WO2011036341A1

WO2011036341A1 - Arrangement in tail threading of a fiber web forming machine, apparatus for the arrangement and a fiber web forming machine

Info

Publication number: WO2011036341A1
Application number: PCT/FI2010/050729
Authority: WO
Inventors: Anssi Toivanen; Mikko Hakuli; Erkki Jaatinen; Veli-Pekka Koljonen
Original assignee: Metso Paper, Inc.
Priority date: 2009-09-23
Filing date: 2010-09-21
Publication date: 2011-03-31
Also published as: FI20095975A; FI20095975A0

Abstract

The invention relates to an arrangement in tail threading of a fibre-web forming machine, which is fitted to a twin-wire draw drying section, and which includes at least one belt conveyor (10), for threading the web-threading tail (22), to be fitted in connection with a drying cylinder (11.1,11.2), which belt conveyor (10) includes a frame structure (31) and at least two return rolls (16, 17) in it, a belt loop (20) penetrable by air, which is arranged to run over the return rolls, vacuum means (21) for creating a vacuum in the belt loop, and which arrangement includes, in addition, a doctor device (23) fitted, in front of the belt conveyor, on the web-threading-tail (22) arrival side (24), the width of which doctor device is arranged to mainly correspond to the path of the web-threading tail. At least the belt conveyor is equipped with a linear-motion mechanism (54, 55), for moving it to the web-threading position and correspondingly away from it. In addition, the invention also relates to a device for the arrangement and a fibre-web forming machine equipped with the arrangement or the device.

Description

ARRANGEMENT IN TAIL THREADING OP A FIBRE-WEB FORMING MACHINE, APPARATUS FOR THE ARRANGEMENT, AND A FIBRE-WEB FORMING MACHINE

The present invention relates to an arrangement in tail thread- ing of a fibre-web forming machine, which is fitted to a twin- wire draw drying section, and which includes at least one belt conveyor, for threading the web-threading tail, to be fitted in connection with at least one drying cylinder, which belt conveyor includes

- a frame structure and at least two return rolls,

- a belt loop penetrable by air, which is arranged to run over the return rolls,

- vacuum means for creating a vacuum in the belt loop, and which arrangement includes, in addition, a doctor device fitted in front of the belt conveyor, on the threading-tail arrival side, the width of which doctor device is arranged to correspond principally to the path of the threading tail. In addition, the invention also relates to an apparatus for the arrangement and a fibre-web forming machine equipped with the arrangement or device.

Finnish patent application number 20045068 and WO application publication number 03018909 disclose some examples of web- threading devices according to the prior art, based on vacuum- belt conveyors. In the disclosed vacuum-belt conveyors, the travel of the threading tail on the surface of the belt loop is based on the friction between the threading tail and the belt loop. In addition, the friction is proportional to the magnitude of the vacuum arranged inside the belt loop.

When web-threading devices known from the prior art are applied in drying sections based on twin-wire technology, uncertainty arises in web threading. Particularly in twin-run geometry, the threading tail easily wraps itself around the drying cylinder, i.e. the web-threading device passes it through'. The same problem also appears if the threading tail flutters strongly in the cross-machine direction.

Further, problems are also caused by the fact that a vacuum- belt conveyor (for example, the applicant's, known by the trade name DoubleForce 1) must be located only a few millimetres away from the drying cylinder. In that case, the wire of the belt conveyor can be easily broken if the threading tail wraps itself around the drying cylinder. In addition, the drying section must be made sufficiently cool for the duration of the web threading, so that the tail will not burn onto the drying cylinder. This delays running up production. Yet another problem is caused by the fact that it must be possible to move the vacuum belt conveyor away from the web line or the surface of the cylinder, so that it will not interfere with production running, or the changing of the fabrics.

A solution, in which a doctor element, for ensuring that the web-threading tail detaches from the surface of the drying cylinder, is fitted in front of the vacuum belt conveyor, is known from FI patent number 118182. The doctor element is supported on the vacuum belt conveyor. This makes it difficult to implement, especially in a twin-wire drying section, in which there is little space, and in which the vacuum belt conveyor must be able to be rotated to and from the web-threading position.

