Explosive and thermic compositions or charges – Containing inorganic nitrogen-oxygen salt
Reexamination Certificate
2001-03-02
2003-07-08
Delcotto, Gregory (Department: 1751)
Explosive and thermic compositions or charges
Containing inorganic nitrogen-oxygen salt
C149S074000, C149S088000, C149S092000
Reexamination Certificate
active
06589375
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to gas generant compositions. In particular, the invention is directed to low solids gas generant compositions containing basic copper nitrate, and having a relatively low flame temperature.
BACKGROUND
Single use, i.e., “one shot” gas generators are well known in the art, and have become commonplace for many applications. In general, such gas generators are used to perform work in an emergency or in an a situation requiring the one-time production of a working gas. For such applications, the gas must be provided on demand in a consistent manner with high reliability. That is, the gas must be provided in the amount and at the pressure required, and the gas generator must operate with high reliability when generation of the gas is required. Typical applications include, but are not limited to, inflating automotive air bags, dispersing munitions from a cruise missile with air bags, inflating safety devices, such as buoyancy devices. e.g., life rafts and life preservers, inflating temporary structures, such as airplane escape slides, moving mechanical devices, such as pistons and rotary actuators, and providing inert gas for fire suppression, etc.
Although pressurized gas stored in a pressure vessel may be utilized in certain applications, pressurized gas sources are large and heavy. As a result, many applications may be performed more efficiently and more reliably using a pyrotechnic gas generating device that produces warm or hot gases from the combustion of a pyrotechnic gas generating material. In general, pyrotechnic gas generators produce more energy per unit mass and per unit volume than do compressed gas devices. They are also typically more reliable, as gas may leak out of the pressurized gas systems during storage, resulting in the release of an insufficient amount of gas when the device is finally operated.
The performance requirements of pyrotechnic gas generators vary in accordance with different applications, where the gas produced must meet certain requirements for temperature, toxicity, and corrosiveness. As the choice of pure pyrotechnic gas generators is limited by the selection of gas generant compositions, the development of a gas generant to meet certain performance criteria, such as burn rate, operating pressure, mechanical integrity of the gas generant grains, operational temperature range, and water content, is somewhat of an art. The development of a gas generant generally requires a number of compromises to meet those performance requirements in addition to requirements for gas temperature, toxicity, and corrosiveness. For example, the toxicity and corrosiveness of the effluent gases are of particular concern in many inflatable devices, such as where an inflatable device is used in a confined environment in which humans are present; e.g., automotive air bags. The pyrotechnic gas generants used in such devices often must compromise performance to provide an acceptably low toxicity and corrosiveness in the gas composition.
Inflatable devices also typically require a relatively cool gas to prevent damage to the material from which the inflatable device is fabricated. A relatively cool gas may also be required to keep the inflatable device fully inflated for sustained periods of time, depending on the temperature of the environment. Where the gas used to inflate an inflatable device is significantly hotter than the surrounding environment when the device is initially inflated, the pressure within the device will decrease shortly after the inflation is complete as the gas cools, resulting in at least a partial deflation of the inflated device. Extra gas may be added to the inflatable device to maintain the required inflation pressure after the gas within the device cools. However, the device may be over inflated when the hot gases are initially discharged into the device, potentially rupturing the inflatable device during inflation.
Some early prior art air bag inflators used a sodium azide/metal oxide based gas generant compositions to inflate the air bags. The sodium azide/metal oxide compositions burn at relatively cool temperatures, on the order of from about 1000° to about 1200° C., and have burn rates sufficiently fast to provide the required air bag inflation times with reasonable gas generant grain sizes and inflator operating pressures. However, those compositions also produce a large amount of unwanted solid combustion products, which, typically, account for about 60 percent of the initial weight of the composition, and include a large percentage of sodium oxide, a highly caustic and corrosive material capable of damaging lung tissues if inhaled in any significant quantity. As a result, filtration is required to remove the solid combustion products from the inflation gases. To provide a sufficiently cool gas, prior art pyrotechnic gas generators thus generally require complex filtration and heat sinking assemblies within the gas generator to remove unwanted solid combustion byproducts and heat from the gas before the gas exits the gas generator. The requirement to thoroughly filter out this toxic solid combustion product significantly adds to the cost and complexity of the filtration system within the sodium azide based air bag inflators. Moreover, sodium azide is highly toxic and hazardous to the environment, making the manufacture and the disposal of old or fired sodium azide based inflators costly and hazardous.
More recent prior art pyrotechnic air bag inflators use pyrotechnic gas generant compositions that are more environmentally friendly than sodium azide based compositions. However, to achieve the same performance as the original sodium azide based inflators in prior art “non-azide” based gas generants generally requires a higher flame temperature than that of the original sodium azide based compositions, requiring additional heat sinking. Cooler burning non-azide based formulations are available, but typically have lower burning rates than azide formulations, and produce high levels of unwanted solid products of combustion, such that complex filtration is required. The prior art non-azide based gas generant formulations also tend to produce higher levels of toxic compounds in their effluent gases, such as, e.g., carbon monoxide, oxides of nitrogen, and hydrogen cyanide.
Hybrid inflators have been developed to mitigate the limitations of the newer non-azide based formulations. Hybrid inflators use a pressurized gas that is heated by a pyrotechnic gas generant to inflate the air-bag. The pressurized gas reduces the amount of gas generant required for the application, and provides additional cool gas to mix with the hotter gases provided by the gas generant composition, thus resulting in an overall lowering of the gas temperature. The pyrotechnic gas generant composition provides energy to the gas, allowing the inflator to meet weight and size requirements that cannot be met by compressed gas sources alone. Hybrid gas generators meet the gas temperature and particulate requirements of the air bag inflators at a lower cost than the first generation sodium azide based gas generators. However, hybrid inflators are more complex, and may be less reliable due to the use of pressurized gas. A purely pyrotechnic gas generator using a pyrotechnic composition that meets the performance, gas temperature, and toxicity requirements would be less expensive, less complex, and more reliable. However, a gas generant meeting all the air bag inflator requirements does not exist in the prior art.
A number of prior art second generation air bag gas generators use 5-amino tetrazole as a primary fuel in non-azide based gas generants. Most second generation gas generants provide adequate burn rates and operating pressures, but have flame temperatures as high as from about 2500° to about 3000° C. without the use of a coolant. For example, U.S. Pat. No. 5,035,757 to Poole discloses strontium nitrate as the primary oxidizer for a 5-amino tetrazole fuel in second generation gas generants. This composition is typically sto
Deppert Thomas M.
Dupont James
Knowlton Gregory D.
Ludwig Christopher P.
McFadden Dan
Delcotto Gregory
Talley Defense Systems, Inc.
LandOfFree
Low solids gas generant having a low flame temperature does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low solids gas generant having a low flame temperature, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low solids gas generant having a low flame temperature will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3020107