Patent Application
20080256757
The invention relates to an apparatus for depositing synthetic fibers to form a nonwoven, and to a method for depositing a multiplicity of fibers to form a nonwoven.
In the production of a nonwoven web consisting of synthetic fibers, a multiplicity of extruded filament strands have to be deposited as uniformly as possible to form a sheet-like structure. The filament strands are in this case taken up to a greater or lesser extent, after extrusion and cooling, by a conveying fluid and are led to a deposit belt. In order to achieve conveying and depositing speeds which are as high as possible, methods and apparatuses have proven particularly appropriate in which the take-up nozzle conveys the filament strands into an open system. A method of this type and an apparatus of this type are known, for example, from U.S. Pat. No. 6,183,684. In this case, a take-up nozzle is used in order to take up the synthetic fibers, after extrusion, from a spinning device, draft them and lay them down. The take-up nozzle has a guide duct which has a slit-shaped fiber inlet on a top side. Shortly below the fiber inlet, a plurality of fluid inlets issue into the guide duct, through which fluid inlets a conveying fluid is supplied to the guide duct under the action of an excess pressure. As a result, the fiber strands are drawn into the take-up nozzle and accelerated within the guide duct and are blown out as a fiber stream through the fiber outlet. At the same time, a drafting of the fiber strands takes place, and these are subsequently received directly, for depositing, by a deposit belt. In this case, the fibers impinge, together with the conveying fluid, as a fiber stream onto the deposit belt essentially perpendicularly. By means of such apparatuses and methods, production speeds can be achieved at which the filament strands may reach speeds of up to 8000 m/min.
In order to influence the depositing of the synthetic fibers on the deposit belt, it is known, furthermore, to arrange, in the free space formed between the take-up nozzle and the deposit belt, guide members by which the fiber flow can be varied in order to influence the depositing of the fibers. An apparatus of this type is known, for example, from U.S. Patent Publication No. 2002/0158362 A1. The guide members are held at a long distance from the deposit belt, in order to generate a swirling of air so as to give rise to a traversing movement of the fibers. Consequently, although special effects in the depositing of a nonwoven can be achieved, these nevertheless increasingly lose their action at higher production speeds.
For the production of synthetic nonwoven webs, apparatuses and methods are also known in which the take-up nozzles are connected directly to following guide wells to form a closed system. An apparatus of this type is known, for example, from DE 196 12 142 A1. In closed systems of this type, the fiber stream generated by the take-up nozzle is conducted directly out of the fiber outlet into a guide well which guides the fiber stream until it is laid down on the deposit belt. However, closed systems of this type have the fundamental disadvantage that, because of the guided flow, longer drafting zones and therefore greater distances between the take-up nozzle and the deposit belt have to be maintained. Closed systems are therefore basically suitable only for low and medium production or spinning speeds.
An object of the invention was to provide an apparatus and a method for depositing synthetic fibers to form a nonwoven, of the generic type, in which uniform and controlled layings down of the fibers to form a nonwoven are possible even at higher spinning speeds.
A further object of the invention is to improve an apparatus for depositing synthetic fibers to form a nonwoven, to the effect that, on the deposit belt, a nonwoven is generated which has an essentially constant nonwoven thickness over the entire belt width.
These objects and others are achieved, according to the invention, by means of the apparatuses, and methods described and claimed below.
Advantageous developments of the invention are defined by the features and feature combinations of the claimed invention.
The invention possesses the advantage that the fibers can be guided, free of surrounding influences, in a protected space for depositing. For this purpose, the fiber stream generated by the take-up nozzle is blown out of the free space in an open fiber entry gap formed by the guide members, in order to be guided to the deposit belt within a guide segment formed between the guide members. The guide members in this case form a spatially delimited region above the deposit belt, in which region the fibers are deposited to form the nonwoven. It became apparent, surprisingly, that the air swirling generated during the transition of the fiber stream into the open fiber entry gap did not have adverse effects on the depositing and the guidance of the fiber stream within the guide segment.
