RELATED APPLICATIONThis application is a continuation-in-part of application Ser. No. 07/761,685 filed Sep. 18, 1991 by Jack L. Blumenthal and Nahum Gat and entitled “Apparatus for Inflating a Vehicle Occupant Restraint” now abandoned. The benefit of the earlier filing data of the aforementioned application Ser. No. 07/761,685 has been and hereby is claimed.
FIELD OF THE INVENTIONThe present invention relates to a new and improved apparatus for inflating an inflatable device such as a vehicle occupant restraint.
BACKGROUND OF THE INVENTIONKnown structures for inflating a vehicle occupant restraint are disclosed in U.S. Pat. Nos. 3,806,153, 3,868,124 and 3,895,821. In each of the structures disclosed in these patents, air, or other gas, and solid gas generating material are stored in a container. Upon the occurrence of a high rate of vehicle deceleration indicative of a collision, the gas in the container is released to inflate a vehicle occupant restraint which restrains a vehicle occupant during the collision. Also, upon the occurrence of a high rate of vehicle deceleration which is indicative of a vehicle collision, the gas generating material is ignited. As the gas generating material burns, it forms hot gases or vapors which heat and mix with the stored gas, and the heated mixture of gases flows into the occupant restraint.
SUMMARY OF THE INVENTIONThe present invention provides a new and improved apparatus for inflating an inflatable device such as a vehicle occupant restraint. The apparatus includes a containing means for receiving gases to provide a combustible mixture of the gases. The apparatus also includes an igniter means for igniting the mixture of gases to warm and increase the pressure of gas in the containing means. The apparatus further includes a directing means which directs gas from the containing means to the inflatable device.
Preferably, the mixture of gases includes an inert gas, a flammable fuel gas and an oxidizer gas. The inert gas is preferably nitrogen or argon or a mixture of nitrogen and argon. The fuel gas is preferably hydrogen or methane or a mixture of hydrogen and methane but may be any other flammable gas. The oxidizer gas is preferably oxygen. Alternatively, the inert gas can be eliminated and a combustible gas mixture that is very fuel lean could be used. A small amount of an inert tracer gas such as helium may also be added to assist in leak checking the apparatus.
The containing means may take a variety of different forms. In one embodiment of the invention, the containing means is a single container for containing the inert gas, the fuel gas, and the oxidizer gas as a mixture of gases. Alternatively, the single container may contain the very fuel lean combustible gas mixture.
In another embodiment, a first container contains the fuel gas, a second container contains the oxidizer gas, and the containing means defines a combustion chamber which receives the fuel gas and oxidizer gas and in which the mixture of gases is ignited. In this embodiment the amount of oxidizer gas used is in excess of a stoichiometric amount to support combustion of the fuel gas.
In accordance with the present invention, the rate of inflation of the inflatable device can be controlled to provide a desired volume of the inflatable device at a given time after ignition of the fuel gas. The rate of inflation of and the pressure in the inflatable device can be controlled by selecting the amount of fuel gas and oxidizer gas to yield, a desired burning rate which in turn determines the predetermined volumetric rate of flow of warm gas into the inflatable device. Alternatively or additionally, the rate of inflation can be controlled by flow control orifices or the like through which the gas flows into the inflatable device. Another technique for controlling the time required for inflation is to change the number of locations in the containing means at which the fuel gas is ignited.
An improved igniter means is provided for igniting a mixture of gases. The igniter means is operable to transmit energy through an imperforate wall portion of the containing means. The energy transmitted through the imperforate wall portion of the containing means effects ignition of ignitable material in the containing means. Specifically, an ignitable charge located adjacent to an outer side of the imperforate wall portion of the containing means is ignitable to cause ignition of an ignitable charge which is disposed adjacent to an inner side of the imperforate wall portion of the containing means. In accordance with another feature of the igniter means, an elongated core in a frangible sheath is disposed in the containing means. The elongated core is ignited with a resulting shattering of the sheath and spewing of incandescent reaction products into the containing means.
