CA1316030C

CA1316030C - Seam construction for papermaking fabrics

Info

Publication number: CA1316030C
Application number: CA000613487A
Authority: CA
Inventors: Robert L. Crook
Original assignee: Niagara Lockport Industries Inc
Current assignee: Niagara Lockport Industries Inc
Priority date: 1988-12-01
Filing date: 1989-09-27
Publication date: 1993-04-13
Anticipated expiration: 2010-04-13
Also published as: EP0402448A1; EP0402448A4; WO1990006386A1; FI903823A0; US4896702A

Abstract

Abstract Of The Disclosure A seamed papermaking fabric having a multilayer base fabric includes an endless woven fabric forming a tubular belt that is flattened to form a base fabric with at least one helical coil Reaming member inserted between opposing sidewall portions at each respective lengthwise extremity of the base fabric. The helical axes of the seaming members extend transverse to the lengthwise direction of the fabric and the coils of the seaming member extend through space between adjacent machine direction yarns and supportably engage the machine direction yarns. The opposed lengthwise extremities of the base fabric are joined together by interengagement of the coils of the respective seaming members and insertion of the pintle member axially through the interengaged coils to form a seamed endless fabric of substantially twice the predetermined thickness.

Description

~ 13~30 SEAM CONSTRUCTION FOR PAPERMLAKIN(~ FABRICS

Backqround Of The Invention This invention relates to the field of seam construction for joining the ands of a length of papermaking fabric to rend0r that fabric endless. More particularly, it r~lates to a seaming technique for~use with a mu1tilayer layer base fabric. Even more 6pecifically, it relates to a helical coil seam for such a fabric.
Seamed papermaking fabrics, that is, those having seams that may be assembled and disassembled on a papermaking machine without the requirement of stitching or weaving, have been avaiIable but have presented problems, primarily in the premature failure of the seamed area. These prior art fabrics can be divlded into two basi~ categories, the first havlng seams formed outside of the weaving loom and the second having seams ~formed in the weaving loom.
In the first category of fabrics, those having seams formed outside the wea~ing loom, the fabrics have generally been flat woven with an independent seam structure attached to the ends of the fabric, such as by sewing a woven tape onto the fabric or piercin~ it with clipper hooks. These structures have provided poor caliper and den ity pro$ile~ in the seam area. Other . .
structures, such as Gisbourne, U.S. 4,244,084, have formed a gap near the end of the fabric with the fabric end then folded back over a helical coil to lock the seam loops into the fabric.

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Thi~ stxucture again provide~ poor caliper and density profile~
in the ~eam area due to the old back thicknes~, and the strength and life of the seam i~ lLmited to the ~trength of the ~titching holding the olded fabric~ ~hese problems have effectively precluded the 6uccessful u~e of any of the~e types of fabric i~ea~ in the wet pre~ section of papsrmaking maohines.
In the second catego~y, in which a pin ~eam is formed during the weaving prscess on the loom, the conventional approaches have constructed such a seam by forming loop~ on two ends around holding cord~ and then weaving the yarn back into the fabric bo~y. This ~eaming technique has suffered disadvantages in that the base fabric composition, construction and thickness hava been dictated by tha requirements of loop formation, as di~tinguished from papermaking con~iderations.
This has required two layers of machine dirsction yarn that are capable of being heat sgt or~resin impregnated to be stiff enough to form loop~. Such ~onstruction has provided an improved ~eam compared to the fir~t category but has still suffered many problems. The~e problems includ0 installation difficultie~ because the 8eam loops are dificult to me~h together because of inconsistent qize, ~hape and orientation a~
a result of the weaving method. Also, the~e ~eams tend to pull apart, due to machine direction yarn failure. Thi~ type of failure ha~ resulted fr~m the requirement of ~ti~f yarns for loop formation, which yarns ha~e intrinsically poar fatigue resi~tance and low elasticity and re6iliency. Another significant problem relate~ to the requirement that the ba~e fabri¢ thickne~ be dictated by the method o~ loop formation and not be designed for op~imal water handling and drainage. This frequenkly results in poor ~heet dewatering, reduced paper machine efficie~cy, reduction in paper quality and a ~hoxt operational life of the fabric. An additional problem relate~
to the 8ub8tantial additional cost in waaving the~e difficult fabrics, resulting in pre~ felt fabric~ ~o woven ~eing as much as 30% more expensive than comparable, nonseamed pr ss felts.

