Safety air bag inflation device

An air bag inflator providing a source of gas, releasable upon command, to inflate a supplemental inflation restraint (SIR) system commonly known as an automobile air bag. Provided is a pressure vessel containing one or more separate chambers for the purpose of storing gaseous fuel(s) and gaseous oxidizer(s) or liquid fuel(s) and liquid oxidizer(s) under pressure with helium as the primary filler gas. The primary function of the helium gas is to serve as a kinetic damper to modulate and control the reaction rate of the fuel(s) and oxidizer(s). Because of its low mass, high thermal conductivity and high heat capacity for its mass, helium is an excellent filler gas. In the case of the gaseous fuel(s) and oxidizer(s) a single chamber is provided. In the case of liquid fuel(s) and oxidizer(s), two or more separate housings are provided for storing the liquid fuel(s) and oxidizer(s). Along with the liquid fuel(s) and oxidizer(s) housings, two separate chambers containing pressurized helium are provided within the pressure vessel. The first helium chamber rapidly pressurizes upon initiation of a gas producing pyrotechnic igniter. This pressure acts on thin membranes on the first chamber side of the separate liquid storage housings to force the liquid fuel(s) and oxidizer(s) into the second chamber where the materials are atomized and mixed. The mixture is ignited by the arrival of hot gases from the igniter directed into the second chamber via the small diameter tube or orifice. The fuel(s) oxidizer(s) mixture burns to produce gaseous reaction products that are released into the air bag by bursting a controlled rupture burst disc.

FIELD OF INVENTION 
This invention is in the field of air bag inflation devices which generate 
pressurized gas and delivers the gas to an automobile safety air bag. 
BACKGROUND OF INVENTION 
Automobiles are equipped with safety devices commonly referred to as "Air 
Bags." Air Bags are designed to protect passengers from direct impact with 
hard interior vehicle parts in the event the vehicle is involved in a 
collision. If the vehicle is involved in a collision, a triggering system 
activates a device which rapidly inflates the air bag. The inflated air 
bag provides a cushion for the passenger to impact, reducing the chance of 
injury, or reducing the severity of injuries resulting from the collision. 
Current air bag inflation devices operate quickly enough to meet current 
industry requirements. The need exists, however, for faster acting air bag 
inflation devices which will satisfy new industry requirements for dealing 
with higher speed front collisions and for certain side impact collisions. 
Passengers sitting near vehicle doors are much closer to the point of 
collision during a side impact than they are to the dashboard or steering 
wheel during a front end collision. Conventional air bag inflation devices 
act too slowly, when inflating air bags in side doors, to protect 
passengers from severe side impacts. 
Gas used to inflate air bags mush not be toxic or cause burn injuries to 
passengers, and it must not present environmental hazards in use or during 
disposal. 
Currently, industry employs two types of air bag inflation devices. One 
type uses sodium azide blended with a suitable oxidant such as 
molybdenum-disulfide or potassium nitrite to control burn characteristics. 
Upon ignition, these devices produce predominantly nitrogen gas which 
evolves from thermal decomposition of the sodium azide. Unfortunately, 
sodium azide is both explosive and a very toxic poison. This creates a 
major risk to passengers, and presents serious disposal problems. 
The second type of device, referred to as a hybrid, involves the storage of 
an inert gas (e.g. argon) under pressure along with a pyrotechnic or 
propellant. This propellant serves two functions. First, at ignition the 
propellant produces heat and gas which pressurizes the argon gas so that 
the argon ruptures a rupture disc (or activates another suitable release 
mechanism) to deliver the argon to the air bag. Second, in some designs, 
the propellant itself produces gas which adds to the stored argon gas 
pressure for release into the air bag. 
In both the azide and hybrid designs, there is a significant quantity of 
pyrotechnic material which, when burned, produces substantial particulate 
reaction products. Great engineering effort is required to filter these 
particulates from the gas delivery stream in order to meet the industry 
requirements for maximum allowed quantities of particulates delivered to 
the air bag. There are also small quantities of toxic gases given off by 
the burning pyrotechnics. It is very difficult to tailor the pyrotechnic 
mixture to sufficiently reduce toxic effluents to meet industry standards. 
