U.S. patent application number 13/266796 was filed with the patent office on 2012-03-08 for fabric, in particular for an airbag.
This patent application is currently assigned to GLOBAL SAFETY TEXTILES GMBH. Invention is credited to Thomas Eschbach, Norbert Huber.
Application Number | 20120058699 13/266796 |
Document ID | / |
Family ID | 42289071 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120058699 |
Kind Code |
A1 |
Huber; Norbert ; et
al. |
March 8, 2012 |
FABRIC, IN PARTICULAR FOR AN AIRBAG
Abstract
A fabric is described, in particular for an airbag, consisting
at least partially of hollow filament yarns (K, S) made of a
polymer material, wherein the fabric has a cover factor DG,
according to Professor Walz, that is equal to the cover factor when
using solid filament yarns of the same diameter.
Inventors: |
Huber; Norbert; (Bad
Sackingen, DE) ; Eschbach; Thomas; (Bad Sackingen,
DE) |
Assignee: |
GLOBAL SAFETY TEXTILES GMBH
Maulburg
DE
|
Family ID: |
42289071 |
Appl. No.: |
13/266796 |
Filed: |
April 30, 2010 |
PCT Filed: |
April 30, 2010 |
PCT NO: |
PCT/EP2010/002662 |
371 Date: |
October 28, 2011 |
Current U.S.
Class: |
442/189 |
Current CPC
Class: |
D03D 15/00 20130101;
D03D 15/44 20210101; D03D 13/008 20130101; D03D 1/02 20130101; B60R
21/235 20130101; D03D 3/02 20130101; D10B 2401/063 20130101; D10B
2505/124 20130101; B60R 2021/23509 20130101; D10B 2331/04 20130101;
D10B 2331/02 20130101; D10B 2401/062 20130101; B60R 2021/23547
20130101; Y10T 442/3065 20150401 |
Class at
Publication: |
442/189 |
International
Class: |
D03D 15/00 20060101
D03D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2009 |
DE |
10 2009 019 638.2 |
Claims
1. A woven fabric, especially for an airbag, comprising, at least
in part, hollow filament yarns of a polymer material, wherein said
woven fabric features a cover factor with a WALZ density equalling
the cover factor when employing solid filament yarns the same in
diameter.
2. The woven fabric as set forth in claim 1, wherein said hollow
filament yarns have a smaller denier than solid filament yarns the
same in diameter and made with the same polymer.
3. The woven fabric as set forth in claim 1, wherein the weight of
said woven fabric employing hollow filaments is lower in the scope
of the lumen percentage as compared to solid filaments.
4. The woven fabric as set forth in claim 1, wherein said weave is
structured as L1/1 or in a higher weave.
5. The woven fabric as set forth in claim 4, further comprising
solid filament yarns the same in diameter and made of the same
polymer, wherein the hollow filament yarns are arranged at
predefined locations of a repeat in the warp and/or weft and are
interwoven in a weave structure higher than L1/1 and with a higher
thread density than that of a L1/1 weave structure.
6. The woven fabric as set forth in claim 4, further comprising
solid filament yarns the same in diameter and made of the same
polymer and that, wherein the hollow threads are incorporated in
stitched weft technology in zones particularly exposed to thermal
stress in an OPW airbag and are interwoven in a weave structure
higher than L1/1 and with a higher thread density than that of a
L1/1 weave structure.
7. The woven fabric as set forth in claim 1, wherein said
percentage of the hollow surface area or lumen percentage of the
hollow filament yarns is in the region of 20% or higher.
8. The woven fabric as set forth in claim 1, wherein said cover
factor has a WALZ density greater than 100%.
9. The woven fabric as set forth in claim 8, wherein said cover
factor has a WALZ density greater than 105%.
10. The woven fabric as set forth in claim 1, wherein said hollow
filament yarns and solid filament yarns are polyester yarns.
11. The woven fabric as set forth in claim 1, wherein said polymer
material is polyester and wherein: a) the yarn diameter, b) the
number of threads per cm, c) the WALZ density cover factor DG, d)
the thickness of the woven fabric, and e) the weight of the woven
fabric correspond to that of a fabric woven from polyamide 6.6
solid filaments.
12. The woven fabric as set forth in claim 1, wherein said woven
fabric features a uniform edge comb resistance.
