US20100109295A1

Movatterモバイル変換

Info

Publication number: US20100109295A1
Application number: US12/655,768
Authority: US
Inventors: David M. McCormick; Robert M. Hardenburg; Bernardo V. Vergara
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-06-02
Filing date: 2010-01-07
Publication date: 2010-05-06
Also published as: DE112006001455T5; JP2008546513A; WO2006130848A2; US20060273564A1; US7654565B2; WO2006130848A3

Abstract

A gas generating system for use in an inflatable vehicle occupant protection system is provided wherein an end closure is coupled to an outer housing at a first end, in a metal-to-metal seal. The gas generating system may also include a baffle system having a plurality of flow orifices defining a flow path for generated gases through an interior of the gas generating system, and a plurality of particulate aggregation surfaces positioned along the flow path of the gases for changing a flow direction of gases impinging on the aggregation surfaces. Each aggregation surface of the plurality of aggregation surfaces is oriented such that a difference between a flow direction of the gases prior to impinging on the aggregation surface and a flow direction of the gases after impinging on the aggregation surface is at least approximately 90°, wherein particulates in gases impinging on the aggregation surfaces aggregate on the surfaces.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional application Ser. No. 60/686,906, filed on Jun. 2, 2005.

BACKGROUND OF THE INVENTION

The present invention relates generally to gas generating systems and, more particularly, to filterless gas generating systems for use in applications such as inflatable occupant restraint systems in motor vehicles.

Installation of inflatable occupant protection systems as standard equipment in all new vehicles has intensified the search for smaller, lighter and less expensive protection systems. Accordingly, since the inflation gas generator used in such protection systems tends to be the heaviest and most expensive component, there is a need for a lighter, more compact, and less expensive gas generating system.

A typical gas generating system includes cylindrical steel or aluminum housing having a diameter and length related to the vehicle application and characteristics of a gas generant composition contained therein. Because inhalation by a vehicle occupant of particulates generated by gas generant combustion during airbag activation can be hazardous, it is desirable to remove particulate material, or slag, produced during combustion of the gas generant. Thus, the gas generating system is generally provided with an internal or external filter comprising one or more layers of steel screen of varying mesh and wire diameter. Gas produced upon combustion of the gas generant passes through the filter before exiting the gas generating system. In a conventional system, the particulates are substantially removed as the gas passes through the filter. In addition, heat from combustion gases is transferred to the material of the filter as the gases flow through the filter. Thus, as well as filtering particulates from the gases, the filter acts to cool the combustion gases prior to dispersal into an associated airbag. However, inclusion of the filter in the gas generating system increases the complexity, weight, and expense of the gas generating system. Thus, a gas generating system construction which removes particulates and cools the generated gases without the need for a filter is desirable.

Variations in the filter components and in the arrangement of the filter material can also unpredictably and adversely affect gas flow through the filter, thereby contributing to ballistic variability of the gas generating system and making the system response less predictable.

Yet another concern involves reducing the size of the inflator thereby reducing the packaging size and providing greater design flexibility in various applications or uses. Furthermore, reducing the size of the inflator reduces the raw material requirements, and may also advantageously reduce the manufacturing complexity, thereby reducing overall manufacturing costs.

Other ongoing concerns with gas generating systems include the ability to achieve any one of a variety of ballistic profiles by varying as few of the physical parameters of the gas generating system as possible and/or by varying these physical parameters as economically as possible.

SUMMARY OF THE INVENTION

The above-referenced concerns may be mitigated or obviated by providing a gas generating system for use in an inflatable vehicle occupant protection system, a system that may if desired be filterless. In one aspect, the gas generating system includes a baffle system having a plurality of flow orifices defining a flow path for generated gases through an interior of the gas generating system, and a plurality of particulate aggregation surfaces positioned along the flow path of the gases for changing a flow direction of gases impinging on the aggregation surfaces. Each aggregation surface is oriented such that a difference between a flow direction of the gases prior to impinging on the aggregation surface and a flow direction of the gases after impinging on the aggregation surface is at least approximately 90°, wherein particulates in gases impinging on the aggregation surfaces aggregate or collect on the surfaces.

