CA1312530C - Double-layer clothing for the sheet forming section of a papermaking machine - Google Patents
Double-layer clothing for the sheet forming section of a papermaking machineInfo
- Publication number
- CA1312530C CA1312530C CA000588281A CA588281A CA1312530C CA 1312530 C CA1312530 C CA 1312530C CA 000588281 A CA000588281 A CA 000588281A CA 588281 A CA588281 A CA 588281A CA 1312530 C CA1312530 C CA 1312530C
- Authority
- CA
- Canada
- Prior art keywords
- transverse
- threads
- layer
- transverse threads
- thread
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/0027—Screen-cloths
- D21F1/0036—Multi-layer screen-cloths
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S162/00—Paper making and fiber liberation
- Y10S162/903—Paper forming member, e.g. fourdrinier, sheet forming member
Abstract
ABSTRACT OF THE DISCLOSURE
A double-layer fabric for the sheet-forming section of a papermaking machine includes an upper layer of transverse threads, a lower layer of transverse threads, and a single system of longitudinal threads which are interwoven with both layers of transverse threads. The transverse threads of the lower layer are woven in pairs in parallel and the transverse threads of the upper layer are positioned above respective pairs of transverse threads.
A double-layer fabric for the sheet-forming section of a papermaking machine includes an upper layer of transverse threads, a lower layer of transverse threads, and a single system of longitudinal threads which are interwoven with both layers of transverse threads. The transverse threads of the lower layer are woven in pairs in parallel and the transverse threads of the upper layer are positioned above respective pairs of transverse threads.
Description
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wusLE-LA~R FAsRIc Eoa T~ SH;EET F(:~RMING
SECTION OF A PAPER~NG MA~INE
The invention relates to a double-layer fabric for thP sheet forming section of a paperma~ing machine made up of two layers of transverse threads which are interwoven with a single system of longitudinal threads.
Fabrics for the sheet forming section of a papermaking machine in which the transverse threads are arranged in two layers and are interwoven wi.th a single system of longitudinal threads are ~enarally designa~ed as double-layer shee~ forming woven abrlcs or, brie~l~, double-l~yer forming fabri~.
Double-layer forming fabrics brought about a substantial improvement in the sheet form~ng characteristics as opposed to a single-layer forming fabrics. The longitudinal stability has been substantially improved by the high degree of filling of the longitudinal threads on the order of 95-110~.
The dewatering characteristics of these forming fabrics are also more favorable because there are not provided any large openings passing through in the vertical direction, and the water is conducted away from the paper pulp through numerous fine, slot-like openings which are predominantly arranged in an oblique direction.
It is possible in the case of double-layer forming fabrics to select the dimensions, the material oharac~eristics and the shape of crimping o~ the two . ,,, .. -.. ,.. ~. . . . .
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wef t systems to be different. For reasons having to do with marking, fine transverse threads of relatively short floating length may be used for the paper side, while ~hick transverse threads having long floatings may be used for the running side. It is possible, furthermore, to utilize different material for the running side. It is customary for the transverse threads of the running side to consist alternatingly of polyester and abrasion-resistant polyamide.
A two-layer forming fabric is understood to be, by contrast, a fabric for the sheet forming sec~ion of a papermakin~ machine, whlch consists of an upper fabric and a lower ~abric, each of whlch are woven complete in themselves rom lcn~itudinal ~hreads and transverse thre~ds wi~h uppe~ fabr1c and the lower fabric belng connected either hy means o specific binding threads or by means of weaving of the longitudinal or the ~ransverse threads of the upper fabric into the lower fabric or vice versa. The upper fabric is fine-meshed in nature. It consists o~ a plurality of thin threads and has lit~le stability in itself. The lower fabric is coarse and consists of thick threads. It imparts to the woven fabric the required longitudinal and transverse stability. The binder ~hreads may extend in a longitudinal direction, in a ~ransverse direction or simultaneously in both directions.
The binder thread is the ~eak point of these two-layer forming fabrics. It frequently is destroyed prematurely due to abrasion from the , ~
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running side or due ~o internal friction between the two layers of woven fabric. U.S. Patent No. 4,592,~96 offers a remedy ~or this. This forming fabric is provided on the running side with transverse threads arranged pairwise and the binding thread no longer lies on the running surface but is nipped by a pair of transverse threads and retained over a~ainst the longitudinal thread crossing thereabove. In the case of two-layered forming fabrics, the connection of the two layers to one another is not strong enough for avoiding mutual relative movement. In the event of alternatin deflection of the forming fabric Viel externally-disposed and internally-disposed quide~
rollers, there r~sults lnternal riction between the two layers of woven f ab~ic .
Due to the high proportion of filler materials in paper for writing and in paper for printing, the abrasive particles of the filler get in between the two layers of woven fabric. The face between the two layers of woven fabric is also highly abraded on account of the relative movement and the filler material. The binding threads are often prem~turely chafed through at the points of contact with the layers of wover. fabric. As a result of this, the layers of woven fabric are separated and the forming fabric becomes unserviceable.
U.S. Patent No. 4,739,80~ describes a forming fabric, which is similar to the double-layer forming fabric but has the finer surface structure of a two-layer forming-fabric. The structure on the paper side is ~n~_ / _ 4 - 1 3 ~ ~ 3 3 0 made to be very fine due to a ~pecific longitudinal thread path and due to the number of transverse threads having been doubled. The running side of this forming fabric L5, by contrast, coarse and very open. Furthermore, successive transverse threads on the paper side are supported in a different manner in that one transverse thread is carried in saddle-like manner by the longitudinal thread, so that it is lying precisely in a transverse direction in the woven fabric, while the next-following transvers~
thread is supported by two adjacent longitudinal threads, one of said longitudinal ~hreads rising to the ~orming fabric surface and the other one descending, so that the supporting o~ the transverse ~hread takes place in a shear-liko manner and the transverse thread 10ating is turned in a manner such that it lles at an angle with respect to ~he ~loatings of the transverse threads supported in a saddle-like manner. In this way, the marking characteristics of the forming fabric are substantially improved. The number of transverse threads in the case of this forming fabric is twice as high on the paper side as on the running side. I~
is in that way possible to achieve substantially higher numbers of transverse threads on the paper side than in the case of a conventional, double-layer forming fabric (with a similar de~ree of ~ineness of the longitudinal threads?. The maxLmum possible number of transverse threads is limited in the case of double-layer forming fabrics on account of weaving technique because the longitudi~al threads always alternate between the upper and lower layer, so that only a limited total number of transverse threads can ~ 3 ~ 3 ~
be shot-in. With a similar total number of transverse threads, the forming fabric according to U.S.
Patent No. 4,739,803 has more threads on the paper side than a conventional forming fabric because the number of threads on the running side is only half as large as that on the paper side.
