EP0498276B1 - Process and apparatus for manufacturing mineral fiber boards and manufactured mineral fiber boards - Google Patents

Abstract

In the process for manufacturing mineral fibreboards, in which mineral fibres wetted with a binder are deposited on a conveyor device to form a mineral-fibre layer, in order to feed them to a continuous-flow oven, during conveyance the mineral-fibre layer is precompressed in thickness in front of the continuous-flow oven and subsequently is folded in length as a result of alternate bulging, the mineral fibres of the mineral-fibre layer are felted, and then the mineral-fibre layer is so compressed in thickness that, after hardening, it has a virtually plane surface, the mineral-fibre layer is felted in a controlled manner in particular regions, in that, when a force which can be applied to the mineral fibres is exerted, the vertical component of the force is maximised in the region to be felted. <IMAGE>

Description

The invention relates to a method for producing mineral fiber boards, in which mineral fibers wetted with a binder are deposited on a conveyor to form a mineral fiber layer in order to feed them to a continuous furnace, in which the mineral fiber layer in the ceiling is also pre-compressed during the conveying in front of the continuous furnace and then is folded in length by mutual bulging, the mineral fibers of the mineral fiber layer are matted and then the mineral fiber layer is compressed in such a way that it has a practically flat surface after curing. The invention further relates to a device which is suitable for performing the method. Finally, it refers to relevant mineral fiber boards.

A large number of measures have been proposed in order to increase the strength of mineral fiber boards, and possibly also their rigidity.

From CH-C-620 861 a method for producing mineral fiber boards is known, in which the mineral fiber boards are pre-compressed and folded. It is thereby achieved that many fibers of the layer come to lie at an angle to the main plate surface, this orientation being maintained if the mineral fiber layer is still compressed in its thickness in such a way that, after a binder has hardened, it becomes a substantially flat surface having. This increases the compressive strength and tensile strength of the finished panel across the panel plane.

A comparable method is also known from DE-A-38 32 773, the longitudinal compression being carried out by bulging the mineral fiber layer in several stages arranged one behind the other until it enters the continuous furnace. This prevents the bulging from being carried out relatively abruptly in the inlet area of the continuous furnace after the mineral fiber layer has been pre-compressed. With this improvement, the method known from CH-C-620 861 can be used for a large number of different types of mineral fibers.

Although good values for the compressive strength and the tensile strength have been obtained with such a fold structure, it has the disadvantage that it tends to unfold, so that both the tensile strength in the longitudinal direction and the bending strength are only low.

According to the proposal of EP-A-0 133 083, these disadvantages are to be overcome by letting the fibers in the inner region of the plate assume as many different directions as possible without the general orientation of the fibers in the longitudinal direction of the plate being markedly changed. Apart from the fact that this process requires considerable effort in its implementation, the end product largely lacks the properties which characterize a mineral fiber plate with a folded structure.

A method of the type mentioned at the beginning and a device for carrying out the method are finally known from DE-A-16 35 620. The fiber layer is then felted over its entire thickness in order to fix the bulges.

It is often necessary to be able to produce mineral fiber boards with very specific strength properties specified by the customer, which requires a precisely defined density profile of the mineral fiber board, in particular perpendicular to the board plane. Such a density profile cannot be generated by the known methods or with known devices.

It is therefore the technical problem on which the invention is based to provide a method with which a mineral fiber board with a predeterminable density profile can be produced, at the same time ensuring that, in particular, the bending strength of the finished mineral fiber board is at least maintained compared to known longitudinally compressed products with continuous matting.

This problem is solved by a method of the type mentioned at the outset with the features of the characterizing part of patent claim 1.

Another object is to develop a device for carrying out the method according to the invention. This is the subject of claim 1. Advantageous refinements of the method and the device are the subject of the respective dependent claims.

Finally, the invention provides a mineral fiber board made by the disclosed method.

According to the method according to the invention, the mineral fiber layer is deliberately matted in certain areas by maximizing the vertical component of the force in the region to be matted when a force can be exerted on the mineral fibers from the outside. Depending on the extent to which the maximum value for the vertical component of the applied force is reached, the mineral fibers are aligned in this area, which means that the mineral fibers are entangled with one another. On the one hand, as already known, the matted areas prevent the longitudinally compressed structure from unfolding, so that the bending strength of known mineral fiber plates can be maintained and the tensile strength in the longitudinal direction does not suffer any losses.

