WO2021209848A1

WO2021209848A1 - A system and a method to manufacture uniformly coated fabric by measuring and adjusting thickness of coatings applied to an uncoated fabric

Info

Publication number: WO2021209848A1
Application number: PCT/IB2021/052719
Authority: WO
Inventors: Gaurav LOHIA
Original assignee: Lohia Corp Limited
Priority date: 2020-04-12
Filing date: 2021-04-01
Publication date: 2021-10-21

Abstract

The invention discloses system and method to measure thickness of polymeric coatings fabrics using measuring gauges and adjust it as necessary. The system employs scanners (5, 5) for measuring the thickness of coatings. The scanners scan the thickness of the coatings (4, 4a) or coated fabrics (2, 3) and assesses whether they have acceptable uniformity. If the uniformity of thickness of coatings (4, 4a) or that of the coated fabrics (2, 3) is outside acceptable margin, the die bolt nozzles through which the polymeric coating melt is applied on the fabric are adjusted automatically/manually to apply more/less coating material as necessary. Fabric may be coated on one or both sides. The system is capable of measuring and adjusting thickness of coatings on one or both sides of the fabric as necessary. The method uses the system of invention to measure thickness of polymeric coatings fabrics and adjust it as necessary.

Description

A SYSTEM AND A METHOD TO MANUFACTURE UNIFORMLY COATED FABRIC BY MEASURING AND ADJUSTING THICKNESS OF COATINGS APPLIED TO AN UNCOATED FABRIC

Field of Invention

The present invention discloses system and method to manufacture uniformly coated fabric by measuring thickness of polymeric coatings on non-woven fabric using measuring gauges and adjusting it as necessary. The fabric may be woven, non-woven type made from plastic, or paper fabric or any underlying substrate that can be applied with a polymer coating.

Background of Invention

Woven fabrics are produced for plurality of applications, including bulk containers, commodities packaging bags, tarpaulins for roof sealing or for protecting from rain or any kind of exposed areas to be protected. The containers or protecting tarpaulins exhibit high strengths and flexibility for making them suitable for packing as well protecting roofs or floors. However, uncoated woven fabric always poses risk of material leakage or entry of moisture into packaged food material. To reduce or eliminate leakage of material from packing, it has been established that interior or exterior polymeric coating on flat or circular woven fabric reduces chances of leakage by filing pores on woven fabric.

One such type of conventional polymeric coating on circular woven fabric is already disclosed in the US patent document US4844958. Objective of this patent is to achieve polymeric coating on tubular woven fabrics. While it refers to coatings in general sense, it does not teach how to ensure and maintain uniformity of polymeric coating on woven fabric.

As disclosed in prior art, polymeric blend is applied on woven fabric though various techniques to provide better bonding, the requirement of film thickness is determined by usage or application of produced product. Although increased film thickness provides better protection to the material to be protected it increases cost of coating and therefore never considered as cost effective solutions. Typically, non-adjusted openings of extrusion die lips distribute non-uniform polymeric coating on woven fabric which adds almost no value to product. On the other hand, this produces inferior fabric which have uneven coating considered as low quality product. Traditionally, operators adjust die lips opening manually based on GSM measurement of sample pieces taken across width of coated woven fabric. This entire process of measurement and correction take significant time which causes loss in production and importantly it is to be repeated for every change in coated film thickness and material Recipe change.

Further, example of measurement of the thickness material layer is disclosed in U.S. patent US 2020/0240776A1 (‘776A1) which describes system and method embodiment for measuring a thickness of material layer using electromagnetic radiation. In some embodiment, a system includes a radiation source configured to direct first radiation towards a first surface of a layer of material having a thickness between the first surface and a second surface opposite the first surface. The first radiation causes the material layer to emit secondary radiation. A filter is positioned between the material layer and a radiation in order to attenuate a portion of the second radiation associated with fluorescence of the material to emit third radiation. Then, the radiation detector is configured to provide a measurement corresponding to the thickness of the material layer based on the detected third radiation. It is evident from the figure 1A, IB & 1C that invention (‘776A1) only refers to the measurement of the thickness of material layer. Further, invention (‘776A1) does not disclose anything about how the single/ double side coating thickness on a fabric is measured. Therefore there is a need to disclose a method of manufacturing a coated fabric with uniform thickness of coating wherein the coating thickness is measured and adjusted as necessary as a part of the manufacturing process.

