Note: Descriptions are shown in the official language in which they were submitted.
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TRANSLATION OF PCT/EP2016/052027
INDUSTRIAL FABRIC, METHOD FOR PRODUCING A NONWOVEN, AND USE OF AN
INDUSTRIAL FABRIC
DESCRIPTION
INTRODUCTION
The invention relates to an industrial fabric, especially for transporting a
web of a nonwoven
during its production, with a product side that is in contact with the
nonwoven and a machine
side that is in contact with conveying devices of a machine for producing the
nonwoven, wherein
the fabric has MD threads oriented in the running direction of the web of the
nonwoven and
CMD threads that are oriented perpendicular to the MD threads and are
interwoven with each
other and there are at least two layers of MD threads that are arranged
stacked in pairs one above
and below each other, and form product contact MD threads and non-product
contact MD
threads, wherein at least the surface of the respective product contact MD
threads facing the
product side has a first material that has a contact angle, measured according
to the Wilhelmy
plate method, of at least 800, preferably at least 90 .
In addition, the invention relates to a method for producing a nonwoven,
especially in the form
of an aerodynamically formed, chemically and/or thermally cured nonwoven,
wherein a web of
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the nonwoven contacts a surface of a conveyor belt and is moved by this belt.
The invention also
relates to the use of an industrial fabric of the type specified above.
In the previously described industrial fabric, the specified contact angle of
the material represents
a measure for the free surface energy of the relevant surface of the MD
threads. In the specified
measurement method in the form of the "Wilhelmy plate method," the contact
angle between a
fluid and a solid is determined. Here, the force acting in the vertical
direction on a vertically
submerged plate (test body) is measured. Typically, the plate is mounted on
the force sensor of a
so-called tensiometer. The contact angle here depends not only on the free
surface energy of the
material to be measured, but also on the surface tension of the fluid to be
used. The previously
specified values of the contact angle here relate to distilled water as a
fluid. A contact angle of 0
means, in this case, that the fluid wets the material completely (spreading).
For a contact angle
between 00 and 90 , the material of the plate can be wetted; at a contact
angle of greater than 90 ,
it cannot be wetted. For so-called ultrahydrophobic materials (usually using
the so-called lotus
effect principle), the contact angle approaches the theoretical limit of 180 .
For pure PET, the
contact angle is approx. 750, for pure PPS it is approx. 90 , while PVDF has a
contact angle of
approx. 105 .
PRIOR ART
Nonwovens are textile fabrics that are produced from fibers of limited length
or endless fibers
(filaments) or cut threads of a wide range of different types, in that the
fibers, filaments, or
threads are joined to form a fiber layer and connected permanently to each
other in some way. In
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particular, nonwovens produced from chemical fibers have increased enormously
in importance
in recent decades and used, for example, for hygienic products (e.g., baby
diapers, etc.), for
medical products, cleaning cloths, or as home textiles and clothing, and also
for a plurality of
technical applications (construction, filtration, automotive engineering,
electrical engineering,
packaging, agriculture, etc.). For example, the production of a nonwoven can
be realized in that a
nonwoven made from fibers is formed with the help of an airflow on an air-
permeable backing
(aerodynamic nonwoven formation). The nonwoven curing can be realized, e.g.,
in a chemical
way by generating an adhesive bond. Here, additional materials, e.g., in the
form of polymer
dispersions (containing, e.g., latex) can be used and/or a thermal curing
method can be used in
which the fiber connection is also achieved by an adhesive bond that is
achieved, e.g., with the
help of thermoplastic fibers. For example, the nonwoven can have fibers made
from two
components, wherein a first, higher-melting-point component (e.g., polyester)
forms a fiber core
that is surrounded by a second component (polyethylene) melting at a lower
temperature. The
fiber composite is thus generated by melting the casing of the two-component
fibers and/or
curing the polymer dispersion in a furnace or a heated drying device.
During its run through the production system, the web of the nonwoven produced
by the process
is guided through the various treatment devices by means of a conveyor belt
having a surface
with which the web is in contact. A plurality of conveyor belts that are
arranged one after the
other in the passage direction are used in the different sections of the
production system.
