ES2222345T3 - SEWED INDUSTRIAL FABRICS. - Google Patents

Abstract

An industrial fabric (20) is woven from machine-direction (MD) (24) and cross-machine-direction (CD) yarns (22), wherein the MD yarns (24) are multicomponent yarns having a plurality of individual strands and at least one thermofusible strand of a thermoplastic material. The at least one thermofusible strand of a thermoplastic material has a melting point lower than that of the individual strands of the multicomponent yarn. Upon application of a heat treatment, the multicomponent yarns are stiffened and the individual strands thereof are held together by the thermoplastic material of the at least one thermofusible strand.

Description

Stitched industrial fabrics.

Background of the invention 1. Field of the invention

The present invention relates to manufacturing of paper and related techniques. More specifically, the present invention consists of an industrial fabric of the variety that can be sewn on the machine, such as a press cloth, which can sew on the machine, for the press section of a machine paper bin.

2. Description of the related technique

During the papermaking process, a band of cellulose fibers is formed by depositing a paste of fibers, that is, an aqueous dispersion of cellulosic fibers, on a moving training cloth in the section of formation of a paper machine. From the suspension drains a large amount of water through the formation fabric, leaving the band of cellulosic fibers on the surface of the fabric of training.

The newly formed cellulosic fiber band advances from the training section to a press section, which It includes a series of grip distances. Fiber band cellulosic passes through the grip distances of the presses supported by a press cloth or, as often happens, between two such press fabrics. In the grip distances of the presses, the band of cellulosic fibers is subjected to forces compression that expel water from it by crushing and that adheres the cellulosic fibers of the band to each other to convert the band of cellulosic fibers on a sheet of paper. The water is accepted by the press fabric or fabrics and, ideally, is not returned to the sheet of paper.

Finally, the sheet of paper advances to a section drying which includes at least one series of cylinders or drums rotary dryers, heated internally by water vapor. The newly formed sheet of paper is directed, by a drying cloth, on a meandering path passing, in sequence, around each of the series of drums, whose dryer fabric keeps the paper sheet in close application against the surface of the drums Heated drums reduce the water content of the sheet of paper, by evaporation, to a desirable level.

It should be appreciated that the training fabrics, Presser and dryer adopt, all of them, the shape of endless loops in the paper machine and they work as conveyors. Should It is also appreciated that papermaking is a process continuous that develops at considerable speeds. That is, the  fiber paste is continuously deposited on the fabric of training in the training section, while a sheet of paper freshly made is continuously rolled into rolls after Leave the drying section.

With reference, at the moment, specifically, to press fabrics, it must be remembered that there was a time when Press fabrics were supplied in endless form. It is due to which a band of newly formed cellulosic fibers is extremely susceptible to distance marking of grip of the presses in case of lack of uniformity in the or in press fabrics. An endless, seamless fabric, such as produced by the procedure known as endless texture, it has a uniform structure both in its longitudinal direction (of the machine) as in its transverse direction (transverse to the machine). A seam, such as the one that can be used to close the press fabric giving it endless shape during installation in a  paper machine, represents a discontinuity in the structure Press fabric uniform. The use of a seam, therefore, remarkably increases the probability that the fiber band cellulose is marked in the grip distance of the press.

For this reason, the seam region of any functional press fabric that can be machine sewn must behave, when subjected to a load, that is, under compression at or in the grip distances, like the rest of the fabric of press, and must have the same water and air permeability as the rest of the press fabric, in order to avoid the appearance periodic marking on the paper product that is manufactured in the sewing region.

Despite considerable technical obstacles who presented these requirements, remained very desirable develop a press fabric that can be machine sewn, due to the relative safety and ease with which a fabric of that class could be installed in the press section. Finally, These obstacles were overcome with the development of press fabrics with seams formed providing sewing loops at the edges transverse of the two ends of the fabric. Sewing loops proper they are formed by threads of the fabric that follow the machine address (MD). The seam closes gathering the two ends of the press fabric, interspersing the loops of sewn on both ends of the fabric and directing a so-called pin or pivot through the step defined by the sewing loops interspersed to block the two ends of the fabric together. Is needless to say that in a paper machine is much easier and it takes a lot less time, install a press fabric that can sew on the machine to install an endless press fabric.

