CA1151981A - Low density multilayer papermaking fabric - Google Patents
Low density multilayer papermaking fabricInfo
- Publication number
- CA1151981A CA1151981A CA000382037A CA382037A CA1151981A CA 1151981 A CA1151981 A CA 1151981A CA 000382037 A CA000382037 A CA 000382037A CA 382037 A CA382037 A CA 382037A CA 1151981 A CA1151981 A CA 1151981A
- Authority
- CA
- Canada
- Prior art keywords
- threads
- thread
- fabric
- layer
- single layer
- 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
Links
- 239000004744 fabric Substances 0.000 title claims abstract description 190
- 239000010410 layer Substances 0.000 claims abstract description 77
- 239000002356 single layer Substances 0.000 claims abstract description 75
- 238000009739 binding Methods 0.000 claims abstract description 29
- 230000027455 binding Effects 0.000 claims abstract description 29
- 239000011800 void material Substances 0.000 claims abstract description 11
- 229940000425 combination drug Drugs 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 18
- 239000007921 spray Substances 0.000 abstract description 3
- 238000009740 moulding (composite fabrication) Methods 0.000 description 12
- 239000000835 fiber Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 3
- 239000000356 contaminant Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 229920000728 polyester Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000007480 spreading Effects 0.000 description 2
- 238000003892 spreading Methods 0.000 description 2
- 101100256746 Mus musculus Setdb1 gene Proteins 0.000 description 1
- 229920001131 Pulp (paper) Polymers 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- OYIKARCXOQLFHF-UHFFFAOYSA-N isoxaflutole Chemical compound CS(=O)(=O)C1=CC(C(F)(F)F)=CC=C1C(=O)C1=C(C2CC2)ON=C1 OYIKARCXOQLFHF-UHFFFAOYSA-N 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 210000003739 neck Anatomy 0.000 description 1
- 239000010898 paper trimming Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000004382 potting Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000009941 weaving Methods 0.000 description 1
- 239000002759 woven fabric Substances 0.000 description 1
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
Landscapes
- Paper (AREA)
- Peptides Or Proteins (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Laminated Bodies (AREA)
- Woven Fabrics (AREA)
Abstract
Abstract of the Disclosure A papermaking fabric of the multilayer type having threads of a multiple layer thread system extending in one fabric direction and threads of a single layer thread system extending in the other fabric direction which are interwoven with the threads of each of the multiple layers. The threads of the single layer thread system are spaced apart from one another, and threads of the several layers are tiered above one another with spacing between tiers, so that the fabric has a significant projected open area that allows spray water to penetrate the fabric. The fabric may also have an increased void volume in its interior and binding points between thread systems that are well spaced from one another to enhance the papermaking qualities of the fabric.
Description
~ ~5~98~
L,OW l)ENSITY MIJI.TII.l~Y]~R
PIL\ PER MA KING ~ABRIC
This invention relates to papermaking fabrics, and more par ticularly to multilayer fabrics characterized by threads of a multiple layer thread system extending in one fabric direction and threads of a single layer thread system extending in the other fabric direction, such single layer threads being interwoven with the threads of each layer of the multiple layer system.
In recent years there has been an increasing use of multilayer fabrics in the wet, or forming end of papermaking machines. Such multilayer fabrics supplant single layer fabrics that consist of a single layer of longitudinally extending threads interwoven with a single layer of transversely extending threads. The multilayer fabrics can pro-vide special advantages, such as improved stretch resistance to tension loads imparted by a papermaking machine, resistance to crimp inter-change between longitudinal and transverse thread systems, greater stiffness that reduces wrinkling of the fabric, better paper sheet sup-port and longer wear life. Because of these advantages the use of multilayer fabrics has been increasing.
Multilayer fabrics usually have one thread systcm comprised of two layers of threads extending transversely, or crosswise to the machine or running direction of the fabric, with each thread of the upper layer being paired with and lying directly above a thread of the lower layer. A second thread system comprises a single layer of threads extending in the longitudinal, or machine direction of the fabric, and each of these threads is interwoven with the threads of both layers of the two layer thread system. Over the years such multi-layer fabrics have been steadily improved and refined to enhance their papermaking qualities. Several of these improvements have concern-ed the development of preferred crimp relationships between the two ~:lS19i~1 thread systems. For example, in U. S. patent No. 4, 071, 050 issued on an application filed July 16, 1973, the longitudinally extending threads of the single layer thread system are interwoven with the upper layer of the two layer thread system in such manner that upon stretching the fabric during manufacture the thread knuckles of both thread systems on the upper fabric surface come into a nearly com-mon plane to achieve a better paper forming surface. In U. S. patent No. 4, 041, 989 issued on an application filed September 30, 1975, the ~nuckles of longitudinally extending threads of the single layer thread system are receded into the fabric on the lower fabric surface to ex-pose the threads of the lower layer of the two layer thread system as the primary wearing elements of the fabric. And, in U. S. patent No.
4, 112, 982 issued on an application filed February 17, 1977, the num-ber of crossovers of the transversely extending threads of the upper layer of the two layer thread system are increased to develop a paper forming surface comprised primarily oE long crosswise thread knuckles to decrease paper marking.
Some additional multilayer fabric structures are shown in U. S.
patent No. 4, 086, 941 issued on an application filed October 26, 1976, wherein a two layer thread system consisting o-f shute threads has the threads of one layer horizontally offset from the threads of the other layer, and in U. S. patent No. 4, 171, 009 issued on an application filed March 22, 1977, in which long knuckles are formed in the single layer thread system on the paperforming side of the fabric by having these threads bind with three to seven threads of the upper layer of the multiple layer thread system. Besides the development of multilayer papermaking fabrics characterized by a single layer thread system extending in one fabric direction, some work has also been done on multiple ply fabrics, as shown in U. S. patent Nos. 3, 885, 602 and 3, 885, 603. In these fabrics each ply has its own interwoven longitu-~15~
dinal and transverse thread systems, and the plies are tied together with threads interweaving between both plies. Such multiple ply fab-rics have not achieved widespread usage as have the multilayer fab-rics .
I~eretofore, multilayer fabrics have been constructed with very high thread densities for the single layer thread system, in order to achieve dimensional stability and to minimize shifting of threads with-in the fabric. Thread density can be measured by multiplying the num-ber of threads per unit width of fabric by the thread diameter, and for the single layer thread system the densities have commonly run near a value of 1. 0. As examples, Fig. 3A of the aforesaid patent No. 4,11", 982 shows the threads of the single layer system lying side by side, and in patent No. 4,171, 009 the density is stated at Col. 3, line 15 as being 1. 05 and above.
This requirement of a high thread density for the single layer thread system can inhibit "knock-off" water showers from loosening edge trim of a paper web from the fabric after it passes the couch roll of a paper forming machine, and in machines where this -trim removal requires assistance in being stripped from the forming fabric multilayer fabrics are not widely used. This has been a particular problem in the manu-facture of brown papers including linerboard, which is one of the major products of the papermaking industry. Another problem with a dense fabric is that closely adjacent threads abutting one another are prone to hold and collect contaminants in the paper pulp or furnish. This makes cleaning of the fabric more difficult as contrasted with a more open weave. Greater downtime of the papermaking machine may be required to remove the contaminants, or if cleaning is not properly conducted the useful life of a fabric may be shortened. For these rea-sons multilayer fabrics have found limited usage in the production of certain paper grades.
llS~
Multilayer fabrics can also present quite difEerent characteris-tics on a papermaking machine than the previously used single layer fabrics which they supplant, and these differences can cause prob-lems in replacing single layer fabrics with multilayer designs. ~'he thickness and bulk of the multilayer fabrics present different drain-age and flow characteristics, and fiber support and retention may also be different, so that adjustments may be necessary in the papermaking process to accommodate multilayer fabrics in installations where the more conventional single layer fabrics have been used. For some papermaking it consequently would be desirable to design multilayer fabrics with characteristics that are more similar to those of single layer fabrics.
The present invention relates to multilayer fabrics for paper-making, and can reside in a fabric having threads of a multiple layer thread system extending in one direction of the fabric, threads of a single layer thread system extending in a direction normal to the threads of the multiple layer system, threads in the upper layer of the multiple layer system being grouped with threads in the lower layer of -the multiple layer system with threads of a group being stacked one above the other, the threads of the single layer system interweaving with the threads of each layer of the multiple layer system, and the projected open area of the fabric being in a range of about 13 to 25 percent of the total fabric area.
