CA1059355A

CA1059355A - Forming wire for use in paper-making, cellulose and similar machines

Info

Publication number: CA1059355A
Application number: CA272,632A
Authority: CA
Inventors: Hans J. Bugge; Ingvald Strandly; Carl O. Swanberg
Original assignee: Nordiska Maskinfilt AB
Current assignee: Nordiska Maskinfilt AB
Priority date: 1976-02-24
Filing date: 1977-02-24
Publication date: 1979-07-31
Also published as: FR2342368B1; NO145924B; NL7701573A; IT1072676B; NO770490L; AT353597B; SE7602211L; AU501367B2; JPS61184000U; BR7701085A; GB1555731A; DE2706235A1; AU2250477A; JPS52121509A; ES456402A1; BE851379A; FR2342368A1; SE397371B; FI770291A; FI60258B

Abstract

ABSTRACT OF THE DISCLOSURE:

A forming fabric for use in paper-making cellulose and similar machines, comprising a first layer of weft threads, which layer is intended in the position of use of the fabric to face the material to be formed, a second layer of weft threads, which layer is intended in the position of use of the fabric to face the machine drive rollers, and synthetic warp threads interweaving said two weft layers. Said first layer of weft threads crosses said warp threads on said outer face of the fabric closest to the material to be formed, in at least 80% of all cross points, or according to the shaft (harness) number used in between 80% and 90% of all cross points, where-by the wefts on the fabric face turned towards the material to be formed float over a large number of warps. The number of cross points on this fabric face thus is reduced, eliminating the tendency of the fabric to cause marking on sensitive paper qualities.

Description

~(~59355 `.
BACK~ROUND OF THE I~VENTI ON
Forming wires for use in paper-making, cellulose and similar machines usually are in the form of a fine-mesh cloth which has been woven endless or otherwise joined into an endless web. As the very basis of good quality paper resides in the web formation itself, the structure of the forming wires is of vital and decisive importance. Until the middle of the fi~ties, all forming wires were manufactured from metal wires.
These metal-wire cloths were useful in all kinds of paper-making machines and for all paper ~ualities. Around the date mentioned, metal-wire cloths, above all in cellulose machines, were replaced by single-layer fabrics of synthetic fibre threads, the so-called synthetic fabrics. The advantage of synthetic fa-brics beyond metal-wire ones primarily resides in their improv-ed wear resistance. Single-layer synthetic fabrics do, however, suffer from the disadvantage of having considerabl~ higher elas-ticity and less stability than cloths made from metal wires of corresponding coarseness. On the large majority of up-to-date paper machines single-layer synthetic fabrics cannot be used at all, or only with difficulty, because of the large size and re-quirements on fabric stability of such machines. Although con-siderable improvements have been made during recent years, only modest success has been achieved with single-layer synthetic fa-brics on machines for e.g. wide and high-speed news-print paper, magazine paper and the so-called tissue paper machines. Also in the case of wide liner, kraft, and sack paper machines, sever-al attempts have failed - despite the use of coarse and thus more stable single-layer synthetic fabrics.
The so-called double-layer synthetic fabrics consisting of two layers of one yarn system and a second yarn system inter-.

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~ ~ connecting these layers have, as a result of their higher : : .
stability, considerably better chances of success on all types of paper-making machines, which several record runs also have evidenced.
A single-layer forming fabric consists of two yarn syst-ems only, the warp and the weft, whereas a double-layer fabric must comprise at least three yarn~ systems. To interweave -these yarn systems into a cloth possessing the same even sur-face structure as a single-layer cloth has hitherto caused the manufacturers large problems. The more complex binding struct-ure of the double-layer fabric involves marking problems, in that the structure of the yarns and/or the irregular mesh size leave traces in the paper sheet in the form of a so-called fa-bric marking. ~he first double-layer synthetic fabrics had a geometrical structure that made it impossible in practice to bring to a common plane the two yar~- systems closest to the mat-erial to be formed. The difference in levels between the knuckles of the warp and weft ya~ns: caused such a pronounced marking that these fabrics were useful only in forming coarse paper qualities.
A considerable improvement i9 offered by the invention described in the Swedish Published Specification No. 366 353.
j The structure described therein makes it possible to locate the weft threads of the layer which in position of use of the fabric faces the material to be formed, essentially tangentially to the fabric plane facing sàid material. The invention provides ~
a double-layer structure which is useful not only for coarse ~-paper ~ualities but also for the manufacture of e.g. newsprint paper.
In the manufacture of magazine and fine paper, the demands

