WO2005082587A1

WO2005082587A1 - Method and device for forming a mat of fibrous material

Info

Publication number: WO2005082587A1
Application number: PCT/SE2005/000088
Authority: WO
Inventors: Leif Håkan ANDERSSON
Original assignee: Metso Panelboard AB
Current assignee: Metso Panelboard AB
Priority date: 2004-02-27
Filing date: 2005-01-27
Publication date: 2005-09-09
Anticipated expiration: 2006-08-27
Also published as: SE526641C2; SE0400484L; CN1956826A; EP1718443A1; PL1718443T3; EP1718443B1; SE0400484D0

Abstract

A method and a device for the continuous forming of a mat of fiber or particle materials, where the material is deposited on a forming web, and where the cross profile of the mat is adjusted substantially in the entire length of the former by raising or lowering the web locally in cross direction in one or several positions. The adjustment is achieved in that longitudinal profiles beneath the forming web can be raised or lowered independently of each other, so that the bottom of the forming installation can assume different forms for compensating for unevenesses in the cross profile. The raising and, respectively, the lowering can be obtained in that wedges on the lower side of the profiles are arranged to slide against wedges placed in recesses on cross supporting beams located beneath.

Description

Method and device for forming a mat of fibrous material

This invention relates to a method and a device for the continuous forming of a mat for the production of fiberboard, particle board or the like, where fiber or particle material from a batching means is deposited on the surface of a movable forming web.

At the manufacture of fiberboard according to the dry process, the fiber mat is formed on a movable forming web and thereafter pressed by hot pressing. The mat can be formed in a single homogeneous layer or in several layers with different properties for fibers, size, moisture etc. The forming of a mat usually is made in a passive way, i.e. by distributing the fibers on a movable web or wire and thereafter adjusting the thickness of the mat by removing fibers from the upper surface of the mat. The forming can be made, for example, by transporting the fibers in an air stream from a fiber bin and depositing them on a wire while simultaneously sucking off air through the wire, or by a purely mechanical depositing of the fibers, or by discharge from a batching bin above a plurality of distribution rolls, which distribute the fibers down on a forming web for forming a mat on the web.

A usual problem is, that a fiber mat obtained in this way shows distinct unevenesses when studying its cross profile. This can be due a.o. to differences in the type of raw material and to local process conditions, which can be of influence to such a great extent that the cross profile of the formed mat can differ considerably from one installation to another. The fiber mat, for example, can show a surplus of material at the outer edges and a deficit of material at the centre, or vice versa. In other cases may be local surpluses or deficits of material somewhere in the width of the mat at an even profile in general.

An uneven cross profile at the manufacture has consequences at the complete fiberboard. The board, for example, at painting will require different amounts of paint in various places because of variations in density caused by the uneven profile. All kinds of after-treatment of the board will yield an uneven result, which, of course, is not desired.

The more it is desired to manufacture thinner board at higher speed, the more this problem is aggravated. One solution presented for bringing about a more even cross profile is to include in the installation a plurality of forming rolls, which operate on different levels above and to some extent in the fiber mat in order to level the upper surface.

Through SE-517 232 a forming method is known where the forming rolls are screw- shaped and their rotation speed and rotation direction can be controlled in order to obtain a controlled movement of material. One problem with these screw-shaped forming rolls is, that they do not work at optimum for levelling the cross profile of thin fiber mats, because there is not so much material to move for achieving the levelling. At high speeds it is also difficult to be able to bring about a sufficient movement before the fiber mat has passed past the forming roll.

The present invention has the object to solve the problems of unevenesses in the cross profile of the mat in a simple and forceful way even at high speeds and thin fiber mats.

A further object is in a simple way to be able to adjust the level of the bottom of a former. These objects are achieved by the method defined in claim 1 and by a device according to claim 3.

By designing the forming installation in such a way, that its bottom can be adjusted vertically locally in cross direction, but substantially in the entire length of the forming web, an installation is obtained where the cross profile simply can be adjusted in the entire length of the former. According to one embodiment, this is achieved in that vertically adjustable longitudinal profiles are mounted below the forming web. By raising or lowering one or several of the longitudinal profiles, a change in the cross profile of the web is obtained. The local raising or lowering in the cross direction becomes equally great in the entire length of the former. The term local adjustment, thus, is to be understood only to be in the cross direction, because the adjustment throughout is in the longitudinal direction.

According to one embodiment the vertical adjustability is achieved, in that the profiles are placed below the web with support by cross beams, which are provided with recesses for receiving the profiles, and that in each recess a wedge with definite angle is placed. Beneath the longitudinal profiles wedges are attached, which have the same pitch and equal angle as the wedges placed in the recesses of the supporting beams. The angle is chosen with a view to the changing desired, i.e. how abruptly the height is desired to be adjusted. By moving the longitudinal profiles different distances in longitudinal direction, it is possible to change the height of the individual profiles by sliding on the respective pair of wedges, and thereby give the bottom of the forming installation a different form. The form of the bottom can then be adjusted so that it compensates for deviations of the cross profile on the formed fiber mat and thereby obtain an even and accurate forming.

The adjustment of the cross profile suitably is carried out on the basis of a number of cumulative measurement values in each position in cross direction. The term position is to be understood as the coordinate of each longitudinal profile in cross direction.

According to one embodiment, the movement of the profiles is carried out by a mechanic means for example a bottlescrew. The conveying belt then must be stopped before a correction can be made.

According to another embodiment, the correction is carried out by an electric adjusting means. In the case of electric adjusting means the forming web must not be stopped, but the adjustment of the cross profile can be made in operation.

These two embodiments have in common, that only one adjustment means is required for each longitudinal profile. It is, thus, possible in a simple and forceful way to adjust the cross profile in the entire length of the former by only one adjustment per profile.

