The present invention relates to an arrangement in a fiber web machine, which includes

- at least one supporting draw, in which the web is arranged to travel supported on one side by a support surface,

- blowing means fitted to at least one supporting draw, in order to create blasts directed to the edge area of the web, which blowing means are in the area of the web and support surface in the cross direction of the machine .

In addition, the invention also relates to an apparatus. The use ,of relatively large tension differences in the group gaps of the drying section of a fiber web machine, i.e. the tensioning of the web, is known from the prior art. One reason for this is an opening/closing throat between a drying cylinder and the drying fibre, which determines the minimum tension difference.

Figure 1 shows a schematic diagram of a group gap of the drying section of a fiber web machine, seen from the side. The edge of the web W is drawn exaggeratedly in the figure, in four differ- ent running states. The edge can be on the drying cylinder 18.1 or detached to different degrees from the surface of the drying cylinder 18.1 in connection with the supporting draw 10.2, in which the web W is supported on one side against the surface of the drying cylinder 18.1. Equally, the group draw can also be a mirror image of the group gap of Figure 1. In that case, the web W would run in the opposite direction and the detaching of the web edge for the drying cylinder would increase in the upward direction. The magnitude of the tension differences is precisely one possible explanation that has been presented for the behaviour of the web edge. It has been suggested that, apart from the paper grade, it is precisely the use of large tension differences that keeps the web edge better attached to the support surface, when it is supported on one side in a gap. However, a large tension difference (for example, of as much as 4 - 5 %) is disadvantageous, for example, in terms of the quality of the end product, so that attempts should be made to reduce the tension difference. In addition, the stock must be ground more due to the large tension differences.

When the tension difference has been reduced, the edge of the web W has been observed to begin detaching in the end portion of the unsupported area 10.2. Further, if the reduction of the tension difference is continued, this will lead to the detach- ing from the cylinder 18.1 taking place as early as the throat 22 opening between the drying fabric 23.1 and the cylinder 18.2. Besides the tension difference, detaching may also be affected by many other factors, for instance, the running speed, the dry substance, and/or the stock.

In addition, the stretching of the unsupported edge of the web, which results in the web detaching from the support surface, causes creases and breaks. The breaks reduce production while creases cause reject, because the edges of the web must later be cut off.

German patent application publication DE 199 53 530 Al discloses a solution for controlling the edges of a moving paper or board web after an opening throat, in which a one-side fabric leaves the web and the web continues to travel, supported on a fabric beneath it. After the opening throat, a blast of air is directed towards the- opening throat using blowing means fitted on top of the web. In other words, the air blast is then directed against the direction of travel of the web. The present invention is intended to create an arrangement and apparatus for a fiber web machine, the construction and operation of which are simple, and by means of which the edges of the web will be certain to remain attached on the support surface while also preventing the stretching of the edge areas of the web. The characteristic features of the arrangement according to the invention are presented in Claim 1 and those of the apparatus in Claim 11. In the invention, blowing means are fitted to at least one draw, a supporting draw, supporting the web one-sidedly against a support surface, in order to create blasts directed at the edge area of the web. The blowing means are adapted mainly to the ¹ shape of the supporting draw and the blasts, at least one of which has a cross-direction component, are directed at an edge area of the web that lies against the support surface. Thus, the support effect of the blasts is made very effective and the edge of the web is made to remain securely against the support surface, thus preventing the web, and particularly its edge areas, from detaching from the support surface.

An example of a position for applying the invention are the group gaps at the beginning of the drying section of a fiber web machine and quite especially the first group gap. A second application position is the web run immediately at the beginning of the drying section, before the first cylinder, on the undersurface of the drying fabric. Thus, the supporting draw can be straight or curved. In addition, the invention can also be applied in the press or drying section, in which the web is supported on only one side, for example by a felt, metal belt, or roll.

The blowing means, by means of which the invention can be implemented, can be a surprisingly simple totality. According to one embodiment, the blowing means can consist of, for example, at least one elongated tube component, in which a blowing arrangement is arranged in the longitudinal direction, for creating blasts ^' . Instead of a tube component, several consecutive tube components, or for example blast plates, can be arranged in the direction of the draw. Thus, the construction and operation of the arrangement and apparatus are very simple and reliable in operation.