Industrial fabrics made from monofilament threads, like those known, for
example, from US
2010/0291824 Al, are typically used as conveyor belts in systems for nonwoven
production with
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aerodynamic nonwoven formation and chemical and/or thermal curing. To prevent
the adhesion
of fibers to the conveyor belt during the nonwoven production, especially
during the heating of
the web of the nonwoven produced during the process, in the previously
mentioned US patent
application, a surface roughness of those surfaces of the conveyor belt that
are in contact with the
nonwoven web is proposed, which should be between 5 pm and 100 gm. In this
way, the
tendency of fibers or other contaminating particles to adhere to the threads
of the conveyor belt is
reduced and the detachment of the cured nonwoven from the conveyor belt is
made easier at
transitions to subsequent conveyor belts or for other types of transport
through the system.
However, despite the previously mentioned microstructuring of the thread
surfaces, previously
known conveyor belts still have too great a tendency toward adhesion and
soiling. With
advancing time of use, the known industrial fabric therefore loses part of its
air permeability, so
that the volume flow through the conveyor belt and the nonwoven produced in
the process
decreases to impermissible values. This leads, in turn, to inadequate heating
of the fibers forming
the nonwoven web, so that the melting of the bicomponent fibers and/or the
wetting of the
polymer dispersion having the bonding properties is inadequate. This results
in insufficient
bonding of the fibers of the nonwoven, so that the strength of the end product
is not satisfactory.
For the operator of a system for producing nonwoven, this means that the
conveyor belts must be
replaced when the air permeability falls below a certain limit value.
Replacing the conveyor belt
causes not only costs due to the necessary purchase of a new conveyor belt,
but also due to the
stoppage of the production system during the belt replacement.
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As is also described in US 2014/0127959 Al, a high surface energy above the
specified value
(realized by corresponding material selection) can also effectively prevent
bonding of fibers or
other contaminating particles during the nonwoven production on a conveyor
belt produced from
the fabric according to the invention and used in a production system. The
service life of the
conveyor belts produced from the fabric according to the invention can be
increased significantly
in this way and the production costs can be reduced accordingly.
In this context, it is particularly important that the known fabric has two
separate fabric layers
whose MD threads are in a stacked arranged relative to each other. In this
way, the product
contact MD threads that are located in the upper of the two layers can be
optimized to the
prescribed effect of reducing the adhesion tendency, while the non-product
contact MD threads
located in the lower layer can be optimized with respect to a different
requirement, namely a
high strength for receiving the necessary tensile stress in the direction of
the MD threads. The
effect of adhesion tendency is not significant with respect to the non-product
contact MD threads,
because these do not contact the nonwoven web to be formed and the fibers used
for this purpose.
The non-product contact MD threads can also have particularly high wear
resistance, in order not
to exhibit excessive wear phenomena due to contact with the deflection devices
(rollers) for
continuing circulation in the system. It is obviously understood that all MD
threads, but also the
CMD threads, must have a sufficient thermal stability, in order to be able to
withstand the
temperatures in the furnaces or drying devices, which reach up to 200 C,
wherein the required
mechanical properties must also be guaranteed even at these temperatures.
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One disadvantage of the two-layer fabric known from US 2014/0127959 Al,
however, is the
high costs of its production and the large fabric thickness. The roughness of
the fabric surface
due to the bonding is also large and the contact surface with a web assumed to
be flat and made
from nonwoven material to be transported is small accordingly.
WO 2009/030033 Al discloses a fabric that is used as a conveyor belt for the
production of a
nonwoven, wherein the web construction of this previously known fabric has no
stacked MD
threads. The previously known fabric construction also has a plurality of CMD
thread layers. An
essential feature of this previously known fabric that can also be constructed
as a spiral fabric is
a deliberately large surface roughness of the threads exposed on the product
side of the fabric in
the range between 5 pm and 100 pm. This arrangement should, on one hand,
reduce the soiling
of the industrial fabric during wetting as the conveyor belt and
simultaneously make the
detachment of the nonwoven web formed on the conveyor belt easier.
