Self piercing cover assembly for air bag having deformable deflector shield

A self piercing cover assembly for concealing an air bag restraint system in a vehicle passenger compartment has a retractable cutter blade that is attached to the underside of an instrument panel next to front end of an invisible door beneath the instrument panel. When the air bag inflates, the cutter blade is pushed up by a deflector shield against the bias of springs and cuts through the instrument panel at several locations making it easier for the door to swing open. The deflector shield is then bent and broken off or deformed by the inflating air bag to provide a shield for protecting against contact with the sharp edges of the cutter blade. The shield and cutter blade retract under the action of the springs so that the shielded cutting edge is below the surface of the instrument panel to provide primary protection against contact with the sharp edges of the cutter blade after the air bag collapses.

BACKGROUND OF THE INVENTION 
This invention relates generally to air bag restraint systems and more 
particularly to a cover assembly for concealing the air bag restraint 
system in a vehicle passenger compartment. 
SUMMARY OF THE INVENTION 
U.S. Pat. 5,035,444 granted to James C. Carter July 30, 1991 discloses a 
self piercing cover assembly for concealing an air bag restraint system in 
a vehicle passenger compartment. The cover assembly has a smooth outer 
cover layer with a layer of foam elastomer between the cover layer and a 
load bearing insert that has a hinged door. The cover assembly also 
includes a three sided cutter on the end of a pivot arm that is hinged on 
the insert. The pivoted cutter is stored between the closed door so that 
it is pivoted upward and cuts through the foam elastomer and cover layers 
at the front and side edges of the door making it easier for the door to 
swing open when the air bag inflates. When fully inflated, the air bag 
bends the pivot arm so that the cutter and hinged door are retained in a 
raised position against a windshield to protect against passenger contact 
with the cutting edges after the air bag collapses. 
The object of this invention is to provide a self piercing cover assembly 
for an air bag that protect against passenger contact with the cutting 
edges after the air bag collapses irrespective of the position of the 
hinged door. 
A feature and advantage of the self piercing cover assembly of this 
invention is that the self piercing cover assembly does not require 
permanent deformation of any part for protecting against passenger contact 
with the cutting edges after the air bag collapses. 
Another feature and advantage of the self piercing cover assembly of this 
invention is that the self piercing cover assembly does not require the 
proximity of the windshield for protecting against passenger contact with 
the cutting edges after the air bag collapses. 
Still another feature and advantage of the self piercing cover assembly of 
this invention is that the self piercing cover assembly does not require 
that the door be retained in a raised or any other particular position to 
protect against contact with the cutting edges after the air bag 
collapses. 
Yet another feature of the self piercing cover assembly of this invention 
is that the cutter automatically retracts as the air bag collapses so that 
the cutting edges are below the surface of the cover assembly to protect 
against contact with the cutting edges after the air bag collapses. 
Still yet another feature of the self piercing cover assembly of this 
invention is that the cutter blade is substantially isolated from the 
passenger compartment when the air bag collapses so that the occupants are 
completely protected against contact with any sharp edges of the cutter 
blade. 
Still yet another feature of the self piercing cover assembly of some 
embodiments of this invention is that the cutter is pushed up by a 
deflector that is deformed to provide a shield to further protect against 
contact with the sharp cutting edges of the cutter after the air bag 
collapses.

DESCRIPTION OF THE INVENTION 
Referring now to the drawing, FIG. 1 shows an instrument panel 10 having an 
air bag restraint system 12 located beneath a self piercing cover assembly 
14 constructed in accordance with this invention. In this particular 
instance, the air bag restraint system 12 is located beneath the shelf 
portion of the instrument panel on the passenger side of the vehicle. 
However the self piercing cover assembly of this invention can be used on 
the driver side as part of the steering wheel; on either side as part of 
the front or facing portion of the instrument panel; or as part of any 
decorative panel in the passenger compartment. 
The air bag restraint system 12 includes an air bag housing 16 that 
encloses a gas generator 18 for supplying an inflatant to an air bag 20 
that is collapsed, folded and packed in the housing 16. The folded air bag 
20 includes an inlet end 22 connected to a passage for flow of the 
inflatant from the gas generator 18 into the air bag. The air bag also 
includes a nose end 24 at the opposite end of the folds that is positioned 
to operate the self piercing cover assembly 14 of this invention when the 
air bag 20 inflates. 
The cover assembly 14 comprises a support 30 of sheet metal or other 
relatively stiff material that is secured beneath the instrument panel 10 
preferably by being insert molded as part of the instrument panel itself. 
