EP0868571A1

EP0868571A1 - Dry end

Info

Publication number: EP0868571A1
Application number: EP96944054A
Authority: EP
Inventors: Werner Goebel; Karlheinz Straub
Original assignee: Voith Sulzer Papiermaschinen GmbH
Current assignee: Voith Patent GmbH
Priority date: 1995-12-22
Filing date: 1996-12-21
Publication date: 1998-10-07
Anticipated expiration: 2016-12-21
Also published as: EP0868571B1; ID15816A; US5987777A; DE19548303B4; DE19548303A1; WO1997023690A1; DE59606968D1

Abstract

The invention relates to a dry end for drying a material web, in particular a paper or cardboard web, having at least one drying group with a plurality of drying cylinders and web guiding rollers and at least one nozzle device for transporting the threading part of the material web along a winding path by means of at least one conveyor band. The dry end is characterised in that groups of at least two nozzle devices (17, 19, 21) located at the same side of the material web (11) follow each other in the direction of transport of the material web (11).

Description

Dryer section

description

The invention relates to a dryer section for drying a material web, in particular paper or cardboard web according to the preamble of claim 1, and also a method according to claim 29.

Dryer sections and methods of the type mentioned here are known (DE 39 41 242 AI). At the start of the production of a material web, for example a paper-making machine, the material web emerging from a press section is first discharged into a scrap collection area before the first dryer section adjoining the press section. It is also conceivable to guide the material web from the press section to the first drying cylinder, the drying group adjoining the press section, and to discharge it from there to a reject collection area. In order to thread the material web through the dryer section, a threading strip, also referred to as a ribbon, is first cut off from the driver's edge of the material web in the longitudinal direction (machine direction) and this is threaded through the dryer section - preferably at full working speed of the paper-making machine - without displacing it laterally . The threading strip must have drying cylinders and web guide rollers Run through the dryer section in a meandering shape. It is therefore necessary to guide and stabilize this strip so that it does not wrap around drying cylinders, which leads to an interruption in the threading process. From the known dryer section, nozzle devices, for example blow air tubes, are known which extend at least across the width of the threading strip and serve to remove the latter from a drying cylinder and to transfer it to the web guide roller, as seen in the conveying direction of the material web. It has been found that the threading-in of the threading strip is not carried out safely in all cases, so that a threading-in process often has to be stopped and repeated and cleaning of the drying section becomes necessary.

It is therefore an object of the invention to provide a dryer section which is characterized by improved threading behavior.

To solve this problem, a drying section is proposed which has the features mentioned in claim 1 and which is characterized in that at least (one) / two nozzle devices are arranged one behind the other for transferring a threading strip from a drying cylinder to a subsequent web guide roll, apply gas flow to one and the same side of the material web. Such a dryer section is characterized by a simple structure and by a reliable threading behavior. An embodiment of the drying section is preferred, in which the nozzle devices are mounted on a scraper which interacts, for example, with a drying cylinder and is arranged directly in the transfer area between a drying cylinder and a web guide roller, preferably loaded with vacuum. The air flow generated by the nozzle devices can thus act directly on the material web which is located in the area of the free running path between the drying cylinder and the web guide roller.

Another embodiment of the dryer section is preferred, which is characterized in that the nozzle devices emit a gas stream with a defined flow direction. The various nozzle devices or their gas flows are directed so that on the one hand the material web is safely detached from the drying cylinder, that on the other hand it is securely placed on the web guide roller and finally can be transferred from the web guide roller (vacuum-assisted) to the next drying cylinder.

An embodiment of the dryer section is particularly preferred, which is characterized in that the nozzle devices have individual or slot nozzles. The use of individual nozzles enables the material web to be acted upon by a strong, directed air flow, which, for example, reliably detaches the material web from the drying cylinder. The use of slot nozzles stabilizes the threading strip so that it does not become tangled during threading can twist, which would lead to malfunctions in the operation of the machine for producing a material web.

Further configurations of the dryer section result from the remaining subclaims.

It is a further object of the invention to provide a method with which a threading strip can be safely guided through a dryer section.

