CA2447191C - Apparatus for detaching a web threading tail from a moving surface - Google Patents

Abstract

The invention relates to an apparatus (10) for detaching a Web-threading tail (16) from a moving surface (11.1) . The web-threading tail (16) is arranged to be cut in such a way that a point part (16'), which is essentially narrower than that actual threading width of the web-threading tail (16),is created and is then arranged to be spread out to the actual threading width of the web-threading tail (16), and in which the apparatus (10) arranged in connection with the moving surface (11.1) includes a belt loop (28) permeable by air, which is arranged to rotate, supported by turnover rolls (29, 30), in the direction of travel of the web-threading tail (16) and to move the detached web-threading tail (16) forward. In order to detach the web-threading tail (16) from the moving surface (11.1), a vacuum effect is arranged in connection with the first turnover roll (29) of the said turnover rolls (29,30).

Description

APPARATUS FOR'DETACHING A WEB THREADING TAIL FROM A MOVING
SURFACE

The present invention relates to an apparatus for detaching a web-threading tail from a moving surface, in which the web-threading tail is arranged to be cut in.connection with the moving surface, in such a way that a point part, which is essentially narrower than that actual threading width of the web-threading tail, is created and is then arranged to be spread out to the actual threading width of the web-threading tail, and in which the apparatus arranged in connection with the moving surface includes a belt loop permeable by air, which is arranged to rotate, supported by turnover rolls, in the direction of travel of the web-threading tail and to move the detached web-threading tail forward.

Generally carrier rope systems are used for tail threading in the finishing-section totalities after the dryer section of paper and board machine, for instance, in connection with the dryer groups located before and after coating stations, or, instance, in connection with the calender. Nowadays,. however, the trend is to not use them, on account of their uncertain operation and even dangerousness. This has led to the develop-ment of ropeless apparatuses, in which various kinds of guide plates combined with air blasts. are used for threading the tail. Particularly in the dryer section, doctors have also been used to transfer the web-threading tail from the dryer cylin-ders to the guide plates. In a doctor, a blade or a blast can be used. The doctors, guide plates, and blasts can also be separate.

The doctoring result achieved with an air blast is, however, generally poor, which leads to breaks in tail threading.
Attempts are often made to improve the doctoring result by increasing the power of the blast, but then the blast often interferes with the movement of the web-threading tail. As blasts have nearly only a guiding effect, they cannot be used to tension the web-threading tail. In addition, the nozzles used to create the blasts are sensitive to changes in condi-tions and their control is also imprecise. Doctor blades in contact with the surface of a drying cylinder wear in use and their construction is complex. In practice, web threading must be assisted with manually operated blast pipes, or even manually, which substantially reduces work safety.
Further, apparatuses based on belt loops have also been developed. In these, the web-threading tail, which has been guided onto a belt loop is propelled forwards by the rotation of the belt loop and by a vacuum arranged inside it. One such apparatus is disclosed in EP publication 1 205 415 A2. Even in such an apparatus, special means are still required for detaching the web-threading tail from the moving surface and guiding it onto the belt loop.

Because the known apparatus solutions have not provided a satisfactory way of taking hold of the web-threading tail, attempts. have been made to shape the actual point part. of the web-threading tail in such a way as to achieve the smoothest possible catching of the tail and guiding of it forwards.
Publication US-6,379,502 Bl discloses a manner of cutting the web-threading tail, in which, during the cutting of the tail, its point part is arranged to be substantially narrower than the threading width of the rest of the tail. After cutting, the cutted sharp shape point part of the tail is spread to its actual threading width, for example, using precisely the web-threading tail cutting device. This publication discloses a special moveable doctor device, which is used to detach the cutted point part of the web-threading tail from the moving surface and then to guide it onto a closed belt-loop conveyor, to be carried forward. This makes the apparatus quite complex, precisely in the case of the special detaching devices.

However, it is really difficult to take hold, in a controlled manner, this kind of a widening point part with a sharp shape, for example, precisely when using known web-threading devices based on blasts and/or doctoring. It is well known that the point of the tail, which is sharp or at least cut to be substantially narrower than the threading width of the web-threading tail, will continue to travel adhering tightly on the surface of the roll. Despite the new kind of shaping of the point of the tail, the known types of web-threading device described above cannot be used to achieve satisfactory detaching, taking hold, or sending forward of the web-threading tail, because the blast effect directed at the narrow point part must be aimed very precisely and otherwise too the very narrowness of the point part of the tail makes it difficult to control with blasts.
The present invention is intended to create a new type of apparatus for detaching a web-threading tail from a moving surface, which is smaller and more reliable in operation than previously and by means of which the drawbacks of the prior art can be eliminated.

