FI86567C - Method of pointing a paper web and arranging the control of the pointing tape of a web - Google Patents

Description

86567

Method for paper web head export and device for web head export tape control Förfarande vid spetsdragning av en pappersbana och anordnlng vid styrning av spetsdragningsbandet av en bana 5

The invention relates to a method in a paper machine multi-cylinder dryer for paper web heading, in which the paper web is guided by a serpentine-like path with two wire feeds after drying cylinders and / or single wire the blow pipe is moved from its operating position to the rest position and said blows are cut off.

The invention further relates to a device with a drying section of a paper machine for controlling a web headband, the device comprising one or more blow tubes 20 through which blows can be directed to control the headband with a drying section, the device comprising a blow tube with nozzle holes and / or an opening attached to a pivotable, rotatable and / or linearly movable body part arranged to be moved by an actuator so that the blow tube 25 is brought to the operating position at the headband and to the rest position moved out of the machine.

As is already known, the drying section of a paper machine uses a so-called single-wire export or two-wire export. In this case, rope guide devices are generally used in the head export of the web, by means of which the headband cut from the full-width web is passed over the drying cylinders, after which the headband is applied to the full-width web. The main drive rope with its wheels is quite an expensive and complex system and is prone to malfunctions. For this reason, an attempt has been made to provide the web head 35 without a head thread rope, and rope-free head threading methods have been applied especially in single-wire export. Here, in part, we refer to a journal article by Sam Palazzolo: "No-draw drying," Tappi Journal, September 1990, p. 225-228.

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As stated in the above-mentioned magazine article, when using a single wire export, the difficulty in the head export is that the head belt tends to follow the smooth surface of the drying cylinder and not the drying wire as it runs from the drying cylinder to the next suction turning cylinder or roll. In order to ensure that the headband specifically follows the drying wire, air nozzle arrangements have been used in accordance with the above-mentioned magazine article, one of which is placed before each reversing cylinder and through which nozzles air jets are blown to control the passage of the headband. This is to ensure that the headband remains on the 10 drying wires. After the headband reaches the suction zone of the reversing cylinder, the belt rests on it to the next drying cylinder.

The disadvantage of the blowing arrangement described above is that if the headband 15 has passed in connection with the scraper blade acting against the drying cylinder, the headband cannot be obtained from there without manually operated auxiliary blows. In head export, however, there is a need to drop the headband from at least the lower surface of some drying cylinders with a scraper blade into the wreck handling system below. This has not been possible without difficulty in previously known rope-free web heading arrangements.

On the other hand, it is already known to use air blowing devices arranged in connection with scraper beams in the drying section, but these blowing devices are generally used for air conditioning the drying section and their nozzles blow the entire transverse width of the web. Blowing devices operating in connection with a scraper have also been used as an aid to the head export, but they have had several drawbacks and as such are not suitable for use in a poor head export. With regard to said previously known devices, reference is made, by way of example, to FI patents and publication publications Nos. 50263, 54954, 62571 and FI patent applications Nos. 833590 and 894609. Some of the above-mentioned publications disclose blowing devices located downstream of the press section.

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The main object of the present invention is to provide new solutions to the problems discussed above so that said drawbacks are largely avoided.

5 The applicant's earlier FI application No. 904841 (filed on October 1, 1990) discloses a method in which the head export strip is guided by air blows extending its considerable or full width from a normal scraper bar across the entire width of the web to a certain area of its scraper blade tip. at a small angle of 10 to the plane of the scraper blade.

Round. FI application 904841 discloses a device in which it is considered new that the blowing device is integrated in connection with the beams of normal, full-width scrapers of drying cylinders. Said blowing device comprises a transverse nozzle tube or a similar nozzle arrangement with a plurality of parallel nozzle openings or a corresponding nozzle slot located near the end of the scraper bar on the treatment side of the machine. The blowing direction of said nozzles is directed at a certain small angle to the plane 20 of the blade of said full-width scraper in the region of the tip acting against the surface of its drying cylinder.

Em. The blows assisting and guiding the head removal of FI application 904841 are placed specifically in full-width scraper bars. However, from the point of view of the safety of the head export and the air consumption, the placement of the scraper bar is not always the best, because normal scrapers are not available in all the places where head blowing would be needed. The use of heavy scraper bars extending over the entire width of the paper machine for the sole purpose of head blowing becomes quite expensive.