In order as far as possible to generate low swirls at the transition of the fiber stream out of the free space into the fiber entry gap, the development of the invention proved particularly appropriate in which the guide member arranged on the belt exit side is formed by a rotatably mounted roller which with the deposit belt forms a shaping gap for the nonwoven. In this case, both for the fiber inlet and for the depositing of the fibers, a favorable guide contour within the guide segment is provided, by means of which a particularly advantageous depositing of the fiber on the deposit belt is achieved. On account of the roller contour, the fiber impingement angle can be influenced in such a way that the fibers can impinge onto the deposit belt at an angle of <90°. Consequently, even at high speeds of the guided fibers, a gentle and careful depositing of the fibers on the deposit belt is achieved. The kinetic energy accompanying the impingement of the fibers can advantageously be included in the formation of the nonwoven. Moreover, the nonwoven acquires an essential uniform thick structure over the entire width of the deposit belt, without being damaged in the shaping gap between the deposit belt and the roller.
In order to allow the entry of the fiber stream into the open fiber entry gap without substantial air swirls, the development of the apparatus according to the invention is preferably used in which the guide member arranged on the belt inlet side is formed by a second rotatably mounted roller which is held in contact with the deposit belt. Moreover, in this case, essentially wear-free sealing off with respect to surrounding influences can be generated on the deposit belt.
The guidance of the fibers within the guide segment and the depositing of the fibers in the lower region of the guide segment can be influenced in a desirable way by virtue of the development according to the invention of the apparatus, in such a way that at least one of the rollers has a perforated roller casing which is connected inside it to a pressure chamber formed. By the pressure chamber being connected to a pressure source or to suction extraction, additional air flows can be generated within the guide segment. In this case, for example, pulsating compressed air variations within the pressure chamber can also be formed, so that special effects in the depositing of the nonwoven are generated.
The drive of the rollers preferably takes place by means of the conveying movement of the deposit belt, so that the rollers are held in frictional contact with the deposit belt. It is also possible, however, to assign at least one electric drive to the rollers.
The development of the apparatus according to the invention, in which at least one of the rollers is assigned a ferromagnetic means which cooperates with a magnet, preferably an electromagnet, arranged on an underside of the deposit belt, in such a way that a pressure force acts between the roller and the deposit belt, is particularly advantageous in the formation of a shaping gap between the roller and the deposit belt. Fine adjustment can thereby be carried out, so that a pressure force optimal in each case acts between the roller and the deposit belt as a function of the filament strength of the fibers and of the weight per unit area of the nonwoven. Moreover, influencing the pressure force between the roller and the deposit belt allows an optimal sealing function with respect to the surroundings, so that, for example, a sucking in of extraneous air or the generation of air vortices at the sealing points is avoided.
Since apparatuses of this type are conventionally used for the production of different nonwovens, the development of the invention leads to particular flexibility in which the guide member arranged on the wall exit side or the deposit belt is assigned a height adjustment device, by means of which a shaping gap formed between the guide member and the deposit belt can be changed. In addition, a further optimization for the guidance and depositing of the fibers is afforded in that, to change the guide segment formed between the guide members, at least one of the guide members is held so as to be adjustable transversely with respect to the suction nozzle.
In order to receive and discharge continuously the air quantity supplied through the suction nozzle, the deposit belt has formed below it an adjustable suction port, by means of which a suction extraction device is connected to the underside of the deposit belt. In this case, the suction port can be varied in its size between two cover plates held displaceably with respect to one another, so that, depending on the depositing of the fibers, an optimized and uniform reception and discharge of the conveying fluid take place.
A further improvement in the flexibility of the apparatus according to the invention is afforded in that the guide members and the deposit belt are held on a lifting table which is movable between the take-up nozzle and the deposit belt in order to change a deposit height. By the guide members being tied up to the deposit belt, the entire free space between the guide members and the take-up nozzle is available for adjustment. Furthermore, the take-up nozzle could likewise be designed to be adjustable in height.
Moreover, it is proposed that the outlet orifice of the take-up nozzle be assigned at least one conveying means which is held at a distance from the guide members below the take-up nozzle. Further fiber guidance relevant for the formation of the nonwoven can consequently be set.
The method according to the invention for depositing a multiplicity of fibers to form a nonwoven combines the particular advantages of an open system, in which the fiber stream is blown directly into a free space, with a controlled and reproducible and also reliable depositing of the fibers to form a nonwoven. Surrounding influences caused, for example, by extraneous air are reduced to a minimum during depositing in spite of the open system.
