Projectile for initiating inflation of a motor vehicle inflatable safety system

A projectile for releasing a gas or other suitable fluid to initiate operation of an inflator in a motor vehicle inflatable safety system. In one embodiment, the projectile has a plurality of intersecting, concave, and inclined faces which taper to a point at the tip of the projectile. This projectile is positioned on the convex side of a dome-shaped disk which isolates the inflator from an expandable confinement. When a condition is detected requiring operation of the inflator, the projectile is freely propelled toward the disk to controllably separate the disk along lines coinciding with the edges defined by the intersecting faces of the projectile to reduce the potential for portions thereof breaking or tearing off and entering the flow from the inflator to the confinement.

FIELD OF THE INVENTION 
This invention generally relates to the field of motor vehicle inflatable 
safety systems and, more particularly, to such systems which initiate 
inflation by using a projectile to separate an isolating barrier in a 
controlled manner and create a flow path from an inflator to an inflatable 
confinement. 
BACKGROUND OF THE INVENTION 
Inflatable safety systems for motor vehicles have undergone significant 
development efforts in recent years due in part to an increased awareness 
as to their effectiveness. These inflatable safety systems are typically 
activated upon receipt of a signal from an appropriate detector or sensor 
which indicates that inflation of the confinement is required. A variety 
of inflators are used by these systems to expand the confinement in a 
manner which provides certain advantages. Many systems initiate inflation 
by "removing" an isolation between the confinement and the inflator. 
Thereafter, some inflating medium, whether it be pressurized gases, gases 
generated by combustion of a propellant, a mixture thereof, or other 
suitable fluids, is supplied to the confinement. 
A portion of the development efforts for inflatable safety systems have 
concentrated upon or at least addressed controlling the flow from the 
inflator to the confinement after inflation has been initiated. In order 
to provide a reliable inflatable safety system, not only must there be a 
sufficient flow of the inflating medium to the confinement in a timely 
manner, but the confinement itself must remain structurally intact 
throughout operation. One proposed alternative for achieving these two 
fundamental objectives concentrates on the material selection for various 
components of the inflator. 
U.S. Pat. No. 3,567,245 to Ekstrom, issued Mar. 2, 1971, discloses 
utilizing certain materials for the barrier which provides the initial 
isolation between the inflator and the confinement. In one embodiment, the 
isolating barrier is a friable or fragmentable material which is 
disintegrated or comminuted by the activation of an explosive device 
positioned therewithin to initiate inflation. The resultant materials, 
which are apparently of a sufficiently small size, are then forced through 
various passageways by the exiting pressurized fluid used for inflation 
and thus presumably enter the confinement. The utilization of an 
elastomeric material, particularly an RTV rubber, in this type of 
configuration is also suggested since the resultant materials allegedly do 
not damage the confinement due to their resiliency. Another embodiment 
includes an isolating barrier having preformed grooves thereon such that 
when the explosive device is activated, the barrier breaks into sections 
defined by the grooves. These resultant sections are able to pass through 
the passageways so as to not block the flow of fluid to the confinement, 
and thus also presumably enter the confinement. 
U.S. Pat. No. 3,900,211 to Russell et al., issued Aug. 19, 1975, discloses 
selecting an appropriate material for the component used to release a 
poppet to initiate inflation. Generally, a poppet is positioned in a 
discharge conduit connected to a source of pressurized fluid to initially 
prohibit flow therefrom. A support tube assists in maintaining the poppet 
in this closed position and also separates the poppet from a pyrotechnic 
charge. Upon receiving a signal that inflation is required, the 
pyrotechnic charge is activated to disintegrate the supporting structure. 
The pressure exerted on the face of the poppet by the stored fluid 
thereafter moves the poppet to expose a discharge outlet to initiate the 
flow. Due to the positioning of the support tube between the poppet and 
the pyrotechnic charge and the travel of the poppet toward the charge 
after the activation thereof, the disclosure indicates that there is no 
expulsion of support tube or pyrotechnic residue in the fluid stream. 
In recognition that fragments or other foreign materials generated upon 
activation of the inflator may enter into the flow and adversely affect 
the overall performance of the inflatable safety system, such as by 
restricting the flow rate through blocking passageways to the confinement 
or by damaging the confinement when propelled against the interior 
surfaces thereof, filtering-type devices were incorporated to remove these 
fragments and other foreign materials. U.S. Pat. Nos. 3,618,980 to Leising 
et al., issued Nov. 9, 1971; U.S. Pat. No. 3,822,895 to Ochiai, issued 
Jul. 9, 1974; and U.S. Pat. No. 4,114,924 to Kasagi et al., issued Sep. 
