Apparatus And Method For Depositing Synthetic Fibers To Form A Non Woven Web

Abstract

AbstractThe invention relates to an apparatus and a method for depositing synthetic fibers to form a non-woven web, in which method the synthetic fibers are guided in the form of a blowing stream through a drawing unit for being deposited on a deposit belt. For this purpose, inside the guidance distance between a blast opening of the drawing unit and the deposit belt, several guidance means are arranged, which form a guidance channel above the deposit belt, wherein the guidance means form a channel opening of the guidance channel at a distance from the blast opening of the drawing unit. In order to achieve constant strength in the deposition of the fiber strands in the non-woven web, the distance between the outlet of the drawing unit and the channel opening of the guidance channel is larger than half the guid¬ance distance according to the invention, wherein the guidance width of an open space formed between the outlet of the drawing unit and the channel opening of the guidance channel is larger than that of the guidance channel.

Information

Applicants

Inventors

Specification

Apparatus And Method For Depositing Synthetic Fibers To Form A Non-woven
Web
The invention relates to an apparatus for depositing synthetic fibers to form a non-woven web according to the preamble of claim 1 and a method for depositing a plurality of fibers to form a non-woven web according to the preamble of claim 19.
When producing a non-woven web of synthetic fibers, a plurality of extruded fi¬ber strands have to be deposited as evenly as possible to form a textile fabric. The fiber strands are drawn off using a feed fluid more or less after the extrusion and cool-down processes and are guided to a deposit belt. The distribution of the fi¬bers on the deposit belt is preferably desired to be such that the non-woven web formed therefrom has uniform strength both in the machine direction (MD) and in the cross direction (CD). For controlling the deposition of the fibers, it is known to insert guidance means in the region of a guidance distance, which can be ad¬justed between the draw-off nozzle and the deposit belt. Guidance means of this type influence the guidance of the fibers up to their deposition on the surface of the deposit belt.
Thus, for example, an apparatus and a method are disclosed in the pAiropean Pat¬ent Specification EP 1 138 813 Al, in which method the guidance means are de¬signed as side walls and are arranged to form a guidance channel, which expands in a V-shaped manner towards the deposit belt. Between the guidance channel and the drawing unit there is an open space, the linear extension of which is selected such that the air blasts discharged from the draw-off nozzles can enter into the opening of the guidance channel in a substantially straight manner. The fibers are guided through the guidance channel for stretching and depositing them on the deposit belt, the depositing pattern of the fibers being determined by the shape and the air conduction inside the guidance channel. Thus, this method results in uni¬form deposit ellipses of the fibers on the surface of the deposit belt. Irregularities
2

can develop in the non-woven web in the form of lumps due to large deflections of the filament curtain in the machine direction.
The apparatus disclosed in EP 1 138 813 Bl relates to a so-called melt-blown pro¬cess in which the freshly extruded fibers are drawn off immediately by means of a hot air blast of the drawing unit discharged from the nozzle capillary. For the pur¬pose of cooling the fibers, the latter are thus initially guided immediately through an open space in which the ambient air can be used for cooling the fibers. In order to achieve a thorough stretching of the fiber strands, the guidance distance from the drawing unit up to the deposit belt is substantially determined by the guidance channel.
If the fibers are initially cooled down after the melt-spinning and are received in the solid state through a drawing unit and are blown for being deposited on the deposit belt, the guidance channel can be formed by the guidance means over the entire length of the guidance distance. An apparatus of this type is disclosed in EP 1 340 842 Al by way of example. Here, the fibers are guided inside the guidance distance through several guidance means arranged to form a guidance channel. The guidance channel comprises several channel constrictions, which create a diffuser effect. Diffusers of this type lead to a restriction of the mobility of the fibers with the result that relatively small deposit ellipses of the fiber strands are formed on the surface of the deposit belt. In order to, in spite of that, create the most uniform non-woven web possible, the exhaust equipment disposed beneath the deposit belt comprises several sections for the purpose of discharging the air blast, thereby ensuring that the fibers rest on the deposit belt in a stable manner. However, such a measure enables only a small degree of control over the guid¬ance of the fibers up to their deposition on the surface of the deposit belt. In this respect, it is thus only possible to achieve fiber deposits with relatively small de¬posit ellipses. Another disadvantage of closed systems of this type is that due to the guided flow, it is necessary to maintain longer stretching zones and thus larger distances between the draw-off nozzle and the deposit belt.