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that the fabric causes no marking are very high, among other reasons because the slightest tendency of the fabric to cause marking, affects the printability of the paper. ~he fabric structure described in the Swedish Published Specification No. 366 353 in several respects has proved suitable for use on many magazine paper machines, but its existing weak marking tendency, noticeable particularly diagonally with respect to the direction of travel of the fabric and the paper, has lim-ited its usefulness in these positions.
In the fabric structure described in this Published Specification, each warp thread is made to bind or interweave separately with the layer of we~t threads which in position of use of the fabric faces the material to be formed. In this manner, the outer face of the fabric will comprise a large number of ~hort warp and weft float lengths.
A further development of the structure accordinq to the Swedish Published Specification No. 366 353 is described in the Swedish Published Specification No. 385 486. The invention in accordance with this patent application likewise concerns a structure wherein the interconnecting synthetic warp threads also interweave separately with the weft threads of the layer of weft threads which in position of use faces the material to be Eormed. It is characteristic of the structure in accordance with the 5wedish Published Specification No. 385 ~86 that the weft yarn on the opposite side of the fabric which side in position of use thereof faces the dewatering members and thus is exposed to abrasion, is located tangentially to a plane positioned beyond the plane: which is at a tangent to the warp threads interconnecting the layers. Owing to this structure, the wear resistance is increased in that a proportionally lar~er portion . . ., . , , . ~ : ~ ~ , ;
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~~~ of the wear on the fabric is transferred to the practically unloaded weft yarns.
SU~MARY OF 'I''HE INVENTION
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The present invention relates to a synthetic forming ,.; - ~
fabric for use in paper-making, cellulose, and similar machines, of the kind comprising a first layer of weft threads which in position of use of the fabric faces the material to be formed, ,~ a second layer o~f weft threads, and synthetic warp threads in-terconnecting the weft layers. It is characteristic of the in- ;
vention that the first layer of weft threads crosses said warp threads on the external side of the fabric closest to the mat-erial to be formed, in 80~ or more of all the cross points.
; Through the subject invention, the warp knuckles on the outer face of the fabric are limited to a minimum, and in-stead this fabric face is formed to an essential degree by the weft or cross-direction yarn. This structure diminishes the demand that the two yarn systems are to be located tangentially to the outer plane of the fabric, without causing a negative ;
effect on the marking tendency. In addition, the number of ;¦
~, 20 binding points on the external face of the fabric is considerably ~ ~
¦ reduced, which also has proved to be cleaxly beneficial from a ;¦
;¦ marking point of view.
~ BRIEF DESCRIP'I'ION OF THE D~A~ATINr-',fS
'il -'I In the following the invention will be described in ~de-tail with reference to the accompanying drawings, wherein , Figs. 1 A-C illustrate in one plan view and two sectional -; views the fabric structure shown and illustrated in the Swedish Published Specification No. 366 353.

, Figs. 2 A-E illustrate in one plan view and five sectional views a fabric structure in accordance with the invention, ,.` E3 ' 1~59355 ~ wherein Figs. 2~ and 2C are respectively a longitudinal sect-ional view along line 2B-2B and a cross-sectional view along ling 2C-2C of Fig. 2A and wherein Figs. 2D and 2E are respect-ively a similar longitudinal sectional view and a cross-sectional view but wherein the warp thread has a somewhat different ex-tension (configuration~, and wherein Fig. 2F is a further long-itudinal sectional view. -Figs. 3 A-C, ~ A-C, 5 A-C, 6 A-C, and 7 A-C show further examples of five additional fabric structures in accordance with the invention, wherein the figures designated A are plan views of the fabric in question, the figures designated B are long-itudinal sectional views along the lines designated B-B and the figures designated C are cross-section views along the lines designated C-C.
DETAILED DESCRIPTION OF PRFE'ERR~D EMBODIM~NTS
The fabric in accorclance with Figs. 1 ~-C exemplify the already known and used abric structure consisting of two layers 11, 12 of synthetic weft thEeads and synthetic warp threads 13 interconnecting ~the two weft layers. The layer of weft threads which in position of use of the fabric is to face the material to be formed and which makes up the outer face of the endlessly woven fabric is designated by reference number 11, whereas the j inner face of the fabric which is turned towards the drive rollers is designated by reference number 12. Each weft layer 11, 12 as well as the warp thread layer 13 interconnecting the weft layers consist of seven threads a-g each one of which has its specific weaving pattern. ~AJithin the textile technique, a weave of this structure is known as a seven-shaft (harness) , weave. It is characteristic of this structure that the outer layer 11 of weft threads and the warp threads 13 interconnecting . ,, ~

