Deployment door for use in a vehicle occupant restraint apparatus

An apparatus (10) comprises an inflatable occupant restraint (18) which, when inflated, protects an occupant in a vehicle passenger compartment. A deployment door (12) covers an opening (19) through which the occupant restraint (18) is deployed upon inflation of the occupant restraint. The deployment door (12) comprises a relatively soft first material layer (60) and a relatively hard second material layer (70). The relatively hard second material layer (70) includes (i) a first surface (77) which underlies the relatively soft first material layer (60), (ii) an inner surface (74) which is engaged by the occupant restraint (18) when the occupant restraint is inflated and (iii) a projecting portion (76) projecting beyond the first surface (77) and adhered to adjacent relatively soft material (66) of the soft first material layer (60). The projecting portion (76) and the adjacent relatively soft material (66) define a break line (30) such that the projecting portion and the adjacent relatively soft material move away from each other along the break line to uncover the opening (19) when the inflatable occupant restraint (18) is deployed into the passenger compartment.

TECHNICAL FIELD 
The present invention relates to a vehicle occupant restraint apparatus 
which includes an inflatable vehicle occupant restraint, such as an air 
bag, and particularly relates to a deployment door which covers an opening 
through which the inflatable vehicle occupant restraint is deployed upon 
inflation of the inflatable vehicle occupant restraint. 
BACKGROUND ART 
Deployment doors for use in an inflatable vehicle occupant restraint 
apparatus are known. A deployment door forms an interior portion of the 
vehicle, such as a portion of the instrument panel or the interior of the 
vehicle door, depending upon where the inflatable occupant restraint is 
mounted. A deployment door covers an opening through which an inflatable 
occupant restraint, such as an air bag, is deployed upon inflation of the 
air bag. When the air bag inflates, the air bag presses against the 
deployment door to open the deployment door. 
It is desirable to have a deployment door which is relatively soft to the 
touch, while at the same time rigid enough to provide the door with 
strength. Typically, tear lines have been molded in the deployment door so 
that the material of the door tears along the tear lines, and the door 
pivots open. The molding of tear lines in the deployment door is 
relatively difficult because such tear lines must be relatively thin. The 
materials used to make a deployment door generally become more brittle at 
low temperatures and may thus be more likely than other materials to 
suffer unintended breakage at the tear lines when cold. Also, since the 
tear lines are relatively thin, they could break during handling and/or 
installation of the deployment door. 
Further, it is desirable that the deployment door fit properly with the 
surrounding vehicle structure, such as the vehicle instrument panel, and 
have a finish which is appropriate for the surrounding vehicle structure. 
Still further, it is desirable to have a deployment door which can be 
manufactured reliably and at a reasonable cost. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an apparatus comprises an 
inflatable vehicle occupant restraint, such as an air bag, which when 
inflated, protects an occupant in a vehicle passenger compartment. A 
deployment door covers an opening through which the inflatable occupant 
restraint is deployed upon inflation of the inflatable occupant restraint. 
The deployment door comprises a relatively soft first material layer and a 
relatively hard second material layer. The relatively soft first material 
layer has an outer surface which is exposed to the vehicle passenger 
compartment. The relatively hard second material layer includes (i) a 
first surface which underlies the soft first material layer, (ii) an inner 
surface which is engaged by the inflatable occupant restraint when the 
inflatable occupant restraint is inflated and (iii) a projecting portion 
projecting beyond the first surface and adhered to adjacent relatively 
soft material of the soft first material layer. The projecting portion and 
the adjacent relatively soft first material define a break line. The 
projecting portion and the adjacent relatively soft material move away 
from each other along the break line to uncover the opening when the 
inflatable occupant restraint is deployed into the vehicle passenger 
compartment. 
