Abstract:
Apparatus for use in passenger inflatable air-bag safety systems for preventing activation of an activator inflator from causing premature activation of any inflator not yet activated by system programming. The apparatus includes structure for isolating the pressure releasing construction from shock waves created when an inflator is activated and takes the form of mechanical barriers that isolate each inflator release structure from exposure to shock waves.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to safety systems for protecting vehicular passengers, such as those traveling in automobiles and aircraft, and more particularly to those safety systems which utilize passive restraints, such as air bags and similar inflatable restraints which require almost instantaneous inflation from gas sources, such as compressed air or the reaction products of pyrotechnic inflator cartridges. 
     Inflatable gas cushions (air bags) are widely used in certain types of passenger carrying vehicles, most prevalently in land based automotive equipment. Generally, passive passenger restraints, such as inflatable gas bags are filled by compressed air or other gases and are located in the automobile steering column and in other fixed locations within the automobile, such as the dashboard and side panels. In the event of sudden deceleration of the vehicle, as in a crash, sensors identify the event and the compressed air or other gas is released to expand the bags at high speed directly towards the passenger. Air bags have generally proven to be effective in alleviating to some extent injuries which might otherwise be occasioned by virtue of a passenger striking a rigid surface within the vehicle. On the other hand it has now become apparent through experience that in some instances occupants require protection from the rapid inflation of the aribag system itself. 
     It has in the past been proposed, for various reasons, to inflate the protective air or gas filled cushion gradually, usually by sequentially releasing inflating gas, so that the full force of deployment of the bag was extended over a longer period of time. Control of the rate of bag inflation might be desired for example, in response to the position of the vehicle occupant to be restrained, or as a function of the ambient temperature or even as a function of the severity of the impending crash event. 
     U.S. Pat. No. 5,460,405 which was issued Oct. 24, 1995 discloses a passenger protective inflating system in which an inflator assembly  20  is provided which contains a plurality of inflating gas sources  22 ,  24 ,  26  and  28  that are capable of supplying different volumes of gas, depending upon the instructions issued by controller  50 . These four sources of inflating gas may be activated either simultaneously or in sequence depending upon the values received by controller  50  from sensors  52 ,  72  and  70 . 
     A different type of multi-stage gas inflating apparatus is the subject of U.S. Pat. No. 3,972,545 which, in this case, discloses the use of separate quantities of ignitable materials contained within chambers  16  and  17  that are separated by a consumable partition  15 . The reaction of combustible materials within chambers  16  and  17  are initiated by means of squibs  19  and  20  which can be fired either separately or simultaneously, depending upon the severity of the emergency situation that has been sensed. 
     When utilizing multiple sources of inflating gas, for example separate containers of compressed air, in which the gases are expanded and released suddenly in pulsed sequence into a common duct which flows the gas toward the cushion, a reverse pressure shockwave often results from the activation or firing of the first container of gas; this shockwave is then responsible for the premature activation or firing of the second or subsequent additional containers. Since sequential activation is undertaken to alleviate the severity of cushion expansion, the essentially simultaneous activation of all gas sources by the shock wave vitiates the original reason for sequential gas release. 
     OBJECTS OF THE INVENTION 
     It is a principal object of this invention to provide a passenger restraint system in which multiple inflator cartridges are provided and in which means is included to ensure that operation of one inflator cartridge is not responsible for premature activation of cartridges to be fired later. 
     It is an additional object of this invention to provide a multiple source inflator system in which transmission of a pressure wave between the first activated of a plurality of pressurized gas containers cannot effect premature activation and release of gas from containers programmed to be later released. 
     An additional object of this invention is to provide an inflation system utilizing multiple gas inflator sources in which sources can be sequentially fired and in which the shockwave generated by the first operated inflator container is shielded from additional inflator by means of suitable pressure isolating apparatus. 
     A further object of this invention is to provide a multiple source inflator system in which at least some of the inflator cartridges are provided with shielding apparatus that prevent activation of the cartridges by reason of shock waves occurring from earlier activation of other cartridges. 