According to one embodiment, the blowing means can be equipped with an operating-device mechanism. Using it, they . can be moved into the draw and also away from the draw. Thus, the arrangement and apparatus are not sensitive to breakdowns, indeed the blowing means can even be made to self-retract away from the supporting draw _/ in a possible breakdown situation in the fiber web machine, or during tail threading.

Through the invention, a fiber web machine can be run using a small tension difference and/or a high running speed and/or reducing the tensive-strength ratio. In addition, through the invention the energy required for stock grinding can also be saved. Other additional advantages achieved by using the invention appear in the description portion and the characteristic features in the Claims.

The invention, which is not restricted to the embodiment pre- sented in the following, is described in greater detail with reference to the accompanying figures, in which shows the problem according to the prior art in the behaviour of the web edge in the drying section of a fiber web machine, shows the drying section of one fiber web machine and example positions for the arrangement,

shows the start of the drying section according to Figure 2 and some examples of the locations of the arrangement, in greater detail,

Figure 4 shows a perspective view of examples of the application of the arrangement,

Figures 5a - 5c show the application examples of Figure 4, examined from different directions,

Figure 6 shows application examples of the operating-device mechanism of the blowing means ,

Figure 7 shows one example of the blowing component and its end construction, and

Figure 8 shows schematically one example of the dimensions relating to the arrangement of the tube component, seen in the machine direction .

Figure 2 shows a schematic side view of one example of the drying section 38 of a fiber web machine. The fiber web machine can be, for example, a paper or board machine, a cellulose machine, or a tissue machine.

A hood 14, the main purpose of which is to prevent heat from escaping, shown in principle by broken lines, is arranged around the drying section 38. Consecutive groups 16.1, 16.2, 16 are fitted inside the hood 14 in the drying section 38. The drying group 16.1, 16.2, 16 includes cross-direction elongated and cylindrical machine components supported rotatably at both ends in the web-forming machine. The drying cylinders 18', 18, by means of which the web is dried, and turnover rolls 19 are shown as such a- machine component in Figure 2.

The drying section 38 of the web-forming machine of Figure 2 includes seven consecutive drying groups 16.1, 16.2, 16. In this case, the drying groups 16.1, 16.2, 16 are all single-wire draws. Here, each drying group 16.1, 16.2, 16 is formed of alternating drying cylinders 18, 18' and vacuum rolls 19 acting as turnover rolls, arranged on different levels, through which one drying wire 23.1, 23.1, 23 is arranged to run as a supported endless loop, in order to carry the web. The drying group 16.1, 16.2, 16 is defined by the drying-fabric circula- 5 tion 23.1, 23.2, 23.

When the web being manufactured on the fiber web machine is brought to the start of the drying section 38 from the machine section 28 preceding the drying section 38, it is guided to a

10 closing throat formed by the first drying cylinder 18' and the drying wire 23.1. In other words, the web presses against the hot outer surface of the jacket of the drying roll 18'. Next, the drying wire 23.1 runs around the vacuum roll 19, the vacuum effect created by which together with the pocket space of the

15 vacuum roll (not shown) extends through the drying wire 23.1, keeping the web under control until the next closing throat. Thus, the web is taken through the consecutive drying groups 16.1, 16.2, 16, while the web dries at the same time. At least some of the drying groups of the drying section 38 can also be

20 double-wire draws (not shown) . In that case, there will be hot drying cylinders in the upper and lower rows of the drying group .

In the drying section 38 according to Figure 2, there can be at 25 least one web draw arranged as a gap supported on only one surface, the supporting draw 10.1, 10.2. In the .supporting draw 10.1, 10.2, the web lacks two-sided support. Thus, in the supporting draw 10.1, 10.2, the web is carried in the machine direction on a one-sided support against the support surface 30 18.1, 23.1. Without support on both sides, the web can be allowed to live also in the cross direction, which, from Figure 4, is marked with the reference marking CD.