13. The woven fabric as set forth in claim 1, wherein a thread
density (number of threads per cm) of the woven fabric is the same
or higher as when employing solid filaments with the same diameter
and with the same woven structure.
14. The woven fabric as set forth in claim 1, wherein a woven
thickness is the same or higher as when employing solid filaments
with the same diameter and with the same woven structure.
15. The woven fabric as set forth in claim 1, wherein the fabric is
woven as an OPW incorporating single-ply and two-ply zones, wherein
the fabric further comprises substantially elongated tubular
structures or tubes running in the warp or weft direction, said
single-ply zones containing hollow filaments.
16. The woven fabric as set forth in claim 15, wherein said thread
system running transversely to the tubes incorporates either solid
filaments or hollow filaments.
17. The woven fabric as set forth in claim 15, wherein said thread
system running transversely to the tubes is configured in an
alternating thread sequence.
18. The woven fabric as set forth in claim 15, wherein said
elongated tubular structures or tubes running in the warp and weft
direction are configured as hollow filaments and the single-ply
zones are formed of solid filaments especially in the direction of
particular tensile stress.
Description
[0001] The present invention relates to a woven fabric,
particularly for an airbag comprising at least in part hollow
filament yarns of a polymer material.
[0002] Such woven fabrics are known for example, from EP 0 616 061
B1 of AKZO in which the contact or filter wovens disclosed therein
are woven with differing thread densities and yarns differing in
diameter. The first disadvantage of this is that the woven is still
too heavy despite the use of hollow threads, there being no need
here to emphasize the ever-increasing demands in automobile
production for a reduction in weight.
[0003] The woven solid and hollow threads in the woven fabric
disclosed therein have the same denier since the inventor based his
assumptions on the required high air permeability and high strength
woven necessitating solid and hollow threads equal in yarn strength
and thus equal cross-sectionally in material mass. Due to the
differences in diameter of solid threads and hollow threads the
result of working both types of thread into a textile web is a
woven fabric haphazard in thickness due to the density of solid
threads than that of hollow threads being higher. Also unfavourable
is that such woven fabrics are difficult to coat evenly. Employing
hollow threads may also add to the thickness of the fabric,
resulting in voluminous airbags with the drawback of higher package
volume. The woven fabric as it reads from EP 0 616 061 B1 varies
regionally in cover factor and thus also in its air permeability
which (unlike as deduced in EP 0 616 061 B1) is evident from the
cover factor as correctly calculated by the method in obtaining the
WALZ density. Differences in the air permeability of a woven fabric
are highly unfavourable in the case of an airbag, since it makes it
impossible to reliably define the "useful life" of the airbag, in
other words how long it remains deployed in actually meeting its
requirement.
[0004] It is known to enhance the thermal capacity of wovens with
hollow fibers or incorporating hollow threads. To make use of this
effect EP 0 616 061 B1 employs hollow fiber and solid fiber yarns
differing in denier which, however, results in the drawbacks as
already cited.
[0005] On top of this, it reads from EP 0 616 061 B1 that exceeding
a hollow surface area percentage of 40% results in a stiffening of
the fibers and thus a deterioration in the folding ability of the
airbag woven whilst establishing, for example, that yarns made
fully or partly of hollow fibers have a denier ranging from 200 to
1100 dtex with the problem that any smaller dtex proves difficult
to produce and any larger dtex cannot be made use of because of the
folding ability becoming so poor.
[0006] It is important to note that in this case producing the
hollow filaments is achieved by maintaining the yarn denier with an
increase in the lumen (filament void), i.e. resulting in the
polymer material in the hollow filament jacket equalling the
polymer material of the solid filament. Added to this is the lumen
increasing the thread diameter. This is why although the structures
described in EP 0 616 061 B1 require fewer threads/cm the
interweave (ondulation) of the thicker yarns and thus also the
resistance to unravelling in the weave of warp and weft threads are
diminished, however. Apart from this the hollow filaments become
all the more less flexible the thicker the thread walls (ring
surface area) with the disadvantage of there being a higher
resistance to ondulation.
[0007] The present invention is based on the object of proposing a
woven fabric for an airbag in which the drawbacks of prior art are
avoided or at least greatly diminished.
