METHOD AND DEVICE FOR MAKING WET LAID NON WOVENS

Abstract

Method for producing wet-laid non-woven fabrics, with which an aqueous suspension comprising fibres is laid down on a screen and is dewatered using suction boxes under the screen to form a sheet of non-woven web which is removed from the screen and guided to at least one subsequent treatment unit before the non-woven web can be wound, and transferring of the non-woven web from the screen to the at least one subsequent treatment unit and/or transferring of the non-woven web to interfaces between treatment units on the start of production and/or after an interruption in production, using a web feed, wherein web is fed via a temporarily closed draw of a free draw between the screen and the at least one subsequent treatment unit and/or of a free draw at an interface between treatment units, and the respective temporarily closed draw is produced via air flows, which lift off an end feeding strip as part of the running non-woven web by blowing, adhere same to a transport path device by generating negative pressure and lift up same at the following treatment unit by suction.

Claims

1. A method for making wet laid non wovens, in which method an aqueous suspension comprising fibers is deposited onto a wire and in order for a sheet of a non woven web to be formed is dewatered by suction boxes below the wire, said non woven web, prior to being capable of being wound-up, being removed from the wire and being guided to at least one subsequent treatment units, and transferring the non woven web from the wire to the at least one subsequent treatment unit, and/or transferring the non woven web at junction points between treatment units in the case of a production start-up and/or upon a production interruption with the aid of a web feeding, characterized in that web feeding is performed by way of a transfer that in each case is temporarily closed and is part of a free transfer between the wire and the at least one subsequent treatment unit and/or of a free transfer at a junction between treatment units, and that the transfer that in each case is temporarily closed is generated by air flows which by blowing lifts an end feeding strip as part of the running non woven web, by generating negative pressure attach said end feeding strip to a transportation path installation, and by suctioning pick up said end feeding strip at the respective subsequent treatment unit.

2. The method as claimed in claim 1, wherein the end feeding strip is lifted from the wire by way of compressed air.

3. The method as claimed in claim 1, wherein the end feeding strip is transported by way of a vacuum conveyor belt.

4. The method as claimed in claim 1, wherein the end feeding strip is transported by way of an air baffle installation.

5. The method as claimed in claim 3, wherein transporting the end feeding strip is performed by attaching the latter to a lower side of the transportation path installation.

6. The method as claimed in claim 1, wherein suctioning on the respective subsequent treatment unit is performed by means of suction trap installation below a wire belt of the subsequent treatment unit.

7. The method as claimed in claim 1, wherein the air flows of the transfer that is temporarily closed are mutually adapted for configuring a uniform web transfer in the region of the transfer.

8. A device for carrying out the method as claimed in claim 1, the device comprising a wet non wovens plant having a fiber suspension installation, a wire installation, at least one subsequent treatment unit, and having at least one free transfer at a junction between the wire installation and the subsequent treatment unit and/or at a junction between two subsequent treatment units, said transfer by way of air flow installations of a web feeding installation being temporarily closable for a cut end feeding strip, said air flow installations being positioned in such a manner that the end feeding strip as part of the running non woven web is removed by a compressed-air installation, is transferred by a transportation path installation that generates negative pressure, and is picked up by an air suction installation of the subsequent treatment unit.

9. The device as claimed in claim 8, wherein in order for the non woven web to be removed, a suction installation by means of which a transfer position is positionable in the free transfer toward the subsequent treatment unit is provided the compressed-air installation so as to be downstream thereof in the running direction of the non woven web.

10. The device as claimed in claim 8, wherein the transportation path installation that generated negative pressure are configured as a vacuum conveyor belt or as an air baffle installation.

11. The device as claimed in claim 8, wherein the transportation path installation has a lower side that is configured as a suction face.

12. The device as claimed in claim 8, wherein in order for a transferred end feeding strip to be picked up, the subsequent treatment unit on the entry side has a suction trap installation which is connected to a controller installation for controlling lifting, transferring, and picking up of an end feeding strip in the temporarily closed transfer.

