DE102005042634A1 - Method and device for producing filament yarns by melt spinning - Google Patents

Abstract

After emerging from the spinneret, the filaments are cooled by a flow of air in the blowing section (10) and then proceed through the chimney (12B) to the wind-up. The walls (26, 28) of the chimney converge towards the exit. A section (32) is porous e.g. less than 50 % in length and having a porosity of 20 to 40 %, to allow air to escape. With a rectangular chimney only one wall need be porous and additional controlled suction can be provided to assist the flow. Independent claims are included for the following: (1) A chimney in which the access doors have a porosity of less than 20 %, preferably 4 to 8 %; (2) A melt spinning process using such a chimney in which the boundary layer on the inner chimney walls is maintained without interruption along its whole length; (3) A melt spinning process of this kind in which some air can escape from the chimney prior to the exit.

Description

The This invention relates to a melt spinning process for the manufacture of filament yarns, in particular in the form of synthetic threads coarser Titers (> 500 dtex) such as so-called BCF (Bulked Continuous Filament) for use in the shape of carpet yarn, T & I (technical and industrial) yarns and tire cord. The invention sees also innovations in the corresponding devices and facilities for the Preparation before.

The Production and processing of filament yarn by melt spinning is basically in Book "Synthetic Fibers "by Franz Fourné (Carl Hanser Verlag, Munich) Page 273 to 455 (hereafter referred to as "Fourné"). The systematics of nomenclature is on pages 720 to 722. Additional explanations are in the article "thread cooling at Melt spinning "in the journal man-made fibers / textile industry, April 1978, pages 315 to 323, and in the technical article "Blasschächte - the state of the art" in man-made fibers / textile industry, June 1987, pages 542-550.

The so-called Blasschächte (also called Blaskammer or Anblaskammer), with their associated Fadenfallröhren (also called downpipe or chute or spinning shaft or shaft shaft), form an important group of facilities in a melt spinning plant - Fourné, pages 348-368. These facilities will be described in more detail below on the basis of 1 explains why a detailed explanation is not given here. The invention is particularly intended for use in a plant where the cooling air is added to the filaments in a cross-flow cooling zone below the spinneret - see Fourné, page 348. The preferred solution comprises a rectangular cross-air blower shaft - see Fourné, page 352. Such solutions provide for the supply of conditioned air into the blower shaft. This step involves considerable costs. It is therefore important that the designed cooling effect is not distorted by uncontrollable air currents in the system.

Out DE-A-4104404 is a blow chamber with an air-permeable chamber wall and one opposite her Chamber wall is known, which is impermeable to an upper and a lower outlet opening for the cooling air.

Out DE-A-19514866 it is known in the spin shaft at least one of lateral outer walls, which parallel to the cooling air flow runs, with Air passage openings to provide. These openings are connected to an exhaust.

• – ein oberer Schachtteil mit rechteckigem Querschnitt, konstanter Breite zwischen den Schacht-Seitenwänden und in Abzugsrichtung verjüngender Tiefe zwischen Schacht-Vorder- und -Rückwand;
• – ein mittlerer Schachtteil mit rechteckigem Querschnitt, sich in Abzugsrichtung verjüngender Tiefe und wahlweise verjüngender Breite; und
• – ein unterer Schachtteil mit konstantem Querschnitt, welcher bis nahe an das Abzugssystem reicht, wobei
• – Luft nahe dem Austritt aus dem mittleren Schachtteil abgezogen wird.

From EP-B-1173634 it is known to provide a cooling system with inter alia the following parts:

• - An upper shaft portion with a rectangular cross section, constant width between the shaft side walls and in the withdrawal direction tapering depth between manhole front and rear wall;
• - A middle shaft part with rectangular cross-section, in the withdrawal direction tapering depth and optionally tapering width; and
• - A lower shaft portion with a constant cross section, which extends to close to the trigger system, wherein
• - Air is withdrawn near the exit from the middle part of the shaft.

Out DE-A-10323532 discloses a yarn well which is so gas-permeable, that on the circumference of the shaft and essentially over its whole length such a free flow cross-section arises that the entrained from the Anblaskammer blast air without pressure build-up can flow radially out of the yarn slot.