BRIEF DESCRIPTION OF THE DRAWINGSThe foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following specification with reference to the accompanying drawings, in which:
FIG. 1 is a schematic illustration of one embodiment of the present invention;
FIG. 2 is a schematic illustration of a second embodiment of the present invention;
FIG. 3 is a schematic illustration of a third embodiment of the present invention;
FIG. 4 is a sectional view of part of a vehicle occupant safety apparatus constructed in accordance with the present invention;
FIG. 5 is a graphic illustration of performance characteristics of a typical vehicle occupant safety apparatus constructed in accordance with the invention;
FIG. 6 is a schematic illustration of a fourth embodiment of the present invention;
FIG. 7 is a schematic illustration of a fifth embodiment of the present invention;
FIG. 8 is an enlarged fragmentary schematic illustration of a portion of the apparatus of FIG. 7; and
FIG. 9 is a sectional view, taken generally along theline9—9 of FIG.8.
DESCRIPTION OF EMBODIMENTS OF THE INVENTIONEmbodiment IThe present invention may be embodied in a number of different structures. As representative, FIG. 1 illustrates the present invention as embodied in a vehicleoccupant safety apparatus10. The vehicleoccupant safety apparatus10 includes an inflatable vehicle occupant restraint12 and apparatus for inflating the vehicle occupant restraint.
Upon the occurrence of a high rate of vehicle deceleration which is indicative of a vehicle collision, thevehicle occupant restraint12 is inflated to restrain movement of an occupant of the vehicle. The inflatablevehicle occupant restraint12 is inflated into a location in the vehicle between the occupant and certain parts of the vehicle, such as the steering wheel, instrument panel or the like, before the occupant moves relative to those parts and forcibly strikes the parts during a vehicle collision. The inflated vehicle occupant restraint12 absorbs kinetic energy of the occupant's movement and restrains the occupant's movement so that the occupant does not forcibly strike parts of the vehicle. Such a vehicle occupant restraint may be inflated by different gases. Notwithstanding the gas used to inflate thevehicle occupant restraint12, the vehicle occupant restraint is commonly referred to as an air bag.
Thevehicle occupant restraint12 is inflated by a flow of gas form acontainer14. Thecontainer14 has achamber16 which holds amixture18 of gases. Themixture18 of gases preferably includes a fuel gas, an oxidizer gas for supporting combustion of the fuel gas, and an inert gas. The inert gas is preferably nitrogen, argon or a mixture of nitrogen and argon. The oxidizer gas is preferably oxygen. The fuel gas is preferably hydrogen, but may be methane, or a mixture of hydrogen and methane which is a gaseous hydrocarbon.
Alternatively, the mixture of gases incontainer14 may be an oxidizer gas and a fuel gas in amounts which provide a very fuel lean mixture, i.e., the amount of oxidizer gas exceeds that amount required to support combustion of the fuel gas.
Themixture18 of gases in thecontainer14 readily combusts, when ignited, but otherwise is not explosive. As such, themixture18 of gases could have many different compositions. The fuel gas may be 2 to 16 molar percent of themixture18 of gases. The oxidizer gas may be 7 to 98 molar percent of themixture18 of gases. The balance is inert gas which may be 0 to 91 molar percent of themixture18 of gases. Preferably, themixture18 of gases includes 10-14 molar percent hydrogen, 15-25 molar percent oxygen, and 61-75 molar percent inert gas.
Themixture18 of gases in thecontainer14 is normally under pressure. The pressure depends upon such factors as the volume of thevehicle occupant restraint12 to be inflated, the time available for inflation, the inflation pressure desired, the volume of the container for themixture18 of gases, and the percentage of each of the gases in themixture18 of gases. Normally, themixture18 of gases in thecontainer14 may be at a pressure of 500 to 5,000 pounds per square inch (psi). Preferably, themixture18 of gases in thecontainer14 is at a pressure of 1,000 to 3,000 psi. However, the invention is applicable to any mixture of gases regardless of pressure.