According to EP-A-O 085 363, the marking characteristics and the retention of the fibers are improved in that an additional supporting thread is inserted ~ithout binding it in subsequent to each structural thread in a single-layer or the paper side of a double-layer forming fabric. ~his serves to reduce the mesh size and the fibers of the paper pulp are better supported. E~'or rea~on~ having to do with weavirlg t~chnolo~y, it .i~ not pos~ible! how~v~r, to still weave-in further, additional threads once a maximum po~slble thread density of the double-layer forming fabric has been attained. The number of transverse threads of the original weave construction must be reduced by about one-third in order to arrive, with additional threads, at about the same total number of transverse threads.
lt has turned out in practice that the forming fabric~ according to the EP-A-O 085 363 and U.S. Patent No. 4,739,803 sub~tantially improve the forming fabric marking and retention. Care must be taken, however, upon weaving of these double-layer fabrics that the transverse threads are lying one above the other. This presents because the position of the upper and the threads relative to one another changes on ~ 3 ~ r~ ~3~
account of the crimping exchange phenomena occurring during heat setting. During weaving, the transverse threads are still laid in substantially uncrimped state into the composite structure of the longitudinal threads. The longitudinal threads are looped around the two layers of the inserted transverse threads and initially form the outermost points of the woven fabric on the paper side as well as also on the running side. It is only upon heat setting at very high longitudinal tension and with the ac~ion of heat that the longitudinal threads are stretched and force the transverse threads to crimp. There is thus formed, for instance, the long transverse threacl floa-ting on the running ~ide, which in the finished formin~ fabric extends out oE the plane c~ the woven fabric and def:ine~ the abrasion ~ureace o~
the forming fabric. This i~ then called the weft runner. At the same time the longitudinal thread is on account of the high longitudinal tension urged to the inside of the woven fabric. It is in that way protected from abrasion on the running ~ide or is at least exposed to abrasion only after the volume of the transverse threads has already largely been spent. Simultaneously with these crimp exchange phenomena, the transverse threads slip above one another, and it is extremely difficult to weave the woven fabric in a manner such that all of the transverse threads are lying perfectly above one another over the full length and width of -the forming fabric.
In the case of a forming fabric having a width of 9 meters and having 70 longitudinal threads/centimeter, 11 ~ 3 ~
the formlng fabr~c has, in all, 63,000 longitudinal thr~ads. When the number of transverse thre~ds 1~ 30 transverse threads/cm in the upper layer and 30 transverse thre2ds/cm in the lower layer a forming fabric having a length o 45 meter~
has 135,000 transverse thread pairs ln all. In the case of a 7-harnes~ weave, the re3ulS is 1215 million transverse thread floatings which must: all be lying one neatly above the other. If sllppa~e of one uppar transverse thread relative to a lower one occurs at only a single location, then this location wlll cause, at the high operating speeds of the forming fabrics, an inadmissible marking on the paper web, and the entire forming fabric will beco~e unserviceable.
It i~ extrflordinarily diicult to attain, with so many lonqitudinal threads and so many transverse thread pflirs, a perfect super-position which really does remain the same. The abric tension must already upon weaving be maintained precisely over the full width of the loom and, of course, over the full length of the forming fabrlc. Furthermore, all of the transverse threads must have exactly the same characteristics in the cold state upon weaving a~
well as also at the high temperatures during the setting procedure. For the woven fabric to become resistant to abrasion, polyester threads and polyamide threads are alternatingly woven into the fabric on the running 3ide. The~e two working materials exhibit very different behavior, especially upon settinq. If a good super-position of the upp~r transverse thread above the lower transver~e ,3 ~ 3 ~
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polyester thread i8 attained, then the next upp~r trangvers~ thread 81ips of cf the transverse polyamide thread di~posed below it. Minor offset~
already bring about very di~tinct marking~ in the paper. ~urthermore, the polyamid~_ monofilament crimp-~ under tension and the action of heat in a different way than does the polyester monofilament.
Thi 8 depends upon temperature and tension. The result i~ that the longitudinal thread on the running side, when the polyamide thread i8 woven in, is embedded less deeply within the woven fabric than when the polyester threads are interlaced. While it i~ possible to reduce these crlmplng differences by selecting pllysicAl characteristic3 that are a~
favorable a~ possible, it 1~ neverthele~ not po~sible to entirely avoid the~e diferences in th~
inner structure of the forming ~bric.
These problems are encountered in the production of all double-layer forming fabrics. They ar~
particularly seriou~ in the ca~e of the forming I fabr~c constructions according to EP-A-0 085 363 and U.S. Patent No. 4,739,803 wherein ths lnner structur~
i8 from the very o~tset less balanced due to the absence o every second transverse thread on the running side. Slipping off of the transverse threads i9 a phenomenon that i8 particularly marked in the ca~e of these woven fabrics.
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In addition, the number of tran~verse thr~ads on the running side is less in the case of the~e forming fabrics and on account of that the distances ~etween transver.se tllreads are substantially greater than i 9 .~ 3 J
th~ caYe o double-layer forming fabric-~ having u like number of transverse threads i~ the upper and in the lower layer. Con~iderlng that at the hlgh ~peed of modern paper~aklng machines for printing paper of greater than lO00 m/min. hydrodynamie pressure waves, which go out from the running ~ide, have a deci^qlve inEluence on marXing, the large distance betw~en transverse threads on the running side ha~ a disadvantageous effect in regard to marking. The intensity of the pre~sure waves depends upon the distance between succe~sive tran~verse threads. When woven fabrics with only half the number of transverse thread~ on the running side are used, it sometime~
happen~ that insupportably extenqive tran~verse thread markings become visible in the paper web. Tho density o~ the line~ o the marklng in the paper web i8 not such as to correspond to each lower transverse thread but, rather, only to every ~econd tran3ver~e thread on the running side; this i~ the tran~vers~
polyamlde thread. The cau~e~ for this are the above-described differences in the super-po~itioning (slipping-off) and the crimping differences between polyamlde and polye~ter. In some instances, the otherwise 80 interesting advantages which the~e forming fabrics provide for are in this way brought to nothing.
Another negative factor encountered by woven fabrics having a low number of transverse threads on the running side i~ entrainment of water. These woven fabrics are closed on the paper side but very open at the bottom. Larger quantities of water are retained in the open ~pace of the. woven fabric opening~ and .. . . , . . . . _ . . . .
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are then 1ung-out upon the deflection over gulde roller~.
It i~ known from German appllcation DE-A-31 46 3~5 to improve retentlon in the case of a double-layer papermaking machine forming fabric in that the longitudinal thread3 on the paper ~ide and/or on the running ~ide are conducted at least over some distance in p~rallel pairwise. m e parallel guiding of the longitudinal threads is of a nature such that the threads of the paper web are supported by way of an areal structure, thus avoiding the distinct impressions of individual longitudinal threads upon the paper web.
Europesn Patent ~pplicutlon EP-A-O 117 ~56 d~cribo~
a two-layor papermaking machlne forming fabric, ln which the warp threads of the lower layer~ are lnterwoven pairwise in parallel over the entire extent thereof. It iB made po~ible thereby to produce, on the one hand, double-layer paper~aking machine forming fabrics and, on the other hand, two-layer papermaking machine forming fabrlcs with warp threads of like diameter in the same warp thread density.
A two-layer papermaking machlne forming fabric is known from ~erman Application DE-A-34 45 367, ln which the lower woven fabric contain~, for the purpose of avoiding hlqh tensions in the binding threads, two group~ of transverse threads, the first group of which being interwoven in a l:l-weave and the second group in a l:n-weave w~th the warp threads ~3~2~3~
of the lower woven fabric, with successive transverse threads of varying weave construction, which define double crimpings on the inner side of the lower woven fabric, contacting, and with the long n-crimps defining on the outer side a plane of wear. In that respect, n denotes an off number greater than 1.
The invention solves the problem of designing a double-layer papermaking machine forming fabric in a manner such that the danger of slippage of the upper transverse threads relative to the lower transverse threads is substantially reduced.
Accordingly, the present invention provides a double-layer fabric for the sheet forming section of a papermaking machine, comprising an upper layer of transverse threads (1) and a lower layer of tran~ver3e throad~ (2,3) and including a ~lngl~ ~stom o~
longikudinal thread~ (4), which are interwoven with both layers of transver~e threads (1,2,3), where~n ~a.id transverse threads (2,3) of said lower layer are woven in parallel in pairs wherein the transverse threads of each pair are always running adjacent to each other and are never separated by a longitudinal thread passing between them and with one transverse thread (1) of the upper layer being positioned above each transverse thread pair (2,3) in the lower layer.