In another aspect of the invention the threads of the upper layer of the multiple layer system are horizontally spaced from one another, the threads of the lower layer of the multiple layer system are similar-ly spaced horizontally from one another, and the threads of the single layer thread system are spaced apart to have a thread density of aboul;
0. 50 to 0. 65 with a resultant projected open area for the fabric being within 13 to 25 percent of the total fabric area.
ii51~B~
The design of such a p~permaking fabric is a complex under-taking involving several interrelated factors. It i6 necessary to ob-tain proper knuckle heights on both surfaces of the fabric. On the lower, or wear surface that travels over and around the component parts of the associated papermaking machine it is normally desirable to have floats or knuckles of the cross machine threads predominate, so as to withstand abrasion and take the physical wear to which a fab-ric is subjected. The machine direction threads are then recessed from the outermost fabric surface formed by the knuckles of the cross machine threads, so as to retain a greater percentage of their cross section area throughout fabric life and thereby better withstand the longitudinal stresses that are imposed upon the fabric in driving it around the rolls, foils and suction boxes of the paper machine. On the upper, or paper supporting surface of the fabric it is desirable to have the thread knuckles provide sufficient support areas for the paper sheet being formed to obtain good release of the sheet from the fabric. For some papers the spacing and heights of the knuckles should be arranged to minimize marking. The relative knuckle lengths and heights of the machine direction and cross machine direction threads can also affect fiber orientation, which may produce different paper characteristics.
The design of the fabric should also provide uniEorm drainage and uni-form fiber support across the fabric surface. To obtain such uniformity it is desirable to have the threads of both thread systems extend sub-stantially straight, when viewed in the plane of the fabric, with minimal lateral crimp, in order to maintain uniform spacing between threads.
The threads of the two systems should also satisfactorily interlock with one another where they bind at crossover points to develop stability and prohibit relative shifting of the threads.
Another design factor is the permeance to water flow. The drainage rate and turbulence of water flowing through a fabric may affect the papermaking qualities of a fabric. For example, drainage rates are a factor in determining the amount of water that can be in-cluded in the furnish. For a more open fabric with a higher rate of drainage more water can be used while maintaining the same degree of water content in the paper web at the point where the paper sheet releases from the fabric. With the use of more water, a better dis-persion of fibers can be achieved to enhance the paper being produced.
These various factors have been accommodated in the multi-layer fabric of the present invention. A major improvement has been a reduction in the volume of thread material used in the single layer thread system, which system preferably extends in the longitudinal, or machine direction of the fabric. This reduction of thread material in the single layer thread system is achieved by spacing the single layer threads from one another. The reduction in thread material opens up the fabric to develop openings extending straight through the full depth of the fabric. Such openings present direct lines of sight through the fabric which define a projected open area for the fabric. Thus, there are direct paths for water drainage that distinguish from the more tor-tuous water llow paths in prior multilayer papermaking fabrics. The openings allow water sprays to pass directly through the fabric to aug-ment release of paper trimmings from the fabric, and to improve the cleaning characteristics of the fabric. Also, the increased drainage rate that can be obtained allows the papermaker to either add water to his furnish to improve fiber dispersion, or to operate a machine at a faster speed.
In preferred embodiments of the invention, the threads in both thread systems have minimal lateral crimp so as to extend substantially straight as viewed in the plane of the fabric. Also, threads in the multiple layer thread system are grouped together in pairs that com-prise a thread from an upper layer hered above a thread from a lower .
layer, so that threads of a group are in a stacked relation with minimal deviation from vertical alignment. These characteristics of straight threads and vertical stacking develop uniform, rectangular openings throughout the fabric to achieve uniform drainage and fiber support.
In providing these advantages, the invention also can incor-porate long floats on the paper side Ior good fiber support, recessed longitudinal threads on the wear side, adequate knuckle formation to bind the threads in place and dimensional stability. The resulting fabric is particularly suited as a forming medium for the production of linerboard and similar heavy papers. Thus, the advantages of multilayer fabrics are extended to a large segment of paper produc-tion.
In the drawings which illustrate an embodiment of the invention, Fig. 1 is a plan view of a fragmentary portion of a papermak-ing fabric of the invention showing the paper forming surface of the fabric, Fig. 2 is a view in section taken through the plane 2-2 indica-ted in Fig. 1 to illustrate the general contour of a thread in the single layer thread system of the fabric, Fig. 3 is a view in section taken through the plane 3-3 indica-ted in Fig. 1 to show the general contours of a pair of stacked threads in the upper and lower layers of the multilayer thread system of the fabric, Fig. 4 is a top view of a single thread to illustrate the nature of lateral crimp in a thread, Fig. 5 is a top view of a pair of stacked threads in the multi-layer thread system of the fabric, and Fig. 6 is a graph illustrating the void volume within the fab-ric .
Referring to Fig. 1, there is shown a fragmentary portion of ~5~
a paperforming fabric 1 of the present invention suitable for use in the forming, or wet end of a papermaking machine. As is usual in the manufacture of papermaking fabrics, the fabric is woven on a loom from suitable synthetic threads and is fashioned into a large end-less belt that is heat treated and stretched to set the individual threads into their final configurations. However, different materials, both synthetic and natural as well as metal, can be employed if found satis-factory, and the invention is not restricted in this regard or to the man-ner of weaving and finishing of the fabric. The fabric 1 has a paper supporting surface comprising the outer face of the endless belt, and it is this surface that is seen in Fig. 1. This surface is also indicated in Figs. 2 and 3 by the numeral 2, and in the description herein it may be referred to as the upper surface although on the return path in a papermaking machine it may be facing downwardly. The opposite face of the fabric that is on the inside of the endless belt is known as the wear surface, and it travels over rolls, suction boxes and foils of the papermaking machine. In Figs. 2 and 3 it is indicated by the numeral 3, and this wear surface may be referred to as the lower surface of the fabric to distinguish from the upper forming surface. In Fig. 1 a first double headed arrow labeled MD indicates the machine direc-tion of a papermaking machine upon which the fabric 1 may be used, and this direction may also be referred to as the longitudinal direc-tion of the fabric. A second double headed arrow labeled CMD refers to the cross machine direction, or the transverse direction of the fabric .
The fabric 1 is of a double layer construction in which the threads in the cross machine, or transverse direction comprise a two layer thread system as illustrated in Figs. 2 and 3. If the fabric is woven flat in a loom and then subsequently seamed into an endless belt these transverse threads will comprise shute threads extending ll~ii9~1 in the cross machine direction. The fragmentary portion of the fab-ric 1 shown in -the drawings has an upper layer 4 comprised of a set of shute threads 4a through 4i, and a lower layer 5 comprising a set of shute threads 5a through 5i. Each thread of the layer 5 is vertical:Ly aligned with a thre2d of the upper layer 4, so that the threads of the upper and lower layers of the multilayer thread system are stacked in groups of two with substantial horizontal spacing between adjacent groups. The machine, or longitudinal direction threads 6a through 6i comprise a single layer thread system 6 of substantial depth, with each thread 6a-6i interlacing with both the upper and lower layers of shute threads 4 and 5. In a flat woven fabric the threads 6 will com-prise warps that are subsequently seamed at their ends to form a large endless papermaking belt.
The contour of the longitudinal thread 6f seen in Fig. 2 is typical of each thread in the single layer thread system, and although the drawings do not represent exact thread shapes they provide close approximations from an actual fabric sample. The thread 6f has a weave that is repeated every eight threads of each of the upper layer threads 4 and the lower layer threads 5, or as may be alternatively stated a weave repeat of a thread 6 of the single layer thread system has sixteen crossovers with the threads of the two layer thread sys-tem. By crossover is meant the intersection where a thread of one thread system passes across a thread of the other thread system, and a machine direction thread 6 can have two crossovers at a single point where it passes a pair of tiered cross machine threads 4 and 5.
In its weave repeat, the longitudinal thread 6f will pass above and around a first thread 4a of the upper layer to form a binding point therewith. It then runs under the next successive three threads 4b, 4c, and 4d, so as to be sandwiched between the upper and lower thread layers 4 and 5 as an interior thread. Next, the longitudinal ~151~81 thread 6f interlaces downwardly through the bottom layer 5 to pass under and around the thread 5e to bind with a single thread of the lower layer.
The longitudinal thread 6 then interlaces upwardly through the lower layer 5 and again runs as an interior thread for three successive groups of stacked cross machine threads to complete the weave repeat. The major portion of the length of a weave repeat of the thread 6f thus lies between the upper and lower cross machine layers 4, 5, as an interior thread buried inside the fabric. In the fabric 1 illustrated in the draw-ings each thread 6 is an interior thread at three-fourths of its cross-10 overs, and in the practice of the invention the single layer threads arepreferably in the interior position for at least two-thrids of their cross-overs .
