Surface mount initiators

An initiator assembly includes an SMI assembly board onto which at least a first and a second initiator are surface mounted. The first and second initiators each include a respective surface mount initiator board with which a respective igniter element is respectively mounted. Corresponding multi-initiator assemblies for automotive airbag inflator devices as well as automotive airbag inflator device combinations are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

The subject matter of this application is related to prior U.S. patent application Ser. No. 13/688,839, filed on 29 Nov. 2012 and prior U.S. patent application Ser. No. 13/688,893, now U.S. Pat. No. 9,010,803, filed on 29 Nov. 2012. The disclosure of each of these related patent applications is hereby incorporated by reference herein and made a part hereof, including but not limited to those portions which specifically appear hereinafter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to initiators and, more particularly, to design, fabrication and processing of initiators such as described more fully below, such as sometimes herein as “surface mountable” or “surface mounted.”

2. Discussion of Related Art

Initiators find common usage in a variety of applications. One prominent use of initiators is in motor vehicle occupant safety restraint systems.

It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag,” that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins being inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an “inflator.”

Various types of inflator devices have been disclosed in the art for the inflation of an airbag such as used in inflatable restraint systems.

One type of known inflator device derives inflation gas from a combustible pyrotechnic gas generating material which, upon ignition, generates a quantity of gas sufficient to inflate the airbag. Such inflator devices often include a gas generant material stored within the inflator device housing and an initiator in combination with the housing that actuates the gas generant material. The initiator typically includes a reactive charge in combination with electrical connectors. A signal sent through the electrical connector(s) actuates the reactive charge, which produces reaction products that actuate the gas generant material.

In view of possibly varying operating conditions and, in turn, possibly varying desired performance characteristics, inflatable safety restraint technology has led to the development of what has been termed “adaptive” or “Smart” inflator devices and corresponding inflatable restraint systems. With an adaptive inflator device, output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.

Pyrotechnic inflators typically may have one or more chambers containing gas generant. Adaptive pyrotechnic inflators having gas generant material in two chambers, which are independently ignited via respective initiators or igniters, have been referred to as “dual stage” inflators. In practice, each such gas generant material-containing chamber is oftentimes referred to as a “combustion chamber” as the gas generant material therein contained is burned or otherwise reacted to produce or form gas such as may be used to inflate an associated inflatable restraint airbag cushion.

Dual stage inflators typically may have several contemplated actuation or firing scenarios. In a first such scenario, only the gas generant material in a first or primary chamber and associate initiator device is actuated whereby a fixed quantity of inflation gas is produced thereby. In a second possible scenario, the first or primary initiator is first actuated whereby gas generant material in a first chamber is first reacted to start to produce or form inflation gas and after a predetermined or preselected delay, a secondary initiator is then actuated whereby gas generant material in the second chamber is reacted to also produce or form inflation gas. In a third possible scenario, both the primary and the secondary initiators are actuated whereby a gas generant material in a first chamber and a gas generant material in a second chamber are actuated simultaneously to produce or form inflation gas from the gas generant material in each of the chambers.

Through the selection and use of an appropriate such actuation or firing scenario, inflator output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.

Current state of the art automotive airbag technology oftentimes employs dual stage inflators (smart inflators) in an effort to achieve desired or necessary performance requirements.

FIG. 1shows a n example of a dual stage inflator assembly, generally designated by the reference numeral110, and shown in a static state or condition, e.g., prior to actuation.

The inflator assembly110includes a housing construction112having a generally cylindrical external outline and such as formed of two structural components, i.e., a lower shell or base portion114and an upper shell or diffuser cap portion116. The diffuser cap portion116is in the general form of an inverted bowl and includes a top wall120and a cylindrical sidewall122, which includes a plurality of spaced, preferably, generally uniformly spaced gas exit ports124.

The base portion114includes first and second mounting openings, designated by the reference numerals126and130, respectively. The base portion114also includes a peripheral bracket132that extends radially outward from the housing112and such as may serve to form an interface attachment which is used to attach the inflator assembly110to a vehicle.

The housing112is configured to define a central first chamber134. The first chamber134contains or houses a supply of a first gas generant material, such as typically in the form of a pyrotechnic, not here shown to facilitate illustration and comprehension.