In order to control the deposit of the synthetic fibers on the deposit belt, it is fur¬ther known to arrange a guidance means in the open space formed between the draw-off nozzle and the deposit belt wherein said guidance means can be used to change the fiber stream for the purpose of controlling the deposition of the fibers. An apparatus of this type is disclosed in US 2002/0158362 Al by way of exam¬ple. The guidance means is held at a large distance from the deposit belt in order to create an air swirl for forming a traversing movement of the fibers. Although this helps achieve special effects in the deposit of the non-woven web, this apparatus greatly loses its effectiveness at higher production speeds.
It is the object of the present invention to provide an apparatus and a method for depositing synthetic fibers to form a non-woven web of the generic type in which apparatus or method, it is possible to deposit the fibers in a uniform and controlled fashion to form a non-woven web with very uniform strength in the machine di¬rection and in the cross direction even at higher spinning speeds.
Another object of the invention is to improve an apparatus and a method for de¬positing synthetic fibers to form a non-woven web to such effect that a non-woven web can be created on the deposit belt, said non-woven web having uniform thickness even in the case of a lighter basis weight.
This objective is attained according to the invention by means of an apparatus having the features set forth in claim 1 and by means of a method having the fea¬tures set forth in claim 19.
Advantageous refinements of the inventions have been defined by means of the features and combinations of features set forth in the respective dependent clau¬ses.
The invention is based on the realization that the manner in which the fibers are deposited on the surface of the deposit belt in the case of an open system is sub¬stantially determined by the size of the guidance distance adjusted between the
4

blast opening of the draw-off nozzle and the deposit belt. The following rule ap¬plies here: The larger the guidance distance, the larger the deposit ellipses result¬ing from the fibers during their deposition on the surface of the deposit belt both in the machine direction and in the cross direction. However, large deposit ellipses also involve the risk of irregularities in the formation of the thickness of the non-woven web. For adjusting constant thickness over the entire width and length of the non-woven web, it is necessary to realize small deposit ellipses particularly during the deposit of the fibers. It is here that the invention steps in by suggesting that the fibers be initially blown out in an open space over a relatively large guid¬ance path. Accordingly, a higher mobility of the fibers is possible which would lead to the corresponding large deposit ellipses. Before the fibers impinge on the deposit belt, they are introduced using the guidance means into a guide channel, which leads to a restriction of the mobility of the fibers in the machine direction. Particularly the restriction of the deposit ellipse in the machine direction brings about constancy in the properties of the non-woven web. Thus it is possible to deposit the fibers on the surface of the deposit belt so as to achieve the optimum strength and thickness of the non-woven web. For this purpose the distance be¬tween the outlet of the drawing unit and the opening of the guidance channel is larger than half the guidance distance so as to provide the fibers with sufficiently high mobility before they enter into the guidance channel. The guidance width of the open space formed between the outlet of the drawing unit and the opening of the guidance channel is larger than the width of the guidance channel.
For the purpose of improving the guidance of the fibers inside the guidance dis¬tance particularly at high speeds, it is further suggested to provide the opening of the guidance channel with the most convergent design possible by arranging or forming guidance means such that the channel opening opens out into a constric¬tion of the guidance channel. Thus the restriction of the mobility of the fibers is achieved by a funnel-shaped partial distance having increasing constriction so as to ensure a secure entry of the fibers into the guidance channel.

It has proved to be particularly advantageous for creating non-woven webs having light basis weights if the guidance width of the open space is at least five times larger than that of the constriction of the guidance channel. It is thus possible to achieve a high degree of uniformity even if the non-woven web has less thickness.
For this purpose, the width of the constriction of the guidance channel is in the range of 10 mm to 200 mm, wherein the guidance channel receives a constant expansion of the channel constriction preferably toward the deposit belt. Thus it is possible to achieve expansions of the fiber bundles at a short distance from the deposit belt, thereby showing further improvement in the uniformity of the deposition of the non-woven web.
The length of the guidance distance between the blast opening of the drawing unit and the deposit belt is preferably in a range of 100 mm to 700 mm. Thus the de¬sired forms of fiber depositions can be realized depending on the yarn count and polymer type.
According to an advantageous refinement of the invention in order to prevent ex¬change processes with the ambience, the open space on the supply side of the belt and on the discharge side of the belt is shielded from the ambience by means of walls. In order to compensate for pressure differences resulting on the outlet side of the draw-off nozzle in spite of such a closed system, the walls have several ports for suctioning ambient air below the blast opening of the drawing unit. It is thus possible, even with a closed system, to create non-woven webs having in¬creased strength and at the same time high uniformity in the distribution of the fibers.
However, it is also possible to use the ports in the walls for actively blowing in secondary air. This helps achieve additional effects when guiding the fibers.
In order to prevent an impermissible control of the deposit situation of the fibers and the guidance of the non-woven web on the deposit belt particularly in the case of light basis weights of the non-woven web and short guidance distances, the
6