Objects of Invention:

One of the objects of the invention is to provide a system to manufacture a coated fabric of uniform coating thickness by measuring thickness of polymeric coating applied to a fabric as a part of the manufacturing process.

Another object of the invention is to provide a system of adjusting the thickness of the polymeric coating applied to a fabric.

Yet another object of the invention is to provide a system whereby the thickness of the polymeric coating applied to a fabric is uniform.

Another object of the invention is to provide closed loop system to adjust extrusion die openings according to film thickness distribution.

A further object of the invention is to provide a method of measuring and adjusting the thickness of polymeric coatings applied to woven or non-woven fabrics.

Yet another object of the invention is to provide a method of applying polymeric coating to a fabric whereby the thickness of the coated fabric is uniform

Brief Description of Figures:

Figure 1 illustrates complete fabric path movements from the unwinding section to rewinding section.

Figure 2a illustrates top view of Gauge- 1 measurement configuration Figure 2b illustrates sectional view of uncoated fabric and relative locations of gauges w.r.t the extrusion die Figure 2c illustrates sectional view of one side coated fabric and the coating distribution on one side coated fabric

Figure 3 illustrates the scanning pattern of Gauge- 1 on uncoated and one side coated woven fabric

Figure 4 illustrates top and side view of Gauge-2 measurement configuration

Figure 5 illustrates Scanning pattern of Gauge-2 on both sides coated woven fabric

Figure 6 illustrates Auto Die closed loop control system

Figure 7 illustrates correspondence between first profile scan (15) & second profile scan (16) of Gauge-1

Figure 8 illustrates correspondence between first profile scan (15), second profile scan (16) & third profile scan (17) by Gauge -2

Figure 9 illustrates mapping of scanning profiles w.r.t extrusion die

Figure 10 illustrates mapping of scanning profiles w.r.t extrusion die for wide width woven fabric List of Parts:

1. Uncoated fabric

2. One side coated fabric

3. Both sides coated fabric 4. First coating layer of polymeric material; 4a - second coating layer of polymeric material 5. Gauge- 1

5a Gauge- 1 radiating unit or device 5b Gauge- 1 receiving unit or device 6. Gauge -2

6a Gauge-2 radiating unit or device 6b Gauge-2 receiving unit or device

7. Input roller

8. Upstream feed or guide roller 8a Tum-bar guide roller

8b Downstream guide roller

9. Extrusion device

10. Output roller

11. Gauge-1 home position 12. Gauge- 1 limit position

13. Gauge-2 home position

14. Gauge-2 limit position

15. First scanning profile

16. Second scanning profile 17. Third fabric scanning profile

18. Extrusion die; 18a Die bolts

19. Gauges data processing & acquisition system

20. Auto die controls

21. Auto die closed loop system Summary of Invention:

The invention discloses an apparatus for manufacturing a uniformly coated fabric by measuring and adjusting the thickness of polymeric coatings applied to fabrics as a part of the manufacturing process. An uncoated fabric is applied with a first coating on one side or face and a second coating on the other side or face. The apparatus employs scanners for the purpose of measuring the thickness of coatings. The scanners scan the thickness of the coatings and assesses whether they fall within acceptable level of uniformity. If the uniformity of thickness is outside the acceptable margin, the die bolt nozzles through which the polymeric coating melt is applied on the fabric are adjusted automatically or manually to apply coating material as may be necessary. Fabric may be coated on one or both sides. The system of invention is capable of measuring and adjusting thickness of coatings on one or both sides of the fabric as necessary. The method of measuring and adjusting the thickness of polymeric coatings applied to fabric comprises the steps of: scanning the uncoated fabric and measuring its thickness t_uc, and establishing a first scanning profile apply a coating material on one side of fabric through die bolt nozzle scanning the one-side-coated fabric and measuring its thickness t_0Sc, and establishing a second scanning profile, assessing the uniformity of the thickness of first coating, adjusting the die bolt settings so that the first coating has the required level of uniformity, applying a coating to the uncoated side of the one-side-coated fabric - scanning the two-sides-coated fabric and measuring its thickness tbsc, and establishing a third scanning profile, and assessing the uniformity of the thickness of second coating, adjusting the die bolt settings so that the second coating has the required level of uniformity. The scanners of the system travel across the fabric in a direction perpendicular to the direction of travel of the fabric. The thickness of the first and second coatings is calculated as the difference between t_0Sc and t_uc, and and t_osc, respectively. In order to improve the accuracy of the measurement and consequently that of the uniformity of the thickness distribution, the scanners of the apparatus scan the moving fabric at specific profiles. In particular, the best accuracy is obtained if the first, second, and the third scanning profiles overlap. In other words best accuracy is achieved by ensuring that all three thickness measurements - t_0Sc, t_uc, and t_bsc are taken at same points along the scanning path of the scanners, the scanners measure the thicknesses at same locations along the fabric.