The apparatus according to the invention is simple and small in size, so that it can be easily placed between structures.
By means of the apparatus, the point part of a web-threading tail, which is arranged to be substantially narrower than the conventional threading width of the tail, can be both dependably detached from a moving surface and moved forward in a controlled manner to the next web-threading device, or component totality. In addition, the apparatus's power requirement is small and its operation is easily controlled.
The apparatus also permits a certain degree of freedom in locating web-threading devices relative to the cross-direction of the web.

In the following, the invention is examined in greater detail with reference to the accompanying drawings showing some embodiments of the invention, in which Figure 1 shows a side view of an end of a dryer sec-tion equipped with an apparatus according to the invention, Figure 2 shows a perspective view of the location of the apparatus according to the invention at the end of a dryer section, Figures 3a, 3b show a schematic example of the formation of the point part of a web-threading tail, Figure 4 shows a partial cross-section of the appara-tus shown in Figures 1 and 2, Figure 5a shows a schematic drawing of a top view of the apparatus of Figure, 4, Figures 5b-5d show partial cross-sections of variations of the apparatus of Figure 4, Figure 6 shows a side view of a second embodiment of the apparatus of Figure 4, and Figure 7 shows a top view of the embodiment of Figure 6.

Figure 1 shows the point of application of an apparatus 10 according to the invention on a paper machine. Besides paper machines, the apparatus 10 can also advantageously be used in board machines. The figure shows a side view of the dryer section, and particularly the end of it. In this embodiment, the dryer section is formed of rotating cylindrical pieces arranged on two levels. These form dryer groups 60, of which Figure 1 shows the latter half of the last group. In this single-wire dryer section, the heated drying cylinders 11.1 are on the upper level and the vacuumed suction rolls 11.2 are on the lower level.
In such a single-wire dryer section, the paper web. 62 is supported on a single drying wire 13. Lead rolls 12 are arranged above the dryer section for the drying wire 13 and the wire 13 is arranged to travel in such a way that, in connection with the drying cylinders 11.1, the paper web 62 travels 5 between the drying wire 13 and the drying cylinder 11.1, while, in connection with the suction rolls 11.2, the paper web 62 travels outside the drying wire 13, so that the wire 13 travels between the suction roll 11.2 and the web 62. In the area between the drying cylinders 11.1 and the suction rolls 11.2, the web 62 travels supported on the drying wire 13. Inverted dryer groups are also possible, in which case the operational components formed by the dryer group 60 are arranged in an opposite manner to that shown, as are also twin-wire-draw dryer sections, in which case there are also drying cylinders in place of the suction rolls 11.2 and there are guide rolls for both the upper and the lower wire, in the pockets formed by the cylinders (not shown).

Before the end of the dryer section, in this application example for instance, three drying cylinders 11.1 before the end, there is, in the pocket formed by the cylinder 11.1 and rolls 11.2, a water-cutting device according to the prior art, such as a double water cutter 61, the basic technique of which is referred to in publication WO-98/33974. Other types of apparatus based on liquid cutting can also be used, there being also no restrictions on their positioning in a dryer section.
At the end of the dryer section, after the final drying cylinder 11.1, there is a web-threading device 10 according to the invention, which will be examined in greater detail later..
Figure 2 shows a schematic perspective view of the end of the dryer section shown in Figure 1. Using the water cutting device 61 shown in Figure 1, it is possible to cut the web-threading tail in. the machine direction, i.e. not only to form a web-threading tail 16, but also to cut it in the transverse direction of the web 62. In cutting transversely, a point part 16', which is substantially narrower than the conventional width of a web-threading tail 16, is cut in the web-threading tail 16. The point part 16' can be preferably have a sharp shape, which reach on a slant the uniform threading width of the web-threading tail 16, as shown in Figure 2.