6~ ~h~ bi~
A~ a result of difficulties noted above, it is an object of the present invention to provide an improved, seamed papermaking fabric in which the weave characteristics are dictated by the pexformance de~ired of the fabric and not the requir~ment~ of the ~eam and in which the load bearing yarn may be chosen for papermaking need~ and not ~Lmply to form loop80 Ano~her ob~ect is to provide such a fabric in w~ich the ~eam is for~ed outside the wea~ing loom and which i8 capable of using a ~eam material that does not require c08tly heat setting or re~in Lmpregnation of the ba~e fabric. It is another ob~ect to provide such a fabric in which pin 8eam8 may be ~ormed quickly and economically in a fabric that is engine~red to have de~irable papermaking charact~ri~tics. Yet another ob~ect of the present invention to provide a eamed papermaking fabric havinq a multilayer base fabric along with a removable pin seam. To achieve these, as well a~ other ob~ects~ the invention provides a seamed papermaking fabric having a multilayer base fabric, and it comprises an endless woven fabric forming a tubular belt having a sidewall of predetermined weave, thicknes~, width and length, a~ mea~ured circumferentially around the tubular belt, with that 1: ~1 3~3~

belt being flattened to foxm a ba~e fabric of twice the predetermined thickne~s with at laast ona helical coil seaming member inserted bet~een the opposing ~idewall portions at each respec~ive leng~hwise extre~ity of the base ~abric, with the opposed lengthwise extremities of the base fabric being ~oined together by interen~agement of the coila of the seaming mamber~
and in~ertion of a pintle me~ber axially through the interengag d coilsO The helical a~i~ of each ~uch seaming member extends transver~e to the lengthwise direction of th~
fabric, and the coil~ of the ~eaming member extend th:rough ~pace~ between adjacent machine direction yarns and supportably engage the machine direction yarns to support the ~eaming member against forces ~upplied outwardly of the respective lengt~wise extremities of the ba~e fabri~.

Description of the Drawings SeveraI pre~erred embodiment~ sf the fabric of this .

invention ~ill be described in detail below in which Fig. 1 is a ~implified ~chematic representation of an andless woven fabric for u~e with this invention;
Fig. 2 illu~trates the ~tep~ of insertion of tha helical coil sea~ing members into a f1attened andle~ woven fabric of Fi~. l;
Fig. 3 i~ a fragmentary top plan view, partially in section, of a fabric ma~ufactured according to the present invention, including a felt batt needled into tha ba~e abric;
Fig. 4 i~ a ~che~atic elavational view taken along line 4-4 of Fig. 3;

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F.ig. 5 i~ a schematic elevational view of the se~m of a fabric ~imilar to that illu~trated in Fig. 4 but with additional cu~hioning elements;
Fig. 6 i~ an elevational view of the seam of a fabric of another embodiment of the present invention;
Fig. 7 is a schematic elevational view of a m~ltiple pin seam variation of the fabric of Fig. 6; and FigO 8 i~ a sectio~al vie~ taken along line 8-8 o~ Fig. 7.