30 When placing the headland blowers permanently in normal full-length scraper beams in accordance with the above-mentioned FI application 904841, blowing devices must not be obtained, for example, when the machine is running out of the paper machine, eg for cleaning or other maintenance.

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The main object of the present invention is therefore to further develop the headband control solutions presented in FI application 904841 so that the disadvantages discussed above are avoided.

In order to achieve the above and later objects, the method of the invention is mainly characterized in that the blows guiding the headband are directed from the blow tube to the opening nip delimited by the adjacent cylinder surface and the wire.

10

The device according to the invention, in turn, is mainly characterized in that said blowpipe is connected to a short scraper blade having a scraper blade width equal to or slightly greater than the width of the headband, and that said blowpipe nozzles are aligned to direct air -laan.

The invention can be applied in drying cylinder groups with both single-wire and double-wire threads, if necessary along the entire length of the drying section. In connection with single wire export, the invention is suitable for use in both normal and inverted groups. According to the available data, the invention is most preferably applicable in connection with a single wire export.

25

According to the invention, head-blowing devices, with or without a scraper blade, can be placed in a light construction in precisely those places where head-blowing blows are required, regardless of the location of the actual full-length normal scrapers.

It should be emphasized that in addition to the short blowing pipes according to the invention and possible scrapers, the scraper blowing arrangements described in the above-mentioned FI patent application 904841 can be used in connection with conventional scrapers.

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If a short scraper blade is used in the device of the invention, the air jets are preferably directed to the tip area of the scraper blade at a suitable small angle to the blade plane so that the blows are turned along the cylinder surface preceding the blade, the blowing effect extending deep enough into the nip. Thus, a sufficient support and transfer effect of the blows on the headband is realized. Naturally, enough energy must be used in the blows to provide a reliable transfer effect.

The invention will now be described in detail with reference to some preferred embodiments of the invention shown in the figures of the accompanying drawing, to the details of which the invention is not intended to be limited.

Figure 1 shows a schematic side view of the positioning principle of scraper blows in the area of a single wire export.

Figure 2 shows the positioning positions of the headland blows in the inverted two-wire outlet in a manner similar to Figure 1.

20

Figure 3 shows an application of the head thread blows of the invention in a drying section in which the head thread strip is introduced from a normal single wire group to a free spaced single wire group.

Figure 4 shows the guidance of the headband from the single wire group to the double wire group with a free gap, assisted by the blows according to the invention.

Fig. 5 shows, corresponding to the previous figures, an application of the head-export blow according to the invention from the two-wire export via a free space 30 to the second two-wire export.

Figure 6 shows an application of the scraper blows according to the invention at the end of the drying section in connection with the last lower cylinder.

Fig. 7 shows, correspondingly to the previous figures, the application of the headland blows of the invention in single-wire export in connection with a bevel cutter gap.

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Figure 8 shows a head-blowing according to the invention when guiding a head-band from a normal single-wire group supported on an inverted single-wire group.

Fig. 9 shows a machine direction view of a head thrust tube according to the invention turned to the operating position.

Fig. 10 shows the same as Fig. 9 seen from above and supplemented by a pneumatic diagram.

10

Fig. 11 shows in an operative position a device according to the invention in which a short block scraper and scraper blows are used in connection with its blade.

Fig. 12 is a schematic top view of a blowpipe linearly displaced by the air cylinder to the operating position and the rest position.

Fig. 13 shows a blowpipe linearly displaced by the air cylinder to the operating and rest position.

20

Fig. 14 shows, in a manner similar to Figs. 12 and 13, a spring-loaded blower tube linearly movable by an air cylinder.

Fig. 15 is a side view of a blown pipe with a fragmentary scraper. Figure 15 may be a section XV-XV of Figure 11.

Fig. 16 shows an axonometric pattern of a linearly movable blowpipe with a blade, the blade of which can be turned to the operating position and the rest position.

30:. Fig. 17 shows a principle of the pivot control of the device according to Fig. 16.

Figure 18 shows an alternative blowpipe control principle.

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Fig. 1 schematically shows successive groups of cylinders Rx and Rz with single wire outlets, in the upper row of which there are heated drying cylinders 10 and in the bottom row of reversing cylinders 20 with torn and grooved outer casing. correspondingly in the top row.

