FI76145B - TORKTYG. - Google Patents

Description

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SUOMI FINLAND

(Fl) (21) Patent application - Patentansökning 783268 (22) Application date - Ansökningsdag 26.10.78

National Board of Patents and Registration (23) Start date-Giltighetsdag 26.10.78

Patent- och registersty releen (41) Became public-Biivit offentiig 29.04.79 (44) Date of dispatch and publication: 31.05.88

Ansökan utlagd och utl.skriften publicarad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed - Begörd priority 28.10.77 17.05.78 USA (US) 846355, 906434 (71) JWI Ltd., Suite 428, 1 Westmount Square, Montreal, Quebec, Canada-Canada ( CA) (72) John Gordon Buchanan, Ottawa, Ontario,

Donald George MacBean, Ottawa, Ontario, Canada-Canada (CA) (74) Oy Kolster Ab (54) Drying fabric - Torktyg

The invention relates to a drying fabric for a paper machine comprising a plurality of interwoven warp and woven monofilament plastic polymer fibers woven with a warp filling of about 100%.

In papermaking, e.g. in a flat wire paper machine, an aqueous suspension of cellulosic fibers comprising one part by weight or less of fibers in 99 parts by weight or more of water is passed to an endless rotating forming fabric woven from metal or synthetic filaments. As this belt, folding fabric, or "wire", as it is called, passes through dewatering devices such as register rollers, dewatering tubes, and suction boxes, the water content of the suspension supported by the fabric is reduced to about 80-85%.

The thin fibrous web, which now supports itself, is removed from the forming fabric and passed through one or more pressing sections where it passes over the surface of other endless belts of relatively thick fabric, one or both of which may be a needled synthetic or natural fiber sheet. These / 2 76145 belts, called wet felts, convey a web of nip from press rolls where more residual water is pressed into absorbent felts until the water content drops to about 65%, at which point it is generally impractical to try to remove more water by direct extraction such as compression or vacuum.

The paper web is then taken to the drying section of the machine, where the rest of the water is removed by an evaporation process which is accelerated by heat. The drying section comprises a series of large, hollow cast iron or steel cylinders over which the paper web passes like a serpentine. The cylinders rotate synchronously to facilitate the passage of the web. Heat is supplied by condensing steam inside each cylinder, and the web is kept in intimate contact with the heated surfaces of the drying cylinders by means of drying fabrics.

In order to provide sufficient drying capacity, for example, the newsprint drying section may comprise about 50 drying cylinders, each about 150 cm in diameter and arranged in the top and bottom rows of four, or in five separate groups.

To describe the large size of the drying section of a modern paper machine, it should be mentioned that its total length can be about 60 m, width about 12 m and height about 12 m. The paper web can pass through the drying section at speeds up to 900 m / min, so that any part of the web may linger in the drying section for only as little as 15 s, during which time the web is reduced to a normal dry sheet of paper.

The purpose of the drying fabrics is to hold the paper web against the heated surfaces of the rotating drying cylinders, to provide more efficient heat transfer to the web by partially eliminating the air insulation layer adhering to the surface of the cylinder. The drying fabrics are also intended to prevent the paper web from wrinkling.

The conventional drying section has an upper and a lower drying fabric. The upper fabric passes over the upper portion of the periphery of the upper drying cylinders, holding the paper web against it, while the lower fabric passes under the lower portion of the periphery of the lower drying cylinders, holding the paper against it. The fabrics are guided by fabric intermediate rollers placed between the cylinders.

The drying fabrics operate in a particularly opposite environment, where they are alternately taken to a hot and wet environment and, on the other hand, to a hot and dry environment. They must be flexible in the longitudinal direction of the machine so that they can be easily bent around the felt rollers. They should have good dimensional stability and durability under the stress, temperature, and humidity conditions that prevail in the drying section of the paper machine. Generally, drying fabrics are woven from either natural or 3,764,145 synthetic fibers to form a relatively fluffy fabric with good absorption properties and high porosity to promote the removal of moisture from the paper web. To achieve these results, the yarns are woven close together and sometimes in several layers to form a relatively impermeable fabric. To reduce the permeability even further, puffed staple fiber yarns, some of which contain asbestos, are sometimes woven. However, these fabrics show an unwanted tendency to contain enough water to rewet the sheet. They also become increasingly difficult to clean from a variety of foreign substances, such as sizing agents, clay-like fillers and resins, rubbers, waxes, and pestle, causing the fabric to clog so that it must be cleaned or replaced frequently.

