CA1269025A - Woven multilayer papermaking fabric having increased stability and permeability and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A papermaking fabric and method therefor is dis-closed which may be used as a support fabric or a carrier fabric for paper material on a papermaking machine. The fabric, designated generally as (A) includes a first layer (B) of warp yarns extending in a machine direction. A
second layer of warp yarns is included in the fabric ver-tically spaced from the first layer. The warp yarn of the first and second layer form stacked pairs which reinforce the fabric in a machine direction to enhance its stability.
At the same time, the stacked pairs may be spaced apart in a crossmachine direction sufficiently to provide a desired degree of openness and fabric permeability. Fabric openness in the range of thirty percent or more of the total fabric area can be had in accordance with the fabric of the present invention without sacrificing the structural stability. A
single weft system is interwoven with the first and second warp layers (B and C) in a balanced weave pattern that maintains the warp yarns of the respective layers stacked.
The balanced weave pattern of the weft resists lateral shifting of the stacked warp yarns to prevent them from becoming side-by-side. In a preferred embodiment, the fabric is utilized as a base fabric for a resinous layer which supports the paper and has an embossed surface which makes a corresponding pattern in the paper, such as in towel grade paper.

Description

I~O~N IIUI.TILA~I~R P-~E'KRIIAI~INU F~BRIC ~INa INCRK~SKD STABILIT~ AND ~R~ABILITY ~ND ~KT~OD

The lnventlon relates to woven permeable rabrlc whlch supports paper stock durlng the manuracture Or paper on a papermaklng machlne. In partlcular, the lnventlon 18 dlrected to a multilayer rabrlc havlng increased structural stablllty ln a machlne dlrectlon ln whlch the fabrlc travels on the papermaklng machlne whlle stlll afrordlng a hlgh degree Or permeablllty whlch racllltates drylng Or the paper.
The ~abrlc Or the lnventlon has appllcatlon as a support fabrlc ror dlrectly supportlng a paper web on a papermaklng machlne. The rabrlc has further appllcatlon as a carrler rabrlc for carrylng a layer Or materlal whlch contact~ the paper lnstead Or the paper contactlng the rabrlc dlrectly. A
carrler rabrlc 18 typlcally utlllzed ln the manufacture Or embossed paper products as a base fabrlc. In such an appll-catlon, a layer Or materlal 18 embedded ln or carrled on the base rabrlc whlch 18 embossed to lmprlnt a deslred pattern on the paper sheet contacted by the embossed layer. The load ln the machlne dlrectlon 18 carrled malnly by the base fabrlc and not the embossed layer. For drylng purposes, the carrler rabrlc must have a hlgh degree Or openness and alr permeabll-lty 80 that surrlclent alr 18 dellvered through the ba~e rabrlc and the embossed layer, whlch 18 also permeable for , '~
- --drylng. C~ier fabrics must have surrlclent load bearln~ ca-pablllty rOr bearing the losds ln the machlne dlrectlon whlch are the most severe.
Heretofore, slngle layer rabrlcs have been utlllzed as carrler and support fabrlcs whlch have one warp system and one weft system. In order ror a slngle layer fabric to have an open area above thlrty percent the machlne dlrectlon yarns become spread apart to such an extent that rabrlc sta-blllty ln the machlne dlrectlon becomes too low. In order to achleve deslred pro~ected open areas above thlrty percent, a slngle layer rabrlc must be made Or thln warp and weft yarns ~e.g. 0.10 to 0.20 mm dlameter). The slngle layer rabrlcs have utlllzed low warp and wert counts per centl-meter, rOr example, 20 ends or plcks per centlmeter. Under these condltlons, the slngle layer fabrlc tends to stretch unacceptably whlle travellng ln the machlne dlrectlon. Ir ad-dltlonal machlne dlrectlon yarns are utlllzed ln order to strengthen the fabrlc, the open area Or the fabrlc 18 reduced resultlng ln the permeablllty Or the fabrlc belng below de-slred levels.
A slngle layer rabrlc 18 dlsclosed ln Unlted States Patent No. 4,2c1,688 havlng a plurallty Or domlnatlng floats on opposlng races Or the rabrlc. Every alternatlng wert has a long knuckle to one race, and every other weft has a long knu¢kle to the opposlte face. The pro~ected open area Or the : . ' ' '. ~ -.