These known arrangements see an individual treatment for each Thread in front. Also in the case of EP-A-1173634, where several threads side by side provided in a shaft, it has been or separating plates between the individual filament bundles to insert identical conditions for the individual bundles up to ensure their respective merger. When spinning from Multifilament yarns with coarser ones Titers are usually not provided with partitions.

task The invention is, by the targeted guidance of the air flows and compliance of certain pressure gradients in the whole blower shaft / downpipe system a sufficiently vortex-free airflow without backflow too achieve, so that the yarn formation at least not significantly through these influencing factors are impaired.

These The object is achieved by the features of claims 1, 16, 20 and 22.

embodiments will be described below with reference to the figures. It shows:

1A schematically a view of a melt spinning plant according to the prior art

1B a side view of the same location

2 schematically a view of a blowgap / downpipe system according to the prior art

3 schematically a known modification of the arrangement according to the 1

4 in the 4A a front and in the 4B a side view of a first embodiment according to the present invention

5 in the 5A a front and in the 5B a side view of a second embodiment according to the present invention

6 in the 6A a front and in the 6B a side view of a third embodiment according to the present invention

7 in the 7A a front and in the 7B a side view of a fourth embodiment according to the present invention

8th a diagram for explaining flow conditions in the downpipe

9 a schematic representation of a modification of the arrangement according to the 2 and or 3

10 a schematic representation of a modification of the arrangement according to the 4 , and

11 schematically a modification of the arrangement according to the 9 ,

The 1A and 1B show schematically a tire cord spinning-stretch winding machine, as shown in Fourné (page 282). The reference numerals denote the following elements:

a

spinning beam with nozzle blocks (not shown)

c

spinning pumps

d

Spin pump drives

f

Spinning extruder

i

blowing shaft

k

downspout

n

Quick-winding heads (turret winder)

r

drafting system with hot-draw godets

w

Dyphylverdampfer

y

air-conditioned Supply air.

The filament bundles run in pairs through the downpipe usually to about 0.3 to 1 m below the downpipe end, where they are ever together to a closed thread leads together. The individual threads have a lateral distance of about 30 to 100 mm from each other. In the production of coarser denier yarns such as BCF and engineering yarns, as well as tire cord, air is added to the process in large quantities to cool the extruded filaments. This takes place in the blow shaft (i, 1 ). The air, together with the filaments, from the spinning mill through the chute (k, 1 The air quantity depends essentially on the mass to be cooled - the throughput [kg / h] - Other parameters influencing the air volume are the spun polymer, the single filament titer and the spinning speed.

By the general further development, in particular of the BCF production process, are meanwhile much higher Process speeds possible as before. This will also increase the maximum mass flow rate of BCF Machines significantly increased. This also makes it necessary the amount of cooling air significantly increase.

in this connection can be observed that the conventional manholes (drop tube) only insufficient are suitable to transport large amounts of air, without the through the chute led filaments negative influence. The filaments are mainly by phenomena unsteady currents, like backflows, Flow separation, Turbulence and flow distortions, negatively influenced. This creates undesirable movements of the filaments which in the extreme case an inadmissible contact of filaments in the blow duct, directly or later the process to filament breaks to lead can.

These statements can be closer to the diagram in the 8th be explained theoretically. A drop tube with a rectangular cross section has an inlet with the width H. If the outlet has the same width H, the distance of the outermost filaments (left and right) to the corresponding side wall S from top to bottom is constantly larger. This creates in the vicinity of the side walls S ratios, which favor return flows R. Whether such backflows arise in a particular case, depends on the operating conditions, eg. B. from the take-off speed of the filament bundles and / or from the amount of air supplied. For predetermined flow conditions it will be possible to prevent such reverse flows through guide walls W. The use of such baffles is possible because the filament bundles (in the 8th not shown) are summarized below the downpipe to a thread. The inlet width to the drafting system r ( 1 ) is therefore narrower than the outlet width of the spinnerets. (Not shown). The guide walls W would ideally be viewed from the front than ever to make a curve (without kink), which follow the optimal flow lines between the inlet width H and the narrow outlet width h. However, these optimum ratios could only be achieved for a predetermined set of operating conditions, while in practice a downer has to operate with different sets of operating parameters. Below are various considerations for the practical design of a downpipe set up, this tube can be used flexibly enough for the intended operating range.