ports are coupled by means of an air intake channel to a suction inlet having an inlet opening that is turned away from the deposit belt. It is thus possible for the ambient air to be suctioned from zones that are not critical for the deposition of the non-woven web on the deposit belt.
For designing the guidance channel, the guidance means can be provided with any design and shape. A refinement of the invention that has proved to be particularly advantageous is one in which the guidance means are each designed at both the sides by means of a molded thin sheet, wherein the thin sheets cooperate with the deposit belt and the non-woven web for sealing the guidance channel. It is thus possible to realize particularly random shapes of the guidance channel and the channel opening in order to achieve the desired guidance of the fibers.
In a particularly preferred refinement of the invention, one clamping end of the molded thin sheet is fixed in the region of the channel opening while a deforma¬tion end is held flexibly in the region outside the guidance channel. By moving the deformation end relative to the clamping end, it is thus possible to vary the shape of the respective thin sheet. Here, the thin sheet is preferably held such that it contacts the deposit belt or the non-woven web.
For sealing the guidance channel, the guidance means are preferably designed in such a way that an oblong sealing gap is designed between the deposit belt or the non-woven web and the guidance means. It is thus possible to prevent a grinding contact between the deposit belt and, for example, a thin sheet designed as a guid¬ance means and also between the non-woven web and the thin sheet. The deposit region is sealed over the length and height of the sealing gap alone. For this pur¬pose the guidance means can also be formed, for example, by solid structural ele¬ments, which form a milled or molded profile of the guidance channel.
Alternatively, another refinement of the invention has also proved to be advanta¬geous in which the guidance means arranged on the discharge side of the belt is formed by means of a pivoted roller which could form a forming gap for the non-
7

woven web with the deposit belt, for example. This helps ensure a high imperme¬ability of the guidance channel in relation to the ambience.
The guidance means arranged on the supply side of the belt can likewise be de¬signed preferably as a pivoted roller, which is held such that it contacts the deposit belt.
Another refinement of the invention that has proved to be particularly advanta¬geous for sealing the guidance channel is one in which the rollers each have a resilient roller jacket. The resilient roller jacket can be formed, for example, by means of a soft material such as an elastomer wound around a hard core. How¬ever, it is also possible to form the roller using a sheet metal jacket guided on the surface of the deposit belt.
The use of the device according to the invention can be improved particularly by assigning a height adjusting device to the guidance means and/or to the deposit belt according to an advantageous refinement of the invention. Said height adjust¬ing device can be used to change the length of the guidance distance and/or the height of the forming gap between the guidance means and the deposit belt.
It is further suggested to design at least one of the guidance means such that it can be displaced transversely to the drawing unit so as to be able to adjust the width of the guidance channel, particularly the size of the channel constriction.
In order to continuously absorb and discharge the air quantity supplied by the draw-off nozzle, an adjustable exhaust port is designed below the deposit belt, by means of which exhaust port an exhaust equipment is connected to the lower side of the deposit belt. In doing so, the size of the exhaust port can be changed be¬tween two covering surfaces held such that they can be displaced in relation to one another so as to absorb and discharge the feed fluid optimally and uniformly depending on the deposition of the fibers.
8

Since in the case of rapid processes and greater differences in the width of the open space and that of the channel constriction, there exists the risk of the fibers hitting the guidance means during their entry into the guidance channel, a refine¬ment of the invention has proved to be particularly useful in which several electri¬cal charge inducers are provided in order to create a positive charge on the fibers and on the guidance means. This helps support the movement of the fibers toward their entry into the guidance channel. The like polarization charges of the fibers and the guidance means prevent the adhesion of the fibers to the surfaces of the guidance means and support the entry of the fibers into the guidance channel. .
The method according to the invention for depositing a plurality of fibers to form a non-woven web combines the special advantages of an open system in which the fiber stream is blown out immediately into an open space, with those of a con¬trolled, reproducible and secure deposition of the fibers to form a non-woven web. In spite of the open system, ambient influences caused, for example, by external air are reduced to a minimum during the deposition of the fibers. However, the method according to the invention is also advantageously applicable in closed systems in order to create the fibers to form a non-woven web with uniform strength and thickness in the machine direction and cross direction.
The apparatus according to the invention and the method according to the inven¬tion are distinguished by a stable and reproducible deposition of the fibers to form a non-woven web with high uniformity, where both high spinning and production speeds are possible. The invention is applicable both for producing so-called spun-bond and melt-blown non-woven webs. Here, the fiber material and non-woven requirement can be selected in any desired setting depending on the fiber type.
The apparatus according to the invention and the method according to the inven¬tion will be described in detail below on the basis of some exemplary embodi¬ments and with reference to the attached figures, of which:

Fig. 1 schematically shows a view of a first exemplary embodiment of the appa¬ratus according to the invention
Fig. 2 schematically shows a cross-sectional view of the exemplary embodiment shown in Fig. I
Fig. 3 is a functional diagram of the exemplary embodiment shown in Fig. 1 and 2
Fig. 4 schematically shows a cross-sectional view of another exemplary em¬bodiment of the apparatus according to the invention
Fig. 5 schematically shows a cross-sectional view of another exemplary em¬bodiment of the apparatus according to the invention
Fig. 1 and 2 schematically show a first exemplary embodiment of the apparatus according to the invention for depositing synthetic fibers to form a non-woven web and for implementing the inventive method. Fig. 1 shows a lateral view of the exemplary embodiment while Fig. 2 schematically shows a cross-sectional view thereof. The subsequent description applies to both the figures unless express ref¬erence is made to any one of the figures.
The exemplary embodiment shown in Fig. 1 and 2 shows a parallelepiped draw¬ing unit 1, which is usually arranged below a spinning device. Drawing units of this type are known in general and have been explained in detail in [United States Patent Specification] US 6.183.684 Bl or US 7,172,398 B2. The aforementioned publications may be referred to in this respect; only the essential parts have been included in the following.
The drawing unit 1 comprises a middle conveying channel 5, which is delimitated on an upper side of the drawing unit 1 by a slot-shaped fiber inlet 2 and on the lower side of the drawing unit 1 by a blast opening 3. The conveying channel 5 is provided with a slot-shaped design and it extends substantially over the overall length of the parallelepiped drawing unit 1. On the longitudinal sides of the con¬veying channel 5 there are designed several fluid inlets 38 which are connected to a fluid connection 4. A feed fluid, preferably compressed air, is supplied by means
10