The support 30 includes a door 32 that closes a rectangular opening 34 in 
the support 30. The door 32 is connected to the support 30 by a hinge 33 
at the back end. The front end of the door 32 is spaced from an edge of 
the rectangular opening 34 to maintain a slot 36 at the front end of the 
door 32 when it is in the closed position as shown in FIG. 2. 
The outer surface of the support 30 and the hinged door 32 is bonded to a 
layer of a suitable energy absorbing elastomeric foam, such as urethane 
foam that forms a cushion 38 in an underlying relationship to a polymeric 
skin or shell 40 of vinyl or the like that forms an outer decorative 
surface of the instrument panel 10 The skin 40 does not have any break 
lines, tear lines or weakened sections that are visually perceivable from 
the exterior of the instrument panel 10 so as to detract from its 
aesthetic appearance. Thus the self piercing cover assembly 14 of this 
invention provides an invisible door arrangement for the deployment of the 
air bag 20. 
The support 30 of the cover assembly 14 has a depending bracket 42 that 
holds the air bag housing 16 beneath the rectangular opening 34 in spaced 
alignment with the door 32. A piercing member 43 is disposed in the space 
between the door 32 and the air bag 20 that is provided by the bracket 42. 
The piercing member 43 is attached to the underside of the support 30 near 
the slot 36 by a slide so that it translates from a retracted position 
beneath the instrument panel 10 as shown in FIGS. 2 and 4 to an extended 
position projecting through the instrument panel 10 as shown in FIG. 3. 
The slide comprises a plurality of posts 44 attached to the support 30 and 
bracket 42 and collars 46 surrounding the posts 44 that are attached to 
the piercing member 43. The slide also includes coil springs 48 around the 
posts 44 that bias the collars 46 down against the bracket 42 to retain 
the piercing member 42 in the retracted position shown in FIGS. 2 and 4. 
The slide also includes stops 50 surrounding the upper ends of the posts 
44 and coil springs 48 that engage the collars 46 to limit the outward 
movement of the piercing member 43 as shown in FIG. 3. 
The piercing member 43 comprises a cutter blade 52 that is aligned with the 
slot 36 at the front end of the door 32. The cutter blade 52 has a saw 
tooth cutting edge 54 that provides a plurality of sharp cutting points 
56. These cutting points 56 cut through the cushion 38 and skin 40 at 
several locations to provide a tear line at the front end of the door 32 
when the piercing member 43 is raised to the extended position shown in 
FIG. 3. 
The piercing member 43 is raised by means of a deflector shield 58 that is 
attached to the piercing member 43 in cantilever fashion. The deflector 
shield 58 is disposed in the space beneath the support 30 provided by the 
bracket 42 so that it lies between the air bag 30 that is packed in the 
air bag housing 16 and the door 32. The deflector shield 58 is made of a 
deformable material, such as sheet metal, so that it can be deformed to an 
upright orientation to provide a shield for protecting against contact 
with the sharp edges of the cutter blade 52 as shown in FIGS. 3 and 4. 
When the deflector shield 58 is deformed to the upright orientation, it is 
adjacent the exposed side of the cutter blade 52, that is, the side that 
faces toward the door 32. The deflector shield 58 may be scored or 
otherwise weakened to promote bends in the deflector shield 58 at desired 
locations so that the deflector shield bends over the top of the cutter 
blade 52 as shown in FIG. 4. 
The self piercing cover assembly 14 operates in the following manner. When 
the gas generator 18 is triggered due to a predetermined vehicle 
deceleration, the air bag 20 inflates at the nose end 24 first and then 
progressively back toward the inlet end 22. Consequently the nose end 24 
engages the shield 58 and the initial load of the inflating air bag pushes 
the deflector shield 58 outwardly against the bias of the coil springs 44 
until the piercing member 42 reaches its extended position shown in FIG. 
3. In this extended position, the cutting blade 52 projects through the 
slot 36 and the cutting edge 54 cuts through the cushion 38 and skin 40 at 
several locations. This forms a greatly weakened tear line at the front of 
the door 32 that is easily ruptured by the door 32 itself as it is 
subsequently pivoted outwardly by the force of the inflating air bag 20. 
In this regard, it should be noted that the size and number of the sharp 
cutting points 56 can be varied to meet the particular needs of the 
materials that are used in the cushion 38 and skin 40 of the instrument 
panel 10. 
When the tear line is formed, the collars 46 engage the stops 50 limiting 
outward movement of the piercing member 43 so that the inflating air bag 
cannot push it beyond the extended position. When the piercing member 42 
stops moving, the force of the inflating air bag 20 deforms the deflector 
shield 58 from its original generally horizontal orientation shown in 
phantom to an upright orientation adjacent the exposed side of the cutting 
blade 52 as shown in solid lines in FIG. 3. 