In one specific embodiment, themixture18 of gases is dry air and hydrogen. The mixture of dry air and hydrogen may range from 86 molar percent air and 14 molar percent hydrogen to 92 molar percent air and 8 molar percent hydrogen. However, it is presently preferred to have a range from 90 molar percent air and 10 molar percent hydrogen to 87 molar percent air and 13 molar percent hydrogen.
Upon the occurrence of sudden vehicle deceleration, adeceleration sensor22, of any known and suitable construction, activates anigniter24 in thechamber16 to ignite the fuel gas in themixture18 of gases. The combustion of the fuel gas is supported by the oxidizer gas. As the fuel gas burns, the pressure in thechamber16 rises due to warming of the gases by the heat of combustion created by burning of the fuel gas and the formation of additional gases or vapors produced by combustion of the fuel gas. After a predetermined time, or when a predetermined pressure is reached in thechamber16, anend wall28 of thecontainer14 bursts, and warm gas flows into thevehicle occupant restraint12 through a flow controller orifice. As the gas flows into thevehicle occupant restraint12, the gas inflates thevehicle occupant restraint12 into a predetermined position for restraining a vehicle occupant.
If the amount of hydrogen is less than about 8 molar percent, difficulty may be encountered in igniting the hydrogen. If the amount of hydrogen is more than 14 molar percent, unacceptable pressures and/or temperatures may be created in thevehicle occupant restraint12. Preferably, the fuel gas is included in themixture18 of gases in an amount so that it is substantially consumed by combustion in thecontainer14. Thevehicle occupant restraint12 is thus inflated almost exclusively, in the case where inert gas is used, by inert gas, combustion products and any remaining oxidizer gas or, in the case where inert gas is not used, by the remaining oxidizer gas and combustion products.
As the gas flows from thecontainer14 into thevehicle occupant restraint12, the gas expands and cools. In addition, air from the environment around thesafety apparatus10 may be aspirated into thevehicle occupant restraint12 as the vehicle occupant restraint is inflated. This aspirated air will also cool the gas in thevehicle occupant restraint12.
Since the fuel gas in themixture18 of gases burns to generate heat which increases the pressure of the gas in thechamber16, the total volume of gas which must be stored in thecontainer14 to inflate thevehicle occupant restraint12 to a desired pressure is minimized. Additionally, since combustion of the fuel gas produces gaseous material, i.e., water vapor, instead of solid material, there is no need for a particulate filter or the like.
Thecontainer14 in thesafety apparatus10 is shown in greater detail in FIG.4. As shown in FIG. 4, thecontainer14 comprises acylindrical tank30. Thetank30 defines thechamber16 containing themixture18 of gases Thetank30 must be made of a material impervious to the gases contained in the container. Therefore, thetank30 may be made of a suitable metal, such as steel or aluminum, and may have a glass lining. A cylindricalgas flow diffuser32 surrounds thetank30. Thediffuser32 has a plurality ofgas flow openings35.
Anigniter housing34 extends through an opening at one end of thetank30, and supports theigniter24. Theigniter24 can be any one of many known types of igniters. Thus, the igniter can be a spark plug, flash bulb igniter (as shown, for example, in U.S. Pat. No. 3,695,179), or a pyrotechnic igniter. Thespecific igniter24 shown in FIG. 4 is a known squib containing a pyrotechnic material which is preferably zirconium potassium perchlorate. A single igniter, as shown in FIG. 4, or a plurality of igniters can be used. The percentage of fuel gas in themixture18 of gases may be varied to facilitate ignition of the fuel gas by the igniter or igniters.
Acylindrical manifold40 extends through an opening in the end of thetank30 opposite theigniter24 and also extends through an adjacent opening in thediffuser32. Acircular end wall42 of the manifold40 located inside thetank30 has a centrally locatedcontrol orifice44. Acylindrical side wall46 of the manifold40 has a circumferentially extending array ofgas flow openings48 located between thetank30 and thediffuser32. Theend wall28, shown schematically in FIG. 1, is a burst disk supported inside the manifold40 between thecontrol orifice44 and thegas flow openings48.