In a further aspect, the present invention provides a multi-layer fabric for the sheet forming section of a papermaking machine, comprising an upper woven fabric and at least one lower woven fabric connected therewith, wherein said upper woven fabric is a double-layer fabric comprising an upper layer of transverse threads, a lower layer of transverse threads and a single system of longitudinal threads which are interwoven with both layers of transverse threads with said -transverse threads of said lower layer being woven in parallel in pairs with .' ~l3 ~ -`i3 - lla -the transve_ s5 threads of each pair always running adjacent to each other and never separated by a longitudinal thread passing between th~em and with one trans;Jerse thread of the upper layer being positioned above ea~h transverse thread pair in t:he lower layer and wherein said upper woven fabric is connected to the lower woven fab~ic by means of one of the transverse threads of a plurality of said pairs of transverse threads of said upper woven fabric which are interwoven with a longitudinal thread of said lower woven fabric.
The forming fabric according to the invention is produced in a manner such that there are interwoven, in lieu of one lower transverse thread, two transverse threads of about a 20~ to 30% smaller diameter, but otherwise include~ unchanged features of construction.
~here~ore, the number of tran~verse thread~ .in the lower layer has been doubled as opposed to the forming fabr~cs acaording to EP-~-O 085 363 and U.S. Patent No.
4,739,803.
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Surprisingly the doubling 4f the number of transverse threads in the lower layer does not require any reduction in number of transverse threads in the upper layer. Hence each transverse filamen~
pair of the lower layer has the effect only of that of a single transverse thread on the number of transverse threads attainable overall..
In the production of the forming fabric according to the invention the weaving sequence is of a nature such that there is interwoven one lower transver.se thread of one pair then there is interwoven an upper transverse thread and finally the other transver.se thread of the pair is interwoven. Hence the two transverse threads of the bottom layer are nst interwoven directly in succession but, rathex, the upper transverse thread is interwoven in between.
In addi~ion to improvlng the stability o~ the forming fabric structure the resistance to abrasion also i5 increased in the case of the forming fabric according to the invention as the entire volume of transverse threads in the lower layer available for abrasion is higher. If there are for instance interwoven two transverse threads of a thickness of 0.18 mm each, in lieu of one transverse thread of a thickness of O.22 mm then the volume of material of the lower transverse threads is increased overall, by about 34%. The result of this is an lmprovement in resistance to abrasion and on account of that an increase in the service life.
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;~ It generally applies that the diameter of the lower transverse threads is at least equal to that of the upper transverse threads, and that it may be up to 30% larger.
As has been mentioned at ~he outset, it is customary in the case of papermaking machlne forming fabrics to use on the running side alternatlely transvers~
threads of a different material, in particular, alternatingly polyamide and polyester. In the forming fabric according to the invention, each pair of transverse threads consists preferably of one polyester thread and one polyamide thread, generally of a polyester monofilament and a polyamide monofilament. In that way, each longitudinal thread always binds the same combination of transverse threads each time it is looped around the trarlsverse threads on the running side. It is on account of this that there æ e no longer any differences between the individual longitudinal thread crimps on the running side and the uniformity of the running side is substantial}y improved. The varying characteristics of the materials which the transverse threads are made of, namely polyamide and polyester, '3 no longer have any disadvantageous effects. Due to the lower thickness of the bo~tom transverse ~hreads as compared w~th a papermaking machine forming fabric having otherwise unchanged eatures of construction, the thickness of the lower layer is also reduced and simultaneously the open area of the lower layer diminished. The distances between the transverse 3 thread pairs are decreased on account of that, thus further reducing the danger of marking.
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The forming fabric according to the invention and the upper woven fabric of the multi-layer forming fabric according to the invention o~herwise exhibit features ~ypical of a double-layer ~orminS7 fabric. In particular, the upper transverse threads are iner than the lower transverse threads, the difference being, however, not as distinct as in the case of prior art, as in the case of the fonming fabric of the invention each individual lower transverse thread is thinner than what is customarily the case. The longitudinal threads and the transverse threads generally are monofilaments. The upper transverse threads and the longitudinal threads as a rule are polyester-monofilaments. The forming fabric may be woven flat or endless. The longltudinal ~hreads, for instance, may be multi-filaments particularly in the case of an endless weave. The formin~ abric for papermaking machines according to the invention may be woven in any number of harnesses. A
seven-harness, an eight-harness, a ten-harness, a fourteen-harness or a sixteen-harness weave is, in particular, expedient.
Transverse threads interwoven pairwise are ~nown in the case of single-layer and two-layer or multi-layer papermaking machine forming fabrics. There does not, however, exist ln the case of these papermaking machine orming fabrics any danger of displacement of transverse threads that are positioned vertically above one another, or else such a displacement does not have any serious influence on the marking characteristics. Multi-layer formlng fa~rics with ~ransverse threads conducted in parallel pairwise in ~. .
. . :, .
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one of the layers are known from the U.S. Patent NoO
4,636,426 and U.S. Patent No. 4,592,396. In the former case, the two transverse threads of a pair are bound to one another over their entire length through a hydrophilic, water-absorbing polyester, so that the two transverse threads act as a single thread having a flat cross-section. In the second instance, what is concerned is a two-layer forming fabric, in which the transverse threads of the lower layer are conducted pairwise in parallel so as to enclose between themselves and the crossing longitudinal thread a transverse binder thread, so that said transverse binder thread is largely out of the way of any abrasion.
In the drawings:
Figure 1 i~ a sectional view in the longitudinal direction of a forming fabric with lower transver~e thread~ interwoven pairwise in parallel:
Figure 2 is an enlarged cutaway portion of Figure 1;
Figure 3 is a sectional view in the longitudinal direction of another embodiment of a double-layer forming fabric with lower transverse threads interwoven pairwise in parallel;
Figure 4 is a view of the running side of the forming fabric according to Figure 1;
Figure 5 is a cross-sectional view of a further embodiment of a double-layer forming fabric with - 16 - ~3~
lower transverse threads interwoven pairwise in parallel;
Figure 6 is a longitudinal sectional view of ~he further embodiment shown in Figure S; and Figure 7 is a longitudinal sectional view of an embodiment of a multi-layer forming fabric, in which the upper layer is a double-layer woven fabric, which corresponds to the forming fa`bric depicted in Figure 1.
The double layer forming fabric shown ln Figures 1 and 4 comprises upper transverse threads 1 and lower transverse threads 2 and 3 whlch are woven in pairs in parallel and are interwoven with longitudlnal j threads 4. The upper transverse threads 1 foxm, together w1~h the lon~itudinal threads 4, the paper side 5 of the forming fabric, on which sheet formation takes place. The lower transverse threads 2 and 3 define the running side 6 of the forming fabric which faces most of the rollers and the guidance elements of the papermaking machine.
The longitudinal thread 4 generally do not take part in the formation of the running side since they are important with respect to the longitudinal stability of the papermaking machine forming fabric and should, on account of that, be exposed as little as possible to any abrasion. In the production of the forming 1, fabric, this is achieved in ~hat there is exerted, upon thermo-setting, a correspondingly high ,~ .
- 17 - ~3~30 lengthwise tenslon into the forming fabric, so that the lower crimps of the longitudinal thread~ 4 are drawn upwardly.
The forming fabric illustrated in Figures 1 and 4 coincides substan~ially with the papermak~ng machine i forming fabric accordin~ to Figures l and 2 and ¦ Example 1 of U.S. Patent No. 4,7~9~803, with the exception, however, of the paired lower transverse threads 2, 3. The papermaking machine~ forming fabric was produced with the following clata, in which respect there have been indicated, as far as relevant, the values subsequent to weaving and thermo-setting:
Dlameter of the longitudlnal th~eads 0.17 mm Density of the longltudlnal threads S4/61 per cm Diameter of the upper transverse threads 0.17 mm Density of the upper transverse threads 34/32 per cm Material of the upper transverse thread~
and of the longitudinal threads: Polyester Diameter oP the lower transverse threads 0.18 mm Density of the lower transverse threads 17/16 pairs per cm Material of the lower transverse threads Polyester . and polyamide 6.0 alter-natingly L~
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Thickness of the woven fabric 0.674 mm Free distance a (Figure 2) of the lower transverse threads 0.265 mm.
