Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PROCESS FOR DETERMINING FEATURES OF A FABRIC
BACKGROUND
Field of the Invention
My invention relates to characterizing the surface of a papermaking fabric. In
specific examples, my invention relates to apparatuses, processes, and systems
for
determining the characteristics of the contact surface of a fabric that is
used for three-
dimensional structuring of a web in a papermaking process.
Related Art
In processes of forming paper products, such as tissue paper and paper towels,
three-
dimensional shaping is conducted while the papermaking web is still highly
deformable, i.e., when the papermaking web has a high water content. Often,
this
three-dimensional shaping of the web is conducted on a woven structuring
fabric.
The fabric provides a contact surface made up of knuckles in the yarns of the
fabric,
with pockets being formed in the fabric between the knuckles. When the
papermaking web is applied to the fabric, portions of the web contact the
knuekles,
and other portions of the web are drawn into the pockets. Before being removed
from the fabric, the web is dried to a point such that its shape is fixed or
locked.
Domes are thereby formed in the dried web where the web was drawn into the
pockets in the fabric, and the domes are present in the finished paper
product.
Hence, the paper product has a distinct three-dimensional structure formed, in
part,
by the knuckle and pocket characteristics of the structuring fabric.
Because the contact surface of a structuring fabric directly relates to the
shape of the
finished product, the choice of a structuring fabric is often based on the
shape of the
product that is desired. It is difficult, however, to characterize the contact
surface of
a structuring fabric based on a simple visual inspection of the fabric. While
the
knuckles of the fabric can easily be seen, it is often difficult to accurately
determine
the sizes of the knuckles, difficult to determine the areas of the pockets
between the
knuckles, and difficult to determine the depth of the pockets into which the
papermaking web is drawn during the papermaking process. As such, there have
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Date Recue/Date Received 2020-07-23
been previous techniques that attempt to quantify the characteristics of the
contact
surface of the fabric, for example, using formulas based on the yarn
parameters of
the fabric. It has been found, however, that such formulas are often not
accurate
enough to characterize the contact surface of the fabric in a manner that
allows for an
accurate prediction of the paper product structure that will be formed with
the fabric.
Additionally, the contact area characteristics will often change as the fabric
is run on
a papermaking machine. For example, wear on the surface of the fabric will
generally increase the lengths of the knuckles, thereby changing the
structuring that
will be imparted on the web by the fabric. Thus, formulas for determining the
contact surface characteristics that are applicable to initial fabric
configurations will
not necessarily apply to fabrics that have become worn over time.
It would be beneficial, therefore, to provide a technique for accurately
characterizing
the contact area characteristics of a structuring fabric that is used in a
papermaking
process. Moreover, it would be beneficial to provide a technique that can
easily
determine the contact area characteristics as the fabric becomes worn, over
time,
while the fabric is mounted on a papermaking machine.
SUMMARY OF THE INVENTION
According to a first aspect, my invention provides a process of determining
features
of a fabric. The process includes forming a representation of a portion of a
surface of
the fabric, the representation showing locations and sizes of knuckles and
pockets in
the surface of the fabric, generating an image of the portion of the surface
of the
fabric 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 knuckles displayed image. The process further includes
drawing
guidelines in the displayed image such that the guidelines (1) pass through
the center
of the outlined knuckle, (ii) pass through the other knuckles, (Hi) form a
shape that
surrounds areas of the image that correspond to *here the pockets are formed
between the knuckles. The outline and guidelines are drawn using an image
analysis
program stored in a non-transitory computer-readable medium.
Date Recue/Date Received 2020-07-23
According to a second aspect, my invention provides a process of determining
features of a fabric. The process includes forming a representation of a
portion of a
surface of the fabric, with the representation showing locations and sizes of
knuckles
and pockets in the surface of the fabric, and the representation being one of
a print of
the fabric surface and a photograph of the surface of the fabric. The process
further
inc hides generating an image of the portion of the surface of the fabric
based on the
representation, displaying at least a portion of the image on a screen
associated with
a computer having a processor, determining the sizes and locations of the
knuckles in
the display of the representation, and determining the sizes and locations of
the
pockets in the display of the representation. The process also includes
drawing a unit
cell for the portion of the surface of the fabric in the displayed image,
wherein the
unit cell is defined by guidelines that (I) pass through the centers of the
knuckles and
(ii) form shapes that surround areas of the image that correspond to where the
pockets are formed between the knuckles. At least one property of the surface
of the
fabric is calculated based on properties of the unit cell formed by the
guidelines, and
the outline and guidelines are drawn using an image analysis program stored in
a
non-transitory computer-readable medium.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a paper machine that uses a structuring
fabric.
FIG. 2 is a top view of a section of a structuring fabric.
FIGS. 3A and 3B are views of contact surface printing apparatus according to
the
invention.
FIG. 4 is a detailed view of the pressing section of the print forming
apparatus shown
in FIGS. 3A and 3B.
FIGS. 5A through 5D are examples of prints of structuring fabric made
according to
the invention.
FIGS. 6A through 6E show the steps of establishing a coordinate system for the
structuring fabric print.
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Date Recue/Date Received 2020-07-23
FIGS. 7A, 7B, and 7C show the application of the analytic technique herein
applied
to a photograph of the knuckles of a fabric.
FIGS. 8A and 8B show an alternative analytic technique applied to a photograph
and
print of the knuckles of a fabric.
FIG. 9 shows the application of the analytic technique to determine a pocket
surrounded by knuckles in a structuring fabric.
FIG. 10 shows the application of the analytic technique to determine the depth
of the
pocket shown in FIG. 8.
FIGS. 11A and 11B show the application of the analytic techniques applied to
an
image of a paper product and its structuring fabric.
DETAILED DESCRIPTION OF THE INVENTION
My invention relates to apparatuses, processes, and systems for determining
the
characteristics of the contact surface of a fabric that is used in a
papermaking
process. As will be apparent from the discussion below, "characteristics of
the
contact surface of a fabric" refers to the characteristics of the contact
surface that
result from the knuckle and pocket configuration that makes up the contact
surface of
the fabric. In specific embodiments, my invention is adapted for use with
structuring
fabrics that are used for three-dimensional structuring of a web in a
papermaking
process. Such structuring fabrics are often constructed with yams made from,
for
example, polyethylene terephthalate (PET), polyester, polyamide,
polypropylene,
and the like. As will be further explained below, the particular contact
surface of a
structuring fabric will have a significant effect on the structure of the
paper product,
and my invention utilizes techniques for characterizing aspects of the contact
surface.
It should be noted, however, that my invention is applicable with any type of
fabric
that is used in a papermaking process, including fabrics that are used for
purposes
other than structuring the web.
Figure 1 shows an example of a through air drying (TAD) papermaking process in
which a structuring fabric 48 is used to form the three-dimensional structure
of the
paper product. To begin the process, furnish supplied through a head box 20 is
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Date Recue/Date Received 2020-07-23
directed in a jet into the nip formed between a forming fabric 24 and a
transfer fabric
28. The forming fabric 24 and the transfer fabric pass between a forming roll
32 and
a breast roll 36. The forming fabric 24 and transfer fabric 28 diverge after
passing
between forming roll 32 and breast roll 36. The transfer fabric 28 then passes
through 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
structuring
fabric 48. In some instances, it will be advantageous to apply some amount of
vacuum as indicated through vacuum assist boxes 52, in a transfer zone 56,
particularly, when a considerable amount of fabric crepe is imparted to the
web in
transfer zone 56 by a rush transfer wherein the transfer fabric 28 is moving
faster
than the structuring fabric 48.