of the fluid connection 4 so as to create an excess pressure in the conveying chan¬nel 5 in relation to the ambience.
The drawing unit 1 is arranged at a distance above a deposit belt 6. The width of the deposit belt 6 extends over the entire length of the drawing unit 1. The deposit belt 6 is preferably guided as an endless conveyor over several conveyor rollers 39, one of which is shown in Fig. 2. The deposit belt is driven such that it is di¬rected transversely to the longitudinal side of the drawing unit 1. The deposit belt 6 thus moves continuously in a guidance direction, which is indicated in Fig. 1 and Fig. 2 using arrows. The deposit belt 6 is designed to be permeable to air, wherein an exhaust equipment 22 is arranged on the lower side of the deposit belt 6 in a deposit region designed vertically below the drawing unit I.
The region between the drawing unit 1 and the deposit belt 6 is used for guiding the fiber strands 20 drawn off from the spinning device. The distance between the blast opening 3 on the lower side of the drawing unit 1 and the surface of the de¬posit belt 6 is referred to as the guidance distance here. The guidance distance is divided into several sections, in order to achieve a defined guidance with respect to a desired position of the fiber strands 20 on the surface of the deposit belt 6. Directly below the drawing unit 1 there is provided an open space 18, which has a large guidance width with the result that the blown air stream discharged together with the fiber strands 20 from the blast opening 3 can be expanded freely. For this purpose, the open space 18 is shielded from the ambience by means of laterally extending separation walls 14.1 and 14.2. In the upper region of the separation walls 14.1 and 14.2 there are designed several suction ports 15.1 and 15.2, through which external air is suctioned due to the vacuum created by the blowing air stream directly on the lower side of the drawing unit 1. For this purpose the suction port 15.1 in the separation wall 14.1 is coupled to the air intake channel 16.1, which has a suction inlet 17.1 on one free end. The suction inlet 17.1 has an inlet opening, which is directed upwards and is turned away from the deposit belt 6. The suction ports 15.2 of the opposite separation wall 14.2 are likewise con¬nected to an air intake channel 16.2. The air intake channel 16.2 likewise has a
11

suction inlet 17.2 with an upwardly directed suction inlet opening. Particularly in the case of very short guidance distances between the drawing unit 1 and the de¬posit belt, it is thus possible to prevent an influence exerted over the deposit of the non-woven web due to the suction of external air into the open space 18. Due to the upwardly directed suction inlets 17.1 and 17.2, the external air suctioned by the blowing stream is withdrawn from an ambience, which is not critical for de¬positing the fibers on the deposit belt 6. Thus it is also possible to select relatively short guidance distances for producing fine and light non-woven webs.
The open space 18 extends over a length, which exceeds at least half the guidance distance. In this respect, the blowing stream expands increasingly with its pro¬gressive motion with the result that a correspondingly large mobility of the fiber strands is achieved both in the machine direction of the deposit belt, also referred to as MD in short, and also in a cross direction thereto.
In the further course of the guidance distance, the open space 18 is delimited by the guidance means 7.1 and 7.2, which form a guidance channel 9 for receiving the blowing stream. For this purpose, one of the guidance means 7.1 is arranged on a belt discharge side 10 and the second guidance means 7.2 is arranged on the opposite belt supply side 11. The guidance means 7.1 and 7.2 are each formed by a pivoted roller 12.1 and 12.2. The guidance channel 9 formed between the guid¬ance means 7.1 and 7.2 thus substantially comprises three sections, which bring about the guidance of the blowing stream in the extension of the open space 18. At the end of the open space 18, the guidance means 7.1 and 7.2 form a channel opening 8, which opens into a channel constriction 35 convergently. The channel constriction 35 represents the smallest guidance width inside the guidance channel 9. The channel constriction 35 gives way to a divergent channel outlet 36 with the result that the blowing stream expands again after its initial constriction due to a constant expansion of the channel constriction. At the end of the guidance channel 9, the fiber strands 20 are deposited on the deposit belt 6. The deposit region, which represents the end of the guidance channel 9, is shielded from the ambience with a sealing effect by each of the rollers 12.1 and 12.2. The direct frictional con-
12