In another aspect of the invention, the gas generating system includes an outer housing including a combustion chamber, a baffle system, and may also include a high gas-yield, low solids-producing gas generant composition positioned in the combustion chamber. The baffle system includes a plurality of flow orifices defining a flow path for gases generated by combustion of the gas generant composition, the flow path extending between the combustion chamber and an exterior of the gas generating system, and a plurality of particulate aggregation surfaces positioned along the flow path of the gases for changing a flow direction of gases impinging on the aggregation surfaces, wherein particulates in gases impinging on the aggregation surfaces aggregate on the surfaces.

In yet another aspect of the present invention, the present inflator includes an end closure that is cold-worked or otherwise compressed within an outer housing, the end closure containing a body bore groove, and the housing or outer tube containing a flange pressed within the groove, thereby providing a body bore seal in a metal to metal contact. Stated another way, the present invention includes an inflator housing having a first end and a second end, the housing coupled to an end closure at the first end in a metal-to-metal seal.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings illustrating embodiments of the present invention:

FIG. 1 is a cross-sectional side view of a first embodiment of a gas generating system in accordance with the present invention;

FIG. 1A is an enlarged view of a portion ofFIG. 1 showing projected gas flow paths and projected particulate aggregation surfaces therealong;

FIG. 2 is a cross-sectional side view of a second embodiment of a gas generating system in accordance with the present invention;

FIG. 2A is an enlarged view of a portion ofFIG. 2 showing projected gas flow paths and projected particulate aggregation surfaces therealong; and

FIG. 3 is a schematic view of an exemplary gas generating system as employed in a vehicle occupant protection system, in accordance with the present invention.

FIG. 4 is a cross-sectional side view of a first embodiment of a gas generating system in accordance with the present invention, wherein an annular flange or flare is shown as formed about the periphery of the outer housing prior to compressing within a recessed portion or groove formed within an end closure within the outer housing.

DETAILED DESCRIPTION

The present invention broadly comprises a gas generating system that is fabricated without the wire mesh filter required in earlier designs for removing particulate materials from a stream of inflation gas. The design utilizes a tortuous path gas flow concept to cool the gas and to retain solids in the device in order to minimize flame and particulates from exiting the device. Selection of suitable gas generant compositions capable of combusting to produce inflation gas without an undue quantity of particulates further obviates the need for a filter. Obviating the need for a filter enables the gas generating system to be simpler, lighter, less expensive, and easier to manufacture.

FIG. 1 shows one embodiment of a gas generatingsystem10 in accordance with the present invention.Gas generating system10 is generally constructed of components made from a durable metal such as carbon steel or iron, but may also include components made from tough and impact-resistant polymers, for example. One of ordinary skill in the art will appreciate various methods of construction for the various components of the inflator. U.S. Pat. Nos. 5,035,757, 6,062,143, 6,347,566, U.S. Patent Application Serial No. 2001/0045735, WO 01/08936, and WO 01/08937 exemplify typical designs for the various inflator components, and are incorporated herein by reference in their entirety, but not by way of limitation.

Referring toFIG. 1,gas generating system10 includes a substantially cylindricalouter housing12 having a first end12a, a second end12bopposite the first end, and a wall12cextending between the ends to define a housing interior cavity.Outer housing12 is made from a metal or metal alloy and may be a cast, stamped, deep-drawn, extruded, or otherwise metal-formed. A nozzle12dis formed at housing second end12bcontaining one or moregas exit orifices12efor enabling fluid communication between an interior of the housing and an associated inflatable device (for example, an airbag or a safety belt pretensioner incorporated into a vehicle occupant protection system.) In the embodiment shown inFIG. 1,outer housing12 and nozzle12dare deep drawn as a single piece. Gas exit orifice(s)12eare then provided in outer housing second end12bby drilling, punching, or other suitable means.