Because the web still has a high moisture content when it is transferred to
the
structuring fabric 48, the web is deformable such that portions of the web can
be
drawn into pockets formed between the yarns that make up the structuring
fabric 48
(the formation of pockets in a fabric will be described in detail below). As
the
structuring fabric 48 passes around the through air dryers 60 and 64, the
consistency
of the web is increased, for example, from about 60% to about 90%. The web is
thereby more or less permanently imparted with a shape by the structuring
fabric 48
that includes domes where the web is drawn into the pockets of the structuring
fabric
48. Thus, the structuring fabric 48 provides a three-dimensional shape to the
web
that results in a paper product having the dome structures.
To complete the paper forming process, the web is transferred from the
structuring
fabric 48 to the Yankee cylinder 68 without a major degradation of its
properties by
contacting the web with adhesive sprayed onto Yankee cylinder 68 just prior to
contact with the translating web. After the web reaches a consistency of at
least
about 96%, light creping is used to dislodge the web from Yankee cylinder 68.
While Figure 1 demonstrates one type of process in which a structuring fabric
is used
to impart a three-dimensional shape to a paper product, there are many other
papermaking processes in which a structuring fabric can be used to impart a
three-
dimensional structure to the paper product. For example, a structuring fabric
may be
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Date Recue/Date Received 2020-07-23
used in a papermaking process that does not utilize through air drying (TAD).
An
example of such a non-TAD process is disclosed in U.S. Patent No. 7,494,563.
As
will be appreciated by those skilled in the art, the invention disclosed
herein is not
limited to being used in any particular papermaking process, but rather, may
be
.. applied to fabrics used in a wide variety of papermaking processes.
Figure 2 is a view of a portion of the web facing side of a structuring fabric
200. The
fabric 200 includes warp yams 202 that would run in the machine direction (MD)
when the fabric 200 is used in a papermaking process, and weft yams 204 that
run in
the cross machine direction (CD) when the fabric 200 is used in a papermaking
process. The warp and weft yarns 202 and 204 are woven together so as to form
the
structure of fabric 200. It should be noted that, when looking down on Figure
2, in
the web-contacting surface of the structuring fabric 200, some of the depicted
yarns
202 and 204 are below the plane that contacts the web during the papermaking
process, i.e., the contact surface of the fabric 200. The upper-most points of
the
yarns 202 and 204 that define the plane of the contact surface are the
knuckles 206
and 208. That is, the knuckles 206 and 208 form the actual contact surface of
the
forming fabric 200. Pockets 210 (shown as the outlined areas in Figure 2) are
defined in the areas between knuckles 206 and 208. During a papermaking
operation, portions of the web can be drawn into the pockets 210, and it is
the
portions of the web that are drawn into the pockets 210 that correspond to the
domes
in the finished paper product, as also described above.
It should be noted that a structuring fabric may not initially be manufactured
with
knuckles, such as the knuckles 206 and 208 in Figure 2. Instead, knuckles are
often
formed by sanding or grinding one of the surfaces of the structuring fabric.
Further,
as the structuring fabric is used in a papermaking operation, wear on the
surface of
the structuring fabric may further increase the length of the knuckles. As
will be
described below, the present invention provides for determining
characteristics of the
knuckles, including characteristics of the knuckles as the fabric is subjected
to
wearing.
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Date Recue/Date Received 2020-07-24
It should also be noted that a structuring fabric can take on numerous forms,
depending on, for example, the weave pattern of the warp and weft yarns and
the size
of the yarns. The structuring fabric 200 depicted in Figure 2 includes
knuckles 206
that are formed on the warp yarns 202 and knuckles 208 that are formed on the
weft
yarns 204. This may have resulted from the fabric 200 being sanded or worn to
the
point that the knuckles are formed on both the warp and weft yarns 202 and
204.
With less sanding, however, the fabric 200 might have only knuckles 206 on the
warp yarns 202, and not on knuckles 208 on weft yarns 204, or vice versa.
Numerous configurations of weft and warp yarns in structuring fabrics are
known in
the art, and the numerous configurations allow for differently shaped paper
products
to be formed with the fabrics.
An apparatus and a technique for forming a print of the contact surface formed
by the
knuckles of a fabric is shown in Figures 3A and 313. Figure 3A is a side view
of a
contact surface printing apparatus 300, and Figure 3B is a front view of the
contact
surface printing apparatus 300. This apparatus 300 includes a C-shaped frame
structure 302 with first and second arms 303 and 305. A first plate 304 is
movably
supported by the first arm 303, and a stationary second plate 306 is supported
by the
second arm 305. A print of the knuckles of a fabric 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 for
actuating
movement of the first plate 304 towards the second plate 306. In some
embodiments, hydraulic pump 308 is hand-operated, with a release valve for
allowing the first plate 304 to be retracted from the second plate 306. The
pump 308,
however, can take many other forms so as to effect movement of the first plate
304.
The pump 308 may be connected to a transducer and transducer indicator 310 for
measuring the pressure applied by the pump 308 to the first plate 304 as the
first
plate 304 is pressed against the second plate 306. As a specific example, an
ENERPACO Hydraulic Hand Pump Model CST-18381 by Actuant Corp. of
Milwaukee, Wisconsin, can be used. As a specific example of the pressure
transducer, a Transducer Techniques Load Cell Model DSM-5K with a
corresponding indicator, made by Transducer Techniques, Inc., of Temecula,
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Date Recue/Date Received 2020-07-23
California, can be used. Of course, in other embodiments, the pump 308 and
transducer and transducer indicator 310 may be combined into a single unit.
The frame 302 of the contact surface printing apparatus 300 includes wheels
312
adjacent to the front end of the frame 302, as well as a mount 313 that may be
used
to hold the pump 308 and/or transducer 310. One or more wheels provided to the
frame 312 make the frame 302 easier to move. An advantageous 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
313,
the print apparatus 300 may be easily moved about sections of a fabric that is
mounted on a papermaking machine. As will certainly become appreciated by
those
skilled in the art, the ability to form prints of the contact surface of a
fabric while the
fabric is mounted to a papermaking machine, and, thus, characterize the fabric
according to the techniques described below, provides numerous benefits. As
but
one example, the wearing of a fabric on a papermaking machine can easily be
monitored by using the contact surface printing apparatus 300 so to take
prints of the
knuckles of the fabric after different periods of operation of the papermaking
machine.
While the contact surface printing apparatus 300 shown in Figures 3A and 313
includes a frame structure 302 that connects the first and second plates 304
and 306,
in other embodiments, a contact surface printing apparatus may not include
such a
single frame structure 302. Instead, the first and second plates 304 and 306
may be
non-connected structures that are individually aligned to form, the print of a
fabric.
In still other embodiments, the plates 304 and 306 may take vastly different
forms
from those depicted in Figures 3A and 311. 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 is rolled across the extended surface. The term
"plate," as used
herein, is a broad term that encompasses any structure sufficient for
contacting
and/or supporting the components for making the print of the fabric.
Additionally, as
is clear from the description above, the relative motion of the first and
second plates
304 and 306 in any embodiment could be reversed, such that the second plate
306 is
made movable while the first plate 304 is held stationary.
