Apparatus and method for depositing synthetic fibers to form a non-woven web

An apparatus and method for depositing synthetic fibers to form a non-woven web includes guiding the synthetic fibers by a blowing stream through a drawing unit for depositing on a deposit belt. Multiple guidance elements are arranged inside the guidance distance between a blast opening of the drawing unit and the deposit belt, and form a guidance channel above the deposit belt. The guidance elements form a channel opening at a distance from the blast opening of the drawing unit. In order to achieve constant strength in the deposition of the fiber strands, the distance between the outlet of the drawing unit and the channel opening of the guidance channel is larger than half the guidance distance, and 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 the guidance channel.

TECHNICAL FIELD

The invention relates to an apparatus for depositing synthetic fibers to form a non-woven web and a method for depositing a plurality of fibers to form a non-woven web.

BACKGROUND

When producing a non-woven web of synthetic fibers, a plurality of extruded fiber 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 fibers 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 elements in the region of a guidance distance, which can be adjusted between the draw-off nozzle and the deposit belt. Guidance elements 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 European Patent Specification EP 1 138 813 A1, in which method the guidance elements are designed 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 uniform deposit ellipses of the fibers on the surface of the deposit belt. Irregularities 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 B1 relates to a so-called melt-blown process in which the freshly extruded fibers are drawn off immediately by a hot air blast of the drawing unit discharged from the nozzle capillary. For the purpose 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 elements over the entire length of the guidance distance. An apparatus of this type is disclosed in EP 1 340 842 A1 by way of example. Here, the fibers are guided inside the guidance distance through several guidance elements 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 ellipsis of the fiber strands are formed on the surface of the deposit belt. In order to, in spite of this, create the most uniform non-woven web possible, the exhaust equipment disposed beneath the deposit belt includes 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 guidance 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 deposit 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 further known to arrange a guidance elements in the open space formed between the draw-off nozzle and the deposit belt wherein the guidance elements 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 A1 by way of example. The guidance elements are 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.

SUMMARY

An apparatus and a method for depositing synthetic fibers to form a non-woven web of the generic type is provided which deposits the fibers in a uniform and controlled fashion to form a non-woven web with very uniform strength in the machine direction and in the cross direction even at higher spinning speeds.

In one embodiment, the apparatus and method deposits synthetic fibers to form a non-woven web to such effect that a non-woven web can be created on the deposit belt, the non-woven web having uniform thickness even in the case of a lighter basis weight.

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 substantially determined by the size of the guidance distance adjusted between the blast opening of the draw-off nozzle and the deposit belt. The following rule applies here: The larger the guidance distance, the larger the deposit ellipses resulting 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 providing that the fibers be initially blown out in an open space over a relatively large guidance 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 elements into a guide channel, which leads to a restriction of the mobility of the fibers in the machine direction. In particular, 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 between 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 distance 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 elements such that the channel opening opens out into a constriction 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 provide 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 desired forms of fiber depositions can be realized depending on the yarn count and polymer type.

According to one embodiment of the invention, in order to prevent exchange 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 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 increased 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 ports are coupled by 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 elements can be provided with any design and shape. One embodiment that has proved to be particularly advantageous is one in which the guidance elements are each designed at both the sides by a moulded 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 one embodiment, one clamping end of the molded thin sheet is fixed in the region of the channel opening while a deformation 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 elements 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 elements. It is thus possible to prevent a grinding contact between the deposit belt and, for example, a thin sheet designed as a guidance element 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 purpose the guidance elements can also be formed, for example, by solid structural elements, which form a milled or molded profile of the guidance channel.

Alternatively, another embodiment has also proved to be advantageous in which the guidance elements arranged on the discharge side of the belt is formed by a pivoted roller which could form a forming gap for the non-woven web with the deposit belt, for example. This helps ensure a high impermeability of the guidance channel in relation to the ambience.

The guidance elements arranged on the supply side of the belt can likewise be designed preferably as a pivoted roller, which is held such that it contacts the deposit belt.

Another embodiment that is advantageous for sealing the guidance channel is one in which the rollers each have a resilient roller jacket. A soft material such as an elastomer wound around a hard core can form the resilient roller jacket, for example. However, 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 disclosed herein can be improved particularly by assigning a height-adjusting device to the guidance elements and/or to the deposit belt according to one embodiment. The height adjusting device can be used to change the length of the guidance distance and/or the height of the forming gap between the guidance elements and the deposit belt.

It is further suggested to design at least one of the guidance elements 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, whereby an exhaust port of exhaust equipment is connected to the lower side of the deposit belt. In doing so, the size of the exhaust port can be changed between 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.

