Note: Descriptions are shown in the official language in which they were submitted.
213 3 9 4 0 PAT~NT
INFLATOR A8SEMBLY
Field of the Invention
The present invention relates to an apparatus for
S inflating an inflatable device such as an air bag which
restrains an occupant of a vehicle during vehicle
deceleration indicative of a collision.
Backqround of the Invention
~n apparatus for inflating an inflatable vehicle
occupant restraint, such as an air bag, is disclosed in
U.S. Patent No. 5,184,846. The apparatus disclosed in the
'846 patent includes a container which stores gas for
inflating the vehicle occupant restraint. The apparatus
also includes an ignition chamber which contains an
ignitable propellant material. The propellant material,
when ignited, produces combustion products including heat
and gas for augmenting the gas in the container. The
ignition chamber is closed by a piston which blocks fluid
communication between the propellant material in the
ignition chamber and the gas in the container.
The apparatus disclosed in the '~46 patent further
includes an iyniter for igniting the propellant material
_ ~ ~ 3 3 ~ ~ ~
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upon the occurrence of a vehicle collision. The resulting
combustion products cause the gas pressure in the ignition
chamber to increase to an elevated level. The gas pressure in
the ignition chamber then moves the piston into an actuated
position. When the piston moves into the actuated position,
it opens the container to release the gas to flow from the
container to the vehicle occupant restraint. The piston also
opens fluid communication between the ignition chamber and the
container. The combustion products in the ignition chamber
are thus released to flow into the container to increase the
pressure and quantity of the gas in the container.
Summary of the Invention
In accordance with a first broad aspect of the
present invention, an apparatus for inflating an inflatable
device includes a pressure vessel means, an ignitable material
and a cup member. The pressure vessel means defines a sealed
storage chamber containing inflation fluid for inflating the
inflatable device. The pressure vessel means has walls which
encircle an axis and which define a ring shaped portion of the
storage chamber centered on the axis. The pressure vessel
means further has a closure wall which is rupturable to open
an outlet opening through which the inflation fluid flows
outward from the storage chamber. The ignitable material
produces combustion products including heat for heating and
pressurizing the inflation fluid in the storage chamber.
The cup member is located radially inward of the
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ring shaped portion of the storage chamber, and has a piston
portion which is movable between an unactuated position and an
actuated position. The piston portion of the cup member
includes a plunger means for rupturing the closure wall upon
movement of the piston portion from the unactuated position to
the actuated position. The cup member further has a
rupturable portion which holds the piston portion in the
unactuated position.
The apparatus further includes an igniter means for
igniting the ignitable material and for causing pressure to
develop a thrust against the cup member. The thrust ruptures
the rupturable portion of the cup member, and propels the
piston portion of the cup member from the unactuated position
to the actuated position.
According to a second broad aspect, the present
invention provides apparatus for inflating an inflatable
device, said apparatus comprising: means for defining a sealed
storage chamber containing inflation fluid for inflating the
inflatable device, said means having walls which encircle an
axis and which define a ring shaped portion of said storage
chamber which is centered on said axis, said means further
having a closure wall which is rupturable to open an outlet
opening through which said inflation fluid flows outward from
said storage chamber; an ignitable material which produces
combustion products including heat for heating and
pressurizing said inflation fluid in said storage chamber; a
burst cup located radially inward of said walls which define
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said ring shaped portion of said storage chamber, said burst
cup including a chamber wall means for enclosing said
ignitable material in a combustion chamber; said burst cup
having a piston portion which is movable between an unactuated
position in which said piston portion blocks the passage of
said combustion products from said combustion chamber to said
storage chamber and an actuated position in which said piston
portion does not block the passage of said combustion products
from said combustion chamber to said storage chamber, said
piston portion of said burst cup including a plunger means for
rupturing said closure wall upon movement of said piston
portion from said unactuated position to said actuated
position, said burst cup further having a rupturable portion
which holds said piston portion in said unactuated position;
and igniter means for igniting said ignitable material and for
thus causing said combustion products to develop a thrust
against said chamber wall means, said thrust rupturing said
rupturable portion of said burst cup and propelling said
piston portion of said burst cup from said unactuated position
to said actuated position.
