U.S. patent application number 12/217327 was filed with the patent office on 2009-01-08 for gas generant.
Invention is credited to Sean P. Burns, Jeffrey W. Halpin, Deborah L. Hordos, Paresh S. Khandhadia, Jason Newell, Graylon K. Williams.
Application Number | 20090008003 12/217327 |
Document ID | / |
Family ID | 40220521 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090008003 |
Kind Code |
A1 |
Burns; Sean P. ; et
al. |
January 8, 2009 |
Gas generant
Abstract
The present invention includes a gas generator 10 that
incorporates a gas generating composition 12 and a scavenging
additive 16 in heterogeneous but vapor/gaseous communication with
the gas generating composition 12. The scavenging additive retains
moisture/contaminants typically evolving over time at relatively
higher temperatures. The present invention further includes a gas
generating system 180 incorporating the gas generator 10.
Inventors: |
Burns; Sean P.; (Almont,
MI) ; Halpin; Jeffrey W.; (Harrison Township, MI)
; Williams; Graylon K.; (Warren, MI) ; Khandhadia;
Paresh S.; (Troy, MI) ; Hordos; Deborah L.;
(Troy, MI) ; Newell; Jason; (LaSalle, CA) |
Correspondence
Address: |
L.C. Begin & Associates, PLLC
510 Highland Avenue, PMB 403
Milford
MI
48381
US
|
Family ID: |
40220521 |
Appl. No.: |
12/217327 |
Filed: |
July 2, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11542302 |
Oct 2, 2006 |
|
|
|
12217327 |
|
|
|
|
60722168 |
Sep 30, 2005 |
|
|
|
Current U.S.
Class: |
149/46 ;
149/108.2; 149/45; 149/61; 149/70; 149/88; 149/92 |
Current CPC
Class: |
C06D 5/06 20130101; B60R
2021/2648 20130101; C06B 23/02 20130101 |
Class at
Publication: |
149/46 ; 149/45;
149/88; 149/61; 149/70; 149/108.2; 149/92 |
International
Class: |
C06B 31/28 20060101
C06B031/28; C06B 31/08 20060101 C06B031/08; C06B 31/00 20060101
C06B031/00; C06B 31/02 20060101 C06B031/02; C06B 43/00 20060101
C06B043/00 |
Claims
1. A gas generator comprising: a gas generating composition
comprising a first oxidizer and a first fuel; and a scavenging
additive selected from adsorbents, absorbents, chemical reactants,
and mixtures thereof, said scavenging additive provided in
vapor/gaseous communication with said gas generant composition
within said gas generator, in heterogeneous relationship with said
gas generant composition.
2. The gas generator of claim 1 wherein said first oxidizer is
selected from metal and nonmetal nitrates; metal nitrites, metal
and nonmetal perchlorates, metal oxides, basic metal nitrates, said
first oxidizer provided at about 0.1 to 80% by weight of the gas
generant composition.
3. The gas generator of claim 1 wherein said first fuel is selected
from derivatives of bis-(1(2) H-tetrazol-5-yl)-amine including its
anhydrous acid, its acid monohydrate, mono-ammonium salt of
bis-(1(2) H-tetrazol-5-yl)amine, metal salts, and complexes
thereof; azoles, metal salts of azoles, nonmetal and metal salts of
nitramine derivatives of azoles; guanidines; salts of guanidines;
nitro derivatives of guanidines; azoamides; nitrate salts of
azoamides, and mixtures thereof; said second fuel provided at about
0.1-50% by weight of the gas generant composition.
4. The gas generator of claim 1 wherein said adsorbents,
absorbents, chemical reactants, and mixtures thereof are selected
from the group including molecular sieves, zeolites, calcium oxide,
and calcium sulfate.
5. The gas generator of claim 1 wherein said gas generating
composition further comprises a second additive selected from
silicon, silicon dioxide, fused silicon, silicones; silicates;
natural minerals including clay, mica, and silica; lubricants
including graphite, magnesium stearate, boron nitride, molybdenum
sulfide, and mixtures thereof, said second additive provided at
about 0.1 to 10% by weight of the gas generant composition.