19, 1978, are representative of these efforts. Leising et al. discloses in 
one embodiment the positioning of a vane structure between a propellant 
chamber and an inflatable bag. When a collision is sensed and the 
propellant within the propellant chamber is ignited, the by-products 
thereof flow through the vane structure. Heavier particles are thrust 
outwardly by the vanes and are directed to a trap where they are retained 
until converted into a gas or until the bag is inflated. However, the 
gases generated by the burning of the propellant flow to the confinement. 
In another embodiment, a screen structure is used to prevent molten liquid 
masses of propellant from entering into the inflatable bag while allowing 
gases to pass through alternate passageways. 
Ochiai discloses a filtering apparatus positioned in the discharge area of 
a receptacle containing a source of an inflating gas. A cup-shaped 
barrier, having a convex side which faces the stored gas and a concave 
side which contains a rupture inducing means, initially contains the gas 
within the receptacle. When the cup-shaped barrier is ruptured, gas flows 
through the filter and to the gas bag. However, the broken pieces of the 
cup-shaped barrier are prevented from entering the gas bag by the filter. 
Kasagi et al. discloses positioning a collecting chamber between an 
inflator and an inflatable safety bag to collect fragments or pieces 
generated by the removal of the initial isolating structure between the 
inflator and the inflatable bag. More particularly, the collecting chamber 
is positioned near a bent portion (illustrated as a 90.degree. bend) of 
the conduit connecting the inflator and bag in substantial alignment with 
the conduit prior to making the bend. Consequently, as the gas and any 
fragments generated by removal of the isolating barrier approach the 
collecting chamber, the inertial forces possessed by the heavier fragments 
direct them to continue into the aligned collecting chamber where they are 
trapped while the gases flow around the bend in the conduit and are 
directed to the inflatable bag. Various other embodiments address 
structural modifications of the collecting chamber and/or the conduit, as 
well as the positioning of certain collecting materials within the 
collecting chamber. 
The above-described filtering-type devices for controlling flow from the 
inflator to the confinement suffer from a number of deficiencies. For 
instance, filtering or collecting devices may not retain all of the 
particles generated upon activation of the inflator. Consequently, some 
particles may pass through the filtering device and become lodged in a 
passageway to restrict the flow to the confinement or some may enter the 
confinement, both of which may adversely affect performance of the 
inflatable safety system. Even if the filtering device properly functions 
and retains all of the generated particles, this may in and of itself 
introduce a further flow restriction to the confinement by blocking an 
entire passageway or a portion thereof. Furthermore, these filtering-type 
devices also add to the material and subsequent maintenance costs of the 
inflator. 
As a result of the above deficiencies with systems which address 
controlling flow by concentrating on the by-products generated by the 
removal of the isolation between the inflator and the confinement, recent 
efforts have begun to utilize methods of initiating inflation which reduce 
the quantity of activation by-products. One possible alternative is the 
use of a projectile to "remove" the isolating member. 
Representative of punching-type projectiles include U S. Pat. Nos. 
3,788,667 to Vancil, issued Jan. 29, 1974, and U.S. Pat. No. 3,869,143 to 
Merrell, issued Mar. 4, 1975, which generally disclose the use of a 
ramming, piston-like member to remove a barrier isolating the inflator 
from the confinement after an appropriate signal is received by the 
respective activating apparatus. These barriers have grooves formed 
thereon to provide predetermined break lines such that when the ramming 
member impacts the barrier, the barrier is completely removed from its 
supporting structure to initiate inflation. 
French Patent No. 2,557,251, issued Jun. 28, 1985, discloses releasing a 
fluid under pressure by using a projectile. More particularly, a plurality 
of metal particles (i.e., lead shot) are directed to and "burst" a 
cup-shaped diaphragm to release the pressurized fluid. Not only does there 
not appear to be a mechanism for trapping the lead shot after having been 
fired (i.e., the lead shot may restrict flow by collecting in a passageway 
and/or may enter the confinement to which the source is connected), but it 
does not appear that the referenced "bursting" of the disk by the 
disclosure would indicate any desire to reduce the amount of byproducts 
generated upon activation. 
U.S. Pat. No. 3,836,170 to Grosch et al., issued Sep. 17, 1974, generally 
discloses a variety of projectiles for initiating inflation. In one 
embodiment, a piston-like ramming member is used to remove the isolating 
barrier which has rupture lines placed thereon and is therefore similar to 
that disclosed by Vancil and Merrell discussed above. In another 
embodiment, a cylindrically-shaped projectile positioned in a tubular 
guide is directed toward the isolating barrier by the activation of a 
pyrotechnic charge. A trap positioned beyond the barrier collects the 
projectile, the by-products of the activation of the pyrotechnic charge, 
and presumably portions of the isolating barrier, all of which allegedly 
do not impede the flow of gas through the plurality of exiting 
passageways. Another embodiment utilizes a blunt nosed projectile (i.e., 
one which tapers to a degree but not to a point) and an isolating barrier 
which appears from the drawings to be dished out on the downstream side of 
the projectile which is exposed to a portion of the source of compressed 
gas. When the blunt-nosed projectile impacts the dished out barrier on its 
substantially planar side, the barrier is allegedly torn in a star-shaped 
manner and the projectile and other by-products of activation are caught 
in a trap so that the flow of gas is not impeded. Although the blunt-nosed 
projectile embodiment is alleged to produce a star-shaped tear in the 
isolating barrier, this particular design would not produce a consistent 
tear-pattern on the barrier. Initially, it would appear that a portion of 
the barrier, coinciding essentially with the area of the blunt-nosed face 
of the projectile, would be "punched out" by the impact of the projectile 
and become completely separated from other portions of the barrier. 
