CA1293275C - Deflector ring for use with inflators for passive restraint devices - Google Patents

Abstract

DEFLECTOR RING FOR USE WITH INFLATORS FOR PASSIVE RESTRAINT DEVICES ABSTRACT A vehicle passive restraint device comprising an air bag positioned between an occupant of the vehicle and an interior portion thereof for protecting the occupant from an impact with the interior portion in the event of a collision involving the vehicle; a generator for producing a sufficient quantity of a gaseous combustion product to inflate the air bag means in an interval occurring between the collision and the impact in order to prevent the impact; and a deflector ring positioned between the air bag and the generator for attaching the bag to the generator and extending a sufficient distance into an interior portion of the air bag for preventing hot combustion gases and particulates produced within the generator from impinging directly against an inner surface of the bag. The deflector ring is stamped from a relatively light weight material utilizing conventional stamping equipment without the necessity of subjecting the ring to any machining treatment. The ring possesses sufficient structural strength to position and maintain the air bag in relation to the generator when the generator is actuated in order to inflate the air bag.

Description

3~
~ fJ7~

DEFLECTOR RING FOR USE WITH INFLATORS
FOR PASSIVE RESTRAINT DEVICES

Field of the Invention The invention relates to an inflator apparatus capable of producing a sufficient quantity of a gaseous combustion product to inflate a passive restraint device such as an automobile air bag. More particularly, it concerns the use of a ring-shaped member to prevent the impingement o~ hot gases and/or particulate materials directly upon the inner surface of the air bag.

Back~round of the_ nvention During the deployment of a passive restraint device in the event of a collision involving a vehicle in which the device is installed, gases and particulate combustion products, produced at temperatures in excess of l,000F during the initial portion of the propellant burning cycle, impin~e directly upon the fabric of the bag. If no protective measures are taken, such as: l) by incorporating additional, i.e., "sacrificial", layers of ~abric into the bag at the point where it is contacted by tha hot gases and the energetic particulates, or 2) by installing a deflection member between the ganerator and the air bag, this impingement may result in the bag beaoming burned through, with a resultant failure o~
the restraining device to per~orm as desired.
Manufacturers of currently marketed air bag systems have ge~erally ~lected to do both, i.e~, by providing a sacrificial lay~r and a gas de~lection member. The deflection members in current use, however, are expen~iYe, machined parts which are fabricated from heavy steel plate and which can not be stampéd with conventional stamping equipment. This adds both to the cost of the lnflator and the weight of the completed assembly.
As is well known in the automotive art, any increase in vehicle weight is to be avoided if possible due to its negative impact upon gas mileage. The main function of these machined me~bers appears more directed to simply attaching an ~3Z75 air bag to a ga~ generator rather than to de~lecting hot gases and particulate~ away from the fabric of the bag since they do not extend any appreciable distance into ~he mouth of the bag.
Further, with regard to the means for inflating air bag systems such as those described herein, many forms of gas generators or inflators utilizing combustible solid ~uel gas generating compositions are known~ Commonly encountered features among generators utilized for this purpose are the inclu ion within a housing of a ga~ generant composition and means to filter and to cool the gas, positioned between the composition and the gas discharge orifices, as defined by the generator housing.
one such gas generator includes an annular reaction or combustion chamber which is bounded by an outer casing or housing structure. The combustion chamber encloses a rupturable container or cartridge that is hermetically sealed and which contains therein a solid gas generant in pelletized form, surrounded by an annular filter. This generator further includes a central ignition or initiator tube and a toroidal filter chamber adjoining and encircling the combustion chamber. An inner casing or hou~ing structure is located in close surrounding and supporking relationship to the rupturable container, the inner casing being formed by a cylinder having uniformly spaced peripheral ports or orifices near one ~nd. These orifices provide exit holes for the flow of ga~ from the combustion cha~ber.
Alternately, a generator housing may be provided, comprising first and second structural components or shells, specifically, a first or diffuser shell and a second or base shell. Both shells are forged and heat treated, a~ter which they underga machining to obtain a proper fit~ The first structural component, i.e., the diffuser sh~ll, is formed with three integral concentric cylinders which ~orm the inner structural walls o~ the inflator and which define chambers therein containing the solid gas generant, ignition materials, -3~ 5 and ~ilter~, as well as providing exit openings or ports for the passaga of thQ gasses from chamber to chamber and subse-~uently into the protective air bag.
The second structural component of this embodiment, known as the base shell, may utilize an electrical initiator (squib) for igniting thP main propellant charge as well as a flange for attaching an air bag thereto. It also provides three concentric mating surfaces for the concentric cylinders of the diffuser shellO The three concentric cylinder~ of the diffu-ser shell ~re thus join~d to the corresponding concentricmating surfaces located upon the base shell.
Gas generators, or in~lators, of the type described above, must withstand enormous thermal and machanical stresses for a short period during the gas generation process. Thus, in~lators that have bean and are currently being used with automobile or other vehicle air bags have previously been fabricated using steel for the casing and other structural housing components, with these components bei~g joined together by screw threads, roll crimping or welding.
The recent emphasis on weight reduction for the purpose o~ fuel conservation in motorized vehicles, however, has created a need and a demand for a lighter weight inflation system. This is o~ particular importance in a crash protec-tion system for the driver wherein the inflator is mounted on the vshicl2's steerin~ wheel. The availability of a lighter weight inflator for installation at this location further en~bl~s a reduction to be made in the weight of the vehicle's steering wheel and the steering column on which the inflator i~ mountQd.
In this regard, some recently in~roduced inflator devices utilize aluminum casing materials. While this does alleviate somewhat the problem o~ excessive generator weight, aluminum generators tend to be more expensive in terms of production costs than the stamped stainless steel models currently in general use. More importantly, however, aluminum also tends -4- ~Z~75 to lo~e considerable strength at elevated temperatures, which become~ of concern should the airbag system be exposed to a car ~ire. Since the gas generator is a pressure vessel, as noted above, concern exists over the possible fragmentation of a waakened al~minum generator casing upon a sudden overpres-surization of ~h8 device due to an ignition caused by such a fire.