rabrlC i9 limlted.
Unlted States Patent No. 4,314,589 dlscloses a double layer fabrlc havlng two weft layers and a slngle wArp layer. The warps lle next to each other almost wlthout any spaclng between adJacent warps provldlng llttle or no pro-~ected open area. Unlted States Patent No. 4,359,069 dls-closes a double layer rabrlc hsvlng a sln~le warp yarn system extendlng ln the machlne dlrectlon and a double layer weft yarn system ln the cross-machlne dlrectlon. The yarns of the slngle layer warp system are spaced apart from one another wlth a yarn denslty of 0.50 to 0.65. Thls warp denslty ln the machine dlrectlon cannot be lowered, as otherwlse the fabrlc stablllty would drop too much. Thls provldes a pro-Jected open area Or only 13 to 25 percent Or the total fabrlc area. The warp yarns ln the machlne dlrectlon have to bear the load when the fabrlc runs on the papermaklng machlne.
Patent 4,359,069 teaches recesslng the sln61e layer warp sys-tem whlch extends ln the machlne directlon between the two layers of the weft yarn 80 the warp yarns are removed from wear, lt is thought that thls wlll enable the warp yarns to better wlthstand the longltudlnal stresses and provlde a longer fabrlc llre. Unlted States Patent No. 4,344,465 dls-closes a double layer formlng fabrlc havlng two functlon sldes. However, there 18 only one layer of load bearlng ma-chlne dlrectlon yarns. There are machlne dlrectlon yarns on 3~5 he psper su~port slde Or the rabrlo which do not bear load~.
Internatlonal Publloatlon No. ~PCT) W0 80/01086, V. S. Patent No. 4,356,225, and European Patent Appllcatlon No. EP 0 123 431 A2, descrlbe multllayer wet felt deslgns.
The technology for weavln~ multilayered rabrlcs ror relt bases was begun prlmarily to lncrease vold volume under pres-sure. These press felt base rabrlcs are preferably woven endless. Due to the ~ulte dlfferent obJectlves ln desl~nlng these rabrlcs, none Or these descrlbed deslgns show a struc-turally stable weave pattern and a pro~ected open area ln the range Or thlrty percent or more as ln the case of the present lnvention.
European Patent Appllcatlon No. EP 0 135 231 Al dlscloses a slngle layer flat ¢arrler fabrlc used as a carrier Or an embossed layer which lmprlnts paper.
Thus, lt can be seen that the prlor slngle layer and multllayer rabrlcs are llmlted ln thelr capaclty to pro-vlde both hlgh degrees Or proJected open area and structural stablllty ln the machlne dlreotlon.
A¢cordingly, an lmportant obJect Or the present lnventlon 18 to provlde a method and rabrlc wlth lmproved fabrlc stablllty ln the machlne dlrectlon whlle malntalnlng a proJected open fabrlc area whlch racllltates use Or the rab-rlc as a support or carrler fabrlc on papermaklng machlnes.
Stlll another lmportant obJect Or the present ln-3(3~5 ver.tlon 18 to provlde a woven multllayered papermaklng rabrlchavlng an lncrea~ed number Or load bearlng warp yarns extend-lng ln a machlne dlrectlon whlle malntalnlng a ~ur~lclent dlstance between adJacent warp yarns to allow rOr a proJected open area Or at least thlrty percent Or the total fabrlc area.
Stlll another important obJect Or the present ln-ventlon 18 to provlde a hlghly permeable woven rabrlc ror use on paper machlnes and the llke and method therefor whereln the load bearlng machlne dlrectlon yarns are doubled ln thelr denslty wlthout a decrease ln the proJected open area Or the fabrlc .
Yet another lmportant obJect Or the present inven-tlon 18 to to provlde a woven multllayered papermaklng fabrlc havln~ a ~lrst warp layer and a second warp layer, both of whlch contaln load bearlng warp yarns extendlng ln a machlne dlrectlon, whlch are lnterwoven wlth a slngle weft yarn whlch malntalns the warp yarns Or the rlrst and second layers ln stacked palrs whlch may be spaced apart sufrlclently to pro-vlde a deslred open area ln the rabrlc.

