Hybrid inflator with bore and burst disk

A cylindrically shaped hybrid inflator comprising: a pressure vessel filled with pressurized inflation gas, comprising a center body (22) having a first (24a) and a second (24b) end, a first exit orifice (29) located between the first and second end, a frangible disk (32) closing the orifice (29) and a pyrotechnic element for causing the disk to rupture and permit inflation gas to exit the orifice; a first cylindrical portion (50) sealingly attached to the first end and a second cylindrical portion sealing attached to the second end.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention generally relates to hybrid inflators. 
U.S. Pat. No. 5,351,988 is illustrative of a typical cylindrically-shaped 
hybrid inflator. The inflator includes a pressure vessel filled with an 
inert gas. One end of the pressure vessel is enclosed by a frangible disk. 
Positioned outside of the pressure vessel portion of the hybrid inflator 
are one or more exit ports. These exit ports historically have been 
located on one side of the inflator body. Upon actuation of the inflator, 
the frangible disk is broken and inflation gas flows asymmetrically into 
an air bag. If a more uniform air flow through the inlet or neck of the 
air bag is desired, the hybrid inflator is typically housed within a 
manifold such as that illustrated in U.S. Pat. No. 5,308,108. The use of 
the manifold obviously increases the weight of the overall unit. 
It is an object of the present invention to provide an improved hybrid 
inflator. A further object of the present invention is to provide a hybrid 
inflator having a symmetric air flow relative to the body of the inflator. 
Accordingly the invention comprises a hybrid inflator comprising: a 
pressure vessel filled with pressurized inflation gas, comprising a center 
body having a passageway and a first and a second end, a first exit 
orifice located between the first and second end, a frangible disk closing 
the orifice and first means for causing the disk to rupture and permit 
inflation gas to exit the orifice; a first cylindrical portion sealingly 
attached to the first end and a second cylindrical portion sealingly 
attached to the second end. In the preferred embodiment of the invention 
the exit orifice is located midway between the ends of the first and 
second cylindrical portions. The passageway of the center body includes 
facing converging nozzles having throats positioned on either side of the 
exit orifice. 
Many other objects and purposes of the invention will be clear from the 
following detailed description of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
Reference is made to FIGS. 1 and 2 which illustrate a hybrid inflator 20 
having a centrally located, hollow body 22 having an internal wall 23, 
defining a tapered through passageway or passage 25 and ends 24a and 24b. 
The body includes an upper section 26 and a lower section 28. The body 22 
is preferably fabricated by, but not limited to molding or casting bronze, 
steel or other suitable material. The upper section 26 includes an opening 
or exit orifice 29 and an annular ledge 30 about the orifice. The ledge 29 
supports a frangible, thin burst disk 32 that is peripherally welded 
thereon. The through passage 25 includes facing first and second 
converging nozzles 94a and 94b situated laterally on either side of the 
burst disk 32. Each nozzle 94a and 94b includes an upwardly curving end or 
throat portion 96a and 96b which channels the inflation gas flow generally 
upwardly, toward the orifice 29 and which encourages inflation gas to flow 
generally perpendicular to a longitudinal axis 31 running the length of 
the inflator and then directly into an air bag 102 positioned adjacent the 
inflator. The upper section 26 additionally includes a fill passage 34 
sealed by a ball or metal plug 36 that is welded in place after the 
inflator is pressurized with an inert inflation gas such as Argon or 
equivalent. Each end 24a and 24b includes an annular slot or groove 40a 
and 40b respectively. Positioned on each slot or groove 40a and 40b is an 
edge 40 of a respective cylindrical closure member 50. Each member may be 
welded or brazed to the body (see numeral 43). The central body 22 and two 
closure members 50 define the pressure vessel 100 of the inflator 20. Each 
cylindrical member 50 is typically fabricated of steel and includes a wall 
52 and end 54. The wall 52 and end 54 may be integrally formed as 
illustrated or alternatively, the end can be welded to a hollow, 
cylindrical sleeve. The lower section 28 of the body includes a central 
bore 60. Threadably received within the bore 60 is a pyrotechnic assembly 
generally shown as 80 comprising a squib 82 which includes a quantity of 
fast-burning propellant, an adjacently positioned larger quantity of 
slow-burning propellant 84, both of which are located within a generant 
housing 86. The generant housing includes a passage 90 which may be sealed 
by a second burst disk 92 to isolate the propellant 84 from the stored, 
pressurized inflation gas. As can be seen, the contoured walls 85 of the 
generant housing 86 form part of the nozzle throats 96a,b. A sliding 
piston 110 may optionally be located within passage 90. The piston 110 may 
include a through bore 112 through which products of combustion of the 
burning propellant may flow. 
In operation upon receipt of an activation signal communicated to the squib 
82, an intense flame is created causing the propellant 84 to burn. As the 
pressure builds up within the passage 90, the burst disk 92 is opened. The 
products of combustion produced upon the burning of the propellant 84 heat 
the inflation gas within the pressure vessel 100. The products of 
combustion (heat, flame or shock wave) also bear upon the burst disk which 
may cause the burst disk to rupture. If the sliding piston 110 is employed 
the buildup of pressure will propel the piston into the burst disk 32 
opening same. Alternately, the burst disk 32 may be ruptured in response 
to the buildup of pressure within the pressure vessel, however, this would 
slightly delay the opening of the burst disk in comparison to directly 
using the products of combustion or using the piston. Thereafter, the 
heated inflation gas is communicated to an adjacently positioned air bag 
102. 
Reference is briefly made to FIG. 5 which illustrates an alternate 
embodiment of the invention. The center body 22 proximate the orifice 29 
is provided with threads 150. A deflector cap 160 is secured to the body 
22 such as by using complementary threads. The deflector cap 160 includes 
a plurality of orifices 162 therein to deflect the inflation gasses 
radially (see arrows 164) relative to the center body 22 as shown in FIG. 
6. 
Many changes and modifications in the above described embodiment of the 
invention can, of course, be carried out without departing from the scope 
thereof. Accordingly, that scope is intended to be limited only by the 
scope of the appended claims.