The blower shaft / downpipe system according to 1 is again schematically in the 2 shown. As Fourné shows, today's blowholes are 10 ( 2 ) for the cross-flow cooling usually rectangular in cross-section. The front wall, which is in the 2 is viewed directly, is usually equipped with service door, which release the access to the interior of the blower shaft when opening. These doors are usually "porous" (permeable to air) to allow some pressure or flow equalization between the interior of the blower shaft and the environment 2 is not apparent, is permeable to the ingress of cooling air into the cooling space below the spinnerets (in 2 not shown, see Fourné, pages 348 and 352, respectively).

At the bottom of the blower shaft 10 close the downpipe 12 an, which is usually an upper part 14 with a constant cross section and a lower part 16 having a taper. The taper is through converging ("tapered") sidewalls 18 . 20 formed, wherein the rear and front walls are in approximately parallel (vertical) planes. In principle, all walls of the downcomer are impermeable to air currents to shield the "air" within the pipe from interfering environmental influences, but in practice it is often impossible to avoid smaller openings in the structure which allow unwanted airflows also enter between the blower shaft and the downpipe.

The strings 22 . 24 running from the spinnerets in a straight line (seen from the front) down on the first yarn guide (not shown) in the inlet part of the drafting system (r, 1 ). As already explained, they are in the blower shaft 10 subjected to a Querblasluftkühlung. The downpipe 12 Down running Filamentbündeln (dashed lines drawn center lines) tear each a large amount of air from the blow shaft 10 with itself - see Fourné, pages 184 to 192, in particular page 191. By the convergent ("conical") shape of the lower part 16 of the drop tube, the cross section at the lower end is 5 to 10 times smaller than at the upper end. Under today's operating conditions, the air speed therefore increases against the lower end of the downpipe 12 very strong and can z. T. higher than the thread speed. The high air velocities lead to a strong turbulent flow and to a restless running of the threads. The "kink" in the wall surfaces where the convergent lower part 16 at the top 14 with a constant flow cross-section, can lead to boundary layer separation, which favors the turbulence. (see "Technical Fluid Mechanics, Volume I: Basics" 9th edition, Springer Verlag 1988, author Bruno Eck, from page 127) .The cross-sectional profile from top to bottom preferably has no extensions, because the risk of boundary layer separation in the case of a cross-sectional widening very much higher than in the case of a rejuvenation The high air velocity at the lower end of the downpipe 12 , which is generated at least in part as a side effect of the cross-sectional taper, can also in Spinnfinish order in the inlet part of the drafting system (r, 1 ) have a disruptive effect.

When emerging from the spinnerets (not shown), the individual filaments of a thread over a larger area evenly distributed (in 2 only the centerline of each bundle is shown). These filament bundles taper steadily and become at the lower end of the drop tube 12 combined into a compact thread. The in the blower shaft 10 and in the upper part 14 of the downpipe 12 In the interior of the filament bundles moving air must therefore be in the lower part 16 of the downpipe 12 emerge laterally from the tapering filament bundles. It has approximately the speed of the filaments and contributes to increasing the average air velocity in this part of the downpipe 12 at.

Furthermore arise laterally in the upper part 14 of the downpipe 12 Whirl. These vortices cause backflow of air and thus an increase in turbulence. In addition, the vertebrae are unstable locally and temporally and move with the threads 22 . 24 downward. In the upper part 14 new eddies are constantly forming again. Also this effect leads to a strong restlessness in the case of the downpipe 12 ongoing threads 22 . 24 , Through the troubled run, the filaments can touch each other. In the upper part of the blower shaft 10 the filaments are still soft and sticky, when they touch there they stick together. In the subsequent process stages, this leads to running disturbances or yarn breaks.

3 shows an improved arrangement for the blow duct 10 and the downpipe 12A , The case pipe 12A is conically formed over its entire length, that the side walls 26 . 28 converge downwards and taper the flow cross-section downwards. The distance between the outermost filaments and the sidewalls 26 . 28 of the downpipe 12A is thus more or less constant. A vortex formation and backflow are prevented over the entire length of the downpipe. This arrangement of the downpipe has been used in the "Pathfinder" BCF system of Maschinenfabrik Rieter AG, but with relatively short downpipe lengths of about 1m, but this pipe length is not suitable / sufficient for all applications.

