EP1762644A1 - Process and apparatus for the meltspinning of filament yarns - 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 invention relates to a melt spinning process for the production of filament yarns, in particular in the form of synthetic yarns having coarser titers (> 500 dtex) such as so-called BCF (Bulked Continuous Filament) for use in the form of carpet yarn, T & I (technical and industrial) yarns and tire cord. The invention also provides innovations in the corresponding devices and devices for the production.

State of the art

The production and processing of filament yarn by melt spinning is basically described in the book " Synthetic Fibers "by Franz Fourné (Carl Hanser Verlag, Munich) pages 273 to 455 described (hereinafter "Fourné"). The system of nomenclature can be found on pages 720 to 722. Additional explanations are in the article " Thread cooling in melt spinning "in the journal Man-made Fibers / Textile Industry, April 1978, pages 315 to 323 , as well as in the article " Blasschächte - the state of the art "in man-made fibers / textile industry, June 1987, pages 542-550 to find.

The so-called Blasschächte (also called Blaskammer or Anblaskammer), with their associated thread trap tubes (also called just downpipe or chute or spin shaft or shaft shaft), form an important group of facilities in a melt spinning plant - Fourne, pages 348-368. These facilities will be explained in more detail below with reference to Figure 1, which is why a detailed explanation is omitted 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 a blow chamber with an air-permeable chamber wall and a chamber wall opposite it is known, which is impermeable to an upper and a lower outlet opening for the cooling air.

Out DE-A-19514866 It is known to provide in the spinning shaft at least one of the lateral outer walls, which runs parallel to the cooling air flow, with air passage openings. 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.

Out EP-B-1173634 It is known to provide a cooling system with, inter alia, the following parts:

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

Out DE-A-10323532 a thread chute is known, which is gas-permeable, that on the circumference of the shaft and substantially over its entire length, such a free flow cross-section arises that the entrained from the Anblaskammer, Blasluftstrom can flow radially out of the yarn chute without pressure build-up.

These known arrangements provide an individual treatment for each thread. Also in the case of EP-A-1173634 Where several threads are provided side by side in a well, it has been proposed to insert baffles between the individual filament bundles to ensure identical conditions for the individual bundles until their respective combination. At the Spinning of multifilament yarns with coarser titers, however, will normally not provide partitions.

The object of the invention is to achieve a sufficiently vortex-free air flow without backflow through the targeted guidance of the air flows and compliance with certain pressure curves throughout the blower shaft / downpipe system, so that the yarn formation is at least not significantly affected by these factors.

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

Figur 1A

schematisch eine Ansicht einer Schmelzspinnanlage gemäss dem Stand der Technik

Figur 1B

eine Seitenansicht der gleichen Anlage

Figur 2

schematisch eine Ansicht eines Blasschacht-/Fallrohrsystems gemäss dem Stand der Technik

Figur 3

schematisch eine bekannte Modifikation der Anordnung gemäss Figur 1

Figur 4

in der Figur 4A eine Vorder- und in der Figur 4B eine Seitenansicht einer ersten Ausführung gemäss der vorliegenden Erfindung

Figur 5

in der Figur 5A eine Vorder- und in der Figur 5B eine Seitenansicht einer zweiten Ausführung gemäss der vorliegenden Erfindung

Figur 6

in der Figur 6A eine Vorder- und in der Figur 6B eine Seitenansicht einer dritten Ausführung gemäss der vorliegenden Erfindung

Figur 7

in der Figur 7A eine Vorder- und in der Figur 7B eine Seitenansicht einer vierten Ausführung gemäss der vorliegenden Erfindung

Figur 8

ein Diagramm zur Erklärung von Strömungsverhältnisse im Fallrohr

Figur 9

eine schematische Darstellung einer Modifikation der Anordnung gemäss der Figur 2 und/oder 3

Figur 10

eine schematische Darstellung einer Modifikation der Anordnung gemäss der Figur 4, und

Figur 11

schematisch eine Modifikation der Anordnung gemäss der Figur 9.