The present invention is intended to create an arrangement in the web threading of a fibre-web forming machine, which is simple to implement, and which permits the arrangement also to be used in positions with limited space. In addition, the invention is intended to create a device improving the operating reliability of a web-threading device. The characteristic features of the arrangement according to the invention are stated in Claim 1 and the characteristic features of the device are stated in Claim 16. In the arrangement according to the invention, at least the belt conveyor is equipped with at least a linear motion mechanism for moving it to, and correspondingly also from the web- threading position. By means of the linear motion, at least the belt conveyor is made to move certainly away from the threading position in connection with the machine elements, so that it thus will not disturb production, especially if the doctor device too is carried in connection with the belt conveyor to form a device package that is partly moveable and in which the devices are arranged tightly in connection with each other. On the other hand, the doctor device can also be equipped with its own fixed carriers. In that case too, the belt conveyor, which, in its operating position, is arranged tightly after the doctor device, can be moved away from the threading position.

According to one embodiment, the linear motion of at least the belt conveyor, or even of the belt conveyor and the doctor device attached to it, can take place at a small angle deviating from the machine's cross direction. In other words, at least the belt conveyor can be taken to its web-threading position at a slant relative to the width direction of the machine, thus avoiding a collision between the belt conveyor and, for example, the cylinder and/or doctor device. Thus, the belt conveyor can also be taken immediately behind the doctor device, without a risk of collision. On the other hand, the removal of the belt conveyor from the web-threading position can also be performed using slanting linear motion, without danger of damage. According to one embodiment, the arrangement can also include support for the belt conveyor and the doctor device, which, according to one embodiment, can be common to both of them. A common support allows the two operational devices to be fitted tightly next to each other with sufficient precision. This precision challenge increases, if at least one of the devices must be moved to, and correspondingly from, the web-threading position. In that case, when the moveable device is being moved to the threading position, it must be brought into a cramped space, while allowing for the other device that is already in the space, and/or the moving threading surface.

A common support for the belt conveyor and the doctor device simplifies arranging the doctor device in connection with the belt conveyor, particularly in cramped positions with limited space. In addition, the use of a common support achieves a precise placing of the belt conveyor and doctor device relative to each other, because it substantially affects the functionality of the arrangement in practice, when transferring the threading tail from the doctor device to the belt conveyor. One important advantage of a common support is thus the functional totality of devices located in a cramped space and tightly next to each other, which also permits at least the belt conveyor to be moved away from the threading position and correspondingly also returned to the threading position close to the doctor device .

According to one embodiment, air-blasts can be integrated in the blade-holder profile of the doctor device for one or more purposes. For example, detaching and draw blasts. The use of blasts achieves more reliable web threading and, in addition, allows the belt conveyor to be placed more freely, for example, closer to the web line during running. The air feed for the blasts can be taken from the feed line of the belt conveyor. In that case, the doctor blasts do not require their own blast- forming means. The actual threading device does not require alterations, so that the invention has good applicability to existing installations as well. The invention is also compatible with belt-conveyor transfer devices, and a conveyor equipped with the invention can be moved using articulated arms and linear guides. Numerous other significant advantages are achieved by means of the invention. These are, for example, a wider running window for intermittent steam in the drying section, a considerable reduction in belt-conveyor wire breaks, the more general elimi- nation of leakage problems, and the permitting of cross-direction flutter in the threading tail.

The device according to the invention and its loading, using, for example, a spring mechanism, can also be applied, for example, in blast-plate threading devices. Other additional advantages achieved by means of the invention appear in the description portion and its specific features in the accompanying Claims. The invention, which is not restricted to the embodiments presented in the following, is described in greater detail with reference to the accompanying drawings, in which

Figure 1 shows a side view of one example of the drying section of a fibre-web forming machine, equipped with the arrangement according to the invention,

Figure 2 shows an axial view of one example of an embodiment of the arrangement according to the invention, on a belt conveyor,

Figure 3 shows a second embodiment of the device according to the invention, not yet installed in its operating location,

Figure 4 shows a second example of an embodiment of an application location the device according to the invention applied to a blast-plate web-threading device,

Figure 5 shows a third example of an embodiment of the arrangement according to the invention, seen from the machine direction, and Figure 6 shows a schematic drawing of the movement mechanism of web-threading devices relative to the machine's cross direction, seen from the machine direction.

