U.S. patent application number 09/767156 was filed with the patent office on 2001-06-28 for low permeability side curtain airbag cushions having extremely low coating levels.
Invention is credited to Li, Shulong, Sollars, John A. JR..
Application Number | 20010005660 09/767156 |
Document ID | / |
Family ID | 25078643 |
Filed Date | 2001-06-28 |
United States Patent
Application |
20010005660 |
Kind Code |
A1 |
Li, Shulong ; et
al. |
June 28, 2001 |
Low permeability side curtain airbag cushions having extremely low
coating levels
Abstract
Coated inflatable fabrics, more particularly airbags to which
very low add-on amounts of coating have been applied, are provided
which exhibit extremely low air permeabilities. The inventive
fabrics are primarily for use in automotive restraint cushions
which require low permeability characteristics (such as side
curtain airbags). Traditionally, heavy, and thus expensive,
coatings of compounds such as neoprene, silicones and the like,
have been utilized to provide such required low permeability. The
inventive fabric utilizes an inexpensive, very thin coating to
provide such necessary low permeability levels. Thus, the inventive
coated airbag possesses a coating of at most 3.0 ounces per square
yard, most preferably about 0.8 ounces per square yard, and
exhibits a leak-down time (a measurement of the time required for
the entire amount of gas introduced within the airbag at peak
pressure during inflation to escape the airbag at 10 psi) of at
least 5 seconds as well as very low packing volumes (for more
efficient use of storage space within a vehicle). All coatings, in
particular elastomeric, preferably, though not necessarily,
non-silicon coatings, and coated airbags meeting these criteria are
intended to reside within the scope of this invention.
Inventors: |
Li, Shulong; (Spartanburg,
SC) ; Sollars, John A. JR.; (LaGrange, GA) |
Correspondence
Address: |
Terry T. Moyer
P.O. Box 1927
Spartanburg
SC
29304
US
|
Family ID: |
25078643 |
Appl. No.: |
09/767156 |
Filed: |
January 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09767156 |
Jan 22, 2001 |
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09501467 |
Feb 9, 2000 |
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09501467 |
Feb 9, 2000 |
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09350620 |
Jul 9, 1999 |
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6177366 |
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09350620 |
Jul 9, 1999 |
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09335257 |
Jun 17, 1999 |
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6177365 |
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09767156 |
Jan 22, 2001 |
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09406264 |
Sep 24, 1999 |
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6220309 |
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Current U.S.
Class: |
442/71 ;
442/59 |
Current CPC
Class: |
Y10T 442/3008 20150401;
D06N 3/0002 20130101; Y10T 442/3472 20150401; B60R 2021/23514
20130101; B60R 2021/23547 20130101; Y10T 428/1307 20150115; Y10T
442/2049 20150401; D03D 1/02 20130101; B32B 27/12 20130101; Y10T
428/1362 20150115; Y10T 442/3545 20150401; B60R 21/235 20130101;
Y10T 442/20 20150401; D06N 3/186 20130101; D06N 3/14 20130101; Y10T
442/2098 20150401; Y10T 442/2139 20150401; B60R 2021/0018 20130101;
D03D 11/02 20130101; Y10T 428/13 20150115; Y10T 442/3561 20150401;
B60R 21/232 20130101; Y10T 442/3553 20150401; Y10T 442/3496
20150401 |
Class at
Publication: |
442/71 ;
442/59 |
International
Class: |
B32B 005/02 |
Claims
What is claimed is:
1. A coated side curtain airbag exhibiting a packing volume factor
of at most about 0.05; wherein at least a portion of said coated
side curtain airbag is coated with an elastomeric coating; and
wherein said coated side curtain airbag exhibits a characteristic
leak-down time after inflation of at least 5 seconds.
2. The airbag of claim 1 wherein said airbag comprises fibers
possessing an average denier of at most 525.
3. The airbag of claim 2 wherein said fibers possess an average
denier of at most 420.
4. The airbag of claim 3 wherein said fiber possess an average
denier of at most 315.
5. A coated side curtain airbag exhibiting a packing volume factor
of at most about 0.05; wherein at least a portion of said coated
side curtain airbag is coated with an elastomeric coating; wherein
said coated side curtain airbag exhibits a characteristic leak-down
time after inflation of at least 5 seconds; and wherein said
inflatable fabric comprises at least two layers of fabric in
certain discrete areas of the fabric and at least one single fabric
layer at a discrete area within said fabric, wherein the weave
diagram for such an inflatable fabric does not exhibit more than
three consecutive unfilled blocks in any row or column.
6. The airbag of claim 5 wherein said elastomeric composition
comprises polyurethane.
7. The airbag of claim 5 wherein said coated fabric is woven and
comprises polyamide yarns.
8. The airbag of claim 7 wherein said polyamide yarns are formed
from nylon 6,6 fiber.
9. The airbag of claim 8, wherein said polyamide yarns are
multifilament yarns characterized by an average linear density of
between about 210 and 630 denier.
10. The airbag of claim 9, wherein wherein said multifilament yarns
are characterized by a filament linear density of about 4 denier
per filament or less.
11. The airbag of claim 6, wherein said elastomeric polyurethane
composition is polycarbonate polyurethane.
12. The airbag of claim 5 wherein said packing volume factor is at
most about 0.048.
13. The airbag of claim 12 wherein said packing volume factor is at
most about 0.046.
14. The airbag of claim 13 wherein said packing volume factor is at
most about 0.044.
15. The airbag of claim 14 wherein said packing volume factor is at
most about 0.041.
16. The airbag of claim 15 wherein said packing volume factor is at
most about 0.393.
17. A coated side curtain airbag exhibiting a packing volume factor
of at most about 0.05; wherein at least a portion of said coated
side curtain airbag is coated with an elastomeric coating; wherein
said coated side curtain airbag exhibits a leak-down time after
inflation of at least 5 seconds; and wherein said inflatable fabric
comprises at least two layers of fabric in certain discrete areas
of the fabric and at least one single fabric layer at a discrete
area within said fabric, wherein only two separate weave densities
are present within the area directly adjacent to said single fabric
layer.
18. The airbag of claim 17 wherein said elastomeric composition
comprises polyurethane.
19. The airbag of claim 17 wherein said coated fabric is woven and
comprises polyamide yarns.
20. The airbag of claim 19 wherein said polyamide yarns are formed
from nylon 6,6 fiber.
21. The airbag of claim 20, wherein said polyamide yarns are
multifilament yarns characterized by an average linear density of
between about 210 and 630 denier.
22. The airbag of claim 21, wherein wherein said multifilament
yarns are characterized by a filament linear density of about 4
denier per filament or less.
23. The airbag of claim 18, wherein said elastomeric polyurethane
composition is polycarbonate polyurethane.
24. The airbag of claim 17 wherein said packing volume factor is at
most about 0.048.
25. The airbag of claim 24 wherein said packing volume factor is at
most about 0.046.
26. The airbag of claim 25 wherein said packing volume factor is at
most about 0.044.
27. The airbag of claim 26 wherein said packing volume factor is at
most about 0.041.
28. The airbag of claim 27 wherein said packing volume factor is at
most about 0.393.
29. A coated side curtain airbag exhibiting a packing volume factor
of at most about 0.05; wherein at least a portion of said coated
side curtain airbag is coated with an elastomeric coating; wherein
said coated side curtain airbag exhibits a leak-down time after
inflation of at least 5 seconds; and wherein said inflatable fabric
comprises at least two layers of fabric in certain discrete areas
of the fabric and at least one narrow single fabric layer at least
two discrete areas within said fabric, wherein said at least one
narrow single fabric layer is formed solely from a basket weave
pattern of an even number of yarns, at most 12 yarns in width,
wherein at least two discrete narrow areas of single fabric layers
are present within said inflatable fabric, wherein said at least
two areas of single fabric layers are separated by an area of at
least two layers of fabric, and wherein the width of each single
layer is from 4 to 8 yarns in length.