A method of producing a press fabric that can join the paper machine with a seam of this kind, It is knitting the flat fabric. In this case, the warp threads are the press fabric threads running in the machine direction (MD). To form the sewing loops, the warp threads of the ends of the fabric are turned and woven into a certain distance back into the body of the fabric, in a direction parallel to The warp threads. Another technique, much more preferable, is a modified shape of endless texture that is normally used to produce a loop of endless cloth. In endless texture modified, weft or fill threads, are continuously woven reciprocating through the loom, forming at each step a loop in one of the edges of the fabric that is woven when passing around a loop formation spike. As the weft thread, or thread of padding, which eventually becomes the thread in the MD of the fabric press, it is continuous, the sewing loops thus obtained are more strong than any that can be produced by weaving warp ends again at the ends of a woven fabric flat.

Originally, in press fabrics that can sewing on the machine used single monofilament strands both in the machine direction and in the transverse direction to she. The relative stiffness of the monofilament ensures that it they will get the demanded good loop formation properties sewn However, experience showed that henras Unique monofilament are difficult to knit and do not have the sufficient elasticity in the machine direction for many classes of current presses. Often failures occurred due to traction and breakage of seams.

Another difficulty arose due to the very structure open, rigid and incompressible of woven base fabrics to from single monfilament. For some applications in the papermaking, this incompressibility does not constitute a problem and may even be ideal. However, for places where the dehydration capacity of the auxiliary fabric is bad or where qualities of paper sensitive to brand formation, softer base fabric and more is needed compressible.

A more compressible base fabric can be obtained weaving with paired monofilament threads or with threads multifilament, instead of single monofilament threads. Do not However, threads of these types do not have the necessary stiffness to offer a good loop formation or to maintain the seam area integrity during loop collation required when sewing is to be closed. Also, like the threads of these types are twisted, the loops formed with them they have to rotate around geometric axes found in the planes formed by the loops. When this rotation occurs, known as the secondary helix effect, it causes the loops to rotate abandoning its ideal orientation, necessary for interleaving. Such displacement makes it difficult, if not impossible, properly insert the loops at each end of the fabric press during closing, as well as directing the pivot through the step defined by interleaved loops.

In the prior art various attempts to overcome these difficulties by making threads not monofilament, loop formation, lying on the MD, act as monofilaments In U.S. Patent No. 5,005,610, the threads in the MD on a cloth for paper machines that can sew on the machine, have a composite structure, including braided monofilament strands. The braided thread forms loops of sewn that withstand deformation and that, since they are in balance in regards to torsion, they form sewing loops not susceptible to rotation due to the "propeller effect secondary "abandoning the geometry of the ideal plane of the sewing.

In U.S. Patent No. 5,204,150, the threads in the MD of a fabric for paper machines that can sew on the machine, they are matched / twisted, extruded threads from a resin that partially melts during curing by heat of the fabric, giving the threads in the MD a character similar to the monofilament Even when they are not in balance due to the torsion and pairing, fusion bonding caused by partial fusion of the individual ends prevents the rotation of the loops away from the geometry of the ideal seam.

In U.S. Patent No. 5,391,419, the threads in the MD of a fabric for paper machines that can sewing on the machine are matched / twisted threads that have a coating that gives the thread a similar structure To a monofilament. The coating can be permanent, semipermanent or soluble. Even though the threads may not be in equilibrium, the coating prevents the rotation of the loops.

In U.S. Patent No. 5,514,438, the threads in the MD of a fabric for paper machines that can sew on the machine, they have a soul of wired monofilaments surrounded by a multifilament sheath. The cover of multifilaments binds wired monofilaments together and prevents any of the monofilaments of the soul block the defined step by the interleaved loops formed by the threads in the MD during the sewn

Finally, in US Patent No. 5,875,822, the threads in the MD of a fabric for paper machines which can be sewn on the machine, they are matched / twisted threads and they form sewing loops along the edges located along width at both ends of the fabric. A sewing propeller Monofilament is attached to the sewing loops at each end. The sewing propellers are used to join the fabric giving it a shape endless, thus providing a fabric that has threads paired / twisted lying on the MD with joining means monofilament

The present invention represents an approach different to provide an industrial fabric that can be sewn in the machine, which has paired / twisted wires lying on the MD with sewing loops that maintain its integrity and its Appropriate orientation during sewing.