[0008] This object is achieved in accordance with the invention by
a woven fabric, especially for an airbag, comprising at least in
part hollow filament yarns of a polymer material, characterized in
that said woven fabric features a cover factor with a WALZ density
equalling the cover factor when employing solid filament yarns the
same in diameter. The woven fabric in accordance with the invention
now makes it possible to advantage to specifically utilize a
property of hollow filaments in which the thermal capacity or
thermal resistance of the woven fabric is enhanced with no change
in the high cover factor and high edge comb resistance for a weight
less than that of known woven fabrics. To advantage in employing
hollow fiber yarns and solid fiber yarns in accordance with the
invention, stiffness, thickness and cover factor remain constant.
The edge comb resistance (a measure of the seam strength) is even
increased to advantage. The woven fabric in accordance with the
invention is especially suitable for airbags for passenger
restraint systems in automotive and aircraft applications.
[0009] Because the diameter of hollow fiber yarns and solid fiber
yarns is the same the woven fabric in accordance with the invention
is lighter than an equivalent woven fabric except for the hollow
fibers, this reduction in weight corresponding to the lumen
percentage. It is fortunate that the packing density of an airbag
made of the woven fabric in accordance with the invention remains
constant so that there is no need to alter the module dimensions
when making use of the woven fabric in accordance with the
invention. Yet another significant advantage is that the lower
weight of the woven now makes it possible to improve the mass
acceleration during the highly dynamic deployment phase of the
airbag to advantage. In addition to this the hollow threads the
same in diameter e.g. in combination with solid threads can now be
processed to advantage into a uniform textile web.
[0010] The present invention is based on a woven structure wherein
[0011] the denier of the hollow filaments becomes less with
increasing lumen percentage, [0012] yarn diameter, thread density
and cover factor remain the same, [0013] the walls of the ring
surface areas of the hollow filaments become thinner with
increasing lumen percentage, and [0014] the equation: reduction in
lumen percentage=reduction in weight holds.
[0015] Definition of lumen percentage: the lumen percentage is an
indication in percentage of the lumen (void) of a hollow filament
as compared to the total cross section of the hollow filament.
[0016] Whilst as known from prior art woven fabrics a (negative)
increase in the stiffness of the hollow filaments occurs the higher
the percentage of the hollow surface area, in the design basic to
the woven fabric in accordance with the invention the higher the
lumen the thinner the wall of the ring surface area becomes which
fortunately does not result in an increase in the flexural rigidity
of the hollow filaments.
[0017] Due to the thinner wall of the ring surface area weaving the
threads the same in diameter is done the same as with solid
filaments. With woven fabrics having a high cover factor the
actually round hollow filaments form at the interweaves the
corresponding reversal by oval kinking, advantageously enhancing
the edge comb resistance (more frictional resistance).
[0018] For example, in accordance with the invention hollow
filaments can be woven in a thread sequence (warp and/or weft) of
solid to hollow filaments, e.g. 1 thread solid filament and 1
thread hollow filament.
[0019] In making use of the woven fabric in accordance with the
invention it is now possible to also employ to advantage a hollow
thread in stitched weft technology (see German patent DE 101 15 890
B2) in zones of a one-piece-woven (OPW) airbag particularly exposed
to thermal stress. This is possible only with the woven fabric in
accordance with the invention because since all threads are the
same in diameter the disadvantage of any thick/thin effect
resulting in an uneven OPW surface can now be avoided.
[0020] In one advantageous aspect of the invention the woven fabric
is characterized in that said hollow filament yarns have a smaller
denier than solid filament yarns the same in diameter and made with
the same polymer resulting in the many advantages to be further
discussed later on. For instance, rigidity, thickness and cover
factor of the woven are constant. This simplifies the production of
uniform woven fabrics (see above). The edge comb resistance (as a
measure of seam strength) is higher than that of comparable woven
fabrics made of solid filaments.
[0021] In another advantageous aspect of the invention the woven
fabric is characterized in that it comprises solid filament yarns
the same in diameter and made of the same polymer and that the
hollow filament yarns are arranged at predefined locations of a
repeat in the warp and/or weft and are interwoven in a weave
structure higher than L1/1 and with a higher thread density than
that of a L1/1 weave structure. This now makes it possible to
advantage to arrange the hollow fiber yarns, for example, in
thermally critical zones of a woven fabric or OPW specific to the
technological and design engineering requirements.