30. The airbag of claim 29 wherein said elastomeric composition
comprises polyurethane.
31. The airbag of claim 29 wherein said coated fabric is woven and
comprises polyamide yarns.
32. The airbag of claim 31 wherein said polyamide yarns are formed
from nylon 6,6 fiber.
33. The airbag of claim 32, wherein said polyamide yarns are
multifilament yarns characterized by an average linear density of
between about 210 and 630 denier.
34. The airbag of claim 33, wherein wherein said multifilament
yarns are characterized by a filament linear density of about 4
denier per filament or less.
35. The airbag of claim 30, wherein said elastomeric polyurethane
composition is polycarbonate polyurethane.
36. The airbag of claim 29 wherein said packing volume factor is at
most about 0.048.
37. The airbag of claim 36 wherein said packing volume factor is at
most about 0.046.
38. The airbag of claim 37 wherein said packing volume factor is at
most about 0.044.
39. The airbag of claim 38 wherein said packing volume factor is at
most about 0.041.
40. The airbag of claim 39 wherein said packing volume factor is at
most about 0.393.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending application
Ser. No. 09/501,467, filed Feb. 9, 2000, which is a
continuation-in-part of Ser. No. 09/350,620, filed on Jul. 7, 1999,
which is a continuation-in-part of Ser. No. 09/335,257, filed on
Jun. 17, 1999; this application is also a continuation-in-part of
co-pending application Ser. No. 09/406,264, filed on Sep. 24, 1999.
These parent, grand-parent, and great-grandparent applications are
herein entirely incorporated by reference.
FIELD OF THE INVENTION
[0002] All U.S. Patents cited herein are entirely incorporated by
reference.
[0003] This invention relates generally to coated inflatable
fabrics and more particularly concerns airbag cushions to which
very low add-on amounts of coating have been applied and which
exhibit extremely low air permeability. The inventive inflatable
fabrics are primarily for use in automotive restraint cushions that
require low permeability characteristics (such as side curtain
airbags). Traditionally, heavy, and thus expensive, coatings of
compounds such as neoprene, silicones and the like, have been
utilized to provide such required low permeability. The inventive
fabric utilizes an inexpensive, very thin coating to provide such
necessarily low permeability levels. Thus, the inventive coated
inflatable airbag possesses a coating comprising an elastomeric
material (or materials) in contact with the target fabric wherein
the elastomeric material possesses a tensile strength of at least
2,000 psi and an elongation at break of at least 180%. The coating
is then applied to the airbag surface in an amount of at most 3.0
ounces per square yard (and preferably forms a film). The inventive
airbag exhibits a characteristic leak-down time (defined as the
ratio of inflated bag volume to bag volumetric leakage rate at 10
psi) of at least 5 seconds after inflation. The resultant airbag
cushions, particularly low permeability cushions exhibiting very
low rolled packing volumes, are intended to reside within the scope
of this invention.
BACKGROUND OF THE PRIOR ART
[0004] Airbags for motor vehicles are known and have been used for
a substantial period of time. A typical construction material for
airbags has been a polyester or nylon fabric, coated with an
elastomer such as neoprene, or silicone. The fabric used in such
bags is typically a woven fabric formed from synthetic yarn by
weaving practices that are well known in the art.
[0005] The coated material has found acceptance because it acts as
an impermeable barrier to the inflation medium. This inflation
medium is generally a nitrogen or helium gas generated from a gas
generator or inflator. Such gas is conveyed into the cushion at a
relatively warm temperature. The coating obstructs the permeation
of the fabric by such gas, thereby permitting the cushion to
rapidly inflate without undue decompression during a collision
event.
[0006] Airbags may also be formed from uncoated fabric which has
been woven in a manner that creates a product possessing low
permeability or from fabric that has undergone treatment such as
calendaring to reduce permeability. Fabrics which reduce air
permeability by calendaring or other mechanical treatments after
weaving are disclosed in U.S. Pat. Nos. 4,921,735; 4,977,016; and
5,073,418 (all incorporated herein by reference).
[0007] Silicone coatings typically utilize either solvent based or
complex two component reaction systems. Dry coating weights for
silicone have been in the range of about 3 to 4 ounces per square
yard or greater for both the front and back panels of side curtain
airbags. As will be appreciated by one of ordinary skill in this
art, high add on weights substantially increase the cost of the
base fabric for the airbag and make packing within small airbag
modules very difficult. Furthermore, silicone exhibits very low
tensile strength characteristics that do not withstand high
pressure inflation easily without the utilization of very thick
coatings.
[0008] The use of a particular type of polyurethane as a coating as
disclosed in U.S. Pat. No. 5,110,666 to Menzel et al. (herein
incorporated by reference) permits low add on weights reported to
be in the range of 0.1 to 1 ounces per square yard but the material
itself is relatively expensive and is believed to require
relatively complex compounding and application procedures due to
the nature of the coating materials. Patentees, however, fails to
disclose any pertinent elasticity and/or tensile strength
characteristics of their particular polyurethane coating materials.
Furthermore, there is no discussion pertaining to the importance of
the coating ability (and thus correlated low air permeability) at
low add-on weights of such polyurethane materials on side curtain
airbags either only for fabrics which are utilized within driver or
passenger side cushions. All airbags must be inflatable extremely
quickly; upon sensing a collision, in fact, airbags usually reach
peak pressures within 10 to 20 milliseconds. Regular driver side
and passenger side air bags are designed to withstand this enormous
inflation pressure; however, they also deflate very quickly in
order to effectively absorb the energy from the vehicle occupant
hitting the bag. Such driver and passenger side cushions (airbags)
are thus made from low permeability fabric, but they also deflate
quickly at connecting seams (which are not coated to prevent air
leakage) or through vent holes. Furthermore, the low add-on
coatings taught within Menzel, and within U.S. Pat. No. 5,945,186
to Li et al., would not provide long-term gas retention; they would
actually not withstand the prolonged and continuous pressures
supplied by activated inflators for more than about 2 seconds, at
the most. The low permeability of these airbag fabrics thus aid in
providing a small degree of sustained gas retention within driver
and passenger airbag cushions to provide the deflating cushioning
effects necessary for sufficient collision protection. Such airbag
fabrics would not function well with side curtain airbags, since,
at the very least, the connecting seams which create the pillowed,
cushioned structures within such airbags, as discussed in greater
detail below, would exhibit too high a leakage rate upon inflation
at requisite high gas pressures. As these areas provide the
greatest degree of leakage during and after inflation, the
aforementioned patented low coating low permeability airbag fabrics
would not be properly utilized within side curtain airbags, in
particular side curtain airbags intended to provide extended
rollover protection.
[0009] As alluded to above, there are three primary types of
different airbags, each for different end uses. For example,
driver-side airbags are generally mounted within steering columns
and exhibit relatively high air permeabilities in order to act more
as a cushion for the driver upon impact. Passenger-side airbags
also comprise relatively high air permeability fabrics which permit
release of gas either therethrough or through vents integrated
therein. Both of these types of airbags are designed to protect
persons in sudden collisions and generally burst out of packing
modules from either a steering column or dashboard (and thus have
multiple "sides"). Side curtain airbags, however, have been
designed primarily to protect passengers during side crashes
provide rollover protection by retaining their inflation state for
a long duration, and generally unroll from packing containers
stored within the roofline along the side windows of an automobile
(and thus have a back and front side only). Side curtain airbags
therefore not only provide cushioning effects but also provide
protection from broken glass and other debris. As such, it is
imperative that side curtain airbags, as noted above, retain large
amounts of gas, as well as high gas pressures, to remain inflated
throughout the longer time periods of the entire potential rollover
situation. To accomplish this, these side curtains are generally
coated with very large amounts of sealing materials on both the
front and back sides. Since most side curtain airbag fabrics
comprise woven blanks that are either sewn, sealed, or integrally
woven together, discrete areas of potentially high leakage of gas
are prevalent, particularly at and around the seams. It has been
accepted as a requirement that heavy coatings were necessary to
provide the low permeability (and thus high leak-down time)
necessary for side curtain airbags. Without such heavy coatings,
such airbags would most likely deflate too quickly and thus would
not function properly during a rollover collision. As will be well
understood by one of ordinary skill in this art, such heavy
coatings add great cost to the overall manufacture of the target
side curtain airbags. There is thus a great need to manufacture low
permeability side curtain airbags with less expensive (preferably
lower coating add-on weight) coatings without losing the aging,
stability, and permeability characteristics necessary for proper
functioning upon deployment. To date, there has been little
accomplished, if anything at all, alleviating the need for such
thick and heavy airbag coatings from side curtain airbags.