The in the blower shaft 10 But in the horizontal direction supplied cooling air is also in the case of 3 deflected downwards by the running filaments. She moves with the threads through the downpipe 12A down and exits at high speed at the bottom of the downpipe. This has a detrimental effect on the lubrication of the threads in the inlet part of the drafting part of the machine. Further - the strong pumping action of the downwardly moving threads can also be seen at least in the lower part of the blower shaft 10 create a negative pressure. This is caused by unavoidable gaps and openings in the blower shaft 10 Air sucked from the environment. The amount of air in the system is thereby increased uncontrollably. This "false air" is usually not conditioned and can maintain a constant temperature and humidity of the air in the blower shaft 10 render impossible. The in the blower shaft 10 incoming air also creates eddies and disturbs the smooth threadline.

Around the subsidized down Limit the air flow, the cross section at the bottom of the Downpipe smaller chosen become. Leading but again to an increase in the exit velocity of the Air at the bottom of the downpipe and does not solve the problem.

versions the invention

A Substantial improvement can be achieved by having at least one Wall of the downpipe above a part of their length breathable is designed. From the air-permeable wall elements flows a part of the downflowing Air off. The main air flow in the downpipe is by this measure the downward decreasing cross-section largely adapted. The Air velocity in the downpipe thus does not increase towards the lower end or only insignificantly. A very slightly accelerated down flow may be advantageous, since experience shows slightly accelerated flows less tend to vortex formation. The side openings in the downpipe can one or more pages about a part or over the whole length be attached to the downpipe. They can also be completely circumferential accomplished be. The arrangement according to The invention nevertheless differs from DE-A-10323532 in that the cross section of the new downpipe tapers downwards.

The 4 A, B together show a first embodiment for the lateral discharge of the air from the downcomer 12B where the shape of the pipe 12B , in particular the side walls 26 respectively. 28 , opposite the pipe 12A remained unchanged. The back wall 30 ( 4B ) of the downpipe 12B Ie the downcomer wall on the same side as the blow duct wall 36 with the openings for the blowing air inlet into the blowing shaft 10 - is in the lower section 32 , adjacent to the air or thread outlet 34 , provided with openings. These openings are designed as side air outlets, ie the rear wall 30 has now been made permeable to air. This is preferably done by the section 32 the back wall 30 is formed by a perforated plate. The lateral openings could also z. B. are formed by a sieve. The openings should definitely be an unwanted escape of the threads from the downpipe 12B prevent.

The sum of the flow-free areas created by the openings relative to the total area of the perforated section 32 the back wall 30 determines the so-called "porosity" of this wall section 32 , Depending on the structure and free surface of these elements can thus be a targeted dosage of the section 32 outgoing airflow can be achieved. The porosity and total area of the perforated section together determine the flow resistance to lateral flows in this section. This resistance should be chosen such that there is a slight overpressure (eg in the range of 0.1 to 3 Pascal, preferably in the range of 0.1 to 1 Pascal) at all points in the vicinity of the walls of the downpipe with respect to the environment. This can be ensured that no ambient air penetrates into the downpipe, the cross-sectional taper also does not lead to an intolerable increase in speed of the remaining air.

The porosity of or a perforated portion is conveniently in the range 5 to 50% and preferably in the range 20 to 40%. The total length of the perforated walls is preferably not more than 50% of the total length of the walls of the downpipe.

5 and 6 show further embodiments of the formation of the downpipe 12C ( 5 ) respectively. 12D ( 6 ), wherein in both embodiments each have a porous section 32 the respective back wall 30 ( 5 ) respectively. 30A ( 6 ) is provided. To achieve the desired optimum pressure and Ge speed can be achieved over the entire length of the downpipe, the downpipe 12C from an upper part 36 and a lower part 38 be formed. The side walls 26A . 28A are designed so that they are in the upper part 36 with a first cone angle, and in the lower part 38 converge with a second cone angle. The "kink" between adjacent parts can therefore, in comparison to the arrangement according to the 2 , which reduces the risk of boundary layer separation at these sites. The lower part 38 includes the porous section 32 the back wall 30 , where the back wall 30 and the front wall 40 still standing in respective vertical planes. This results in an approximation of lateral inner surfaces of the downpipe 12C which each form a continuous curve and thereby reduce the risk of boundary layer detachment.