Summary of the Invention In accordance with the teachings of the present invention a vehicle passive restraint device is prcvided, comprising an air bag positioned between an occupant of the vehicle and an interior portion thereof. This air bag protects the occupant from an impact with the interior portion of the vehicle in the`
event of a collision. The device further comprises a gas generator for producing a sufficient quantity of a gaseous combustion product to inflate the air bag within the interval between a collision involving the vehicle in which it is installed and an impact of the occupant with the interior ~o portion o~ the vehicle, in or~er to prevent this impact.
Additionally, the device comprises a deflector ring positioned between the air bag and the generator for attaching the air bag to the generator. The deflector ring extends a sufficient distanae into the interior of the air bag to prevent hot combu tion gases and particulate materials producsd as a result of the combustion reaction occurring within the generator from impinging directly against an inner sur~acc of the bag.
~he deflQctor ring is stamped ~rom a relatively light-wQigh~ material utiliæing conventional stamping equipmentwithout the nscessity of machining this member in any manner whatsoever. In addition, the ring member poss~sses sufficient struc~ural streng~h to position and maintain the air bag in relation to the generator when the generator is actuated in order to inflate the air bag.

-5- ~2~3~75 In one embodiment of the invention, the deflector ring is stamped from a relatively lightweight material utilizing conventional stamping equipment. The material currently utilized for this purpose is low-carbon steel~ which is of sufficient durability to resist damage by the hot gases and particulates exhausted from the generator during its firing phase. A number of alternate compositions, such as aluminum, titanium and even stainless steel, i.e., metals having a high degree of strength and low weight may, however, be chosen for use in stamping and deflector ring. The even lower weight of these materials would thus be useful in decreasing the weight of the entire passive restraint assembly.
As a xesult of the stamping process described above, the deflector ring is produced as a circular member having a "J-shaped" cross~sectional configuration. Additionally, the ringfurther comprises a pluralit~ of mounting holes defined by a base portion thereo~, these holes being evenly spaced along the circumference of the rinS~. The deflector ring is mounted upon a mounting plate by fastening means which are inserted through apertures defined by the plate and thereafter through the mounting holes in the deflector ring. These fastening means may be, for example, screws, bolts or rivets. Alternate fastening means such as adhesives may also be used. The J-shaped deflector ring is mounted such that a shorter leg portion of the ring i5 positioned adjacent to the generator whereupon the remaining longer leg portion thereof is positioned at a location relatively removed from the generator.
In an alternate embodiment of the invention, the vehicle passive restraint device comprises the air bag, generator and deflector ring as described above wherein the generator is comprised o~ a base plate and a diffuser plate having a peripheral portion sealingly connected to a corresponding por~ion o~ ~he base plate so as ~o form a portion of a generator housing. The base plate and diffuser plate are ~3;~7S

connected by engaging means passing perpendicularly through both plates. These connector means are capable of permitting a minimal separation between both the di~fuser plate and the base plate in the event of an overpressurization of the generator to safely direct gas away from the generator housing~
The ~enerator housing defines at least three concentric-ally aligned toroidal zones. A first such zon0 contains means for igniting a gas generating composition. A second zone contains a solid gas generating composition operable upon ignition to produce gas and particulate reaction products. A
third æone contains filtration means to cool the gas and to trap the particulate products. The third zone is further provided with a plurality o~ orifices for discharging gas from the generator housing.
In the embodiment described above, the deflector ring is stamped from a relatively ligh~weight material, i.e., a sheet of low carbon steel, with conventional stamping equipment.
Various other metals, such as aluminum, titanium and stainless steel, may be useful, as noted above, as replacements for the low carbon steel due to their decreased weight in comparison to the steel. The deflector ring o~ thi~2 embo~iment is stamped as a circular member having a J-shaped cross-sectional configuration. The ring further comprises a plurality of mounting holes through a base portion thereo~ which are evenly spaced along the circumference of the ring.
In a further embodiment of the invention, the deflector ring is mounted upon a mounting plate by fasteners inserted through apertures defined by the plate which pass through a layer of the air bag material sandwiched between the mounting plate and the deflector ring and therea~ter through the mounting holes in the de~lector ring. These ~asteners may be, for example, screws, bolts or rivets. Additionally, an adhesive may also be used to fasten the deflector ring to the mounting plate. The deflector ring is mounted such that a -7- ~2~327S