To achieve this object, a method with the feature steps mentioned in claim 29 is proposed. It is distinguished by the fact that at the transition from a drying cylinder to a web guide roller, the material web is subjected to at least two / (one) gas streams, with a particularly safe, trouble-free transfer of the threading strip from one drying cylinder to a subsequent one Can guarantee web guide roller.

An embodiment of the method is preferred which is characterized in that the gas streams are activated within a drying section at different times. It is thus possible to adapt the activation of the gas streams to the course of a threading strip within the dryer section and thus to significantly reduce the energy required to generate the gas stream.

An embodiment of the method is particularly preferred which is characterized in that the gas flows are generated by means of a clocked air flow. The timing leads to the fact that the material web is safely detached from a drying cylinder by high-energy pulses, on the other hand to the fact that the amount of air required for the generation of the gas streams can be significantly reduced.

Further embodiments result from the other subclaims.

The invention is explained in more detail below with reference to the drawing. Show it:

Figure 1 is a schematic side view of part of a dryer section;

FIG. 2 shows a perspective view of a doctor part of a drying section and

Figure 3 is a schematic side view of several drying cylinders and vacuum-assisted web guide rollers of a dryer section.

The dryer section described below is generally suitable for machines for the production of material webs. It is particularly suitable for machines for the production of paper and cardboard webs. In the following it is assumed that the drawing shows parts of a papermaking machine.

FIG. 1 shows, in a highly schematic side view, part of a drying section 1, namely a drying cylinder 3 and a web guide roller 5 of a drying group 7. A conveyor belt 9, also referred to as a dryer fabric, is partially looped meandering around the drying cylinder 3 and the web guide roller 5. In this case, between the surface of the drying cylinder 3 and the conveyor belt 9 there is a material web 11, which is only indicated by dashed lines and which is arranged on the outside in the region of the web guide roller 5.

Between the drying cylinder 3, which here, as indicated by an arrow, rotates clockwise and the counterclockwise rotating web guide roller 5, there is a free running path 13 within which the material web 11 only rests on the conveyor belt 9 and not comes into contact with a drying cylinder or a web guide roller. On the surface of the drying cylinder 3 there is a scraper 15, which prevents the reel from being wound around the drying cylinder 3 in the event of a web break. It also serves to transfer a threading strip, also referred to as a ribbon, which is separated from the material web 11 in the edge region of the material web 11 when the paper-making machine starts, onto the web guide roller 3. Depending on its function, the scraper 15 thus extends over the entire width of the drying cylinder or only over a partial area, which is preferably on the driver's side of the machine. Here, three nozzle devices 17, 19 and 21 are attached to the scraper 15. The first nozzle device 17, viewed in the direction of conveyance of the material web or the conveyor belt, is the foremost nozzle device. It comprises a blow pipe 23 from which a gas stream 25 emerges. This is directed essentially opposite to the conveying direction of the conveyor belt 9 and encloses an angle a with the surface of the scraper 15 facing the material web 11, which is in the range from -10 ° to 25 °, but preferably in the range -5 ° to 15 °. A negative angle denotes a direction of the gas flow 25 which is directed against the surface of the scraper 15. The gas stream 25 strikes the surface of the drying cylinder 3 and virtually shuts off the threading strip if it sticks to the surface of the drying cylinder.

The subsequent second nozzle device 19 in turn has a blowpipe 27 from which a gas stream 29 emerges. This gas stream 29 forms an angle β with the surface of the scraper 15, which is in the range from 116 ° to 130 °, preferably in the range from 116 ° to 125 °. The gas stream 29 which emerges from the blow pipe 27 is thus directed essentially in the direction of the conveying direction of the conveyor belt 9.