[0022] In yet another advantageous aspect of the invention the
woven fabric is characterized in that it comprises solid filament
yarns the same in diameter and made of the same polymer and in that
the hollow threads are arranged in stitched weft technology in
zones of a OPW particularly exposed to thermal stress whilst being
interwoven to a higher degree and with a higher thread density as
compared to a L1/1 weave. In still a further advantageous aspect of
the invention the woven fabric is characterized in that the
percentage of the hollow surface area of the hollow filament yarns
is in the region of 20% and more which proved to be particularly an
advantage in tests.
[0023] In another advantageous aspect of the invention the woven
fabric is characterized in that the cover factor has a WALZ density
greater than 100% which proved to be of special advantage as
regards the strength of the woven fabric in an airbag employed as a
passenger safety item.
[0024] In yet another advantageous aspect of the invention the
woven fabric is characterized in that the cover factor has a WALZ
density greater than 105%.
[0025] In still a further advantageous aspect of the invention the
woven fabric is characterized in that the weight of the woven
fabric employing hollow filaments is lower in the scope of the
lumen percentage as compared to solid filaments. This lower weight
of the variant of the woven fabric as compared to known prior art
variants now achieves an improved mass acceleration to particular
advantage during the highly dynamic deployment phase of the
airbag.
[0026] In yet another advantageous aspect of the invention the
woven fabric is characterized in that said effective denier
relevant to establishing the WALZ density cover factor is higher
than the denier at the start by the shrinkage as triggered.
[0027] In a further advantageous aspect of the invention the woven
fabric is characterized in that hollow threads are incorporated in
stitched weft technology in zones particularly exposed to thermal
stress in an OPW airbag.
[0028] In another advantageous aspect of the invention the woven
fabric is characterized in that said polymer material is polyester
and a) the yarn diameter (d), b) the thread diameter per cm, c) the
WALZ density cover factor DG, d) the thickness of the woven fabric
and e) the weight of the woven fabric corresponding to that of a
fabric woven from polyamide 6.6 solid filaments.
[0029] The woven fabric in accordance with the invention can thus
also be woven with polyester yarns incorporating hollow filaments
wherein the higher specific weight of the polyester as compared to
that of polyamide as regularly employed nowadays is compensated by
a correspondingly selected lumen of the hollow fibers due to the
roughly 21% reduction in weight achieved in accordance with the
invention.
[0030] In yet another advantageous aspect of the invention the
woven fabric is characterized in that its thread density is the
same as when employing solid filaments the same in diameter and
with the same woven structure.
[0031] In still a further advantageous aspect of the invention the
woven fabric is characterized in that its woven thickness is the
same as when employing solid filaments the same in diameter and
with the same woven structure.
[0032] In another advantageous aspect of the invention the woven
fabric is woven as a OPW incorporating single-ply and two-ply zones
characterized in that it comprises substantially elongated tubular
structures or tubes running in the warp or weft direction, said
single-ply zones containing hollow filaments.
[0033] Both from the above description as well as as listed in
Tables A and B the example embodiments mainly involve a woven
fabric featuring high density and being uncoated. Further
advantageous aspects of the invention claim how it is possible to
employ hollow filaments of a polymer material the lumen percentage
of which corresponds to the reduction in the yarn denier and thus
the yarn diameter correspondingly with no change to that of the
corresponding solid filament thread having a denier which is higher
by the lumen percentage, for example, as a tubed woven fabric
incorporating tubes running in the warp or weft direction. For this
purpose, because of the high tensile stress, two-ply woven tubes
are incorporated with solid filaments in the direction of the
tensile stress. The single-ply zones contain hollow filaments to
save weight. The thread system (as a rule the weft threads) running
transversely to the tubes can incorporate either solid filaments or
hollow filaments or in an alternating sequence depending on the
function involved.
[0034] In yet another advantageous aspect of the invention the
woven fabric is characterized in that the thread system running
transversely to the tubes can incorporate either solid filaments or
hollow filaments.
[0035] In yet a further advantageous aspect of the invention the
woven fabric is characterized in that the thread system runs
transversely to the tubes in an alternating thread sequence.