A hlghly permeable woven multllayer pspermaklng rabrlc havlng lncreased fabrlc stablllty ln a machlne dlrectlon and method therefor 18 dlsclosed. The fabrlc lncludes a paper support slde and a roller contact slde racllltatlng travel as an endless belt ln the mschlne dlrectlon. The rabrlc comprlses a rlrst warp layer Or rlrst load bearlng warp yarns extendlng ln the machlne dlrectlon on the paper support slde Or the fabrlc, and a second layerof second load bearlng warp yarns extendlng ln the machlne dlrectlon on the roller contact slde Or the fabric. Stacked warp yarn palrs are derlned by respectlve ones Or the rlrst and second warp yarns Or the rlrst and second warp layers arranged ln a superpo~ed posltlon one over the other. The stacked warp yarn palrs are spaced apart next ad~acent one another ln a cross-machlne dlrectlon ln the rabrlc to provlde a deslred rabrlc open area. A warp balanclng weft yarn 18 lnterwoven wlth the rlrst and second wflrp layers to blnd the rlrst and second warp yarns ln the stacked palrs. The warp balanclng weft yarn 18 lnterwoven ln a weave pattern whlch malntains the warp yarns stacked upon one another and ln general vertical allgnment ln the weave pattern. A fabrlc havlng lncreased fabrlc stablllty ln the machlne dlrectlon 18 provlded yet havlng a hlgh degree Or openness and permeablll-ty ln a range greater than thlrty percent Or the total fabrlc area.

The constructlon deslgned to carry out the lnven-tlon wlll herelnafter be descrlbed, together wlth other reatures thereor.

~Z~9025 The lnventlon wlll be more readlly understood rrom a readlng Or the followlng speclrlcatlon and by rererence to the accompanyln~ drawlngs rormlng a part thereof, whereln an example Or the inventlon 18 shown and whereln:
Figure l 18 a perspectlve vlew lllustratlng a par-tlal dryer sectlon Or a conventlonal papermaklng machlne utl-llzln~ a woven multllayer rabrlc and method ln accordance wlth the present lnventlon;
Flgure 2 18 an extended sectlonal vlew as may be taken along llne 2-2 Or F16ure 4;
Flgure 3 18 an elevatlon lllustratlng the woven multllayer rabrlc and metbod Or the present lnventlon applled as a carrler rabrlc;
Flgure 3A 18 a top plan vlew Or the fabrlc Or Flgure 3.
Flgure 4 18 a plan vlew lllustratlng woven multl-layer papermaklng rabrlc and method ln accordance wlth the present lnventlon;
Flgure 5 18 an end sectlonal vlew or the rabrlc Or Fl~ure 4;
F18uro 6 18 a soctlonal vlow taken along llne 6-6 Or Flguro 4;
Flgure 7 18 a sectlonal vlew taken along llne 7-7 Or Flgure 4; and Fl~ure 8 18 a sectlonal vlew taken along llne 8-8 :' ~ ' .

, . ' ,, ', ' ' ' , ' ` ~ ' ` ' - ~

0~5 Or Flgure 4.

The lnventlon relates to a woven multllayer rabrlc and method for a papermaking rabrlc and the like. In partlcu-lar, the fabrlc has appllcatlon to the dryer sectlon Or a papermaklng machlne whereln the Pabrlc may be used as a sup-port fabrlc or a carrler fabrlc. Slnce the detalls Or paper-maklng machlnes are well known ln the art, only so much Or a papermakln6 machlne as 18 necessary to an understandln6 Or the lnventlon wlll be lllustrated.
Accordlngly, Flgure 1 18 a slmpllrled lllustratlon Or a portlon Or a dryer sectlon Or a papermaklng machine whereln a contlnuous sheet llke web W Or paper stock materlal 18 travellng from left to rlght. In practice, several dryer sections may be utlllzed ln successlon to dry the paper ln stages. Numerous dlrrerent types Or dryers may be utlllzed ln a dryer sectlon Or a conventlonal papermaklng machlne, and the partlcular dryer lllustrated ln Flgure l 18 ror purposes Or explanation only. The dryer section includes an upper and lower array Or horlzontally dlsposed heated dryer cyllnders whlch may be elther or a perforated or lmperforated construc-tlon. The upper array Or heated cyllnders lncludes cyllnders 10, 12, and 14. The lower array includes cylinders 16 and 18. The contlnuous web W Or paper 18 recelved from a press sectlon and passed ln a serpentlne manner about the dryer 30;~'~

