US20110101662A1 - Solid propellant/liquid type hybrid gas generator - Google Patents

Abstract

A gas generator comprising a housing having a mixing chamber and a pyrotechnic charge in the housing. A container having a liquid therein is disposed in the housing and has an open end and a closed end, with an end cap closing the open end and having a piston portion removably connected thereto and being movable within the liquid container to pressurize the liquid therein when the piston portion is separated from the end cap. The piston portion is positioned to be exposed to combustion gas from the pyrotechnic charge when it is ignited and is separable from the end cap when the combustion gas exceeds a predetermined pressure. In another embodiment, the liquid container may be a collapsible tube. The closed end of the liquid container has a weakened portion constructed to be opened when the pressure of the liquid in the container exceeds a predetermined pressure. The pyrotechnic charge and the weakened portion of the liquid container are in fluid communication with the mixing chamber so that combustion gases from the ignition of the pyrotechnic charge mix with and vaporize the liquid in the mixing chamber to generate a non-toxic, low temperature, low particulate inflation gas.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates generally to a gas generating device and more specifically, to a gas generating device which mixes liquid with the hot gaseous combustion products of a solid propellant or pyrotechnic charge.
• 2. Description of the Related Art
• Various gas generating arrangements have been proposed for the purposes of inflating a safety restraint device such as an airbag. However, many of these arrangements have simply released the hot combustion products into the inflatable device with very little modification other than filtering to remove particulate matter.
• In order to modify the gaseous products which are generated by the combustion of a solid propellant such as sodium azide mixed with an oxidizer such as potassium perchlorate, it has been proposed in U.S. Pat. No. 3,785,674 issued on Jan. 15, 1974 to Poole et al. to include a coolant chamber in the gas generator and to fill this chamber with a liquid halocarbon such as and to arrange for the halocarbon liquid to atomize in the nitrogen rich environment to reduce the temperature of the gas which is used to inflate the safety restraint (airbag). However, in this arrangement the gaseous combustion products are released directly into a chamber which contains the halocarbon liquid and which is closed by a burst disc. This of course, requires heating the liquid to its boiling point. The resulting mixture of gaseous halocarbon and hot combustion products is reactive, and part of the halocarbon decomposes. The decomposition of halocarbon results in the formation of lower molecular weight halogen compounds (including HCl and HF), which are toxic. For this reason, halocarbons are not used in hybrid airbag inflators.
• U.S. Pat. No. 3,862,866 issued on Jan. 28, 1975 in the name of Timmerman et al. describes an arrangement which is essentially similar to the Poole et al. device, with the basic exception that water is used in place of halocarbon liquid. However, this arrangement is such that a slug of unvaporized liquid is apt to be shot out of the device only to result in the water being sprayed like a shower of rain throughout the interior of the airbag.
• Thus, while these arrangements may find application as fire extinguishers of the nature disclosed in U.S. Pat. No. 5,449,041 issued on Sep. 12, 1995 in the name of Galbriath, wherein a solid propellant charge is ignited and used to drive a volume of liquid having flame suppressing capabilities, against a fire in a manner which suppresses and extinguishes it, they have failed to make the most efficient use of the cooling effect possible with the liquid used.
• Another problem that these arrangements have failed to address is that of low temperature climates in which liquids, such as water, are apt to freeze and thus fail to achieve cooling of any degree, and/or even hinder the operation of the device by generating a block of solid material (ice) that is apt to either block the exits or turn into a missile which is fired out of the device in a highly undesirable manner.
• The above problem is further aggravated in that the use of halocarbon liquids, which would tend to alleviate the freezing problem, are now severely restricted in light of various environmental considerations.
SUMMARY OF THE INVENTION
• It is an object of the present invention to provide a gas generating device for airbags and the like, which achieves thorough mixing of the pyrotechnic combustion gas and liquid that results in an efficient cooled gas high yield and which therefore achieves an efficient use thereof.
