Mineral wool is extensively used for insulation purposes and for this purpose the mineral wool is often offered for sale in the shape of mats or batts. The term mineral wool encompasses all types of man made vitreous fibers (MMVF) like rock wool, slag wool and glass wool.

The mineral wool mats are traditionally manufactured by pouring molten mineral material onto a spinning wheel rotating at high speed. The spinning wheel produces the fibres which are drawn into a spinning chamber by blowing and suction means and at the same time the fibres are applied with binder from spraying nozzles. The fibres are collected on a conveyor to form a mat with a desired thickness. The mat may be subjected to further treatment like compression or folding by passing a pendulum, before the binder on the fibres is cured in the curing oven. The different techniques for forming mats of mineral wool are well-known to persons skilled in the art.

GB No. 774,043 discloses a curing oven for mineral wool.

The mineral wool is passed between two endless conveying bands or belts of perforated sheets, and the mineral wool may be slightly compressed.

In US 4,028, 051 another type of curing oven is disclosed, by use of which it is possible to prepare mineral wool using a higher compression degree and thereby obtaining a

higher density. This oven comprises two endless conveying bands, where the conveying bands are composed of iron supports and plates linked and driven by chains. When the mineral wool passes through these conveying bands, the bands have sufficient strength to hold the material compressed during the curing. At the entrance to the curing zone the mineral material is compressed to a thickness which is substantially smaller than the distance between the conveying bands. This is a necessary step since the mineral wool cannot be fed in between the bands without being highly pre-compressed or it will be pressed and become frayed in between the plates of the conveying bands as the plates move along to the bending around the driving wheel.

In general it is not desired to compress the mats of mineral wool beyond a certain point as the fibres may be destroyed causing the material to loose compression strength. On the other hand if the mineral wool in the mats is not compressed sufficiently, there is a risk that the mineral wool may be caught in gaps in the conveyor, which may tear part of the mineral fibres up from the surface of the mat leaving fluffy tops in the surface. It is highly undesired to have out-pressed tops or fluffy material sticking out from the surface of the cured material. Cutting off such tops and out sticking fluffy material will undesirably increase the production-cost.

The object of the present invention is thus to provide a curing oven for mineral material as well as a set of slats for an endless conveyor for the curing oven and a method of curing a binder incorporated into the mineral material by use of the curing oven by which the above drawbacks can be avoided.

Another object of the invention is to provide a curing oven having a smooth surface with little or no. tendency to create protruding material in the cured mineral wool.

These and other objects are achieved by the invention as defined in the claims.

The invention relates to a set of slats for an endless conveyor comprising a plurality of perforated slats. Each of the slats preferably has a shape like a box with a rectangular cross section. The box has preferably a width of 100-300 mm, a lenght of 1000-4000 mm and a height of 30-250 mm. In a preferred embodiment the box has dimensions of 130 mm x 1900 mm x 50 mm. Preferably the slats have a stiffness which is sufficient to withstand the pressure from the compressed mineral wool.

Each of the slats comprises a contact surface, defined as the surface which is supposed to be in contact with the mineral material, when the set of slats is collected to an endless conveyor, and the mineral material is compressed between said conveyor and another corresponding conveyor. Looking at the slats in non- collected condition the contact surface of each slat is constituted by one substantially planar surface. The contact surface has an essentially rectangular cross section. The contact surface preferably has the dimensions of 100-200 mm x 1000-4000 mm. In a preferred embodiment the dimension is 150 mm x 1900 mm.

Each of the slats also comprises two opposing side edges, a front edge and a rear edge. The two opposing side edges of the slat are preferably parallel to each other.

In a preferred embodiment each slat of the set of slats is substantially equal to each other. The length of the front edges of each of the slats is preferably at least 2 times the length of the side edges, even more preferably the length of the front edges is at least 5 times the length of the side edges.

The slats are preferably made of a material selected from the group consisting of steel, stainless steel, iron, ceramics, plastic or any electrically isolating material.

The slats could also be made of a combination of the above-mentioned materials.