shorter leg portion of the ring is positioned adjacent to the genexator wher~upon the remaining, longer leg portion thereof is positioned at a location relatively removed from the generator.
In another e~bodiment of the invention, the means for engaging the ba~e plate with the diffuser plate of the g~nerator hou~ing is a plurality o~ rivet members arranged around the outer peripheral portion of the generator housing.
Further, both the di~fuser plate and the bas~ plate additionally co~prise corresponding flanges located along the out~r peripheral portion thereof. Each flange defines at least one aperture therethrough for attaching the generator to a mounting plate as well as to the deflector ring. In the embodiment described above, the diffuser plate and the base plate of the generator housiny are at least partially connected along their peripheral edges by a light weld.
In a still further embodiment of the invention, the ~irst zone o~ the generator contains an enhancer packet comprising a homogenQous mixture of an ignition enhancing material and an auto ignition composition. Additionally, the second zone of the generator ~urther comprises pre-filtering means located along an outer peripheral portion thereof comprising at least one layer of a screening material positioned so as to remove a portion of the particulate products from the gas.
In another embodiment of the invention, the third zone of tha generator includes a first portion containing first ~ilt~ring means for removal of a major portion of the particu-lat~ reaction produc~s from the gas and a second portion cont~ining second and third filterlng means for removing substantially all of any remaining particulate reaction products from the gas~ Prior to the complete pressurization of the generatQr, the gas passes through the ~irst filtering means prior to passing throuyh ~e second filtering means and subsequently through the third filtering means. Once the first filtering means is subs~antially pressurized, however, -8- ~Z~275 which occurs almo~t instantly, the gas no longer ~lows into the ~ir~t filtering means, but rather it flows directly into the second filtering means. The inertia of the relatively heavier metal particulates, however, carries them directly into the first ~iltering means.
The fir~t filtering means comprises a chamber substantially filled with a plurality of unaligned metal fibers (such as ste~l wool fibers). The second filtering means comprises a screen haviny a predetermined mesh size.
This mesh size is sufficient to prevent the passage therethrough of substantially all of the particulate reaction products from the gas. The third filtering mean~ comprises a screen h~ving a mesh size relatively narrower than that utilized with the second filtering means. The gas exits the generator housing through a plurality of diffu~ion ports located along the peripheral portion of the diffuser plate, adjacent and exterior to the third filtering means.
A still further embodiment of applicants' vehicle passive rastraint device comprises an air bag, a gas generator and a deflector ring. The generator utilized in this embodiment comprises a housing constructed of a relatively lightweight, corrosion rQsistant, high tensile strength material. The housing defines at least three concentric toroidal zones. A
fir~t zone contain~ means for igniting a ga~ generating CO~poBition. A second zone contains a solid gas generating composition operable upon ignition to produce gas and parti-culate raaction products. A third zone con~ains fil~ration means to cool the gas and to trap the reaction products. The third zone i~ further provided with a plurality of gas discharge orifices.
The gas generator of this embodiment additionally compri-se~ a base plate and a diffuser plate having a peripheral portion thereof sealingly connected to a coxresponding portion of the base plate so as to form a portion of a generator housing. The base plate and the diffuser plate are connected -9~

by ~ngaging means passing perpendicularly through both the di~fu~er plate and the base plate. These engaging means are capable of permitting a minimal separation between both plates in the event of an overpressurization of the generator in order to safely direct gas away from the housing.
Also included in this embodiment of the generator are means for igniting the solid gas generating composition located within an aperture in a central portion of the base plate. An enhancer packet comprisiny a homogeneous mixture of an ignition enhancing material and an auto ignition co~position is located in th,e first zone of the generator housing. Further, spacer means are positioned between the solid gas generating composition and the generator housing to prevent abrasion of the gas generating composition caused due to contact with an inner surface of the housing.
Additionally included within the embodiment dascribed above are prefiltering means located along a peripheral portion o~ the first zone of the generator between the solid gas generating composition and the third zone of the genera-tor. Further, filtering means are located in the third zoneof the generator and aomprise a first portion ~or removal of a major portion o~ the particulate reaction products from the gas and a second portion for removing substantially all of any remaining partiaulate reaction products. Subsequent ~o the pres9urization of the generator, the gas passes through the second portion of the filtering means prior to passing through th~ third portion. As noted above, the heavier particulates fly dir~ctly into the first portion of the filter where they are subsequently trapped. The yenerator housing ~urther comprises a plurality of gas diffusion ports located along the peripheral portion of the dif~user plate.
I~ the embodiment described above, the solid gas genexating composition is pr~vided in the form o~ a plurality of pressed toroidal disks in stacked relation, each disk 35 having means to permit air to circula~e around at least a ~3~:7~

portion of one of its surfaces. The gas produced by the combustion of the toroidal disks is cooled and cleaned by passing through the pre~iltering and filtering means.

Brief Description of the Drawings Fig. 1 is a perspective view demonstrating a preferred location for applicants' passive restraint system as described harein;
Fig. 2 i~ a bottom perspective view of applicants' pass-ive rastraint system;
Fig. 3 is a sectional view of applicants' restraintsystem tak~n through line 3-3 of Fig. 2; and Fig. 4 is a perspective Vi2W of a deflector ring member for use with applicants' passive restraint system, constructed according to t~e invention.

