U.S. patent application number 09/767250 was filed with the patent office on 2001-07-26 for low permeability airbag cushionshaving film coatings of extremely low thickness.
Invention is credited to Li, Shulong, Sollars, John A. JR..
Application Number | 20010009829 09/767250 |
Document ID | / |
Family ID | 25078936 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009829 |
Kind Code |
A1 |
Sollars, John A. JR. ; et
al. |
July 26, 2001 |
Low permeability airbag cushionshaving film coatings of extremely
low thickness
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 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 comprises a film laminated on at
least a portion of the target fabric surface wherein the film
possesses a tensile strength of at least 2,000 and an elongation at
break of at least 180%. The film provides a low permeability airbag
cushion exhibiting a leak-down time of at least 5 seconds as well
as a very low packing volume (for more efficient use of storage
space within a vehicle) for the target side curtain airbag.
Inventors: |
Sollars, John A. JR.;
(LaGrange, GA) ; Li, Shulong; (Spartanburg,
SC) |
Correspondence
Address: |
Milliken & Company
P. O. Box 1926
Spartanburg
SC
29304
US
|
Family ID: |
25078936 |
Appl. No.: |
09/767250 |
Filed: |
January 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09767250 |
Jan 22, 2001 |
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09557643 |
Apr 25, 2000 |
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09557643 |
Apr 25, 2000 |
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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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09767250 |
Jan 22, 2001 |
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09406264 |
Sep 24, 1999 |
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6220309 |
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Current U.S.
Class: |
442/76 ; 442/182;
442/218; 442/242 |
Current CPC
Class: |
B60R 2021/23514
20130101; D03D 1/02 20130101; B32B 27/12 20130101; B60R 21/235
20130101; Y10T 442/3545 20150401; Y10T 442/2049 20150401; B60R
21/232 20130101; Y10T 428/1307 20150115; B32B 27/02 20130101; Y10T
442/3008 20150401; Y10T 442/3553 20150401; D06N 3/186 20130101;
D06N 3/183 20130101; Y10T 442/3472 20150401; Y10T 442/3301
20150401; Y10T 428/1362 20150115; Y10T 442/3496 20150401; Y10T
428/13 20150115; D03D 11/02 20130101; Y10T 442/2139 20150401; Y10T
442/3561 20150401 |
Class at
Publication: |
442/76 ; 442/182;
442/218; 442/242 |
International
Class: |
B32B 005/18; B32B
005/22 |
Claims
What is claimed is:
1. A side curtain airbag exhibiting a packing volume factor of at
most 0.05 to at least a portion of the surface of which a laminate
film has been applied; wherein said side curtain airbag exhibits a
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 side curtain airbag exhibiting a packing volume factor of at
most 0.05 to at least a portion of the surface of which a laminate
film has been applied; wherein said side curtain airbag exhibits a
leak-down time after inflation of at least 5 seconds; and wherein
said side curtain airbag 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 a side curtain airbag does not exhibit more than
three consecutive unfilled blocks in any row or column.
6. The airbag of claim 5 wherein said laminate film comprises
polyurethane.
7. The airbag of claim 5 wherein said airbag fabric layers are
woven and comprise polyamide yarns.
8. The airbag of claim 5 wherein said airbag is a one-piece woven
side curtain airbag.
9. The airbag of claim 7 wherein said polyamide yams are formed
from nylon 6,6 fiber.
10. The airbag of claim 9, wherein said polyamide yarns are
multifilament yarns characterized by a average linear density of
between about 210 and 630 denier.
11. The airbag of claim 10, wherein wherein said multifilament
yarns are characterized by a filament linear density of about 4
denier per filament or less.
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 side curtain airbag exhibiting a packing volume factor of at
most 0.05 to at least a portion of the surface of which a laminate
film has been applied; wherein said coated side curtain airbag
exhibits a leak-down time after inflation of at least 5 seconds;
and wherein said airbag 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 airbag, 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 laminate film comprises
polyurethane.
19. The airbag of claim 17 wherein said airbag fabric layers are
woven and comprise polyamide yams.
20. The airbag of claim 17 wherein said airbag is a one-piece woven
side curtain airbag.
21. The airbag of claim 19 wherein said polyamide yams are formed
from nylon 6,6 fiber.
22. The airbag of claim 21, wherein said polyamide yams are
multifilament yams characterized by an average linear density of
between about 210 and 630 denier.
23. The airbag of claim 22, wherein wherein said multifilament yams
are characterized by a filament linear density of about 4 denier
per filament or less.
