Abstract:
A pressurized container includes a vessel defining a chamber therein. A housing that is connected to the vessel defines an outlet that is fluidly separated from the chamber by a closure member. A moveable member may be seated within and form a seal with the housing and abut the closure member. Activation of an initiator propels the moveable member through the closure member, thereby fluidly connecting the chamber and the outlet. Also, the chamber might include a first portion and a second portion, wherein an isolator member substantially fluidly separates the first portion and the second portion. Gas released from the first portion initially inflates an air bag associated with the pressurized container and gas released from the second portion maintains the inflation of the air bag for a time.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of the earlier U.S. Utility patent application to Michael Fink entitled “INFLATOR FOR VEHICLE PROTECTION APPARATUS,” Ser. No. 10/815,298, filed Mar. 31, 2004, which is a continuation of U.S. patent application Ser. No. 10/364,117, filed on Feb. 10, 2003, now U.S. Pat. No. 6,719,016, entitled “INFLATOR FOR VEHICLE PROTECTION APPARATUS”, which is a divisional of U.S. patent application Ser. No. 09/632,339, filed on Aug. 3, 2000 now U.S. Pat. No. 6,543,806, entitled “INFLATOR FOR VEHICLE PROTECTION APPARATUS”, the disclosures of all of which are hereby incorporated entirely herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     This invention generally relates to pressurized containers, and more specifically relates to an inflator for a vehicle protection apparatus. 
     2. Background Art 
     Inflatable vehicle restraints such as air bags are used for protecting vehicle occupants during collisions. When the vehicle undergoes a collision a sensor detects the rapid change in motion and provides an electrical signal to activate an inflator, which rapidly expands an air bag to provide a protective cushion of restraint for an occupant in various impact conditions. 
     Many types of inflators have been disclosed in the art for inflating an inflatable restraint system. One type utilizes a stored compressed gas, which is released to inflate the restraint system. Another type utilizes a combustible gas generating material, such as sodium azide, which upon ignition generates a quantity of hot gas to inflate the restraint. In yet another type, a combination of a compressed stored gas and a combustible material are both used to inflate the restraint. Inflators using combustible gas are often considered unsafe because of the heat that they generate. However, compressed gas inflators have often been unreliable or they have released compressed gas at an excessive rate that causes air bags to injure vehicle occupants. 
     SUMMARY 
     Therefore, there existed a need to provide a reliable inflator that will inflate a vehicle restraint without generating excess heat. The present invention provides a pressurized container that includes a hollow vessel defining a chamber therein. A housing that is connected to the vessel defines an outlet that is fluidly separated from the chamber by a closure member. A moveable member is seated within and forms a seal with the housing and abuts the closure member. When an initiator is activated, a charge within the initiator is ignited to produce expanding gases that burst a body of the initiator and propel the moveable member through the closure member, thereby fluidly connecting the chamber and the outlet. The moveable member may break through the closure member before the seal with the housing is broken so that the moveable member acts like a piston. 
     A pressurized container might include an obstruction partially blocking an outlet path and another initiator that breaks the obstruction when activated, thereby further opening the outlet path. 
     Also, the chamber might include a first portion and a second portion, wherein an isolator member substantially fluidly separates the first portion and the second portion. A passage fluidly connects the first portion of the chamber and the second portion of the chamber. This dual chamber configuration might be useful where it is desirable to keep a device inflated over a period of time. 
     The pressurized container might include a main path fluidly connected to the outlet, a first secondary path that connects the main path to the chamber, and a second secondary path that also connects the main path to the chamber. If the pressurized container includes two secondary paths, a first closure member can fluidly separate the outlet from the chamber of the vessel along the first secondary path, and a second closure member can fluidly separate the outlet from the chamber of the vessel along the second secondary path. Activation of a first initiator breaks the first closure member, thereby fluidly connecting the chamber and the outlet along the first secondary path and the main path, and activation of a second initiator breaks the second closure member, thereby fluidly connecting the chamber and the outlet along the second secondary path and the main path. If the pressurized container includes either the first and second secondary paths as described, or the pressurized container includes the obstruction to the outlet path, an initial flow is minimal, and when the obstruction is removed or the second secondary outlet path is opened, then the flow of pressurized gas is increased. In this way, the initial force of an inflatable device such as an air bag is minimized during the initial flow stage, but the flow is substantially increased during the latter flow stage so that the device is rapidly inflated. 
     The present invention also provides a pressurized container that includes a hollow vessel defining a chamber and a housing connected to the vessel that defines an outlet. The outlet is fluidly separated from the chamber by a closure member, so that activation of an initiator breaks the closure member, thereby fluidly connecting the chamber and the outlet. The vessel and the closure member may be a single unitary member so that the closure member, the vessel, and a plug in the vessel form a sealed barrier around the chamber. Also, the housing and the closure member may be a single unitary member, wherein the housing is inertia welded to the vessel to form the chamber. Having the barrier around the chamber be formed by unitary members provides superior prevention against leakage of compressed gas from the chamber during storage. 
     The present invention also provides a method of releasing a pressurized fluid from a container. The method includes the steps of breaking a closure member that fluidly separates the pressurized fluid from an outlet of the container, thereby allowing the fluid to escape to the outlet along an outlet path, and breaking an obstruction that is partially blocking the outlet path, thereby further opening the outlet path. 
     The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, where like designations denote like elements. 
         FIG. 1  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
         FIG. 2  is a partial sectional view of the embodiment of  FIG. 1  in an activated condition. 
         FIG. 3  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
         FIG. 4  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
         FIG. 5  is a partial sectional view of the embodiment of  FIG. 4  in an activated condition. 
         FIG. 6  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
         FIG. 7  is a partial sectional view of the embodiment of  FIG. 6  in an initial flow stage condition. 
         FIG. 8  is a partial sectional view of the embodiment of  FIG. 6  in a latter flow stage condition. 
         FIG. 9  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
         FIG. 10  is a partial sectional view of the embodiment of  FIG. 9  in an initial flow stage condition. 
         FIG. 11  is a partial sectional view of the embodiment of  FIG. 9  in a latter flow stage condition. 
         FIG. 12  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
         FIG. 13  is a partial sectional view of an embodiment of the present invention in an unactivated condition. 
     
    
    
     DESCRIPTION 
     Referring to  FIG. 1 , a pressurized container or inflator  10  generally includes a vessel  12  that houses compressed gas, such as helium. A closure member  14  forms a closure of the vessel  12 . A housing  16  is attached to vessel  12  and defines an outlet  18  therein that is preferably fluidly separated from the compressed gas only by closure member  14 . Housing  16  houses an initiator  20  and a moveable member or projectile  22  that abuts closure member  14  on a side opposite from the compressed gas. Referring now to  FIG. 2 , when initiator  20  is activated, initiator  20  propels projectile  22  through closure member  14 , out of housing  16 , and into vessel  12 , thereby breaking closure member  14  and allowing the compressed gas to escape through outlet  18  and inflate a vehicle restraint such as an air bag (not shown). Also, gas could escape through multiple outlets to inflate the vehicle restraint. 