It is also possible to generate any desired density profile in these by specifying the corresponding areas. With continuous or step-by-step or step-by-step density transitions, this enables the best possible adjustments to be made to product specifications in terms of strength can be achieved. In the matted areas, bulk densities in the order of 80 to 220 kg / m³ can be achieved, while in the non-matted areas of the mineral fiber board there is a bulk density in the range of 30 to 150 kg / m³.

Maximizing the vertical component of the force can be achieved, for example, by inserting at least one needle or pin into the mineral fiber layer, the relative speed between the needle or pin and the mineral fibers being minimized in the area to be matted. In this case, the force transmission between the needle or pin and the mineral fibers, supported by the adhesive forces of the binder, is particularly great.

A device for producing mineral fiber boards, in particular for carrying out the method according to claim 1 or claim 2, a conveyor for conveying a mineral fiber layer and a pre-press for thickness pre-compression of the mineral fiber layer, a device for longitudinally compressing the mineral fiber layer by mutual bulging, one downstream of the device for longitudinal compression Felting device and a continuous furnace further comprises a transfer belt device, the felting device being arranged directly upstream of the transfer belt device and the continuous furnace being immediately downstream of the transfer belt device.

Furthermore, a device is provided for the felting device which maximizes the vertical component of the force transmitted from the felting device to the mineral fibers of the mineral fiber layer.

The device for the vertical component can be realized, for example, by means of a needle board machine with oscillating needles, which thus immerse to different depths in the areas of the mineral fiber layer to be matted in accordance with this oscillating movement, the speed of movement of the needles essentially being a sine function with minimal speed at the reversal points follows the oscillating movement.

It is particularly preferred if the needles are provided at least in sections with at least one beard projecting from the peripheral surface of the needle or, alternatively or in combination with it, at least one notch receding from the peripheral surface. In general, a plurality of such beards or notches will be provided, which are spaced apart from one another in the longitudinal direction of the needle. These beards or the projections which are formed between adjacent notches take the fibers with them when the needle board is moved, so that the desired power transmission can take place in a particularly simple manner. This measure has an advantageous effect in combination with the "sinusoidal" movement of the needles themselves.

Needles of different lengths can also be provided, which in turn are provided with beards or notches. It is thus achieved that in certain areas only the longer needles arranged further apart act, in others the entirety of the now closely adjacent needles, which causes a different degree of matting.

It is also possible not to provide the needles with beards or notches over their entire length, but rather, for example, only in the region of their lower end section.

The needle board machine can be designed to act only on one side of the mineral fiber layer. For most applications, however, it will be expedient if the needle board machine has two needle boards arranged opposite one another, which are each provided with a plurality of needles on the side facing the mineral fiber layer.

The device for the vertical component of the force can also be formed by at least one rotating metal brush, the rotational speed of which can be selected. Here the brush pens look similar to the beards on the needles of the needle boards. In this embodiment, the device is preferably used when it is intended to act on surface areas of the mineral fiber layer, the pin length or needle length of the brushes essentially corresponding to the layer thickness of the surface area of the mineral fiber layer to be matted and the closest distance of the rollers approximately to the thickness of the mineral fiber plate to be produced . Here, too, the choice of device parameters can determine the extent to which matting is to take place, it being readily possible to adapt to the desired layer thickness of the end product.

For surface treatment, it has also proven to be particularly advantageous if the felting device comprises both at least one brush roller and a needle board machine. The brush would have advantages in the continuous processing of the mineral fibers, but the needle intensity is too low here, so that repeated passes through the plates or a large number of brushes would be necessary for good results. To avoid this In addition, needle board machines are used that provide better needling, although the more complex drive means that more equipment is required.

