Abstract
A substrate of a paper machine clothing has a usable region formed with through-channels that are non-cylindrical with a cross-sectional area becoming smaller from an upper side to a middle region of the substrate. An upper rim of at least one of the through-channels directly contacts an upper rim of at least one neighboring through-channel and the upper rims have common local maximum. A sectional plane parallel to the thickness direction of the substrate defines an intersecting line with a sidewall of a neighboring through-channel. The intersecting line has a convexly shaped first portion, a concavely shaped second portion, and a third portion that is again convexly shaped going from the at least one common local maximum toward the middle region of the substrate. There is also described a method of producing such a paper machine clothing.
Claims
1. A paper machine clothing, comprising: a substrate having an upper side, a lower side, two lateral edges, and a usable region between said two lateral edges, the usable region having formed therein a plurality of through-channels each extending along a central axis through said substrate and connecting said upper side with said lower side; said through-channels being non-cylindrical with a cross-sectional area becoming smaller along a thickness direction of said substrate from said upper side to a middle region of said substrate between said upper side and said lower side; an upper rim of at least one of said through-channels directly contacting an upper rim of at least one neighboring through-channel of said plurality of through-channels; said upper rims of both said neighboring through-channels having at least one common local maximum; wherein a sectional plane parallel to the thickness direction of said substrate, including said at least one common local maximum and including or intersecting the central axis of at least one of said neighboring through-channels defines an intersecting line with a sidewall of said at least one of said neighboring through-channels; and wherein said intersecting line includes a convexly shaped first portion, a concavely shaped second portion, and a convexly shaped third portion in the thickness direction of the substrate from the at least one common local maximum toward the middle region of said substrate.
2. The paper machine clothing according to claim 1, wherein any intersecting line that is defined by intersecting said substrate with a sectional plane that is parallel to the thickness direction of said substrate and includes the at least one common local maximum includes the first portion that is convexly shaped, the second portion that is concavely shaped and the third portion that is again convexly shaped along the thickness direction of the substrate from the at least one common local maximum toward the middle region of said substrate.
3. The paper machine clothing according to claim 1, wherein a first inflection point between said first portion and said second portion of the intersecting line is located closer to the at least one local maximum than to the middle region of the substrate.
4. The paper machine clothing according to claim 3, wherein the first inflection point between said first portion and said second portion of the intersecting line, and a second inflection point between said second portion and said third portion of the intersecting line are located in an upper fourth of the substrate.
5. The paper machine clothing according to claim 1, wherein: at least 90% of said through-channels in the usable region of said substrate have an upper rim that directly contacts an upper rim of at least one other neighboring through-channel of the plurality of through-channels in the usable region of said substrate; said upper rims of a majority of the directly neighboring through channels have at least one common local maximum; a sectional plane being parallel to the thickness direction of said substrate, including the at least one common local maximum and including or intersecting the central axis of at least one of the corresponding neighboring through-channels defines an intersecting line with a sidewall of the one of the corresponding neighboring through-channels; the intersecting line has a first portion that is convexly shaped, a second portion that is concavely shaped, and a third portion that is convexly shaped along the thickness direction of said substrate from the at least one common local maximum toward the middle region of said substrate.
6. The paper machine clothing according to claim 4, wherein all of said through-channels in the usable region of said substrate have the upper rim that directly contacts an upper rim of all other neighboring through-channels, and said upper rims of all of the directly neighboring through channels have at least one common local maximum.
7. The paper machine clothing according to claim 1, wherein less than 5% of a surface on the upper side of said substrate in its usable region is flat and substantially orthogonal to the thickness direction of said substrate.
8. The paper machine clothing according to claim 7, wherein 0% of the surface on the upper side of said substrate in its usable region is flat and substantially orthogonal to the thickness direction of said substrate.
9. The paper machine clothing according to claim 1, wherein between 70% and 90% of a surface on the lower side of said substrate is flat and substantially orthogonal to the thickness direction of said substrate.
10. The paper machine clothing according to claim 9, wherein about 80% of the surface on the lower side of said substrate is flat and substantially orthogonal to the thickness direction of said substrate.
