A vehicle airbag (12) includes an inflatable bag (20) and an inflation-controlling member (40) which is coupled to the bag (20). The inflation-controlling member (40) includes a releasable connection (42) and a stretchable section (44). The releasable connection (42) remains intact during initial stages of the inflation process so that the inflation-controlling member (40) extends to an initial length L.sub.initial and the bag (20) assumes an initial shape. The releasable connection (42) releases during intermediate stages of the inflation process so that the inflation-controlling member (40) extends to an intermediate length L.sub.intermediate and the bag (20) assumes an initial shape. The stretchable section (44) stretches during the final stages of the inflation process so that the inflation-controlling member (40) extends to a final length L.sub.final and the bag (20) assumes a final shape.

FIELD OF THE INVENTION 
This invention relates generally, as indicated, to an airbag 
inflation-controlling member. More particularly, the present invention 
relates to an inflation-controlling member that, when incorporated into an 
airbag, allows for a three-stage inflation process in which an 
out-of-position occupant will be protected and an in-position occupant's 
contact with the bag will be of a relatively gentle nature. 
BACKGROUND AND SUMMARY OF THE INVENTION 
An airbag assembly is commonly installed in a vehicle to protect an 
occupant in the event of a crash or collision. A typical airbag assembly 
comprises a reaction device, an airbag coupled to the reaction device, and 
an inflator also coupled to the reaction device. The reaction device is 
coupled to a structural component of the vehicle. For example, in a 
passenger-side airbag assembly, the airbag assembly will commonly be 
incorporated into the dashboard or instrument panel of the vehicle. 
The airbag will almost always include a bag which is made of a flexible 
fabric, such as nylon, and which is designed to be fully inflated to a 
desired geometry. For example, in a passenger-side airbag assembly, the 
bag will usually be adapted to inflate to a roughly cylindrical or 
pillow-like shape. The bag will include portions defining a chamber and a 
mouth portion defining an inflation fluid inlet which communicates with 
the chamber. 
At the onset of a crash or collision, the inflator supplies inflation fluid 
to the bag to inflate the airbag towards the occupant. More particularly, 
the inflation fluid flows through the bag inlet and into the chamber to 
inflate the airbag. During the inflation process, the kinetic energy of 
the inflation fluid imposes forces upon the airbag. The airbag is 
subjected to initial forces during initial stages of the inflation 
process, intermediate forces during intermediate stages of the inflation 
process, and final forces during final stages of the inflation process. 
An airbag is generally designed so that when it is fully inflated to a 
final shape, a front or "occupant-contacting" portion of the airbag will 
contact an occupant situated in the expected position in the associated 
vehicle seat. In this manner, the in-position occupant is cushioned 
against impact with a structural part of the vehicle. For a passenger-side 
airbag, an in-position occupant is situated adjacent the side of the 
vehicle opposite the steering wheel and his/her torso is located adjacent 
the back of the passenger seat. 
As the occupant contacts the airbag, he/she will be subjected to any forces 
created during the inflation process which are not absorbed by the airbag. 
Thus, if an airbag does not adequately absorb such forces, the occupant 
may be subjected to them. Accordingly, one of applicant's airbag design 
concerns is the dissipation of these forces prior to the airbag contacting 
the occupant so that his/her contact will be of a relatively gentle 
nature. 
Another of applicant's airbag design concerns is the protection of an 
out-of-position occupant. As was indicated above, an airbag is generally 
designed so that its occupant-contacting portion will contact an occupant 
situated in the expected position. However, in some instances, an occupant 
may not be positioned in this manner and may instead be situated towards 
the center of the seat and closer to the instrument panel. 
The present invention provides an airbag inflation-controlling member which 
controls the shape of an inflatable bag and absorbs forces imposed on the 
bag during the inflation process. Specifically, the inflation-controlling 
member causes the bag to assume a shape compatible with protecting an 
out-of-position occupant during the initial stages of the inflation 
process. Additionally, the inflation-controlling member dissipates kinetic 
energy prior to the bag contacting an in-position occupant so that such 
contact will be of a relatively gentle nature. 