Figure 1 shows a side view of one example of the drying section of a fibre-web forming machine, equipped with the arrangement according to the invention. In the arrangement shown in the figure, there are five belt conveyors 10 for carrying the web- threading tail over the draws in the twin-wire drying section. The belt conveyors 10 belong to the arrangement, which is used especially for threading and guiding a web-threading tail in paper, board, and other similar fibre-web forming and finishing machines. In Figure 1, the belt conveyors 10 are shown in the operating position, i.e. in the threading position. During normal operation of the drying section, the conveyors 10 can be moved to the rest position.

A doctor device 23 is fitted in front of at least some of the belt conveyors 10, on the web-threading tail arrival side. It can be used to detach the web-threading tail from the moving surface 18 and guide it onto the belt conveyor 10.

In the known manner, the drying cylinders 11.1, 11.2 belonging to the drying section are arranged in two rows. However, Figure 1 shows neither the frame structures of the drying section, nor the bearing arrangements of the drying cylinders. In addition, in each row, there are auxiliary rolls 12.1, 12.2 between the drying cylinders 11.1, 11.2, which are used to guide the drying fabrics 13.1, 13.2 to travel through the consecutive drying cylinders 11.1, 11.2 in the row. However, while running, the web travels alternately from one row to the other. Thus, when production is started, the web-threading tail must first be taken from an opening throat 14 from one row, over the draw, to a closing throat 15 of the other row. In Figure 1, the threading tail in the draw is shown by a broken line. Each throat 14, 15 is formed at each time between the drying cylinder and wire of the same row. In practice, for the web threading to succeed, a belt conveyor 10, or some other web-threading device must be arranged in each draw. For example, there can be 20 - 30 belt conveyors in a drying section.

Thus, the arrangement includes at least one belt conveyor 10 to be fitted in connection with a drying cylinder 11.1, 11.2, and a doctor device 23 fitted in front of it, for carrying the web- threading tail. In practice, there are numerous belt conveyors in the arrangement, by means of which the web-threading tail is taken through the fibre-web forming machine, when production is started. Figure 2 shows an axial view of one example of an embodiment of the sub-components of the arrangement according to the invention. An individual conveyor 10 includes at least two return rolls 16, 17, which are supported by bearings on the frame structure 31 of the conveyor 10. According to one embodiment, the return rolls 16, 17 can be, for example, grooved rolls.

The frame structure 31 of the conveyor 10 is formed of side plates, which are supported on each other by suitable transverse structures. In addition, the conveyor 10 includes a belt loop 20, which is fitted around the return rolls 16, 17. In addition, the belt loop 20 is arranged to rotate in the direction of travel of the threading tail 22, supported by the return rolls 16, 17. In addition, a drive motor (not shown) is connected to at least one of the return rolls 16, 17, and thus to move the threading tail 22 in the web-forming machine.

A vacuum can be produced inside the belt loop 20, in the area between the return rolls 16, 17, with the aid of, for example, a vacuum box, Coanda blowing, or foil strips, more generally vacuum means (not shown) . In such a case, the belt loop 20 is usually an wire permitting air to penetrate. Also at least one, like, for example, the first return roll 16 on the threading- tail 22 arrival side 24, can have a vacuum, in order to bring the threading tail 22 under control on the belt conveyor 10. The means for creating the vacuum are not presented here in 5 greater detail.

In order to increase the operational capability of the belt conveyor 10, and thus also the success of the web threading, a doctor device 23 is fitted in connection with the belt conveyor

10 10, at least when it is in the threading position, in front of the belt conveyor 10 on the threading-tail 22 arrival side 24. By means of the doctor 23, the threading tail 22 can be detached from the surface 18 of the drying cylinder 11.1, 11.2, according to the embodiment of Figure 1. In practice, the belt

15 conveyor 10 is held onto the surface 18 of the drying cylinder 11.1, 11.2 by means of the doctor 23. The length of the doctor 23 in the axial direction of the cylinder 11.1, 11.2 can correspond to the length of the conveyor 10, or it can even be slightly wider than the conveyor, thus permitting lateral

20 flutter in the threading tail 22. More generally, the width of the doctor device 23 can be arranged to correspond mainly to the path of the threading tail 22. This means that the doctor 23 will be substantially narrower than full-width doctors, for example. A fibre-web forming machine equipped with a doctor

25 device 23 according to the invention has no need of full-width doctors, which offers great advantages in many ways.