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 elements during their entry into the guidance channel, in one embodiment several electrical charge inducers are provided in order to create a positive charge on the fibers and on the guidance elements. 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 elements prevent the adhesion of the fibers to the surfaces of the guidance elements and support the entry of the fibers into the guidance channel.

The method 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 controlled, 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 and the method disclosed herein 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.

DETAILED DESCRIPTION

FIGS. 1 and 2schematically show a first example embodiment of the apparatus according for depositing synthetic fibers to form a non-woven web and for implementing the inventive method.FIG. 1shows a lateral view of the example embodiment whileFIG. 2schematically shows a cross-sectional view thereof. The subsequent description applies to both the figures unless express reference is made to any one of the figures.

The example embodiment shown inFIGS. 1 and 2shows a parallel-piped drawing unit1, which is usually arranged below a spinning device. Drawing units of this type are known in general and have been explained in detail in U.S. Pat. No. 6,183,684 B1 and/or U.S. Pat. No. 7,172,398 B2. The contents and teachings of which are hereby incorporated by reference in their entirety.

The drawing unit1includes a middle conveying channel5, which is delimitated on an upper side of the drawing unit1by a slot-shaped fiber inlet2and on the lower side of the drawing unit1by a blast opening3. The conveying channel5is provided with a slot-shaped design and it extends substantially over the overall length of the parallel-piped drawing unit1. On the longitudinal sides of the conveying channel5there are designed several fluid inlets38which are connected to a fluid connection4. A feed fluid, preferably compressed air, is supplied by the fluid connection4so as to create an excess pressure in the conveying channel5in relation to the ambience.

The drawing unit1is arranged at a distance above a deposit belt6. The width of the deposit belt6extends over the entire length of the drawing unit1. The deposit belt6is preferably guided as an endless conveyor over several conveyor rollers39, one of which is shown inFIG. 2. The deposit belt is driven such that it is directed transversely to the longitudinal side of the drawing unit1. The deposit belt6thus moves continuously in a guidance direction, which is indicated inFIG. 1andFIG. 2using arrows. The deposit belt6is designed to be permeable to air, wherein exhaust equipment22is arranged on the lower side of the deposit belt6in a deposit region designed vertically below the drawing unit1.

The region between the drawing unit1and the deposit belt6is used for guiding the fiber strands20drawn off from the spinning device. The distance between the blast opening3on the lower side of the drawing unit1and the surface of the deposit belt6is 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 strands20on the surface of the deposit belt6. Directly below the drawing unit1there is provided an open space18, which has a large guidance width with the result that the blown air stream discharged together with the fiber strands20from the blast opening3can be expanded freely. For this purpose, the open space18is shielded from the ambience by laterally extending separation walls14.1and14.2. In the upper region of the separation walls14.1and14.2there are designed several suction ports15.1and15.2, through which external air is suctioned due to the vacuum created by the blowing air stream directly on the lower side of the drawing unit1. For this purpose the suction port15.1in the separation wall14.1is coupled to the air intake channel16.1, which has a suction inlet17.1on one free end. The suction inlet17.1has an inlet opening, which is directed upwards and is turned away from the deposit belt6. The suction ports15.2of the opposite separation wall14.2are likewise connected to an air intake channel16.2. The air intake channel16.2likewise has a suction inlet17.2with an upwardly directed suction inlet opening. Particularly in the case of very short guidance distances between the drawing unit1and the deposit 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 space18. Due to the upwardly directed suction inlets17.1and17.2, the external air suctioned by the blowing stream is withdrawn from an ambience, which is not critical for depositing the fibers on the deposit belt6. Thus it is also possible to select relatively short guidance distances for producing fine and light non-woven webs.

The open space18extends over a length, which exceeds at least half the guidance distance. In this respect, the blowing stream expands increasingly with its progressive 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 space18is delimited by the guidance elements7.1and7.2, which form a guidance channel9for receiving the blowing stream. For this purpose, one of the guidance elements7.1is arranged on a belt discharge side10and the second guidance elements7.2are arranged on the opposite belt supply side11. The guidance elements7.1and7.2are each formed by a pivoted roller12.1and12.2. The guidance channel9formed between the guidance elements7.1and7.2thus essentially includes three sections, which bring about the guidance of the blowing stream in the extension of the open space18. At the end of the open space18, the guidance elements7.1and7.2form a channel opening8, which opens into a channel constriction35convergently. The channel constriction35represents the smallest guidance width inside the guidance channel9. The channel constriction35gives way to a divergent channel outlet36with 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 channel9, the fiber strands20are deposited on the deposit belt6. The deposit region, which represents the end of the guidance channel9, is shielded from the ambience with a sealing effect by each of the rollers12.1and12.2. The direct frictional contact between the rollers12.1and12.2and the deposit belt6and also the surface of the non-woven web21helps achieve a sealing effect from the external air. For this purpose the rollers12.1and12.2can comprise a resilient roller jacket13. 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 rollers12.1and12.2are in frictional contact with the deposit belt6with the result that the rotational movement of the rollers12.1and12.2is generated by friction by the conveying movement of the deposit belt6. Alternatively, each of the rollers12.1and12.2could also have a separate drive. The roller12.2rests directly against the surface of the deposit belt6or on a support material. The roller12.1on the belt discharge side10forms a forming gap19with the upper side of the deposit belt6, through which forming gap the non-woven web21can be formed additionally after the deposit of the fiber strands20.