More particularly, the present invention provides a vehicle airbag 
comprising an inflatable bag and an inflation-controlling member which is 
coupled to the bag. The inflation-controlling member extends through the 
chamber of the bag during the inflation process and controls the shape of 
the bag. The inflation-controlling member includes a releasable connection 
and a stretchable section. The releasable connection remains intact during 
the initial stages of the inflation process so that the 
inflation-controlling member extends to an initial length and the bag 
assumes an initial shape. The releasable connection releases during 
intermediate stages of the inflation process so that the 
inflation-controlling member extends to an intermediate length and the bag 
assumes an intermediate shape. The stretchable section stretches during 
the final stages of the inflation process so that the 
inflation-controlling member extends to a final length and the bag assumes 
a final shape. The initial shape of the bag is designed to protect an 
out-of-position occupant and the final shape of the bag is designed to 
protect an in-position occupant. 
Preferably, the inflation-controlling member comprises a tether having a 
first end attached to the bag and a second end also attached to the bag. 
The releasable connection and the stretchable section are positioned on 
the tether intermediate the first and second ends. The first end of the 
tether is attached to the mouth portion of the bag and the second end of 
the tether is attached to the occupant-contacting portion of the bag. 
More preferably, the inflation-controlling member is a three-piece tether 
comprising a first end piece, a second end piece, and a central piece 
joining the first end piece to the second end piece. The first and second 
end pieces include the first and second ends of the tether, respectively. 
The releasable connection joins intermediate portions of the first and 
second end pieces together and the central piece comprises the stretchable 
section of the inflation-controlling member. The releasable connection may 
be formed with break-away stitching. The stretchable section may be made 
of a material having a 45.degree. weave pattern. 
Thus, the present invention provides a tether-like member for controlling 
the shape of an inflatable bag and absorbing forces imposed on the bag 
during an inflation process. When incorporated into an airbag, the 
tether-like member allows for a three-stage inflation process in which an 
out-of-position occupant will be protected and an in-position occupant's 
contact with the bag will be of a relatively gentle nature. 
In the past, airbags have been developed which incorporate tether-like 
members having either a releasable connection or a stretchable section. 
For example, U.S. Pat. No. 3,879,056 to Kawashima et al. discloses an 
airbag including a member which is secured to side portions of the bag. 
The member includes a central folded part having a releasable connection 
formed by break-away stitching. The releasable connection is designed so 
that when an occupant contacts the bag, the stitching is broken, the 
central folded part is released, and the member expands from a first 
length to a second length. In this manner, the rebounding force of the 
airbag is absorbed or dissipated. 
Additionally, U.S. Pat. No. 4,966,389 to Takada discloses an airbag in 
which four tether-like members extend between, and are connected to, the 
mouth portion of the bag and the occupant-contacting portion of the bag. 
The members are connected to the mouth portion of the bag by a fastener 
which includes resilient portions composed of 45.degree. bias material. 
During the latter stages of the inflation process, the members abruptly 
arrest the movement of the occupant-contacting portion of the bag thereby 
imposing significant high tensile forces on the members. The resilient 
portions of the fastener absorb the high tensile forces to prevent 
separation of the members from the mouth of the bag. 
Thus, the prior art discloses tether-like members having either a 
releasable connection or a stretchable section. However, the prior art 
members are not believed to allow for a three-stage inflation process in 
which an out-of-position occupant will be protected and an in-position 
occupant's contact with the bag will be of a relatively gentle nature. 
Applicant therefore believes that a need remains, and that present 
invention satisfies such a need, for an inflation-controlling member which 
accommodates design criteria associated with both out-of-position and 
in-position occupants.