US 7,121,306 B2 discloses a technical fabric with MD threads in a stacked
arrangement. Some
of the shown embodiments disclose fabric with a single layer of CMD threads.
The previously
known fabric should be used, in particular, as paper machine fabric or as
filter fabric. For this
application, a fabric is to be created whose opposing fabric surfaces can be
different, in particular,
can have different physical properties. In addition, the seam being used
should have a lower
tendency to leave undesired marks on the paper web, while simultaneously,
however, having
high strength. The problem of fibers adhering to the fabric according to US
7,121,306 B2 is not
discussed in that publication.
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Finally, from US 2003/0175514 Al, filaments are also known, from which are
produced threads,
textile fabric produced from these two elements, and associated production
methods. The
previously known filaments have a two-component structure with a filament core
made from a
material with a high tensile strength and a filament casing with a material
that has a contact angle
of greater than 90 and is typically made from halogenated hydrocarbons, e.g.,
PTFE. The
known filaments and the threads or fabric produced from these filaments should
be water-
repellent, so that the textile fabric produced from these products will be
impermeable to water. In
contrast, the textile fabric should be breathable, i.e., permeable for water
vapor and other gases.
Preferably, the previously known filaments should be spun as stacked fibers
into thread and then
into fabric for use as clothing, tents, or camping products. A use of the
fibers for technical fabric,
such as special bond types for fabrics, is also provided for to a lesser
degree.
OBJECT
The invention is based on the objective of providing an industrial fabric, for
a use as a conveyor
belt in a system for producing nonwoven, that has a very low tendency to
adhere to fibers during
the processing step of nonwoven curing, and therefore has a long service life,
but is also
characterized by a small fabric thickness, low surface roughness, and reduced
production costs.
SOLUTION
Starting from an industrial fabric of the type described above, the previously
mentioned objective
is achieved according to the invention in that the fabric has a single layer
of CMD threads and a
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respective cross section of the product contact MD threads has at least two
areas of which a first
area is made from the first material and a second area is made from the second
material, wherein
a significant, preferably predominant, portion of a tensile force acting on
the respective product
contact MD thread can be transferred by the second area and the cross section
of the product
contact MD threads has a second area in the form of a core and a first area in
the form of a casing
surrounding the core, wherein the product contact MD threads are preferably
coextruded or
extruded in two successive steps and the MD threads have a flattened,
preferably rectangular
cross section, wherein a ratio of a height of the cross section to a width of
the cross section is
preferably between 1:1.2 and 1:10, preferably between 1:1.5 and 1:4.
The fabric construction according to the invention is very special because it
has only a single
CMD layer despite the stacked MD thread layers, i.e., the fabric involves a
conventional one-
layer fabric (plain weave). The thickness of such a fabric is significantly
reduced compared with
fabrics with multiple layers of CMD threads, which produces, e.g., increased
flexibility and the
ability to realize smaller radii on deflection rollers. The material use is
significantly reduced in
contrast with known fabrics with multiple layers of CMD threads, so that the
fabric according to
the invention can be produced economically. Contributing to this result is
also that, according to
the invention, there are not multiple, independent, i.e., standalone, fabric
layers that must be
bound to each other by binding CMD threads. Despite this minimalist design
with respect to the
number of CMD thread layers, due to the two stacked layers of MD threads, it
is possible to
simply differentiate the fabric properties between the product side and
machine side. In particular,
the anti-stick properties required on the product side for reducing the
tendency to become soiled
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can be combined in a very simple way with the strength and durability
properties required on the
machine side.
In addition, a respective cross section of the product contact MD threads has
at least two areas on
which a first area is made from the first material and a second area is made
from the second
material, wherein a significant, preferably predominant part of a tensile
force acting on the
respective product contact MD thread can be transferred by the second area.
Because there are only a limited number of materials with a high surface
energy, as is required in
the present case, and the relevant materials are often relatively expensive,
the use of this special
"anti-stick material" should be limited to the amount necessary for achieving
the desired effect.