    
    
     Additional object and advantages of this invention will be in part obvious and in part explained by reference to the accompanying specification and drawings, in which: 
     FIG. 1 is a perspective view of the inflator system of this invention as it would be attached to a supporting structure within a vehicle such as an aircraft; 
     FIG. 2 is a side elevation, partly in section, taken along the line  2 — 2  of FIG. 1; 
     FIG. 3 is a sectional view taken along the line  3 — 3  of FIG. 1; 
     FIG. 4 is a perspective of one form of valving arrangement that can be used to prevent the blow back of a pressure surge between one inflator and another when both are connected into a common plenum; 
     FIG. 5 is an enlarged fragmentary sectional view showing one form of an anti-blow back valve according to this invention in its open position; 
     FIG. 6 is a sectional view taken along the line  6 — 6  of FIG. 1; 
     FIG. 7 is a sectional view of a portion of FIG. 2; 
     FIG. 8 is a sectional view of an isolator apparatus in which more than one inflator cartridge is disposed within a common volume; 
     FIG. 9 is a side view of a pressure isolating membrane, as mounted on an inflator cartridge; 
     FIG. 10 is a sectional view taken along this line  10 — 10  of FIG. 9; and 
     FIG. 11 is a schematic illustrating the manner in which the pressure isolating membrane of FIGS. 9 and 10 expands to permit gas to be vented from the inflator cartridge. 
    
    
     SUMMARY OF THE INVENTION 
     The apparatus of this invention involves a system in which a multiplicity of sources of high pressure gas are sequentially activated to deploy an inflatable air cushion in a vehicle system. In the specific systems illustrated, there are two sources of inflating gas, although it should be recognized that more than two gas sources can be used if desired. As illustrated, the source of inflating gas comprise two inflator cartridges that are in the form of elongated tubular containers having initially sealed pressure outlet passages located in the wall of the cartridge. In the usual construction the outlets are sealed by frangible membranes that rupture when a cartridge is activated; but other sealing and releasing construction can as well be used. Activating or firing squibs are used to ignite combustible materials contained within the containers and appropriate sensing and firing circuitry are connected to the sources of inflating gas so that they are released at desired, preselected time intervals. 
     The invention includes providing apparatus which surrounds a portion of the outer cylindrical surface of the gas cartridges to define a volume so that gas escaping through the initially sealed outlet passages of the cartridges will be confined and directed toward an outlet port. When each cartridge has its own individual gas receiving chamber, the outlet port from each chamber is sealed by means for releasing pressure from a first and each remaining cartridge. The means takes the form of a one way valving mechanism which, when opened, permits the passage of gas into means defining a gas receiving volume such as a plenum that in turn collects the gas and directs it to tubing for transport to the inflatable member. Although a variety of one way valves could be used to insure that there can be no transmission of a pressure wave from one inflator to the other the present invention utilizes a unique flapper type valve that is simple and inexpensive but which serves to preclude reverse gas pressure transmission within the gas collecting plenum from effecting firing still unfired cartridges. 
     The invention also provides apparatus where a plurality of inflator cartridges are situated within, or at least partially situated within, a housing that defines a plenum chamber that collects gas emanating from all of the inflator cartridges as they are sequentially activated. In this apparatus pressure isolating means is associated directly with each individual inflator cartridge to preclude premature activation of cartridges which might otherwise be caused by activation of the first cartridge. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     At the onset it should be noted that the safety system of the present invention has applicability in any type of passenger vehicle, although it will be described primarily in conjunction with aircraft application where the apparatus described would be located in the space beneath a passenger seat. The description is therefore not intended to be limiting in scope but only illustrative of one safety system that can utilize the invention. For a more detailed description of the invention reference is made to FIG. 1 of the drawings where the numeral  10  identifies one construction of apparatus with which this invention is concerned. Numeral  11  identifies a broken away portion of supporting structure which could be a plate attached to the substructure of an aircraft seat, for example. It is not necessary that a plate be used as any type of structure could be used to support the components of the safety system. A pair of spaced apart supporting brackets  12  and  13  are attached to the plate  11  and each of a somewhat L-shaped configuration to provide recesses  14  and  15  for purposes to be described later. Bracket elements  12  and  13  are secured to plate  11  but can be supported by any other suitable type of supporting structure. 