Both the hybrid and azide technologies require major engineering studies to 
formulate pyrotechnic chemical compositions, particle sizes and 
distributions, and ignition train mechanisms which satisfactorily control 
the chemical and pressure-time delivery characteristics of the inflation 
device. This means that variations in pressure-time delivery requirements 
between one car model and another require major engineering effort. In 
most cases, this also requires reconfiguration of the containment vessel 
and mounting hardware. 
SUMMARY OF PRESENT INVENTION 
The present invention is applied to automobile safety air bag systems. In 
one form, a propellant explosive is employed to propel a moveable piston 
to further compress pre-pressurized gas. The propellant explosive, piston 
and pre-pressurized gas are sealed within a cylinder by a precision 
rupture disc. The cylinder is provided with a solid chemical explosive 
electrically activated initiator. When the propellant explosive is ignited 
by the initiator, the burning propellant explosive drives the piston to 
further pressurize either a noncombustible or combustible pre-pressurized 
gas on the other side of the piston. When the precision rupture disc 
fails, the highly pressurized gas is released through a venturi into the 
air bag, inflating the air bag. Other forms of the invention do not use a 
piston, but inert gas along with the products of combustion, directly fill 
the air bag. 
Briefly, there are four major concepts. The first concept involves an 
active, mechanical pressurization of a stored prepressurized inert gas, 
such as argon or helium, contained in a cylinder under pressure. A 
gas-producing, energetic material contained behind a moveable piston is 
ignited. The energetic material burns, producing hot, expanding gas which 
propels the piston to further compress the prepressurized inert gas. A 
precision disc ruptures at a predetermined pressure, releasing gas into 
the air bag. The piston continues to force gas out of the cylinder, 
providing a continuous high pressure driving force which adds enough 
energy to keep the gas from cooling significantly. Finally, the piston 
embeds itself into the end of the cylinder, providing a seal which 
prohibits propellant gases from reaching the air bag. The propellant gases 
(now predominantly water) then cool and condenses inside the cylinder 
while still totally contained. Thus, a pure inert gas is delivered to the 
air bag. No particles or toxic gases are delivered. 
The second concept involves using inert gas to kinetically deep reactions 
in combustible gas mixtures. As used herein, "inert" means chemically 
non-reactive. As used herein, "kinetic" refers to the rate or speed at 
which the chemical reaction take place between the reactive components of 
the system and molecular interactions thereof. As used herein, "damping" 
refers to the modulation and control of the rate of chemical reaction and 
the molecular interaction thereof. Therefore the presence of the inert 
kinetic damping gas molecules modulates and controls the chemical reaction 
rate of combustion and thereby the molecular reaction products formed. A 
mixture of prepressurized gases made up of an inert kinetic damping gas 
(e.g. argon or helium), along with oxygen, and a fuel gas (e.g. propane, 
hydrogen or any other combustible gas) is contained in a cylinder. This 
gas mixture is ignited by an energetic initiator, such as one containing 
100 milligrams of zirconium potassium perchlorate. The combustible gas 
burns with the oxygen to produce a hot gas which further pressurizes the 
cylinder to burst a rupture disc, releasing the gas reaction products into 
the air bag. The proper ratio of oxygen, combustible gas and inert 
kinetic-damping gas, in conjunction with varying the precision rupture 
disc design parameters, permits reaction rate control that is both 
accurate and reproducible. This system permits precise tailoring of the 
reaction products, and their delivery rate of specific air bag 
requirements. The key to this concept is the kinetic damping effect of the 
inert gas. Varying the fuel-gas/oxygen ratios and the pressure of the 
inert kinetic-damping gas through a wide range of compositions results in 
fuel/oxygen mixtures which are incombustible at one extreme, exhibit 
controlled combustion over a range of compositions, and exhibit detonation 
mixtures at the other extreme. The precision rupture disc design 
parameters are very important in this concept since the burst pressure and 
containment time govern the extent of the reaction and the reaction 
product ratios. 
When combustible gases contain carbon (e.g. propane), the ratio of carbon 
dioxide to carbon monoxide must be controlled to minimize production of 
carbon monoxide in order to meet stringent delivery requirements. When the 
combustible gas is hydrogen, the predominant reaction product of hydrogen 
and oxygen is water vapor. Therefore, using hydrogen as the fuel results 
in water vapor, along with the inert gas and a small amount of excess 
oxygen being delivered to the air bag. Toxic gas and particulate problems 
are totally eliminated. Since in this design the gases can be stored at 
relatively low pressures, inflater design is significantly simpler then 
present designs. 
