When manufacturing rockwool and other types of mineral wool there is often used a so called cascade spinning machine. Such a machine generally comprises 2-4 spinner wheels in the form of cylindrical steel cylinders having substantially horizontal and parallel shafts. The cylinders are cooled and they are brought to rotate rapidly. The cylinders are arranged to receive and fibrate a stream of molten mineral in that one of the spinner wheels receives a free falling stream of molten mineral. The molten mineral sticks to said spinner wheel and forms a so called ring of molten mineral. A substantial portion of the molten mineral, however, is thrown onto the succeeding spinner wheel on which a corresponding ring of molten mineral is formed. The excess of molten mineral is thrown onto a third spinner wheel, or back to the first spinner wheel in case the spinning machine is formed with only two spinner wheels.

Each such spinning machine has a limited capacity. By "capacity" is thereby meant the amount of mineral wool having an acceptable quality which can be manufactured per time unit with an acceptable exploiting of the molten mineralic material. It always is an aim to provide as high yield as possible and it is therefore important that as high amount as possible of the molten material sticks to the spinner wheel, and that as little amount as possible of the molten material, preferably no molten material at all, is thrown off in advance. This always has been a problem and has caused lots of work, and several solutions of said problem has been suggested. The suggested solutions have been based on one out of two main ideas, namely either to give the supplied stream of molten mineral a high impact energy and/or to spread the stream of molten mineral over a larger part of the spinner wheel length (width).

In the Swedish patent 443.133 there is suggested a way of providing the desired widening of the stream of molten mineral. This is possible by applying, in a suitable way, a force against the stream of molten mineral, for instance a force from a gas flow. Said force alternatively can be provided in that a stationary or a rotatating deflector is introduced in the stream of molten mineral.

The present invention relates to a method and an apparatus by means of which it is possible to substantially more simply and more safely than heretofore provide the desired widening of the stream of molten mineral.

Thus, the invention relates to method of supplying molten mineral to a cascade spinning machine having several, mainly cylindrical spinner wheels for the manufacture of mineral wool, whereby the molten mineral is supplied to the spinner wheels, and from which spinner wheels particles of the molten mineral are being thrown out while being fibrated.

For providing a widening of the stream of molten mineral a free falling stream of molten mineral is fed to a splitting device which splits the stream of molten mineral into two part streams each of which separately hits one or two spinner wheels.

Said part streams also can be further split by two additional splitting devices so that four part streams are being formed before said streams hit the spinner wheel or wheels.

According to one embodiment of the invention all part streams hit one and the same spinner wheel, and according to another embodiment of the invention each one of two part streams hits one of two like large spinner wheels mounted on about the same height and close to each other.

The invention also relates to an apparatus for splitting up the free falling stream of molten mineral. The splitting apparatus basically comprises a tube, preferably a metal tube having a good thermal conductivity, for instance a copper tube.The tube is mounted substantially horizontally. A cooling medium, for instance water, flows through the tube. The tube can be U-shaped, for instance so that the branches of the tube are placed close to each other and above each other, or so that there is a horizontal tube piece between the branches which piece is the actual splitting part thereof.

The branches of the tube may be flattened from the sides at some place thereof. Also, at least the upper branch of the U-shaped tube may be bent down in a V-formation at a longitudinal place thereof. In case the splitting device basically comprises a horizontal splitting piece this can be flattened from the sides or bent down in a V-shape at a place thereof.

The invention now is to be described with reference to the accompanying drawings.

In the drawings figure 1 shows a first embodiment of an apparatus for perfoming the method according the invention. Figures 2a and 2b show, diagrammatically and in cross sections, two alternative ways of splitting a stream of molten mineral i accordance with the invention. Figures 3a and 3b correspondingly show how the stream of molten mineral is spread over three successive spinner wheels. Figure 3c is a side view of the three spinner wheels illustrated in figures 3a and 3b. Figure 4 diagrammatically illustrates how the stream of molten mineral is widened on two parallel spinner wheels. Figures 5a and 5b show a specially formed splitting device, and figure 6 shows an alternatively shaped splitting device. Figure 7 likewise shows an alternatively formed splitting device.

Figure 1 shows a stream 1 of molten mineral coming from a not illustrated melting furnace and flowing down along a melt flute 2 and therefrom, as a free falling stream 1 ' of molten mineral down towards a not illustrated cascade spinning machine. A splitting device 3 (genereally referred to as a splitter) is mounted between the melt flute 2 and the spinning machine.The splitting device or splitter 3 is formed as a U-shaped tube having two branches 4 and 4', which are substantially horizontal and located above each other. Further there is a not illustrated means for supplying and discharging a cooling medium 5 arranged so that the cooling medium 5 can flow through the tube. The freely falling stream 1 ' of molten mineral will, after leaving the melt flute 2, hit the splitter 3, whereby the stream of molten mineral becomes split into two part streams 6 and 7. Each of said part streams 6 and 7, separately of each other, hits a spinner wheel. By splitting the stream 1 ' of molten mineral into two part streams 6 and 7 a wider stream of molten mineral is obtained already when it hits the first spinner wheel, and an enlarged portion of the molten mineral thereby sticks to the spinner wheel. Thereby the so called spinning yield becomes

increased. The splitter can be formed in various ways. The splitter should be made of a material having a good thermal conductivity, preferably of a copper tube or a similar material.