As seen in Fig. 3, each thread 4h and 5h has eight crossovers with the longitudinal threads 6a-6h in one complete repeat of its weave pattern. The thread 4h of the upper layer binds at the point 7 with a single thread 6a by interlacing downwardly through the single layer system to pass beneath and around such thread 6a and then interlacing upwardly back to the top of the fabric 1. The thread 4h then passes above seven successive threads 6b-6h at their respective crossovers 20 to complete its weave repeat, after which it will again interlace down-wardly through the threads 6 to commence the next cycle of its pattern by binding at point 8 with thread 6i. By the term binding, or binding point is meant the interlacing of a thread of one thread system through another thread system to pass around the opposite side of a thread or threads of such other system, and then interlacing back through the other thread system to form a relatively short knuckle that holds the thread systems together.
The threads 5a-5i of the bottom layer 5 of the multilayer thread system each have a weave repeat of eight longitudinal threads 6, 30 and the general contour of each thread 5a-5i is substantially an inver-115~981 sion of the threads of the upper layer 4. As seen in Fig. 3, there is a binding point 9 at which the thread 5h interlaces upwardly through the single layer thread system 6 and passes above and around the single thread 6e, so as to bind therewith, and then back downwardly through the layer of threads 6 to return to the undersurface of the fab-ric 1. The binding point 9 is equally spaced in the transverse direc-tion from the binding points 7 and 8 at which the upper thread 4h is in binding engagement with threads 6a and 6i. This equal spacing com-prises three interior machine direction threads 6 on each side of the binding point 9 between it and the next binding point 7, 8. This pro-duces a balanced weave pattern in which the binding points along a pair, or group of tiered cross machine threads are spaced a maximum distance from one another. While such a symmetrically balanced pattern can be achieved in a fabric having an even numbered weave repeat for the multilayer threads, in weave repeats of odd numbersJ
such as in a seven shaft or nine shaft fabric, an exact, symmetrical balance is not possible, but a substantial balance can be obtained in which the number of interior single layer threads to one side of a bind-ing point differs by only one from the number of interior single layer threads on the opposite side of the binding point. The term substantial balance is used to mean this condition as well as a symmetrical bal-ance .
As seen in Figs. 1 and 3, the longitudinal threads 6a through 6i of the single layer thread system 6 are spaced apart from one another, and this spacing coupled with the spacing between adjacent, tiered groups of the multilayer thread system provides openings 10 (see Fig. 1) that extend straight through the fabric 1. Such openings 10 when viewed from above, or beneath the fabric provide direct lines of sight through the fabric which constitute a projected open area. The fabrics 3u of the invention have a projected open area that may range between 115~9~31 13 to 25 percent of the total fabric area, which range suhstantially co-incides with that of single layer fabrics which the invention is intended to supplant. Such an open area affords ready passage of water straight through the fabric 1, so that water showers located on one side of the fabric can impinge upon paper adhering on the opposite fabric side to lift the paper off the fabric and release it from engagement with the fabric. The open area also allows a flushing action from shower sprays to cleanse and clean the fabric during each revolution around the paper machine, to thereby inhibit the collection and permanent ad-hesion of contaminants that are present in the furrlish from which the paper web is formed.
The spacing between the single layer threads 6 is preferably achieved by spreading the threads 6 from one another, rather than by reducing their diameters. This creates relatively longer floats for the multiple layer threads 4 and 5. This increased float length on the paper forming side of the fabric increases the prominence of the cross-wise threads for supporting fibers and paper, and the short knuckles of the single layer threads need not be relied upon for fiber and paper support to the same degree as in fabrics with shorter float lengths.
Thus, one aspect of the invention is the development of longer cross-wise floats for improving sheet support. The spreading of the single layer threads relatively reduces the single layer thread count, and the ratio of single layer thread count to the thread count of a layer of the multilayer thread system may be 1. 4 and lower.
As an example of the invention, a fabric was woven flat with the warp threads in the loom comprising the single layer thread sys-tem 6. Such threads were . 35 mm (. 0138 inch) in diameter of usual polyester monofilament. The upper and lower shute threads 4, 5 form-ing the two crosswise layers of the multiple layer thread system were polyester monofilaments each having a diameter of . 40 mm (. 0157 inch).
1~5~
The upper layer 4 was of a relatively stiffer monofilament than the lower layer, which was of a usual material. The final mesh count for the single layer of warp threads 6 was forty-three threads per inch, and for each layer 4, 5 of shute threads was 35 per inch. These di-rnensions provide a calculated projected open area of 18. 3 percent.
The density of the warp, or single layer thread system was 0. 593, and that of the shute, or multiple layer system (assuming perfect stacking) was 0. 55. For fabrics of the invention the single layer thread density is preferably within a range of about 0. 50 to 0. 65.
The finished fabric had a difference between the knuckle heights of the warp (longitudinal) threads 6 and shute (crosswise) threads 4 on the upper, or paper side of the fabric of . 0085 inch, with the shute extending above the warp. This plane difference is represented by the distance 11 in Figs. 2 and 3. On the lower, or wear side of the fabric the shute (crosswise) knuckles extended . 0120 inch outside of the warp (longitudinal) knuckles to be the major wearing elements of the fabric, and the plane difference on the wear side is represented by the dis-tance 12 in Figs. 2 and 3. The total fabric thickness was . 0595 inch, the fabric had a high resistance to stretching, and the air permeability was 758 cubic feet per minute per square foot at 0. 5 inch of water pressure drop. This latter figure compares favorably with sing]e mesh fabrics, and indicates a greater opening for water drainage than in prior multilayer fabrics.
Referring again to the balanced binding point positions shown in Fig. 3, the number of interior threads 6 between the binding point 7 and the binding point 9 comprises a set of three threads 6b, 6c and 6d.
On the opposite side of the binding point 9, the number of interior threads 6 between the binding points 9 and 8 comprises a second set of three threads 6f, 6g and 6h. This results in a substantial spacing ~0 between binding points 7, 8, 9 along the lengths of the stacked threads 4h, 5h. ~s a result, the lateral forces acting upon the single layer threads 6 that are created by the in-terlacings of the multiple layer threads 4h, 5h through the single layer is minimized. These forces tend to develop lateral crimp in the threads 6, and by minimizing the lateral forces undesirable lateral crimp in the single layer threads 6 is avoided to obtain substantially straight threads. This results in substantially rectangular openings 10 in the fabric. To achieve a mini-mal lateral crimp in the thread system 6 the number of interior single layer threads 6 between successive binding points along the upper and lower threads of a stacked group in the multilayer thread system is preferably at least two threads. In the embodiment of the drawings, the number is shown as three, which has provided good minimization of lateral crimp in the single layer thread system.
A method of rneasuring lateral crimp of a thread is illustrated in Fig. 4, which shows an isolated thread 6 of the single layer system as viewed from above, or in the plane of the fabric. For illustration, the curvature of this thread 6 is exaggerated. An envelope within which the thread 6 lies is defined by the tangent lines 13 on opposite sides of`
the thread 6. If the thread diameter D is subtracted from the width of the envelope E, and the remainder is then divided by the diameter D
the result is a dimensionless value for lateral crimp. For fabrics of the invention lateral crimp can be held within a value of 0. 33 and less.
A high degree of stacking for vertical groups in the multiple layer thread system is another characteristic of preferred forms of the invention. In Fig. 5 there is represented a stacked group of threads of the multiple layer thread system as seen from above, or in the plane of the fabric. They comprise one thread 4 from the upper layer and its paired underlying thread 5 from the lower layer. The curva-ture of these two threads and of the sideward offsets O between the threads are exaggerated -for the purpose of illustration. In a perfect ~15~
stacking of one thread 4 above its mate 5 there -would be no offsets O.
The degree of of Eset, or stacking fac-tor, at any point along the length of two threads 4, 5 of like diameter can be calculated by dividing the offset O by the thread diameter. I'he maximum stacking factor for a fabric like that of Fig. 1 should not exceed a value of 0. 4, and the average value along the thread lengths should not exceed a value of 0. 2. If the upper and lower threads in the multiple layer thread sys-tem are of different diameters, then the stacking factor is determined by measuring the offset O of the smaller thread and dividing by the average of the two diameters.
The use of a relatively stiff thread material for the upper lay-er 4 in the multiple layer thread system causes the thread knuckles of the single layer thread system 6 to be more elevated at their bind-ing points, so as to rise toward the plane of the knuckle crests of the upper layer of the multiple layer thread system. This may further im-prove fiber and sheet support. The stiffer material has also been found to reduce lateral crimp in the multilayer threads and improve stacking.
Stifness is indirectly related to tensile strength, and measurements of loads to produce one percent of thread elongation at uniform diameters have been made for threads of the multilayer system. The ratio of this tensile measurement of stiffer upper layer threads to less stiff lower layer threads has ranged upwardly to a value of 2. 25.