Summary of the invention

Accordingly, the objective of the present invention is to provide an industrial fabric that can be sewn on the machine with multicomponent threads in the MD, with sewing loops that they retain their proper orientation and integrity necessary to sewing

This objective is achieved in accordance with the claim 1 using, as threads in the direction of the machine (MD), multicomponent threads comprising a plurality of individual strands of yarn and at least one hot melt strand of a thermoplastic material, in which the thermoplastic material of said at least one hot melt thread has a melting point smaller than that of individual strands of thread multi-component Consequently, when applying a heat treatment at any given length of the multicomponent thread to a temperature above the melting point of the hot melt thread, but inferior to the individual strands of thread, the material thermoplastic melts and flows entering the defined spaces between the individual strands of thread and, at the end of the treatment thermal, solidifies again and stiffens the multicomponent thread and holds together, at that given length, its strands of thread individual. This ensures that the sewing loops formed by multicomponent threads will retain proper orientation and integrity required for sewing.

In addition, the inclusion of one or more threads Hot melts in the multicomponent wire makes it possible to control the thread stiffness based on the number and / or sizes of the hot melt strands included. In turn, this allows you to control the elasticity and compressibility of the fabric to a greater extent than that was possible in fabrics made of strands without threads hot melts.

Multicomponent threads can be threads paired monofilament, paired multifilament, multifilament or matched / twisted threads or combinations of same. By paired / twisted thread should be understood any variety of yarn used in the production of machine fabrics bins with multiple ends or filaments, which twist together to a desired extent and, in many cases, they are combined or they match, then, with other filaments of the same type or of a type different. During the pairing operation, the components of the thread are combined by twisting them counterclockwise individual components Paired / twisted threads can be considered, consequently, as multicomponent threads. The threads  multi-component, alternatively, can be twisted strands or knitted. In any case, the multi-component thread includes, at least, a hot melt thread.

The individual strands of thread included in the multi-component yarn typically have cross section circular, although it should be understood that they can have any of a variety of other cross-sectional form, such as rectangular, oval or multilobed. The multicomponent thread, produced by matching / twisting, braiding or knitting your components, can have a cross section that is not circular shape.

The present industrial fabric that can be sewn on the machine can be woven following an endless texture technique modified from a system of threads in the MD and a system of threads in the transverse direction to the machine (CD), in which the threads according to the MD are the multicomponent threads before described. Alternatively, the industrial fabric can be knitted flat, the threads being in the MD, the warp threads during the process of texture, also in this case, multicomponent threads. In each case, the industrial fabric has a rectangular shape, with a length, one width, two longitudinal edges and two edges on the sense of width

In the modified endless texture technique, the threads in the MD (multicomponent threads) extend in reciprocating continuously along the industrial fabric between the two edges in the sense of width and form a first plurality of sewing loops along one of the two edges in the direction of the width and a second plurality of sewing loops at along the other of said edges in the sense of width. To the apply the heat treatment described above, which could be carried out at any time during the process of manufacturing, even in the thread formation stage, the threads multi-component and sewing loops formed from them, they are stiffened and the plurality of their individual thread strands they are held together by the thermoplastic material of said at minus a thermofusible strand of the multicomponent thread.

On the other hand, when the industrial fabric is woven flat, extending the warp threads from its two edges in the sense of width are turned back and woven into a certain distance back into the body of the fabric, to form the sewing loops

The industrial fabric is united by giving it a shape endless inserting the sewing loops of the first plurality with the sewing loops of the second plurality and directing a pivot through the step defined by the sewing loops interspersed to close the seam of the loops, blocking together the two edges of the fabric in the sense of width.

It should be understood that multicomponent threads they can also be used in the direction transverse to the machine (CD) to improve the stability on the fabric CD. In an endless woven structure, with or without seam, the stiffness of the thread on the CD is directly related to the number of threads in the MD and on the CD that can be included in a fabric. The use, at knitting, with a thread of less stiffness, allows a margin of titles wider, and especially taller. When the present multicomponent thread in the direction transverse to the machine, the number of threads in the MD and in the CD can be increased of the fabric, and the multi-component thread can be stiffened properly after knitting, by heat application.

The present multi-component thread can also be used as a thread in the machine direction (MD) in a flat woven fabric to be joined to give it endless shape with a woven seam, because it can be designed so that adopt the curl required to form such seam.

The present invention will now be described with more complete detail, often referring to figures identified in the following.