11. The paper machine clothing according to claim 1, wherein a shape of a cross-sectional area of at least one of said through-channels of the plurality of through-channels changes along the thickness direction of said substrate from said upper side to said lower side.
12. The paper machine clothing according to claim 11, wherein the shape of the cross-sectional area is substantially more elliptical in an upper region of said through-channel than in a lower region of said through-channel.
13. The paper machine clothing according to claim 11, wherein the shape of the cross-sectional area in the upper region of said through-channel has a first dimension extending in cross-machine direction and a second dimension extending in machine direction, and the first dimension is smaller than the second dimension.
14. The paper machine clothing according to claim 11, wherein the shape of the cross-sectional area in the upper region of said through-channel has a first dimension extending in cross-machine direction and a second dimension extending in machine direction, and wherein the first dimension is larger than the second dimension.
15. The paper machine clothing according to claim 1, wherein on the lower side of said substrate a shape of a cross-sectional area of said through holes is substantially circular.
16. The paper machine clothing according to claim 1, wherein at least 90% of all through-channels in the usable region of said substrate are arranged in a non-checkered pattern.
17. A method of producing a paper machine clothing, the method comprising: providing a substrate having a first surface and a second surface, wherein the first surface and the second surface are substantially planar and parallel to each other; and using a laser for forming a plurality of non-cylindrical through holes into a usable region of the substrate, and thereby: forming at least some of the plurality of through holes that are neighboring each other to partially overlap one another; controlling the laser during a formation of the plurality of non-cylindrical through holes such that the upper rims of the overlapping through-holes have at least one common local maximum; wherein a sectional plane being parallel to the thickness direction of the substrate, including the at least one common local maximum and including or intersecting a central axis of at least one of the overlapping through-holes, defines an intersecting line with a sidewall of the at least one of the overlapping through-holes; and wherein the intersecting line has a first portion that is convexly shaped, a second portion that is concavely shaped, and a third portion that is convexly shaped along the thickness direction of the substrate from the at least one common local maximum toward a middle region of the substrate.
18. The method according to claim 17, which comprises producing the paper machine clothing according to claim 1.
19. The method according to claim 17, wherein, once all the through holes have been formed into the usable region of the substrate, at least one of the first surface and the second surface in the usable region has disappeared by at least 90%.
20. The method according to claim 17, which comprises blowing cooled air onto the substrate during the step of forming the through holes into the substrate.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
(1) FIG. 1 is an illustration of the processes of perforating a substrate via laser drilling according to U.S. Pat. No. 5,837,102;
(2) FIG. 2 is a plan view of a substrate 20′ that is placed under tension between two rollers R;
(3) FIGS. 3A, 3B, 3C are cross-sectional views illustrating a radially outer, first surface and an opposite, radially inner, second surface;
(4) FIG. 4 shows a section of a substrate comprising a single through hole of a first type;
(5) FIG. 4A shows an enlarged view of the through hole in FIG. 4;
(6) FIG. 5 shows a section of a substrate comprising a single through hole of a second type;
(7) FIG. 5A shows an enlarged view of the through hole in FIG. 5;
(8) FIG. 6 shows a sectional view along the lines A-A and B-B in FIG. 4 and along the line C-C in FIG. 5;
(9) FIG. 7 shows a sectional view along the line D-D in FIG. 5;
(10) FIG. 8 shows a section of a substrate comprising a plurality of through holes of the first type;
(11) FIG. 9 shows a section of a substrate comprising a plurality through holes of the second type;
(12) FIG. 10 shows a sectional view along the lines E-E and F-F in FIG. 8 and along the line G-G in FIG. 9;
(13) FIG. 11 shows a sectional view along the line H-H in FIG. 9;
(14) FIG. 12 shows a sectional view similar to the sectional view of FIG. 10, but with a third type of through holes;
(15) FIG. 13 shows a section of a substrate similar to the one shown in FIG. 8, but with the through holes arranged in a non-checkered pattern;
(16) FIG. 14 shows a section of a substrate similar to the one shown in FIG. 9, but with the through holes arranged in a non-checkered pattern;
(17) FIG. 15 shows a section of a substrate comprising a plurality of through holes of a fourth type;
(18) FIG. 16 also shows a section of a substrate comprising a plurality of through holes of the fourth type;
(19) FIG. 17 shows a sectional view along the lines J-J and K-K in FIG. 15;
(20) FIG. 17A shows an enlarged view of a “pin-like-structure” in FIG. 17;
(21) FIG. 18 shows a sectional view along the lines L-L and M-M in FIG. 16; and
(22) FIG. 18A shows an enlarged view of a “pin-like-structure” in FIG. 18.