Detailed Description of the Preferred Embodiments Gas generators of the type described herain are useful for the rapid generation of large volumes of gas, the amount and type of gas to be generated being determined, at least in part, by the type of combusti~le generant composi~ion chosen for use in the generator, the amount thereof and the burning surface provided thereby. The gas produced may be toxic or non-toxic, noxious or non-noxious depending upon the desired application and the starting materials chosen.
At the present time, the most widespread commercial application for such generators has involved their use in producing a sufficient volume of gas within a suitably short interval, i.e., within about 35 60 milliseconds, ~or inflating an air cu~hion device, i.e., an air bag, in an automobile passive restraint system. The following description of the invention, given with reference to the attached drawing figures, will there~ore be directed to such a use.

On8 must keep in mind, however, that while the generator described below represents an inflator ~or use with a pre-ferred embodiment of the invention, the deflector ring member disclosed herein may be utilized in conjunction with a variety of inflators of varying construction. The precent inventio~
should thus not b~ limited simply to the embodiments described herein but rather it should be considered to encompass such modifications and embodiments as may be envisioned by those of ordinary skill ~n the related art.
Referring initially to FIG. l, there is illustrated, in perspective; a vehicle occupant restraint system designed for installation within, for example, the steering column of a motor vehicle such as an automobile for protecting the driver thereof. It should be noted, however, that the 'Sair bag"
application herein described may also include, in the event of a collision betw~en the automobile and a second stationary or moving ob-;ect, the use of one or more of such generators to inflate at least one passive restraint located within the ~one normally occupied by a driver and passengers traveling within the vehicle.
This view depicts a substantially circular steering wheel lO positioned upon stee~ing po~t 12 and connected to a mechan-ism (not shown) for turning the front wheels of the vehicle from side to side. Located within a central portion of wheel lO is housing 14 formed o~ opposing side msmbers 16, 18 and cov~r member 20. Generator 22 which i8 operatively associatad wi~h air bag 24, is s~cured in position within housing 14 by mounting plate 36. Plate 36 may be connected to generator 22 with the use of ap~r~ures 35 de~ined by flanges 30, 32, throu~h which may b~ passed connecting elements such as rivets, bolts or screws (not shown). ~ir bag 24 is folded for storage and packed atop generator 22 in preparation for its use. Cover member 20 is suhsequently installed to hide the entire assembly from sight and to improve the aesthetic appearance of the vehicle's interior.

32~S

Generator 22 of the invention is preferably constructed of a material, such as 301 annealed stainless steel, which is lighter, stronger and more corrosion resistant than the material often u6ed in the prior art to construct such devi-ces, e.g., 4130 steel. In ~act, a generator unit constructedof the annealed stainless steel described above may be up to 40% lighter than a generator constructed to the same dimen-sion with 4130 ~t~el. This weight reduction has been accomplished without sacrificing high temperature tensile strength which does sccur, for example, if a lightweight material such as aluminum or titanium is used to construct the generator. The inventiGn should not b~ limited to the partic-ular material, i.e., 301 annealed stainless steel, described above, however, since thrre are a number of materials, well known to those in the art, which combine the features of reduced weight and high strength, even at elevated temperature~ (such as those which may occur during a car fire).
Turning now to FIG. 2, this view depicts both the lower, i.e., base plate 26 and the upper, i.e., diffuser plate 28 which compr.ise generator 22 of the present invention. These two plates 26, 28 are prefera~ly ~oined at mounting flanges 30, 32 which may be attached with the use of connecting elements such as rivets, screws, bolts, etc. to mounting plate 36 (shown in phantom). Flanges 30, 32 are preferably sealed with a small, resistive 360 plasma or laser weld for sealing the peripheral portions of plates 26, 28 together.
This weld serves to seal the flange mating area to prevent gas leakage therethrough during normal operation of generator 22 so that the gases formed as combus~ion products exit the generator through a plurality of dif~usion ports 34 defined by diffuser plate 28. In the event generator 22 becomes overpressurized for any reason, this weld is blown -13- ~ 2l3 3 z~ 5 opan by the expanding gas. This arrangement serves ~o release tha gas away ~rom the occupant in a safe, ductile manner without rupturing the housing of the in~Iator.
The use of a weld as described above contrasts with the usual prior art method of sealing the generator housing in which the peripheral edges of the generator are normally crimped together. The weld used with the present generator thus acts as a sa~ety valve to prevent the explosive projec-tion of metal shards from the generator's housing through the interior portion of the vehicle with consequent injury and/or death to any occupants thereo~.
A co~mon cause of su~h overpressurizati.~n in generators constructed for use in a motor vehicle passive restraint sys~em is a car fire. The high ~emperatures encountered as a result thereo~ often act to reduce the strength of the metal generator casing prior to setting o~ the main propellant charge therein. Generators utilized for other applications may, of course, become overpressurized due to the influence of other factors known to those in the art.
A ~econd feature in the design of applicants' gas gener-ator is the use o~ rivets 38 for joining base plate 26 and di~user plate 28. Rivets 3~ replace c05~1y threads or unreliable structural welds commonly relied upon in previous inflator designs. The gas generator unit of the invention is thu~ designed to open in a manner similar to that of a clam ~hell in order to release excess pressu,xe rather ~han explod-ing i~ the propellant s~ored within the genera~or becomes d~teriorated under unusual conditions, such as when the device is expo~ed to a fire.
Under the abnormal conditions described above, the weld connecting the peripheral portions of flanges 30 and 32 is fractured due to the impact of the rapidly generated gases which thus gradually releases the pressure within the gener-ator. This permits the two halves of the unit, i.e., base plate 26 and dif~user plate 28 to move apart in a mann~r -14- ~Z~3~75 si~llar to the opening of a clam's shell, yet remaining s~cured proximate to each other by rivets 38. Rivets 38 thus extend perpendicularly to plates 26, 28 from a point on the outer sur~ac~ o~ base plate 26, passing through the inner portion of the generator to the out~r surface of diffuser 28.
FIG. 3 displays several of the same features of generator 22 which have previously been described with regard to FIG. 2.
These features ha~e therefore been designated with the same numbers in both Figs.
FIG. 3 is a sectional view of applicants' generator 22 further illustrating the clamshell sealing arrangement between ba ~ pla~e 26 and diffuser plate 28 with tho use of rivets 38, and depicting the sinuous path taken by the gas flow within the generator to filter and cool the combustion product. This~
tortuous gas path, which is another novel feature o~ th~
applicants' invention, will be furth~r described in detail below. While the basic method of operation for generators 22 o~ the type disclosed herein is well known and need not be ~urther disclosed, applicanks' generator has several novel feature5 which will be described below in further detail.
Applicants' in~lator device 22 defines three concentric-ally arranged toroidally shaped chambers whîch may be desig-nated a~ ignition chamber (A) combustion chamber (B) and filtration chamber (C) as one moves from tha center to the periphery of the gas generator~ Ignition chamber (A), the innermost annular portion of the generator, comprises an ignition means, such as, preferably, an electrically activated initiating squib 40 as depicted in FIG. 3. Squib 40, contain-ing a ~mall charge of elec~rically igni~able combustible material, may ba connected to at least on~ remote sen ing device (not shown~, of a type well known in the art located within, for example, the front bumper or side fender of an automobile, by electrical leads 42 a, b.