tact between the rollers 12.1 and 12.2 and the deposit belt 6 and also the surface of the non-woven web 21 helps achieve a sealing effect from the external air. For this purpose the rollers 12.1 and 12.2 can comprise a resilient roller jacket 13. This helps generate relatively small contact pressing forces, which, for example, prevent the so-called polymer droplets from pressing into the deposit belt when the plant is started up.
The rollers 12.1 and 12.2 are in frictional contact with the deposit belt 6 with the result that the rotational movement of the rollers 12.1 and 12.2 is generated by friction by means of the conveying movement of the deposit belt 6. Alternatively, each of the rollers 12. J and 12.2 could also have a separate drive. The roller 12.2 rests directly against the surface of the deposit belt 6 or on a support material. The roller 12.1 on the belt discharge side 10 forms a forming gap 19 with the upper side of the deposit belt 6, through which forming gap the non-woven web 21 can be formed additionally after the deposit of the fiber strands 20.
For implementing and supporting the fiber deposit for forming the non-woven web, the exhaust equipment 22 is disposed on the lower side of the deposit belt 6. The exhaust effect of the exhaust equipment 22 is limited to the deposit region of the guidance channel 9. The exhaust equipment 22 comprises an adjustable ex¬haust port 23, which is assigned directly to the deposit region on the deposit belt 6. The exhaust port 23 is formed between two mobile cover plates 24.1 and 24.2. Each of the cover plates 24.1 and 24.2 can be moved horizontally relative to one another. For sealing the exhaust port 23, sealing elements 25 are provided on the lower side of the deposit belt 6 so as to prevent external air from entering from the lower side of the deposit belt 6.
In order to explain the functioning of the exemplary embodiment shown in Fig. 1 and 2 and the method according to the invention implemented by means of said embodiment, one may refer to the schematic diagram shown in Fig. 3 for the fol¬lowing description. Fig. 3 shows the guidance distance formed between the draw¬ing unit 1 and the deposit belt 6 with its sub-sections. The guidance distance,

which is marked with the capital letter C, can basically be divided initially into two sub-sections. A first sub-section extends from the lower side of the drawing unit 1 up to the upper side of the guidance means 7.1, 7.2 and represents the length of the open space 18. This section of the guidance distance is marked with the capital letter D. The open space 18 formed in this section D of the guidance distance has a relatively large guidance width marked with the capital letter A. The guidance width A of the open space 18 is substantially constant over the en¬tire guidance distance D and extends over the width of the drawing unit 1. Here, the size of the guidance width A is selected so as to enable a free unobstructed exit of the blowing stream generated by the drawing unit 1 at the blast opening 3. The natural course of the blowing stream is illustrated using the dash-dotted boundaries, which extend with increasing expansion from the blast opening 3 up to the deposit belt 6. The fiber strands 20 are guided inside this blowing stream. As the distance from the blast opening 3 increases, an increasing freedom of movement of the fiber strands thus results inside the blowing stream, which free¬dom of movement would lead to a deposit of the fiber strands with large deposit ellipses in their further course without any interruption.
The second section of the guidance distance C is a guidance channel 9, which is designed with a substantially narrower guidance width in relation to that of the open space 18. The guidance width of the guidance channel 9 is marked with the capital letter B. The length of the guidance channel 9 results from the difference between the overall guidance distance C and the length D of the open space 18. Here, the length D is selected such that a free mobility of the blowing stream is possible without restriction at least over 50% of the entire guidance distance, pre¬ferably over 60% of the entire guidance distance C. Thus D > 0.5*C.
The guidance channel 9 formed between the guidance means 7.1 and 7.2 has a channel constriction 35, which brings about a restriction of the blowing stream. It has proved to be particularly advantageous here that the guidance width A of the open space 18 is at least 5 times larger than the channel constriction 35 having the guidance width B. Thus A > 5*B. It is thus possible to achieve the desired effects

for restricting the blowing stream. It is of particular relevance to the guidance of the blowing stream inside the guidance channel 9 that a funnel-shaped entrance up to the channel constriction 35 is ensured by means of a convergent channel open¬ing 8. The repeat expansion of the guidance channel 9 immediately after the chan¬nel constriction 35 by means of a divergent channel output 36 enables the uniform distribution of the fiber strands inside the blowing stream hitting the deposit belt. It has been seen that the deposits of the fiber strands thus generated resulted in a non-woven web, which exhibited high strengths in the machine direction and in the cross direction and a high degree of uniformity in the mass distribution. There is also constant strength, which has positive effects particularly in the case of non-woven webs having relatively small basis weights.
In the exemplary embodiment shown in Fig. 1 and 2, particularly good results were achieved in the deposition of the fiber strands and formation of non-woven webs for guidance distances, whose length C lies in the range of 100 mm to max. 700 mm. Here, in the lower region of the guidance distance, the channel constric¬tion of the guidance channel is designed with a guidance width B in the range of 10 mm to max. 200 mm. In contrast, the open space 18 is designed with a guid¬ance width A in the range of 300 mm to 1000 mm.
Fig. 4 schematically shows the cross-sectional view of another exemplary em¬bodiment of the apparatus according to the invention for implementing the method according to the invention. Unlike the afore-mentioned exemplary em¬bodiment, which is used for producing so-called spun-bond non-woven webs, the exemplary embodiment shown in Fig. 4 is used for producing melt-blown non-woven webs.
For this purpose, the drawing unit 1 is disposed immediately on a lower side of a spinneret 31. The spinneret 31 has a plurality of nozzle holes 32 disposed in a row-shaped arrangement transversely to a deposit belt 6. The nozzle hole 32 o-pens directly into a conveying channel 5, in which the blast nozzles 33.1 and 33.2 blow a blowing stream for drawing off the fiber strands extruded from the nozzle