The drying fabrics are usually woven with about 100% warp filling, as shown in the figures of this application. The matter is well known among those skilled in the art. Warp filling is defined as the number of warps in a given space in relation to the assumed total space, the warp filling can be more than 100% when more warp yarns than the one in question have been woven into the available space. it is possible to place the space on one floor. Fabrics with a nominal 100% warp fill generally have an actual calculated warp fill that ranges from 80 to 125%, as in the fabric of the present invention. Values above 100% are obtained by crimping and crimping the warp yarns transversely.

Permeability is an important property of a drying fabric and a measure of its air permeability. The low permeability fabric resists air passage and tends to absorb steam, while the high permeability fabric allows free passage of air and steam.

As mentioned, the drying fabrics were previously made of cotton or wool in the usual way, and sometimes contain asbestos fibers. As synthetic yarn materials evolve, conventional fabrics are gradually being replaced by fabrics containing synthetic yarns. These can be woven as simple or very complex weaves in 2-, 3- or more layers of relatively large-diameter monofilament yarns or multi-strand yarns spun from a plurality of small-diameter filaments.

Of the new synthetic yarns, monofilaments are preferred because the resulting fabric has a longer life, is easy to clean, does not loosen fibers, and does not absorb too much 76,145 moisture. During the cycle when the fabric is in contact with the sheet on the surface of the drying cylinder, the low moisture content and the high permeability promote the transfer of heat to the web. The high permeability of the fabric also has a beneficial effect on the ventilation of the dryer pockets, resulting in a more uniform moisture profile in the web. However, the high permeability of fabrics made of monofilament yarns alone is in some cases disadvantaged by the excessive movement of air in the dryer pockets, which results in the sheet starting to flutter. This problem increases as the speed of the machine increases, and a point is soon reached where the flutter, especially in the first and second parts of the dryer, where the web is wet and weak, is strong enough to cause it to break. The effect of fabric permeability on dryer pocket ventilation and sheet flutter has been described by Race, Wheeldon et al. (Pin, July 1968, Vol. 51 No. 7), and they have shown that air circulation in dryer pockets is more affected by permeability than fabric surface roughness, as previously it was assumed. The movement of air in the dryer pockets is caused by the moving fabric carrying air layers.

On the surface of the fabric, the velocity of the air layer is the same as the velocity of the fabric, and as the distance from the surface of the fabric increases, the velocity of the air decreases. As the fabric wraps around the roll, the air inside is caught in a nip between the roll and the fabric, and if the fabric is sufficiently permeable, the air inside is pumped through, connecting it to the airflow outside the fabric, where: the combined velocity of the two airflows is greater than the fabric speed. . As the fabric passes around the roll, the outer air layers tend to travel away from the roll due to centrifugal forces that cause tangential air movement. This results in a large mass of air moving sideways out of the pockets when high permeability fabrics are used in high speed machines.

Experiments performed by Race, Wheeldon, et al. Show that as the fabric speed increases, the air speed of the dryer felt rollers through the fabric increases, especially at speeds above 1500 rpm. They also show that as the permeability of the fabric decreases, the amount of air pumped into the dryer pockets decreases accordingly. Thus, a low permeability drying fabric can be used at low speeds and helps to achieve high drying efficiencies, but at high speeds, especially in the first and second parts of the dryer, it is necessary to use low permeability fabrics in the range 15-60 m / min / m . Thus, in high speed machines, it is often not practical to take advantage of the easy cleanability of monofilament fabrics due to their inherently high permeability.

"Permeability" is expressed, for example, as the number of cubic meters of air passing through a square meter of fabric per minute when the pressure drop after penetration of the fabric is 12.7 mm of water. One device for measuring air permeability is the Frazier Air Permeometer.

