| abstract |
The present invention is directed to a high thermal efficiency inflator having a thermal efficiency of greater than about 90 percent, to passive restraint systems utilizing the high thermal efficiency inflator of the invention, and to a method of inflating inflatable objects. The high thermal efficiency inflator has a housing having an inner surface, and defining an interior volume. The housing contains a pressurized gas at a first pressure in the interior volume; and a pyrotechnic material for producing heat upon combustion. The pyrotechnic material has a burn rate that is accelerated at the first pressure, and is subjected to the first pressure of the pyrotechnic material within the housing. In addition, the pyrotechnic material is substantially free of thermal contact with the housing, and is stored within the interior volume of the housing at a distance from the inner surface of the housing. The pyrotechnic material is in thermal contact with an ignitor for initiating combustion of the pyrotechnic material upon receipt of an initiation signal. A seal maintains the pressurized gas at the first pressure within the interior volume, where the means will open when the gas attains a predetermined second, higher pressure upon heating of the pressurized gas by combustion of the pyrotechnic material to allow an inflation gas to pass from the housing. Because of the burning rate of the propellant, the pressure of the gas, and the distance between the pyrotechnic material and the housing, significant contact between the burning pyrotechnic material and the inner surface of the housing is substantially prevented, and may be further reduced by utilizing internal insulators and a frangible central charge holder. As a result, at least about 90 percent of the heat produced by the combustion is transferred to the inflation gas, and no more than about 10 percent of the heat is transferred to the housing, resulting in a thermal efficiency of the high thermal efficiency inflator of at least about 90 percent, and an increase in temperature of the housing of no more than about 20° C. during functioning of the high thermal efficiency inflator. |