[0010] Furthermore, there is a current drive to store such low
permeability side curtain airbags within very thin, preferably,
though not necessarily, cylindrically shaped modules. Since these
airbags are generally stored within the rooflines of automobiles,
and the area available is quite limited, there is always a great
need to restrict the packing volume of such restraint cushions to
their absolute minimum. However, the previously practiced low
permeability side curtain airbags have proven to be very cumbersome
to store in such cylindrically shaped containers at the target
automobile's roofline. The actual time and energy required to roll
such heavily coated low permeability articles as well as the
packing volume itself, has been very difficult to reduce.
Furthermore, with such heavy coatings utilized, the problems of
blocking (i.e., adhering together of the different coated portions
of the cushion) are amplified when such articles are so closely
packed together. The chances of delayed unrolling during inflation
are raised when the potential for blocking is present. Thus, a very
closely packed, low packing volume, low blocking side curtain low
permeability airbag is highly desirable. Unfortunately, the prior
art has again not accorded such an advancement to the airbag
industry.
OBJECTS AND BRIEF DESCRIPTION OF THE INVENTION
[0011] In light of the background above, it can be readily seen
that there exists a need for a low permeability, side curtain
airbag that utilizes lower, and thus less expensive, amounts of
coating, and therefore exhibits a substantially reduced packing
volume over the standard low permeability type side curtain
airbags. Such a coated low permeability airbag must provide a
necessarily long leak-down time upon inflation and after long-term
storage. Such a novel airbag and a novel coating formulation
provides marked improvements over the more expensive, much higher
add-on airbag coatings (and resultant airbag articles) utilized in
the past.
[0012] It is therefore an object of this invention to provide a
coated airbag, wherein the coating is present in a very low add-on
weight, possessing extremely high leak-down time characteristics
after inflation and thus complementary low permeability
characteristics. Another object of the invention is to provide an
inexpensive side curtain airbag cushion. A further object of this
invention is to provide an highly effective airbag coating
formulation which may be applied in very low add-on amounts to
obtain extremely low permeability airbag structures after
inflation. An additional object of this invention is to provide an
airbag coating formulation which not only provides beneficial and
long-term low permeability, but also exhibits excellent long-term
storage stability (through heat aging and humidity aging testing).
Yet another object of the invention is to provide a low
permeability side curtain airbag possessing a very low rolled
packing volume and non-blocking characteristics for effective
long-term storage within the roofline of an automobile.
[0013] Accordingly, this invention is directed to an airbag cushion
comprising a coated fabric, wherein said fabric is coated with an
elastomeric composition in an amount of at most 3.0 ounces per
square yard of the fabric; and wherein said airbag cushion, after
long-term storage, exhibits a characteristic leak-down time of at
least 5 seconds. Also, this invention concerns an airbag cushion
comprising a coated fabric, wherein said fabric is coated with an
elastomeric composition; wherein said elastomeric composition
comprises at least one elastomer possessing a tensile strength of
at least 2,000 psi and an elongation of at least 180%; and wherein
said airbag cushion, after long-term storage, exhibits a
characteristics leak-down time of at least 5 seconds. Additionally,
this invention encompasses a coated airbag cushion which exhibits a
packing volume factor (measured as the rolled diameter of the
airbag cushion divided by the measured depth of coverage measured
from the attachment point of the target automobile's roofline to
lowest point of coverage below the roofline after inflation) of at
most 0.05.
[0014] The term "characteristic leak-down time" is intended to
encompass the measurement of time required for the entire amount of
inflation gas introduced within an already-inflated (to a peak
initial pressure which "opens" up the areas of weak sealing) and
deflated airbag cushion upon subsequent re-inflation at a constant
pressure at 10 psi. It is well known and well understood within the
airbag art, and particularly concerning side curtain (low
permeability) airbag cushions, that retention of inflation gas for
long periods of time is of utmost importance during a collision
that results in rollover and other subsequent problems. Side
curtain airbags are designed to inflate as quickly as driver- and
passenger-side bags, but they must deflate very slowly to protect
the occupants during roll over and side impact. Thus, it is
imperative that the bag exhibit a very low leakage rate after the
bag experiences peak pressure during the instantaneous, quick
inflation. Hence, the coating on the bag must be strong enough to
withstand the shock and stresses when the bag is inflated so
quickly. Thus, a high characteristic leak-down time measurement is
paramount in order to retain the maximum amount of beneficial
cushioning gas within the inflated airbag. Airbag leakage after
inflation (and after peak pressure is reached) is therefore closely
related to actual pressure retention characteristics. The pressure
retention characteristics (hereinafter referred to as "leak-down
time") of already-inflated and deflated side curtain airbags can be
described by a characteristic leak-down time t, wherein: 1 t (
second ) = Bag volume ( ft 3 ) Volumetric leakage rate ( SCFH *) at
10 Psi .times. 3600
[0015] *SCFH: standard cubic feet per hour. It is understood that
the 10 psi constant is not a limitation to the invention; but
merely the constant pressure at which the leak-down time
measurements are made. Thus, even if the pressure is above or below
this amount during actual inflation or after initial pressurizing
of the airbag, the only limitation is that if one of ordinary skill
in the art were to measure the bag volume and divide that by the
volumetric leakage rate (at 10 psi), the resultant measurement in
time would be at least 5 seconds. Preferably, this time is greater
than about 9 seconds; more preferably, greater than about 15
seconds; and most preferably, greater than about 20 seconds.
[0016] Likewise, the term, "after long-term storage" encompasses
either the actual storage of an inventive airbag cushion within an
inflator assembly (module) within an automobile, and/or in a
storage facility awaiting installation. Furthermore, this term also
encompasses any storage which is intended to simulate such
long-term storage (through oven-aging, as one example) as well.
Such a measurement is generally accepted, and is well understood
and appreciated by the ordinarily skilled artisan, to be made
through comparable analysis after representative heat and humidity
aging tests. These tests generally involve 107.degree. C. oven
aging for 400 hours, followed by 83.degree. C. and 95% relative
humidity aging for a subsequent 400 hours and are universally
accepted as proper estimations of the conditions of long-term
storage for airbag cushions. Thus, this term encompasses such
measurement tests. The inventive airbag fabrics must exhibit proper
characteristic leak-down times after undergoing such rigorous
pseudo-storage testing.
[0017] The inventive elastomeric coating composition must comprise
at least one elastomer that possesses a tensile strength of at
least 2,000 psi and an elongation to break of greater than about
180%. Preferably, the tensile strength is at least 3,000 psi, more
preferably, 4,000, and most preferably at least about 6,000 (the
high end is basically the highest one can produce which can still
adhere to a fabric surface). The preferred elongation to break is
more than about 200%, more preferably more than about 300%, and
most preferably more than about 600%. These characteristics of the
elastomer translate to a coating that is both very strong (and thus
will withstand enormous pressures both at inflation and during the
time after inflation and will not easily break) and can stretch to
compensate for such large inflation, etc., pressures. Thus, when
applied at the seams of a side curtain airbag, as well as over the
rest of the airbag structure, the coating will most preferably
(though not necessarily) form a continuous film. This coating acts
to both fill the individual holes between the woven yarns and/or
stitches, etc., as well as to "cement" the individual yarns in
place. During inflation, then, the coating prevents leakage through
the interstitial spaces between the yarns and aids in preventing
yarn shifting (which may create larger spaces for possible gas
escape).