6. The gas generator of claim 1 wherein said scavenging additive is
provided at about 0.05 to 10% by weight of the gas generant
composition.
7. The gas generator of claim 1 wherein said gas generating
composition further comprises a binder selected from cellulose
derivatives, polyalkenes carbonates, and mixtures thereof, said
binder provides at about 0.1 to 10% by weight of the gas generant
composition.
8. A gas generating system comprising the gas generator of claim
1.
9. A vehicle occupant protection system comprising the gas
generator of claim 1.
10. The gas generator of claim 1 wherein said gas generating
composition comprises the mono-ammonium salt of bis (1(2)
H-tetrazol-5-yl)-amine at about 0.1 to 50% by weight of the gas
generant composition, phase stabilized ammonium nitrate at about
0.1 to 80% by weight of the gas generant composition, and,
molecular sieves provided at about 0.1 to 10% by weight of the gas
generant composition.
11. The gas generator of claim 1 wherein said first oxidizers are
selected from ammonium nitrate, phase stabilized ammonium nitrate,
potassium nitrate, strontium nitrate, potassium nitrite, potassium
chlorate, potassium perchlorate, ammonium perchlorate, iron oxide,
copper oxide, basic copper, nitrate, basic iron nitrate and mixture
thereof.
12. The gas generator of claim 1 wherein said first fuel is
selected from a potassium, sodium, strontium, copper, boron and
zinc salt of bis-(1(2)H-tetrazol-5-yl)-amine; 5-aminotetrazole;
potassium 5-aminotetrazole; mono-ammonium salt of
5,5-bis-1H-tetrazole and di-ammonium salt of 5,5-bis-1H-tetrazole;
5-aminotetrazole nitrate; nitraminotetrazole; dipotassium
5-nitraminotetrazole; mono-ammonium nitraminotetrazole and
di-ammonium nitraminotetrazole; dicyandiamide; guanidine nitrate;
nitroguanidine; azodicarbonamide, azodicarbonamidine di-nitrate;
and mixtures thereof.
13. A gas generator comprising: a gas generating composition
comprising a first oxidizer and a first fuel; and a scavenging
additive selected from adsorbents, absorbents, chemical reactants,
and mixtures thereof, said scavenging additive provided in
vapor/gaseous communication with said gas generant composition
within said gas generator, in separate but proximate relationship
to said gas generant composition.
14. A gas generator comprising: a gas generating composition
comprising a first oxidizer and a first fuel, said gas generant
composition provided in pressed form; and a scavenging additive
selected from adsorbents, absorbents, chemical reactants, and
mixtures thereof, said scavenging additive provided in
vapor/gaseous communication with said gas generant composition
within said gas generator, and sprinkled about said gas generant
composition in heterogeneous relationship thereto.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending
U.S. application Ser. No. 11/542,302 and claims the benefit
thereof.
TECHNICAL FIELD
[0002] The present invention relates generally to gas generating
systems, and to gas generant compositions employed in gas generator
devices for automotive restraint systems, for example.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to gas generant compositions
that upon combustion produce a relatively small amount of solids
and a relatively abundant amount of gas. It is an ongoing challenge
to reduce the amount of solids and increase the amount of gas
thereby decreasing the filtration requirements for an inflator. As
a result, the filter may be either reduced in size or eliminated
altogether thereby reducing the weight and/or size of the
inflator.
[0004] An equally important challenge is to manufacture gas
generants that exhibit relatively low sensitivity with regard to
impact, friction, or electrostatic discharge stimuli.
[0005] Yet another challenge with gas generant compositions that
produce relatively small amounts of solids, sometimes known as
"smokeless" compositions, is that not all non-metallic constituents
contribute to stable ballistic performance when subjected to
environmental conditioning. In fact, one fuel that is favored
because of its propensity to produce all or mostly gas is
bis-1(2)H-tetrazol-5-yl)-amine (BTA-1NH3) and derivatives thereof.