The development of the method according to the invention in which the fibers are shaped to form the nonwoven by means of a pressure force acting between a rotating roller and the deposit belt constitutes a particularly advantageous method variant in which, on the one hand, a high sealing action of the guide segment is generated and, on the other hand, nonwoven formation with an essentially constant nonwoven thickness is generated without damage to the nonwoven. It proved particularly advantageous if the pressure force between the roller and the deposit belt is generated by means of a controllable electromagnet. Optimized pressure forces can thus be set, depending on the filament cross section and nonwoven strength.
The apparatus according to the invention having the features according to one embodiment constitutes an advantageous design for generating by magnetic means a pressure force acting between a roller and a deposit belt.
For this purpose, preferably, the magnet is of beam-shaped design and is arranged on an underside of the deposit belt. The magnetically conveying means cooperating with the magnet are assigned to the roller, so that an attraction force determined by the magnet acts on the roller. Such a design has the advantage, moreover, that the roller assumes an essentially unchanged position on the deposit belt.
The ferromagnetic means may in this case be formed directly by a roller casing or, alternatively, by an iron roll which is arranged freely rotatably inside the roller.
In order to obtain optimized sealing off of the deposit region both on the exit side and on the inlet side of the deposit belt, preferably a second roller is also held freely rotatably in contact with the deposit belt on the inflow side of the take-up nozzle, said second roller having a ferromagnetic means and cooperating with a second magnet on the underside of the deposit belt.
So that the pressure forces between the roller and the deposit belt can be influenced, particularly for shaping the nonwoven, the magnet is preferably formed by a controllable electromagnet, so that, by current being applied to the electromotor, the intensity and therefore the magnitude of the pressure force can be varied.
The apparatus according to the invention and the method according to the invention are distinguished by a stable and reproducible depositing of the fibers to form a nonwoven, high spinning and production speeds being possible. In this case, any desired setting can be carried out as a function of the fiber type, fiber material and nonwoven requirement. There is also the possibility of carrying out the settings by means of controllable actuators which, for example, are activated in an automated manner by means of a control device according to the stipulation of process or product parameters.
The apparatus according to the invention and the method according to the invention are described in more detail below by means of some exemplary embodiments, with reference to the accompanying figures in which:
The exemplary embodiment according to
The take-up nozzle 1 has a middle conveying duct 5 which is delimited on a top side of the take-up nozzle 1 by a fiber inlet 2 and on the underside of the take-up nozzle 1 by a fiber outlet 3. The conveying duct 5 is of slit-shaped design and extends essentially over the entire length of the parallelepipedal take-up nozzle 1. On the longitudinal sides of the conveying duct 5, a plurality of fluid inlets, not illustrated here, are formed, which are connected to a fluid connection 4. By means of the fluid connection 4, a conveying fluid is supplied which has an excess pressure with respect to the atmosphere in the conveying duct 5.
The take-up nozzle 1 is arranged at a distance above a deposit belt 6. The deposit belt 6 has a belt width which extends over the entire length of the take-up nozzle 1. The deposit belt 6 is preferably guided as an endless belt via a plurality of conveying rolls and is driven so as to be directed transversely with respect to the longitudinal side of the take-up up nozzle 1. The deposit belt 6 therefore moves continuously in a guidance direction which is identified in the figure by an arrow. The deposit belt 6 is of air-permeable design, a suction extraction device 31 being arranged on the underside of the deposit belt 6 in a deposit region formed vertically below the take-up nozzle 1.
In the region between the take-up nozzle 1 and the deposit belt 6, a travel is formed which is divided into a free space 17 formed directly below the take-up nozzle 1 and a guide segment 9 assigned to the deposit belt 6. The guide segment 9 is formed by the guide members 7.1 and 7.2 which on a top side form, opposite the take-up nozzle 1, a fiber entry gap 8. For this purpose, the guide member 7.1 is arranged on a belt exit side 10 and the guide member 7.2 is arranged on the opposite belt inlet side 11. In this case, the guide members 7.1 and 7.2 are formed in each case by a roller 12.1 and 12.2 held so as to be rotatably mounted. The roller 12.1 on the belt exit side 10 and the roller 12.2 on the belt inlet side 11 are in each case in frictional contact with the deposit belt 6, so 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. The roller 12.2 in this case bears directly against the surface of the deposit belt 6 or on a coating material. The roller 12.1 on the belt exit side 10 forms with the top side of the deposit belt 6 a shaping gap 19 by means of which a nonwoven 21 is deposited and shaped.
