Device and method for aerodynamic web formation

Abstract

The invention relates to a device and a method for aerodynamic web formation, comprising at least one rotatable opening roller (2) provided with needles or clothing, a device for generating an air flow (4), a guide element (5), and an air-permeable deposition surface positioned below the opening roller (2), wherein the opening roller (2) is designed to spin out fibers (3) by means of high rotational speed, said fibers being deposited on the air-permeable deposition surface by means of the air flow (4), wherein the air flow (4) is guided between the opening roller (2) and the guide element (5) and directed onto the air-permeable deposition surface, on which the air and fibers (3) separate, and the fibers (3) are transported away from the opening roller (2) by means of the air-permeable deposition surface. The invention is characterized in that at least one nozzle arrangement (11) is positioned between the opening roller (2) and the guide element (5) and designed to generate at least one air jet (10) which is directed onto the clothing of the opening roller (2), wherein the at least one air jet (10) acts counter to the flow direction of the air flow (4).

Description

[0001] Title: Device and method for aerodynamic nonwoven formation

[0002] Description

[0003] The invention relates to a device and a method for aerodynamic nonwoven formation, in which fibers are dissolved by various processes and deposited by an air stream onto an air-permeable drum or belt. Nonwovens with nearly isotropic properties and a basis weight of usually greater than 100 g / m² are produced. 2 . The processes for dissolving the nonwovens usually comprise a final dissolving roller provided with needles or clothing, from which the fibres are deposited on an air-permeable drum or an air-permeable belt by means of an air stream with the additional effect of positive and / or negative pressure.

[0004] For example, DE 1020170062535 A1 and EP 1672110 B1 show airlay cards in which the fibers are deposited from an opening roller onto a screen belt by an air stream. The air stream is guided between the opening roller and an air baffle. With this principle, an unwanted fiber backflow occurs at the opening roller, even though the opening roller should be completely unloaded. This fiber backflow is undesirable because it is associated with uneven fiber deposition, which leads to an uneven basis weight. To prevent this, a cutting knife is installed below the opening roller, approximately tangential to the opening roller, and can be positioned close to the screen belt. The cutting knife also has more than its advantages. Due to the negative pressure between the opening roller and the cutting knife, if the setting is too tight, the cutting knife can collide with both the opening roller and the screen belt.Additionally, the temperature of the cutting knife must be monitored, as it can become extremely hot during the process and thus cause excessive deformation. Even with the cutting knife optimally adjusted, fibers will continue to run around the opening roller because the cutting knife cannot reach into the opening roller's clothing.

[0005] Based on this prior art, it is the object of the invention to improve a device and a method for aerodynamic web formation in such a way that the fiber backflow in the opening roller is further reduced when the fibers are deposited on a roller or a belt.

[0006] This object is achieved by a device for aerodynamic nonwoven formation according to the preamble of claim 1 with the characterizing features. The device has at least one final rotatable opening roller provided with needles or clothing, furthermore a device for generating an air stream, a guide element, and an air-permeable deposit arranged below the opening roller. Fibers are ejected from the rotatable opening roller by centrifugal force and deposited isotropically onto the air-permeable deposit by the air stream. The air stream is guided between the opening roller and the guide element and directed onto the air-permeable deposit, where a separation of air and fibers takes place. The fibers are transported away from the opening roller by means of the air-permeable deposit.

[0007] The invention includes the technical teaching that at least one nozzle arrangement is arranged between the opening roller and the guide element, which nozzle arrangement is designed to generate an air jet directed onto the clothing of the opening roller, wherein the air jet acts counter to the flow direction of the air stream.

[0008] The core idea of ​​the invention is to replace the previous cutting knife device with an air jet. The air jet is directed onto or into the clothing of the opening roller and causes an increased release of the fibers from the opening roller. At the same time, the air jet forms an air curtain for the opening roller, which is shielded from the fibers that impact and are swirled up on the air-permeable tray. The backflow of fibers into the opening roller is reduced. The device is low-maintenance and has the advantage that the previous disadvantages (component collision, deformation) are completely avoided due to the mechanical properties of the previous cutting knife.

[0009] The term "air flow" refers to a high-volume flow across the working width of the carding machine, generated by fans or blowers and directed by the arrangement of the surrounding components. An air jet is a high-pressure flow generated by nozzles, which is directed in a targeted manner and narrower in width, forming an air blade.