When combined with other gas generant constituents such as an
oxidizer, and formed into a gas generant composition, this fuel
contributes to greater amounts of gas upon combustion of the
composition.
[0006] Furthermore, some gas generants, such as those formed by the
combination of the monoammonium salt of
bis-(1(2)H-tetrazol-5-yl)-amine (BTA-1NH3) with ammonium nitrate or
phase stabilized ammonium nitrate (PSAN) exhibit many favorable
qualities, such as high gas production, and therefore are useful in
automotive passenger restraints. BTA-1NH3 is a high energy,
high-nitrogen fuel that exhibits excellent stability and very
favorable levels of hygroscopicity and sensitivity. The properties
of ammonium nitrate and potassium nitrate when co-precipitated
include minimal or no sensitivity when subjected to impact,
friction, and electrostatic discharge stimuli. One concern with
PSAN-containing propellants is that they exhibit less-than
desirable behavior with regard to ballistic properties,
particularly with respect to thermal shock conditioning when
ballistically tested at elevated temperatures.
[0007] It is also required that airbag inflators be subjected to
environmental conditioning, such as high temperature heat aging,
thermal aging, thermal cycling, thermal shock, humidity cycling,
and so forth. It is therefore desirable to have a gas generant and
inflator system that performs the same regardless of conditioning.
The present invention provides a solution to many of these
possibilities.
[0008] Many gas generants are moisture-sensitive due to the
inherent hygroscopicity of many common components including
oxidizers such as nitrate salts, naturally occurring hydrates of
fuels such as 5-aminotetrazole, bis-(1(2)H-tetrazol-5-yl)-amine,
carboxymethyl cellulose and its salts, clays, and others. It is
therefore imperative that these types of gas generants are kept dry
for repeatable performance.
[0009] Moisture or volatile contaminants can be introduced to gas
generating systems in many ways. A few examples include: improperly
processed gas generants that contain excess moisture; moisture
introduced to the system via humidity during assembly; moisture
introduced to the system during environmental conditioning such as
high humidity cycling or salt spray; moisture introduced to the
system via decomposition of materials within the system such as
auto-ignition materials, seals, gaskets, greases, and other gas
generator constituents. The use of certain additives, preferably
zeolites such as molecular sieves, calcium sulfate (Drierite.TM.),
or calcium oxide can minimize, and in some cases eliminate any
problems that may occur in these situations.
[0010] Accordingly, it would be an improvement in the art to
provide compositions that contain BTA-1NH3 that contribute to a
"smokeless" gas generant composition, or one that when combusted
produces 90% or more of gas as a product, while yet passing thermal
cycling standards.
SUMMARY OF THE INVENTION
[0011] The above-referenced concerns are resolved by gas generators
containing gas generating compositions including a fuel such as
BTA-1NH3 and an oxidizer such as phase stabilized ammonium nitrate.
The gas generator contains a separate additive or contaminant
scavenger such as molecular sieves. The separate additive is an
adsorbent or absorbent contained within the gas generator to
facilitate scavenging of any moisture or volatiles as it evolves or
occurs within the propellant bed. It has been found that the
addition of adsorbents or absorbents such as molecular sieves has
resulted in compositions that are now able to withstand typical
thermal cycling/thermal shock tests.
[0012] The use of certain additives, preferably zeolites such as
molecular sieves, calcium sulfate (Drierite.TM.), or calcium oxide
can minimize, and in some cases eliminate contaminants occurring
within the inflator over time. In particular, molecular sieves
function to better retain moisture and other contaminants in the
presence of relatively high temperatures such as 107 degrees
Celsius, thereby ensuring predictable performance of associated
inflators. Stated another way, molecular sieves retain
moisture/contaminants at elevated temperatures at least as high as
107 degrees Celsius thereby facilitating consistent performance
predictability of inflators incorporating one or more types of
these additives.
