ES2828530T3 - Procedure to determine the characteristic features of a tissue - Google Patents

Abstract

A procedure for determining characteristic features of a tissue (48, 312), the procedure comprising: forming a representation of a portion of a surface of the tissue, the representation showing the locations and sizes of the knots (206, 208) and the pockets (210) on the surface of the fabric (48, 312); generating an image (600) of the tissue surface portion (48, 312) from the representation; displaying at least a portion of the image (600) on a screen associated with a computer having a processor; the procedure characterized by drawing a contour (602A) around at least one of the nodes (206, 208) displayed in the image (600); and drawing guides (610, 612) in the displayed image (600) so that the guides (i) pass through the center of the contoured node, (ii) pass through other nodes displayed in the image, and (iii) constitute a shape that surrounds the areas of the image (600) that correspond to the sites where the pockets (210) are formed between the nodes (206, 208), in which the outline (602A) and the guides (610, 612 ) are drawn using an image analysis program stored on a non-transient, computer-readable medium.

Description

DESCRIPTION

Procedure to determine the characteristic features of a tissue

BACKGROUND

Field of the invention

My invention relates to characterizing the surface of a tissue for making paper. In specific examples, my invention relates to apparatus, methods and systems for determining the characteristics of the contact surface of a fabric that is used for the three-dimensional structuring of a web in a process for the manufacture of paper.

Related art

In the processes of forming paper products, such as tissue paper and paper towels, the three-dimensional shaping is carried out while the papermaking belt is still highly deformable, that is, when the papermaking belt It has a high water content. Often this three-dimensional shaping of the band is carried out on a structured fabric. The fabric provides a knotted interface in the yarns of the fabric, with pockets that are formed in the fabric between the knots. When the papermaking band is applied to the fabric, portions of the band come into contact with the knots and other portions of the band are drawn into the pockets. Before being removed from the fabric, the band is dried to a point where its shape becomes fixed or locked. Thus, domes are formed on the dry web where the web has entered the pockets of the fabric and the domes are present in the finished paper product. Thus, the paper product has a distinct three-dimensional structure formed, in part, by the knot and pocket characteristics of the structural fabric.

Since the contact surface of a structural fabric is directly related to the shape of the finished product, the choice of a structural fabric is often based on the shape of the product that is desired. However, it is difficult to characterize the interface of a structural fabric based on a simple visual inspection of the fabric. While the knots of the fabric can be easily seen, it is often difficult to determine the exact size of the knots, it is difficult to determine the areas of the pockets between the knots, and it is difficult to determine the depth of the pockets into which it is inserted. the papermaking belt during the papermaking process. As such, there have been prior techniques that attempt to quantify the interface characteristics of the fabric, for example, using formulas based on the yarn parameters of the fabric. However, it has been found that such formulas are often not accurate enough to characterize the contact surface of the fabric in a way that allows an accurate prediction of the structure of the paper product that will be formed with the fabric. Also, the characteristics of the contact area will often change as the fabric is passed through a papermaking machine. For example, wear on the surface of the fabric in general will increase the length of the knots, thus changing the structure that will be transmitted to the web by the fabric. Therefore, the formulas for determining interface characteristics that are applicable to initial fabric configurations will not necessarily apply to fabrics that have worn away over time.

Document US2003085013 discloses a method for determining characteristic features of a tissue with the use of image analysis. The method comprises the characteristic features of the preamble of the present claim 1.

Therefore, it would be advantageous to provide a technique to accurately characterize the contact area characteristics of a structural fabric that is used in a papermaking process. Furthermore, it would be advantageous to provide a technique that can easily determine the characteristics of the contact area as the fabric wears, over time, while the fabric is mounted on a papermaking machine.

SUMMARY OF THE INVENTION

According to a first aspect, my invention provides a method for determining characteristics of a fabric. The method includes forming a representation of a portion of a surface of the fabric, the representation showing the locations and sizes of knots and pockets on the surface of the fabric, generating an image of the portion of the fabric surface based on the representation, displaying at least a portion of the image on a screen associated with a computer having a processor, and drawing an outline around at least one of the nodes displayed in the image. The procedure further includes drawing guides in the image displayed so that the guides (i) pass through the center of the contoured node, (ii) pass through other nodes displayed in the image, and (iii) constitute a shape that circle the areas of the image that correspond to the places where the pockets form between the knots. The outline and guides are drawn using an image analysis program stored on a non-transient, computer-readable medium.

According to a further aspect, the method also includes drawing a unit cell for the portion of the tissue surface in the displayed image, wherein the unit cell is defined by guides that (i) pass through the centers of the knots and (ii) they constitute shapes that surround areas of the image that correspond to the places where the pockets are formed between the knots. At least one property of the tissue surface is calculated from the properties of the unit cell formed by the guides.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a paper machine using a structural fabric.

FIG. 2 is a top view of a section of a structural fabric.

FIG. 3A and 3B are views of the contact surface of a recording apparatus according to the invention.

FIG. 4 is a detailed view of the pressing section of the impression forming apparatus shown in FIGS. 3A and 3B.

FIGS. 5A to 5D are examples of impressions of the structural fabric made in accordance with the invention. FIGS. 6A to 6E show the steps of establishing a coordinate system for printing the structural fabric.

FIGS. 7A, 7B and 7C show the application of the analytical technique applied herein to a photograph of the knots of a tissue.

FIGS. 8A and 8B show an alternative analytical technique applied to a photograph and an impression of the knots of a fabric,

FIG. 9 shows the application of the analytical technique to determine a pocket surrounded by knots in a structural tissue,

FIG. 10 shows the application of the analytical technique to determine the depth of the pocket shown in FIG. 8.

FIGS. 11A and 11B show the application of analytical techniques applied to an image of a paper product and its structural fabric.

DETAILED DESCRIPTION OF THE INVENTION

My invention relates to apparatus, procedures and systems for determining the characteristics of the contact surface of a fabric that is used in a process for the manufacture of paper. As will be apparent from the following discussion, "fabric contact surface characteristics" refers to the contact surface characteristics that result from the configuration of the knots and pockets that make up the fabric contact surface. In specific embodiments, my invention is adapted for use with structural fabrics that are used for the three-dimensional structuring of a web in a papermaking process. Such structural fabrics are often constructed with yarns made from, for example, polyethylene terephthalate (PET), polyester, polyamide, polypropylene, and the like. As will be explained in more detail below, the particular contact surface of a structural fabric will have a significant effect on the structure of the paper product, and my invention uses techniques to characterize aspects of the contact surface. However, it should be noted that my invention is applicable to any type of fabric used in a papermaking process, including fabrics used for purposes other than web structuring.