According to a third broad aspect the present
invention provides apparatus for inflating an inflatable
device, said apparatus comprising: means for defining a sealed
storage chamber containing inflation fluid for inflating the
inflatable device, said means having walls which encircle an
axis and which define a ring shaped portion of said storage
chamber centered on said axis, said means further having a
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closure wall which is rupturable to open an outlet opening
through which said inflation fluid flows outward from said
storage chamber; a first ignitable material which produces
first combustion products including heat for heating and
pressurizing said inflation fluid, said first ignitable
material being located in said storage chamber radially inward
of said ring shaped portion of said storage chamber; an
ignition cup located radially inward of said walls which
define said ring shaped portion of said storage chamber, said
ignition cup having a piston portion which is movable between
an unactuated position and an actuated position, said piston
portion of said ignition cup including a plunger means for
rupturing said closure wall upon movement of said piston
portion from said unactuated position to said actuated
position, said piston portion of said ignition cup further
including a wall means for defining a pressure chamber; said
ignition cup further including a rupturable means for holding
said piston portion in said unactuated position, said
rupturable means blocking fluid communication between said
pressure chamber and said storage chamber; and igniter means
for igniting said first ignitable material, said igniter means
including a second ignitable material which produces second
combustion products, said igniter means directing said second
combustion products into said pressure chamber to develop a
thrust against said piston portion of said ignition cup, said
thrust rupturing said rupturable means to open fluid
communication between said pressure chamber and said storage
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chamber, said thrust further propelling said piston portion of
said ignition cup from said unactuated position to said
actuated position.
Brief description of the Drawinqs
Further features of the present invention will
become apparent to those skilled in the art to which the
present invention relates from reading the following
description with reference to the accompanying drawings, in
which:
Fig. 1 is a view of a vehicle steering column and a
vehicle occupant restraint apparatus constructed as a first
embodiment of the present invention;
Fig. 2 is a perspective view, partly in section, of
parts of the apparatus of Fig. 1;
Fig. 3A is a side view of the parts shown in Fig. 2;
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_4- ~ 2133990
Fig. 3~ is a view showing the parts of Fig. 3A in a
partially actuated condition;
Fig. 4 is a view showiny the parts of Fig. 3A in a
fully actuated condition;
Fig. 5 is an enlarged side view, partly in section, of
parts shown in Fiqs. 2-4;
Fig. 6 i5 a side view, partly in section, of parts of
a vehicle occupant restraint apparatus which is constructed
as a second embodiment of the present invention; and
Fig. 7 is a view showing the parts of Fig. 6 in an
actuated condition.
Description of Preferred Embodiments
A first embodiment of the present invention is a
vehicle occupant restraint apparatus 10, as shown in Fig.
1. The apparatus 10 includes an inflatable air bag 12, an
! inflator 14 and a cover lG. The air bag 12 is received
over the inflator 14 in a folded condition, as shown
schematically in Fig. 1. The inflator 14 has a plurality
of gas outlet openings 1~ which direct gas from the
inflator 14 to the air bag 12 when the air bag 12 is to be
inflated. The cover 16 encloses the air bag 12 and the
inflator 14 and has a relatively weak portion 20. The air
bag 12, the inflator 14 and the cover 16 are parts of a
module 22 which is mounted on a vehicle steering column 24
at the center of ~he steering wheel 26.
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As shown schematically in Fiy. 1, the vehicle occupant
restraint apparatus lO further includes an electrical
circuit 30. The electrical circuit 30 includes a power
source 32, which is preferably the vehicle battery or a
capacitor, and a normally open switch 34. The switch 34 is
preferably part of a deceleration sensor 36. The
deceleration sensor 36 senses the occurrence of a
predetermined amount of vehicle deceleration indicative of
a collision, and closes the switch 34 upon sensing the
occurrence of such deceleration. When the switch 34 is
closed, electric current passes through the inf lator 14 to
actuate the inflator 14.
When the inflator 14 is actuated, a large volume of
inflation fluid, preferably an inert gas, emerges rapidly
from the gas outlet openings 1~ and f lows into the air bag
~, 12 to inf late the air bag 12. As the air bag 12 begins to
inflate, it moves forcefully against the cover 16 and
breaks the cover lG at the relatively weak portion 20. As
the air bag 12 continues to inflate, it moves outward past
the broken cover 16 and into the space between the driver
of the vehicle and the steering wheel 26 to restrain
movement of the driver.