Detailed Description of Invention:

The present invention discloses an apparatus and a method for manufacturing a uniformly coated fabric by measuring and adjusting thickness of coatings applied to woven fabric. The apparatus uses electromagnetic radiation for this purpose. The arrangement includes a radiation source configured to direct radiation towards woven material moving in between a radiating source unit and radiation receiving unit. The invention is not only limited to radiating and receiving unit placed face-to-face, the purpose of the invention can also be achieved by single source device which have inbuilt or on same side radiating and detecting means or any kind of arrangement meant for the purpose of thickness measurement which must be capable to measure uncoated and coated fabric both. Also, while electromagnetic radiation is preferred, any other type of signals and a method of sending and receiving signals for this purpose can be used.

Figure 1 shows a schematic view of the system/apparatus of the invention. It shows a system/apparatus of applying polymeric coating to both sides of a fabric. The thickness of coatings is measured and adjustment to the desired coating thickness depending on the deviation of the measured thickness from the required thickness. It shows two gauges - gauge- 1 (5) and gauge-2 (6), each having radiating sources to calculate coating thickness mathematically by capturing thickness of the fabric at various stages of coating at different locations. It shows a system wherein incoming uncoated fabric is scanned whereby its thickness is measured at points of scanning to establish the base thickness or the thickness of the uncoated fabric. The system makes similar thickness measurements of fabric with one side coated and fabric with both sides coated. The system aims to collect the thickness measurement data at same points in order that there is good correlation between the three sets of measurements so that ultimately the measured thickness of the coating layers is accurate. The system also allows adjustment - made on the basis of the deviation of the measured thickness from the required thickness of the coating layers (4 and 4a) - to the polymer extrusion equipment that actually lays coating layers (or the coating application equipment) on the fabric so that the coating thickness is within the required limits and has the required level of uniformity across the fabric. Typical coating application equipment is in the form of an extrusion die (18) that has multiple die bolts (18A).

The system described in detail here uses two gauges for scanning and thickness measurement. However, it is possible to use further gauges to improve the accuracy of measurement and adjustment of the coating application equipment.

Purpose of taking measurements at different points is to determine how much correction or adjustment is required to be made to individual extrusion die bolt in order to maintain uniform coating thickness across the fabric width.

In the system described here (Figure 1), the first gauge or scanner and the thickness measurement device - guage-1 (5) - is located just after the fabric unwinding section and the second gauge - or scanner and the thickness measurement device - gauge-2 (6) - is located after extrusion die (18). Alternatively, gauge-2 may be located downstream of the output roller (10), which rolls out coated fabric. As will be evident from the ensuing discussion that follows, gauge-1 measures the base thickness, i.e. the thickness of the uncoated fabric and also the thickness of fabric coated on one side or one-side-coated fabric, and gauge-2 scans and measures thickness of the fabric that is coated on both sides or two-sided-coated fabric (or both-sides-coated fabric).

For the purpose of this description, one-side-coated fabric (2) means a fabric having a first layer of coating (4) applied to one side of the uncoated fabric (1). Similarly, the both-sides-coated fabric (3) has the first layer of coating (4) and a second layer of coating (4a) applied across width of uncoated fabric (1) on either of its sides or faces.