By using the set of slats for an endless conveyor it is possible to produce a conveyor for conveying mineral wool through a curing oven without having the above-described drawbacks. In other words the mineral wool has a highly decreased tendency to create protruding material in the surface of the cured mineral wool batts or mats, especially along the gap following the zig-zag line between the slats.

The front edges and the rear edges of the slats comprise a plurality of fingers. These fingers of the front edges of the slats are complementary to the fingers of the rear edges of the slats so that the front edge fingers of one lamella can be in mesh with the rear edge fingers of another lamella. The fingers in mesh serve as a support surface between neighbouring slats, which support surface forms a substantially continuous contact surface between the neighbouring slats.

Each finger comprises a fingertip. The fingertip is bent downwardly from the contact surface in a bending angle

defined as the angle between the tangent to the contact surface of the slat at the finger base and the tangent to the contact surface of the slat at the fingertip. The bending angle is at least 2 degrees, preferably at least 3 degrees.

In a preferred embodiment of the slats the fingers of the front edge and the rear edge have substantially equal shape and size. The fingers preferably have a length from finger base to finger tip between 3 and 40 mm, more preferably between 8 and 30 mm, and even more preferably around 25 mm.

By using a set of slats, wherein the length of the fingers is within the above-mentioned interval, the tendency of a conveyor produced from said slats to create protruding material or out-sticking fluffy material on the surface of the cured mineral wool mat is highly reduced. Consequently it is possible to obtain a cured mineral batt or mat with a substantially even surface so that detection of the traces of the gap between fingers on the wool surface can hardly take place.

In another preferred embodiment of the slats each of the fingers of the front edge and the rear edge is divided into a non-bending base section closest to the finger base and a bending tip section closest to the finger tip, wherein the tip section constitutes between 1/4 and 3/4 of the finger length. Thereby the surface of the final conveyor band collected from the slats may have optimal bending characteristics, and the front and rear edges of the slats appear to have rounded edges which do not damage the mineral wool. Moreover the mineral wool will not be trapped between the fingers.

The invention also relates to a curing oven comprising two or more endless curing conveyors for transporting mineral wool through a curing zone. The curing oven comprises at least one feeding conveyor for feeding the mineral wool to the curing zone, and the two or more curing conveyors comprise a plurality of perforated slats. Each of the slats comprises a contact surface, which contact surface is essentially rectangular. The slats further comprise two opposing side edges and furthermore a front edge and a rear edge. The front edges and the rear edges of the slats comprise a plurality of fingers. Each finger comprises a finger tip, which finger tip is bent downwardly from the contact surface of the slats. The slats are linked to each other via two or more connecting means so that the contact surfaces of the slats constitute the contact surface of the conveyor. The conveyor is driven by at least one driving means preferably placed at the exit of the curing zone. When the conveyor is moved by the driving means, the fingers of the front edges of one slat are complementary to the fingers of the rear edges of the slat in front of the one slat, and the bending of the fingers is sufficient to allow the fingers to form a plane or bend downwardly from the surface of the conveyor in such a way that the mineral wool is not being trapped between the fingers of the slats, when said mineral wool gets in contact with said conveyor. The mineral wool is not trapped when the conveyor moves through the curing oven and in particular the mineral wool is not trapped when the slats move around the driving means. Consequently undesired protruding fibre material from the surface of the mineral wool is avoided.

The typical conveyor band of a conventional curing oven normally consists of a number of rigid slats which unfortunately produces protruding marks or ridges in the surfaces of the mineral wool. However, it has surprisingly been found that with the curing oven comprising one or more endless feeding conveyors according to the invention the drawback of producing protruding marks or ridges in the surfaces of the mineral wool is avoided.

In a preferred embodiment of the curing oven according to the invention the mineral wool gets in contact with the curing conveyor at a position where curvature-radius of the conveyor trajectory is at least 250 mm. In this embodiment the best properties with regard to compression are achieved.

Preferably the two or more endless curing conveyors comprise a plurality of perforated slats as described above.

In a preferred embodiment of the curing oven the slats are linked to each other via one or more connecting means, and the connecting means preferably are one or more chains.