[0013] Accordingly, the present invention includes a gas generator
containing a gas generating composition and a scavenging additive
that is provided within the gas generator in heterogenous
relationship with the gas generating composition, and in
vapor/gaseous communication therewith.
[0014] In further accordance with the present invention, a gas
generator and a vehicle occupant protection system incorporating
the gas generant composition and scavenging additive are also
included.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional side view showing the general
structure of an inflator in accordance with the present
invention.
[0016] FIG. 2 is a schematic representation of an exemplary vehicle
occupant restraint system containing a gas generant composition in
accordance with the present invention.
[0017] FIG. 3 is a graphical representation of ballistic
performance of an inflator not containing an additive such as an
adsorbent or absorbent in accordance with the present
invention.
[0018] FIG. 4 is a graphical representation of ballistic
performance of an inflator containing an additive such as an
adsorbent or absorbent in accordance with the present
invention.
DETAILED DESCRIPTION
[0019] The present invention includes gas generator or gas
generating system that in accordance with the present invention,
incorporates an additive separate from and functioning as an
adjunct to gas generating compositions containing BTA-1NH3 or other
fuels that, when added at relatively low levels, stabilizes the
propellant grains when subjected to thermal cycling or thermal
shock conditioning, as required for use in the automotive industry.
These formulations generally contain the constituents described
below although other constituents known in the art may be employed
as well.
[0020] As shown in FIG. 1, the gas generant 12 is contained within
a gas generant chamber 14 of the inflator 10. The scavenging
additive 16 is intermingled or sprinkled in heterogeneous
relationship to the gas generant 12. It should be emphasized that
the additive 16 need not be mixed directly with the gas generant
12, but is instead added to the bed to act independently of the gas
generant 12 thereby scavenging various contaminants and moistures
due to decomposition over time for example.
[0021] Gas generating compositions of the present invention contain
a first oxidizer selected from the group including nonmetal and
metal nitrate salts such as ammonium nitrate, phase-stabilized
ammonium nitrate, potassium nitrate, strontium nitrate; nitrite
salts such as potassium nitrite; chlorate salts such as potassium
chlorate; metal and nonmetal perchlorate salts such as potassium or
ammonium perchlorate; oxides such as iron oxide and copper oxide;
basic nitrate salts such as basic copper nitrate and basic iron
nitrate, and mixtures thereof is provided. The first oxidizer is
generally provided at about 0.1-80 wt % of the gas generant
composition, and more preferably at about 10-70 wt %.
[0022] An optional secondary oxidizer may also be provided within
the gas generant compositions, and is selected from the oxidizers
described above, and when included is generally provided at about
0.1-50 wt %, and more preferably at about 0.1-30 wt %. The total
combined oxidizer component is nevertheless only provided at about
0.1-80 wt % of the gas generant composition.
[0023] The gas generant composition contains a first or primary
fuel selected from the group containing derivatives of
bis-(1(2)H-tetrazol-5-yl)-amine, including its anhydrous acid and
its acid monohydrate, mono-ammonium salt of
bis-(1(2)H-tetrazol-5-yl)-amine, metal salts of
bis-(1(2)H-tetrazol-5-yl)-amine including the potassium, sodium,
strontium, copper, boron, zinc salts of BTA-1NH3, and complexes
thereof; azoles such as 5-aminotetrazole; metal salts of azoles
such as potassium 5-aminotetrazole; nonmetal salts of azoles such
as mono- or di-ammonium salt of 5, 5'-bis-1H-tetrazole; nitrate
salts of azoles such as 5-aminotetrazole nitrate; nitramine
derivatives of azoles such as 5-nitraminotetrazole; metal salts of
nitramine derivatives of azoles such as dipotassium
5-nitraminotetrazole; nonmetal salts of nitramine derivatives of
azoles such as mono- or di-ammonium 5-nitraminotetrazole and;
guanidines such as dicyandiamide; salts of guanidines such as
guanidine nitrate; nitro derivatives guanidines such as
nitroguanidine; azoamides such as azodicarbonamide; nitrate salts
of azoamides such as azodicarbonamidine dinitrate; and mixtures
thereof, and is generally provided at about 0.1-50 wt %, more
preferably 0.1-30 wt %.