The third concept involves injecting a combustible liquid (e.g. ethanol) 
into a mixture of oxygen and inert kinetic-damping gas. The mixture is 
ignited, producing carbon dioxide, water vapor and inert gas. The inert 
gas kinetically damps the reaction, preventing detonation, and controlling 
the reaction rate. The reaction produces heat and gas which pressurizes 
the cylinder to burst a precision rupture disc. As in the former design, 
the precision rupture disc design plays a very important part in 
controlling the extent of the reaction. 
The fourth concept involves injecting two reactive liquids (e.g. hydrogen 
peroxide and methyl alcohol, among many other combinations such as 
hydrogen peroxide and other combustible liquids) from separate storage 
cells into a combustion chamber containing a mixture of prepressurized 
oxygen and inert kinetic-damping gas. The combining liquids are ignited, 
producing heat and gas which pressurize the cylinder to burst a precision 
rupture disc. As in the former design, the precision rupture disc plays a 
very important part in controlling the extent of the reaction. 
There are many advantages to each of these four design concepts. Their 
construction requires only inexpensive and non-toxic materials. Delivery 
gases avoid particulate problems and can be made totally non-toxic. A wide 
range of delivery requirements can be easily met without major engineering 
effort or hardware changes. Fabrication technology is fairly simple and 
far less hazardous to employees than current technologies. The fabrication 
technology is much less capital intensive than current technologies, and 
disposal costs are minimal when compared to present practice. 
In a first embodiment, the pre-pressurized gas is non-combustible. The 
moving piston further pressurizes the pre-pressurized gas until the 
precision rupture disc fails at a predetermined pressure, releasing the 
highly pressurized gas into the air bag. 
In a second embodiment, the pre-pressurized gas consists of a combustible 
gas, oxygen and an inert kinetic-damping gas. The gas mixture is capable 
of compression ignition. The moving piston compresses the gas mixture, 
raising the gas temperature to the auto-ignition point. The inert 
kinetic-damping gas prevents detonation and controls combination. The 
ignition gas further increases the cylinder pressure until the precision 
rupture disc fails at a predetermined pressure, releasing the gas into the 
air bag. 
In a third embodiment the device is much like the second, except that two 
or more pre-pressurized hypergolic or compression ignition gases, 
separated by baffles, are used. An inert kinetic-damping gas and a 
precision rupture disc are used. 
In a fourth embodiment no piston is used. The ignition of combustible 
propellant gases mixed with inert kinetic-damping gas directly inflates 
the air bag. When ignited, the combustion of fuel and oxygen adds heat, 
causing the cylinder pressure to rise bursting the precision rupture disc 
at a predetermined pressure. Combustion products filling the air bag are a 
mixture of safely breathable inert gas, oxygen and water vapor, along with 
very small, acceptable traces of other gases. The expanded cylinder is 
left empty and inert. 
In a fifth embodiment a liquid fuel is injected into a pre-pressurized 
mixture of oxygen and inert kinetic-damping gas, or a liquid oxidant is 
injected into a pre-pressurized mixture of hydrogen and inert 
kinetic-damping gas. The liquid fuel along with the high temperature 
igniter products are rapidly dispersed into the oxygen/inert gas mixture, 
igniting the dispersing fuel. Likewise the liquid oxidant along with the 
high temperature igniter products are rapidly dispersed into the 
hydrogen/inert gas mixture, igniting the mixture. Combustion of the 
fuel/oxidant mixture generates gas and heat, causing the cylinder pressure 
to rise, bursting the precision rupture disc at a predetermined pressure. 
Combustion products filling the air bag are a mixture of safely 
breatheable gases, consisting of inert gas, oxygen and water vapor, along 
with acceptable traces of other gases. The expended cylinder is left empty 
and inert. 
In a sixth embodiment two separately stored reactive liquids are injected 
and ignited in a combustion chamber containing pre-pressurized inert 
kinetic-damping gas and a small amount of oxygen. Combustion of the fuel 
generates gas and heat, causing the cylinder pressure to rise, bursting a 
precision rupture disc at a predetermined pressure. Combustion products 
filling the air bag are a mixture of safely breatheable gases, consisting 
of inert gas, oxygen and water vapor, along with acceptable traces of 
other gases. The expended cylinder is left empty and inert. A precision 
rupture disc is used. 