The doctor 23 can be based on implementations known from the prior art, or which are still under development. The doctor 23 30 can consist of a holder 30, in which a place is arranged for a doctor blade 34 to be set against the moving surface 18.

According to one embodiment, at least one air blast 25, 26 for the web-threading tail 22 can be arranged in the blade holder 35 30. According to a first embodiment, the blast can be, for example, a detaching blast 26. By means of the detaching blast 26, which is, for example, parallel to the doctor blade and thus at least to some extent opposite to the direction of travel of the web-threading tail 22, the web-threading tail 22 is helped to detach from the moving surface 18, for example from the surface 18 of the cylinder 11.1, 11.2. The detaching blast is created by leading compressed air from openings 26 , which can be, for example, holes or gaps. In other words, the air blasts 25, 26 can be created without separate nozzles. According to one embodiment, the angle between the blowing direction of the detaching-blast openings 26 and the doctor blade 34 can be, for example, 15 - 30°.

After being detached by the doctor blade 34 and the detaching blast 26, the threading tail 22 is carried forward by the belt loop 20. According to one embodiment, in order to ensure that this operation is set in motion, also a threading blast 25 in the direction of travel may be used in the blade holder 30 along with, or instead of the detaching blast 26. The threading blast is created by leading compressed air from the openings 25. The threading blast 25 is used to ensure the transfer of the web-threading tail 22 from the doctor 23 to the belt conveyor 10. The angle between the detaching blast 26 and the threading blast 25 can be, for example, 120 - 150°. A comprehensive vacuum effect, which is sure to take hold of the web- threading tail 22, is then created by the combined effect of the air blasts 25, 26. This brings certainty to the operation of the device 10.

The diameters of the blast 25, 26 holes can be, for example, 1- 3 mm, more particularly 1,5 - 2,5 mm. The air consumption will then remain reasonable. In addition, separate nozzles are unnecessary. Depending on the grammage of the web-like material 22 being transported and the distance it is transported, the distance of the holes is selected case-specifically. Generally, the distance between the holes can be 10 - 50 mm, more particularly 20 - 40 mm, in such a way that the larger the holes, the farther they are from each other. Instead of being in a straight line, the holes can be positioned to overlap or be at an angle to each other, in order to orientate the vacuum effect as desired. The blasts 25, 26 can be in a shoulderless or flat 5 plate.

The blast 25, 26 openings can also be formed as gaps. The use of gaps creates extremely even air blasts and, in addition, the noise of air discharging from gaps is less than that of air

10 from holes. The width of the gaps can be, for example, 0,05 - 1 mm, more particularly 0,1 - 0,5 mm. The gaps too can be located in a straight line, or suitably overlapping, so that comprehensive and even air blasts 25, 26 will be achieved. The length of the gaps depends mainly on the case-specific require-

15 ments and the width of the gap.

Due to the simple construction and the small amount of friction, a wide variety of pressures can be used in the blasts 25, 26. According to one embodiment, the pressure can be, for

20 example, 0,25 - 7 bar, and even more particularly 0,5 - 2 bar.

In that case, even with a low pressure a significant force for transporting a web-like material 22 is achieved. On the other hand, a high pressure can also be used, which can be utilized especially to achieve a sufficiently high flow velocity. In

25 other words, the arrangement can also be used in high-speed fibre-web forming machines.

