Insulation chutes are manufactured in known methods in tubular form as parisons from mineral wool, the wool being usually in form of a web, which web is folded to a defined web width and thickness from the primary web coming from the manufacturing of the mineral wool. This folded web is usually rolled to storage rolls of a defined size, which storage rolls are then taken to the manufacturing apparatus of the insulation chutes as needed. In the manufacturing apparatus of the insulation chutes a winding web of a defined thickness in sawn from these storage rolls, which web is then fed to a winding device of the parisons. The sawing is performed at the rim of the roll as the roll rotates supported by a suitable apparatus. In view of the uninterrupted operation of the manufacturing machinery of the parisons, it is essential that the winding web can be fed to the winding apparatus essentially continuously. The problem in achieving the continuous operation is the time required for changing the storage rolls in the sawing apparatus.

The problem of the continuous operation caused by the change of the storage rolls is solved in the known art by cutting first a over-thick ply web from the storage roll. In a subsequent sawing step where the actual thickness of the web directed to the winding, the part that exceeds the thickness of the web actually required is cut from the ply web and directed aside to be wound as a supplement for future use into a supplemental roll in an appropriate device included in the apparatus. When the storage roll in the sawing stage is sawn to its end, the web directed to the winding is then sawn from the supplemental roll during the time that is required for changing the storage roll. An apparatus according to this kind of operation is disclosed, for example, in U. S. patent no. 5,155, 889.

With this known arrangement is achieved a continuous feed of the web for winding as required by the operation of the winding apparatus. However, the mineral wool that is directed to the supplemental roll creates a problem in this arrangement. The mineral wool that is directed to the supplemental roll is forced to undergo multiple rolling and sawing

treatments. The result of these treatments is a densification of the web, which may be significant, even to that extend that when manufacturing certain sizes of the parisons the density of the web coming from the supplemental roll into the winding is twice as high as the density of the web coming from the storage roll. Multiple sawing causes naturally also dust problems and shortening of the average fibre length, which adds to the densification of the web.

Another problem is related to the starting and ending stage of the sawing of the storage roll.

The storage roll is rolled to a relative loose roll from the primary web without a rolling core, because of which the centre boss of the roll is located undeterminable in the roll, and on the other hand the roll is not exactly round and smooth at its rim. Even though the roll is rotated at its sawing point before the sawing is started in order to round the roll, there still remains indefiniteness in the roll due to the said reasons, which causes thickness changes and even holes at the starting end of the web sawn from the roll. These irregularities can be smoothed up to a certain point with the control of the sawing of the web taken from the supplemental roll. However, the wool compressed in the supplemental roll is not very suitable for smoothing the irregularities at the starting or ending end of the storage roll.

In the known art the winding web is also fed by unwinding it straight from the storage roll, but this operation comprises other disadvantages. In the first place, the layers of the web build-up to each other relatively firmly, which causes great difficulties at the unwinding of the roll layer by layer. The web going to the winding has unavoidably significant fluctuations of thickness.

A method in accordance with the current invention does not comprise the said problems, the characterizing features of the method being stated in the attached claim 1. The characterizing features of an apparatus useful for carrying out the method are defined in the attached claim 2.

Next, the invention is described in more detail with reference to the attached drawings, where Figures la-lc shows an apparatus for carrying out the invention at different stages;

Figure 2 shows diagrammatically a cutting device of the apparatus and parts of the apparatus connected to it; and Figure 3 shows a cross-section of a parison for an insulation chute, in which is established a coating at the inner side of the parison in accordance with the current invention.

In figure 1 is described as an example the starting end of a manufacturing apparatus of parisons for insulation chutes, where a mineral wool web fed into the winding of parisons is created with operations in accordance with the current application. In the figures is shown two mineral wool storage rolls 1 and 2. The storage roll 2 located at the upper sawing station is at the operational stage of figure la about to run out. Sawing has been started a moment before from the storage roll 1 brought to the lower sawing station. Simultaneous sawing of the storage rolls 2 and 1 is carried out until the storage roll 2 has run out. During the simultaneous sawing the sawing stations are controlled so, that the thickness of the web 4 coming from the storage roll 2 gradually decreases and the thickness of the web 3 coming from the storage roll 1 correspondingly increases so, that a winding web 5 of a required thickness is created from the joined webs for feeding to the winding. When the storage roll 2 has ran out, the sawing continues wholly from the storage roll 1 as a web 3, the thickness of which web is then adjusted to the required thickness of the winding web 5. This operation is repeated and correspondingly controlled when the storage roll 1 has been sufficiently worn out in due time.

In the disclosed apparatus, the storage rolls 1 and 2 are placed on endless conveyors 6 and 7 moving in loop track, which conveyors simultaneously form a part of an apparatus used in rotating the rolls during the sawing. The conveyors 6 and 7 are advantageously belt conveyors, the width of the conveyors essentially equalling the width of the mineral wool web wound on storage rolls 1 and 2. The rotating apparatus of the sawing station comprises also support rollers 8 and 9, as well as a pressing rolls 10 and 11.

The sawing of the web (3 and 4) of defined thickness from the storage rolls 1 and 2 is carried out with a band-saw 12. The saw band of the band-saw is controlled to move as a loop, the horizontal parts of the loop moving near the top surfaces of the conveyors 6 and 7

and reach over the cross dimension of the conveyors. The vertical parts of the saw band loop move at the outer side of the width of the conveyors between the top surfaces of the conveyors, and the direction of the movement is from down to up in one sides of the conveyors and from up to down on the opposite sides of the conveyors. In the embodiment shown in the figure, the height position of the conveyors 6 and 7 is described as adjustable during the sawing. The band-saw is mounted as fixed, so the height position of the conveyors 6 and 7 defines the distance between the top surface of the conveyors and the saw band of the band-saw moving above it. This distance defines the thickness of the web 3 and 4, sawn from the storage rolls 1 and 2 respectively. The adjustment possibilities can also be achieved with combinations of the position adjustment movements of the saw and the conveyors.

In the place of the conveyors 6 and 7, and rollers 8, 9,10, 11 can other apparatus combinations also be used for rotating the storage rolls 1 and 2, by which the roll can be kept rotating in place in relation to the saw 12.

When compared to the known state of the art, the method and the apparatus of the present invention allows the feeding of the mineral wool web of the desired thickness to a winding apparatus so, that the feeding is continuous in conformity with the requirements of the winding apparatus. The changing of the storage rolls does not cause any thickness variations of the web coming to the winding, whereby the quantity of the mineral wool actually fed to the winding can reliably be controlled by controlling the length of the web fed to the winding.

The current apparatus allows also a simple arrangement for a coating to be arranged on the surface of the central opening of the parisons. The coating can be added as a web of a suitable material onto the winding web 5, when foremost the coating fed to the inner surface of a parison is easily established due to the slanted starting web end created by a cutting device 13. The cutting device comprises in the shown embodiment of a braking roll 15, which is parallel to the turning roll of the conveyer 16 conveying the wool web to the winding. When the control of the apparatus notices a wool web of suitable length for winding of a parison on the conveyor 16, the previous conveyor is stopped and roll 15 is pushed against the upper surface of the conveyor so, that the wool web is caught between the roll and the conveyor. Thus, when the conveyor continues its advancement movement and the roll 15 is braking, the web is torn apart essentially slanted, as shown in figure 2.