[0018] The utilization of such high tensile strength and high
elongation at break components permits the consequent utilization,
surprisingly, of extremely low add-on weight amounts of such
coating formulations. Normally, the required coatings on side
curtain airbags are very high, at least 3.0 ounces per square yard
(with the standard actually much higher than that, at about 4.0).
The inventive airbag cushions require at most 3.0 (preferably less,
such as 2.0, more preferably 1.8, still more preferably, about 1.5,
and most preferably, as low as 0.8) ounces per square yard of this
inventive coating to effectuate the desired high leak-down (low
permeability). Furthermore, the past coatings were required to
exhibit excellent heat and humidity aging stability. Unexpectedly,
even at such low add-on amounts, and particularly with historically
questionable coating materials (polyurethanes, for example), the
inventive coatings, and consequently, the inventive coated airbag
cushions, exhibit excellent heat aging and humidity aging
characteristics. Thus, the coating compositions and coated airbags
are clearly improvements within this specific airbag art.
[0019] Of particular interest as the elastomer components within
the inventive elastomeric compositions are, specifically,
polyamides, polyurethanes, acrylic elastomers, hydrogenated nitrile
rubbers (i.e., hydrogenated NBR), fluoroelastomers (i.e.,
fluoropolymers and copolymers containing fluoro-monomers),
ethylene-vinylacetate copolymers, and ethylene acrylate copolymers.
Also, such elastomers may or may not be cross-linked on the airbag
surface. Preferably, the elastomer is a polyurethane and most
preferably is a polycarbonate polyurethane elastomer. Such a
compound is available from Bayer Corporaiton under the tradename
Impranil.RTM., including Impranil.RTM. 85 UD, ELH, and EHC-01.
Other acceptable polyurethanes include Bayhydrol.RTM. 123, also
from Bayer; Ru 41-710, EX 51-550, and Ru 40-350, both from Stahl
USA. Any polyurethane, or elastomer, for that matter, which
exhibits the same tensile strength and elongation at break
characteristics as noted above, however, are potentially available
within the inventive coating formulation and thus on the inventive
coated airbag cushion. In order to provide the desired leak-down
times at long-term storage, however, the add-on weights of other
available elastomers may be greater than others. However, the upper
limit of 3.0 ounces per square yard should not be exceeded to meet
this invention. The desired elastomers may be added in multiple
layers if desired as long the required thickness for the overall
coating is not exceeded. Alternatively, the multiple layer coating
system may also be utilized as long as at least one elastomer
possessing the desired tensile strength and elongation at break is
utilized. In particular, such a coating system may include, as one
example, a polyurethane-based bottom layer (for good tensile
strength for low air permeability)(with an optional adhesion
promoter present between the layer and the fabric) and a second
layer of silicone (to provide excellent aging resistance, for
example). Other types of such multiple coating systems are
disclosed within grand-parent application Ser. No. 09/350,620,
above fully incorporated by reference.
[0020] Other possible components present within the elastomer
coating composition are thickeners, antioxidants, flame retardants,
coalescent agents, adhesion promoters, and colorants. In accordance
with the potentially preferred practices of the present invention,
a dispersion (either solvent- or water-borne, depending on the
selected elastomer) of finely divided elastomeric resin is
compounded, or present in a resin solution, with a thickener and a
flame retardant to yield a compounded mix having a viscosity of
about 8000 centipoise or greater. A polyurethane is potentially
preferred, with a polycarbonate polyurethane, such as those noted
above from Bayer and Stahl, most preferred. Other potential
elastomeric resins include other polyurethanes, such as
Witcobond.TM. 253 (35% solids), from Witco, and Sancure, from
BFGoodrich, Cleveland, Ohio; hydrogenated NBR, such as Chemisat.TM.
LCH-7335X (40% solids), from Goodyear Chemical, Akron, Ohio; EPDM,
such as EP-603A rubber latex, from Lord Corporation, Erie, Pa.;
butyl rubber, such as Butyl rubber latex BL-100, from Lord
Corporation; and acrylic rubber (elastomers), such as HyCar.TM.,
from BFGoodrich. This list should not be understood as being
all-inclusive, only exemplary of potential elastomers. Furthermore,
the preferred elastomer will not include any silicone, due to the
extremely low tensile strength (typically below about 1,500 psi)
characteristics exhibited by such materials. However, in order to
provide effective aging and non-blocking benefits, such components
may be applied to the elastomeric composition as a topcoat as long
as the add-on weight of the entire elastomer and topcoat does not
exceed 3.0 ounces per square yard and the amount of silicone within
the entire elastomer composition does not exceed 20% by weight.
Additionally, certain elastomers comprising polyester or polyether
segments or other similar components, may not be undesirable,
particularly at very low add-on weights (i.e., 0.8-1.2 oz/yd.sup.2)
due to stability problems in heat and humidity aging (polyesters
easily hydrolyze in humidity and polyethers easily oxidize in
heat); however, such elastomers may be utilized in higher add-on
amounts as long, again, as the 3.0 ounces per square yard is not
exceeded.
[0021] Among the other additives particularly preferred within this
elastomer composition are heat stabilizers, flame retardants,
primer adhesives, and materials for protective topcoats. A
potentially preferred thickener is marketed under the trade
designation NATROSOL.TM. 250 HHXR by the Aqualon division of
Hercules Corporation which is believed to have a place of business
at Wilmington, Del. In order to meet Federal Motor Vehicle Safety
Standard 302 flame retardant requirements for the automotive
industry, a flame retardant is also preferably added to the
compounded mix. One potentially preferred flame retardant is
AMSPERSE F/R 51 marketed by Amspec Chemical Corporation which is
believed to have a place of business at Gloucester City N.J. Primer
adhesives may be utilized to facilitate adhesion between the
surface of the target fabric and the elastomer itself. Thus,
although it is preferable for the elastomer to be the sole
component of the entire elastomer composition in contact with the
fabric surface, it is possible to utilize adhesion promoters, such
as isocyanates, epoxies, functional silanes, and other such resins
with adhesive properties, without deleteriously effecting the
ability of the elastomer to provide the desired low permeability
for the target airbag cushion. A topcoat component, as with
potential silicones, as noted above, may also be utilized to
effectuate proper non-blocking characteristics to the target airbag
cushion. Such a topcoat may perform various functions, including,
but not limited to, improving aging of the elastomer (such as with
silicone) or providing blocking resistance due to the adhesive
nature of the coating materials (most noticeably with the preferred
polyurethane polycarbonates).
[0022] Airbag fabrics must pass certain tests in order to be
utilized within restraint systems. One such test is called a
blocking test which indicates the force required to separate two
portions of coated fabric from one another after prolonged storage
in contact with each other (such as an airbag is stored).
Laboratory analysis for blocking entails pressing together coated
sides of two 2 inch by 2 inch swatches of airbag fabric at 5 psi at
100.degree. C. for 7 days. If the force required to pull the two
swatches apart after this time is greater than 50 grams, or the
time required to separate the fabrics utilizing a 50 gram weight
suspended from the bottom fabric layer is greater than 10 seconds,
the coating fails the blocking test. Clearly, the lower the
required separating shear force, the more favorable the coating.
For improved blocking resistance (and thus the reduced chance of
improper adhesion between the packed fabric portions), topcoat
components may be utilized, such as talc, silica, silicate clays,
and starch powders, as long as the add-on weight of the entire
elastomer composition (including the topcoat) does not exceed 3.0
ounces per square yard (and preferably exists at a much lower
level, about 1.5, for instance).
[0023] Two other tests which the specific coated airbag cushion
must pass are the oven (heat) aging and humidity aging tests. Such
tests also simulate the storage of an airbag fabric over a long
period of time upon exposure at high temperatures and at relatively
high humidities. These tests are actually used to analyze
alterations of various different fabric properties after such a
prolonged storage in a hot ventilated oven (>100.degree.C.)