• It is a further object of this invention to provide such a gas generating device which maintains the coolant liquid at a temperature above its freezing point and thus maintains the device properly operable irrespective of the climate in which the safety device associated with the gas generator is used.
• In brief, the above objects are achieved by an arrangement wherein the combustion of a relatively small pyrotechnic charge is used to pressurize a chamber of a suitable type of liquid, and force it out of the chamber into a mixing chamber wherein it is caused to intimately mix and vaporize in a high speed stream of gas resulting from the combustion of the charge. The sensible heat of the combustion products is absorbed by the liquid which is accordingly converted into a large volume of liquid vapor. The mixture of vaporized liquid and combustion gas is used to inflate the airbag with a non-toxic, low temperature, low particulate atmosphere.
• In one embodiment of the invention, which may be used for any suitable airbag inflator application, such as a side impact inflator, an elongated, generally cylindrical housing, comprises at one end an igniter, a booster charge disposed inwardly of the igniter, and a pyrotechnic charge or solid propellant of any suitable type disposed inwardly of the booster charge. A cup-type partition surrounds the inner portion of the pyrotechnic charge and is provided with a plurality of first orifices on the periphery thereof spaced from the inner periphery of the housing, and one or more second orifices in the inner end thereof.
• A chamber tube is disposed inwardly of the cup-type partition and comprises a cap at the end thereof adjacent to the partition, the cap being removably secured to the chamber tube and being slidable therein. The other end of the chamber tube is closed and comprises a thin or weakened section that will fail or open when exposed to a predetermined pressure. The chamber tube is filled with a suitable liquid such as an aqueous solution of a freezing point depressant such as calcium chloride. The periphery of the chamber tube is spaced inwardly from the inner periphery of the housing to provide an annular channel between the chamber tube and the housing for the combustion gases from the pyrotechnic charge when ignited that flow out of the first peripheral orifices in the cup-type partition for the propellant.
• The other end of the housing comprises a mixing chamber that is defined by an inner housing member having an inner end disposed adjacent to the closed end of the chamber tube, the inner end of the inner housing member having an aperture in alignment with the weakened portion in the closed end of the chamber tube. The second partition comprises a plurality of peripheral third orifices that are spaced inwardly from the inner periphery of the housing and are in communication with the annular gas flow channel between the chamber tube and the housing that is turn in communication with the first peripheral orifices and the cup-type partition surrounding the propellant. At its outer end, the inner housing member is secured to or formed integrally with a flow manifold having a plurality of equally spaced radial exhaust ports for connection to a manifold and/or an airbag or the like.
• In the operation of the one embodiment, the actuation of the igniter causes ignition of the booster charge and the propellant to generate combustion gas that flows out of the first peripheral orifices in the partition, through the annular flow channel surrounding the chamber tube and into the mixing chamber through the peripheral third orifices in the inner housing member at the end of the housing. The combustion gases also flow axially through the second orifice or orifices in the inner end of the partition to create sufficient pressure against the adjacent chamber cap to cause it to separate from the chamber tube and move inwardly therein to pressurize the liquid in the chamber tube. The increased pressure in the chamber tube causes the weakened portion at the closed end thereof to open to allow the pressurized liquid to flow into the mixing chamber through the aperture in the adjacent inner end of the inner housing member.
• In the mixing chamber, the combustion gas and pressurized liquid are intimately mixed to vaporize the liquid. The sensible heat of the combustion products is absorbed by the liquid which is accordingly converted into a large volume of liquid vapor. The mixture of vaporized liquid and combustion gas then flows out of the radial exhaust ports of the flow manifold to inflate an airbag or the like with an essentially non-toxic, low temperature, low particulate atmosphere.
• In another embodiment of the invention for an airbag inflator or the like, the housing can be circular or of short, compact cylindrical construction, and the igniter, booster charge and propellant can be spaced radially rather than longitudinally from the chamber tube. The operation of this embodiment is essentially the same as that of the one embodiment described herein.