     Referring back to  FIG. 1 , and describing inflator  10  in more detail, vessel  12  is preferably a hollow cylindrical member that includes a radial wall  30  that defines a fill hole  32  therein. A weld ball  34  preferably forms a closure or plug of fill hole  32 . However, fill hole  32  may be closed or plugged in some other fashion that allows vessel  12  to be filled with pressurized gas and sealed. A circumferential wall  36  extends upwardly from radial wall  30  to define a chamber  38  therein (directional terms such as bottom, top, upwardly, and downwardly are used herein for convenience in referring to the drawings and the inflator may be oriented in any of several positions when in use). An upper terminus  40  of circumferential wall  36  extends inwardly to form an annular flange distal from radial wall  30 . 
     Housing  16  preferably includes an end cap housing  46  that is primarily a circumferential wall  48  that includes a lower terminus  50  that extends inwardly to form an annular flange that abuts upper terminus  40  of vessel  12 . Preferably lower terminus  50  abuts upper terminus  40  and is secured thereto by an inertia weld or a friction weld thereby securing vessel  12  to housing  16 . Accordingly, chamber  38  extends upwardly within the lower portion of housing  16 . However, vessel  12  may be secured to housing  16  in many other ways so long as chamber  38  remains sealed. End cap housing  46  preferably defines an outlet or outlet orifice  18  that extends radially therethrough. End cap housing  46  also defines a pin hole  52 . 
     A projectile housing  54  preferably includes an upper circumferential wall  56  that is seated within circumferential wall  48  of end cap housing  46 . A radial wall  58  preferably extends inwardly from a lower terminus of circumferential wall  56  and defines a beveled hole  60  therein. A projectile casing  62  is preferably a circumferential wall that extends from radial wall  58 . Projectile housing  54  also defines a downwardly-facing annular groove  64  and a radially extending pin hole  66 . 
     An initiator retainer  70  is seated within upper circumferential wall  56  of projectile housing  54 . Initiator retainer  70  includes a circumferential wall  72  and a radial wall  74  extending inwardly from a bottom edge of circumferential wall  72 . Radial wall  74  defines a centrally located beveled hole  76  therein. Initiator retainer  70  defines a radially extending pin hole  78  therein. 
     A pin  80  extends through pin hole  52  of end cap housing  46 , through pin hole  66  of projectile housing  54  and into pin hole  78  of initiator retainer  70 . Preferably pin  80  is sized to produce an interference fit with one or more of pin holes  52 ,  66 ,  78 . 
     Initiator  20  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  82 . A flange  84  extends radially outwardly from an upper portion of cylindrical body  82 . Flange  84  is seated within beveled hole  60  of projectile housing  54  and beveled hole  76  of initiator retainer  70  to secure initiator  20  within housing  16 . Initiator  20  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. 
     Projectile  22  preferably includes a circumferential wall  88  that is seated within casing  62 . However, the casing and the projectile may be some other structure. For example, the casing may extend within the circumferential wall of the projectile. A radial wall  90  extends inwardly from a bottom edge of circumferential wall  88  so that projectile  22  forms an upwardly facing cavity  92  that receives body  82  of initiator  20 . Also, some moveable member may be used that is not a projectile (by “projectile” is meant a moveable member that is propelled freely away from the casing). For example, the moveable member&#39;s motion may be stopped after it has been propelled through the closure member, but before it has left the casing. 
     Closure member  14  is preferably a radial wall or plate having an upwardly facing first side  94  and a downwardly facing second side  96 . Closure member  14  extends inwardly from end cap housing  46  and is preferably formed with end cap housing  46  as a unitary member. Radial wall  90  of projectile  22  preferably abuts first side  94  to support closure member  14  against the force of pressurized gas within chamber  38 . This allows closure member  14  to be thin and it still provides the structural integrity needed to keep the pressurized gas from prematurely breaking closure member  14 . 
     An annular filter  98  is seated within annular groove  64  of projectile housing  54  and extends downwardly until it abuts a shoulder of end cap housing  46 . 
     Vessel  12  is preferably made from an aluminum alloy such as 7075-T6 aluminum. Preferably, vessel  12  is manufactured and treated by a cold impact process, which will produce sufficient strength to withstand high pressures from within chamber  38 . Further, the cold impact process aligns the grain structure of the aluminum so that leakage of gas is prevented. 
     End cap housing  46  and closure member  14  are preferably a unitary member made from 7075-T6 aluminum. End cap housing  46  and closure member  14  are preferably cold impacted, although they may be hot forged. Hot forging, as with the cold impact process, produces a part with good strength and grain alignment properties. Hot forging may be desirable to produce members having more complex structures. 
     Projectile housing  54 , initiator retainer  70 , and projectile  22  are preferably all made from stainless steel or high strength aluminum, and are preferably manufactured using a screw machine. These members need not have the high degree of grain alignment needed for vessel  12 , end cap housing  46 , and closure member  14 . However, they should be made of a material that has good strength and corrosion-resistance properties. Additionally, projectile  22  is preferably made from stainless steel or high strength aluminum so that it can resist heat and pressure produced by initiator  20  when initiator  20  is activated. 
     In assembling inflator  10 , lower terminus  50  of end cap housing  46  is welded to upper terminus  40  of vessel  12 . This weld is preferably an inertia weld or a friction weld because such a welds are resistant to leakage. The inertia or friction weld creates the inwardly extending annular flanges of lower terminus  50  of end cap housing  46  and the upper terminus  40  of vessel  12 . 
     Then, an initiator assembly is formed by first pressing projectile  22  into casing  62  of projectile housing  54  to preferably form an interference fit. Initiator  20  is then inserted into beveled hole  60  of projectile housing  54  so that flange  84  is seated within the beveled portion of hole  60 , and body  82  extends through hole  60  and into cavity  92  of projectile  20 . Initiator retainer  70  is then pressed within circumferential wall  56  of projectile housing  54 . Preferably, initiator retainer  70  and projectile housing  54  form an interference fit. Filter  98  is then positioned in annular groove  64  of projectile housing  54 . 
     The resulting initiator assembly is then preferably pressed within circumferential wall  48  of end cap housing  46  until radial wall  90  of projectile  22  abuts closure member  14 . Pin holes  52 ,  66 , and  78  are preferably then drilled so that they all align. Pin  80  is preferably then pressed into pin holes  52 ,  66 , and  78  to fix end cap housing  46 , projectile housing  54 , and initiator retainer  70  of housing  16  together. 