According to Fig. 1, the drying wire 11 guided by the guide rollers 11a contributes serpentially to the drying cylinders 10 and 10 sideways so that the web W to be dried by the drying cylinders 10 comes into direct contact with the heated smooth surface of the cylinders 10 and the web W wherein it is held inside the cylinder 20 by a vacuum 15 acting through its perforation and groove (not shown) in its jacket. For the straight runs of the wire 11 and the web W, in which they pass together from the drying cylinders 10 to the turning cylinders 20, blow boxes 15 can be arranged on the wire 11 side, e.g. devices marketed by the applicant maintaining a suitable vacuum on the side of the wire 11 which ensures that the web W remains on the surface of the wire 11 in said straight runs. Blow boxes 15 are often not necessary.

The invention uses head-blowing devices separate and independent of the actual scraper bar in connection with a single-wire or double-wire outlet in positions where it is necessary to guide the head-on strip R in nips N- which open along the surface of the wire.

According to the invention, either independent blowpipes with a width of the headband 30 or blowpipes connected to a short scraper with a blade extending substantially the width R of the headband are used.

Figures 1-8 show different positions of the blowing devices according to the invention. When the positions in question have a full-width nor-35 paint scraper beam, a headland blowpipe is placed in accordance with the principles of the above-mentioned FI patent application 904841. In positions β 86567 where there is no normal scraper or where the normal scraper is too far from the track line for blast bar operation or where the scraper can be omitted due to the device according to the invention, and where the airflow control 5 of the headband R is required, a short scraper blade 14 according to the invention is used. with or without a blowpipe 22, which can be moved to the operating position and the rest position on the side of the machine, where the device is not in the way of other functions and where it can be easily cleaned and maintained.

10

The blowing device according to the invention can advantageously be arranged to be controlled automatically in connection with other head-drive automation.

Although the object of the invention is to provide a rope-free head, in connection with the invention in some respects a rope guide can also be used, if necessary, with a drying section or paper finishing devices, such as on-machine calenders or coating devices.

Figures 9-18 show some preferred embodiments of the device, to which we will return later.

The following describes the preferred placement positions of the head end lever holding device in Figures 1-8 in different drying sections at different points thereof. It should be emphasized that although in Figures 1-8 the blow pipes 22 are generally shown in connection with a scraper bar 12, which may be a full length or a short scraper according to the invention, only the blow pipe 22 not provided with a scraper can be used in the blow device placement positions shown in Figures 1-8. There are several different examples of these device implementations in Figures 9-18.

30

Figures 1 show the use of scraper blows in the single wire export area in groups Rx and R2. Scraper beams 12 are arranged in connection with the lower surface of the drying cylinders 10 of the top row, at least one of which is a short scraper bar. One or more scraper bars may be a full-length normal 35 scraper bar. The scraper beams 12 use a blow tube 22 which is directed towards the tip of the scraper blade 14 (blows Fx) into an open nip i: 9 86567 N- to guide the headband R to follow the wire 11. A full width or short scraper blade 14 from the surface of the cylinder 10 and is guided further by blowing the Fx wire 11 following the -5 ground.

According to Figure 2, the blowing control of the headband has been used in an inverted single wire array R1 (where the drying cylinders 10 'are in the bottom row and the reversing cylinders 20' are in the top row. Scraper beams 12 are arranged on the upper surface of the cylinders 10 '. extending only in the region of the headband R. The other scraper beams 12 may be full-width and provided with a full-width blade 14. Blows Fx are directed to the N-bottom of the opening nip via the blow tubes 22 or independent corresponding blow tubes 15 and guide the headband T in connection with its export. to follow the drying wire 11. In the group space, the strip R is transferred to the drying wire of the next group R2 with the aid of a box 15. In Fig. 2, a second blow pipe 30 is further arranged in connection with the scraper beams 12, through which blows F2, 20 are directed. guide the headband over the pivot cylinder 20 '. The latter wire 11 passes over the suction roll 13 and on to the next group R2.

Figure 3 shows an embodiment of the invention in which the previous group Rx is a normal single wire group 25 with a wire 11 guided by rollers 11a, in which the drying cylinders 10 are in the top row and the turning cylinders 20 in the bottom row. The web VI and the headband R are guided through the free space W0 to the next inverted group R2, where the drying cylinders 10 'are in the bottom row and the reversing cylinders 20' in the top row.

