METHOD AND DEVICE FOR CONTINUOUS FORMING OF MATS OF DIFFERENT WIDTHS OF MATERIAL Technical Field The present invention relates to a method and device for continuous form- ing of mats of material containing lignocellulose of different widths, which mats are intended to form boards, where disintegrated material containing lignocellulose is fed from a feeding out unit in the form of a material flow to a forming station com- prising at least one forming belt and at least one forming roll, the forming roll working directly into the mat.

Background of the Invention Upon producing boards of material containing lignocellulose, such as parti- cle boards and fibreboards according to the dry method (MDF, HDF, LDF etc.), first the material containing lignocellulose is disintegrated into particles or fibre bundles. Subsequently these are dried and glue-coated and formed to a continu- ous mat in one or several forming stations. The mat is pre-pressed and subse- quently finish-pressed to boards under pressure and heat in a continuous or dis- continuous press.

The material containing lignocellulose can be mixed with other materials, <BR> <BR> for example plastics, waste paper, glass fibres, disintegrated minerals etc. , prior to forming or during the forming process. Upon producing boards it is essential that these have homogeneous properties over the whole board surface. These proper- ties are, inter alia, thickness, transverse tensile strength, bending and breaking strength, painting properties etc. Since these properties are dependent on the density of the board, it is important that the forming is effected with a good preci- sion so that the density of the board is the same over the whole board surface. In order to achieve this, during the forming process the particles or fibre bundles must be distributed as homogenously as possible, both longitudinally and trans- versely, over the whole formed surface.

Conventional forming equipments for forming boards of material contain- ing lignocellulose are often mechanical. These usually comprise at least one feeding out unit comprising a dosing bin or dosing container where the material is intermediately stored and subsequently it is dosed down, free falling, to a forming unit where the material is laid down on a forming belt, i. e. a conveying belt. Fur-

ther, upon producing fibre boards, a scalping roll is often used subsequent to forming, which mills off any unevenness in the surface of the mat to improve the forming precision.

SE 511 259 discloses the use of a number of forming rolls which work di- rectly into a mat during the forming on a forming belt. The forming rolls provide a transverse distribution effect, and are positioned in such a way that a final mat is formed directly by the rolls. Thus, the milling off process of a board formed from a mat can be avoided. The forming rolls are provided with forming blades which can be attached to the forming roll by welding or casting.

SE 510 416 discloses a device for continuous forming of a mat of material containing lignocellulose where a mat compressor and a mat trimming system are arranged at the forming belt of the device, in order to form the mat prior to its pressing. Further, SE 510 416 discloses a method to control the width of the board without being forced to remove side portions by means of a circular saw or mill units in order to adjust the width of the board after pressing. This adjustment of the width is achieved by separating walls which already during the forming set the width of the mat.

However, the above mentioned forming rolls, which are arranged to work directly into a mat during its forming, are not arranged to be adjusted to different widths of a forming station having adjustable width, for example, since conven- tional forming rolls provided with tool units are usually constructed of only one drum or tube unit, to which surface said tool units are attached. Therefore, these forming rolls have not been possible to use, for example in the kind of forming sta- tions having adjustable width, without causing circulation of material during the forming of the mat and the work of the forming roll into the mat, since the forming rolls could not extend across the whole width of the forming station for different widths. The circulation of material makes the forming of a mat with a flat mat sur- face more difficult.

The Object of the Invention Thus, the object of the present invention is to provide a continuous forming of mats of different widths of material containing lignocellulose, during which forming the forming rolls are working directly into the mat, and the width of the

forming station can be changed, without any circulation of material during the forming of the mat and the work of the forming roll into the mat.