[0024] The gas generant composition may also contain an optional
additive selected from the group including silicone compounds;
elemental silicon; silicon dioxide; fused silica; silicones such as
polydimethylsiloxane; silicates such as potassium silicates;
natural minerals such as talc and clay; lubricants such as graphite
powder or fibers, magnesium stearate, boron nitride, molybdenum
sulfide; and mixtures thereof; and when included is generally
provided at about 0.1-10%, and more preferably at about 0.1-5%.
[0025] An optional binder may be included in the gas generant
composition and is selected from the group of cellulose derivatives
such as cellulose acetate, cellulose acetate butyrate,
carboxymethycellulose, salts of carboxymethylcellulose,
carboxymethyl cellulose acetate butyrate; silicone; polyalkene
carbonates such as polypropylene carbonate and polyethylene
carbonate; and mixtures thereof, and when included is generally
provided at about 0.1-10%, and more preferably at about 0.1-5%.
[0026] All percentages for the constituents described herein are
presented as weight percents of a total gas generant weight.
[0027] In accordance with the present invention, the scavenging
additive 16 is any additive that will absorb, adsorb, or chemically
react with water and/or other volatiles that may be detrimental to
stability or performance of gas generants and inflation devices. An
example of an absorbent includes calcium sulfate as it forms a
hydrate. An adsorbent may be selected from molecular sieves,
montmorillonite clay, other zeolites, silica gel, and mixtures
thereof, as these compounds can adsorb and contain H.sub.2O and
NOx. Molecular sieves are preferred because of their enhanced
ability to retain moisture/contaminants at relatively higher
temperatures thereby ensuring they do not interfere with the
combustion reaction of the gas generant composition. An example of
a chemical reactant is calcium oxide as it will react with water to
form stable solid products. The scavenging additive 16 is generally
provided at about 0.1-10 wt %, and more preferably at about 0.1-5
wt % of the total weight of the gas generant.
[0028] Nevertheless, it will be appreciated that gas generators of
the present invention preferably contain at least one or more moles
of scavenging additive per mole of contaminant that evolves over
time. Accordingly, each gas generant composition may be evaluated
on an iterative basis as to what amounts of
contaminant/volatiles/moisture will evolve or decompose over time,
and the amount of scavenging additive may then be determined. In
practice, although not required, the scavenging additive should be
provided in excess amounts thereby ensuring that each mol of
volatile/contaminant/moisture is either adsorbed, absorbed, or
reacted with the additive thereby ensuring the integrity of the gas
generator performance upon combustion of the gas generant. The
weight percent amounts given above are designed with this approach
in mind.
[0029] An optional binder is selected from the group of cellulose
derivatives such as cellulose acetate, cellulose acetate butyrate,
carboxymethycellulose, salts of carboxymethylcellulose,
carboxymethyl cellulose acetate butyrate; silicone; polyalkene
carbonates such as polypropylene carbonate and polyethylene
carbonate; and mixtures thereof, and when included is generally
provided at about 0.1-10%, and more preferably at about 0.1-5%.
[0030] All percentages for the constituents described herein are
presented as weight percents of a total gas generant weight.
[0031] It has been determined that the addition of small amounts of
adsorbents or absorbents to these formulations provides a gas
generant which exhibits all of the favorable properties listed
above, and, more importantly, exhibits stable ballistic performance
when subjected to thermal cycling or thermal shock
conditioning.
[0032] The monoammonium salt of BTA-1NH3, when combined with PSAN,
exhibits many favorable qualities for use in automotive passenger
restraints and combines to form preferred gas generating
compositions. BTA-1NH3 is a high energy, high-nitrogen fuel which
exhibits excellent stability and very favorable levels of
hygroscopicity and sensitivity. The properties of ammonium nitrate
and potassium nitrate, for example, are well known throughout the
propellant industry. PSAN, more specifically, exhibits no
sensitivity when subjected to impact, friction, or electrostatic
discharge stimuli.