Figure 2 shows the situation immediately after the web-thread-ing tail 16 has been detached from the drying cylinder 11.1.
For reasons of simplicity, the drying wire is not shown at all in the figure. The actual detaching from the moving surface, which is in no way restricted by this example of a drying cylinder, but can be understood very broadly, takes place using a vacuum, which is formed inside the drum 18 of the device 10.
The blasts used in the prior art to detach the web-threading tail 16 are then unnecessary. Generally, the apparatus 10 also includes means 22, arranged after the drum 18 in the direction of travel of the web-threading tail 16, for guiding the web-threading tail 16 detached from the drying cylinder 11.1, and transferring it to the next web-threading point (not shown).
The rest of the web 62 continues to travel on the surface of the cylinder 11.1, until it is detached from the cylinder 11.1 by a doctor 63 and led to broke processing or similar.
Figures 3a and 3b show an example of one way of cutting the point part 16' of the web-threading tail 16 and, in this connection, also of cutting it off completely. In both figures, .an arrow shows the, direction of travel of the moving web 62.
The nozzles 61.1, 61.2 of the water cutting device 61 are initially run on essentially the same machine-direction line, as shown in Figure 3a. After this, the second nozzle 61.2 is begun to be moved, in a manner that is as such known, in the cross-direction of the machine, so that, after its movement, the width of the web-threading tail 16 cut by the nozzles 61.1, 61.2 corresponds to the width.of the web-threading tail 16, which is, as such, conventional, being, for example, 300 - 500 mm (Figure 3b) . The movement of the second nozzle 62.2 is shown in Figure 3a by the arrow attached to it.

The nozzle 61.2 is preferably moved as rapidly as possible, because already at the web-threading stage, the web 62 too is running at nearly the production speed of the machine. The shape of the point part 16' of the web-threading tail 16 that is thus created is sharp and short, allowing the web-threading tail 16 to reach its standard width as soon as possible and preventing narrowly shaped point part area 16' from causing, for example, control problems. It should be noted, that cutting can be performed, and thus the point part 16' also shaped using different kinds of movements of the nozzles 61.1, 61.2, and that the manner described above is in no way restrictive. As a second application example, the nozzles 61.1, 61.2 can first of all be moved in such a way that, starting from the cutting width of the web-threading tail 16, they first of all approach each other, without, however, touching and then immediately separate back to the cutting width of the web-threading tail (not shown). Further, as a third application example, the nozzles 61.1, 61.2 are moved in such a way that they now touch each other and move crosswise relative to each other, thus changing places relative to the initial situation.

As is known, the web-threading tail 16 moving between the drying cylinder 11.1 and the wire 13 tends to adhere to the surface of the hot drying cylinder 11.1, after the opening gap 14 (Figure 1). Thus, the web-threading tail 16 must first of all be detached from the surface of the drying cylinder 11.1 and then guided forward to its next location. According to the invention, after the opening gap 14, a vacuum is used to detach the web-threading tail 16 from the surface of the drying cylinder 11.1.

Figure 4 shows a first embodiment of the apparatus 10 according to the invention in greater detail as a partial cross-section.
The apparatus 10 includes a belt loop 28 permeable by air as the guide means 22 for the detached web-threading tail 16. The belt loop 28 is arranged to rotate, supported on turnover rolls 29 and 30, in the direction of travel of the web-threading tail 16.
Thus, the web-threading tail 16 cut narrower from a point part 16' can be guided over a sufficiently long distance and more precisely than in the prior art. An essential feature of the apparatus 10 according to the invention is that the first 29 of the turnover rolls is the said vacuum drum 18.

A vacuum box 24 is fitted inside the drum 18, and generally covers 20 - 70 preferably 30 - 60 % of the inner circumference of the drum. In Figure 4, the vacuum box 24 covers about one half of the inner circumference of the drum 18. For this distance, the web threading tail 16 is arranged to travel on the surface of the drum 18. The jacket 19 of the drum 18 is in cross section, so that the holes 23 are clearly visible.

The drum 18 is thus arranged after the opening gap 14 and separately from the surface of the drying cylinder 11.1, so that it does not wear and it has no effect on the drying cylinder 11.1. Generally, the gap is 2 - 10 mm, preferably 3 - 6 mm. This gives greater freedom and tolerances than previously in positioning the drum 18. The web-threading tail 16, with a narrower cutted point part 16' is thus detached using the rotating drum 18, in connection with which a vacuum is arranged.
The smallness of the gap means that only a small vacuum is required. The detaching of the web-threading tail 16 from the drying cylinder 11.1 can, however, be ensured by using a greater vacuum, without, however, disturbing the movement of the web-threading tail 16.

The use of a vacuum avoids blasts that interfere with the movement of the web-threading tail 16. In addition, the vacuum can be easily regulated while the rotating drum 18 also guides the web-threading tail 16. The drum 18 can also be dimensioned to be advantageously small, so that it is simple to place it in different positions in the gap. In addition, the drum 18 is unaffected by variations in conditions.