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Date Recue/Date Received 2020-07-23
Figure 4 is a detailed view of Section A of the contact surface printing
apparatus 300
shown in Figure 3A, with the apparatus 300 being set up to make a print of a
section
of a fabric 312. The fabric 312 is positioned between the plates 304 and 306,
and a
strip of pressure measurement film 314 is positioned against the structuring
fabric
312. Between the pressure measurement film 314 and the first plate 304 is one
or
more sheets of paper 316. Between the fabric 312 and the second plate 306 is a
strip
ol rubber 318.
Pressure measurement film is a material that is structured such that the
application of
force upon the film causes mierocapsules in the film to rupture, producing an
instantaneous and permanent, high-resolution image in the contacted 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 pressure measurement
film is PRESSUREX-MICROO by Sensor Products, Inc., of Madison, New Jersey.
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 need not provide an indication of the actual pressure applied by the
fabric to the
film, but rather, the pressure measurement film need only provide a print
image
showing the contact surface formed by the knuckles of a fabric.
The pressure applied to plate 304 when Conning a print of fabric 310 on
pressure
measurement film 314 can be selected so as to simulate the pressure that would
be
applied to a web against the fabric 312 in an actual papermaking process. That
is,
the pump 308 may be used to generate a pressure (as measured by transducer
310) on
the plate 304 that simulates the pressure that would be applied to a web
against the
fabric 312 in a papermaking process. In the papermaking process described
above in.
conjunction with Figure 1, the simulated pressure would be the pressure that
is
applied to the web against the fabric 48 to the Yankee cylinder 68. In some
papermaking processes, such as the process described in aforementioned U.S.
Patent
No. 7,494,563, the pressure applied to the web against the fabric is generally
in the
range of six hundred psi. Accordingly, to simulate this .papermaking process,
six
hundred psi of pressure would be applied by the hydraulic pump 308 to the
plate 304
when forming the image of the knuckles of fabric 312 in the pressure
measurement
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Date Recue/Date Received 2020-07-23
film 314. For such an operation, it has been found that medium pressure 10-50
MPa
Prescale film by FujiFilm can provide a good image of the knuckles of a
structuring
fabric.
Referring again to Figure 4, the paper 316 acts as a cushion to improve the
print of
the fabric 312 tbrtned on the pressure measurement film 314. That is, paper
316
provides compressibility and a smooth surface, such that the knuckles of the
fabric
312 may "sink" into the pressure measurement film 314, which, in turn, forms a
high.
resolution image of the knuckles in the film 314. To provide these properties,
construction and kraft are examples of types of paper that could be used for
the paper
316.
The strip of rubber 318 creates a level contact surface for supporting the
fabric 314.
In embodiments of the invention, the plates 304 and 306 are made of a metallic
material, such as steel. A steel plate would most likely have imperfections
that
reduce the quality of the print of the knuckles of the fabric formed in the
pressure
measurement paper 316. The paper 316 and the rubber 318 that are used between
the
plates 304 and 306, and the pressure measurement film 314 and the fabric 312,
however, provide more level contact surfaces than the surfaces of the metallic
plates
304 and 306, thereby resulting in better images being formed in the pressure
measurement film 314. Those skilled in the art will recognize that other
materials as
alternatives to the paper 316 and rubber 318 may be used as structures to
provide the
level surfaces between the plates 304 and 306 of the apparatus 300.
In other embodiments, a print is made of the knuckles of a fabric in materials
other
than pressure measurement film. Another example of a material that can be used
to
form prints of a film is wax paper. A print of the contact surface of a fabric
may be
made in a wax surface by pressing the contact surface of a fabric against wax
paper.
The print in the wax paper could be made using the plates 304 and 306 in the
print
forming apparatus 300 described above, or with other configurations of the
plates.
The wax paper print can then be analyzed in the same manner as a pressure
measurement film, print, as will be described below.
Date Recue/Date Received 2020-07-23
Figures 5A through 5D show examples of prints of knuckles formed in pressure
measurement film using the contact surface printing apparatus 300. In these
prints,
the distinctive shapes and patterns of the knuckles of the fabrics can be
seen. As
discussed above, the knuckles form the contact surface for the fabric. Hence,
high
resolution prints of the knuckles in a pressure measurement film, such as
those
shown in Figures 5A through 51), provide an excellent representation of the
contact
surface of a fabric.
Next, a system for analyzing the prints of knuckles, such as those shown in
Figures
5A through 5D, will be described. In the system, graphical analysis will be
conducted on a conventional computer system. Such a computer system will
include
well-known components, such as at least one computer processor (e.g., a
central
processing unit or a multiple processing unit) that is connected to a
communication
infrastnicture (e.g., a communications bus, a cross-over bar device, or a
network). A
further component of the computer system is a display interface (or other
output
interface) that forwards video graphics, text, etc., for display on a display
screen.
The computer system may still further include such common components as a
keyboard, a mouse device, a main memory, a hard disk drive, a removable-
storage
drive, a network interface, etc.
As a first step in the analysis, a print of the contact area of the knuckles
of a fabric is
convened to a computer readable image using a photoscanner. Any type of
photoscanner may be used to generate the computer readable image. In certain
embodiments, however, a photoscanner having at least 2400 dpi has been found
to
provide a good image for analysis. With the resolution of the scan of the
image, an
imaging analysis program (as will be described below) can apply an exact scale
to
the image. As will be described below, the exact scaling will be used in the
calculation of the surface characteristics of the structuring fabric.
The scanned image may be stored in a non-transitory computer-readable medium
in
order to facilitate the analysis described below. A non-transitory computer
readable
medium, as used herein, comprises all computer-readable media except for a
transitory, propagating signal. Examples of non-transitory computer readable
media
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Date Recue/Date Received 2020-07-23
include, for example, a hard disk drive and/or a removable storage drive,
representing a disk drive, a magnetic tape drive, an optical disk drive, etc.
The scanned image, as well as characteristics of the contact surface scanned
image
that are determined according to the techniques described below, may be
associated
with a database. A "database," as used herein, means a collection of data
organized
in such a way that a computer program may quickly select desired pieces of the
data,
e.g., an electronic filing system. In some implementations, the term
"database" may
be used as shorthand for "database management system."
In order to perform quantitative analysis of the scanned print image, an image
analysis program is used with the scanned images of the knuckles of a fabric.
Such
an image analysis program is developed, for example, with computational
software
that works with graphical images. One example of such computational
development
software is MATHMATICAt by Wolfram Research, LLC, of Champaign, Illinois.
As will be described below, the image analysis program will be used to
specifically
identify the knuckles in the fabric print image of the structuring fabric,
and, with
known scaling of the fabric print image, the image analysis program can
calculate the
sizes of the knuckles and estimate sizes of the pockets.
When analyzing the scanned image, any size area that includes a plurality of
knuckles and a pocket could be used for the analysis described below. In
specific
embodiments, it has been found that a 1.25 inch by L25 inch area of an image
of a
fabric allows for a good estimation of properties, such as pocket sizes using
the
techniques described herein. In particular, it has been found that when an
image is
formed with a .2400 dpi resolution (discussed above), and using a 1.25 inch by
1.25
inch area of an image for the analysis, a good characterization, of the
contact surface
can be conducted. Of course, other resolutions and/or area may also provide
good
results.
Figure 6A through 6E depict the steps of identifying the knuckles in a
magnified
portion of the scanned image of a print using the image analysis program.