As shown in greater detail in Figs. 2-4, the inflator
14 includes a pressure vessel 40 and an actuator assembly
Z5 42. The pressure vessel 40 contains pressurized gas, which
is preferably argon at approximately 3000 psi, for
inflating the air bag lZ. The actuator assembly 42
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operates to release the gas from the pressure vessel 40
when the switch 34 in the electrical circuit 30 ~Fig. 1) is
closed upon the occurrence of a vehicle collision, as
described above. The actuator assembly 42 further operates
to increase the pressure and quantity of the gas.
The pressure vessel 40 has a plurality of walls which
define a sealed storage chamber 44. The walls of the
pressure vessel 40 include an outer wall 46, a core wall
48, an upper end wall 50 and a lower end wall 52, each of
which is preferably formed of stainless or low carbon
steel. The outer wall 46 extends as a ring around a
central axis 54, and has a C-shaped radial section which is
open at the radially inner side of the radial section. The
outer wall 46 thus has an annular upper edge surface 56 and
an annular lower edge surface 58, both of which are
, centered on the axis 54.
The core wall 48 has a tubular shape centered on the
axis 54, and extends axially between the upper and lower
edge surfaces 56 and 5~ of the outer wall 46. The core
wall 48 and the outer wall 46 thus define a radially outer
portion 60 of the storage chamber 44 which extends
circumferentially entirely around the axis 54 in the shape
of a ring.
A plurality of first inner edge surfaces 62 of the
core wall 48 define a circumferential row of first gas flow
openinys 64 extending radially through the core wall 48
near the upper end of the core wall 48. A plurality of
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. .
second inner edge surfaces 66 of the core wall 48 similarly
define a circumferential row o~ second gas flow openings 68
extending radially through the core wall 48 near the lower
end of the core wall 48.
The upper end wall 50 of the pressure vessel 40 has a
circular flange portion 70 projecting radially outward from
a cylindrical body portion 72, both portions being centered
on the axis 54. The flange portion 70 of the upper end
wall 50 is supported on a circular, radially extending
upper shoulder surface 74 of the core wall 48. The body
portion 72 of the upper end wall 50 has a circular lower
edge surface 76 and an inner peripheral surface 75 which
define a central outlet opening 77 in the body portion 72
below the flange portion 70. The body portion 72 further
has a plurality of inner edge surfaces 78 above the flange
portion 70. The inner edge surfaces 78 define the gas
outlet openings 18 in a row extending circumferentially
around the axis 54. The upper end wall 50 of the pressure
vessel 40 is thus designed as a diffuser for the gas.
The lower end wall 52 of the pressure vessel 40 also
has a circular shape centered on the axis 54, and is
supported against a circular, radially extending lower
shoulder surface 80 on the core wall 48. The lower end
wall 5Z has upper and lower side surfaces 82 and 84,
respectively. An inner edge surface 86 of the lower end
wall 52 defines a circular opening ~8 extending through the
center of the lower end wall 52. The adjoining surfaces of
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the outer wall 4G, the core wall 48, the upper end wall 50
and the lower end wall 52 are connected to each other by
welds (not shown) so as to block leakage of gas between the
adjoining surfaces. The outer wall 46 is preferably
friction welded to the core wall 48, but could be MIG
welded to the core wall 48. The core wall 48 is preferably
MIG welded to the upper and lower end walls 50 and 52.
The pressure vessel 40 further includes a closure wall
90 and an inner diffuser wall 92. The closure wall 90 is a
circular burst disk with a flat peripheral portion 94 and a
dome shaped central portion 96. The peripheral portion 94
of the closure wall 90 is welded, preferably TIG welded, to
the lower edge surface 7G of the upper end wall 50. The
central portion 9G of the closure wall 90 extends across
the opening 77.
~, The inner diffuser wall 92 has a cylindrical shape
with upper and lower end surfaces 98 and 100, respectively.
The upper end surface 98 is welded, preferably TIG welded,
to the peripheral portion 94 of the closure wall 90. A
plurality of inner edge surfaces 104 of the inner diffuser
wall 92 define a circumferential row of gas flow openings
106 extending radially through the inner diffuser wall 92.
As shown in Figs. 2-4, the actuator assembly 42 is
supported in the inflator 14 radially inward of the core
wall 4~. The actuator assembly 42 includes a burst cup
150, an iyniter 152, and a body of ignitable propellant
material 154.