[0036] In still another advantageous aspect of the invention the
woven fabric is characterized in that the tubes running in the warp
and weft direction are configured as hollow filaments and the
single-ply zones are formed of solid filaments especially in the
direction of particular tensile stress. This woven fabric has the
following advantages: where the tubes need to comply with the
function of being particularly suitable to withstand thermal
stress/insulation, the tubes are produced in the warp and weft
direction as hollow filaments, the single-ply intermediate zone
then advantageously consisting of solid filaments in the direction
of particular tensile stress.
[0037] Wovens featuring hollow filaments in the sense of the
invention comprise a uniform surface (no thick/thin effects) making
them excellently suitable for coating by means of which a woven
fabric of hollow filaments features a specific additional function
in which the weight of the coating is compensated for by the
reduction in the basic weight of the supporting woven (hollow
filament woven). In addition to this, the hollow filament located
oval where interweaved results in a larger surface area for bonding
the coating mass.
[0038] The woven fabric in accordance with the invention consisting
of solid or hollow filaments featuring the same density, thickness
or especially edge comb resistance is suitable for an engineered
agglomerated filament system without influencing the seam
structure. The examples described in the following involve either
substituting solid filaments by hollow filaments or an
agglomeration in engineering the weave.
[0039] For clarification it is understood that a woven fabric in
accordance with the invention also includes a one-piece woven (OPW)
airbag. I.e. an airbag might be produced from a sheet woven in
accordance with the invention incorporating hollow fibers the same
in thickness, alternating in warp and/or weft thread with solid
fibers or might be produced in OPW technology.
[0040] The denier of a yarn is defined as the weight in grams
(dtex) of a thread 10,000 m long and thus the denier equates to the
basic surface area--where hollow filaments are concerned only of
the ring surface area encompassing the void--of the thread mass
multiplied by the specific weight and length of 10,000 m.
[0041] The thread diameter d of hollow filaments is equated from
the total basic surface area F.sub.ring plus F.sub.lumen as
follows:
F tot or ring = dtex ( mm 2 ) g / cm 3 .times. 10 , 000
##EQU00001##
[0042] From F.sub.ring the total surface area F.sub.tot is equated
in mm.sup.2 taking into account the lumen percentage. The thread
diameter d is equated with respect to the cover factor as
formulated by the WALZ density as follows;
d = Ftot ( mm ) 0.885 ##EQU00002##
[0043] This terminology of the various terms involved presently
serves to explain that hollow fiber yarns are hollow threads or
synthesized filament yarns incorporating filaments having an
internal void whose percentage of the hollow surface area is
referenced to the total cross-sectional surface area of the
filaments.
[0044] The German definition of cover factor (DG)as formulated by
the WALZ density reads from "Die Gewebedichte I" and "Die
Gewebedichte II" on pages 330 to 366 of the publication
"Textilpraxis" dating back to 1947 published by the Robert
Kohlhammer-Verlag in Stuttgart, Germany. Equating the cover factor
DG is based on determining the yarn count, settings and knowing the
density of the fiber material employed. The cover factor DG % as
formulated by the WALZ density is
cover factor: DG %=(dk+ds).sup.2 . fk . fs
where: dk/ds=substance diameter of warp or weft yarn in mm;
fk/fs=warp or weft thread count per cm;
[0045] The substance diameter of solid filament yarns equates as
follows:
dks = dtex ks 88.5 density g / cm 3 ( mm ) ##EQU00003##
[0046] (Note that the above formula applies only to plain weaves
(cover factor I), where other weaves higher than plain, i.e. L1/1
the resulting cover factors are to be multiplied by certain
factors, e.g. twill 2:1=0.7, twill 2:2=0.56, twill 3:1=0.56, twill
4:4=0.38, satin 1:4=0.49, panama 2:2=0.56, in thus obtaining cover
factor II).
[0047] Interpretation of equating cover factor (DG) as formulated
by the WALZ density:
[0048] 1. Effective Denier:
[0049] The effective denier equates from the circular surface area
for solid threads and from the ring surface area for hollow
threads.
[0050] 2. Thread Diameter
[0051] The thread diameter (d) is relevant for calculating the
cover factor and in the case of hollow filaments it equates from
the total cross-sectional surface area (ring+hollow surface
area).