In a particular embodiment, the gas generating system is a micro gas generator withouter housing12 having an outer diameter of approximately 20 mm, usable in, for example, a side seat inflator or a safety belt pretensioner. However, the characteristics of the embodiments described herein may be incorporated into gas generating systems of many alternative sizes, usable for a variety of different applications.

In an alternative embodiment (not shown), the gas exit orifices may be incorporated into a gas exit manifold which is formed separately from the outer housing and then welded or otherwise suitably fixed to the outer housing during assembly of the gas generating system.

In another alternative embodiment (not shown), a small quantity of a filter material may be incorporated into the outer housing second end proximate the gas exit orifices to filter combustion products from the inflation fluid prior to gas distribution. Any suitable metallic mesh filter or woven wire cloth may be used, many examples of which are known and obtainable from commercially available sources (for example, Wayne Wire Cloth Products, Inc. of Bloomfield Hills, Mich.)

In accordance with the present invention, and as exemplified inFIG. 4, anend closure14 is cold-worked or otherwise metal-formed within outer housing first end12a.End closure14 has formed therealong aperipheral shoulder14a, a central orifice14b, and a peripheral cavity or recessed portion14c. In accordance with the present invention, an annular flange or protrusion14dof housing first end12a(shown as a dotted line in a pre-cold-worked state inFIG. 4, and also shown as compressed within the groove14c), is drawn through a die to cold-work and thereby compress the flange within the groove14c. Other known metal-forming methods may also be employed. The diameter of the inflator may be effectively reduced by eliminating the need for a typical seal such as an o-ring at the end closure and outer housing interface within groove14c, and also by compressing the annular flange14dwithin groove14c. It will be appreciated that the volume of the annular flange or protruding portion14dis at least approximately or substantially equal to the volume defined by the groove12c. Accordingly, a flush metal-to-metal contact is formed at the interface of groove14cand flange14donce the substantially assembled inflator is drawn and compressed through a die having a smaller diameter than the outer diameter of the annular flange14dprior to cold-working. By cold-working the outer tube orhousing12 to fit within groove14c, thehousing12 is compressed to provide sufficient strength in accordance with customer specifications while simplifying the manufacturing process by reducing surface treatment or assembly of additional parts such as an o-ring. As shown in the embodiment shown inFIG. 1, the portion14dof outer housing first end12ais pressed into peripheral cavity14cto secure the end closure toouter housing12 and at the same time provide hermetic sealing of the inflator.

The cold-work technique of fitting and sealing theend closure14 within the housing end12aresults in the ability to substantially reduce the diameter of the inflator to less than one inch outer diameter, while yet retaining the structural and other design requirements surrounding the shorting clip or ignition assembly, as determined by the customer. One embodiment exhibits an outer diameter of approximately 20 millimeters, thereby decreasing the packaging size and also increasing the design flexibility with regard to the particular application, as a side inflator within a seat for example.

Peripheral shoulder

14ais configured so that an end portion a wall16bof an ignition cup16 (described in greater detail below) having a predetermined outer diameter may be positioned to abutshoulder14a.End closure14 may be stamped, extruded, die cast, or otherwise metal formed and may be made from carbon steel or stainless steel, for example. Although not required, if desired, an O-ring or seal (not shown) may be seated along an outer edge ofend closure14 to seal the interface between theend closure14 and housing wall12c.

Referring again toFIG. 1, anignition cup16 is positionedadjacent end closure14, and is nested withinouter housing12 for a portion of the housing length.Ignition cup16 has a base portion16aand an annular wall16bextending from the base portion toabut end closure14. Base portion16aand wall16bdefine a cavity16cfor containing a pyrotechnic compound18 (for example, a known booster composition) therein. At least one ignitiongas exit orifice16eis formed inignition cup16 for release of ignition compound combustion products whenignition compound18 is ignited. An annular recess is formed in base portion16aand is dimensioned so that an end portion of an annular inner housing22 (described below) having a predetermined inner diameter may be positioned within the recess to aid in locating and securinginner housing22 withinouter housing12.Ignition cup16 may be stamped, extruded, die cast, or otherwise metal formed and may be made from carbon steel or stainless steel, for example.

