Tear seam for air bag module cover

A vehicle safety apparatus (10) comprises a protection device (12) which is inflatable from a deflated condition to an inflated condition into an occupant compartment of the vehicle to help protect an occupant of a vehicle. The apparatus (10) includes a cover (20) for covering the protection device (12). The cover (20) has an inner side surface (24) and an opposite outer side surface (26) which is exposed to the vehicle occupant compartment. The cover (20) has a predetermined weakened portion (30) which is rupturable upon inflation of the protection device (12) to enable inflation of the protection device into a condition to help protect the vehicle occupant. The predetermined weakened portion (30) of the cover (20) includes an opening (56) in the outer side surface (26) of the cover (20). A member (80) on the outer side surface (26) of the cover (20) overlies the opening (56) in the cover.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The present invention relates to a cover for an air bag module. In 
particular, the present invention relates to an air bag module cover 
having a predetermined weakened portion, or tear seam. 
2. Description of the Prior Art 
A typical air bag module includes an air bag and an inflator. In the event 
of sudden vehicle deceleration of a magnitude which requires protection of 
a vehicle occupant, the inflator is actuated to inflate the air bag into a 
position to help protect the occupant. 
The air bag module commonly includes a cover with one or more predetermined 
weakened portions, or tear seams, to enable the cover to open and allow 
the air bag to inflate into a position to help protect the occupant. A 
tear seam typically comprises a groove in the back (inner) surface of the 
cover. It is desirable that the tear seam be relatively easy to open but 
at the same time not be visually evident to an occupant of the vehicle. 
SUMMARY OF THE INVENTION 
The present invention is a vehicle safety apparatus comprising a vehicle 
occupant protection device which is inflatable from a deflated condition 
to an inflated condition into an occupant compartment of the vehicle to 
help protect an occupant of a vehicle. The apparatus includes a cover for 
covering the protection device. The cover has an inner side surface and an 
opposite outer side surface which is exposed to the vehicle occupant 
compartment. The cover has a predetermined weakened portion which is 
rupturable upon inflation of the protection device to enable inflation of 
the protection device into a condition to help protect the vehicle 
occupant. The predetermined weakened portion of the cover includes an 
opening in the outer side surface of the cover. A member on the outer side 
surface of the cover overlies the opening in the cover.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention relates to a cover for an air bag module and, in 
particular, to an air bag module cover having a predetermined weakened 
portion, or tear seam. As representative of the present invention, FIG. 1 
illustrates an air bag module 10. The air bag module 10 is mounted on a 
vehicle steering wheel (not shown). The module 10 could alternatively be 
mounted on a different portion of a vehicle, such as a vehicle instrument 
panel, a seat, a door, or a vehicle roof adjacent a door. 
The module 10 includes an air bag illustrated schematically at 12 in FIG. 
1. Other inflatable vehicle occupant protection devices that can be used 
in accordance with the invention include, for example, inflatable seat 
belts, inflatable knee bolsters, inflatable head liners or side curtains, 
and knee bolsters operated by inflatable air bags. 
The module 10 also includes an inflator shown schematically at 14 which has 
one or more fluid outlets for directing inflation fluid into the air bag 
12 upon actuation of the inflator. The inflator 14 may be a pyrotechnic 
inflator which uses the combustion of gas-generating material to generate 
inflation fluid in the form of gas to inflate the air bag 12. The module 
10 alternatively could include an inflator which contains a stored 
quantity of pressurized inflation fluid, or a combination of pressurized 
inflation fluid and ignitable material for heating the inflation fluid. 
The module 10 includes a cover 20 for enclosing the air bag 12 and the 
inflator 14. The cover 20 is made from a material which is strong enough 
to protect the parts of the air bag module 10 which are enclosed within 
the cover. The material of the cover 20 is sufficiently flexible or 
deformable so that it can be resiliently deformed inwardly by pressure 
from an occupant of the vehicle. 
The cover 20 has a main body portion 22 which has inner and outer side 
surfaces 24 and 26 (FIG. 2). The main body portion 22 of the cover 20 
includes a fixed part 28 (FIG. 1) of the cover. Fasteners (not shown) such 
as rivets extend through the fixed part 28 of the cover 20 to secure the 
cover to the steering wheel or other vehicle portion on which the module 
10 is mounted. The air bag 12 when in the deflated condition is packed 
inside the cover 20, in engagement with the inner side surface 24 of the 
cover. 