Figure 3 shows a rough schematic diagram showing in greater 35 detail the start of the drying section 38 according to Figure 2. Now the reference numbers 10.1 and 10.2 refer to two one- sidedly supported draws. The first of these draws 10.1 is before the first drying cylinder 18' of the drying section 38. Here, there web is taken to the drying fabric 23.1, supported by runnability components, such as blowing boxes 39 (the appli- cant's PressRun item). The runnability components can be based, for example, on the creation of a vacuum supporting the web against the fabric 23.1. In the first draw 10.1, the fabric

23.1 acting as a support surface is thus on the upper surface of the web and the draw 10.1 closes in a closing throat formed by the fabric 23.1 and the drying cylinder 18'. The second draw

10.2 is between the first and second drying group 16.1, 16.2 (inset in Figure 3, and Figure 4) . In it, the last drying cylinder 18.1 of the drying group 16.1 acts as the draw of the web W. The draw 10.2 is supported one-sidedly, starting from the opening throat 22 formed by the drying cylinder 18.1 and the fabric 23.1 arranged to run through the guide roll 29.

As can be seen from the inset in Figure 3 and' from Figure 4, blowing means 12 are fitted in the drying section 38 to at least one one-sidedly supported supporting draw 10.2, which in this case is a group gap. Figures 5a - 5c show schematically the example application of Figure 4, seen from different directions. As the figures show, the blowing means 12 are arranged to form blasts 20 directed at the edge area 13 of the web W. The blasts 20 are formed using air or some other gaseous medium 41 using the blowing means 12, which are suitably directed to the edge area 13 of the web W and at the surface of the web W against the support surface 18.1 at the point of impact of the blast 20, and prevent the edges 13 of the web W from detaching and thus hold the edges 13 of the web W on the surface of the drying cylinder .18.1 acting as the support surface. At the same time, the stretching of the edges 13 of the web W due to detaching is also prevented. When in the operating position, the blowing means 12 can be on top of the web W and thus also of the drying cylinder 18.1 acting as the support surface. In other words, the blowing means 12 are, in the machine's cross-direction CD (Figures 4 - 7), in the area of the web W and the support surface 18.1, and in this case even more particularly on top of them. Thus, the 5 blowing means 12 are outside the fabric circulations 23.1, 23.2, 23. The blowing means 12 are used to improve the runnability of the fiber web machine and the quality of the web , especially its edge areas 13. In addition, the tension difference between the drying groups 16.1, 16.2 can be reduced, 10 because the blasts 20 hold the edge 13' of the web W securely on the support surface 18.1.

According to one embodiment, the blowing means 12 can include at least one elongated tube component 15, which can be arranged

15 mainly in the shape of the supporting draw 10.2. In other words, the blowing-device arrangement 12, will then consist of at least one tube component 15, covering operationally the edge 13' of the web W for a specific length in the direction of travel of the web W. The tube component 15 can be fitted to a

20 free length of the fabric 23.1, 23.2, except, however, for safety zones, which prevent the tube component 15 from striking the fabrics 23.1, 23.2 or other nearby structures. The length of the tube component 15 can be, for example 100 - 1200 mm, more particularly 300 - 900 mm, in the direction of travel of

25 the- web W. Instead of a single tube component 15, several shorter tube components (not shown) can also be used to create the desired effect.

In the group gap of the drying section 38, the tube component 30 15 is curved, with a radius that is slightly greater than the radius of the drying cylinder 18.1. Of course, a tube component 15 with a radius corresponding to that of the drying cylinder 18.1, or even slightly less, may be possible. The tube component 15 acts as a kind of manifold, to which at least one 35 blowing arrangement 27 (Figure 7) is fitted, arranged in an inline configuration 17, in the longitudinal direction of the draw 10.2 and thus also of the tube component 15. The blowing arrangement 27 is fitted to the tube component 15 in such a way that, when the tube component 15 is in the operating position in the group gap, the blowing arrangement 27 is pointed towards the edge area 13 of the web W, to create blasts 20 aimed at it. Such a tube component 15 with a simple construction and shape can be easily arranged in a cramped one-sidedly supported draw 10.2. An elongated tube component 15 adapted to the edge area 13 of the web W and to the shape of the draw 10.2 can also be easily retracted from the draw 10.2, for example, in connection with a web break.