     Chamber  38  is preferably then filled with a pressurized gas through fill hole  32  in vessel  12 . The gas is preferably helium, but it may be any of several other types of gas or mixtures of gases. After chamber  38  is filled, weld ball  34  is positioned in fill hole  32  and is welded therein preferably by a resistance weld. Inflator  10  is then positioned within a module and outlet  18  is fluidly connected to an inflatable safety device such as an air bag. Initiator  20  is connected to the control for the safety device so that initiator  20  will be timely activated by the control for the safety device. 
     Referring to  FIG. 2 , when initiator  20  is activated, the charge within body  82  is ignited, thereby producing expanding gases. The expanding gases burst body  82  and creates pressure within cavity  92 , which propels projectile  22  through closure member  14 . Preferably, circumferential wall  88  of projectile  22  remains within casing  62  so that projectile  22  acts as a piston until projectile  22  breaks through closure member  14 . Projectile  22  and fragments from closure member  14  and body  82  are propelled into chamber  38 . With closure member  14  broken, pressurized gas within chamber  38  is allowed to escape along an outlet path through filter  98  and through outlet  18 . The gas will then inflate the inflatable safety device. Filter  98  prevents projectile  22  and fragments from closure member  14  and body  82  from escaping through outlet  18 . 
     Referring now to  FIG. 3 , an alternative inflator  110  is shown, wherein the last two digits of reference numbers for features that correspond to features discussed above with reference to  FIGS. 1–2  have the same last two digits. Vessel  112 , closure member  114 , and end cap housing  146  are all part of a unitary member. Also, rather than a radial wall, vessel  112  includes a necked closed formed end  130  that is preferably formed by either secondary necking or roll forming. Inflator  110  is advantageous in that the only welded closure of chamber  138  is the fill hole  132  that is filled by weld ball  134 . Thus, the likelihood of leakage through a welded joint is decreased. Otherwise, the embodiment shown in  FIG. 3  is the same as the embodiment of  FIGS. 1 and 2  in structure and function. 
     Referring now to  FIG. 4 , an alternative pressurized container or inflator  210  generally includes a vessel  212  that houses compressed gas, such as helium. A closure member  214  forms a closure of vessel  212 . A housing  216  is attached to vessel  212  and defines an outlet  218  therein that is preferably fluidly separated from the compressed gas only by closure member  214 . Housing  216  houses an initiator  220  and a projectile  222  that abuts closure member  214  on a side opposite from the compressed gas. Referring now to  FIG. 5 , when initiator  220  is activated, initiator  220  propels projectile  222  through closure member  214 , out of housing  216 , and into vessel  212 , thereby breaking closure member  214  and allowing the compressed gas to escape through outlet  218  and inflate a vehicle restraint such as an air bag (not shown). 
     Referring back to  FIG. 4 , and describing inflator  210  in more detail, vessel  212  is preferably a hollow cylindrical member that includes a bottom end cap  230  including a radial wall that defines a fill hole  232  therein. A weld ball  234  preferably forms a closure or plug of fill hole  232 . However, fill hole  232  may be closed or plugged in some other fashion that allows vessel  212  to be filled with pressurized gas and then sealed. A circumferential wall  236  extends upwardly from bottom end cap  230  to define a chamber  238  therein. An upper terminus  240  of circumferential wall  236  extends inwardly to form an annular flange distal from bottom end cap  230 . 
     Housing  216  preferably includes an end cap housing  246  that is primarily a circumferential wall  248  that includes a lower terminus  250  that extends inwardly to form an annular flange that abuts upper terminus  240  of vessel  212 . Preferably lower terminus  250  abuts upper terminus  240  and is secured thereto by an inertia or friction weld thereby securing vessel  212  to housing  216 . Accordingly, chamber  238  extends upwardly within the lower portion of housing  216 . However, vessel  212  may be secured to housing  216  in many other ways so long as chamber  238  remains sealed. End cap housing  246  preferably defines an outlet or outlet orifice  218  that extends radially therethrough. End cap housing  246  also includes a lower rib  252  that extends radially inwardly from circumferential wall  248  and an upper rib  253  that extends radially inwardly from circumferential wall  248 . 
     A projectile housing  254  preferably includes a circumferential wall  256 . Circumferential wall  256  defines a beveled hole  260  therein, and a lower portion of circumferential wall  256  forms a casing  262 . Circumferential wall  256  also defines an outwardly-facing annular groove  264 . 
     An initiator retainer  270  is seated within upper rib  253  of end cap housing  246 . Initiator retainer  270  includes an upper circumferential wall  272  and a radial wall  274  extending inwardly from a bottom edge of upper circumferential wall  272 . Radial wall  274  defines a centrally located beveled hole  276  therein. Initiator retainer  270  also defines a lower circumferential wall  278  that is crimped to engage annular groove  264 , thereby securing projectile housing  254  to initiator retainer  270 . This crimped design may be used instead of the design shown above in  FIGS. 1–2 . In fact, the crimped design is advantageous in many embodiments because the whole initiator assembly may be secured before it is input into the end cap housing. 
     Initiator  220  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  282 . A flange  284  extends radially outwardly from an upper portion of cylindrical body  282 . Flange  284  is seated within beveled hole  260  of projectile housing  254  and beveled hole  276  of initiator retainer  270  to secure initiator  220  within housing  216 . Initiator  220  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. 
     Projectile  222  preferably includes a circumferential wall  288  that is seated within casing  262 . A radial wall  290  extends inwardly from a bottom edge of circumferential wall  288  so that projectile  222  forms an upwardly facing cavity  292  that receives body  282  of initiator  220 . 
     Closure member  214  is a radial wall having an upwardly facing first side  294  and a downwardly facing second side  296 . In this embodiment, closure member  214  is a stainless steel disc that is welded to the bottom surface of lower rib  252  of end cap housing  246 . Radial wall  290  of projectile  222  preferably abuts first side  294  to support closure member  214  against the force of pressurized gas within chamber  238 . This allows closure member  214  to be thin and it still provides the structural integrity needed to keep the pressurized gas from prematurely breaking closure member  214 . 
     An annular filter  298  is seated within projectile housing  254  and extends between upper rib  253  and lower rib  252 . 
     Projectile housing  254  and initiator retainer  270  are preferably made from steel with a screw machine. End cap housing  246  is preferably made from steel by a cold impact process. Circumferential wall  236  of vessel  212  is preferably steel tubing, and bottom end cap  230  of vessel  212  is preferably a drawn steel cup. Closure member  214  is preferably made from stainless steel. 
     In assembling inflator  210 , an initiator assembly is formed by first pressing projectile  222  into casing  262  of projectile housing  254  to preferably form an interference fit. Initiator  220  is then inserted into beveled hole  260  of projectile housing  254  so that flange  284  is seated within the beveled portion of hole  260  and body  282  extends through hole  260  and into cavity  292  of projectile  220 . Initiator retainer  270  is then pressed so that lower circumferential wall  278  receives circumferential wall  256  of projectile housing  254 . Lower circumferential wall  278  is then crimped to engage annular groove  264  thereby securing projectile housing  254  to initiator retainer  270 . 