DETAILED DESCRIPTION OF THE INVENTION
(23) FIG. 4 shows a section of a substrate 20 which section is indicated by a dashed square. The substrate 20 comprises a first surface 22 and an opposite second surface 24 (see FIG. 6), wherein the first surface 22 and the second surface 24 are substantially planar and parallel to each other.
(24) A single through hole 31 of a first type is provided in the center of the section of the substrate 20. FIG. 6 shows a cross-sectional view which is taken through the through hole 31 along line A-A or line B-B of FIG. 4. As can be seen from FIGS. 4 and 6, the through hole 31 extends through the substrate 20 in its thickness direction TD along a central axis CA of the through hole 31, the central axis CA being indicated by a dashed line in FIG. 6. Thus, the through hole 31 connects the first surface 22 with the second surface 24 of the substrate 20. The through hole 31 is substantially funnel shaped with a cross-sectional area becoming continuously smaller when going in the thickness direction TD from the first surface 22 to the second surface 24. The cross-sectional area of a through hole 31 is obtained by cutting the through hole 31 with a plane that is oriented perpendicular to the thickness direction TD of the substrate 20. In this embodiment the shape of the cross-sectional area of the through hole 31 is always circular, no matter at which height level of the substrate the cross-sectional area is taken.
(25) The through hole 31 has a circular upper rim 34 where a sidewall of the through hole 31 ends and the flat first surface 22 begins. The circular upper rim 34 has a diameter A, as shown in FIG. 4A. Furthermore, the through hole 31 has a circular lower rim 36 where the sidewall of the through hole 31 ends and the flat second surface 24 begins. The circular lower rim 36 has a diameter a, as also shown in FIG. 4A. Diameter A of the upper rim is larger than diameter a of the lower rim.
(26) FIG. 5 shows another section of a substrate 20 which section is also indicated by a dashed square. The substrate 20 comprises a first surface 22 and a second surface 24 (see FIG. 7), wherein the first surface 22 and the second surface 24 are substantially planar and parallel to each other.
(27) A single through hole 32 of a second type is provided in the center of the section of the substrate 20. FIG. 6 shows a cross-sectional view which is taken through the through hole 32 along line C-C of FIG. 5 and FIG. 7 shows a cross-sectional view which is taken through the through hole 32 along line D-D of FIG. 5. As can be seen from FIGS. 5, 6 and 7, the through hole 32 extends through the substrate 20 in its thickness direction TD along a central axis CA of the through hole 32, the central axis CA being indicated by a dashed line in FIGS. 6 and 7. Thus, the through hole 32 connects the first surface 22 with the second surface 24 of the substrate 20. The through hole 32 is substantially funnel shaped with a cross-sectional area becoming continuously smaller when going in a thickness direction TD from the first surface 22 to the second surface 24. The cross-sectional area of the through hole 32 is obtained by cutting the through hole 32 with a plane that is oriented perpendicular to the thickness direction TD of the substrate 20. In this embodiment the shape of the cross-sectional area of the through hole 32 is not constant but changes when going along the thickness direction TD of the through hole 32. In an upper region of the substrate 20, i.e. in a region close to the first surface 22, the through hole 32 is more oval or elliptical, whereas in a lower region of the substrate 20, i.e. in a region close to the second surface 24, the through hole 32 is more or completely circular. The shape of the cross-sectional area of the through hole 32 preferably changes continuously along the thickness direction TD of the substrate 20.