Summary of the Invention The solution of the present invention to the above mentioned problem is to provide a method, a forming roll, and a device providing a radical improvement of the forming process by a method of the kind defined in the preamble of claim 1, comprising the special measures that teeth attached to the forming roll engage into the mat, and that the longitudinal extension of the forming roll is adjusted to a selected width. The result of this is that the forming rolls, the purpose of which is to provide a transverse distribution effect of the disintegrated material, level any un- evenness and tear up pieces of fluff in the surface of the mat, can be longitudinally shortened or extended and be adjusted to the width of a forming station. This can be achieved rapidly and easily without any long stoppage of production. The con- sequence is that the forming rolls can extend across the whole width of the form- ing station at different settings of width of the forming station preventing circulation of material during the forming since a form of sealing at different widths of the forming station can be provided at the longitudinal sides of the forming station.

Consequently, the present invention provides the possibility to combine forming rolls provided with teeth with a forming station having an adjustable width without a circulation of material during a continuous adjustment of the width of the forming station.

Further, the present invention provides a forming roll of the kind defined in the preamble of claim 3, comprising the special features that the forming roll is provided with teeth, and that the longitudinal extension of the forming roll is ad- justable. Preferably, the forming roll is adjustable in such a way that it can extend across the whole width of the forming station at different width settings of the forming station. Preferably, the teeth have essentially the same extension from the centre of rotation of the forming roll, in order to provide an even engagement in the mat surface.

According to an advantageous embodiment of the forming roll according to the present invention, the forming roll comprises at least two forming roll units movable in relation to each other, the teeth of respective forming roll unit are ar- ranged in at least one comb unit attached to respective forming roll unit, which

comb unit extends along the longitudinal extension of the forming roll, respective comb unit being partially movable along the adjacent forming roll unit.

According to a further advantageous embodiment of the forming roll according to the present invention, the extension of the comb unit of a forming roll unit extends along the longitudinal extension of the forming roll, separated from and parallel with the extension of the comb unit of an adjacent forming roll unit along the longitudinal extension of the forming roll. Preferably, respective forming roll unit comprises two or more comb units separated from each other and ex- tending parallel with each other, a comb unit moved along an adjacent forming roll unit extending between two comb units of said adjacent forming roll unit. By mounting the teeth on the forming roll units in the form of comb units which are ar- ranged to be moved between and parallel with the comb units of an adjacent forming roll unit, the width of the forming roll can be changed, and consequently the forming station can be adjusted to a required width and still having the forming rolls extending across the whole width of the forming station.

The present invention also provides a device of the kind defined in the pre- amble of claim 10, comprising the special features that the forming roll is provided with teeth, and that the longitudinal extension of the forming roll is adjustable. Ad- vantageous embodiments emerge from claim 11.

Further, the present invention achieves a method for producing boards of material containing lignocellulose, which method comprises the measure that form a mat from disintegrated material, the method comprising the special measures mentioned in claim 1 or 2.

The present invention also achieves a plant for producing boards of containing lignocellulose, which plant comprises a device for forming a mat, said device comprising the special features mentioned in claim 10 or 11.

Such a method and plant, respectively, for producing boards present those advantageous described above regarding the method, forming roll, and device for forming a mat.

Emerging from above in the disclosure of the background of the invention, the term material does not only imply material containing lignocellulose, but also any other material, such as plastics, waste paper, glass fibres, disintegrated min- erals etc. The material can be of different sizes and forms, and comprise fibres and/or fibre bundles, for example.

Further advantageous embodiments of the present invention emerge from the remaining enclosed claims.

Brief Description of the Drawings The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which: Fig. 1 is a schematic side view of a conventional forming equipment for boards, Fig. 2 is a front view of an embodiment of the forming roll according to the invention showing its longitudinal extension as seen from the direction of movement of the forming belt, and Fig. 3 is a turned view of an embodiment of the forming roll according to the invention seen at an angle from the side.

