Fire extinguishers – Portable vessels – Gas pressure
Reexamination Certificate
2000-09-13
2003-02-04
Ganey, Steven J. (Department: 3752)
Fire extinguishers
Portable vessels
Gas pressure
C169S012000, C149S019100, C252S002000
Reexamination Certificate
active
06513602
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to gas generators and to methods of generating a gas. In particular, the invention is directed to gas generators that may be used in any application requiring the relatively rapid generation of a gas, such as, e.g., inflation devices, fire suppression devices, and propulsion devices.
BACKGROUND OF THE INVENTION
Gas generators are useful in many applications, including the inflation of inflatable objects, such as, e.g., aircraft escape slides, life rafts, and vehicular passive restraints, i.e., air bags and inflatable seat belts. Gas generators are also used as propulsion devices, such as rocket and jet engines, which release a large quantity of hot gas at high speed, producing thrust. Gas generators have also been found to be useful as fire extinguishers and fire suppression devices.
There are three generic types of gas generators: pressurized gas, pure pyrotechnic, and hybrid. Pressurized gas gas generators produce 100 percent of the generated gas from a stored pressurized gas, while pyrotechnic gas generators produce all of the gas from the combustion of a solid, liquid, or gaseous pyrotechnic material. Hybrid gas generators use the combustion of a pyrotechnic material to heat and expand a pressurized gas, and may produce a portion, typically from less than 10 percent to over 90 percent, of the generated gas from combustion products produced by the combustion of the pyrotechnic material.
Pressurized gas gas generators provide the coolest gas, and have a gas flow rate that can be regulated with time. Pressurized gas generators, such as, e.g., carbon dioxide fire extinguishers, typically comprise a tank containing a compressed or liquefied gas, a valve to maintain the compressed or liquefied gas within the tank during storage and for releasing the gas when needed, an outlet, and means for directing the released gas, such as a nozzle or conduit. As a result, pressurized gas gas generators tend to be large and heavy, and are often expensive. In addition, as a gas cools as it expands, pressurized gas gas generators may freeze up before all of the gas is released. Where the gas is carbon dioxide, a substantial portion of the gas may not be released, as the gas becomes sufficiently cold to produce solid dry ice within the tank. The storage temperature of the gas generator can also have a large effect on pressure of the stored gas, as the pressure of the gas varies directly with the absolute temperature of the gas. For example, the pressure of a given volume of gas at 0° C. is only about 73 percent of the pressure of the same volume of gas at 100° C. As a result, the rate of gas generation is significantly reduced at low temperatures, and is significantly increased at high temperatures. In addition, a gas generator designed to produce a given pressure of gas at a given temperature will produce a lower pressure of gas for the same volume at low temperatures, and a higher pressure at high temperatures.
Pure pyrotechnic gas generators comprise a housing, a pyrotechnic gas generating material, which may be a solid, a liquid, or a gas, an igniter for initiating combustion of the pyrotechnic gas generating material, and an outlet. The output of pyrotechnic gas generators is a hot gas, produced by the combustion of the pyrotechnic material, and has a temperature of at least about 1000° C., which is near the limit of thermal acceptability in many applications. In addition, the housing of such devices becomes very hot during operation, as the combustion occurs within and in contact with the housing, heating the housing. Tortuous gas paths and/or heat sinks can be and are sued to reduce the temperature of the gas and the housing. As a result, however, pyrotechnic gas generators are heavy. In addition, pyrotechnic gas generators may require filters to remove particulates and heat from the gas stream in many applications, which also adds to the weight of the device. However, pyrotechnic gas generators are smaller and lighter than pressurized gas devices. Moreover, in most applications for propulsion devices, the temperature of the gas causes a rapid expansion of the gas, helping to provide thrust.
Because of deficiencies in cost, heat, toxicity, and performance, pure pyrotechnic gas generators are replaced with hybrid gas generators in some applications. Hybrid gas generators comprise a housing, containing a pyrotechnic material and a compressed gas, which is preferably inert, an igniter for initiating combustion of the pyrotechnic material, and a sealed outlet, which maintains the compressed gas within the housing, and opens to release the gas when the pressure of the gas is increased to a predetermined pressure upon heating of the gas by the combustion of the pyrotechnic material. Hybrid gas generators vary in performance, but the best provide a clean gas that is significantly cooler than that provided by pyrotechnic devices. The best hybrid gas generators for many applications are now less expensive than pyrotechnic devices, as a result of design improvements, and are now being installed in applications where pure pyrotechnic designs were typically used, such as, e.g., steering wheel air bag inflators.
As discussed above, gas generators have been shown to be useful in fire suppression, e.g., carbon dioxide and HALON® fire extinguishers. Fire suppression is typically achieved with the use of physical and/or chemical mechanisms to extinguish flaming and non-flaming or smoldering fires. The physical mechanism involves the physical displacement of oxidizer by the fire extinguishing composition and/or the absorption of an amount of heat sufficient to lower the temperature of the combusting materials below the ignition point by the molecules of a fire extinguishing composition, either of which terminates combustion. Generally, as the number of atoms in an extinguishment molecule increases the number of degrees of vibrational freedom also increases, and, thus, the heat capacity of the molecule increases, increasing the heat removal capacity of the extinguishment molecule. Physical suppression methods are most effective when directed at the base of the fire, where the fuel for the fire is typically located.
The chemical mechanism, on the other hand, involves interruption of the free radical fire-propagation chain reactions, which generally occur in the flames of a fire. The free radical fire-propagation chain reactions are the various reactions involving molecular oxygen and free radicals such as atomic hydrogen, atomic oxygen, and hydroxyl that often produce flame as well as the heat that keeps a fire burning. It has been speculated that halogen atoms, such as atomic bromine and iodine when present in sufficient numbers, disrupt these chain-propagation reactions, terminating both the chain reactions and combustion. Halides are ranked for their fire suppression capabilities, i.e., fluorine/fluorides are assigned a value of 1, chlorides 5, bromides 10, and iodides 16. That is, iodine is 16 times more effective than fluorine/fluorides. As a result, chemical suppression methods are generally most effective when directed into the flames of a fire where the free radical fire-propagation chain reactions occur and may be terminated.
A variety of agents and techniques are currently used for fire suppression, utilizing a chemical mechanism, a physical mechanism, or a combination of chemical and mechanical mechanisms. One conventional agent is pressurized water that extinguishes solely by thermal energy absorption. Water-based devices are not suitable, however, for use on electrical or flammable-liquid fires. Carbon dioxide, CO
2
, and dry-chemical extinguishers, now in use, typically displace oxygen and absorb thermal energy. However, dry-chemicals can leave a corrosive residue that is undesirable in many applications, such as electronic equipment. For use against grease fires, sodium bicarbonate extinguishers, potassium bicarbonate, urea-based potassium bicarbonate, and potassium chloride extinguishers are effective, but these can also leave a heavy
Lewis Donald J.
Magenot Michael C.
Olander Donald E.
Ganey Steven J.
Holden Jerry
Titus John D.
Universal Propolsion Company
LandOfFree
Gas generating device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas generating device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas generating device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3140356