DETAILED DESCRIPTION 
Referring now to the drawings in detail, and initially to FIG. 1-3, an 
airbag assembly 10 is schematically shown which incorporates an airbag 12 
according to the present invention. The airbag assembly 10 further 
comprises a reaction device 14 and an inflator 16. Although not 
specifically shown in the drawings, the airbag 12 and the inflator 16 are 
coupled to the reaction device 14 in a suitable manner. The reaction 
device 14 is adapted to be coupled to a structural part of a vehicle. The 
illustrated airbag assembly 10 is a passenger-side airbag assembly and is 
designed to be incorporated into the dashboard or instrument panel of a 
vehicle. 
The airbag 10 comprises a bag 20 which is made of a flexible fabric, such 
as nylon. In the illustrated passenger-side airbag assembly 10, the bag 20 
is adapted to be fully inflated to a roughly cylindrical or pillow-like 
shape. (See FIG. 3.) The bag 20 includes portions defining a chamber 22 
and a mouth portion 30 defining an inflation fluid inlet 31 which 
communicates with the chamber 22. 
At the onset of a crash or collision, the inflator 16 supplies inflation 
fluid to the airbag 12. More particularly, the inflation fluid flows 
through the bag inlet 31 and into the chamber 22 to inflate the bag 20. 
During the inflation process, the kinetic energy of the inflation fluid 
imposes forces upon the bag 20. The bag 20 is subjected to initial forces 
during the initial stages of the inflation process (see FIG. 1), 
intermediate forces during the intermediate stages of the inflation 
process (see FIG. 2), and final forces during the final stages of the 
inflation process (see FIG. 3). 
In the illustrated embodiment, the mouth portion 30 comprises a hem 32 
which defines a channel for a retainer 33. (See FIG. 4.) Although not 
specifically shown in the drawings, the retainer 33 may be used to secure 
the airbag 12 to the reaction device 14. The mouth portion 30 additionally 
includes a heat shield 34 which surrounds a top region of the inflation 
fluid inlet 31 and which shields the chamber-defining portions of the bag 
20 from heat transferred by the inflator 16. A series of stitch lines 35 
pass through the two layers of the hem 32 to capture the retainer 33 
within the hem 32. The top stitch lines 35 also pass through the heat 
shield 34 to secure the heat shield to top regions of the hem 32. The 
stitch lines 35 are designed to withstand any forces exerted during the 
inflation process. 
The airbag 12 is designed so that when the bag 20 is fully inflated, an 
"occupant-contacting" portion 36 of the airbag will contact an occupant 
situated in the expected position, or an in-position occupant. The 
occupant-contacting portion 36 (which is one of the chamber-defining 
portions of the bag 20) is located on a front region of the bag 20) 
approximately opposite of the fluid inlet 31. An internal fold 37, 
approximately 45-55 millimeters wide, is formed in a central region of the 
occupant-contacting portion 36 and projects into the chamber 22. (See 
FIGS. 5 and 6.) The internal fold 37 is held intact by a stitch line 38 
which is designed to withstand any forces exerted during the inflation 
process. 
The airbag 12 further comprises an inflation-controlling member 40 which is 
coupled to the bag 20 and which extends through the chamber 22. The member 
40 controls the shape of the bag 20 and absorbs forces imposed on the bag 
20 during the inflation process. More particularly, the 
inflation-controlling member 40 causes the bag 20 to assume a shape 
compatible with protecting an out-of-position occupant during the initial 
stages of the inflation process. Additionally, the inflation-controlling 
member 40 dissipates kinetic energy prior to the bag 20 contacting an 
in-position occupant so that such contact will be of a relatively gentle 
nature. 
The inflation-controlling member 40 includes a releasable connection 42 and 
a stretchable section 44. The releasable connection 42 remains intact 
during the initial stages of the inflation process so that the 
inflation-controlling member 40 extends to an initial length L.sub.initial 
and the bag 20 assumes an initial shape. (See FIG. 1.) The releasable 
connection 42 releases during intermediate stages of the inflation process 
so that the inflation-controlling member 40 extends from the initial 
length L.sub.initial to an intermediate length L.sub.intermediate and the 
bag 20 assumes an intermediate shape. (See FIG. 2.) The stretchable 
section stretches during the final stages of the inflation process so that 
the inflation-controlling member 40 extends from the intermediate length 
L.sub.intermediate to a final length L.sub.final and the bag assumes a 
final shape. (See FIG. 3.) 