In the embodiment according to the 6 are the side walls 26A . 28A compared to the embodiment according to the 5 remained unchanged. The back wall 30A and front wall 40A but now run in the lower part 38 of the downpipe 12D also together to the cross section of the downpipe at the outlet 34A to narrow even more in the lower part. This further reduces the risk of backflow and vortex formation in the "dead corners" near the lower air outlet.

Further improvements in the control of the various air flows can be achieved by means of an arrangement 7 be achieved. The shape of the downpipe 12F is the shape of the downpipe 12B ( 4 ) alike, especially in that the walls 26 . 28 also over the entire length of the downpipe 12F converge down. The front wall and back wall 30B are also arranged in respective vertical planes in this case. Instead of a single perforated section 32 in the back wall 30 , like in the 4 are shown, but are in the embodiment according to the 7 several (in this case, three) perforated sections 42 . 44 . 46 ( 7B ) in the back wall 30B intended. This allows a further improvement of the flow conditions within the downpipe by adjusting the lengths or the porosity of the respective sections 42 . 44 . 46 to the flow conditions within the pipe.

In order to further increase the adaptability of the system, the airflow exiting laterally from the downcomer can be regulated in its entirety or subdivided by suitable means. The appropriate means include z. B: Flaps, fans, etc. In the embodiment according to 7 z. B. the laterally emerging air streams in a closed exhaust system 50 ( 7B ) and can be dosed individually with throttle valves D1, D2 and D3. The air is sucked off by a fan V. The whole device is thus less sensitive to pressure fluctuations in the vicinity of the downpipe. Such disturbing pressure fluctuations can be in a building z. B. arise through the opening and closing of doors. With this embodiment, the pressure and velocity course in the downpipe can be optimized in a simple manner.

By these designs succeeded in developing a design or a design system that or a flow in the chute, even with larger ones Air volumes do not adversely affect the filament movement in the chute. For this purpose, the flow should preferably stationary and be designed swirl-free. It's not just about optimization the flow, there are also boundary conditions such as the air velocity at the outlet the filaments at the lower end of the downpipe, the pressure curve in to include the whole system and the handling.

The invention is not limited to the embodiments according to the 4 to 7 limited. Advantageous effects can also be achieved if porous (air-permeable) sections are provided in the wall structure of an otherwise conventional downpipe. Such an arrangement is shown schematically in FIG 9 shown where the reference 10 again designates the blow duct and the downpipe an upper part 52 and a lower part 54 having. The flow cross section in the upper part 52 is substantially constant over its length and approximately equal to the flow area at the transition from the blow shaft 10 , The flow cross-section in the lower part 54 tapers down substantially similar to the previously known solutions associated with the 1 and 2 were declared. The execution according to the 9 differs from the known solutions in that the rear wall of the downer tube part 54 a lower porous or air-permeable section 32 which is at the exit 34 borders. Also in this case, the part 54 according to the principles of 5 to 7 be adjusted. The length L of the upper part 52 is, viewed in the flow direction, preferably not more than 10% of the total length of the downpipe.

It is also possible, or practically unavoidable, to influence the flow conditions, in particular the pressure, in the blow duct by influencing the flow conditions in the downpipe. Due to the suitable design of the downpipe, in particular a harmful negative pressure or overpressure in the blower shaft can be avoided. To extend this advantage even further, the service door in the front wall of the blower shaft 10 designed with a relatively low porosity to the incoming and outgoing air quantity limit this position to a minimum. The doors of today conventional blowholes are usually designed with a porosity in the range of 50%, ie about 50% of the total surface of the doors is released for the inflow and outflow of air. A blower shaft for use with a drop tube according to this invention preferably has service doors with a porosity not greater than 20% and typically in the range 4 to 8%. The free flow openings are preferably distributed over the entire surface of the service doors.