However, assuming no punched out portion is produced, the potential for 
portions of the barrier breaking off and entering the flow still exists. 
Although thee is no explicit disclosure as to the type of surface forming 
the tapered portion of the projectile, it appears from the drawings that 
this surface is smooth. Consequently, this surface would not cut or 
otherwise separate the barrier in a predetermined manner as it passed 
therethrough, but instead the barrier would tear along lines dictated, in 
part, by the stresses in the barrier. 
As a general rule of manufacturing processes, the thickness of a piece of 
metal stock determines, in part, the radius of a bend which may be formed 
without cracking or shearing the stock in the region of the bend. When the 
radius of a bend in a piece of stock becomes less than the initial 
thickness thereof, the potential for the development of cracks in the bend 
or the shearing of the stock in this region increases. Consequently, when 
it is desirable to achieve a cutting action in this region, the stock may 
be "bent" at a radius which is less than the thickness thereof, and 
preferably at a radius which is significantly less than the thickness to 
ensure shearing or cutting takes place in this region. 
Assuming that the blunt-nosed projectile configuration of Grosch et al. 
would not completely punch out any portion of the isolating barrier, the 
smooth surface over the tapered portion of the projectile would, based 
upon the foregoing, bend versus cut the barrier as it passed therethrough 
since there is no disclosed "edge" which would cause a controlled cut or 
shear (i.e., the radius of the tapered surface is not, from the drawings, 
less than the thickness of the isolating barrier). The resultant bending 
of the barrier by the penetrating projectile would therefore cause the 
barrier to "tear" along lines dependent upon, in part, the existing 
stresses in the barrier. Therefore, the separation of the barrier by the 
blunt-nosed projectile configuration of Grosch et al. is not controlled 
(i.e., the pattern for the tearing will typically vary dependent upon 
various factors), thereby creating the potential for separating the 
barrier in a manner which would result in portions thereof breaking off 
and entering the flow. 
French Patent Nos. 1,147,005, issued Nov. 18, 1957, and 2,543,658, issued 
Oct. 5, 1984, each generally disclose a projectile for releasing a 
pressurized fluid from a container. The disclosed projectiles taper to a 
point and appear to be continuously smooth over the entire tapered 
surface. The apparent smoothness of the tapered portions of the projectile 
would also produce inconsistent and uncontrolled results in "removing" or 
separating a barrier as discussed above due to the resultant bending of 
the barrier (based upon the radius of the tapered portion) and subsequent 
uncontrolled "tearing" of the barrier along lines dependent, in part, upon 
the stresses therewithin. In fact, French Patent No. 2,543,658 discloses 
that the projectile utilized therein actually "shatters" the isolation 
which would generate and introduce numerous particles into the system, and 
thus does not even recognize the desirability of controlling the amount of 
byproducts generated by separation of the barrier. 
Canadian Patent No. 967,192, issued May 6, 1975, discloses another 
projectile head design for releasing a compressed gas. A spring loaded 
plunger extends through a bottle of compressed gas. When a collision is 
sensed, the plunger is driven through the diaphragm which isolates the 
compressed gas from the inflatable member to release the gas. The end of 
the plunger appears to have a series of unjoined (i.e., non-intersecting), 
inclined planar surfaces which, although tapered, do not appear to taper 
to a point. The resultant projectile is thus of the blunt-nosed 
configuration utilized by Grosch et al. which suffers from the above-noted 
deficiencies. Moreover, it is not apparent from the drawings and the 
disclosure does not appear to indicate that this projectile head 
configuration would cut an isolating member in a consistent manner to 
reduce fragmentation. Since the inclined faces of the projectile do not 
intersect, the edges formed by the inclined faces would bend versus cut 
the barrier, due to the radius of the edge in relation to the diaphragm, 
resulting in the type of inconsistent and uncontrolled "tearing" of the 
diaphragm as addressed above. 