Brief description of the drawings

Figure 1 is a schematic view, in perspective, of an industrial fabric that can be sewn on the machine;

Figure 2 is a schematic view, in perspective, of the two ends of the industrial fabric that can sew on the machine, before being joined together;

Figure 3 is a cross-sectional view taken in the direction of the warp, of the industrial fabric;

Figure 4 is a cross-sectional view, taken in the direction of the weft, of the seam region of the industrial fabric; Y

Figure 5 is a cross-sectional view, analogous to that offered in Figure 4, of the seam region of an alternative embodiment of the industrial fabric.

Detailed description of the preferred embodiment

Turning now specifically to the figures, the Figure 1 is a schematic perspective view of a fabric industrial 10 that can be sewn on the machine. The fabric 10 adopts the shape of an endless loop once its two ends 12, 14 have been joined together in sewing 16.

Figure 2 is a schematic view, in perspective, of the two ends 12, 14 of the industrial fabric 10 which can be sewn on the machine before its mutual union. At wide, at the edges of each of the two ends 12, 14, there are a plurality of sewing loops 18. To join the two ends 12, 14 with each other, they meet by alternating and intermingling, or interleaving, for this purpose, the sewing loops 18 of one end with those of the other. Interleaved sewing loops 18 define a step to through which a pin or pivot, a member or thread mode thread, to secure the ends 12, 14 one with other.

Figure 3 illustrates a cross section taken in the warp direction of an industrial fabric 20 in which can be practiced in the present invention. 20 fabric it is shown woven in a duplex texture, although it must be understood that such texture is represented only as an example and that the invention could be implemented with 20 woven fabrics with other textures, such as one, two, three or more layer textures, or stratified including several layers of fabric. The fabric 20 can be a base fabric for a press fabric and, consequently, can be associated, by needle treatment, with one or more layers of fibrous material, of fibers cut on one or both sides, or it can be coated in some way. Alternatively, the cloth 20 can be used in one of the other sections of the machine litter bin, that is, in the training or drying sections, or as a basis for a treatment tape for the paper industry (PIPB) coated with a polymer resin. In addition, the fabric 20 can be used as a corrugated tape or as a base thereof; like cloth pasta former, such as a double thickener belt grip distance; or like other process tapes Industrial

The fabric 20 is woven using a technique of modified endless texture. In such a situation, the warp threads 22 finally become the wires in the transverse direction to the machine (CD) and the weft threads 24 are converted, finally, in the threads in the machine direction (MD), when reference is made to the orientations of the threads in relation to the machine on which the fabric 20 is installed.

The warp threads 22, the threads on the CD of the fabric 20 that can be sewn on the machine, can be any of the types of yarn used to weave fabric bases for paper machines or PIPB, or for the other fabrics and tapes before mentioned. That is, as warp threads 22 can be used monofilament threads, which are monofilament strands used alone, or multicomponent threads, as described in what precedes.

On the other hand, weft threads 24, threads in the MD of the fabric 20 that can be sewn on the machine, they are threads multi-component As described above, the threads multi-component can be paired monofilament threads, paired multifilament, multifilament or threads paired / twisted, or combinations thereof. The threads multi-component can also be braided wires or knitted

In any case, the strands of thread individual comprising the warp threads 22 (threads in the CD) and branch threads 24 (threads in the MD), are extruded from of synthetic polymer resin materials, such as resins of polyamide, polyester, polyether ketone, polypropylene, polyamide, polyolefin, polyphenylene sulfide (PPS) and resins of poly (ethylene terephthalate) (PET) and copolymers of same, and incorporated into the threads according to techniques well known in the textile industry and, in particular, in the industry of fabrics for paper machines.

The weft threads 24 (threads in the MD), in addition to have a plurality of individual strands of thread, include also at least one thermofusible strand of thermoplastic material, whose thermoplastic material has a melting point lower than the of the individual strands of thread that make up the thread multi-component As a consequence, when applying a treatment thermal at a temperature higher than the melting point of the strand hot melt, but lower than the melting point of the strands of individual thread of the multi-component thread, the material thermoplastic stiffens the multi-component thread and loops of sewn 18 formed with it, and keeps the strands of thread together Multicomponent thread individual. This ensures that the loops sewing formed by multicomponent threads will maintain the proper orientation and integrity required for sewing. He thermoplastic material can be, for example, polyamide 66, 6 low melting polyamide or polyurethane.