The fiber entry gap 8 formed on the top side of the rollers 12.1 and 12.2 is of essentially funnel-shaped design with respect to the free space 17 due to the roller casings of the rollers 12.1 and 12.2. The interspace between the rollers 12.1 and 12.2 forms the guide segment 9 in which the fiber stream blown in via the fiber entry gap 8 is guided for depositing onto the deposit belt 6. The guide segment 9 extends as far as the top side of the deposit belt 6, the rollers 12.1 and 12.2 in each case providing shielding with respect to the surroundings. Owing to the direct frictional contact between the rollers 12.1 and 12.2 and the deposit belt 6 and also the nonwoven surface of the nonwoven 21, sealing off with respect to extraneous air is achieved.
The rollers 12.1 and 12.2 have in each case a perforated roller casing 13 which is gas-permeable. Inside the rollers 12.1 and 12.2 is provided in each case a pressure chamber which is connected to a suction source 16 or to a pressure source 18 via an air connection 15. In the exemplary embodiment according to
During operation, a conveying fluid is supplied to the take-up nozzle 1. The conveying fluid used is preferably compressed air from a compressed air source, which flows into the conveying duct 5 with an excess pressure in the range of 0.1 to 5 bar, preferably in a range of 0.5 to 3 bar excess pressure. As a result, the fiber strands 20 threaded into the conveying duct 5 via the fiber inlet 2 are taken up continuously from a spinning device, not illustrated here. In the spinning device, the fibers are melt-spun beforehand from a polymer material in an arrangement in the form of a row and are subsequently cooled. Within the conveying duct 5, the fiber strands 20 are accelerated by the conveying fluid and are blown out jointly through the fiber outlet 3 as a fiber stream into the free space 17. The fiber stream which is composed of the fibers and the conveying fluid is in this case blown perpendicularly through the fiber outlet 3 in the direction of the deposit belt 6. After running through the free space 17, the fiber stream, together with the fiber strands 20, is blown into the fiber entry gap 8 formed by the guide members 7.1 and 7.2. Owing to the shape and configuration of the guide segment 9 and of the guide members 7.1 and 7.2, the fiber stream is guided in the direction of the deposit belt 6. Within the guide segment 9, the fiber strands 20 impinge onto the deposit belt 6 at an impingement angle desired by the fiber stream being influenced and on the surface of the deposit belt 6 form the nonwoven 21 which is discharged continuously in the conveying direction by the deposit belt 6. The suction flow generated on the roller 12.1 on the belt exit side 10 causes a deflection of the fiber stream, so that the fiber strands 20 impinge onto the deposit belt 6 at an impingement angle of <90°. In this case, a particularly careful depositing of the fibers takes place, so that, even at high fiber speeds in the range 3500 m/min. to 8000 m/min., no intensive catching between the surface of the deposit belt 6 and the individual fibers 20 occurs. Moreover, the shaping gap 19 set by the roller 12.1 and the deposit belt 6 will cause the nonwoven 21 to acquire a nonwoven thickness which is essentially constant over the entire belt width. Damage to the nonwoven surface is ruled out on account of the rotational movement of the roller 12.1.
The apparatus according to the invention and the method according to the invention thus allow a uniform reproducible depositing of a nonwoven which can take place in a controllable way even at high fiber speeds. In this case, on the one hand, the advantages of the high draft, which are known from the blowing of the fiber stream out into a free space, and also the deposit mechanisms known per se only in closed systems are advantageously combined by virtue of the invention. In spite of the reservation that air swirls occur at the transition between the free space and the guide segment, it was possible, surprisingly, to generate highly uniform and relatively smooth fiber stream profiles. In particular, configuring the guide members as rollers afforded a very gentle transition of the fiber stream out of the free space to the guide segment.
In the exemplary embodiment, illustrated in
A conveying means 33.1 and 33.2 is arranged in each case on each side of the take-up nozzle 1 directly on the side of the fiber outlet 3. The conveying means 33.1 and 33.2 are in this case formed by pivotable guide battens which are held pivotably on the underside of the take-up nozzle. By the conveying means 33.1 and 33.2 arranged on the outlet side of the take-up nozzle 1, additional flow variations of the fiber stream can be generated, which influence both entry into the fiber entry gap 8 and the depositing of the fiber strands 20.