When the fuel gas in themixture18 of gases in thechamber16 is ignited by theigniter24, combustion of the fuel gas generates heat and gaseous products of combustion which increase the pressure in thechamber16. When the increasing pressure in thetank30 reaches a predetermined level, theend wall28 bursts. Pressurized gas then flows from thechamber16 through the manifold40 to thegas flow openings35 in thediffuser32, and through thegas flow openings35 into thevehicle occupant restraint12.
FIG. 5 illustrates graphically the relationship between the pressure in thechamber16 and the volume of gas in thevehicle occupant restraint12 during operation of the vehicleoccupant safety apparatus10. The pressure in thechamber16 is represented in FIG. 5 by the curve P. The scale for the curve P is shown on the left side of FIG.5. The volume of gas in thevehicle occupant restraint12 is represented in FIG. 5 by the curve V. The scale for the curve V is shown on the right side of FIG.5. At time T0, the fuel gas in themixture18 of gases in thechamber16 is ignited, and the pressure in thechamber16 begins to increase above the storage pressure Psas a result of the combustion. At time T1, theend wall28 bursts and the pressurized gas begins to flow into thevehicle occupant restraint12. The volume of gas in thevehicle occupant restraint12 then begins to increase, as indicated by the curve V. The pressure in thechamber16 initially remains constant of continues to rise after the end wall is opened since the combustion process continues to generate heat and causes the gas mixture to expand at a rate faster than the gas flows out through theorifice44 into thevehicle occupant restraint12. As the combustion nears completion, the pressure in thechamber16 decreases as the pressurized gas moves from thechamber16 into thevehicle occupant restraint12. As the pressure in thechamber16 decreases, the volume of gas in thevehicle occupant restraint12 increases until thevehicle occupant restraint12 is fully inflated for the purpose of restraining a vehicle occupant.
FIG. 5 is merely representative of the operation of a vehicle occupant restraint inflator in accordance with the present invention. The curves shown in FIG. 5 can be modified in a number of ways to tailor the volume versus time curves so that inflation of the vehicle occupant restraint may be tailored for a specific application for a specific vehicle. For example, the time to inflate thevehicle occupant restraint12 fully can be reduced by increasing the fuel gas content of themixture18 of gases and/or by increasing the oxidizer gas content. Additionally or alternatively, the number of locations at which the fuel gas in themixture18 of gases is ignited and/or the area of thecontrol orifice44 can be increased. Further, combination of these changes can be used to decrease the time to inflate the vehicle occupant restraint17. Conversely, the time to inflate thevehicle occupant restraint12 fully can be increased by, for example, decreasing the fuel gas content and/or the oxidizer gas content of themixture18 of gases.
Embodiment I described above is the preferred embodiment of the present invention. Below are descriptions of other embodiments of the present invention which are alternative ways to practice the invention.
Embodiment IISince the embodiment of the invention illustrated in FIG. 2 is generally similar to the embodiment of the invention illustrated in FIG. 1, similar numerals are utilized to designate similar components, the suffix letter “a” is added to the numerals designating the components of the embodiment of the invention illustrated in FIG. 2 to avoid confusion.
Avehicle safety apparatus10a (FIG. 2) includes an inflatablevehicle occupant restraint12a which is inflated by a flow of a gas from a container14a. The container14a has achamber16a in which a mixture18a of gases is held. Like themixture18, the mixture18a of gases includes a fuel gas, an oxidizer gas for supporting combustion of the fuel gas, and inert gas. Alternatively, the mixture18a of gases may be a very fuel lean combustible gas mixture of a fuel gas and an oxidizer gas. Also, the mixture18a of gases may be under pressure.