The reference precision rupture disc is a crucial part of the design of 
these devices. It is a relatively thin metal disc inscribed with a pattern 
of grooves which serve as stress risers. The precision rupture disc are 
indefinitely contain the pre-pressurized gases stored in the device. The 
inscribed grooves accurately induce and control failure of the precision 
rupture disc when the device is activated. The rupture disc opens into a 
pattern of corresponding recesses inside the venturi empty, directing a 
smooth flow of gas into the air bag. 
The precision rupture disc affects the inflation device in several ways. 
The total pressure before rupture governs both the reaction product 
ratios, and the extent of reaction before rupture. The sudden drop of 
pressure which occurs when the precision rupture disc fails quenches the 
reaction. This prevents expelling burning gases into the air bag. The 
extent of disc deformation before rupture governs the total reaction time 
and the time to first pressure in the bag. The sharp internal corners in 
the bottom of the inscribed grooves on the precision rupture disc serve as 
stress risers which induce the precision rupture disc to fail along the 
inscribed grooves. Failure along these grooves results in the forming of 
"V" shaped petals which plastically deform into their corresponding 
recesses at the entrance to the venturi. The shape of the entrance to the 
venturi acts as a kinetic energy absorber to collect the petals as they 
deform, not allowing the petals to accelerate toward the venturi opening. 
This guarantees that no disc petals will be torn off and ejected into the 
air bag. The deformed petals also determine the effective gas orifice 
size, which, in turn, governs the rate at which the inflating gas will 
pressurize the air bag. 
The expansion portion of the venturi is provided with inlets through which 
ambient air is drown by the Bernoulli effect created by the rapidly moving 
inflater gas as it traverses the surface of the venturi and empties into 
the air bag. This resulting mixture of non-toxic gas and ambient air 
rapidly inflates the air bag. The addition of ambient air permits the 
total device to be small and to use a higher initial gas temperature while 
keeping the final ejected gas temperature at an acceptable level. None of 
the aforementioned devices, however, requires these air inlets in the 
venturi to operate properly. The venturi technology just allows for 
smaller, higher temperature versions of the device. 
Several of the devices or combinations of components can be arranged in a 
battery tailored to various passenger weights, passenger in-car positions, 
and to specific vehicle collision velocities.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
Reference is made to FIG. 1 which shows device 18 in its installed 
condition, at rest and ready to function. The cylinder 20 is a strong 
structural member containing a pre-pressurized gas 22 (e.g. argon or 
helium or a mixture of hydrogen, oxygen, and an inert kinetic-damping gas, 
such as argon of helium), a piston 24, propellant explosive 26, initiator 
28, and a precision rupture disc 30. An air bag 32 is connected to 
cylinder 20 by a venturi 34. The venturi 34 is provided with several air 
inlets 36. 
The pre-pressurized gas 22 can be a chemically inert gas in a first 
embodiment, or it can also be a mixture of fuel and oxidizer capable of 
compression ignition, along with an inert kinetic-damping gas in a second 
embodiment. The pre-pressurized gas 22 is sealed within the walls of the 
cylinder 20 by initiator 28 and by rupture disc 30. The rupture disc 30 is 
the weakest structural member containing the pre-pressurized gas 22. The 
precision rupture disc 30 is sufficiently strong to contain and seal 
indefinitely the prepressurized gas 22 within cylinder 20. The 
pre-pressurized gas 22 is maintained at pressure until the initiator 28 
ignites the propellant explosive 26. The piston 24 separates, but does not 
hermetically seal the pre-pressurized gas 22 from the propellant explosive 
26. Therefore, propellant explosive 26 is also pressurized with the same 
pressure as the pre-pressurized gas 22, equalizing pressure on both sides 
of the piston 24. The initiator 28 is installed within the cylinder 20 in 
such a way as to permanently seal the cylinder 20. The venturi 34 
communicates with the interior of the air bag 32 and with the ambient air 
via the air inlets 36. The precision rupture disc seals the 
pre-pressurized gas 22 within the cylinder 20. 