As already related to the 3 has been explained, it is possible the arrangement according to the 9 to improve in that the side walls of the downcomer over the entire length of the tube converge downwards, as in the 9 is indicated by dashed lines, according to this invention, the air-permeable portion 32 would be retained. This gives a better approximation to the ideal conditions associated with the 8th were explained, with even better approximations by the additional cone angle according to the 4 to 6 can be achieved, but at higher production costs. Based on 10 Now another improvement will be explained.

The 10 shows with solid lines a version that in principle the execution according to the 4 is the same, the blow shaft 10 in the 10 is shown without shading. With dashed lines it has been indicated that the side walls S of the downpipe 12 could be continued upward in the blower shaft. In this embodiment, therefore, the blow duct is also partially tapered down and the downpipe joins it without discontinuities in the cross-sectional profile. The distance between the outermost filaments and the nearest wall can therefore be kept exactly constant in this embodiment both partially in the blow duct and in the downpipe. Furthermore, the "flow kink" that normally appears at the wall transition between the blow duct and the downcomer can be avoided.

One Downpipe according to This invention preferably has a length from the blow duct to the air outlet at the lower end of at least 2.5 m, preferably 3 to 5 m. The Air velocity at the exit (lower end) is between 0 and 7 m / sec, preferably between 2 and 4 m / sec. The filament speed when exiting the downpipe is normally 12 to 20 m / sec., preferably about 14 to 16 m / sec.

The embodiments according to the figures are all designed for spinning plants, which have two threads per position, ie per downpipe. The invention is applicable even if more than two threads per position, for. B. up to 12 threads per position, are provided. For this reason, the drop tube is rectangular in cross section. With a high number of filament bundles per position, partitions may be provided within the blow duct and the downcomer. In the preferred solution, however, separate drop tubes are provided so that the filament bundles pass in pairs through a drop tube, with the bundles of a pair adjacent the sidewalls. The maximum possible convergence of the sidewalls is then given by the path of the outermost filaments until merger. The same considerations determine the maximum possible convergence of the back and front walls of the downpipe. Although the filament bundles are preferably assigned in pairs to the drop tubes of a system, it is possible to assign several (at least two) bundle pairs to a common blow shaft. Such an arrangement is shown schematically in FIG 11 shown, wherein the use of the reference numerals 10 . 52 . 54 . 32 and 34 in the 11 the use of the same characters in the 9 equivalent.

The Design principles according to enable this invention a downpipe design that also provides a largely stationary, vortex-free air flow different air flow rates results. The downpipe can now be designed such that boundary layer stripping as far as possible be prevented. expedient In this context, a blowing duct / downpipe design is included the over the entire length no sudden cross-sectional changes are present.

The invention should not be limited by reference to a particular theory of operation. The following explanations are therefore presented only in the context of an explanation of possible relationships between the measures specifically proposed. Further research may prove that these theoretical explanations need to be changed at least in part:
The cooling air introduced into the blower shaft has potential (pressure) energy. The high pumping action of the filament bundles converts this potential energy into kinetic energy, increasing the air velocity, reducing the pressure, and increasing the effect in the downpipe , on the one hand because the filament speed is increased by the stretching of the filaments and on the other hand because of the narrowing of the downpipe cross-section.The overall effect can go so far that the air in some section of the system, usually in the lower part of the downpipe but possibly even in the lower part of the blower, opposite the environment has negative pressure. By means of smaller, unavoidable openings in the wall structure, ambient air then mixes with the cooling air. As a result, the amount of air in the system is further increased and the effect of the previous air conditioning of the cooling air is partially canceled. One now counteracts these complex interactions by reducing the amount of air in at least one section of the downpipe by draining. This can limit the increase in air velocity and the risk of negative pressure. The air pressure in this section must be higher than the ambient pressure or the pressure in the receiving vessel.

• – einer oder mehreren (seitlichen oder rundherum wirkenden) Absaugungen über einen oder mehrere Teilbereiche des Fallrohres, und/oder
• – ein Fallrohrdesign, das aus zwei oder mehreren Teilstücken mit unterschiedlichem Konuswinkel zusammengesetzt ist und/oder
• – einem Fallrohrdesign, bei dem mindestens einen der Teilstücke in zwei Ebenen konisch ausgebildet ist.