For implementing and supporting the fiber deposit for forming the non-woven web, the exhaust equipment22is disposed on the lower side of the deposit belt6. The exhaust effect of the exhaust equipment22is limited to the deposit region of the guidance channel9. The exhaust equipment22comprises an adjustable exhaust port23, which is assigned directly to the deposit region on the deposit belt6. The exhaust port23is formed between two mobile cover plates24.1and24.2. Each of the cover plates24.1and24.2can be moved horizontally relative to one another. For sealing the exhaust port23, sealing elements25are provided on the lower side of the deposit belt6so as to prevent external air from entering from the lower side of the deposit belt6.

In order to explain the functioning of the example embodiment shown inFIGS. 1 and 2, and the method implemented by the embodiment, reference will now be made to the schematic diagram shown inFIG. 3.FIG. 3shows the guidance distance formed between the drawing unit1and the deposit belt6with 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 unit1up to the upper side of the guidance elements7.1,7.2and represents the length of the open space18. This section of the guidance distance is marked with the capital letter D. The open space18formed 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 space18is substantially constant over the entire guidance distance D, and extends over the width of the drawing unit1. 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 unit1at the blast opening3. The natural course of the blowing stream is illustrated using the dash-dotted boundaries, which extend with increasing expansion from the blast opening3up to the deposit belt6. The fiber strands20are guided inside this blowing stream. As the distance from the blast opening3increases, an increasing freedom of movement of the fiber strands thus results inside the blowing stream, which freedom 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 channel9, which is designed with a substantially narrower guidance width in relation to that of the open space18. The guidance width of the guidance channel9is marked with the capital letter B. The length of the guidance channel9results from the difference between the overall guidance distance C and the length D of the open space18. 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, preferably over 60% of the entire guidance distance C. Thus, D>0.5*C.

The guidance channel9formed between the guidance elements7.1and7.2has a channel constriction35, which brings about a restriction of the blowing stream. Preferably, the guidance width A of the open space18is at least 5 times larger than the channel constriction35having 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 channel9that a funnel-shaped entrance up to the channel constriction35is provided by a convergent channel opening8. The repeat expansion of the guidance channel9immediately after the channel constriction35by a divergent channel output36allows for 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 example embodiment shown inFIGS. 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 a maximum of about 700 mm. Here, in the lower region of the guidance distance, the channel constriction of the guidance channel is designed with a guidance width B in the range of 10 mm to maximum of about 200 mm. In contrast, the open space18is designed with a guidance width A in the range of 300 mm to about 1000 mm.

FIG. 4schematically shows the cross-sectional view of another example embodiment of the apparatus disclosed herein for implementing the method disclosed herein. Unlike the afore-mentioned example embodiment, which is used for producing so-called spun-bond non-woven webs, the example embodiment shown inFIG. 4is used for producing melt-blown non-woven webs.

In this embodiment, the drawing unit1is disposed immediately on a lower side of a spinneret31. The spinneret31has a plurality of nozzle holes32disposed in a row-shaped arrangement transversely to a deposit belt6. The nozzle hole32opens directly into a conveying channel5, in which the blast nozzles33.1and33.2blow a blowing stream for drawing off the fiber strands extruded from the nozzle holes32. The blowing stream exits together with the fiber strands from a blast opening3of the drawing unit1and is blown into an open space18designed directly below the drawing unit1. The open space18is not shielded from the ambience so as to allow for a free flow of the blowing stream. The open space18thus has an unlimited guidance width, which is determined exclusively by the free ambience.

In the lower third of the guidance distance, the guidance channel9is arranged between the guidance elements7.1and7.2directly above the deposit belt6. The shape of the guidance channel9is substantially identical to that shown in the example embodiment illustrated inFIGS. 1 and 2. Hence it requires no further explanation and one may refer to the previous description for the same.