[0010] The air-permeable support can be designed as a perforated belt or drum. The belt or drum can have a suction device to assist in the isotropic deposition of the fibers. The belt can be oriented horizontally, so the guide element can be arranged vertically or at an angle downward.

[0011] The nozzle arrangement can extend over the entire working width of the opening roller so that a continuous air curtain is created across the working width.

[0012] Because the nozzle arrangement can be positioned on or in a trough located below the opening roller, the effective direction of the air jet is simultaneously determined, counter to the effective direction of the air flow. Using an additional nozzle arrangement located above the opening roller, whose air jet is directed onto the opening roller's clothing, the removal of fibers from the opening roller can be enhanced.

[0013] A uniform deposition of the fibers into an isotropic web is enhanced by the fact that the nozzle arrangements generate a continuous air flow across the working width of the opening roller.

[0014] Alternatively, the nozzle arrangements can generate a pulsed or intermittent air jet across the working width of the opening roller.

[0015] When using two nozzle arrangements, a continuous air jet is preferably generated by the lower nozzle arrangement, which forms an air curtain against the air flow. The nozzle arrangement positioned above the opening roller can generate a pulsating or intermittent air jet.

[0016] Based on the previously described prior art, the object of the invention is to improve a method for aerodynamic web formation in such a way that the fiber backflow in the opening roller is further reduced when the fibers are deposited on a roller or a belt.

[0017] The object is achieved on the basis of a method for producing an isotropic nonwoven according to the preamble of claim 9 with the characterizing features.

[0018] In the method according to the invention, fibers from an opening roller are deposited onto an air-permeable tray by means of a guided air stream, separated from the air, and transported away from the opening roller by means of the air-permeable tray. An air jet directed at the opening roller's clothing completely separates the fibers from the opening roller's clothing, while simultaneously shielding the opening roller from swirling fibers. The previous mechanical cutting knife is replaced by a pneumatic air blade, which is maintenance-free and cannot collide with the air-permeable tray or the opening roller.

[0019] The orientation of at least one air jet can act against the air flow, so that a flow channel for the fibers is created, which is limited on one side by the guide element and on the other side by the air jet.

[0020] The formation of the isotropic nonwoven can be improved by applying suction to the air-permeable deposit. This simultaneously reduces the rebound of the fibers onto the belt or drum. By directing an additional air jet (10a) from above the opening roller (2) onto the clothing of the opening roller (2), the removal of the fibers from the opening roller can be improved.

[0021] The further air jet can be aligned parallel and in the same direction as the air flow at a flat angle of up to approx. 30° to the air flow, without crossing it.

[0022] Because at least one air jet extends over the entire working width of the opening roller, a uniform fiber deposition on the air-permeable deposit is achieved.

[0023] Preferably, the opening roller is exposed to at least one continuous air jet. Alternatively, the opening roller can be exposed to at least one intermittent or pulsed air jet. The type of air jet can influence the removal of fibers from the opening roller clothing, depending on the fiber quality (fiber length, surface).

[0024] Further measures improving the invention are described in more detail below together with the description of a preferred embodiment of the invention with reference to the figures.

[0025] They show:

[0026] Fig. 1 : A detailed view of an Airlay carding machine according to the state of the art;

[0027] Fig. 2: A detailed view of an airlay carding machine according to the invention;

[0028] Fig. 3: Another embodiment of the airlay carding according to the invention.

[0029] Fig. 1 shows a detailed illustration of a prior art airlay carding machine. Opened fibers 3 are fed to an opening roller 2 via an upstream machine component, which here is designed as a feed roller 1. The opening roller 2 has a clothing or needles on its circumference, with which the fibers 3 are taken over between the opening roller 2 and the feed roller 1 and transported further. The opening roller 2 can have a diameter of 250 mm to 800 mm and is operated at a speed of 2,500 rpm to 4,000 rpm, so that the fibers are ejected from the clothing at a high peripheral speed by centrifugal force. The opening roller 2 can be covered and shielded on the underside by means of a trough 9 to prevent unwanted air currents and fiber transport on the clothing. Below the opening roller 2 there is a belt 7 which can be designed as a sieve belt.The belt 7 is preferably arranged horizontally or inclined downwards. Alternatively, a perforated drum can be used. The belt 7 or the drum must be permeable to air. An air stream 4 is directed tangentially onto the circumference of the opening roller 2, which intensifies the removal of the fibers 3 from the clothing of the opening roller 2 and deposits them in a random layer on the belt 7. The air stream 4 acts on the side of the opening roller 2 on which the fibers are deposited onto the belt 7. The speed of the air stream 4 is on the order of magnitude of the surface speed of the opening roller 2 and is generated across the entire working width of the opening roller 2 from 1 m to 5.5 m. The air stream 4 is generated by a blower / fan and is directed tangentially to the opening roller 2.