Description Of A Preferred.Embodiment A preferred embodLment of the papermaking fabric of the present invention, and the ba~ic 8tQp8 of making that fabricl are illustrated in ~igs. 1 through 4. The ba~e fabric, generally indicated by reference numeral 2, is woven a~ an endles~ woven tubular belt having weft yarn~ 4, which will ultLmately become machine direction yarns in the finished fabric,- and warp yarns 6, which will become cross direc~ion yarn~ in the completed fabric. In one e~ample the warp yarns may be cabled nylon 610 monofilament, with the weft yarn~ being a three ply nylon 6, with a re~in coating for enhanced stiffness and wear resistance. This base weave may conveniently be a four~shed (two by two) endle~s woven tubular belt having a pxedetermined width mea ured betw~en axial edges of the belt and a predetermined l~ngth mea~ured circumferentially around the tubular belt that i~ sub~tantially twice the length of the de~ired fini~hed fa~ric.
As shown in Fig. 1, tha belt 2 pre~erably i8 woven with a removable cord 8 at each of oppo~ing extremiti~ of the slightly fIattened tubular belt 2 9 aB ~h~wn in Fig. 1. The fabric is woven to form the tubular bel~ 2, having it~ predetermined thicknes~ and weave and a predetermined width measured between opposed a~ial edges, one of which i8 ~hown a~ edge 10 in Fig. 3, of the belt. Thi~ tubular belt 2 is then flattened to form a base fabric of sub~tantially twice that predetermined thickne~
with the opposing portions of th~ sidswall of the tubular belt being closely ad~acent one another. Thi~ provides æuch a flattened tubular belt having a flattaned length between the l~ngthwi~e extremities thereof of about half the predetermined circumferential length.
Upon removal of the cords ~ and, if necessary, adjacent warp yarns 6 proxLmal the lengthwise extremitie~ o~ the flattened tubular belt 2, ~piral coil seaming members 12 and 12' are then inserted in~ide the tubular sidewall portion of the belt 2 where those cord~ 8 have been remo~ed. The spiral Beaming members 12 an~ 12' may be formed of any of a number suitable synthetic materials, ~uch as nylon or polyether-ethyl ketone (PEEK) and preferably ha~ coil dLm nsions and spacing such that one loop of the coil pro~ect~ between each ad~acent pair of weft yarns 4~ with the dia~eter of the coil being ganerally equal to or slightly less than the total thickne~s of the flattened tubular belt 2, as illustrated in FigO 4. Thus, each of the coil seaming member~ la and 12' engages each of what become the machine direction yarns 4, with the helical axis of the seaming member~ 12 extending transverse to the lengthwise direction of the ba~e fabric and Rupportably engaging the machine direction yarn~ to support that seaming member again~t force applied outwardly of the re~pective lengthwise extremities o~ the base fabric. Preferably al80, the two coils 12 an~ 12' 7 13~ ~3~
~ra of ld13ntical pi~ch, dla~net~r ~nd materl~ u~ ~xe wound oppo~itely, one being ~ hand hellx ~nd the other ~eln~ a r~ h~n~ helix, ~co provide ~or in~e~e~hing in a m~nn~x to be de~cribed below.
~ ~hown in Figs. 2, 3 and 4, ~he lengthwi~a extr~s~ e~ o~
tbe ~lat~ened tubular be)t 2 are then bxc:~lght together ~rith ~he respec:~ive ~oil~ nd 12 ~ lnt0r~r~qaging onè ~nothex and a pintle membe~ 1 4 i~ inser~s3d thro-lgh tha i~akereng~g~d coll t~
loc3c ~h~m togeth~r t~ ~or~ ~ continuou~ l~op~d base fabri~, with th~ cc~ ar~d 12 ' m~intaining the thi~ es8 ~f the ba~e fabx~ c ~t the 86~.
~ P the ~abrlc 1~ ko 3;~e u~ed ~ heet ~ ing ~a~ri¢ ~
withvu~ addition~ a~ be ~ n~ neodled intc~ ~he base ~a~ic, lt may now l; e mounted to ~ papern~akin~ ma~hine by r~3mov~1 of pin~l~ 14, pl~ g ~he ab~i~ 3round th~ paper~Aaklng ~olle~ ~nd r~inse~tlon of tha~ plntl~3 membe:c 14, rendering the 8~rua~ure raady fo~ UBe. ~owe~er~, the ~dvanta~eo~ chara~teri~tic~ of the ~al~ic of thl~ vf3rltion en~ lt ~c) be ~d in f~brlc~ n~ 4, pre~ fel~ Por the wo~ pr~ porti~n o~ a paper~a~lng opar~tion.
~o complete ~ab~ication o~ ~h~ pro~ ~alt, a ~uit~ble batt 16 1B
needle~ to ~T~d ~hrough on~ ~ide, preforably the ~he~t ~mtng ~i~e, o~ khel fl~t~ened tubu:lar ~a~e fabr~c 2~ a~ shown in ~q~.
3 ~nd 4. This n~edling conv~lently continues ov~r the ~ea~
por~c i Oll to pro~ride a cont~ nuQus b~tt ~llr~ce without ~ gap at ~he se~m. A ~npîe~ but~ ~pllca 18 n~ay ~e cu~ thr~ugh the batt Rt ~ he seam ~r~a to enable the ~aSrl~ o be ~pened at the ~eam by r~3~0Yal oi~ ~h~ pintle 14. Such Jle~dling o~ tlle batt 16 not only applis~ th~t batt bu~ also ~e~d to lock tosJeth~r the two bas~ ~bric ~idewal~ p~rtlon~ to ~o:~ ~ n~edled, se~m~d, ~ou~sle 1 3 ~ 6 ~ 3 ~