(with or without humid conditions) for 2 or more weeks. For the
purposes of this invention, this test was used basically to analyze
the air permeability of the coated side curtain airbag by measuring
the characteristic leak-down time (as discussed above, in detail).
The initially produced and stored inventive airbag cushion should
exhibit a characteristic leak-down time of greater than about 5
seconds (upon re-inflation at 10 psi gas pressure after the bag had
previously been inflated to a peak pressure above about 15 psi and
allowed to fully deflate) under such harsh storage conditions.
Since polyurethanes, the preferred elastomers in this invention,
may be deleteriously affected by high heat and humidity (though not
as deleteriously as certain polyester and polyether-containing
elastomers), it may be prudent to add certain components within a
topcoat layer and/or within the elastomer itself. Antioxidants,
antidegradants, and metal deactivators may be utilized for this
purpose. Examples include, and are not intended to be limited to,
Irganox.RTM. 1010 and Irganox.RTM. 565, both available from CIBA
Specialty Chemicals. This topcoat may also provide additional
protection against aging and thus may include topcoat aging
improvement materials, such as, and not limited to, polyamides, NBR
rubbers, EPDM rubbers, and the like, as long as the elastomer
composition (including the topcoat) does not exceed the 3.0 ounces
per square yard (preferably much less than that, about 1.5 at the
most) of the add-on weight to the target fabric.
[0024] Other additives may be present within the elastomer
composition, including, and not limited to, colorants, UV
stabilizers, fillers, pigments, and crosslinking/curing agents, as
are well known within this art.
[0025] The substrate to which the inventive elastomeric coatings
are applied to form the airbag base fabric in accordance with the
present invention is preferably a woven fabric formed from yarns
comprising synthetic fibers, such as polyamides or polyesters. Such
yarn preferably has a linear density of about 105 denier to about
840 denier, more preferably from about 210 to about 630 denier.
Such yarns are preferably formed from multiple filaments wherein
the filaments have linear densities of about 6 denier per filaments
or less and most preferably about 4 denier per filament or less. In
the more preferred embodiment such substrate fabric will be formed
from fibers of nylon, and most preferred is nylon 6,6. It has been
found that such polyamide materials exhibit particularly good
adhesion and maintenance of resistance to hydrolysis when used in
combination with the coating according to the present invention.
Such substrate fabrics are preferably woven using fluid jet weaving
machines as disclosed in U.S. Pat. Nos. 5,503,197 and 5,421,378 to
Bower et al. (incorporated herein by reference). Such woven fabric
will be hereinafter referred to as an airbag base fabric. As noted
above, the inventive airbag must exhibit extremely low permeability
and thus must be what is termed a "side curtain" airbag. As noted
previously and extensively, such side curtain airbags (a.k.a.,
cushions) must retain a large amount of inflation gas during a
collision in order to accord proper long-duration cushioning
protection to passengers during rollover accidents. Any standard
side curtain airbag may be utilized in combination with the low
add-on coating to provide a product which exhibits the desired
leak-down times as noted above. Most side curtain airbags are
produced through labor-intensive sewing or stitching (or other
manner) together two separate woven fabric blanks to form an
inflatable structure. Furthermore, as is well understood by the
ordinarily skilled artisan, such sewing, etc., is performed in
strategic locations to form seams (connection points between fabric
layers) which in turn produce discrete open areas into which
inflation gasses may flow during inflation. Such open areas thus
produce pillowed structures within the final inflated airbag
cushion to provide more surface area during a collision, as well as
provide strength to the bag itself in order to withstand the very
high initial inflation pressures (and thus not explode during such
an inflation event). Other side curtain airbag cushions exist which
are of the one-piece woven variety. Basically, some inflatable
airbags are produced through the simultaneous weaving of two
separate layers of fabric which are joined together at certain
strategic locations (again, to form the desired pillowed
structures). Such cushions thus present seams of connection between
the two layers. It is the presence of so many seams (in both
multiple-piece and one-piece woven bags) which create the
aforementioned problems of gas loss during and after inflation. The
possibility of yarn shifting, particularly where the yarns shift in
and at many different ways and amounts, thus creates the quick
deflation of the bag through quick escaping of inflation gasses.
Thus, the base airbag fabrics do not provide much help in reducing
permeability (and correlated leak-down times, particularly at
relatively high pressures). It is this seam problem which has
primarily created the need for the utilization of very thick, and
thus expensive, coatings to provide necessarily low permeability in
the past.
[0026] Recently, a move has been made away from both the
multiple-piece side curtain airbags (which require great amounts of
labor-intensive sewing to attached woven fabric blanks) and the
traditionally produced one-piece woven cushions, to more specific
one-piece woven fabrics which exhibit substantially reduced floats
between woven yarns to substantially reduce the unbalanced shifting
of yarns upon inflation, such as in Ser. Nos. 09/406,264 and
09/668,857, both to Sollars, Jr., the specifications of which are
completely incorporated herein and described in greater depth
hereafter:
[0027] The term "inflatable fabric" hereinafter is intended to
encompass any fabric which is constructed of at least two layers of
fabric which can be attached and/or sealed to form a bag article.
The inventive inflatable fabric thus must include double layers of
fabric to permit such inflation, as well as single layers of fabric
either to act as a seal at the ends of such fabric panels, or to
provide "pillowed" chambers within the target fabric upon
inflation. The term "all-woven" as it pertains to the inventive
fabric thus requires that the inflatable fabric having double and
single layers of fabric be produced solely upon a loom. Any type of
loom may be utilized for this purpose, such as water-jet, air-jet,
rapier, and the like. Patterning may be performed utilizing
Jacquard weaving and/or dobby weaving, particularly on fluid-jet
and/or high speed rapier loom types.
[0028] The constructed fabric may exhibit balanced or unbalanced
pick/end counts; the main requirement in the woven construction is
that the single layer areas of the inflatable fabric exhibit solely
basket-weave patterns. These patterns are made through the
arrangement of at least one warp yarn (or weft yarn) configured
around the same side of two adjacent weft yarns (or warp yarns )
within the weave pattern. The resultant pattern appears as a
"basket" upon the arrangement of the same warp (or weft) yarn to
the opposite side of the next adjacent weft (or warp) yarn. Such
basket weave patterns may include the arrangement of a warp (or
weft) yarn around the same side of any even number of weft (or
warp) yarns, preferably up to about six at any one time, most
preferably up to about 4.
[0029] The sole utilization of such basket weave patterns in the
single layer zones provides a number of heretofore unexplored
benefits within inflatable fabric structures. For example, such
basket weave patterns permit a constant "seam" width and weave
construction over an entire single layer area, even where the area
is curved. As noted above, the standard Oxford weaves currently
utilized cannot remain as the same weave pattern around curved
seams; they become plain weave patterns. Also, such basket weave
seam patterns permit the construction of an inflatable fabric
having only plain woven double layer fabric areas and single layer
"seams" with no "floats" of greater than three picks within the
entire fabric structure. Such a fabric would thus not possess
discrete locations where the air permeability is substantially
greater than the remaining portions of the fabric. Additionally,
such a weave structure permits the utilization of as low as two
different weave densities (patterns, etc.) in the area of the
produced seam. Thus, the seam itself is of one weave pattern and
the weave pattern in the area directly adjacent to the seam is
another weave pattern. No other patterns are utilized in that
specific seam area. By directly adjacent, it is intended that such
a described area is within at most 14 yarn-widths, preferably as
low as 2 yarn-widths, and most preferably between about 4 and 8
yarn-widths, from the actual seam itself. Such a limitation on
different weave densities has never been accomplished in all-woven
airbags in the past.
[0030] Generally, the prior art (such as Thornton et al., supra)
provides seam attachments exhibited at least three different weave
densities within the directly adjacent area of the seams
themselves. Furthermore, the prior art weaving procedures produce
floats of sometimes as much as six or seven picks at a time.