-15- 1~327~

The ignition chamber also contains enhancer packet 44 having a quantity of an enhancer material, such as a commonly employed boron potassium nitrate (BKN03) mix~ure which is preferably employed in a powdered form 46(a) in order to S provide the maximuu available burning surface for the fastest possible respon~e. Other rapidly combustible materials known to those in the art ~ay be utilized for the same purpose but applicants have obtained a consistently high degree o~ per-formance with the u~e of BKN03.
While BKN03 is very successful in igniting the main propellant charge located in ccmbustor chamber (B), it su~f~rs from a serious deficiency in that the autoignition temperature of this material is extremely high, i.e., from about 600-700F. Since the compositions chosen ~or the main propellant charge of generator 22 ignite at an even hiyher temperature in the conditions normally encountered in, for example, a car fire, the ignition material within the unit would be at a temparatuxe in excess of 60bF be~ore ignition would take place.
In such a situation, the generator housing would be subjected to even higher temperatures, i.e., in the range of from 800-900F, and the main propellant charge would also be at a high temperature, perhaps 400-500F. Under these condi-tions, under laws of temperature and pressure well known to those skilled in the propellant art, the propellant charge would burn very rapidly and generate gas at an extremely high pr~ssur~, thus creating a situation wherein an explosive frag~entation of the weakened generator housing was a distinct possibility.
Applicants have therefore incorporated an autoignition material 46(b) with the BKN03 in enhancer packet 4~. This material i~ capahle of autoignition at a lower temperature than BKN03. Its use would result in an ignition of the main propellant charge while this charge was at a much lower temperature than that described above. ~hus, the propellant 12~327S

charge may be burned at a much lower rate and produces a significantly lower pressure. This additional "auto ignition"
material is preferably a stabilized nitrocellulo~e composition such as IMR 4895 which autoignites at less than about 400F.
This pref~rred material is produced by the DuPont Corporation, but any material capable of performing in this manner would be acceptable for use in the present invention.
The end eff~ct of combining such an auto-ignition mater-ial with; for ~xample, the BKN03 enhancer composition so as to render this mixture an i~tegral part of applicants' ignition chain is to prevent a weakening of the generator housing, thus diminishing or altogether removing the chanc~ o~ an explosive overpressurization. rhis removes one potential danger to passengers and/or bystanders in the event o~ a car fire.
Combustion chamber (B) of the present gas generator 22 is formed from an outer, toroidally shaped, three-sided combustor cup 48, open along one longitudinal plane, which concentric-ally surrounds inner combustion container 50, configured to fit within cup 48. It is hermetically sealed by member 52 to prevent the entrance of moisture. Memb~r 52 may be, for example, crimped along both its inner (i.e., in the vicinity of the igniter cha~ber) and outer peripheral edges so as to maintain container 50 in a closed condition prior to the operation of the generator unit.
Cup 4~ is preferably formed of a metal, such ~s aluminum, to taXe advantage of its s~rength and heat conduc~ing proper-tie~. Optionally, however, cup 48 may be constructed of a thermoplastic material which is both cheaper and ea~ier to manufacture, i.e., by a molding technique. One consideration with the u~e of such a plastic, how~ver, is the possible formation of toxic hydrocarbon reaction products, which should be avoided in order to preven~ the exposure of th~ vehicle's occupant~ to the effects of a toxic gas when the generator of the invention is used for air bag applications.