In the embodiment shown inFIG. 1, a rupturable, fluid-tight seal (not shown) is positioned acrossignition cup orifice16eto fluidly isolate cavity16cfrom amain combustion chamber22aformed downstream ofignition cup16, prior to activation of the gas generating system. The seal is secured to a face of ignition cup base portion16aand forms a fluid-tight barrier between cavity16candmain combustion chamber22a. Various known disks, foils, films, tapes, or other suitable materials may be used to form the seal.

Referring again toFIG. 1, a quantity of apyrotechnic compound18 is contained within cavity16c. In the embodiment shown inFIG. 1,pyrotechnic compound18 is a known or suitable ignition or booster compound, whose combustion ignites a second, maingas generant charge28 positioned incombustion chamber22a. In an alternative embodiment,pyrotechnic compound18 in cavity16ccomprises the main gas generant charge for the gas generating system. This alternative embodiment may be used in applications in which a relatively small amount of inflation gas (and, therefore, a correspondingly smaller amount of gas generant) is needed. One or more autoignition tablets (not shown) may be placed in cavity16c, allowing ignition ofpyrotechnic compound18 upon external heating in a manner well-known in the art.

Referring again toFIG. 1, anigniter assembly20 is positioned and secured within end closure central orifice14bso as to enable operative communication between cavity16ccontainingignition compound18 and an igniter20aincorporated into the igniter assembly, for ignitingignition compound18 upon activation of the gas generating system.Igniter assembly20 may be secured in central orifice14busing any one of several known methods, for example, by welding, crimping, using an interference fit, or by adhesive application. An igniter assembly suitable for the application described herein may be obtained from any of a variety of known sources, for example Primex Technologies, Inc. of Redmond, Wash. or Aerospace Propulsion Products by, of The Netherlands.

The recess inignition cup16 is adapted to accommodate a first end portion of aninner housing22 therealong. In the embodiment of the gas generating system shown inFIG. 1,inner housing22, in combination withcenter plate26 and bulkhead30 (described below) define amain combustion chamber22acontaining a main gas generant composition28 (described in greater detail below.)Inner housing22 is spaced apart from outer housing wall12cto form an annulargas flow passage23 extending betweeninner housing22 andouter housing12.Inner housing22 includes at least one and preferably a plurality of gas exit apertures22bformed therealong to enable fluid communication betweencombustion chamber22aandgas flow passage23. Upon activation of the gas generating system,combustion chamber22afluidly communicates with ignition cup cavity16cby way ofignition cup orifice16e.

In the embodiment shown inFIG. 1,inner housing22 telescopes or tapers down from a first, relatively larger inner diameter enclosing center plate26 (described below) andcombustion chamber22a, to a second, relatively narrower inner diameter proximate outer housing second end12b. Thus, the width of gas flow passage23 (defined as half of the difference between an inner diameter ofouter housing12 and an outer diameter ofinner housing22, where inner housing is positioned coaxially with outer housing12) may vary along the length ofinner housing22. In a particular embodiment, the width ofgas flow passage23 varies along the length ofinner housing22 from between a low-end value of approximately 0.5 mm. to a high-end value of approximately 3 mm. A second end ofinner housing22 includes an end portion which is rolled inwardly to form an annular orifice.

Inner housing

22 also has at least onesecond orifice30dformed along the relatively narrow diameter portion of the inner housing to enable fluid communication betweengas flow passage23 and an interior of a baffle member34 (described in greater detail below).

In analternative embodiment110 of the gas generating system (shown inFIG. 2), a second end portion ofinner housing122 is formed without the reduction in diameter and is seated along a recess formed in a baffle element40 (described below), thereby positioning and securinginner housing122 radially inwardly fromouter housing12. Thus, in this embodiment, the width ofgas flow passage23 is substantially constant along the length ofinner housing122. In a particular embodiment, the width ofgas flow passage23 is approximately 1 mm. along the length ofinner housing22.