Figure 1 shows an example of an air-drying (TAD) papermaking process in which a structural fabric 48 is used to form the three-dimensional structure of the paper product. To begin the process, the raw material supplied through a head box 20 is directed in a jet into the recess formed between a formation fabric 24 and a transfer fabric 28. The formation fabric 24 and the transfer fabric pass between a forming roller 32 and a leading roller 36. The forming fabric 24 and the transfer fabric 28 diverge after passing between the forming roller 32 and the leading roller 36. The transfer fabric 28 then passes through the dewatering zone 40 in which suction boxes 44 remove moisture from the web and transfer fabric 28, thereby increasing the consistency of the web, for example, from about 10% to about 25% prior to transfer of the web to the structural fabric 48. In some cases, it will be advantageous to apply a certain amount of vacuum as indicated through the vacuum boxes 52, in a transfer zone 56, particularly when a considerable amount is transmitted of fabric crepe to web in transfer zone 56 by rapid transfer in which transfer fabric 28 moves faster than structural fabric 48.

Since the band still has a high moisture content when transferred to the structural fabric 48, the band is deformable so that portions of the band can be stretched into pockets formed between the threads that make up the structural fabric 48 (the pocket formation in a fabric will be described in detail below). As the structural fabric 48 passes around the through air dryers 60 and 64, the consistency of the web increases, for example, from about 60% to about 90%. Thus, the band is more or less permanently shaped by the structural fabric 48 which includes domes where the band is inserted into the pockets of the structural fabric 48. Thus, the structural fabric 48 provides a three-dimensional shape to the band. resulting in a paper product that has dome structures.

To complete the paper forming process, the web is transferred from the structural fabric 48 to the Yankee cylinder 68 without significant degradation of its properties by contacting the web with spray adhesive on the Yankee cylinder 68 just prior to contacting the translation band. Once the band reaches a consistency of at least about 96%, light creping is used to remove the band from the Yankee cylinder 68.

While Figure 1 shows one type of process in which a structural fabric is used to impart a three-dimensional shape to a paper product, there are many other papermaking processes in which a structural fabric can be used to impart a structure. three-dimensional to the paper product. For example, a structural fabric can be used in a non-air drying (TAD) papermaking process. An example of such a non-TAD procedure is disclosed in US Patent No. 7,494,563, the disclosure of which is incorporated by reference in its entirety. As those skilled in the art will appreciate, the invention disclosed herein is not limited to use in any particular papermaking process, but can be applied to fabrics used in a wide variety of papermaking processes.

Figure 2 is a view of a web-facing portion of a structural fabric 200. The fabric 200 includes warp yarns 202 that run in the machine direction (MD) when fabric 200 is used in a papermaking process, and weft yarns 204 running in the cross machine direction (CD) when fabric 200 is used in a papermaking process. Warp and weft yarns 202 and 204 are woven together to form fabric structure 200. It should be noted that, when looking down at Figure 2, at the web-contacting surface of structural fabric 200, some of the yarns 202 and 204 shown are below the plane that contacts the web during the papermaking process, that is, the fabric contact surface 200. The uppermost points of the yarns 202 and 204 that Defining the plane of the contact surface are nodes 206 and 208. That is, nodes 206 and 208 form the actual contact surface of forming fabric 200. Pockets 210 (shown as contoured areas in Figure 2) are defined in the areas between nodes 206 and 208. During a papermaking operation, portions of the web may be inserted into pockets 210, and it is the portions of the web that are inserted into pockets 210 that are slid. put with the domes of the finished paper product, as also described above.

It should be noted that a structural fabric cannot be initially made with knots, such as knots 206 and 208 in Figure 2. Instead, knots are often formed by sanding or polishing one of the surfaces of the structural fabric. Also, since structural fabric is used in a papermaking operation, wear on the surface of the structural fabric can further increase the length of the knots. As will be described below, the present invention provides for the determination of knot characteristics, including knot characteristics when the fabric is subject to wear.

It should also be noted that a structural fabric can take numerous forms, depending, for example, on the weave pattern of the warp and weft yarns and the size of the yarns. The structural fabric 200 depicted in Figure 2 includes knots 206 that are formed in the warp yarns 202 and knots 208 that are formed in the weft yarns 204. This may be due to the fabric 200 being sanded or worn down to the point where knots are formed in both the warp and weft yarns 202 and 204. However, with less sanding, the fabric 200 could have only 206 knots in the warp yarns 202, and not at knots 208 in the weft yarns 204, or vice versa. Numerous warp and weft yarn configurations are known in the art in structural fabrics, and the numerous configurations allow different shaped paper products to be formed with the fabrics.

In Figures 3A and 3B there is shown an apparatus and technique for forming an impression of the interface formed by the knots of a fabric. Figure 3a is a side view of a contact surface printing apparatus 300, and Figure 3B is a front view of a contact surface printing apparatus 300. This apparatus 300 includes a C-shaped support structure 302 with a first and a second arm 303 and 305. A first plate 304 is movably supported by the first arm 303, and a second fixed plate 306 is supported by the second arm 305. A tissue knot impression is formed between the first and second plates 304 and 306, as will be described in detail below.

The first plate 304 is operatively connected to a hydraulic pump 308 to drive movement of the first plate 304 toward the second plate 306. In some embodiments, the hydraulic pump 308 is manually actuated, with a release valve to allow that the first plate 304 retracts from the second plate 306. However, the pump 308 can take many other forms to effect movement of the first plate 304. The pump 308 can be connected to a transducer and a transducer indicator 310 to measure the pressure applied by the pump 308 to the first plate 304 when the first plate 304 is pressed against the second plate 306. As a specific example, an ENERPAC® hydraulic hand pump model CST-18381 from Actuant Corp. of Milwaukee can be used, Wisconsin. As a specific example of the pressure transducer, a Transducer Techniques model DSM-5K load cell with a corresponding indicator, manufactured by Transducer Techniques, Inc., of Temecula, California, can be used. Of course, in other embodiments, the pump 308 and the transducer and transducer indicator 310 can be combined into a single unit.

The bracket 302 of the contact surface printing apparatus 300 includes wheels 312 adjacent to the front end of the bracket 302, as well as a bracket 313 that can be used to hold the pump 308 and / or the transducer 310. One or more wheels provided to the bracket 312 make bracket 302 easier to move. An advantageous characteristic feature of the contact surface printing apparatus 300, according to embodiments of the invention, is its portability. For example, with a configuration as shown in Figures 3A and 3B, the printing apparatus 300 can easily be moved around sections of a fabric that is mounted on a papermaking machine. As those skilled in the art will no doubt appreciate, the ability to form contact surface impressions of a fabric while the fabric is mounted on a papermaking machine and therefore characterize the fabric in accordance with the techniques described below, provides numerous benefits. Just as an example, the wear of a fabric on a papermaking machine can be easily monitored by using the touch surface printing apparatus 300 to take impressions of the knots of the fabric after different periods of machine operation to the manufacture of paper.

