WO2015091942A2

WO2015091942A2 - Method and apparatus for scattering fibers, such as chips

Info

Publication number: WO2015091942A2
Application number: PCT/EP2014/078727
Authority: WO
Inventors: Reijo KÄRPPÄ
Original assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Current assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Priority date: 2013-12-20
Filing date: 2014-12-19
Publication date: 2015-06-25
Anticipated expiration: 2016-06-20
Also published as: FI125435B; WO2015091942A3; CN204549325U

Abstract

Method for scattering fibers, such as chips, in surface chip scattering, in which method chips are scattered to form a chip mat (9) on a moving belt conveyor (10) or corresponding, in which method two sets of scattering rollers (1, 2) are used for the scattering, both sets being formed of rollers arranged side by side and being essentially one above the other and being arranged above the belt conveyor (10). The invention is implemented in such a way that a gas flow (5) is arranged between the roller sets (1, 2), the direction of which gas flow is opposite with respect to the direction of travel of the rollers of the roller sets, and that a gas flow (12) in the same direction as the gas flow between the roller sets (1, 2) is arranged, if necessary, to below the lower roller set (2). The object of the invention is also an apparatus for implementing the method.

Description

METHOD AND APPARATUS FOR SCATTERING FIBERS, SUCH AS CHIPS

The object of the present invention is a method for scattering fibers, such as chips, in surface chip scattering, in which method chips are scattered to form a chip mat on a moving belt conveyor or corresponding, in which method two sets of scattering rollers are used for the scattering, both sets being formed of rollers arranged side by side and being essentially one above the other and being arranged above the belt conveyor. The object of the invention is also an apparatus for implementing the method.

The purpose of scattering is to bring about the desired type of chip mat before pressing it into chipboard. The aim in a chip mat is e.g. to get the finer fraction onto the surface and the coarser fraction into the middle.

Mechanical roller scattering, in which there is one scattering roller set and with which good scattering accuracy can be achieved, i.e. little variation in the square meter weight of the scattered chip mat, is known in the art from e.g. FI patent 90746.

FI patent application 20060437 and FI patent 122575 are, for their part, known to use a gas flow for improving the fractionating of chips in roller scattering, in which one scattering roller set is in use.

In addition, known from FI patents 97112 and 117129 as well as DE patent application 19513306 are various methods to apply two roller sets one above the other to roller scattering.

The thin surfacing papers of chipboard that are used nowadays require greater and greater density of the ground surface of the chipboard, i.e. the surface must be formed from a fine and fibrous chip fraction. In addition, the surface must be free of large chip particles of over 0.5 mm.

Known in the art therefore are apparatuses based both on wind scattering and on roller scattering. There are no serious problems in a wind scatterer when the scatterer is in good condition in all respects, but the difficult adjustability of a wind scatterer causes problems, resulting in surface quality problems and production losses. In addition, a wind scatterer easily becomes dirty, which causes many cleaning standstills and more production losses. A wind scatterer also has a rather high energy requirement and they are large in size.

A problem with a roller scatterer is obtaining by means of a roller set and chamber wind a sufficient fine and fibrous fraction for the grinding layer. On high-capacity lines the conveying of a fibrous fraction to the grinding layer is impossible, because the roller scatterer conveys almost all the fiber to the downstream end, from where it is impossible to get it by means of wind to the start end through the thick multiple chip curtain. In addition, overlarge (over 0.5 mm) chip particles escape through the roll gaps of the start end and these chips are visible on the surface of the board after grinding.

The aim of the present invention is to achieve a method that can achieve high scattering accuracy, as a result of the leveling effect of the roller set, the relatively low suction air speed, and the relatively shallow drop height below the roller set, and that can simultaneously also achieve an advantageous chip fractionating result requiring a tall scattering chamber and relatively high speed of the gas flow. The method according to the invention is characterized in that a gas flow is arranged between the roller sets, the direction of which gas flow is opposite with respect to the direction of travel of the rollers of the roller sets, and in that a gas flow in the same direction as the gas flow between the roller sets is arranged, if necessary, to below the lower roller set.

One preferred embodiment of the method according to the invention is characterized in that the speeds of the gas flows are arranged adjustably.

Another preferred embodiment of the method according to the invention is characterized in that the speed of the gas flow between the lower roller set and the belt conveyor is adjusted to be smaller than the speed of the gas flow between the roller sets, or the flow in question is prevented altogether.

Yet another preferred embodiment of the method according to the invention is characterized in that for improving scattering accuracy a means evening out input turbulence is arranged in the input aperture of the chamber for evening out the gas flow of the chamber between the roller sets.