cyllnders a~ lllustrated. Water and other ~lulds wltr.ln the pa~er web are evaporated due to the paper contsctlng the heated cyllnder~. The paper web W 18 gulded through the dryer sectlon and held ln contact wlth the heated cyllnders by means Or an upper permeable dryer fabrlc 22 and a lower permeable dryer rabrlc 24. Dryer rabrlcs 24 and 22 are ~den-tlcal ln thelr constructlon, and are constructed in accor-dance wlth the rabrlc and method Or the present lnventlon as wlll be more rully explalned hereafter. Slnce the rabrlcs are ldentlcal, descrlptlon Or the lnventlon wlll be made by reference to fabrlc 22 only whlch herelnafter 18 referred to as fabrlc A. By contactlng the paper web W, the dryer fab-rics press and malntaln the web ln lntlmate heat transrer relatlonshlp wlth the dryer cyllnders whereby the cyllnders remove water or other rlulds from the web. The drylng pro-cess 18 outwardly rrom the heated cyllnders through the paper web and throu~h the dryer rabrlc. Thus surrlclent permea-bility of the fabric must be had in order to facilitate drying of the fabric.
The rabrlc 18 ln the form Or endless belts whlch travel over machlne belt rollers 26. The rabrlc travels ln lts endless belt configuratlon ln a machlne dlrectlon as shown ln the dlrectlon Or arrow 28. Durlng the repeated travel Or the fabrlc over the belt rollers ln the machlne dlrectlon, the fabrlc comes under conslderable stress ln the machlne directlon due to the motlon of the endless travel and the heat transrer rrom the heated cyllnders. If the fabrlc should stretch out of shape, its use as a paper support or carrler fabrlc becomes dlmlnlshed to the polnt of useless-ness.
Whlle the above descrlbes the use of the fabrl¢ ln a conventlonal dryer section Or a papermaklng machlne, the rabrlc has partlcular advantages ror use ln through alr drylng systems for tlssue and towel grades of paper. In thls appllcatlon, the fabrlc 18 used as a carrler rabrlc wlth an embossed layer embedded ln the fabrlc whlch lmprlnts the paper web. The use of a carrler fabrlc and an embossed layer ln a papermaklng machlne wlth a through alr dryer ls lllus-trated ln European Patent Appllcatlon, Publlcatlon No. 0 135 231, flled on August 16, 1984.
As a base fabrlc, fabrlc permeabllltles ln the range Or lO00 to 1200 crm can be had ln accordance wlth the lnstant lnvention wlth the lncreased stabillty ln the machlne dlrectlon provlded by the double warp system, and 30 percent or more open area. The base fabrlc carrylng a reslnous em-bossed layer as shown ln Flgures 3 and 3A has a lower per-meablllty but 18 stlll sufflclent for drylng purposes. Thls decrease of alr permeablllty between the base fabrlc wlthout the reslnous layer and the base fabrlc carrying t~e reslnous la~er depends on the slze, shape, and pattern of the holes ln o25 the reslnous layer.
Referrlng now ln more detall to the drawlngs, Flgure 4 19 a top plan vlew from a paper support slde desl6-nated generally as 29 Or a ~abrlc lllustratlng woven multl-layer rabrlc A constructed ln acaordance with the pre~ent lnventlon. The machine dlrectlon 18 lndlcated by the arrow 28 and the cross-machlne dlrectlon 18 lllustrated by arrow 30.
It can thus be seen that a rlrst warp layer B conslstlng Or flrst wàrp yarns 32, 34, 36 and 38, repeatedly numbered across the rabrlc as lllustrated ln Flgures 4-8, lles on the paper support slde Or the fabrlc A. The warp yarns extend ln the machlne dlrectlon 28. The warp yarns are woven ln a rour-shed repeat wlth a slngle weft system whlch conslsts o~
a weft yarn 40. The weft 40 18 woven ln rour plcks 40a, 40b, 40c, and 40d whlch repeats ltselr.
As can best be seen ln Figure 4-8 and 2~ there 18 a se¢ond warp layer C whlch conslsts Or a number Or second warp yarns 42, 44, 46, and 4~, repeatedly numbered across the rabrlc, extendlng ln the machlne dlrectlon. The second warp layer 18 the roller contact slde deslgnated generally as 49 Or the fabrlc whlch contacts the belt rollers 26 when travel-lng ln the machlne dlrectlon ln an endless manner.
As can best be seen ln Flgures 5 through 8, the warp yarns Or the rlrst warp layer B and the warp yarns Or the second warp layer C are stacked on top Or each other.