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 0.05 to at least a portion of the surface of which a
laminate film has been applied; wherein said coated side curtain
airbag exhibits a leak-down time after inflation of at least 5
seconds; and wherein said airbag comprises at least two layers of
fabric in certain discrete areas of the airbag 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
airbag, 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 yams in length.
30. The airbag of claim 29 wherein said laminate film comprises
polyurethane.
31. The airbag of claim 29 wherein said airbag fabric layers are
woven and comprise polyamide yams.
32. The airbag of claim 29 wherein said airbag is a one-piece woven
side curtain airbag.
33. The airbag of claim 31 wherein said polyamide yams are formed
from nylon 6,6 fiber.
34. The airbag of claim 33, wherein said polyamide yams are
multifilament yams characterized by an average linear density of
between about 210 and 630 denier.
35. The airbag of claim 34, wherein wherein said multifilament yams
are characterized by a filament linear density of about 4 denier
per filament or less.
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-in-part of co-pending
application Ser. No. 09/557,643, filed on Apr. 25, 2000, which is a
continuation-in-part of co-pending application Ser. No. 09/501,467,
filed on 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 applications are
herein entirely incorporated by reference.
FIELD OF THE INVENTION
[0002] 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 comprises a film laminated on at least a portion
of the target fabric surface wherein the film possesses a tensile
strength of at least 2,000 and an elongation at break of at least
180%. The film provides a low permeability airbag cushion
exhibiting a leak-down time of at least 5 seconds wherein the film
is present on the surface in an amount of at most 3.0 ounces per
square yard of the fabric.
BACKGROUND OF THE PRIOR ART
[0003] 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 yam by
weaving practices that are well known in the art.
[0004] The coated material has found acceptance because it acts as
an impermeable barrier to the inflation medium. This inflation
medium is generally a nitrogen 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 hot gas, thereby permitting the cushion to rapidly
inflate without undue decompression during a collision event.
[0005] 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. No. 4,921,735; U.S. Pat. No.
4,977,016; and U.S. Pat. No. 5,073,418 (all incorporated herein by
reference).
[0006] 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 and elongation at break characteristics which do
not withstand high pressure inflation easily without the
utilization of very thick coatings.
[0007] The use of certain polyurethanes as coatings 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 not be coated. 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.
[0008] 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 rollover crashes by
retaining its 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, humidity, 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.
[0009] Furthermore, there is a current drive to store such low
permeability side curtain airbags within 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
[0010] 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 high 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.
[0011] 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.
[0012] Accordingly, this invention is directed to an airbag cushion
comprising a coated fabric, wherein said fabric is laminated with a
film, wherein said film is present 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 a laminate film; wherein said laminate film
possesses a tensile strength of at least 2,000 and an elongation of
at least 180%; and wherein said airbag cushion, after long-term
storage, exhibits a characteristic leak-down time of at least 5
seconds. Additionally, this invention encompasses a coated airbag
cushion which exhibits a rolled packing volume factor (measured as
the quotient of the rolled diameter of the airbag cushion to 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 multiplied by the square root of the
yarn diameter for the particular denier yarns constituting the
airbag itself) of at most 1.20.
[0013] 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.
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 exhibits 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 rate 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 rate t, wherein: 1 t (
second ) = Bag volume ( ft 3 ) Volumetric leakage rate ( SCFH * )
at 10 Psi .times. 3600 * SCFH : standard cubic feet per hour .
[0014] 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 rate 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 (measured by
the amount leaking out of the target airbag during steady state
inflation 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.