While the contact surface printing apparatus 300 shown in Figures 3A and 3B includes a support structure 302 connecting the first and second plates 304 and 306, in other embodiments, a surface printing apparatus of Contact may not include a single such support structure 302. Instead, the first and second plates 304 and 306 may be unconnected structures that are individually aligned to form the impression of a tissue. In still other embodiments, plates 304 and 306 may take very different shapes from those shown in Figures 3A and 3B. For example, one of the plates 304 and 306 could be formed as an extended surface, while the other plate is formed as a circular structure that rolls across the extended surface. The term "plate", as used herein, is a broad term encompassing any structure sufficient to contact and / or support the components that perform the impression of the fabric. Furthermore, as is clear from the above description, the relative movement of the first and second plates 304 and 306 in any embodiment could be reversed, so that the second plate 306 becomes movable while the first plate 304 remains fixed.

Figure 4 is a detailed view of section A of the contact surface printing apparatus 300 shown in Figure 3A, with the apparatus 300 configured to print a section of a tissue 312. The tissue 312 is placed between plates 304 and 306, and a strip of pressure measurement film 314 is placed against structural tissue 312. Between pressure measurement film 314 and first plate 304 are one or more sheets of paper 316. Between the fabric 312 and the second plate 306 there is a rubber band 318.

Pressure measurement film is a material that is structured in such a way that the application of force on the film causes the microcapsules in the film to rupture, producing an instantaneous and permanent high resolution image in the contact area of the film. . An example of such a pressure measurement film is sold as Prescale film by Fujifilm Holdings Corporation of Tokyo, Japan. Another example of a pressure measurement film is PRESSUREX-MICRO® from Sensor Products, Inc. of Madison, NJ. Those skilled in the art will recognize that other types of pressure measurement films could be used in the printing techniques described herein. In this regard, it should be noted that for the analysis techniques described below, the pressure measurement film does not need to provide an indication of the actual pressure applied by the tissue to the film, but rather the pressure measurement film only you need to provide a print image showing the interface formed by the knots of a fabric.

The pressure applied to the plate 304 when a fabric impression 310 is formed on the pressure measurement film 314 can be selected to simulate the pressure that would be applied to a web against the fabric 312 in an actual papermaking process. That is, pump 308 can be used to generate a pressure (measured by transducer 310) on plate 304 that simulates the pressure that would be applied to a web against tissue 312 in a papermaking process. In the papermaking process described above in conjunction with Figure 1, the simulated pressure would be the pressure applied to the web against the tissue 48 to the cylinder. Yankee 68. In some papermaking processes, such as the process described in the aforementioned US Patent No. 7,494,563, the pressure applied to the web against the fabric is generally in the range of 600 psi. Accordingly, to simulate this papermaking process, the hydraulic pump 308 would apply a 600 psi pressure to the plate 304 when the tissue knots 312 are imaged on the pressure measurement film 314. For such In operation, it has been found that FujiFilm Medium Pressure 1050 MPa Prescale Film can provide a good image of knots in a structural fabric. Referring again to Figure 4, the paper 316 acts as a cushion to enhance the impression of the fabric 312 formed on the pressure measurement film 314. That is, the paper 316 provides compressibility and a smooth surface so that the Knots in tissue 312 can "sink" into pressure measurement film 314, which, in turn, forms a high-resolution image of knots in film 314. To provide these properties, construction and kraft are examples of types. of paper that could be used for 316 paper.

The rubber band 318 creates a level contact surface to support the tissue 314. In embodiments of the invention, the plates 304 and 306 are made of a metallic material, such as steel. Most likely, a steel plate has imperfections that reduce the quality of the tissue knot print formed on the 316 pressure measuring paper. The 316 paper and 318 rubber used between the 304 and 306 plates , and the pressure measurement film 314 and tissue 312, however, provide more level contact surfaces than the surfaces of the metal plates 304 and 306, resulting in better images formed on the pressure measurement film. 314. Those skilled in the art will recognize that other materials can be used as alternatives to paper 316 and rubber 318 as structures to provide the level surfaces between plates 304 and 306 of apparatus 300.

In other embodiments, an impression of the knots of a fabric is made on materials other than the pressure measurement film. Another example of a material that can be used to form film prints is wax paper. An impression of the contact surface of a fabric can be made on a wax surface by pressing the contact surface of a fabric against wax paper. Printing on the waxed paper could be performed using plates 304 and 306 in the impression-forming apparatus 300 described above, or with other configurations of the plates. The wax paper print can then be analyzed in the same way as a pressure measurement film print, as will be described below.

Figures 5A to 5D show examples of knot prints formed on a pressure measurement film using the touch surface printing apparatus 300. The distinctive shapes and patterns of knot tissues can be seen in these prints. As discussed above, the knots form the contact surface of the tissue. Thus, high resolution knot prints on pressure measurement film, such as those shown in Figures 5A to 5D, provide an excellent representation of the contact surface of a tissue.

Next, a system for analyzing knot impressions, such as those shown in Figures 5A to 5D, will be described. In the system, the graphical analysis will be carried out on a conventional computer system. Said computer system will include well-known components, such as at least one computer processor (for example, a central processing unit or a multiple processing unit) that is connected to a communication infrastructure (for example, a communication bus, a communication device). crossbar or a net). Another component of the computer system is a display interface (or other output interface) that outputs video graphics, text, etc., for display on a display screen. The computer system may further include common components such as a keyboard, a mouse device, a main memory, a hard disk drive, a removable storage unit, a network interface, and so on.

As a first step in the analysis, an impression of the contact area of the knots of a tissue is converted into a computer-readable image using a photographic scanner. Any type of photographic scanner can be used to generate the computer-readable image. In certain embodiments, however, a photographic scanner having at least 2400 dpi has been found to provide a good image for analysis. With the resolution of the image scan, an image analysis program (as will be described below) can apply an exact scale to the image. As will be described below, the exact scale will be used in calculating the surface characteristics of the structural tissue.

The scanned image can be stored on a non-transient, computer-readable medium to facilitate the analysis described below. A non-transient, computer-readable medium, as used herein, comprises all computer-readable media except a transient and propagating signal. Examples of non-transient, computer-readable media include, for example, a hard disk drive and / or a removable storage unit, representing a disk drive, a magnetic tape drive, an optical disk drive, and so on.