     Supported within the recesses  14  and  15  of the mounting blocks  12  and  13  are the actual sources of inflating gas and the means for controlling the gas so that sequential firing will not occasion the premature firing of a second (or other subsequent) source of gas upon the firing of the squib associated with the initial gas source. Specifically, a pair of inflating gas sources in the form of elongated, cylindrical cartridges  21  and  22  are held in position, within recess  14  on the left end, as viewed in FIG. 1, by means of a supporting strap  23 . The opposite ends of cartridges  21  and  22  are situated within the recess  15  of block  13  so that each end of the containers are in abutting relationship with the vertically extending walls of notches  14  and  15 . This mounting construction in which the ends of the cartridges  21  and  22  abut against the vertical walls of the recesses  14  and  15  prevents longitudinal shifting of inflators  21  and  22  upon activation. 
     As best seen in FIG. 2 of the drawings, each of the inflators  21  and  22  have openings  25  that are sealed with rupturable or otherwise pressure releasing elements  26  that will vent the interior of each inflator when a firing squib (not shown) causes the gas within an inflator to expand. Surrounding the openings  25  on each inflator which characteristically are sealed by a frangible membrane, is a gas receiving structure  30  that completely surrounds a portion of the entire outer periphery of each of the inflators  21  and  22 . Each structure  30  is comprised of an upper (as viewed in the drawings) section  31  and a lower section  32 , which when placed together define recesses  33  and  34 . Recesses  33  and  34  receive the inflators  21  and  22  and provide a gas containing volume  35  which is defined by the outer walls of the inflators and the inner walls of the structure  30 . The gas isolating structure  30  sealingly encloses both containers at each end by means of container-conforming sealing gaskets  40  (see FIG. 6) and by means of flat gaskets  41  which are located between mating surfaces of the upper half  31  of isolator  30  and a lower half  32  of isolating structure  30 . In an alternative design the structure  30  could be constructed as two individual bodies that are separate from each other so that no flat gaskets  41  are required to create separate volumes  35 . 
     As can be seen by reference to FIG. 3, when gas exits from each of the inflators  21  and  22  it flows into the volume  35  which is formed within the isolating structure  30  in the area immediately surrounding the normally sealed openings  25 . As the gas exits from openings  25  it flows around the containers  22  and  21  toward the gas exit ports  42  and  43 , respectively and on into a gas receiving structure  45  that forms a plenum into which gas will flow from all inflators as they are activated. 
     One of the principal problems involved in the use of sequentially operated gas inflators arises from the fact that when the first of the inflators is activated, there is an immediate release of extremely high pressure gas. This gas creates a shockwave which can then be transmitted into contact with non-activated inflators which are to be fired at a later time, thereby possibly causing premature activation of the non-activated inflators. To prevent premature firing upon firing of the first inflator, the present invention utilizes unidirectional gas flow means that is operably mounted between the volume  35  associated with each inflator and the gas receiving structure  45  to prevent transmission of reverse gas pressure through structure  45  from one volume  35  into another. Reverse shock wave propagation can be effectively foreclosed by an apparatus comprising a one-way valve mechanism that will permit the flow of gas from each gas inflator as it is created but which will prevent reverse transmission of a pressure wave that arises from the earlier firing of any other inflator. 