• In a still further embodiment of the invention, the chamber tube is a flexible tube that is collapsed by the combustion gas pressure to cause a weakened portion at the one end thereof to open to allow the pressurized liquid therein to flow into the mixing chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1A is a side elevational view, with parts broken away, of one embodiment of the gas generator of the present invention;
• FIG. 1B is a side elevational view likeFIG. 1A showing a modified gas generator construction;
• FIG. 1C is a side elevational view likeFIG. 1A showing a further modified gas generator construction;
• FIG. 2 is a side elevational view, with parts broken away, of another embodiment of the gas generator of the present invention;
• FIG. 2A is a side elevational view likeFIG. 2, with parts broken away, of a further embodiment of the gas generator.
• FIG. 3A is a side elevational view, with parts broken away, of a still further embodiment of the gas generator; and
• FIG. 3B is a top plan view, with parts broken away, of the gas generator shown inFIG. 3A.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1A shows one embodiment of the present invention in the form of agas generator10 that may be used as a side impact or other inflator for an airbag or the like. Thegas generator10 comprises an elongated, generallycylindrical housing12 formed of any suitable metal or other material having anigniter14 of any suitable type at one end thereof. Abooster charge16 of any suitable type is disposed inwardly of theigniter14 and a pyrotechnic charge orsolid propellant18 of any suitable type is disposed inwardly of thebooster charge16. A cup-like partition20 surrounds the inner portion of the pyrotechnic charge orpropellant18 and has a reduceddiameter end portion22 with a plurality offirst orifices24 in the periphery thereof and a second orifice ororifices26 in the inner end thereof.
• Achamber tube28 is disposed in thehousing12 inwardly of theend portion22 of thepartition20 and is of a diameter less than the internal diameter of thehousing12 to provide an annulargas flow channel30 therebetween that is in communication with thefirst orifices24 in the periphery of theend portion22 of thefirst partition20. Thechamber tube28 comprises anend cap32 that is removably connected thereto and is disposed adjacent to theend22 of thepartition20. Thechamber tube28 andend cap32 may be formed of any suitable material and may be connected together in a suitable manner. As an illustrative example, thechamber tube28 andend cap32 may be formed of a suitable plastic such as polypropylene that has low moisture permeability and is resistant to high and low temperatures. Theend cap32 may be adhesively or otherwise connected to thechamber tube28 and provided with aninner piston portion34 that is slidable within thechamber tube28 when separated from theend cap32 by exposure to a predetermined pressure. As an illustrative example, thepiston portion34 may be connected to theend cap32 by a weakened orfrangible section36.
• Thechamber tube28 is filled with a suitable liquid, such as a calcium chloride and water mixture to prevent freezing of the liquid when exposed to low temperatures and boiling of the liquid when exposed to high temperatures. As an illustrative example, the calcium chloride may be mixed with water to a concentration level of between 20 to 40% by weight which provides protection against freezing down to −50° C. and against boiling up to 115° C. Within the scope of the present invention, other suitable liquids may be used within the knowledge of one skilled in the art.
• The other end of thechamber tube28 is closed and is provided with a weakenedportion40 that is constructed to be opened when exposed to a predetermined liquid pressure within the chamber tube to create an exit opening for the liquid under pressure therein. Aninner housing member42 extends inwardly from the other end of thehousing12 and comprises aninner end portion44 with anaperture46 disposed adjacent to and in alignment with the weakenedportion40 of thechamber tube28. Theinner housing member42 comprises a plurality ofthird orifices48 in the periphery thereof that are in communication with theannular flow channel30 between thechamber tube28 and thehousing12. Theinner housing member42 defines a mixingchamber50 therein for combustion gas flowing inwardly through theorifices48 and pressurized liquid flowing inwardly from thechamber tube28 through theaperture46 in theend portion44.
• Theinner housing member42 may be connected at its outer end to aflow manifold52 of any suitable type that may have a plurality ofopenings54 for thrust-neutral operation and may be connected in any suitable manner to a manifold (not shown) and/or an airbag (not shown).