Preferably, the relatively hard second material layer comprises a single 
piece of molded thermoplastic material and the relatively soft first 
material layer comprises a single piece of thermoplastic material which is 
molded to the hard second material layer. Also, preferably, the outer 
surface of the relatively soft first material layer lies flush with a 
surface of the projecting portion.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate a vehicle occupant restraint apparatus 10 that 
comprises an inflatable air bag 18 and an air bag reaction canister 16. 
The reaction canister 16 is secured to the vehicle by any suitable means, 
such as a bracket structure and fasteners (not shown). The air bag 18 is 
wrapped around and secured to a retaining ring 13 (FIG. 2) in a known 
manner. The retaining ring 13 is securely attached to the reaction 
canister 16 by suitable fasteners (not shown). The air bag 18 is, 
therefore, securely attached to the reaction canister 16. 
The air bag 18 has an opening 17 through which inflation fluid can flow 
into the interior of the air bag to inflate the air bag. An actuatable 
inflator 22 is secured in a chamber portion 24 of the reaction canister 
16. The inflator 22 may be secured in any suitable manner to the reaction 
canister 16. As illustrated by way of example in the drawings, the 
inflator 22 has a threaded stud 26 which extends through the reaction 
canister 16. A nut 28 is screwed onto the stud 26 to attach the inflator 
22 securely to the reaction canister 16. The inflator may have a number of 
studs, like stud 26, onto which nuts, like nut 28, are screwed to attach 
the inflator 22 to the reaction canister 16. 
The air bag 18 is folded and stored in an air bag storage compartment 20 of 
the reaction canister 16. The folded and stored air bag 18 is deployed 
into the vehicle passenger compartment upon occurrence of a vehicle 
collision requiring air bag deployment. The reaction canister 16 has an 
opening 19 (FIG. 4) through which the air bag 18 is deployed. The reaction 
canister 16 as schematically illustrated is mounted in the vehicle 
instrument panel 14. 
A deployment door 12 closes the opening 19 through which the air bag 18 is 
deployed into the vehicle passenger compartment. The deployment door 12 is 
preferably aligned flush with the vehicle instrument panel 14 when the 
door 12 is in the closed position. 
The deployment door 12 comprises a relatively soft first material layer 60 
and a relatively hard second material layer 70. The hard second material 
layer 70 includes a body portion 78 (FIG. 3) which lies between the air 
bag 18 and the soft first material layer 60. The hard second material 
layer 70 includes an inner surface 74 which is presented toward and 
engaged by the air bag 18 when the air bag 18 is inflated. The hard second 
material layer 70 further includes a major side surface 77 which lies 
opposite the inner surface 74. The major side surface 77 is adhered to a 
major side surface 67 of the soft first material layer 60. The soft first 
material layer 60 includes (i) a first outer surface portion 62 which lies 
opposite the major side surface 67 and is exposed to the vehicle passenger 
compartment and (ii) a second outer surface portion 69 which is also 
exposed to the vehicle passenger compartment. 
The hard second material layer 70 has a projecting portion 76 which extends 
away from the body portion 78 toward the vehicle passenger compartment. 
The projecting portion 76 has an outer surface 72 which is shown in the 
drawings as exposed to the vehicle passenger compartment. The outer 
surface 72 of the projecting portion 76 lies flush with the first and 
second outer surface portions 62, 69 of the soft first material layer 60, 
as shown in FIG. 3. The outer surface 72 could, if desired, be painted or 
coated or otherwise decorated, as desired, to be compatible with the 
vehicle interior. An interconnecting surface 75 of the hard second 
material layer 70 extends between the outer surface 72 and the inner 
surface 74. 
The projecting portion 76 of the hard second material layer 70 has a 
U-shape, when viewed from the vehicle passenger compartment. Thus, the 
outer surface 72 (as shown in FIG. 1) is exposed as a U-shaped surface on 
the vehicle instrument panel 14. The outer surface 72 includes a 
horizontally extending portion 90 extending across the deployment door 12 
near the bottom of the deployment door. The outer surface 72 also includes 
vertically extending portions 92, 94. The portions 92, 94 extend parallel 
to each other vertically from the opposite ends of the horizontally 
extending portion 90 and terminate near the top of the deployment door 12. 