Both gauges (5 and 6) cany out the scanning operation by moving orthogonally to the direction of movement of fabric. The stretch over which the gauges travel depends on the fabric width. Since gauge- 1 scans both uncoated and one-side- coated fabrics, and which travel alongside each other (see Figure 2-a), the stretch over which gauge- 1 travels is such that it spans two fabric widths. The arrangement by which the uncoated fabric (1) and one-side-coated fabric (2) are made to travel side-by-side will vary from equipment manufacturer to equipment manufacturer and will be known to a person skilled in the art.

Top half of Figure 2a illustrates arrangement for measuring thickness of the uncoated fabric (1). Figure 2b shows view along section ‘a’ taken in Figure 2a. The double arrow indicated in Figure 2a next to gauge- 1 (5) suggests that gauge- 1 (5) moves across the width of the fabric (1) in a direction perpendicular to fabric travel direction. Bottom half of Figure 2a shows the one-side-coated fabric (2) which runs alongside the uncoated fabric (1), and which is also scanned by gauge- 1 (5) while measuring the thickness of the first coating layer (4). Figure 2c shows view along section b taken in Figure 2a. One key aspect of the present invention is that gauge-1 (5) scans and measures the thickness of uncoated fabric (1) and that of the first coating layer (4) of the one- side-coated fabric (2) at same points. This is achieved by carefully establishing scanning profiles of two sets of scanning. For example, when gauge- 1 scans the uncoated fabric, it establishes a first scanning profile (15), whereby thickness data is collected at a first predetermined number of discrete points of the fabric. Another key aspect of the present invention is that the data collection points correspond to the die bolts of the extrusion die. Further aspect of the present invention is evident when first layer of coating (4) is applied to the uncoated fabric (1) and the one-side-coated fabric (2) travels side-by-side to the uncoated fabric (1) and approaches gauge-1 (5) for getting scanned. According to an embodiment of the invention, the points at which gauge- 1 collects thickness data on the one-side coated fabric and thus establishes a second scanning profile (16) which correspond as exactly as possible to the specific points of the first scanning profile. This is illustrated in Figure 7.

Figure 3 shows first and second scanning profiles (15, 16) carried out using gauge- 1. It shows two strips - one of the uncoated fabric (1) and the other being a one-side-coated fabric (2) - traveling under guage- 1. During scanning of uncoated fabric (1), gauge-1 (5) moves from its home position (11) to its limit position (12) following the first scanning profile (15). During the scanning operation, gauge- 1 (5) measures thickness of the uncoated fabric (1) at the first predetermined number of discrete points. In one aspect of the invention, the number and location of the point of measurement of thickness along the first scanning profile (15) correlate to the number of die bolts in the extrusion die (18) and their locations along the extrusion die. This correspondence is schematically shown in Figure 9.

Gauge-1 starts its travel across the uncoated fabric (1) from the home position (11) and follows a predetermined first scanning profile (15) Once it scans the full width of the uncoated fabric (1) it stops the scanning activity and continues its travel towards its limit position 12. Once it reaches the limit position (12), it awaits the one-side-coated fabric to arrive. The uncoated fabric after having undergone the first scanning profile (15) undergoes the coating stage whereby it is converted into the one-side-coated fabric (2), which in turn undergoes the scanning process under gauge-1 (5). Gauge-1 (5), which is stationary at the limit position (12), starts its reverse journey so as to scan the one-side-coated fabric (2). In a key aspect of the invention, the second predetermined number of discrete points at which gauge- 1 measures thickness of the one-side-coated fabric (2) to establish the second scanning profile (16) corresponds to the points at which gauge-1 (5) had measured the thickness of the uncoated fabric (1). Thus there is a correspondence between the points of thickness measurements along first and second scanning profiles (15, 16) - see Figure 7. Basically, start of gauge-1 to follow profile (15) is taken as master and other profile scannings are slave motions.