[0015] Alternatively, and in a manner of measurement with
uninflated side curtain airbags, the term "leak-down time" may be
measured as the amount of time required for at half of the
introduced inflation gas to escape from the target airbag after
initial peak pressure is reached. Thus, this measurement begins the
instant after peak initial pressure is reached upon inflation (such
as, traditionally, about 30 psi) with a standard inflation module
which continues to pump gas into the target airbag during and after
peak initial pressure is reached. It is well understood that the
pressure of gas forced into the airbag after peak initial pressure
is reached will not remain stable (it decreases during the
subsequent introduction of inflation gas), and that the target
airbag will inevitably permit escape of a certain amount of
inflation gas during that time. The primary focus of such side
curtain airbags (as noted above) is to remain inflated for as long
as possible in order to provide sufficient cushioning protection to
vehicle occupants during rollover accidents. The greater amount of
gas retained, the better cushioning effects are provided the
passengers. Thus, the longer the airbag retains a large amount of
inflation gas, and consequently the greater the characteristic
leak-down time, the better cushioning results are achieved. At the
very least, the inventive airbag must retain at least half of its
inflated gas volume 5 seconds subsequent to reaching peak initial
pressure. Preferably, this time is 9 seconds, more preferably 15
seconds, and most preferably 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. 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 16 days, followed
by 83.degree. C. and 95% relative humidity aging for 16 days 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 coating, here a film, must possess 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, 6,000, and most preferably at
least about 8,000 (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 film 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. The film itself is produced prior to actual
contact with the target airbag cushion, or fabric, surface. In
order to apply such a film, a lamination procedure must be
performed through the simultaneous exposure of heat and pressure
over the film while in contact with the target surface. The
laminate may be applied over any portion of the target structure,
although preferably it coats the entire cushion or fabric. Also,
more than one laminated film may be present on the target cushion
as one type of film (possessing certain tensile strength and
elongation characteristics) may be preferably applied to certain
discrete areas of the target cushion while a different film with
different characteristics may be selected at other locations (such
as at the seams). The only requirement is that the final product
exhibit the aforementioned high leak-down properties. This film
appears to act by "cementing" the contacted individual yams in
place and possibly preventing leakage through open areas between
woven yams and/or stitches. During inflation, then, the coating
prevents leakage through the interstitial spaces between the yams
and aids in preventing yam 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 films.
Normally, the required coatings (which are not films, but actual
coating formulations applied to the surface which then may form
non-laminated films) on side curtain airbags are very high, at
least 3.5 ounces per square yard (with the standard actually much
higher than that, at about 4.0). The inventive airbag cushions
require merely about 2.7 ounces per square yard of the desired film
coating (preferably less, such as about 2.5, more preferably about
2.2, still more preferably, less than 2.2) 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 desired films are
polyurethanes, although any film which possesses the same desired
tensile strength and elongation characteristics noted above may
function within this inventive low permeability airbag cushion.
Copolymers of polyurethanes, polyamides, and the like, may be
utilized, as merely one type of example. Also, such films may or
may not be cross-linked on the airbag surface. Preferably, the film
is a polyurethane and most preferably is a polycarbonate
polyurethane or a polyurethane film based on polytetramethylene
glycol diol (available from Deerfield Urethane, Inc., Ivyland, Pa.,
under the tradename Dureflex.TM. PT9400). This specific film
exhibits a tensile strength of 8,000 psi and an elongation at break
of about 600%. Such a film may be added in an amount of as low as
2.2 ounces per square yard on the desired cushion and still provide
the requisite high leak-down time characteristics. Of course, any
other film meeting the characteristics as noted above is
encompassed within this invention; however, the add-on weights of
other available films may be greater than this preferred one,
depending on the actual tensile strength and elongation properties
available. However, the upper limit of 3.0 ounces per square yard
should not be exceeded to meet this invention. The desired films
may be added in multiple layers if desired as long the required
thickness for the overall coating is not exceeded. Alternatively,
the multiple layer film/coating system may also be utilized as long
as at least one film possessing the desired tensile strength and
elongation at break is utilized and the requisite low permeability
is exhibited.
[0020] Other possible components present within or on these films
are thickeners, antioxidants, flame retardants, coalescent agents,
adhesion promoters, and colorants. In accordance with the
potentially preferred practices of the present invention, a primer
adhesive coating is first applied to the target cushion surface or
to the laminate film as a tie-coat to enhance the adhesion between
the laminate film and the fabric cushion. Upon drying of this first
layer, the desired film is then laminated through heat and pressure
to the selected areas of the target surface for a sufficient time
to effectuate lamination. Preferably, the preferred film (or films)
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 film as a topcoat as long as the add-on weight of the entire
film and topcoat does not exceed 3.0 ounces per square yard.
Additionally, elastomers comprising polyester or polyether segments
or other similar components, are 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 topcoat formulations as long, again,
as the 3.0 ounces per square yard is not exceeded.
[0021] Among the other additives particularly preferred within or
on the film (or films) 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. As
noted above, primer adhesives may be utilized to facilitate
adhesion between the surface of the target fabric and the film
itself. Thus, although it is preferable for the film to be the sole
component of the entire coating 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 film
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 film (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] The substrate to which the thin film 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 yam
preferably has a linear density of about 105 denier to about 840
denier, more preferably from about 210 to about 630 denier. Such
yams are preferably formed from multiple filaments wherein the
filaments have linear densities of about 7 denier per filaments or
less, more preferably about 6 dpf or less, and most preferably
about 4 dpf 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 yam shifting, particularly where the yams 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.