The two nozzle devices 17 and 19 are preferably arranged at a very short distance next to one another and are located in the region of the front edge of the scraper 15 which bears against the drying cylinder 3. The second nozzle device 19 can optionally be dispensed with. Their use depends on the material web properties, in particular also on their moisture and basis weight. On the opposite edge of the scraper 15 facing away from the drying cylinder 3, the third nozzle device 21 is arranged, which in turn comprises a blow pipe 31 from which a gas stream 33 emerges. The gas stream 33 runs approximately transversely to the conveying direction. tion of the conveyor belt 9. It strikes the surface of the web guide roller 5 approximately tangentially and serves to place the threading strip on the conveyor belt running on the suctioned surface of the web guide roller 5. The gas stream 33 forms an angle δ with the surface of the scraper 15, which can be in the range from 65 ° to 130 ° and which preferably has an angle range from 80 ° to 125 °.

The threading strip is peeled off from the surface of the drying cylinder 3 by the gas flow 25 of the first nozzle device 17 directed against the conveying direction of the material web 11 and is placed against the surface of the conveyor belt 9. The second nozzle device 19 is used to stabilize the threading strip on the surface of the conveyor belt 9 and, seen in the conveying direction of the conveyor belt 9, immediately follows the first nozzle device 17. In order to ensure that the threading strip remains on the surface of the web guide roller 5 and does not get into the basement below the dryer section 1, the threading strip is positioned on the conveyor belt running on the suctioned surface of the web guide roller 5 with the aid of the third nozzle device 21 ¬ bilized.

The conveyor belt 9 is porous. A negative pressure acting in the area of the web guide roller 5 additionally serves to hold the threading strip on the wrapping area of the web guide roller 5 on the conveyor belt 9. The negative pressure is also used in the operation of the paper manufacturing machine to stabilize the material web 11 on the surface of the web guide roller 5.

A control 35 is assigned to the nozzle devices 17 to 21 and is connected to the nozzle devices 17, 19 and 21 by lines 37, 39 and 41 indicated by dashed lines. The control 35 can each be assigned to a group of nozzle devices assigned to a scraper 15. It is also possible to coordinate the nozzle devices of a plurality of scrapers within a drying group via a single control 35. Finally, it is conceivable that control of all the nozzle devices is assigned to one drying group.

The control 35 can be provided with solenoid valves 43, 45 and 47 assigned to each line 37, 39 and 41 and have air volume adjusters 49, 51 and 53 which are provided in the lines 37, 39 and 41 or are integrated in the control 35. Finally, the control 35 also comprises a clock circuit 55, which makes it possible to generate a pulsating air flow. The clock circuit 55 is designed such that the clock frequency can be varied in a range from 0.1 Hz to 5 Hz, preferably from 0.2 Hz to 2 Hz, the proportion of blowing time and pause being able to be selected differently . It can also be provided that the clock frequency in the individual nozzle devices is different.

FIG. 2 shows a perspective view of the scraper 15, which is also shown in FIG. 1. The same parts are provided with the same reference numbers, so that in this respect reference can be made to the description of FIG. 1. The scraper 15 preferably extends over the entire width of the paper making machine. The nozzle devices 17, 19 and 21 are designed such that they are assigned only to one threading strip, which is not shown here and which is only carried out through a drying section 1 during a threading process.

The blowpipes 23 and 27 are fastened on their side facing the end face of the scraper 15 by means of a clamping device 57, which enables the blowpipes 23 and 27 to be rotated. The blow pipes 23 and 27 are mounted in a guide 59 at their ends.

Correspondingly, a clamping device 61, which interacts with a guide 63, is provided for the blowpipe 31 of the third nozzle device 21.

The nozzle devices 17, 19 and 21 can have single or slot nozzles. In the exemplary embodiment shown here, the first nozzle device 17 has individual nozzles 65 which comprise short blow pipe sections which extend radially from the blow pipe 23. In FIG. 2 it is indicated that the blow pipe 27 is provided with slot nozzles 67. The blow pipe 31 also has slot nozzles 69 according to FIG.

The individual nozzles 65 are assigned a preferably wedge-shaped cover 71, the tip of which points against the direction of movement of the material web and has the cutouts 73, each in the area of the individual nozzles 65 are arranged. The cover 71 serves to prevent material scrap from getting stuck to the individual nozzles 65, which is particularly effective if the individual nozzles are pivoted into the area of the cutouts 73 and are therefore very protected.

