Automotive instrument panel having an integral airbag

An automotive instrument panel having a concealed airbag. A molded substrate having first and second surfaces and an aperture therethrough receives an airbag. A curved metal door is secured to the first surface of the substrate by a plurality of fasteners extending through the substrate. The metal door has a generally U-shaped slot with first and second ends being spaced apart a distance greater than the length of the aperture. The slot is positioned radially outwardly of the aperture. The door also has a plurality of indentations to maintain a curved shape conforming with the surface of the substrate. A molded covering overlies the first surface of the door and is secured thereto with an intermediate layer of foam. A foam gasket overlies the slot between the door and the substrate. A foam impermeable layer is placed between the gasket and door to prevent injected foam from impregnating the foam gasket and interfering with the opening of the door. An airbag chute is secured to the second surface of the substrate by the attaching fasteners. The airbag causes the metal door to fold along the line between the first and second ends of the slots.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of manufacturing an automotive 
instrument panel having a concealed airbag. More particularly, the present 
invention relates to a method of forming an airbag-receiving opening in a 
plastic substrate by imaging a light beam through the substrate and 
forming a fracturable opening path in the instrument panel. 
2. Description of the Related Art 
It is known to manufacture an automotive airbag having a seamless covering. 
One such device is described in U.S. Pat. No. 5,447,328, issued Sep. 5, 
1995. The reference teaches a hinged metal door secured to a plastic 
substrate. The hinge is secured to both the plastic substrate and the 
metal door and folds when the airbag is inflated. A deep groove directly 
overlying the perimeter of the metal door forms a weakened section in the 
covering that tears when the door is opened. An airbag door and cover of 
this construction is difficult to manufacture because a metal hinge must 
be secured to only one edge of the plastic substrate. It is also difficult 
to form a deep groove in the covering that directly overlies the perimeter 
of the metal door. The groove construction taught in the U.S. Pat. No. 
5,447,328 patent extends almost to the surface of the plastic substrate, 
making it difficult to inject foam in the vicinity of the groove. It is 
desirable to inject foam between the cover and the door to secure the two 
components without causing the foam to impede the opening of the door. 
It is also known that the rapid force needed to deploy an airbag causes 
stress on the molded plastic substrate when the door is attached to only 
one edge. Various frames may be attached to the perimeter of the airbag 
opening to make the substrate more rigid. An example of this construction 
is illustrated in U.S. Pat. No. 5,393,088 issued Feb. 28, 1995. A metal 
frame is secured within the aperture of a plastic substrate. A door is 
attached to one side of the frame with a hinge. The metal frame keeps the 
substrate from deforming under the impact of an inflating airbag. 
Finally, it is also known to use a laser to score an instrument panel to 
form a weakening pattern. The laser completely penetrates the substrate 
and foam and partially penetrates the covering to form the weakening 
pattern. A method of forming this weakening pattern is described in U.S. 
Pat. No. 5,744,776 and is incorporated herein by reference. The U.S. Pat. 
No. 5,744,776 reference teaches bonding the substrate to the covering 
inside the weakened section. This results in the substrate being 
positioned in front of the deploying airbag. The rigid plastic substrate 
must be restrained. It is desirable to form an instrument panel with an 
aperture in the substrate for the airbag. This eliminates the need to 
restrain or tether the cutout section of substrate. 
It is an advantage of the present invention to provide a seamless airbag 
covering having a hinged door that is secured to a substrate. It is a 
further object of the present invention to provide an easily 
manufacturable method of forming an aperture in the substrate by means of 
a laser beam by forming a cut-out section that is not adhered to the 
covering. It is also an advantage of the present invention to provide a 
method of removing a cutout section of the substrate and forming an 
airbag-receiving aperture in an instrument panel. The process further 
includes forming a fracturable opening through the covering in one 
operation. 
These and other problems of the related art are overcome by the present 
invention. 
SUMMARY OF THE INVENTION 
The present invention is directed to a method of manufacturing an 
automotive instrument panel having a concealed airbag using the following 
steps. A molded plastic substrate having first and second surfaces 
receives a metal door having a peripheral portion and a generally U-shaped 
slot with first and second ends defining a foldable flap. The line between 
said first and second ends defines a folding axis for the flap. The door 
is secured to the substrate first surface panel exterior surface. A 
covering is positioned over the door and substrate. A foam is injected 
between the substrate and covering to secure the covering to the substrate 
and said door. A high intensity light beam is imaged on the substrate 
second surface in the area overlying said slot. The light beam completely 
penetrates the substrate and foam and partially penetrates the covering. 
The light beam is directed through the slot in the metal door and creates 
a fracturable opening path in the substrate, foam and covering. The light 
beam is also imaged on the substrate second surface in the area overlying 
said folding axis and completely penetrates the substrate and contacts the 
metal door. The light beam severs a cutout section of the substrate. The 
cutout section of substrate is removed to form an aperture through the 
substrate for an airbag. An airbag is secured behind the aperture. The 
airbag has sufficient force to fracture the opening path and fold the door 
when activated. 