Preferably the curing oven comprises two curing conveyors placed opposite to each other and with their contact surfaces facing each other. The contact surfaces are preferably parallel and with a distance between them, which create space for the mineral wool to be cured in the curing oven. The two conveyors are driven by rotating driving means which rotate in the opposite direction of the rotation in order to transport the mineral wool

through the curing zone. The driving means are preferably driving chain wheels and chains. The conveyors move with approximately the same speed to avoid introducing unwanted tensions into the mineral wool. The conveyors comprise slats which are substantially equal to each other.

The invention also relates to a method of curing a binder in a mineral wool material by using a curing oven as previously described, which method comprises the steps of: i) compressing the mineral wool in a feeding zone composed of an upper and a lower compression surface, wherein at least one of the compression surfaces is constituted by the feeding conveyor; ii) transporting the mineral wool to the curing zone under compression; iii) treating the mineral wool in the curing zone with heat by blowing hot air through the perforated slats and the material, said slats comprising a plurality of fingers; iv) transporting the mineral wool with cured binder out of the curing station.

In a preferred embodiment of the method according to the invention the mineral wool is transported on a feeding conveyor into the entrance between the curing conveyors, wherein the mineral wool is brought into contact with the upper and lower curing conveyor. The mineral wool is then compressed between the upper and lower curing conveyor and the thickness and the density of the mineral wool batt or mat are hereby determined. The mineral wool is

not trapped between the fingers of the slats during the process.

The term a binder as used herein comprises any material which is suited as a binder or binding agent in mineral fibre materials for the above products. Preferably the binder is a heat curing binder.

The invention will now be illustrated with some preferred embodiments according to the invention with reference to a drawing in which Figure 1 and 2 illustrates a slat according to the invention.

Figure 3 illustrates a feeding conveyor comprising a plurality of perforated slats according to the invention.

Figure 4 illustrates a slat according to the invention.

In figure 1 is seen a cross section of a slat according to the invention in the direction front edge to rear edge and from the bottom. The slat 1 comprises a number of perforations 2 which will allow hot air to pass through the slat and into the mineral wool to be cured.

Furthermore the slat 1 comprises a number of fingers 3 on the front edge and a number of fingers 4 on the rear edge. The fingers 3 and 4 are arranged to be in mesh with fingers from neighbouring slats as indicated on the figure, where the fingers 4 on the rear edge of the slat 1 are in mesh with the fingers 5 on the front edge of the neighbouring slat.

In figure 2 a slat according to the invention is seen in the direction of side edge to side edge. The slat 6 comprises fingers 7 at the front edge and fingers 8 at the rear edge. The downward bending of the fingers 7 and 8 are seen at the points 9 and 10.

Figure 3 shows the principle when a set of slats is connected to form a conveyor, which is moved around a curve 13. The slats 11 form an endless conveyor 12, which is forced to move around a curve 13 by means of a driving roller chain 14 and a roller 15 as indicated on the figure. The slats 11 are connected to the driving roller chain 14 via girders 16. During the movement around the curve 13 the fingers 17 on the front edge and the fingers 18 on the rear edge on neighbouring slats are not in mesh with each other. During the movement after the curve 13 the fingers 17 on the front edge and the fingers 18 on the rear edge on neighbouring slats are in mesh with each other. The fingers 17 and 18 are bending downwardly towards the driving roller chain 15 in such a way that the fingers do not protrude above the planes defined by the contact surfaces 19 of the slats 11.

Figure 4 a and b shows an embodiment of the invention in more details. Figure 4a shows a conveyor 20 with slats 21 according to the invention. During the bending of the conveyor 20 the fingers 22 and 23 are in mesh with each other and do not protrude from the surface 24 of the conveyor. Figure 4b shows the conveyor 20 in a linear movement where the slats 21 are in line relationship. The fingers 22 and 23 are pointing away from the surface 24 which is in contact with the mineral wool. The surface 24 is substantially uniform and planar.

Figure 4c shows an embodiment according to the prior art.

The conveyor 25 is constituted by a number of slats 26.

When the conveyor 25 is in a bending mode, the end pieces 27 and 28 will protrude and from the surface 26 and may cause damage to mineral wool in contact with the surface 26.