The scanned image, as well as the characteristics of the scanned image of the contact surface that are determined according to the techniques described below, can be associated with a database. A "Database", as used herein, means a collection of data organized in such a way that a computer program can quickly select desired chunks of data, for example, an electronic filing system. In some implementations, the term "database" may be used as an abbreviation for "database management system".

To perform a quantitative analysis of the scanned impression image, an image analysis program is used with the scanned images of the knots of a tissue. Said image analysis program is developed, for example, with computer software that works with graphic images. An example of such computational development software is MATHMATICA® from Wolfram Research, LLC, of Champaign, Illinois. As will be described below, the image analysis program will be used to specifically identify the knots in the tissue impression image of the structural tissue and, with a known scale of the tissue impression image, the image analysis program can calculate the sizes of the knots and estimate the sizes of the pockets.

When analyzing the scanned image, any size area that includes a plurality of knots and a pocket could be used for the analysis described below. In specific embodiments, it has been found that a 3.175 cm by 3.175 cm (1.25 inches by 1.25 inches) area of an image of a fabric allows a good estimate of properties, such as pocket sizes using the techniques described in this document. In particular, it has been found that when an image is formed with a resolution of 2400 dpi (discussed above), and using an image area of 3.175 cm by 3.175 cm (1.25 inches by 1.25 inches) for analysis , a good characterization of the contact surface can be carried out. Of course, other resolutions and / or areas can also provide good results.

Figures 6A to 6E depict the steps of identifying knots in an enlarged portion of the scanned image of a print using the image analysis program. Initially, as shown in Figure 6A, an enlarged portion of an image 600 is viewed on the display screen of the computer system running the analysis program. Image 602, which can be formed using the printing technique described above, shows knots 602. In conjunction with using image 600 with the analysis program, the scale of image 600 can be entered into an analysis program. This scale can be entered, for example, as 2400 dpi, from which the analysis program can apply the SC scale to the 600 image. The analysis program will use the scale to calculate the sizes and positions of the nodes, such as outlined below.

Figures 6B and 6C show the steps of identifying a specific node 602A using the analysis program. The node 602A is initially selected based on its location in a central area of the enlarged image 600. At this stage, an approximate outline of the node 602A is applied. Rectangular box 604, which may have a shape stored in the analysis program, is initially applied around node 602A to initiate the node identification procedure. The initial shape of the rectangular box 604 can then be further refined to match the shape of the knot 602A, as shown in Figure 6C. In this case, ends 606 and 608 are reshaped to be more rounded and thus more closely correspond to the ends of knot 602A. Although not shown, further refinements could be made to the contour of the knot 602A until the match is sufficient. These refinements could be made by further enlarging the image 600.

As shown in Figure 6D, after node 602A is identified by contour, guides 610 and 612 are drawn. Guides 610 and 612 are each drawn so that they pass through the center of node 602A and extend straight through the centers of the other knots. In particular, guides 610 and 612 are also drawn so as not to cross the areas where pockets are formed in the fabric, which are known to correspond to the areas between groups of knots. By drawing the guides 610 and 612 straight between the centers of the knots, the guides 610 and 612 do not cross the area of the pockets that are formed between the knots.

After drawing guides 610 and 612, as shown in Figure 6E, more guides are drawn. These guides are drawn similarly to guides 610 and 612, that is, through the center of the knots and not through areas where pockets are formed. To aid in the guideline construction procedure, a lower magnification may be used. With the guides, in fact, a coordinate system is established for the positions of the nodes. Therefore, the analysis program can now identify the size and shape of the nodes based on contour 602A, and can identify the locations of the nodes as determined by the points where the guides intersect. The analysis program also has the SC scale of the image input 600. It follows that the analysis program can apply the scale to the contour of the node 602A and the position of the node to calculate the actual sizes and spacing of the nodes. . Also note that the analysis program can calculate the frequency of the guides, such as the number of times the guides 612 cross the guide 610 per unit length. The frequency of each set of guides 610 and 612 will be used in calculations of fabric properties and in other aspects of the invention, as will be described below.

It should be noted that, as shown in Figures 6D and 6E, the knots are all approximately the same size and all approximately the same shape, and the knots are regularly spaced along the guides. This is not surprising, as most paper machine fabrics are manufactured with very consistent thread patterns, resulting in consistent knot sizes and positions. Consistency in knot size, shape, and location allows accurate estimates of the size and shape of all knots on the interface of a fabric based on a single selected knot, or a limited number of identified knots, and a close estimate of node sizes and locations can be achieved without identifying each node. Of course, for even greater accuracy, more than one knot could be identified and the contours and guides could be drawn on different portions of an image.

As shown in Figure 6E, guides 610 and 612 define a plurality of unit cells. A particular unit cell 613 is shown between guide segments 610A, 610B, 612A, and 612B. Unit cell 613, in fact, demonstrates the minimum repeat pattern in tissue and the maximum pocket size allowed. It should be noted that while the fabric shown in Figures 6A to 6E has approximately one warp knot per unit cell, other fabrics may have more than one warp knot and / or more than one weft knot per cell. unitary. In other words, the unit cells defined by knot patterns will vary with different weaving patterns.

As will be readily apparent to those skilled in the art, any or all of the steps shown in Figures 6A to 6E can be performed by a user on a display screen or, alternatively, they can be automated to be performed after the execution of the test. analysis program. That is, the analysis program can be configured to automatically identify the nodes as the dark areas of the images, outline the nodes, and then draw the guides based on the identified nodes in the manner described above.

Once the selected knot has been identified, and after the guides are established through the knots, multiple fabric properties can be calculated using the knot sizes and positions determined by the analysis program. To perform such calculations, the knot size and positioning data can be exported from the analysis program to a conventional spreadsheet program to calculate the tissue properties. Table 1 shows examples of the determinations made by the analysis program and the calculations that are derived from these determinations.

TABLE 1

The fabric imaged 600 only included knots 602 in the warp threads. Other fabrics, however, may include knots in the weft yarns, such as the fabrics that formed the prints in Figures 5B and 5D. With such fabrics, the knots of the weft yarns can be identified using the contouring technique described above, and the guides can be drawn through the weft knots using the technique described above.

While the contact surface of a fabric can be characterized by using an impression of the knots of the fabric that is formed, for example, with the contact surface printing apparatus 300, in other embodiments, a Image of the tissue contact surface in a different way. An alternative to forming an impression of the knots of the fabric is to photograph the knots of a fabric and then use the procedures and techniques described above to analyze an image formed from the photograph. In this sense, a photograph with 2400 dpi has been found to provide sufficient high and low resolution to be analyzed by the techniques described herein.