Therefore, there is the possibility of being able to form a "coating" on a
base material (second
material) to form the product contact MD threads or their surface facing the
product side. The
cross section of the product contact MD threads not needed by the anti-stick
material can be
made from a second material (base material) that has good mechanical
properties and
simultaneously a low price. The coating can here make up only a small portion
of the total cross
section of the thread (less than 20%).
The "coating" of the product contact MD threads according to the invention can
be realized
using a so-called wet coating method or alternatively a plasma coating method
(in a vacuum or
under atmospheric conditions), or in principle using any other conceivable
coating method.
While the binding of the coating material to the base material takes place by
means of adhesion
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during a wet coating method, cohesive bonds that are more durable in
comparison with adhesive
bonds are formed in a plasma coating method.
The two-component construction of a product contact MD thread according to the
invention is
provided in that the cross section of the product contact MD threads has a
second area in the
form of a core and a first area in the form of a casing surrounding the core,
wherein such product
contact MD threads are preferably produced using a coextrusion method or a 2-
step extrusion
method (1' step = core, 2'd step = casing). As an alternative to "coatings,"
such coextruded or 2-
step extruded threads have a casing thickness in the range between 0.02 mm and
0.07 mm,
preferably between 0.03 mm and 0.06 mm. The risk that the anti-stick material
is mechanically
worn away in these two first areas over time so that the anti-stick properties
of the fabric
according to the invention are lost is prevented by the material thickness
selected to be
sufficiently large without additional means during the coextrusion or 2-step
extrusion method.
The cross section of the MD threads or a part of it and/or the cross section
of the CMD threads or
a part of it has a flattened, especially rectangular, in particular, flat
rectangular shape. For
rectangular cross section, the height-width ratios are between 1:1.2 and 1:10
(height : width),
preferably between 1:1.5 and 1:4.
Preferably, the MD threads or a part of them and/or the CMD threads or a part
of them are
constructed as monofilaments. The cross section of the CMD threads or a part
of it can have a
round, elliptical, or oval or polygonal and/or flattened, in particular,
rectangular, shape.
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Preferably, the first area, i.e., the anti-stick material, is made from a
fluorine-containing polymer,
for example, a PVDF, an ETFE, or a PTFE or copolymers of polyethylene with the
previously
mentioned fluorine-containing polymers, and the second area, i.e., the core
material is made from
polyester, polyamide, polyphenylene sulfide, polyether ether ketone,
polypropylene, aramid,
polyethacetone, or polyethylene naphthalate.
The tendency of the fibers forming the nonwoven to stick to the fabric
according to the invention
can be further reduced if at least the material of a surface facing the
product side at least with the
CMD threads that can be in contact with the web of the nonwoven to be formed
or that could
receive fibers from this web has a contact angle, measured according to the
Wilhelmy plate
method, of greater than 80 , preferably greater than 90 , even more preferred
greater than 1000
.
Especially for binding types in which a not insignificant part of the contact
surface with the
nonwoven web is also formed by the CMD threads, the anti-stick properties are
very
advantageous.
The CMD threads preferably have a round cross section, which improves the
ability to form a
web. Typically, the MD threads are the warp threads in the web production of
the fabric
according to the invention, while the CMD threads are the weft threads of the
fabric.
To achieve a large contact surface, especially on the product side of the
fabric, a CMD thread
with a larger diameter and a CMD thread with a smaller diameter can be
arranged alternately one
after the other, wherein the CMD threads with the smaller diameter bind with
the MD threads
and are preferably made from a material that has a contact angle of greater
than 80 , preferably
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greater than 90 , even more preferred greater than 1000, at least on a surface
facing the product
side.
In addition, a part of the MD threads and/or the CMD threads can be
electrically conductive.