Inner housings

22 and122 may be extruded, deep drawn, or otherwise metal-formed from a metal or metal alloy.

Referring toFIG. 1, aperforate center plate26 is press fit or otherwise suitably secured withinhousing12. In the embodiment shown inFIG. 1,center plate26 is dimensioned so as to form an interference fit withinner housing22 and is positioned to abut base portion16aofignition cup16. At least one orifice26ais provided incenter plate26 to enable fluid communication betweengas exit orifice16einignition cup16 and gas generantcombustion chamber22aformed ininner housing22.Center plate26 is made from a metal or metal alloy and may be a cast, stamped, drawn, extruded, or otherwise metal-formed. A rupturable, fluid-tight seal (not shown) may be positioned across orifice(s)26ato fluidly isolate booster cavity16cfromcombustion chamber22aprior to activation of the gas generating system. The seal is secured to a face ofcenter plate26 and forms a fluid-tight barrier between ignition cup cavity16candcombustion chamber22a. Various known disks, foils, films, tapes, or other suitable materials may be used to form the seal.

Referring again toFIG. 1,gas generant composition28 is positioned withincombustion chambers22a. It has been found that the gas generator embodiments described herein operate most favorably with a high gas-yield, low solids-producing gas generant composition, such as a “smokeless” gas generant composition. Such gas generant compositions are exemplified by, but not limited to, compositions and processes described in U.S. Pat. Nos. 6,210,505, and 5,872,329, each incorporated by reference herein. As used herein, the term “smokeless” should be generally understood to mean such propellants as are capable of combustion yielding at least about 85% gaseous products, and preferably about 90% gaseous products, based on a total product mass; and, as a corollary, no more than about 15% solid products and, preferably, about 10% solid products, based on a total product mass. U.S. Pat. No. 6,210,505 discloses various high nitrogen nonazide gas compositions comprising a nonmetal salt of triazole or tetrazole fuel, phase stabilized ammonium nitrate (PSAN) as a primary oxidizer, a metallic second oxidizer, and an inert component such as clay or mica. U.S. Pat. No. 5,872,329 discloses various high nitrogen nonazide gas compositions comprising an amine salt of triazole or tetrazole fuel, and phase stabilized ammonium nitrate (PSAN) as an oxidizer.

In the embodiment shown inFIG. 1, a bulkhead ordivider30 is press-fit, roll-crimped, or otherwise suitably secured withininner housing12 along the reduced-diameter portion of the inner housing, so as to maintain the divider in position within the housing when the divider is subjected to gas pressures acting on either side of the divider.Bulkhead30 partitionsinner housing22 to define achamber30awithin inner housing proximate the outer housing second end. The portion of innerhousing enclosing chamber30aincludesapertures30dformed therein to enable fluid communication betweengas flow passage23 andchamber30a. A gas tight seal is effected betweendivider30 andinner housing22, thereby preventing leakage of gas fromcombustion chamber22atoward gas exit nozzle12dwithout transiting annulargas flow passage23, as described below.Divider30 may be formed by stamping, casting, or any other suitable process from a metal or metal alloy.

Referring again toFIG. 1, abaffle member34 is provided for channeling a flow of gas enteringinner housing22 fromgas flow passage23 into gas exit nozzle12d.Baffle member34 includes anannular base portion34aand an annular sleeve34bextending from the base portion intoinner housing22 to define a baffle member interior in fluid communication with thegas flow passage23. The baffle member interior is also in fluid communication with an interior of nozzle12d.Base portion34ais positioned and secured between a second end portion ofinner housing22 and outer housing gas exit nozzle12dto secure the baffle member withinhousing12. A rupturable, fluid-tight seal (not shown) may be positioned across an end portion of annular sleeve portion34bto fluidly isolate innerhousing end chamber30afrom outer housing gas exit nozzle16d. Various known disks, foils, films, tapes, or other suitable materials may be used to form the seal.