The airbag 12 is designed so that when the inflation-controlling member 40 
reaches the initial length L.sub.initial, and the bag 20 assumes its 
initial shape, the airbag 12 will protect an out-of-position occupant. As 
is best seen by referring to FIG. the initial shape of the illustrated bag 
20 is a "double-hump" shape. The inflation-controlling member 40 limits 
the outward movement of the occupant-contacting portion 36 of the bag 20 
so that the bag takes on this initial "squashed" shape, when viewed from 
the side. 
The airbag 12 is also designed so that when the inflation-controlling 
member 40 is extended to the intermediate length L.sub.intermediate, and 
the bag 20 assumes its intermediate shape, the bag 20 is approaching, but 
has not reached, the fully inflated cylindrical or pillow-like shape of 
the bag 20. When the stretchable section 44 is stretched, and the 
inflation-controlling member 40 is extended to the final length 
L.sub.final, the bag 20 is fully inflated to its final shape. In this 
final shape, the airbag 12 is designed to protect an in-position occupant. 
The stretching of the section 44 (which causes the inflation-controlling 
member 40 to extend from the intermediate length L.sub.intermediate to a 
final length L.sub.final) dissipates kinetic energy created during the 
inflation process. In this manner, an in-position occupant's contact with 
the bag 20 is of a relatively gentle nature. 
In the preferred embodiment, the initial length L.sub.initial is 
approximately 96 millimeters, the intermediate length L.sub.intermediate 
is approximately 488 millimeters, and the final length L.sub.final is 
approximately 614-664 millimeters. Thus, the intermediate length 
L.sub.intermediate is at least three times, and preferably approximately 
five times, as great as the initial length L.sub.initial. Additionally, 
the final length L.sub.final is at least ten percent longer, and 
preferably twenty-five to thirty-six percent longer, than the intermediate 
length L.sub.intermediate. 
As is explained in more detail below, the releasable connection 42 is of a 
strength which withstands the initial forces but is overcome by the 
intermediate forces. In this manner, the releasable connection 42 remains 
intact during the initial stages of the inflation process, thereby 
allowing the inflation-controlling member 40 to extend to the initial 
length L.sub.initial and the bag 20 to assume the initial shape and 
further, in this manner, the releasable connection 42 releases during the 
intermediate stages of the inflation process, thereby allowing the 
inflation-controlling member 40 to extend to the intermediate length 
L.sub.intermediate and the bag 20 to assume the intermediate shape. 
As is also explained in more detail below, the stretchable section 44 is 
not affected, or stretched, during the initial or intermediate stages of 
the inflation process. Additionally, the elongation properties of the 
stretchable section 44 are such that the section will be elongated by the 
final forces. Thus, the stretchable section 44 is elongated only during 
the final stages of the inflation process, thereby allowing the 
inflation-controlling member 40 to extend from the intermediate length 
L.sub.intermediate to the final length L.sub.final. 
The inflation-controlling member 40 extends between, and is connected to, 
the mouth portion 30 and the occupant-contacting portion 36 of the bag 20. 
More particularly (see FIG. 4), a first end 46 of the 
inflation-controlling member 40 is sandwiched between the two layers of 
the bag hem 32 and is secured to the hem 32 by the stitch lines 35. 
Additionally (see FIGS. 5 and 6), a second end 48 of the 
inflation-controlling member 40 is attached to the internal fold 37 of the 
occupant-contacting portion 36 by a "BOX-X" stitch pattern 49. The stitch 
pattern 49 is also designed to withstand any forces exerted on it during 
the inflation process. 