SUMMARY OF THE INVENTION 
The present invention releases gases or other fluids in a manner which does 
not result in any significant amount of foreign materials entering the 
flow from the source of such gases or fluids. In one embodiment, the 
present invention includes a housing having a source of gas or other 
appropriate fluid, a barrier to initially contain the gas within the 
housing, and a projectile positioned on one side of the barrier. When 
release of the gas is desired, the projectile is propelled toward the 
barrier to penetrate, pass through, and separate the barrier in a 
controlled manner which creates a path for the flow of gas from the 
housing. Due to the controlled separation of the barrier, the barrier 
remains substantially intact after being penetrated by the projectile 
which reduces the potential for the generation of fragments or other 
foreign materials. Consequently, the potential for a restricted flow due 
to collection of debris in passageways connecting the source of gas and 
the article to receive the gas, as well as the potential for such debris 
actually entering the article, is significantly reduced. Therefore, the 
present invention is particularly useful in inflatable safety systems for 
motor vehicles. 
The configuration of the projectile contributes to the performance of the 
present invention, namely by controlling the separation of the barrier. 
One embodiment of the projectile utilizes a plurality of inclined, 
intersecting faces which converge to substantially a point at the tip of 
the projectile. The pointed tip of the projectile effectively penetrates 
the barrier and the intersection of the adjacent faces produces a 
plurality of edges which, as the projectile passes through the barrier, 
cut the barrier along lines defined by these edges. In order to further 
enhance the definition of these edges to obtain a more effective cutting 
action, which further improves the controlled separation of the barrier, 
the faces of the projectile in another embodiment are concavely-shaped to 
effectively "raise" the edges to a sharper degree. 
The effective result of the above-described configuration of the projectile 
is that the barrier is separated into a number of substantially 
triangularly-shaped petals coinciding with the number of faces and edges 
possessed by the projectile. These individual petals each remain attached 
to the perimeter of the barrier and point in the direction of the flow. 
Consequently, the barrier is separated in a controlled manner by the 
described cutting action of the projectile to produce an end configuration 
for the barrier which reduces the potential for portions thereof breaking 
off and entering the flow. 
The configuration of the barrier itself also contributes to the performance 
of the present invention. In one embodiment, the barrier is a dome-shaped 
disk having a concave and convex side. Preferably, the concave side is 
exposed to the pressurized gas which is therefore exerting forces thereon, 
while the convex side faces the projectile. This configuration is 
advantageous in that when the projectile initially contacts the convex 
portion of the disk in its central region, the disk is dimpled which 
increases the stresses in the disk. Consequently, as the projectile 
penetrates the disk and the above-defined edges of the projectile initiate 
the separation lines thereon by the described cutting action, the disk 
stresses introduced by the dimpling, as well as the forces exerted on the 
concave side of the disk by the pressurized gas, assist in the separation 
of disk along lines defined by the edges of the projectile. 
Based upon the foregoing, it can be appreciated that the present invention 
is particularly useful with inflatable safety systems for motor vehicles 
which generally consist of some type of inflator and an expandable 
confinement. In this regard, the projectile is suitably attached to a 
squib or other similar electroexplosive device which is commonly connected 
to a collision, impact, or deceleration detector. When an appropriate 
signal is received by the squib, the projectile is propelled through the 
barrier to yield the above-described results. Thereafter, the inflator 
supplies the gas or another fluid to the confinement by a variety of 
methods. The flow of gas thus provided to the confinement is essentially 
free from debris which could potentially adversely affect the performance 
of the inflatable safety system. 
The present invention offers a number of advantages not previously provided 
for by known gas release mechanisms for inflatable safety systems. For 
instance, the present invention concentrates on reducing the materials 
generated in releasing the gas. Consequently, the need for additional and 
sometimes complex connectors between the inflator and the confinement is 
eliminated. Relatedly, the need for additional components such as filters, 
which may not effectively remove all particles and which may also become 
plugged to further adversely affect the performance of the inflator, is 
also eliminated. By choosing an appropriate number of inclined faces and 
thus cutting edges for the projectile, the present invention consistently 
releases a gas without generating an amount of fragments which could 
adversely affect the performance of the inflator and/or the inflatable 
confinement.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be described with reference to the accompanying 
drawings which illustrate the pertinent features thereof. Generally, the 
present invention is an apparatus which releases gases or other fluids 
from a container without introducing any significant amount of fragments 
or other debris into the flow from the container. Although the present 
invention may be used in all applications where it is desirable to release 
any source of gas or other fluid, the fragmentation reduction feature of 
the present invention makes it particularly useful in motor vehicle 
inflatable safety systems. 
Referring to FIG. 1, a typical inflatable safety system 22 is generally 
illustrated. The primary components of such an inflatable safety system 22 
include a detector 26, an inflator 30, and an expandable confinement 158. 
When the detector 26 senses a condition requiring expansion of the 
confinement 158, a signal is sent to the inflator 30 to release gases or 
other suitable fluids from the inflator 30 to the confinement 158 via the 
conduit 154. Although one particular type of inflator 30 will be described 
herein, it will be appreciated that the present invention may be used with 
a wide variety of inflators 30, including those which only contain a 
source of pressurized gas or other fluid, those which utilize a source of 
pressurized gas in combination with a propellant which is ignited at some 
point during inflation to augment the flow, or those systems which utilize 
only the ignition and subsequent combustion of a propellant to expand the 
confinement 158. 