Figure 7A shows an example of a photograph 700 of the portion of a tissue for making knotted paper 702a, and Figures 7B and 7C show the application of the analytical technique described above to the image generated from from photograph 700. Photograph 700 in Figure 7A shows tissue 701 along with a ruler R. When the photograph is converted into an image for use with the analysis program, the scale of image 700A can be entered from the photographed ruler R. That is, the ruler R in image 700A provides an input from which the analysis can scale the image. The displayed image 700A, along with the scale s C, is shown in Figure 7b.

To identify the sizes and locations of knots in an image obtained from a photograph of the fabric, the same techniques described above can be used with an image of an impression of the fabric. For example, image 700A in Figure 7C shows a contoured node 702A and guides 710 and 712. With the location and size data of the nodes from the analysis program, all the calculations described can be carried out. above to characterize the contact surface of the tissue 700 that was photographed. Table 2 below shows the results of calculations of the surface characteristics of a fabric, with one set of calculations derived from an impression of the fabric and a second set of calculations derived from a photograph of the fabric.

TABLE 2

The results shown in Table 2 demonstrate that the contact surface characterization calculations achieved by the photography technique closely correspond to the calculations achieved by tissue printing.

The techniques described above provide a good estimate of the properties of a fabric, particularly when the shapes of the unit cells formed by the guide segments are substantially rectangular. However, in cases where the shapes of the unit cells formed by the guides are not rectangular, parallelograms, an alternative technique can be used to provide more accurate estimates of tissue properties. An example of this alternative technique is shown in Figure 8A, which is an image generated from a photograph of the surface of a tissue using the image analysis program described above. In this figure, a unit cell 813 is defined by guide segments 810A, 810B, 812A, and 812B. The unit cell 813 formed by the guide sections 810, 810B, 812A and 812B has a parallelogram shape substantially rectangular. In this parallelogram, an angle 9 is defined at corner A where guide segments 810A and 812B intersect, and angle 9 is also defined at corner B where guide segments 810B and 812A intersect. This angle 9 can be easily determined using the image analysis program from the difference in the orientation angles of the guides. In addition, the image analysis program can also determine the distance between guide segments 810A and 810B ("DIST1") and the distance between guide segments 812A and 812B ("DIST2") from the image scale. as generally described above. Having determined the intersection angle 9, the DIST1, and the DIST2, the unit cell area (UCA) can be calculated using Formula (1) or Formula (2):

UCA = (DIST 1 / sin 0 ⁾ * DIST 2 (1)

UCA - (DIST 2 / sin 8 ⁾ * DIST 1 (2)

Formulas (1) and (2) are derived from the standard formula for calculating the area of a parallelogram, namely, Area = length of base * height, where DIST1 or DIST2 is used as the height of the parallelogram, then the length of the base is calculated from the sine of angle 9 and the other from DIST 1 or DIST2.

Table 3 shows examples of determinations made by the analysis program and the calculations that are derived from those determinations when using the alternative technique based on a non-rectangular parallelogram unit cell area calculation.

TABLE 3

It should be noted that, although some of the characteristics of TABLE3 are determined or calculated in the same way as those previously described in TABLE1, the density of the nodes, the total contact area of the nodes of the warp or weft, contact area ratio, area contribution percentage, pocket area estimate, and pocket density characteristics are calculated differently in TABLE3 than in TABLE1. By taking into account the non-rectangular parallelogram shape of the unit cells, these different calculations provide more accurate estimates of the characteristics of tissues that have non-rectangular parallelogram-shaped unit cells.

Figure 8B is an impression of a fabric made with the techniques described above. In this case, the fabric has very little rectangular unit cells, with one of the angles 9 at the corners of the parallelograms defining the unit cells at approximately 140 degrees. In order to demonstrate the difference between the first described techniques, which are not specifically adapted for parallelogram-shaped unit cells, and the technique for non-rectangular parallelogram-shaped unit cells, two sets of calculations were performed on the tissue, and the results are as shown in TABLE 4.

TABLE 4

It should be noted that, although some of the properties shown in TABLE 4 are the same for the two calculations, the total area of contact within the plane and the density of the pockets are different. Since the computational procedure adapted for non-rectangular parallelogram unit cells uses measurements that more closely match the actual underlying shape and structure of the tissue shown in Figure 8B, it follows that the total in-plane contact area (that is, the percentage of the fabric that corresponds to the knots) and the density of the pockets determined with the calculation technique adapted specifically for unit cells in the shape of a non-rectangular parallelogram are more exact. And, as those skilled in the art will appreciate, the total in-plane contact area and the density of the pockets of a fabric significantly affect the properties of a papermaking fabric. Therefore, non-rectangular parallelogram calculations provide more accurate estimates of important properties of a tissue. Another important characteristic of a papermaking fabric is the depth to which the web can be inserted into the pockets of the fabric during the papermaking process. As discussed above, domes are formed in the final paper products that correspond to the portions of the web that were inserted into the pockets of the fabric. Thus, the depth of the pockets of a papermaking fabric directly affects the paper product formed using the fabric. Techniques for determining the depth of pockets in a fabric will now be described.

Figure 9 shows an enlarged photograph of a structural tissue. With the photograph, and using the image analysis program described above, four nodes K1 to K4 are identified. A parallelogram has been drawn in a way that connects nodes K1 to K4, drawing the lines of the parallelogram so that they do not cross the area of pockets that is formed between nodes K1 to K4. With the parallelogram drawn, a direction line of the PL profile can be drawn that passes from node K1, through the center of the pocket, to node K3. The direction line of the PL profile will be used to determine the depth of the pockets using a depth measuring instrument, as described below. Note that the direction line of the PL profile from node K1 and node K3 passes through the center of the pocket. As will be described below, the depth of the pockets of a structural fabric is determined as the depth in the pocket to which cellulosic fibers could penetrate in the papermaking process. In the case of the fabric shown in Figure 9, the maximum depth of fiber migration is in the center of the pocket. It follows that a profile direction line could alternatively be drawn from knot K2 to knot K4 passing through the center of the pocket, and the alternative profile direction line could be used to determine the depth of the pockets. described below. Those skilled in the art will also recognize that different structural fabrics will have different knot and pocket configurations, but a profile direction line could easily be determined for different structural fabrics in the same way that the profile direction line is determined as shown. in Figure 9.