As indicated above, the thread multi-component includes at least one hot melt strand of the thermoplastic material That is, it can include one, two, three or more hot melts. The hot melt thread can be monofilament or multifilament and can be of cross section not circular. It can be an extruded thread or a strand cut from of a film of thermoplastic material. It can also be consisting of one or more threads obtained or cut from a band of non-woven material, of polyamide or polyurethane, of low melting temperature Bands of this non-woven material Type are available from Sharnet.

When knitting fabric 20 by a procedure of modified endless texture, weft threads 24 are woven fabrics continuous way in reciprocating through the loom, forming in each passed a sewing loop on one of the two edges located at width of the fabric 20 that is being woven, as it passes around a loop formation spike. Several schemes are available, described and claimed in U.S. Patent No. 3,815,645 of Codorniu to weave fabrics for paper machines that they can be sewn on the machine by modified endless texture, and can be used in the implementation of this invention.

Figure 4 is a cross section, taken in the direction of the weft, of the sewing region of the fabric 20, at Finish the modified endless texture process. The threads of weft 24, which are finally the threads in the MD of the fabric 20, are weave around a spike 26 shaped loops continuous, to provide the sewing loops 18.

It will be appreciated that the formation pin 26 of loops must be removed to arrange the fabric 20 in a way in which can easily be installed on a particular machine. Be you will also appreciate that since the weft threads 24 (threads in the MD) are multicomponent threads, the sewing loops 18 can rotate, starting from the ideal geometry of the sewing loops, illustrating the effect of secondary propeller, and deform so soon as the looping pin 26 is removed, hindering the subsequent sewing or making it impossible to get.

For this reason, the heat treatment that stiffens and strengthens multicomponent threads is carried out before removing the loop pin 26. Should it can be appreciated, however, that the heat treatment can be carried out before or after knitting the fabric 20, even at the stage of thread formation In addition, when the fibrous fiber material cut must be treated with needles to form the fabric 20, the heat treatment can be carried out before or after needle treatment, although treatment is preferred thermal after needle treatment because the material  thermoplastic of said at least one thermofusible strand improves the anchorage of the fibrous material of cut fibers to the base fabric twenty.

The industrial fabric joins to give it the shape endless inserting the sewing loops 18 at one end of the fabric with those at the other end and directing a pivot through the step defined by interleaved sewing loops 18. Alternatively, as shown in Figure 5, which represents another cross section of the seam region of the fabric 20 taken in the direction of the machine, propellers of sewing 28 to the sewing loops 18 which can be used to join the fabric 20 in the form of an endless loop.

Specifically, sewing propellers 28 can be interspersed with sewing loops 18 and join them by connection wires 30. In this way, the fabric 20 with threads multi-component in the machine direction, can be equipped with monofilament sewing loops in the form of individual turns of sewing propellers 28.

Sewing propellers 28 can be propellers monofilament, preferably extruded polyamide resin. He diameter of the monofilament can be, for example, 0.40 mm or 0.50 mm During the installation of the fabric 20 in a machine bin, for example, the individual turns of the propellers 28 of  sewn, which are monofilamentary, can be easily intercalated between them and join each other directing a pivot 32 to through the passage defined by the interspersed turns. They can insert threads 34 into sewing propellers 28 to ensure that the seam region has characteristics similar to the rest of the fabric 20. Connection wires 30 and the filling threads 34 can be threads of the same type used as warp threads 22 (threads on the CD) of the fabric 20. The pivot 32 can be a single strand of monofilament, multiple strands of monofilament not twisted or matched, twisted, braided or knitted together, or one or more strands of any of the threads multicomponent described above for use as threads in the MD (weft threads 24) of the fabric 20.

Those of ordinary skill in the art have modifications to the foregoing will be evident, but not would make the invention so modified out of reach of the attached claims.

Claims (25)