In an alternative embodiment (shown inFIG. 2), abaffle member40 includes a substantiallycircular base portion40aabuttinginner housing22, and a substantially cylindrical wall40bextending frombase portion40a. Wall40bis in fluid communication withgas flow passage23.Base portion40aand wall40bcombine to define abaffle chamber40cfor receiving therein combustion products from combustion ofinflation gas generant28 incombustion chamber22a, in a manner described below.Baffle chamber40cis also in fluid communication withnozzle12. A gas-tight seal is effected between bafflemember base portion40aandinner housing22, thereby preventing leakage of gas fromcombustion chamber22atoward gas exit nozzle12dwithout transiting annulargas flow passage23. A recess is formed in bafflemember base portion40afor receiving therealong the second end portion ofinner housing22, for positioning and securing the inner housing second end within the gas generating system. At least one (and preferably a plurality) of orifices40dis formed in wall40bfor enabling flow of combustion products received fromgas flow passage23. In the embodiment shown inFIG. 2, several orifices40dare spaced apart approximately 90° along a periphery of wall40b. A rupturable, fluid-tight seal (not shown) may positioned across an entrance to gas exit nozzle12dto fluidly isolatebaffle chamber40cfrom outer housing gas exit nozzle12d. Various known disks, foils, films, tapes, or other suitable materials may be used to form the seal.

Particulates (especially the heavier particulates) suspended in the generated gases will have greater momentum and dynamic inertia than the gases in which they are suspended, and do not change direction as readily as the gases. Thus, the particulates will tend to collide with and aggregate upon surfaces along the gas flow path. It is also desirable to provide sufficient aggregation surface area at or near the portions of the gas generator interior where the particulates are likely to aggregate, in order to accommodate the aggregation of particulates. In addition, the more numerous the changes in direction in the gas flow, the more opportunities are provided for aggregation of the particulates.

It is believed that the particulates are most likely to aggregate upon surfaces on which they impinge with a relatively high velocity and/or on surfaces which produce a relatively severe change in direction of the gas flow. In one embodiment, this is achieved by providing aggregation surfaces oriented such that a difference between a flow direction of the gases prior to impinging on an aggregation surface and a flow direction of the gases after impinging on the aggregation surface is at least approximately 90°. In a particular embodiment of the present invention, each aggregation surfaces of the plurality of aggregation surfaces is substantially perpendicular to the flow direction of the gases impinging on the respective aggregation surface. Thus, at least a portion of the particulates striking the aggregation surfaces adhere to the surfaces, or aggregate on the surfaces, rather than changing direction with the remainder of the gas flow.

To maximize the probability of aggregating the particulates along the internal surfaces of the gas generator, it is desirable to maximize the number of collisions with the internal surfaces (and thus, the number of changes in direction of the gases), the velocity at which the particulates impact the internal surfaces, and the severity of changes of direction (more severe changes in gas flow direction of making it more likely that the particulates will temporarily stop, or that their velocity will be drastically reduced when they impinge upon an aggregation surface).

FIG. 1A shows a projected gas flow path (indicated by arrows A) through the gas generating system when combustion of the gas generant begins. Referring toFIG. 1, it may be seen thatorifices22b,30d, and the opening into annular sleeve34bdefine a flow path for generated gases through an interior of the gas generating system to nozzlegas exit orifices12e. In addition, the arrangement of the various gas generating system components described above provides a plurality of particulate aggregation surfaces positioned along the flow path of the gases for changing a flow direction of gases impinging on the surfaces, so that particulates in gases impinging on the aggregation surfaces will collect or aggregate on the surfaces.

In operation of the embodiment shown inFIGS. 1 and 1A, upon receipt of a signal from a crash sensor, an electrical activation signal is sent to igniter20a. Combustion products from the igniter expand into ignition cup cavity16c, ignitingbooster compound18 positioned in cavity16c. Products from the combustion ofbooster compound18 proceed out of cavity16cthroughignition cup orifice16eand intocombustion chamber22a, ignitingmain gas generant28. When themain gas generant28 has been fully ignited by the booster composition, the main gas generant begins to change phase from a solid to a liquid, then to a gas.