The doctor 23 holder 30 can be of, for example, plastic, plastic composite, or also drawn aluminium profile. Two adjacent

30 cavities, for example, which run in the longitudinal direction of the doctor 23, and in which holes have been machined to create blast openings, can be formed in the holder 30. There can also be separate cavities forming air connections for the detaching and threading blasts 25, 26, so that the blasts 25,

35 26 can be controlled independently of each other. The arrangement also includes support 50 for the belt conveyor 10 and the doctor device 23, which can be common to both of them. In the case according to the embodiment, an arm 41 is fitted to the structures of the belt conveyor 10. The doctor 5 device 23 is carried on one end 40 of the arm 41, in connection with the belt conveyor 10. Because the doctor 23 is short in length and thus also relatively light, compared, for example, to full-length doctors, the moment caused by the doctor 23 will remain small and carriers implemented from only one end will be

10 sufficient for it. In the conveyor 10, the carrier arm 41 can be on the side of the outer edge of the drying section, where it will not disturb production or collect strips of web forming in a break situation. According to one embodiment, the arm 41 can be attached by the collar 19 to the exit side 27 of the

15 belt conveyor 10, for example, to its feed line 21, or even more generally to its existing carrier arrangements. In that case, the arm 41 is mainly on a line joining the frame line of the conveyor 10, which will facilitate the approximate positioning of the doctor 23. Thus, it is very simple to add the

20 device 23 according to the invention to existing constructions.

The carrier arrangements of the doctor 23 on the side on the feed line 21 of the conveyor 10 also offer the advantages in arranging the air blasts 25, 26. The feeding of the air blasts

25 25, 26 can then be taken from the belt conveyor's 10 feed line 21. Sufficiently little blowing power is bled from the conveyor for this to have no substantial effect on its operation. In addition, a small bled air flow will be quite sufficient for the relative short doctor 23. At least some of the air-blast

30 25, 26 feed lines 43 can be arranged inside the arm 41, so that they too are protected and thus cannot collect break web. The feed lines 43 can continue as an air connection over the entire length of the doctor 23.

35 The arrangement can also include loading elements 32 for loading the doctor 23 against the moving surface 18. According to one embodiment, the loading elements 32 can be fitted to the arm 41, for example, at its end 42 next to the doctor 23. One example of a loading element 32 is a coil spring 29, which is fitted around a shaft 28 fitted to the end 42 of the arm 41, and which is arranged in such a way that the coil spring 29 presses the doctor blade 34 through its holder 30 against the moving surface 18, such as the surface 18 of the cylinder 11.1, 11.2 (Figure 1) . In the shaft 28, there can be an arrester lever 33, which limits the movement of the doctor 23 and is supported on the arm 41, and by means of which contact of the doctor 23 with the cylinder 11.1, 11.2 is prevented (Figure 1) .

The mechanical loading element 32 is reliable in operation and additionally permits a situation, in which the loading system of the doctor 23 does not require its own solenoid valves or piping, more generally a separate rotating mechanism, for the doctor 23 to be brought into contact with the drying cylinder 11.1, 11.2. In addition, thanks to the spring element 29, the doctor loading remains constant for the entire wearing time of the doctor blade 34. In other words, a continuous loading is created on the doctor 23 by means of the loading elements 32. Of course, the construction of the loading elements can vary in different embodiments and they can also be implemented in other ways. The use of the loading element 32 also permits the com- pact device package formed by the belt conveyor 10 and the doctor device 23 to be brought against the moving surface 18. The spring loading 32 receives the contact against the surface 18 being doctored, when the device package is taken next to the cylinder 11.1, 11.2 for web threading. At the same time, the spring loading forms the loading of the doctor device 23 for doctoring the threading tail 22.

In the case according to the embodiment, the belt conveyor 10 and also the doctor device 23 connected to it is equipped with at least a linear-motion mechanism 54, 55, for moving it into the threading position and correspondingly away from it into the protection of the frame of the machine. The mechanism equipped with an operating device includes a set of arms 55, which is connected, for example, to the frame structures of the belt conveyor 10, or to the feed line 21. Part of the set of arms 55 acts as the piston rod of the medium-operated linear- motion device. The mechanism also includes the cylinder part 54 of the operating device, relative to which the piston rod 55 can move in and out. The linear-motion mechanism is supported from the cylinder 54 on support 50 belonging to the arrange- ment, which is now common to both the belt conveyor 10 and the doctor device 23. The support 50 includes a common support frame 51 for the belt conveyor 10 and the doctor device 23 connected to it, to which is fitted a carrier 53 equipped with an operating-device linear-motion mechanism 54, 55, for the belt conveyor 10 and the doctor device 23. The doctor device 23 is preferably supported moveably in connection with the belt conveyor 10, so that the linear motion moves both of these to the web-threading position, at the same time using spring means 32 to press the doctor device 23 against the moving surface 18.