(28) Thus, the through hole 32 has an elliptical upper rim 35 where a sidewall of the through hole 32 ends and the flat first surface 22 begins. The elliptical upper rim 35 has a first diameter A and a second diameter B measured orthogonally thereto, as indicated in FIG. 5A. Furthermore, the through hole 32 has a circular lower rim 36 where the sidewall of the through hole 32 ends and the flat second surface 24 begins. The circular lower rim 36 has a diameter a, as also shown in FIG. 5A. The second diameter B of the upper rim 35 is larger than the first diameter A of the upper rim 35. The first diameter A of the upper rim 35 is larger than the diameter a of the lower rim 36. Preferably, the second diameter B of the upper rim 35 is at least 5%, more preferably at least 10%, even more preferably at least 15% larger than the first diameter A of the upper rim 35.
(29) Several of such non-cylindrical through holes are arranged in such a close relationship that they partially overlap each other in the substrate. Examples of such arrangements for the through holes 31 of the first type and the through holes 32 of the second type are shown in FIGS. 8 and 9, respectively. To be more precise, nine corresponding through holes 31, 32 arranged in a checkered pattern are shown in these figures. The through holes 31, 32 each have a respective lower rim 36. Furthermore, for the sake of clarity, also the corresponding upper rims 34, 35 of the through holes 31, 32 are shown, even though these upper rims 34, 35 do not exist anymore as such in the final product. Instead, in the final product, i.e. in the finally perforated substrate 20, through-channels 30 are formed having a respective upper rim 38 that is at least partially delimited by the upper rim 38 of a neighboring through-channel 30. As shown in FIGS. 8 and 9, the originally existing flat or planar first surface 22 of the substrate 20 has completely disappeared after the perforation of the substrate 20 in the usable region UR thereof. The reason for the complete disappearance of the originally flat first surface 22 of the substrate 20 is that the through holes 31, 32 have been laser-drilled and that the material of the substrate 20 that has been evaporated by the energy of the laser at least partially condenses again on the first surface 22, thus forming a “pin-like-structure” 40 that will be explained in more detail below. As a consequence, the upper rim 38 of a corresponding through-channel 30 does not extend within a plane but is rather a closed line that extends three-dimensionally. It should be noted that the upper rim 38 of the through-channel 30 may extend partially below the originally flat first surface 22 of the substrate 20 and/or extend partially above the originally flat first surface 22 of the substrate 20.
(30) FIGS. 10 and 11 represent views similar to the ones shown in FIGS. 6 and 7, respectively, but now with several neighboring through holes 31, 32 that form the through-channels 30 in the substrate 20 of the final product. In FIG. 10 a location (see reference sign 38) of the upper rim 38 of the through-channel 30 of FIG. 8 is shown that represents an absolute minimum of the upper rim 38. In other words, the upper rim 38 has the largest distance to the originally flat first surface 22 of the substrate 20 which surface 22 is indicated by a dotted line in FIG. 10. The surface of the substrate 20 has a saddle point at this location of the upper rim 38.
(31) In FIG. 11 a location (see reference sign 38) of the upper rim 38 of the through-channel 30 of FIG. 9 is shown (according to the section along line H-H of FIG. 9) that represents an absolute minimum of the upper rim 38 of this through-channel 30. In other words, the upper rim 38 has the largest distance to the originally flat first surface 22 of the substrate 20 which surface 22 is also indicated by a dotted line in FIG. 11. The surface of the substrate 20 has a saddle point at this location of the upper rim 38. A section along line G-G of FIG. 9 is represented by the drawing of FIG. 10. At the location of the upper rim 38 shown in this figure, the upper rim only has a local minimum. Thus, the ridges that separate two neighboring through-channels 30 from each other are higher when following the line G-G compared to the ridges when following the line H-H of FIG. 9. Consequently, the substrate has anisotropic properties.