The invention enables the manufacture of an instrument panel having no 
visible indication of an airbag opening. The fracturable opening path does 
not create visible holes or marks on the appearance surface of the 
covering. A light beam detector positioned opposite of the light beam 
senses the intensity of light passing through the covering and causes the 
light beam to move or reduce power prior to forming a visible mark on the 
covering. 
The invention also includes an automotive instrument panel having a 
concealed airbag made by the forgoing method. The panel includes a molded 
substrate to having first and second surfaces and an aperture receiving an 
airbag therethrough. A metal door is secured to the substrate first 
surface. The door has a peripheral portion and a generally U-shaped slot 
with first and second ends spaced apart. The U-shaped slot overlies the 
three perimeter sides of the aperture and defines a foldable flap. A 
covering overlies the door and substrate. Foam injected between the door 
and covering secures the covering to the substrate and door. 
The foam and covering include a fracturable opening path within the slot. 
The opening path is made from a series of apertures formed through the 
foam and into the covering by a light beam and enables the foam and 
covering to fracture along the path. An airbag secured to the substrate 
second surface positioned behind the aperture has sufficient force to 
fracture the opening path and fold said door when activated. 
The invention may be easily manufactured because the covering, door, foam 
and substrate are all assembled prior to forming an aperture in the 
substrate. The U-shaped slot enables the light beam to penetrate the foam 
and covering through from the second surface of the substrate. Because the 
aperture is directly aligned over the U-shaped slot, the airbag and 
fracturable opening are always properly positioned when assembled. 
These and other desired objects of the present invention will become more 
apparent in the course of the following detailed description and appended 
claims. The invention may best be understood with reference to the 
accompanying drawings wherein illustrative embodiments are shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The invention as illustrated in FIGS. 1-6 teaches a method of manufacturing 
an instrument panel having a concealed airbag. The present invention will 
be described through a series of drawings, which illustrate the laser 
scoring operations claimed. The invention will also be described as a 
method of manufacturing an automotive instrument panel, however other 
components may also be manufactured using the same or similar process, 
technique and equipment, and are included within the invention described 
herein. 
The following items are a word list of the items described in the drawings 
and are reproduced to aid in understanding the invention; 
10 instrument panel 
12 substrate 
14 covering 
16 door 
18 fasteners 
20 U-shaped slot 
22 flap 
24 first end 
26 second end 
28 folding axis 
30, 32, 34 tabs 
36 J-shaped slot 
38 folding axis 
40 gasket 
42, 44 foam impermeable layers 
46 foam 
48 laser 
50 light beam 
52 detector 
54 fracturable opening path 
56 areas 
58 airbag chute 
60 airbag 
62 cross-car beam 
FIG. 1 is an exploded perspective view of an automotive instrument panel 10 
having a plastic molded substrate 12 and a molded flexible covering 14. 
The substrate 12 is formed in the usual manner of injection molding from 
materials selected to be durable, lightweight and low-cost. Suitable 
materials for the substrate 12 include polyolefin. Especially preferred is 
polystyrene or styrene malaeic anhydride (SMA). The covering 14 is 
pre-molded in the final desired shape for attachment to the substrate 12. 
Suitable materials for the covering 14 include thermoplastic olefins. 
Especially preferred are thermoplastic urethanes, polyvinyl chlorides 
(PVC) or PVC-urethane blends. A variety of methods are known for molding 
the flexible covering including slush molding, thermoform molding, vacuum 
molding, spray molding and injection molding. A steel door 16 is attached 
to a curved surface of the substrate 12 with a plurality of fasteners 18 
welded around the perimeter of the door 16. The fasteners 18 extend 
through the substrate 12 and secure the door 16 to the substrate. 
A generally U-shaped slot 20 forms a foldable flap 22 in the door 16. The 
slot 20 has a first end 24 and a second end 26. The flap 22 generally 
folds along a folding axis 28 that is a line between the first end 24 and 
the second end 26. The door 16 is manufactured from relatively soft (low 
carbon) steel that bends when the force of the airbag is applied against 
the flap 22. The flap 22 is generally positioned to open upwardly towards 
the windshield when the instrument panel 10 is installed within a vehicle. 
The covering 14 has no visible markings or indentations on the surface 
displayed to the passenger to reveal the location of the airbag. 
The door 16 is stamped from a sheet of steel to have the generally U-shaped 
slot 20 and a series of tabs 30, 32, 34 as shown in FIG. 2. The tab 30 is 
illustrated in its prebent state made by cutting or stamping a J-shaped 
slot 36 as shown. The tab 30 is folded under the slot 20 along the folding 
axis 38, as shown in tabs 32, 34. The tabs 30, 32, 34 serve to prevent an 
inward movement of the flap 22 toward the airbag. Alternatively, tabs 30, 
32, 34 may be a steel section welded or fastened to the door 16. The door 
16 may be curved to match the curved shape of the instrument panel 10. 
The door 16 is secured to the substrate 12 as shown in FIG. 3. A urethane 
foam gasket 40 having foam impermeable layers 42, 44 is placed between the 
door 16 and the substrate 12. The thickness of the gasket 40 is shown 
greatly enlarged for clarity. The door 16 is secured to the substrate 12 
with a series of fasteners 18. The fasteners 18 generally have a flat head 
and are welded to the door 16. Rivets or any other attachment means may be 
used for the fasteners 18. 