nozzle holes 32. The blowing stream exits together with the fiber strands from a blast opening 3 of the drawing unit 1 and is blown into an open space 18 designed directly below the drawing unit 1. The open space 18 is not shielded from the ambience so as to enable a free flow of the blowing stream. The open space 18 thus has an unlimited guidance width, which is determined exclusively by the free ambience.
In the lower third of the guidance distance, the guidance channel 9 is arranged between the guidance means 7.1 and 7.2 directly above the deposit belt 6. The shape of the guidance channel 9 is substantially identical to that shown in the ex¬emplary embodiment illustrated in Fig. 1 and 2. Hence it requires no further ex¬planation and one may refer to the previous description for the same.
In this exemplary embodiment, thin sheets 26.1 and 26.2 form the guidance means. The thin sheets 26.1 and 26.2 are held opposite to one another, each of said thin sheets 26.1 and 26.2 comprising a clamping end 27 and a deformation end 28. The thin sheets 26.1 and 26.2 are held in a fixed manner on the clamping end 27. The thin sheets 26.1 and 26.2 have a circular curvature and are supported with one section at the end of the guidance channel 9 against the upper side of the deposit beh 6 or the upper side of the deposited non-woven web 21. Due to this, the guidance channel 9 in the deposit region is shielded from the ambience and an entrance of external air is prevented. The deformation ends 28 of the thin sheets
26.1 and 26.2 are designed outside the guidance channel 9. The position of the deformation ends 28 can be changed. Thus the shapes of the thin sheets 26.1 and
26.2 can be deformed for changing the guidance channel 9, for example, for ex¬panding the channel constriction.
The shape of the guidance channel 9 between the thin sheets 26.1 and 26.2 is identical to that of the preceding exemplary embodiment. Hence one may refer to the previous description for this purpose.

On the lower side of the deposit belt 6, an exhaust equipment 22 is arranged in the deposit region. The exhaust equipment 22 is substantially identical to that of the previous exemplary embodiment. Therefore it requires no further explanation he-
re.
The exemplary embodiment shown in Fig. 4 of the apparatus according to the invention for implementing the method according to the invention represents an open system as opposed to the exemplary embodiment shown in Fig. 1 and 2. He¬re, the open space 18 is connected directly to the ambience with the result that a free exchange can take place between the blowing stream and the ambience. Par¬ticularly when using heated fluid streams, as is often common practice in the case of melt-blown systems, it is thus possible to bring about additional cooling effects on the fiber strands.
At this point it must be mentioned expressly that the guidance means 7.1 and 7.2 in the exemplary embodiment shown in Fig. 4 could be replaced by the rollers 12.1 and 12.2 shown in Fig. 1 and 2 and vice versa. It is likewise possible to de¬sign the apparatus shown in Fig. 1 and 2 as an open system having an open space.
In the exemplary embodiment shown in Fig. 4, the guidance means 7.1 and 7.2 and the deposit beh 6 are arranged on a lifting table (not illustrated here). A dou¬ble arrow with the reference numeral 40 indicates the lifting table only symboli¬cally. The guidance distance below the drawing unit 1 can thus be set by adjusting the height of the guidance means 7.1 and 7.2 and of the deposit belt. Furthermore, the mobility and the deformability of the guidance means 7.1 enables an adjust¬ment of the forming gap 19 formed between the guidance means 7.1 and the de¬posit belt 6.
Fig. 5 schematically shows the cross-section of another exemplary embodiment of the apparatus according to the invention for implementing the method according to the invention. The exemplary embodiment shown in Fig. 5 is substantially
17