Description

[0019] FIG. 1a schematically shows a side view of a wet non wovens plant having a free suspension installation, a wire installation, a hydroentanglement installation, and a dewatering belt;

[0020] FIG. 1b schematically shows the end sections of a wet non wovens plant, having a dryer and a winder;

[0021] FIG. 2 in an enlarged and schematic manner shows an exemplary embodiment of a web feeder for the junctions X, Y according to FIG. 1a;

[0022] FIG. 3 shows a second exemplary embodiment of a web feed for the junctions X, Y according to FIG. 1a;

[0023] FIG. 4 schematically shows a plan view of the exit side end region of the wire installation in the region of the junction X according to FIG. 1a.

[0024] The invention relates to a method and to a device for making wet laid non wovens. A wet non wovens plant 1 that is provided in an exemplary manner to this end is illustrated in FIG. 1a and FIG. 1b.

[0025] Accordingly, a fiber suspension installation 2, a wire installation 3, at least one subsequent treatment unit 4, and optionally a winder 5 are sequentially disposed. A hydroentanglement installation is provided as the at least one treatment unit 4 in the case of the wet non wovens plant 1 illustrated in FIG. 1a and FIG. 1b. Further treatment units 6, 7 are furthermore provided. The treatment unit 6 is a drying wire, for example, and the treatment unit 7 is a dryer, for example.

[0026] The wire installation 3 is illustrated as an inclined wire former. Alternative configurations of the wire installation 3 can be used. A junction 8 is provided between the wire device 3 and the subsequent treatment unit 4. For example, a junction 9 is provided between the treatment unit 4 and the treatment unit 6. When the non woven web 10 is fed, both junctions 8, 9 are configured as free transfers.

[0027] In the case of a production start, or upon a production interruption, it is necessary for the non woven web 10 to be fed in order for the spacing in the region of the junctions 8, 9 to be overcome.

[0028] It has been established according to the invention that the non woven web 10 produced with wet non woven products on an inclined wire machine such as is illustrated in an exemplary manner as a wire installation 3 in FIG. 1a has an adequate strength in order for the material to be taken from the wire 11 by blowing. This is highlighted in FIGS. 2 and 3 in conjunction with FIG. 4.

[0029] The method according to the invention for making wet laid non wovens provides that an aqueous suspension having fibers is deposited onto a wire 11 of the wire installation 3 for the formation of a sheet of a non woven web 10 that is removed from the wire 11 and is dewatered by suction boxes 12 under the wire and, prior to the non woven web 10 being finally windable onto a roll 23, is infed to at least one subsequent treatment unit 4.

[0030] The non woven web in the case of a production start and/or upon a production interruption from the wire 11 to the at least one subsequent treatment unit 4 and/or at a junction 9 between two treatment units 4, 6 is transferred with the aid of a web feeding 13.

[0031] Referring to FIG. 2 to FIG. 4, web feeding 13 is performed by way of a transfer that in each case is temporarily closed and is part of a transfer that is free per se between the wire 11 and the at least one following treatment unit 4 and/or of a free transfer at a junction 9 between treatment units 4, 6.

[0032] The transfer that in each case is temporarily closed of a web feed 13 is generated by way of air flows. These air flows act on an end feeding strip 14 which is cut by means of a cutting installation 16 which acts on the non woven web 10 at the exit side of the wire 11. The end feeding strip 14 is severed from the remaining web 15 of the non woven web 10 by means of the cutting installation 16. Web feeding is performed by way of the end feeding strip 14, while the remaining web 15 drops into a pulper 17.

[0033] According to the invention, the end feeding strip 14 as part of the running non woven web 10 is lifted from the wire 11 by blowing by means of a compressed air installation 18. The end feeding strip 14, on account of negative pressure being generated on a transportation path installation 19, is attached to a transportation path that is formed by the transportation path installation 19 and is picked up by suctioning on the respective subsequent treatment unit 4. Suctioning on the subsequent treatment unit 4 is performed by means of a vacuum catching device 21, for example.