When the same forming fabric is produced respectively with a single lower transverse thread of a diameter of 0.22 mm instead of with a pair of transverse threads of a diameter of 0.18 mm, the thickness of the woven fabric is 0.716 mm and the free spacing between the lower transverse threads 0.~05 mm. lt will be recognized from this that in the case o~ the papermaking machine forming fabric according to the invention the lower layer is distinctly thinner and no longer as extremely open.
Figure 3 shows another exemplary embodiment with another weave construction, in which the upper layer of transverse threads 1 consists alternately of polyester-monofilaments of a diameter of 0.11 and O.î8 mmO The remaining design features are unchanged as concerns the state subsequent to weaving as well as the state subsequent to thermo-setting.
Figures 5 and 6 pertain to s-till anokher exemplary embodiment, in which the double-layer papermaking machine forming fabric disclosed in Figures 5a and 5b of EP-A-O 245 851 was modified in accordance with the subject invention in that each one of the transverse threads of the lower layer was substituted by a pair.
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The subject invention also covers embodiments, in which the uppermost woven fabric 7 of a multi-layer forming fabric is defined by a woven fabric, which corresponds to one of the above described double-layer forming fabrics ~Figure 7). In that regard, the upper woven fabric 7 is connected to the lower woven fabric 8 by means of one transverse thread 2 of a pair of transverse threads conducted in parallel which is interwoven with a longitudinal thread 9 of the lower woven fabric 8. The structure of the upper woven fabric 7 is in that respect not adversely affected at the binding sites 10 between the two woven fabrics 7, 8, since the longitudinal thread 4 of the upper woven fabric 7 follows the course it normally follows on account of the fact that the course of the other transverse thread 3 has not been changed. Ag a result of this, there are no depressions on the paper side 5 at the binding si.te~ which would .resu:Lt in a noticeable mark.ing in the paper. It is al80 possible ko uti:l.ize a double-layer woven fabric a~ the lower woven .Eabric, .in lieu of the single-layer woven fabric which is shown in Figure 7.
wusLE-LA~R FAsRIc Eoa T~ SH;EET F(:~RMING
SECTION OF A PAPER~NG MA~INE
The invention relates to a double-layer fabric for thP sheet forming section of a paperma~ing machine made up of two layers of transverse threads which are interwoven with a single system of longitudinal threads.
Fabrics for the sheet forming section of a papermaking machine in which the transverse threads are arranged in two layers and are interwoven wi.th a single system of longitudinal threads are ~enarally designa~ed as double-layer shee~ forming woven abrlcs or, brie~l~, double-l~yer forming fabri~.
Double-layer forming fabrics brought about a substantial improvement in the sheet form~ng characteristics as opposed to a single-layer forming fabrics. The longitudinal stability has been substantially improved by the high degree of filling of the longitudinal threads on the order of 95-110~.
The dewatering characteristics of these forming fabrics are also more favorable because there are not provided any large openings passing through in the vertical direction, and the water is conducted away from the paper pulp through numerous fine, slot-like openings which are predominantly arranged in an oblique direction.
It is possible in the case of double-layer forming fabrics to select the dimensions, the material oharac~eristics and the shape of crimping o~ the two . ,,, .. -.. ,.. ~. . . . .
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,/ - 2 - 1 31253D
wef t systems to be different. For reasons having to do with marking, fine transverse threads of relatively short floating length may be used for the paper side, while ~hick transverse threads having long floatings may be used for the running side. It is possible, furthermore, to utilize different material for the running side. It is customary for the transverse threads of the running side to consist alternatingly of polyester and abrasion-resistant polyamide.
A two-layer forming fabric is understood to be, by contrast, a fabric for the sheet forming sec~ion of a papermakin~ machine, whlch consists of an upper fabric and a lower ~abric, each of whlch are woven complete in themselves rom lcn~itudinal ~hreads and transverse thre~ds wi~h uppe~ fabr1c and the lower fabric belng connected either hy means o specific binding threads or by means of weaving of the longitudinal or the ~ransverse threads of the upper fabric into the lower fabric or vice versa. The upper fabric is fine-meshed in nature. It consists o~ a plurality of thin threads and has lit~le stability in itself. The lower fabric is coarse and consists of thick threads. It imparts to the woven fabric the required longitudinal and transverse stability. The binder ~hreads may extend in a longitudinal direction, in a ~ransverse direction or simultaneously in both directions.
The binder thread is the ~eak point of these two-layer forming fabrics. It frequently is destroyed prematurely due to abrasion from the , ~
_ 3 _ ~ 3~
running side or due ~o internal friction between the two layers of woven fabric. U.S. Patent No. 4,592,~96 offers a remedy ~or this. This forming fabric is provided on the running side with transverse threads arranged pairwise and the binding thread no longer lies on the running surface but is nipped by a pair of transverse threads and retained over a~ainst the longitudinal thread crossing thereabove. In the case of two-layered forming fabrics, the connection of the two layers to one another is not strong enough for avoiding mutual relative movement. In the event of alternatin deflection of the forming fabric Viel externally-disposed and internally-disposed quide~
rollers, there r~sults lnternal riction between the two layers of woven f ab~ic .
Due to the high proportion of filler materials in paper for writing and in paper for printing, the abrasive particles of the filler get in between the two layers of woven fabric. The face between the two layers of woven fabric is also highly abraded on account of the relative movement and the filler material. The binding threads are often prem~turely chafed through at the points of contact with the layers of wover. fabric. As a result of this, the layers of woven fabric are separated and the forming fabric becomes unserviceable.
U.S. Patent No. 4,739,80~ describes a forming fabric, which is similar to the double-layer forming fabric but has the finer surface structure of a two-layer forming-fabric. The structure on the paper side is ~n~_ / _ 4 - 1 3 ~ ~ 3 3 0 made to be very fine due to a ~pecific longitudinal thread path and due to the number of transverse threads having been doubled. The running side of this forming fabric L5, by contrast, coarse and very open. Furthermore, successive transverse threads on the paper side are supported in a different manner in that one transverse thread is carried in saddle-like manner by the longitudinal thread, so that it is lying precisely in a transverse direction in the woven fabric, while the next-following transvers~
thread is supported by two adjacent longitudinal threads, one of said longitudinal ~hreads rising to the ~orming fabric surface and the other one descending, so that the supporting o~ the transverse ~hread takes place in a shear-liko manner and the transverse thread 10ating is turned in a manner such that it lles at an angle with respect to ~he ~loatings of the transverse threads supported in a saddle-like manner. In this way, the marking characteristics of the forming fabric are substantially improved. The number of transverse threads in the case of this forming fabric is twice as high on the paper side as on the running side. I~
is in that way possible to achieve substantially higher numbers of transverse threads on the paper side than in the case of a conventional, double-layer forming fabric (with a similar de~ree of ~ineness of the longitudinal threads?. The maxLmum possible number of transverse threads is limited in the case of double-layer forming fabrics on account of weaving technique because the longitudi~al threads always alternate between the upper and lower layer, so that only a limited total number of transverse threads can ~ 3 ~ 3 ~
be shot-in. With a similar total number of transverse threads, the forming fabric according to U.S.
Patent No. 4,739,803 has more threads on the paper side than a conventional forming fabric because the number of threads on the running side is only half as large as that on the paper side.