[0030] To align the air flow 4, an air guide element 5 is arranged at a distance from the opening roller 2, so that a channel is formed between the opening roller 2 and the air guide element 5. The distance or gap between the opening roller 2 and the guide element 5 can be between 50 mm and 500 mm and is completely filled by the air flow 4. The air flow 4 with the fibers 3 released from the opening roller 2 strikes the belt 7 or the drum, whereby a separation of the air flow 4 and the fibers 3 occurs. The air flow 4 is discharged through the belt 7 or the drum, whereby a suction box in the belt 7 or in the drum can further intensify this effect. The fibers 3 are deposited on the belt 7 in a random position, whereby the deposition of the fibers 3 is disordered in all three spatial axes. In order to reduce the backflow of fibers, a cutting knife 6 is used, which is arranged tangentially to the circumference of the opening roller 2 just above the belt 7.The cutting knife 6 is also arranged on the side of the opening roller 2 on which the fibers 3 are deposited and can be integrated into the trough 9 or attached to it. This cutting knife 6 forms a channel with the guide element 5 in which the air flow 4 is guided onto the belt 7 or the drum. The cutting knife 6 reduces turbulence of the air flow 4 in the direction of the opening roller 2, which occurs due to the impact of the air flow 4 on the belt 7. In order to keep the backflow of fibers as low as possible, the cutting knife 6 must be arranged very close to the belt 7 and to the drum and the opening roller 2. Due to the flow velocity of the air flow 4, areas with pressure differences arise which can pull the cutting knife 6 into the clothing of the opening roller 2 or cause the belt 7 to flutter or vibrate. Fibers can collect on the cutting knife. If these are then pulled in, the furniture may be damaged.Heating of the cutting blade 6 and guide element 5 can also cause deformation of the components. Since the cutting blade 6 cannot engage the clothing of the opening roller 2, the opening roller 2 will always be covered with fibers even behind the imaginary detachment point.

[0031] Figure 2 shows the preferred embodiment of the airlay carding machine according to the invention, in which the cutting knife 6 is replaced by at least one air jet 10 extending across the working width of the opening roller 2. The air jet 10 is generated by a nozzle arrangement 11, which can be arranged below the opening roller 2, for example laterally on or in the trough 9. The nozzle arrangement 11 extends across the entire working width of the opening roller 2 and generates an air jet 10 across the working width, which can be constant in terms of pressure and volume. The air jet 10 is only a few millimeters wide and differs from the air stream 4, which is generated at a lower pressure but with a higher volume. The air jet 10 can be generated continuously or intermittently.

[0032] Essential to the invention is the alignment of the air jet 10 into the clothing of the opening roller 2, preferably substantially opposite to the direction of action of the air flow 4, whereby the fibers 3 are completely released from the clothing. In order to minimize fiber backflow, the nozzle arrangement 11 is positioned such that the air jet 10 is directed between the opening roller 2 and the direction of action of the air flow 4, thus shielding the opening roller 2 from the swirling fibers 3. The nozzle arrangement 11 does not have to be arranged on the trough 9, but can be positioned arbitrarily and far away from the opening roller 2 without the air jet 10 intersecting the air flow 4. This has the advantage of avoiding a collision between the nozzle arrangement 11 and the opening roller 2. Furthermore, the nozzle arrangement 11 is low-maintenance and low-wear.

[0033] In the exemplary embodiment in Figure 3, the air guiding element 5 is arranged vertically inclined in the material transport direction, whereby the air flow 4 also conveys the fibers 3 onto the belt 7 at a vertical incline in the material transport direction. Depending on the system configuration, the conveyor belt 7 with the suction box 8 can also be arranged inclined upwards or downwards. The nozzle arrangement 11 is arranged next to the trough 9 and the air jet 10 acts against the air flow 4 and forms an air curtain with which the swirled fibers 3 are shielded from the opening roller 2. In this exemplary embodiment, the air jet 10 is also directed against the direction of the air flow 4 onto the clothing of the opening roller 2. However, it is not directed parallel to the air flow 4, but does not cross it either. A further nozzle arrangement 11a is arranged above the opening roller 2 and likewise directed onto the clothing of the opening roller 2.Their air jet 10a causes further fibers 3 to be released from the opening roller 2, which are then entrained by the air stream 4. The orientation of the additional air jet 10a essentially corresponds to the orientation of the air stream 4 and is directed from above the opening roller 2 downwards. The arrangement of the additional nozzle arrangement 11a is also designed to prevent any crossing or interruption of the air stream 4. Here, too, a parallel alignment of the air stream 4 and the air jet 10 is possible, but not necessary. The illustration in Figure 3 shows that the two flow directions 4, 10 can diverge slightly.