Into inner container 50 is placed the main propellant charge 54t which may be supplied in a variety of physical forms. It may, for example, be poured as a powder or it may be inserted in the form o~ a number of substantially circular pellets, ranging in size from that of an aspirin tablet to an Alka-Seltze~. Applicants have determined, however, that superior results are obtainable by forming the propellant charge into a series of pressed, flat, toroidal discs which may be maintained in a spaced arrangement so as to provide the maximum possible burning surface. This spaced arrangement is obtainable with the use of one or more raised rldges (not shown) or spacers extending upwardly from a portion of each disc, perpendicular to its longitudinal diameter which facilitates the passage of a flame front in the space thus created therebetween.
A variety of compositions, well known to those of ordinary skill in the art, may be utilized as the main propellant charge for the gas generator described herein.
Applicants prefer, for use in their present generator, the variou~ compositions described in U.S~ Patent no. 3,895,098 to John F. Pietz, issued July 15, 1975, now reissued as Re 32,584 and entitled METHOD AND COMPOSITION FOR GENERATING
NITROGEN GAS, which is assigned o~ record to the assignee of the present invention. Chief among these propellant compositions are those propellants comprising a mixture of sodium azide with copper oxide.
Alternatively, compositions substituting nickel and iron oxidi~ers may be utili~ed, but these generants, although capable of a slightly higher effective gas output than the CuO/NaN3 mixture described above, often re~uire the addition of an ammonium perchlorate burn rate enhancer to reach their full potential (as disclosed in U.S. Patent no. 4,604,151 issued on May 8, 1986 to Knowlton and Pietz, entitled METHOD A~D COMPOSITION FOR

-18- ~Z~33~75 GENERATING NITROGEN GAS INCLUDING AMMONIUM PERCHLORATE
CATALYST. This patent is also assigned of record to the present Assignee). Since, as discussed above, a large number of different generant compositions are operable within the present generator 22, the present invention should not be limited to the compositions disclosed above.
In an alternatQ embodiment of the inve~tion, the propellant may be molded or extruded into a single porous grain which conform~ to the volume and the shape of ~he combuster cup. Such a grain may be utilized with either a metal, e.g., aluminum, or plastic cup as di~closed above. An important ~eature to consider with the use of such a porous propellant grain is to ensure that the grain is formed having a sufficient degree of porosity to provide a sufficient burning surface to permit the flame front to advance through the grain with sufficient speed so as to provide a sufficient volume of gas within, ~or example, the 35-60 millisecond period describ~d above.
The main propellant charge is insulated against abrasion caused by contacting the top and/or bottom portions of inner combustion container 50 by the use of inert spacer pads 56, 58. Pads 56, 58 may be formed, for ex~mple, ~rom a ceramic ~iber pad of a mixture of alumina oxide and silica oxide and sold undar the trade name of Fiber~rax~ by Sohio Carborundum, Inc. of Niagara Falls, N.Y., a division of Standard Oil Corp.
Al~o contained within container 50 is pre-filter ~0, comprised of a series of fine-meshed metal screens to trap particulate mat~rial within the gas flow created by the combustion of propellant charge 54.
Upon ignition of the mixture 46 a, b withln enhancer packet 44 by, for example, ignition s~uib 40, the hot gases thu~ produced pass through gas ports 62 located between the ignitlon chamber and khe combustion chamber (as defined by 7~i combu~ter cup 48) and impinge against the inner annular portion of container 50, thus rapidly heating container 50 and the propellant charge within.
Upon reaching the required ignition temperature for propellant 54, which may vary depending upon the propellant chosen, the walls of container 50 burst at a number of locations which abut gas ports 64 (preferably thirteen in number, although the amount may be varied~, thus permitting the gas produced as a product of the combustion of propellant 54 to pass through prefiltering zone 60 and subsequently out of container 40 through gas ports 64.
once the gas exits through ports 64, it enters slag filter 66 until this filter is completely pressurized. Filter 66 is comprised of a twisted layer of a coarse steel wool ma~erial, capable of removing most of the remaining particu-late material from the gas flow while also reducing the temperature of the flow. As the combustion of propellant 54 continues, forming additional gaseous products which exit through port 64 and enter filter 66, the gas bypasses filter 66 and flows directly into filter 68, although the heavier particulates deviate from this path to fly directly into filter 66 where they are subsequently trapped. Filtar 68 comprises several layer~ of mesh screen 68 a, b having a steadily decreasing mesh size from the inside out, which are ~5 separated by a spacer pad 6~c of the type previously de~cribed. The cooled, filtered gas then escapes from the generator through a plurality o~ diffuser ports 3~ located around a peripheral portion of di~fuser plate 28.
~s mentioned above, howaver, the combustion reaction of the solid gas generating material produces a gaseous product at an elevated temperature. This gaseous product often contains parkiculate materials which can damage or destroy the integrity of the air bag by impin~ing directly against its inner surface. Applicants have now de~ised a deflector ring having a "J"-shaped cross-sectional configuration which may be -20~ 2~