In this device, air is drawn by a variable speed fan through a square foot portion of the fabric 1 and then tested through an upper and lower chamber connected by a series of interchangeable orifices calibrated to measure the amount of pressure difference. The fan speed is increased until the upper chamber reaches the 0.5 inch vacuum indicated by the pressure gauge. The vacuum, measured in the water tunnel from the lower chamber, is read from another connected pressure gauge, and this value is entered into a table where the reading is converted into cubic feet of air per minute per square foot of fabric.

While in a conventional drying system the problem of sheet fluttering can be solved using a low permeability drying fabric, another method to alleviate this problem is known as a single fabric drying system. In this method: one drying fabric is used to guide the paper web like a serpentine through the drying sections of a paper machine. The paper is introduced into the first upper cylinders, e.g. with a cloth below, and passes through the entire drying section in substantially contact with the fabric, so that it is between the fabric and the cylinders in the top row and outside the fabric around the cylinders in the bottom row.

The main advantage of a single fabric drying system is that the paper web is partially supported by the fabric as it passes between rows of drying cylinders, and the flutter of the sheet is then reduced or can be completely eliminated.

Other important advantages of a single fabric drying system are the reduction in drying fabric costs and the elimination of felt rolls as well as 76145 single sets of stretch and guide rollers, which are no longer needed. Also, since the lower row of cylinders is no longer stressed by a separate lower drying felt, waste paper can be removed more easily in the event of paper breaks.

A disadvantage of the single fabric system is that when applied to existing drying sections in which all drying cylinders are the same size and operated at the same speed by interconnected gears, a conventional monofilament fabric with a high modulus of elasticity is relatively inextensible and tends to force the upper cylinders to has a larger effective diameter, due to the paper layer, to rotate at a lower speed. This braking effect on the cylinders with a force tending to stretch the fabric puts considerable strain on the traction sheave, and although the paper web is quite thin, the strain has been sufficient to cause abnormal wear of the gear teeth and bearings and, in some cases, structural fractures.

The elongation of the fabric, called the fabric tension, caused by the difference in the distance traveled by the fabric over the cylinders, is within the elastic range of the fabric and is proportional to the thickness of the paper web. The load, expressed as the torque acting on the gears of the drying cylinder, is proportional to the combined effect of the thickness of the paper and the modulus of elasticity of the fabric. As a practical example, in the drying section of one fabric, where the thickness of the paper web is only 0.3 mm, the calculated torque acting on the drive wheels of the upper cylinder is 4,000 Nm. From this, it appears that the problem of wheel wear and structural breakage can be greatly alleviated by using a fabric with a lower modulus of elasticity so that it stretches more easily and can absorb the stress caused by differences in paper thickness due to differences in paper thickness.

Although the above example illustrates the amount of stress that can be caused by a relatively thin paper web, it is clear that differences in drying cylinder diameters due to wear or thermal expansion due to temperature differences can also cause abrasive effects that can be mitigated by using a low modulus drying fabric.

7 76145

The stress problem can be overcome in those cases where it is possible to disengage the upper gear from the lower gear so that only either the upper or lower cylinders are engaged in traction. In such cases, the disengaged cylinders derive their rotational motion from the drying fabric, and it does not matter if they rotate at different speeds. However, there are some machines in which it is not possible to disengage the other traction wheels, and it is in these cases that a fabric with a low modulus of elasticity can be used advantageously.

Another disadvantage of a single fabric drying system is the relative thickness of a conventional fabric. For example, when a wet paper web comes from the upper drying cylinder where it passes under the fabric, to the lower drying cylinder where it passes over the fabric, it is stretched due to differences in diameters. This elongation, or paper tension, is proportional to the thickness of the fabric. Due to its easy expansion, the wet paper web adapts to the tension. However, as it continues its journey from the lower drying cylinder to the upper drying cylinder, a negative tension is created, and because the wet paper web is not elastic, it detaches from the fabric and curls outward so that it may fold or crease before falling under the fabric with the upper drying cylinder blade. It is therefore obvious that it is advantageous to use as thin a drying fabric as possible in a single fabric system.

The present invention provides a drying fabric for use in a paper machine with reduced permeability and a reduced modulus of elasticity. Said drying fabric comprises a plurality of monofilaments woven into the fabric, which are polymeric plastic warp and weft strands, at least those warp strands extending longitudinally of the machine having a flattened cross-sectional shape, the long axis of the cross-section being parallel to the fabric plane and oblique openings in the fabric of the fabric to reduce the permeability of the fabric evenly throughout.