Upon the occurrence of a high rate of vehicle deceleration, adeceleration sensor22a activates anopener60 to puncture mechanically anend wall28a of the container14a. Theopener60 can comprise a piston which is moved against theend wall28 by an explosive charge. Preferably, at the same time, thedeceleration sensor22a activates anigniter24a to ignite the fuel gas in the mixture18a of gases. Thus, in the embodiment of the invention illustrated in FIG. 2, the container14a is opened by theopener60 simultaneously with ignition of the fuel gas in the mixture18a of gases by theigniter24a. Alternatively, the mixture of gases may be ignited a short time after the puncturing of the end wall in order to get a slightly “softer” of slower initial flow of gas into the vehicle occupant restraint. Additionally, the mixture of gases may be ignited prior to opening theend wall2828a. As the fuel gas burns, the gas in thechamber16a is heated. The heated gas flows from thechamber16a through the opening in theend wall28a of the container14a into thevehicle component restraint12a to inflate the vehicle occupant restraint.
The mixture18a of gases could have many different compositions. The preferences for composition of the mixture18a of gases are the same as those described above concerning themixture18. In one specific embodiment, the mixture18a of gases includes dry air to which approximately eleven molar percent hydrogen gas is added as the fuel gas. Prior to opening of thecontainer16a by theopener60 and ignition of the hydrogen gas in the mixture18a of gases, the mixture18a of gases is held in the container14a at a pressure of approximately 2,000 psi. The preferences for storage pressure for the mixture18a of gases also are the same as those described above concerning themixture18.
Embodiment IIIA third embodiment of the invention is illustrated in FIG.3. Since the components of this embodiment of the embodiments of the invention illustrated in FIG. 1 and 2, similar numerals are utilized to designate similar components, the suffix letter “b” is associated with the numerals of FIG. 3 to avoid confusion.
Avehicle safety apparatus10b (FIG. 3) includes avehicle component restraint12b which is inflated by a flow of gas from acontainer14b to restrain movement of an occupant of a vehicle. Thecontainer14b includes anupper compartment70 having anend wall28b and alower compartment72. The upper andlower compartments70 and72 are separated from each other by an intermediate wall74. Theupper compartment70 contains apressurized gas78 which is not combustible. Thelower compartment72 contains apressurized mixture80 of gases. Themixture80 of gases preferably contains a fuel gas, an inert gas and an oxidizer gas for supporting combustion of the fuel gas in a mixture with the inert gas. Alternatively, themixture80 of gases may be an oxidizer gas and a fuel gas in amounts which provide a very fuel lean mixture.
Upon the occurrence of sudden vehicle deceleration, adeceleration sensor22b activates anopener60b to puncture thecontainer end wall28b mechanically. Since thegas78 in theupper compartment70 is held under pressure, thegas78 flows from theupper compartment70 into thevehicle occupant restraint12b when theend wall28b is punctured.
As thegas78 flows from theupper compartment70 into thevehicle occupant restraint12b, the pressure in theupper compartment70 is reduced. Consequently, the pressure differential between themixture80 of gases in thelower compartment72 and thegas78 in theupper compartment70 increases. When a predetermined pressure differential has been established between the gases in the upper andlower compartments70 and72, the intermediate wall74 bursts to connect thelower compartment72 in fluid communication with theupper compartment70. This results in thelower compartment72 being connected in fluid communication with thevehicle occupant restraint12b through theupper compartment70.
Bursting of the intermediate wall74 by the pressure differential is detected by asensor86. Alternatively, thesensor86 may detect that the wall74 has deflected beyond a certain preset position. Upon detecting that the intermediate wall74 has burst or deflected beyond a certain preset position, thesensor86 activates anigniter88 to ignite the fuel gas in themixture80 of gases. Ignition and the resulting burning of the fuel gas in themixture80 of gases heats the gas in thelower compartment72. As the gas in thelower compartment72 is heated, the pressure in thelower compartment72 increases. Therefore, the rate of flow of gas through the intermediate wall.74 and theend wall28b to thevehicle occupant restraint12b increases and the volume of gas available for inflating thevehicle occupant restraint12b increases.