The warp yarns 32 and 42 derlne a rlrst staoked palr 52. The war~ yarn~ 34 and 44 derlne a second stacked palr 54. The warp yarns 36 and 46 derlne a thlrd stacked palr 56. The warp yarns 38 and 48 dePlne a rourth stacked palr 58. The warp balanclng wert yarn 40 lnterweaves wlth the warp yarns Or the respectlve stacked palrs ln such a manner that a balanced weave 18 provlded whereln the warp yarns, 32 and 42, ror example, are malntalned ln thelr atacked conrlguratlon.
The tendency Or the warp yarns to shlft laterally ln the warp yarn palrs 18 prevented by the lllustrated balanced weave pattern Or the wert yarn 40.
By notlng the over, between, under, between repeat pattern of the alternatlng plcks (Flgures 5 - 8) oP the warp balanclng wert system, the blndlng Or the warp yarns lnto vertlcally stacked palrs and balanclng errect or the weave pattern can readlly be seen. The balanced weave pattern malntalns the stacked conrlguratlon Or the warps. The cro~s-over polnt 59 Or the wert 18 staggered ln the wert dlrectlon across the warps as can best be seen ln Flgure 4. A
varlatlon Or the above balanced weave pattern can be achleved by lnterchanglng the plck 40c shown ln Flgure 7 wlth the plck 40d shown ln Figure 8. Thls results ln a broken, stag8ered pattern Or the cross-over polnts Or the weave ln the wert dlrectlon. In thls pattern, the rlrst two cross-over polnts ~: are ln a stralght dlagonal. The thlrd cross-over polnt 18 : ~ 12 ::

`

- , ' ~ ' : ' :
.
' . :. , 3V'~5 shlrted over a thlrd warp to a rourth warp and then the cross-over polnt 19 shlrted baok ln a dlagonal to the thlr warp. Thls weave pattern also malntalns the warp yarns ln a stacked palr ln a sultably stacked conflguratlon. However, ln thls weave pattern, the two warp yarns pass together be-tween two adJacent plcks. In the rlrst descrlbed balanced weave pattern, there are no two plcks between whlch the warp yarns slmultaneously pass, whlch provldes a sllghtly better balanced weave pattern.
The balanced weave pattern Or the wert yarn 40 conslsts Or a rour-shed repeat pattern whereln a rlrst plck 40a Or the wert yarn 40 passes over a rlrst stacked palr 52, between the warp yarns Or the second stacked palr 54, under the yarns Or the thlrd stacked palr 56, and between the yarns Or the rourth stacked palr 58. In the broadest sense, the pattern passes over and under every other palr Or stacked warp yarns whlle passlng between the yarns Or an lntermedlate stacked palr dlsposed between every other stacked palr. By passlng between the yarns arter passlng over and under the prevlous palr Or stacked yarns, the tendency Or the warp yarns to shlrt laterally beslde each other 18 substantially reduced thus malntalnlng the warp yarns on top Or each other.
Flgure 6 shows the second plck Or the weft yarn 40 at 40b.
Flgure 7 lllustrates the thlrd plck Or the wert yarn at 40c, and Flgure 8 the fourth plck Or the weft yarn at 40d.

`. ~.
' .

~ ',~;!3()'~5 ~ eferrlng agaln to Flgure 4, lt can be seen that the stacked pairs Or warp yarns are spaced conslderably ln the cro~s-machlne dlrection 30 80 that open area~ 60 are provlded whlch provlde a pro~ected open area of thlrty per-cent or more Or the total fabrlc area. Slnce the load bear-lng warp yarn~ 32 through 38 and 42 through 48 are stacked underneath each other, the errectlve denslty Or load bearlng warp yarns 18 doubled without decreaslng the open area Or the rabrlc. Increased structural stablllty 18 provlded in the machlne dlrection wlthout decrease ln the permeablllty or open area Or the fabrlc. Thls 18 partlcularly advantageous when the fabrlc 18 used as a carrler fabrlc for another layer 62 as can best be seen ln Flgure 3. The layer 62 ls typlcal-ly a materlal such as resln havlng an embossed outer surrace 64 whlch lmprlnts a pattern upon the paper web W supported thereon. The layer 62 18 perforated at 66 to allow rOr the flow or molsture and alr therethrough. The erfectlve permea-blllty Or the layer 62 and drylng Or the paper W thereon wlll be surrlclently provlded only lr the open area and permea-blllty Or the carrler rabrlc A 18 surrlclent. Not only 18 the open area Or the carrler fabrlc constructed ln accordance wlth the method Or the present lnventlon adequate, but the structural stablllty Or the fabrlc Or the lnstant lnventlon 18 partlcularly advanta6eous for carrying the layer 62 due to the extra loads lmparted thereon ln the machlne dlrectlon.