For discharge and for assisting the depositing of the fibers for forming a nonwoven, a suction extraction device 31 is arranged on the underside of the deposit belt 6. In this case, the suction extraction action of the suction extraction device 31 is limited to the deposit region of the guide segment 9. The suction extraction device 31 has an adjustable suction port 34 which is assigned directly to the deposit region on the deposit belt 6. The suction port 34 is in this case formed between two displaceably arranged cover plates 35.1 and 35.2. Each of the cover plates 35.1 and 35.2 can be displaced horizontally in relation to one another.
In the exemplary embodiment illustrated in
In the exemplary embodiment, illustrated in
In order to obtain reliable frictional contact between the rollers 12.1 and the deposit belt 6 and also the roller 12.2 and the deposit belt 6, each roller 12.1 and 12.2 is assigned in each case ferromagnetic means 22 and a magnet 23. The design of the ferromagnetic means 22 and of the magnet 23 is identical for each roller 12.1 and 12.2, and therefore the design is explained in more detail by the example of the roller 12.1. The ferromagnetic means 22 is formed directly by the roller casing 13 which consists of a ferromagnetic material. On the underside of the deposit belt 6 is provided a magnet carrier 36 which extends essentially over the entire belt width and which carries the beam-shaped magnet 23. The magnet 23 is preferably formed by an electromagnet which, by current being applied, exerts magnetization and consequently an attraction force with respect to the roller casing 13. The roller casing 13 of the roller 12.1 is thus attracted in the direction of the deposit belt 6. In this case, a pressure force acting between the roller 12.1 and the deposit belt 6 builds up and acts directly on the nonwoven 21 in the shaping gap 19. The application of the current to the electromagnet 23 is in this case selected in such a way that, on the one hand, sufficient sealing off with respect to the inflow instances of extraneous air is obtained and, on the other hand, no damage to the nonwoven 21 occurs.
On the opposite side, the roller 12.2 is attracted in the same way by means of a casing 13 formed from ferromagnetic material and the second magnet 23 arranged on the underside of the deposit belt 6, so that the roller casing 13 is held directly against the surface of the deposit belt 6 and leads to a sealing off of the guide segment 9 between the rollers 12.1 and 12.2.
In the exemplary embodiment illustrated in
In the free space 17, two conveying means 33.1 and 33.2 are assigned directly to the fiber outlet 3 of the take-up nozzle 1, the conveying means 33.1 and 33.2 being formed in each case by freely rotatable rolls which are designed to be adjustable in their position in and opposite to the conveying direction of the deposit belt.
The function of the apparatus for forming the nonwoven, as illustrated in
To fix the rollers 12.1 and 12.2, the ferromagnetic means 22 is formed in each case by an iron roll 37 which is arranged rotatably inside the roller 12.1 or the roller 12.2. By means of the magnet 23 arranged on the underside of the deposit belt 6, the iron roll 37 is attracted in the direction of the deposit belt 6 and leads to the reliable bearing of the roller 12.1 against the top side of the nonwoven 21 or to a reliable bearing of the roller 12.2 against the top side of the deposit belt 6. The magnet assigned to the roller 12.1 on the belt exit side 10 is designed as an electromagnet 23 which can be activated via a control unit 38 and a control device 39. In this case, process data, such as, for example, fiber cross sections and weight per unit area or nonwoven thickness, can be preset for the control device 39. By means of a stored optimization program, a current size is determined from the process parameters and is predetermined via the control unit 38 for the application of current to the electromagnet 23. The application of current to the electromagnet 23 leads to an attraction force and consequently to a pressure force between the roller 12.1 and the deposit belt 6, said pressure force being adapted to the respective process parameters.
In the design, illustrated in
The exemplary embodiments, illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 051 244.5 | Oct 2005 | DE | national |
The present application is a Continuation of International Application No. PCT/EP2006/010234, filed Oct. 24, 2006, and which designates the U.S. The disclosure of the referenced application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2006/010234 | Oct 2006 | US |
| Child | 12108965 | US |