Theupper compartment70 may be filled with dry air at a pressure of 2,000 psi. The mixture of gases in thelower compartment72 could have many different composition at different pressures. Thelower compartment72 may be filled with a mixture of gases at a pressure of 2,000 psi. Themixture80 of gases in thelower compartment72 may consist of 85 to 90 molar percent dry air and 10 to 15 molar percent hydrogen gas. It is contemplated that theupper compartment70 could be filled with nitrogen gas and thelower compartment72 could be filled with a mixture of nitrogen gas, hydrogen gas, and an oxidizer gas. The mixture of gases in thelower compartment72 could also have any composition and/or storage pressure described above concerning themixture18 of gases in the embodiment of FIG.1.
Although it is preferred to connect thelower compartment72 in fluid communication with theupper compartment70 and thevehicle occupant restraint12b by rupturing the intermediate wall74 when a predetermined pressure differential is established between the upper andlower compartments70 and72, the upper andlower compartments70 and72 of thecontainer14b could be connected in fluid communication in a different manner. For example, an opener, similar to theopener60b, could be provided to puncture the intermediate wall74 mechanically. Operation of the opener to puncture the intermediate wall74 and simultaneous operation of theigniter88 to ignite the fuel gas in themixture80 of gases would take place at a predetermined time interval after thedeceleration sensor22b detects the occurrence of sudden vehicle deceleration.
Embodiment IVA fourth embodiment of the invention is illustrated in FIG.6. In this embodiment, hydrogen is stored under pressure in acontainer100, and oxygen is stored under pressure in acontainer101.Container100 has anoutlet102 in communication with acombustion chamber104 defined by a containing means106. Thecontainer101 also has anoutlet108 in communication with thecombustion chamber104.
Theoutlet102 has aflow control orifice110 and aburst disk112. When theburst disk112 opens, hydrogen flows into thecombustion chamber104 of the containing means106. The flow of hydrogen is controlled, in part, by the area of theflow control orifice110. Theoutlet108 has aflow control orifice114 and aburst disk116. When theburst disc116 opens, oxygen flows into thecombustion chamber104 of the containing means106. The flow of oxygen is controlled, in part, by the area of theflow control orifice114. Thus, when theburst disks112,116 open, the containing means106 receives gases, i.e., hydrogen and oxygen, to provide a combustible mixture of hydrogen and oxygen.
Asuitable igniter130 is associated with the containing means106. Theigniter130, when actuated, ignites the mixture of gases in thecombustion chamber104 of the containing means106 to increase the pressure and warm the gas in thecombustion chamber104. The gas is directed from thecombustion chamber104 through aflow control orifice131 and anoutlet conduit132 into the inflatablevehicle occupant restraint134. Theflow control orifice131 in part controls the gas flow rate to the inflatable occupant restraint and the pressure in thecombustion chamber104. The inflatablevehicle occupant restraint134 may be as described above in embodiment I.
Asuitable opener device140 is associated with theburst disk112. When theopener device140 is actuated, theburst disk112 is opened. Also, asuitable opener device142 is associated withburst disk116. When theopener device142 is actuated, theburst disk116 is opened.
Theopener devices140,142 are actuated by a vehicle deceleration sensor sensing rapid vehicle deceleration as indicative of a collision. As a result, the hydrogen and oxygen flow into and mix together incombustion chamber104. The vehicle deceleration sensor also actuates theigniter130 which, in turn, ignites the mixture of hydrogen and oxygen in thecombustion chamber104. Ignition of the mixture of gases in thecombustion chamber104 warms the gas and increases the pressure of the gas in thecombustion chamber104. The gas then flows into thevehicle occupant restraint134.
The amount of hydrogen and oxygen which are stored incontainers100,101 may vary. It is desired that the amount of hydrogen in thecombustion chamber104 is approximately 10 molar percent of the total of the hydrogen and oxygen in thecombustion chamber104 and the amount of oxygen in thecombustion chamber104 is approximately 90 molar percent of the total of the hydrogen and oxygen in thecombustion chamber104. This provides oxygen substantially in excess of that needed to support combustion of the hydrogen. Thus, the vehicle occupant restraint is inflated by the oxygen and products of combustion of the mixture of gas in thecombustion chamber104. The products of combustion include water vapor.