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The burst cup 150 has a plunger portion 160 and a base
162. The plunger portion 160 of the burst cup 150 has a
relatively narrow cylindrical shape centered on the axis
54, and includes an upper end wall 164 which closes the
upper end of the burst cup 150. The base 162 of the burst
cup 150 has a wider cylindrical shape centered on the axis
54, and includes both a circular, radially extending
intermediate wall 165 and a cylindrical side wall 166 of
the burst cup 150. The cylindrical side wall 166 is open
at the lower end of the burst cup 150, and has a
cylindrical outer surface 168 which adjoins the cylindrical
inner surface 170 of the core wall 48. The cylindrical
outer surface lG8 thus extends over the second gas flow
openings 68 in the core wall 48.
The cylindrical side wall lG6 of the burst cup 150
, further includes a flange 172 at its lower end, and has a
circular lower edge surface 174. The lower edge surface
174 has a recessed portion 176. The recessed portion 176
of the lower edge surface 174 defines a rupturable stress
riser portion 178 of the burst cup 150 between the recessed
porti.on 176 and the cylindri.cal outer surface 168.
The flange 172 on the burst cup 150 is closely
received between adjoining surfaces of the core wall 48 and
the lower end wall 52 of the pressure vessel 40. One or
more welds (not shown), preferably TIG welds, connect the
adjoining surfaces of the flange 172, the core wall 48 and
the lower end wall 5Z securely to each other to block
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leakage of gas between those adjoining surfaces. A
radially inner portion 180 of the storage chamber 44 is
thus defined between the burst cup 150, the core wall 48,
the upper end wall 50, and the closure wall 90. The
radially inner portion 180 of the storage chamber 44
communicates with the radially outer portion 60 through the
first gas flow openings G4 in the core wall 48.
As shown in detail in Fig. 5, the igniter 152 includes
a cylindrical metal casing 190 containing an ignition
charge material 192. The ignition charge material 192 is
ignited upon the passage of e]ectric current between a pair
of electrical terminals 194, as is known. When the
ignition charge material 192 is ignited, it produces
combustion products which rupture the casing 190 and emerqe
upwardly ~rom the casing 190. The ignition charge material
'I 192 preferably comprises Bl~N03, but could have any suitable
alternative composition known in the art.
As further shown in detail in Fig. 5, the igniter 152
includes a nylon body 200 and a metal retainer 202 which
support the casing 190 and the terminals 194. The body 200
has major inner surfaces 204 and 206 defining a cylindrical
compartment 20~ in which the casing 190 is received. The
body 200 also has a pair of minor inner surfaces 210
defining passages 212 through which the terminals 194
extend outward from the compartment 208. The casing 190
and the terminals 194 are received closely within the
compartment 208 and the passages 212, respectively, so as
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to block leakage of gas between the adjoining surfaces of
the casing 190, the body 200 and the terminals 194.
The body 200 of the igniter 152 further has a
cylindrical outer surface 220. A recessed portion 222 of
the outer surface 220 defines a circumferentially extending
notch 224. The notch 224 defines a rupturable stress riser
portion 22G of the body 200 radially between the notch 224
and the compartment 208. The stress riser portion 226
breaks under the force of the combustion products emerging
from the casing 190, and thus ensures that the force of the
combustion products will not break the body 200 at a
different location where the combustion products could leak
downwardly out of the igniter 152.
A cylindrical lower end portion 230 of the body 200
includes an inwardly projecting flange 232, and engages
complementary shaped surfaces of an upper end portion 234
of the retainer 202, as shown in Fig. 5. The lower end
portion 230 of the body 200 and the upper end portion 234
of the retainer 202 thus establish a mechanical interlock
which holds the body 200 on the retainer 202.
The retainer 202 further has a circular base plate
portion 236 with upper and lower side surfaces 238 and 240.
A cylindrical inner surface 242 of the retainer 202 defines
a cavity 244 at the center of the retainer 202. The
terminals 194 extend through the cavity 244 from the body
200 to the plane of the lower side surface 240 of the
retainer 202.
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As shown in Figs. 2-4, the igniter 152 extends axially
into the burst cup 150 in the opening 88 at the center of
the lower end wall 52 of the pressure vessel 40.