The combination of individual nozzles and slot nozzles selected here for the blowpipes 23, 27 and 31 has proven particularly useful because the bundled air or gas stream 25 emerging from the individual nozzles 65 very effectively reduces the adhesive forces between the material web 11 and the surface of the dryer - Overcomes kenzylinders 3, which are particularly high especially when the material web is still relatively damp. The slot nozzles 67 and 69 of the blowpipes 27 and 31 build up a uniform air curtain, which prevents the threading strip from twisting and ensures particularly reliable guidance.

From Figure 2 it can be seen that the mounting of the blowpipes is very simple, so that the adjustment of the gas flows can be carried out easily. It is also possible to easily reproduce the blowpipe setting.

A pulsating air flow can be generated by the control 35, which leads to a significant reduction in the air volume required for the detachment and guidance of the threading strip. The short, intensive impulses of the gas streams nevertheless ensure that the threading strip is reliably detached from the drying cylinder. A paper jam on the scraper 15 is avoided with high certainty by the nozzle devices 17, 19 and 21. At the same time, there is a very safe and trouble-free transfer of the threading strip from a drying cylinder to a subsequent web guide roller.

In order to ensure a safe transfer of the threading strip, all drying cylinders in a drying section are preferably provided with a scraper and with nozzle devices, as was explained with reference to FIGS. 1 and 2. The scraper can be designed as a cleaning scraper or transfer scraper, the transfer scraper generally being substantially shorter than the cleaning scraper. It is also conceivable to combine the nozzle devices with removal scrapers.

A reliable transfer of the threading strip is ensured by the fact that different types of nozzles are used in connection with the blowpipes of the nozzle devices. The individual nozzles 65 enable the adhesive forces to be surmounted reliably. The slot nozzles 67 and 69 of the blowpipes of the second and third nozzle devices 19 and 21 enable the threading strip to be transferred safely.

The control 35 is preferably designed in such a way that the blowpipes 65 are only pressurized with compressed air in the area of the dry end in which the threading strip is currently located. Nozzle devices that the threading strip has not yet reached remain depressurized, so that the need for compressed air is significantly reduced. A A further reduction in the compressed air requirement is achieved in that the control 35 has a clock circuit 55 which enables a pulsating air flow. The threading of the threading strip is so secure that an additional cable guide can be dispensed with.

FIG. 3 shows several drying cylinders 3, 3 ′ and 3 ″ arranged next to one another in one plane of a drying group 7 which is part of a drying section 1. Below the drying cylinders, web guide rollers 5, 5 * and 5 ' ¹ are arranged, also in one plane.

It can be seen from FIG. 3 that the distance from the center of the drying cylinder 3 to the center of the web guide roller 5, measured in the horizontal direction, is identified by x and the distance from the center of the web guide roller 5 to the center of the subsequent drying cylinder 3 'by y . Scraper 15, 15 * and 15 '* are assigned to drying cylinders 3, 3' and 3 ' ¹ , which are constructed as shown in FIGS. 1 and 2 and have nozzle devices which, for reasons of better clarity in FIG. 3 were not reproduced.

The distances x and y are selected depending on the design of the web guide rollers 5, 5 'and 5''. The inequality x <y is preferably maintained for the distances if the web guide rolls are designed as so-called suction rolls. In the event that vacuumed rolls are used as web guide rolls, the inequality x y y is chosen for the distances. With such an outage design of the drying group 7 results in a particularly secure transfer of the threading strip with the aid of the nozzle devices 17, 19 and 21 provided on the scrapers 15.

It turns out that the arrangement of the nozzle devices cannot be viewed in isolation, but that the distances x and y can also be optimized in order to ensure an optimal transfer of the threading strip.