This can be achieved especially in that, on an outer casing of the cross
section of the relevant
threads, there is carbon that forms a conductive layer. The carbon coating can
be produced, for
example, with the help of the typical coating method, especially by a plasma
coating method. If
the fabric has an electrically conductive construction, at least in the form
of distributed
individual threads (for example, every fifth or eighth MD thread or CMD thread
could have an
electrically conductive construction), an electric field could be generated
around the industrial
fabric used as a circulating belt, which can further suppress the adhesion of
fibers during the
production of the nonwoven. The introduction of the voltage necessary for
generating the electric
field is realized by the deflection devices (rollers), which are typically
metallic and come in
contact with the machine side of the fabric.
A seam with especially good load bearing properties for an endless belt is
produced if a seam
connecting two fabric ends is closed to form an endless conveyor belt, wherein
the seam is a
spiral seam that has two seam spirals that extend over the entire width of the
conveyor belt and
are each turned in or hooked into loops of MD threads of opposing fabric ends
and both are
coupled with each other by a closing wire extending over the entire width of
the conveyor belt.
The excellent anti-stick properties of the actual product side of the fabric
are also produced in the
area of the spiral seam if the seam spirals are each made from a thread whose
cross section has at
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least two areas, namely one in the form of a core and the other in the form of
a casing
surrounding the core, wherein the casing is made from a material that has a
contact angle,
measured according to the Wilhelmy plate method, of at least 800, preferably
at least 90 , even
more preferred at least 1000
.
The objective specified above is also achieved according to the invention by a
method for
producing a nonwoven, especially an aerodynamically formed and chemically
and/or thermally
cured nonwoven, in which a web of the nonwoven is moved onto a surface of the
conveyor belt
in a production system in which, according to the invention, the conveyor belt
is made from an
industrial fabric according to one of Claims 1 to 10.
Finally, the objective forming the basis of the invention is also achieved by
the use of an
industrial fabric according to one of Claims 1 to 10 as a conveyor belt for
transporting a web of a
nonwoven during its production, especially during its aerodynamic formation
and chemical
and/or thermal curing in a furnace or a heating device.
EMBODIMENT
The invention will be explained in more detail below with reference to an
embodiment of a
system for producing a nonwoven, as well as several embodiments of industrial
fabric from
which a conveyor belt for use in a production system can be made.
Shown are:
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Fig. 1: a schematic illustration of the production steps for a nonwoven,
Fig. 2: a longitudinal section, an industrial fabric in a first embodiment,
Fig. 3: a longitudinal section through an industrial fabric in a second
embodiment,
Fig. 4: a cross section through the fabric according to Fig. 4 in the area of
a first CMD thread,
Fig. 5: like Fig. 4 but in the area of a second CMD thread,
Fig. 6: a cross section through an MD thread,
Fig. 7: a longitudinal section through an industrial fabric in a fourth
embodiment in the area of
seam loops,
Fig. 8: a section of a top view of two ends of an industrial fabric for
closing the seam, and
Fig. 9: a perspective view of a fabric according to the invention in a fifth
embodiment in the area
of a spiral seam.
A system 1 shown in Figure 1 is used for producing an aerodynamically formed
and both
thermally and also chemically cured nonwoven that leaves the system 1 at the
position 2 as an
endless web. The nonwoven is formed from a fiber pulp, mixed with two-
component fibers and a
very water-absorbent plastic granulate. The two-component fibers have a core
made from
polypropylene with a higher melting point and a casing made from polyethylene
surrounding the
core with a lower melting point. The starting materials are fed by means of a
feeder 3 to a
forming belt 4 where a material layer is formed. With the help of a transfer
belt 5, the nonwoven
web is transferred to a spraying device 6 where a coating of a polymer
dispersion with bonding
properties is applied. For passing through the spraying device 6, the nonwoven
web is
transported by a belt 7.
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Downstream of the spraying device 6, the nonwoven web is fed into a first
drying device 8
(furnace) where the web is transported by a conveyor belt 9. In the drying
device 8, the casings
of the two component fibers are melted and the polymer dispersion sprayed in
the spraying
device 6 is hardened. This produces the cohesion of the fibers of the
nonwoven.
Downstream of the first drying device 8, the nonwoven web is fed by a belt 10
through a second
spraying device 11 before it is guided by a second conveyor belt 12 through a
second drying
device 13. A final curing of the nonwoven web is performed in a curing device
14 where the
nonwoven web is transported with the help of a third conveyor belt 15.