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

Figure 1A

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

FIG. 1B

a side view of the same plant

FIG. 2

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

FIG. 3

schematically a known modification of the arrangement according to FIG. 1

FIG. 4

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

FIG. 5

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

FIG. 6

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

FIG. 7

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

FIG. 8

a diagram for explaining flow conditions in the downpipe

FIG. 9

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

FIG. 10

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

FIG. 11

schematically a modification of the arrangement according to FIG. 9

State of the art

• a - Spinnbalken mit Düsenblöcke (nicht gezeigt)
• c - Spinnpumpen
• d - Spinnpumpenantriebe
• f -Spinnextruder
• i - Blasschacht
• k - Fallrohr
• n2 - Schnellspulköpfe (Revolverspulautomat)
• r - Streckwerk mit Heissstreckgaletten
• w - Diphylverdampfer und Diphyl-Leitung
• y - klimatisierte Zuluft.

Figs. 1A and 1B schematically show a tire cord spun-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 - spinning pump drives
• f Spider extruder
• i - Blowing shaft
• k - downpipe
• n2 - quick-winding heads (revolver-winder)
• r - drafting system with hot stretch godets
• w - Diphyl evaporator and Diphyl line
• y - conditioned air supply.

The filament bundles run in pairs through the downpipe usually to about 0.3 to 1 m below the downpipe end, where they ever merged into a closed thread become. 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 blower shaft (i, Fig. 1). The air is, together with the filaments, passed from the spinning screens through the chute (k, Fig. 1) in the "first floor". The amount of air depends essentially on the mass to be cooled - the throughput [kg / h]. Other parameters that affect the amount of air are the spun polymer, the filament titer and the spinning speed.

Due to the general further development, in particular of the BCF production process, significantly higher process speeds are now possible than before. This also significantly increases the maximum mass throughput of BCF machines. This also makes it necessary to increase the amount of cooling air considerably.
Here it can be observed that the conventional downpipes (downpipes) are only insufficiently suitable for transporting large amounts of air without adversely affecting the filaments guided through the chute. The filaments are adversely affected mainly by the appearance of unsteady flows, such as backflow, flow separation, turbulence and flow distortions. This results in unwanted movements of the filaments which in extreme cases an impermissible contact of filaments in the blow duct, which can lead to filament breaks directly or later in the process.

These statements can be explained in more detail theoretically with reference to the diagram in FIG. 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 L (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 backflow R 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 have such backflows R by baffles W to prevent. The use of such baffles W is possible because the filament bundles (not shown in FIG. 8) are combined below the drop tube to form one thread each. The inlet width into the drafting system r (FIG. 1) is therefore narrower than the outlet width from 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 optimal 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 blow-shaft / down-pipe system according to FIG. 1 is shown again schematically in FIG. As Fourné shows, the current Blasschächte 10 (Figure 2) for cross-flow cooling are usually rectangular in cross-section. The front wall, which is directly viewed in Figure 2, is normally equipped with service doors, which release the access to the interior of the blowing duct when opening. These doors are usually "porous" (air permeable) to allow some pressure or flow equalization between the interior of the blow duct 10 and the environment. The rear wall, which is not apparent in Figure 2, is permeable to air, to allow the entry of the cooling air into the cooling space below the spinnerets (not shown in Fig. 2, see Fourné, page 348 and 352).

At the bottom of the blowing shaft 10, the downpipe 12 adjoins, which usually has an upper part 14 with a constant cross-section and a lower part 16 with a taper. The taper is formed by converging ("tapered") sidewalls 18, 20 with the back and front walls in approximately parallel (vertical) planes. In principle, all walls of the downpipe are impermeable to air currents in order to shield the "air budget" within the pipe from interfering influences from the environment. In practice, however, it is often impossible to avoid smaller openings in the structure, which unwanted air currents enable. Ambient air can also enter between the blow duct 10 and the downpipe 12.