identical to that shown in Fig. 1 and 2. Hence only the differences are explained below and the previous description may be referred to in all other respects.
In the exemplary embodiment shown in Fig. 5, the drawing unit 1 and the open space 18 are designed identically to that of the preceding exemplary embodiment shown in Fig. 1 and 2. For designing the guidance channel 9, the guidance means 7.1 and 7.2 are formed by molded thin sheets 26.1 and 26.2. The shape of the gui¬dance channel 9 is selected by means of the curvature of the thin sheets in such a way that at the end of the open space, a convergent channel opening 8 opens out into a channel constriction 35. The channel constriction 35 gives way to an expan¬sion, which leads to a divergent channel output 36. On the side facing the deposit belt 6, the thin sheets 26.1 and 26.2 each have oblong legs 37, which extend paral¬lel to the deposit belt 6 and form a sealing gap 29.1 and 29.2 with the deposit belt 6 or with the non-woven web 21. The length of the sealing gap 29.1 and 29.2 is selected such that the deposit region is completely shielded inside the guidance channel 9 on the deposit belt 6.
Any frictional contact between the guidance means 7.1 and 7.2 with the non-woven web 21 or the deposit belt 6 is thus prevented on the upper side of the de¬posit belt.
The exhaust equipment 22 provided on the lower side of the deposit belt likewise has oblong sealing lips 38.1 and 38.2 in order to prevent the entry of external air from the ambience.
In the exemplary embodiment shown in Fig. 5, a charge inducer 34.1 is provided in front of the entrance of the drawing unit 1 and another charge inducer 34.2 is provided in the region of the guidance means 7.1 and 7.2. The charge inducer 34.1 creates an electrostatic, preferably positive charge on the fiber strands 20. Like¬wise, the charge inducer 34.2 creates an electrostatic charge on the thin sheets 26.1 and 26.2. The charges of the fiber strands 20 and the charges of the guidance means 7.1 and 7.2 are of like polarization. Thus by charging the fiber strands and the guidance means, it is possible to optimize the entry and constriction of the
18

blowing stream inside the guidance distance. The fiber strands move away from the contour of the guidance means 7.1 and 7.2. Additionally, a negative charge could be created on the lower side of the deposit belt 6 with the result that an ad¬ditional tractive force can be generated on the depositing fiber strands. It is thus possible to create additional effects when depositing the fiber strands to form a non-woven web.
The structure and arrangement of the components of the exemplary embodiments, shown in Fig. 1 to Fig. 5, of the apparatus according to the invention for imple¬menting the method according to the invention are illustrated by way of example. It is essential here that for depositing the fibers on the deposit belt, said fibers are initially guided in an open space in order to then meet the deposit belt after a con¬striction of the blowing stream in a closed deposit region. In doing so, those guid¬ance means are particularly suitable, which enable a stable and reproducible guid¬ance and deposition of the fiber strands.
19

List of reference numerals
1 Drawing unit
2 Fiber entrance
3 Blast opening
4 Fluid connection
5 Conveying channel
6 Deposit belt
7.1,7.2 Guidance means
8 Channel opening
9 Guidance channel
10 Belt discharge side
11 Belt supply side
12.1, 12.2 Roller
13 Roller jacket
14.1,14.2 Separation wall
15.1, 15.2 Suction port
16.1, 16.2 Air intake channel
17.1,17.2 Suction inlet
18 Open space
19 Forming gap
20 Fiber strands
21 Non-woven web
22 Exhaust equipment
23 Exhaust port
24.1,24.2 Cover plate
25 Sealing element
26.1,26.2 Thin sheet
27 Clamping end
28 Deformation end
29.1, 29.2 Sealing gap
30 Height adjusting device
20

31 Spinneret
32 Nozzle hole
33.1,33.2 Blast nozzles
34.1,34.2 Charge inducers
35 Channel constriction
36 Channel output
37.1,37.2 Leg
38 Fluid inlet
39 Conveyor roller
40 Lifting table

Claims
1. Apparatus for depositing synthetic fibers (20) to form a non-woven web
(21), said apparatus comprising a drawing unit (1), with a deposit belt (6),
which is arranged below the drawing unit (1) and is driven such that it is
directed transversely to a longitudinal side of the drawing unit (1) and with
several guidance means (7.1, 7.2) provided in a guidance distance (C) de¬
signed between a blast opening (3) of the drawing unit (1) and the deposit
belt (6), one of the guidance means (7.1) being arranged on a belt dis¬
charge side (10) and an opposite guidance means (7.2) being arranged on a
belt supply side (11) directly above the deposit belt (6) to form a guidance
channel (9), through which guidance channel (9) the fibers (20) are guided
for deposition on the deposit belt (6), the guidance means (7.1, 7.2) form¬
ing a channel opening (8) of the guidance channel (9) at a distance (D)
from the blast opening (3) of the drawing unit (1),
said apparatus being characterized in that
the distance (D) between the blast opening (3) of the drawing unit (1) and the channel opening (8) of the guidance channel (9) is larger than half the guidance distance (C) and that the guidance width of an open space (18) formed between the blast opening (3) of the drawing unit and the channel opening (8) of the guidance channel (9) is larger than that of the guidance channel (9).
2. Apparatus according to claim 1,
characterized in that
the channel opening (8) of the guidance channel (9) is designed conver-gently by the guidance means (7.1, 7.2), wherein the channel opening (8) opens out into a channel constriction (35) of the guidance channel (9).