Additionally the purpose of the invention is to achieve an apparatus for implementing the method, which apparatus is characterized in that a gas flow is arranged into the chamber between the upper and lower roller set, the direction of which gas flow is opposite with respect to the direction of travel of the rollers of the roller sets, and in that a gas flow is arranged, if necessary, to between the lower roller set and the belt conveyor, which gas flow is in the same direction as the gas flow arranged to between the roller sets.

One preferred embodiment of the apparatus according to the invention is characterized in that a means evening out turbulence of the gas flow is arranged in the input aperture of the chamber between the upper and lower roller set.

Another preferred embodiment of the apparatus according to the invention is characterized in that plate-type elements preventing turbulence of the gas flow are arranged in the chamber between the upper and lower roller set.

Yet another preferred embodiment of the apparatus according to the invention is characterized in that the speed of the gas flow that is between the lower roller set and the belt conveyor is adjusted to be smaller than the speed of the gas flow that is between the upper and lower roller set, or the flow in question is prevented altogether.

With the method and apparatus based on mechanical roller scattering according to the invention, therefore, it is possible to implement fractionating scattering and also, owing to the shallow drop height as well as the low speed of the gas flow to be used in the shallow drop chamber in question, high scattering accuracy. In the invention the good properties of wind scattering and of roller scattering are combined. By means of the invention sufficient fine and fibrous chips are obtained for the grinding layer. The adjustments needed for optimizing scattering accuracy in the invention are easy to implement and on the whole there is little need for adjustment. In the apparatus according to the invention also dirt accretion hampering operation does not occur.

The invention is also well suited to those types of special cases in which an advantageous surface layer fractionated by means of a gas flow is required, but in which a large gas flow being directed onto the surface to be scattered causes an error, e.g. dust stripes in the top surface scattering. This type of case is presented in patent publication US8398905, in which the top surface layer is scattered onto a chip layer in which there are longitudinal or lateral strands for obtaining the desired differences in density in the final product. It is necessary, therefore, to scatter the chips of the top surface onto the peaks of the strands, onto the slopes of the strands or into the valleys between them. If this type of top surface scattering is performed with a form of scattering based on an active gas flow, such as with wind scattering, the result is that chips and dust are fractionated as they descend obliquely from above in different ways, depending on whether the chips meet a peak of the strands, a slope of the strands or a valley between strands (the chips fly farther in the valleys than at the point of the strands). The strands also cause uneven turbulence in the relatively strong gas flow. All this is visible as detrimental stripes and errors on the surface of the final product.

In the scattering according to the invention chips that are already fractionated drop from the gaps between the rollers of the lower roller set essentially perpendicularly onto the surface to be scattered, because the drop height and the speed of the gas flow can be minimized. Consequently, a similar even scattering result is obtained regardless of whether the chips drop onto the peaks of the aforementioned strands, onto the slopes of the strands or into the valleys between them.

In the following, the invention will be described in more detail by the aid of some preferred embodiments with reference to the attached drawings, wherein

Fig. 1 presents an apparatus according to the invention for scattering chips.

Fig. 2 presents an apparatus according to one preferred embodiment of the invention for scattering chips.

Fig. 3 presents an apparatus, according to another preferred embodiment of the invention, for scattering chips.

Fig. 4 presents an apparatus, according to yet another preferred embodiment, for scattering chips.

Fig. 1 thus presents a chip scattering apparatus according to the invention. The chips to be scattered are fed from a scattering bunker 3, in a manner that is per se known in the art, to a first, i.e. an upper, roller set 1, which is formed from rollers that are side by side, and from where the chips drop into a relatively tall fractionating chamber 4, in which they are sorted effectively by means of a gas flow 5. The speed of the gas flow can, if necessary, be adjusted.

In the gas flow the finer, light, dusty and thinnest fibrous portions 6 fly farthest to improve the surface quality of the final product, whereas the heavier and coarser, typically grainy fractions 7 displace only a little or not at all and remain inside the final product below the fine surface. The chips fractionated in the manner described above fall for the most part onto the rollers of the actual lower scattering roller set 2 arranged below the chamber 4, said roller set evening out and further enhancing the fractionating. From the roll gaps between these rollers the chips drop preferably via a chamber 8 arranged to be as shallow as possible to become a chip mat 9 on the scattering belt conveyor 10.

A gas flow 12 is also arranged, if necessary, into the shallow chamber 8. To prevent turbulence impairing the scattering accuracy this gas flow 12 of the shallow chamber 8 can, if necessary, be adjusted so as to be sufficiently low and free of turbulence or it can be prevented completely e.g. by means of a flap 13. Overlarge particles unsuited to the final product go over the roller set 2 and they are removed from the process in a manner known in the art on a transverse conveyor 11.