The threads 22, 24 run from the spinnerets in a straight line (seen from the front) down to the first thread guide (not shown) in the inlet part of the drafting system (r, Figure 1). As already explained, they are subjected to a Querblasluftkühlung in the blower shaft 10. The down in the downpipe 12 Filamentbündel 22, 24 (dashed lines drawn center lines) each entrain a large amount of air from the blow shaft 10 with it - see Fourné, page 184 to 192, in particular page 191. By the convergent ("conical") Shape of the lower part 16 of the downpipe is the cross section at the lower end 5 to 10 times smaller than at the upper end. Under today operating conditions, therefore, the air velocity rises very strongly against the lower end of the downpipe 12 and 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 adjoins the top part 14 with a constant flow cross-section, can lead to boundary layer detachments, which favors the turbulence. (please refer " Technical Fluid Mechanics, Volume I: Fundamentals "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 is much higher than in the case of a taper. The high air velocity at the lower end of the drop tube 12, which is generated at least in part as a side effect of the cross-sectional taper, may also interfere with the spin finish order in the inlet part of the drafting system (r, Fig. 1).

Upon exiting the spinnerets (not shown), the individual filaments of a thread 22, 24 are evenly distributed over a larger area (only the centerline of each bundle is shown in FIG. 2). These filament bundles 22, 24 taper steadily and are combined at the lower end of the drop tube 12 into a compact thread. The moving air in the blower shaft 10 and in the upper part 14 of the drop tube 12 in the interior of the filament bundles 22, 24 must therefore laterally exit from the tapering filament bundles 22, 24 in the lower part 16 of the drop tube 12. She has approximate the speed of the filaments and contributes to increase the average air velocity in this part of the downpipe 12 at.

In addition arise laterally in the upper part 14 of the downpipe 12 vortex. These vortices cause backflow of air and thus an increase in turbulence. In addition, the vertebrae are not stable locally and with time and move with the threads 22, 24 downwards. In the upper part 14 then constantly new vortex form again. This effect also leads to a great deal of restlessness in the threads 22, 24 running through the drop tube 12. The filaments can touch one another due to the restless running. In the upper part of the blow 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.

FIG. 3 shows an improved arrangement for the blow duct 10 and the downpipe 12A. The drop tube 12A is formed conically over its entire length, that the side walls 26, 28 converge down and taper the flow cross-section downwards. The distance of the outermost filaments to the side walls 26, 28 of the downpipe 12A is thus more or less constant. Vortex formation and backflow are inhibited over the entire length of the drop tube 12A. This arrangement of the downpipe 12A has been used in the "Pathfinder" BCF system of Maschinenfabrik Rieter AG, but with relatively short downpipe lengths of approx. 2.5m. However, this tube length is not suitable / sufficient for all applications.

However, the cooling air supplied in the blowing duct 10 in the horizontal direction is also deflected downward in the case of FIG. 3 by the running filaments. It moves with the threads 22, 24 down through the drop tube 12A and exits at high speed at the lower end of the drop tube. This has a detrimental effect on the lubrication of the threads in the inlet part of the drafting part of the machine. Next - the strong pumping action of the downwardly moving threads 22, 24 may also generate a negative pressure at least in the lower part of the blow shaft 10. As a result of unavoidable gaps and openings in the blow duct 10 air is sucked from the environment. The amount of air in the system is thereby increased uncontrollably. This "false air" is usually not conditioned and can make it impossible to maintain a constant temperature and humidity of the air in the blow shaft 10. The air flowing into the blower shaft 10 also creates eddies and disturbs the smooth threadline.

In order to limit the amount of air conveyed down, the cross section at the lower end of the downpipe can be made smaller. However, this again leads to an increase in the exit velocity of the air at the lower end of the drop tube 12A and does not solve the problem with it.

Embodiments of the invention

A significant improvement can be achieved by making at least one wall of the downpipe over part of its length permeable to air. From the air-permeable wall elements flows from a part of the downwardly flowing air. The main air flow in the downpipe is largely adapted by this measure the downwardly decreasing cross-section. The air velocity in the downpipe thus does not rise to the lower end or only insignificantly. A very slightly accelerated downward flow may be advantageous, since experience has shown that slightly accelerated flows are less prone to vortex formation. The side openings in the downcomer may be attached to one or more sides over part or the entire length of the downcomer. They can also be designed completely around the circumference. The arrangement according to the invention nevertheless differs from the DE-A-10323532 in that the cross section of the new downpipe tapers downwards.