The apparatus 10 is used specifically to thread and guide the web-threading tail. During the normal operation of the dryer section, the apparatus 10 according to the invention can be turned to the rest position. For this purpose, the apparatus 10 is. supported rotatably on an articulated arm in the structure of the dryer section (not shown). By suitable dimensioning, the apparatus 10 can be made to move simply a sufficient distance from the drying cylinder 11.1 and the web 62., In addition, the apparatus 10 can be easily and rapidly turned from the rest position to the operating position and back again. In practice, the drum 18 can be turned to a distance of up to 100 mm from the drying cylinder 11.1. Correspondingly, the distance from the web 62 is at least 40 mm.

Thus, the web-threading tail 16 is detached from the moving surface of the drying cylinder 11.2 and at the same time moved by means of the belt loop 28 towards the next webrthreading point. Further, at least one foil list 31 is arranged between the turnover rolls 29 and 30, inside the belt loop 28, in order to create a vacuum 'effect on the surface of the belt loop 28.
The web-threading tail 16 will then remain firmly on top of the belt loop 28, making the operation of the apparatus 28 particu-larly reliable.

The vacuum is thus created in the area of the. belt loop 28, mainly with the aid of two foil strips 31. Generally there are 1 - 3 foil strips, preferably only one. In addition, the distance between the turnover rolls 29 and 30 is, in practice, 200 - 600 mm, preferably 300 - 500 mm. Thus, the apparatus 10 according to the invention becomes especially short, compared to known belt applications. In addition, thanks to the suction turnover roll 29, little additional vacuum effect is required, so that fewer foil strips 31 than before are needed. Corre-spondingly, the apparatus 10 can be made sufficiently wide.

5-According to one embodiment of the invention, the suction inside the belt loop 28 is created with the aid of a foil effect, without actual devices creating suction. The foil effect arises, when the point. of a foil strip 31 is in contact with, or nearly in contact with the moving surface of the belt 10 28. The air from the intake side of the foil strip'31 is then directed downwards guided by the leading edge of the foil strip 31 and a. vacuum is created at the downstream.edge of the foil strip 31. The foil effect can be boosted using Coanda blasts, which are usually optional and adjustable. Instead of, or in addition to the foil effect, other ways of creating a vacuum can naturally also be used.

The web-threading tail 16 can also be tensioned using the apparatus according to the invention. Tension is' achieved by rotating the belt 28 at a higher speed than the web 62. It is then possible to use a small difference in speed, as the web-threading tail 16 adheres to the belt 28. By using a .suitable difference in speed, the web-threading tail 16 can be kept tight, thus ens,a.ring the success of the web threading. In practice, a speec 2 - 5 % higher than that of the web is used.
The vacuum effect will keep the web-threading tail 16 firmly on the belt 28. The upper surface of the belt 28 may be roughened, which will improve the ability of the apparatus to detach the web-threading tail 16 from the drying cylinder 11.1.
In the disclosed apparatuses, the diameter of only the drum is about 300 mm. In belt applications, the turnover. roll 29 is considerably smaller. A belt application can even be narrower than the web-threading tail 16, thanks to the covering suction effect. A belt application can be dimensioned case-specifi-cally.

Figure 5a shows a schematic drawing of one belt application of the apparatus 10 according to the invention. A belt loop 28, which moves in the direction shown by the arrow, is supported on turnover rolls 29 and 30. The web-threading tail 16, which is now cut in such a way that the transverse transfer speed of the second nozzle 61.2 increases when it approaches the point corresponding to the standard width of the web-threading tail 16, is guided on top of the belt loop 28. Correspondingly, Figures 5b - 5d show a surprising solution, by means of which the belt loop 28 is made to remain firmly held on top of the turnover rolls 29, 30. According to the invention, at least one longitudinal guide element 35 is arranged in the belt loop 28, a corresponding space 36 being arranged in connection with the turnover rolls 29 and 30, in order to hold the belt loop 28 on the turnover rolls 29 and 30. In practice, the guide element can be a.protrusion 37 attached to the belt loop 28, or a fold 38 in the belt loop 28. The protrusion 37 can, for example, easily be glued to the belt loop 28, which in practice is usually a short and narrow wire.
The fold shown in Figure 5d can formed simply by weaving a suitable crease into the wire 28. Figure 5b shows two different applications at the opposite ends of the drum. The crease can also be at the edges of the wire, in which case the machining in the jacket 19 of the drum 18 will be unnecessary. Corre-spondingly, the space 36 can be a corresponding recess 39 arranged in the jacket of the turnover rolls 29 and 30. In the ways shown, the belt loop will remain in place without being tensioned and despite the loosening caused by heat. In addi-tion, it will be unnecessary to camber the turnover rolls 29, 30.