[0052] 3. How Thread Size, Density and Interweave Interrelate:
[0053] The surface area resulting for an interweave (in L1/1)
equates from (dk+ds).sup.2 in mm.sup.2. The quotient of 100
mm.sup.2: (dk+ds).sup.2 corresponds to the maximum number of
interlacings per cm.sup.2=100%. The product of
f.sub.k.times.f.sub.s corresponds to the number of interweaves
attained per cm.sup.2.
[0054] The following comments are illustrated by FIGS. 1 to 4 in
which:
[0055] FIG. 1 is a diagrammatic illustration of a section of a
weave design.
[0056] FIG. 2 is a diagrammatic illustration of an example of
homogenous tile of polymer.
[0057] FIG. 3 is a diagrammatic illustration of an example of a
"sandwich" tile.
[0058] FIG. 4 is a diagrammatic illustration of a warp and weft
interweave of hollow filaments.
[0059] FIG. 5 is a diagrammatic illustration of an example of a
tubed woven incorporating warp or weft tubes in a first
variant.
[0060] FIG. 6 is a diagrammatic illustration of a further example
of a tubed woven incorporating warp or weft tubes in a second
variant.
[0061] Referring now to FIG. 1 there is illustrated
diagrammatically a section of a L 1/1 weave design together with
the corresponding warp and weft section.
[0062] Equating cover factor (DG) as formulated by the WALZ density
is thus given by:
100 .times. fk .times. fs 100 ( dk + ds ) 2 = DG % ##EQU00004## (
dk + ds ) 2 .times. fk .times. fs = DG % ##EQU00004.2##
[0063] The diameter (d) used as that of the thread is the geometric
correct value in (mm), i.e. the substance diameter for solid
filaments and the total diameter of ring and hollow surface area
(F.sub.tot) for hollow filaments.
[0064] EP 0 616 061 B1 teaches that just a 20% fraction of the
hollow surface area increases the thermal resistance by approx.
175%. This conclusion is based on the following computation model:
The assumed surface area of 1 m.sup.2 with a weight of 210
g/m.sup.2 is divided by the specific weight in g/m3. The result
(FIG. 2) is the thickness dv of a homogenous polymer tile of 1
m.sup.2, in the example cited, of 0.18 mm at PA 6.6.
[0065] Referring now to FIG. 2 there is illustrated an example of a
homogenous polymer tile of 1 m.sup.2.
[0066] The wall thickness as thus established is divided by the
coefficient of thermal conductivity (.quadrature.) resulting in the
thermal resistance Rw (K/W) of the full surface area. The thermal
resistance Rw of the hollow surface areas is computed on the same
principle, e.g. for a lumen of 20% with two different media.
[0067] Referring now to FIG. 3 there is illustrated an example of a
"sandwich tile" of 1 m.sup.2 wherein the "outer walls" A
encompassing the lumen L with a "thickness" of 0.036 mm have a
thickness dh of 0.09 mm.
[0068] Summing the thermal resistances Rw of the wall and of the
hollow surface area results in a thermal resistance approx. 175%
higher than that of the solid surface area. Comparing the thermal
resistance of a solid filament to that of a hollow filament with a
lumen of 20%--as computed with the same parameters--results in a
relative increase of Rw of >300% in the body of the yarn. In
both models the thermal transition is assumed perpendicular or
radial to the wall surface area. The model as it reads from EP 0
616 061 B1 is based on a closed polymer tile, not taking into
account the structural features of a textile surface area (weave,
ondulation), however.
[0069] By contrast, the model as it reads from the present
invention is based on the geometrically correct structure of the
yarn body but covers only the thermal transition in the radial
direction. Taking into account the structure of the woven fabric
(yarn body interweave, type of weave, cover factor %) the direction
of the thermal stress differs with respect to the yarn body, i.e.
radial to axial. In addition to this it needs to be remembered that
when the thermal stress acts radially the thermal resistance in the
ring surface area is less than in the lumen and thus the direction
in which the thermal stress is active is non-linear.
[0070] Referring now to FIG. 4 there is illustrated
diagrammatically a section of a plain weave (L 1/1) showing how the
hollow filaments K and S are interwoven in the warp and weft
direction. With thermal stress acting perpendicular to the textile
surface area in the direction of the arrow V the thermal transition
in the run of the thread correspondingly differs.