According to EP-A-O 085 363, the marking characteristics and the retention of the fibers are improved in that an additional supporting thread is inserted ~ithout binding it in subsequent to each structural thread in a single-layer or the paper side of a double-layer forming fabric. ~his serves to reduce the mesh size and the fibers of the paper pulp are better supported. E~'or rea~on~ having to do with weavirlg t~chnolo~y, it .i~ not pos~ible! how~v~r, to still weave-in further, additional threads once a maximum po~slble thread density of the double-layer forming fabric has been attained. The number of transverse threads of the original weave construction must be reduced by about one-third in order to arrive, with additional threads, at about the same total number of transverse threads.
lt has turned out in practice that the forming fabric~ according to the EP-A-O 085 363 and U.S. Patent No. 4,739,803 sub~tantially improve the forming fabric marking and retention. Care must be taken, however, upon weaving of these double-layer fabrics that the transverse threads are lying one above the other. This presents because the position of the upper and the threads relative to one another changes on ~ 3 ~ r~ ~3~
account of the crimping exchange phenomena occurring during heat setting. During weaving, the transverse threads are still laid in substantially uncrimped state into the composite structure of the longitudinal threads. The longitudinal threads are looped around the two layers of the inserted transverse threads and initially form the outermost points of the woven fabric on the paper side as well as also on the running side. It is only upon heat setting at very high longitudinal tension and with the ac~ion of heat that the longitudinal threads are stretched and force the transverse threads to crimp. There is thus formed, for instance, the long transverse threacl floa-ting on the running ~ide, which in the finished formin~ fabric extends out oE the plane c~ the woven fabric and def:ine~ the abrasion ~ureace o~
the forming fabric. This i~ then called the weft runner. At the same time the longitudinal thread is on account of the high longitudinal tension urged to the inside of the woven fabric. It is in that way protected from abrasion on the running ~ide or is at least exposed to abrasion only after the volume of the transverse threads has already largely been spent. Simultaneously with these crimp exchange phenomena, the transverse threads slip above one another, and it is extremely difficult to weave the woven fabric in a manner such that all of the transverse threads are lying perfectly above one another over the full length and width of -the forming fabric.
In the case of a forming fabric having a width of 9 meters and having 70 longitudinal threads/centimeter, 11 ~ 3 ~
the formlng fabr~c has, in all, 63,000 longitudinal thr~ads. When the number of transverse thre~ds 1~ 30 transverse threads/cm in the upper layer and 30 transverse thre2ds/cm in the lower layer a forming fabric having a length o 45 meter~
has 135,000 transverse thread pairs ln all. In the case of a 7-harnes~ weave, the re3ulS is 1215 million transverse thread floatings which must: all be lying one neatly above the other. If sllppa~e of one uppar transverse thread relative to a lower one occurs at only a single location, then this location wlll cause, at the high operating speeds of the forming fabrics, an inadmissible marking on the paper web, and the entire forming fabric will beco~e unserviceable.
It i~ extrflordinarily diicult to attain, with so many lonqitudinal threads and so many transverse thread pflirs, a perfect super-position which really does remain the same. The abric tension must already upon weaving be maintained precisely over the full width of the loom and, of course, over the full length of the forming fabrlc. Furthermore, all of the transverse threads must have exactly the same characteristics in the cold state upon weaving a~
well as also at the high temperatures during the setting procedure. For the woven fabric to become resistant to abrasion, polyester threads and polyamide threads are alternatingly woven into the fabric on the running 3ide. The~e two working materials exhibit very different behavior, especially upon settinq. If a good super-position of the upp~r transverse thread above the lower transver~e ,3 ~ 3 ~
/
polyester thread i8 attained, then the next upp~r trangvers~ thread 81ips of cf the transverse polyamide thread di~posed below it. Minor offset~
already bring about very di~tinct marking~ in the paper. ~urthermore, the polyamid~_ monofilament crimp-~ under tension and the action of heat in a different way than does the polyester monofilament.
Thi 8 depends upon temperature and tension. The result i~ that the longitudinal thread on the running side, when the polyamide thread i8 woven in, is embedded less deeply within the woven fabric than when the polyester threads are interlaced. While it i~ possible to reduce these crlmplng differences by selecting pllysicAl characteristic3 that are a~
favorable a~ possible, it 1~ neverthele~ not po~sible to entirely avoid the~e diferences in th~
inner structure of the forming ~bric.
These problems are encountered in the production of all double-layer forming fabrics. They ar~
particularly seriou~ in the ca~e of the forming I fabr~c constructions according to EP-A-0 085 363 and U.S. Patent No. 4,739,803 wherein ths lnner structur~
i8 from the very o~tset less balanced due to the absence o every second transverse thread on the running side. Slipping off of the transverse threads i9 a phenomenon that i8 particularly marked in the ca~e of these woven fabrics.
!
In addition, the number of tran~verse thr~ads on the running side is less in the case of the~e forming fabrics and on account of that the distances ~etween transver.se tllreads are substantially greater than i 9 .~ 3 J
th~ caYe o double-layer forming fabric-~ having u like number of transverse threads i~ the upper and in the lower layer. Con~iderlng that at the hlgh ~peed of modern paper~aklng machines for printing paper of greater than lO00 m/min. hydrodynamie pressure waves, which go out from the running ~ide, have a deci^qlve inEluence on marXing, the large distance betw~en transverse threads on the running side ha~ a disadvantageous effect in regard to marking. The intensity of the pre~sure waves depends upon the distance between succe~sive tran~verse threads. When woven fabrics with only half the number of transverse thread~ on the running side are used, it sometime~
happen~ that insupportably extenqive tran~verse thread markings become visible in the paper web. Tho density o~ the line~ o the marklng in the paper web i8 not such as to correspond to each lower transverse thread but, rather, only to every ~econd tran3ver~e thread on the running side; this i~ the tran~vers~
polyamlde thread. The cau~e~ for this are the above-described differences in the super-po~itioning (slipping-off) and the crimping differences between polyamlde and polye~ter. In some instances, the otherwise 80 interesting advantages which the~e forming fabrics provide for are in this way brought to nothing.
Another negative factor encountered by woven fabrics having a low number of transverse threads on the running side i~ entrainment of water. These woven fabrics are closed on the paper side but very open at the bottom. Larger quantities of water are retained in the open ~pace of the. woven fabric opening~ and .. . . , . . . . _ . . . .
1312~3~
are then 1ung-out upon the deflection over gulde roller~.
It i~ known from German appllcation DE-A-31 46 3~5 to improve retentlon in the case of a double-layer papermaking machine forming fabric in that the longitudinal thread3 on the paper ~ide and/or on the running ~ide are conducted at least over some distance in p~rallel pairwise. m e parallel guiding of the longitudinal threads is of a nature such that the threads of the paper web are supported by way of an areal structure, thus avoiding the distinct impressions of individual longitudinal threads upon the paper web.
Europesn Patent ~pplicutlon EP-A-O 117 ~56 d~cribo~
a two-layor papermaking machlne forming fabric, ln which the warp threads of the lower layer~ are lnterwoven pairwise in parallel over the entire extent thereof. It iB made po~ible thereby to produce, on the one hand, double-layer paper~aking machine forming fabrics and, on the other hand, two-layer papermaking machine forming fabrlcs with warp threads of like diameter in the same warp thread density.
A two-layer papermaking machlne forming fabric is known from ~erman Application DE-A-34 45 367, ln which the lower woven fabric contain~, for the purpose of avoiding hlqh tensions in the binding threads, two group~ of transverse threads, the first group of which being interwoven in a l:l-weave and the second group in a l:n-weave w~th the warp threads ~3~2~3~
of the lower woven fabric, with successive transverse threads of varying weave construction, which define double crimpings on the inner side of the lower woven fabric, contacting, and with the long n-crimps defining on the outer side a plane of wear. In that respect, n denotes an off number greater than 1.