Figure 3 shows a device 23 for a web-threading arrangement in a fibre-web forming machine, which can be applied in operation, for example, in connection with a vacuum-based web-threading device 10, 100. The device 23 is now shown not installed in connection with the arrangement. The web-threading device 10, 100, to which the device 23 can be fitted, can be carried on the fibre-web forming machine. At least one feed line 21, by means of which the factor creating the vacuum can be produced in the threading device 10, 100, can be fitted to the vacuum connection of the threading device 10, 100. The feed line 21 can also act as the carrier means of the threading device 10, 100, or the threading device 10, 100 can also be equipped separately with actual carrier means (reference numbers 51 and 53 in Figure 5) , by means of which the threading device 10, 100 is supported on the frame of the fibre-web forming machine (reference number 56, Figure 5) . The device is a doctor 23 that can be fitted directly to the threading device 10, 100 on the threading-tail 22 arrival side 24, and which can be carried on the threading device 10, 100, for example, on the feed line 21, or other existing frame carriers 51, 53 of the threading device 10, 100. The doctor device 23 includes a blade holder 30, in which a place for a doctor blade 34 is fitted and at least one blast 25, 26, which is fitted to the blade holder 30.

Another example of the web-threading device, in which the device 23 according to Figure 2 or 3 can be applied, is, besides the belt conveyor 10 described above, also a threading device 100 based on blast plates and shown in Figure 4. In it, the same reference numbers as in the device 10 of Figure 2 are used for components that are functionally similar. The basic technology of a threading device 100 based on blast plates is disclosed in, for example, FI patent number 78528. However, it can be stated that, in general, in such devices 100 there is a threading surface, on which air blasts are used to form a vacuum effect, with the aid of a so-called Coanda effect. In other words, the web-like material seeks to follow the threading surface, while at the same time air blasts in the direction of travel of the web-like material carry the material forward.

Figure 5 shows a third example embodiment of the arrangement according to the invention, seen from the machine direction. The same reference numbers as in the embodiment of Figure 2 are used for components that are functionally similar. Now too, at least the belt conveyor 10 is equipped with at least a linear- motion mechanism 54, 55, for moving it to, and correspondingly away from the threading position. The mechanism can be a similar type of cylinder-piston operating device to that already described earlier in the embodiment of Figure 2.

The arrangement now also includes support 50 for the belt conveyor 10 and the doctor device 23, which is common to both of these, at least on the level of the machine frames. The support 50 includes a common support frame 51, fitted to the machine frame 56, for both the belt conveyor 10 and the doctor device 23. Fitted to the support frame 51 is a fixed cross- direction carrier arm 52 for the doctor device 23, and a car- rier arm 53, equipped with a linear-motion mechanism 54, 55 for the belt conveyor 10. In addition to linear motion, the belt- conveyor 10 carrier 53 can also be equipped with a rotation mechanism 58 for rotating the carrier 53 at least in the vertical direction. The rotation mechanism 58 can be used to perform the final alignment and contact of the belt conveyor 10 and, in addition, of the possible doctor device 23, with the web- threading surface 18, especially if they are brought to the threading position at a small angle. In other words, by means of the rotating movement of the arm 53, the belt conveyor 10 by itself can be rotated in such a way that its arrival side 24 can be aligned with the exit side of the doctor device 23, as required by web threading. On the other hand, when the belt conveyor 10 and the doctor device 23 are in the same moveable device package, both can be rotated through the carrier arm 53, in such a way that the blade 34 of the doctor 23 presses against the surface 18 and its spring loading begins to act on the surface 18. Using the upper cylinder 11.1, the device package can be rotated upwards when being transferred to the web- threading position, and correspondingly downwards using the lower cylinder 11.2.