Specifically, the body 200 of the igniter 152 is received
closely in the opening 88, and the upper side surface 238
of the retainer 202 abuts the lower side surface 84 of the
lower end wall 52. One or more welds (not shown),
preferably comprising a TIG weld between the lower end wall
52 and the base plate portion 236 of the igniter 152, bloc~
leakage of gas outward through the opening ~8 between the
igniter 152 and the lower end wall 52. A sealed combustion
chamber 260 is thus defined within the burst cup 150. The
combustion chamber 260 is closed at the upper end of the
burst cup 150 by the upper end wall 164, and is closed at
the lower end of the burst cup 150 by the igniter 152 and
the lower end wall 52 of the pressure vessel 40.
The body of ignitable propellant material 154 is
contained within the combustion chamber 260. In the
preferred embodiments of the invention, the propellant
material 154 is formed as a ring shaped body extending
circumferentially around the axis 54, and has the following
composltion:
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._
% BY Weiqht Inqredient
73 % Potassium perchlorate
8.7% Dioctyl adipate
6.6% Polyvinyl chloride
5 0.05% Carbon Black
0.15~ Stabilizers (Boron,
Chromium)
11.5% Potassium nitrate
Alternatively, the propellant material 154 could have
any other suitable composition known in the art, and also
could be formed in one or more pieces as known in the art.
An elastomeric cushioning ring 270, preferably formed of
silicone, holds the ring shaped body of propellant material
154 firmly in place between the intermediate wall 165 of
the burst cup 150 and the lower end wall 52 of the pressure
vessel 40.
A cylindrical igniter shield 280 also is located
within the combustion chamber 2G0. The igniter shield 280
extends closely around the cylindrical outer surface 220 of
the body 200 of the igniter 152, and extends axially from
the lower end wall 52 to the intermediate wall 165 of the
burst cup 150. The igniter shield 280 thus protects the
igniter 152 from damage which might otherwise be caused by
the intermediate wall 165 of the burst cup 150.
Specifically, the combustion chamber 260 is not pressurized
before the inflator 14 is actuated, while the storage
chamber 44 is fil].ed with the pressurized gas. The
pressure differential between the combustion chamber 260
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and the radially inner portion 1~0 of the storage chamber
44 causes the intermediate wall 165 of the burst cup 150 to
deflect downward toward the igniter 152. The igniter
shield Z80 blocks the downward deflection, as shown in Fig.
3A, while the storage chamber 44 is filled with the
pressurized gas.
When the inflator 14 is assembled into the module 22
shown in Fig. 1, the electrical circuit 30 extends through
the igniter 152 between the terminals 194. Therefore, when
the vehicle experiences a collision, the ignition charge
material 192 is ignited as a result of the passage of
electric current between the terminals 194 upon closing of
the switch 34. The combustion products which then emerge
from the casing 190 move forcefully against the burst cup
150 so as to lift the intermediate wall 165 upward from the
position shown in Fig. 3A to the position shown in Fig. 3B.
The intermediate wall 165 is thus moved off of the igniter
shield 2~0 to clear the way for the combustion products to
move throughout the combustion chamber 260 and into contact
with the propellant material 154 to ignite the propellant
material ~54. As the propellant material 154 burns in the
combustion chamber 260, it produces further combustion
products including heat and gas. As a result, the gas
pressure within the combustion chamber 260 increases
rapidly to an elevated level.
The increasing gas pressure within the combustion
chamber 260 results in a force which acts axially upward
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against the burst cup 150. When the force of the
increasing gas pressure reaches a predetermined elevated
level, it ruptures the stress riser portion 178 of the
burst cup 150. A severed piston portion 290 of the burst
5 cup 150 is thus released, as shown in Fig. 4, for movement
axially upward under the influence of the force of the gas
pressure within the combustion chamber 260. The force of
the gas pressure within the combustion chamber Z60 then
acts as a thrust which propels the piston portion 290 of
the burst cup 150 axially upward from the position of Fig.
3B to the position of Fig. 4. The lower end surface 100 of
the inner diffuser wall 92 serves as a stop surface to
limit upward movement of the piston portion 290 of the
burst cup 150.
When the piston portion 290 of the burst cup 150 moves
, axially upward from the position of Fig. 3B to the position
of Fig. 4, the plunger portion 160 of the burst cup 150
moves forcefully against and through the central portion 96
of the closure wall 90. The plunger portion 160 of the
burst cup 150 thus ruptures the closure wall 90 to open the
outlet opening 77 and to release the gas from the storage
chamber 44. Additionally, the portion of the cylindrical
side wall 166 which is included in the piston portion 290
of the burst cup 150 moves axially away from the second gas
25 flow openinys 68 in the core wall 48 to uncover the inner
ends of the second gas flow openings 68. The pressurized
combustion products within the combustion chamber 260 are
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thus released to flow radially outward through the second
gas flow openings 68 and into the radially outer portion 60
of the storage chamber 44. The heat and gaseous components
of those combustion products then increase the temperature,
pressure and quantity of the gas in the storage chamber 44.