layer laminated wet pre~ felt. If desired, tha batt may be needled into ths ba~e fabric in a manner to cause the ba t to project outwardly of bo~h ~he sheet for~ing side ~nd tha machine side of the fabric, to reduce wear on the machine ~ide.
As an example of the u~e of thi~ invention, where the warp yarn is two ply, two cable, .~08 nylon woven at 16 yarns to the inch, and the weft yarn i~ an 840 denier, 3 ply nylon woven to provide about 20 yarns per inch in the final fabric, the base fabric weight using the con~truction of thi~ invention wa~ about 2.5 oz.~sq.ft., although weights up to more th~n 3.0 oz./sq.ft.
are also available. Thus, a press felt at a finished weight of fi.0 oz./6q. ft. may con~ist of between 48% and 58% batt compared to prior art seamed felt~ that are at least 65% batt. This con~truction thus provides for a lower level of compaction and filling of collapsed batt structure r which would limit water draina~e.
Fig8. 5 through 8 illustrate additional improved embodiment~ of the ~abric of thi~ invention. For example, in Fig. S the se~m structure is further improved by the in~ertion of cushioning yarn~ 20 and 20' axially within each re~pective helical coil 12 and 12' and interposed between the coils of the seamlng members 12 and 12' and the ad~acent machine direction weft yarn 4 of the base fabric 2. These cu~hioning yarns, which may coDveniently be a ~pun nylon yarn of about 400 denier, cushion engagement between the machine direction yarns 4 and the seaming member coils 12 and 1~' to reduce possible abrasion of the yarns 4 by the coils 12 and 12'. While the papenmaking fabric of Fig. 5 i~ shown without the felt batt shown in Fig. 4, ~ 3 ~

it is to be understood that ~uch batt may be used with thi~
alternative structure of Fig. 5 with equal facility.
AS shown in Figs. 6 through 8, the ~eaming technique of the present invention may also be ukilized to crea$e papermaking fabric having more th n two layers of the ba~;e fabric. Instead of weaving the original tubular base fabric to have a single layer sidewall, a8 in Yig. 1, the fabric may be originally woven as a multilayer endless, tublllar fabric having at least two layers of machine direction we f t yarns, ~uch as radially outer yarns 22 and radially inner yarns 24, along with cros~ direction warp yarns 26 and 28. If desired, both ~he radially inner layer 22 and radially outer layar 24 of machine direction weft yarn may have substantially the sama weave with substantially the same number of ~uch yarns per inch, as represented in Fig. 6.
Alternatively, as ~hown in Fiys. 7 and 8, the weave engaging the radially outer layer of machine direction yarns 22 may be di~ferent, and suitably ~ay be a finer weave than that of the radially inner layer of machine direction yarns 24, to provide a finer ~urface ~or supporting papar to be formed thereupon.
In ths embodLment illustrated in Fig. 6, the helical coil seaming menbers 12 and 12' are in~erted at each length~ise extremity of the base fabric 2 with the coils of those seaming ~e~ber~ e~tending through ~paces between and supportably engaging adjacent machine direction yarns of all, in this case two, layer~ o~ the machine direction yarn~ 22 and 24. As with the embodiment of Figs. 1 through 41 the coil seaming member~ 12 and 12' are ~elected ~uch that the di~meter of the coil is substantially equal to or slightly smaller than th~ total flattened thickness o~ the ba~e fabric 2, that is, less than or ~ 3 ~