Finally, the final
nonwoven web is guided with the help of a discharge belt 16 to the output
(position 2) of the
system 1.
One problem of known systems is that the spaces in conveyor belts 9, 12 become
clogged with
non-bound fibers, so that the permeability of the conveyor belts 9, 12
decreases and sufficient air
can no longer be guided into the drying devices 8, 13 through the nonwoven
web. The heat
transfer to the nonwoven web is then inadequate, which leads to inadequate
cohesion of the
fibers and thus inadequate strength of the nonwoven web, because the necessary
temperatures
can no longer be achieved. A remedy is now created according to the invention
by a fabric that is
shown in Figures 2 to 8 and will be explained in more detail below.
Figures 2 and 3 each show a longitudinal section, i.e., a section parallel to
the threads oriented in
the running direction of the nonwoven web, through industrial fabric 30, 40.
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Figure 2 shows a fabric 30 with only one layer of CMD threads 31, but, in
turn, two MD threads
32 and 33 in a stacked arrangement. These have the same profile within the
fabric; these are
therefore so-called double threads. The MD threads 32, 33 always maintain
their orientation
relative to each other, i.e., they are not turned toward or with each other.
The MD thread 32 that
is arranged on the product side PS of the fabric 30 thus lies above the MD
thread 33 arranged on
the machine side MS. With their surface areas facing each other, the MD
threads 32 and 33
oriented in a stacked arrangement are in direct contact. As still to be
explained below, the MD
threads 32, 33 have a flattened rectangular cross section, so that, in the
fabric composite, a stable
stack and maintenance of the arrangement can be achieved relative to each
other.
An industrial fabric 40 shown in Figure 3 contains CMD threads 41 and 42
arranged in a single
CMD layer. In addition, two layers of MD threads 43 and 44 are present in the
fabric 40, wherein
the MD threads 44 are arranged on the machine side MS and the MD threads 43
are arranged on
the product side PS. As also produced, in particular, from the cross-sectional
illustrations
according to Figures 4 and 5, the CMD threads 42 that have a smaller diameter
are binding
threads (see Figure 5), while the CMD threads 41 having a larger diameter are
to be designated
as pure filling threads and run in a relatively straight line through the
fabric 40 (see Figure 4). It
can be seen that the CMD threads 41 separate each pair of MD threads 43, 44
from each other
(Figure 4), while the MD threads 43, 44 in the area of the CMD threads 42
contact each other
directly, i.e., are in planar contact with each other. In the case of the
fabric 40, the MD threads 43,
44 are the warp threads and the CMD threads 41, 42 are the weft threads.
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Figure 6 shows a cross section through an individual MD thread, how it can be
used in the
fabrics 30, 40 on the product side PS (MD threads 32, 43). The flattened
rectangular MD thread
has a core 61 (thread core) and a casing 62 (thread casing) surrounding this
core. The outer
contour of the core 61 is rectangular and has a height 63 of 0.36 mm and a
width 64 of 1.07 mm.
The casing 62 is also rectangular in its outer contour and has a height 65 of
0.45 mm and a width
66 of 1.20 mm. A thickness 67 of the casing 62 is produced on its longitudinal
sides of approx.
0.045 mm. The casing 62 is formed of a material with especially high surface
energy, such as,
for example, PVDF. In contrast, the core 61 is made from a material with good
mechanical
properties with especially high tensile strength, e.g., polyester (PET). Both
the material of the
core 61 and also of the casing 62 offer a sufficiently large temperature
resistance up to 200 C.