Referring now to Fig. 6, this graph represents the void volume of a fabric having a single layer thread system formed of 43 warp threads per inch of . 35 mm diameter, and a multiple layer thread sys-tem comprised of . 35 mm diameter shute woven in 35 threads per inch for each layer. The ordinate of the graph represents depth within the fabric, and indicates that the fabric had a thickness of 1. 33 mm. The lower scale on the abscissa represents in percent the solid cross sec-tion area of the fabric, and the upper scale on the abscissa represents ~:~5~
in percent the void area, or space, within the fabric. Data for the graph was obtained by potting a sample piece of fabric itl a suitable resin, so as to firmly hold the fabric threads in place, and then care-fully grinding away the fabric and at successive levels measuring the area occupied by the threads.
The upper curve 14 represents the upper shute, or layer 4. of the multiple layer thread system, with area to the left of the curve being the solid fraction represented by such upper layer. The lower curve 15 represents the lower shute, or layer 5 of the multiple layer thread system, and the middle curve 16 represents the warp, or single layer thread system 6. Curve 17 is an addition of the three thread curves 14, 15, and 16, so that the space to the left of the composite curve 17 represents the total volume of the fabric threads. The space to the right of the curve 17 conversely represents the free space, or void volume within the -fabric.
The point 18 of curve 17 indicates the greatest restriction with-in the fabric to water flow and the level within the fabric at which such restriction occurs. The void volume within the fabric is at a maximum near the upper and lower fabric surfaces, and upon progression toward the fabric center the void volume decreases, or necks down, to the point 18. The percent of open area at this point 18 is a major deter-minant of the drainage and flow characteristics of the fabric, and in the graph of Fig. 6 the smallest void volume is about 47%. This con-trasts with measured values for typical single layer fabrics of 25 to 32 percent, and illustrates that multilayer fabrics of the invention, in which the density of the threads of the single layer thread system is reduced, can compare favorably with the flow characteristics of single layer fabrics which they supplant. Preferably the smallest void volume at any level within fabrics of the invention is no less than forty percent.
Although the foregoing discussion has related primarily to llSlg~l L`abrics for the forming, or wet end of a paper machineJ fabrics of the invention also can be used in ~ifferent sections of a papermaking ma-chine where advantages of the invention rnay be realized. The in-vention provides a multilayer fabric of significant projected open area coupled with a substantial minimum void volume. Water flow through the fabric is greatly improved, and -the use of multilayer fabrics can be e~tended to new applications.
L,OW l)ENSITY MIJI.TII.l~Y]~R
PIL\ PER MA KING ~ABRIC
This invention relates to papermaking fabrics, and more par ticularly to multilayer fabrics characterized by threads of a multiple layer thread system extending in one fabric direction and threads of a single layer thread system extending in the other fabric direction, such single layer threads being interwoven with the threads of each layer of the multiple layer system.
In recent years there has been an increasing use of multilayer fabrics in the wet, or forming end of papermaking machines. Such multilayer fabrics supplant single layer fabrics that consist of a single layer of longitudinally extending threads interwoven with a single layer of transversely extending threads. The multilayer fabrics can pro-vide special advantages, such as improved stretch resistance to tension loads imparted by a papermaking machine, resistance to crimp inter-change between longitudinal and transverse thread systems, greater stiffness that reduces wrinkling of the fabric, better paper sheet sup-port and longer wear life. Because of these advantages the use of multilayer fabrics has been increasing.
Multilayer fabrics usually have one thread systcm comprised of two layers of threads extending transversely, or crosswise to the machine or running direction of the fabric, with each thread of the upper layer being paired with and lying directly above a thread of the lower layer. A second thread system comprises a single layer of threads extending in the longitudinal, or machine direction of the fabric, and each of these threads is interwoven with the threads of both layers of the two layer thread system. Over the years such multi-layer fabrics have been steadily improved and refined to enhance their papermaking qualities. Several of these improvements have concern-ed the development of preferred crimp relationships between the two ~:lS19i~1 thread systems. For example, in U. S. patent No. 4, 071, 050 issued on an application filed July 16, 1973, the longitudinally extending threads of the single layer thread system are interwoven with the upper layer of the two layer thread system in such manner that upon stretching the fabric during manufacture the thread knuckles of both thread systems on the upper fabric surface come into a nearly com-mon plane to achieve a better paper forming surface. In U. S. patent No. 4, 041, 989 issued on an application filed September 30, 1975, the ~nuckles of longitudinally extending threads of the single layer thread system are receded into the fabric on the lower fabric surface to ex-pose the threads of the lower layer of the two layer thread system as the primary wearing elements of the fabric. And, in U. S. patent No.
4, 112, 982 issued on an application filed February 17, 1977, the num-ber of crossovers of the transversely extending threads of the upper layer of the two layer thread system are increased to develop a paper forming surface comprised primarily oE long crosswise thread knuckles to decrease paper marking.
Some additional multilayer fabric structures are shown in U. S.
patent No. 4, 086, 941 issued on an application filed October 26, 1976, wherein a two layer thread system consisting o-f shute threads has the threads of one layer horizontally offset from the threads of the other layer, and in U. S. patent No. 4, 171, 009 issued on an application filed March 22, 1977, in which long knuckles are formed in the single layer thread system on the paperforming side of the fabric by having these threads bind with three to seven threads of the upper layer of the multiple layer thread system. Besides the development of multilayer papermaking fabrics characterized by a single layer thread system extending in one fabric direction, some work has also been done on multiple ply fabrics, as shown in U. S. patent Nos. 3, 885, 602 and 3, 885, 603. In these fabrics each ply has its own interwoven longitu-~15~
dinal and transverse thread systems, and the plies are tied together with threads interweaving between both plies. Such multiple ply fab-rics have not achieved widespread usage as have the multilayer fab-rics .
I~eretofore, multilayer fabrics have been constructed with very high thread densities for the single layer thread system, in order to achieve dimensional stability and to minimize shifting of threads with-in the fabric. Thread density can be measured by multiplying the num-ber of threads per unit width of fabric by the thread diameter, and for the single layer thread system the densities have commonly run near a value of 1. 0. As examples, Fig. 3A of the aforesaid patent No. 4,11", 982 shows the threads of the single layer system lying side by side, and in patent No. 4,171, 009 the density is stated at Col. 3, line 15 as being 1. 05 and above.
This requirement of a high thread density for the single layer thread system can inhibit "knock-off" water showers from loosening edge trim of a paper web from the fabric after it passes the couch roll of a paper forming machine, and in machines where this -trim removal requires assistance in being stripped from the forming fabric multilayer fabrics are not widely used. This has been a particular problem in the manu-facture of brown papers including linerboard, which is one of the major products of the papermaking industry. Another problem with a dense fabric is that closely adjacent threads abutting one another are prone to hold and collect contaminants in the paper pulp or furnish. This makes cleaning of the fabric more difficult as contrasted with a more open weave. Greater downtime of the papermaking machine may be required to remove the contaminants, or if cleaning is not properly conducted the useful life of a fabric may be shortened. For these rea-sons multilayer fabrics have found limited usage in the production of certain paper grades.
llS~
Multilayer fabrics can also present quite difEerent characteris-tics on a papermaking machine than the previously used single layer fabrics which they supplant, and these differences can cause prob-lems in replacing single layer fabrics with multilayer designs. ~'he thickness and bulk of the multilayer fabrics present different drain-age and flow characteristics, and fiber support and retention may also be different, so that adjustments may be necessary in the papermaking process to accommodate multilayer fabrics in installations where the more conventional single layer fabrics have been used. For some papermaking it consequently would be desirable to design multilayer fabrics with characteristics that are more similar to those of single layer fabrics.
The present invention relates to multilayer fabrics for paper-making, and can reside in a fabric having threads of a multiple layer thread system extending in one direction of the fabric, threads of a single layer thread system extending in a direction normal to the threads of the multiple layer system, threads in the upper layer of the multiple layer system being grouped with threads in the lower layer of -the multiple layer system with threads of a group being stacked one above the other, the threads of the single layer system interweaving with the threads of each layer of the multiple layer system, and the projected open area of the fabric being in a range of about 13 to 25 percent of the total fabric area.
In another aspect of the invention the threads of the upper layer of the multiple layer system are horizontally spaced from one another, the threads of the lower layer of the multiple layer system are similar-ly spaced horizontally from one another, and the threads of the single layer thread system are spaced apart to have a thread density of aboul;
0. 50 to 0. 65 with a resultant projected open area for the fabric being within 13 to 25 percent of the total fabric area.
ii51~B~
The design of such a p~permaking fabric is a complex under-taking involving several interrelated factors. It i6 necessary to ob-tain proper knuckle heights on both surfaces of the fabric. On the lower, or wear surface that travels over and around the component parts of the associated papermaking machine it is normally desirable to have floats or knuckles of the cross machine threads predominate, so as to withstand abrasion and take the physical wear to which a fab-ric is subjected. The machine direction threads are then recessed from the outermost fabric surface formed by the knuckles of the cross machine threads, so as to retain a greater percentage of their cross section area throughout fabric life and thereby better withstand the longitudinal stresses that are imposed upon the fabric in driving it around the rolls, foils and suction boxes of the paper machine. On the upper, or paper supporting surface of the fabric it is desirable to have the thread knuckles provide sufficient support areas for the paper sheet being formed to obtain good release of the sheet from the fabric. For some papers the spacing and heights of the knuckles should be arranged to minimize marking. The relative knuckle lengths and heights of the machine direction and cross machine direction threads can also affect fiber orientation, which may produce different paper characteristics.