     The resulting initiator assembly is then preferably pressed within upper rib  253  of end cap housing  246 . Filter  298  is positioned within end cap housing  246 . Closure member  214  is preferably then welded to lower rib  252  of end cap housing  246  by a laser weld. Bottom end cap  230  is then welded to circumferential wall  236  distal from end cap housing  246 , preferably by an inertia or friction weld. 
     Lower terminus  250  of end cap housing  246  is welded to upper terminus  240  of vessel  212 . This weld is preferably an inertia or friction weld because such welds are resistant to leakage. 
     Chamber  238  is preferably then filled with a pressurized gas through fill hole  232  in vessel  212 . The gas is preferably helium, but it may be any of several other types of gas. After chamber  238  is filled, weld ball  234  is positioned in fill hole  232  and is welded therein preferably by a resistance weld. Inflator  210  is then positioned within a module and outlet  218  is fluidly connected to an inflatable safety device such as an air bag. Initiator  220  is connected to the control for the safety device so that initiator  220  will be timely activated by the control for the safety device. 
     Referring to  FIG. 5 , when initiator  220  is activated, body  282  bursts and propels projectile  222  through closure member  214 . Preferably, circumferential wall  288  of projectile  222  remains within casing  262  so that projectile  222  acts as a piston until projectile  222  breaks through closure member  214 . Projectile  222  and fragments from closure member  214  and body  282  are propelled into chamber  238 . With closure member  214  broken, pressurized gas within chamber  238  is allowed to escape along an outlet path through filter  298  and through outlet  218 . The gas will then inflate the inflatable safety device. Filter  298  prevents projectile  222  and fragments from closure member  214  and body  282  from escaping through outlet  218 . 
     Referring now to  FIG. 6 , a pressurized container or inflator  310  generally includes a vessel  312  that houses compressed gas, such as helium. A first closure member  314  and a second closure member  315  form a closure of vessel  312 . A housing  316  is attached to vessel  312  and defines an outlet  318  therein that is preferably fluidly separated from the compressed gas only by closure members  314 ,  315 . Housing  316  houses a first initiator  320 , a second initiator  321 , a first projectile  322  that abuts first closure member  314  on a side opposite from the compressed gas, and a second projectile  323  that abuts second closure member  315  on a side opposite from the compressed gas. 
     Referring now to  FIG. 7 , when first initiator  320  is activated, first initiator  320  propels first projectile  322  through first closure member  314 , out of housing  316 , and into vessel  312 , thereby breaking first closure member  314  and allowing the compressed gas to escape through a first secondary outlet path  324 , through a main outlet path  326 , and though outlet  318 . The compressed gas begins to inflate a vehicle restraint such as an air bag (not shown). 
     Referring now to  FIG. 8 , when second initiator  321  is activated, second initiator  321  propels second projectile  323  through second closure member  315 , out of housing  316 , and into vessel  312 , thereby breaking second closure member  315  and allowing the compressed gas to escape to main outlet path  326  through a second secondary outlet path  328  in addition to first secondary outlet path  324 . The flow of compressed gas into the vehicle restraint is then increased substantially beyond the flow prior to activation of second initiator  321  when the gas could escape only through first secondary outlet path  324 . 
     The initial slow flow of gas, and the later increased flow is safer in that the force of an initial blow to a potential occupant is decreased because of the smaller initial flow of compressed gas. However, the later increased flow is sufficient to timely inflate the vehicle restraint. The advantages to such a flow and the timing of increasing flow are described in U.S. Pat. No. 5,820,162 to Fink, issued Oct. 13, 1998, which is incorporated herein by reference. 
     Referring back to  FIG. 6 , and describing inflator  310  in more detail, vessel  312  is preferably a hollow cylindrical member that includes a radial wall  330  that defines a fill hole  332  therein. A weld ball  334  preferably forms a closure or plug of fill hole  332 . However, fill hole  332  may be closed or plugged in some other fashion that allows vessel  312  to be filled with pressurized gas and then sealed. A circumferential wall  336  extends upwardly from radial wall  330  to define a chamber  338  therein. An upper terminus  340  of circumferential wall  336  extends inwardly to form an annular flange distal from radial wall  330 . 
     Housing  316  preferably includes an end cap housing  346  that defines a first cylindrical recess  348 , a second cylindrical recess  349 , and an orifice  350  therebetween. First secondary outlet path  324  extends through first recess  348 , through orifice  350  and to second recess  349 . Second secondary outlet path  328  extends into second recess  349 . First secondary outlet path  324  and second secondary outlet path  328  meet within second recess  349  and main outlet path  326  extends from second recess  349  through outlet  318 . A lower annular terminus  351  of end cap housing  346  extends radially inwardly to form an annular flange that abuts upper terminus  340  of vessel  312 . Preferably lower terminus  351  abuts upper terminus  340  and is secured thereto by an inertia or friction weld thereby securing vessel  312  to housing  316 . Accordingly, chamber  338  extends upwardly within the lower portion of housing  316 . However, vessel  312  may be secured to housing  316  in many other ways so long as chamber  338  remains sealed. End cap housing  346  preferably defines an outlet or outlet orifice  318  that extends radially therethrough. End cap housing  346  also defines a first pin hole  352  extending into first recess  348  and a second pin hole  353  extending into second recess  349 . 
     A first projectile housing  354  preferably includes an upper circumferential wall  356  that is seated within first recess  348  of end cap housing  346 . A radial wall  358  preferably extends inwardly from a lower terminus of circumferential wall  356  and defines a beveled hole  360  therein. A projectile casing  362  is preferably a circumferential wall that extends from radial wall  358 . Projectile housing  354  also defines a downwardly-facing annular groove  364  and a radially extending pin hole  366 . 
     A first initiator retainer  370  is seated within upper circumferential wall  356  of first projectile housing  354 . Initiator retainer  370  includes a circumferential wall  372  and a radial wall  374  extending inwardly from a bottom edge of circumferential wall  372 . Radial wall  374  defines a centrally located beveled hole  376  therein. Initiator retainer  370  also defines a radially extending pin hole  378  therein. 
     A first pin  380  extends through first pin hole  352  of end cap housing  346 , through pin hole  366  of first projectile housing  354  and into pin hole  378  of first initiator retainer  370 . Preferably first pin  380  is sized to produce an interference fit with one or more of pin holes  352 ,  366 ,  378 . 
     First initiator  320  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  382 . A flange  384  extends radially outwardly from an upper portion of cylindrical body  382 . Flange  384  is seated within beveled hole  360  of projectile housing  354  and beveled hole  376  of initiator retainer  370  to secure first initiator  320  within housing  316 . First initiator  320  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. 
     First projectile  322  preferably includes a circumferential wall  388  that is seated within casing  362 . A radial wall  390  extends inwardly from a bottom edge of circumferential wall  388  so that first projectile  322  forms an upwardly facing cavity  392  that receives body  382  of first initiator  320 . 