[0071] This results in the following advantage: when both solid
filaments as well as hollow filaments are worked into a textile
surface--or in OPWs--then in surface areas subjected to thermal
stress the hollow filaments preferably also need to be woven in a
more engineered structure, e.g. basket weave where the cover factor
is higher (cover factor II).
[0072] Referring now to FIG. 5 there is illustrated a diagrammatic
illustration of an example of a tubed woven incorporating tubes
oriented in warp or weft direction in a first variant in which the
reference numeral 2 identifies tubes incorporating solid filaments
in the tensile stress direction shown, in this case as an example,
in an "inflated" honeycomb structure. The reference numeral 4
identifies single-ply intermediate portions incorporating solid
filaments in the tensile stress direction between the tubes 2
whilst reference numeral 6 identifies the corresponding system of
solid or hollow filaments as transverse threads.
[0073] Referring now to FIG. 6 there is illustrated a diagrammatic
illustration of a further example of a tubed woven incorporating
warp or weft tubes in a second variant. In this variant the
reference numeral 12 identifies tubes incorporating hollow
filaments in the warp and weft direction shown, here as an example,
in an "inflated" honeycomb structure. The reference numeral 14
identifies single-ply intermediate portions incorporating solid
filaments in the tensile stress direction between the tubes 12
whilst reference numeral 16 identifies the corresponding system of
hollow filaments as transverse threads.
[0074] To show how the invention can be engineered example variants
thereof are summarized in the following.
Here the Example Variants I and II
TABLE-US-00001 [0075] TABLE A Comparison of a standard article to
example variants I and II of the woven fabric in accordance with
the invention Ex. I with predefined denier in same Example II with
predefined cover factor Standard - Article cover factor with hollow
filaments and D' with hollow filaments starting denier - effective
- dtex 474/72 380/72 390/72 nominal shrinkage - % 8.2 5.4 5.4 lumen
- % -- 20 20 F tot - mm.sup.2 0.04158 0.04167 0.042868 F ring-
mm.sup.2 -- 0.03333 0.034294 = 80% F lumen - mm.sup.2 -- 0.00834
0.008574 = 20% D' - mm 0.2304 0.23066 0.23395 warp count/dm 224.8
220 224.8 weft count/dm 209.2 220 209.2 basecloth weight -
g/m.sup.2 239 189 193 crimp - % (K/S) 11/7 11/6 11/7 thread
length/m.sup.2 - m 2495 + 2238 = 4733 m 2442 + 2332 = 4774 m 4733 m
effective denier dtex 505 396 407 F tot.- mm.sup.2 0.044295 0.04306
0.044295 F ring- mm.sup.2 -- 0.03472 0.035721 F lumen - mm.sup.2 --
0.00834 0.008574 D' - mm 0.2378 0.23447 0.2378 triggered shrinkage
- % 6.14 4 4 cover factor DG - % 106.4 106.4 106.4 fabric thickness
- mm 0.36 0.35 0.36 max. tensile stress - warp N/5 cm 3322 2603
2737 max. tensile stress - weft N/5 cm 3305 2786 2726 21% reduction
in weight 19% reduction in weight
[0076] The above Table A compares a standard article (all-solid
fiber) to example variants I and II (all-hollow fiber) of the woven
fabric in accordance with the invention illustrating how
substituting solid filaments by hollow filaments of the same
polymer in a textile surface area of consistent cover factor
achieves a reduction in the denier and in the weight of woven by
the lumen percentage for the same thread diameter (d).
[0077] The intention is to substitute the high cover factor of the
standard article (prior art) engineered in polyamide 6.6 (PA 6.6)
solid filaments by a surface area engineered at least partly in PA
6.6 hollow filaments for the same cover factor.
[0078] The cover factor of the woven fabric is needed because of
the LD in conjunction with with an uncoated application and high
seam strength (edge comb resistance). As regards strength and
weight the woven fabric as specified in the standard article is
"over-engineered".
Example Variant I
[0079] Example variant I is based on an existing yarn of PA 6.6 in
a denier of 380/72 dtex with a lumen of 20%. Taking into account
the specific shrinkage values--the ratio of the resulting shrinkage
to the nominal shrinkage (hot air shrinkage of the yarn) being
defined and depending on how it is finished--the corresponding
number of threads of the finished fabric (22.times.22 Fd/cm) is
established from the predefined cover factor of 106.4% as
formulated by the WALZ density on the basis of the thread diameter
in the finished fabric (after shrinkage).