The covering 14 is overlaid the substrate 12 and the door 16. The covering 
14 is secured to the substrate 12 and the door 16 in a foaming operation. 
The covering 14 is juxtaposed the substrate 12 and is spaced a fixed 
distance apart. The distance between the covering 14 and the substrate 12 
forms a space for receiving foam 46. Suitable foam materials include 
polymer foams. Especially useful are polyurethane foams. Polyurethane 
foams demonstrate good adhesion to each of the substrate, covering and 
door. The foam 46 secures the covering 14 to the substrate 12 and the door 
16. To aid in securing the foam 46 to the door 16, the door may be 
electro-coated. The coating prevents rust and also promotes adhesion of 
the foam. A space is created between the slot 20 and the gasket 40. The 
foam 46 is allowed to freely move along the surface of the substrate 12 
and the door 16. The foam 46 contacts the layer 42 and is prevented from 
impregnating the gasket 40 or seeping behind the door 16. In the absence 
of the layer 42, the foam 46 may pass through the slot 20 and impregnate 
the foam gasket 40. This may cause the foam 46 to adhere to the flap 22 
and impede its ability to remove the cutout section of substrate. 
After the foam is allowed to cure, an intense light beam scores the 
instrument panel 10. A laser 48 images a focused beam of light 50 onto the 
back surface substrate 12. The beam 50 cuts an aperture 52 through the 
substrate 12, gasket 40, layers 42, 44 and foam 46. The beam 50 is aligned 
to pass through the slot 20. The beam 50 partially penetrates the covering 
14. As the beam 50 begins to penetrate the covering 14, it is detected by 
a light detector 52 positioned opposite to the laser 48. A controller (not 
shown) receives a signal from the detector 52 and signals the laser 48 to 
move along the opening path 54 or to reduce power to the laser 48. 
Laser scoring ratio is dependent on cover, foam and substrate materials, 
and airbag deployment performance. Cutting path 54 can be tailored in 
depth and length (either continues or interrupted) to provide the best 
system performance. Minimum radii of the laser cutting path 54 are at the 
corners opposite the folding axis is 25 mm when measured in a plane 
perpendicular to the airbag deployment direction. 
The beam 50 completely penetrates the substrate 12, gasket 40 and layers 
42, 44 but only partially penetrates the covering 14. The covering is 
scored to form an easily fracturable opening path 54, but the outer 
surface of the covering 14 displayed to the passengers is not visibly 
marred. The laser 48 is moved along the substrate 12 as shown in FIGS. 4 
and 5. In the areas 56 that overlies the tabs 30, 32, 34, the beam 50 does 
not penetrate through the foam 46 or covering 14. The substrate 12 is 
however completely severed. The areas 56 are relatively small and the 
airbag has sufficient force to tear through these areas of covering 14 and 
foam 46. Similarly, the beam 50 does not penetrate through the door 16 
along the folding axis 28. The system controller moves the beam along the 
areas backed by steel without the detector 52 sensing the beam 50. 
After the laser 48 has been moved along the opening path 54, a cutout 
section 58 of the substrate 12 is severed and removed as shown in FIGS. 5 
and 6. The flap 22 and tabs 30, 32 and 34 are exposed through the under 
surface of the instrument panel 10 as shown in FIG. 6. 
The detector 52 measures the light output of the laser as it forms the 
opening path 54 as shown in FIGS. 3 and 4. A series of measurements are 
reported to the controller. If any of the measurements are too large, this 
signifies that the light beam 50 has made too large an aperture in the 
covering 14. This may mar the appearance of the instrument panel 10 or 
weaken the covering and cause premature failure. Because these 
imperfections may not be easily visible, the controller may be programmed 
to direct the laser 48 to form a large and visible aperture through the 
covering 14, thus rendering the instrument panel 10 useless. This may be 
used as a control device to mark panels that were not produced in 
accordance with a predefined process. Instrument panels not produced in 
accordance with these process parameters may not operate correctly and are 
destroyed by the laser. This may also serve as a manufacturing record for 
each panel to track processing variables such and the number and dimension 
of the scoring apertures. 
An airbag chute 58 and airbag 60 are secured to the under surface of the 
substrate 12 by means of the attaching fasteners 18, as shown in FIG. 7. 
The instrument panel 10 is installed within a vehicle (not shown), usually 
adjacent a cross-car beam 62. In the event of a collision, the airbag 60 
inflates and passes through the chute 58. The rapidly expanding airbag 60 
pushes the flap 22 outwardly. The flap 22 causes the covering 14 to sever 
along the fracturable opening path 54 as the airbag door 16 opens. 
The invention has been described as a method of manufacturing an automotive 
instrument panel using the drawings and description provided. While the 
best modes for carrying out the invention have been described in detail, 
those familiar with the art to which this invention relates will recognize 
various alternative designs and embodiments for practicing the invention 
as defined by the following claims.