The invention solves the problem of designing a double-layer papermaking machine forming fabric in a manner such that the danger of slippage of the upper transverse threads relative to the lower transverse threads is substantially reduced.
Accordingly, the present invention provides a double-layer fabric for the sheet forming section of a papermaking machine, comprising an upper layer of transverse threads (1) and a lower layer of tran~ver3e throad~ (2,3) and including a ~lngl~ ~stom o~
longikudinal thread~ (4), which are interwoven with both layers of transver~e threads (1,2,3), where~n ~a.id transverse threads (2,3) of said lower layer are woven in parallel in pairs wherein the transverse threads of each pair are always running adjacent to each other and are never separated by a longitudinal thread passing between them and with one transverse thread (1) of the upper layer being positioned above each transverse thread pair (2,3) in the lower layer.
In a further aspect, the present invention provides a multi-layer fabric for the sheet forming section of a papermaking machine, comprising an upper woven fabric and at least one lower woven fabric connected therewith, wherein said upper woven fabric is a double-layer fabric comprising an upper layer of transverse threads, a lower layer of transverse threads and a single system of longitudinal threads which are interwoven with both layers of transverse threads with said -transverse threads of said lower layer being woven in parallel in pairs with .' ~l3 ~ -`i3 - lla -the transve_ s5 threads of each pair always running adjacent to each other and never separated by a longitudinal thread passing between th~em and with one trans;Jerse thread of the upper layer being positioned above ea~h transverse thread pair in t:he lower layer and wherein said upper woven fabric is connected to the lower woven fab~ic by means of one of the transverse threads of a plurality of said pairs of transverse threads of said upper woven fabric which are interwoven with a longitudinal thread of said lower woven fabric.
The forming fabric according to the invention is produced in a manner such that there are interwoven, in lieu of one lower transverse thread, two transverse threads of about a 20~ to 30% smaller diameter, but otherwise include~ unchanged features of construction.
~here~ore, the number of tran~verse thread~ .in the lower layer has been doubled as opposed to the forming fabr~cs acaording to EP-~-O 085 363 and U.S. Patent No.
4,739,803.
~3~2~
- 1~
Surprisingly the doubling 4f the number of transverse threads in the lower layer does not require any reduction in number of transverse threads in the upper layer. Hence each transverse filamen~
pair of the lower layer has the effect only of that of a single transverse thread on the number of transverse threads attainable overall..
In the production of the forming fabric according to the invention the weaving sequence is of a nature such that there is interwoven one lower transver.se thread of one pair then there is interwoven an upper transverse thread and finally the other transver.se thread of the pair is interwoven. Hence the two transverse threads of the bottom layer are nst interwoven directly in succession but, rathex, the upper transverse thread is interwoven in between.
In addi~ion to improvlng the stability o~ the forming fabric structure the resistance to abrasion also i5 increased in the case of the forming fabric according to the invention as the entire volume of transverse threads in the lower layer available for abrasion is higher. If there are for instance interwoven two transverse threads of a thickness of 0.18 mm each, in lieu of one transverse thread of a thickness of O.22 mm then the volume of material of the lower transverse threads is increased overall, by about 34%. The result of this is an lmprovement in resistance to abrasion and on account of that an increase in the service life.
// - 13 - ~3~3~f~
/
;~ It generally applies that the diameter of the lower transverse threads is at least equal to that of the upper transverse threads, and that it may be up to 30% larger.
As has been mentioned at ~he outset, it is customary in the case of papermaking machlne forming fabrics to use on the running side alternatlely transvers~
threads of a different material, in particular, alternatingly polyamide and polyester. In the forming fabric according to the invention, each pair of transverse threads consists preferably of one polyester thread and one polyamide thread, generally of a polyester monofilament and a polyamide monofilament. In that way, each longitudinal thread always binds the same combination of transverse threads each time it is looped around the trarlsverse threads on the running side. It is on account of this that there æ e no longer any differences between the individual longitudinal thread crimps on the running side and the uniformity of the running side is substantial}y improved. The varying characteristics of the materials which the transverse threads are made of, namely polyamide and polyester, '3 no longer have any disadvantageous effects. Due to the lower thickness of the bo~tom transverse ~hreads as compared w~th a papermaking machine forming fabric having otherwise unchanged eatures of construction, the thickness of the lower layer is also reduced and simultaneously the open area of the lower layer diminished. The distances between the transverse 3 thread pairs are decreased on account of that, thus further reducing the danger of marking.
.
_~
:
~3~c3~
, - 14 -!
, .
The forming fabric according to the invention and the upper woven fabric of the multi-layer forming fabric according to the invention o~herwise exhibit features ~ypical of a double-layer ~orminS7 fabric. In particular, the upper transverse threads are iner than the lower transverse threads, the difference being, however, not as distinct as in the case of prior art, as in the case of the fonming fabric of the invention each individual lower transverse thread is thinner than what is customarily the case. The longitudinal threads and the transverse threads generally are monofilaments. The upper transverse threads and the longitudinal threads as a rule are polyester-monofilaments. The forming fabric may be woven flat or endless. The longltudinal ~hreads, for instance, may be multi-filaments particularly in the case of an endless weave. The formin~ abric for papermaking machines according to the invention may be woven in any number of harnesses. A
seven-harness, an eight-harness, a ten-harness, a fourteen-harness or a sixteen-harness weave is, in particular, expedient.
Transverse threads interwoven pairwise are ~nown in the case of single-layer and two-layer or multi-layer papermaking machine forming fabrics. There does not, however, exist ln the case of these papermaking machine orming fabrics any danger of displacement of transverse threads that are positioned vertically above one another, or else such a displacement does not have any serious influence on the marking characteristics. Multi-layer formlng fa~rics with ~ransverse threads conducted in parallel pairwise in ~. .
. . :, .
~ 3 ~ 3 ~
one of the layers are known from the U.S. Patent NoO
4,636,426 and U.S. Patent No. 4,592,396. In the former case, the two transverse threads of a pair are bound to one another over their entire length through a hydrophilic, water-absorbing polyester, so that the two transverse threads act as a single thread having a flat cross-section. In the second instance, what is concerned is a two-layer forming fabric, in which the transverse threads of the lower layer are conducted pairwise in parallel so as to enclose between themselves and the crossing longitudinal thread a transverse binder thread, so that said transverse binder thread is largely out of the way of any abrasion.
In the drawings:
Figure 1 i~ a sectional view in the longitudinal direction of a forming fabric with lower transver~e thread~ interwoven pairwise in parallel:
Figure 2 is an enlarged cutaway portion of Figure 1;
Figure 3 is a sectional view in the longitudinal direction of another embodiment of a double-layer forming fabric with lower transverse threads interwoven pairwise in parallel;
Figure 4 is a view of the running side of the forming fabric according to Figure 1;
Figure 5 is a cross-sectional view of a further embodiment of a double-layer forming fabric with - 16 - ~3~
lower transverse threads interwoven pairwise in parallel;
Figure 6 is a longitudinal sectional view of ~he further embodiment shown in Figure S; and Figure 7 is a longitudinal sectional view of an embodiment of a multi-layer forming fabric, in which the upper layer is a double-layer woven fabric, which corresponds to the forming fa`bric depicted in Figure 1.
The double layer forming fabric shown ln Figures 1 and 4 comprises upper transverse threads 1 and lower transverse threads 2 and 3 whlch are woven in pairs in parallel and are interwoven with longitudlnal j threads 4. The upper transverse threads 1 foxm, together w1~h the lon~itudinal threads 4, the paper side 5 of the forming fabric, on which sheet formation takes place. The lower transverse threads 2 and 3 define the running side 6 of the forming fabric which faces most of the rollers and the guidance elements of the papermaking machine.