Initially,
as shown in Figure 6A, a magnified portion of an image 600 is viewed on the
display
screen of the computer system running the analysis program. The image 602,
which
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Date Recue/Date Received 2020-07-23
may be formed using the print technique described above, shows the knuckles
602.
Along with using the image 600 with the analysis program, the scaling of the
image
600 can be input into an analysis program. Such a scaling may be input, for
example, as 2400 dpi, from which the analysis program can apply the scale SC
to the
image 600. The analysis program will then use the scale to calculate the sizes
and
positions of the knuckles, as described below.
Figures 6B and 6C shows steps for identifying a specific knuckle 602A using
the
analysis program. The knuckle 602A is initially selected based on its location
at a
center region of the magnified image 600. In this step, a rough outline of the
knuckle
602A is applied. The rectangular box 604, which may be a stored shape in the
analysis program, is initially applied around the knuckle 602A in order to
initiate the
knuckle identification process. The initial rectangular box 604 shape may then
be
more closely refined to match the shape of the knuckle 602A, as shown in
Figure 6C.
In this ease, the ends 606 and 608 are reshaped to be more rounded, and, thus,
more
closely correspond to the ends of the knuckle 602A. Although not shown,
further
refinements could be made to the outline of the knuckle 602A until a
sufficient
match is made. Such refinements might be conducted by further magnifying the
image 600.
As shown in Figure 6D, after the knuckle 602A is identified by the outline,
guidelines 610 and 612 are drawn. The guidelines 610 and 612 are each drawn so
as
to pass through the center of the knuckle 602A, and extend in straight lines
through
the centers of the other knuckles. Notably, the guidelines 610 and 612 are
also
drawn so as to not cross the areas where pockets are fonned in the fabric,
which are
known to correspond to the areas between groups of knuckles. By drawing the
guidelines 610 and 612 straight between the centers of the knuckles, the
guidelines
610 and 612 do not cross the area of the pockets that are formed between the
knuckles.
After the guidelines 610 and 612 are drawn, as shown in Figure 6E, further
guidelines are drawn. These guidelines are drawn in a similar manner to
guidelines
610 and 612, i.e., through the centers of the knuckles and not passing through
areas
where pockets are formed. To aid in the process of drawing the guidelines, a
lower
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Date Recue/Date Received 2020-07-23
magnification may be used. With the guidelines, a coordinate system is, in
effect,
established for the positions of the knuckles. The analysis program,
therefore, can
now identify the size and shape of the knuckles based on the outline 602A, and
can
identify the locations of the knuckles as determined by the points wherein the
guidelines cross. The analysis program further has the scale SC of the image
600
input. It follows that the analysis program can apply the scale to the outline
knuckle
602A and the knuckle positioning to calculate the actual sizes and spacing of
the
knuckles. Note as well that the analysis program may calculate the frequency
of the
guidelines such as the number of times that the guidelines 612 cross guideline
610
per a unit length. The frequency of each set of the guidelines 610 and 612
will be
used in calculations of properties of the fabric, 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 knuckles are all
about the
same size and all about the sarn.e shape, and the knuckles are regularly
spaced along
the guidelines. This is not surprising inasmuch as most fabrics for
papermaking
machines are manufactured with highly consistent yarn patterns, which results
in
consistent knuckle sizes and positions. The consistency in size, shape, and
placement of the knuckles allows for accurate estimates of the size and shapes
of all
the knuckles on the contact surface of a fabric based on a single selected
knuckle, or
on a limited number of identified knuckles, and a close estimate of the sizes
and
locations of the knuckles can be achieved without identifying each knuckle. Of
course, to achieve even further accuracy, more than one knuckle could be
identified,
and the outlines and guidelines could be drawn at different portions of an
image.
As shown in Figure 6E, the guidelines 610 and 612 define a plurality of unit
cells. A
particular unit cell 613 is shown between guideline segments 610A, 610B, 612A,
and
61213. The unit cell 613, in effect, demonstrates the minimum repeating
pattern in
the fabric, and the maximum allowable pocket size. It should be noted while
the
fabric shown in Figures 6A through 6E has about one walla knuckle per unit
cell,
other fabrics may have more than one warp knuckle and/or more than one weft
knuckle per unit cell. In other words, the unit cells defined by knuckle
patterns will
vary with different fabric patterns.
14
Date Recue/Date Received 2020-07-23
As will be readily apparent to those skilled in the art, any or all of the
steps shown in
Figures 6A through 6E can either be performed by a user on a display screen,
or
alternatively, may be automated so as to be performed upon execution of the
analysis
program. That is, the analysis program may be configured to automatically
identify
knuckles as the darkened regions of images, outline the knuckles, and then
draw the
guidelines based on the identified knuckles in the manner described above.
After the selected knuckle has been identified, and after the guidelines are
established through the knuckles, multiple properties of the fabric may be
calculated
using knuckle sizes and positions determined by the analysis program. To
perform
such calculations, the knuckle size and positioning data can be exported from
the
analysis program to a conventional spreadsheet program to calculate the
properties of
the fabric. Examples of the determinations made by the analysis program and
the
calculations that follow from such determinations are shown in Table 1.
TABLE 1
Characteristic of the Fabric Determination/Calculation
Knuckle Length (KL) determined based on outline of identified
warp
knuckle or identified weft knuckle
Knuckle Width (KW) determined based on outline of identified
warp
knuckle or identified weft knuckle
Frequency of Guidelines (f) determined based on guidelines drawn
through
knuckles
freq 1= frequency of the first set of parallel
lines (per inch or cm)
freq 2= frequency of the second set of parallel
lines (per inch or cm)
Rounding Radius (r) determined based on outline of identified
warp
knuckle and/or identified weft knuckle, the
rounding radius is the level of rounding that is
application to the corners of rectangular objects
Knuckle Density Per Unit Cell determined based on the number of warp or
(KDUC) (knuckles per unit cell) weft knuckles identified within a cell
Date Recue/Date Received 2020-07-23
LG-Co-eft knuckle Area (UKA) warp UKA warp KW x warp KL, ((2 x warp
r)--it(warp r)2)
weft UK.A = weft KW x weft Kr, ((2 x weft
02-7r(weft r)2)
Knuckle Density (KD) F = freq 1x freq 2
warp KD F x warp KDUC
weft KD =I? x weft K.DUC
Total Warp or Weft Knuckle warp area % = warp KD x warp UK.A,
Contact Area (%)
weft area % = weft KD weft UKA
Total % In-Plane Knuckle Contact I TKCA warp area % + weft area %
Area
GA) Area Contribution (AC) % wimp AC = [warp UKA /(warp UKA. weft
UKA)1 x 100
% weft AC = [weft UKA /(warp UKA + weft
UKA)] x 100
Pocket Area Estimate (PA) PA = (1/(freq I x freq 2)) (warp UKA x
warp
KDUC) (weft UKA x weft KDUC)
Pocket Density (PD) (pockets per PD = freq x freq 2
square inch or centimeter)
The fabric from which image 600 was obtained only included knuckles 602 on the
warp threads. Other fabrics, however, may include knuckles on the weft
threads,
such as the fabrics that formed the prints in Figures 5B and 5D, With such
fabrics,
the knuckles on the weft threads can be identified using the outlining
technique
described above, and the guidelines can be drawn through the weft knuckles
using
the technique described above.