Figures 4, A and B together show a first embodiment for the lateral discharge of the air from the downcomer 12B, wherein the shape of the tube 12B, in particular the side walls 26 and 28, respectively, has remained unchanged with respect to the tube 12A. The back wall 30 (FIG. 4B) of the downcomer 12B - ie the downcomer wall on the same side as the blower duct wall with the openings for the blast air inlet into the blower shaft 10 - is in the lower portion 32, adjacent to the air or thread outlet 34, with Provided openings. These openings are designed as side air outlets, ie the Rear wall 30 has now been made permeable to air. This preferably takes place in that the section 32 of the rear wall 30 is formed by a perforated plate. The lateral openings could also be formed, for example, by a sieve. The openings should definitely prevent unwanted leakage of the threads from the drop tube 12B during piecing.

The sum of the flow-free surfaces generated by the openings in relation to the total area of the perforated section 32 of the rear wall 30 determines the so-called "porosity" of this wall section 32. Depending on the structure and free surface of these elements, a targeted metering of the outgoing air stream in section 32 can be achieved become. The porosity and total area of the perforated section together determine the flow resistance to lateral flows in this section. This resistance should be selected 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 12B with respect to the environment , This can be ensured that no ambient air penetrates into the downpipe 12B, wherein the cross-sectional taper also does not lead to an intolerable increase in the speed of the remaining air.

The porosity of the or a perforated section 32 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 drop tube 12B.

Figures 5 and 6 show further embodiments for the formation of the drop tube 12C (Fig. 5) and 12D (Fig. 6), wherein in both embodiments depending on a porous portion 32 of the respective rear wall 30 (Fig. 5) and 30A (Fig 6). In order to achieve the desired optimum pressure and velocity over the entire length of the downpipe, the drop tube 12 C may be formed of an upper part 36 and a lower part 38. The side walls 26A, 28A are configured to converge in the upper part 36 at a first cone angle, and in the lower part 38 at a second cone angle. The "kink" between adjacent parts Therefore, in comparison to the arrangement according to FIG. 2, it can be reduced in size, which reduces the risk of boundary layer separation at these locations. The lower part 38 comprises the porous portion 32 of the back wall 30, with the back wall 30 and the front wall 40 still standing in respective vertical planes. This results in an approach to lateral inner surfaces of the downpipe 12C, each of which form a continuous curve and thereby reduce the risk of Grenzschichtabllosungen.

In the embodiment according to FIG. 6, the side walls 26A, 28A have remained unchanged with respect to the embodiment according to FIG. However, the rear wall 30A and front wall 40A now also converge in the lower part 38 of the drop tube 12D in order to narrow the cross section of the drop tube 12D at the outlet 34A in the lower part 38 even further. Thereby, the risk of backflow and vortex formation in "dead corners" near the lower air outlet 34A can be further reduced.

Further improvements in the control of the various air flows can be achieved by an arrangement according to FIG. The shape of the drop tube 12F is similar to the shape of the drop tube 12B (Fig. 4), particularly in that the walls 26, 28 also converge down the entire length of the drop tube 12F. The front wall and rear wall 30B are also arranged in respective vertical planes in this case. Instead of a single perforated section 32 in the rear wall 30; As shown in FIG. 4, however, in the embodiment according to FIG. 7, a plurality (in this case, three) perforated sections 42, 44, 46 (FIG. 7B) are provided in the rear wall 308. This allows for further improvement of the flow conditions within the downcomer 12F by adjusting the lengths or porosity of the respective sections 42, 44, 46 to the flow conditions within the tube 12F.

In order to further increase the adaptability of the system, the airflow exiting laterally from the drop tube 12F may be regulated as a whole or divided into partial flows by suitable means D1, D2, D3. The appropriate means D1, D2, D3 include z. B: Flaps D1, D2, D3, fans V etc. In the embodiment according to FIG. For example, the laterally exiting air streams are introduced into a closed exhaust system 50 (Figure 7B) and may individually with throttles D1, D2 and D3 are dosed. 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 12F. 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 drop tube 12F can be easily optimized.