One embodiment of an inflator 30 with which the present invention may be 
used is illustrated in FIG. 2. Generally, the inflator 30 includes a 
stored gas housing 34 which contains a source of pressurized gas, a 
pressurized, dome-shaped isolating disk 38 which contains the gas within 
the stored gas housing 34 until a condition requiring inflation is sensed 
by the detector 26 (FIG. 1), an activator assembly 58 which effects the 
release of the gas from the stored gas housing 34 by separating the disk 
38 in a controlled manner (discussed in detail below) to initiate flow to 
the confinement 158 (FIG. 1), and a gas generator 110 which augments the 
flow to the confinement 158 (FIG. 1) after the initial expansion thereof 
by ignition and subsequent combustion of a propellant 146 contained 
therein. 
In operation of the inflator 30 of FIG. 2, the detector 26 (FIG. 1) will 
sense a condition requiring operation of the inflatable safety system 22 
and thereafter send a signal through the leads 78 to the activation 
assembly 58 which is positioned in close proximity to the disk 38. The 
activation assembly 58 includes an electroexplosive device 74 having a 
projectile 82 appropriately attached thereto. Upon receipt of this signal, 
the electroexplosive device 74 propels the projectile 82 toward the disk 
38 to penetrate and separate the disk 38 in a controlled manner (discussed 
below) to allow to begin flowing from the stored housing 34, through the 
interior discharge ports 66, the discharge connector 62, the exterior 
discharge ports 70, the conduit 154, and into the confinement 158. Due to 
the effective diameter of the projectile 82, it is unable to pass through 
the exterior discharge ports 70 and is thus retained within the inflator 
30 during inflation. 
A gas generator 110 is coaxially positioned within the stored gas housing 
34 to augment the flow to the confinement 158 after having been initially 
expanded by the flow of pressurized gas from the stored gas housing 34. 
This augmented flow is initiated in response to certain changing 
conditions, one of which is a change in pressure, and thus the inflator 30 
utilizes a reference chamber 114 having a pressurized gas contained 
therein by a cup-shaped, bistable diaphragm 118 which assists in 
activating a propellant 146 contained within a propellant chamber 142. 
In its first position, the convex surface of the diaphragm 118 is exposed 
to the gas within the reference chamber 114 while its concave surface is 
exposed to the gas within the stored gas housing 34 via the plurality of 
pressure ports 126 positioned in the wall of the gas generator 110 and the 
divider 130 positioned between the diaphragm 118 and the propellant 
chamber 142. Consequently, as gas flows from the stored gas housing 34 to 
the confinement 158 after the above-described controlled separation of the 
disk 38 by the projectile 82, the pressure on the initial concave surface 
of the diaphragm 118 decreases in relation to the pressure within the 
reference chamber 114 which continues to exert forces on the convex 
surface of the diaphragm 118. After a certain differential pressure 
develops, the diaphragm 118 rapidly inverts into its second position 
(i.e., the convex surface now faces the propellant chamber 142) to propel 
an impacting mass 122 into engagement with a percussion primer 138 to 
ignite the propellant 146. The propellant gases generated by the 
combustion of the propellant 146 then exit the propellant chamber 142 
through the gas generator ports 150 to augment the flow to the confinement 
158 through the above described passageways. 
An important aspect of the present invention is the controlled separation 
of the disk 38 in a manner which not only allows for a sufficient, timely 
flow from the inflator 30 to the confinement 158 (FIG. 1), but which 
allows the disk 38 to remain substantially intact to significantly reduce 
the amount of foreign materials which are generated upon activation of the 
inflator 30. The configuration of the projectile 82 contributes to this 
controlled separation of the disk 38 and embodiments of the projectile 82 
are illustrated in FIGS. 3-8. Although the disk 38 is illustrated as being 
dome-shaped in FIGS. 2, 9-10, and 15, the advantages of which will be 
discussed below, other configurations may be appropriately separated by 
the projectile 82 in the desired controlled manner. 
Specifically referring to FIGS. 3-5, the projectile 82 includes a plurality 
of inclined, intersecting faces 86 which converge to a point at the tip 90 
of the projectile 82. The intersection of these faces 86 thereby define a 
plurality of edges 94 which are used to initiate separation of the disk 38 
along lines coinciding with the edges 94. As will be discussed in more 
detail below, preferably each face 86 is of substantially the same size 
and configuration, resulting in the edges 94 being substantially equally 
spaced to separate the disk 38 into substantially equally-sized petals 54, 
each of which remain attached to a rim 42 positioned on the perimeter of 
the disk 38 and which point in the direction of the flow as illustrated in 
FIGS. 11-12 and 15. 
The pointed tip 90 allows the projectile 82 to effectively penetrate the 
disk 38 without removing any significant material portions thereof (i.e., 
no significant portion of the disk 38 is punched out and separated from 
remaining portions of the disk 38 by the penetrating projectile 82). As 
the projectile 82 advances through the disk 38, the edges 94 cut the disk 
38 along lines coinciding with the edges 94. This cutting action is 
achievable since the projectile 82 tapers outwardly from its tip 90 to the 
base 98 (i.e., the effective diameter of the projectile 82 increases from 
the tip 90 to the base 98). Moreover, each edge 94 possesses a sufficient 
"sharpness" to cut or shear the pressurized disk 38 along lines coinciding 
with the edges 94. This is a primary requirement in achieving controlled 
separation of the disk 38 to produce a consistent end configuration 
thereof which will remain substantially intact throughout operation of the 
inflator 30 so as to not adversely affect the performance thereof by 
introducing fragments or other foreign materials into the flow. The 
cutting or shearing of the disk 38 is greatly enhanced by the high stress 
level in the disk 38 due to pressure of the gas on the concave side 50 of 
the disk 38. 
As a general rule of manufacturing process, the thickness of a piece of 
metal stock determines, in part, the radius of a bend which may be formed 
without cracking or shearing the stock. When the radius of a bend for a 
piece of metal stock becomes much smaller than the initial thickness of 
the stock, the potential for the development of cracks in the bend or the 
actual shearing of the stock in this region increases. Consequently, if it 
is desirable to achieve a cutting or shearing action in this region, the 
stock should be bent at a radius which is much less than its thickness. 
The thickness of a typical disk 38 used by inflators 30 of the type 
described herein is approximately 0.010 inch. Therefore, based upon the 
foregoing general rule, the radius "R" defined by the intersection of the 
faces 86 of the projectile 82 which defines an edge 94, best illustrated 
in FIG. 6, should be less than 0.010 inch in order to achieve the desired 
cutting action. However, in order to ensure that the desired cutting or 
shearing action is achieved in these regions, the radius R should be 
significantly less than the thickness of the disk 38, and in this case the 
radius R should thus preferably be less than 0.002 inch. 
In order to enhance the definition of the edges 94 on the projectile 82, 
the faces 86 may have a certain degree of concavity as best illustrated in 
FIGS. 3, 4, and 7, although such concavity is not necessarily required 
(i.e., the edges 94 may already have a sufficiently small radius to 
produce the desired cutting action described above). The faces 86 taper 
downwardly from the edges 94 to produce the desired concavity. 
Consequently, the edges 94 are in essence "raised" to enhance separation 
of the disk 38 by producing a more effective cutting action. As can be 
appreciated, although a certain increased definition of the edges 94 will 
enhance the controlled separation of the disk 38 along the predetermined 
lines defined thereby, the point may be reached where such definition will 
undesireably increase the potential for portions thereof to break off from 
the remainder of the projectile 82 when passing through the disk 38. 
For purposes of comparison with the projectile 82 of FIGS. 3-8 and its 
configuration which allows for controlled separation of the disk 38 by the 
cutting or shearing thereof along predetermined lines, consider the 
conical projectile 162 of the type illustrated in FIG. 13 which is unable 
to consistently produce an end configuration of a disk 38 similar to that 
illustrated in FIGS. 11-12 and 17. The radius of the smooth, tapered 
surface 166 of the conical projectile 162 does not approach that which 
will induce shearing of the disk 38 in the region of the bend based upon 
the above-discussed principles of bending (i.e., the radius of the tapered 
surface is not sufficiently small to shear the disk 38 along predetermined 
lines). As the conical projectile 162 passes through the disk 38, the 
bending thereof will cause the disk 38 to tear along lines which coincide, 
in part, with the stresses within the disk 38, which may vary from case to 
case dependent upon a number of factors. An expected typical end 
configuration of a disk 38 using the conical projectile 162 is thus 
illustrated in FIG. 14. As is evident by the configuration of the disk 38 
in FIG. 14, the results are essentially unpredictable and there then 
exists a potential for portions of the barrier 38 breaking off and 
entering the flow from the inflator 30. 
Although the "sharpness" of each edge 94 of the projectile 82 is important 
to achieving the desired cutting action to produce a controlled separation 
of the disk 38, there are other contributing factors. For instance, the 
degree of the taper of the edges 94, as defined by the angle of 
inclination of the faces 86, affects the cutting action. In one 
embodiment, the faces are inclined at an angle of 45.degree. relative to 
the longitudinal axis of the projectile 82 (or 45.degree. relative to a 
horizontal plane touching the tip 90 as illustrated in FIG. 4) to provide 
an effective cutting action. Although the length of the edges 94 is 
directly affected by this angulation and the effective diameter of the 
projectile 82, the required length is more a function of the diameter of 
the disk 38 to be separated (discussed below), but it is nonetheless 
desirable for the length of each edge 94 to be substantially equal. In 
addition, the edges 94 of the projectile 82 should completely extend to 
the base 98 of the projectile 82 and maintain the above-described 
"sharpness" over the entire length thereof to in effect abruptly end the 
cut (although it may be continued by other forces as discussed below). Any 
rounding off of the edges 94 before reaching the base 98 of the projectile 
82 will potentially result in an uncontrolled tearing of the disk 38 after 
the projectile 82 passes therethrough to increase the potential for the 
breaking off of portions thereof. 
The projectile 82 should also be configured from its base 98 to its bottom 
102 so as to not interfere with the separation lines produced by the edges 
94 (i.e., the base 98 should substantially linearly connect the ends of 
the edges 94 such that if there are six edges 94, the projectile 82 will 
be substantially hexagonal). It may also be necessary or desirable to 
flatten out portions 100 of the projectile 82. Furthermore, the hardness 
of the projectile 82 and its edges 94 should preferably be quantitatively 
greater than that of the disk 38 to ensure the desired cutting action is 
achieved. Since a typical disk 38 is made from inconel 625, one suitable 
material for the projectile 82 is stainless steel. 
When the above-described configuration of the projectile 82 penetrates and 
passes through a substantially circular disk 38, the cutting action 
produces an end configuration of a disk 38 which has a number of 
triangularly-shaped petals 54, which remain attached to the rim 42 of the 
disk 38, and which coincide with the number of edges 94 and faces 86 of 
the projectile 82 as illustrated in FIGS. 11-12 and 17. For instance, if 
the projectile 82 has six similarly sized faces 86, the separated disk 38 
will consistently have six similarly sized petals 54 as illustrated in 
FIG. 11, whereas if the projectile 82 has three similarly sized faces 86, 
the separated disk 38 will consistently have three similarly sized petals 
54 as illustrated in FIG. 12. 
The resultant number of petals 54 into which the disk 38 is separated 
directly affects the desired reduction in potential for portions of the 
disk 38 breaking off and entering the flow. For instance, as the number of 
petals 54 decreases, there is naturally a corresponding increase in their 
individual size. Consequently, the "width" of the base of these petals 54 
where they remain attached to the rim 42 of the disk 38 also increases. 
When this base width of the petals 54 increases to a certain degree, the 
point may be reached where the material stresses in this region may 
promote an uncontrolled tearing of the disk 38. As a result, portions of 
the disk 38, although initially separated in a controlled manner by the 
projectile 82, may tear or break off because of these stresses and 
subsequently enter the flow from the inflator 30. 
Increasing the number of petals 54 reduces the individual size thereof and 
thus the "width" of the petals 54 where attached to the rim 42 of the disk 
38, which thus also reduces stresses in the disk 38 in these regions. 
However, as the number of petals 54 is increased, the point may be reached 
where the base of the petals 54 becomes sufficiently small such that 
individual petals 54 may break or be torn off by the flow from the 
inflator 30. Moreover, the point will be reached where the plurality of 
intersecting faces 86 will approach a smooth surface such as possessed by 
the conical projectile 162 illustrated in FIG. 13. (i.e., the radius R 
(FIG. 6) of the edges 94 will increase such that the desired cutting 
action will not be achievable due to the above-discussed bending 
principles). Consequently, the disk 38 will tear in a manner dictated not 
by the cutting action of the edges 94, but primarily by the stresses in 
the disk 38 generated by the bending action of the projectile 82, thereby 
increasing the potential for portions thereof to break or tear off and 
enter the flow. Again, an expected end configuration of a disk 38 after a 
projectile 82 possessing too many edges 94 which approaches the 
configuration of the conical projectile 162 of FIG. 13 has passed 
therethrough is illustrated in FIG. 14. 
Based upon the foregoing, in order to achieve the desired cutting action to 
consistently produce an end configuration of a disk 38 which will not 
introduce any significant amounts of material into the flow, the number of 
faces 86 and thus edges 94 for the projectile 82 could range from 4-10, 
and preferably should range from 5-8. A hexagonal projectile 82 (i.e., six 
faces 86) has produced particularly desirable results. 
The projectile 82 of the described configuration is propelled toward the 
disk 38 to produce the desired controlled separation thereof. In this 
regard, the projectile 82 is initially attached to the end of the 
electroexplosive device 74 as best illustrated in FIGS. 2 and 15. Numerous 
methods may be used to attach the projectile 82 to the electroexplosive 
device 74 such as by molding, crimping, or using an adhesive. When the 
detector 26 (FIG. 1) senses a condition requiring expansion of the 
confinement 158 (FIG. 1), the electroexplosive device 74 (FIGS. 2 and 15) 
is activated to propel the projectile 82, without the use of an external 
guide or other similar bore, toward the disk 38 (FIGS. 2 and 16). Since an 
external guide is not used, the projectile 82 may have a cavity 106 
positioned on its bottom 102 such that the forces of the electroexplosive 
device 74 are concentrated thereon as best illustrated in FIGS. 7-8. In 
order to enhance this desired concentration of forces, an extension 75 of 
the electroexplosive device 74 which contains, for instance, black powder, 
may fit within the cavity 106 of the projectile 82 (FIGS. 7-8). 