EXAMPLE 1
[0033] To form comparative compositions, dry mixes of formulations
containing the various constituents described above were prepared
in a known manner. The dry material was then tableted, loaded into
inflators, and subjected to Thermal Shock conditioning (100 Cycles,
-40 C to 90 C). These formulations indicated an increase in
aggressive ballistic performance when deployed at 85 C.
[0034] Next, the same process was used to prepare gas generants
containing the various constituents described above, and a small
amount of additive was added to each inflator. A ratio of 100:1 was
used for the mass of gas generant to additive. The additive
employed was 13X Type Molecular Sieves because of its inert
chemical tendencies and ability to scavenge moisture and other
volatiles, and retain these contaminants at relatively higher
temperatures such as 107 degrees Celsius. The gas generant
contained little, if any, moisture. After thermal shock
conditioning, it was found that the ballistic performance of the
inflators was nearly identical to the baseline inflators. The gas
generant contained almost exactly the same amount of moisture after
conditioning as it did before testing. The increase in ballistic
stability due to the addition of molecular sieves is somewhat
counterintuitive as is does not appear to be moisture-related
phenomena. This unexpected result of the use of additives such as
molecular sieves is repeatable, and produces a novel method of
stabilizing gas generants that have otherwise been deemed
unsuitable for use in the automotive industry.
EXAMPLES 2 and 3
[0035] A composition was made by combining 72.53% PSAN, 27.22%
BTA-1NH3, and 0.25% M5 fumed silica and grinding with ceramic media
in a Sweco vibratory grinder for 10 minutes. This powder was then
pressed into 1/4'' diameter by 0.125'' thick tablets. Driver side
inflators were built with 25.0 g of this pressed gas generant into
two different configurations: one contained no scavenging
additives; the other contained 0.25 g of 13X zeolite in the form of
8-12 mesh beads poured directly into the gas generant chamber
thereby intermingling the additive in heterogeneous relationship
with the gas generating composition. As used throughout this
specification and in the claims, the term "heterogeneous" is meant
to indicate that the additive or 13X zeolite is added to a bed of
pre-mixed substantially homogeneous gas generant composition made
as known in the art. The gas generant is preferably but not
necessarily pressed into tablets for example, with the 13X zeolite
"heterogeneously" distributed about the tablets, in separate and
proximate orientation to the gas generant. As such, the term
"heterogeneous" is meant to convey a separate but proximate
orientation between the gas generating composition and the 13X
zeolite, when viewed from a macroscopic perspective. Stated yet
another way, the term "heterogeneous" is meant to convey that the
13X zeolite is not a part of the gas generant composition, but is
instead separately added to the bed of homogeneous gas generant
composition already in the inflator. The term "heterogeneous" is
not meant to convey separate and proximate orientation between the
gas generant composition and the 13X zeolite when viewed from a
microscopic perspective, or when viewed as the solid particulate
separation between an oxidizer and a fuel, for example, that one
would see when viewing solid particulates that make up a
homogeneous gas generant composition. As such, the term
"heterogeneous" would not describe or apply to a desiccant or
desiccating constituent contained within a gas generant
composition. The inflators were sealed and subjected to the thermal
shock specification (100 thermal shock cycles between -40 C and +90
C). Inflators were pulled out after 50 cycles and 100 cycles. All
inflators were tested at +85 C and compared to the baseline
results.
[0036] Without the addition of 13X zeolite, and as shown in FIG. 3,
the ballistic curves indicate that changes occurred in the gas
generant after 50 cycles. After 100 cycles the ballistic
performance was somewhat aggressive and did not meet desired
thermal shock specifications.
[0037] With the addition of 0.25 g of the 13X zeolite, all
inflators were in the same range as the baseline curve, or the
inflator not subject to thermal shock testing, and therefore easily
passed the desired thermal shock specifications. The ballistic
curves are shown in FIG. 4.