[0034] The explanations pertaining to the web feeding 13 at the junction 8 apply in an analogous manner to the web feeding 13 at the junction 9.

[0035] It has been established according to the invention that wet non woven products have an adequate strength when the latter have been dewatered on a wire installation 3 which is configured as an inclined wire machine, for example. This applies in particular also when long fibers are used for producing the non woven web. On account of this strength of the non woven web as produced by the wire installation 3, the wire web for web feeding can be released from the wire 11 by compressed air from the compressed air installation 18. The end feeding strip 14 that is raised from the wire 11 has sufficient stability in order to be transferred to the transportation path installation 19 by compressed air. The transportation path installation 19 in FIG. 2 is illustrated as an air baffle. The transportation path installation 19 in FIG. 3 is configured as a vacuum conveyor belt. By virtue of the air flows that exist, both transportation path installations 19 of FIG. 2 and FIG. 3 form negative pressure preferably on the lower side of the transportation path installation 19. On account thereof, it is possible for the raised end feeding strip 14 that is guided by way of the compressed air of the compressed air installation 18 to be moved to the subsequent treatment unit 4. The end feeding strip 14 is picked up by the vacuum catching installation 21 on a wire belt 20 of the subsequent treatment unit 4.

[0036] The transfer of the end feeding strip 14 thus achieved represents a temporarily closed transfer. To this extent, it is essential that controlled raising, transferring, and subsequent controlled picking up is possible on account of the configuration according to the invention.

[0037] As is illustrated in FIG. 1a, the treatment unit 4 is a hydroentanglement unit, for example. The end feeding strip 14 can be further stabilized by way of such hydroentanglement. On the free transfer subsequent to this hydroentanglement, at the junction 9, the transfer of the end feeding strip can again be raised from the wire belt 20 of the treatment unit 4 by compressed air and, based on the same principle, by way of a transportation installation 19 that generates negative pressure can be transferred to a next wire belt 22 of a subsequent treatment unit 6. According to FIG. 1a, this further treatment unit 6 is a vacuum dewatering unit, for example.

[0038] The end feeding strip 14 after the wire belt 22 of such vacuum dewatering is most often sufficiently stable in order to be able to be introduced into a rope cutter. Raising can again be performed by way of the wire belt by compressed air. The end feeding strip 14 can be caught by an air baffle or a further wire belt and be transferred to a rope cutter. The transfer of the end feeding strip 14 as described by way of the temporarily closed transfer can be readily carried out at production speeds between 200 and 250 m/min and more.

[0039] Once the end feeding strip 14 has been guided through the dryer, for example the treatment unit 7, and a quality assurance unit 25 up to the winder 5, the non woven web 10 on the wire installation 3 can be run at the full product width. After the wire installation 3, the wet non woven herein is sufficiently stable in order to be guided also by way of the entire product width directly by way of a free transfer to the next treatment unit.

[0040] In the case of the production speeds just mentioned, any change in the raising of the non woven web can rapidly lead to web ruptures. Therefore, a variable vacuum suction box 26 that is displaceable along the wire belt 11 is preferably fitted below the wire belt 11 of the wire installation 3. Once the non woven web runs at full width on the production line, the position of the product web lift can be defined with this vacuum suction box 26 precisely by way of an adjustment of the vacuum suction box 26, on the one hand, and of the setting of the vacuum, on the other hand. The free transfer between the vacuum suction box 26 of the wire installation 3 and the vacuum catching installation 21 of the subsequent treatment unit 4 can thus be defined in a precise manner. Unequal raising of the product web is prevented. The product web tension between the two wire belts 11, 20 is preferably controlled by way of a slack regulator. The same explanations apply to the junction 9 between two treatment units 4, 6.

[0041] According to the invention, the non woven web can be transferred in a more cost-effective manner as compared to conventional solutions, and the controlled free transfer moreover offers a cost-effective solution for guiding a product web.

[0042] The aforementioned slack control can be complemented by a control device for controlling lifting, transferring, and picking up an end feeding strip 14 at the junctions 8, 9 having a web feeding 13.