From the explanations for Figures 1 to 3 it can be seen that for the transfer behavior, the arrangement of the nozzle devices on a scraper, the orientation of the gas streams flowing out of the nozzle devices and the arrangement of the drying cylinders and web guide rollers interacting with the scraper must be selected optimally in order to achieve a to ensure safe transfer. The first and second nozzle devices 17 and 19 are arranged one behind the other in the immediate vicinity, while the distance from the third nozzle device 21 is considerably greater. In addition, the gas flows of the nozzle devices are aligned in accordance with the angle information in order to achieve an optimal detachment of the threading strip from the surface of the drying cylinder 3 and a reliable transfer to the conveyor belt running on the suctioned surface of the web guide roller 5. In order to achieve a good peeling effect, the first nozzle device 17 is provided with individual nozzles 65, while the other two nozzle devices 19 and 21 have slot nozzles in order to ensure reliable guidance of the threading strip. Finally the spacing ratios of two adjacent drying cylinders to the web guide roller between them should be selected as explained in FIG. 3 in order to ensure a reliable transfer of the threading strip.

In the following, the method for transferring a threading strip within a drying section is discussed, which is used to dry a material web, in particular a paper or cardboard web. It is known that an edge strip, which is also referred to as a ribbon or threading strip, is cut off from a material web during a threading process, for example by means of a tip cutter, and that this threading strip, preferably at full operating speed of the machine for producing a material web the dryer section is led. The threading strip runs in a meandering fashion around the drying cylinders and web guide rollers of the dryer section, it being guided in the area of the drying cylinders between the conveyor belt and the surface of the drying cylinders and freely running on the surface of the web guide rollers. The transfer from a drying cylinder to a subsequent web guide roller is problematic since the threading strip sticks to the surface of the drying cylinder due to adhesive forces. It must therefore be detached from this surface and fed onto the conveyor belt. The threading strip must then be guided further with the conveyor belt to the web guide roller and run around it. The removal of the threading strip from the surface of the drying cylinder and the transfer to it the conveyor belt and onto the surface of the web guide roller are carried out in the method according to the invention with the aid of at least two / (one), preferably three, gas streams which serve on the one hand to remove the threading strips while overcoming the adhesive forces from the surface of the Peel off the drying cylinder, on the other hand place it on the surface of the conveyor belt and hold it on the surface of the subsequent web guide roller. The adhesion forces are overcome by a first gas stream directed essentially counter to the conveying direction of the material web or the threading strip. Because the direction of the gas flow is adjustable, its effect can be optimized. It has been shown that for peeling off the threading strip from the surface of the drying cylinder, the gas flow should form an angle of -10 ° to 25 ° with the surface of a scraper to which the nozzle device emitting the gas flow is attached. An angle a of -5 ° to approximately 15 ° has proven particularly useful. The selected angle a depends on the material properties and the moisture content of the threading strip.

A second gas flow can be applied to the threading strip, which acts on the threading strip immediately after the first one and essentially runs transversely to its direction of conveyance. This gas flow ensures that the threading strip peeled off from the drying cylinder and transferred to the conveyor belt remains securely on the conveyor belt and is placed on the surface of the web guide roller. The angle of the second gas stream can in turn be adapted to the material properties and the moisture content of the threading strip. It can be in a range from 116 ° to 130 °. An angle β of 116 ° to 125 ° has proven particularly useful.

Finally, a possible third gas flow acts at a distance from the two gas flows, which serves in particular to hold the threading strip securely on the web guide roller and to stabilize it there. It is aligned in such a way that the threading strip can be guided around the web guide roller and reaches the subsequent drying cylinder. The angle of the third gas stream is again adjustable, so that material properties and moisture content of the threading strip can be taken into account. The angle δ of the third gas stream can be 65 ° to 130 °. A nozzle device which emits a gas stream which forms an angle δ of 80 ° to 125 ° with the surface of the scraper to which the nozzle device is attached has proven particularly useful.

Since the threading of the threading strip is preferably carried out at full working speed, which is in a range from 500 m / min to 2400 m / min, not inconsiderable amounts of gas or air are required to generate the gas streams mentioned, especially the gas streams are preferably generated at all transfer areas between a drying cylinder and a subsequent web guide roller. To reduce the gas requirement in the method used here, the gas flows are controlled so that they are within a dryer section can be activated and deactivated at different times. In particular, the gas streams are activated only where the beginning of the threading strip is within the dryer section. This means that areas which the beginning of the threading strip has not yet reached or which it has already passed through are not subjected to gas flows, so that the gas or air requirement is reduced.