Figure 10 is a screen shot of a program used to determine the profile of a pocket of the structural tissue shown in Figure 9. The screen shot was formed with a VHX-1000 digital microscope manufactured by Keyence Corporation of Osaka, Japan. The microscope was equipped with the VHX-H3M application software, also provided by Keyence Corporation. The microscopic image of the pocket is shown at the top of Figure 10. In this image, knots K'1 and K'3 and the pocket between the knots can be easily seen. A depth determination line DL has been drawn from point D to point C, with the depth determination line DL passing through nodes K'1 and K'3 and through the center of the pocket. The depth determination line DL is drawn to closely approximate the determination line of the profile PL shown in Figure 8. That is, from inspection of the depth determination line DL obtained using the image knots and pockets shown in Figure 9, a user can draw the depth determination line DL on the microscopic image shown in Figure 10, with the depth determination line DL passing to through the areas that correspond to knots K'3 and K'1 and the central part of the pocket.

With the depth determination line DL drawn, the digital microscope can be instructed to calculate the depth profile of the pocket along the depth determination line DL, as shown at the bottom of Figure 10. The profile of the pocket is highest in the areas corresponding to the K'3 and K'1 knots, and the profile falls to its lowest point in the center of the pocket. The depth of the pocket is determined from this profile starting from the height of nodes K'3 and K'1, which is marked by line A on the depth profile. As with two knots in a structural fabric measured to this degree of accuracy, knots K'3 and K'1 are not exactly the same height. Therefore, the height A is determined as an average between the two heights of the nodes K'3 and K'1. Pocket depth is determined by ending at a point just above the lowest point on the depth profile, marked by line B on the depth profile. As will be appreciated by those skilled in the art, the depth of the pocket from line A to line B roughly corresponds to the depth in the pocket to which cellulosic fibers in the web can migrate in a papermaking process. Note that the VHX-H3M software (discussed above) forms the total depth profile from a plurality of fragments in the direction of tissue thickness. Also, note that when forming the depth profile, the VHX-H3M software employs a filtering function to smooth the depth profile formed from the thickness fragments. It should be noted that the measured pocket depth will vary slightly from pocket to pocket on a fabric. However, we have found that an average of five pocket depths measured for a structural fabric provides a good characterization of pocket depth.

While a digital microscope is used in the embodiments described above to determine pocket depth, other instruments can alternatively be used to determine pocket depth with the techniques described herein. For example, in other embodiments, a laser profilometer (or "laser profiler") can be used to determine pocket depth in a manner similar to the digital microscope described above. A laser profiler can determine a pocket depth profile that can be used to determine pocket depth in the same way that the depth profile generated with the digital microscope is used to determine pocket depth, as described previously. An example of such a laser profiler is a TALYSURF® CLI high resolution 3D surface profiling system manufactured by Taylor Hobson, Ltd. of Leicester, UK. In still other embodiments, an online laser profile measurement device ("laser line scanner") can be used to determine the depth of pockets in a tissue with the techniques described herein. An example of such a laser line scanner is a LJ-V7000 series high speed online profile inspection device manufactured by Keyence Corporation.

When using a laser profiler or laser line scanner, the same steps can be used to determine pocket depth as described above in conjunction with a digital microscope. That is, as shown in Figure 9, knots and a pocket are determined from a representation of the surface of a structural fabric. The laser profiler or laser line scanner is configured to determine a depth profile through the pocket from one knot to another knot, that is, the laser profiler or laser line scanner scans along the oriented line as the line PL in Figure 9. From this measured profile, the depth of the pockets can be determined analogously to the procedure described above in conjunction with Figure 10. To perform the analysis of the depth profile measured by the laser profiler or the laser scanner, various can be used analytical software programs. An example is surface metrology software provided by TrueGage of North Huntingdon, Pennsylvania,

Each of the alternative depth measurement instruments, ie digital microscope, laser profiler or laser line scanner, can offer certain advantages. For example, a digital microscope could provide a very accurate measurement of pocket depth. On the other hand, a laser profiler is generally an easy instrument to use and can therefore provide a quick measurement of pocket depth. To mention another example, a laser line scanner has the ability to rapidly collect large volumes of data and therefore measure many depth profiles in a short period of time. In this sense, an embodiment of my invention includes the use of a laser line scanner to determine the depth profiles of the pockets of a structural fabric that is operating in a papermaking machine. In this embodiment, the laser line scanner is positioned adjacent to the structural tissue in the machine, with the laser line scanner measuring the depth profiles of the pockets as the tissue passes through the scanner. As those skilled in the art will appreciate, a structural fabric in a papermaking machine can move at speeds in excess of 914 meters per minute (3000 feet per minute). However, a laser line scanner, such as the aforementioned LJ-V7000 series inspection system from Keyance Corporation, has the ability to measure thousands of depth profiles per second. Accordingly, a laser line scanner has the ability to measure pocket depths in the structural fabric by moving rapidly, thus providing very useful pocket depth data while the structural fabric is actually used in a papermaking machine. .

It should be noted that regardless of the measuring instruments and the technique used to determine pocket depth, the measured pocket depth will vary slightly from pocket to pocket on a fabric. I have found that, broadly speaking, an average of five pocket depths measured for a structural fabric provides a good characterization of pocket depth. Of course, more or fewer measurements can be made to determine an average pocket depth depending, for example, on the level of accuracy desired in the measurement.

In the pocket depth determination techniques described above, the structural fabric itself is used to determine the depth of the pockets. In some cases, it may be easier to form a representation of the fabric and then determine the depth of the pockets from the representation. For example, a representation of the knot and pocket structure of a fabric can be formed by pressing the contact surface of a fabric against wax paper, as also described above. The wax representation of the tissue can be scanned using one of the techniques described above. For example, a laser line scanner can be used to determine the depth in the wax impression between the knots in the wax impression.

Those skilled in the art will recognize that the effective volume of pockets of a structural fabric is an important property of a structural fabric that can be easily determined once the pocket size is calculated according to one of the techniques described above. The effective volume of a pocket is the product of the pocket cross-sectional area at the surface of the structural fabric (i.e., between the knot surfaces) multiplied by the depth of the pocket in which the cellulosic fibers in the web can migrate during the papermaking process. The cross-sectional area of the pockets is the same as the estimate of the pocket area (PA), as described in TABLE 1 or TABLE 2 above. Thus, the effective volume of the pockets can be calculated simply as the product of the estimate of the area of the pockets and the measured depth of the pockets.