The longitudinal thread 4 generally do not take part in the formation of the running side since they are important with respect to the longitudinal stability of the papermaking machine forming fabric and should, on account of that, be exposed as little as possible to any abrasion. In the production of the forming 1, fabric, this is achieved in ~hat there is exerted, upon thermo-setting, a correspondingly high ,~ .
- 17 - ~3~30 lengthwise tenslon into the forming fabric, so that the lower crimps of the longitudinal thread~ 4 are drawn upwardly.
The forming fabric illustrated in Figures 1 and 4 coincides substan~ially with the papermak~ng machine i forming fabric accordin~ to Figures l and 2 and ¦ Example 1 of U.S. Patent No. 4,7~9~803, with the exception, however, of the paired lower transverse threads 2, 3. The papermaking machine~ forming fabric was produced with the following clata, in which respect there have been indicated, as far as relevant, the values subsequent to weaving and thermo-setting:
Dlameter of the longitudlnal th~eads 0.17 mm Density of the longltudlnal threads S4/61 per cm Diameter of the upper transverse threads 0.17 mm Density of the upper transverse threads 34/32 per cm Material of the upper transverse thread~
and of the longitudinal threads: Polyester Diameter oP the lower transverse threads 0.18 mm Density of the lower transverse threads 17/16 pairs per cm Material of the lower transverse threads Polyester . and polyamide 6.0 alter-natingly L~
~L3~ ~3~
Thickness of the woven fabric 0.674 mm Free distance a (Figure 2) of the lower transverse threads 0.265 mm.
When the same forming fabric is produced respectively with a single lower transverse thread of a diameter of 0.22 mm instead of with a pair of transverse threads of a diameter of 0.18 mm, the thickness of the woven fabric is 0.716 mm and the free spacing between the lower transverse threads 0.~05 mm. lt will be recognized from this that in the case o~ the papermaking machine forming fabric according to the invention the lower layer is distinctly thinner and no longer as extremely open.
Figure 3 shows another exemplary embodiment with another weave construction, in which the upper layer of transverse threads 1 consists alternately of polyester-monofilaments of a diameter of 0.11 and O.î8 mmO The remaining design features are unchanged as concerns the state subsequent to weaving as well as the state subsequent to thermo-setting.
Figures 5 and 6 pertain to s-till anokher exemplary embodiment, in which the double-layer papermaking machine forming fabric disclosed in Figures 5a and 5b of EP-A-O 245 851 was modified in accordance with the subject invention in that each one of the transverse threads of the lower layer was substituted by a pair.
- ~3~2~
The subject invention also covers embodiments, in which the uppermost woven fabric 7 of a multi-layer forming fabric is defined by a woven fabric, which corresponds to one of the above described double-layer forming fabrics ~Figure 7). In that regard, the upper woven fabric 7 is connected to the lower woven fabric 8 by means of one transverse thread 2 of a pair of transverse threads conducted in parallel which is interwoven with a longitudinal thread 9 of the lower woven fabric 8. The structure of the upper woven fabric 7 is in that respect not adversely affected at the binding sites 10 between the two woven fabrics 7, 8, since the longitudinal thread 4 of the upper woven fabric 7 follows the course it normally follows on account of the fact that the course of the other transverse thread 3 has not been changed. Ag a result of this, there are no depressions on the paper side 5 at the binding si.te~ which would .resu:Lt in a noticeable mark.ing in the paper. It is al80 possible ko uti:l.ize a double-layer woven fabric a~ the lower woven .Eabric, .in lieu of the single-layer woven fabric which is shown in Figure 7.
Claims (6)
1. A double-layer fabric for the sheet forming section of a papermaking machine, comprising an upper layer of transverse threads and a lower layer of transverse threads and including a single system of longitudinal threads which are interwoven with both layers of transverse threads, wherein said transverse threads of said lower layer are woven in parallel in pairs wherein the transverse threads of each pair are always running adjacent to each other and are never separated by a longitudinal thread passing between them and with one transverse thread of the upper layer being positioned above each transverse thread pair in the lower layer.
2. A double-layer fabric according to claim 1, wherein one transverse thread of each transverse thread pair is a polyester-monofilament and the other transverse thread of said thread pair is a polyamide-monofilament.
3. A double-layer fabric according to claim 1, wherein the number of upper transverse threads is equal to the number of lower transverse threads.
4. A double-layer fabric according to claim 3, wherein the diameter of the lower transverse threads is about 30%
larger than the diameter of the upper transverse threads.
larger than the diameter of the upper transverse threads.
5. A double-layer fabric according to claim 1, wherein the number of upper transverse threads is half as large as that of said lower transverse threads, and said upper transverse threads and said lower transverse threads have about the same diameter.
6. A multi-layer fabric for the sheet forming section of a papermaking machine, comprising an upper woven fabric and at least one lower woven fabric connected therewith, wherein said upper woven fabric is a double-layer fabric comprising an upper layer of transverse threads, a lower layer of transverse threads and a single system of longitudinal threads which are interwoven wit both layers of transverse threads with said transverse threads of said lower layer being woven in parallel in pairs with the transverse threads of each pair always running adjacent to each other and never separated by a longitudinal thread passing between them and with one transverse thread of the upper layer being positioned above each transverse thread pair in the lower layer and wherein said upper woven fabric is connected to the lower woven fabric by means of one of the transverse threads of a plurality of said pairs of transverse threads of said upper woven fabric which are interwoven with a longitudinal thread of said lower woven fabric.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3801051.8 | 1988-01-15 | ||
| DE3801051A DE3801051A1 (en) | 1988-01-15 | 1988-01-15 | DOUBLE-DAY LOADING FOR THE SHEETING AREA OF A PAPER MACHINE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1312530C true CA1312530C (en) | 1993-01-12 |
Family
ID=6345363
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000588281A Expired - Fee Related CA1312530C (en) | 1988-01-15 | 1989-01-13 | Double-layer clothing for the sheet forming section of a papermaking machine |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4934414A (en) |
| EP (1) | EP0325167B1 (en) |
| JP (1) | JPH02133691A (en) |
| AT (1) | ATE72590T1 (en) |
| BR (1) | BR8806758A (en) |
| CA (1) | CA1312530C (en) |