(32) These anisotropic properties can be used in a beneficial way. For example, the substrate that is perforated in a way as shown in FIGS. 9, 10 and 11 is more stress resistant in the direction parallel to line H-H compared to the direction parallel to line G-G. If line H-H substantially represents the machine direction of the final paper machine clothing the relatively high forces in the machine direction can be absorbed by the substrate 20 while at the same time the substrate 20 provides a relatively large open area on its upper side. Alternatively, if line H-H substantially represents the cross machine direction of the final paper machine clothing the nascent paper web in a forming section can adhere better to the substrate 20 since ridges formed in the substrate 20 between neighboring rows of through channels 30 that extend in cross machine direction are higher than those extending in the machine direction. Consequently, the properties of the substrate 20 can be adjusted to the intended use or the requirements of the paper machine clothing.
(33) FIG. 12 shows a sectional view similar to the cross-sectional view of FIG. 10, but of a third type of through holes. This third type of through holes differs from the first and second type of through holes 31, 32 in that the cross-sectional area of the through hole of the third type and, thus, the cross-sectional area of the corresponding through-channel 30 that is created thereof, continuously increase again when going in the thickness direction TD of the substrate 20 from the middle region MR of the substrate 20 between the upper side and the lower side to the lower side of the substrate 20. In an extreme case, neighboring through holes may not only partially overlap each other on the first side 22 of the substrate 20 but also on the second side 24 thereof.
(34) FIGS. 13 and 14 show a section of a substrate 20 similar to the one shown in FIGS. 8 and 9, respectively, with the difference that the through holes 31, 32 are arranged in a non-checkered pattern. In FIGS. 8 and 9 each through hole 31, 32 has eight neighboring other through holes 31, 32 wherein the distance to four of these eight neighboring through holes 31, 32 is larger than the distance to the remaining four neighboring through holes 31, 32.
(35) In contrast, in the examples shown in FIGS. 13 and 14, each through hole 31, 32 has six neighboring other through holes 31, 32 wherein the distance to all these neighboring through holes 31, 32 is substantially the same (for example corresponding to the smaller distance of the embodiments shown in FIGS. 8 and 9). These six neighboring through holes 31, 32 are arranged in a honeycomb pattern around a corresponding through hole 31, 32 in the middle thereof. With such an arrangement, the density of through-channels 31 in the final substrate 20 can be increased, as well as the open area on the upper side of the substrate 20.
(36) Each of FIGS. 15 and 16 shows a section of a substrate comprising a plurality of through holes of a fourth type. FIGS. 15 and 16 are substantially identical to FIG. 8 which shows a section of a substrate comprising a plurality of through holes of a first type. However, the holes of the fourth type are longer (or the substrate has a larger thickness) compared to the holes of the first type as can be seen by comparing FIGS. 17 and 18 with FIG. 10. It should be noted that this difference is not decisive for the effect of the present invention, especially when taking into account that the figures only represent only schematic drawings anyway. Therefore, the following description of FIGS. 16-18A may equally refer to the embodiment shown in FIG. 8. FIG. 17 represents a sectional view along lines J-J and K-K of FIG. 15 and FIG. 18 represents a sectional view along lines L-L and M-M of FIG. 16. In FIGS. 17 and 18 a detail referring to the “pin-like-structure” 40 is emphasized with a dashed circle and this detail is shown in enlarged views in FIGS. 17A and 18A, respectively.
(37) Lines J-J and K-K in FIG. 15 each describes a sectional plane that is parallel to the thickness direction TD of the substrate 20, that comprises the central axis CA of at least one of two neighboring through-channels 30 the upper rims of which have at least one local maximum 42 in common, and that comprises the at least one local maximum 42. The local maximum 42 is illustrated in detail in FIGS. 17A and 18A, and might be compared to an apex or a mount peak from which the surface of the upper side of the substrate 20 declines in all directions.