Another important property of a structural fabric can be defined as a flat volumetric index for the fabric. Generally speaking, the softness, absorbency and gauge of paper products made from a fabric can be influenced by the contact area of the fabric, that is, the area formed by the surfaces of the knots of the fabric with the that the web comes into contact in the papermaking process. In addition, the softness, absorbency and caliper of paper products can be influenced by the size of the pockets in the fabric. The flat volumetric index provides an indication of the contact area and the size of the pockets, since the flat volumetric index is calculated as the ratio of the contact area (CAR) (as set out in TABLE 1 or TABLE 2 above) multiplied by the effective volume of the pockets (EPV) multiplied by one hundred, that is, CAR * EPV * 100. The ratio of the contact area and the effective volume of the pockets can be calculated using the techniques described above, and then the flat volumetric index for the tissue can be easily calculated.

As those skilled in the art will doubtless appreciate, knowing the characteristics of the knots and pockets of a fabric, such as the sizes and densities of the knots and pockets, provides an in-depth understanding of the fabric. An example application using features involves developing correlations between certain interface features and the resulting paper products. With the correlations, more fabric configurations can be developed, and those configurations can be characterized without testing a full-scale fabric on a papermaking machine. Therefore, the techniques described above Determining the contact surface characteristics of a fabric can save time and resources for fabric manufacturers and / or paper producers experimenting with different fabrics.

The techniques described above can also be used in papermaking tissue wear analysis procedures. In one such method, a first representation of the knots is formed in a medium in a portion of the tissue. This first representation can be a print on pressure measurement film, or the representation can be a photograph of a portion of the tissue and stored in a camera. A first image of the tissue knots is generated based on the first representation, such as by scanning the pressure measurement film or downloading the photograph from the camera. From the generated image, at least one characteristic related to the tissue contact area can be determined as described above. The fabric can then be subjected to wear and tear. If the fabric is mounted on a papermaking machine, wear can be caused by simply operating the papermaking machine. Alternatively, simulated wear can be made on the fabric by sanding or polishing it.

After the fabric has worn away, the procedure of obtaining an image of a portion of the fabric and determining the characteristics of the contact surface is performed again. That is, a second representation of the knots is formed in the tissue portion in a medium, which is used to generate a second image, which in turn is analyzed to determine the surface characteristics of the film. In this sense, the second representation may or may not be taken from the same portion of the fabric as the first representation. Knots in the fabric would be expected to increase in size as a result of wear and tear. Also, new knots can form in the fabric. As part of the interface characterization, increases in knot size can be quantified by comparing the analysis of the second image after wear and the first image before wear. Such a procedure of abrading the tissue and subsequently determining the characteristics of the contact surface can be repeated any number of times and with any given amount of wear between each analysis.

An additional part of analyzing fabric wear includes correlating paper products made using the fabric with changes in contact surface due to wear. For example, before taking the first representation of the fabric, a paper product is formed using the fabric. The properties of the paper product, such as the size of the domes in the product or the caliber of the product, are then correlated with the characteristics of the contact surface determined by the analysis of the first image formed by the first representation. Next, a second paper product is formed using the fabric, after the fabric is subjected to wear and tear and before the second representation of the fabric is taken. The properties of the second formed paper product are then correlated with the characteristics of the contact surface determined by the analysis of the second image. Thus, it can be understood how the formed paper product changes as the particular fabric configuration wears out.

In additional aspects of the invention, the techniques and procedures described above can be used to compare different portions of a fabric, particularly after the fabric has been passed through a papermaking machine for periods of time. It is known that different portions of a fabric will often show different wear due to irregularities in the track that the fabric follows in the papermaking machine. According to different embodiments, surface characterization techniques can be applied, for example, to different portions of a fabric before and after the fabric passes through a papermaking machine. Alternatively, surface characterization techniques can be applied to different portions of the fabric while the fabric is still mounted on the papermaking machine. Thus, it can be understood how different portions of a fabric wear out in a papermaking machine.

According to yet another aspect of the invention, the characterization of the contact surface can be used to obtain a fabric to make a paper product with a particular three-dimensional structure. Figures 11A and 11B demonstrate such a procedure. Figure 11A shows an example of an image 800 of a paper product that is analyzed using the techniques described above. In particular, the paper product has a three-dimensional structure that includes a plurality of domes separated by support areas. As described above, such a paper product can be manufactured using a structural fabric. However, if the specific structural fabric configuration that was used to make said product is not known, a method according to the invention can be used to identify the structural fabric configuration. As shown in Figure 11A, an 802A contour can be drawn on the image of the paper product using the analysis program in a support area of the paper product, which corresponds to the position of a knot of the structural tissue used to manufacture the paper product. In addition, a coordinate system including guides 812 and 814 can be drawn through contour 802A and positions that correspond to other nodes. Note that the domes in the paper product correspond to the pockets in the fabric structure and therefore the coordinate system is drawn without passing through the domes.

After contour 802A is formed and the coordinate system is drawn with guides 812 and 814, as shown in Figure 11A, you can search for matches between contour 802A and the coordinate system and tissue imaging to determine a configuration that produces the three-dimensional structure of the paper product. An example of such a match is shown in Figure 11B, in which the contour 802A and the coordinate system with guides 812 and 814 are superimposed on an image 800A of a tissue. Note that the contour 802A matches the size and shape of a knot in the fabric, and that the guides pass through the knots, but not the areas that correspond to the pockets of the fabric. This match indicates that the fabric shown in image 800A could be used to produce a paper product similar to that shown in image 800.

Matching the contour and coordinate system of a paper product to a particular fabric can be facilitated by creating a search database of known fabrics. This database would include the characteristics of the contact surface of the tissues previously determined, such as the size of the knots, the location, the size of the pockets, etc. After determining the sizes and positions of the knots and pockets of the fabric from the contour and coordinate system formed from the paper product, the database can be searched for fabrics with similar sizes and positions of knots and pockets.

To facilitate the procedure of matching an analyzed image of a paper product and a tissue, additional parameters that are developed in the analysis of the paper product can be used. One of those additional parameters is the frequency with which one set of guides crosses a guide in the other set of guides. Note that a "set" of guides refers to parallel guides, eg, guide 812 and all guides parallel thereto to form one set. In Figure 11A, the frequency of the set of guides that includes the guide 812 would be calculated, for example, by determining with the analysis program the distance between two of the guides that cross the guide 810, measured along a guide 810. For example, if the guides crossing the guide 810 were spaced 0.130 cm apart as measured along the guide 810, then the crossing guides would have a frequency of 7.7 cm-1 (1 / 0.130 cm). A similar frequency calculation could be performed for the other set of guides crossing the guide 812 by measuring the spacing between the guides in this set along one of the guides 812. Once determined, the frequency at the guide spacing for a paper product it could match the predetermined frequency of tissue guide spacing, which has been stored in a searchable database.