Figure 7 shows, as an example in a longitudinal section illustration, the
formation of a seam on a
fabric 45 that must be combined into an endless belt like the fabric 30, 40
already described
above, in order to be able to be used as a conveyor belt 9, 12, 15 in the
system 1. On one seam
end 46 of the fabric 45, seam loops 47 are formed such that a lower MD thread
48 is cut at a
position 49 and the remaining section facing the seam end 46 is removed. In
the channel formed
previously by the MD thread 48, the upper MD thread 50 (product contact MD
thread) of the
associated stacked pair is inserted and fed back with its end 51 up to the
position 49 at which the
lower MD thread 48 (non-product contact MD thread) ends. In this way, the seam
loop 47 made
from the MD thread 48 is formed at the seam end 46. The CMD threads 52 of the
fabric 45
remain undisturbed during this seam formation.
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From Figure 8 it can be seen that for two opposing seam ends 46, 53 of the
fabric 45 to be joined
together to form a closed belt, alternating seam loops 47 were formed from the
MD threads 50
and the adjacent MD threads 50 are left without seam loop formation. For an
offset arrangement
of the seam loops 47 on the opposing seam ends 46, 53, the two seam ends 46,
53 can be pushed
together relative to each other in the direction of the arrows 54, 55 like a
kind of positive-locking
fit. In this way, the rows of seam loops 47 nested with each other form a
continuous seam
channel in which a closing wire 56 is inserted (like a kind of CMD thread),
whereby the seam is
closed and an endless belt is produced.
Figure 9 shows a perspective view of another fabric 70 according to the
invention with an
alternative embodiment of the seam, namely in the form of a spiral seam. An
industrial fabric 70
that has the same construction, apart from the seam ends, as the fabric
according to Figures 3 to 5
has, on two free ends (viewed in the MD direction), chain loops 71 that are
formed from the MD
threads 72, 73 in that these are woven back over a certain length on the
machine side MS of the
fabric 70. In the chain loops 71 whose ends are on a common straight line that
runs perpendicular
to the MD threads 72, 73, a thread 75 with a spiral shape is pulled for the
formation of a spiral
thread 74, that is, through each chain loop 71 individually. The thread 75 has
a round of flattened
cross section and is made from two components, namely a thread core 76 and a
thread casing 77
concentrically surrounding this core in cross section. The thread 75 can be
produced by
coextrusion or by a multi-step extrusion process, in that initially the thread
core 76 is produced
by extrusion and then is surrounded with the material of the thread casing 77
in the course of a
second extrusion process. The casing 77 is made like the surface of the MD
threads 72, 73 facing
the product side PS from a material that has a contact angle, measured
according to the
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Wilhelmy plate method, of at least 800. The closing of the seam is realized
such that both ends of
the fabric 70 are intermeshed with each other with their seam spirals, so that
within the seam
spirals 74 of the two ends, a closing channel 78 is formed in which a not-
shown closing wire is
inserted in a longitudinal direction 79 of the seam spirals 74, whereby the
two fabric ends are
connected to each other.
Due to the surface properties of the threads 75 in the seam area, the risk is
prevented that
undesired adhesion is produced in this area, which could have occurred if the
threads 75 forming
the seam spirals 74 were made from a material with a lower contact angle. The
core 76 present in
this thread 75 makes it possible, through the selection of a material with a
high tensile strength,
to ensure the necessary stability and tensile load bearing capacity of the
seam.
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List of Reference Symbols
1 System
2 Position
3 Pick-up device
4 Forming belt
Transfer belt
6 Spraying device
7 Belt
8 Drying device
9 Conveyor belt
Belt
11 Spraying device
12 Conveyor belt
13 Drying device
14 Curing device
Conveyor belt
16 Discharge belt
30 Fabric
31 CMD thread
32 MD thread
33 MD thread
40 Fabric
41 CMD thread
CA 02975650 2017-08-02
42 CMD thread
43 MD thread
44 MD thread
45 Fabric
46 Seam end
47 Seam loop
48 MD thread
49 Position
50 MD thread
51 End
52 CMD thread
53 Seam end
54 Arrow
55 Arrow
56 Closing wire
61 Core
62 Casing
63 Height
64 Width
65 Height
66 Width
67 Thickness
70 Fabric
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71 Chain loop
72 MD thread
73 MD thread
74 Seam spiral
75 Thread
76 Core
77 Casing
78 Closing channel
PS Product side
MS Machine side
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