stamped from a relatively light weight material such as low car~on steel which weighs less than the previously utilized steel parts which required detailed machining by highly trained la~orers. A number of alternate light weight metals such as titanium, aluminum and stainle,ss steel, may be utilized as r~placements for the low carbon steel currently in use. Applicants' ring costs a great deal less to produce since it may be stamped rather than machined. In addition, the stamping technique utilized by the applicants introduces a great deal less variability into the dim~nsions of ring 72, i.e., with regard to the placement and alignment of ~he mounting holes, etc. Applicants' ring member 72 does, however, retain enough ~trength to secure bag 24 to generator 22 despite its lightweight construction.
In addition, the stamping method now adopted for produc-ing applicants' ring 70 facilitates the fabrication of a ring member which extends ~urther into the mouth of bag 24 than the previously prsduc~d machined rings and which therefore pro-vides a qreater degree of pro~ection against impingement by hot gases and high speed particulates. Applicants' novel deflector ring arrangement thus diminishes or even removes the need (demonstrated by the techniques adopted in the prior art) to provide air bag 24 with a sacrificial layer of fabric, which adds additional labor and therefore additional expense to the manufacturing of an air bag system.
In the embodiment described herein, the gas may be utiliz~d to inflate bag 24 which is attached to mounting plate 36 by deflector ring 70. Mounting plate 36 is prefer~bly a flat metal sheet defining a central aperturP which is confi-gured and adapted for the insertion therathrough of at leastthP diffuser plate por~ion of g~nerator 22. Evenly disposed around the periphery of this central aper~ure are a plurality of mounting holes, pre~erably twelve in number, configured for the passage of mounting means such as screws, bolts, rivets, etc.

-21- ~3Z7S

In one embodiment of the present invention, a mouth portion of air bag 24 is folded over deflector ring 70 of the type illustrated in FIG. 4. The folded portion of air bag 24 is provided with a matching n~mber of mounting holes (not shown) sewn into the ~abric of the bag and spaced so as to permit their alignment with holes 72 in ring 70. once the mouth o~ bag 24 i~ thus aligned, ring 70, together with bag 24 is fastened to a fir3t face of mounting plate 36 with fastener means inserted through the mounting holes from the second (opposite) face of the plate.
In the preferred embodiment of the invention, eight such fasteners are utilized, i.e., two in each quadrant, passing initially through plate 36, then through air bag 24 and finally through deflector ring 70, as shown in FIG. 3. Four unencumbered mounting holes thus remain in both plate 36 and deflector ring 70, one of which is preferably located in each quadrant of plate 36 in a s~are configuration. The diffuser portion of generator 22 is subsequently positioned within the mouth of bag 22 by inserting diffu~er plate 28 through the central aperture in mounting plate 36, thus permitting apertures 35 defined by ~langes 30, 32 of generator 22 to align with the four remaining mounting holes in plate 3~, as well a~ with the corxesponding holes 72 in riny member 70.
Fastener means are then inserted through the aperture in flang~ 30, 32, pas3ing through plate 36, then air bag 24 and finally through hole~ 72 in ring 70. This arrangement firmly mounts generator 22 upon plate 36 in a manner such that the di~u~ion ports 34 of genera~or 22 are located within the mouth o~ bag 24. Ring 70 thu~ provides a barrier between dif~usion ports 34 o~ gen~rator 22 and the inner surface of bag 24 to deflect the hot gasse~ and particulate materials away from direct contact with the inner surface of the bag and into the central portion thereof.

~3~ ~

While it i5 apparent that the invention herein disclosed is well calculated to fulfill the objectiv~s ~tated above, it will be appreciated that numerous modifications and embodi-ments may be devised by those skilled in the art, and it is intended that the appended claims cover all such modifications and embodiments a~ fall within the true spirit and scope of the present invention.

Claims (15)

We claim:

1. A vehicle passive restraint device comprising:

(a) air bag means positioned between an occupant of said vehicle and an interior portion thereof for protecting said occupant from an impact with said interior portion in the event of a collision involving said vehicle;
(b) generator means for producing a sufficient quantity of a gaseous combustion product to inflate said air bag means in an interval occurring between said collision and said impact in order to prevent said impact; and (c) deflector ring means positioned between said air bag means and said generator means for attaching said bag to said generator and extending a sufficient distance into an interior portion of said bag for preventing hot combustion gases and particulates produced within said generator means from impinging directly against an inner surface of said bag means, wherein said deflector ring is mounted such that a shorter leg portion of said ring is positioned adjacent said generator means whereupon the remaining longer leg portion is positioned at a location relatively removed from said generator means;
and wherein said deflector ring means is stamped from a relatively light weight material utilizing conventional stamping equipment without the necessity of subjecting said ring means to any machining treatment and further wherein said ring means possesses sufficient structural strength to position and maintain said air bag means in relation to said generator means when said generator means is actuated in order to inflate said air bag means.

2. The passive restraint device of claim 1 wherein said relatively light weight material is selected from the group consisting of low carbon steel, titanium, stainles steel and aluminum.

3. The passive restraint device of claim 1 wherein said deflector ring means is a circular member having a J-shaped cross-sectional configuration.

4. The passive restraint device of claim 3 wherein said deflector ring further comprises a plurality of mounting holes defined by a base portion thereof, said holes being evenly spaced along the circumference of said ring.

5. The passive restraint device of claim 4 wherein said deflector ring is mounted upon mounting plate means by fasten-ing means inserted through apertures defined by said plate means and thereafter through said mounting holes in said deflector ring.