Referring now to FIG. 2, wherein is shown the same device as FIG. 1, except 
in FIG. 2, the device 18 is beginning to function. The initiator 28 has 
been activated by the vehicle collision detection system (not shown). In 
this figure, the propellant explosive 26 in FIG. 1 has been ignited and is 
being converted to propellant gas 26A. The propellant gas 26A has 
developed sufficient pressure to begin driving piston 24 toward rupture 
disc 30 to further pressurize the pre-pressurized gas 22. The pressure in 
the pre-pressurized gas 22 has not yet become high enough to burst rupture 
disc 30. 
Referring now to FIG. 3, wherein is shown the device 18 during 
mid-function. The piston 24 has been driven sufficiently by the propellant 
gas 26A toward rupture disc 30 to compress and increase the temperature in 
the pre-pressurized gas 22 to auto-ignite the pre-pressurized gas if it is 
combustible. The pressure in the pre-pressurized gas 22 has now become 
high enough to burst the precision rupture disc 30. The precision rupture 
disc 30 has failed along the pre-inscribed grooves 40 in FIG. 13, so that 
the petals 42 in FIG. 14 of the rupture disc 30 open into their 
corresponding pattern 44 in the end of cylinder 20, in FIG. 15. The 
pre-pressurized gas 22, having been released by the failed rupture disc 
30, is moving rapidly through the venturi 34 and into air bag 32. Ambient 
air 46 is being drawn, by the Bernoulli effect, through air inlets 36 and 
is mixing with the pre-pressurized gas 22. 
Referring now to FIG. 4, wherein is shown the air bag 32 completely 
inflated. The piston 24 has stopped, having wedged itself into the beveled 
portion 49 of cylinder 20 and rupture disc 30. The expended propellant gas 
26B, still under residual pressure, is trapped within cylinder 20 by the 
piston 24. The expended propellant gas 26B remains sealed at a safe 
pressure. 
Referring now to FIG. 5, which is similar to FIG. 1, wherein is shown the 
device 18 in its installed condition, at rest and ready to function. In 
this case the device 18 is shown with a baffle 50, provided with a 
membrane 52. This baffle 50 fits within retaining groove 54 in the inner 
surface of cylinder 20. The baffle 50 with membrane 52 forms a gas tight 
seal to isolate component gas 56 (e.g. hydrogen and helium) from component 
gas 58 (e.g. oxygen). Component gases 56 and 58 are dissimilar gases and 
are prepressurized. Component gases 56 and 58 can be gases which are 
ignited by compression ignition when mixed and compressed, or they can be 
hypergolic gases which will self ignite when mixed, regardless of further 
compression. Also, component gas 56 can be a combustible gas mixture 
capable of compression ignition, and component gas 58 may be an inert gas. 
Referring now to FIG. 6, wherein is shown the same device as shown in FIG. 
5 except that the device 18 is beginning to function. The initiator 28 has 
been activated by the vehicle collision detection system (not shown). The 
propellant gas 26 in FIG. 5 has been ignited and is being converted to 
propellant gas 26A. The propellant gas 26A has developed sufficient 
pressure to drive piston 24 toward rupture disc 30, rupturing membrane 52, 
and further compressing pre-pressurized component gas 56 and component gas 
58. The membrane 52 of the baffle 50 is designed to fail when there is a 
relatively small pressure differential between component gas 56 and 
component gas 58, so that membrane 52 fails soon after piston 24 begins to 
move. This increases the pressure of component gas 58. The baffle 50 is 
anchored in retaining groove 54 in cylinder 20, preventing movement of the 
baffle 50. Component gas 58 passes through the opening in baffle 50, 
created by the removal of the membrane 52, as shown by arrows 60. The 
differential pressure between gases 56 and 58, caused by movement of 
piston 24, coupled with the nozzle effect of the opening in baffle 50 
causes the component gas 56 and component gas 58 to be rapidly mixed in 
the space formerly occupied by component gas 56. The pressure in the mixed 
component gas 56 and component gas 58 has not yet become high enough to 
burst the precision rupture disc 30. 