     One apparatus for preventing transmission of a pressure surge can be seen in FIG. 3, where the volume  35  surrounding each inflator connects through openings  42  and  43  into the volume defined by structure  45 . Structure  45  acts as a plenum to receive the gas of both inflators  21  and  22 . Openings  42 ,  43  are normally closed by a one-way valve  50  which can take the form of a membrane or flapper plate  51  valve which is secured along one edge to the lower half  32  of the isolator  30  in such a position that each plate  51  completely blocks openings  42  and  43 . Obviously the valve  50  can be omitted from the first to be fired of the inflators, since no pressure surge can exist prior to the first firing. FIG. 4 shows the manner in which the flapper valve plate  51  may be secured to structure  30  by means of the threaded fasteners  52  although, it will be appreciated that other forms of fasteners can be used as well. Adjacent to the point of attachment it can be seen that there is a V-shaped recess  53  in the plate valve  51  that defines a weakened area where stress concentration will occur when the plate is subjected to pressure from above (see FIG.  4 ). When an inflator is activated the pressure rise within the inflator pushes against plate  51  and causes the plate to pivot about the weakened line  53  as shown in FIGS. 3 and 5. When this occurs the pressure from inflator  21 , assuming it is discharged first for example, will enter into the plenum  45  from port  43  and the shockwave will be prevented from entering into port  42  because upward pressure created against the valve membrane  51  cannot effect its opening. When inflator  22  is activated subsequently, the pressure will vent into plenum  45  and follow the gas already vented into the plenum toward the inflatable cushion (not shown). 
     A modified form of apparatus for preventing the transmission of gas pressure surges between inflator cartridges is illustrated in FIGS. 8-11. Referring to FIG. 8, numeral  60  corresponds to apparatus  10  shown in FIG.  1  and can be attached to the substructure of an aircraft seat in similar fashion. The construction of FIG. 8 includes means for defining a single volume for receiving pressurized gas from a plurality of inflators, as well as means for preventing a pressure surge from effecting undesired, premature firing of cartridges to be fired at a later time in a firing sequence. 
     Apparatus  60  is comprised of two matable halves  61 ,  62  joined by suitable fastening elements, such as threaded fasteners  63 . When assembled, parts  61 ,  62  define a single interior volume  65 , which performs functionally like the plenum chamber  50  of the apparatus illustrated in FIGS. 1-7. Volume  65  contains a plurality of inflator cartridges  66 , which are here shown as two in number for descriptive purposes only. The volume  65  opens into gas release passages created by pipes  67  for the purpose of conducting gas into the inflatable bag. 
     Since the gas created by the inflators  66  is extremely hot when first released into volume  65 , a coating  68  of thermally stable material is supplied as a continuous layer of protective material on the inner walls of mating apparatus halves  61 ,  62 . Layer or coating  68  is indicated schematically by the dotted lines  69  seen in FIG.  8 . Substances such as metal/non-metal refractories are suitable for use as substances that provided a protective thermal barrier. For example oxide and carbide compounds of metals such as aluminum, tungsten, boron, and other metals known in the trade may be used. 
     Each of the cartridges  66  is of the type discussed earlier wherein a normally closed pressure releasing structure exists in each cartridge, usually in the form of a rupturable membrane  26  built into the cartridge wall. In view of the fact that cartridges  66  are contained within single volume  65 , means are required whereby the pressure releasing structure  26  of each cartridge is isolated from the pressurized gas created by a cartridge activated earlier. In the configuration shown in FIGS. 9-11, the means isolating the rupturable membrane  35  is what is in effect a uni-directionally acting valve  70 . This valve  70  is shown as an apparatus comprised of two elements  71  and  72  that are shaped to conform to the outer surface of the cartridge at a location over the rupturable membranes  26 . The two elements can advantageously be made as a single part with a longitudinally extending weakened line  74 . Line  74  acts as a pivot axis which permits the elements  71 ,  72 , to pivot away from each other, as seen in FIG. 11, when the cartridge with which valve  70  is associated is activated. Valve  70  can be mounted on a cartridge through its own spring clamping pressure or can be held in desired position by a suitable, light adhesive. The particular means for mounting valve  70  on a cartridge is not important, so long as elements,  71 ,  72  are free to pivot apart when its associated cartridge is activated. 
     In operation, when the first cartridge, which may or may not have a valve  70  mounted on it, is activated the resulting pressure wave cannot rupture membranes  26  because they are isolated from the pressure by the elements  71  and  72 . Only at such time as when each cartridge is activated by its own firing mechanism will the membrane be ruptured and elements  71  and  72 , pivoted away from the body of the cartridge. 
     While this invention has been described as having certain preferred features and embodiments, it will be understood that it is capable of change and modification within the spirit and scope of the invention and this invention is intended to cover all modifications, additions and variations that fall within the spirit of the invention and within the scope of the appended claims.