The deployment door 12 has a generally rectangular flap portion 86 and a 
generally U-shaped frame portion 88 surrounding in part the flap portion 
86. The flap portion 86 comprises a portion of the soft first material 
layer 60 having the surface portion 62 and a portion of the hard second 
material layer 70. The frame portion 88 comprises another portion of the 
soft first material layer 60 which lies adjacent the U-shaped projecting 
portion 76 of the hard second material layer 70 and has the surface 
portion 69. 
The top end of the flap portion 86 includes a flange 82 (FIG. 2) of the 
soft first material layer 60 and a flange 83 of the hard second material 
layer 70. The flanges 82, 83 are attached to the reaction canister 16 
using suitable fasteners, such as bolts 21 and nuts 23. The flap portion 
86 includes a relatively flat plate portion 64 (FIG. 3) of the soft first 
material layer 60 that extends between the flange 82 of the soft first 
material layer 60 and the projecting portion 76 of the hard second 
material layer 70. The flat plate portion 64 of the soft first material 
layer 60 lies adjacent the body portion 78 of the hard second material 
layer 70. The flap portion 86 has an outer surface which comprises the 
first outer surface portion 62 of the soft first material layer 60 and the 
outer surface 72 of the projecting portion 76 of the hard second material 
layer 70. 
The frame portion 88 includes, at the bottom of the deployment door 12, a 
relatively thick flange portion 84 of the soft first material layer 60 
that extends parallel to the flange 82. The frame portion 88 also includes 
a relatively thin interconnecting portion 66 of the soft first material 
layer 60 that extends between the flange 84 and the projecting portion 76 
of the hard second material layer 70, as best shown in FIG. 3. As shown in 
FIG. 2, the flange portion 84 is attached to the reaction canister 16 
using suitable fasteners, such as bolts 27 and nuts 25. The frame portion 
88 has an outer surface which comprises the second outer surface portion 
69 of the soft first material layer 60. 
The thin interconnecting portion 66 has an interconnecting surface 65 which 
is adhered to part of the interconnecting surface 75 of the hard second 
material layer 70, as shown in FIG. 3. The interconnecting surfaces 65, 75 
are adhered to each other such that an area contact is formed between the 
interconnecting surfaces 65, 75. The area contact is continuous throughout 
the U-shape of the projecting portion 76. Accordingly, the area contact 
between the interconnecting surfaces 65, 75 is U-shaped. 
Each of the first and second material layers 60, 70 comprises thermoplastic 
material. The composition of each of the first and second material layers 
60, 70 can be of various filled, unfilled, alloyed, or composite 
thermoplastic materials. These thermoplastic materials can be injection 
molded, compression molded, or blow molded. 
Preferably, the hard second material layer 70 comprises a single piece of 
molded thermoplastic substrate material such as a thermoplastic polyester 
having a flexural modulus in the range of 40,000 to 120,000 psi in 
accordance with ASTM standard test No. ASTM-D790. The soft first material 
layer 60 preferably comprises a single piece of thermoplastic material 
known as DYM 100, supplied by E. I. DuPont de Nemours, Co., and having a 
flexural modulus in the range of 12,000 to 16,000 psi in accordance with 
ASTM standard test No. ASTM-D790. Thus, the hard second material layer 70 
has about two and one half (2 1/2) to ten (10) times the stiffness of the 
soft first material layer 60. 
To manufacture the deployment door 12, the hard second material layer 70 is 
molded first. The layer 70 is molded by directing thermoplastic material 
which is used to make the hard second material layer 70 into a first 
injection mold. The resulting single piece of molded thermoplastic 
material forms the hard second material layer 70. The hard second material 
layer 70 is then placed into a second injection mold with the inner 
surface 74 engaging one surface portion of the second injection mold and 
the outer surface 72 engaging another surface portion of the second 
injection mold. The thermoplastic material which is used to make the soft 
first material layer 60 is then directed at a relatively high temperature 
into the second injection mold. This thermoplastic material flows around 
the single piece of molded thermoplastic material which forms the hard 
second material layer 70. 