The design of the fabric should also provide uniEorm drainage and uni-form fiber support across the fabric surface. To obtain such uniformity it is desirable to have the threads of both thread systems extend sub-stantially straight, when viewed in the plane of the fabric, with minimal lateral crimp, in order to maintain uniform spacing between threads.
The threads of the two systems should also satisfactorily interlock with one another where they bind at crossover points to develop stability and prohibit relative shifting of the threads.
Another design factor is the permeance to water flow. The drainage rate and turbulence of water flowing through a fabric may affect the papermaking qualities of a fabric. For example, drainage rates are a factor in determining the amount of water that can be in-cluded in the furnish. For a more open fabric with a higher rate of drainage more water can be used while maintaining the same degree of water content in the paper web at the point where the paper sheet releases from the fabric. With the use of more water, a better dis-persion of fibers can be achieved to enhance the paper being produced.
These various factors have been accommodated in the multi-layer fabric of the present invention. A major improvement has been a reduction in the volume of thread material used in the single layer thread system, which system preferably extends in the longitudinal, or machine direction of the fabric. This reduction of thread material in the single layer thread system is achieved by spacing the single layer threads from one another. The reduction in thread material opens up the fabric to develop openings extending straight through the full depth of the fabric. Such openings present direct lines of sight through the fabric which define a projected open area for the fabric. Thus, there are direct paths for water drainage that distinguish from the more tor-tuous water llow paths in prior multilayer papermaking fabrics. The openings allow water sprays to pass directly through the fabric to aug-ment release of paper trimmings from the fabric, and to improve the cleaning characteristics of the fabric. Also, the increased drainage rate that can be obtained allows the papermaker to either add water to his furnish to improve fiber dispersion, or to operate a machine at a faster speed.
In preferred embodiments of the invention, the threads in both thread systems have minimal lateral crimp so as to extend substantially straight as viewed in the plane of the fabric. Also, threads in the multiple layer thread system are grouped together in pairs that com-prise a thread from an upper layer hered above a thread from a lower .
layer, so that threads of a group are in a stacked relation with minimal deviation from vertical alignment. These characteristics of straight threads and vertical stacking develop uniform, rectangular openings throughout the fabric to achieve uniform drainage and fiber support.
In providing these advantages, the invention also can incor-porate long floats on the paper side Ior good fiber support, recessed longitudinal threads on the wear side, adequate knuckle formation to bind the threads in place and dimensional stability. The resulting fabric is particularly suited as a forming medium for the production of linerboard and similar heavy papers. Thus, the advantages of multilayer fabrics are extended to a large segment of paper produc-tion.
In the drawings which illustrate an embodiment of the invention, Fig. 1 is a plan view of a fragmentary portion of a papermak-ing fabric of the invention showing the paper forming surface of the fabric, Fig. 2 is a view in section taken through the plane 2-2 indica-ted in Fig. 1 to illustrate the general contour of a thread in the single layer thread system of the fabric, Fig. 3 is a view in section taken through the plane 3-3 indica-ted in Fig. 1 to show the general contours of a pair of stacked threads in the upper and lower layers of the multilayer thread system of the fabric, Fig. 4 is a top view of a single thread to illustrate the nature of lateral crimp in a thread, Fig. 5 is a top view of a pair of stacked threads in the multi-layer thread system of the fabric, and Fig. 6 is a graph illustrating the void volume within the fab-ric .
Referring to Fig. 1, there is shown a fragmentary portion of ~5~
a paperforming fabric 1 of the present invention suitable for use in the forming, or wet end of a papermaking machine. As is usual in the manufacture of papermaking fabrics, the fabric is woven on a loom from suitable synthetic threads and is fashioned into a large end-less belt that is heat treated and stretched to set the individual threads into their final configurations. However, different materials, both synthetic and natural as well as metal, can be employed if found satis-factory, and the invention is not restricted in this regard or to the man-ner of weaving and finishing of the fabric. The fabric 1 has a paper supporting surface comprising the outer face of the endless belt, and it is this surface that is seen in Fig. 1. This surface is also indicated in Figs. 2 and 3 by the numeral 2, and in the description herein it may be referred to as the upper surface although on the return path in a papermaking machine it may be facing downwardly. The opposite face of the fabric that is on the inside of the endless belt is known as the wear surface, and it travels over rolls, suction boxes and foils of the papermaking machine. In Figs. 2 and 3 it is indicated by the numeral 3, and this wear surface may be referred to as the lower surface of the fabric to distinguish from the upper forming surface. In Fig. 1 a first double headed arrow labeled MD indicates the machine direc-tion of a papermaking machine upon which the fabric 1 may be used, and this direction may also be referred to as the longitudinal direc-tion of the fabric. A second double headed arrow labeled CMD refers to the cross machine direction, or the transverse direction of the fabric .
The fabric 1 is of a double layer construction in which the threads in the cross machine, or transverse direction comprise a two layer thread system as illustrated in Figs. 2 and 3. If the fabric is woven flat in a loom and then subsequently seamed into an endless belt these transverse threads will comprise shute threads extending ll~ii9~1 in the cross machine direction. The fragmentary portion of the fab-ric 1 shown in -the drawings has an upper layer 4 comprised of a set of shute threads 4a through 4i, and a lower layer 5 comprising a set of shute threads 5a through 5i. Each thread of the layer 5 is vertical:Ly aligned with a thre2d of the upper layer 4, so that the threads of the upper and lower layers of the multilayer thread system are stacked in groups of two with substantial horizontal spacing between adjacent groups. The machine, or longitudinal direction threads 6a through 6i comprise a single layer thread system 6 of substantial depth, with each thread 6a-6i interlacing with both the upper and lower layers of shute threads 4 and 5. In a flat woven fabric the threads 6 will com-prise warps that are subsequently seamed at their ends to form a large endless papermaking belt.
The contour of the longitudinal thread 6f seen in Fig. 2 is typical of each thread in the single layer thread system, and although the drawings do not represent exact thread shapes they provide close approximations from an actual fabric sample. The thread 6f has a weave that is repeated every eight threads of each of the upper layer threads 4 and the lower layer threads 5, or as may be alternatively stated a weave repeat of a thread 6 of the single layer thread system has sixteen crossovers with the threads of the two layer thread sys-tem. By crossover is meant the intersection where a thread of one thread system passes across a thread of the other thread system, and a machine direction thread 6 can have two crossovers at a single point where it passes a pair of tiered cross machine threads 4 and 5.
In its weave repeat, the longitudinal thread 6f will pass above and around a first thread 4a of the upper layer to form a binding point therewith. It then runs under the next successive three threads 4b, 4c, and 4d, so as to be sandwiched between the upper and lower thread layers 4 and 5 as an interior thread. Next, the longitudinal ~151~81 thread 6f interlaces downwardly through the bottom layer 5 to pass under and around the thread 5e to bind with a single thread of the lower layer.
The longitudinal thread 6 then interlaces upwardly through the lower layer 5 and again runs as an interior thread for three successive groups of stacked cross machine threads to complete the weave repeat. The major portion of the length of a weave repeat of the thread 6f thus lies between the upper and lower cross machine layers 4, 5, as an interior thread buried inside the fabric. In the fabric 1 illustrated in the draw-ings each thread 6 is an interior thread at three-fourths of its cross-10 overs, and in the practice of the invention the single layer threads arepreferably in the interior position for at least two-thrids of their cross-overs .
As seen in Fig. 3, each thread 4h and 5h has eight crossovers with the longitudinal threads 6a-6h in one complete repeat of its weave pattern. The thread 4h of the upper layer binds at the point 7 with a single thread 6a by interlacing downwardly through the single layer system to pass beneath and around such thread 6a and then interlacing upwardly back to the top of the fabric 1. The thread 4h then passes above seven successive threads 6b-6h at their respective crossovers 20 to complete its weave repeat, after which it will again interlace down-wardly through the threads 6 to commence the next cycle of its pattern by binding at point 8 with thread 6i. By the term binding, or binding point is meant the interlacing of a thread of one thread system through another thread system to pass around the opposite side of a thread or threads of such other system, and then interlacing back through the other thread system to form a relatively short knuckle that holds the thread systems together.