Embodiment VA fifth embodiment of the invention is illustrated in FIGS. 7,8 and9. Since the components of this embodiment of the invention are generally similar to the components of the embodiment of the invention illustrated in FIGS. 1-4, similar numerals will be utilized to designate similar components, the suffix letter “c” is associated with the numerals of FIGS. 7-9 to avoid confusion.
Avehicle safety apparatus10c (FIG. 7) includes a vehicle occupant restraint (not shown) which is inflated by a flow of gas from acontainer14c. Thecontainer14c has achamber16c which holds amixture18c of gases. Themixture18c of gases preferably includes a fuel gas, an oxidizer gas for supporting combustion of the fuel gas, and an inert gas. Alternatively, themixture18c of gases in thecontainer14c may be an oxidizer gas and a fuel gas in amounts which provide a very fuel lean mixture, i.e., the amount of oxidizer gas exceeds the amount required to support combustion of the fuel gas.
Themixture18c of gases in thecontainer14c combusts, when ignited, but otherwise is not explosive. Themixture18c of gases in thecontainer14c is normally under pressure. Themixture18c of gases has the same composition as themixture18 of gases described in conjunction with the embodiment of the invention illustrated in FIGS. 1-4.
Upon the occurrence of sudden vehicle deceleration, a deceleration sensor (not shown), of any known and suitable construction, transmits a signal overconductors150 and152 to activate anigniter24c. Activation of theigniter24c ignites the fuel gas in themixture18c of gases. The combustion of the fuel gas in themixture18c is supported by the oxidizer gas. As the fuel gas burns, the pressure in thechamber16c rises due to heat supplied by theigniter24c and by the burning of the fuel gas.
When a predetermined pressure is reached in thechamber16c, or after a predetermined time, a burst disk (not shown) in aburst disk assembly156, bursts and warm gas flows into the vehicle occupant restraint through one or more flow controlling orifices. As the gas flows into the vehicle occupant restraint, the gas inflates the vehicle occupant restraint into a predetermined position for restraining a vehicle occupant
In accordance with a feature of this embodiment of the invention, theigniter24c is operable to transmit energy through an imperforate wall portion160 (FIG. 8) of thecontainer14c to effect ignition of themixture18c of gases in thecontainer14c. Theigniter24c includes an ignitableouter charge164 disposed adjacent to an importanceouter side surface166 of thewall portion160. Theouter charge164 is enclosed by acylindrical metal housing170 which is welded to the imperforateouter side166 of thewall portion160. Theouter charge164 engages the imperforateouter side166 of thewall portion160.
An ignitableinner charge174 is disposed in engagement with an imperforateinner side176 of thewall portion160. Theinner charge174 is enclosed in acylindrical metal housing178 which is welded to the imperforateinner side176 of thewall portion160. Acircular sealing disk186 blocks exposure of theinner charge174 to the mixture of gases in thechamber18c.
In one specific embodiment of the invention, the ignitableouter charge164 may be RDX (Royal Danish Explosive). However, HMX (Her Majesty's Explosive) could be utilized if desired. Theouter charge164 andinner charge174 both have a cylindrical configuration with a diameter of about 0.100 inches.
In the specific illustrated embodiments of the invention, theinner charge174 is in two sections, a cylindricalouter section180 and a cylindricalinner section182. Theouter section180 is made of pentaerythritol tetranitrate. Theinner section182 is made of boron potassium nitrate (BKNO3). In this specific embodiment of the invention, thecylinder14c is formed of 304 stainless steel vacuum arc remelt. Theportion160 of the cylinder wall between theouter charge164 and theinner charge174 has a thickness of about 0.085 inches.
Theigniter24c also includes anelongated ignition line192. The ignition line193 has anend portion194 disposed adjacent to theinner charge174 and sealingdisk186. The end portion194 (FIG. 8) of theignition line192 is telescopically mounted in thehousing178 so that the end of theignition line192 is in abutting engagement with thesealing disk186 and is closely adjacent to theinner charge174. Theignition line192 has a longitudinal central axis which is coincident with a longitudinal central axis of thecontainer14c. Theignition line192 extends from thehousing178 through a central portion of thecontainer14c toward a right (as viewed in FIG. 7) end portion of the container. Thus, theignition line192 has an end portion196 (FIG. 7) disposed adjacent to theburst disk assembly156.