Although available software to the weaving industry permits
"filling in" of such floats within weave diagrams, such a procedure
takes time and still does not continuously provide a fabric
exhibiting substantially balanced air permeability characteristics
over the entire structure. The basket-weave formations within the
single fabric layers thus must be positioned in the fabric so as to
prevent irregularities (large numbers of floats, for example) in
the weave construction at the interface between the single and
double fabric layers (as described in FIG. 2, below). Another
benefit such basket weave patterns accord the user is the ability
to produce more than one area of single layer fabric (i.e., another
"seam" within the fabric) adjacent to the first "seam." Such a
second seam provides a manner of dissipating the pressure from or
transferring the load upon each individual yarn within both seams.
Such a benefit thus reduces the chances of deleterious yarn
shifting during an inflation event through the utilization of
strictly a woven fabric construction (i.e., not necessarily relying
upon the utilization of a coating as well). The previously
disclosed or utilized inflatable fabrics having both double and
single fabric layer areas have not explored such a possibility in
utilizing two basket-weave pattern seams. Furthermore, such a
two-seam construction eliminates the need for weaving a large
single fabric layer area within the target inflatable fabric. The
prior art fabrics which produce "pillowed" chambers for airbag
cushions (such as side curtains), have been formed through the
weaving of entire areas of single fabric layers (which are not
actually seams themselves). Such a procedure is time-consuming and
rather difficult to perform. The inventive inflatable fabric merely
requires, within this alternative embodiment, at least two very
narrow single fabric layer areas (seams) woven into the fabric
structure (another preferred embodiment utilizes merely one seam of
single layer fabric); the remainder of the fabric located within
these two areas may be double layer if desired. Thus, the inventive
fabric permits an improved, cost-effective, method of making a
"pillowed" inflatable fabric.
[0031] The inflatable fabric itself, as noted above, is preferably
produced from all-synthetic fibers, such as polyesters and
polyamides, although natural fibers may also be utilized in certain
circumstances. Preferably, the fabric is constructed of nylon-6,6,
however, polyesters are also highly preferred. Mixtures of such
fibers are also possible. The individual yarns utilized within the
fabric substrate must generally possess deniers within the range of
from about 40 to about 840; preferably from about 100 to about 630.
Most preferably, such deniers average over the entire airbag fabric
structure at most 525; more preferably average at most 420; and
also preferably average 315 and even as low as 210, if desired. In
such instances of such low average deniers (420 and below), the
thickness of the fabric structure itself is quite low and thus,
with the inventive coating applied at low add-on levels, exhibits
excellent low packing volumes.
[0032] As noted above, coatings should be applied to the surface as
a necessary supplement to reduce the air permeability of the
inventive fabric. Since one preferred ultimate use of this
inventive fabric is as a side curtain airbag which must maintain a
very low degree of air permeability throughout a collision event
(such as a rollover where the curtain must protect passengers for
an appreciable amount of time), a decrease in permitted air
permeability is highly desirable. With such a specific weaving
pattern within the inventive inflatable fabric, lower amounts of
coatings are permissible (as compared to other standard additions
of such materials) to provide desired low inflation gas
permeability. Any standard coating or laminate film, such as a
silicone, polyurethane, polyamide, polyester, rubber (such as
neoprene, for example), and the like, as discussed above, may be
utilized for this purpose and may be applied in any standard method
and in any standard amount on the fabric surface. However, the
necessary amount of such a coating (or layers of coatings or
laminate film or layer of laminate films) required to provide the
desired low permeability is extremely low and is discussed in
greater depth above. Again, the particular weave structures of the
inventive inflatable fabric permits the utilization of such low
coating amounts to provide the desired low permeability
characterstics.
[0033] Additional objects and advantages of the invention will be
set forth in part in the description which follows, and in part
will be obvious from the description, or may be learned by practice
for the invention. It is to be understood that both the foregoing
general description and the following detailed description of
preferred embodiments are exemplary and explanatory only, and are
not to be viewed as in any way restricting the scope of the
invention as set forth in the claims.
[0034] With such an improvement in one-piece side curtain airbags
(and inflatable fabrics), the possibility of high leakage at seams
is substantially reduced. These airbags provide balanced weave
constructions at and around attachment points between two layers of
fabrics such that the ability of the yarns to become displaced upon
inflation at high pressures is reduced as compared with the
standard one-piece woven airbags. Unfortunately, such inventive
one-piece woven bags are still problematic in that the weave
intersections may be displaced upon high pressure inflation such
that leakage will still most likely occur at too high a rate for
proper functioning. As a result, there is still a need to coat such
one-piece woven structures with materials which reduce and/or
eliminate such an effect. However, such one-piece woven structures
permit extremely low add-on amounts of elastomeric coatings for low
permeability effects. In fact, these inventive airbags function
extremely well with low add-on coatings below 1.5 and as low as
about 0.8 ounces per square yard.
[0035] Furthermore, although it is not preferred in this invention,
it has been found that the inventive coating composition provides
similar low permeability benefits to standard one-piece woven
airbags, particularly with the inventive low add-on amounts of high
tensile strength, high elongation, non-silicone coatings; however,
the amount of coating required to permit high leak-down times is
much higher than for the aforementioned Sollars, Jr. inventive
one-piece woven structure. Thus, add-on amounts of as much as 1.5
and even up to about 2.2 ounces per square yard may be necessary to
effectuate the proper low level of air permeability for these other
one-piece woven airbags. Even with such higher add-on coatings, the
inventive coatings themselves clearly provide a marked improvement
over the standard, commercial, prior art silicone, etc., coatings
(which must be present in amounts of at least 3.0 ounces per square
yard).
[0036] Additionally, it has also been found that the inventive
coating compositions, at the inventive add-on amounts, etc.,
provide the same types of benefits with the aforementioned sewn,
stitched, etc., side curtain airbags. Although such structures are
highly undesirable due to the high potential for leakage at these
attachment seams, it has been found that the inventive coating
provides a substantial reduction in permeability (to acceptable
leak-down time levels, in fact) with correlative lower add-on
amounts than with standard siliconeand neoprene rubber coating
formulations. Such add-on amounts will approach the 3.0 ounces per
square yard, but lower amounts have proven effective (1.5 ounces
per square yard, for example) depending on the utilization of a
sufficiently high tensile strength and sufficiently stretchable
elastomeric component within the coating composition directly in
contact with the target fabric surface. Again, with the ability to
reduce the amount of coating materials (which are generally always
quite expensive), while simultaneously providing a substantial
reduction in permeability to the target airbag structure, as well
as high resistance to humidity and extremely effective aging
stability, the inventive coating composition, and the inventive
coated airbag itself is clearly a vast improvement over the prior
airbag coating art.
[0037] Of particular importance within this invention, is the
ability to pack the coated airbag cushions within storage
containers at the roof line of a target automobile in as small a
volume as possible, such as within cylindrically or polygonally
shaped modules. In a rolled, accordion-style, Z-folded (or any
other) configuration (in order to best fit within the storage
module itself, and thus in order to best inflate upon a collision
event downward to accord the passengers sufficient protection), the
inventive airbag may be constricted to a stored shape of as low
volume as possible. It has been found that the best, though not the
only, test of determining the effective low volume exhibited by a
non-inflated side curtain airbag is to roll any bag lengthwise
until it is substantially cylindrical in shape. In such a shape, it
is preferable that the target side curtain airbag have a diameter
of at most 23 millimeters. The term "diameter" is intended to
encompass any cross-section of the inflatable fabric in its rolled
storage configuration such that the length of the stored fabric is
the same as the length of the inflated fabric, and measuring the
greatest distance between opposite points on such a cross-sectional
area. It should and would be well understood by one of ordinary
skill in this particular art that the actual side curtain measured
does not have to be stored in such a specific rolled manner in
practice, only that, in order to assess the rolled packing volume
in terms of diameter compared with depth, the target side curtain
should be first laid flat and then rolled into a substantially
cylindrical shape with the subsequent measurement of diameter then
taken.