The threads 5a-5i of the bottom layer 5 of the multilayer thread system each have a weave repeat of eight longitudinal threads 6, 30 and the general contour of each thread 5a-5i is substantially an inver-115~981 sion of the threads of the upper layer 4. As seen in Fig. 3, there is a binding point 9 at which the thread 5h interlaces upwardly through the single layer thread system 6 and passes above and around the single thread 6e, so as to bind therewith, and then back downwardly through the layer of threads 6 to return to the undersurface of the fab-ric 1. The binding point 9 is equally spaced in the transverse direc-tion from the binding points 7 and 8 at which the upper thread 4h is in binding engagement with threads 6a and 6i. This equal spacing com-prises three interior machine direction threads 6 on each side of the binding point 9 between it and the next binding point 7, 8. This pro-duces a balanced weave pattern in which the binding points along a pair, or group of tiered cross machine threads are spaced a maximum distance from one another. While such a symmetrically balanced pattern can be achieved in a fabric having an even numbered weave repeat for the multilayer threads, in weave repeats of odd numbersJ
such as in a seven shaft or nine shaft fabric, an exact, symmetrical balance is not possible, but a substantial balance can be obtained in which the number of interior single layer threads to one side of a bind-ing point differs by only one from the number of interior single layer threads on the opposite side of the binding point. The term substantial balance is used to mean this condition as well as a symmetrical bal-ance .
As seen in Figs. 1 and 3, the longitudinal threads 6a through 6i of the single layer thread system 6 are spaced apart from one another, and this spacing coupled with the spacing between adjacent, tiered groups of the multilayer thread system provides openings 10 (see Fig. 1) that extend straight through the fabric 1. Such openings 10 when viewed from above, or beneath the fabric provide direct lines of sight through the fabric which constitute a projected open area. The fabrics 3u of the invention have a projected open area that may range between 115~9~31 13 to 25 percent of the total fabric area, which range suhstantially co-incides with that of single layer fabrics which the invention is intended to supplant. Such an open area affords ready passage of water straight through the fabric 1, so that water showers located on one side of the fabric can impinge upon paper adhering on the opposite fabric side to lift the paper off the fabric and release it from engagement with the fabric. The open area also allows a flushing action from shower sprays to cleanse and clean the fabric during each revolution around the paper machine, to thereby inhibit the collection and permanent ad-hesion of contaminants that are present in the furrlish from which the paper web is formed.
The spacing between the single layer threads 6 is preferably achieved by spreading the threads 6 from one another, rather than by reducing their diameters. This creates relatively longer floats for the multiple layer threads 4 and 5. This increased float length on the paper forming side of the fabric increases the prominence of the cross-wise threads for supporting fibers and paper, and the short knuckles of the single layer threads need not be relied upon for fiber and paper support to the same degree as in fabrics with shorter float lengths.
Thus, one aspect of the invention is the development of longer cross-wise floats for improving sheet support. The spreading of the single layer threads relatively reduces the single layer thread count, and the ratio of single layer thread count to the thread count of a layer of the multilayer thread system may be 1. 4 and lower.
As an example of the invention, a fabric was woven flat with the warp threads in the loom comprising the single layer thread sys-tem 6. Such threads were . 35 mm (. 0138 inch) in diameter of usual polyester monofilament. The upper and lower shute threads 4, 5 form-ing the two crosswise layers of the multiple layer thread system were polyester monofilaments each having a diameter of . 40 mm (. 0157 inch).
1~5~
The upper layer 4 was of a relatively stiffer monofilament than the lower layer, which was of a usual material. The final mesh count for the single layer of warp threads 6 was forty-three threads per inch, and for each layer 4, 5 of shute threads was 35 per inch. These di-rnensions provide a calculated projected open area of 18. 3 percent.
The density of the warp, or single layer thread system was 0. 593, and that of the shute, or multiple layer system (assuming perfect stacking) was 0. 55. For fabrics of the invention the single layer thread density is preferably within a range of about 0. 50 to 0. 65.
The finished fabric had a difference between the knuckle heights of the warp (longitudinal) threads 6 and shute (crosswise) threads 4 on the upper, or paper side of the fabric of . 0085 inch, with the shute extending above the warp. This plane difference is represented by the distance 11 in Figs. 2 and 3. On the lower, or wear side of the fabric the shute (crosswise) knuckles extended . 0120 inch outside of the warp (longitudinal) knuckles to be the major wearing elements of the fabric, and the plane difference on the wear side is represented by the dis-tance 12 in Figs. 2 and 3. The total fabric thickness was . 0595 inch, the fabric had a high resistance to stretching, and the air permeability was 758 cubic feet per minute per square foot at 0. 5 inch of water pressure drop. This latter figure compares favorably with sing]e mesh fabrics, and indicates a greater opening for water drainage than in prior multilayer fabrics.
Referring again to the balanced binding point positions shown in Fig. 3, the number of interior threads 6 between the binding point 7 and the binding point 9 comprises a set of three threads 6b, 6c and 6d.
On the opposite side of the binding point 9, the number of interior threads 6 between the binding points 9 and 8 comprises a second set of three threads 6f, 6g and 6h. This results in a substantial spacing ~0 between binding points 7, 8, 9 along the lengths of the stacked threads 4h, 5h. ~s a result, the lateral forces acting upon the single layer threads 6 that are created by the in-terlacings of the multiple layer threads 4h, 5h through the single layer is minimized. These forces tend to develop lateral crimp in the threads 6, and by minimizing the lateral forces undesirable lateral crimp in the single layer threads 6 is avoided to obtain substantially straight threads. This results in substantially rectangular openings 10 in the fabric. To achieve a mini-mal lateral crimp in the thread system 6 the number of interior single layer threads 6 between successive binding points along the upper and lower threads of a stacked group in the multilayer thread system is preferably at least two threads. In the embodiment of the drawings, the number is shown as three, which has provided good minimization of lateral crimp in the single layer thread system.
A method of rneasuring lateral crimp of a thread is illustrated in Fig. 4, which shows an isolated thread 6 of the single layer system as viewed from above, or in the plane of the fabric. For illustration, the curvature of this thread 6 is exaggerated. An envelope within which the thread 6 lies is defined by the tangent lines 13 on opposite sides of`
the thread 6. If the thread diameter D is subtracted from the width of the envelope E, and the remainder is then divided by the diameter D
the result is a dimensionless value for lateral crimp. For fabrics of the invention lateral crimp can be held within a value of 0. 33 and less.
A high degree of stacking for vertical groups in the multiple layer thread system is another characteristic of preferred forms of the invention. In Fig. 5 there is represented a stacked group of threads of the multiple layer thread system as seen from above, or in the plane of the fabric. They comprise one thread 4 from the upper layer and its paired underlying thread 5 from the lower layer. The curva-ture of these two threads and of the sideward offsets O between the threads are exaggerated -for the purpose of illustration. In a perfect ~15~
stacking of one thread 4 above its mate 5 there -would be no offsets O.
The degree of of Eset, or stacking fac-tor, at any point along the length of two threads 4, 5 of like diameter can be calculated by dividing the offset O by the thread diameter. I'he maximum stacking factor for a fabric like that of Fig. 1 should not exceed a value of 0. 4, and the average value along the thread lengths should not exceed a value of 0. 2. If the upper and lower threads in the multiple layer thread sys-tem are of different diameters, then the stacking factor is determined by measuring the offset O of the smaller thread and dividing by the average of the two diameters.
The use of a relatively stiff thread material for the upper lay-er 4 in the multiple layer thread system causes the thread knuckles of the single layer thread system 6 to be more elevated at their bind-ing points, so as to rise toward the plane of the knuckle crests of the upper layer of the multiple layer thread system. This may further im-prove fiber and sheet support. The stiffer material has also been found to reduce lateral crimp in the multilayer threads and improve stacking.
Stifness is indirectly related to tensile strength, and measurements of loads to produce one percent of thread elongation at uniform diameters have been made for threads of the multilayer system. The ratio of this tensile measurement of stiffer upper layer threads to less stiff lower layer threads has ranged upwardly to a value of 2. 25.
Referring now to Fig. 6, this graph represents the void volume of a fabric having a single layer thread system formed of 43 warp threads per inch of . 35 mm diameter, and a multiple layer thread sys-tem comprised of . 35 mm diameter shute woven in 35 threads per inch for each layer. The ordinate of the graph represents depth within the fabric, and indicates that the fabric had a thickness of 1. 33 mm. The lower scale on the abscissa represents in percent the solid cross sec-tion area of the fabric, and the upper scale on the abscissa represents ~:~5~
in percent the void area, or space, within the fabric. Data for the graph was obtained by potting a sample piece of fabric itl a suitable resin, so as to firmly hold the fabric threads in place, and then care-fully grinding away the fabric and at successive levels measuring the area occupied by the threads.