Detailed Description of Preferred Embodiments Fig. 1 shows a conventional forming equipment for boards. The material is fed in via an inlet 1 to a feeding out unit 4, here in the form of a dosing bin. The feeding out unit 4 has an upper feeding back equipment 2, which feeds material, which has been fed in, to the right in the feeding out unit 4, feeding out rolls 3 and a bottom conveying belt 5 which feeds the material to the left towards the outlet of the feeding out unit 4. After feeding out via the feeding out rolls 3 the material falls down in the fall shaft region 6, and can subsequently fall down directly onto a forming belt 7 or onto a layer of rolls 9 arranged in a forming station 8, in which forming station 8 a mat is formed. The layer of rolls 9 comprises several forming rolls which work directly into the mat, and has a transverse distribution effect. The weight of the mat is continuously checked by a scale unit 10 and data from the scale unit 10 are used for controlling the speed of the bottom conveying belt 5.

The sides of the mat are supported by sidewalls 11 before the entry into a pre- press 12.

Fig. 2 shows an embodiment of the forming roll according to the invention showing its longitudinal extension as seen from the direction of movement of the forming belt. The forming roll 13 is provided with several teeth 14 which have es- sentially the same extension from the centre of rotation of the forming roll 13. The two ends 15,16 of the forming roll 13 are pivotally arranged in a suitable way in

the forming equipment such that the forming roll 13 is positioned in the forming station, preferably adjustable, at a suitable distance to the forming belt, the mounting of the two ends 15,16 of the forming roll 13 enabling for the longitudi- nally extension 17 of the forming roll 13 to be adjustable such that the forming roll 13, for example can extend across the whole set width of the forming station.

The forming roll 13 comprises three forming roll units 18, 19,20 which are attached to each other in a telescopic manner, and can be moved in relation to each other along the longitudinal extension 17 of the forming roll 13. A central forming roll unit 18 having the longitudinal extension 18.1 is provided with comb units 21,22, 23,24 visible in this view, which extend essentially parallel with each other, and are provided with teeth regularly spread, intended to work directly into the mat of material intended for forming. This embodiment of the forming roll 13 has comb units positioned symmetrically such that the central forming roll unit 18 has corresponding comb units seen from the opposite perspective. At one end of the central forming roll unit 18 a peripheral forming roll unit 19 is attached in a telescopic manner, having a longitudinal extension 19.1, and is provided with two comb units 25,26 visible in this view. At the other end of the central forming roll unit 18 a second peripheral forming roll unit 20 is attached in a telescopic manner having a longitudinal extension 20.1, and is provided with two comb units 27, 28 visible in this view. These two peripheral forming roll units 19,20 also comprise comb units symmetrically positioned such that these peripheral forming roll units 19,20 have corresponding comb units seen from the opposite perspective.

All comb units 21,22, 23,24, 25,26, 27,28 are attached to respective forming roll unit 18, 19,20 such that every comb unit 21,22, 23,24, 25,26, 27,28 is movable along the adjacent forming roll unit 18,19, 20. The extension of all comb units 21,22, 23,24, 25,26, 27,28 along the longitudinal extension of the forming roll 13 extends separated from and parallel with the extension of the comb units 21,22, 23,24, 25,26, 27,28 of an adjacent forming roll unit along the longi- tudinal extension of the forming roll 13, which results in that, when the forming roll units 18,19, 20 are moved to shorten the longitudinal extension 17 of the forming roll 13, a comb unit 21,22, 23,24, 25,26, 27,28 of a forming roll unit 18,19, 20 extends parallel with and between two comb units 21,22, 23,24, 25,26, 27,28 attached to an adjacent forming roll unit 18,19, 20. The comb units 21,22, 23,24, 25,26, 27,28 can also comprise two or several rows of teeth 14. Thus, the con-

struction of the embodiment of the forming roll 13 in Fig. 2 enables, for example, that the peripheral forming roll unit 19 can be moved towards the centre of the central forming roll unit 18 such that the forming roll unit 19 is positioned in such a manner that the section surface A-A of the forming roll unit 19 is in level with the section surface B-B of the central forming unit 18. Preferably, the movement in- wards and the movement outwards, respectively, of the peripheral forming roll units 19,20 are effected at the same time and to a similar extent such that a sym- metrical condition is provided.

Fig. 3 shows the embodiment of the forming roll according to the invention shown in Fig. 2 seen at an angle from the side with corresponding features of the forming roll shown in Fig. 2.