The inflation-controlling member 40 is preferably a three-piece tether 
comprising a first end piece 50, a second end piece 52, and a central 
piece 54. (See FIGS. 7 and 8.) The tether pieces 50, 52, and 54 are each 
rectangular in shape. The end pieces 50 and 52 are essentially identical 
and approximately 118 millimeters long and approximately 76 millimeters 
wide. The central piece 54 is approximately 144 millimeters long and 
approximately 76 millimeters wide. One end of the piece 50 forms the first 
end 46 of the inflation-controlling member 40. Likewise, one end of the 
piece 52 forms the second end 48 of the inflation-controlling member 40. 
Thus, the end pieces 50 and 52 are attached to the bag 20. The opposite 
ends of the pieces 50 and 52 are attached to the central piece 54 by 
stitching lines 56. (See FIGS. 7 and 8.) The stitching lines 56 extend 
through overlapping regions (approximately 18 millimeters long) of the 
tether pieces. The stitching lines 56 are designed so that the attachment 
will not be destroyed during the inflation process. 
The releasable connection 42 joins intermediate portions of the tether end 
pieces 50 and 52 together. The releasable connection comprises a 
"break-away" stitch line 58. Although not specifically shown in the 
drawings, the stitch line 58 comprises twenty stitches formed from 69 
nylon thread and has an approximately 10 stitch/inch density. The span of 
the stitch line 58 is approximately 2/3 the width of the tether pieces and 
is centrally located relative to the lateral edges of the pieces. 
Additionally, the stitch line 58 is situated on the longitudinal centers 
of the end pieces 50 and 52. Thus, in the preferred embodiment, the span 
of the stitch line 58 is approximately 51 millimeters, and it is 
positioned approximately 94 millimeters from either end of the tether 
pieces 50 and 52. 
The tether pieces 50, 52 and 54 are preferably made of the same material, 
and more preferably made of 840 denier nylon coated on one surface. In the 
orientation of the inflation-controlling member 40 shown in FIGS. 7 and 8, 
the uncoated surfaces of the tether pieces face each other. The material 
of the tether end pieces 50 and 52 has a 90.degree. weave pattern 60. (See 
FIG. 7.) In other words, the fibers of the material are positioned at a 
90.degree. angle relative to either the longitudinal or lateral sides of 
the pieces 50 and 52. This 90.degree. weave pattern (or "bias") prevents 
the end pieces 50 and 52 from stretching or elongating during the 
inflation process. 
The material of the center piece 54 has a 45.degree. weave pattern 62. In 
other words, the fibers of the material are positioned at a 45.degree. 
angle relative to the ends and lateral edges of the piece 54. This 
45.degree. weave pattern (or "bias") allows the central piece 54 to 
stretch or elongate during the final stages of the inflation process. If 
the preferred material is used, the piece will elongate or stretch 50% to 
70%. It should be noted that the elongation or stretching of the central 
piece 54 need not be reversible. Thus, in comparison to an elastic piece, 
the central piece 54 need not return to its pre-elongation state when the 
force causing the elongation is eliminated. 
The stretchable section 44 of the inflation-controlling member 40 consists 
essentially of the central piece 54. During the initial stages of the 
inflation process, the initial forces are absorbed by the tether end 
pieces 50 and 52 and the releasable connection 42. It is only after the 
releasable connection 42 is released, and the tether end pieces 50 and 52 
are separated to extend the inflation-controlling member 40 to the 
intermediate length L.sub.intermediate, that the stretchable section 44 
will be subjected to elongation forces. Thus, the stretchable section 44 
is not affected by the initial and intermediate forces and is not 
elongated until the final stages of the inflation process. 
One may now appreciate that the present invention provides an airbag 
inflation-controlling member that, when incorporated into an airbag, 
allows for a three-stage inflation process in which an out-of-position 
occupant will be protected and an in-position occupant's contact with the 
bag will be of a relatively gentle nature. Although the invention has been 
shown and described with respect to a certain preferred embodiment, it is 
obvious that equivalent alterations and modifications will occur to others 
skilled in the art upon the reading and understanding of this 
specification. The present invention includes all such equivalent 
alterations and modifications and is limited only by the scope of the 
following claims.