While the contact surface of a fabric may be characterized by using a print of
the
knuckles of the fabric that is formed, for example, by the contact surface
printing
apparatus 300, in other embodiments, an image of the contact surface of the
fabric
16
Date Recue/Date Received 2020-07-23
may be obtained in a different manner. An alternative to forming a print of
the
knuckles of the fabric is to photograph the knuckles of a fabric, and then use
the
above-described procedures and techniques for analyzing an image formed from
the
photograph. in this regard, a photograph with 2400 dpi has been found to
provide
sufficient high and low resolution so as to be analyzed by the techniques
described
herein.
An example of a photograph 700 of the portion of a paperrnaking fabric with
knuckles 702a is shown in Figure 7A, and the application of the above-
described
analytic technique to the image generated from photograph 700 is shown in
Figures
7B and 7C. The photograph 700 in Figure 7A shows the fabric 701 next to a
ruler R.
When the photograph is converted to an image for use with the analysis
program, the
scale for the image 700A can be input based on the photographed ruler R. That
is,
ruler R in the image 700A provides an input from which the analysis can apply
a
scale to the image. The displayed image 700A, along with the scale SC, is
shown in
Figure 7B.
To identify the sizes and locations of knuckles in an image obtained from a
photograph of the fabric, the same techniques described above with an image
from a
print of the fabric, may be used. For example, an outlined knuckle 702A and
guidelines 710 and 712 are shown on the image 700A in Figure 7C. With the
knuckle sizing and location data from the analysis program, all of the above-
described calculations may be carried out to characterize the contact surface
of the
fabric 700 that was photographed.
Table 2 below shows the results of the calculations of surface characteristics
for a
fabric, with one set of calculations being derived from a print of the fabric,
and a
second set calculations being derived from a photograph of the fabric.
17
Date Recue/Date Received 2020-07-23
TABLE 2
Print of fabric Photograph of
_______________________________________________________________ fabric
Warp Contact Length (mm) 1.27 1.27
Knuckles
Contact Width (mm) 0.28 0.28
Percent Warp Contact 19.9 20.5
Weft Contact Length (mm) 0.58 0.58
Knuckles
Contact Width (mm) 0.38 0.38
Percent Weft Area I 11.2 11.5
Total In-Plane Total Contact Area 3L1 32.0
Contact
r-Pereent Warp- .4' Warp 1 64 64
Weft Ratio
Weft Area (%) 36 36
Pocket (1/cm2) 58.4 60.2
Density
Fabric Cell l Freq. 1 (1/cm) 7.7 7.7
Definition
Freq. 2 (1/cm) 7.6 7.8
The results shown in Table 2 demonstrate that the contact surface
characterization
calculations achieved using the photograph technique closely correspond to the
Calculations achieved using the print of the fabric.
The above-described techniques provide a good estimate of the properties of a
fabric,
particularly when the shapes of the unit cells formed by the guideline
segments are
substantially rectangular. In cases, however, where the shapes of the unit
cells
formed by the guidelines are non-rectangular, parallelograms, an alternative
technique may be used to provide more accurate estimates of the properties of
the
fabrics. An example of this alternative technique is shown in Figure 8A, which
is an
image generated from a photograph of the surface of a fabric using the above
described image analysis program. In this figure, a unit cell 813 is defined
by the
guideline segments 810A, 8108, 812A, and 8128. The unit cell 813 formed by the
guideline segments 810A, 8108, 812A, and 812B is a substantially non-
rectangular,
18
Date Recue/Date Received 2020-07-23
parallelogram shape. In this parallelogram, an angle 0 is defined at the
corner A
where guideline segments 810A and 8128 intersect, and the angle 0 is also
defined at
the corner B where the guideline segments 8108 and 8I2A intersect. This angle
0
can be readily determined using the image analysis program based on the
difference
in orientation angles of the guidelines. Further, the image analysis program
can also
determine the distance between the guideline segments 810A and 810B ("DIST 1")
and the distance between guideline segments 812A and 8128 ("DIST 2") based on
the scale of the image in the manner generally described above. Having
determined
the intersecting angle 0, the mi. 1, and the DIST 2, the area of the unit cell
(LICA)
can be calculated using either of the Formula (1) or Formula (2):
LICA = (1)1ST 1 / sin 0) x DIST 2 (1)
UCA = (1)1ST 2/ sin 6) x DIST 1 (2)
Formulas (1) and (2) are derived from the standard formula for calculating the
area
of a parallelogram, namely Area = base length x height, where DIST 1 or DIST 2
is
used as the height of the parallelogram, and then base length is calculated
from the
sine of the angle 0 and the other of DIST 1 or DIST 2.
Table 3 shows examples of determinations made by the analysis program and the
calculations that follow from such determinations when using the alternative
technique based on a non-rectangular, parallelogram unit cell area
calculation.
TABLE 3
Characteristic of the Fabric = Determination/Calculation
Knuckle Length (KL) .
determined based on outline of identified warp
knuckle or identified wen knuckle
Knuckle Width (KW) =
determined based on outline of identified warp
knuckle or identified weft knuckle
Frequency of Guidelines (f)
determined based on guidelines drawn through
1
knuckles
freq I¨ frequency of the first set of parallel lines I
(per inch or cm)
fireq 2= frequency of the second set of parallel lines
(per inch or cm)
19
Date Recue/Date Received 2020-07-23
Intersecting Angle of the determined based on guidelines drawn through
Guidelines (0) knuckles
01 orientation angle of the first set of
parallel
lines (degree)
02 orientation angle of the second set of
parallel
lines (degree)
.o = Abs (01 - (12): intersecting angle between the
two sets of guidelines
Rounding Radius (r) determined based on outline of identified
warp
knuckle and/or identified weft knuckle, the
rounding radius is the level of rounding that is
application to the corners of rectangular objects
Knuckle Density Per Unit Cell determined based on the number of warp or
weft
(KDUC) (knuckles per unit cell) knuckles identified within a cell
Unit Cell Knuckle Area (UKA) warp UKA warp KW x warp x warp
r)24t(warp r)2)
weft .UK.A = weft KW x weft KW - ((2 weft 02-
: n(weft r)2)
Knuckle Density (KD) warp KD = PD x warp KDUC
well KD -PD x weft KDUC
Total Warp or Weft Knuckle warp area % = warp KD x warp UKA
Contact Area (%)
weft area % = well K.D x weft UKA
Total % hi-Plane Knuckle TKCA = warp area % + weft area %
Contact Area
% Area Contribution (AC) I % warp AC = [warp UKA /(warp UKA + weft
UKA)] x 100
% weft AC - [weft UKA /(warp UKA + weft
UKA)) x 100
Pocket Area Estimate (PA) IPA= .. (1/PD)- ......................... (warp
UKA x wail) KDUC) - (weft
UKA x weft KDUC)
Pocket Density (PD) (pockets PD = freq 1 x ffreq 2 x sin 0)
per square inch or centimeter)
1
It should be noted that, while some of the characteristics in TABLE 3 are
determined
or calculated in the same manner as those described above in TABLE 1, the
knuckle
density, the total warp or weft knuckle contact area, the contact area ratio,
the percent
Date Recue/Date Received 2020-07-23
area contribution, the pocket area estimate, and the pocket density
characteristics are
calculated differently in TABLE 3 than in TABLE 1. By accounting for the non-
rectangular, parallelogram shape of the unit cells, these different
calculations provide
for more accurate estimations of the characteristics of fabrics that have non-
rectangular, parallelogram shaped unit cells.