     First closure member  314  is preferably a radial wall having an upwardly facing first side  394  and a downwardly facing second side  396 . First closure member  314  extends radially inwardly to form a bottom closure of first recess  348 . First closure member  314  is preferably formed with end cap housing  346  as a unitary member. Radial wall  390  of first projectile  322  preferably abuts first side  394  to support first closure member  314  against the force of pressurized gas within chamber  338 . This allows closure member  314  to be thin and it still provides the structural integrity needed to keep the pressurized gas from prematurely breaking closure member  314 . 
     A first annular filter  398  is seated within annular groove  364  of projectile housing  354  and extends downwardly until it abuts a shoulder of end cap housing  346 . 
     A second projectile housing  454  preferably includes an upper circumferential wall  456  that is seated within second recess  349  of end cap housing  346 . A radial wall  458  preferably extends inwardly from a lower terminus of circumferential wall  456  and defines a beveled hole  460  therein. A projectile casing  462  is preferably a circumferential wall that extends from radial wall  458 . Projectile housing  454  also defines a downwardly-facing annular groove  464  and a radially extending pin hole  466 . 
     A second initiator retainer  470  is seated within upper circumferential wall  456  of second projectile housing  454 . Initiator retainer  470  includes a circumferential wall  472  and a radial wall  474  extending inwardly from a bottom edge of circumferential wall  472 . Radial wall  474  defines a centrally located beveled hole  476  therein. Initiator retainer  470  also defines a radially extending pin hole  478  therein. 
     A second pin  480  extends through second pin hole  353  of end cap housing  346 , through pin hole  466  of second projectile housing  454  and into pin hole  478  of second initiator retainer  470 . Preferably second pin  480  is sized to produce an interference fit with one or more of pin holes  353 ,  466 ,  478 . 
     Second initiator  321  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  482 . A flange  484  extends radially outwardly from an upper portion of cylindrical body  482 . Flange  484  is seated within beveled hole  460  of projectile housing  454  and beveled hole  476  of initiator retainer  470  to secure second initiator  321  within housing  316 . Second initiator  321  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. 
     Second projectile  323  preferably includes a circumferential wall  488  that is seated within casing  462 . A radial wall  490  extends inwardly from a bottom edge of circumferential wall  488  so that second projectile  323  forms an upwardly facing cavity  492  that receives body  482  of second initiator  321 . 
     Second closure member  315  is preferably a radial wall having an upwardly facing first side  494  and a downwardly facing second side  496 . Second closure member  315  extends radially inwardly to form a bottom closure of second recess  349 . Second closure member  315  is preferably formed with end cap housing  346  as a unitary member. Radial wall  490  of second projectile  323  preferably abuts first side  494  to support second closure member  315  against the force of pressurized gas within chamber  338 . This allows closure member  315  to be thin and it still provides the structural integrity needed to keep the pressurized gas from prematurely breaking closure member  315 . 
     A second annular filter  498  is seated within annular groove  464  of projectile housing  454  and extends downwardly until it abuts a shoulder of end cap housing  346 . 
     The components of inflator  310  are preferably made of the same materials and are made by the same manufacturing processes as the corresponding components of inflator  10  discussed above. 
     In assembling inflator  310 , lower terminus  351  of end cap housing  346  is welded to upper terminus  340  of vessel  312 . This weld is preferably an inertia or friction weld because such a weld is resistant to leakage. 
     A first initiator assembly is formed by first pressing first projectile  322  into casing  362  of first projectile housing  354  to preferably form an interference fit. First initiator  320  is then inserted into beveled hole  360  of first projectile housing  354  so that flange  384  is seated within the beveled portion of hole  360 , and body  382  extends through hole  360  and into cavity  392  of first projectile  322 . First initiator retainer  370  is then pressed within circumferential wall  356  of first projectile housing  354 . Preferably, first initiator retainer  370  and first projectile housing  354  form an interference fit. Filter  398  is then positioned in annular groove  364  of first projectile housing  354 . 
     The resulting first initiator assembly is then preferably pressed within first recess  348  of end cap housing  346  until radial wall  390  of first projectile  322  abuts first closure member  314 . Pin holes  352 ,  366 , and  378  are preferably then drilled so that they all align. First pin  380  is preferably then pressed into pin holes  352 ,  366 , and  378  to fix end cap housing  346 , first projectile housing  354 , and first initiator retainer  370  of housing  316  together. 
     Then, a second initiator assembly is formed by first pressing second projectile  323  into casing  462  of second projectile housing  454  to preferably form an interference fit. Second initiator  321  is then inserted into beveled hole  460  of second projectile housing  454  so that flange  484  is seated within the beveled portion of hole  460 , and body  482  extends through hole  460  and into cavity  492  of second projectile  323 . Second initiator retainer  470  is then pressed within circumferential wall  356  of second projectile housing  454 . Preferably, second initiator retainer  470  and second projectile housing  454  form an interference fit. Filter  498  is then positioned in annular groove  464  of second projectile housing  454 . 
     The resulting second initiator assembly is then preferably pressed within second recess  349  of end cap housing  346  until radial wall  490  of second projectile  323  abuts second closure member  315 . Pin holes  353 ,  466 , and  478  are preferably then drilled so that they all align. Second pin  480  is preferably then pressed into pin holes  353 ,  466 , and  478  to fix end cap housing  346 , second projectile housing  454 , and second initiator retainer  470  of housing  316  together. 
     Chamber  338  is preferably then filled with a pressurized gas through fill hole  332  in vessel  312 . The gas is preferably helium, but it may be any of several other types of gas. After chamber  338  is filled, weld ball  334  is positioned in fill hole  332  and is welded therein preferably by a resistance weld. Inflator  310  is then positioned within a module and outlet  318  is fluidly connected to an inflatable safety device such as an air bag. Initiators  320 ,  321  are connected to the control for the safety device so that initiators  320 ,  321  will be timely activated by the control for the safety device. 
     Referring to  FIG. 7 , when first initiator  320  is activated, body  382  bursts and propels first projectile  322  through first closure member  314 . Preferably, circumferential wall  388  of first projectile  322  remains within casing  362  so that first projectile  322  acts as a piston until first projectile  322  breaks through first closure member  314 . First projectile  322  and fragments from first closure member  314  and body  382  of first initiator  320  are propelled into chamber  338 . With first closure member  314  broken, pressurized gas within chamber  338  is allowed to escape along first secondary outlet path  324  and main outlet path  326  and through outlet  318 . The gas will then begin to inflate the inflatable safety device. Filter  398  prevents projectile  322  and fragments from closure member  314  and body  382  from escaping through outlet  318  along first secondary outlet path  324 . 