The roller clearances and rotation speeds of the rollers of the roller sets 1 and 2 can, if necessary, be adjusted and the depths of the surface patterning of the rollers can be varied with methods known in the art for achieving the desired end result.

In Fig. 2, for improving the scattering accuracy, a means 14 evening out input turbulence of the gas flow 5 is added to the input aperture of the chamber 4, to which means, if necessary, a fan 15 can also be connected for compensating pressure loss occurring in the leveling means. The air volume produced by the fans 15 can, if necessary, be adjusted e.g. by changing the speed of rotation of the fans. The means 14 leveling the flow can be e.g. a perforated plate. Its purpose is to make the flow as even as possible throughout its whole cross-section.

In Fig. 3, for further improving the scattering accuracy, plate-like elements 16 preventing turbulence of the gas flow 5 (as known from patent publication FI-122575) are also added to the chamber 4.

Fig. 4 presents a scattering station for a chip mat, in which scattering station the lower surface layer 17 and the upper surface layer 18 are scattered with the method and

apparatuses

21 and 22 according to the invention. Generally also a middle layer 19 is scattered, with either one or more middle chip scattering machines 20, between these layers. For further improving scattering accuracy there is, when producing chip mats of different thicknesses, at least a scattering device 22 of the top surface layer, said device arranged to be movable in the vertical direction with a lifting system 24, with which the free drop height at any given time of the chamber 8 that is under the lower roller set 2 can be optimized/minimized.

The gas flows 5 and 12 are brought about by means of suction arranged via the pipe 25.

It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, but that it can be varied within the scope of the claims presented below.

The characteristic features possibly presented in the description in conjunction with other characteristic features can also, if necessary, be used separately to each other.

Claims

Method for scattering fibers, such as chips, in surface chip scattering, in which method chips are scattered to form a chip mat (9) on a moving belt conveyor (10) or corresponding, in which method two sets of scattering rollers (1, 2) are used for the scattering, both sets being formed of rollers arranged side by side and being essentially one above the other and being arranged above the belt conveyor (10), characterized in that a gas flow (5) is arranged between the roller sets (1, 2), the direction of which gas flow is opposite with respect to the direction of travel of the rollers of the roller sets, and in that a gas flow (12) in the same direction as the gas flow between the roller sets (1, 2) is arranged, if necessary, to below the lower roller set (2).
Method according to claim 1, characterized in that the speeds of the gas flows (5, 12) are arranged adjustably.
Method according to claim 2, characterized in that the speed of the gas flow (12) between the lower roller set (2) and the belt conveyor (10) is adjusted to be smaller than the speed of the gas flow (5) between the roller sets (1, 2), or the flow (12) in question is prevented altogether.
Method according to any of claims 1-3, characterized in that for improving scattering accuracy a means (14) evening out input turbulence is arranged in the input aperture of the chamber for evening out the gas flow (5) of the chamber (4) between the roller sets (1, 2).
Apparatus for scattering fibers, such as chips, in surface chip scattering, which apparatus comprises a scattering bunker (3), an upper scattering roller set (1) arranged below it, which scattering roller set is formed from rollers side by side, arranged below it also a lower scattering roller set (2), which is formed from rollers side by side, and also a belt conveyor (10) arranged to be lowermost, on which belt conveyor a chip mat (9) forms, characterized in that a gas flow (5) is arranged into the chamber (4) between the upper and lower roller set (1, 2), the direction of which gas flow is opposite with respect to the direction of travel of the rollers of the roller sets, and in that a gas flow (12) is arranged to between the lower roller set (2) and the belt conveyor (10), which gas flow is in the same direction as the gas flow (12) arranged between the roller sets (1, 2).
Apparatus according to claim 5, characterized in that a means (14) evening out turbulence of the gas flow is arranged in the input aperture of the chamber (4) between the upper and lower roller set (1, 2).
Apparatus according to claim 5 or 6, characterized in that plate-type elements (16) preventing turbulence of the gas flow are arranged in the chamber (4) between the upper and lower roller set (1, 2).
Apparatus according to any of claims 5-7, characterized in that the speed of the gas flow (12) that is between the lower roller set (2) and the belt conveyor (10) is adjusted to be smaller than the speed of the gas flow (5) that is between the upper and lower roller set (1, 2), or the flow (12) in question is prevented altogether.
Apparatus according to any of claims 5-8, characterized in that the chamber (8) between the lower roller set (2) and the belt conveyor (10) is shallower than the chamber (4) between the upper and lower roller sets (1, 2).