[0025] 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 yams 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:
[0026] The term "inflatable fabric" hereinafter is intended to
encompass any fabric which is constructed of at least two layers of
fabric which can be 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.
[0027] 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.
[0028] 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.
[0029] 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 yam 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.
[0030] 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.
[0031] 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 inventive one-piece woven
structure. Thus, add-on amounts of as much as 1.5 and even up to
about 3.0 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).
[0032] Additionally, it has also been found that the inventive film
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 silicone and neoprene rubber coating
formulations. Such add-on amounts will approach the 2.7 ounces per
square yard limit, but lower amounts have proven effective (2.2
ounces per square yard, for example) depending on the utilization
of a sufficiently high tensile strength and sufficiently
stretchable elastomeric component within the film 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.
[0033] Of particular importance within this invention, is the
ability to pack the laminated 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.
[0034] 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).
[0035] 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 film laminate 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 film 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.
[0036] 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 EMBODIMENT OF THE
INVENTION
[0037] Surprisingly, it has been discovered that any film 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 below about 2.5, more about 2.2, and most
preferably less than about 2.2 ounces per square yard, provides a
coated airbag cushion which exhibits extremely low and extended
permeability upon and after inflation. This unexpectedly beneficial
type and amount of film 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 film coating composition required, the less
expensive the final product. Additionally, a lower required amount
of film coating composition will translate into a decrease in the
packing volume of the airbag fabric within an airbag device. This
benefit thus improves the packability for the airbag fabric.
[0038] The preferred airbag cushion of this invention was produced
in accordance with the following Example:
EXAMPLE
[0039] First, the preferred primer formulation was produced having
the composition:
1 Parts Component by weight Desmoderm .RTM. 43195 (Bayer
Corporation, polyurethane resin) 25 grams Dimethylformamide
(Aldrich, solvent) 75 grams Desmodur .RTM. CB-75N (Bayer,
polyisocyanate adhesion 4 grams promoter)
[0040] This formulation was applied to both sides of a 2.5 liter
size Jacquard woven nylon airbag (of 440 denier fibers), made in
accordance with FIGS. 1 and 2, below. The primer was dried at about
160.degree. C. for about 2 minutes to obtain a dry coating weight
of about 0.25 ounces per square yard on each side. Subsequently, a
2 mil thick polyurethane film (Dureflex.TM. PT9400) was then
laminated on both sides of the primer coated airbag utilizing a
hotpress providing about 80 psi pressure at about 188.degree. C.
with a residence time of about 1 minute. The total polyurethane
film add-on weight on each side of the airbag was about 2.2 ounces
per square yard. The airbag was then rapidly inflated to 30 psi air
pressure. More than 28 seconds elapsed before the air pressure
leaked down to 8 psi. The leakage rate was thus measured at 10 psi
to be about 4 SCFH. The characteristic leak-down time was an
astounding amount, greater than 80 seconds.
DESCRIPTION OF THE DRAWINGS
[0041] 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.
[0042] FIG. 2 is a weave diagram illustrating a potentially
preferred repeating pick pattern formed using repeating plain weave
and basket weave four-pick arrangements.
[0043] FIG. 3 depicts the side, inside view of a vehicle prior to
deployment of the inventive side curtain airbag.
[0044] FIG. 4 depicts the side, inside view of a vehicle after
deployment of the inventive side curtain airbag.
[0045] FIG. 5 depicts a side view of a side curtain airbag.
[0046] FIG. 6 provides a side view of a side curtain airbag
container.
[0047] FIG. 7 provides a cross-sectional perspective of the rolled
airbag to test for the packing volume factor.
DETAILED DESCRIPTION OF THE DRAWINGS
[0048] 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 a
preferred denier of 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 yams 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.
[0049] 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.
[0050] 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.
[0051] FIG. 4 shows the inflated side curtain airbag 126. As noted
above, the airbag 126 is laminated with at most 2.7 ounces per
square of a coating formulation (not illustrated), preferably the
polyurethane film formulation of the EXAMPLE above. 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.
[0052] 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
rolled 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 and multiplied by the square
root of the 420 denier yam diameter will be at least about 1.004.
Larger factors are possible with higher add-on coating weights and
larger yarns. Smaller yams may be utilized with lower or larger
add-on coating weights as well.
[0053] 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).
[0054] 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 laminate 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.
* * * * *