According to one embodiment, the width of the area of effect 13 of the blasts 20 (Figures 5a and 5b) from the edge 13' of the web W can be, for example, 0 - 250 mm. Thus, the area of effect 13 of the blasts 20 can be, for example, 1 - 10 % of the full width of the web W, depending on the machine width. The problem, which the arrangement solves, is typically associated with the very edge area 13 of the web W.. There is thus no need for the blowing tube 15 to protrude very deeply into the supporting draw 10.1, 10.2 in the cross direction CD, which also makes it easier to fit the arrangement in association with a cramped supporting draw 10.1, 10.2 and to retract the tube component 15 from the supporting draw 10.1, 10.2 during a possible breakdown or tail threading. When in the operating location, the blowing- tube component 15, which is elongated in the direction of travel of the web W, is at a distance from the edge 13' of the web W in the machine's cross direction CD. The dimensioning and operating parameters of the blowing means 12 can be defined application-specifically, for example through simulation and/or trial and error. According to one embodiment, the pressure of the blowing medium 41 fed to the tube component 15 and directed from the blowing arrangement 27 to the surface of the web W can be 10 kPa - 1,0 MPa, more particularly 20 kPa - 0,8 MPa, for example 0,6 MPa. When using a low pressure of, for example 20 kPa and a blowing tube 15 with a large mozzle (for example, 3 mm), blower air can be used as the medium 41. Correspondingly, when using small nozzles 27 (for example 1 mm), compressed air at, for example, 0,2 MPa can be used as the blowing medium 41.

The blowing angle a of the blasts 20, created by the blowing arrangement, directed to the surface of the web W (Figure 5a: relative to the level defined by the small distance d between the tube component .15 and the web W) , can be 35° - 75°, more particularly 50° - 70°, for example 60°. At least some of the blasts 20 can then be directed from the draw 10.2 at a slant outwards in the cross direction CD. In other words, at least some of the blasts 20 have a cross-direction CD component B _CD (Figure 8) . The blast from the ends of the tube component 15 can also be directed at the same edge area 13 of the web , at a different angle to the centre part of the tube 15. The distance D (Figure 5a) of the blowing means 12 from the surface of the web W can be 10 - 80 mm, more particularly 20 - 60 mm, for example, 40 mm.

The diameter of the tube component 15 can be, for example, 8 - 50 mm. A blowing arrangement 27 with a curved configuration can be formed from a group of discrete openings arranged in the tube component 15. The openings 27 can be, for example, circular, oval, or gap-shaped. Various nozzles can be fitted to the openings 27, by means of which, for example, a fan-shaped blast of the blowing medium 41 can be created, which will thus be wide and extensive. The openings 27 can be at a distance of, for example,. 20 - 40 mm from each other, which can be even smaller than this at the ends of the tube component 15. Such a tube component 15 with openings 27 is very simple to manufacture. In addition, a curved tube component 15 will also permit the blasts 20 even to partly overlap each other. The mutual distance of the openings 27 in the tube 15 can then be in- creased and operation will be possible with even a smaller amount of air, or a lower pressure.

According to one embodiment, the wall thickness of the tube component 15 can be selected in such a way as to create an effect directing the blast in the opening 27. This is also affected by the diameter of the opening 27. If the diameter of an opening 27 created by drilling is, for example, 1 mm, then the wall thickness of the tube element 15 can be, for example, twice the diameter of the opening 27. A jet of air 20 discharging from the opening 27 can then be directed and guided in the direction of the drill hole. In other words, the wall thickness of the tube component 15 can be adapted to the opening size of the blowing arrangement 27, so as to direct the blast 20 as desired.