~o59355 '- the two weft layers are located ess~ntially tangentially to the outer plane of the fabric. This condition is achieved in that each warp thread 13, in addition to interweaving the two weft layers, also is made to bind separately with the outer layer 11 of weft threads. Qwing to this separate binding, the fabric face turned towards the material to be formed, will consist of a large number of short warp and weft float lengths.
~y a "float length" is to be understood in this connection, the length of thread over which the yarn extends freely without being interwoven with another yarn. With reference to Fig. lC, the float lengths of yarn llg thus are formed as well above warp yarns 13c, 13d, and 13e as above warp yarns 13g and 13a. The wefts thus float over two and three warp threads, respectively.
In a double-layer product, normally having a warp density that is twice that of a single-layer one, it has been found that the large number oE binding or cross points that is a consequence oE
the rnany and short float lengths, tend to form diagonal patterns in the fabric, which in turn cause marking of the paper web. In the structure illustrated in Figs. 1 A-C, such diagonal patterns can easily be traced, e.g. along lines 14-14 and 15-15.
In order to avoid these diagonal patterns the present in-vention provides a fabric wherein the face of the fabric intend-ed to be turned towards the material to be formed, consists of long weEt Eloat lengths and the shortest possible warp float lengths. In thls manner the binding or cross points have been reduced to a minimum, resulting in improved marking qualities, primarily when used wlth extremely sensitive paper qualities.
Figs. 2A-E show a first embodiment of a fabric in accord-ance with the teachings of the present invention. Like the prior art fabric, the novel wire comprises two layers 21, 22 of syn-'' .

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thetic weft threads as well as synthetic warp threads 23 interweaving the two weft layers. Preferably all threads are monofilament threads, but also multifilament threads are use-able. The layer of wet threads which in position of use of the - fabxic is'to face the material to be formed and which consists ' of the outer face of the endless fabricl is designatea 21, '- ' whereas the inner face of the fabric which is turned towards the '~
~ drive rollers, is''designated 22 In accoraance with ~he embodi-;'~
-'^` mént illustràted in Fig.'2F, the latter fabric face is made up by half-the num~er of weft threads'compared with the num~er of ' the outer face of the fabric. On the other hand, these'weft '' threads may be coarser. Like in Figs. lA-C each one of weft . : . - , . . -~ ~ ; ~ layers 21,''22 as well as the interweaving warp threads 23 com~rise .
~ ' seven threads a-g weaving in a different pattern, i~e, the weave ~ , ;.;.,, ~ : , ' ' `~ ' is a so-c~lled seven-shaft weave. The fabric face turned t~w~rds ,, '..',-,'' the material to be formed, consists oE long weEt Eloat lengths.