A further reduction in the air requirement is possible in that, in the method used here, the gas flows are generated by means of a clocked air flow, the clock frequency being in the range from 0.1 Hz to 5 Hz. A clock frequency of 0.2 Hz to 2 Hz has proven particularly useful, with the proportion of blowing time to pause being variable.

In order to ensure reliable detachment of the threading strip from the drying cylinder, punctiform partial flows, which are generated with the aid of individual nozzles, are preferred for the first gas flow which counteracts the conveying direction of the threading strip. These currents allow a particularly safe overcoming of the adhesive forces. In the further course of the threading strip, its secure guidance is of great importance. Flat partial flows are therefore used for the second and third gas flows, which are generated with the aid of slot nozzles. The area-wide application of gas streams to the threading strip leads to a safe and low-fluttering guidance of the threading strip. In particular, this is prevented twisted in the area of the gas streams, which can lead to paper jam and tearing of the threading strip.

The special distribution of the gas streams described here leads to a particularly reliable transfer of the threading strip: since this is initially acted upon by two gas streams lying directly next to one another, a reliable detachment and transfer of the threading strip to the conveyor belt and the surface of the web guide roller can be achieved be guaranteed. The third gas stream then acts at a distance from the two first gas streams and ensures that the threading strip follows the surface of the web guide roller and is deflected to the next drying cylinder. Since the threading strip is exposed to gas streams practically over half of the looping area of the web guide roller, a trouble-free transfer of the threading strip can be ensured.

Claims

Expectations

1. Drying section for drying a web of material, in particular paper or cardboard web, with at least one drying group having a number of drying cylinders and web guide rollers and at least one nozzle device serving for the transfer of a threading strip, through which the web of material by means of at least one transport belt of the meander is passed through, characterized in that - seen in the conveying direction of the material web (11) - groups of at least two / (one) nozzle devices (17, 19, 21) on one and the same side of the material web (11) behind ¬ are arranged opposite each other.

2. Drying section according to claim 1, characterized gekenn¬ characterized in that the nozzle devices (17,19,21) are attached to a scraper (15).

3. Drying section according to claim 1 or 2, characterized in that the - seen in the conveying direction of the material web (11) - foremost, first Düsenein¬ device (17) serves to generate a gas stream (25) which is substantially opposite to the conveying direction ¬ device of the material web (11) runs.

4. Drying section according to claim 3, characterized gekenn¬ characterized in that the gas stream (25) of the first Nozzle device (17) extends at an angle (a) to the surface of the scraper (15) facing the material web (11), which is in the range of -10 ° a a 25 25 ° and preferably in the range of -5 ° a a 15 15 ° lies.

5. Drying section according to one of the preceding claims, characterized in that a nach¬ following second nozzle device (19) serves to generate a gas stream (29) which extends essentially in the conveying direction of the material web (11).

6. dryer section according to claim 5, characterized gekenn¬ characterized in that the gas stream (29) of the second Düsen¬ device (19) at an angle (ß) to the material web (11) facing surface of the scraper (15), which is in the range of 116 ° ≤ β ≤ 130 ° and preferably in the range of 116 ° ≤ β ≤ 125 °.

7. Drying section according to one of the preceding claims, characterized in that a - seen in the conveying direction of the material web (11) last, third nozzle device (21) serves to generate a gas stream (33) which is substantially transverse to the conveying direction of the material web (11 ) runs.

8. Drying section according to claim 7, characterized gekenn¬ characterized in that the gas stream (29) of the third Düsen¬ device (21) at an angle (δ) to the material web (11) facing surface of the sheet bers (15), which is in the range of 65 ° δ 130 130 ° and preferably in the range of 80 ° δ 125 125 °.

9. Drying section according to one of the preceding claims, characterized in that the first nozzle device (17) is arranged near the front edge of the scraper (15).

10. Drying section according to one of the preceding claims, characterized in that the first and second nozzle means (17, 19) are arranged one behind the other at a small distance.

11. Drying section according to one of the preceding claims, characterized in that the third nozzle device (21) is arranged near the rear edge of the scraper (15).