Through these designs, it has been possible to develop a design or a design system that allows a flow in the chute, which does not adversely affect the filament movement in the chute even with larger amounts of air. For this purpose, the flow should be formed as stationary as possible and vortex-free. It is not just about the optimization of the flow, it is also boundary conditions such as the air velocity at the exit of the filaments at the lower end of the downpipe, the pressure curve in the whole system and to include the handling.

The invention is not limited to the embodiments according to FIGS. 4 to 7. 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, where the reference numeral 10 again designates the blow duct and the downpipe has an upper part 52 and a lower part 54. The flow cross section in the upper part 52 is substantially constant over its length and approximately equal to the flow cross section at the transition from the blow shaft 10. The flow cross section in the lower part 54 tapers down substantially equal to the previously known solutions, in connection with the figures 1 and 2 were declared. The embodiment according to FIG. 9 differs from the known solutions in that the rear wall of the downpipe part 54 has a lower porous or air-permeable section 32 which adjoins the outlet 34. In this case too, the part 54 can be adapted according to the principles of FIGS. 5 to 7. The length L _{1 of} the upper part 52, viewed in the flow direction, is preferably not more than 10% of the total length of the drop tube.

It is also possible, or virtually unavoidable, to influence the flow conditions, in particular the pressure, in the blow duct 10 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 blow duct 10 can be avoided. In order to further extend this advantage, the service door in the front wall of the blower shaft 10 can be designed with a relatively low porosity in order to minimize the incoming and outgoing air quantity at this point. The doors of today conventional blast chutes 10 are normally designed with a porosity in the range 50%, d. H. Approximately 50% of the total area of the doors is released for the inflow and outflow of air. A blower shaft 10 for use with a downer 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 has already been explained in connection with FIG. 3, it is possible to improve the arrangement according to FIG. 9 such that the side walls of the downpipe converge downwards over the entire length of the pipe, as indicated in FIG. 9 by dashed lines is, according to this invention, the air-permeable portion 32 would be maintained. This gives a better approximation to the ideal conditions that have been explained in connection with Figure 8, with even better approximations can be achieved by the additional cone angle according to Figures 4 to 6, but at higher production costs. A further improvement will now be explained with reference to FIG.

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

A downcomer 12 according to this invention preferably has a length from the blow duct 10 to the air outlet 34 at the lower end of at least 2.5 m, preferably 3 to 5 m. The air velocity at the outlet (lower end) 34 is between 0 and 7 m / sec, preferably between 2 and 4 m / sec. The filament speed at the exit 34 from the downcomer 12 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, the two threads per position, d. H. 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 downcomers are provided so that the filament bundles pass in pairs through a downspout with the bundles of a pair adjacent the side walls. 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 Figure 11, wherein the use of reference numerals 10, 52, 54, 32 and 34 in Figure 11 corresponds to the use of the same characters in Figure 9.

The design principles according to this invention allow a downpipe design that provides a largely stationary, swirl-free air flow even at different air flow rates. The downpipe can now be designed such that Grenzschichtablösungen be prevented as far as possible. Useful in this connection is a blow duct / downpipe design, in which over the entire length no sudden cross-sectional changes are present.

• Die Kühlluft, die in den Blasschacht eingeführt wird, besitzt potentielle (Druck-) Energie. Gegenüber dem Raum um den Blasschacht bzw. dem Fallrohr (der "Umgebung") herrscht Überdruck. Die hohe Pumpwirkung der Filamentbündel wandelt diese potentielle Energie in kinetische Energie um. Die Luftgeschwindigkeit wird dadurch erhöht, der Druck mindert sich. Die Wirkung wird im Fallrohr gesteigert, einerseits weil sich die Filamentgeschwindigkeit durch das Verstrecken der Filamente erhöht und andererseits wegen der Verengung des Fallrohrquerschnitts. Die Gesamtwirkung kann so weit gehen, dass die Luft in einem gewissen Abschnitt des Systems, normalerweise im unteren Teil des Fallrohres aber allenfalls schon im unteren Teil des Blasschachts, gegenüber der Umgebung Unterdruck aufweist. Durch kleinere, unvermeidbare Öffnungen in der Wandstruktur vermengt sich dann Umgebungsluft mit der Kühlluft.. Dadurch wird die Luftmenge im System weiter erhöht und die Wirkung der vorhergehenden Klimatisierung der Kühlluft wird teilweise aufgehoben. Man tritt nun diesen komplexen Wechselwirkungen entgegen, indem man die Luftmenge in mindestens einem Abschnitt des Fallrohres durch Abfliessen reduziert. Dadurch kann die Erhöhung der Luftgeschwindigkeit und das Risiko eines Unterdrucks in Grenzen gehalten werden. Der Luftdruck in diesem Abschnitt muss höher sein als der Umgebungsdruck bzw. der Druck im empfangenden Behälter.