In Figure 5, a broken line is used to show the rest position of the belt conveyor 10 next to the machine frames. The distance of movement of the belt conveyor 10 in the cross direction CD can be, for example, in the order of about 1 metre, away from the line travelled by the threading tail. The linear-motion mechanism can include slide guides and a cradle arrangement (not shown) arranged to travel in them. In this embodiment too, there are blasts 25, 26 in the doctor device 23, described in greater detail in Figure 2. The connec- tions for the blasts 25, 26 are shown at the right-hand end of the holder 30. At least some, and preferably all of the blasts can be arranged in the shoulderless surface of the holder 30, when the best control of the web-threading tail will be 5 achieved. In addition, between the doctor device 23 and the belt conveyor 10 there can be a flat threading surface 60 after the doctor holder 30, the length of which can be, for example, 100 - 200 mm in the direction of the belt conveyor 10. The threading surface 60 will steady the movement of the tail 22.

10

Further, the arrangement also includes loading elements 59 for loading the doctor 23 against the moving surface 18 and correspondingly also for detaching it. The length of travel of the loading can be, for example, 10 - 40 mm, for example 20 mm.

15 According to one embodiment, at least some of the loading elements can be hose-loading means 59. The compressed-air connections of the loading are shown at the right-hand end of the doctor device 23. According to one embodiment, the opening/loading of the doctor 23, the blast for detaching the tail

20 22 from the doctor 23/carrying it forwards to the belt conveyor 10, the creation of a vacuum in the belt conveyor 10, the transfer of the belt conveyor 10 to the threading/protection position, and the blast from the belt conveyor onwards can all operate using a single pressurized medium, i.e. air. Figure 5

25 shows five connections for the air connections. One of these is in the belt conveyor 10 (when its exit blast will be from an internal pipe) , two are for the loading movement of the doctor 23, and two for the doctor blasts 25, 26. On the other hand, the loading of the doctor blade 34 against the surface 18, for

30 example, can take place by means of hose loading and correspondingly its detaching from the surface 11.1, 11.2 of the cylinder by means of spring loading, which will reduce the number of connections.

35 Figure 6 shows a schematic drawing of an example of the alignment of the belt conveyor 10, and now also the doctor device's 23 movement mechanism connected to it, relative to the cross- direction CD, when viewing the situation from the machine direction, and based on the embodiment of Figure 5, but now with a common structure for the doctor 23 and the belt conveyor 10. The path of movement of the linear-motion mechanism 54, 55 of the belt conveyor 10 can be, surprisingly, arranged to deviate slightly from the machine's cross direction CD. In other words, at least the belt conveyor 10 can be taken to its position during web threading at a small angle a relative to the cross direction CD, which is shown in Figure 6 by an arrow with a broken line. The angle movement of the device package 10, 23 to its web-threading position can be implemented by running it by a linear movement slantingly against the surface 18 of the lower or upper cylinder 11.2, or at least next to it. In this case, the deviation from the machine's cross direction CD is mainly vertical. This avoids the possibility of the belt conveyor 10 colliding with the cylinder 11.1 or the stationary doctor device 23, as is now the case in the embodiment of Figure 5 (doctor) and Figure 6 (cylinder) . This advantage is important, because in the web-threading position the belt conveyor 10 follows the doctor 23 very closely. The belt conveyor 10 itself can be at the end of the piston rod 59 parallel to the machine direction. If the doctor device 23 is a spring-loaded device 23 according to Figure 2, the spring force can take a small alignment deviation while at the same time pressing to load the doctor. Thus, the alignment deviation from the machine's cross direction CD need not necessarily be very great.

Compared to the threading tail being picked directly off cylinder 11.1, 11.2 by the belt conveyor, the arrangement according to the invention can also be used to arrange a small gap between the doctor 23 and the belt conveyor 10, thus preventing the web-threading tail 22 from winding itself around the belt conveyor 10, also reducing the air transported by the belt 20 of the belt conveyor, and improving the operation of the belt conveyor 10. Whether or not there is a gap between the devices, at least the linear motion arranged for the belt conveyor 10 ensures that the parts of the device package are precisely aligned relative to each other and, in addition, that their presence does not disturb production.

It should be understood that the above description and the related figures are only intended to illustrate the present invention. The invention is thus in no way restricted to only the embodiments disclosed or stated in the Claims, but many different variations and adaptations of the invention, which are possible within the scope on the inventive idea defined in the accompanying Claims, will be obvious to one skilled in the art.