According to Fig. 3, the subsector 30 of the last cylinder 10 of the group Rx may have a normal full-length scraper 12A, which may be provided with a wide blow tube 22A of the headband R, from which the blows FA are directed upwards. In addition to the scraper 12A, the short auxiliary scraper 12 according to the invention is used, because the actual scraper 12A is too far from the track line W0 for the reliable operation of the blow FA. Through the blow pipe 22 of the auxiliary scraper 12 according to the invention 35, the blows Fi are directed to the opening nip N so that the head lead strip R is made to follow the open export line W0 10 86567. In connection with the lower cylinders 10 'of the next inverted group R2, there are scraper bars 12, either full-length scrapers or short scrapers according to the invention or just blow pipes, through which blows guiding the N-lead strip R to the surface 5 of the wire 11 are directed to the opening nip. In addition, blows F2 are directed upwards from the same tube 22 or from a separate tube 36, which guide the headband R to continue to pass over the pivot cylinders 20 '.

According to Fig. 4, the previous group Rj is provided with a single wire outlet and 10 has a drying wire 11 guided by the guide rollers 11a. After the guide roll 11b, the web is transferred as a free pull W0 to the double wire group R2 supported by its lower wire 11B. The last free sub-sector of the drying cylinder 10 of the group Rx may have a normal scraper 12A, which may have a blow pipe 22 from which the blowing FA to the opening nip is directed in the N-direction. Since the normal scraper 12A is too far from the line W0 of the web W and the headband R, a short scraper 12 according to the invention with a blow tube 22 is placed before the scraper 12A, from which the blow Fj is guided to the opening nip N- close. The blow Fj controls the headband R to follow the wire 11 before the guide roll 11b. In the latter two-wire-20 group R2, there are upper wire 11A and lower wire 11B guided by guide rollers 13 and two overlapping rows of drying cylinders 10A and 10B. The sector above the first lower cylinder 10B may have a scraper bar 12 with two overlapping blow pipes 22 and 30 on the side or one pipe operating respectively. From the lower tube 22, blows Fx are guided to the opening nip N in the width R of the head guide strip 25 R so that the head guide strip R follows the free traction W0 of the web on the line blown F2 to the closing nip N + between the upper wire 11A and the surface of the cylinder 10A.

Fig. 5 shows an area of the drying section in which both the previous cylinder group R1 and the latter cylinder group R2 are provided with a double-barrel. The web W and the head thread R are passed through the open gap Wn from the former group to the latter group R2. Arranged in the subsector of the last upper cylinder 10A of the previous group R1 is a full-length or 35 only scraper bar 12 of the width of the headband R, to the blade 14 of which blows 11 86S67 F] are directed from the blow tube 22. The upper sector of the first lower cylinder 10B of the latter group R2 may have a full-length or short scraper bar 12 fitted to the N-connection of the opening nip, respectively, blowing F1 from the N-blowing tube 22 and blowing F2 from the upper blowing tube-5 housing to the blade 14. Said blows Fx and F2 direct the headband T line Wp upwards to the closing nip N + between the wire 11A and the first upper cylinder 10A.

Figure 6 shows an embodiment of the invention at the end of the drying section, from which the web 10 Wout is guided out of the hood 50 of the drying section to a winding or finishing device. In connection with the last lower cylinder 10B, a short scraper bar 12 is arranged, the front side of which has a blow pipe 22 through which the blows F ± are directed to the opening nip N- below. In connection with the same beam 12, there is a second blow pipe 30, through which 15 blows F2 are directed upwards, which guide the headband R in the direction Wp to the closing nip N + formed by the last upper cylinder 10A and the wire 11A.

Fig. 7 shows a cylinder group with a single wire outlet, in the free space WpL of which a bevel cutter 40 is used, the blade 41 of which cuts the headband R from the web W and the preceding opening nip N is subjected to blows 25 Fj from the tube 22. The corresponding blowing arrangement is in connection with the opening nip N of the preceding upper cylinder 10. In Figure 7, the web group is further applied to the guide roll 13B under the control of the arrow Wout direction.

Fig. 8 shows an embodiment of the invention in an environment in which the previous cylinder group Rj is a normal single-wire export group and the latter group R2 is an inverted single-wire export group in which the drying cylinders 10 'are in the bottom row and the reversing cylinders 20' are in the top row. For the subsector Rx of the previous group, short or full-length scraper bars 12 are arranged, from the blow pipes 22 of which the blowers Fj guiding the scraper blade 14 R are guided to the opening nip N-direction. In the group gap, the headband R and the web W are transferred from the drying wire 11 to the drying wire 11 'of the latter i2 86567 group. The upper sectors of the lower cylinders 10 'of the latter group are provided with full-length and / or scraper bars 12 of the width of the headband R, in connection with blow tubes 22 and 30 or a corresponding one tube directing the first blows Fx 5 to the opening nip N and the second blows Fz up to the headband R 'over.