The inflating air bag 20 also pushes the door 32 open until it is stopped 
by the windshield 62. The cushion 38 and skin 40 of the instrument panel 
10 may be opened at the sides of the door 32 in any suitable manner, such 
as by the force of the door 32 itself possibly in combination with 
invisible side tear lines in the skin 40. 
Another alternative is to use cutting cables or wires to cut through the 
cushion 38 and skin 40 of the instrument panel 10 at the sides of the door 
as the door is being pivoted open by the inflating air bag 20 as disclosed 
and explained in U.S. patent application Ser. No. 07/990,028 filed Dec. 
14, 1992 and assigned to the assignee of this invention. The cutting 
cables or wires provide the additional benefit of tethering the door 32 
after the instrument panel 10 has been opened up. 
Still another alternative is to use a piercing member that also cuts tear 
lines at the side of the door 32, such as the second embodiment of the 
invention that is explained below in connection with FIG. 6. 
In any event, an important feature of the invention is that the cutter 
blade 52 of the piercing member 43 retracts below the surface of the skin 
40 that is next to the opening 34 as the air bag 20 collapses and the coil 
springs 48 overcome the force of the air bag 20 as shown in FIG. 4. This 
substantially isolates the cutter blade 52 from the passenger compartment 
and protects the occupants against contact with the sharp points 56 of the 
cutting edge 54 of the cutter blade 52. Moreover, the bent deflector 
shield 58 protects the occupants against contact with the sharp points 56 
and cutting edge 54 of the retracted cutter blade 52 even further. 
Consequently the occupants are completely protected against contact with 
the sharp edges of the cutter blade 52 in any position of the door 42 and 
irrespective of the proximity of the windshield 62. Thus the self piercing 
cover assembly 14 of this invention is quite versatile and universal in 
that it can be used in a great variety of applications and locations in 
the passenger compartment. 
Referring now to FIG. 6, it shows a second embodiment of a self piercing 
cover assembly 114 constructed in accordance with this invention that be 
used in conjunction with the instrument panel 10 and air bag restraint 
system 12 shown in FIG. 1. It can also be used in other environments in 
which the self piercing cover assembly 14 can be used, such as those 
discussed above. 
The self-piercing cover assembly 114 of this second embodiment has a 
modified piercing member 143 and a modified deflector shield 145 that are 
different. The remaining components, however, are the same as those of the 
self-piercing cover assembly 14 and corresponding components are 
identified with the same numerals. 
The modified piercing member 143 is disposed in the space between the door 
32 and the air bag 20 that is provided by the bracket 42. The piercing 
member 143 is attached to the underside of the support 30 near the slot 36 
by a slide so that it translates from a retracted position beneath the 
instrument panel 10 as shown in FIG. 6 to an extended position projecting 
through the instrument panel 10 such as that shown in FIG. 3 in connection 
with the piercing member 43 of the first embodiment. 
The modified piercing member 143 comprises a cutter blade 152 that is three 
sided so that it cuts three tear lines. The front side 154 is aligned with 
the slot 3 at the front end of the door 32. The right and left sides 155 
and 156 are aligned with respective slots at the right and left sides of 
the door 32 (not shown). The cutter blade 152 has a saw tooth cutting edge 
158 that provides a plurality of sharp cutting points 160. These cutting 
points 160 cut through the cushion 38 and skin 40 at several locations to 
provide tear lines at the front end and sides of the door 32 when the 
piercing member 143 is raised to the extended position. 
The piercing member 143 is raised by means of a deflector shield 145 that 
is attached to the piercing member 143 in cantilever fashion. The 
deflector shield 145 is disposed in the space beneath the support 30 
provided by the bracket 42 so that it lies between the air bag 30 that is 
packed in the air bag housing 16 and the door 32. The deflector shield 145 
is made of a deformable material and it is indented or scored to provide a 
fracture line 155 near the front blade 154 so that the deflector shield 
153 fractures at a desired location during air bag deployment. 
The self piercing cover assembly 114 operates in the following manner. When 
the gas generator 18 is triggered due to a predetermined vehicle 
deceleration, the air bag 20 inflates at the nose end 24 first and then 
progressively back toward the inlet end 22. Consequently the nose end 24 
engages the deflector shield 145 and the initial load of the inflating air 
bag pushes the deflector shield 145 outwardly against the bias of the coil 
springs 44 until the piercing member 143 reaches its extended position 
where the three sided cutting blade 152 projects through the slots at the 
front and sides of the door 32 and the cutting edge 154 cuts through the 
cushion 38 and skin 40 at several locations. This forms a greatly weakened 
tear line at the front and sides of the door 32 that are easily ruptured 
by the door 32 itself as it is subsequently pivoted outwardly by the force 
of the inflating air bag 20. As before the size and number of the sharp 
cutting points 160 can be varied to meet the particular needs of the 
materials that are used in the cushion 38 and skin 40 of the instrument 
panel 10. 