An I-shaped tear seam 30 is formed in the main body portion 22 of the cover 
20. The tear seam 30 constitutes a weakened portion of the cover 20 which 
is rupturable under the force of the inflating air bag 12 to enable the 
air bag to inflate out of the cover. The tear seam 30 includes four side 
sections 32, 34, 36 and 38, and a linear central or base section 40. 
Each one of the four side sections 32-38 of the tear seam 30 comprises a 
groove formed in the inner side surface 24 of the cover 20. The cover 20 
is weakened at the location of the grooves because the material of the 
cover is thinner at those locations. The grooves do not extend completely 
through the material of the cover 20, to the outer side surface 26 of the 
cover. Thus, there are no openings in the outer side surface 26 of the 
cover, at the location of the four side sections 32-38 of the tear seam 
30. 
The base section 40 of the tear seam 30 has a central portion 50 and 
opposite end portions 52 and 54. The end portions 52 and 54 of the base 
section 40 of the tear seam 30 comprise grooves formed in the inner side 
surface 24 of the cover 20. The cover 20 is weakened at the location of 
the grooves because the material of the cover is thinner at those 
locations. The grooves 52 and 54 do not extend completely through the 
material of the cover 20 to the outer side surface 26 of the cover. Thus, 
there are no openings in the outer side surface 26 of the cover 20 at the 
location of the two end portions 52 and 54 of the base section 40 of the 
tear seam 30. 
The central portion 50 of the base section 40 of the tear seam 30 is formed 
as an opening 56 in the cover 20. The opening 56 is an elongate slot which 
extends completely through the cover 20 from the inner side surface 24 to 
the outer side surface 26. The cover 20 is thereby weakened substantially 
in the area of the central portion 50 of the base section 40 of the tear 
seam 30. The cover 20 is weaker in the area of the central portion 50 of 
the tear seam 30 than at the end portions 52 and 54 of the base section 30 
or at the side sections 32-38 of the tear seam. 
The tear seam 30 partially defines first and second movable parts 60 and 70 
of the cover. Each one of the first and second movable cover parts 60 and 
70 has a generally rectangular configuration. The base section 40 and the 
side sections 32 and 34 of the tear seam 30 extend along three sides of 
the first movable cover part 60. A first hinge portion 62 of the cover 20 
extends along the fourth side of the first movable cover part 60, between 
the two side sections 32 and 34 of the tear seam 30. The first hinge 
portion 62 connects the first movable cover part 60 to the fixed cover 
part 28 for pivotal movement relative to the fixed cover part. 
The base section 40 and the other two side sections 36 and 38 of the tear 
seam 30 extend along three sides of the second movable cover part 70. A 
second hinge portion 64 of the cover 20 extends along the fourth side of 
the second movable cover part 70, between the two side sections 36 and 38 
of the tear seam 30. The second hinge portion 64 connects the second 
movable cover part 70 to the fixed cover part 28 for pivotal movement 
relative to the fixed cover part. 
A member in the form of an emblem 80 covers the opening 56 in the cover 30. 
The emblem 80 may be a decorative emblem which includes indicia such as 
the name or logo of the vehicle manufacturer, or an SRS ("supplemental 
restraint system") designation. The emblem 80 (FIGS. 2 and 3) has an outer 
side surface 82 and an inner side surface 84. The inner side surface 84 of 
the emblem 80 overlies the outer side surface 26 of the cover. The emblem 
80 is longer and wider than the opening 56. As a result, the emblem 80 
covers the entire opening 56. 
The emblem 80 includes a plurality of fasteners 92-98 for securing the 
emblem to the cover 20. Two of the fasteners 92 and 94 are solid pins 
which are located on one side of the base section 40 of the tear seam 30. 
The pins 92 and 94 extend through openings in the second movable part 70 
of the cover 20. End portions of the pins 92 and 94 project past the inner 
side surface of the second movable part 70 of the cover 20, and are 
deformed by heating to secure the emblem 80 to the second movable part of 
the cover. 