1~
abou~ equal to twice the thickne6s of the ~idewall of the fabric as it i8 originally woven, b~fore flattening. The end~ of ~he flattened tubular base fabric ~ are ~oined together ~y interme~hing of the coil seaming members 12 and 12~and the insertion of a pintle member 14~ a~ with the embodiment of Figs.
1 through 4. If the fabric is to be u~ed as a press felt, felt batt may be needled into the b~se fabric in the ~ame manner a8 described wi~h respect to ~i~8. 3 and 4.
The fabric illustrated in Fig~ 7 and 8 represents yet a further Lmprovement in use of the ~eaming technique of this i~vention. As noted above, ths radially outer layer of machine direction yarns 22 in this embodLment may be of smaller diameter than the radially inner layer o~ machine direction yarns 24 to provide for improved sheet smoothness in the paper formed thereupon while maintaining substantial ~tren~th by virtue of the larger yarn~ 24 of the radially inner layer of ~achine direction yarn~. As with the other embodiments, this fabric i~
woven endless u~ing a stratified double layer weave as shown in the ~ectional view of Fig. 8~ taken alon~ line 8-8 of Fig. 7.
As with the other embodiments, the endless woven tube i8 ~lattened with the ends brou~ht together a~ shown in Fig. 7. In a manner analogou~ to that of Fig. 6, a first helical coil ~eaming ~e~ber 30 is inserted from within the endless woven loop fabric with the coils thereof extending through spaces between and supportably engagin~ machine direction yarns of all o~ the layers of the machine direction yarns 22 and 24 at one lengthwise extremity of the base fabric 2. A corresponding first helical coil seaming member 30' i~ likewi~e insQrted in a ~imilar ~anner at the opposita ~uch lengthwi~e extremity of the ba e fabric, al80 engaging all layers of the machine direction yarns. Additionally, a second helical coil ~eaming member 32 i~
inserted into the base fabric with th~ coils thereof extending through ~paces between and supportably engagin~ machine direction yarns 22 of fewer than all laylers of the machine direction yarn in thiæ case only the ou~er layer of machine direction yarns 22. ~t the opposite lengthwise extremity of the base fabric 2 a ~orresponding second helical coil seaminy member 32~ is likewise inserted/ engaging machine direction yarns 22 of fewer than all of the layers o~ the machine direction yarn.
To ~oin the ends of the fabric of Fig. 7 together, the corresponding seaming members 30 and 30~ and 32 and 32' at each lengthwise extremity of the base fabric 2 are interengaged, and respective pintle members 34 and 36 are inserted axially through the interen~aged eoil seaming ~.embers. Thi~ forms a multiple element pin sea~ with each pair of the interengagad seaming me~bers and inserted pintle members providin~ backup support for the other interengaged seaming members and inserted pintle ~embers. Suitably, the numbar o~ coils per inch of axial length of both of the first seaming member~ 30 and 30' is substantially equal to the number of machine direction yarns 24 per inch of the radially inner layer of machine direction yarn s measured transversa to the lengthwise direction of the base fabric.
LikewisQ, the number of coil~ per inch of axial length o both of the second seaming member~ 32 and 32~ preferably is ~ubsta~tially equal to the numbar of machine direction yarn~ ~2 per inch of vne of the layers of machine direction yarns other than the radially innar layer, in thi~ case the radially outer layer, as mes~ured tran~verse to the lengt~wi~a direction o~ the ~ 2 base fabric. In this embodiment the diameter of the coils of the second seamin~ members 32 and 32~ is smaller than the diameter of the coils of ~he first seaming members 30 and 30'.
By the fabric manufacturing technique~ described above, there is provided a papermaking fabric having a removable pin seam that results in little or no change in fabric homogeneity in the seam area. Additional~y, ~hi~ i.nvention provides virtually unlimi~ed selection of machine direc~ion yarn sizes and composition, unlike conventional loop seaming techniques.
~he invention ~urther per~its single and multiple machine direction yarn layers/ so that the seamed fabric can be engineered for the characteristics desirable for the ~pecific papermaking application, largely eliminating concern relating to the creation of a pin seam. AB de cribed with respect to Figs.
6 through 8, this structure provides for su~erimposed base fabrics with helical coil pin seams for enhanced sheet quality, along with capabiIity of using ~ultiple, superimposed coil seaming elements for enhanced ~moothness and: str2ngth, even pro~iding a backup ~oint in case one fails. B~ this technique the h~lical coil seaming members can al80 be inserted into conventional Qndles~ woven fabrics without special equipment and without re~uiring heat setting or r~sin impregnation on the ends of the fabric. Thus, it may be seen that tha fore~oing structure and seæming method provide a significant L~provement in both the fabrication and installation of papermaking fabrics.
While the foregoing describes in detail certain iIlustrative embodLmsnts of the invention, it is to be understood that these description~ are illustrative only of the principles of tha invention are not to be considered limi~ative ~ 3 ~ 3 ~
~ 3 thereof . Becau~e numerous modif ications and variations of the ~tructure will readily occur to those ~killed i~ thl3 art, including the use of numeroua other types of waaves and number~
of seaming coil~ ~ as well as other variation;s r the ~cope of the invention is to be li~nited ~olely by the claims appended hereto.