     Referring to  FIG. 8 , after first initiator  320  is activated, second initiator  321  is activated. The time between activation of first initiator  320  and activation of second initiator  321  may be a set predetermined time or it may be a variable time that will depend on factors, such as the characteristics of the vehicle occupants and the nature of the vehicle collision. When second initiator  321  is activated, body  482  bursts and propels second projectile  323  through second closure member  315 . Preferably, circumferential wall  488  of second projectile  323  remains within casing  462  so that second projectile  323  acts as a piston until second projectile  323  breaks through second closure member  315 . Second projectile  323  and fragments from second closure member  315  and body  482  of second initiator  321  are propelled into chamber  338 . With second closure member  315  broken, pressurized gas within chamber  338  is allowed to escape along first secondary outlet path  324  and second secondary outlet path  328  to main outlet path  326 , and along main outlet path  326  and through outlet  318 . The gas will then finish inflating the inflatable safety device. Filter  498  prevents projectiles  322 ,  323  and fragments from closure members  314 ,  315  and bodies  382 ,  482  from escaping through outlet  318  along second secondary outlet path  328 . 
     Referring now to  FIG. 9 , a pressurized container or inflator  510  generally includes a vessel  512  that houses compressed gas, such as helium. A closure member  514  forms a closure of vessel  512 . A housing  516  is attached to vessel  512  and defines an outlet  518  therein that is preferably fluidly separated from the compressed gas only by closure member  514 . Housing  516  houses a first initiator  520 , a projectile  522  that abuts closure member  514  on a side opposite from the compressed gas, and a second initiator  521  that protrudes into an outlet path  524  and forms an obstruction therein partially blocking outlet path  524 . 
     Referring now to  FIG. 10 , when first initiator  520  is activated, first initiator  520  propels first projectile  522  through first closure member  514 , out of housing  516 , and into vessel  512 , thereby breaking first closure member  514  and allowing the compressed gas to escape through a first secondary outlet path  524 , through a main outlet path  526 , and though outlet  518 . The compressed gas begins to inflate a vehicle restraint such as an air bag (not shown). 
     Referring now to  FIG. 11 , when second initiator  521  is activated, second initiator  521  breaks or bursts, thereby removing the obstruction from outlet path  526  and allowing the compressed gas to escape substantially unobstructed through outlet path  526 . The flow of compressed gas into the vehicle restraint is then increased substantially beyond the flow prior to activation of second initiator  521  when outlet path  526  was partially blocked. As discussed above, the initial slow flow of gas, and the later increased flow is safer in that the force of an initial blow to a potential occupant is decreased because of the smaller initial flow of compressed gas. However, the later increased flow is sufficient to timely inflate the vehicle restraint. 
     Referring back to  FIG. 9 , and describing inflator  510  in more detail, vessel  512  is preferably a hollow cylindrical member that includes a radial wall  530  that defines a fill hole  532  therein. A weld ball  534  preferably forms a closure or plug of fill hole  532 . However, fill hole  532  may be closed or plugged in some other fashion that allows vessel  512  to be filled with pressurized gas and then sealed. A circumferential wall  536  extends upwardly from radial wall  530  to define a chamber  538  therein. An upper terminus  540  of circumferential wall  536  extends inwardly to form an annular flange distal from radial wall  530 . 
     Housing  516  preferably includes an end cap housing  546  that defines a first cylindrical recess  548 , a second cylindrical recess  549 , and an outlet conduit  550  extending from first cylindrical recess  548  to outlet  518 . Thus, outlet path  524  extends through first recess  548 , through outlet conduit  550  and to outlet  518 . A lower annular terminus  551  of end cap housing  546  extends radially inwardly to form an annular flange that abuts upper terminus  540  of vessel  512 . Preferably lower terminus  551  abuts upper terminus  540  and is secured thereto by an inertia or friction weld thereby securing vessel  512  to housing  516 . Accordingly, chamber  538  extends upwardly within the lower portion of housing  516 . However, vessel  512  may be secured to housing  516  in many other ways so long as chamber  538  remains sealed. End cap housing  546  preferably defines a first pin hole  552  extending into first recess  548  and a second pin hole  553  extending into second recess  549 . 
     A projectile housing  554  preferably includes an upper circumferential wall  556  that is seated within first recess  548  of end cap housing  546 . A radial wall  558  preferably extends inwardly from a lower terminus of circumferential wall  556  and defines a beveled hole  560  therein. A projectile casing  562  is preferably a circumferential wall that extends from radial wall  558 . Projectile housing  554  also defines a downwardly-facing annular groove  564  and a radially extending pin hole  566 . 
     A first initiator retainer  570  is seated within upper circumferential wall  556  of projectile housing  554 . First initiator retainer  570  includes a circumferential wall  572  and a radial wall  574  extending inwardly from a bottom edge of circumferential wall  572 . Radial wall  574  defines a centrally located beveled hole  576  therein. First initiator retainer  570  also defines a radially extending pin hole  578  therein. 
     A first pin  580  extends through first pin hole  552  of end cap housing  546 , through pin hole  566  of projectile housing  554  and into pin hole  578  of first initiator retainer  570 . Preferably second pin  580  is sized to produce an interference fit with one or more of pin holes  552 ,  566 , and  578 . 
     First initiator  520  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  582 . A flange  584  extends radially outwardly from an upper portion of cylindrical body  582 . Flange  584  is seated within beveled hole  560  of projectile housing  554  and beveled hole  576  of first initiator retainer  570  to secure first initiator  520  within housing  516 . First initiator  521  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. 
     Projectile  522  preferably includes a circumferential wall  588  that is seated within casing  562 . A radial wall  590  extends inwardly from a bottom edge of circumferential wall  588  so that projectile  522  forms an upwardly facing cavity  592  that receives body  582  of first initiator  520 . 
     Closure member  514  is preferably a radial wall having an upwardly facing first side  594  and a downwardly facing second side  596 . Closure member  514  extends radially inwardly to form a bottom closure of first recess  548 . Closure member  514  is preferably formed with end cap housing  546  as a unitary member. Radial wall  590  of projectile  522  preferably abuts first side  594  to support closure member  514  against the force of pressurized gas within chamber  538 . This allows closure member  514  to be thin and it still provides the structural integrity needed to keep the pressurized gas from prematurely breaking closure member  514 . 
     An annular filter  598  is seated within annular groove  564  of projectile housing  554  and extends downwardly until it abuts a shoulder of end cap housing  546 . 
     Housing  516  defines a beveled hole  660  extending between second recess  549  and outlet conduit  550 . A second initiator retainer  670  is seated within second recess  549 . Second initiator retainer  670  includes a circumferential wall  672  and a radial wall  674  extending inwardly from a bottom edge of circumferential wall  672 . Radial wall  674  defines a centrally located beveled hole  676  therein. Second initiator retainer  670  also defines a radially extending pin hole  678  therein that is aligned with second pin hole  553  of end cap housing  546 . A second pin  680  extends through second pin hole  553  in end cap housing  546  and into pin hole  678  in second initiator retainer  670 , preferably forming an interference fit. 