Within the first chamber134, such as in surrounding relation with the first gas generant material therein contained, is a filter assembly140. Such a filter assembly may include one or more of a combustion screen or filter such as formed of multiple layers or wraps of a metal screen, a filter damper pad or the like.

The inflator assembly110also includes a retainer144such as may serve as a construction expedient to retain the inflator assembly components in proper relative arrangement and prevent undesired flow passage through the assembly.

A first igniter assembly, generally designated by the reference numeral154, is mounted to the housing112in a location within the first chamber134via the first mounting opening126. The first igniter assembly154may take the form of a known pyrotechnic initiator device such as includes, as is known in the art, an igniter or ignition booster cup156wherein is housed a canister158, such as contains an igniter material, not here shown to facilitate illustration and comprehension. The first igniter assembly also includes a first igniter device or squib162in conjunction with an initiator pyrotechnic output composition (not shown), a pyrotechnic output composition containment cup and electrical isolation sleeve163, such as made of metal, and a squib adapter or holder164whereby the igniter assembly154is mounted to or mated with the housing112. As shown, the igniter cup156can take the form of a generally concave member with a cap170and a cylindrical sidewall172forming an interior174. The igniter cup156can be formed of a gas-impermeable material, such as metal, with the cylindrical sidewall172including a plurality of positioned and spaced gas exit orifices (not shown) that are normally (e.g., when the inflator is in a static or prior to actuation state) covered and the passage of material therethrough prevented by means of a pressure sensitive covering or barrier (not shown), such as by means of an adhesive-backed foil seal wrap or the like as is well known in the art. As is known, such covering can be selected to open or rupture upon the application of a predetermined pressure thereagainst from the interior of the igniter cup156.

When actuated, the squib162discharges or otherwise results in the rupture or opening of the ignition material canister158and, in turn, ignition of the igniter material normally contained and subsequently the gas generant material contained within the first chamber134.

In practice, the igniter assembly154is connected or joined to the housing112such as by welding the holder164to the base portion114at the mounting opening126.

The first chamber134also houses or contains a second chamber182. The second chamber182includes a generant cup184, a lid closure185, a second igniter device or squib190in conjunction with an initiator pyrotechnic output composition (not shown), a pyrotechnic output composition containment cup and electrical isolation sleeve191, such as made of metal, and a second squib adapter or holder192whereby the second igniter device190and the associated second chamber182are mounted or mated with the housing112such as via the second mounting opening130.

The generant cup184and the lid closure185cooperate to form a generant cup interior196wherein is desirably placed a selected quantity of a second gas generant material such as typically in the form of a pyrotechnic as described above and not here shown to facilitate illustration and comprehension. The second gas generant material may typically be in the form of a pyrotechnic material and may be either the same or different in composition, shape, size or form, as compared to the first gas generant material.

The generant cup184and the lid closure185further desirably cooperate and function in a manner such as to permit the combustion products formed by reaction of the gas generant material contained within the second chamber182, when properly and desirably actuated, to pass from the second chamber182out into the first chamber134, through the filter assembly140and the exit ports124out from the inflator assembly110and into an associated airbag cushion (not shown). Zone Name: A2,AMD

As will be appreciated, there is a need and demand for improvements in multiple initiator-containing devices and associated assemblies. Previous initiator and inflator devices include those described and/or claimed in EP 0 879 739 B1 (having the counterpart U.S. Pat. No. 6,068, 291, issued 30 May 2000 to Lebaudy et al.); EP 1 160 533 B1 (having the counterpart US 2002/0002924 A1, published 10 Jan. 2002); and U.S. Pat. No. 5,672,841, issued 30 Sep. 1997 to Monk et al.

In view of the numerous and/or varied uses and applications for initiators, improvements in the design, manufacture, operation and/or processing of initiators, such as whereby significant cost reductions can be realized, are highly sought, pursued and valued.

SUMMARY OF THE INVENTION

A general object of the invention is to provide improved initiator assemblies.

A more specific objective of the invention is to overcome one or more of the problems described above.