When the tear lines are formed, the collars 46 engage the stops 50 limiting 
outward movement of the piercing member 143 so that the inflating air bag 
cannot push it beyond the extended position. When the piercing member 143 
stops moving, the force of the inflating air bag 20 bends the deflector 
shield 145 up from its original orientation shown in solid lines in FIG. 6 
until the deflector shield 155 breaks off at the fracture line 155. The 
inflating air bag 20 also pushes the door 32 open until it is stopped by 
the windshield 62. 
In any event, an important feature of this second embodiment of the 
invention is that the cutter blade 152 of the piercing member 143 retracts 
to its original position below the surface of the skin 40 that is next to 
the opening 34 as the air bag 20 collapses and the coil springs 48 
overcome the force of the air bag 20 such as shown in FIG. 4 in connection 
with the piercing member 43. This substantially isolates the cutter blade 
152 from the passenger compartment and protects the occupants against 
contact with the sharp points 160 of the cutting edge 158 of the three 
sided cutter blade 152. 
Thus this second embodiment also protects the occupants against contact 
with the sharp edges of the three sided cutter blade 152 in any position 
of the door 42 and irrespective of the proximity of the windshield 62. The 
self piercing cover assembly 114 is also quite versatile and universal in 
that it can also be used in a great variety of applications and locations 
in the passenger compartment. 
While this second embodiment shows a self piercing cover assembly 114 that 
has a three sided cutter blade 152 and a deflector shield that fractures 
during use, it is to be understood that either of these modifications can 
be used without the other. That is, a three sided cutter blade can be used 
in conjunction with other deflector shields such as the deflector shield 
that is described above in connection with the first embodiment or the 
deflector shield that is described below in conjunction with a third 
embodiment. Similarly, a deflector shield that is designed to fracture 
during use can be used in conjunction with other cutter blades such as the 
cutter blade that is described above in connection with the first 
embodiment and the cutter blade that is described below in conjunction 
with the third embodiment of the invention. 
Referring now to FIGS. 7-9, a third embodiment of a self piercing cover 
assembly 214 constructed in accordance with this invention is shown. This 
third embodiment can also be used in conjunction with the instrument panel 
10 and air bag restraint system 12 shown in FIG. 1 and in other 
environments in which the self piercing cover assembly 14 can be used, 
such as those discussed above. 
The cover assembly 214 comprises an identical support 30 of sheet metal or 
other relatively stiff material that is secured beneath the instrument 
panel 10 preferably by being insert molded as part of the instrument panel 
itself. The support 30 likewise includes a door 32 that closes a 
rectangular opening 34 in the support 30 and the door 32 is connected to 
the support 30 by a hinge at the back end (not shown). The front end of 
the door 32 is spaced from an edge of the rectangular opening 34 to 
maintain a slot 36 at the front end of the door 32 when it is in the 
closed position as shown in FIG. 7. 
The outer surface of the support 30 and the hinged door 32 is bonded to a 
layer of a suitable energy absorbing elastomeric foam, such as urethane 
foam that forms a cushion 38 in an underlying relationship to a polymeric 
skin or shell 40 of vinyl or the like that forms an outer decorative 
surface of the instrument panel 10 The skin 40 does not have any break 
lines, tear lines or weakened sections that are visually perceivable from 
the exterior of the instrument panel 10 so as to detract from its 
aesthetic appearance. Thus the self piercing cover assembly 214 of this 
third embodiment also provides an invisible door arrangement for the 
deployment of the air bag 20. 
The support 30 of the cover assembly 14 has a depending bracket 42 that 
holds the air bag housing 16 beneath the rectangular opening 34 in spaced 
alignment with the door 32. A piercing member 243 is disposed in the space 
between the door 32 and the air bag 20 that is provided by the bracket 42. 
The piercing member 243 is attached to the underside of the support 30 
near the slot 36 by a hinge 244 so that it swings from a retracted 
position beneath the instrument panel 10 as shown in FIGS. 7 and 9 to an 
extended position projecting through the instrument panel 10 as shown in 
FIG. 8. The piercing member 243 has a eyelet near the hinge 244 for 
attaching a coil spring 246. The other end of the coil spring 246 is 
attached to the bracket 42 to biasingly retain the piercing member 243 in 
the retracted position shown in FIGS. 7 and 9. 