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. Opposite the space around the blower shaft or the downpipe (the "environment") there is overpressure. The high pumping action of the filament bundles converts this potential energy into kinetic energy. The air velocity is thereby increased, the pressure decreases. The effect is increased in the drop tube, on the one hand because the filament speed increased by the stretching of the filaments and on the other hand because of the narrowing of the drop tube cross section. The overall effect can go so far that the air in a certain portion of the system, usually in the lower part of the downpipe but possibly even in the lower part of the blower, from the environment has negative pressure. By smaller, unavoidable openings in the wall structure then ambient air mixed with the cooling air .. Thus, 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
• einem Fallrohrdesign, das aus zwei oder mehreren Teilstücken mit unterschiedlichem Konuswinkel zusammengesetzt ist und/oder
• einem Fallrohrdesign, bei dem mindestens eines 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 portions 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 in which at least one of the sections is conical in two planes.

Legend

a

Spinning beam with nozzle blocks (not shown)

c

spinning pumps

d

Spin pump drives

f

Spinning extruder

i

blowing shaft

k

downspout

n2

Quick-winding heads (turret winder)

r

Drawframe with hot-draw godets

w

Diphylic evaporator and Diphyl lines

y

air conditioned supply air

10

blowing shaft

12

downspout

12A

Downpipe Fig. 3

12B

Downpipe Fig. 4

12C

Downpipe Fig. 5

12D

Downpipe Fig. 6

12F

Downpipe Fig. 7

14

upper part of the downpipe 12, upper part

16

lower part of the drop tube 12, convergent lower part

18

Side wall

20

Side wall

22

thread

24

thread

26

Side wall downpipe 12A and 12F

26A

Side wall downpipe 12C

28

Side wall downpipe 12A and 12F

28A

Side wall downpipe 12C

30

Rear wall downpipe 12C

30A

Rear wall downpipe 12D

30B

Rear wall downpipe 12F

32

lower portion of downpipe 12B, 12C, 12D, porous (air-permeable) portion of rear wall 30 and 30A

34

Air or thread outlet

34A

Outlet (air or thread) downpipe 12D

36

upper part downpipe 12C and 12D

38

lower part downpipe 12C and 12D

40

front wall

40A

Front wall downpipe 12D

42

perforated (porous or air-permeable) portion in the rear wall 30B

44

perforated (porous or air-permeable) portion in the rear wall 30B

46

perforated (porous or air-permeable) portion in the rear wall 30B

50

suction

52

upper part downpipe Fig. 9 and 11

54

lower part downpipe Fig. 9 and 11

D1

throttle

D2

throttle

D3

throttle

V

fan

S

Side wall

H

Feeding width

L

Outermost filaments to side wall S

R

backflow

W

baffles

H

spout width

L ₁

Length of upper part 52 (FIGS. 9 and 11)

Claims (25)