Gases and other combustion products generated by combustion ofgas generant28 are forced radially outward at a relatively high velocity toward gas exit apertures22bby the internal pressure ininner housing22. Gases then flow through multiple orifices22bininner housing22 intogas flow passage23, charging the gas flow passage with a pressure which is slightly lower than the pressure within theinner housing22. As the main gas generant burns, both P1 (internal housing pressure) and P2 (gas flow passage pressure) increase at the same rate and gases flow through thegas flow passage23. Products from combustion ofgas generant28 proceed through inner housing gas exit apertures22binto annulargas flow passage23 and alongpassage23 toward the downstream end ofinner housing22. While a portion of the combustion products exitinner housing22 via exit apertures22b, a portion of the combustion products also impinge on inner surfaces ofinner housing22, forcing the flow direction of the gases to change abruptly as they flow along the inner surfaces of the inner housing toward one of exit apertures22b. Impinging of the gases upon the inner surfaces ofinner housing22 at a relatively high velocity causes the particulates to stick to or aggregate on the inner surfaces ofinner housing22.

While a portion of the combustion products proceed through inner housingsecond end apertures30dintochamber30a, a portion of the combustion products also enter aportion70 of the gas flow passage defined by an intersection or abutment of end portions ofinner housing22 andouter housing12, forcing the flow direction of the gases to change abruptly as the gases flow back toward inner housingsecond end apertures30d. Movement of the gases intopassage portion70 at a relatively high velocity causes the particulates to stick to or aggregate on surfaces withpassage portion70.

Gases proceed through inner housingsecond end apertures30dintochamber30a. Particulates remaining in the gas stream upon enteringapertures30dmay impact along an exterior surface of annular sleeve34blocated substantially opposite orifice(s)30dformed alonginner housing22, causing the particulates to stick to or aggregate on the exterior surface of the annular sleeve.

As seen inFIG. 1A, gases deflecting off of annular sleeve34bare forced towarddivider30 in order to reach the hollow center portion of the sleeve leading to nozzlegas exit orifices12e. Thus, particulates in the gases may also impactdivider30 and adhere thereto. Finally, gases proceeding towardnozzle orifices12emay impact aninner end surface12fof the nozzle, causing particulates to adhere thereto prior to exiting of the generated gas fromorifices12e.

As seen from the above description, a series of aggregation surfaces is positioned between the combustion chamber and exit apertures of the gas generating system to impart abrupt changes in velocity to the gas stream, thereby causing particulates suspended in the gas stream to impact the aggregation surfaces so as to adhere thereto. It is believed that a system of aggregation surfaces as described herein acts to trap most of the particulates produced during combustion of the gas generant, without the filter needed in other designs.

When the internal pressure inchamber30areaches a predetermined value, any burst seals positioned therein rupture, permitting gases to flow into the sleeve portion34b, proceeding out of the gas generating system through nozzle12d.

Operation of the embodiment shown inFIGS. 2 and 2A is substantially identical to that described for the embodiment shown inFIGS. 1 and 1A, with gases fromgas flow passage23 proceeding along the path defined by arrows B, flowing through openings40bintobaffle chamber40c, then into nozzle12d, exiting the gas generating system throughgas exit orifices12e. While a portion of the combustion products proceed through inner housingsecond end apertures30dintochamber30a, a portion of the combustion products also enter aportion170 of the gas flow passage defined by an intersection or abutment of end portions ofinner baffle member40 andouter housing12, forcing the flow direction of the gases to change abruptly as the gases flow back toward baffle member apertures40d. Movement of the gases intopassage portion170 at a relatively high velocity causes the particulates to stick to or aggregate on surfaces withpassage portion170.