As a result, a large volume of gas is rapidly directed from
the inflator 14 into the air bag 12 to inflate the air bag
12.
An inflator 300 constructed as a second embodiment of
the present invention is shown in Figs. 6 and 7. The
inflator 300 is a substitute for the inflator 14 in the
vehicle occupant restraint apparatus 10 of Fig. 1. The
inflator 300 thus includes a pressure vessel 302 and an
actuator assembly 304. The pressure vessel 302 contains
lS pressurized gas, which is preferably argon at approximately
~, 3000 psi, for inflating the air bag 12. The actuator
assembly 304 operates to release the gas from the pressure
vessel 302 when the switch 34 in the electrical circuit 30
(Fig. 1) is closed upon the occurrence of a vehicle
20 collision. The actuator assembly 304 further operates to
increase the pressure and quantity of the gas.
The pressure vessel 302 has a plurality of walls which
define a sealed storage chamber 305. The walls of the
pressure vessel 302 include an outer wall 306, a core wall
308, upper and lower end walls 310 and 312, and a closure
wall 314, each of which is centered on an axis 316. The
outer wall 306, the upper end wall 310 and the closure wall
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314 are substantially similar to the corresponding parts of
the pressure vessel 40 in the first embodiment of the
present invention described above. However, the core wall
308 and the lower end wall 312 in the pressure vessel 302
S differ somewhat from the core wall 48 and the lower end
wall 52 in the pressure vessel 40 in that the core wall 308
is formed as one piece with the lower end wall 312. The
walls of the pressure vessel 302 are formed of the same
material and are welded to each other in the same manner as
in the pressure vessel 40.
As in the pressure vessel 40, the adjoining surfaces
of the walls of the pressure vessel 302 are sealed together
by welds (not sllown) so as to block the leakage of gas
between the adjoining surfaces. The walls of the pressure
vessel 302 thus define a radially outer portion 320 of the
storage chamber 305 in the shape of a ring between the core
wall 308 and the outer wall 306. The walls of the pressure
vessel 302 further define a radially inner portion 322 of
the storage chamber 305. The radially inner portion 322
20 has a cylindrical shape extending axially within the core
wall 308 between the upper and lower end walls 310 and 312.
The radially outer portion 320 of the storage chamber 305
and the radially inner portion 322 are in fluid
communication witll each other through first and second gas
flow openi.ngs 324 and 326, respectively, in the core wall
308.
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The pressure vessel 302 further includes an inner
diffuser wall 330 with an upper end portion 332 and a lower
end portion 334. The upper end portion 332 of the inner
diffuser wall 330 is substantially similar to the inner
5 diffuser wall 92 in the first embodiment of the present
invention described above, and thus has a plurality of gas
flow openinqs 336 and an upper end surface 338 which is
welded, preferably TIG welded, to the closure wall 314.
The lower end portion 334 of the inner diffuser wall 330
includes a flange 340 which extends radially outward into
abutting engagement with the cylindrical inner surface 342
of the core wall 308. The flange 340 thus divides the
radially inner portion 322 of the storage chamber 305 into
upper and lower sections 344 and 346 which are located on
axially opposite sides of the flange 340. A cylindrical
, inner surface 350 of the inner diffuser wall 330 defines a
bore 352 centered on the axis 314.
A ring shaped body of ignitable propellant material
360 is contained within the storage chamber 305 in the
lower section 346 of the radially inner portion 322. The
propellant material 360 preferably has the composition set
forth above for the propellant material 154 in the first
embodiment of the present invention. An elastomeric
cushioning ring 362 holds the propellant material 360
25 firmly in place between the lower end wall 312 of the
pressure vesse]. 302 and the flange 340 on the inner
diffuser wal]. 330.