6. A vehicle passive restraint device comprising:
(a) air bag means positioned between an occupant of said vehicle and an interior portion thereof for protecting said occupant from an impact with said interior portion in the event of a collision involving said vehicle;
(b) generator means for producing a sufficient quantity of a gaseous combustion product to inflate said air bag means in an interval occurring between said collision and said impact in order to prevent said impact; and (c) deflector ring means positioned between said air bag means and said generator means for attaching said bag to said generator and extending a sufficient distance into an interior portion of said bag for preventing hot combustion gases and particulates produced within said generator means from impinging directly against an inner surface of said bag means, wherein said deflector ring means is stamped from a relatively light weight material utilizing conventional stamping equipment without the necessity of subjecting said ring means to any machining treatment and wherein said ring means possesses sufficient structural strength to position and maintain said air bag means in relation to said generator means when said generator means is actuated in order to inflate said air bag means;
and wherein said generator means comprises:
a) base plate means;
b) diffuser plate means having a peripheral portion thereof sealingly connected to a corresponding portion of said base plate means so as to form a portion of a housing for the generator, and c) means for engaging said base plate means with said diffuser plate means, said engaging means passing perpendicularyly through both said diffuser and said base plate means and capable of permitting a minimal separation between both said diffuser and said base plate means in the event of an overpressurization of said generator to safely direct gas away from said housing, wherein said generator means comprises at least three concentrically aligned toroidal zones, whereby a first zone contains means for igniting a gas generating composition; a second zone contains a solid gas gener-ating composition operable upon ignition to produce gas and particulate reaction products; and a third zone contains filtration means to cool said gas and to trap said particulate products, said third zone being further provided with orifice means for discharging gas from said housing.

7. The passive restraint device of claim 6 wherein said relatively light weight material is selected from the group consisting of low carbon steel, titanium, stainless steel and aluminum.

8. The passive restraint device of claim 7 wherein said deflector ring means is a circular member having a J-shaped cross-sectional configuration.

9. The passive restraint device of claim 8 wherein said deflector ring further comprises a plurality of mounting holes defined by a base portion thereof, said holes being evenly spaced along the circumference of said ring.

10. The passive restraint device of claim 9 wherein said deflector ring is mounted upon mounting plate means by fasten-ing means inserted through apertures defined by said plate means and thereafter through said mounting holes in said deflector ring.

11. The passive restraint device of claim 10 wherein said deflector ring is mounted such that a shorter leg portion of said ring is positioned adjacent said generator means where-upon the remaining longer leg portion is positioned at location relatively removed from said generator means.

12. The vehicle passive restraint device of claim 6 wherein said means for engaging said base plate means with said diffuser plate means of said generator means is a plur-ality of rivet members arranged around said outer peripheral portion of said generator housing.

13. The vehicle restraint device of claim 6 wherein each of said base plate means and said diffuser plate means further comprises corresponding flange means located along said outer peripheral portion, each said flange means defining at least one aperture therethrough for attaching said generator to a mounting plate and to said deflector ring.

14. The vehicle restraint device of claim 13 wherein said diffuser plate and said base plate are at least partially con-nected along their periphery by a weld.

15. A vehicle passive restraint device comprising:
(a) air bag means positioned between an occupant of said vehicle and an interior portion thereof for protecting said occupant from an impact with said interior portion in the event of a collision involving said vehicle;
(b) generator means for producing a sufficient quantity of a gaseous combustion product to inflate said air bag means in an interval occurring between said collision and said impact in order to prevent said impact; and (c) deflector ring means positioned between said air bag means and said generator means for attaching said bag to said generator and extending a sufficient distance into an interior portion of said bag for preventing hot combustion gases and particulates produced within said generator means from impinging directly against an inner surface of said bag means, wherein said deflector ring means is stamped from a relatively light weight material utilizing conventional stamping equipment without the necessity of subjecting said ring means to any machining treatment and wherein said ring means possesses sufficient structural strength to position and maintain said air bag means in relation to said generator means when said generator means is actuated in order to inflate said air bag means;
wherein said generator means comprises a) a housing constructed of a relatively light weight, corrosion resistant, high tensile strength material, defining at least three concentric toroidal zones, whereby a first zone contains means for igniting a gas generating composition; a second zone contains a solid gas generating composition operable upon ignition to produce gas and particulate reaction products; and a third zone contains filtration means to cool said gas and to trap said reaction products, said third zone being further provided with gas discharge orifice means;
b) base plate means:
c) diffuser plate means having a peripheral portion thereof sealingly connected to a corresponding portion of said base plate means so as to form a portion of a housing for the generator, d) means for engaging said base plate means with said diffuser plate means, said engaging means passing perpendicularly through both said diffuser plate means and said base plate means capable of permitting a minimal separation between both said plate means in the event of an overpressurization of said generator to safely direct gas away from said housing, e) means for igniting said solid gas-generating composition, said ignition means located in an aperture in a central portion of said base plate means;
f) an enhancer packet comprising a homogeneous mixture of an ignition enhancing material and an autoignition composition located in said first zone of said housing means;
g) spacer means between said solid gas-generating composition and said housing to prevent abrasion of said composition due to contact with an inner surface of the housing;
h) prefiltering means located along a peripheral portion of said first zone between said solid gas generating composition and said third zone;

i) filtering means located in said third zone and comprising a first portion for removal of a major portion of said particulate reaction products from said gas, and a second portion for removing substantially all of any remaining particulate reaction products from said gas; and j) gas discharge orifice means comprising a plura-lity of diffusion ports located along said peripheral portion of said diffuser plate means;
wherein said solid gas generating composition is in the form of a plurality of pressed toroidal discs in stacked relation, each disc having means to permit air to circulate around at least a portion of one of its surfaces and whereby the gas produced by the combustion of said toroidal discs is cooled and cleaned by passing through said prefiltering means and thereafter through said filtering means.