• To protect thechamber tube28 from direct contact with hot combustion gases in theannular flow channel30, it may be surrounded by asecond tube56 formed of any suitable material, such as metal. Thesecond tube56 may be secured to theinner housing member42 in any suitable manner and serves to define a smoothannular flow channel30 between it and thehousing12. Thesecond tube56 may be constructed so as not to be parallel or concentric with the inner peripheral surface of thehousing12 for the purpose of varying the width of theannular flow channel30, if desired. Within the scope of the present invention, thesecond tube56 may be omitted, as shown inFIG. 1B.
• In the operation of thegas generator10 shown inFIG. 1A, the actuation of theigniter14 ignites thebooster charge16 and thepyrotechnic charge18 to generate combustion gases that flow out of thefirst orifices24 in the periphery of theend portion22 of thepartition20 into theannular flow channel30 between thechamber tube28 and thehousing12. The hot combustion gases also flow out of the orifice ororifices26 in theend portion22 of thepartition20 into contact with thepiston portion34 of theend cap32 of thechamber tube28. The pressure of the combustion gas on thepiston portion34 serves to separate it from theend cap32 by breaking the weakenedportion36 to cause thepiston portion34 to slide inwardly into the chamber tube and pressurize the liquid therein. The increased liquid pressure causes the failure of the weakenedportion40 in the end of thechamber tube28 to enable the pressurized liquid to flow out of thechamber tube28 through theaperture46 in theadjacent end44 of theinner housing member42 and into the mixingchamber50 thereof. The hot combustion gases flowing through theannular flow channel30 also enter the mixingchamber50 through theorifices48 in the periphery of theinner housing member42 to mix with the liquid entering the mixingchamber50.
• The hot combustion gases and the liquid are intimately mixed in the mixingchamber50 to vaporize the liquid therein. The sensible heat of the combustion products is absorbed by the liquid which is accordingly converted into a large volume of vapor. The mixture of vaporized liquid and combustion gas then flows through theexit orifices54 of theflow manifold52 to inflate an airbag (not shown) or the like with a non-toxic, low temperature, low particulate atmosphere.
• FIG. 1C illustrates another embodiment of agas generator210 that is similar in construction and operation to thegas generator10 shown inFIG. 1A. Like thegas generator10, thegas generator210 shown inFIG. 1C generally comprises ahousing212, anigniter214, abooster charge216, apyrotechnic charge218, a cup-like partition220 surrounding the inner portion of the pyrotechnic charge, achamber tube228 disposed inwardly of thepartition220 and comprising anend cap232 andpiston portion234. The other end of thechamber tube228 is provided with a weakenedportion240 and aninner housing member242 extends inwardly from the other end of thehousing212 and comprises an inner end portion244 with anaperture246 disposed adjacent to and in alignment with the weakenedportion240 of thechamber tube228. Theinner housing member242 comprises a plurality ofthird orifices248 in the periphery thereof that are in communication with theannular flow channel230 between thechamber tube228 and thehousing212. Theinner housing member242 defines a mixingchamber250 therein for combustion gas flowing inwardly through theorifices248 and pressurized liquid flowing inwardly from thechamber tube228 through theaperture246 and the end portion244.
• The embodiment of thegas generator210 shown inFIG. 1C differs from the gas generator shown inFIG. 1A in that the cup-like partition220 does not have first orifices in the periphery thereof and the inner end thereof is provided with a second orifice or orifices226 that are spaced from theend cap232 of thechamber tube228. Accordingly, combustion gases flowing through the second orifices226 in the inner end of thepartition220 simultaneously pressurize thepiston portion234 of thechamber tube228 and theannular flow channel230 leading to theinner housing member242 which defines the mixingchamber250.
• FIG. 2 illustrates a further embodiment of agas generator110 that is similar in operation to thegas generator10 shown inFIG. 1A and is formed with a compact circular or shortcylindrical housing112 for use as an airbag inflator, such as a frontal inflator, or the like.
• In thegas generator110, theigniter114,booster charge116 andpyrotechnic charge118 are positioned in side by side relation next to thechamber tube128 having theend cap132 and themovable piston portion134 disposed therein. The inner or upper closed end of thechamber tube128 is formed with a weakenedportion140 in alignment with anexit orifice146 in apartition147. Theexit orifice146 opens into a mixingchamber150 in the upper portion of aninner housing member142 which has a plurality oforifices148 in the periphery thereof that are exposed to thepyrotechnic charge118 in thehousing112. The mixingchamber150 is in communication with an upper or outer flowmanifold portion152 havingradial openings154 therein for communication with a manifold (not shown) and/or an airbag (not shown).