Fig. 1

eine Vorrichtung zum Herstellen von Mineralfaserplatten, insbesondere zum Durchführen des erfindungsgemäßen Verfahrens, bei der als Verfilzungseinrichtung ein Paar Metallbürsten eingesetzt ist,

Fig. 2

eine weitere Ausführungsform der Vorrichtung zum Durchführen des erfindungsgemäßen Verfahrens, bei der in der Endstufe sowohl ein Paar Metallbürsten als auch eine Nadelbrettmaschine eingesetzt ist,

Fig. 3

eine schematische Darstellung eines ersten Ausführungsbeispieles für eine Nadelbrettmaschine,

Fig. 4

eine schematische Darstellung eines zweiten Ausführungsbeispieles für eine Nadelbrettmaschine,

Fig. 5

eine schematische Darstellung einer dritten Ausführungsform für eine Nadelbrettmaschine, und

Fig. 6

jeweils eine schematische Querschnittsansicht von Mineralfaserplatten, die nach dem erfindungsgemäßen Verfahren hergestellt sind.

The invention will be explained in more detail below by way of example with reference to the accompanying drawings. It shows:

Fig. 1

a device for producing mineral fiber boards, in particular for carrying out the method according to the invention, in which a pair of metal brushes is used as the felting device,

Fig. 2

a further embodiment of the device for carrying out the method according to the invention, in which both a pair of metal brushes and a needle board machine are used in the final stage,

Fig. 3

1 shows a schematic illustration of a first exemplary embodiment of a needle board machine,

Fig. 4

1 shows a schematic illustration of a second exemplary embodiment of a needle board machine,

Fig. 5

a schematic representation of a third embodiment for a needle board machine, and

Fig. 6

each a schematic cross-sectional view of mineral fiber boards, which are produced by the inventive method.

1 shows a device 1 for producing mineral fiber boards, in which mineral fibers are fed to a pre-press 4 via a conveyor device 2 are, in which the mineral fibers are assembled and compressed into a mineral fiber layer 3. The pre-press 4 consists of two rollers 26 and 27 driven in opposite directions with a diameter which is larger than that of the compression rollers used in a device 5 for longitudinal compression.

The mineral fiber layer 3 emerging from the pre-press 4 is fed to this device 5 for longitudinal compression, compression elements being provided, for example the aforementioned rollers or conveyor belts, which are operated in the direction of a continuous furnace 7 with decreasing peripheral speed. This results in a gradual bulging of the mineral fiber layer, which leads to a folding of the layer, the folds being formed essentially transversely to the direction of transport of the mineral fiber layer 3.

Downstream of the device 5 for longitudinal compression is a felting device 8, which consists of two opposing rotating metal brushes 28, 29. These metal brushes 28, 29 extend as rollers over the entire width of the mineral fiber layer 3. A large number of pins or needles are attached to the roller surfaces, the pin length or needle length being essentially the same as the layer thickness of the surface area of the mineral fiber layer 3 to be matted. The closest distance between the outer surfaces of the rollers corresponds approximately to the thickness of the mineral fiber board to be produced. The pins or needles tear fibers preferentially from the bulges of the mineral fiber layer and matt the fibers of neighboring bulges. This not only ensures that the bulges are connected to one another, but at the same time creates a pre-smoothed surface of the mineral fiber layer.

With the aid of a transfer belt 6, which is connected downstream of the felting device 8, the surface of the mineral fiber layer 3 is smoothed further and this mineral fiber layer is fed to the continuous furnace 7.

To carry out the method according to the invention with this device, mineral fibers wetted with a binder are deposited on the conveyor 2. These fibers are fed to the pre-press 4, where they are aligned essentially in the conveying direction. A mineral fiber layer 3 is formed, the thickness of which is determined by the mutual spacing of the rollers 26, 27 of the pre-press 4. The now pre-compressed mineral fiber layer 3 is fed to a device 5 for longitudinal compression, by means of which the mineral fiber layer 3 is folded. In the subsequent felting device 8, the surface areas of the mineral fiber layer are torn open at a preselected depth, so that adjacent bulges of the mineral fiber layer are connected to one another by fibers that are largely isotropically oriented in this area. The surface areas homogenized in this way, namely the top and bottom of the mineral fiber layer, are smoothed on the surface by a transfer belt device 6 from two opposing conveyor belts 24, 25 and fed to the continuous furnace 7 by hardening the mineral fiber layer now prepared according to the invention into a solid plate.