As the thermoplastic material which is used to make the soft first material 
layer 60 flows around the hard second material layer 70, some of the 
thermoplastic material at the projecting portion 76 of the hard second 
material layer 70 melts and chemically bonds with the thermoplastic 
material used to make the soft first material layer 60. As the materials 
cool, a physical bond is formed between the interconnecting portion 66 and 
the projecting portion 76 to hold the hard second material layer 70 and 
the soft first material layer 60 together. The area contact between the 
interconnecting surfaces 65, 75 defines a break line 30 that extends in a 
U-shape horizontally across the deployment door 12 and vertically along 
opposite sides of the deployment door adjacent the outer surface 72 of the 
hard second material layer 70. The break line 30 extends in a U-shape 
along the juncture of the interconnecting surface 65 of the soft first 
material layer 60 and the interconnecting surface 75 of the hard second 
material layer 70. 
When a vehicle collision requiring air bag deployment occurs, inflation 
fluid is directed through the opening 17 into the interior of the air bag 
18 to inflate the air bag. As it inflates, the air bag 18 presses against 
the inner surface 74 of the hard second material layer 70. The pressure of 
the air bag 18 against the inner surface 74 continues to increase until 
the pressure is sufficient to cause the interconnecting surfaces 65, 75 to 
separate from each other along the U-shaped break line 30. 
As the interconnecting surfaces 65, 75 separate along the break line 30, 
the air bag 18 continues to press against the inner surface 74 of the hard 
second material layer 70 of the deployment door 12. The pressure of the 
air bag 18 pivots the flap portion 86 to an open position such as shown in 
FIG. 4, thereby creating the opening 19 through which the air bag 18 is 
deployed into the vehicle passenger compartment. Thus, the deployment door 
12 separates into the frame portion 88, which remains attached to the 
reaction canister 16, and the flap portion 86, which pivots from the 
closed position shown in FIG. 2 to an open position such as shown in FIG. 
4. 
The relatively hard second material layer 70 provides rigidity to the 
deployment door 12, while the relatively soft first material layer 60 
provides the deployment door 12 with the characteristic of being 
relatively soft to the touch. The deployment door 12 also does not have 
slits or thin portions which form a tear line. Further, the deployment 
door 12 can be manufactured easily. 
Another embodiment of the present invention is illustrated in FIG. 5. Since 
the embodiment of the invention illustrated in FIG. 5 is generally similar 
to the embodiment illustrated in FIGS. 1-4, similar numerals are utilized 
to designate similar components, the suffix letter "a" being associated 
with the numerals of the embodiment of FIG. 5 to avoid confusion. 
In the embodiment of FIG. 5, the thickness of the interconnecting portion 
66a is the same as the thickness of the flange portion 84a. Accordingly, 
the interconnecting surface 65a is adhered to a larger area of the 
interconnecting surface 75a, as compared to the interconnecting surfaces 
65, 75 in the embodiment of FIGS. 1-4. 
From the above description of the invention, those skilled in the art to 
which the present invention relates will perceive improvements, changes 
and modifications. Such improvements, changes and modifications within the 
skill of the art to which the present invention relates are intended to be 
covered by the appended claims. Also, although the deployment door 12 
illustrated in FIG. 1 forms a portion of the vehicle instrument panel 14, 
it is contemplated that a deployment door constructed in accordance with 
the present invention may form a portion of the interior of a vehicle door 
for covering an air bag located in the vehicle door. Further, it is 
contemplated that features of the present invention may be used in a cover 
on a vehicle steering wheel for covering an air bag located on the 
steering wheel. Thus, the term "deployment door" as used in this 
application is also intended to mean the cover for an air bag mounted on a 
steering wheel.