[0038] Thus, in one non-limiting example, a 2 meter long
cylindrical roofline storage container, the necessary volume of
such a container would equal about 830 cm.sup.3.(with the volume
calculated as 2[Pi]radius.sup.2) Standard rolled packing diameters
are at least 25 millimeters for commercially available side curtain
airbag cushions (due to the thickness of the required coating to
provide low permeability characteristics). Thus, the required
cylindrical container volume would be at least 980 cm.sup.3.
Preferably, the rolled diameter of the inventive airbag cushion
during storage is at most 20 millimeters (giving a packed volume of
about 628 cm.sup.3) (and up to 23 millimeters and as low as
possible, for example, about 16 millimeters) which is clearly well
below the standard packing volume. Of course, the ability to
provide very low packing volumes in directly related to the
thickness of coating applied to the airbag itself, as well as,
possibly, the denier fibers utilized to produce the bag itself. The
lower the denier, the thinner the bag construction, and thus, the
potential for lower packing volumes. In relation, then, to the
depth of the airbag cushion upon inflation (i.e., the length the
airbag extends from the roofline down to its lowest point along the
side of the target automobile, such as at the windows), a packing
volume equal to the quotient of the particular bag's packed
diameter (again in its rolled state although any other packing
configuration, such as "accordion-style," "Z-fold", and the like,
may be utilized as well as rolling in actual practice) divided by
inventive airbag cushion's depth (which is often, though not
required to be measured, at approximately 17 inches or 431.8
millimeters) should be at most 0.05. Preferably this factor should
be at most 0.486 (21 millimeter diameter), more preferably at most
about 0.0463 (20 millimeters) or 0.044 (19 mm), or 0.0417 (18 mm),
or 0.0394 (17 millimeters). Most preferably, the denier fibers
utilized are about 420 on average and thus with a coating add-on
amount of about 0.8 ounces/square yard provides a packing diameter
of about 18 millimeters (and thus a packing volume factor of about
0.0417).
[0039] The prior art, having extremely thick coatings with
relatively high denier fibers (420 and higher) provides, at best, a
packing diameter of about 24 millimeters which thus provides (with
a coating in excess of 4.0 ounces per square yard, generally) a
packing volume factor of about 0.0556, well above the 0.05 limit
taught above. As discussed above, with lower average denier fibers
utilized within the subject side curtain airbag, the packing volume
may be reduced. Such as within the scope of this invention as the
primary, though not only, aim of reducing such packing volume is to
provide an highly effective (i.e., very low permeability), low
add-on coating to the target side curtain airbag. Of course, the
aforementioned range of factors does not require the airbag depth
to be at a standard of 17 inches, and is primarily a function of
coating thickness, and thus add-on weight, as well as yarn denier.
As should be evident, however, longer (deeper) bags would require
greater diameters in packing within a cylindrical storage
capsule.
[0040] Surprisingly, it has been discovered that any elastomer with
a tensile strength of at least 2,000 psi and an elongation at break
of at least 180% coated onto and over both sides of a side curtain
airbag fabric surface at a weight of at most 3.0 ounces per square
yard, and preferably between 0.8 and 2.0, more preferably from 0.8
to about 1.5, still more preferably from 0.8 to about 1.2, and most
preferably about 0.8 ounces per square yard, provides a coated
airbag cushion which passes both the long-term blocking test and
long-term oven aging test with very low, and extended permeability
upon and after inflation. This unexpectedly beneficial type and
amount of coating thus provides an airbag cushion which will easily
inflate after prolonged storage and will remain inflated for a
sufficient amount of time to ensure an optimum level of safety
within a restraint system. Furthermore, it goes without saying that
the less coating composition required, the less expensive the final
product. Additionally, the less coating composition required will
translate into a decrease in the packaging volume of the airbag
fabric within an airbag device. This benefit thus improves the
packability for the airbag fabric.
[0041] While the invention will be described and disclosed in
connection with certain preferred embodiments and practices, it is
in no way intended to limit the invention to those specific
embodiments, rather it is intended to cover equivalent structures
structural equivalents and all alternative embodiments and
modifications as may be defined by the scope of the appended claims
and equivalence thereto.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] Two potentially preferred elastomer compositions of this
invention was preferably produced in accordance with the following
Tables:
1TABLE 1 Standard Water-Borne Elastomer Composition Component Parts
(per entire composition) Resin (30-40% solids content in water) 100
Natrosol .RTM. 250 HHXR (thickener) 10 Irganox .RTM. 1010
(stabilizer) 0.5 DE-83 R (flame retardant) 10
[0043]
2TABLE 2 Standard Solvent-Borne Elastomer Composition Component
Parts (per entire composition) Resin (30-40% solids content in
solvent) 100 Irganox .RTM. 1010 (stabilizer) 0.5 DE-83 R (flame
retardant) 10
[0044]
3TABLE 3 Standard Solvent-Borne Elastomer Composition Component
Parts (per entire composition) Resin (25-40% solids content in
solvent) 100 Irganox .RTM. 1010 (stabilizer) 0.5 DE-83 R (flame
retardant) 10 Desmodur CB-75 (adhesion promoter) 2
[0045] (The particular resins are listed below in Table 4 and thus
are merely added within this standard composition in the amount
listed to form preferred embodiments of the inventive coating
formulation).
[0046] The compounded compositions exhibited viscosities measured
to be about 15,000 centipoise by a Brookfield viscometer. Once
compounding was complete, the individual formulations were applied
to separate articles being both sides of one-piece Jacquard woven
airbags (having 420 denier nylon 6,6 yarns therein) as discussed
within the Sollars, Jr. application noted above. Such applications
were performed through a fixed gap coating procedure. The bag was
then dried at an elevated temperature (about 300.degree. F. for
about 3 minutes) and thus form to form the necessarily thin
coatings. As noted above, scrape coating may also be followed to
provide the desired film coating; however, fixed gap coating
provides the desired film thickness uniformity on the bag surface
and thus is preferred. Scrape coating, in this sense, includes, and
is not limited to, knife coating, in particular knife-over-gap
table, floating knife, and knife-over-foam pad methods. The final
dry weight of the coating is preferably from about 0.6-3.0 ounces
per square yard or less and most preferably 0.8-1.5 ounces per
square yard or less. The resultant airbag cushion is substantially
impermeable to air when measured according to ASTM Test D737, "Air
Permeability of Textile Fabrics," standards.
[0047] In order to further describe the present invention the
following non-limiting examples are set forth. These examples are
provided for the sole purpose of illustrating some preferred
embodiments of the invention and are not to be construed as
limiting the scope of the invention in any manner. These examples
involve the incorporation of the below-noted preferred elastomers
within the coating formulations of TABLES 1-3, above.
[0048] Each coated bag was first subjected to quick inflation to a
peak pressure of 30 Psi. Air leakage (SCFH) of the inflated bag was
then measured at 10 Psi pressure. The characteristic leak-down time
t(sec) was calculated based on the leakage rate and bag volume.
4TABLE 4 Tensile Elonga- T (sec). T (sec.) Coating add- Example
Number/ Strength tion at Before Post- on weight Elastomer (Psi)
break (%) aging aging* (oz/yd2) 1. Impranil .RTM. 85 6000 400 18.1
16.3 0.8 UD 2. Ex 51-550 3100 320 110.2 105 0.8 3. Impranil .RTM.
7200 300 120.2 125 0.9 ELH 4. Ru .RTM. 41-710 7000 600 27.3 26.4
0.8 5. Ru .RTM. 40-350 7000 500 34.4 36.2 0.8 6. Bayhydrol .RTM.
6000 300 8.6 5.7 0.8 123 7. Dow Corning 700 90 <2 <2 2.1
3625** 8. Silastic 94- 1400 580 <2 <2 1.8 595-HC** 9. Ru
.RTM. 40-415 5000 180 <2 <2 0.8 10. Sancure .RTM. 3000 580
25.2 <2 0.8 861 11. Witcobond .RTM. 6000 600 28.4 <2 0.8 290H
*Aging conditions: 107.degree. C. oven aging for 16 days, followed
by 83.degree. C. and 95% relative humidity aging for 16 days. **The
resins are silicone rubbers.