• The operation of thegas generator110 is the same as that of thegas generator10 shown inFIG. 1A. The ignition of thepropellant118 generates combustion gases that enter the mixingchamber150 through theorifices148 in theinner housing member142. The combustion gases also cause thepiston portion134 to separate from theend cap132 of thechamber tube128 so that thepiston portion134 moves inwardly in thechamber tube128 to pressurize the liquid therein and open the weakenedportion140 in the closed end of thechamber tube128 to cause liquid to flow through theexit opening146 into the mixingchamber150 wherein it mixes with the hot combustion gases entering the mixingchamber150 through theorifices148 in theinner housing member142. The mixed combustion gases and vaporized liquid then enter theflow manifold portion152 through theopenings151 in the mixingchamber150 and exit theopenings154 therein to inflate an airbag (not shown) or the like.
• FIG. 2A illustrates another embodiment of agas generator310 that is similar in construction and operation to thegas generator110 shown inFIG. 2. In thegas generator310, theigniter314 is located in the middle of the lower portion of thehousing312 and is surrounded by apyrotechnic charge318 that is in fluid communication with a mixingchamber350 throughorifices348 in apartition349.
• Achamber tube328 is disposed within thepartition349 above theigniter314 and comprises anend cap332 and amovable piston portion334 removably connected thereto. The upper closed end of thechamber tube328 is formed with a weakenedportion340 in alignment with anexit aperture346 in thepartition349 which opens into the mixingchamber350. Thepiston portion334 is in fluid communication with thepyrotechnic charge318.
• The mixingchamber350 is in fluid communication with a flow manifold (not shown) and/or an airbag (now shown).
• The operation of thegas generator310 is generally the same as that of thegas generator110 shown inFIG. 2. The ignition of thepropellant318 generates combustion gases that enter the mixingchamber350 through theorifices348 in thepartition349. The combustion gases also cause thepiston portion334 to separate from theend cap332 of thechamber tube328 so that the piston portion moves inwardly in thechamber tube328 to pressurize the liquid therein and open the weakenedportion340 in the closed end of thechamber tube328 to cause liquid to flow through theexit opening346 into the mixingchamber350 wherein it mixes with the hot combustion gases entering the mixingchamber350 through theorifices348 in thepartition349. The mixed combustion gases and vaporized liquid then enter a flow manifold (not shown) or the like to inflate an airbag (not shown) or the like.
• FIGS. 3A and 3B illustrate a still further embodiment of agas generator410 that is similar in construction and operation to thegas generators10 and210 shown inFIGS. 1A,1B and1C. Thegas generator410 comprises an elongated, generallycylindrical housing412 formed of any suitable metal or other material having anigniter414 of any suitable type at one end thereof. Abooster charge416 of any suitable type is disposed inwardly of theigniter414 and a pyrotechnic charge orsolid propellant418 of any suitable type is disposed inwardly of thebooster charge416. A cup-like partition420 surrounds thebooster charge416 and pyrotechnic charge orpropellant418 and has a plurality offirst orifices424 in the periphery thereof andsecond orifices426 in theinner end portion422 thereof.
• Achamber tube428 is disposed in thehousing412 inwardly of theend portion422 of thepartition420 and is of a diameter less than the internal diameter of thehousing412 to provide an annulargas flow channel430 therebetween that is in communication with thefirst orifices424 andsecond orifices426 in thepartition420. Thechamber tube428 is a flexible tube having a flat, sealedouter end432 and aninner end433 having a weakenedportion440 that is constructed to be opened when exposed to a predetermined liquid pressure within the chamber tube to create an exit opening for the liquid under pressure therein. Thechamber tube428 may be formed of any suitable material, e.g., a suitable plastic such as polyethylene. Thechamber tube428 is filled with a suitable liquid, such as a calcium chloride and water mixture to prevent freezing of the liquid when exposed to low temperatures and boiling of the liquid when exposed to high temperatures. The calcium chloride concentration may be the same as that described herein with respect to thechamber tube28 inFIGS. 1A and 1B.