Varlous comblnstions Or materlals and yarn dlame-ters and shapes Or yarns may be utllized ln the rabrlc descrlbed hereln. For example, the warp systems B and C may be of one dlameter, and the wert sy~tem 40 may be Or a larger diameter. This provides a stirrer weft yarn which will place more crlmp in the warp yarns. Thls results ln a declded advantage when the ends Or the fabric are Jolned together ln an endless manner at a geam. The crimped warp yarns are more easlly lnterwoven together ln the endless fabrlc and lnter-locked at the seam. Other varlatlons may lnclude the warp system B and the weft system 40 belng ldentlcal, and the warp system C being dlrrerent either ln material, diameterJ or shape. Llkewlse,the wsrp system C and weft system 40 may be ldentlcal, wlth the warp system B belng dirrerent. Further-more, each Or the warp system B, warp system C, and wert 40 can be dlrrerent.
A prererred materlal for the construction Or the rabric 18 polyester. However, polyamld, and high heat reslstant materlals such as Kevlar*or Nomex*brands, as well as other materlals whlch are well known ln a use rOr paper rabrlc manufacturlng, may be utlllzed. At present, round, oval, and rectangular shapes may be used ror the warp yarns.
The weft yarn may be provlded ln a round shape. It may be also deslrable at a later date to utlllze an oval or rectan-gular shape in the wert yarn.
* Trade Mark ~i9(~

A prererred range Or yarn dlameters 1B irom O.lO to 0.20 mm. DependIng on the appllcatlon, larger dlameters Or rlbers may also be utlll~ed. The dlameter, shape, and ma-terlal wlll be determlned by the partloular sppllcatlon belng made of the rabrlc.
In accordance wlth the method or the present lnven-tlon, a method Or weavlng a multllayered papermaklng fabrlc A
havlng a weave pattern whlch provldes lncreased rabrlc sta-billty ln a machlne dlrectlon and hlgh rluld permeablllty ln-cludes the step of weavlng the rlrst warp layer B havlng rlrst load bearlng warp yarns extendlng ln the machlne dlrec-tlon snd weavlng the second layer C havlng second load bear-lng warp yarns extendlng ln the machlne dlrectlon, thu~
doubllng the number Or load bearlng warp yarns. Respectlve ones Or the rlrst and second warp yarns Or sald rlrst and second warp layers are arranged ln the weave pattern to derlne stacked palrs Or warp yarns. A warp balanclng weft yarn 18 woven ln a cross-machlne dlrectlon wlth the rlrst and second load bearlng warp yarns to balance and malntaln the warp yarns ln the stacked palrs. By spaclng the stacked palrs Or warp yarns ln the cross-machlne dlrectlon, a deslred rabrlc permeablllty can be provlded wlthout sacrlrlclng the lncreased rabrlc stablllty in the machine di-rectlon. It has been round qulte advantageous that lr thewert yarn 40 from a slngle weft system 18 woven ln a rour-''.~ ' `

~ ~t~

shed repeat pattern, that the stacked conrlgurntlon of thewarp yarns can be provlded. In the rour-shed repeat pattern, the weft yarn passes over both o~ the yarns ln a rlrst ~tack-ed palr 52, between the warp yarns Or a ~econd stacked palr 54, under both of the warp yarns ln a thlrd stacked pair 56, and between the warp yarns Or a fourth stacked palr 58. Thls re-peat pattern has been round to errectlvely reslst the tenden-cy of the stacked warp yarns to shlrt relatlve to each other ln a lateral dlrectlon, thus malntalnlng them ln thelr vertl-cal orlentatlon on top Or each other. In practlce, the stacked palrs Or warp yarns are spaced ln the cross-machlne dlrectlon to provlde a pro~ected rabrlc open area Or at least thlrty percent of the tokal fabrlc area.
Whlle the term yarn has been used throughout the appllcatlon, lt 18 to be understood that the term yarn encom-passes a monorllament element as well as a multlfilament element. The same 18 true when the term yarn 18 used ln the plural sense.
Whlle a preferred embodlment of the lnventlon has been descrlbed uslng speclrlc terms, such descrlptlon 18 for lllustratlve purposes only, and lt 18 to be understood that changes and varlatlons may be made wlthout departlng rrom the splrlt or scope Or the followlng clalms.

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Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A highly permeable woven multilayer paper-making fabric having increased fabric stability in a machine direction, said fabric being of the type which includes a paper support side and a roller contact side facilitating travel as an endless belt in said machine direction wherein said woven fabric comprises:
a first warp layer of first load bearing warp yarns extending in said machine direction on said paper sup-port side of said fabric;
a second layer of second load bearing warp yarns extending in said machine direction on said roller con-tact side of said fabric;
stacked warp yarn pairs defined by respective ones of said first and second warp yarns of said first and second warp layers arranged in a generally vertically stacked superposed position one over the other;
said stacked warp yarn pairs being spaced apart next adjacent one another in a cross-machine direction in said fabric to provide a desired fabric open area;
a warp balancing weft yarn interwoven with said first and second warp layers to bind said respective ones of said first and second warp yarns in said stacked pairs; and said warp balancing weft yarn interwoven in a warp balancing weave pattern with said stacked pairs of warp yarns which maintain said warp yarns stacked upon one another and in general vertical alignment in said weave pattern;
whereby a fabric having increased fabric sta-bility in the machine direction is provided yet having a high degree of openness and permeability.

2. The fabric of claim 1 wherein said stacked warp yarn pairs are spaced in said cross machine direction and interwoven with said weft yarn to provide a projected open fabric area of thirty percent or more of the total fab-ric area.

3. The fabric of claim 1 wherein said first warp yarns of said first warp layer repeatedly pass over one and under three of said picks of said weft yarn in said warp balancing weave pattern.

4. The fabric of claim 3 wherein said second warp yarns of said second warp layer repeatedly pass over two, under one, and over one of corresponding ones of said picks of said weft yarn in said warp balancing weave pattern.

5. The fabric of claim 1 wherein said warp balancing weft yarn is woven in a four-shed repeat pattern wherein said weft yarn passes over both said warp yarns in a first stacked pair, between the warp yarns of a second stack-ed pair, under the warp yarns of a third stacked pair, and between the stacked warp yarns of a fourth stacked pair.

6. The fabric of claim 5 wherein said warp bal-ancing weft yarn is displaced by one stacked pair of warp yarns in the cross machine direction on each repeat of said weft yarn pattern.

7. In a fluid permeable woven multilayer paper-making fabric having a paper support side and a roller con-tact side of the type which includes a single layer yarn system with yarns extending in a first direction of said fabric and a multiple layer yarn system with yarns extending in a second direction normal to said first direction, wherein said multiple layer yarn system includes a first warp layer consisting of a number of first: load bearing warp yarns ex-tending in said second direction which is in a machine direc-tion in which said fabric travels on a papermaking machine;
and a second warp layer consisting of a number of second load bearing warp yarns extending in said machine direction on said roller contact side of said fabric; said warp yarns of said first and second warp layers being arranged one on top of the other in a generally vertically stacked superposed configuration to define pairs of stacked load bearing warp yarns extending in said machine direction facilitating increased fabric stability in said machine direction; said single layer yarn system consisting of a warp balancing weft yarn woven in a cross-machine direction in a balancing weave pattern which balances said stacked pairs to maintain said warp yarns one on top of the other generally without relative lateral shifting; and adjacent ones of said stacked pairs of warp yarns being spaced apart in a cross-machine direction to provide a desired degree fabric open area and permeability.

8. The fabric of claim 7 wherein said first load bearing warp yarns in said first layer are on said paper sup-port side of said fabric: and said second warp yarns of said second warp layer on said roller contact side of said fabric.

