Clothing for a machine for producing a fibrous material web

Abstract

Clothing is provided for a machine for producing a fibrous web, in particular a paper, board or tissue web. The clothing has a substrate. The substrate has a top side, an underside, two side edges and a useful region between the two side edges. The useful region has a plurality of through-channels, which connect the top side to the underside of the substrate. An inner surface of at least one through-channel, preferably of the majority of all the through-channels, more preferably of all the through-channels in the useful region of the substrate, has a mean roughness depth that is greater than 4 μm, preferably greater than 6 μm, more preferably greater than 8 μm. The clothing of this type is produced using a laser.

Claims

1. A clothing for a machine for producing a fibrous material web, the clothing comprising: a substrate having an upper side, a lower side, two lateral peripheries, and a region between said two lateral peripheries, said region having a plurality of passage ducts formed therein connecting said upper side to said lower side of said substrate, wherein an internal surface of at least one of said passage ducts in said region of said substrate has a mean roughness depth of more than 4 μm and less than 20 μm.

2. The clothing according to claim 1, wherein: said substrate is a laser-drilled substrate; and said passage ducts are incorporated into said substrate by means of a laser.

3. The clothing according to claim 1, wherein a ratio between a minimum diameter of said passage ducts and a thickness of said substrate is between 1:3 and 1:10.

4. The clothing according to claim 1, wherein said substrate has a matrix material with filler particles, wherein a material of said filler particles when irradiated with laser light is able to be brought to a gas phase more slowly or rapidly than said matrix material.

5. The clothing according to claim 4, wherein said filler particles have a mean diameter between 20 μm and 150 μm.

6. The clothing according to claim 1, wherein said substrate is formed from a plurality of layers.

7. The clothing according to claim 6, wherein a basic shape of said passage ducts at a border between two neighboring said layers of said substrate has an offset in a direction which lies in a plane of said substrate.

8. The clothing according to claim 6, wherein the mean roughness depth of said internal surface of at least one of said passage ducts in said region of said substrate within a region of at least one of said layers is less than 4 μm.

9. The clothing according to claim 1, wherein: the fibrous material web is a paper web, a cardboard web, or a tissue web; and said internal surface of all said passage ducts in said region of said substrate has the mean roughness depth being more than 8 μm.

10. The clothing according to claim 1, wherein the mean roughness depth is less than 15 μm.

11. The clothing according to claim 1, wherein a ratio between a minimum diameter of said passage ducts and a thickness of said substrate is between 1:5 and 1:7.

12. The clothing according to claim 4, wherein: said filler particles have a mean diameter between 50 μm and 100 μm; and said filler particles are configured to be substantially spherical.

13. A method for producing a clothing, which comprises the steps of: providing a substrate having an upper side, a lower side, two lateral peripheries, and a region between the two lateral peripheries, the region having a plurality of passage ducts formed therein connecting the upper side to the lower side of the substrate, wherein an internal surface of at least one of the passage ducts in the region of the substrate has a mean roughness depth of more than 4 μm and less than 20 μm; and incorporating at least one of the passage ducts in the region of the substrate into the substrate by means of a laser.

14. The method according to claim 13, wherein prior to the step of incorporating the passage ducts, forming the substrate by adding filler particles to a matrix material which forms a main component part of the substrate, a material of the filler particles when irradiated with laser light is able to be moved to a gas phase more slowly or rapidly than the matrix material.

15. The method according to claim 14, which further comprises forming the substrate with a plurality of layers, wherein a concentration of the filler particles differs between at least two of the layers.

16. The method according to claim 13, which further comprises: forming the substrate from a plurality of layers, wherein the layers are connected to one another by means of an auxiliary agent; and subsequently rolling up the substrate again for the passage ducts to be incorporated.

17. The method according to claim 16, wherein the substrate in a region in which the passage ducts are being incorporated into the substrate by means of the laser is applied to a substantially planar face.

18. The method according to claim 13, wherein at least one of the passage ducts is incorporated into the substrate by means of a single pulse of the laser.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIGS. 1 and 2 show a device known from the prior art for perforating a substrate by means of a laser;

(2) FIGS. 3a-3c shows various bore hole geometries known from the prior art;

(3) FIGS. 4a and 4b show a first embodiment of a passage duct in a clothing according to the invention; and

(4) FIGS. 5a and 5b show a second embodiment of a passage duct in a clothing according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIGS. 1 and 2 schematically show a device 10′ known from the prior art, or a method for drilling passage ducts 30′ into a substrate 20′ by means of a laser, respectively. The laser herein is actuated by a computer or a controller. Said laser emits a laser beam LB perpendicularly onto the upper side 22′ of the substrate 20′. As can be seen in particular in FIGS. 3a-3c, passage ducts 30′ of dissimilar design can be generated by melting and/or sublimating the material of the substrate 20′ with the laser, said passage ducts 30′ in the thickness direction TD of the substrate 20′ extending from the upper side 22′ to the lower side 24′. The substrate 20′ is composed of a plastics material film which per se, that is to say prior to the perforation by the laser, is initially impermeable to liquid. The passage duct 30′ in FIG. 3a has the shape of a straight circular cylinder. In contrast, the passage duct 30′ in FIG. 3b has the shape of a frustum which tapers from the upper side 22′ to the lower side 24′ of the substrate 20′. The passage duct 30′ in FIG. 3c has an hourglass-shaped design, thus a design in which the diameter of the passage duct 30′, proceeding from the upper side 22′, initially tapers toward a central region MR of the substrate 20′ that is disposed between the upper side 22′ and the lower side 24′, and thereafter, proceeding from the central region MR, widens again toward the lower side 24′ of the substrate.

(6) FIG. 2 shows how a continuous substrate 20′ that is tensioned across two rollers R is perforated with a multiplicity of passage ducts 30′ by means of the laser, said passage ducts 30′ being disposed in a substantially checkered manner. The laser herein moves continuously from a lateral periphery 26′ to the lateral periphery 28′ of the substrate 20′ that in the width direction WD is opposite, and back or vice versa, respectively, so as to drill the passage ducts 30′. The passage ducts 30′ herein can be uniformly distributed across the entire width, or else the perforated useful region of the substrate 20′ is narrower, depending on the desired specific application. The substrate 20′ can already represent the completed clothing, for example the completed forming wire of a paper machine, or else may be even further processed. For example, said substrate 20′ can still be provided with at least one layer of staple fibers so as to be used as a press felt in a paper machine. Or else webs of the substrate 20′ can be spiraled in order to be able to achieve larger widths of the clothing.

(7) The respective internal surface 32′ of the passage duct 30′ in the case of this production mode and without any particular preparatory arrangements being made is at all times substantially smooth, that is to say has a mean roughness depth R.sub.z of significantly less than 4 μm. In particular when the passage ducts are disposed so close next to one another that said passage ducts contact or even overlap one another on the upper side 22′ of the substrate 20′, a smooth wall can have a negative effect because excessively rapid dewatering of the fibrous material web which is transported on the clothing takes place on account thereof. The reduction of the dewatering rate is achieved according to the invention in that the roughness of the internal surface 32 of the passage duct 30 is enlarged in a highly targeted manner.

(8) FIGS. 4a and 4b show a fragment of the substrate 20 having a single passage duct 30 according to a first exemplary embodiment of the present invention, said fragment being bordered by a dashed line. FIG. 4a herein shows a plan view onto the upper side 22 of the substrate 20, whereas FIG. 4b shows a sectional view along the sectional plane IVb-IVb from FIG. 4a. The substrate 20 in this exemplary embodiment is a laminate formed from four layers, wherein all the individual layers can have a substantially identical thickness, that is to say the same dimension in the thickness direction TD. The individual layers herein can be connected to one another with an adhesive. The substrate is composed substantially of a polymer basic material. However, as a particularity, in this embodiment filler particles 40, 42 are however added to the two central layers of the substrate 20, wherein the one of the two central layers can comprise exclusively filler particles 40 of a first type, and the other of the two central layers can comprise exclusively filler particles 42 of a second type which is dissimilar to the first type. In theory, both layers could however also comprise the same type of filler particles 40, 42 or both types of filler particles 40, 42. It is to be pointed out that these filler particles in the figures are illustrated only in a schematic and not true-to-scale manner.

(9) The filler particles 40 of the first type in comparison to the matrix material of the substrate 20 have the property that said filler particles 40, when irradiated with laser light, move less rapidly, or not at all, to the melt phase and/or vapor phase. Therefore, these filler particles 40 remain as protrusions 44 on the internal surface 32 of the laser-drilled passage duct 30 and thus ensure turbulences in the flow of the fluid which in the intended use of the clothing according to the invention flows through the passage ducts 30.

(10) The filler particles 42 of the second type in comparison to the matrix material of the substrate 20 have the property that said filler particles 42, when irradiated with laser light, move significantly faster or easily, respectively, to the melt phase and/or vapor phase. Therefore, these filler particles 40 when vanishing leave behind recesses 46 on the internal surface 32 of the laser-drilled passage duct 30 and in this way likewise ensure turbulences in the flow of the fluid which in the intended use of the clothing according to the invention flows through the passage ducts 30.

(11) The roughness of the internal surface 32 of the passage duct 30 and thus the throttling effect on the flow can be set by way of the density of the concentration of the filler particles 40, 42 in the matrix material of the substrate. The mean roughness depth R.sub.z of the internal surface 32 of the passage duct 30 herein is enlarged according to the invention to more than 4 μm, preferably more than 6 μm, furthermore preferably more than 8 μm. The two outermost layers of the substrate 20 in this exemplary embodiment are free of filler particles 40, 42. This is indeed advantageous for preventing the filler particles from developing an undesirable effect when said filler particles in the intended use of the clothing according to the invention come into direct contact with the fibrous material web to be dewatered or with parts of the machine, but this is not mandatory. Conversely, at least one of the two outermost layers can however also contain fillers in a targeted manner, specifically in particular when the fillers serve as release agents.

(12) It is to be noted that the filler particles 40, 42 shown here have a substantially spherical basic shape. This is however likewise not mandatory.

(13) A portion of a substrate 20 having a passage duct 30 according to a second embodiment is shown in FIGS. 5a and 5b. FIG. 5a herein again shows a plan view onto the upper side 22 of the substrate 20, and FIG. 5b shows a sectional view through the passage duct 30 along the section plane V-V in FIG. 5a. The particular features of this second embodiment can be used alternatively to or in combination with the particular features of the first embodiment.

(14) The substrate 20 also in this example is formed as a multi-layer laminate, wherein four layers are present here, the extent of said layers in the thickness direction TD being substantially identical. The particularity of this embodiment is that the basic shape of the passage duct 30 that here corresponds substantially to a frustum which tapers from the upper side 22 to the lower side 24 of the substrate 20 has an offset at the respective borders between two directly neighboring layers of the substrate. This offset leads to protrusions 44 and recesses 46 in the passage duct 30 for the liquid which in the intended use of the clothing according to the invention flows through the passage duct. On account thereof, turbulences which reduce the flow rate in the passage duct 30 are incorporated into the liquid. The protrusions 44 and the recesses 46 ensure that the mean roughness depth R.sub.z of the internal surface 32 of the passage duct becomes more than 4 μm, preferably more than 6 μm, furthermore preferably more than 8 μm. In contrast, the mean roughness depth R.sub.z is again significantly less in the region between two neighboring layer borders. To the extent that the mean roughness depth R.sub.z is to be enlarged also in these regions, the afore-described features of the first exemplary embodiment can be resorted to, for example. However, attention has to be paid to the flow rate in the passage duct 30 not being excessively throttled so that appropriate dewatering of the fibrous material web which in the intended use of the clothing according to the invention is transported on the substrate can take place.

(15) As the inventors have found, the protrusions 44 and the recesses 46 in this embodiment can be reliably and reproducibly generated in that the individual layers of the laminate are connected to one another, or laminated, respectively, by way of an adhesive, preferably a solvent-based polymer resin, the laminate is subsequently rolled up, unrolled again in order to be laser-drilled, and is tensioned on a flat plane substantially in the region of the bore. This effect can be explained by internal stresses in the material which are released again within a short time on account of the effect of heat and force. This effect can be utilized in a targeted manner in order for the roughness in the passage duct 30 to be increased and to thus reduce the flow rate through the passage duct 30.

(16) The present invention has a particularly advantageous effect when the clothing is a forming wire and when the individual passage ducts 30 are placed so tightly beside one another that said passage ducts 30 at least contact, preferably overlap, one another on the upper side 22 or the paper side, respectively, as has been described at the outset.

(17) In the two exemplary embodiments of the present invention shown here the basic shape of the passage duct 30 is always substantially frustoconical. This is however not mandatory. In practice, the passage ducts 30 can also have a basic shape which deviates therefrom to a greater or lesser extent.

LIST OF REFERENCE SIGNS

(18) 10′ Device 20′, 20 Substrate 22′, 22 Upper side 24′, 24 Lower side 26′ Lateral periphery 28′ Lateral periphery 30′, 30 Passage duct 32′, 32 Internal surface 40 Filler particles of a first type 42 Filler particles of a second type 44 Protrusion 46 Recess LB Laser beam MR Central region R Roller TD Thickness direction