As the uncoated fabric (1) unrolls continually, gauge-1 (5) keeps scanning it at predetermined intervals that are dependent on the speed of the coating apparatus. For, each of the first scanning profile (15), there is a corresponding second scanning profile (16), whereby the thickness of uncoated and one -side -coated fabrics (1, 2) are measured for the progressing fabric.

The one-side coated fabric (2), having undergone the second scanning profile (16), is subjected to the second layer of coating (4a) on the remaining uncoated side of the original uncoated fabric (1), thereby converting it into the both-sides- coated fabric (3). The uncoated fabric (1) now has both its sides coated (see Figures 2C and Figure 4). In a further aspect of the invention, thickness of the second layer of coating (4a) is also measured and adjusted to the desired level by making adjustments of the die bolt nozzles. Figures 4 and 5 show a further aspect of the invention, where the thickness of the both-sides -coated fabric (3) is measured. The Top View shown in Figure 4 shows fabric (2) is going through the extrusion die (18) whereby a second layer of coating (4a) is applied to the one-side-coated fabric (2) so as to form both-sides- coated fabric (3), which is also shown in the Side View of Figure 4. The both- sides-coated fabric (3) approaches gauge-2 (6) comprising a gauge-2 radiating unit (6A) and gauge-2 receiving unit (6B). A further key aspect of the invention is that gauge-2 (6) scans the both-sides-coated fabric (3) and measures its thickness preferably exactly at the same points as gauge- 1 (5) had measured during its first and second scanning profiles (15, 16). In doing so, athirst scanning profile (17) is established. There is thus a correspondence (see Figure 8) between the points of thickness measurements along first, second, and third scanning profiles (15, 16, and 17).

The fabric thickness is measured at each of the scanning points which are mapped to die bolts positions. For instance, in the preferred embodiment, if there are ‘n’ number of die bolts in extrusion die (18) then there would be ‘n’ number of thickness measurement sampling points also. However, in other embodiments, the number of die bolts can be more or less as compared to the number of points at which the first and/or second and/or third scanning profiles have been established.

As shown in Figure 2b, the first layer of coating (4) is applied on side 1 of the uncoated fabric (1). The thickness of the uncoated fabric (1) is denoted as t_uc. As we have seen earlier, the scanning points are preferably mapped to the positions of die bolts. Assuming that there are m die bolts in the extrusion die (i.e. 1 to m), the thickness of the uncoated fabric at m discrete points of measurement of the first scanning profile (15) is denoted as t_{uc i}. tuc2, tucm, etc. corresponding to the positions of die bolt 1, die bolt 2, ...die bolt m, respectively. Similarly, the thickness of the one-side-coated fabric (2) is denoted as i, t_osc2, ... m corresponding to die bolt positions 1, 2, ..m, respectively. In one embodiment, the number of discrete points of measurement of first scanning profile (15) may be different from the number of die bolts.

The thickness of the first layer of coating is calculated at all points of measurement during the first and second scanning profiles (15, 16) as the difference between thicknesses calculated during second scanning profile (15) and first scanning profile (16). For example, at die bolt position 1, which corresponds to a mapped point along the first and second scanning profiles, the thickness of first layer of coating is (tosci - t_Uci). In similar fashion, the thickness of the polymer film coating (4) of a single-side-coating fabric (2) at any point along the first (15) and second (16) scanning profiles will be calculated as the difference between the thickness of the fabric coated on one sided minus the thickness of the uncoated fabric: (toscm - tuci), (tosc(m-i) - tud) . (tosci - t_UCm), where 1, 2, ...m indicate the number of a die bolt which is mapped to points of measurements along the scanning profiles.

In the case where the first predetermined number of points and the second predetermined number of points is different, it is preferred that at least some of these points overlap each other. In this case, the thickness of the first layer of coating may be calculated as the difference between the measured thickness of the uncoated fabnc and the one-side-coated fabric at points of the first and second scanning profiles (15, 16) that coincide with each other.