[0038] As shown in FIG. 1, an exemplary inflator incorporates a
dual chamber design to tailor the force of deployment an associated
airbag. In general, an inflator or gas generator 10 containing a
primary gas generant 12 and a scavenging additive 16 formed as
described herein, may be manufactured as known in the art. U.S.
Pat. Nos. 6,422,601, 6,805,377, 6,659,500, 6,749,219, and 6,752,421
exemplify typical airbag inflator designs and are each incorporated
herein by reference in their entirety. It will be appreciated that
the additive 16 is in gaseous or vapor communication with the
propellant 12 prior to combustion of the gas generant 12. The
additive 16 may for example, as shown in FIG. 1 be provided in
juxtaposition to the gas generant 12 within the gas generant
chamber 14, intermingled or heterogeneously arranged about the gas
generant 12.
[0039] Referring now to FIG. 2, the exemplary inflator 10 described
above may also be incorporated into an airbag system 200. Airbag
system 200 includes at least one airbag 202 and an inflator 10
containing a gas generant composition 12 in accordance with the
present invention, coupled to airbag 202 so as to enable fluid
communication with an interior of the airbag. Airbag system 200 may
also include (or be in communication with) a crash event sensor
210. Crash event sensor 210 includes a known crash sensor algorithm
that signals actuation of airbag system 200 via, for example,
activation of airbag inflator 10 in the event of a collision.
[0040] Referring again to FIG. 2, airbag system 200 may also be
incorporated into a broader, more comprehensive vehicle occupant
restraint system 180 including additional elements such as a safety
belt assembly 150. FIG. 2 shows a schematic diagram of one
exemplary embodiment of such a restraint system. Safety belt
assembly 150 includes a safety belt housing 152 and a safety belt
100 extending from housing 152. A safety belt retractor mechanism
154 (for example, a spring-loaded mechanism) may be coupled to an
end portion of the belt. In addition, a safety belt pretensioner
156 containing propellant 12 and autoignition 14 may be coupled to
belt retractor mechanism 154 to actuate the retractor mechanism in
the event of a collision. Typical seat belt retractor mechanisms
which may be used in conjunction with the safety belt embodiments
of the present invention are described in U.S. Pat. Nos. 5,743,480,
5,553,803, 5,667,161, 5,451,008, 4,558,832 and 4,597,546,
incorporated herein by reference. Illustrative examples of typical
pretensioners with which the safety belt embodiments of the present
invention may be combined are described in U.S. Pat. Nos. 6,505,790
and 6,419,177, incorporated herein by reference.
[0041] Safety belt assembly 150 may also include (or be in
communication with) a crash event sensor 158 (for example, an
inertia sensor or an accelerometer) including a known crash sensor
algorithm that signals actuation of belt pretensioner 156 via, for
example, activation of a pyrotechnic igniter (not shown)
incorporated into the pretensioner. U.S. Pat. Nos. 6,505,790 and
6,419,177, previously incorporated herein by reference, provide
illustrative examples of pretensioners actuated in such a
manner.
[0042] It should be appreciated that safety belt assembly 150,
airbag system 200, and more broadly, vehicle occupant protection
system 180 exemplify but do not limit gas generating systems
contemplated in accordance with the present invention.
[0043] The gas generant constituents may be provided by suppliers
such as Sigma Aldrich and Fisher. The additives may also be
supplied by well known suppliers. For example, the molecular sieves
may be supplied by Sigma Aldrich. Furthermore, the molecular sieves
may be provided as categorized in 3A, 4A, 5A, and 13X, in bead or
powder form, in 4-8 or 8-12 mesh, for example. 13X is particularly
preferred.
[0044] It should further be understood that the preceding is merely
a detailed description of various embodiments of this invention and
that numerous changes to the disclosed embodiments can be made in
accordance with the disclosure herein without departing from the
scope of the invention. The preceding description, therefore, is
not meant to limit the scope of the invention. Rather, the scope of
the invention is to be determined only by the appended claims and
their equivalents.
* * * * *