressing member devices 161 of the other pressing member 16b when they meet, thereby enabling each one of the pressing members 16a, 16b to press along at least half of the fibrous sheet 2. Thus, the two pressing members 16a, 16b can pass into and through each other, whereby it is ensured that each half of the panel- shaped building element 3 will be pressed over its entire width. Further, since the pressing members 16a, 16b mainly move in the horizontal plane, it will be easy to control the movement during the pressing step.

The drive arrangement 15 for moving the pressing members 16a, 16b preferably includes two parallel beams 153 carried by the frame 12 and extending over the table 13, and the trolley assemblies151 are carried by and travelling along said beams 153. Suitably, each trolley assembly 151 includes a rotary shaft 162 interconnecting each pair of two trolleys 152 on the same side of the table 13, and said pressing member 16a, 16b is mounted in a plurality of levers 163 fixed to the rotary shaft 162, so that a rotation of the shaft 162 in one direction moves the press member 16a, 16b downward to press against the fibrous sheet 2, and a rotation in the opposite direction lifts the pressing member 16a, 16b up from the fibrous sheet 2. The rotation of the shaft 162 is effected by the second control arrangement 164, which may include at least one lever 1642 fixed to the rotary shaft 162 and at least one electric, pneumatic or hydraulic actuator 1641 for pivoting the lever 1642 to rotate the shaft 162.

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 table 13, trolley assemblies 151 with pressing members 16, and control arrangements 141 , 164, and is adapted to be supported by an elongate support structure and movable back and forth thereon. As best shown in Fig. 1 , the support structure includes two parallel beams 41 , preferably identical, on which the carriage 12 is movable back and forth driven by a drive mechanism. 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. 1 also shows an embodiment where the drive mechanism also includes a second motor 422 for reciprocating the carriage 12.

For continuously feeding a sequence of fibrous sheets 2 through the device 1 , a conveyor assembly (not shown) may be provided. The conveyor assembly 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 13 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. 1-1 1 . 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.

The fibrous sheet 2 to be folded over and pressed to form the preferably low weight, panel-shaped building element 3 may be of various types known to the skilled art worker. However, preferably, the fibrous sheet 2 has a width, a length, and a thickness and on one side a foil cladding (not shown) and on the opposite side with two pairs of lengthwise extending parallel grooves of perpendicularly V-shaped cross-section, one groove being an inner one and the other being an outer one, the two inner grooves forming between them a central sheet portion 23 adapted to form one of the two large faces 30 of the building element 3 and outside of them a lateral sheet portion 24 on each side. The grooves of each pair are spaced apart from each other a distance equal to an intended thickness of the building element 3 reduced by the double thickness of the cladding and defines a narrow inner lateral sheet portion adapted to form a narrow side of the building element 3. Each of the two lateral portions 24 further include an outer wider lateral portion 24a located outside of the outer groove, and the two outer lateral portions 24a are adapted to form the other large face 30 of the building element 3. The device 1 is arranged to fold the fibrous sheet 2 to position the outer lateral portions on top of the central portion 23, the central portion 23 carries spacing elements 25, 26 for providing a desired thickness of the building element 3, and said spacing elements 25, 26 and/or said lateral portions 24 carries an adhesive for fixing the lateral portions 24 to the spacing elements 25, 26, and the pressing members 16a, 16b have a length that is preferably at least as long as the length of the fibrous sheet 2.

In a few words:

Fig. 1 shows on the whole how the board sheet 2 with spacing elements 25, 26 is ready to be formed into a panel-shaped building element 3 by means of the folding and pressing device 1.

Figs. 2, 3 and 4 show that folding units 14 lift up the lateral portions 24 of the fibrous sheet 2, such that the lateral portions 24, including the outer parts 24a, are in their entirety upturned relative to the central portion 23.

Figs. 5 and 6 show that the pressing members 16a, 16b move inward toward the center of the fibrous sheet 2.

Figs. 7 and 8 show that the folding units 14 include fingers 140 that are spaced apart from one another, that the pressing members 16a, 16b, which are

segmented, are being moved in a horizontal direction and through the spaces between the fingers 140, and that the pressing members 16a, 16b are pivotal to permit them to be folded down and press against the lateral portions 24.

Figure 9 shows that the segmented pressing members 16a, 16b are being moved past each other. Hence, an overlapping meeting occurs between the member 16a and the member 16b. This ensures an efficient and even pressing of the entire surface of the lateral portions 24 toward the central portion 23.

Figs 10 and 1 1 show that the pressing members 16a, 16b are being returned to their start position.

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 two pressing members 16a, 16b that move mainly horizontally over the fibrous sheet 2, which has a central portion 23 and two lateral portions 24, to first fold the two lateral portions 24 over the central portion 23 carrying the spacing elements 25, 26, and then press the formed sandwich 23, 24, 25, 26 to form the building element 3, as shown in Fig. 12a. Preferably, a sequence of fibrous sheets 2 is continuously fed through the device 1 , and the device 1 continuously reciprocates to move together with each of the sheets 2 during the folding and pressing thereof.

As shown in Fig. 12b two building elements 3A, 3B may be produced by dividing a building element 3, e.g. as shown in Fig. 12a, lengthwise. Preferably this is achieved by cutting and/or sawing in the middle of a centrally positioned lath 26, that after division will form side laths 26', 26" in each one of the building elements 3A, 3B. Likewise the central portion 23 will form two separate faces 23', 23".

Preferably the cut/division of the building element 3 into the two building elements 3A, 3B is made by sawing or cutting in the lengthwise joint 33 between the two "lateral portions" 24. The two side laths 26', 26" may preferably be used as back sides and/or non-visible sides in a piece of furniture made from the building elements 3A, 3B, as the sides of the laths 26', 26" lack foil cladding.

The present invention has been shown and described herein in what is considered to be one most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art. For instance, it is evident for the skilled person that various kinds of pressing member devices 161 may be used to achieve a desired pressing together of the sheet portions 23, 24, e.g. sliding devices, caterpillar tread like devices. Further, it is evident that the pressing member devices 161 may be moved varying distances (not necessarily symmetric as shown in Fig. 9), e.g. to meet off-centered at the sheet portion 23 (e.g. to produce two building elements 3A, 3B that are of different width).

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.