Referring now to FIG. 7, wherein is shown the same device 18 as is shown in 
FIGS. 5 and 6, except that the piston 24 has travelled far enough toward 
rupture disc 30 to shear the baffle 50 from its retaining groove 54, 
leaving an annular portion of the baffle 50 in retaining groove 54. The 
piston 24 is directly contacting and pushing the baffle 50. The reaction 
gas 62 (resulting from the combustion of component gas 56 and component 
gas 58 in FIG. 6) has not yet reached sufficient pressure to burst the 
precision rupture disc 30. 
Referring now to FIG. 8, wherein is shown the same device 18 as is shown in 
FIGS. 5-7, except the device is now shown nearing the completion of its 
function. The pressure in the reaction gas 62 has become sufficiently high 
that the precision rupture disc 30 has burst. Piston 24 continues to be 
driven by the propellant gas 26A toward rupture disc 30 in order to expel 
the reaction has 62 through venturi 34. Air bag 32 will be filled 
completely to the same condition as shown in FIG. 4. 
Referring now to FIG. 9, wherein is shown the referenced fourth embodiment 
in which no piston is used. A pre-pressurized mixture of combustible has 
64 (e.g. Oxygen and hydrogen) and inert kinetic-damping gas (e.g. argon or 
helium) is sealed within cylinder 20. The initiator 28 will ignite 
combustible gas 64, causing the pressure in cylinder 20 to increase until 
the precision rupture disc 30 fails. A pressurized mixture of fuel gas and 
oxidizer alone would detonate, shattering the containment vessel. The 
inert kinetic-damping gas, used in the correct proportions prevents 
detonation of the fuel gas and oxidizer, and regulates the reaction rate. 
The air bag 32 will be filled similarly to FIG. 4 with a safely breathable 
mixture of totally non-toxic gases. After deflation of air bag 32, the 
cylinder 20 will be inert and depressurized to ambient pressure. 
Referring now to FIG. 10, wherein is shown the referenced fifth embodiment, 
in which a piston is not used. Cylinder 20 contains a mixture of 
pre-pressurized oxygen and inert gas (e.g. helium or argon) 66. The 
cylinder 20 also contains liquid fuel 68, separated from oxygen and inert 
gas 66 by a membrane 52. 
Referring now to FIG. 11, wherein is shown the same device as shown in FIG. 
10, except the initiator 28 has been activated. When the initiator 28 was 
activated, the hot gas generated by the initiator 28 was expelled and is 
dispersing the liquid fuel 68 into the oxygen and inert gas 66. The hot 
gas and particles expelled by the initiator 28 cause the liquid fuel 68 to 
ignite as the liquid fuel 68 encounters the oxygen in the inert gas 66. 
Combustion of liquid fuel 68 is occurring along the combustion front 70 as 
the liquid fuel 68 (e.g. ethyl alcohol) mixes with oxygen and inert gas 66 
(helium and argon). The inert gas does not play as important a roll in 
causing kinetic-damping in this case because combustion can only occur as 
fast as the fuel mixes with the oxygen. A detonation front cannot develop 
because the fuel is not pre-mixed with the oxidizer. The pressure in 
cylinder 20 will increase until the precision rupture disc 30 fails, 
releasing the pressurized gas in cylinder 20 into the air bag 32, as 
previously illustrated in FIG. 4. After the deflation of air bag 32, the 
cylinder 20 will also be depressurized and inert. 
Referring now to FIG. 12, wherein is shown a device 72 similar in principle 
to device 74 shown in FIGS. 10 and 11, with the liquid fuel contained in a 
small fuel charge 76 and in a large fuel charge 78., with both charges 
located in the cylinder end 80. If the collision detection system of the 
vehicle (not shown) activates either the initiator of the small fuel 
charge 76, or the large fuel charge 78 (e.g. ethyl alcohol)--or both fuel 
charges, through leads 82 and/or 84, then the fuel from the appropriate 
charges will be expelled and dispersed into cylinder 20 and ignited. Only 
enough oxygen will be consumed to combust the quantity of fuel injected 
into the inert gas 66. Sufficient pressure will be developed by combustion 
to burst the precision rupture disc 30, regardless of which fuel charge(s) 
are injected. More than two different sizes of fuel charge may be used. 
The air bag 32 will be filled similarly to the air bag in FIG. 4 with the 
required quantity of a safely breathable mixture of gases. After deflation 
of air bag 32, the cylinder 20 will also be depressurized. 