Figure 6 shows an embodiment of the device 40, which can, for example, during a web break or tail threading, be retracted from supporting draw 10.1, 10.2. For this purpose, the tube component 15 belonging to the device 40 can be equipped, for example, with a pneumatic operating mechanism 25, to move it into the draw 10.1, 10.2 (operating position) and correspondingly also away from the draw 10.1, 10.2 to outside the end of the roll 18.1 (break-situation position) . According to one embodiment, the operating-device mechanism 25 can include overload protection 26 to retract the tube component 15 from the supporting draw 10.1, 10.2, during a breakdown or tail threading. According to Figure 6, the operating-device mechanism 25 can be, for example, a double-acting pneumatic cylinder 31, to the end of the piston rod 34 of which the tube component 15 is fitted. The cylinder 31 can be rotatably pivoted at its opposite end, relative to the piston rod 34. According to one embodiment, the overload protection 26 can consist of a slot 35 fitted to the piston rod 34, a catch 33, the point of which fits into the slot 35, and a loading spring 32 fitted to the opposite side of the cylinder 31 relative to the catch 33.

When the tube component 15 is in connection with the supporting draw 10.1, excess pressure is maintained in the cylinder part 31.1 fo the cylinder 31, or there can also be a spring there. The spring 32 presses the operating-device package 31, 34 and especially the rod 34 against the catch 33. When the loading F increases, for example as a result of a plug of web caused by a break, the operating-device totality 31, 34 rotates around the pivot point 36 and as a result the rod 34 and the catch lose their mechanical, click-locking slot-claw contact. The excess pressure loaded in the cylindrical part 31.2 on the piston-rod 34 side moves the nozzle structure 15 to a safe distance from the draw 10.2. By means of a linear movement of the rod 34, the nozzle construction 15 can be moved back to the draw 10.2 using the pressure loaded in the cylindrical part 31.1 of the pivot-point 36 side of the cylinder 31, which acts on the piston 37. Once the nozzle construction 15 has reached its operating position, the point of the catch 33 engages in the slot 35 in the rod 34, due to the loading of the spring 32. The operating-device mechanism 25 and overload protection 26 are very simple in construction and, in addition, reliable in operation.

Figure 7 shows one embodiment of the tube component 15 equipped with a blowing arrangement 27. The blowing arrangement can be formed, for example, of a group of in-line 17 blowing openings 27 in the longitudinal direction of the tube 15, i.e. in the direction of the draw of the web W. As can be seen from Figure 7, according to one embodiment, the openings belonging to the blowing arrangement 27 can be arranged in the tube component 15 in at least one, or as in this case, even several rows 17, 30. If the blowing arrangement 27 is in two or more rows 17, 30 (or if the invention is implemented, for example, using two parallel blowing tubes 15) , then pressures and/or hole sizes differ- ing from each other can be used in the blowing holes 27 of the different rows 17, 30. Equally, the pressures and hole sizes can also differ in the direction of the draw 10.1, 10.2. The preferred embodiment is a single row of holes 17 with the same pressure and hole size.

In addition, the blast angles ot _lr a ₂ of the different rows 17, 30 can differ from each other. In that case, every second blowing opening in the direction of the draw 10.1, 10.2 can blow medium 41 onto the web W at a first angle a ₁ and every other blowing opening at a second angle ₂ . Thus, a more even blowing effect, covering a greater area from the edge of the web W, is created on the edge 13' of the web . According to the embodiment shown in Figure 7, the tube component 15 can also be equipped with at least one end shaping 21. The end shaping 21 can be rounded, for example a spherical surface, the blowing arrangement 27 fitted to which being directed not only to the edge area 13 of the web W, but also at a slant towards the throat 22, 24. In addition, the end shaping 21 can include a flat surface (not shown) arranged to be smoot- h, which is directed against the fabrics 23.1, 23.2. Thus, the tube component 15 can be taken safely very close to the moving surface and can be used to obtain a comprehensive . effect over a relatively large length of the supporting, draw.

According to one embodiment, at least the end of the tube component 15 that faces the openings throat 22 can be equipped with blasts 20 directed towards the throat 22. This will ensure from the beginning that the edge 13' of the web W will remain attached to the support surface. The blast 20 can equally be directed not only to the opening throat 22, but also to the closing throat 24. The mutual distance of the blowing openings 27 at the ends of the tube component 15 can be less than the 20 - 40 mm stated above, even only a few millimetres. The support blasts 20 directed to the edge 13' of the web W can then be made to continue also partly in the direction of travel of the web and against it.

