The invention relates to an inflator that may be used for
inflating an airbag.
WO 99/12775 A
teaches a device for inflating an airbag with compressed gas from a vessel.
In this prior art device it is necessary that the device components have exact dimensions
to avoid deviations in the force transmitted by a locking element for opening a
gas pressure container intended to inflate an airbag. In addition to requiring several
components to provide a locking feature at least one additional sealing component
is required to provide an air-tight containment for the gas under pressure. Ideally,
improved reliability and better precision can be achieved by reducing the number
The device of the present invention as set forth in Claim
1 overcomes this problem by providing a compressed gas filled inflator has a sealing
cap closure having a frangible chamber wall open to the compressed gas which is
sealed to an annular abutment wall with an outlet opening or passageway for discharging
the compressed gas when a triggering device breaks the frangible chamber wall so
the outlet opening or passageway is opened.
- Figure 1 is a longitudinal section of a prior art device.
- Figure 2 is a longitudinal section of a first embodiment of the invention.
- Figure 3 is a cross section of the first embodiment shown in figure 2 taken
at line 3-3 in figure 2.
- Figure 4 is a view of the first embodiment of figure 3 wherein the triggering
device is activated thereby breaking the frangible chamber wall of the sealing cap
- Figure 5 is a perspective view of the sealing cap closure.
- Figure 6 is an enlarged cross sectional view of the sealing cap closure.
Figure 1 shows a prior art inflator 90 taught in
WO 99/12775 A
that can be used for inflating an airbag with compressed gas from a vessel.
A gas storage vessel 100 includes an inflation head 104 that is contiguous to an
outlet opening 103. The outlet opening is closed by a sealing element 115 that can
be metal foil. The sealing element 115 is attached to a supporting disc 118 that
is located in the outlet opening 103. The supporting disc 118 is in turn supported
by a centrally arranged locking element 121 at an abutment 122 against the opening
forces exerted upon said sealing element 115 by the gas pressure inside the vessel
100. An opening device is fitted with a triggering mechanism 130 which, when actuated,
displaces locking element 121 and the sealing element 115, thereby opening the container
outlet 103 and inflating an airbag through the exhaust port housing 150. The locking
element 121 can be moved out of the locking position by a laterally acting force
that is produced by a piston 131 propelled by the triggering mechanism 130, to open
the gas outlet opening 103. It is suggested that to ensure that a pressure container
will open and that an appropriate amount of gas will be released, a throttling member
149 having a flow restrictor opening 132 be provided in the gas storage vessel 100
in the path of gas exhaust upstream from the outlet opening 103, with a pressure
chamber 146 between said throttling 149 and the outlet opening 103 in the bottleneck.
In the known device, the load on the supporting disc 118 produced by the compressed
gas is conveyed via the centrally located locking element 121 into the abutment
122 that is rigid with the vessel 100 containing compressed gas. For this purpose,
it is necessary that the device components have exact dimensions in order to avoid
deviations from the force transmission in the longitudinal axis of the locking element.
Figures 2-6 show an inflator 91 according to the present
invention for inflating an airbag. Each of the devices employs a means for sealing
the storage vessel 100 and storing compressed gas within the vessel with little
or no leakage.
With reference to figure 2 the prior art inflator 90 shown
in figure 1 has been modified to create an inflator 91 by replacing the sealing
element 115, the supporting disk 118, the locking element 121, and the abutment
122 with a single sealing cap closure 20 of the present invention. Optionally the
throttle 149 can be replaced as well.
With reference to figure 3 the gas storage vessel 100 of
the inflator 91 necks down to have walls 2 that abut with walls 105 of the inflation
head 104 that is contiguous with the outlet passageway or opening 103. Annular abutment
walls 106 project inwardly from the walls 105 of the inflation head 104 to define
the passageway or opening 103. A sealing cap closure 20 is inserted from the gas
vessel direction through the passageway 103 as shown. A flange 21 on the cap closure
20 extends outwardly around an open end of the cap closure 20 and is sealed in an
air-tight manner to a surface of the abutment wall 106, preferably welded to the
abutment wall 106.
A triggering mechanism 130 is aligned with a portion 20
of the cap closure as shown. The triggering mechanism 130 when actuated generates
gas that drives a piston 131 into the cap closure 20 breaking the cap closure 20
along a frangible portion 28 of a chamber wall allowing the compressed gases to
escape and be released out of the exhaust ports 152 of the housing 150 attached
to the inflation head 104 as illustrated in figure 4.
Interposed at the connection of the inflation head 104
and the exhaust port housing 150 is a filter or screen 30 which blocks any fragments
from the closure cap 20 from escaping into the inflating airbag through the exhaust
port openings 152. As shown the filter or screen 30 is preferably convexly curved
in the direction of the impinging cap portions for increased strength.
The closure cap 20 as shown in figures 2 and 3 has an internal
chamber 27 open to the compressed gas which is stored at pressure P1
of about 600 kPa as measured at ambient temperatures of about 25°C. Downstream
of the compressed gas on the opposite side of the cap closure 20 the pressure P2
in the inflation head 104 is approximately 1.0 bar or at atmospheric conditions.
Once the inflator triggering device 130 is activated the piston 131 breaks the wall
of a chamber portion 24 of the cap closure 20 along a seam line 28 between the larger
chamber portion 24. As shown the torn opening can be sized to act as a throttle
or choke point to control the rate of gas release and thereby eliminate the throttle
element 149 previously required in the prior art inflator if so desired.
The sealing cap closure 20 is illustrated in figures 5
and 6. The perspective view of the cap closure 20 shows the smooth outer surfaces
of the cap closure 20 which is preferably made from a single piece of drawn metal
or other structurally stable material produced in a deep draw process. The cap closure
20 as shown is preferably made of steel or aluminum or an alloy of such materials
having a thickness of about 0.5 mm prior to the drawing process. The cap closure
20 has a sealing flange 21 at the end of the enlarged chamber portion 22 as previously
noted. The enlarged chamber portion 22 is flared down 26 to a reduced sized closed
end chamber portion 24 as shown. Between the two chamber portions 22, 24 a thin
seam 28 having a thickness tmin is preferably provided to insure the
part breaks consistently at a known location. The chamber walls of each chamber
portion 22 and 24 have a thickness greater than the minimum thickness tmin.
Alternatively this seam line 28 can be on the internal surface or the external surface
of the cap closure 20 and cut or otherwise formed along seam line 28 by laser cutting,
machining, chemically etching or otherwise produced if so desired.
This secondary step to form the frangible tear or seam
line 28 is believed optional to accommodate any variations in material thickness
when forming the cap part 20 and is an optional manufacturing step that can be eliminated
assuming the dimensional characteristics can be controlled to provide a reliable
fracture by the piston 131 when it strikes the cap closure 20 upon triggering the
triggering means 130.
In a further alternative embodiment of the present invention
the cap closure 20 can be broken open by the explosive force of the triggering means
130 being directed onto the frangible portion of the cap closure without requiring
the assistance of the piston 131. In such an optimal design the triggering means
130 would employ a squib or ignition device with a sufficient amount of ignition
propellant to provide a force that impinges the cap closure 20 to cause the tearing
or fracturing of the frangible portion along the thin seam line 28. Although not
shown this alternative would be very similar to the device shown in figure 1, but
without the piston 131.
As illustrated the sealing cap closure 20 is ideally suited
for use with inflators employing a compressed gas. This includes hybrid inflators
having a pyrotechnic charge as well.