     Second initiator  521  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  682 . A flange  684  extends radially outwardly from an upper portion of cylindrical body  682 . Flange  684  is seated within beveled hole  660  of end cap housing  546  and beveled hole  676  of second initiator retainer  670  to secure second initiator  521  within housing  516 . Body  682  extends into outlet conduit  550  to form a partial blockage of outlet path  524 . Second initiator  521  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. Also, body  682  of second initiator  521  may include an outer reinforcing sleeve to prevent premature breakage of body  682  due to the force of air flow before second initiator  521  is activated. 
     An annular filter  698  preferably spans outlet conduit  550  and surrounds body  682  of second initiator  521 . 
     The components of inflator  510  are preferably made of the same materials and are made by the same manufacturing processes as the corresponding components of inflator  10  discussed above. 
     In assembling inflator  510 , lower terminus  551  of end cap housing  546  is welded to upper terminus  540  of vessel  512 . This weld is preferably an inertia or friction weld because such a weld is resistant to leakage. 
     A first initiator assembly is formed by first pressing first projectile  522  into casing  562  of projectile housing  554  to preferably form an interference fit. First initiator  520  is then inserted into beveled hole  560  of second projectile housing  554  so that flange  584  is seated within the beveled portion of hole  560 , and body  582  extends through hole  560  and into cavity  592  of projectile  522 . First initiator retainer  570  is then pressed within circumferential wall  556  of projectile housing  554 . Preferably, first initiator retainer  570  and projectile housing  554  form an interference fit. Filter  598  is then positioned in annular groove  564  of projectile housing  554 . 
     The resulting first initiator assembly is then preferably pressed within first recess  548  of end cap housing  546  until radial wall  590  of projectile  522  abuts closure member  514 . Pin holes  552 ,  566 , and  578  are preferably then drilled so that they all align. First pin  580  is preferably then pressed into pin holes  552 ,  566 , and  578  to fix end cap housing  546 , projectile housing  554 , and first initiator retainer  570  of housing  516  together. 
     Filter  698  is inserted through hole  660  so that it spans conduit  550 . Second initiator  521  is preferably then seated within beveled hole  660  of end cap housing  546  and second initiator retainer  670  is pressed into second recess  549  of end cap housing  546 . Second pin  680  is preferably then pressed into second pin hole  553  of end cap housing  546  and into pin hole  678  of second initiator retainer  670 . 
     Chamber  538  is preferably then filled with a pressurized gas through fill hole  532  in vessel  512 . The gas is preferably helium, but it may be any of several other types of gas. After chamber  538  is filled, weld ball  534  is positioned in fill hole  532  and is welded therein preferably by a resistance weld. Inflator  510  is then positioned within a module and outlet  518  is fluidly connected to an inflatable safety device such as an air bag. Initiators  520 ,  521  are connected to the control for the safety device so that initiators  520 ,  521  will be timely activated by the control for the safety device. 
     Referring to  FIG. 10 , when first initiator  520  is activated, body  582  bursts and propels projectile  522  through closure member  514 . Preferably, circumferential wall  588  of projectile  522  remains within casing  562  so that projectile  522  acts as a piston until projectile  522  breaks through closure member  514 . Projectile  522  and fragments from first closure member  514  and body  582  of first initiator  520  are propelled into chamber  538 . With first closure member  514  broken, pressurized gas within chamber  538  is allowed to escape along outlet path  524  and through outlet  518 . The gas will then begin to inflate the inflatable safety device. 
     Referring to  FIG. 11 , after first initiator  520  is activated, second initiator  521  is activated. The time between activation of first initiator  520  and activation of second initiator  521  may be a set predetermined time or it may be a variable time that will depend on factors, such as the characteristics of the vehicle occupants and the nature of the vehicle collision. When second initiator  521  is activated, body  682  bursts, thereby substantially removing the obstruction in outlet path  524 . With obstruction or body  682  broken, pressurized gas within chamber  538  is allowed to escape along outlet path  524  and through outlet  518  without being partially blocked. The gas will then finish inflating the inflatable safety device. Filter  698  prevents fragments of body  682  from escaping through outlet  518 . 
     Referring now to  FIG. 12 , an alternative inflator  710  is shown that is similar in structure and function to the inflator  510  discussed above. The last two digits of reference numbers for features in  FIG. 12  that correspond to features discussed above with reference to  FIGS. 9–11  have the same last two digits. In the embodiment shown in  FIG. 12 , the outlet conduit  750  extends upwardly so that outlet  718  is defined in the top of end cap housing  746 , rather than in the side as in  FIGS. 9–11 . Thus, second recess  749  extends inwardly from the side of end cap housing  746  and second pin  880  extends downwardly from the top of end cap housing  746 . Also, a circumferential wall  877  extends from radial wall  874  and is crimped to engage flange  884  of second initiator  721 . Otherwise, the embodiment shown in  FIG. 12  is the same as the embodiment of  FIGS. 9–11  in structure and function. 
     Referring to  FIG. 13 , a pressurized container or inflator  910  generally includes a vessel  912  that houses compressed gas, such as helium. A closure member  914  forms a closure of the vessel  912 . A housing  916  is attached to vessel  912  and defines an outlet  918  therein that is preferably fluidly separated from the compressed gas only by closure member  914 . Housing  916  houses an initiator  920  and a projectile  922  that abuts closure member  914  on a side opposite from the compressed gas. When initiator  920  is activated, inflator  910  operates similarly to inflator  10  above, with some exceptions described below. 
     Referring still to  FIG. 13 , and describing inflator  910  in more detail, vessel  912  is preferably a hollow cylindrical member that includes a radial wall  930  that defines a fill hole  932  therein. A weld ball  934  preferably forms a closure or plug of fill hole  932 . However, fill hole  932  may be closed or plugged in some other fashion that allows vessel  912  to be filled with pressurized gas and sealed. A circumferential wall  936  extends upwardly from radial wall  930  to define a chamber  938  therein. An upper terminus  940  of circumferential wall  936  extends inwardly to form an annular flange distal from radial wall  930 . Circumferential wall  936  also defines an annular upwardly-facing shoulder  941  between radial wall  930  and upper terminus  940  that supports an isolator member or isolator plate  942  thereon. Isolator plate  942  defines a centrally-located passage or bleed orifice  943  therein that fluidly connects an upper portion of chamber  938  from a lower portion of chamber  938 . Passage  943  can be any form of fluid communication between the two portions of chamber  938 . For example, it could be a clearance about the periphery of isolator plate  942 . A retainer sleeve or circumferential wall  944  abuts the upper periphery of isolator plate  942  and extends upwardly to abut the annular flange of upper terminus  940  of circumferential wall  936 . 