Figure 8 shows •schematically one example of the dimensions relating to the arranging of the tube component 15, the arrangement being examined particularly from the point of view of the impact point A of the blasts 20. The distance L of the tube component 15 from the point of impact A of the blast 20 on the surface of the web can be, for example, 100 mm. The blast 20 will then strike the edge area 13 of the web . In particular, the blast 20 strikes near the edge 13' of the web W in such a way that most of the blast 20 strikes the web , holding it onto the support surface 18.1. In pilot-stage tests, it has been observed that, if the point of impact A of the blast 20 misses the edge 13' of the web W, for example, by 20 mm or more, problems begin to appear at the edge 13'. On the other hand, the tube 15 can be moved up to 50 mm farther from the edge 13' of the web W in the cross direction CD, so that the blast 20 will strike the web W earlier by a corresponding distance. In that case too, the support effect of the blast 20 will remain up to the edge 13' of the web W.

The blowing arrangement 27 is fitted to the blowing means 12 in such a way that the points of impact A of the blasts 20, which support the web W against the support surface 18.1, are consecutively in a line in the direction of travel of the web W. According to one embodiment, shaping of the blowing openings 27 can also be used to help to form the support pattern A into, for example, an oval shape in the direction of travel of the web .

It can be seen from Figure 8 that the blast 20 has a component B _CD in the cross direction CD of the machine. In the case of the embodiment of Figure 8, the angle a is 60 degrees. If the angle a is increased, the tube component 15 can be moved closer to the surface of the roll/web W (i.e. the distance D can be reduced) , so that the support effect of the flow will be maintained when moving the point of impact A farther away and vice versa . In addition to the arrangement, the invention also relates to the blowing apparatus 12 itself, which is arranged to be used to create blasts 20 directed at the edge area 13 of the web W, and which can be fitted on a fiber web machine, in connection with a supporting draw 10.1, 10.2, in which the web W is ar- ranged to travel supported one-sidedly against the support surface 18.1, 23.1. The apparatus 12 is very simple in construction and operation and can be easily retrofitted to existing fiber web machines. In the following, the operation of the arrangement and apparatus on a fiber web machine, more generally the method for improving the runnability of the machine, is explained. First of all, tail threading is performed, during which the threading tail is spread to a full-width web W for production. The blow- ing apparatus 12 can then be in its home position outside the end of the roll- 18.1. After tail threading, once the web W has been spread to its full width in the cross direction CD of the machine, and the machine is running at its normal speed, the blowing means 12 (to both edges) are taken into connection with at least one one-sidedly supported supporting draw 10:1, 10.2 of the fiber web machine. Once the blowing means 12 has been taken to its operating position in the supporting draw 10.1, 10.2, the blasts 20 can be started by feeding the blowing medium 41 to the means.12. By means of the blowing medium 41, blasts 20 directed to the edge area 13 of the web W are formed in the portion of the web W that is against the support surface 18.1. When the blowing means 12 is in its ru ning-time position and blowing, production is simultaneously run on the full-width web W. Thus, the blasts 20 are started only once the device 12 is in its blowing position in the supporting draw 10.1, 10.2. The moving of the blowing means 12 and its operation in general can be linked to the machine's break-monitoring automation.

When beginning to use new fabrics, the dry substance of the web W can be lower than normal, which can limit the machine's running speed due to edge detachment. This problem too can be reduced through the invention. If the' edge detachment is great, when the apparatus 12 is being run to its operating position, it may be necessary to momentarily increase the drive, reduce the speed, increase the press loading, or reduce the square weight, so that the means 12 will not strike the edge 13' of the web W.

In pilot-stage tests, it has been observed that, by fitting the arrangement to the first group gap, the edges of the web W can be made to remain attached to the cylinder 18.1, even at the drying cylinder of the following group gap. Thus, it is sufficient for the arrangement to be arranged in only one point in at least some of the drying groups of the drying section 38 and, by using it, to obtain an effect covering the entire drying section. The apparatus can be installed in possible problem positions even in later group gaps, or web-processing devices, such as a calendering device in the drying section. It must 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 versed in the art .