Consequently, the need for a separate external guide, which increases 
material costs and which may require further structural considerations, is 
eliminated. Instead, the projectile 82 motion is initially guided by the 
fit of the cavity 106 of the projectile 82 over the extension 75 of the 
electroexplosive device 74. 
The configuration of the disk 38 also contributes to the controlled 
separation by the projectile 82. A dome-shaped disk 38 which has a concave 
side 46 and a convex side 50 may be used to achieve similar results as 
best illustrated in FIGS. 9-10 and as generally illustrated in FIGS. 2 and 
15. Preferably, the concave side 46 is exposed to the gas within the 
stored gas housing 34 (FIG. 2) while the convex side 50 is positioned to 
face the projectile 82 (FIG. 2). This particular configuration offers a 
number of advantages in reducing the number of fragments generated upon 
release of the gas from the stored gas housing 34 and in permitting the 
electroexplosive device 74 with its attendant lead wires 76 to be 
positioned outside the pressurized compartment of the stored gas housing 
34. 
Referring to FIGS. 15-17, the disk 38 will initially be in a stressed 
condition due to the exertion of forces on the concave side 46 thereof by 
the pressurized gas within the stored gas housing 34 (FIG. 2). When the 
projectile 82 is propelled toward and initially contacts the disk 38, the 
disk 38 will "dimple" in as illustrated in FIG. 16 and begin to "pierce" 
the disk 38. This dimpling of the disk 38 further increases the stresses 
therewithin. When the disk 38 is penetrated by the projectile 82, these 
stresses are released and assist in the separation of the disk 38 along 
the lines defined by the edges 94 of the projectile 82 (i.e., the desired 
cutting action is enhanced). Further contributing to the controlled 
separation of the disk 38 along these lines is the flow of gas from the 
stored gas housing 34. Consequently, the end result is a plurality of 
petals 54 of substantially similar size which point in the direction of 
the flow which further reduces the potential for portions thereof breaking 
off and entering the flow from the inflator 30 as illustrated in FIG. 17. 
When using a disk 38 of the above described "dome-shaped" configuration, 
the diameter of the projectile 82 need not necessarily be similar to that 
of the disk 38 to ensure that controlled separation thereof is achieved. 
For instance, due to the stresses in the disk 38 resulting from the 
above-described initial "dimpling" of the disk 38 from the projectile 82 
and the forces exerted on the concave side 46 of the disk 38 by the gas 
from the stored gas housing 34, the edges 94 of the projectile 82 do not 
have to cut the disk 38 all the way to the rim 42 to achieve full 
separation. As long as the controlled cut has reached a certain distance, 
these other forces will complete the separation of the disk 38 in a 
controlled manner without significantly increasing the risk for portions 
thereof breaking off. In fact, the diameter of the projectile 82 may be 
approximately one-half of that of the disk 38 without generating or 
undesirably increasing the potential for generating any significant amount 
of fragments. 
In operation of the present invention when incorporated into an inflatable 
safety system 22 of the type illustrated in FIGS. 1-2, the detector 26 
will send a signal to the electroexplosive device 74 when activation of 
the inflatable safety system 22 is required. After the electroexplosive 
device 74 receives the signal, the projectile 82 is propelled through the 
disk 38 to achieve the above-desired results. When a hexagonally 
configured projectile 82 has been initially positioned approximately 1/4" 
from the disk 38 and propelled toward the disk 38 at an initial velocity 
ranging from 500-600 feet/second, particularly desirable results have been 
obtained. Thereafter, gas will flow from the stored gas housing 34 into 
the confinement 158 without any significant amount of foreign materials 
therein which could adversely affect performance of the inflatable safety 
system 22. Moreover, since the diameter of the projectile 82 is greater 
than that of the individual interior and exterior discharge ports 66, 70, 
the projectile 82 will be retained within the inflator 30 during operation 
so as to not enter the confinement 158. 
The foregoing description of the invention has been presented for purposes 
of illustration and description. Further, the description is not intended 
to limit the invention to the form disclosed herein. Consequently, 
variations and modifications commensurate with the above teachings, and 
the skill or knowledge of the relevant art, are within the scope of the 
present invention. The embodiments described hereinabove are further 
intended to explain best modes known of practicing the invention and to 
enable others skilled in the art to utilize the invention in such, or 
other, embodiments and with the various modifications required by the 
particular applications or uses of the invention. It is intended that the 
appended the claims be construed to include alternative embodiments to the 
extent permitted by the prior art.