     Housing  916  preferably includes an end cap housing  946  that is primarily a circumferential wall  948  that includes a lower terminus  950  that extends inwardly to form an annular flange that abuts upper terminus  940  of vessel  912 . Preferably lower terminus  950  abuts upper terminus  940  and is secured thereto by an inertia weld or a friction weld thereby securing vessel  912  to housing  916 . Accordingly, the upper portion of chamber  938  extends upwardly within the lower portion of housing  916 . However, vessel  912  may be secured to housing  916  in many other ways so long as chamber  938  remains sealed. End cap housing  946  defines a pin hole  952  extending radially therethrough. 
     A projectile housing  954  preferably includes a radial wall  958  that defines a beveled hole  960  therein. Radial wall  958  preferably also defines an outlet hole  961  therein that forms part of outlet  918 . A projectile casing  962  is preferably a circumferential wall that extends from radial wall  958 . Projectile housing  954  also defines a downwardly-facing annular groove  964 . 
     An initiator retainer  970  is seated within circumferential wall  948  of end cap housing  946 . Initiator retainer  970  includes a circumferential wall  972  and a radial wall  974  extending inwardly from a bottom edge of circumferential wall  972 . Initiator retainer  970  defines an outlet hole  975  that is aligned with outlet hole  961  of projectile housing  954  and that extends upwardly to form part of outlet  918 . Radial wall  974  also defines a centrally located beveled hole  976  therein. Initiator retainer  970  defines a radially extending pin hole  978  therein. 
     A pin  980  extends through pin hole  952  of end cap housing  946  and into pin hole  978  of initiator retainer  970 . Preferably pin  980  is sized to produce an interference fit with one or more of pin holes  952  and  978 . 
     Initiator  920  is preferably a standard initiator that includes a small pyrotechnic charge housed within a cylindrical body  982 . A flange  984  extends radially outwardly from an upper portion of cylindrical body  982 . Flange  984  is seated within beveled hole  960  of projectile housing  954  and beveled hole  976  of initiator retainer  970  to secure initiator  920  within housing  916 . Initiator  920  is preferably an initiator of the kind known as “popcorn” or pin style initiators that includes zirconium potassium perchlorate as a pyrotechnic material and that includes a bridge wire that ignites the pyrotechnic material when a current is passed through it. 
     Projectile  922  preferably includes a circumferential wall  988  that is seated within casing  962 . However, the casing and the projectile may be some other structure. For example, the casing may extend within the circumferential wall of the projectile. A radial wall  990  extends inwardly from a bottom edge of circumferential wall  988  so that projectile  922  forms an upwardly facing cavity  992  that receives body  982  of initiator  920 . 
     Closure member  914  is preferably a radial wall having an upwardly facing first side  994  and a downwardly facing second side  996 . Closure member  914  extends inwardly from end cap housing  946  and is preferably formed with end cap housing  946  as a unitary member. Radial wall  990  of projectile  922  preferably abuts first side  994  to support closure member  914  against the force of pressurized gas within chamber  938 . This allows closure member  914  to be thin and it still provides the structural integrity needed to keep the pressurized gas from prematurely breaking closure member  914 . 
     An annular filter  998  is seated within annular groove  964  of projectile housing  954  and extends downwardly until it abuts a shoulder of end cap housing  946 . 
     The components of inflator  910  are preferably made from the same materials and by the same processes as corresponding components of inflator  10  discussed above. Isolator plate  942  and retainer sleeve  944  are preferably both made of aluminum, such as 6061-T6 aluminum. 
     In assembling inflator  910 , isolator plate  942  and retainer sleeve are placed within vessel  912  and lower terminus  950  of end cap housing  946  is welded to upper terminus  940  of vessel  912 . This weld is preferably an inertia weld or a friction weld because such a welds are resistant to leakage. The inertia or friction weld creates the inwardly extending annular flanges of lower terminus  950  of end cap housing  946  and the upper terminus  940  of vessel  912 . The inwardly extending flange of upper terminus  940  holds retainer sleeve  944  in place, and retainer sleeve  944  holds isolator plate  942  in place. 
     Then, an initiator assembly is formed by first pressing projectile  922  into casing  962  of projectile housing  954  to preferably form an interference fit. Initiator  920  is then inserted into beveled hole  960  of projectile housing  954  so that flange  984  is seated within the beveled portion of hole  960  and body  982  extends through hole  960  and into cavity  992  of projectile  922 . Filter  998  is then positioned in annular groove  964  of projectile housing  954 . The resulting assembly is then preferably placed within circumferential wall  948  of end cap housing  946 . Initiator retainer  970  is then pressed within circumferential wall  948  of end cap housing  946 . Preferably, initiator retainer  970  and circumferential wall  948  form an interference fit, although projectile housing  954  need not form an interference fit with circumferential wall  948 . Pin holes  952  and  978  are preferably then drilled so that they align and outlet holes  961  and  975  are drilled so that they align. Pin  980  is preferably then pressed into pin holes  952  and  978  to fix end cap housing  946  and initiator retainer  970  of housing  916  together. 
     Chamber  938  is preferably then filled with a pressurized gas through fill hole  932  in vessel  912 . The gas is preferably a mixture of helium and carbon dioxide because the larger carbon dioxide molecules will bleed more slowly through bleed orifice  943 , while the smaller helium molecules quickly escapes from the upper portion of chamber  938 . Any of several other types of gas or mixtures of gases may work. For example, helium may be mixed with some other gas having larger molecules, such as argon. Also, it may be desirable to mix helium and carbon dioxide in other inflator applications where it is desirable to have part of the gas escape quickly and part of the gas escape slowly. 
     After chamber  938  is filled, weld ball  934  is positioned in fill hole  932  and is welded therein preferably by a resistance weld. Inflator  910  is then positioned within a module and outlet  918  is fluidly connected to an inflatable safety device such as an air bag. Initiator  920  is connected to the control for the safety device so that initiator  920  will be timely activated by the control for the safety device. 
     When initiator  920  is activated, body  982  bursts and creates pressure within cavity  992 , which propels projectile  922  through closure member  914 . Preferably, circumferential wall  988  of projectile  922  remains within casing  962  so that projectile  922  acts as a piston until projectile  922  breaks through closure member  914 . Projectile  922  and fragments from closure member  914  and body  982  are propelled into chamber  938 . With closure member  914  broken, pressurized gas within the upper portion of chamber  938  is allowed to quickly escape along an outlet path through filter  998  and through outlet  918 . The gas will then inflate the inflatable safety device. After the upper portion of chamber  938  is substantially emptied, gas will continue to slowly escape through bleed orifice  943  and out outlet  918  to keep the inflatable safety device inflated for a longer period of time than would occur with inflator  10 . This is preferable in inflatable safety devices such as rollover protection air bags where the safety device needs to stay inflated over a period of time. Filter  998  prevents projectile  922  and fragments from closure member  914  and body  982  from escaping through outlet  918  during inflation of the safety device. The depth of isolator plate  942  can be adjusted to meet different requirements of prolonged safety device inflation. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. For example, individual features from each of the several embodiments described can be used with other features from other embodiments.