Claims

1. Arrangement in tail threading of a fibre-web forming machine, which is fitted to a twin-wire draw drying section, and which includes at least one belt conveyor (10) , for threading the web-threading tail (22) , to be fitted in connection with at least one drying cylinder (11.1, 11.2), which belt conveyor (10) includes

- a frame structure (31) and at least two return rolls (16, 17) in it,

- a belt loop (20) penetrable by air, which is arranged to run over the return rolls (16, 17),

- vacuum means (21) for creating a vacuum in the belt loop (20),

and which arrangement includes, in addition, a doctor device (23) fitted in front of the belt conveyor (10), on the web- threading-tail ( 22 ) arrival side (24), the width of which doctor device (23) is arranged to mainly correspond to the path of the web-threading tail (22) , characterized in that at least the belt conveyor (10) is equipped with a linear-motion mechanism (54, 55) , for moving it to the web-threading position and correspondingly away from it.

2. Arrangement according to Claim 1, characterized in that the path of the linear-motion mechanism (54, 55) is arranged to deviate from the machine' s cross direction (CD) .

3. Arrangement according to Claim 1 or 2, characterized in that the arrangement includes support (50) for the belt conveyor (10) and the doctor device (23), which is common to both of them.

4. Arrangement according to Claim 3, characterized in that the support (50) includes a common support frame (50) for the belt conveyor (10) and the doctor device (23), to which are fitted

- a fixed carrier (52) for the doctor device (23), - a carrier (53) , equipped with a said linear-motion mechanism (54, 55), for the belt conveyor (10) .

5. Arrangement according to Claim 3, characterized in that the 5 doctor device (23) is carried on the structures of the belt conveyor ( 10 ) .

6. Arrangement according to Claim 5, characterized in that, at one of its ends (40), the doctor device (23) is carried on an

10 arm (41) on the structures of the belt conveyor (10) .

7. Arrangement according to any of Claims 1 - 6, characterized in that the carrier (53) of the belt conveyor (10) is equipped with at least a vertical rotation movement mechanism (58).

15

8. Arrangement according to any of Claims 1 - 7, characterized in that at least one blast (25, 26) is arranged in the doctor device (23), for the web-threading tail (22).

20 9. Arrangement according to Claim 8, characterized in that the doctor device (23) includes a holder (30), in which a place is arranged for the doctor blade (34) and the said at least one blast (25, 26) is arranged in the blade holder (30) .

25 10. Arrangement according to Claim 8 or 9, characterized in that the blast is a detaching blast (26) , by means of which the web-threading tail (22^') is arranged to be detached from the moving surface (18).

30 11. Arrangement according to any of Claims 8 - 10, characterized in that the blast is a threading blast (25) , by means of which the web-threading tail (22 ) is arranged to be transferred from the doctor device (23) to the belt conveyor (10) .

12. Arrangement according to any of Claims 8 - 11, characterized in that at least some of the blasts (25, 26) are arranged on a shoulderless surface.

5 13. Arrangement according to any of Claims 1 - 12, characterized in that the arrangement includes loading elements (32, 59) for loading the doctor device (23) against the moving surface (18) and correspondingly detaching it.

10 14. Arrangement according to any of Claims 6 - 13, characterized in that the arm (41) is arranged rotatably in connection with the belt conveyor (10).

15. Arrangement according to any of Claims 1 - 14, character- 15 ized in that a threading surface (60) is arranged between the doctor device (23) and the belt conveyor (10).

16. Device for an arrangement according to any of Claims 1 - 15, which device is a doctor device (23), which is fitted in

20 the direction of travel of the web-threading tail (22) immediately before the web-threading device (10), characterized in that the doctor device (23) includes a blade holder (30), in which a place is arranged for a doctor blade (34), and at least one blast (25, 26), which is arranged in the blade holder (30).

25

17. Device according to Claim 16, characterized in that the web-threading device is a belt conveyor (10) .

18. Device according to Claim 16, characterized in that the 30 web-threading device is a blast plate (100) .

19. Fibre-web forming machine, characterized in that it includes at least one arrangement according to any of Claims 1 - 15, or at least one device (10, 100) according to any of Claims

35 16 - 18.