• Aninner housing member442 extends inwardly from the other end of thehousing412 and comprises aninner end portion444 with anaperture446 disposed adjacent to and in alignment with the weakenedportion440 of thechamber tube428. Theinner housing member442 comprises a plurality ofthird orifices448 in the periphery thereof that are in communication with theannular flow channel430 between thechamber tube428 and thehousing412. Theinner housing member442 defines a mixingchamber450 therein for combustion gas flowing inwardly through theorifices448 and pressurized liquid flowing inwardly from thechamber tube428 through theaperture446 in theend portion444 of theinner housing member442. Theinner housing member442 may be connected at its outer end to aflow manifold452 of any suitable type that may have a plurality ofopenings454 for thrust-neutral operation and may be connected in any suitable manner to a manifold (not shown) and/or an airbag (not shown).
• To protect thechamber tube428 from direct contact with hot combustion gases in theannular flow channel430, it may be surrounded by asecond tube456 formed any of suitable material, such as metal. Thesecond tube456 may be secured to theinner housing member442 in any suitable manner and serves to define a smoothannular flow channel430 between it and thehousing412. Thesecond tube456 may be constructed so as not to be parallel or concentric with the inner-peripheral surface of thehousing412 with the purpose of varying the width of theannular flow channel430, if desired. Within the scope of the present invention, thesecond tube456 may be omitted, as shown inFIG. 1B.
• In the operation of thegas generator410 shown inFIGS. 3A and 3B, the actuation of theigniter414 ignites thebooster charge416 and thepyrotechnic charge418 to generate combustion gases that flow out of thefirst orifices424 and thesecond orifices426 in thepartition420 into contact with the adjacent flat end of thechamber tube428 and into theannular flow channel430 between thechamber tube428 and thehousing412. The pressure of the combustion gas on theflexible chamber tube428 causes it to collapse to pressurize the liquid therein. The increased liquid pressure causes the failure of the weakenedportion440 in the inner end of thechamber tube428 to enable the pressurized liquid to flow out of thechamber tube428 through theaperture446 in theadjacent end444 of theinner housing member442 and into the mixingchamber450 thereof. The hot combustion gases flowing through theannular flow channel430 enter the mixingchamber450 through theorifices448 in the periphery of theinner housing member442 to mix with the liquid entering the mixingchamber450.
• The hot combustion gases and the liquid are intimately mixed in the mixingchamber450 to vaporize the liquid therein. The sensible heat of the combustion products is absorbed by the liquid which is accordingly converted into a large volume of vapor. The mixture of the vaporized liquid and combustion gas then flows through theexit orifices454 of theflow manifold452 to inflate an airbag (not shown) or the like with a non-toxic, low temperature, low particulate atmosphere.
• Within the scope of the present invention, the components of thegas generators10,110,210,310 and410 can be formed of any suitable materials, the pyrotechnic charge can be any suitable type of charge or propellant, and the liquid in the chamber tube can be any suitable type of liquid.
• While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (4)

1-19. (canceled)

20. A gas generator comprising:

a housing having a mixing chamber;

a pyrotechnic charge in said housing;

a flexible container in said housing having a liquid therein, said flexible container having an outer closed end adjacent to said pyrotechnic charge and an inner end having a weakened portion constructed to be opened when the pressure of the liquid therein exceeds a predetermined pressure;

said pyrotechnic charge and said weakened portion of said liquid container being in fluid communication with said mixing chamber;

whereby when said pyrotechnic charge is ignited, the combustion gas therefrom enters said mixing chamber and also contacts said flexible liquid container to collapse it to pressurize the liquid therein and open said weakened portion when the liquid pressure exceeds the predetermined pressure to enable liquid to flow from said liquid container into said mixing chamber wherein the liquid and combustion gas are mixed to vaporize the liquid and cool the combustion gas.

21. The gas generator ofclaim 20 wherein said mixing chamber is defined by an inner housing member disposed within said housing adjacent to said inner end of said flexible liquid container, said inner housing having an aperture disposed adjacent to and in alignment with said weakened portion of said liquid container.

22. The gas generator ofclaim 20 wherein said liquid container has a flat sealed outer end adjacent to said pyrotechnic charge.

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