So, equation- 1 for thickness of the first coating layer (4) at the location of die bolt 1, denoted as t_fCi measured by gauge-1 is as follows:

As described earlier, Figure 5 shows a third scanning profile (17) generated by gauge-2 (6) for the both-sides-coated fabric (3). Scanning using gauge-2 (6) starts from gauge-2 limit position (14) towards gauge-2 home position (13). In one key aspect of the invention it is ensured that gauge-2 (6) scans the fabric (3) to collect thickness data preferably at same points identified during first and second scanning profiles (15, 16) resulting from scanning of the uncoated and one-side- coated fabrics (1, 2). As described previously, all individual die bolts, i.e. die bolts- 1 to die bolts-m, are mapped to one-side-coated fabric (2) while the individual die bolts from the (m+k) position to (n) are mapped to Side-2 of the one-side-coated fabric (2) which are just overlapped to die bolt (m+k) to (n). Here, ‘k’ is offset added to 'm' number of die bolts (18a) already mapped with un coated fabric (1) for mapping with other side coating on one side coated fabric (2) as shown in Figure 2a. As per process requirement, a person known to system can set ‘k’ value from numeric ‘ G onwards.

During scanning of both-sides-coated fabric (3) which is mapped to die bolt position - m+k have tbsc(m+k> thickness and both-side-coated fabric (3) mapped to die bolt position -‘n’ will have tbscn thickness. So, polymer film (4) thickness for a double-side -coated fabric (3) which is mapped to die bolt position-(m+k) will be (tbsc(m+k) - tosci))· In similar fashion, polymer film (4) thickness which is mapped to single side coating fabric will be calculated as (tbsc(m+i> -tosci), ... (tbscn - m).

Therefore equation-2 for thickness of the second coating layer (4a) at the location of die bolt 1, denoted as t_sci measured by gauge-2 is as follows:

In a further aspect of the invention, according to calculated differential values of polymer fdm (4), either machine automation regulate die bolt settings (21) or visually show it to operator for manual setting of die bolts to minimize or eliminate thickness variation to maximum possible level.

The preceding description is one of the auto die measurement systems, as shown in Figure 6, where the said system comprises of sensors i.e gauge- 1 (5) and gauge- 2 (6) for converting physical signal into electrical data signal. Gauges data processing & acquisition system (19) acquire continuous data from sensors, process acquired data as per equations- 1 & 2 for each die bolt mapping. Once deviation with respect to set coating thickness is known to system against each die bolts, gauges data processing and acquisition system (19) generates commands for auto die control (20) to adjust die bolts of extrusion die (18) to minimize error between set and actual polymeric coating thickness.

As shown in Figure 2(b) & Figure 2(c), which shows side view of gauge-1 (5) comprises a radiating unit (5a) and receiving unit (5b), respectively. They are arranged such that to position each other face-to-face, as shown in Figure 2, one acts as electromagnetic radiator and the other one acts as receiver. Similarly, as shown in Figure 4, gauge-2 Radiating unit (6a) and gauge-2 receiving unit (6b) face each other. Again, arrangement of gauge- 1 (5) and gauge-2 (6) into their sub units being placed on the opposite sides of fabric is not necessary: there are possibilities that better measurement configuration can be achieved by placing the respective radiating and receiving units on the same side of the respective fabrics or by using some kind of electromagnetic reflecting arrangement. Hence, present invention can be accomplished by all kind of Gauging systems which can be used to measure or estimate polymeric coating layer /film ‘4’ precisely which have minimum possible measurement variations.

In an alternate embodiment, a person skilled in art can opt for uniform both side coated fabric (3) thickness instead of maintaining uniform coating thickness on each side of uncoated fabric (1). Here, all techniques of polymeric coating (4, 4a) thickness measurement would be followed by applying same equations 1 & 2 as described in earlier description. However, auto die closed loop system (21) will adjust die bolts (18a) mapped from 1 to n such that sum of coated fabric (3) thickness is constant throughout width of fabric. In this case, equation of total coated fabric (3) thickness at any particular die bolt location would be as follows:

In another alternate embodiment, apparatus as shown in figure 1 can be utilized for single side coated product also by a person known to system. In this case, gauge- 1 would be employed to measure thickness of un-coated fabric and gauge-2 for measurement of one side coated fabric. Basically, this kind of application is required in case of wide width fabric which cannot be operated parallelly as shown in Figure 2a. Similar to method described for both side coated fabric, here die bolts will be mapped uniformly from 1 to n as shown in Figure 10. Equation 1 will be followed to adjust die bolts setting as done earlier in case of both side coated fabric.