Figures 6 and 7 .show a second embodiment of the apparatus according to the invention. In this case, the belt loop 28 is 550-mm wide and it is described with a dashed line. In this case too, two turnover rolls 29 and 30 are used, supported by which the belt loop 28, rotates. According to the aforemen-tioned, a suction effect is arranged in connection with the first turnover roll 29. Grooves 40 that essentially cover the entire circumference of the drum are used in place of a perforated jacket. Longitudinally arranged grooves 40 cover substantially the entire circumference of the turnover roll 29, the total surface area of the grooves 40 being 10 - 30 %, preferably 15 - 25 % of the surface area of the turnover roll 29. In addition to this, a chamber 41, in which a vacuum is arranged, is arranged inside the belt loop 28. The vacuum of the chamber 41 extends through the grooves 40 to the belt loop 28, thus creating the force required to detach the web-thread-ing tail 16. The, chamber 41 is bounded by a foil strip 31 and by a blast plate 42 extending from it. The chamber 41 is also bounded by a base plate 43 and by the feed pipe 44 of the blast plate 42. This prevents the unnecessary spread of the vacuum and disturbances in the operation of the foil strip .31. Air discharging from the blast plate 42 exhausts from the side of the apparatus 10 before the second turnover roll 30 and partly through the belt loop 28. The use of the solution in question achieves an extremely compact construction, which is, in addition, powerful and operationally reliable.

The construction of the apparatus 10 is new in other ways too.
The vacuum is preferably created using compressed air, making separate fans unnecessary. In the embodiment shown, a venturi pipe 45 is used, with a ring nozzle 46 attached to it. The compressed air blown from the small hole of the ring nozzle 46 creates a flow in the ' venturi pipe 45 and thus a sufficient vacuum in the apparatus. The venturi pipe 45 is also connected to an intermediate pipe 47, which is correspondingly connected to the chamber 41 by a angle pipe 48. In addition, a drum motor 49 creates the force required to rotate the belt loop 28. In other words, the motor 49 is inside the second turnover toll 30. In addition, the motor 49 is fitted to the side at the attachment, point, so that the centre of gravity of the appara-tus is close to the attachment point. Further, the motor 49 is connected to the intermediate pipe 47, so that the flow removes the heated air from the motor 49.

Compressed air is also used in connection with the blast plate 42. For this purpose there is a transverse feed pipe 44 and compensating pipes 50, which terminates in the actual blast pipe 51 connected to it. In the blast pipe 51, the compressed air is distributed evenly over the width of the belt loop 28 and then discharges through the holes in the blast pipe 51, creating the aforesaid Coanda blast (not shown). The foil strip 31 and the Coanda blast create a powerful vacuum soon after the first turnover roll 29. Closer to the second turnover roll 30, the vacuum effect diminishes, allowing the web-threading tail 16 to detach naturally from the surface of the belt loop 28.
The detaching can be ensured by means of an air doctor 52, arranged in connection with the second turnover roll 30 (Figure 7). Figure 6 shows only the direction of the blasts of the air doctor. The first blast detaches the web-threading tail 16 from the surface of the belt loop 28 while the second guides it forward.

In addition to what is described above, the apparatus according to the invention can also be used elsewhere in a paper machine.
One example is coating stations and the dryer groups arranged in connection with them. Further, several applications for the apparatus according to 'the invention can be found in the calender.

Using the apparatus according to the invention will ensure the detaching, from a 'moving surface, of a web-threading tail 16, cut to an substantially narrower point part 16', and its transfer to the next web-threading point. The use of a vacuum avoids air blasts and the difficulty of directing them. The vacuum required is also advantageously low, being well under 0,1 bar.

The apparatus according to the invention is versatile and easily adaptable. Using the apparatus 10, the web-threading tail 16 can be detached reliably even at high speeds and with different paper grades. In addition, it can be installed in different positions. Retrofitting is also easy. The elements can be rotated in a manner suitable at each time. Generally, electric or pneumatic motors are used, which are preferably arranged connected to, or even inside a turnover roll. Espe-cially the exhaust air from 'a pneumatic motor can be. used to form the vacuum inside the drum. Particularly in a drum application, the upper limit of the speed of rotation is very high, allowing a pneumatic motor to be used to rotate the drum at a clear overspeed, relative to the surface.