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Claims

1. A seamed papermaking fabric having a multilayer base fabric and comprising an endless woven fabric forming a tubular belt having a sidewall of predetermined width measured between opposed axial edges of said tubular belt, predetermined length measured circumferentially around said tubular belt, predetermined weave, and predetermined thickness;
said tubular belt being flattened to form a base fabric of substantially twice said predetermined thickness with opposing portions of said tubular belt sidewall adjacent one another and having a flattened length between lengthwise extremities of said base fabric of about half said predetermined circumferential length;
at least one helical coil seaming member inserted between said opposing sidewall portions at each respective lengthwise extremity of said base fabric, with the helical axis of said seaming member extending transverse to the lengthwise direction of said fabric, and the coils of said seaming meter extending through spaces between adjacent machine direction yarn and supportably engaging said machine direction yarns to support said seaming member against force applied outwardly of said respective lengthwise extremity of said base fabric;
said opposed lengthwise extremities of said base fabric being joined together by interengagement of said coils of the respective said seaming members and insertion of a pintle member axially through said interengaged coils to form a seamed endless fabric of substantially twice said predetermined thickness .

2. The fabric of claim 1 wherein the outside diameter of each of said helical coil seaming members is less than twice said predetermined thickness, whereby the outside diameter of the coil seaming member is less than the total thickness of the base fabric.

3. The fabric of claim 1 further comprising a cushioning yarn extending axially within each said helical coil seaming member and interposed between said coils of said seaming member and said adjacent machine direction yarns of said fabric belt to cushion engagement between said yarns and said seaming member coils.

4. The fabric of claim 3 wherein said cushioning yarn comprises spun nylon yarn.

5. The fabric of claim 1 wherein said predetermined weave of said endless woven tubular belt comprises a weave having a single layer of machine direction yarns, whereby the flattened tubular base fabric forms a double layer fabric with the coil seaming members inserted between the two layers.

6. The fabric of claim 1 wherein said predetermined weave of said endless woven tubular belt comprises a weave having a plurality of layers of machine direction yarns, whereby the flattened tubular base fabric forms a fabric having more than two layers of weft yarns, including a radially outer layer and at least one radially inner layer with at least one helical coil seaming member at each of the opposed ends of the flattened tubular belt extending through and engaging yarn from all layers of said weft yarns to form a base fabric having more than two layers.

7. The fabric of claim 1 wherein said predetermined weave of said endless woven tubular belt comprises a weave having at least two layers of machine direction yarns including a radially inner layer and a radially outer layer of said tubular belt, and said fabric further comprises a plurality of said helical coil seaming members inserted at each lengthwise extremity of said base fabric, with said coils of at least a first said seaming member extending through spaces between and supportably engaging adjacent machine direction yarns of all said layers of said machine direction yarns of the respective lengthwise extremity of said base fabric, and said coils of at least a second said seaming member extending through spaces between and supportably engaging adjacent machine direction yarns of fewer than all said layers of said machine direction yarns of said respective lengthwise extremity of said base fabric, whereby interengagement between pairs of corresponding seaming members, one at each lengthwise extremity of the base fabric, and insertion of respective pintles therethrough, provides for a multiple element pin seam with each pair of interengaged coil seaming members and inserted pintle providing backup support for the other interengaged coil seaming members and inserted pintles.

8. The fabric of claim 7 wherein the number of said coils per inch of axial length of both of said first seaming members is substantially equal to the number of machine direction yarns per inch of said radially inner layer of machine direction yarn.
measured transverse to the lengthwise direction of said base fabric.

9. The fabric of claim 7 wherein the number of said coils per inch of axial length of both of said second seaming members is substantially equal to the number of machine direction yarns per inch of one of said layers of machine direction yarns other than said radially inner layer, as measured transverse to the lengthwise direction of said base fabric.