[0034] Reference symbol

[0035] 1 feed roller

[0036] 2 opening roller

[0037] 3 Fibers 4 Airflow

[0038] 5 Guide element

[0039] 6 cutting knives

[0040] 7 volumes

[0041] 8 Suction box 9 Trough

[0042] 10, 10a Air jet

[0043] 11 , 11a Nozzle arrangement

Claims

Patent claims 1. A device for aerodynamic nonwoven formation, comprising at least one rotatable opening roller (2) provided with needles or clothing, a device for generating an air stream (4), a guide element (5), and an air-permeable deposit arranged below the opening roller (2), wherein the opening roller (2) is designed to spin out fibers (3) at high speed, which are deposited onto the air-permeable deposit by means of the air stream (4), wherein the air stream (4) is guided between the opening roller (2) and the guide element (5) and directed onto the air-permeable deposit, on which a separation of air and fibers (3) takes place, and the fibers (3) are transported away from the opening roller (2) by means of the air-permeable deposit, characterized in that at least one nozzle arrangement (11) is arranged between the opening roller (2) and the guide element (5), which nozzle arrangement is designed to generate at least one air jet (10),which is directed towards the clothing of the opening roller (2), wherein the at least one air jet (10) acts against the flow direction of the air stream (4).

2. Device according to claim 1, characterized in that the nozzle arrangement (11) extends over the entire working width of the opening roller (2).

3. Device according to claim 1, characterized in that the nozzle arrangement (11) is arranged on or in a trough (9) which is located below the opening roller (2).

4. Device according to claim 1, characterized in that the air-permeable storage is designed as a belt (7) or drum.

5. Device according to claim 2, characterized in that the belt (7) or the drum has a suction device.

6. Device according to claim 1, characterized in that a further nozzle arrangement (11a) is arranged above the opening roller (2), the air jet (10a) of which is directed onto the clothing of the opening roller (2).

7. Device according to one of the preceding claims, characterized in that the nozzle arrangement (11, 11a) generates an air jet (10, 10a) which is continuous over the working width of the opening roller (2).

8. Device according to one of the preceding claims 1 to 6, characterized in that the nozzle arrangement (11, 11a) generates a jet of air (10, 10a) which is intermittent or bursts over the working width of the opening roller (2).

9. A method for producing an isotropic nonwoven fabric, in which fibers (3) are ejected from an opening roller (2) by means of centrifugal force and deposited onto an air-permeable deposit and separated from the air by means of a guided air stream (4), and the fibers (3) are transported away from the opening roller (2) by means of the air-permeable deposit, characterized in that the fibers (3) are released from the clothing of the opening roller (2) by means of at least one air jet (10) which is directed onto the clothing of the opening roller (2), and the air jet (10) shields the opening roller (2) from fibers whirling back.

10. Method according to claim 9, characterized in that the air jet (10) acts against the air flow (4) and is directed from the air-permeable deposit onto the opening roller (2).

11. Method according to claim 9, characterized in that the air-permeable storage is vacuumed.

12. Method according to claim 9, characterized in that a further air jet (10a) is directed from above the opening roller (2) onto the clothing of the opening roller (2).

13. Method according to claim 12, characterized in that the further air jet (10a) is aligned parallel and rectified to the air flow (4) at a shallow angle of up to approximately 30° to the air flow (4).

14. Method according to claim 9 to 13, characterized in that the at least one air jet (10, 10a) extends over the entire working width of the opening roller (2).

15. Method according to one of the preceding claims 9 to 14, characterized in that the opening roller (2) is acted upon by at least one continuous air jet (10, 10a).

16. Method according to one of the preceding claims 9 to 14, characterized in that the opening roller (2) is acted upon by at least one intermittent air jet (10, 10a).

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