I figure 2a there is diagrammatically shown how the stream of molten mineral 1 ' hits the splitter 3 and is thereby split into two part streams 6 and 7. For further widening the stream of molten mineral 1 ' several additional splitting devices can be mounted under the first splitter 3 so that also each of the part streams 6 and 7 is split into two additional part streams. This is illustrated in figure 2b. In this case the stream 1 ' of molten mineral hits the splitter 3, whereby the part streams 6 and 7 are formed. Thereafter the part stream 6 hits a further splitting device or splitter 8 which splits the part stream 6 into additional part streams 9 and 10. Likewise the part stream 7 hits the splitting device 1 1 which forms additional part streams 12 and 13.

Figures 3a and 3b shows the principle for the widening of the stream of molten mineral as compared with the known art. For the sake of clearness three spinner wheels are illustrated on a line. In fact the spinner wheels, however, are arranged as shown in figure 3c.

In figure 3a the stream 1 ' of molten mineral directly hits the first spinner wheel 14 of a cascade spinning machine. Thereby a melt ring 15 is formed on the spinner wheel 14. When the stream 1 ' of molten mineral hits the hext spinner wheel 16 it has become slightly widened, and the melt ring 17 is additionally widened on the spinner wheel 16. From there the stream of molten mineral is moved on and hits a still further spinner wheel 18, on which the melt ring 19 is still more widened.

In figure 3b is shown what happens when the stream 1 ' of molten mineral is split into two part streams 6 and 7 which both hit the first spinner wheel 14'. Thereby two melt rings 15' and 15" are formed on said first spinner wheel 14', the total width of which is greater than the width of the melt ring 15 of figure 3a. When the molten mineral is thrown over to the second spinner wheel 16 ^* and sticks thereto there are formed two melt rings 17 ^* and 17" also on this spinner wheel 16' each of which is wider than the melt rings 15' and 15" on the first spinner wheel 14', and which have a total width which is greater than the that of the melt ring 17 of figure 3a. When thereafter the molten mineral, which is moved on to a

further spinner wheel 18', sticks to said spinner wheel a still greater amount of the molten mineral sticks thereto so that one single melt ring 19' is formed the width of which is greater that the width of the melt ring 19 of figure 3a.

Figure 3c shows how the spinner wheels 14, 16 and 18 are arranged in a three wheel spinner machine. The arrows in the figure show the direction of rotation of the spinner wheels. It is also evident from the figure that the stream of molten mineral 1 ' first hits the spinner wheel 14 and is thereafter thrown on to the spinner wheel 16 and then to the spinner wheel 18.

In a spinning machine having only two spinner wheels of about the same size and having parallel shafts and arranged on the same vertical level it may be advantageous that each of the the two part strems hits one of the spinner wheels on opposite sides of the central line of the spinner wheel. In figure 4 is shown how the stream of molten mineral is widened in a two weel spinning machine is used. The splitting device 3 is arranged so that the part stream 6 hits the spinner wheel 20 whereby a primary melt ring 21 is formed thereon. At the same time the part stream 7 hits the spinner wheel 22 and a corresponding melt ring 23 is formed thereon. Molten mineral from the melt ring 21 is then moved from the spinner wheel 20 to the spinner wheel 22 thereby forming a secondary melt ring 24 thereon. Likewise molten mineral from the melt ring 23 of the spinner wheel 22 is moved to the spinner wheel 20 thereby forming a secondary melt ring 25 thereon. The four melt rings 21 , 23, 24 and 25 have a total width which is substantially greater than the total width of the two melt rings which would have been formed in case a non-split molten stream would first have hit the first spinner wheel, corresponding to the spinner wheel 20, and would then have been thrown over to a second spinner wheel, corresponding to the spinner wheel 22.

Figures 5a and 5b show a special embodiment of the splitting device 3. In said embodiment the branches 4 and 4' och the splitting device are flattened from the sides thereof. By forming the tube branches accordingly it is possible to provide a guiding of the stream 1 ' of molten mineral, i.e. to give said stream a special flowing path. The splitter tube parts 8 and 1 1 of figure 2b also may be flattened like the tube part 4 of figure 5a.

It is also possible to guide the stream 1 ' of molten mineral in that the branch 4 of the splitting device 3, which is hit by the mineral stream 1 ', be bent to a V-formatioπ as shown in figure 6. Also the branches of the parts 8 and 1 1 of figure 2b, which are hit by the part streams 6 and 7, may be formed with such V-shape.

Another embodiment of the splitting device is shown in figure 7. In this embodiment the splitting device is formed with two branches 27 and 28 and a with a horizontal piece of tube 29 interconnecting said branches.

The horizontal piece of splitter tube 29 is the actual splitting device. For guiding the stream of molten mineral said tube piece 29 may be shaped like the branches of the splitting device shown in figures 5 and 6, in the meaning that it can be flattened from the sides or it can be bent down in a V-formation at the place where the molten mineral hits the splitter.