A further embodiment of the present invention is shown in FIG. 2. The device shown in this figure differs from that of FIG. 1 in the configuration of the felting device, while the others Device elements with which the device shown in Fig. 1 are structurally identical and functionally the same. The folded mineral fiber layer, which was formed during the passage through the device for longitudinal compression, is now fed to a felting device 8, which consists of two needle boards 30, 31 lying opposite one another, which are lifted off or lowered onto the mineral fiber layer 3 with the aid of a suitable drive can. These needle boards 30, 31 have, on their side facing the mineral fiber layer 3, an arrangement of needles by means of which, depending on their configuration, a density distribution determined by the respective degree of matting can also be formed inside the mineral fiber layer.

3 shows a schematic representation of a first embodiment of a needle board 30 with a plurality of needles 32 directed towards the mineral fiber layer 3, of which only four are shown here. The lifting movement of the needle board 30 is indicated by the representation of four positions. Each needle 32 is provided with beards 33 projecting from the circumferential surface of the needle, which in the example shown here are arranged at an approximately constant distance from one another on the needle. The needle board 30 is operated in such a way that the vertical needle speed essentially follows a sine function which is superimposed on an oscillating change in immersion depth. The maximum stroke of the needle board 30 can be, for example, 60 mm. The upper reversal point of the lifting movement is placed so that the needle board 30 is extended from the mineral fiber layer 3, while it is fully or only half immersed in the respective mineral reversal points 3, so that either the entirety of the whiskers 33 acts or only approximately the Half of the whiskers 33 in the lower area of the needles 32. The sinusoidal speed curve when the needles 32 are immersed and retracted means that fibers are only carried along by the whiskers 33 in certain areas. Due to the high vertical speed in the central area, the beards 33 cannot take any fibers with them because of the overcompensated adhesive forces there. When approaching the lower reversal points, however, the needle speed is reduced to zero, so that the beards pick up 33 fibers and redirect the vertical direction. In the arrangement of the beards 33 and needles 32 chosen in FIG. 3 and an oscillating immersion depth change, for example between a first depth at the boundary between a central area B and a surface-distant C and a second depth at the boundary between a surface-near region A and the Area B in combination with the sinusoidal course of motion of the needles 32 becomes the area A close to the surface, the adjoining area B becomes less matted, for example only half as much as the area A. achieve a multiple gradation of the degree of matting.

In order to develop the step-like effect of the felting in a different, particularly simple manner, an arrangement of the needles 32 with beards 33 according to FIG. 4 can be selected. About half of the total number of needles 32, 34 is shortened, so that their effect on region A near the surface of the mineral fiber layer 3 is limited. The other half of the needles 34 acts both in the area A and in the adjoining area B. The area A is again heavily matted, the Area B matted to a lesser extent, whereby a clear gradation is achieved here. When using several different needle lengths, a multiple gradation of the degree of matting can also be achieved here.

5 shows a third exemplary embodiment of a needle board, in which the needle board 30 carries a plurality of needles 35, which are each provided with beards 33 only in their lower end section. The needles 35 or beards 33 act, again in combination with the sinusoidal movement speed, only in an area B lying away from the surface, while the area A close to the surface remains practically completely unaffected. As explained above, in area A the speed of the needles 35 is too high for fibers to be taken along.

Depending on the application, only a needle board 30, needle boards on both sides of the mineral fiber layer 3, as shown in FIG. 2, or a combination of differently designed needle boards, optionally in combination with metal brushes 28, 29, as also shown in FIG. 2, will be selected .

In this case, the needle boards 30, 31, as can be seen in FIG. 2, are expediently followed by two opposing rotating metal brushes 28, 29 which correspond to those as have already been described in connection with FIG. 1. This felting device consisting of needle boards 30, 31 and metal brushes 28, 29 is in turn followed by a transfer belt device 6, which consists of two conveyor belts 24, 25 lying opposite one another and which smoothes the surfaces of the mineral fiber layer 3.

6 a shows a section of a mineral fiber plate 3 produced by the method according to the invention, in which the surface areas 36, 37 are treated. In the middle region 38 the fold structure created by the longitudinal compression is preserved, while in the surface regions 36, 37 this orientation of the fibers is raised, so that an essentially homogeneous, isotropic fiber layer has formed there. FIG. 6 (b) shows a section of a mineral fiber plate which has been produced using the needle board according to FIG. 5. Here, the central area 39 is homogenized, while the areas near the surface show their uninfluenced fold structure.