Although in principle all scraper blades can only be carried out using a short scraper bar 12 and blade 14 or only a blow tube 10, practically not all full length scraper bars can be removed from the machine because, for example due to track breaks, some normal scrapers have to be left in the machine. On the other hand, scrapers often have to be placed in the machine so far from the path of the paper web W that the blows from these scrapers no longer work properly and the use of headfinders or blower tubes 22 with blows Fj according to the invention is very justified, sometimes downright necessary.

According to Figures 9 and 10, the blowing device comprises a blowing tube 22 fixed to the body part 21, with a series of nozzle holes 23 through which blows Fj guiding the edge strip R can be aligned. The chute 22 is fixed to the device body 21, a pivot shaft 21a connected to the body portion of the drive side of the paper machine 30 in the direction of arrow C, shown to be translated in Figures 9 and 10 and its position on the back of the machine 25 outside of the rest position. For turning the body 21 of the blowing device, it is connected to the piston rod 24b of the air cylinder 24. The air cylinder 24 is connected at one end by a pivot pin 24a to the body part 30. A pressure of e.g. 7 bar is directed into the system via a pipe 17. The pressure in the double-acting cylinder 24 is controlled via a diverter valve 29, a pipe 30 25 and pressure relief valves 26. From the same pipe 17, the air entering the blowers F1 through the changeover valve 20 and the pressure relief valve 27 is directed to the blowing pipe 22 via the pipe 16. Valves 28 and 29 are preferably arranged to be controlled by the automatic headland.

Fig. 11 shows a device provided with a short blowpipe 22 slightly longer than the width L of the headband R, which is attached to the pivotable body part 21 of the device 21. In connection with the blowpipe 22 there is a scraper blade 14, the tip of which can be directed towards the tip as shown above. control blows F1.

5 Figure 12 shows a device comprising a guide rod 21b is shown at the other end of which is attached to the blowing tube 22. Guide rod 21b has a body portion 31 of the guide 32 of an air cylinder 24 linearly displaceable on the inside of the paper machine dryer section in its position, shown in Figure 12 to the rest position of the arrow A directions.

10

Fig. 13 shows a linearly displaceable blow tube 22 attached to the piston 24c of the piston 24c of the hydraulic cylinder 24. The piston rod 24b of the air manifolds is the same, through which the blow air is passed in the direction of arrow D from the air cylinder 24 puffs Fx air.

15 T Imasyl inter i 24 has two functions and is connected via pipes 2'i to a changeover valve 29, by means of which the blow pipe 22 can be controlled to the operating position, whereby at the same time the blow Fi is switched on at the same time.

Fig. 14 shows a blowpipe 22 which is otherwise similar to that shown in Fig. 13, except that the air cylinders 24 are single-acting and provided with a return spring 23. By means of a changeover valve 29, the blowpipes 22 are actuated, the air coming from the pipe 17 to the pipe 18 25 without a pressure reducing valve 26 through the various air cylinders 24, whose piston 24c presses the air pressure in the direction of arrow A in its position, the same blowing Fx will affect the air passing through the piston rod 24b of arrow D direction.

Fig. 15 is a machine direction vertical cross-section XV-XV of the blow tube 22 of Fig. 11 and an associated short scraper extending the width of the headband R, comprising a scraper blade 14 attached to its holders 14a. Said holders 14a are fixed by means of a loop 14b and a screw 14c to a blow pipe 22, through which a set of nozzle holes 23 blows F! towards the tip of the scraper blade 14 i4 86567. Fig. 15 shows the scraper blade 14 in the position 14 'turned off in connection with the connection of the smooth surface 10 "of the cylinder 10.

Figures 16, 17 and 18 outline the operation 5 of the device according to Figure 15 and its various details. According to Fig. 16, the blow pipe 22 is connected to the piston rod of the air cylinder 24, e.g. as shown in Fig. 13 or 14. The rotation of the scraper blade 14 from the position 14 'to the operating position 14 against the cylinder surface 10 "is achieved e.g. by the structure shown in Figures 17 and 18 which operates so that when the piston 24c 10 of the cylinder 24 and its arm 24b approach the outer end position, the guide pin moves in the groove 34b. The blade 14 'may rotate to the operating position shown in Fig. 15. The piston rod 24b may have a cross-section similar to that shown in Fig. 18 with a plurality of guide grooves 36 with guide pins 35 attached to the air cylinder 24 controlling the rotational movement of the piston rod 24b so that the scraper blade 14 moves shown in Figure 15 from the rest position 14 'in the direction of arrow B toimiasentoonsa 14 of the cylinder surface 10' to scrape against the strip R from the cylindrical surface 10 '.