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The actuator assembly 304 in the inflator 300 includes
an ignition cup 370 and an igniter 372. The ignition cup
370 has a cylindrical shape centered on the axis 31G, and
has a piston portion 374 and a base 376. The piston
portion 374 of the ignition cup 370 has a cylindrical
plunger wall 380 which is closed at its upper end, a
circular, radially extending intermediate wall 38Z, and a
cylindrical side wall 384. The base 376 of the ignition
cup 370 also has a cylindrical side wall 386, and has an
open lower end which is defined in part by a flange 388. A
recessed peripheral surface portion of the ignition cup 370
defines a circumferential notch 390. The notch 390 in turn
defines a rupturable stress riser portion 392 of the
ignition cup 370 which is located axially between the
piston portion 374 and the base 376. The flange 388 at the
~, lower end of the ignition cup 370 is supported against an
annular lower shoulder surface 394 of the lower end wall
312.
The igniter 372 is the same as the igniter 152 in the
first embodiment of the present invention described above.
The igniter 372 thus has a cylindrical body 39G and a
circular base wall 398. The igniter 372 is centered on the
axis 316, with the body 396 adjoining the inner surfaces of
the intermediate wall 382 and the side walls 384 and 38G of
the ignition cup 370. The base wall 398 of the igniter 372
adjoins the lower surfaces of the flange 388 on the
ignition cup 370 alld the lower end wall 312 of the pressure
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vessel 302. One or more welds (not shown), preferably TIG
welds, block the leakage of gas between the adjoining
surfaces of the lower end wall 312, the ignition cup 370
and the base wall 398 of the igniter 372. The igniter 372
and the ignition cup 370 thus define a sealed pressure
chamber 400 within the ignition cup 370. An igniter shield
like the igniter shield 280 is not needed in the second
embodiment of the invention because the intermediate wall
382 of the ignition cup 370 has an outer surface area which
is small enough to preclude inward deflection of the
intermediate wall 382 under the pressure of the gas in the
storage chamber 305.
When the igniter 372 is actuated upon closing of the
switch 34 in the electrical circuit 30 (Fig. 1), the
igniter 372 expels combustion products into the pressure
chamber 400. The gas pressure within the pressure chamber
400 then increases rapidly to an elevated level at which
the force of the gas pressure acting against the ignition
cup 370 ruptures the stress riser portion 392 of the
ignition cup 370. The force of the gas pressure in the
pressure chamber 400 then acts as a thrust which propels
the piston portion 374 of the iynition cup 370 axially
upward from the position shown in Fig. 6 to the position
shown in Fig. 7. The cylindrical inner surface 350 of the
inner diffuser wall 330 guides the side wall 384 of the
piston portion 374 along the axis 31G so that the piston
portion 374 remains centered on the axis 316 as it moves
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from the position of Fig. 6 to the position of Fig. 7. The
upper end wall 310 of the pressure vessel 302 limits upward
movement of the piston portion 374, as shown in Fig. 7.
When the piston portion 374 of the ignition cup 370
5 moves from the position of Fig. 6 to the position of Fig.
7, it ruptures the closure wall 314 to release the gas from
the storage chamber 305. Additionally, the piston portion
374 of the ignition cup 370 releases the pressurized
combustion products in the pressure chamber 400 to flow
radially outward between the side wall 384 of the piston
portion 374 and the side wall 386 of the base 376. Those
combustion products thus move into the lower section 346 of
the storage chamber 305 to ignite the propellant material
360. The combustion products which result from combustion
15 of the propellant material 360, including heat and gas,
flow radially outward through the second gas flow openings
326 in the core wall 308 and throughout the storage chamber
305 to increase the pressure and quantity of the gas in the
storage chamber 305. Like the inflator 14 described above,
the infla~or 300 thus supplies a large volume of
pressurized gas which rapidly inflates the air bag 12.
However, the operation of the inflator 300 differs somewhat
from the operation of the inflator 14 in that the pressure
vessel 302 is opened substantially simultaneously with
ignition of the propellant material 360. In comparison,
the pressure vessel 40 is opened after the combustion
products of the propellant material 154 have developed the
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thrust which severs and moves the piston portion 290 of the
burst cup 150. The combustion products of the propellant
material 154 thus mix with the gas to increase the pressure
and quantity of the gas as the pressure vessel 40 is
opened. The combustion products of the propellant material
360 mix with the gas after the pressure vessel 302 is
opened. The inflator 300 thus tends to inflate the air bag
12 more gradually.
~rom the above description oE the invention, those
skilled in the art will perceive improvements, changes and
modifications. Such improveménts, changes and
modifications within the skill of the art are intended to
be covered by the appended claims.