In one aspect of the invention, there is provided an initiator assembly that includes a surface mount or surface mountable initiator (SMI) assembly board onto which at least a first and a second initiator are surface mounted. The first initiator includes a first container closed by a first solid body. The first container contains a supply of a first igniter material. The first initiator also includes a first igniter element disposed within the first container. Upon actuation, the first igniter element is in reaction initiating communication with the first igniter material. The first initiator further includes a first surface mount initiator board disposed between the first igniter element and the first solid body. First and second electrical contacts of the first initiator pass through the first solid body and the first surface mount initiator board in electrical contact with the first igniter element. The second initiator includes a second container closed by a second solid body. The second container contains a supply of a second igniter material. The second initiator includes a second igniter element disposed within the second container. Upon actuation, the second igniter element is in reaction initiating communication with the second igniter material. The second initiator further includes a second surface mount initiator board disposed between the second igniter element and the second solid body. First and second electrical contacts of the second initiator pass through the second solid body and the second surface mount initiator board in electrical contact with the second igniter element.

In specific embodiments of such initiators assemblies:1. the first and/or the second initiator is/are wave soldered to the SMI initiator board;2. the first and/or the second igniter element(s) is/are reflow soldered to respective surface mount devices;3. the first and/or the second igniter element(s) is/are selected from a group that includes a hot wire, a foil bridge and a thin film;4. the first and/or the second igniter materials is an ignition pyrotechnic; and5. the initiator assembly is a part, component or in combination in or with an automotive airbag inflator device.

In another aspect of the invention, there is provided a multi-initiator assembly for an automotive airbag inflator device. In accordance with one embodiment, such a multi-initiator assembly includes an SMI initiator board onto which a plurality of initiators are surface mounted. The plurality of initiators includes at least a first initiator and a second initiator. The first initiator includes a first container closed by a first solid body. The first container contains a supply of a first igniter material. The first initiator also includes a first igniter element disposed within the first container. Upon actuation, the first igniter element is in reaction initiating communication with the first igniter material. The first initiator further includes a first surface mount initiator board disposed between the first igniter element and the first solid body. First and second electrical contacts of the first initiator pass through the first solid body and the first surface mount initiator board in electrical contact with the first igniter element. The second initiator includes a second container closed by a second solid body. The second container contains a supply of a second igniter material. The second initiator also includes a second igniter element disposed within the second container. Upon actuation, the second igniter element is in reaction initiating communication with the second igniter material. The second initiator further includes a second surface mount initiator board disposed between the second igniter element and the second solid body. First and second electrical contacts of the second initiator pass through the second solid body and the second surface mount initiator board in electrical contact with the second igniter element.

As used herein, references to a “surface mount initiator”, “surface mountable initiator” or “SMI” are to be generally understood to refer to an initiator which includes or wherein connector lead features are directly mounted or disposed onto an associated plate or board, such as a PC board, for example.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides improved initiator assemblies and associated initiator-containing combinations such as including automotive airbag inflator devices such as for use in motor vehicle occupant safety restraint systems, for example.

As described in greater detail below, SMI initiator assemblies with connector lead features directly mounted or disposed onto an associated plate or board, such as a PC board, for example, open up new options for initiating device integrated into an assembly and can offer processing advantages that cannot be attained or realized by, through, or with conventional initiator assemblies.

Turning first toFIGS. 2-4, there is shown or illustrated an initiator assembly, generally designated by the reference numeral210, in accordance with one embodiment of the invention.

The initiator assembly210includes an SMI initiator board212onto which at least a first and a second initiator,214and216, respectively, are surface mounted.

The first initiator214includes a fragmentable generally cylindrical first container220. The first container220includes a generally cylindrical side wall222with an open first end224generally opposite a closed second end226. As shown, the second end226can be closed by generally planar upper wall228. A first solid cylindrical body230closes the container open end224. The body230has a side wall232adapted to mate with the container side wall222. Adjacent the container open end224, the container side wall222includes a lip portion234such as extends about the solid body230in a closure securing or retaining alignment.

Advantageously, the container220comprises a thin, light metal such as aluminum. The container planar upper wall228can, if desired, include weakened lines or areas (not shown) in order to be able to more easily and specifically open under the effect of an increase in the pressure within the container.