Figure 8B is a print of a fabric made with the above-described techniques. In
this
case, the fabric has very non-rectangular unit cells, with one of the angles
Oat the
corners of the parallelograms defining the unit cells being about 140 degrees.
In
order to demonstrate the difference between the first techniques described,
which are
not specifically adapted for parallelogram shaped unit cells, and the
technique for a
non-rectangWar, parallelogram unit cells, two sets of calculations were
performed on
the fabric, with the results being shown in TABLE 4.
TABLE 4
Without With
I Parallelogram Parallelogram
Calculation Calculation
Warp Contact Length (mm) 0.00 0.00
Knuckles ___________________________________________
Contact Width (mm) 0.00 0.00
Percent Warp 0.0 0.0
Contact Area
Weft Contact Length (mm) 1.98 1.98
Knuckles ____________________________
Contact Width (mm) 0,28 0.28
--
Percent Weft 25.4 16.5
Contact Area
Total In-Plane Total Contact Area 1 25.4 16.5
Contact
Percent Warp- Warp Area (%) 0.0 0.0
Weft Ratio
Weft Area (%) 100.0 100.0
21
Date Recue/Date Received 2020-07-23
Pocket (1/cm2) 47.3 30.7
Density
Fabric Cell Freq. 1 (1/cm) 5.7 5.7
Definition __________________________
Freq. 2 (1/cm) 8.3 8.3
it should be noted that, while some of the properties shown in TABLE 4 are the
same
for the two calculations, the total in-plane contact area and the pocket
density are
different. Given that the calculation method adapted for non-rectangular,
parallelogram unit cells utilizes measurements that more closely matches the
actual
underlying shape and structure of the fabric shown in Figure 8B, it follows
that the
total in-plane contact area (i.e., the percentage of the fabric that
corresponds to
knuckles) and the pocket density determined with the calculation technique
specifically adapted for non-rectangular, parallelogram unit cells are more
accurate.
And, as those skilled in the art will appreciate, the total in-plane contact
area and the
pocket density of a fabric significantly affect the paper-making properties of
a fabric.
Thus, the non-rectangular, parallelogram calculations provide more accurate
estimations for important properties of a fabric.
Another important characteristic of a papermaking fabric is the depth to which
the
web can be drawn into pockets in the fabric during the papermaking process. As
discussed above, domes are formed in final paper products that correspond to
the
portions of the web that were drawn into the pockets in the fabric. Hence, the
pocket
depth of a papermaking fabric directly affects the paper product thrmed using
the
fabric. Techniques for determining the pocket depth of a fabric will now be
described.
Figure 9 shows a magnified photograph of a structuring fabric. With the
photograph,
and using the image analysis program described above, four knuckles K1 to K4
are
identified. A parallelogram has been drawn in a manner that connects the
knuckles
K1 to K4, with the lines of the parallelogram being drawn to not pass through
the
pocket area that is formed between the knuckles K1 to K4. With the
parallelogram
drawn, a profile direction line PL can be drawn that passes from the knuckle
K!,
through the center of the pocket, to knuckle K3. The profile direction line PL
will be
22
Date Recue/Date Received 2020-07-23
used to determine the pocket depth using a depth measurement instrument, as
described below. Note that the profile direction line PL from knuckle K.1 and
knuckle K3 passes through the center of the pocket. As will be described
below, the
pocket depth of a structuring fabric is determined as the depth in the pocket
to which
the cellulosic fibers could penetrate in the paper making process. In the case
of the
fabric shown in Figure 9, the maximum fiber migration depth is at the center
of the
pocket. It follows that a profile direction line could alternatively be drawn
from
knuckle K2 to knuckle K4 passing through the center of the pocket, and the
alternative profile direction line could be used for the pocket depth
determination.
described below. Those skilled in the art will also recognize that different
structuring fabrics will have different configurations of knuckles and
pockets, but a
profile direction line could easily be determined for different structuring
fabrics in
the same manner as the profile direction line is determined as shown in Figure
9.
Figure 10 is screenshot of a program used to determine the profile of a pocket
of the
structuring fabric shown in Figure 9. The screenshot was formed using a VHX-
1000
Digital Microscope manufactured by Keyence Corporation of Osaka, Japan. The
microscope was equipped with VFIX-H3M application software, also provided by
Keyence Corporation. The microscopic image of the pocket is shown in the top
portion of Figure 10. In this image, the knuckles K' I and K'3 and the pocket
between the knuckles can easily be seen. A depth determination line DL has
been
drawn from point D to point C, with the depth determination line DL passing
through.
the knuckles K'l and IC.3 and through the center of the pocket. The depth
determination line DL is drawn to closely approximate the profile
determination line
PL that is shown in Figure 8. That is, based on inspection of the depth
determination
line DL derived using the knuckle and pocket image shown in Figure 9, a user
can
draw the depth determination line DI, in the microscopic image shown in Figure
10,
with the depth determination line DL passing through the areas that correspond
to the
knuckles K'3 and K '1 and the center portion of the pocket.
With the depth determination line DL drawn, the digital microscope can then be
instructed to calculate the depth profile of the pocket along the depth
determination
tine DL, as is shown in the bottom portion of Figure 10. The profile of the
pocket is
highest at the areas corresponding to the knuckles K'3 and K' I , and the
profile falls
23
Date Recue/Date Received 2020-07-23
to its lowest point at the center of the pocket. The pocket depth is
determined from
this profile as starting from the height of the knuckles K'3 and K.'1., which
is marked
by the line A on the depth profile. As with any two knuckles of a structuring
fabric
measured to this degree of precision, the knuckles K'3 and K' I do not have
the exact
same height. Accordingly, the height A is determined as an average between the
two
heights of the knuckles K'3 and K' I. The pocket depth is determined as ending
at a
point just above the lowest point of the depth profile, marked by the line B
on the
depth profile. As those skilled in the art will appreciate, the depth of the
pocket from
line A to line B approximately corresponds to the depth in the pocket to which
the
cellulosic fibers in the web can migrate in a papermaking process. Note that
the
VHX-H3M software (discussed above) forms the full depth profile from a
plurality
of slices in the thickness direction of the fabric. Also, note that in forming
the depth
profile, the VFIX-H3M software employs a filtering function to smooth the
depth
profile formed from the thickness slices. It should be noted that the measured
pocket
depth will slightly vary from pocket to pocket in a fabric. We have found,
however,
that an average of five measured pocket depths for a structuring fabric
provides a
good characterization of the pocket depth.
While a digital microscope is used in the above-described embodiments to
determine
the pocket depth, other instruments may alternatively be used to determine
pocket
depth with the techniques described herein. For example, in other embodiments,
a
laser profilometer (or "laser profiler") may be used to determine pocket depth
in a
similar manner as the above-described digital microscope. A laser profiler can
determine a depth profile of a pocket that can be used to determine the pocket
depth
in the same manner as the depth profile generated using the digital microscope
is
used to determine pocket depth, as described above. An example of such a laser
profiler is a TALYSURFO CLI high-resolution 31) surface profiling system
manufactured by Taylor Hobson, Ltd., of Leicester, United Kingdom. In still
other
embodiments, an inline laser profile measurement device ("laser line scanner")
may
be used to determine the pocket depth of a fabric with the techniques
described
herein. An example of such a laser line scanner is an LI-V7000 series high-
speed
inline profile inspection device manufactured by Keyence Corporation.