In figures 2C and 2E, the weft yam 21g forms continuous float , .
lengths above warp yarns 23d, 23e, 23f, 23g, 23a,- and 23b whereas the weft yarn 21g only binds with one single one, 23c, of the .
; 20 seven warp yarns. The weft layer which in position of use faces 'the material to be formed, thus crosses the waxp threads on the external ~ace of the fabric six times out of seven, i.e. in nearly 86~ of all cross points. ' ' ' '' Pigs. 3 A-C - 7 A-C inclusive show examples of five other ' embodi~ents of fabric structures. The fabric illustrated in Figs. 3 A-C consists of one outer weft layer 31 and one inner weft layer 32 as well as layers of warp threads 33, each warp layer comprising five threads a-e weaving in different ways, i.e.
a five-shaft weave. Each weft ~hread on the outer face of the endless fabric floats over four warp threads (for example weft '~
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:1~593~5 - thread 31c above warp threads 33e, 33a, 33b, and 33c) and is interwoven with the fifth warp thread 33d. The threads of the outer weft layer thus crosses the warp threads on the outer face of the fabric in four cross points out of five, or in 80% of the cross points.
The fabric structure illustrated in Figs. 4A-C comprises one outer weft layer 41 and one inner weft layer 42 as well as layers of warp threads 43, interwoven in a six-shaft binding.
Each layer consists of threads a-f each one weaving in a differ-ent way. Each weft thread on the outer face of the endless fabric floats over five warp threads (e.g. weft thread alf over warp threads 43f, 43a, 43b, 43c, and 43d) and is interwoven with the sixth warp thread 43e. The threads of the outer weft layer thus cross the warp threads on the outer face of the fabric in five cross points out of six, or in somewhat more than 83%
of the cross points.
The structure illustrated in Figs. 5 A-C consists of one outer weft layer 51 and one inner weft layer 52 as well as warp thread layers 53 woven toge~her into a eight-shaft 20 ~inding. Each layer consists of threads a-h, each one weaving in its specific manner. Each weft thread on the outer face of ;
the endless fabric has float lengths extending over seven warp threads (e.g. weft thread 51h above warp threads 53g, 53h, 53a, 53b, 53c, 53d, and 53e) and is interwoven with the eighth warp thread 53f. The threads of the outer weft layer 51 thus cross the warp threads on the outer face of the~fabric in seven cross points out of eight, or in 87.5% of all cross points.
The structure illustrated in Figs. 6A-C comprises one outer weft layer 61 and one inner weft layer 62 as well as 30 layers of warp threads 63 interconnected into a nine-shaft - l~)S935S
binding. Each layer comprises threads a-i, each one weaving in its particular weaving pattern. Each weft thread on the outer face of the endless fabric has float lengths extending over eight warp threads (e.g. weft thread 61 over warp threads 63d, 63e, 63f, 63g, 63h, 63i, 63a, and 63b) and is interwoven with the ninth warp thread 63c. The threads of the outer weft layer thus cross the warp threads on the outer face of the fabric in eight cross points out of nine, or in almost 89% of the cross points.
The structure illustrated in Figs. 7A-C consists of one outer weft layer 71 and one inner weft layer 72 as well as layers of warp threads 73 interconnected into a ten-shaft bind-ing. Each layer consists of threads a-j, each one weaving in a different manner. Each weft thread on the outer face of the end-less fabric has float lengths extending above nine warp threads (e.g. weft thread 71j above warp threads 73e, 73f, 73g, 73h, 73i, 73j, 73a, 73b, and 73c) and is interwoven with the tenth warp thread 73d. The threads of the outer weft layers thus cross the warp threads on the outer ace ofthefabric in nine cross points out of ten, or in 90% of the cross points.
The modifications of the structure described above in accordance with the invention are to be regarded as examples only, and may be multiplied within the scope of the appended claims.
For instance, shaft numbers higher than ten-shaft are possible.
The interweaving of the inner weft layer ofthe fabric which in position of use is to be turned towards the drive rollers of the machine, with its warp layer need not either be identical with that of the outer weft layer thereof, as illustrated in the draw-ings ! but may be effected in a different way. Nor need the number of weft threads, thread dimensions, or the material of the two _ g _ ~3 :

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" . ': ~ . . ,.,1 , , , .' ~ 1059355 `~ weft layers be identical. Also within the same weft layer and/
or warp layer, thread dimensions and materials may vary.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An improved synthetic forming fabric for use in paper-making, cellulose and similar machines, comprising a first layer of weft threads facing the material formed on the fabric, a second layer of weft threads in position facing the machine drive rollers, and synthetic warp threads interweaving said two layers of weft threads, the improvement comprising said first layer of weft threads crossing said warp threads on the outer face of said fabric closest to the material to be formed, in at least 80% of all cross points.

2. An improved synthetic forming fabric as claimed in claim 1, wherein on said outer face of said fabric, turned towards the material formed, each thread of said first layer of weft threads crosses six out of seven successive said warp threads.

3. An improved synthetic forming fabric as claimed in claim 1, wherein on said outer face of said fabric, turned towards the material formed, each thread of said first layer of weft threads crosses four out of five successive said warp threads.

4. An improved synthetic forming fabric as claimed in claim 1, wherein on said outer face of said fabric, turned towards the material formed, each thread of said first layer of weft threads crosses five out of six successive said warp threads.

5. An improved synthetic forming fabric as claimed in claim 1, wherein on said outer face of said fabric, turned towards the material formed, each thread of said first layer of weft threads crosses seven out of eight successive said warp threads.

6. An improved synthetic forming fabric as claimed in claim 1, wherein on said outer face of said fabric, turned towards the material formed, each thread of said first layer of weft threads crosses eight out of nine successive said warp threads.

7. An improved synthetic forming fabric as claimed in claim 1, wherein on said outer face of said fabric, turned towards the material formed, each thread of said first layer of weft threads crosses nine out of ten successive said warp threads.

8. An improved synthetic forming fabric as claimed in claim 1, wherein said threads of said two layers of weft threads as well as the warp threads interweaving said weft layers, are syn-thetic monofilament threads.

9. An improved synthetic forming fabric as claimed in claim 1, comprising said fabric constructed with a weave pattern in-corporating shaft numbers ranging from 5 to 24.