According to still another embodiment, the adjustment of the floor is connected to a continuous cross profile meter in order to make possible a fully automatic adjustment of the cross profile.

Several other alternatives, of course, can be imagined to obtain vertical adjustability of the longitudinal profiles. The height position of the individual profiles, for example, can be adjusted hydraulically or pneumatically.

The invention is described in greater detail in the following, with reference to some embodiments and the accompanying drawings. Fig. 1 shows an installation for the manufacture of fiberboard, where vertically adjustable longitudinal profiles are placed across the width of the forming web beneath the conveying belt.

Fig. 2 shows a longitudinal profile according to one embodiment of the invention.

Fig. 3 shows an embodiment of the invention, where the raising and, respectively, lowering of the longitudinal profiles is achieved by sliding on a pair of wedges.

Fig. 4 shows the position of a wedge pair where a raising of a longitudinal profile relative to the basic position in Fig. 3 is achieved.

Figure 1 shows a device according to the invention. A forming roll 1 is provided across the width of the former. On the lower side of the forming web 2 a plurality of longitudinal profiles 3 are placed mutually spaced. The profiles can be arranged, for example, at a distance of approx. 100 mm from each other. The profiles can be raised and lowered independently of each other.

Figure 2 shows an embodiment of the invention. The longitudinal profile 3 is provided with a number of wedges 4 on the lower side of the profile. The wedges are placed at the same distance from each other in the longitudinal direction as the cross supporting beams 6. The supporting beams are provided with recesses, in which wedges 5 with the same pitch and same angle are placed. The wedges 4,5 are placed so that they together give the longitudinal profiles a horizontal position. The recesses are worked so that they form lateral support for the longitudinal profiles.

According to Fig. 2 a mechanical adjustment means 7 is mounted between one of the wedges attached to the lower side of the profile and the next cross supporting beam. The mechanical adjustment means can be, for example, a bottlescrew. By adjusting the screw the wedge slides downward or upward along the opposed wedge surface, and the profile is lowered or raised in the entire length of the former. The adjustment means can also be electrical. At one embodiment the adjustment means are connected to a cross profile meter and the adjustment can be carried out automatically on the basis of the measurement result. A stopping means 8 is provided at each end of the single longitudinal profiles. The stopping means is a mechanical stopper in the longitudinal direction and simultaneously prevents the longitudinal profiles from leaving their respective recess.

Figure 3 shows in detail a recess 6 and the respective wedge pair 4,5. The wedges placed on the lower side of the profiles 3 preferably are greater than the corresponding wedges 5 placed in the recesses of the longitudinal supporting beams. The size of the wedges is decided by the size of the movement desired to be made in longitudinal direction.

The wedges preferably are mounted so that they from their basic position can move an equal distance in both directions in longitudinal direction, so that the achievable maximum elevation is equally great as the maximum lowering. The gear ratio, i.e. the size of the movement in longitudinal direction required for achieving a certain raising/lowering, is decided by the choice of the angle of the wedges. An angle of 15°, for example, yields a ratio of 1 :4, i.e. a movement in longitudinal direction of 40 mm yields an adjustment in vertical direction of ±5 mm. At the embodiment where the wedges are mounted so that they from the basic position can move an equal distance in both directions in longitudinal direction, this implies that a movement of 20 mm in one direction yields a lowering of 5 mm, and an equally long movement in the opposite direction yields a raising of 5 mm. The wedges, however, can be mounted so that the basic position only renders possible raising alternatively lowering. The wedges can also be mounted so that more raising than lowering, or vice versa, is possible. Figure 3 illustrates a wedge pair in basic position, and Figure 4 shows the location of the wedges and longitudinal profile after a movement. In Figure 4 is shown how a movement in longitudinal direction causes a raising b of the longitudinal profile compared with the basic position in Figure 3.

The invention, of course, is not restricted to the embodiments shown, but can be varied within the scope of the claims.

Claims

1. A method for the continuous forming of a fiber mat for the manufacture of fiberboard, particle board or the like, comprising the discharge of fiber or particle material from a batching means and depositing the fiber material on the surface of a moving forming web (2) constituting the bottom of the forming installation, characterized in that the bottom of the forming installation is adjusted by raising or lowering the forming web in one or several positions in its entire length locally in cross direction, by means of longitudinal profiles (3) which are placed beneath the forming web substantially in its entire length and which can be raised and lowered independently of each other.

2. A device for the continuous forming of a fiber mat for the manufacture of fiberboard or the like, comprising the discharge of the fiber material from a batching means and depositing of the fiber material on the surface of a moving forming web constituting the bottom of the forming installation, in which beneath the continuous forming web in the direction of the web a plurality of longitudinal profiles (3) are placed in spaced relationship, and that these profiles are vertically adjustable independently of each other for adjusting the level of the forming web, characterized in that the profiles (3) are sunk in cross supporting beams (6) provided with recesses for the profiles, and that in each recess and on the lower side of the opposed profile a wedge is placed, where the wedges (4,5) have the same pitch and are mounted with the same angle, and that one or several of the longitudinal profiles are moved by adjustment means in longitudinal direction by sliding on the wedges, so that the web is raised or lowered locally in cross direction substantially in its entire length.

3. A device as defined in claim 2, characterized in that the movement takes place by mechanical adjustment means (7).

4. A device as defined in claim 2, characterized in that the movement takes place by electric adjustment means.

5. A device as defined in claim 4, characterized in that the electric adjustment means is connected to a continuous cross profile meter for automatically adjusting the cross profile.

6. A device as defined in claim 3 or 4, characterized in that at least one adjustment means is connected to one of the wedges mounted on the lower side of each profile.