24
Date Recue/Date Received 2020-07-23
When using a laser profiler or a laser line scanner, the same steps for
determining the
pocket depth may be used as are described above in conjunction with a digital
microscope. That is, as shown in Figure 9, the knuckles and a pocket are
determined
based on a representation of the surface of a structuring fabric. The laser
profiler or
laser line scanner is then set to determine a depth profile across the pocket
from one
knuckle to another knuckle, i.e., the laser profiler or laser line scanner
scans across
the line oriented as the line PL in Figure 9. From this measured profile, the
pocket
depth can be determined in an analogous manner to that method described above
in
conjunction with Figure 10. For performing analysis of the depth profile
measured
by the laser profiler or laser scanner, various analytic software programs may
be
used. One example is surface metrology software provided by TrueGage of North
Huntingdon, Pennsylvania.
Each of the alternative depth measurement instruments, i.e., digital
microscope, laser
profiler, or laser line scanner, may offer certain advantages. For example, a
digital
microscope might provide a highly precise measurement of pocket depth. On the
other hand, a laser profiler is generally an easy instrument to work with, and
thereby
can provide a quick measurement of pocket depth. As another example, a laser
line
scanner has the ability to quickly collect large volumes of data, and, thus,
measure
many depth profiles in a short period of time. In this regard, an embodiment
of my
invention includes using a laser line scanner to determine pocket depth
profiles of a
structuring fabric that is running on a papennaking machine. In this
embodiment, the
laser line scanner is positioned adjacent to the structuring fabric on the
machine, with
the laser line scanner measuring the pocket depth profiles as the fabric
travels past
the scanner. As will be appreciated by those skilled in the art, a structuring
fabric in
a papermaking machine may travel at speeds greater than 3,000 feet per minute.
Yet,
a laser line scanner, such as the aforementioned IJ-V7000 series inspection
system
by Keyance Corporation, has the ability to measure thousands of depth profiles
per
second. Accordingly, a laser line scanner has the ability to measure the
pocket depth
in the quickly moving structuring fabric, thereby providing highly useful
pocket
depth data while the structuring fabric is in actual use on a paperrnaking
machine.
It should be noted that, regardless of the measurement instruments and
technique
used to determine pocket depth, the measured pocket depth will slightly vary
from
Date Recue/Date Received 2020-07-23
pocket to pocket in a fabric. 1 have found that, generally speaking, an
average of five
measured pocket depths for a structuring fabric provides a good
characterization of
the pocket depth. Of course, more or fewer measure measurements can be
performed
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 structuring
fabric
itself is used to determine the pocket depth. In some cases, it may be easier
to form a
representation of the fabric, and then determine the pocket depth from the
representation. For example, a representation of the knuckle and pocket
structure of
a fabric can be formed by pressing the contact surface of a fabric against wax
paper,
as is also described above. The wax representation of the fabric can then be
scanned
using one of the above-described techniques. For example, a laser line scanner
can
be used to determine the depth in the wax print between the knuckles in the
wax
print.
Those skilled in the art will recognize that the effective volume of the
pockets of a
structuring fabric is an important property of a structuring fabric that can
easily be
determined once the pocket size is calculated according to one of the above-
described techniques. The effective volume Oa pocket is the product of the
cross-
sectional area of the pocket at the surface of the structuring fabric (i.e.,
between the
knuckle surfaces) multiplied by the depth of the pocket into which cellulosic
fibers in
the web can migrate during the papennaking process. The cross-sectional area
of the
pockets is the same as the estimate of the pocket area (PA), as described in
TABLE I.
or TABLE 2 above. Thus, the effective pocket volume may be calculated simply
as
the product of the pocket area estimate and the measured pocket depth.
Another important property of a structuring fabric may he defined as a planar
volumetric index for the fabric. Generally speaking, the softness, absorbency,
and
caliper of paper products made using a fabric may he influenced by the contact
area
of the fabric, that is, the area formed by the knuckle surfaces of the fabric
that the
web contacts in the papermaking process. Further, the softness, absorbency,
and
caliper of the paper products may be influenced by the size of the pockets in
the
fabric. The planar volumetric index provides an indication of the contact area
and
26
Date Recue/Date Received 2020-07-23
pocket size, as the planar volumetric index is calculated as the contact area
ratio
(CAR) (as set forth in TABLE 1 or TABLE 2 above) multiplied by the effective
pocket volume (EPV) multiplied by one hundred, i.e., CAR x EPV x 100. The
contact area ratio and the effective pocket volume may be calculated using the
techniques described above, and thereafter the planar volumetric index for the
fabric
may easily be calculated.
As will certainly be appreciated by those skilled in the art, knowing
characteristics of
the knuckles and pockets of a fabric, such as knuckle and pocket sizes and
densities,
provides a deep understanding of the fabric. One example of the application
using
the characteristics involves developing correlations between certain contact
surface
characteristics and resulting paper products. With the correlations, further
fabric
configurations can be developed, and those configurations can be characterized
without testing a full-scale fabric on a papermaking machine. Thus, the
techniques
described above for determining contact surface characteristics of a fabric
may save
time and resources for both fabric manufacturers and/or paper producers that
are
experimenting with different fabrics.
The above-described techniques can also be used in methods of analyzing the
wear
on a papermaking fabric. In one such method, a first representation of the
knuckles
in a portion of the fabric is formed in a medium. This first representation
may be a
print on a pressure measurement film, or the representation may be a
photograph of a
portion of the fabric and stored in a camera. A first image is generated of
the
knuckles of the fabric 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 contact area
of the
fabric may be determined as described above. The fabric may then be subjected
to
wearing. If the fabric is mounted on a papermaking machine, the wearing may
come
about simply by operating the papermaking machine. Alternatively, a simulated
wearing may be performed on the fabric by sanding or grinding.
After the fabric is worn, the. process of obtaining an image of a portion of
the fabric
and determining contact,. surface characteristics is again performed. That is,
a second
representation of the knuckles in the portion of the fabric is formed in a
medium,
27
Date Recue/Date Received 2020-07-23
which is used to generate a second image, which in turn is analyzed to
determine the
surface characteristics of the film. In this regard, the second representation
may or
may not be taken from the same portion of the fabric as the first
representation. It
would be expected that knuckles in, the fabric would increase in size as a
result of the
wearing. Further, new knuckles may be formed in the fabric. As part of the
contact
surface characterization, increases in the knuckle sizes can be quantified by
comparing the analysis of the second image after wearing and the first image
before
wearing. Such a process of wearing the fabric and thereafter determining the
contact
surface characteristics may be repeated any number of times, and with any
given
amount of wearing between each analysis.
A further part of analyzing the wear on the fabric includes correlating the
paper
products made using the fabric with the changes in the contact surface due to
the
wearing. For example, before the first representation is taken of the fabric,
a paper
product is formed using the fabric. Properties of the paper product, such as
the size
of domes in the product or the caliper of the product, are then correlated
with the
contact surface characteristics determined through analysis of the first image
formed
by the first representation. A second paper product is then formed using the
fabric,
after the fabric is subject to wearing and before the second representation is
taken of
the fabric. Properties of the second-formed paper product are then correlated
with
the contact surface characteristics determined through analysis of the second
image.
Thus, an understanding can be achieved of how the formed paper product changes
as
the particular fabric configuration is worn.