The fabric of this invention has the advantage of being easy to clean and non-absorbent. An important advantage of a flattened warp is that it has an almost rectangular cross-sectional pattern with a lower bending resistance with respect to its longer 8 76145 axis than with a coaxial circular cross-section, and therefore warps. Also, due to the lower profile of the flattened warp, the diagonal openings in the fabric that allow air to pass through are thus reduced in size.

A further feature of the flattened warp is that when the long axis of the rectangular cross-section is parallel to the weft yarns, the fabric becomes more rigid against torsion about its longitudinal axis, but allowing easy bending of the fabric about an axis parallel to the weft thread, and around smaller diameter rollers in the drying system.

Although the reduced permeability is substantially achieved by using a flattened warp, a further reduction in permeability, which is also a feature of the invention, can be achieved by using roono-filament weft filaments having a cross-sectional pattern shaped to substantially conform to the horizontal to reduce the space between adjacent weft strands.

The invention is also characterized by the use of a round or shaped weft that is relatively flexible compared to the warp, so that during the weaving process, and later under any stressful conditions, it tends to conform to the shape of the tissue slits, shrink them and reduce permeability even more than before.

A further feature of the invention is the use of a round or shaped polymeric weft which is hollow (tubular) so that it adapts even more easily to the shape of the slits in the fabric.

An important advantage of flattened monofilament warp, together with round or shaped monofilament fiber, is that it provides low permeability to a completely monofilament drying fabric without the need to add fluffy yarns, as described in Canadian Patent No. 861,275, which absorb dirt and moisture, or increase dust. weft yarns formed of fine staple fibers having a low bending resistance, lowering the resistance of the fabric to bending with respect to its longitudinal axis.

9 76145

Another advantage of using flattened warp threads is that the points of contact or cruising points (contact area) between the warp and the weft increase, which helps to stiffen the fabric against bending with respect to its longitudinal axis.

Another advantage of a flattened warp according to the present invention is that the fabric woven therefrom is relatively thin and has been found to have an elastic modulus of only about half that of a similar fabric woven from a conventional round warp. As explained above, the low thickness dimension and low modulus of elasticity are particularly advantageous if the fabric is used in a single fabric drying system.

In accordance with the foregoing features, in a broad sense, the present invention provides a drying fabric for use in a paper machine comprising a plurality of interwoven warp and weft monofilaments which are polymeric plastic fibers and which are woven with a warp filling of about 100%. At least those monofilament warp threads extending in the longitudinal direction of the machine have a flattened cross-sectional pattern, the longer axis of the cross-sectional pattern being parallel to the plane of the fabric. The lowered profile of the flattened strands forms limited oblique openings in the fabric of the fabric to reduce the permeability of the fabric evenly throughout.

Weft threads extending in the cross-machine direction may have either a circular cross-section, or a shaped cross-section to substantially conform to the tissue weft openings naturally formed by the warp threads to further reduce permeability. In a further embodiment of the invention, some or all of the weft strands may be hollow plastic strands or strands formed from a plastic material that is relatively flexible relative to the warp thread material so as to be able to conform to tissue slit shapes to partially and further reduce penetration. .

The fabric of the present invention achieves the lowest permeability when, in addition to the flattened warp, it has shaped weft threads substantially corresponding to the weft openings of the fabric, and weft threads that are relatively flexible compared to the warp threads.

A preferred embodiment of the present invention will be described with reference to the examples illustrated in the accompanying drawings, in which Figure 1 is a schematic view of a typical drying section used in a paper machine; Fig. 2 is a schematic view of a typical single fabric drying section: Fig. 3 is an enlarged sectional view of a portion of a drying fabric showing woven round monofilament warp and weft threads as currently in use; Figures 3A and 3B are sectional views taken along section lines A-A and B-B in Figure 3; Fig. 4 is an enlarged sectional view of a fabric structure similar to that of Fig. 3, but using warp threads flattened in cross section to form an improved drying fabric according to the present invention; Figures 4A and 4B are sectional views taken along section lines A-A and B-B in Figure 4; Fig. 5 is an enlarged sectional view of a conventional monofilament conventional 4-stem 8-fold double-drying fabric; Figures 5A and 5B are sectional views taken along section lines A-A and B-B in Figure 5; Fig. 6 is an enlarged sectional view of the drying fabric shown in Fig. 5, but using flattened warp threads to obtain the improved drying fabric of the present invention; Figures 6A and 6B are sectional views taken along section lines A-A and B-B in Figure 6; Fig. 7 is an enlarged sectional view of a flattened monofilament warp thread used in the drying fabric of the present invention.