Another parameter that can be calculated to facilitate the procedure of matching the contoured knots and the guides of a paper product with a particular fabric is the angle relative to the guides of a set from a reference line. For example, the scale line SC in Figure 11A could be used as a reference and the angle a could be determined between the scale line SC and a set of guides. The angle from the SC scale line to the other set of guides could also be determined. Once determined, matches could be searched between the angles from the reference to the guide sets for a paper product and the previously determined angles from the reference to the guide sets for fabrics, which have been stored in a database of search.

While the procedures described above are described in terms of matching a paper product to a known fabric, it will be readily appreciated that other embodiments include selecting a known fabric made on a desired, but not yet produced, three-dimensional paper structure. . That is, a knot or knot outline could be created on a blank image, and a knot and pocket pattern could be created by drawing guides on the blank image. The matches between the created image and a known tissue could then be searched in the manner described above.

In yet another embodiment, a fabric could be designed and manufactured from the analysis of a paper product image or from a created image representing a configuration of knots and pockets. In this procedure, the warp and weft threads are chosen to correspond to the desired knot and pocket configuration, as determined by analyzing the image of the paper product or created on a blank image. Techniques for producing fabrics with particular weave patterns of warp and weft yarns are well known in the art. Thus, a fabric could be produced with the chosen configuration of warp and weft yarns.

In other embodiments of my invention, the fabric characterization techniques described herein can be used to modify the configuration of a first papermaking fabric to produce a new second papermaking fabric that it has different characteristics. In these embodiments, at least one characteristic of the knots or pockets of the first tissue for papermaking is determined with the techniques described above. The feature can be, for example, one or more of the features described in TABLE 1 or TABLE 2 above. Furthermore, the characteristic may be the depth of the pockets or the effective volume of the pockets, which are determined according to the techniques described above. From the determined feature (s), a modified fabric design is created in which the feature (s) are changed. For example, the depth of the pockets can be increased from the depth of the pockets measured in the first papermaking fabric. Those skilled in the art will appreciate the factors that determine the characteristics of a papermaking fabric and, as such, will appreciate how the design of the first papermaking fabric can be altered to produce the new papermaking fabric. that has the different characteristics. For example, a The appearance of the fabric, such as one or more yarn diameters, yarn densities, yarn shapes, weave patterns, and the heat setting used to bond the yarns together, could be altered to produce the second papermaking fabric that has the modified characteristic (s). One of the many examples of tissue manufacturing techniques for papermaking that use some of these factors can be seen in US Patent No. 6,350,336.

In addition to, or in conjunction with, embodiments for modifying the configuration of a papermaking fabric design, the characteristics of paper products made using the structural fabrics can be used in developing a fabric for making paper. paper that has particular characteristics. For example, the characteristics of a first papermaking fabric can be determined using the techniques described above. The first papermaking fabric can also be used to make a papermaking product, for example, using the papermaking processes described above. The characteristics of the paper product can then be determined and then correlated with the determined characteristics of the first papermaking fabric. For example, the densities and heights of the domes formed in the paper product can be measured by examining the domes under a microscope. As discussed above, domes are formed in pockets of tissue for papermaking. It follows that the density and depth of the pockets determined in a papermaking fabric can be correlated with the density and height of the domes found in a paper product that was manufactured with the papermaking fabric. . These correlations can then be used to determine which paper product could be expected to be made from another papermaking fabric that has comparable characteristics. Furthermore, as described above, a new design of papermaking fabric could be developed, with characteristics adjusted to produce paper products with modified characteristics as desired.

Although this invention has been described in certain specific exemplary embodiments, many additional modifications and variations will be apparent to those skilled in the art in light of this disclosure. Therefore, it should be understood that the present invention may be practiced in a manner other than that specifically described. Thus, exemplary embodiments of the invention are to be considered in all respects as illustrative and not restrictive, and the scope of the invention is to be determined solely by the claims.

Claims (7)

1. A procedure to determine the characteristic features of a tissue (48, 312), the procedure comprising: forming a representation of a portion of a surface of the fabric, the representation showing the locations and sizes of the knots (206, 208) and pockets (210) on the surface of the fabric (48, 312); generating an image (600) of the tissue surface portion (48, 312) from the representation; displaying at least a portion of the image (600) on a screen associated with a computer having a processor; the procedure characterized by drawing an outline (602A) around at least one of the nodes (206, 208) displayed in the image (600); Y draw guides (610, 612) in the displayed image (600) so that the guides (i) pass through the center of the contoured node, (ii) pass through other nodes displayed in the image, and (iii) constitute a shape that surrounds the areas of the image (600) that correspond to the places where the pockets (210) are formed between the nodes (206, 208), wherein the outline (602A) and the guides (610, 612) are drawn using an image analysis program stored on a non-transient, computer-readable medium. The method according to claim 1, further comprising a step of determining at least one of the length of the contoured knot (206, 208), the width of the contoured knot (206, 208) and the locations of the knots. (206, 208) along the guides (610, 612), wherein the determination is made by the image analysis program. The method according to claim 2, wherein the shape surrounding the image areas (600) that correspond to the sites where the pockets (210) are formed between the knots (206, 208) is a parallelogram. The method according to claim 3, further comprising a step of calculating at least one of a percentage of the surface of the fabric (48, 312) that corresponds to the knots and a density of the pockets, wherein the calculation uses the determinations of the length of the contoured knot (206, 208), the width of the contoured knot (206, 208), and the locations of the knots (206, 208) along the guides (610, 612). The method according to claim 1, wherein the representation is formed by one of (i) pressing the tissue against a pressure measuring film, (ii) taking a photograph of the tissue, and (iii) pressing the tissue against wax paper. 6. The method according to any one of the preceding claims, wherein the method further comprises: determining the sizes and locations of the nodes (206, 208) in the representation display; draw a unit cell (613) for the portion of the tissue surface in the displayed image (600), in which the unit cell (613) is defined by the guides (610, 612) that (i) pass through the centers knots (206, 208) and (ii) constitute shapes that surround areas of the image that correspond to the sites where the pockets (210) are formed between the knots (206, 208); Y calculate at least one property of the tissue surface from the properties of the unit cell (613) formed by the guides (610, 612), wherein the outline and guides (610, 612) are drawn using an image analysis program stored on a non-transient, computer-readable medium. The method according to claim 6, wherein the calculating step includes a step of calculating at least one of a percentage of the fabric surface that corresponds to the knots (206, 208) and a density of the pockets (210), and in which the calculation uses the sizes of the nodes (206, 208) along the guides (610, 612). Ċ