1. An industrial fabric, comprising: a system of threads in the direction of the machine (MD) and a system of threads in the direction transverse to the machine (CD), said threads of the said system of threads in the MD being interwoven with said threads of the said system of threads in the CD for forming said industrial fabric of rectangular shape, which has a length, a width, two surfaces, two longitudinal edges and two edges in the width direction, characterized in that said threads in the MD are multicomponent threads comprising a plurality of strands of individual yarn and at least one thermofusible strand of a thermoplastic material, said at least one thermofusible strand having a melting point lower than said individual strands of yarn so that, when applying a heat treatment, said multicomponent threads are stiffened and said plurality of individual strands of yarn thereof are held together by said thermoplastic material of said at least one thermo strand usable 2. An industrial fabric as claimed in claim 1, said industrial fabric being closed to adopt an endless shape by sewing loops, during installation on a machine, wherein said threads of said thread system in the MD they are interwoven with said threads of said wire system on the CD by a modified endless texture technique, extending said threads in the MD in reciprocating continuously in said length of said industrial fabric, between said two edges in the width direction and forming a first plurality of sewing loops along one of said two edges in the width direction and a second plurality of loops of sewn along the other of said two edges in the direction of the width, so that said industrial fabric joins adopting an endless form by interleaving said first plurality of sewing loops with said second plurality of sewing loops and directing a pivot through the step defined by the loops of sewn interleaved to close said loop seam. 3. An industrial fabric as claimed in claim 1, said industrial fabric being closed to adopt an endless shape through a spike seam, during installation on a machine, wherein said threads of said thread system in the MD they are interwoven with said threads of said wire system on the CD by a flat texture technique, being said threads in the MD along said two edges in the direction of the width and fabrics again in said industrial fabric to form a first plurality of sewing loops along one of said two edges in the width direction and a second plurality of sewing loops along the other of said two edges in the width direction, so that said industrial fabric joins adopting an endless form by interleaving said first plurality of sewing loops with said second plurality of sewing loops and directing a pivot through the step defined by the loops of sewn interleaved to close said spike seam. 4. An industrial fabric as claimed in claim 1, wherein said threads of said system of threads in the MD are interwoven with said threads of said system of threads on the CD by a flat texture technique, joining said two edges in the width direction of said industrial fabric with each other by a knitted seam to give said fabric Industrial endless shape. 5. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are matched monofilament threads. 6. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are matched multifilament threads. 7. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are multifilament threads. 8. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are matched / twisted threads. 9. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are threads selected from the group consisting of monofilament threads paired, multifilament threads paired, threads multifilament, matched / twisted threads and combinations of same. 10. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are knitted threads. 11. An industrial fabric as claimed in claim 1, wherein said multicomponent threads are braided threads 12. An industrial fabric as claimed in claim 1, wherein said strands of thread individual of said multicomponent threads are extruded to from a polymer resin material. 13. An industrial fabric as claimed in claim 12, wherein said resin material Polymer is selected from the group consisting of polyamide, polyester, polyether ketone, polypropylene, polyamide, polyolefin, polyphenylene sulfide (PPS) and poly (terephthalate) resins of ethylene) (PET) and copolymers thereof. 14. An industrial fabric as claimed in claim 1, wherein said thermoplastic material of said at least one hot melt strand is selected from the group that consists of polyamide 66, low melting polyamide 6 and polyurethane. 15. An industrial fabric as claimed in claim 1, wherein said at least one strand Hot melt is a monofilament. 16. An industrial fabric as claimed in claim 1, wherein said at least one strand Hot melt is a multifilament. 17. An industrial fabric as claimed in claim 1, wherein said at least one strand hot melt is a strand cut from a film of said material thermoplastic 18. An industrial fabric as claimed in claim 1, wherein said at least one strand Hot melt is a strand of a nonwoven material. 19. An industrial fabric as claimed in claim 1, wherein said threads on the CD are, also, said multicomponent threads. 20. An industrial fabric as claimed in claim 1, further comprising at least one layer of fibrous material of cut fibers attached to one of said two surfaces of it. 21. An industrial fabric as claimed in claims 2 or 3, further comprising: a first sewing propeller that has a plurality of turns interspersed with said sewing loops of said first plurality on one of said two edges in the address of the width of said industrial fabric and attached to them for at least one connecting wire that extends in transverse direction to the machine; Y a second sewing propeller that has a plurality of turns interspersed with said sewing loops of said second plurality on the other of said two edges in the address of the width of said industrial fabric and attached to them for at least one connecting wire that extends in transverse direction to the machine, so that said industrial fabric joins adopting an endless shape by interleaving said turns of said first sewing propeller with said turns of said second propeller sewing and directing a pivot through the step defined by the interleaved turns to close said loop seam. 22. An industrial fabric as claimed in claim 21, wherein said first and said second sewing propellers are monofilament propellers. 23. An industrial fabric as claimed in claim 22, wherein said monofilament propellers they have been extruded from a polyamide resin. 24. An industrial fabric as claimed in claim 21, further comprising at least one thread of filling inside said first sewing propeller. 25. An industrial fabric as claimed in claim 21, further comprising at least one thread of filling inside said second sewing propeller.