Coating thickness is measured from set value in process. So, if set value is 25 micron and achieved thickness is 25 micron then it is defined as accurate or in other words more close the actual value w.r.t set value it is called as better.

Empirically, Synchronization of scanning profiles at three measurement instances is proven to be known better solution, however, not only limited to this measurement technique. It is become apparent to those skilled in the art that any modifications or change covering disclosures are understood as being included in scope of the invention.

Claims

1. A system to manufacture uniformly coated fabric by measuring and adjusting thickness of coatings applied to an uncoated fabric (1) in an automated fabric coating line to convert said uncoated fabric (1) first into a one-side coated fabric (2) and then a both-sides-coated fabric (3), characterised in that said system comprises a set of scanning and thickness measuring gauges, a thickness data acquisition and processing unit, and an auto-die-control unit to automatically adjust die bolts used for applying coating layers to said, wherein said set of scanning and thickness measurement gauges consist of at least two gauges, namely gauge- 1 (5) and gauge-2 (6), said gauge-1 being capable of measuring at a first predetermined number of discrete points the thickness of uncoated fabric (1) along a first scanning profile (15) across the width of said uncoated fabric (1), and measuring at a second predetermined number of points the thickness of the one-side-coated fabric (2) along a second scanning profile (16) across the width of said one-side-coated fabric (2), said gauge-2 being capable of measuring at a second predetermined number of discrete points along a third scanning profile (17) across the width of said both-sides-coated fabric (3) the thickness of said both- sides-coated fabric (3), said data acquisition and processing unit being capable of calculating thickness t_fC of a first coating layer (4) of said one-side coating as the difference between the measured thickness at points along said second and first scanning profiles (16, 15), and calculating the amount of variation in t_fC at the measured points, said data acquisition and processing unit being capable of calculating thickness t_sc of a second coating layer (4a) of said both-sides-coated fabric (3) as the as the difference between the measured thickness at points along said third and said second scanning profdes (17, 16), and calculating the amount of variation in t_sc at the measured points, said auto-die control unit being capable, on the basis of the assessed variation in t_fC and t_sc, of automatically adjusting the nozzles of said die bolts to regulate the amount of polymer extruded from said die bolts so as to produce said first coating layer (4) and said second coating layer (3) of uniform thickness.

2. The system as claimed in claim 1, wherein said each of said discrete points of measurement along said first scanning profile (15) coincides with a corresponding discrete point along said second scanning profile (16).

3. The system as claimed in claims 1 and 2, wherein said each of said discrete points of measurement along said third scanning profile (17) coincides with a corresponding discrete point along said first and second scanning profiles (15, 16).

4. The system as claimed in claims 1 and 2, wherein said uncoated fabric (1) and said one-side-coated fabric (2) travel side-by-side.

5. The system as claimed in claims 1 to 4, wherein said gauge-1 has a gauge-1 radiating unit (5a) and a gauge-1 receiving unit (5b) which may be placed on different sides of fabrics (1 or 2), and wherein said gauge-2 has a gauge-2 radiating unit (6a) and a gauge-2 receiving unit (6b) which may be placed on different sides of fabrics (1 or 2).

6. The system as claimed in claim 5, wherein said gauge-1 comprises a single unit with built-in radiating unit and a receiving unit, such that sending of radiating signal and receiving it is carried out on the same side of the fabric (1 or 2).

7. The system as claimed in claim 5 and 6, wherein gauge-2 comprises a single unit with built-in radiating unit and a receiving unit, such that sending of radiating signal and receiving it is carried out on the same side of the fabric (3).

8. The system as claimed in claims 5 to 7, wherein said radiation is electromagnetic.

9. The system as claimed in claims 5 to 7, wherein said radiation is selected from a group comprising ultrasonic, laser, capacitive.