10. The fabric of claim 7 wherein said weave has two layers of said machine direction yarns including said radially inner layer and said radially outer layer, and each said lengthwise extremity of said base fabric includes a first said first seaming member extending through and supportably engaging both said layers of said machine direction yarns, with each said first seaming member interengaging both the other said first seaming member at the opposed lengthwise extremity of said base fabric and a first pintle extending axially through said first seaming members, and a second said second seaming member extending through said supportably engaging only said radially outer layer of machine direction yarns with each said second seaming member interengaging both the other said second seaming member at the opposed lengthwise extremity of said base fabric and a second pintle extending axially through both said second seaming members.

11. The fabric of claim 10 wherein the diameter of said coils of said second seaming members is smaller than the diameter of said coils of said first seaming members.

12. The fabric of claim 10 wherein the number of said coils per inch of axial length of both of said second seaming members is substantially equal to the number of machine direction yarns per inch of said radially outer layer of machine direction yarns measured transverse to the lengthwise direction of said base fabric.

13. The fabric of claim 1 wherein said seamed fabric has a machine side and a sheet side and wherein said sheet side includes a layer of batt affixed to said fabric and extending outwardly from said sheet side of said base fabric, whereby is formed a papermaking felt fabric.

14. A method of making a seamed papermaking fabric having a multilayer base fabric, comprising the steps of endless weaving a tubular belt fabric having a predetermined width measured between opposed axial edges of said tubular belt, predetermined length measured circumferentially around said tubular belt, predetermined weave, and predetermined thickness;
flattening said tubular belt to form a base fabric of substantially twice said predetermined thickness with opposing portions of the sidewall of said tubular belt being closely adjacent one another and said flattened tubular belt having a flattened length between lengthwise extremities thereof of about half said predetermined circumferential length;
inserting at least one helical coil seaming member between said opposing sidewall portions at each respective lengthwise extremity of said base fabric, with the helical axis of said seaming member extending transverse to the lengthwise direction of said base fabric and the coils of said seaming member extending through spaces between adjacent machine direction yarns and supportably engaging said machine direction yarns to support said seaming member against force applied outwardly of said respective lengthwise extremity of said base fabric; and joining together said opposed lengthwise extremities of said base fabric by interengagement of said coils of the respective said seaming members and insertion of a pintle member axially through said interengaged coils to form a seamed endless fabric of substantially twice said predetermined thickness.

15. The method of claim 14 further comprising insertion of a cushioning yarn axially within each said helical coil seaming member and interposed between said coils of said seaming member and said adjacent machine direction yarns of said base fabric to cushion engagement between said yarns and said seaming member coils.

16. The method of claim 14 wherein said tubular belt fabric is woven to have at least two layers of machine direction yarns including a radially inner layer and a radially out layer, and said step of inserting said seaming members comprises insertion of a plurality of said seaming members at each said lengthwise extremity of said base fabric, including for each said extremity inserting at least a first said seaming member with the coils thereof extending through spaces between and supportably engaging adjacent machine direction yarns of all said layers of said machine direction yarns of the respective lengthwise extremity of said base fabric, and inserting at least a second said seaming member with the coils thereof extending through spaces between and supportably engaging adjacent machine direction yarns of fewer than all said layers of said machine direction yarns, and the corresponding said seaming members at each lengthwise extremity of said base fabric are interengaged and respective pintle members are inserted axially therethrough, whereby is formed a multiple element pin seam with each pair of interengaged seaming members and inserted pintle member providing backup support for the other interengaged seaming members and inserted pintle members.

17. The method of claim 16 wherein said tubular belt fabric is woven to have two layers of machine direction yarns, including said radially inner and said radially outer layer, and said step of inserting said seaming members comprises, for each said lengthwise extremity of said base fabric, inserting a first seaming member extending through and supportably engaging both said layers of said machine direction yarns, with each said first seaming member interengaging both the other said first seaming member at the opposed lengthwise extremity of said base fabric and a first pintle extending axially through aid interengaged first seaming members, and inserting a second seaming member extending through and supportably engaging only said radially outer layer of said machine direction yarns, with each said second seaming member interengaging both the other said second seaming member at the opposed lengthwise extremity of said base fabric and a second pintle extending axially through said interengaged second seaming members.

18. The method of claim 14 wherein said seamed fabric has a machine side and a sheet side and wherein the method includes the step of affixing to said sheet side of said base a layer of batt to form a papermaking felt fabric.