Figure 1 schematically shows a smaller part of a typical drying section in a paper machine (not shown). The drying cylinders in the top row are generally indicated by reference numeral 10 and in the bottom row by reference numeral 11. The paper web 13 passes, like a serpentine, over the upper and lower drying cylinders, as shown. The endless top fabric 14 holds the paper web 13 tightly against the top cylinders 10 as it passes partially around the first top cylinder, around the felt roll 15, partially around the remaining top cylinders 10 and other intermediate felt rolls 15, then around the return roll 16, then passing the guide and tension rollers. 24 and 23, respectively, and over the steam-heated drying roll 17 to remove some of the residual moisture from the fabric, and then over the second return rollers 16 before passing over the first drying cylinder again after making a full turn. Similarly, the endless lower fabric 76145 fabric 18 holds the paper web 13 tightly against the lower drying cylinders as it passes around these intervening lower felt rolls 19, return rollers 21, tension roll 25, guide roll 26, lower fabric drying roll 22 and other return rollers 21, substantially as shown. These areas bounded by the paper web 13 as they approach and leave the drying cylinder and the drying fabric, leaving the previous cylinder, rotating on the felt roll, and approaching the next drying cylinder are called pockets 12. It is in these pockets 12 that a large amount of moisture evaporates from the heated paper web. Proper ventilation of these pockets 12 causes moisture to escape from the system and maintains the balance of the evaporation process.

Figure 2 schematically shows a typical drying section in which all cylinders are of substantially the same diameter and are operated at the same speed per minute on a common gear. As in Figure 1, the upper row drying cylinders are generally indicated by reference numeral 10 and the lower row 11. One endless fabric 14 passes like a serpentine over the first upper cylinder, down around the first lower cylinder, up around the second upper cylinder, down around the second lower cylinder, etc., then passes around a return roller 16, a guide roller 24, a tensioning roller 23, a steam-heated drying roller 17, and other return rollers 16, as shown. The paper web 13 is introduced under the fabric to the first upper cylinder, as it travels with the fabric between it and the upper cylinders, and outside the fabric at the lower row cylinders. It is noted that with respect to the fabric, due to the thickness of the paper web, the effective diameter of the upper cylinders is now larger than the diameter of the lower cylinders, by an amount twice the thickness of the paper.

Figure 3 generally shows the structure of a plain weave synthetic fabric previously used at 30, with reference numeral 31 denoting successive warp threads and 32 consecutive weft threads. In this structure, each warp thread 31 passes over the first weft thread 32, under the second, over the third, etc. Similarly, the adjacent warp thread passes under the first weft thread, over the second, under the third, etc. means the center-to-center distance of the adjacent weft threads 32. In Figure 3B, x "denotes the shortest distance of the adjacent warp threads 31 in vertical section at the tangent point between the warp and the weft, thus representing 12 7614 5 the largest diagonal opening that allows air to pass through the fabric 30.

Referring to Figures 4, 4A and 4B, they show the same fabric structure 30 'made of monofilament warp threads 31' flattened to such an extent that their short axis “b” (see Figure 7) is only about half (1/2) of the diameter of a circular warp 31 having a corresponding cross-sectional area.

Comparing the fabrics of Figures 3 and 4, it is apparent, due to the lower bending resistance of the rectangular cross-section, that the flattened warp 31 'corrugates more easily so that the center-to-center distance Sj in Figure 4 is smaller than S · ^ in Figure 3. Also, due to flattened warp from the flat profile, the distance "y" in Fig. 4B is considerably smaller than the corresponding distance "x" in Fig. 3B. similarly, due to the smaller distance of the weft strands 32 ', which is the distance S2, the area of the nearly triangular opening based on the distance "y" in Fig. 4B is much smaller than the area based on the distance "x" in Fig. 3B.