In the process of the gases flowing out of the propellant body, into thegas flow passage23, into the baffle member, then out of the gas exit nozzle12d, all of the metal parts contacted by the gases and the tortuous path that the gases flow through provide cooling of the gases. This provides sufficient cooling of the gases so that no additional components (such as a heat sink device or a filter) are required. In addition, because additional cooling devices are not required, the gases provided by the consumed gas generant have an efficiency greater than those produced by existing gas generator system designs.

Referring now toFIG. 3, an embodiment of thegas generating system10 described above may also be incorporated into any of a variety of vehicle occupant protection system elements. In one example, the 20 mm diameter version of the gas generating system previously described is incorporated into asafety belt assembly150 for pretensioning the safety belt.

FIG. 3 shows a schematic diagram of one exemplary embodiment of an exemplarysafety belt assembly150.Safety belt assembly150 includes a safety belt housing152 and asafety belt100 extending from housing152. A safety belt retractor mechanism154 (for example, a spring-loaded mechanism) may be coupled to an end portion of the belt. In addition, asafety belt pretensioner156 may be coupled tobelt retractor mechanism154 to actuate the retractor mechanism in the event of a collision. Typical seat belt retractor mechanisms which may be used in conjunction with the safety belt embodiments of the present invention are described in U.S. Pat. Nos. 5,743,480, 5,553,803, 5,667,161, 5,451,008, 4,558,832 and 4,597,546, incorporated herein by reference. Illustrative examples of typical gas-actuated pretensioners with which the safety belt embodiments of the present invention may be combined are described in U.S. Pat. Nos. 6,505,790 and 6,419,177, incorporated herein by reference.

Safety belt assembly

150 may also include (or be in communication with) a crash event sensor158 (for example, an inertia sensor or an accelerometer) operates in conjunction with a crash sensor algorithm that signals actuation ofbelt pretensioner156 via, for example, activation of igniter20a(not shown inFIG. 3) incorporated into the gas generating system. U.S. Pat. Nos. 6,505,790 and 6,419,177, previously incorporated herein by reference, provide illustrative examples of pretensioners actuated in such a manner.

Referring again toFIG. 3,safety belt assembly150 may also be incorporated into a broader, more comprehensive vehicleoccupant restraint system180 including additional elements such as anairbag system200.Airbag system200 includes at least oneairbag202 and agas generating system201 coupled toairbag202 so as to enable fluid communication with an interior of the airbag.Airbag system200 may also include (or be in communication with) acrash event sensor210.Crash event sensor210 operates in conjunction with a known crash sensor algorithm that signals actuation ofairbag system200 via, for example, activation of airbaggas generating system10 in the event of a collision.

It should be appreciated thatsafety belt assembly150,airbag system200, and more broadly, vehicleoccupant protection system180 exemplify but do not limit uses of gas generating systems contemplated in accordance with the present invention. In addition, it should be appreciated that a gas generating system incorporating a plurality of particulate aggregation surfaces and a high gas-yield, low solids-producing gas generant composition as described herein may be used in the airbag system or in other vehicle occupant protection system elements requiring a gas generating system for operation.

In yet another aspect of the invention, a method of manufacturing an inflator may be described as follows:

- 1. Providing an outer housing having a first end and a second end, and a periphery.
- 2. Forming an outer protrusion, or annular flange, about the periphery at the first end.
- 3. Providing an end closure having a recessed portion, or a groove.
- 4. Inserting the end closure within the outer housing at the first end, thereby laterally aligning the outer protrusion and the recessed portion; and
- 5. Compressing the outer protrusion within the recessed portion. Compressing includes cold-working or otherwise metal-forming the coupling of the protrusion and recessed portion.

An inflator and a vehicle occupant protection system containing an inflator formed by the method described above are also included. The text describing theend closure14 coupled to the first end12aofhousing12, given above, is incorporated herein by reference, to fully inform the reader of the details of this method.

It will be understood that the foregoing description of the present invention is for illustrative purposes only, and that the various structural and operational features herein disclosed are susceptible to a number of modifications, none of which departs from the spirit and scope of the present invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined only by the appended claims and their equivalents.