[0080] The square meter weight as computed from thread densities,
crimp and effective denier (after shrinkage) is lower by the
percentage of the lumen (lumen %) and the maximum tensile forces in
N/5 cm are correspondingly reduced.
[0081] Thanks to its cover factor the woven fabric has the
necessary seam strength (edge comb resistance).
Example Variant II
[0082] In example variant II a woven fabric of PA 6.6 hollow
filaments was produced having exactly the same parameters (cover
factor %, thread diameter, thread density) as the "standard
article". Starting with the necessary effective denier as needed
and taking into account the shrinkage value (triggered shrinkage)
the nominally denier is obtained retrogradedly.
[0083] The reduction in the square meter weight corresponding to
the lumen percentage and the maximum tensile forces in the warp and
weft direction are reduced by the same percentage as practically
the same absolute values because of the difference in the thread
densities in the warp and weft direction. As regards a biaxial
tensile stress of the woven fabric these same values are an
advantage. The example variant II now makes it possible to
substitute the so-called standard article woven fabric with
improved technical conditions for its use (no longer "over
engineered", lighter) by a hollow filament woven fabric.
Example Variant III
[0084] Yet another example variant (III) will now be detailled with
respect to Table B in reenacting the known standard article of PA
6.6 employing polyester hollow filaments having the same parameters
as the finished woven. The approach is the same as that of example
variant II in also proving that polyester can be put to use in
airbag woven fabrics because of it being better cost-effective.
[0085] The intention is to produce the woven fabric (standard
article) in a dense structure of PA 6.6, dtex 470, 22.times.21 with
cover factor=106.4% in L 1/1 with the same density and same
thickness (diameter) of the thread in making use of a corresponding
PES hollow filament thread.
[0086] Substituting solid filaments by hollow filaments of another
polymer material in a textile surface area having the same constant
density results in the same denier and same woven weight--see Table
B--for the same thread diameter (d) and a lumen % corresponding to
the percentage of the difference in the specific weight of both
polymers.
TABLE-US-00002 TABLE B PA-woven PES-woven standard- hollow- Term
(dimension) article filament starting denier 474/72 477 effective
in dtex lumen - % -- 20 F ring [mm.sup.2] -- 0.034582 F lumen
[mm.sup.2] -- 0.008645 F tot [mm.sup.2] 0.04158 0.043227 D [mm]
0.2304 0.2349 warp thread [/dm] 224.8 224.8 weft thread [/dm] 209.2
209.2 crimp -% [warp/weft] 11/7 2.9/4.8 fabric weight [g/m.sup.2]
239 222 thread length in [m/m.sup.2] 4.733 4.505,6 effective denier
[dtex] 505 492 F ring [mm.sup.2] -- 0.03565 F lumen [mm.sup.2] --
0.008645 F tot [mm.sup.2] 0.044295 0.044295 D' [mm] 0.2378 0.2378
triggered shrinkage [%] 6.14 3 (0.97) cover factor DG - % 106.4
106.4
[0087] Using PES hollow filament with 20% lumen (void in the fiber)
makes it possible to produce a woven fabric having the same cover
factor, and this despite the higher special weight (+21%) in the
same weight class.
[0088] Taking into account the differences in the yarn and
shrinkage values and crimp conditions the reduction in weight
equates to the lumen %.
[0089] Mixing hollow filaments the same in diameter in the textile
surface areas of solid filaments results in the same cover factor
and reduction in weight for the same weave (e.g. plain L 1/1). In
zones particularly exposed to thermal stress the thread diameter
for hollow filaments can be correspondingly increased by a higher
weave structure for the same cover factor (DG II).
EXAMPLES
[0090] a) Sheet woven alternating 1 solid filament thread with 1
hollow filament thread in the warp and weft direction, results in a
woven which is lighter with the same remaining structure. [0091] b)
Sheet woven incorporating hollow filaments in predefined locations
in the warp and/or weft direction in a higher weave structure,
results in enhanced resistance to thermal stress. [0092] c) OPW
employing hollow filaments in stitched weft technology, also
possible in a higher weave structure, results in enhanced
resistance to thermal stress.
* * * * *