In the following, the claims are defined, within the scope of which the inventive idea is defined, the various details of the invention may vary and differ from those set forth above by way of example only.

Claims (10)

A method of tip-pulling a paper web (W) in the multi-cylinder dryer of a paper machine, in which the paper web (W) is guided along a serpentine-shaped web over drying cylinders (ΙΟΑ, dubb) for double wire draws and / or for single wire draws over drying cylinders ( 10; 10 ') and break cylinders (20; 20') or rollers on a drying wire (11), substantially without tip drawing lines, in which method a blowpipe (22) is transmitted in functional position to blow blown (F2) such guides 10. the tip pull band (R) and after controlling the tip pull band (R), said blow tube (22) is transferred from the functional position to a rest position and said blows (F2) are interrupted, characterized in that the blows (F2) controlling the tip pull band are directed from the blow tube nip (N-) which opens and which is restricted by the cylinder surface (10 ") in contact with it and the wire. 2. A method according to claim 1, characterized in that in the process the tip drawing band (R) is detached from the cylinder surface (10 ") with a short blade blade (14) of substantially the same width as the tip drawing band (R), wherein said blisters ( F2) is most preferably directed at the tip of the blade. Method according to Claim 1 or 2, characterized in that the second method also uses a second blow tube (30), through which directing blows guiding the tip pull band (R) which are opposite in relation to the aforementioned blows (F2) are used. Method according to any one of claims 1-3, characterized in that, except with said blades (F2), the tip drawing band (R) 30 with such blasts is controlled mainly directed towards the tip of the blades (12) of full width soin is placed on the free sector of the drying cylinders (10,10 '). 5. A method according to any of claims 1-3, characterized in that the method is applied to the single-wrap feature area of the nip 86567 (N-) which opens in the drying portion of the paper machine, to the double-wrap area and / or in the group spaces in the drying portion. . Apparatus for guiding the tip pull band (R) of a web (W) at the drying portion of a paper machine, the apparatus comprising one or more blowing tubes (22), through which one can direct blows (Ft) by means of which blows the tip pulling belt (R) is guided on the drying portion which comprises a blow tube provided with nozzle heels (23) and / or with an opening secured to a pivotable, rotatable and / or linearly movable body part (21a, 21b) which is arranged to be movable with a functional device (24) so that the blow tube (22) can be brought into a functional position at the tip pull band (R) and in a resting position outside the machine, characterized in that said blow tube (22) is connected in connection -15 see with a short blade (14), the width of which the blade (14) corresponds to the width of the tip pull band (R) or is slightly longer than that, and that the nozzles of said blower ring tubes (22) are directed to direct the air blasts (F :) in a wedge-shaped nip space (N-) which opens and is limited by the cylinder surface (10 ") next to the blow tube (22) and the wire. Device according to claim 6, characterized in that the device comprises a body part (21), to which is attached a blowpipe (22), which body part (21) is connected to a joint shaft (21) in connection with the body part (30) on the lower side. of the paper machine or other equivalent body part, and that said body part (21) is joined to a functional device, most preferably air cylinder (24) to swing said device around the joint (21) in functional position and eat the side in a resting position. Device according to claim 6, characterized in that the blowing tube (22) of the device is connected to a conduit (21b) or in the piston shaft (24b) of a functional device to a linearly movable functional position and back to a resting position. Device according to any one of claims 6-8, characterized in that the blowing pipe (22) is connected to the piston shaft (24) of an air cylinder (24), which at the same time acts as a supply pipe for blowing air, and that the air to be measured in said air cylinder (24) can move the blow tube (22) in a functional position therefrom, it can be returned to the rest position with compressed air controlled by a valve (29) or by the force of a return spring (33). 10. Device according to any one of claims 6-9, characterized in that the blade (14) arranged in connection with the blowing tube (22) is arranged to be pivoted in connection with the cylinder surface 10 (10 ") from a rest position (14 '). by twisting the blow tube (22).