In further aspects of the invention, the above-described techniques and
processes
may be used to compare different portions of a fabric, particularly, after the
fabric
runs on a papermaking machine over periods of time. It is known that different
portions of a fabric will often show different wearing due to inconsistencies
in the
track that the fabric follows in the papermaking machine. According to
different
embodiments, the surface characterization techniques can be applied, for
example, to
different portions of a fabric before and after the fabric is run on a
papermaking
machine. Alternatively, the surface characterization techniques can be applied
to
different portions of the fabric while the fabric is still mounted on the
papermaking
28
Date Recue/Date Received 2020-07-23
machine. Thus, an understanding can be achieved of how different portions of a
fabric are worn in a papemiaking machine.
According to yet another aspect of the invention, the contact surface
characterization
can be used to obtain a fabric for making a paper product with a particular
three-
dimensional structure. Figures 11A and I 1B demonstrate such a process. Figure
11A shows an example of an image 800 of a paper product that is analyzed using
the
above-described techniques. Notably, the paper product has a three-dimensional
structure that includes a plurality of domes separated by land areas. As
described
above, such a paper product can be made using a structuring fabric, if,
however, the
specific structuring fabric configuration that was used to make such a product
was
not known, a process according to the invention can be used to identify the
structuring fabric configuration. As shown in Figure 11A, an outline 802A can
be
drawn on the image of the paper product using the analysis program in a land
area of
the paper product, which corresponds to the position of a knuckle in the
structuring
fabric used to make the paper product. Further, a coordinate system including
guidelines 812 and 814 can be drawn through the outline 802A, and the
positions that
correspond to other knuckles. Note that the domes in the paper product
correspond
to the pockets in the structuring fabric, and accordingly, the coordinate
system is
drawn without passing through the domes.
After the outline 802A is formed and the coordinate system with guidelines 812
and
814 are drawn, as shown in Figure I IA, the outline 802A and coordinate system
may
be matched to images of fabrics so as to determine a configuration that
produces the
three-dimensional structure of the paper product. An example of such a match
is
shown in Figure 118, wherein the outline 802A of and coordinate system with
guidelines 812 and 814 are overlaid upon an image 800A of a fabric. Note that
the
outline 802A matches the size and shape of a knuckle in the fabric, and that
the
guidelines pass through the knuckles, but not the areas that correspond to
pockets in
the fabric. This matching 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 outline and coordinate system from a paper product to a
particular
fabric may be facilitated by creating a searchable database of known fabrics.
Such a
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Date Recue/Date Received 2020-07-23
database would include the previously-determined contact surface
characteristics of
fabrics, such the knuckle sizes, locations, pocket sizes, etc. After
determining the
sizes and positions for the knuckles and pockets of the fabric from the
outline and
coordinate system formed from the paper product, the database could be
searched for
fabrics with similar sizes and positions of knuckles and pockets.
To facilitate the process of matching an analyzed image of a paper product
with a
fabric, additional parameters may be used that are developed in the analysis
of the
paper product One such additional parameter is the frequency that one set of
guidelines crosses a guideline from the other set of guidelines. Note, a "set"
of
guidelines refers to parallel guidelines, e.g., the guideline 812 and all the
guidelines
parallel thereto to form a set. In Figure 11A, the frequency of the set of
guidelines
that includes guideline 812 would be calculated, for example, having the
analysis
program determining the distance between two of the guidelines crossing
guideline
810, as measured along one guideline 810. For example, if the guidelines
crossing
guideline 810 were spaced 0.130 cm apart as measured along the guideline 810,
then
the crossing guidelines would have a frequency of 7.7 cm-1 (1/0.130 cm). A
similar
frequency calculation could be done for the other set of guidelines that cross
guideline 812 by measuring the spacing between the guidelines of this set
along one
of the guidelines 812. Once determined, the frequency in the guideline spacing
for a
paper product could be matched to the previously determined frequency of
guideline
spacing for fabrics, which have been stored in a searchable database.
Another parameter that can be calculated to facilitate the process of matching
the
outlined knuckle and guidelines from a paper product to a particular fabric is
the
angle to the guidelines 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 cc could be
determined
between the scale line SC and one set of the guidelines. The angle from the
scale
line SC to the other set of guidelines could also be determined. Once
determined, the
angles from the reference to the sets of guidelines for a paper product could
be
matched to the previously determined angles from the reference to the sets of
guidelines for fabrics, which have been stored in a searchable database.
Date Recue/Date Received 2020-07-23
While the above-described methods 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, an outline knuckle or knuckles could be
created
in a blank image, and a knuckle and pocket pattern could be created by drawing
guidelines in the blank image. The created image could then be matched with a
known fabric in the manner described above.
In yet another embodiment, a fabric could be designed and manufactured based
on
the analysis of a paper product image or based on a created image representing
a
knuckle and pocket configuration. In this method, warp and weft yarns are
chosen to
correspond to the desired knuckle and pocket configuration, as determined by
analysis of the paper product image or created in 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 warp and
weft
yarn configuration.
In other embodiments of my invention, the fabric characterization techniques
described herein can be used to modify the configuration of a first pacemaking
fabric in order to produce a new, second papermaking fabric having different
characteristics. In these embodiments, at least one knuckle or pocket
characteristic
of the first papermaking fabric is determined with the above-described
techniques.
The characteristic may be, for example, one or more of the characteristics
described
in TABLE 1 or TABLE 2 above. Further, the characteristic may be the pocket
depth
or effective pocket volume, which are determined according to the above-
described.
techniques. Based on the determined characteristic(s), a modified fabric
design is
created wherein the characteristic(s) are changed. For example, the pocket
depth
may be increased from the pocket depth 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 may be altered to produce the new pacemaking fabric having
the different characteristics, For example, an aspect of the fabric such as
one or more
of yarn diameters, yarn densities, yam shapes, weave patterns, and the heat
setting
used to bond the yarns together, could be altered to produce the second
pacemaking
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Date Recue/Date Received 2020-07-23
fabric that has the modified characteristic(s). One of many examples of
papermaking
fabric manufacturing techniques utilizing some of these factors can be seen in
U.S.
Patent No. 6,350,336.
In addition to, or in conjunction with, the embodiments for modifying the
configuration a papermaking fabric design, the characteristics of paper
products
made using the structuring fabrics can be used in the development of a
papermaking
fabric having particular characteristics. For example, the characteristics of
a first
papermaking fabric can be determined using the above-described techniques. The
first papermaking fabric can also be used to make a papermaking product, for
example, using the papermaking methods described above. The characteristics of
the
paper product can then be determined, and thereafter 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 with a microscope. As discussed above, the domes are formed in the
pockets
of the papermaking fabric. It follows that the pocket density and pocket depth
determined in a papermaking fabric can be correlated to a dome density and
dome
height found in a paper product that was made using the papermaking fabric.
Such
correlations can then be used to determine what paper product could be
expected to
be made with another papermaking fabric having comparable characteristics.
Further, as described above, a new papermaking fabric design could be
developed,
with adjusted characteristics in order 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 would be apparent to
those skilled in the art in light of this disclosure. It is, therefore, to be
understood
that this invention may be practiced otherwise than as specifically described.
Thus,
the exemplary embodiments of the invention should be considered in all
respects to
be illustrative and not restrictive, and the scope of the invention to be
determined by
any claims supportable by this application and the equivalents thereof, rather
than by
the foregoing description.
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Date Recue/Date Received 2020-07-24