12. Drying section according to one of the preceding claims, characterized in that the distance from the third nozzle device (21) to the second nozzle device (19) is substantially greater than the distance from the second nozzle device (19) to the first nozzle device (17).

13. Drying section according to one of the preceding claims, characterized in that the Düsen¬ devices (17,19,21) have individual nozzles (65) and / or slot nozzles (67,69).

14. Dryer section according to one of the preceding claims, characterized in that the first nozzle device (17) has individual nozzles (65).

15. Drying section according to claim 14, characterized by a cutout (73) for the individual nozzles

(65) having cover (71) for the first nozzle device (17).

16. Drying section according to one of the preceding claims, characterized in that the second

Nozzle device (19) can comprise slot nozzles (67).

17. Dryer section according to one of the preceding claims, characterized in that the third nozzle device (21) can comprise slot nozzles (69).

18. Drying section according to one of the preceding claims 2 to 17, characterized in that the scraper (15) is designed as a cleaning, removal or transfer scraper.

19. Drying section according to one of the preceding claims 2 to 18, characterized in that all drying cylinders (3) of the drying section (1) are provided with a scraper (15), each of which has at least two / (one) nozzle devices (17, 19) , 21).

20. Drying section according to one of the preceding claims, characterized in that the Düsen¬ devices (17,19,21) are designed as blowpipes. 21. Drying section according to one of the preceding claims, characterized by a control

(35) for the nozzle devices (17, 19,

21).

22. Dryer section according to claim 21, characterized in that the control (35) is assigned to one or more nozzle devices of a dryer group or a dryer section.

23. Drying section according to claim 21 or 22, characterized in that the control (35) each has a solenoid valve (43, 45, 47) for each nozzle device (17, 19, 21).

24. Drying section according to one of claims 21 to 23, characterized in that the control (35) has the air volume adjuster (49, 51, 53) assigned to the nozzle devices (17, 19, 21).

25. Drying section according to one of the preceding claims 21 to 24, characterized in that the control (35) for generating a pulsating air flow comprises a clock circuit (55).

26. Drying section according to one of the preceding claims, characterized in that the distance

(x) between a drying cylinder (3) and a subsequent web guide roller (5) and the distance (y) between the web guide roller (5) and a subsequent drying cylinder (3 ') is selected depending on the embodiment of the web guide roller (5) .

27. Drying section according to claim 26, characterized in that the distance (x) is smaller than the distance (y) when a suction roll is used as the web guide roll (5).

28. Drying section according to claim 26, characterized in that the distance (x) is greater than or equal to the distance (y) when a suction roll is used as the web guide roll (5).

29. A method for transferring a threading strip within a drying section for drying a web of material, in particular paper or cardboard web, in particular a drying section according to one of claims 1 to 28, characterized in that one of a drying cylinder (3) at least two / (one) gas streams (25, 29, 33) are acted upon by a web guide roll (5) overlapping insertion strip of the material web (11).

30. The method according to claim 29, characterized in that the threading strip of the material web (11) is acted upon by a first gas stream (25) directed essentially counter to the direction of conveyance of the material web (11).

31. The method according to claim 29 or 30, characterized in that the threading strip of the material web (11) is acted upon with a second gas stream (29) directed essentially in the conveying direction of the material web (11).

32. The method according to any one of claims 29 to 31, characterized in that the threading strip of the material web (11) with a substantially gas flow (33) directed transversely to the conveying direction of the material web (11) is applied.

33. The method according to any one of claims 29 to 32, characterized in that the gas flows within a dryer section (1) are activated and deactivated at different times.

34. The method according to any one of claims 29 to 33, characterized in that the gas flows are activated only where the threading strip is located.

35. The method according to any one of claims 29 to 34, characterized in that the gas flows are generated by means of a clocked air flow.

36. The method according to claim 35, characterized gekenn¬ characterized in that the clock frequency of the clocked air flow is 0.1 Hz to 5 Hz, preferably 0.2 Hz to 2 Hz, wherein the proportion of blowing time and pause can be selected differently.