The upper curve 14 represents the upper shute, or layer 4. of the multiple layer thread system, with area to the left of the curve being the solid fraction represented by such upper layer. The lower curve 15 represents the lower shute, or layer 5 of the multiple layer thread system, and the middle curve 16 represents the warp, or single layer thread system 6. Curve 17 is an addition of the three thread curves 14, 15, and 16, so that the space to the left of the composite curve 17 represents the total volume of the fabric threads. The space to the right of the curve 17 conversely represents the free space, or void volume within the -fabric.
The point 18 of curve 17 indicates the greatest restriction with-in the fabric to water flow and the level within the fabric at which such restriction occurs. The void volume within the fabric is at a maximum near the upper and lower fabric surfaces, and upon progression toward the fabric center the void volume decreases, or necks down, to the point 18. The percent of open area at this point 18 is a major deter-minant of the drainage and flow characteristics of the fabric, and in the graph of Fig. 6 the smallest void volume is about 47%. This con-trasts with measured values for typical single layer fabrics of 25 to 32 percent, and illustrates that multilayer fabrics of the invention, in which the density of the threads of the single layer thread system is reduced, can compare favorably with the flow characteristics of single layer fabrics which they supplant. Preferably the smallest void volume at any level within fabrics of the invention is no less than forty percent.
Although the foregoing discussion has related primarily to llSlg~l L`abrics for the forming, or wet end of a paper machineJ fabrics of the invention also can be used in ~ifferent sections of a papermaking ma-chine where advantages of the invention rnay be realized. The in-vention provides a multilayer fabric of significant projected open area coupled with a substantial minimum void volume. Water flow through the fabric is greatly improved, and -the use of multilayer fabrics can be e~tended to new applications.
Claims (14)
1. In a multilayer papermaking fabric having a single layer thread system with threads extending in one direction of the fabric and a multiple layer thread system with threads extending in a di-rection normal to the threads of the single layer system, the com-bination of:
threads in an upper layer of said multiple layer thread sys-tem being grouped with threads in a lower layer of said multiple layer thread system, with threads of a group being stacked one above the other;
threads of said single layer thread system interweaving with the threads of each layer of the multiple layer thread system; and the projected open area of the fabric being within 13 to 25 percent of the total fabric area.
threads in an upper layer of said multiple layer thread sys-tem being grouped with threads in a lower layer of said multiple layer thread system, with threads of a group being stacked one above the other;
threads of said single layer thread system interweaving with the threads of each layer of the multiple layer thread system; and the projected open area of the fabric being within 13 to 25 percent of the total fabric area.
2. A fabric as in claim 1, wherein the void volume at any level within the fabric is no less than 40%.
3. A fabric as in claim 1 wherein the lateral crimp of threads in both thread systems is within a value of 0.33 as mea-sured by subtracting the thread diameter from the width of the thread envelope in the plane of the fabric and dividing the resultant by the thread diameter.
4. A fabric as in claim 1 wherein the threads of a stacked group in the multiple layer thread system have an average stacking factor not exceeding a value of 0.2.
5. A fabric as in claim 1 wherein a thread of the single layer thread system interlaces through the upper and lower layers of the multiple thread system to pass around the outside of threads of the upper and lower layers to form knuckles that are recessed within the knuckles of the threads of the upper and lower layers.
6. A fabric as in claim 1 wherein a thread of the single layer thread system is in an interior position between the upper and lower layers of the multiple layer thread system for at least two thirds of its crossovers with said upper and lower layers.
7. A fabric as in claim 1 wherein the binding points along a stacked group of multilayer threads are spaced in a substantially balanced pattern.
8. A fabric as in claim 1 wherein the binding points along a stacked group of multilayer threads are equally spaced from one another.
9. A fabric as in claim 1 wherein a thread of the single layer thread system binds around only a single thread of the upper layer of the multiple layer thread system and around only a single thread of the lower layer of the multiple thread system in each weave repeat.
10. A fabric as in claim 9 wherein a thread of the single layer thread system has a weave repeat of eight groups of threads of the multiple layer thread system.
11. A multilayer papermaking fabric as in claim 1, where-in:
the upper thread of a group has a weave repeat pattern of passing over a number of threads of the single layer system and then passing under a single thread of the single layer system to form a binding point with the single layer thread system;
the lower thread of a group has a weave repeat pattern of passing under a number of threads of the single layer system and then passing over a single thread of the single layer system to form a binding point with the single layer thread system; and the number of single layer threads residing in an interior position between a binding point of the upper thread and a binding point of the lower thread being at least two.
the upper thread of a group has a weave repeat pattern of passing over a number of threads of the single layer system and then passing under a single thread of the single layer system to form a binding point with the single layer thread system;
the lower thread of a group has a weave repeat pattern of passing under a number of threads of the single layer system and then passing over a single thread of the single layer system to form a binding point with the single layer thread system; and the number of single layer threads residing in an interior position between a binding point of the upper thread and a binding point of the lower thread being at least two.
12. A fabric as in claim 11 wherein the binding points along a stacked group of multilayer threads are in a substantially balanced spacing from one another.
13. In a multilayer papermaking fabric of interwoven threads having a single layer thread system with threads extending in one di-rection of the fabric and a multiple layer thread system with threads extending in the other fabric direction, the combination of:
threads in an upper layer of said multiple layer thread sys-tem being horizontally spaced from one another, and threads in a lower layer of said multiple layer thread system also being horizontally spaced from one another;
threads of said single layer thread system interlacing with threads of both the upper and lower layers of said multiple layer thread system, and being spaced apart from one another with the spacing between threads being such that the thread density of the single layer thread system is within a range of about 0.50 to 0.65;
and the projected open area of the fabric being within 13 to 25 percent of the total fabric area.
threads in an upper layer of said multiple layer thread sys-tem being horizontally spaced from one another, and threads in a lower layer of said multiple layer thread system also being horizontally spaced from one another;
threads of said single layer thread system interlacing with threads of both the upper and lower layers of said multiple layer thread system, and being spaced apart from one another with the spacing between threads being such that the thread density of the single layer thread system is within a range of about 0.50 to 0.65;
and the projected open area of the fabric being within 13 to 25 percent of the total fabric area.
14. A fabric as in claim 13, wherein the multiple layer thread system includes a thread layer with threads that are stiffer than other threads of such system.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/182,090 US4359069A (en) | 1980-08-28 | 1980-08-28 | Low density multilayer papermaking fabric |
| US182,090 | 1980-08-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1151981A true CA1151981A (en) | 1983-08-16 |
Family
ID=22667015
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382037A Expired CA1151981A (en) | 1980-08-28 | 1981-07-20 | Low density multilayer papermaking fabric |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4359069A (en) |
| EP (1) | EP0046899B1 (en) |