Figures 5, 5A and 5B illustrate a double-drying fabric 40 of the fully monofilament 4-stem 8-fold weave formula, a type commonly used in the paper industry. In Fig. 4, successive warp threads are indicated by reference numerals 41, 42, 43 and 44. The weft is paired into two layers and numbered 48-57 as shown. In this structure, the warp thread 41 passes alternately over the first weft thread pair 50-51, between the second pair 52-53, under the third pair 54-55, between the fourth pair 56-57, etc. The next adjacent warp thread passes between the first pair of weft threads, over the second pair, the third between the pair and below the fourth pair. Similarly, the following third and fourth warp threads are woven starting under and between the first pair of weft threads, respectively.

Sj is the center-to-center distance of the weft thread pairs 52.53 and 54.55, and "x" is again (see Fig. 5B) the shortest distance between adjacent warp threads in vertical section at the tangent point of the warp and weft. In Fig. 5A, P denotes the shortest distance between the intersecting pairs of warp threads in the vertical plane halfway between the pairs of weft threads.

13,761 45

Typical air permeability values of conventional fabrics of conventional densities shown in Figure 5 range from 2 to 120 m / min / m. To reduce permeability, with a structure of the type described above, it is common to add fluffy yarns between a few monofilament weft strands, as indicated at 58 in this figure. Fluffy yarns are normally made from staple fibers that fluff and fill the space between the wefts.

Figures 6, 6A and 6B have the same fabric 40 'as shown in Figure 5, but the warp threads 41f to 44' are flattened as in Figure 4. It is again apparent that the distances and "y" in Figures 6 and 6B are less than the corresponding distances and " x "in Figures 5 and 5B. The distance “q_Tt in Fig. 6A does not differ much from the corresponding distance“ p ”in Fig. 5A, but again, due to the reduced distance, the area of the aperture bounded by dimension" q "is much smaller than the area of the aperture bounded by dimension" p ".

As also seen in Figure 6, as an alternative to fluffy staple fiber yarns, we propose additional monofilament threads 59 to be woven into the fabric. As further shown in Figure 6, the additional strands may have a diamond-shaped or rectangular cross-sectional surface marked 60 to fill even more of the openings 61 in the fabric, without making the fabric susceptible to collecting more foreign matter or carrying more water. Although not shown, when three or more layers of weft strands 50, 51 are used, two or more openings 61 are formed in the area between adjacent pairs of weft strands, i.e. in the area between the cross-fabric distances, some or all of these openings being filled according to the invention. shaped weft.

In addition, all of the weft strands may be made of a polymeric plastic material that is more flexible during weaving stress or other fabric treatment, whereby the weft strands are formed to fill more and more fabric openings and further reduce the permeability of the fabric.

For each of these fabric types, a decrease in the distances S2 and and "xM and" yM results in a decrease in the size of the openings in the fabric, and a consequent decrease in permeability. By using suitably flattened monofilament warp threads and suitably shaped and possibly more flexible weft threads, the permeability of the fabric 3 2 can be reduced to 15-75 m / min / m without resorting to fluffy fluffy "fuller" yarns with their expected disadvantages.

A typical conventional monofilament drying fabric, as shown in Figure 5, usually has a thickness of more than 1.7 mm and an elastic modulus of more than 900 kp / cm. According to the invention, a woven test fabric, shown in Fig. 6, having warp threads flattened in a ratio of 2: 1 and fixed in a normal manner. The average thickness was 1.5 mm and the average modulus of elasticity was 480 kp / cm. In general, according to the invention, the thickness of the woven fabric will be in the range 0.9 to 1.7 mm and the modulus of elasticity 270-540 kp / cm.

The warp yarns and shaped weft yarns of the present invention can be made by a mechanical winding machine by winding 0.2 to 1.0 mm thick monofilament strands between a pair of rollers to flatten them, or similarly flat or shaped strands can be extruded from a specially shaped nozzle or made by cutting like. The cross-sectional shape of the flattened monofilament thread is seen in Figure 7, where "a" is the width and "b" is the thickness. Possible cross-section of the flattened monofilament warp thread 2.

the cutting area would be 0.07 to 0.5 mm and the possible ratio a: b would be from 1.1: 1 to 3: 1.