9. The fabric of claim 7 wherein said stacked pairs of warp yarns in said first and second warp layers are spaced in said cross-machine direction to provide a fabric having a projected open area of thirty percent or more of the total fabric area.

10. The fabric of claim 7 wherein said weft yarn is woven in a four-shed repeat pattern wherein said weft yarn passes over both said warp yarns in a first stacked pair, be-tween said warp yarns in a second stacked pair, under both said warp yarns in a third stacked pair, and between said warp yarns in a fourth stacked pair.

11. A method of weaving a multilayered papermaking fabric having a weave pattern which provides increased fabric stability in a machine direction and high fluid permeability comprising:
weaving a first warp layer having first load bearing warp yarns extending in said machine direction;
weaving a second warp layer having second load bearing warp yarns extending in said machine direction;
weaving a weft yarn in the cross-machine direction with said warp yarns in said first and second layers;
weaving respective ones of said first and second warp yarns of said first and second warp layers on top of each other to define stacked pairs of warp yarns in said weave pattern;

weaving weft yarn in a cross-machine direction with said first and second load bearing warp yarns in said first and second layers to balance and maintain said warp yarns in said stacked pairs; and spacing said stacked pairs of warp yarns in said cross-machine direction to provide a high fabric perme-ability while providing said increased fabric stability in said machine direction.

12. The method of claim 11 including weaving said weft yarn in a four-shed repeat pattern wherein said weft yarn passes over both of said warp yarns in a first stacked pair, between said warp yarns of a second stacked pair, under both of said warp yarns of a third stacked pair, and between said warp yarns of a fourth stacked pair.

13. The method of claim 11 wherein said stacked pairs of warp yarns are spaced in said cross-machine direc-tion to provide a projected fabric open area of thirty per-cent or more of the total fabric area.

14. The method of claim 11 wherein one of said first warp yarns in one of said stacked pairs is woven in a repeat pattern wherein said first warp yarn passes under one pick of said weft yarn and over the next consecutive three picks of said weft yarn, and the second warp yarn in said stacked pair correspondingly passes under two picks of said weft yarn, over one pick of said weft yarn, and under one pick of said weft yarn.

15. A method of weaving a papermaking fabric to provide a fabric having increased fabric stability in a ma-chine direction while having a substantial open area to pro-vide a highly permeable fabric comprising weaving a plurality of warp layers in the machine direction consisting of load bearing warp yarns stacked on top of each other in said fab-ric; weaving a warp balancing weft yarn with said warp yarns in said warp layers in a balanced weave pattern to prevent shifting of said stacked warp yarns and define stacked pairs of said warp yarns; and spacing said stacked warp yarns apart sufficiently in a cross-machine direction to provide a projected open area generally greater than thirty percent of the total fabric area.

16. The method of claim 15 including weaving a first warp layer consisting of first load warp yarns extend-ing in said machine direction on a paper support side of said fabric and weaving a second warp layer consisting of second load bearing warp yarns extending in said machine direction on a roller contact side of said fabric.

17. The method of claim 16 including weaving said first warp yarns in a stacked pair woven in a repeat pattern wherein said first warp yarn passes under one pick of said weft yarn, and over the next three consecutive picks of said weft yarn.

18. The method of claim 17 wherein said second warp yarn of said stacked pair is woven in said repeat pat-tern with said first warp yarn wherein said second warp yarn passes correspondingly under two picks and then over and under the next consecutive two picks of said weft yarn.

19. The method of claim 16 including weaving said weft yarn in a four-shed repeat pattern which includes pass-ing said weft yarn over both warp yarns of a first stacked warp yarn pair, passing said weft yarn between said warp yarns of a second stacked warp yarn pair, passing said weft yarn under both warp yarns of a third stacked warp yarn pair, and passing said weft yarn between said warp yarns of a fourth stacked warp yarn pair.

20. The method of claim 16 including weaving said first warp yarns in said first warp layer repeatedly under one pick of said weft yarn and then consecutively over the next three picks of said weft yarn, while weaving said second warp yarns of said second warp layer under two picks of said weft yarn, over one pick of said weft yarn, and under a next pick of said weft yarn.

21. The method of claim 11 including affixing a perforated resinous layer to one side of said fabric which contacts said paper.

22. The fabric of claim 1 including a resinous layer carried by said fabric for contacting said paper including passages facilitating flow of air through said fabric and resinous layer.