Drop tube (12) having 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 cross section over the length of the drop tube in the thread running direction at no Point increases and the wall structure at least one longitudinal portion which is not permeable to air, and at least one air-permeable longitudinal section, wherein the arrangement and size of the air-permeable part are selected such that there is a slight overpressure at all locations in the vicinity of the walls of the downpipe. Downpipe (12) according to claim 1, characterized in that the air-permeable portion (32, 42, 44, 46) is provided in a wall portion, where the flow cross-section tapers. Downpipe (12) according to claim 1 or 2, characterized in that the wall structure has a plurality of longitudinal sections which are not permeable to air, as well as a plurality of air-permeable longitudinal sections. Downpipe (12) according to one of the preceding claims, characterized in that the porosity of the or an air-permeable portion (32, 42, 44, 46) in the range 5 to 50%, preferably in the range 20 to 40%. Drop tube (12) according to one of the preceding claims, characterized in that the total length of the air-permeable walls (32, 42, 44, 46) is not more than 50% of the total length of the walls of the drop tube. Drop tube (12) according to one of the preceding claims, characterized in that the flow cross-section is rectangular, and only one wall of the wall structure with an air-permeable portion (32, 42, 44, 46) or more air-permeable portions is provided. Downpipe (12) according to one of the preceding claims, characterized in that the air-permeable or at least one air-permeable portion (32, 42, 44, 46) with a suction (50) is in flow communication. Downpipe (12) according to claim 7, characterized in that a means (D1, D2, D3) for influencing the flow between the wall portion (42, 44, 46) and a suction means (V) is provided. Drop tube (12) according to claim 7 or 8, characterized in that a plurality of air-permeable portions (32, 42, 44, 46) are present and at least two air-permeable portions (32, 42, 44, 46) with the suction (50) in fluid communication stand. Drop tube (12) according to one of the preceding claims, characterized in that the ends are open and the shaft cross-section changes continuously over the length of the shaft. Drop tube (12) according to one of the preceding claims, characterized in that the tube (12) has a rectangular cross section and at least two opposing walls converge over the entire length of the tube. Downpipe (12) according to claim 11, characterized in that the walls converge steadily. Drop tube (12) according to claim 11, characterized in that the walls have at least two sections with different convergence angles. Downpipe (12) according to one of the preceding claims, characterized in that adjoins the end with the larger flow cross-section of a blower shaft (10). Downpipe (12) according to claim 14, characterized in that there are no discontinuous changes in the flow cross-section at the transition from the blow duct (10) to the downpipe or chute (12). Downpipe (12) according to claim 14 or 15, characterized in that the blowing duct (10) has service doors with a porosity of not more than 20% and preferably in the range of 4 to 8%. Drop tube (12) according to claim 16, characterized in that the free flow openings are distributed over the entire surface of the service doors. Blowing shaft (10) characterized by service doors with a porosity not greater than 20% and preferably in the range 4 to 8%. Blowing shaft (10) according to claim 18, characterized in that the free flow openings are distributed over the total area of the service doors. A method for spinning a filament strand (22, 24) from a melt, which solidifies after filament formation in a cooling shaft, wherein cooling air in a first shaft section (10) added to the filaments, accelerated by the filaments in the direction of movement of the filament bundle and then by another Manhole section (a chute) (12) is forwarded together with the filament bundle, wherein the flow cross-section gradually narrows in the flow direction, characterized in that over the entire length or the entire circumference of the other chess section (12), the air flow is an interface at the Inner surface of the shaft wall forms and continuously sustains. A method according to claim 20, characterized in that over the entire length of the further shaft section (12), the air flow over the entire shaft cross-section is directed substantially in the direction of movement of the bundle and maintains this condition continuously. A method for spinning a filament strand (22, 24) from a melt, which solidifies after filament formation in a cooling shaft, wherein cooling air in a first shaft section (10) added to the filaments, accelerated by the filaments in the direction of movement of the filament bundle and then by another Manhole section (a chute) (12) with the filament bundle together to the shaft outlet (34) is passed, wherein over at least part of the further shaft section of the flow cross-section gradually narrows in the flow direction, characterized in that air before the shaft exit (34) evades the shaft, the exiting air flow is set so that there is a slight overpressure at all points in the vicinity of the walls of the downpipe. A method according to claim 22, characterized in that no air is added to the filaments between the first duct section and the exit. A method according to claim 22 or 23, characterized in that air which is discharged from the shaft is sucked off by means of a ventilator (V) and possibly recirculated as cooling air. Method according to one of the preceding claims 22 to 24, characterized in that the air velocity at the outlet 7 m / sec. does not exceed.

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