[0049] As noted above, Examples 1-6 work extremely well and are
thus within the scope of this invention. Examples 10 and 11 show
some limitations, polyester based elastomers (Witcobond.RTM. 290H)
exhibit excellent heat aging (oxidation) stability but tend to
hydrolyze easily at high humidity; polyether based elastomers
(Sancure.RTM. 861) have excellent hydrolysis resistance, but poor
oxidation performance. However, these elastomers have proven to be
acceptable permeability reducers at higher add-on weights below the
maximum of 3.0 ounces per square yard. Furthermore, although
silicones show excellent resistance to heat aging and hydrolysis
(humidity aging), they, however, possess limited tensile strength
and tear resistance resistance. Natural rubber, SBR, chloroprene
rubbers and others containing unsaturated carbon double bonds have
excellent hydrolysis resistance. But the unsaturated carbon double
bond that gives their elasticity oxidizes readily and the
properties of the rubber change after heat aging. Elastomers that
have good physical properties and excellent resistance to
hydrolysis and oxidation are preferred for this application.
Polyurethanes based on polycarbonate soft segments are the
preferred materials for this application.
[0050] The airbag of Example 3 exhibited a sliding coefficient of
friction constant of roughly 0.6. A comparative thick
silicone-coated side curtain airbag which included a non-woven
layer, exhibited a constant of about 0.8.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a cross-sectional view of an inventive all-woven
inflatable fabric showing the preferred double and single layer
areas including two separate single layer areas.
[0052] FIG. 2 is a weave diagram illustrating a potentially
preferred repeating pick pattern formed using repeating plain weave
and basket weave four-pick arrangements.
[0053] FIG. 3 depicts the side, inside view of a vehicle prior to
deployment of the inventive side curtain airbag.
[0054] FIG. 4 depicts the side, inside view of a vehicle after
deployment of the inventive side curtain airbag.
[0055] FIG. 5 depicts a side view of a side curtain airbag.
[0056] FIG. 6 provides a side view of a side curtain airbag
container.
[0057] FIG. 7 provides a cross-sectional perspective of the stored
airbag within the container of FIG. 6.
DETAILED DESCRIPTION OF THE DRAWINGS
[0058] Turning now to the drawings, in FIG. 1 there is shown a
cross-section of a preferred structure for the double fabric layers
12, 14, 18, 20, 24, 26 and single fabric layers 16, 22 of the
inventive inflatable fabric 10. Weft yarns 28 (exhibiting
preferably deniers of about 420 each) are present in each of these
fabric layer areas 12, 14, 16, 18, 20, 22, 24, 26 over and under
which individual warp yarns 38, 40, 42, 44 (also exhibiting deniers
preferably of about 420) have been woven. The double fabric layers
12, 14, 18, 20, 24, 26 are woven in plain weave patterns. The
single fabric layers 16, 22 are woven in basket weave patterns.
Four weft yarns each are configured through each repeating basket
weave pattern within this preferred structure; however, anywhere
from two to twelve weft yarns may be utilized within these single
fabric layer areas (seams) 16, 22. The intermediate double fabric
layer areas 18, 20 comprise each only four weft yarns 28 within
plain weave patterns. The number of such intermediate weft yarns 28
between the single fabric layer areas 16, 22 must be in multiples
of two to provide the maximum pressure bearing benefits within the
two seams 16, 22 and thus the lowest possibility of yarn shifting
during inflation at the interfaces of the seams 16, 22 with the
double fabric layer areas 12, 14, 24, 26.
[0059] FIG. 2 shows the weave diagram 30 for an inventive fabric
which comprises two irregularly shapes concentric circles as the
seams. Such a diagram also provides a general explanation as to the
necessary selection criteria of placement of basket-weave patterns
within the fabric itself. Three different types of patterns are
noted on the diagram by different shades. The first 32 indicates
the repeated plain weave pattern throughout the double fabric
layers (12, 14, 18, 20, 24, 26 of FIG. 1, for example) which must
always initiate at a location in the warp direction of 4X +1, with
X representing the number of pick arrangement within the diagram,
and at a location in the fill direction of 4X+1 (thus, the pick
arrangement including the specific two-layer
plain-weave-signifying-block 32 begins at the block four spaces
below it in both directions). The second 34 indicates an "up-down"
basket weave pattern wherein an empty block must exist and always
initiate the basket-weave pattern at a location in the warp
direction of 4X+1, with X representing the number of repeating pick
arrangements within the diagram, and at a location in the fill
direction of 4X+1, when a seam (such as 16 and 22 in FIG. 1) is
desired (thus, the pattern including the pertinent signifying
"up-down" block 34 includes an empty block within the basket-weave
pick arrangement in both the warp and fill directions four spaces
below it). The remaining pattern, which is basically a "down-up"
basket weave pattern to a single fabric layer (such as 16 and 22 in
FIG. 1) is indicated by a specifically shaded block 36. Such a
pattern must always initiate at a location in the warp direction of
4X+1 and fill of 4X+3, or warp of 4X+3 and fill of 4X+1, when a
seam is desired. Such a specific arrangement of differing "up-down"
basket weave 34 and "down-up" basket weave 36 pattern is necessary
to effectuate the continuous and repeated weave construction
wherein no more than three floats (i.e., empty blocks) are present
simultaneously within the target fabric structure. Furthermore,
again, it is believed that there has been no such disclosure or
exploration of such a concept within the inflatable fabric art.
[0060] As depicted in FIG. 3, an interior of a vehicle 110 prior to
inflation of a side curtain airbag (not illustrated) is shown. The
vehicle 110 includes a front seat 112 and a back seat 114, a front
side window 116 and a back-side window 118, a roofline 120, within
which is stored a cylindrically shaped container 122 comprising the
inventive side curtain airbag (not illustrated). Also present
within the roofline 120 is an inflator assembly 124 which ignites
and forces gas into the side curtain airbag (126 of FIG. 4) upon a
collision event.
[0061] FIG. 4 shows the inflated side curtain airbag 126. As noted
above, the airbag 126 is coated with at most 2.5 ounces per square
of a coating formulation (not illustrated), preferably polyurethane
polycarbonate. The inventive airbag 126 will remain sufficiently
inflated for at least 5 seconds, and preferably more, as high as at
least 20 seconds, most preferably.
[0062] FIG. 5 shows the side curtain airbag 126 prior to storage in
its uninflated state within the roofline cylindrically shaped
container 122. The thickness of the airbag 126, measured as the
packing diameter (as in FIG. 7, below) as compared with the depth
of the airbag measured from the roofline cylindrically shaped
container 122 to the bottom most point 128 of the airbag 126 either
in its uninflated or inflated state at most 0.05. Larger factors
are possible with higher add-on coating weights and larger yarns.
Smaller yarns may be utilized with lower or larger add-on coating
weights as well which meet this limitation as well.
[0063] FIGS. 6 and 7 aid in understanding this concept through the
viewing of the rolled airbag 126 as stored within the container 122
along line 2. The diameter measurement of the airbag 126 of Example
3, above, is roughly 20 millimeters. The standard depth of side
curtain airbags is roughly 17 inches, or about 431.8 millimeters.
Thus, the preferred packing volume factor is about 0.046 (20
mm/431.8 mm). A comparative silicone-based thick coating add-on
weight of about 4.0 ounces per square yard provided a diameter of
about 25 millimeters for a factor of about 0.0579 (25 mm/431.8
mm).
[0064] There are, of course, many alternative embodiments and
modifications of the present invention which are intended to be
included within the spirit and scope of the following claims. In
particular, it is to be understood that any side curtain airbag of
any production method and structure which exhibits low permeability
measurements with very low coating add-on amounts, and specifically
meets the packing volume (be it as a rolled fabric, or packed
accordion-style, or other packed configuration) limitations noted
above is within the scope of this invention.
* * * * *