The first container220contains a supply of a first igniter material such as in the form of an ignition pyrotechnic, not shown to facilitate illustration and comprehension of the drawing. Various igniter materials such as known in the art can be used and broader practice of the invention is not necessarily limited by or to the use of specific igniter materials.

As will be appreciated by those skilled in the art and guided by the teachings herein provided, suitable such first containers and first solid bodies can take various shapes and forms and the broader practice of the invention is not necessarily limited by or to specific shapes or forms of such containers and solid bodies. In practice, however, suitable such containers are often in the shape or form of a fragmentable cylindrical element or cup open at one of its ends and having a volume appropriate to accommodate the desired load or quantity of igniter material to be therein contained. Further, suitable solid bodies are commonly of a shape or form to complement an open end or opening of or in the associated container.

The solid body230desirably functions as a barrier or wall impermeable to the reaction products formed or produced upon actuation of the initiator. This body230is preferably made of a material such as rubber.

A surface mount device (SMD) plate236(not shown inFIG. 3) is included and serves or acts to position or assisting in positioning the first initiator214flat on the SMI assembly board212such as to assist in the securing of the first initiator214to the board212such as by wave soldering or reflow soldering, as described in greater detail below. The SMD plate236is preferably made in a thermoplastic material such as, for example, polyphthalamide (PPA).

A first igniter element240, such as in the form of a bridge element, is disposed within the first container220such that upon actuation, the first igniter element240is in reaction initiating communication with the first igniter material disposed or contained within the container220. In particular applications, suitable such igniter elements can include or take the form of a hot wire, a foil bridge or a thin film, for example. It is to be understood, however, that the broader practice of the invention is not necessarily limited to use with specific or particular types or forms of igniter elements.

A first surface mount initiator board242is disposed within the container220between the first igniter element240and the first solid body230. Such surface mount initiator boards can be suitably made of or from a variety of materials including FR4 glass epoxy resin composites, for example.

The first initiator214also includes first and second electrical contacts,244and246, that pass through the first solid body230and the first surface mount initiator board242in electrical contact with the first igniter element240. In particular, each of the electrical contacts244and246has an end at or proximate the generally planar upper face248of the surface mount initiator board242. As shown, connector lead features250joining the contacts244and246with the igniter element240in electric transfer communication are desirably surface mounted, e.g., are directly mounted or disposed onto the surface mount initiator board242.

The second initiator216is generally similar to the above-described first initiator214and, to avoid unnecessary repetition includes:

a fragmentable generally cylindrical container260such as contains a supply of a second igniter material (not shown) such as in the form of an ignition pyrotechnic and which second igniter material may be the same or different in composition, shape, size or form, as compared to the first igniter material;

the first container260includes a generally cylindrical side wall262with an open first end264generally opposite a closed second end266;

the second end266is closed by generally planar upper wall268;

a first solid cylindrical body270closes the container open end264;

the body270has a side wall272adapted to mate with the container side wall262;

adjacent the container open end264, the container side wall262includes a lip portion274such as extends about the solid body270in a closure securing or retaining alignment;

a surface mount device (SMD) plate276is included and serves or acts to position or assisting in positioning the initiator216flat on the SMI assembly board212such as to assist in the securing of the initiator216to the board212such as, in this case by wave soldering;

the second container260contains a supply of a second igniter material, not shown to facilitate illustration and comprehension of the drawing;

a second igniter element280, similar to the first igniter element discussed above, is disposed within the second container260such that upon actuation, the igniter element280is in reaction initiating communication with the igniter material contained or disposed within the container260;

a second surface mount initiator board282is disposed within the container260between the igniter element280and the solid body270;

the initiator216also includes first and second electrical contacts,284and286, that pass through the solid body270and the surface mount initiator board282in electrical contact with the igniter element280;

each of the electrical contacts284and286(not shown) has an end at or proximate the generally planar upper face288of the surface mount initiator board282; and

connector lead features290that join the contacts (only shown for contact284) with the igniter element280in electric transfer communication are desirably surface mounted, e.g., are directly mounted or disposed onto the surface mount initiator board282.

In the initiator assembly210, the first initiator214and the second initiator216are shown as desirably wave soldered to the SMI initiator board212such as through the inclusion of wave solder joint trace inputs to electrical connections, e.g., interconnects,294.

As identified above, the SMD plates236and276can advantageously function to position or assisting in positioning the respective first and second initiators,214and216, flat on the SMI assembly board212such as to assist in the securing of the initiators to the board such as by wave soldering or reflow soldering. That is, the SMD plates desirably serve to prevent or avoid the initiator leads being “free floating” and prevent or avoid the initiator being unstable such as to undesirably tip or lean when placed into its designated solder mount location.

The first initiator214and the second initiator216each include reflow solder joints forming traces between associated electrical contacts and igniter elements.

As will be appreciated by those skilled in the art and guided by the teachings herein provided, in general in order for a discrete electronic component to be “wave solderable”, the component generally needs to be able to rest on a respective associated board or plate in such a way as to maintain or hold its respective position during and through the soldering process. In the case of the subject surface mount initiator assemblies, one such mounting configuration would be to have the two firing leads project through a “thru-hole” solder land in the SMI assembly board. The solder wave contacts and connects the leads and the solder land as it goes through the wave soldering process and thus creates the solder joint. In accordance with one preferred embodiment of the invention, the ability of a component to be properly situated in position on an SMI assembly board is realized through the use of a “SMD Plate” which provides a stable surface under the initiator to hold the initiator upright through the process. This same feature of an SMD Plate can be used both for wave soldering and solder reflow processing methods such as herein described and provided.

Initiator assemblies that are wave solderable, however, can significantly expand options for integration of initiators into higher assemblies, such as inflators. For example, working under the assumption that an initiator would need to have a soldered connection with an associated initiator board, there are various techniques by which this can be accomplished. One technique would be to hand solder the initiator onto the board. However, because of the relative high amount of labor associated with such a soldering technique, such method is generally not preferred. Another technique option would be to place the initiator onto the face of a respective SMI assembly board where solder paste had been applied and then put that assembly through a reflow furnace to flow the solder paste to the initiator pins (similar to what would be done with a modern surface mount electrolytic capacitor). A third technique option is a thru-lead connection with the SMI assembly board, giving a manufacturer an option for processing via wave soldering. So the fact that the initiator would be configured in such a way as to allow for wave soldering as an attachment method, creates the desirability.

Turning toFIGS. 5-7, there is shown or illustrated an initiator assembly, generally designated by the reference numeral510, in accordance with another embodiment of the invention.

The initiator assembly510is in many respects similar to the initiator assembly210shown inFIGS. 2-4and describe above. To simplify and facilitate description and discussion, elements, components and/or features in the initiator assembly510that correspond to the above-described elements, components and/or features of the initiator assembly210are similarly using similar500series reference numerals.

For example, similar to the initiator assembly210, the initiator assembly510includes a SMI initiator board512onto which at least a first and a second initiator,514and516, respectively, are surface mounted.

The first initiator514includes a fragmentable generally cylindrical first container520such as contains a supply of a first igniter material (not shown). The first container520includes a generally cylindrical side wall522with an open first end524generally opposite a second end526closed by generally planar upper wall528. A first solid cylindrical body530closes the container open end524. The body530has a side wall532adapted to mate with the container side wall522. Adjacent the container open end524, the container side wall522includes a lip portion534such as extends about the solid body530in a closure securing or retaining alignment.

The generally planar container upper wall528, however, is shown as including one or more lines of reduced thickness529such as to facilitate desired opening or rupture of the respective container upon actuation of the respective igniter element.

A surface mount device (SMD) plate536is included and serves or acts to position or assisting in positioning the first initiator514flat on the SMI assembly board512such as to assist in the securing of the first initiator514to the board512such as by wave soldering or reflow soldering, as described in greater detail therein.

A first igniter element540, such as described above, is disposed within the first container520such that upon actuation, the first igniter element540is in reaction initiating communication with the first igniter material disposed or contained within the container520.

A first surface mount initiator board542is disposed within the container520between the first igniter element540and the first solid body530.

The first initiator514includes first and second electrical contacts,544and546, that pass through the solid body530and the surface mount initiator board542in electrical contact with the igniter element540. In particular, each of the electrical contacts544and546has an end at or proximate the generally planar upper face548of the surface mount initiator board542. As shown, connector lead features550joining the contacts544and546with the igniter element540in electric transfer communication are desirably surface mounted, e.g., are directly mounted or disposed onto the surface mount initiator board542.

The initiator514differs from the initiator214in that the initiator514is shown as including respective SMI terminals595illustrated as splayed out pins. In this embodiment, such splayed out SMI terminal pins are featured to facilitate and assist in reflow type soldering. This is in contrast to the axial pin terminal design applied in the previously described embodiment and such as may provide a “through-hole” interface with the SMI assembly board such as may be preferred in conjunction with wave soldering.

The second initiator516is generally similar to the above-described first initiator514and includes:

a fragmentable generally cylindrical container560;

the container560includes a generally cylindrical side wall562with an open first end564generally opposite a closed second end566;

the second end566is closed by generally planar upper wall568having one or more lines of reduced thickness569such as to facilitate desired opening or rupture of the respective container upon actuation of the respective igniter element;

a solid cylindrical body570closes the container open end564;

the body230has a side wall572adapted to mate with the container side wall562;

adjacent the container open end564, the container side wall562includes a lip portion574such as extends about the solid body570in a closure securing or retaining alignment;

a surface mount device (SMD) plate576is included and serves or acts to position or assisting in positioning the first initiator514flat on the SMI assembly board512such as to assist in the securing of the first initiator514to the board512such as by wave soldering or reflow soldering;

the container560contains a supply of a second igniter material, not shown to facilitate illustration and comprehension of the drawing;

a second igniter element580, similar to the first igniter element540discussed above, is disposed within the second container560such that upon actuation, the igniter element580is in reaction initiating communication with the igniter material contained or disposed within the second container560;

a second surface mount initiator board582is disposed within the container560between the igniter element580and the solid body570;

the initiator516also includes first and second electrical contacts,584and586, that pass through the solid body570and the surface mount initiator board582in electrical contact with the igniter element580;

each of the electrical contacts584and586has an end at or proximate the generally planar upper face588of the surface mount initiator board582;

the connector lead features590that join the contacts584and586with the igniter element580in electric transfer communication are desirably surface mounted, e.g., are directly mounted or disposed onto the surface mount initiator board582; and

In initiator assemblies such as herein provided, the general function of the initiators is to release energy in the form of heat and pressure upon receipt of a constant current pulse stimulus. A current signal received, either through conductive pins or an alternate conductive route, travels through the selected igniter element which, in the case of a resistive element causes it to rapidly heat. That heat is transferred to an associated ignition material such as in the form of a pyrotechnic composition and such as has been consolidated against the igniter element and held with a constant load via the container and its associated attachment features. A function of the surface mount initiator board is to provide an electrical interface between the connector pins in the adjoining connector and the igniter element. It also provides a mounting surface for the igniter element. The solid body, such as in the form of a rubber seal can desirably serve to provide an elastic interface to which the container can be joined or secured, such as by being crimped inward thereagainst. The solid body can also desirably act or serve as a seal against moisture intrusion. The SMD plate provides stability to the initiator in its mount against the adjoining initiator assembly board. The SMD plate also can desirably act or serve as a design control feature to assure that the initiator is electrically insulated from any traces on the initiator assembly board.

As identified above, initiator assemblies such as herein provided can find use in various applications including, for example, such as in or as a part of an automotive airbag inflator device, battery disconnects, trunk lifters, pyro connecting devices, etc.

Turning toFIGS. 8-10, there is shown an automotive airbag inflator device base assembly810with an initiator assembly812integrally molded with an inflator base814, in accordance with one embodiment of the invention. It will be appreciated that other inflator device components such as customary inflator device components such as diffusers, filters, gas generants, outer housing, etc, have been omitted to simplify the figures and facilitate viewing of relevant SMI multi-initiator assembly components.

The initiator assembly812is similar to the initiator assembly210and forms a subassembly that includes an SMI initiator board820onto which at least a first and a second initiator,822and824, respectively, are surface mounted, such as described above.

As shown inFIG. 8. the automotive airbag inflator device base assembly810includes an overmolding826such as made or formed of materials including but not necessarily limited to nylon 6; nylon 6,12; and polypropylene, for example.

As shown, such as through the inclusion of such an overmolding826, the initiator assembly812can desirably be integrally molded such as to be formed in one part with an automotive airbag inflator device component, in this case the inflator base814. Those skilled it the art and guided by the teachings herein provided will understand and appreciate that such an integrally molded approach is a relatively low cost approach for creating the embodiment that would interface with the higher level assembly. Injection molding of such a component can desirably reduce either or both processing costs and/or the number of individual components required in an assembly.

As shown, the automotive airbag inflator device base assembly810also only includes a single mounting opening830for use in association with initiator assembly812. In contrast, many present day inflator devices require or include multiple mounting openings, e.g., mounting openings for each initiator device therein contained. While molding is a process that has previously been used in certain state of the art single stage inflators, prior dual stage inflators have required the use of welding to join igniter adapters to inflator device chamber walls in order to maintain the necessary degree or level of chamber wall strength required to ensure safe operation of the inflator device upon actuation. Through the need for only a single mounting opening in the inflator chamber wall, inflator chamber wall strength is sufficiently maintained that mold processing can now be advantageously applied to such inflator devices.

Those skilled in the art will understand and appreciate that the invention provides opportunities for significant savings in areas such as ease of manufacture, operation or both with regard to motor vehicle occupant safety restraint systems and components such as inflator devices that significant economic benefits can be realized through the practice of the invention. For example, in typical or common airbag inflator design, the initiator is hermetically sealed via design & process methods and then installed in an inflator assembly which also is hermetically sealed such to ensure proper and desired long term operability. The inclusion of two levels of hemeticity increases product cost. Through the practice and application of the invention, the increase in cost due to the inclusion of the redundancy of having both an internal seal, e.g., an initiator seal, as well as an inflator seal, can be reduced and preferably avoided. That is, as an initiator typically sits within the sealed inflator body for the life of the product, the inflator seal can function to fulfill the same need for the initiator assembly. The approach of integrating the initiator assembly design within the inflator body and removing the need for a redundant hermetic seal can result in reductions in manufacturing cost by eliminating an additional seal such as a laser weld as well as the need for an in-process inspection for that additional seal.

In dual initiator or “smart” applications, the overall cost of the airbag initiating function can also be reduced by integrating both initiator subassemblies into a design in which both initiating devices share a common board mount. For example, with a multi-initiator assembly such as described herein, multiple initiating device(s) is/are installed on a SMI assembly board, such as with previously applied solder paste at the electrical contact location, and then permanently attached through a solder reflow process. Further, the invention permits initiators to be desirably strategically placed within an inflator such as to ignite different stages of the inflator. Moreover, the SMI assembly boards can be appropriately and suitably customized for particular inflator applications such as satisfy or meet the specific or particular needs of an application.

Further cost savings advantages can be realized as inflator assemblies such as herein provided can reduce the need for or eliminate commonly applied initiator design features such as charge holders and gold plating on electrical connections pins, for example.

Cost saving advantages can also be realized as the inflator assemblies in accordance with the invention can utilize components, e.g., cup, SMD Plate, leads, rubber seal and ignition element, such as are already are readily available components used in the electronics industry. By using common or readily accessible commodity components, extremely competitive component pricing can be realized.

Thus the invention provides an initiator assembly wherein one or more separate initiator devices, such as each including a container containing a supply of igniter material and an igniter element in reaction initiating communication with the igniter material, are surface mounted directly onto a SMI assembly board. As will be appreciated, such surface mounting of initiator devices opens up a realm of possibilities that are not currently available with conventional initiator assemblies. For example, in a higher level assembly that requires multiple initiators to drive a higher level device, those initiators can be mounted on the SMI assembly board such as via solder joints rather than individually mounted using conventional means, e.g., welding, crimping, etc. Consequently, attachment process can desirably be simplified and accomplished at a reduced cost, as compared to conventional mounting techniques.