The other two fasteners 96 and 98 are breakaway pins which are located on 
the other side of the base section 40 of the tear seam 30. The pins 96 and 
98 extend through openings in the first movable part 60 of the cover 20. 
End portions of the pins 96 and 98 project past the inner side surface of 
the first movable part 60 of the cover 20, and are deformed by heating to 
secure the emblem 80 releasably to the first movable part of the cover. 
The vehicle includes known means (not shown) for sensing a collision 
involving the vehicle and for actuating the inflator 14 in response to the 
sensing of a collision. The means may include a deceleration sensor and 
vehicle electric circuitry for actuating the inflator 14 in response to 
sensing a vehicle deceleration indicative of a vehicle collision having a 
severity greater than a predetermined threshold value. 
In the event of a vehicle collision of a magnitude greater than the 
predetermined threshold value, the sensing means provides an electrical 
signal over lead wires to the inflator 14. The inflator 14 is actuated in 
a known manner. Inflation fluid flows out of the inflator 14 and into the 
air bag 12. The rapidly flowing inflation fluid causes the air bag 12 to 
inflate in an upward direction as viewed in FIG. 2. 
The inflating air bag 12 pushes outward against the inner side surface 24 
of the cover 20. The force of the inflating air bag 12 causes the cover 20 
to rupture along the tear seam 30, which is the predetermined weakened 
portion of the cover. The first and second movable parts 60 and 70 of the 
cover 20 open sufficiently that the air bag 12 inflates into a position to 
help protect the vehicle occupant. The amount of force required to rupture 
the tear seam 30 and open the cover 20 is reduced because a part of the 
tear seam (the central portion 50 of the base section 40) is an opening 
rather than simply a groove like the remainder of the tear seam. At the 
same time, the emblem 80 covers the opening 56 and protects the air bag 12 
until the inflator 14 is actuated. 
As the first and second movable parts 60 and 70 of the cover 20 open, the 
breakaway pins 96 and 98 on the emblem 80 rupture. The emblem 80 is 
therefore no longer secured to the first movable part 60 of the cover 20, 
but only to the second movable part 70 of the cover as shown in dot-dash 
lines in FIG. 2. The emblem 80 moves with the second movable cover part 70 
as the cover 20 opens. The solid pins 92 and 94 retain the emblem 80 on 
the second movable cover part 70 when the cover 20 opens. 
FIG. 4 illustrates portions of an air bag module 10a which is constructed 
in accordance with a second embodiment of the present invention. The air 
bag module 10a is similar in construction to the air bag module 10 (FIGS. 
1-2) and similar parts are given the same reference numerals with the 
suffix "a" added for clarity. 
In the air bag module 10a, the central portion 50a of the base section 40a 
of the tear seam 30a comprises a series of discrete openings or 
perforations 56a, rather than one continuous opening as in the air bag 
module 10. All the individual openings 56a are covered by the one emblem 
80a. The openings 56a are configured and located to ensure that the 
central portion 50a of the base section 40a of the tear seam 30a is still 
weaker and easier to rupture than the remaining portions of the tear seam 
30a. 
FIG. 5 illustrates portions of an air bag module 10b which is constructed 
in accordance with a third embodiment of the present invention. The air 
bag module 10b is similar in construction to the air bag module 10 (FIGS. 
1-2) and similar parts are given the same reference numerals with the 
suffix "b" added for clarity. 
In the air bag module 10b, the cover 20b forms a part of the instrument 
panel 80 of a vehicle. The cover 20b has a U-shaped tear seam 30b 
including a base section 40b and two side sections 82. The base section 
40b comprises an opening 56b in the cover 20b which extends for the entire 
length of the base section. The opening 56b is covered by one emblem 80b 
which, in the illustrated embodiment, is a piece of trim such as wood 
trim. 
From the above description of the invention, those skilled in the art will 
perceive improvements, changes and modifications. For example, the emblem 
may be a functional device rather than a decorative one. For example, the 
emblem may comprise a switch or a control or an indicator for one or more 
vehicle functions such as radio or speed control. Such improvements, 
changes and modifications within the skill of the art are intended to be 
covered by the appended claims.