Although theend portion196 of theignition line192 is shown in FIG. 7 as being unsupported, a support could be provided on the inner side of theburst disk assembly156 or the side wall of thecontainer14c. Also, if desired, theignition line192 could be offset to one side of the central axis of thecontainer14c.
The ignition line192 (FIG. 8) includes acylindrical sheath202. Thesheath202 is fabricated of a frangible material such as plastic, ceramic, or a composite material. Anelongated core204 is disposed within thesheath202. Thecore204 is formed of non-detonative, ignitive material and has a high heat of combustion.
Thecore204 is formed in threecylindrical strands206,208, and210 (FIG. 9) which are enclosed by an imperforate cylindrical side wall of thesheath202. Thestrands206,208 and210 include longitudinally extendingsupport elements214 coated with a non-detonative ignitive mixture of powdered fuel, oxidant and a suitable binder. Thesupport elements214 are fabricated of a material such as glass fibers, metal or a polymeric material.
The area bounded by thesheath202 is larger than the transverse cross-sectional area of thecore204. Therefore, there arespaces220 between thecore strands206,208,210 and thesheath202 and between the core strands themselves. An adherentpowdery ignition layer222, composed of the same material as thestrands206,208,210, is disposed on the inner side of thesheath202.
Theignition line192 is commercially available from Explosive Technology in Fairfield, Calif. and is known as ITLX. Although theignition line192 has been disclosed as having acylindrical sheath202 and acore204 formed of threestrands206,208 and210, it is contemplated that theignition line192 could have many different constructions, such as those shown in U.S. Pat. No. 4,220,087, issued Sep. 7, 1980 and entitled “Linear Ignition Fuse”.
Upon the occurrence of sudden vehicle deceleration, the deceleration sensor (not shown) transmits a signal over thelines150 and152 to effect ignition of theouter charge164. Ignition of theouter charge164 results in vibration of theimperforate wall portion160 of thecontainer14c. The force transmitted by vibration of thewall portion160 between thecharges164 and174 causes ignition of thesection180 of theinner charge174. The ignites thecharge section182. Ignition of thecharge sections180 and182 of theinner charge174 destroys thesealing disk186 and ignites the core204 at theend portion194 of theignition line192.
Upon ignition of thecore204, the ignition reaction is propagated at a very high speed, on the order of 1,000-5,000 meters per second, along theignition line192. As the reaction travels along theignition line192, thesheath202 is shattered. Shattering thesheath202 results to small, incandescent particles of reaction products being radically projected from theignition line192.
Heat provided by the ignition of theignition line192 quickly heats the gas immediately adjacent to the surface of thesheath202 to a temperature of approximately 1,000° F. This ignites thecombustible mixture18c of gases in thechamber16c. In addition, the small, incandescent particles of reaction products projected from theignition line192 as thesheath202 is shattered are effective to ignite themixture18c of combustible gases at locations speed from the ignition line.
Thus, theignition line192 performs the dual functions of heating themixture18c of gases in thecontainer14c and of igniting the mixture of gases. Since theignition line192 adds a substantial amount of heat to themixture18c of gases, a lower amount of the fuel gas is required than would be the case if a different type of igniter was utilized.
From the above description of the invention, those skilled in the art will perceive applications, improvements, changes and modifications to the present invention. For example, the gas in the container101 (FIG. 6) might include an inert gas, such as nitrogen, as well as oxygen. In an alternative to the FIG. 6 embodiment, an inert gas might be stored under pressure in a separate container similar to thecontainer100 and101. The apparatus of the present invention may also be used for inflating devices other than an inflatable vehicle occupant restraint known as an air bag. For example, the apparatus of the present invention may be used to inflate an inflatable vehicle seat belt, a raft, an escape chute, etc. Such applications, improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.