It must be understood that the above description and the related figures are only intended to illustrate the apparatus according to the present invention. The invention is therefore in no way intended to be restricted to the embodiment disclosed above or defined in the Claims, instead many different varia-tions and adaptations of the invention, which are possible within the scope of the inventive idea defined in the accompa-nying Claims, will be obvious to one versed in the art.

Claims (18)

1. An apparatus (10) for detaching a web-threading tail (16) from a moving surface (11.1), in which the web-threading tail (16) is arranged to be cut in such a way that a point part (16'), which is essentially narrower than that actual threading width of the web-threading tail (16), is created and is then arranged to be spread out to the actual threading width of the web-threading tail (16), and in which the apparatus (10) arranged in connection with the moving surface (11.1) includes a belt loop (28) permeable by air, which is arranged to rotate, supported by turnover rolls (29, 30), in the direction of travel of the web-threading tail (16) and to move the detached web-threading tail (16) forward, wherein in order to detach the web-threading tail (16) from the moving surface (11.1), a vacuum effect is arranged in connection with a first turnover roll (29) of the turnover rolls (29, 30).

2. The apparatus according to Claim 1, wherein the first turnover roll (29) is arranged at a distance from the said moving surface (11.1), which distance is 2 to 10 mm.

3. The apparatus according to Claim 2, wherein the distance is 3 to 6 mm.

4. The apparatus according to any one of Claims 1 to 3, wherein in order to create the vacuum effect, the first turnover roll (29) is formed by a drum (18), with a perforated jacket (19), and inside which a vacuum is also arranged.

5. The apparatus according to Claim 4, wherein in order to create the vacuum, inside the drum (18) there is arranged a vacuum box (24), which covers 20 to 70 % of the inner circumference of the drum (18).

6. The apparatus according to Claim 5, wherein the vacuum box covers 30 to 60% of the inner circumference of the drum.

7. The apparatus according to any one of Claim 1 to 3, wherein in order to create the vacuum effect, grooves (40) are arranged in the first turnover roll (29), and the turnover roll (29) is arranged to delimit a chamber (41), inside which there is also a vacuum arranged, arranged inside the belt loop (28).

8. The apparatus according to Claim 7, wherein grooves (40) are arranged longitudinally and cover substantially the entire circumference of the turnover roll (29), the total surface area of the grooves (40) being 10 - 30 %, of the surface area of the turnover roll (29).

9. The apparatus according to Claim 8, wherein the surface area of the grooves is 15 to 25%.

10. The apparatus according to any one of Claims 1 to 9, wherein the apparatus (10) is supported rotatably on an articulated arm, in order to turn the apparatus (10) between the web-threading and rest positions.

11. The apparatus according to any one of Claims 1 to 10, wherein the distance between the turnover rolls (29, 30) is 200 to 600 mm.

12. The apparatus according to claim 11, wherein the distance between the turnover rolls is 300 to 500 mm.

13. The apparatus according to any one of Claims 1 to 12, wherein 1 to 3 foil lists are fitted inside the belt loop (28).

14. The apparatus according to Claim 13, wherein a single foil list is fitted inside the belt loop.

15. The apparatus according to any one of Claims 1 to 3 and 7 to 14, wherein at least one longitudinal guide member (35) is arranged in the belt loop (28), a space (36) corresponding to which is arranged in connection with the turnover rolls (29, 30), in order to hold the belt loop (28) on the turnover rolls (29, 30).

16. The apparatus according to Claim 15, wherein the guide member is a protrusion attached to the belt loop (28), or a fold (38) in the belt loop and the space (36) is a corresponding recess (39) arranged in a jacket (19) of the turnover roll (29).

17. The apparatus according to any one of Claims 4 to 6, wherein at least one longitudinal guide member (35) is arranged in the belt loop (28), a space (36) corresponding to which is arranged in connection with the turnover rolls (29, 30), in order to hold the belt loop (28) on the turnover rolls (29, 30).

18. The apparatus according to Claim 17, wherein the guide member is a protrusion attached to the belt loop (28), or a fold (38) in the belt loop and the space (36) is a corresponding recess (39) arranged in the jacket (19) of the turnover roll (29).