The piercing member 243 comprises a curved cutter blade 252 that has a saw 
tooth cutting edge 254 is like the cutting edge 54 shown in FIG. 5 and 
that is aligned with the slot 36 at the front end of the door 32. The saw 
tooth cutting edge 254 provides a plurality of sharp cutting points 256 
that cut through the cushion 38 and skin 40 at several locations to 
provide a tear line at the front end of the door 32 when the piercing 
member 243 is raised to the extended position shown in FIG. 83. 
The piercing member 243 is raised by means of a deflector shield 258 that 
is attached to the bottom of the curved cutter blade 252 in cantilever 
fashion. The deflector shield 258 is disposed in the space beneath the 
support 30 provided by the bracket 42 so that it lies between the air bag 
20 that is packed in the air bag housing 16 and the door 32. The deflector 
shield 258 is made of a deformable material, such as sheet metal, so that 
it can be deformed up and over the curved cutter blade 252 to provide a 
shield for protecting against contact with the sharp edges of the cutter 
blade 252 as shown in FIG. 9. When the deflector shield 258 is deformed, 
it is adjacent the exposed side of the cutter blade 152, that is, the side 
that faces toward the door 32. 
The self piercing cover assembly 214 operates in the following manner. When 
the gas generator 18 is triggered due to a predetermined vehicle 
deceleration, the air bag 20 inflates at the nose end first and then 
progressively back toward the inlet end. Consequently the nose end engages 
the deflector shield 258 and the initial load of the inflating air bag 
pushes the deflector shield 258 outwardly against the bias of the coil 
spring 246 until the piercing member 243 reaches its extended position 
shown in FIG. 8. In this extended position, the cutting blade 252 projects 
through the slot 36 and the cutting edge 254 cuts through the cushion 38 
and skin 40 at several locations. This forms a greatly weakened tear line 
at the front of the door 32 that is easily ruptured by the door 32 itself 
as it is subsequently pivoted outwardly by the force of the inflating air 
bag 20. In this regard, it should be noted again that the size and number 
of the sharp cutting points 256 can be varied to meet the particular needs 
of the materials that are used in the cushion 38 and skin 40 of the 
instrument panel 10. 
When the tear line is formed, the curved blade 252 engages the instrument 
panel 10 limiting outward movement of the piercing member 243 as shown in 
FIG. 8 so that the inflating air bag cannot push it beyond the extended 
position. When the piercing member 243 stops moving, the force of the 
inflating air bag 20 bends the deflector shield 258 from its original 
orientation and shape shown in FIG. 7 up and over the exposed side of the 
cutting blade 252 as shown in FIG. 9. 
The inflating air bag 20 also pushes the door 32 open until it is stopped 
by the windshield 62 as shown in FIG. 8. The cushion 38 and skin 40 of the 
instrument panel 10 may be opened at the sides of the door 32 in any 
suitable manner, such as by the force of the door 32 itself possibly in 
combination with invisible side tear lines in the skin 40, with cutting 
cables or wires to cut through the cushion 38 and skin 40 of the 
instrument panel 10 at the sides of the door as the door is being pivoted 
open by the inflating air bag 20 or with other suitable alternatives as 
indicated above. 
In any event, it is also an important feature of this third embodiment that 
the curved cutter blade 252 of the piercing member 243 retracts below the 
surface of the skin 40 that is next to the opening 34 as the air bag 20 
collapses and the coil spring 246 overcomes the force of the air bag 20 as 
shown in FIG. 9. This substantially isolates the curved cutter blade 252 
from the passenger compartment and protects the occupants against contact 
with the sharp points 256 of the cutting edge 254 of the cutter blade 252. 
Moreover, the bent deflector shield 258 protects the occupants against 
contact with the sharp points 56 and cutting edge 54 of the retracted 
cutter blade 52 even further. 
Consequently the occupants are completely protected against contact with 
the sharp edges of the curved cutter blade 252 in any position of the door 
42 and irrespective of the proximity of the windshield 62. Thus the self 
piercing cover assembly 214 of this invention is also quite versatile and 
universal in that it can be used in a great variety of applications and 
locations in the passenger compartment. 
The invention has been described in an illustrative manner, and it is to be 
understood that the terminology which has been used is intended to be in 
the nature of words of description rather than of limitation. 
Obviously, many modifications and variations of the present invention in 
light of the above teachings may be made. It is, therefore, to be 
understood that, within the scope of the appended claims, the invention 
may be practiced otherwise than as specifically described.