3. Apparatus according to claim 2,
characterized in that
the guidance width (A) of the open space (18) is at least five times larger than the guidance width (B) of the channel constriction (35) of the guid¬ance channel (9) (A > 5B).
4. Apparatus according to one of the claims 2 or 3,
characterized in that
the guidance width (B) of the channel constriction (35) of the guidance channel (9) is in the range of 10 mm to 200 mm, wherein the guidance channel (9) has a divergent channel output (36) towards the deposit belt (6).
5. Apparatus according to one of the claims 1 to 4,
characterized in that
the guidance distance between the blast opening (3) of the drawing unit (1) and the deposit belt (6) has a length (C) in the range of 100 mm to 700 mm.
6. Apparatus according to one of the claims 1 to 5,
characterized in that
the open space (18) on the belt supply side (11) and on the belt discharge side (10) is shielded from the ambience by means of walls (14.1, 14.2).
7. Apparatus according to claim 6,
characterized in that
the walls (14.1, 14.2) comprise several suction ports (15.1, 15.2) below the blast opening (3) of the drawing unit (I) for suctioning ambient air.

8. Apparatus according to claim 7,
characterized in that
one air intake channel each (16.1, 16.2) is assigned to the suction ports (15.1, 15.2), which air intake channel comprises on its end a suction inlet (17.1, 17.2) having an inlet opening turned away from the deposit belt (6).
9. Apparatus according to one of the claims 1 to 8,
characterized in that
the guidance means (7.1, 7.2) on both the sides (10, 11) are each formed by a molded thin sheet (26.1, 26.2), wherein the thin sheets (26.1, 26.2) work together with the deposit belt (6) and the non-woven web (21) for sealing the guidance channel (9).
10. Apparatus according to claim 9,
characterized in that
the molded thin sheets (26.1, 26.2) comprise a clamping end (27) in the region of the channel opening (8) and a deformation end (28) in the region outside the guidance channel (9), wherein the shape of the respective thin sheet (26.1, 26.2) can be changed by moving the deformation end (28) re¬lative to the clamping end (27).
11. Apparatus according to one of the claims 1 to 10,
characterized in that
for sealing the guidance channel (9), an oblong sealing gap (29.1, 29.2) is designed between the deposit belt (6) or the non-woven web (21) and the guidance means (7.1, 7.2).

12. Apparatus according to one of the claims 1 to 8,
characterized in that
the guidance means (7.1) arranged on the belt discharge side (10) is for¬med by means of a pivoted roller (12.1), which forms a forming gap (19) with the deposit belt (6) for the non-woven web (21).
13. Apparatus according to claim 12,
characterized in that
the guidance means (7.2) arranged on the belt supply side (11) is formed by a second pivoted roller (12.1) [sic: (12.2)], which is held such that it is in contact with the deposit belt (6) or an incoming non-woven web.
14. Apparatus according to claim 12 or 13,
characterized in that
the rollers (12.1, 12.2) each have a resilient roller jacket (13).
15. Apparatus according to one of the preceding claims,
characterized in that
a height adjusting device (40) is assigned to the guidance means (7.1, 7.2) and/or the deposit belt (6), by means of which height adjusting device the length (C) of the guidance distance and/or a forming gap (19) formed be¬tween the guidance means (7.1) and the deposit belt (6) can be changed.
16. Apparatus according to one of the claims 1 to 15,
characterized in that
for changing the channel constriction (35) of the guidance channel (9), said constriction being designed between the guidance means (7.1, 7.2), at least one of the guidance means (7.1, 7.2) is held such that it is displace-able transversely to the drawing unit (1).
17. Apparatus according to one of the preceding claims,
25

characterized in that
below the deposit belt (6) an adjustable exhaust port (23) is designed, by means of which an exhaust equipment (22) is connected to the lower side ofthedeposit belt (6).
18. Apparatus according to one of the preceding claims,
characterized in that
several electrical charge inducers (34.1, 34.2) are provided in order to cre¬ate an electrostatic charge on the fibers (20) and on the guidance means (7.1,7.2).
19. Method for depositing a plurality of fibers to form a non-woven web, in
which method the fibers are blown after being melt-spun onto a driven de¬
posit belt in a row-shaped arrangement,
said method being characterized in that
after being blown out in a guidance distance, the fibers initially pass through a broad open space, which extends over at least half the length of the entire guidance distance up to the deposit belt, then enter into a nar¬rower guidance channel at the end of the open space and are deposited at the end of the guidance channel to form the non-woven web.
20. Method according to claim 19,
characterized in that
in the transition from the open space to the guidance channel, the fibers are guided through a convergent channel opening and after passing through a channel constriction, are guided through a divergent channel output on the deposit belt.
26

21. Method according to claim 19 or 20,
characterized in that
the blowing stream of the guidance channel is shielded from the ambience and is absorbed and discharged by means of an exhaust equipment below the deposit belt.
22. Method according to one of the claims 19 to 21,
characterized in that
the blowing stream inside the open space is shielded from the ambience, wherein external air is supplied by means of a natural suction effect or an air injection only in the region surrounding the blast opening for blowing out the fibers.
23. Method according to one of the claims 19 to 21,
characterized in that
the blowing stream inside the open space works together with an ambient air.

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