10. The system as claimed in claims 1 to 9, wherein said first, second and third predetermined number of points is same.

11. The system as claimed in claim 1 , wherein said data acquisition and processing unit being capable of calculating thickness t_fC of a first coating layer (4) thickness t_sc of a second coating layer (4a) of said both-sides-coated fabric (3) as the as the difference between the measured thickness at points along said third and said second scanning profiles (17, 16), said auto-die control unit being capable of automatically adjusting the nozzles of said die bolts to regulate the amount of polymer extruded from said die bolts so as to produce said first coating layer (4) and said second coating layer (3) of uniform thickness.

12. A method of manufacturing coated fabrics by measuring and adjusting thickness of coatings applied to an uncoated fabric (1) in an automated fabric coating line to convert said uncoated fabric (1) first into a one-side coated fabric (2) and then a both-sides-coated fabric (3) using the system as claimed in claims 1 to 9, characterised in that said method comprises the steps of: a. scanning an uncoated fabric (1) and measuring its thickness t_uc at a first predetermined number of points and establishing a first scanning profile (15) b. applying coating to one side of said uncoated fabric (1) c. scanning the one-side-coated fabric and measuring its thickness t_0Sc at a second predetermined number of points and establishing a second scanning profile (16), d. determining the thickness of the first coating layer (4) at individual measuring points as the difference between t_0Cs and t_uc at said first predetermined discrete points e. assessing the variation of the thickness of said first coating layer (4) on the basis of the measured thickness of step d, f. adjusting the die bolt settings to vary the amount of coating polymer coming out of the die bolt nozzles on the basis of the measured thickness variation of step e so that the thickness t_& of first coating layer (4) of the one-side-coated fabric (2) has the required level of uniformity, g. applying coating to the uncoated side of one -side-coated fabric (2) h. scanning the two-sides-coated fabric (3) and measuring its thickness tbsc at discrete points and establishing a third scanning profile, i. determining the thickness t_sc of the second coating layer (4a) at individual measuring points as the difference between tbsc and tosc at said first predetermined discrete points, j . assessing the variation of the thickness of said second coating layer (4a) on the basis of the measured thickness of step i, k. adjusting the die bolt settings to vary the amount of coating polymer coming out of the die bolt nozzles on the basis of the measured thickness variation of step j so that the second coating layer (4a) of the both-sides-coated fabric (3) has the required level of uniformity.

13. The method as claimed in claim 12, wherein said each of said discrete points of measurement along said first scanning profile (15) coincides with a corresponding discrete point along said second scanning profile (16), and wherein said each of said discrete points of measurement along said third scanning profile (17) coincides with a corresponding discrete point along said first and second scanning profiles (15, 16).

14. The method as claimed in claims 12 and 13, wherein said gauge-1 has a gauge- 1 radiating unit (5a) and a gauge- 1 receiving unit (5b) which may be placed on different sides of fabrics (1 or 2), and wherein said gauge-2 has a gauge-2 radiating unit (6a) and a gauge-2 receiving unit (6b) which may be placed on different sides of fabrics (1 or 2).

15. The method as claimed in claims 12 to 14, wherein said gauge-1 comprises a single unit with built-in radiating unit and a receiving unit, such that sending and receiving of radiating signal is carried out on the same side of the fabric (1 or 2), and wherein said gauge-2 comprises a single unit with built-in radiating unit and a receiving unit, such that sending and receiving of radiating signals is carried out on the same side of the fabric (3).

16. The method as claimed in claims 12 to 15, wherein said radiation is electromagnetic.

17. The method as claimed in claims 12 to 16, wherein said radiation is selected from a group comprising ultrasonic, laser, capacitive

18. The method as claimed in claims 12 to 17, wherein said first, second and third predetermined number of points is same.

19. The method as claimed in claim 12, wherein adjusting the die bolt settings to vary the amount of coating polymer coming out of the die bolt nozzles on the basis of the measured thickness variation of steps e and j, so that the one-side-coated fabric (2) of step e, and the both-sides -coated fabric (3) of step i have the required level of uniformity in the thickness of respective coated fabrics (2, 3).

20. A two-sided-coated fabric (3) characterised in that said fabric (3) is manufactured using the apparatus as claimed in claims 1 to 11 and the method as claimed in claims 12 to 19, wherein thickness of coatings is uniform.