| DE (2) | DE3801051A1 (en) |
| ES (1) | ES2029906T3 (en) |
| FI (1) | FI890169A (en) |
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| DE3923938A1 (en) * | 1989-07-19 | 1991-01-31 | Oberdorfer Fa F | FORMING FABRICS FOR THE WET SECTION OF A PAPER MACHINE |
| DE3938159A1 (en) * | 1989-11-16 | 1991-05-23 | Oberdorfer Fa F | COMPOSITE FABRICS FOR PAPER MACHINE BENCH |
| US5101866A (en) * | 1991-01-15 | 1992-04-07 | Niagara Lockport Industries Inc. | Double layer papermakers fabric having extra support yarns |
| DE4302031C1 (en) * | 1993-01-26 | 1993-12-16 | Heimbach Gmbh Thomas Josef | Fourdrinier for paper mfg. machine for large contact surface area - comprises oven plastics filaments with gp. in sub-gps. shrunk for longitudinal filaments side by side, for flexibility |
| US5421375A (en) * | 1994-02-28 | 1995-06-06 | Wangner Systems Corporation | Eight harness double layer forming fabric with uniform drainage |
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| US6896009B2 (en) * | 2003-03-19 | 2005-05-24 | Weavexx Corporation | Machine direction yarn stitched triple layer papermaker's forming fabrics |
| GB0317248D0 (en) * | 2003-07-24 | 2003-08-27 | Voith Fabrics Gmbh & Co Kg | Fabric |
| US7243687B2 (en) * | 2004-06-07 | 2007-07-17 | Weavexx Corporation | Papermaker's forming fabric with twice as many bottom MD yarns as top MD yarns |
| US7195040B2 (en) * | 2005-02-18 | 2007-03-27 | Weavexx Corporation | Papermaker's forming fabric with machine direction stitching yarns that form machine side knuckles |
| US8182195B2 (en) * | 2005-04-27 | 2012-05-22 | Allan J Mayhew | Protective pillow |
| JP2006322109A (en) * | 2005-05-19 | 2006-11-30 | Nippon Filcon Co Ltd | Industrial two-layered woven fabric |
| US20060278294A1 (en) * | 2005-06-08 | 2006-12-14 | Voith Fabrics Patent Gmbh | Hybrid warp exchange triple layer forming fabric |
| US7484538B2 (en) * | 2005-09-22 | 2009-02-03 | Weavexx Corporation | Papermaker's triple layer forming fabric with non-uniform top CMD floats |
| US7219701B2 (en) * | 2005-09-27 | 2007-05-22 | Weavexx Corporation | Papermaker's forming fabric with machine direction stitching yarns that form machine side knuckles |
| DE102005060301A1 (en) * | 2005-12-16 | 2007-06-21 | Voith Patent Gmbh | Paper machine clothing |
| DE102005060299A1 (en) * | 2005-12-16 | 2007-06-21 | Voith Patent Gmbh | papermaker |
| US7275566B2 (en) | 2006-02-27 | 2007-10-02 | Weavexx Corporation | Warped stitched papermaker's forming fabric with fewer effective top MD yarns than bottom MD yarns |
| DE102006016660C5 (en) * | 2006-04-08 | 2009-09-03 | Andreas Kufferath Gmbh & Co Kg | Upper side, in particular paper side, and paper machine screen |
| US7580229B2 (en) | 2006-04-27 | 2009-08-25 | Hitachi Global Storage Technologies Netherlands B.V. | Current-perpendicular-to-the-plane (CPP) magnetoresistive sensor with antiparallel-free layer structure and low current-induced noise |
| US8075857B2 (en) * | 2006-10-18 | 2011-12-13 | Ecolab Usa Inc. | Apparatus and method for making a peroxycarboxylic acid |
| DE102006061114A1 (en) * | 2006-12-22 | 2008-06-26 | Voith Patent Gmbh | Fabric tape for a machine for producing web material and method for producing such a fabric tape |
| US7487805B2 (en) * | 2007-01-31 | 2009-02-10 | Weavexx Corporation | Papermaker's forming fabric with cross-direction yarn stitching and ratio of top machined direction yarns to bottom machine direction yarns of less than 1 |
| US7624766B2 (en) | 2007-03-16 | 2009-12-01 | Weavexx Corporation | Warped stitched papermaker's forming fabric |
| US20090183795A1 (en) * | 2008-01-23 | 2009-07-23 | Kevin John Ward | Multi-Layer Papermaker's Forming Fabric With Long Machine Side MD Floats |
| US7766053B2 (en) * | 2008-10-31 | 2010-08-03 | Weavexx Corporation | Multi-layer papermaker's forming fabric with alternating paired and single top CMD yarns |
| US8251103B2 (en) * | 2009-11-04 | 2012-08-28 | Weavexx Corporation | Papermaker's forming fabric with engineered drainage channels |
| JP6243193B2 (en) * | 2013-11-01 | 2017-12-06 | 日本フエルト株式会社 | Felt for papermaking |
| CN104195716B (en) * | 2014-08-29 | 2016-05-04 | 海安县君权滤布有限公司 | A kind of belt-type filter cloth that is applied to belt vacuum filter |
| KR102606679B1 (en) * | 2023-10-04 | 2023-11-30 | 주식회사 한스갤러리 | Eco-friendly fabric for blankets and its manufacturing method |
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|---|---|---|---|---|
| GB501204A (en) * | 1937-08-23 | 1939-02-23 | Thomas Hindle | Improvements in paper makers dryer felts |
| US4344464A (en) * | 1980-07-11 | 1982-08-17 | Huyck Corporation | Endless forming fabrics with bi-crimp characteristics |
| DE3146385C2 (en) * | 1981-11-23 | 1985-10-31 | Hermann Wangner Gmbh & Co Kg, 7410 Reutlingen | Double-layer fabric as a covering for paper machines |
| US4423755A (en) * | 1982-01-22 | 1984-01-03 | Huyck Corporation | Papermakers' fabric |
| SE435739B (en) * | 1983-02-23 | 1984-10-15 | Nordiskafilt Ab | DOUBLE TEXTILE TYPE FORMATION WIRES |
| DE3329739C1 (en) * | 1983-08-17 | 1985-01-10 | Hermann Wangner Gmbh & Co Kg, 7410 Reutlingen | Multi-layer covering for paper machines |
| DE3445367C1 (en) * | 1984-12-12 | 1986-08-14 | F. Oberdorfer, 7920 Heidenheim | Composite fabric as a paper machine screen |
| GB8531540D0 (en) * | 1985-12-21 | 1986-02-05 | Scapa Porritt Ltd | Papermachine &c fabrics |
| DE3615304A1 (en) * | 1986-05-06 | 1987-11-12 | Wangner Gmbh Co Kg Hermann | COVER FOR THE SHEET FORMING PART OF A PAPER MACHINE |
| EP0224276B1 (en) * | 1986-05-06 | 1990-03-28 | Hermann Wangner GmbH & Co. KG | Screen cloth for the wet end of a paper-making machine |
| DE3635000A1 (en) * | 1986-10-14 | 1988-04-21 | Oberdorfer Fa F | DOUBLE-LAYER PAPER MACHINE SCREEN WITH COARSE-TEXTURED RUNNING SIDE AND FINE-STRUCTURED PAPER SIDE |
| DE3635632A1 (en) * | 1986-10-20 | 1988-04-21 | Wangner Gmbh Co Kg Hermann | COVER FOR THE SHEET FORMING PART OF A PAPER MACHINE |
-
1988
- 1988-01-15 DE DE3801051A patent/DE3801051A1/en not_active Withdrawn
- 1988-12-16 BR BR888806758A patent/BR8806758A/en not_active Application Discontinuation
-
1989
- 1989-01-13 DE DE8989100521T patent/DE58900822D1/en not_active Expired - Lifetime
- 1989-01-13 CA CA000588281A patent/CA1312530C/en not_active Expired - Fee Related
- 1989-01-13 AT AT89100521T patent/ATE72590T1/en active
- 1989-01-13 EP EP89100521A patent/EP0325167B1/en not_active Expired - Lifetime
- 1989-01-13 ES ES198989100521T patent/ES2029906T3/en not_active Expired - Lifetime
- 1989-01-13 US US07/296,731 patent/US4934414A/en not_active Expired - Fee Related
- 1989-01-13 FI FI890169A patent/FI890169A/en not_active Application Discontinuation
- 1989-01-17 JP JP1009628A patent/JPH02133691A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| US4934414A (en) | 1990-06-19 |
| DE58900822D1 (en) | 1992-03-26 |
| EP0325167A1 (en) | 1989-07-26 |
| EP0325167B1 (en) | 1992-02-12 |
| FI890169A (en) | 1989-07-16 |
| ATE72590T1 (en) | 1992-02-15 |
| JPH02133691A (en) | 1990-05-22 |
| BR8806758A (en) | 1989-10-17 |
| DE3801051A1 (en) | 1989-07-27 |
| ES2029906T3 (en) | 1992-10-01 |
| FI890169A0 (en) | 1989-01-13 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |