Abstract
A nonwoven web made of plastic fibers and having a web thickness less than 2 mm (preferably less than 1.5 mm) and a grammage less than 30 g/m.sup.2 (preferably less than 25 g/m.sup.2) and conveyed this web in a travel direction so that it physically contacts a guide or treatment roller. A stabilization plate extending in and transversely to the travel direction of the nonwoven web is provided upstream or downstream of the roller in the travel direction, and the nonwoven web is guided in the travel direction past the stabilization plate such that a spacing between a face of the stabilization plate turned toward the nonwoven web and the nonwoven web face is 0 to 20 mm (preferably 0.1 to 10 mm, and very preferably 0.2 to 5 mm).
Claims
1. A method of guiding a nonwoven web made of continuous plastic fibers, the method comprising the steps of: providing a nonwoven web having a web thickness less than 2 mm and a grammage less than 30 g/m.sup.2; conveying the web in a travel direction; physically contacting the conveyed nonwoven web with a guide or treatment roller; providing a stabilization plate extending in and transversely to the travel direction of the nonwoven web upstream or downstream of the roller in the travel direction, the stabilization plate having a substantially planar face turned toward and spaced wholly from the web to form an empty clearance gap between the web and the plate such that a cushion of air is created between the stabilization plate and the web to keep the web flat, the plate being of a length measured in the travel direction of the nonwoven web that is greater than a radius of the roller; and guiding the nonwoven web in the travel direction past the stabilization plate such that a spacing between a face of the stabilization plate turned toward the nonwoven web and the nonwoven web face is at most 20 mm.
2. The method defined in claim 1, wherein the conveyed nonwoven web is a spunbond or melt-blown web.
3. The method defined in claim 1, further comprising the step of: providing an upstream conveyor section upstream of the roller; providing a second stabilization plate at and spaced from the upstream conveyor section; guiding the web upstream of the roller between the upstream conveyor section and the second stabilization plate.
4. The method defined in claim 1, further comprising the step of: providing a downstream conveyor section downstream of the roller; providing a second stabilization plate at and spaced from the downstream conveyor section; guiding the web between the downstream conveyor section and the second stabilization plate.
5. The method defined in claim 1, wherein the stabilization plate is below the web, the method further comprising the step of: maintaining a spacing between an upper face of the stabilization plate and a lower face of the nonwoven web.
6. The method defined in claim 1, wherein the stabilization plate is above the web, the method further comprising the step of: maintaining a spacing between a lower face of the stabilization plate and an upper face of the nonwoven web.
7. The method defined in claim 1, further comprising the step of: providing a deflection plate adjacent the web; and deflecting air entrained by the web away from the web.
8. The method defined in claim 1, wherein the nonwoven web is conveyed at a travel speed greater than 600 m/min.
9. The method defined in claim 1, wherein the nonwoven web is guided in a manner free of gas pressurization in the region of the stabilization plate.
10. The method defined in claim 1, wherein the roller is part of a roller assembly having two rollers forming a nip, the method further comprising the step of: passing the web in the direction through the nip.
11. An apparatus for guiding a nonwoven web made of continuous plastic fibers and having a web thickness less than 2 mm and a grammage less than 30 g/m.sup.2, the apparatus comprising a guide or treatment roller; means for conveying the web in a travel direction and physically contacting the conveyed nonwoven web with the roller; a stabilization plate extending in and transversely to the travel direction of the nonwoven web upstream or downstream of the roller in the travel direction, a face of the plate being planar, parallel to, and spaced transversely of the direction from the web by an empty clearance gap of at most 20 mm such that a cushion of air is created between the stabilization plate and the web to keep the web flat, the plate being spaced upstream or downstream from the roller in the travel direction by 0.2 mm to 500 mm, a length of the plate in the direction being greater than a radius of the roller.
12. The apparatus defined in claim 11, wherein the roller is part of a roller assembly having an upper and a lower roller and the means for conveying passes the web first over the upper roller and then under the lower roller.
13. The apparatus defined in claim 11, wherein the roller is part of a roller assembly having two rollers forming a nip and the means for conveying passes the web in the direction through the nip.
14. The apparatus defined in claim 11, wherein the stabilization plate is stationary.
15. The apparatus defined in claim 12, further comprising: a deflection plate adjacent the web and oriented to deflect air entrained by the web away from the web.
Description
BRIEF DESCRIPTION OF THE DRAWING
(1) The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:
(2) FIG. 1 is a schematic view of a nonwoven-web guide assembly according to the prior art;
(3) FIG. 2 is a schematic view of a first embodiment of a nonwoven-web guide assembly according to the invention;
(4) FIG. 3 is a schematic view of a second embodiment as in FIG. 2;
(5) FIG. 4 is a schematic view of a third embodiment as in FIG. 2;
(6) FIG. 5 is a schematic view of a fourth embodiment as in FIG. 2;
(7) FIG. 6 is a schematic view of a first embodiment of a nonwoven-web guide assembly according to the invention having treatment rollers;
(8) FIG. 7 is a schematic view of a second embodiment as in FIG. 6; and
(9) FIG. 8 is a schematic view of a third embodiment as in FIG. 6.
SPECIFIC DESCRIPTION OF THE INVENTION
(10) As seen in FIG. 1 a prior-art nonwoven-web guide assembly according to the invention carries out a method according to the invention of guiding a nonwoven web 1 made of plastic fibers conveyed in a travel direction F. The plastic fiberspreferably and in the embodimentare continuous plastic filaments advantageously composed of a thermoplastic. Such a web is typically made by depositing the filaments forming the web on an upper reach of a horizontally extending foraminous web through which air is drawn downward. The deposited filaments are compressed into the coherent web 1.
(11) In the embodiment according to the drawings, the nonwoven web 1 may be a spunbond nonwoven web. In particular, it is within the scope of the invention to use a nonwoven web laminate as the nonwoven web, where the laminate preferably comprises at least one spunbond nonwoven web and one melt-blown nonwoven web; particularly preferably is a laminate having a layering sequence of spunbond nonwoven web/melt-blown nonwoven web/spunbond nonwoven web (SMS). It is within the scope of the invention that the nonwoven web 1 has a web thickness d of less than 2 mm, and preferably a grammage less than 20 g/m.sup.2, particularly preferably less than 15 g/m.sup.2.
(12) The nonwoven web 1 comes into physical contact with guide rollers 2 and/or treatment rollers 3 (FIGS. 6-8). FIG. 1 shows a guide roller assembly 4 that comprises a plurality of the guide rollers 2, preferably two. FIGS. 6-8 show a treatment assembly 5 comprised of a plurality of the treatment rollers 3, preferably two.
(13) FIG. 1 shows a nonwoven-web guide assembly according to the prior art. Here, the nonwoven web 1 is guided only via the vertically spaced upper and lower guide rollers 2 of an S-shaped guide roller assembly 4. Air is then entrained on the nonwoven web upper faces 1 by of the nonwoven web 1. The air current resulting from the air entrained leads first to the nonwoven web 1 being lifted from the upper guide roller 2 as indicated in FIG. 1 and thus being guided in a functionally unreliable manner. In addition, the air entrained on the upper face of the nonwoven web 1 forms an air current downstream of the guide roller assembly 4 on a downstream section of the traveling nonwoven web 1 (right side of FIG. 1) and the nonwoven web 1 being then bunged out. These deformations may, due to the air currents, result in undesired nonhomogeneities in the nonwoven web 1 as well as necessitate a higher web tension for reliable guiding of the nonwoven web 1. Such higher web tension may result in an undesired reduction in the width of the nonwoven web 1.
(14) FIGS. 2 to 5 illustrate a nonwoven-web guide assembly analogous to FIG. 1, having means or components according to the invention. In FIG. 2, the nonwoven web 1 is again passed through an S-shaped guide roller assembly 4 formed by upper and lower guide rollers 2 spaced one immediately above the other. A planar stabilization plate 6 extending in and transversely to the travel direction F of the nonwoven web 1 is provided at a spacing upstream or immediately upstream of the guide roller assembly 4 in the travel direction F or spacedly upstream/immediately upstream of the upper guide roller 2. In the embodiment according to FIG. 2, the stabilization plate 6 is below the nonwoven web 1 with its horizontal and planar upper face at a spacing a below the nonwoven web. The spacing a may be between 0.1 and 3 mm in this embodiment. The stabilization plate 6, which is below the nonwoven web 1 in FIG. 2, makes it possible to control air entrained by the lower face of the nonwoven web 1 in a functionally reliable manner.
(15) In the embodiment in FIG. 2, a deflection plate 7 in the shape of a flat baffle is positioned downstream of the guide roller assembly 4 or downstream of the upper guide roller 2 of this guide roller assembly 4. This flat deflection plate 7 upwardly diverts air carried along on the upper face of the traveling nonwoven web 1, so that the air current is not present on the nonwoven web 1 further conveyed downstream of the guide roller assembly 4, as in the embodiment in FIG. 1. The flat deflection plate 7 is preferably and in this embodiment of arcuate shape, such that the air guided along with the nonwoven web 1 is deflected upward. Comparative observation of FIGS. 1 and 2 shows that with the measures according to the invention, the disturbing air influences or air currents that can be recognized in FIG. 1 can be effectively avoided.
(16) FIG. 3 shows another embodiment of the nonwoven-web guide assembly according to the invention. Here, as in the embodiment of FIG. 2, a stabilization plate 6 is set at a spacing a below the nonwoven web 1 immediately upstream of the guide roller assembly 4 in the travel direction F. Instead of the flat deflection plate 7 in the embodiment according to FIG. 2, another stabilization plate 6 is set at a spacing a above the nonwoven web 1 immediately downstream of the guide roller assembly 4. The adverse effects, depicted on the right side of FIG. 1, of the air current entrained by the nonwoven web 1 and deflected via the upper guide roller 2 are also avoided due to the fact that the nonwoven web 1 downstream of the guide roller assembly 4 is shielded from this disadvantageous air current by the stabilization plate 6 positioned above the nonwoven web 1.
(17) FIG. 4 shows an embodiment similar to FIG. 2. Here, however, the second stabilization plate 6 is set at a spacing a below the nonwoven web 1 immediately downstream of the guide roller assembly 4. The adverse effects of the above-described air current are still effectively avoided. The nonwoven web 1 can continue being guided over the second stabilization plate 6 in a more functionally reliable manner and without deformation as an air cushion trapped between the web 1 and the downstream or second stabilization plate 6 keeps the web 1 flat.
(18) In the embodiment according to FIG. 5, a stabilization plate 6 at a spacing a above the nonwoven web 1 is positioned immediately upstream of the guide roller assembly 4, as seen in the travel direction F of the nonwoven web 1. This stabilization plate 7 provided above causes the air guided along on the upper face of the nonwoven web 1 to be unable to adversely affect or apply pressure as shown on the right of FIG. 1 to the nonwoven web 1 continuing to be guided downstream of the guide roller assembly 4. In order to avoid the adverse effects of the air guided along on the lower face of the nonwoven web 1, a flat deflection plate 7 is provided under the nonwoven web 1 immediately upstream of the guide roller assembly 4 such that air entrained on the lower face of the nonwoven web 1 is diverted away from the nonwoven web 1 by this flat deflection plate 7 and not trapped under the web 1 to bulge it upward as in FIG. 1. For this purpose, this flat deflection plate 7 has a deflection tongue or upstream edge 8 set at a small spacing u from the lower nonwoven web face, and the flat deflection plate 7 is bent downward coming out from this deflection tongue 8 so that it is concave toward the web 1 and downstream. The deflection tongue 8 effectively downwardly deflects or diverts the air entrained on the lower face of the nonwoven web 1 via the bending of the flat deflection plate 7. This effectively prevents the nonwoven web 1 from floating, as it were, above the upper guide roller 1 as shown in FIG. 1.
(19) FIG. 6 shows another embodiment of the nonwoven-web guide assembly according to the invention. Here, the traveling nonwoven web 1 is guided through a narrow treatment gap or nip 9 between the upper treatment roller 3 and the lower treatment roller 3 of a treatment roller assembly 5. The treatment roller assembly 5 may be a calender roller assembly. Advantageously, at least one treatment roller 3 of this calender roller assembly or treatment roller assembly 5 is heated. The nonwoven web 1 is still guided over a deposition screen belt 10 on which it is formed upstream of this treatment roller assembly 5 in the travel direction. In order to prevent the adverse effects of air pulled along by the upper face of the nonwoven web 1, a stabilization plate 6 at a spacing a above the nonwoven web 1 is positioned immediately upstream of the treatment roller assembly 5.
(20) In the embodiment according to FIG. 7, as well, a treatment roller assembly 5 is shown like that of FIG. 6. The nonwoven web 1 guided through the treatment gap 9 of the treatment roller assembly 5, is passed between upper and lower stabilization plates 6 immediately upstream of the treatment roller assembly 5. The stabilization plates 6 are each positioned at the spacing a above or below the nonwoven web 1. Adverse effects of the air entrained both on the upper face and on the lower face of the nonwoven web 1 can be effective prevented with this arrangement.
(21) In the embodiment according to FIG. 8, the nonwoven web 1 is also guided through a treatment roller assembly 5 composed of two treatment rollers 3. The nonwoven web 1 that passes through the treatment gap 9 is guided past a stabilization plate 6 immediately upstream of the treatment roller assembly 5. The stabilization plate 6 is provided at the spacing a below the nonwoven web 1. Moreover, a flat deflection plate 7 above the nonwoven web 1 is provided immediately upstream of the treatment roller assembly 5 and above the stabilization plate such that this flat deflection plate 7 catches air entrained on the upper face of the nonwoven web 1 and deflects it away from the nonwoven web 1. For this purpose, the flat deflection plate 7 has a deflection tongue 8 set at a small spacing u from the upper nonwoven web face. The flat deflection plate 7 is bent upward starting from this deflection tongue 8. The deflection tongue 8 upwardly deflects air entrained on the upper face of the nonwoven web 1 via the arcuate shape of the flat deflection plate 7