| AT (1) | ATE19112T1 (en) |
| AU (1) | AU547945B2 (en) |
| CA (1) | CA1151981A (en) |
| DE (1) | DE3174311D1 (en) |
| FI (1) | FI75378C (en) |
| MX (1) | MX157800A (en) |
| NZ (1) | NZ198002A (en) |
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| DE3036409C2 (en) * | 1980-09-26 | 1983-01-20 | Hermann Wangner Gmbh & Co Kg, 7410 Reutlingen | Double-layer screen for the screen part of a paper machine |
| DE3146385C2 (en) * | 1981-11-23 | 1985-10-31 | Hermann Wangner Gmbh & Co Kg, 7410 Reutlingen | Double-layer fabric as a covering for paper machines |
| JPS6081391A (en) * | 1983-10-07 | 1985-05-09 | 三菱重工業株式会社 | Endless belt |
| CN1003767B (en) * | 1984-10-17 | 1989-04-05 | 联邦工业气体有限公司 | Improvement in pesticidal treatment of animals |
| US4642261A (en) * | 1984-12-21 | 1987-02-10 | Unaform Inc. | Papermakers fabric having a tight bottom weft geometry |
| US5114777B2 (en) | 1985-08-05 | 1997-11-18 | Wangner Systems Corp | Woven multilayer papermaking fabric having increased stability and permeability and method |
| US4709732A (en) * | 1986-05-13 | 1987-12-01 | Huyck Corporation | Fourteen harness dual layer weave |
| DE3705345A1 (en) * | 1987-02-19 | 1988-09-01 | Oberdorfer Fa F | COMPOSITE FABRIC AS A COVER FOR THE SHEET FORMING PART OF A PAPER MACHINE |
| US5052448A (en) * | 1989-02-10 | 1991-10-01 | Huyck Corporation | Self stitching multilayer papermaking fabric |
| DK0536320T3 (en) * | 1990-06-29 | 1995-02-20 | Procter & Gamble | Paper making tape and method for making same using different lighting transmission technique |
| US5275700A (en) * | 1990-06-29 | 1994-01-04 | The Procter & Gamble Company | Papermaking belt and method of making the same using a deformable casting surface |
| US5260171A (en) * | 1990-06-29 | 1993-11-09 | The Procter & Gamble Company | Papermaking belt and method of making the same using a textured casting surface |
| US5098522A (en) * | 1990-06-29 | 1992-03-24 | The Procter & Gamble Company | Papermaking belt and method of making the same using a textured casting surface |
| US6248210B1 (en) | 1998-11-13 | 2001-06-19 | Fort James Corporation | Method for maximizing water removal in a press nip |
| US6733626B2 (en) | 2001-12-21 | 2004-05-11 | Georgia Pacific Corporation | Apparatus and method for degrading a web in the machine direction while preserving cross-machine direction strength |
| ATE440984T1 (en) * | 2001-10-29 | 2009-09-15 | Albany Int Corp | HIGH SPEED SPUNBOBBED BONDS PRODUCTION |
| US7959761B2 (en) | 2002-04-12 | 2011-06-14 | Georgia-Pacific Consumer Products Lp | Creping adhesive modifier and process for producing paper products |
| WO2004033793A2 (en) | 2002-10-07 | 2004-04-22 | Fort James Corporation | Fabric crepe process for making absorbent sheet |
| US8398820B2 (en) | 2002-10-07 | 2013-03-19 | Georgia-Pacific Consumer Products Lp | Method of making a belt-creped absorbent cellulosic sheet |
| US7789995B2 (en) | 2002-10-07 | 2010-09-07 | Georgia-Pacific Consumer Products, LP | Fabric crepe/draw process for producing absorbent sheet |
| US7442278B2 (en) | 2002-10-07 | 2008-10-28 | Georgia-Pacific Consumer Products Lp | Fabric crepe and in fabric drying process for producing absorbent sheet |
| US7662257B2 (en) | 2005-04-21 | 2010-02-16 | Georgia-Pacific Consumer Products Llc | Multi-ply paper towel with absorbent core |
| US7494563B2 (en) | 2002-10-07 | 2009-02-24 | Georgia-Pacific Consumer Products Lp | Fabric creped absorbent sheet with variable local basis weight |
| EP1567718B1 (en) * | 2002-11-07 | 2013-04-17 | Georgia-Pacific Consumer Products LP | Absorbent sheet exhibiting resistance to moisture penetration |
| US7297226B2 (en) | 2004-02-11 | 2007-11-20 | Georgia-Pacific Consumer Products Lp | Apparatus and method for degrading a web in the machine direction while preserving cross-machine direction strength |
| DE102004016640B3 (en) * | 2004-03-30 | 2005-08-11 | Andreas Kufferath Gmbh & Co. Kg | Fourdrinier, especially for a papermaking machine to produce toilet paper, is of two bonded woven layers with an increased weft count in the upper layer |
| US8293072B2 (en) | 2009-01-28 | 2012-10-23 | Georgia-Pacific Consumer Products Lp | Belt-creped, variable local basis weight absorbent sheet prepared with perforated polymeric belt |
| DK2492393T3 (en) | 2004-04-14 | 2016-09-12 | Georgia Pacific Consumer Products Lp | Absorbent product with high CD stretch and low tensile strength ratio obtained with a high dry matter content tekstilcrepe method |
| US7503998B2 (en) | 2004-06-18 | 2009-03-17 | Georgia-Pacific Consumer Products Lp | High solids fabric crepe process for producing absorbent sheet with in-fabric drying |
| US8178025B2 (en) | 2004-12-03 | 2012-05-15 | Georgia-Pacific Consumer Products Lp | Embossing system and product made thereby with both perforate bosses in the cross machine direction and a macro pattern |
| DE102005035559A1 (en) * | 2005-07-29 | 2007-02-01 | Voith Patent Gmbh | Paper machine clothing |
| US8540846B2 (en) | 2009-01-28 | 2013-09-24 | Georgia-Pacific Consumer Products Lp | Belt-creped, variable local basis weight multi-ply sheet with cellulose microfiber prepared with perforated polymeric belt |
| EP3103920B1 (en) | 2006-05-26 | 2019-07-10 | GPCP IP Holdings LLC | Fabric creped absorbent sheet with variable local basis weight |
| US8409404B2 (en) * | 2006-08-30 | 2013-04-02 | Georgia-Pacific Consumer Products Lp | Multi-ply paper towel with creped plies |
| US7644738B2 (en) * | 2007-03-28 | 2010-01-12 | Albany International Corp. | Through air drying fabric |
| WO2009018274A1 (en) * | 2007-07-30 | 2009-02-05 | Astenjohnson, Inc. | Warp-tied forming fabric with selective warp pair ordering |
| DE102008000915A1 (en) * | 2008-04-01 | 2009-10-08 | Voith Patent Gmbh | Press felt and process for its production |
| WO2010033536A2 (en) | 2008-09-16 | 2010-03-25 | Dixie Consumer Products Llc | Food wrap basesheet with regenerated cellulose microfiber |
| DE102008043917A1 (en) | 2008-11-20 | 2010-05-27 | Voith Patent Gmbh | Press felt and process for its production |
| DE102010017055A1 (en) * | 2010-05-21 | 2011-11-24 | Andritz Technology And Asset Management Gmbh | forming wire |
| US9267240B2 (en) | 2011-07-28 | 2016-02-23 | Georgia-Pacific Products LP | High softness, high durability bath tissue incorporating high lignin eucalyptus fiber |
| US9309627B2 (en) | 2011-07-28 | 2016-04-12 | Georgia-Pacific Consumer Products Lp | High softness, high durability bath tissues with temporary wet strength |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3143150A (en) * | 1961-10-18 | 1964-08-04 | William E Buchanan | Fabric for fourdrinier machines |
| US3296062A (en) * | 1965-06-24 | 1967-01-03 | Us Rubber Co | Belt fabric |
| US4071050A (en) * | 1972-09-01 | 1978-01-31 | Nordiska Maskinfilt Aktiebolaget | Double-layer forming fabric |
| US3885602A (en) * | 1973-11-21 | 1975-05-27 | Creech Evans S | Woven fourdrinier fabric |
| US3885603A (en) * | 1973-11-21 | 1975-05-27 | Creech Evans S | Papermaking fabric |
| SE385486B (en) * | 1974-10-10 | 1976-07-05 | Nordiska Maskinfilt Ab | PROPAGATION WIRE FOR PAPER, CELLULOSE OR SIMILAR MACHINES AND MANUFACTURED THE SAME |
| SE397371C (en) * | 1976-02-24 | 1980-08-07 | Nordiska Maskinfilt Ab | PREPARATION VIRUS FOR PAPER, CELLULOSA OR SIMILAR MACHINES |
| FR2346489A1 (en) * | 1976-04-02 | 1977-10-28 | Martel Catala Et Cie Sa Ets | IMPROVEMENTS IN CANVAS FOR PAPER MACHINES AND THEIR MANUFACTURING PROCESSES |
| US4086941A (en) * | 1976-10-26 | 1978-05-02 | Huyck Corporation | Biplanar papermaker's belt |
| US4314589A (en) * | 1978-10-23 | 1982-02-09 | Jwi Ltd. | Duplex forming fabric |
| AR226563A1 (en) * | 1979-10-17 | 1982-07-30 | Albany Int Corp | FABRIC TO BE USED AS A FELT DRYER FOR A PAPER SHEET IN FORMATION, IN A PAPER MAKING MACHINE |
-
1980
- 1980-08-28 US US06/182,090 patent/US4359069A/en not_active Expired - Lifetime
-
1981
- 1981-07-20 CA CA000382037A patent/CA1151981A/en not_active Expired
- 1981-08-11 DE DE8181106266T patent/DE3174311D1/en not_active Expired
- 1981-08-11 NZ NZ198002A patent/NZ198002A/en unknown
- 1981-08-11 AT AT81106266T patent/ATE19112T1/en not_active IP Right Cessation
- 1981-08-11 EP EP81106266A patent/EP0046899B1/en not_active Expired
- 1981-08-14 AU AU74086/81A patent/AU547945B2/en not_active Expired
- 1981-08-27 MX MX188912A patent/MX157800A/en unknown
- 1981-08-27 FI FI812645A patent/FI75378C/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| US4359069A (en) | 1982-11-16 |
| ATE19112T1 (en) | 1986-04-15 |
| EP0046899B1 (en) | 1986-04-09 |
| EP0046899A3 (en) | 1982-03-17 |
| FI812645L (en) | 1982-03-01 |
| EP0046899A2 (en) | 1982-03-10 |
| AU547945B2 (en) | 1985-11-14 |
| NZ198002A (en) | 1984-08-24 |
| AU7408681A (en) | 1982-03-04 |
| MX157800A (en) | 1988-12-15 |
| FI75378B (en) | 1988-02-29 |
| FI75378C (en) | 1988-06-09 |
| DE3174311D1 (en) | 1986-05-15 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |