CA1095243A - Solid propellant gas generator - Google Patents
Solid propellant gas generatorInfo
- Publication number
- CA1095243A CA1095243A CA305,691A CA305691A CA1095243A CA 1095243 A CA1095243 A CA 1095243A CA 305691 A CA305691 A CA 305691A CA 1095243 A CA1095243 A CA 1095243A
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- Canada
- Prior art keywords
- openings
- wall
- annular
- container
- exit ports
- Prior art date
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Abstract
SOLID PROPELLANT GAS GENERATOR
Abstract of the Disclosure A gas generator includes an annular hermetically sealed combustion chamber containing a charge of propellant and an initiator. The combustion chamber is enclosed within an inner housing having an annular wall supporting an annular wall of the combustion chamber. An outer housing surrounds the combustion chamber and inner housing and includes an outer annular wall spaced radially of the annular wall of the inner housing to define a plenum. The outer annular wall includes a series of radially opening exit ports.
A plurality of layers of wrapped fine mesh and coarse mesh screen in the plenum filter and cool the gas from the combus-tion chamber. In one embodiment, the wall of the inner housing is provided with annular axially spaced bands of radial openings of gradually decreasing size, with the largest size openings being most axially remote from the exit ports. The annular wall of the chamber ruptures through the largest openings when the pressure in the combustion chamber reaches a predetermined limit. Should this limit be exceeded the openings of one or more of the other bands are opened to pro-vide pressure relief from the combustion chamber. In another embodiment varying size openings are intermixed. In a third embodiment, the openings are slot shaped with their open ends most axially remote and their closed ends most axially adjacent to the exit ports.
Abstract of the Disclosure A gas generator includes an annular hermetically sealed combustion chamber containing a charge of propellant and an initiator. The combustion chamber is enclosed within an inner housing having an annular wall supporting an annular wall of the combustion chamber. An outer housing surrounds the combustion chamber and inner housing and includes an outer annular wall spaced radially of the annular wall of the inner housing to define a plenum. The outer annular wall includes a series of radially opening exit ports.
A plurality of layers of wrapped fine mesh and coarse mesh screen in the plenum filter and cool the gas from the combus-tion chamber. In one embodiment, the wall of the inner housing is provided with annular axially spaced bands of radial openings of gradually decreasing size, with the largest size openings being most axially remote from the exit ports. The annular wall of the chamber ruptures through the largest openings when the pressure in the combustion chamber reaches a predetermined limit. Should this limit be exceeded the openings of one or more of the other bands are opened to pro-vide pressure relief from the combustion chamber. In another embodiment varying size openings are intermixed. In a third embodiment, the openings are slot shaped with their open ends most axially remote and their closed ends most axially adjacent to the exit ports.
Description
: :
:
~:~i ****************
.I This invention rela~es generally to inflators and more particularly to solid propellant gas generators ~or ~'.'........................ , ~
,, 1 ~k 1, , ; .
-!
I
... . .. .
. .. ~. ~ ..
5~3 inElating various inflatable articles, such as inf]atable occupant restraint cushions.
Solid propellant gas generators are we]l known in the prior art. Generally such inflators include an annular or cylindrical combustion chamber containing a predetermined charge of solid propellant material and an - electrica:L initiator for initiating burning of the pro-pellant to generate gas Eor inflating an inflatable article.
The gas may flow either radially or axially Erom the coMbus~
tion chamber through fixed area openings, and then through a plenum to -the exit ports from the generator to the interior ;
of the article to be inflated. The plenum may contain both filtel-iny clnd cooling materlal as well as a neutralizer The burn rate of the propellant in the combustion chamber is dependent on the pressure level in the combus-tion chamber. The higher the pressure level, the greater the burn rate. The burn rate of the propellant is also affected by the temperature of both the propellant and the charnber~
The colder the propellant and the chamber, the lower the pressure in the chamber and consequently the slower the burn rate. Alternatively, if the prope]lant and chamber are hot~
the pressure in the combustion chamber will be greater and the burn rate will be greater.
Prior art gas generators normally include a fixed number of openings from the combustion chamber. Such openings provide a fixed gas passage area from the combustion chamber. Should the burn rate in the chamber exceed a pre-determined minimum, there is no compensa-tion or pressure relief for the increased volume of gas generated in the combustion chamber.
" . , . ,, ~ , . .... , ,, ~ . . .
~13e-~2~ 3 ~ he gas generator of this in-vention okvia-tes variations in the burn rate and pressure by providing a variable area gas passage arrangement from ~he combustion chamber to the article to be inElated. The gas passage arrangemen-t from the combustion chamber provides a pre~
determined minimum yas passage area and permits increased gas passage areas in accordance with the pressure in the combustion chamber.
In this invention, the propellant and initiator are located in an annular sealed aluminum container. The outer annular wall of the container is supported by an annular outer wall of an inner housing which is spaced radially of an annular oute~ wall of an outer he,using and cooperatively defines therewith a plenum. The annular outer wall of the outer housing contains the exit ports which are spaced peripherally about such wall and open radially of the yenerator. In one embodiment, the annular wall of the inner housing is provided with a plura]ity of axially spaced bands of openings of decreasing size. The bands of openings are normally closed by the outer annular wall of the combustion chamber. The band oE largest siæe openings is located most axially remote from the exit ports.
The portions of the chamber wall opposite the largest size openings will rupture therethrough to provide a predetermined minimum gas passage area whenever the pressure in the chamber exceeds a predetermined minimum level necessary to inflate the article to be inflated. The next band of smaller size openings is-axially closer to the exit portsO
Should the pressure in the combustion chamber exceed a second higher predetermined minimum level, then the portions , . . . . ,~
of the cha~T~er wall oppcsite tllese openings will rupture therethrough to provide an increased yas passage area from ~he cilamber. The next band of even smaller size is a~ially closest to the e~it ports. Should the pressure :in the combustioll chamber exceed a third predetermilled level, the portions of the chamber wall opposite these openings will rupture to provide for an even grea-ter increased ~as passage area from the chamber~ The number of rows or hands of openings and the size and shape of such openings will vary with the propellant used and the environmental conditions of use of the generator. However, at least two bands of openings should be provided~
In another emhodiment, varying size cpenings are interrnixed. In this embodiment, the portions of the chamber wall opposite the largest size openings will be first to rupture, and those portions opposite the next largest size openings will be next to rupture. The intermixed openings will he located as axially remote as possible from the exit ports.
In a third embodiment, the openings are slot shaped with their open ends most axially remote from the exit ports and their closed ends most axially adjacent.
The portions of the chamber wall opposite the open ends of the openings will rupture when the chamber pressure exceeds the predetermined minimum level. Additional portions of the chamber wall opposite additional portions of the slots may thereafter rupture should the pressure in the combustion chamber exceed'the second and third predetermlned levels hereinbefore mentioned.
43 -;:
The p]enum between the outer annular wal]s o~
the inner and outer housings contains a plurality o~ laye,s of wrapped screen material. ~oarse mesh screen material, such as 10 mesh, is located adjacent both walls. E~ine meish screen material, such as 30 mesh, is located intermediate the coarse mesh screen material. ~ neutralizer may be provided in the plenum iE necessary. The inner and outer housings as well as the combustion chamber and layers of screen material are designed so as to be manufactured in a very simple and economical manner without machining. ~-The primary feature of this invention is that i-t provides an improved gas generator wherein the gas passage area from the combustion cllamber to an article to be inflated increases as the pressure in the combustion chamber increases. Another feature is that the gas passage area is provided by a number of normally closed passages ~ ~ -from the combustion chamber, with certain sucll passages being normally opened when the pressure in the combustion chamber exceeds a predetermined level and additional passages being opened when the pressure e~ceeds highe~ ^
predetermined levels. A further feature is that the normally closed passages are provided by an annular ruptur- ~;
able wall of the chamber supported by an annular wall of an inner housing, with the annular housing wall being provided with a number of openings therethrough, the portions of the chamber wall opposite the openings being rupturable therethrough under pressure in the chamher to provide the gas passage area from the combustion chamber.
Yet another feature in one embodiment is that the openings are of varying size and the size of the passages opened is dependent on the pressure ].evel in the combustion chamber.
Yct a further feature is that the varying size openings are arranged in axially spaced annular bands of decreasi.ng size openings, with the laxge.st size openings being most axially remote fr~m the gas generator exlt port:s provlded in an outer annular wall of an outer generator houslng, the outer wall being spaced radially of the inner wall to cooperatively define a plenum. Still another feature in another embod.iment is that the varying size openings are intermixed and located as axially remote as possible from the exit ports. S-till a further feature in another embodi-ment is that the openings are of elongated slot shape with their open ends most axially remote from the exit ports, the extent of the chamber wall rup-turing thxough the openings from their open ends to their closed ends being dependent on the pressure level in the combustion chamber. Yet another feature is that the plenum defined by the inner and outer housing walls contains a plurality of layers of wrapped screen mate.rial of coarse and fine mesh, the layers adjacent the inner and outer walls being of coarse mesh and the layers therebetween being of fine mesh.
These and other features of -this .invention will be readily apparent from the following specification and drawings wherein:
Figure 1 is a sectional view of a gas generator according to this invention mounted within an inflatable occupant restraint cushion and secured to a conventional automobile steeriny wheel.' Figure 2 is a view taken generally along line
:
~:~i ****************
.I This invention rela~es generally to inflators and more particularly to solid propellant gas generators ~or ~'.'........................ , ~
,, 1 ~k 1, , ; .
-!
I
... . .. .
. .. ~. ~ ..
5~3 inElating various inflatable articles, such as inf]atable occupant restraint cushions.
Solid propellant gas generators are we]l known in the prior art. Generally such inflators include an annular or cylindrical combustion chamber containing a predetermined charge of solid propellant material and an - electrica:L initiator for initiating burning of the pro-pellant to generate gas Eor inflating an inflatable article.
The gas may flow either radially or axially Erom the coMbus~
tion chamber through fixed area openings, and then through a plenum to -the exit ports from the generator to the interior ;
of the article to be inflated. The plenum may contain both filtel-iny clnd cooling materlal as well as a neutralizer The burn rate of the propellant in the combustion chamber is dependent on the pressure level in the combus-tion chamber. The higher the pressure level, the greater the burn rate. The burn rate of the propellant is also affected by the temperature of both the propellant and the charnber~
The colder the propellant and the chamber, the lower the pressure in the chamber and consequently the slower the burn rate. Alternatively, if the prope]lant and chamber are hot~
the pressure in the combustion chamber will be greater and the burn rate will be greater.
Prior art gas generators normally include a fixed number of openings from the combustion chamber. Such openings provide a fixed gas passage area from the combustion chamber. Should the burn rate in the chamber exceed a pre-determined minimum, there is no compensa-tion or pressure relief for the increased volume of gas generated in the combustion chamber.
" . , . ,, ~ , . .... , ,, ~ . . .
~13e-~2~ 3 ~ he gas generator of this in-vention okvia-tes variations in the burn rate and pressure by providing a variable area gas passage arrangement from ~he combustion chamber to the article to be inElated. The gas passage arrangemen-t from the combustion chamber provides a pre~
determined minimum yas passage area and permits increased gas passage areas in accordance with the pressure in the combustion chamber.
In this invention, the propellant and initiator are located in an annular sealed aluminum container. The outer annular wall of the container is supported by an annular outer wall of an inner housing which is spaced radially of an annular oute~ wall of an outer he,using and cooperatively defines therewith a plenum. The annular outer wall of the outer housing contains the exit ports which are spaced peripherally about such wall and open radially of the yenerator. In one embodiment, the annular wall of the inner housing is provided with a plura]ity of axially spaced bands of openings of decreasing size. The bands of openings are normally closed by the outer annular wall of the combustion chamber. The band oE largest siæe openings is located most axially remote from the exit ports.
The portions of the chamber wall opposite the largest size openings will rupture therethrough to provide a predetermined minimum gas passage area whenever the pressure in the chamber exceeds a predetermined minimum level necessary to inflate the article to be inflated. The next band of smaller size openings is-axially closer to the exit portsO
Should the pressure in the combustion chamber exceed a second higher predetermined minimum level, then the portions , . . . . ,~
of the cha~T~er wall oppcsite tllese openings will rupture therethrough to provide an increased yas passage area from ~he cilamber. The next band of even smaller size is a~ially closest to the e~it ports. Should the pressure :in the combustioll chamber exceed a third predetermilled level, the portions of the chamber wall opposite these openings will rupture to provide for an even grea-ter increased ~as passage area from the chamber~ The number of rows or hands of openings and the size and shape of such openings will vary with the propellant used and the environmental conditions of use of the generator. However, at least two bands of openings should be provided~
In another emhodiment, varying size cpenings are interrnixed. In this embodiment, the portions of the chamber wall opposite the largest size openings will be first to rupture, and those portions opposite the next largest size openings will be next to rupture. The intermixed openings will he located as axially remote as possible from the exit ports.
In a third embodiment, the openings are slot shaped with their open ends most axially remote from the exit ports and their closed ends most axially adjacent.
The portions of the chamber wall opposite the open ends of the openings will rupture when the chamber pressure exceeds the predetermined minimum level. Additional portions of the chamber wall opposite additional portions of the slots may thereafter rupture should the pressure in the combustion chamber exceed'the second and third predetermlned levels hereinbefore mentioned.
43 -;:
The p]enum between the outer annular wal]s o~
the inner and outer housings contains a plurality o~ laye,s of wrapped screen material. ~oarse mesh screen material, such as 10 mesh, is located adjacent both walls. E~ine meish screen material, such as 30 mesh, is located intermediate the coarse mesh screen material. ~ neutralizer may be provided in the plenum iE necessary. The inner and outer housings as well as the combustion chamber and layers of screen material are designed so as to be manufactured in a very simple and economical manner without machining. ~-The primary feature of this invention is that i-t provides an improved gas generator wherein the gas passage area from the combustion cllamber to an article to be inflated increases as the pressure in the combustion chamber increases. Another feature is that the gas passage area is provided by a number of normally closed passages ~ ~ -from the combustion chamber, with certain sucll passages being normally opened when the pressure in the combustion chamber exceeds a predetermined level and additional passages being opened when the pressure e~ceeds highe~ ^
predetermined levels. A further feature is that the normally closed passages are provided by an annular ruptur- ~;
able wall of the chamber supported by an annular wall of an inner housing, with the annular housing wall being provided with a number of openings therethrough, the portions of the chamber wall opposite the openings being rupturable therethrough under pressure in the chamher to provide the gas passage area from the combustion chamber.
Yet another feature in one embodiment is that the openings are of varying size and the size of the passages opened is dependent on the pressure ].evel in the combustion chamber.
Yct a further feature is that the varying size openings are arranged in axially spaced annular bands of decreasi.ng size openings, with the laxge.st size openings being most axially remote fr~m the gas generator exlt port:s provlded in an outer annular wall of an outer generator houslng, the outer wall being spaced radially of the inner wall to cooperatively define a plenum. Still another feature in another embod.iment is that the varying size openings are intermixed and located as axially remote as possible from the exit ports. S-till a further feature in another embodi-ment is that the openings are of elongated slot shape with their open ends most axially remote from the exit ports, the extent of the chamber wall rup-turing thxough the openings from their open ends to their closed ends being dependent on the pressure level in the combustion chamber. Yet another feature is that the plenum defined by the inner and outer housing walls contains a plurality of layers of wrapped screen mate.rial of coarse and fine mesh, the layers adjacent the inner and outer walls being of coarse mesh and the layers therebetween being of fine mesh.
These and other features of -this .invention will be readily apparent from the following specification and drawings wherein:
Figure 1 is a sectional view of a gas generator according to this invention mounted within an inflatable occupant restraint cushion and secured to a conventional automobile steeriny wheel.' Figure 2 is a view taken generally along line
2-2 of Figure 1.
F;gure~ 3 is a view of a portion of Fiyure ]
accordin~ to one embodiment.
Figure 4 i.s a view of a porti.on of Figure 1 according to another embodiment, and Figure 5 is a view of a portion of F;.gure ].
accordi.ny to a further embodi.ment.
- Referring now to the drawings, a conven-tional --steering wheel ]0 includes a p]urality of spokes 12 which extend radially from a circular central hub por-tion 14 An inflatable occupant restralnt cushion 16 is secured to the hub portion 14 in a manner to be described and ls shown in a partially inflated condition for i.llustrative purposes ~nly. Normal.ly, this cushion is disposed in a folded condition about a gas generator 18 accordiny to this invention. A suitable conventional p].astic housin.g `
or cover, not shown, covers both the folded cushion and the inflator.
The gas generator 18 includes a hermetically sealed cylindrical or annular comhustion chamber 20 which is provided by a cup shaped member 22 of thin aluminum haviny secured thereto ~y crimping or otherwise a dome shaped closure or cover 24, also of aluminum. Both the member 22 and cover 24 can be conventionally manufactured in the same manner that aluminum beer cans are currently conventionally manufactured. A conventional electric initiator 26 is arranyed axially within the chamber 20 and sealed at 28 in a conventional manner to the centrally apertured circular lower or base wall of the member 22.
The combu.stion chamber 20 is filled with a predetermined charge of solid propellant 30 such as sodium azide or ~.
, . . .
2~3 lead azide based compounds. Such compounds burn when electrically initiat~d by the ini-tiator 26 and produce gas ~hich is used, as will be further described, to inflate the cushion 16. `-Although not shown, the electrical initiator 26 is connected in a conventional manner with a source of power and suitable sensors, either acceleration or velocity responsive, or both, so as to be initiated when the vehicle receives a pu]se of predetermined amplitude and time or experiences a predetermined change in velocity in a predetermined time.
An inner cup shaped annular housing 32 includes an upper circular wail 34 which abuts the cèntral portion of the cover 24 of the combustion chamber 20. Housing 32 also includes a cylindrical or annular outer wall 36 which surrounds and abuts the annular outer wall 38 of chamber 20 Wall 36 includes three axially spaced annular rows or bands of circular openings 40, 42 and 44 respectively, Figure 3 In the specific embodiment shown, there are 24 openings 40 of approximately 5 mm diameter, 30 openings 42 of approxi~
mately 3 mm diameter, and 30 openings 44 of approximately 2.5 mm diameter. The openings of each band are equally spaced about the ~all 36 and each band defines a predetermined gas passage area, as will be described.
Wrapped about the wall 36 are a number of layers 46 of coarse mesh screen materlal, such as 10 mesh.
Wrapped about the layers 46 are a number of layers 48 or fine mesh screen material, such as 30 mesh. Wrapped about the layers 48 are a number of layers 50 of coarse mesh screen material, such as 10 mesh.
. . .
The comhustion chamber 20 the housing 32 lnd the layers Qf screen material are housed wi~hin an outer cylindrical or annular housiny 52 which includes a lower cup shaped member 54 and an upper cup shaped member 56 provided wi-th respective abutting flanges 58 and 60. The base of initiator 26 extends outwardl~ through a central opening in the circular or annular base wall of member 54 and is secured -to this wall in a conventional manner such as by a C-shaped clip 62 received wi-thin a circular slot in the base of the initiator. The base wall of housing 54 abuts and supports the base wall of chamber 20 and the base wall of housing 56 abuts and supports the base wall of housing 32.
The ou.ter c~-lindrical or annul.ar wal~. portions 64 of member 54 and 66 of member 56 define an outer annular wall of housing 52 which is located in radially spaced relationship to the outer annular wall 36 of housing 32.
The outer annular walls of housing 32 and 52 and portions of the base walls of members 54 and 56 cooperatively define a plenum 68 for receiving and housing -the wrapped layers 46 48 and 50 of screen material. The wall portion 66 is further provided with an annular row of radial openings or exit ports 70 which provide for passage of the gas from the infla-tor to the interior of the cushion 16 in order to inflate the cushion for use as a passenger restraint.
Separated portions 72 of the flange 58 are return bent or crimped over flange 60 in order to se~ure the members 54 -and 56 to each other.
The portions of flange 58 intermediate portions 72 and flange 60 are provided with aligned tapped openings 74 for receipt of bolts 76 which secure the generator 18 to '~
~Cj~3 the hub portion 14 of the sceering wheel as well as clamp the central apertured portion of the cushion 16 between flange 58 and such hub portion to seal the cushlon 16 to ambient.
When the vehicle in which the inflator is mounted receives an acceleration pulse of predetermined amplitude - and time or experiences a prede-termined velocity change within a predetermined -time, the initiator 26 is connected to a source of power and initiates burning of the propel:Lant 30 within the combustion chamber 20. As the propellant burns, the pressure within the combustlon chamber rises.
When such pressure exceeds a first predetermined minimum level necesscr~ for inflation of cushion 16, the portions of wall 38 opposite openings 40 wi:Ll rupture outwardly through such openings to provide a predetermined nminimum gas passage area to permit the gas from the burning pro-pellant to pass through the layers 46, 48 and 50 of filter-ing and cooling screen material and thence through the exit ports 70 to the cushion 16 in order to initiate inflation of the cushion.
The portions of wall 38 opposite the largest size openings 40 will always rupture first. Since these openings are most axially remote from the exit ports 70, the gas will pass through the greatest area of the layers of screen material. Should the pressure within the combustion chamber not exceed a second higher predetermined minimum ,-level, only those portions of the wall 38 opposite openings 40 will rupture. However, should the pressure exceed the I ~
second higher predetermined minimum level due to temperature I ~;
variations of the propellant or chambert or other variations, then certain or all of the portions of wal.1 38 opposite openlngs 42 will additionally rupture -through such openings to provide additional gas passage area l-rom the combustion chamber. ~I~he gas passing through the . .:
openings 42 will pass through a lesser area of the layers of screen material since these openings are axially closer to the exit ports 70. However, the gas will still be adequate].y filt~red and cooled before it passes into cushi.on 16.
Should the pressure in the combustion chamber exceed a third higher predetermined minimum level, certain :
or all of the portions of wall 38 opposite openings 44 w:i.ll additlonally rupture to provide a maximum gas passa(Je area to the cushion.
The gas passage area defined by openings 40 and wall 38, after rupture thereof, will always be provi.ded ~ ~
when the initiator 26 ignites the propellant and the ~- .
pressure in the combustion chamber exceeds the first predetermined minimum level. Thus, the generator provides a certain minimum gas passage area to the cushion and the actual gas passage area up to a maximum, gas passing through all openings 40, 42, 44, wi].l depend on the pressure , :
in the combustion chamber and will vary with such pressure. ~.
The pressure at which the portions of wall 38 ¦:~
rupture through their respective openings can be set by controlling the wall thickness of wall 38 opposite the ¦~
openings of each.band. The thickness opposite each band ::
may be the same or may vary. ::
The layers 46 o~ coarse mesh screen material. ~:
a3jacent to wall 36 permit the portions of the wall 38 to ~
~. : , . ~ . .
5:2~3 rupture out~?ardly throuqh their respective openings without interer~nce. Such ]ayers also act to trap unhurned or partially burned partic]es of propellant and prevent their ~low from the cornbustion chamber to the cushion. The layers 50 o:E coarse mesh screen material adjacent ~he wall portions 64 and 66 of housing S2 collect the gas a~ter the gas has flowed throu-~h -the layers-46 and 48 and duct such gas to the ports 70. The layers 48 of flne mesh screen material act to cool the gas.
It can be seen from the foregoing description that the combustion chan~er 20 can be made with existing knowledge and on existing equipment in a very simple and economical manner. Likewise the inner housing 32 and the ou-ter housing ~2 can be made with the use of conventional stamping techniques without requiring machining.
Figure ~ shows another embodiment of the invention wherein the inner liousing 32 is provided with intermixed openings 40' and 42' rather than with separate or discrete bands of openings as shown in Figure 3. These openings and the portions of wall 38 juxtaposed thereto will function in the same manner as previously described to provide a certain minimum gas passage area when the pressure level in the combustion chamher exceeds the first predetermined minimum leve3.
Should the second predetermined minimum level be exceeded, then certain or all of openings 42' may additionally be opened. In this embodiment as in the first embodiment, at least the largest size openings 40, 40' and smaller size openings 42, 42' will be ~rovided. The smallest size - openings 44 may be provided in this embodiment as in the first embodim~nt ~ if deemed necessary. Likewise, the size as well as the shape of the openings may be set in accordance with -the gas passage areas desired when the pressure in the combustion chamber 20 exceeds certain le-vel~.
Figure 5 shows a third embodiment of -the inventioII.
In this embodiment of the invention, the inner housincJ 32 is ~ provided with an annular series of elongated openings or slots 78. The open ends of the slots are most axia].ly remote from the exit ports 70 while the closed ends are `~
axially adjacent to such exit ports. Should the pressure `~
in the combustion chamber exceed the first predetermined minimum level, the porti.ons of wall 38 opposite the open end portions of the slots will rupture therethrough to provide the certain minimum gas passage area from the combustion chamber. Should the pressure level exceed the second higher predetermined minimum level, then addi~ional portions of ~ ~
wall 38 between the open and closed ends of the s3ots 78 ;
will rupture therethrough. Likewise should the pressure ; ~, in the combustion chamber exceed the third highest predeter-mined minimum level, then the portions of wall 38 opposite the closed end portions of the slots 78 will rupture therethrough to provide the maximum gas passage area to the cushion.
The gas generator of this invention thus provides a certain minimum gas passage area from the combustion chamber whenever the pressure level in the combwstion chamber exceeds a first predetermined minimwrn level necessary for inflation of the cushion 16. Should the pressure level exceed ot:her predetermiIIed minimwm le~els, then additional gas passage area from the cosflbustion chamber is provided. The total area will thus vary in accordance ~ith the pressure in the combustion chamber.
Thus this invention provides an improved gas generator.
F;gure~ 3 is a view of a portion of Fiyure ]
accordin~ to one embodiment.
Figure 4 i.s a view of a porti.on of Figure 1 according to another embodiment, and Figure 5 is a view of a portion of F;.gure ].
accordi.ny to a further embodi.ment.
- Referring now to the drawings, a conven-tional --steering wheel ]0 includes a p]urality of spokes 12 which extend radially from a circular central hub por-tion 14 An inflatable occupant restralnt cushion 16 is secured to the hub portion 14 in a manner to be described and ls shown in a partially inflated condition for i.llustrative purposes ~nly. Normal.ly, this cushion is disposed in a folded condition about a gas generator 18 accordiny to this invention. A suitable conventional p].astic housin.g `
or cover, not shown, covers both the folded cushion and the inflator.
The gas generator 18 includes a hermetically sealed cylindrical or annular comhustion chamber 20 which is provided by a cup shaped member 22 of thin aluminum haviny secured thereto ~y crimping or otherwise a dome shaped closure or cover 24, also of aluminum. Both the member 22 and cover 24 can be conventionally manufactured in the same manner that aluminum beer cans are currently conventionally manufactured. A conventional electric initiator 26 is arranyed axially within the chamber 20 and sealed at 28 in a conventional manner to the centrally apertured circular lower or base wall of the member 22.
The combu.stion chamber 20 is filled with a predetermined charge of solid propellant 30 such as sodium azide or ~.
, . . .
2~3 lead azide based compounds. Such compounds burn when electrically initiat~d by the ini-tiator 26 and produce gas ~hich is used, as will be further described, to inflate the cushion 16. `-Although not shown, the electrical initiator 26 is connected in a conventional manner with a source of power and suitable sensors, either acceleration or velocity responsive, or both, so as to be initiated when the vehicle receives a pu]se of predetermined amplitude and time or experiences a predetermined change in velocity in a predetermined time.
An inner cup shaped annular housing 32 includes an upper circular wail 34 which abuts the cèntral portion of the cover 24 of the combustion chamber 20. Housing 32 also includes a cylindrical or annular outer wall 36 which surrounds and abuts the annular outer wall 38 of chamber 20 Wall 36 includes three axially spaced annular rows or bands of circular openings 40, 42 and 44 respectively, Figure 3 In the specific embodiment shown, there are 24 openings 40 of approximately 5 mm diameter, 30 openings 42 of approxi~
mately 3 mm diameter, and 30 openings 44 of approximately 2.5 mm diameter. The openings of each band are equally spaced about the ~all 36 and each band defines a predetermined gas passage area, as will be described.
Wrapped about the wall 36 are a number of layers 46 of coarse mesh screen materlal, such as 10 mesh.
Wrapped about the layers 46 are a number of layers 48 or fine mesh screen material, such as 30 mesh. Wrapped about the layers 48 are a number of layers 50 of coarse mesh screen material, such as 10 mesh.
. . .
The comhustion chamber 20 the housing 32 lnd the layers Qf screen material are housed wi~hin an outer cylindrical or annular housiny 52 which includes a lower cup shaped member 54 and an upper cup shaped member 56 provided wi-th respective abutting flanges 58 and 60. The base of initiator 26 extends outwardl~ through a central opening in the circular or annular base wall of member 54 and is secured -to this wall in a conventional manner such as by a C-shaped clip 62 received wi-thin a circular slot in the base of the initiator. The base wall of housing 54 abuts and supports the base wall of chamber 20 and the base wall of housing 56 abuts and supports the base wall of housing 32.
The ou.ter c~-lindrical or annul.ar wal~. portions 64 of member 54 and 66 of member 56 define an outer annular wall of housing 52 which is located in radially spaced relationship to the outer annular wall 36 of housing 32.
The outer annular walls of housing 32 and 52 and portions of the base walls of members 54 and 56 cooperatively define a plenum 68 for receiving and housing -the wrapped layers 46 48 and 50 of screen material. The wall portion 66 is further provided with an annular row of radial openings or exit ports 70 which provide for passage of the gas from the infla-tor to the interior of the cushion 16 in order to inflate the cushion for use as a passenger restraint.
Separated portions 72 of the flange 58 are return bent or crimped over flange 60 in order to se~ure the members 54 -and 56 to each other.
The portions of flange 58 intermediate portions 72 and flange 60 are provided with aligned tapped openings 74 for receipt of bolts 76 which secure the generator 18 to '~
~Cj~3 the hub portion 14 of the sceering wheel as well as clamp the central apertured portion of the cushion 16 between flange 58 and such hub portion to seal the cushlon 16 to ambient.
When the vehicle in which the inflator is mounted receives an acceleration pulse of predetermined amplitude - and time or experiences a prede-termined velocity change within a predetermined -time, the initiator 26 is connected to a source of power and initiates burning of the propel:Lant 30 within the combustion chamber 20. As the propellant burns, the pressure within the combustlon chamber rises.
When such pressure exceeds a first predetermined minimum level necesscr~ for inflation of cushion 16, the portions of wall 38 opposite openings 40 wi:Ll rupture outwardly through such openings to provide a predetermined nminimum gas passage area to permit the gas from the burning pro-pellant to pass through the layers 46, 48 and 50 of filter-ing and cooling screen material and thence through the exit ports 70 to the cushion 16 in order to initiate inflation of the cushion.
The portions of wall 38 opposite the largest size openings 40 will always rupture first. Since these openings are most axially remote from the exit ports 70, the gas will pass through the greatest area of the layers of screen material. Should the pressure within the combustion chamber not exceed a second higher predetermined minimum ,-level, only those portions of the wall 38 opposite openings 40 will rupture. However, should the pressure exceed the I ~
second higher predetermined minimum level due to temperature I ~;
variations of the propellant or chambert or other variations, then certain or all of the portions of wal.1 38 opposite openlngs 42 will additionally rupture -through such openings to provide additional gas passage area l-rom the combustion chamber. ~I~he gas passing through the . .:
openings 42 will pass through a lesser area of the layers of screen material since these openings are axially closer to the exit ports 70. However, the gas will still be adequate].y filt~red and cooled before it passes into cushi.on 16.
Should the pressure in the combustion chamber exceed a third higher predetermined minimum level, certain :
or all of the portions of wall 38 opposite openings 44 w:i.ll additlonally rupture to provide a maximum gas passa(Je area to the cushion.
The gas passage area defined by openings 40 and wall 38, after rupture thereof, will always be provi.ded ~ ~
when the initiator 26 ignites the propellant and the ~- .
pressure in the combustion chamber exceeds the first predetermined minimum level. Thus, the generator provides a certain minimum gas passage area to the cushion and the actual gas passage area up to a maximum, gas passing through all openings 40, 42, 44, wi].l depend on the pressure , :
in the combustion chamber and will vary with such pressure. ~.
The pressure at which the portions of wall 38 ¦:~
rupture through their respective openings can be set by controlling the wall thickness of wall 38 opposite the ¦~
openings of each.band. The thickness opposite each band ::
may be the same or may vary. ::
The layers 46 o~ coarse mesh screen material. ~:
a3jacent to wall 36 permit the portions of the wall 38 to ~
~. : , . ~ . .
5:2~3 rupture out~?ardly throuqh their respective openings without interer~nce. Such ]ayers also act to trap unhurned or partially burned partic]es of propellant and prevent their ~low from the cornbustion chamber to the cushion. The layers 50 o:E coarse mesh screen material adjacent ~he wall portions 64 and 66 of housing S2 collect the gas a~ter the gas has flowed throu-~h -the layers-46 and 48 and duct such gas to the ports 70. The layers 48 of flne mesh screen material act to cool the gas.
It can be seen from the foregoing description that the combustion chan~er 20 can be made with existing knowledge and on existing equipment in a very simple and economical manner. Likewise the inner housing 32 and the ou-ter housing ~2 can be made with the use of conventional stamping techniques without requiring machining.
Figure ~ shows another embodiment of the invention wherein the inner liousing 32 is provided with intermixed openings 40' and 42' rather than with separate or discrete bands of openings as shown in Figure 3. These openings and the portions of wall 38 juxtaposed thereto will function in the same manner as previously described to provide a certain minimum gas passage area when the pressure level in the combustion chamher exceeds the first predetermined minimum leve3.
Should the second predetermined minimum level be exceeded, then certain or all of openings 42' may additionally be opened. In this embodiment as in the first embodiment, at least the largest size openings 40, 40' and smaller size openings 42, 42' will be ~rovided. The smallest size - openings 44 may be provided in this embodiment as in the first embodim~nt ~ if deemed necessary. Likewise, the size as well as the shape of the openings may be set in accordance with -the gas passage areas desired when the pressure in the combustion chamber 20 exceeds certain le-vel~.
Figure 5 shows a third embodiment of -the inventioII.
In this embodiment of the invention, the inner housincJ 32 is ~ provided with an annular series of elongated openings or slots 78. The open ends of the slots are most axia].ly remote from the exit ports 70 while the closed ends are `~
axially adjacent to such exit ports. Should the pressure `~
in the combustion chamber exceed the first predetermined minimum level, the porti.ons of wall 38 opposite the open end portions of the slots will rupture therethrough to provide the certain minimum gas passage area from the combustion chamber. Should the pressure level exceed the second higher predetermined minimum level, then addi~ional portions of ~ ~
wall 38 between the open and closed ends of the s3ots 78 ;
will rupture therethrough. Likewise should the pressure ; ~, in the combustion chamber exceed the third highest predeter-mined minimum level, then the portions of wall 38 opposite the closed end portions of the slots 78 will rupture therethrough to provide the maximum gas passage area to the cushion.
The gas generator of this invention thus provides a certain minimum gas passage area from the combustion chamber whenever the pressure level in the combwstion chamber exceeds a first predetermined minimwrn level necessary for inflation of the cushion 16. Should the pressure level exceed ot:her predetermiIIed minimwm le~els, then additional gas passage area from the cosflbustion chamber is provided. The total area will thus vary in accordance ~ith the pressure in the combustion chamber.
Thus this invention provides an improved gas generator.
Claims (3)
1. In combination with a vehicle having an inflatable occupant restraint cushion, a gas generator for inflating the cushion comprising, an outer housing includ-ing an annular wall having a series of exit ports adjacent an axial end thereof, a combustion chamber within the outer housing and including an annular hermetically sealed container enclosing propellant and including a pressure rupturable annular wall spaced relative to the annular wall of the housing, annular gas filtering and cooling screen means in the annular space between the annular wall of the housing and the annular wall of the container and extending axially between the axial ends thereof, means operable when the pressure within the container exceeds a first predeter-mined level upon burning of the propellant for providing a first annular series of gas passage openings through the container wall opposite the screen means and adjacent the axial end of the container wall axially remote from the exit ports to pass the gas from the container axially through the screen means to the exit ports, and means operable when the pressure within the container exceeds a second predetermined higher level for providing a second annular series of gas passage openings through the container wall opposite the screen means and axially remote from the exit ports to pass the gas from the container axially through the screen means to the exit ports, the first series of openings providing a first gas passage area and the second series of openings providing a second gas passage area less than the first area, at least a portion of the first openings being most axially remote from the exit ports and a portion of the second openings being less axially remote from the exit ports.
2. In combination with a vehicle having an inflatable occupant restraint cushion, a gas generator for inflating the cushion comprising, an outer housing including an annular wall having a series of exit ports adjacent an axial end thereof, a combustion chamber within the outer housing and including an annular hermetically sealed container enclosing propellant and including a pressure rupturable annular wall spaced relative to the annular wall of the housing, an inner annular wall supporting the annular wall of the container, annular gas filtering and cooling screen means in the annular space between the annular wall of the housing and the inner annular wall and extending axially between the axial ends thereof, said inner wall including a first annular series of gas passage openings therethrough opposite the screen means and adjacent the axial ends of the inner and container walls axially remote from the exit ports, the container wall normally closing said openings and being rupturable therethrough when the pressure within the container exceeds a first predetermined level upon burning of the propellant to pass the gas from the container axially through the screen means to the exit ports, said inner wall including a second annular series of gas passage openings therethrough opposite the screen means and axially remote from the exit ports, the second series of openings being normally closed by the container wall, the container wall being rupturable therethrough when the pressure within the container exceeds a second predetermined higher level to provide for additional passage of gas from the container axially through the screen means to the exit ports, the first series of openings providing a first gas passage area and the second series of openings providing a second gas passage area less than the first area, at least a portion of the first openings being most axially remote from the exit ports and a portion of the second openings being less axially remote from the exit ports.
3. In combination with a vehicle having an inflatable occupant restraint cushion, a gas generator for inflating the cushion comprising, a combustion chamber including an annular hermetically sealed container enclosing propellant, an inner housing including an annular wall surrounding a pressure rupturable annular wall of the con-tainer and including a plurality of generally elongated openings normally closed by the container wall, an outer housing including an annular wall spaced radially of the inner housing annular wall and including a series of exit ports, end portions of the elongated openings in the inner housing wall most axially remote from the exit ports being opened by rupture of the portions of the container wall opposite thereto when the pressure level within the container exceeds a first predetermined minimum level upon burning of propellant to thereby provide a predetermined gas passage area from the combustion chamber to the exit ports, the adjacent portions of the openings being opened by rupture of the container wall opposite thereto when the pressure level in the container exceeds a second predetermined minimum level to thereby provide additional gas passage area from the container to the exit ports.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US83011777A | 1977-09-02 | 1977-09-02 | |
| US830,117 | 1977-09-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1095243A true CA1095243A (en) | 1981-02-10 |
Family
ID=25256349
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA305,691A Expired CA1095243A (en) | 1977-09-02 | 1978-06-19 | Solid propellant gas generator |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1095243A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0800964A3 (en) * | 1996-04-08 | 1997-12-17 | Daicel Chemical Industries, Ltd. | An airbag inflator and an airbag apparatus |
-
1978
- 1978-06-19 CA CA305,691A patent/CA1095243A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0800964A3 (en) * | 1996-04-08 | 1997-12-17 | Daicel Chemical Industries, Ltd. | An airbag inflator and an airbag apparatus |
| US6196581B1 (en) | 1996-04-08 | 2001-03-06 | Daicel Chemical Industries, Ltd. | Airbag inflator and an airbag apparatus |
| US6234521B1 (en) | 1996-04-08 | 2001-05-22 | Daicel Chemical Industries, Ltd. | Airbag inflator and an airbag apparatus |
| US6409214B2 (en) | 1996-04-08 | 2002-06-25 | Daicel Chemical Industries, Ltd. | Airbag inflator and an airbag apparatus |
| US6695345B2 (en) | 1996-04-08 | 2004-02-24 | Daicel Chemical Industries, Ltd. | Airbag inflator and an airbag apparatus |
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| Date | Code | Title | Description |
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| MKEX | Expiry |