(38) According to the present invention, the outline of the substrate 20 in the sectional view of FIGS. 17 and 17A comprises a first portion 44 that is convexly shaped, a second portion 46 that is concavely shaped and a third portion 48 that is again convexly shaped when going in the thickness direction TD of the substrate 20 from the at least one common local maximum 42 toward the middle region MR of the substrate 20. In this exemplary embodiment, the first portion 44 is directly connected to the second portion 46 at a first inflection point 50 and the second portion 46 is directly connected to the third portion 48 at a second inflection point 52. In in the sectional view of FIGS. 17 and 17A the “pin-like-structure” 40 has a substantially symmetrical outline. Therefore, the outline does not only comprise a first, second and third portion 44, 46, 48 as described above on the left hand side in FIG. 17A but also on the right hand side in this figure. It should be noted, however, that the outline of the “pin-like-structure” 40 as shown in FIGS. 17 and 17A does not have to be symmetrical. For example it is possible that the outline is somehow deformed to one side.
(39) Lines L-L and M-M in FIG. 16 each describes a sectional plane that is parallel to the thickness direction TD of the substrate 20, and that comprises the at least one local maximum 42. However, this sectional plane—in contrast to the one shown in FIGS. 17 and 17A— does neither comprise nor intersect the central axis CA of any of the shown through-channels 30. As shown in FIGS. 18 and 18A also the outline of the substrate 20 in this sectional plane comprises a first portion 44* that is convexly shaped, a second portion 46* that is concavely shaped and a third portion 48* that is again convexly shaped when going in the thickness direction TD of the substrate 20 from the at least one common local maximum 42 toward the middle region MR of the substrate 20. In this exemplary embodiment, the first portion 44* is directly connected to the second portion 46* at a first inflection point 50* and the second portion 46* is directly connected to the third portion 48* at a second inflection point 52*. In in the sectional view of FIGS. 18 and 18A the “pin-like-structure” 40 has also a substantially symmetrical outline. Therefore, the outline does not only comprise a first, second and third portion 44*, 46*, 48* as described above on the left hand side in FIG. 18A but also on the right hand side in this figure. It should be noted, however, that the outline of the “pin-like-structure” 40 as shown in FIGS. 18 and 18A does not have to be symmetrical. For example it is possible that the outline is somehow deformed to one side. Preferably, any outline of the substrate in the region of the “pin-like-structure” 40 comprises a first portion that is convexly shaped, a second portion that is concavely shaped and a third portion that is again convexly shaped when going in the thickness direction TD of the substrate 20 from the at least one common local maximum toward the middle region MR of the substrate 20, no matter what sectional plane has been chosen to define the outline, as long as the sectional plane is parallel to the thickness direction TD of the substrate 20 and comprises the local maximum 42.
(40) In FIGS. 17, 17A, 18 and 18A, a dotted line indicates the original first surface 22 of the substrate 20. Preferably, the material that is located above this dotted line in the final product is material that has first been evaporated during the formation of the through-channels 30 by laser-drilling and has then been condensed again. The inventors have found out that by correspondingly adjusting parameters, such as the power of the laser, the pulse length and the location of the focus of the laser, it is possible to create the “pin-like-structure” 40 relatively easily during the perforation of the substrate.
(41) In laser drilled substrates known from the prior art, there is either no material above the dotted line that represents the original first surface 22 of the substrate 20, or there is material above this line, but only in the form of a smooth hill or ridge as indicated by a dashed line in FIGS. 17A and 18A. However, the formation of the “pin-like-structure” 40 is not know from the prior art.
(42) The “pin-like-structure” 40 is advantageous because—especially when the laser drilled substrate is used as a forming fabric—it supports the fiber web punctually, thus providing a very good and equal dewatering for the fiber web substantially over its complete surface, thus, avoiding markings.
(43) The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: 20′, 20 substrate 22′, 22 first surface 24′, 24 second surface 26′ first lateral edge 28′ second lateral edge 30′, 30 through-channel 31 through hole of first type 32 through hole of second type 34 circular upper rim of through hole 35 elliptical upper rim of through hole 36 circular lower rim of through hole 38 upper rim of through-channel 40 pin-like-structure 42 local maximum 44, 44* first portion that is convexly shaped 46, 46* second portion that is concavely shaped 48, 48* third portion that is convexly shaped 50; 50* first inflection point 52; 52* second inflection point a, b diameter of lower rim A, B diameter of upper rim CA central axis LB laser beam MR middle region R roller TD thickness direction WD width direction