For all forms of application it has proven to be advantageous to have the stroke frequency of the needle board, i.e. the frequency for the sine function to choose from the range of 5 to 25 Hz.

Claims (13)

1. A method for producing a sheet of mineral fibers, wherein

   - mineral fibers wetted with a binder are disposed on a conveyor (2) for forming a layer of mineral fibers (3), to feed them into a through-type furnace,

   - the layer of mineral fibers (3) is pre-compressed in its thickness and then folded in its length by bulging in alternate directions, during conveyance outside of the through-type furnace,

   - the mineral fibers of the layer of mineral fibers (3) are felted, and

   - the layer of mineral fibers (3) is then compressed so that it has a practically smooth surface after hardening,

   characterized in that

   - the layer of mineral fibers (3) is felted in specific areas by maximizing, with a force being chargeable onto the mineral fibers by at least a needle or a pin, the force component orthogonal to the plane of the layer of mineral fibers.
2. A method according to claim 1, characterized in that

   - the vertical component of the force is maximized by inserting at least a needle (32, 34, 35) or a pin into the layer of mineral fibers (3), minimizing, in the area to be felted, the relative velocity between needle or pin and the mineral fibers.
3. A device for producing sheets of mineral fibers, having

   - a conveyor (2) for conveying a layer of mineral fibers (3),

   - a prepress (4) for pre-compressing in thickness of the layer of mineral fibers (3),

   - a device (5) for compressing in length the layer of mineral fibers (3) by bulging in alternate directions

   - a felting device (8) downstream of the device (5) for compressing in length, and

   - a through-type furnace (7),

   characterized in that

   - it has a transfer conveyor (6), the felting device (8) being disposed directly in front of the transfer conveyor (6) and the through-type furnace (7) being disposed directly behind the transfer conveyor, and

   - the felting device (8) comprises a device having at least a needle or a pin (32, 34, 35), which maximizes the component of the force transmitted vertically to the mineral fibers of the layer of mineral fibers (3) by the felting device (8).
4. A device according to claim 3, characterized in that

   - the felting device (8) is a needle board machine (30, 31) having oscillating needles (32, 34, 35), the rate of motion of which following essentially a sine function with minimum velocity at the reversal points of the oscillating motion.
5. A device according to claim 4, characterized in that

   - the needles (32, 34, 35) at least in sections are provided with at least a bit (33) projecting from the circumferential surface of the needle.
6. A device according to claim 4 or 5, characterized in that

   - needles of different length are provided.
7. A device according to any of claims 4 to 6, characterized in that

   - the needle board machine has two opposing needle boards (30, 31),

   - which are provided each, on the side facing the layer of mineral fibers (3), with a plurality of needles (32, 34, 35).
8. A device according to claim 3, characterized in that

   - the felting device (8) has at least a rotating metal brush (28, 29), the rotating velocity of which being selectively controllable.
9. A device according to claim 8, characterized in that

   - it has two opposing, rotating metal brushes (28, 29), each consisting of a cylinder, on which a plurality of pins or needles is mounted,

   - the pin length or needle length being essentially the layer thickness of the surface area (36, 37) to be felted of the layer of mineral fibers (3) and

   - the narrowest clearance of the cylinders being approximately the thickness of the sheet of mineral fibers (3) to be produced.
10. A device according to any of claims 3 to 9, characterized in that

    - the felting device (8) comprises at least a brush cylinder (28, 29) as well as a needle board machine (30, 31).
11. A sheet of mineral fibers produced in accordance with the method according to claim 1 or 2, characterized in that

    - with respect to at least one surface (36, 37), the fibers close to the surface are felted.
12. A sheet of mineral fibers produced in accordance with the method according to claim 1 or 2, characterized in that

    - the extent of the felting increases gradually or continuously in the direction to at least one surface (36, 37).
13. A sheet of mineral fibers produced in accordance with the method according to claim 1 or 2, characterized in that

    - it is felted in its middle portion (39), whereas, with respect to at least one surface, the fibers close to the surface are not felted.

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