The warp density of this invention would preferably be in the range of 12 to 40 threads per centimeter and the weft density would preferably be in the range of 4 to 40 threads per centimeter.

Claims (17)

A drying fabric for a paper machine comprising a plurality of interwoven warp (31 '; 41'-44') and weft monofilament plastic polymer filaments (32 '; 50-57, 59.60) woven with about 100% warp use , characterized in that at least those warp threads (31 '; 41'-44) extending in the longitudinal direction of the machine have a flattened cross-sectional shape, the long axis (a) of the cross-section being parallel to the plane of the fabric (30'; 40 ') and that the lowered profile (b) of the flattened warp threads (31 '; 41'-44') is adapted to form limited oblique openings (y) in the fabric of the fabric to reduce the permeability of the fabric to be uniform throughout. Drying fabric according to claim 1, characterized in that the width to thickness ratio of the flattened warp threads (31 *? 41 * -44 *) is about 2: 1. The drying fabric according to claim 1, characterized in that the width to thickness ratio of the flattened warp threads (31 *; 41'-44 *) is approximately in the range of 1.1: 1 to 3: 1. Drying fabric according to claim 1, characterized in that at least some of the weft threads (60) are shaped to substantially conform to the horizontal openings (61) in the direction of the interwoven fabric, which the woven warp threads (41'-44 ') naturally form, thus reducing adjacent weft fibers. space between. Drying fabric according to claim 2 or 3, characterized in that at least some of the weft threads (60) are shaped to substantially conform to the horizontal transverse openings (61) in the intermediate fabric, which the woven warp threads (41'-44 ') naturally form, thus reducing adjacent weft the space between the fibers. Drying fabric according to Claim 1, 2 or 3, characterized in that the weft threads (50,52,54,56 ... 51,53,55,57, ... 59,60) are in two or more layers, the interwoven warp threads (41'-44 ') defining gaps between them in the region between adjacent weft strands, the gaps forming at least one horizontal plane of openings (61) in one horizontal plane of the fabric (40'), the monofilament-polymeric plastic weft strands (59,60) extending at least a few horizontal orientations through its aperture and being substantially adapted to conform to the apertures to further reduce the permeability of the fabric. Drying fabric according to Claim 4, characterized in that at least some of the weft strands (60) have a substantially diamond-shaped cross-section. Drying fabric according to Claim 4, characterized in that at least a few weft strands (59) are hollow. Drying fabric according to Claim 4, characterized in that at least some of the weft threads (50 to 57, 59, 60) are relatively flexible compared with the warp threads (41 * to 44 '). Drying fabric according to claim 1, characterized in that one layer of weft threads (32 ') is used, at least some of the threads being shaped to substantially conform to the horizontal openings formed by the woven warp threads (31 *) to further reduce the permeability of the fabric (30'). Drying fabric according to Claim 1, characterized in that the permeability of the fabric (30 '; 40') is approximately in the range of 3 to 21 15-75 m / min / m as measured by a Frazier Air Permeometer, depending on the flattened warp threads (31 '). 4 ^ -441) cross-sectional area. Drying fabric according to claim 1, characterized in that the fabric (30 '; 40') is a thin, low modulus drying fabric with low permeability. Drying fabric according to Claim 12, characterized in that the fabric (30 '; 40') has a permeability of approximately 3 to 15 m / min / m, measured with a Frazier Air Permeometer, depending on the flattened warp threads (31). *; 41 * —44 *) cross-sectional area. Drying fabric according to Claim 12, characterized in that the modulus of elasticity is in the range from 270 to 540 kp / cm. Drying fabric according to Claim 1, 2 or 3, characterized in that the flattened warp threads (31 ^ 4 ^ -441) have a rectangular cross-section. 15,761 45 Use of a drying fabric according to claim 1 in a single fabric drying system, wherein the fabric (30 *; 40 *) passes like a serpentine between the upper (10) and lower rows (11) of drying cylinders (20) connected by gears connected to each other by a gear system and supports the paper web ( 13) along its serpentine orbit around the cylinders. 17,761 45