The invention thus makes it possible to design a blow duct / downpipe system in such a way that the air flows are regulated and / or controlled and supplied away. Advantageous in this context is a downpipe design with

• - One or more (lateral or all-around) suction over one or more sections of the downpipe, and / or
• - A downpipe design, which is composed of two or more sections with different cone angle and / or
• - A downpipe design, wherein at least one of the sections is conical in two planes.

Claims (25)

Drop tube with a wall structure, which forms a first flow cross section at one end and a second flow cross section at the other end, wherein the second cross section is smaller than the first cross section, characterized in that the wall structure at least one longitudinal portion which is not air-permeable, and at least one having air-permeable longitudinal section. Downpipe according to Claim 1, characterized in that the air-permeable portion is provided in a wall portion where the flow cross-section rejuvenated. Downpipe according to Claim 1 or claim 2, characterized in that the wall structure more Longitudinal sections, which are not permeable to air, as well as several air-permeable longitudinal sections having. Downpipe according to one of the preceding claims, characterized in that the porosity of the or an air-permeable portion in the range 5 to 50%, preferably in the range 20 to 40%. Downpipe according to one of the preceding claims, characterized in that the total length of the air-permeable walls is not more than 50% of the total length the walls of the downpipe amounts. Downpipe according to one of the preceding claims, characterized in that the flow cross section rectangular is, and only one wall of the wall structure with an air-permeable section or several air-permeable Sections is provided. Downpipe according to one of the preceding claims, characterized in that the air-permeable or at least one air-permeable portion with a suction in flow connection stands. Downpipe according to Claim 7, characterized in that a means for influencing the flow is provided between the wall portion and a suction means. Downpipe according to Claim 7 or 8, characterized in that a plurality of air-permeable sections are present and at least two air-permeable sections with the suction in fluid communication stand. Downpipe according to one of the preceding claims, characterized in that the ends are open and the shaft cross-section steadily over the length of the shaft changes. Downpipe according to one of the preceding claims, characterized in that the tube has a rectangular cross-section and at least two opposing walls over the whole Length of the Tube converge. Downpipe according to Claim 11, characterized in that the walls are continuous converge. Downpipe according to Claim 11, characterized in that the walls have at least two sections having different convergence angles. Downpipe according to one of the preceding claims, characterized in that at the end with the larger flow cross-section connects a blower shaft. Downpipe according to Claim 14, characterized in that no discontinuous changes in the flow cross-section at the transition from the blower shaft to the downpipe or downpipe. Downpipe according to claim 14 or 15, as characterized in that the blower shaft service door with a porosity not greater than 20%, and preferably in the range 4 to 8%. Downpipe according to Claim 14, characterized in that the free flow openings on the total area the service doors are distributed. Blowing shaft marked by service door with a porosity not bigger as 20% and preferably in the range 4 to 8%. Blowing shaft according to Claim 18, characterized in that the free flow openings over the total area the service doors are distributed. A method of spinning a filament strand a melt that after filament formation in a cooling shaft solidified, with cooling air in a first shaft section added to the filaments, through the Accelerated filaments in the direction of movement of the filament bundle and then through a further shaft section (a chute) with the filament bundles is forwarded together, wherein the flow cross-section in the flow direction gradually eingt, characterized in that over the entire length or the air flow around the entire circumference of the further shaft section Boundary layer on the inner surface the shaft wall forms and continuously sustains. Method according to claim 20, characterized in that that over the whole length the further shaft section, the air flow over the entire shaft cross-section is directed substantially in the direction of movement of the bundle and this Condition continuously maintained. A method of spinning a filament strand a melt that after filament formation in a cooling shaft solidified, with cooling air in a first shaft section added to the filaments, through the Accelerated filaments in the direction of travel direction of the filament bundle and then through a further shaft section (a chute) with the filament bundles is forwarded together to the shaft exit, whereby at least a part of the further shaft section of the flow cross-section in the flow direction gradually narrows, characterized in that air before the shaft exit evades from the shaft. Process according to Claim 22, characterized in that between the first manhole section and no air is added to the filaments at the exit. Process according to Claim 22 or 23, characterized in that out of the shaft escaping air sucked by a fan and possibly as cooling air is returned. Process according to one of the preceding claims 22 to 24, characterized in that the air velocity at Outlet 7 m / sec. does not exceed.