Referring now to FIGS. 13, 14, and 15 wherein is shown details of precision 
rupture disc 30. The rupture disc 30 is of adequate strength to 
indefinitely retain the pre-pressurized gas in all design variants. The 
sharp internal corners, of fillets, in the bottom of the shallow inscribed 
grooves 40 provide stress risers in the rupture disc 30 so that when gas 
pressure reaches a predetermined level, cracks form at the sharp fillets 
at the bottom of the inscribed grooves 40. The cracks propagate through to 
the opposite surface of the rupture disc 30, causing the rupture disc to 
fail, as shown in FIG. 14, thus releasing the highly pressurized gas. 
Failure along these grooves results in the forming of "V" shaped petals 
which plastically deform into their corresponding recesses at the entrance 
to the venturi. The shape of the entrance to the venturi acts as a kinetic 
energy absorber to collect the petals as they deform, not allowing the 
petals to be torn off and accelerated toward the venturi opening. This 
guarantees that no disc petals will be ejected into the air bag. The 
precision rupture disc 30 shown in FIG. 14 and FIG. 15 has been ruptured. 
The thickness 86 of the precision rupture disc 30 controls the pressure of 
the gas needed to cause the rupture. When the pressure exceeds the 
strength of the precision rupture disc, the disc ruptures along the 
inscribed grooves 40 in FIG. 13. This leaves petals 42 in FIG. 14 and FIG. 
15 bent away due to pressure exerted by gas within the cylinder. 
Referring now to FIG. 16 which is a graph showing upper and lower industry 
performance specifications for passenger side air bags compared with the 
typical output performance of the present invention. 
The graph ordinate 88 shows pressure in kilo Pascals from 0 to 1200. (6.895 
kPa=1 pound per square inch). The abscissa 90 shows time from 0 to 80 
milliseconds. Lower line 92 shows the lower industry specification, while 
middle line 94 illustrates the upper industry specification for inflaters 
of this type. Together, these lines set forth model year 1999 maximum and 
minimum auto industry requirements for this system. Upper line 96 
illustrates the pressure-time performance which the present invention is 
capable of producing within the size and weight requirements spelled out 
by the industry for devices of this type. The present invention more than 
adequately meets the industry specifications. As can be observed, the 
present invention produces pressure buildup that is both greater and 
earlier than industry requirements. This allows for great flexibility in 
the sizing, tailorability and configuration of an inflater built with the 
present invention technology. 
Referring now to FIG. 17 wherein is shown the device omitting the piston. 
The cylinder 20 contains an initiator 28, two reactive liquids fuels 68A 
and 68B, which are segregated from each other and sealed within their 
cells by membranes 52A and 52B. Reaction chamber 99 may contain a 
pressurized inert gas (e.g. argon or helium) sealed within the cylinder 20 
by precision rupture disc 30. The reaction chamber 99 and the initiator 
expansion chamber 95 are connected by ignition tube 97. Therefore, the 
initiator expansion chamber 95 also may contain the pressurized inert gas. 
The ignition tube 97 equalizes the pressure between the inert gas in the 
reaction chamber 99 and the initiator expansion chamber 95. 
Referring now to FIG. 18 wherein is shown the same device as in FIG. 17 
except that the device is functioning. The initiator 28 has functioned, 
filling what was the initiator expansion chamber 95 in FIG. 17 with the 
hot expanding gaseous combustion products and particles of the initiator 
28. The hot gaseous products of the initiator 28 have ruptured the 
membranes 52A and 52B of FIG. 17, and are causing the injection of liquid 
fuel components 68A and 68B into reaction chamber 99 through injectors 98A 
and 99B. The action of the hot gas pressure and the geometry of the 
injectors is causing the liquid fuel components to atomize and become 
integrally mixed in the reaction chamber 99. A jet of the hot gaseous 
combustion products from initiator 28 has also passed through ignition 
tube 97 and has entered the reaction chamber 99 at the same time as the 
liquid fuel components 68A and 68B arrive. This jet of hot gaseous 
combustion products has ignited the mixing fuel components. The reaction 
of the liquid fuel components 68A and 68B has produced reaction product 
gases and heat which have increased the pressure inside the cylinder 20, 
bursting the precision rupture disc 30. The reaction gases are inflating 
the air bag, not shown.