In the present example embodiment, thin sheets26.1and26.2form the guidance elements. The thin sheets26.1and26.2are held opposite to one another, each of the thin sheets26.1and26.2including a clamping end27and a deformation end28. The thin sheets26.1and26.2are held in a fixed manner on the clamping end27. The thin sheets26.1and26.2have a circular curvature and are supported with one section at the end of the guidance channel9against the upper side of the deposit belt6or the upper side of the deposited non-woven web21. Due to this, the guidance channel9in the deposit region is shielded from the ambience and an entrance of external air is prevented. The deformation ends28of the thin sheets26.1and26.2are designed outside the guidance channel9. The position of the deformation ends28can be changed. Thus, the shapes of the thin sheets26.1and26.2can be deformed for changing the guidance channel9, for example, for expanding the channel constriction.

The shape of the guidance channel9between the thin sheets26.1and26.2is identical to that of the preceding example embodiment. Hence one may refer to the previous description for this purpose.

On the lower side of the deposit belt6, exhaust equipment22is arranged in the deposit region. The exhaust equipment22is substantially identical to that of the previous example embodiment. Therefore it requires no further explanation here

The example embodiment shown inFIG. 4represents an open system as opposed to the example embodiment shown inFIGS. 1 and 2. In the present embodiment, the open space18is connected directly to the ambience with the result that a free exchange can take place between the blowing stream and the ambience. Particularly 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 elements7.1and7.2in the example embodiment shown inFIG. 4could be replaced by the rollers12.1and12.2shown inFIGS. 1 and 2and vice versa. It is likewise possible to design the apparatus shown inFIGS. 1 and 2as an open system having an open space.

In the example embodiment shown inFIG. 4, the guidance elements7.1and7.2and the deposit belt6are arranged on a lifting table (not illustrated here). A double arrow with the reference numeral40indicates the lifting table only symbolically. The guidance distance below the drawing unit1can thus be set by adjusting the height of the guidance elements7.1and7.2and of the deposit belt. Furthermore, the mobility and the deformability of the guidance elements7.1allows for an adjustment of the forming gap19formed between the guidance elements7.1and the deposit belt6.

FIG. 5schematically shows the cross-section of another example embodiment of the apparatus according disclosed herein for implementing the method disclosed herein. The example embodiment shown inFIG. 5is substantially identical to that shown inFIGS. 1 and 2. Hence only the differences are explained below and the previous description may be referred to in all other respects.

In the example embodiment shown inFIG. 5, the drawing unit1and the open space18are designed identically to that of the preceding example embodiment shown inFIGS. 1 and 2. For designing the guidance channel9, the guidance elements7.1and7.2are formed by molded thin sheets26.1and26.2. The shape of the guidance channel9is selected by way of the curvature of the thin sheets in such a manner that at the end of the open space, a convergent channel opening8opens out into a channel constriction35. The channel constriction35gives way to an expansion, which leads to a divergent channel output36. On the side facing the deposit belt6, the thin sheets26.1and26.2each have oblong legs37, which extend parallel to the deposit belt6and form a sealing gap29.1and29.2with the deposit belt6or with the non-woven web21. The length of the sealing gap29.1and29.2is selected such that the deposit region is completely shielded inside the guidance channel9on the deposit belt6.

Any frictional contact between the guidance elements7.1and7.2with the non-woven web21or the deposit belt6is thus prevented on the upper side of the deposit belt.

The exhaust equipment22provided on the lower side of the deposit belt likewise has oblong sealing lips38.1and38.2in order to prevent the entry of external air from the ambience.

In the example embodiment shown inFIG. 5, a charge inducer34.1is provided in front of the entrance of the drawing unit1and another charge inducer34.2is provided in the region of the guidance elements7.1and7.2. The charge inducer34.1creates an electrostatic, preferably positive charge on the fiber strands20. Likewise, the charge inducer34.2creates an electrostatic charge on the thin sheets26.1and26.2. The charges of the fiber strands20and the charges of the guidance elements7.1and7.2are of like polarization. Thus by charging the fiber strands and the guidance elements, it is possible to optimize the entry and constriction of the blowing stream inside the guidance distance. The fiber strands move away from the contour of the guidance elements7.1and7.2. Additionally, a negative charge could be created on the lower side of the deposit belt6with the result that an additional 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 example embodiments, shown inFIG. 1toFIG. 5, of the apparatus according to the invention for implementing the method according to the invention are illustrated by way of example only. It is important that for depositing the fibers on the deposit belt, the fibers are initially guided in an open space in order to then meet the deposit belt after a constriction of the blowing stream in a closed deposit region. In doing so, those guidance elements are particularly suitable, which allows for a stable and reproducible guidance and deposition of the fiber strands.

LIST OF REFERENCE NUMERALS