Air Bag Assembly for Motor Vehicles

a. Field of Invention

The present invention pertains to an improved air bag assembly for motor vehicles particularly suited for installation in a small space, such as the steering wheel, and more particularly, to an air bag assembly with coupling means to insure that the assembly is installed in a motor vehicle safely and correctly.

b. Description of the Prior Art

Typically an air bag assembly for a motor vehicle consists of a mechanical or electrical sensor, a gas generator connected to the sensor and a bag arranged for inflation from gasses from said generator. In operation, when the sensor detects that the motor vehicle is subjected to a deceleration of a preset magnitude and duration, it sets off the gas generator which in turn inflates the bag. During the installation or removal of the assembly, the sensor should be disarmed to insure that the gas generator is not activated accidentally, for example if the assembly is dropped, or jarred. This problem is especially important for assemblies with mechanical sensors. However, once the assembly is installed the sensor should be armed; otherwise the air bag assembly is non-functional and therefore useless. However, prior art assemblies had no installation or disassembly provisions which operated satisfactorily.

Therefore it is an objective of the present invention to provide an assembly in which the sensor is automatically disarmed when not installed onto the vehicle, and is armed when the installation of the gas generator is completed.

A further objective is to provide an assembly with means of assuring that the installation of the system cannot be completed if the sensor is disabled.

A further objective is to provide an assembly which can be installed easily and without the use of special tools.

Other objectives and advantages of the invention shall become apparent from the following description.

The present invention pertains to a self-contained air bag system disposed in a well formed in the steering wheel. The system includes a cover for the well, an inflatable air bag disposed in the cover, a gas generator disposed in the well and various hardware for mounting the above mentioned elements on the steering wheel. These various elements cooperate to insure that the gas generator is armed and the cover is installed only if the gas generator is properly installed in the well. Removal of the gas generator automatically disarms it.

FIG. 1 shows a plan view of a steering wheel with an air bag assembly constructed in accordance with this invention;

FIG. 2 shows a plan view similar to FIG. 1 showing a well within the steering wheel for housing the assembly;

FIG. 3 shows a top view of the gas generator for the assembly;

FIG. 4 shows a bottom view of the gas generator of FIG. 3;

FIG. 5 shows a side view of the gas generator of FIGS. 3 and 4;

FIG. 6 shows the gas generator installed in the steering wheel well, with the sensor disarmed;

FIG. 7 shows the gas generator of FIG. 6 with the sensor armed;

FIG. 8 is partial side-sectional view taken along line 8--8 in FIG. 7;

FIG. 9 shows a bottom view of the steering wheel cover with the air bag;

FIG. 10 shows a side sectional view of the air bag assembly installed in the steering wheel; and

FIG. 11 shows an exploded side view of the assembly.

Referring now to the Figures, FIG. 1 shows a top view of an assembled steering wheel 10 having a rim 12 joined by several spokes 14 to a central hub 16. Although the shape of the hub 16 is immaterial for the present invention, in the embodiment of FIG. 1, the hub 16 is generally rectangular. Disposed on two lateral sides of the hub there are a plurality of switches 18 associated with the operation of the motor or its accessories. Also mounted on hub 16 is a cover 20. The cover 20 is secured to the wheel 10 as described below.

FIG. 2 shows the steering wheel 10 with the cover 20 and other air bag elements removed. As seen in FIGS. 2 and 10, steering wheel 10 is formed with a well 22 holding a metal backing plate 24. Backing plate 24 defines a circular opening with a lip 26 which is interrupted by three arcuate notches 28, 30, 32. Notches 28 and 30 extend over an arc of circular much smaller than notch 32.

The well 22 is also provided five through holes for mounting the cover 20. Four of these holes 34, 36, 38 and 40 are always exposed while the fifth hole 42 is covered by a sliding plate 44 Sliding plate 44 is slidably mounted on backing plate 24 and has an arcuate slot 46 engaged by two guiding pins 48, 50. A spring (not shown) disposed below the sliding plate 44 is used to bias this sliding plate 44 to the position shown in FIG. 2 wherein the sliding plate 44 covers hole 42.

A shaft 53 extends upwardly from the bottom of well 22. As seen in FIG. 2, shaft 53 has a D-shaped cross-section.

Well 22 is also used to hold a gas generator 54 shown in detail in FIGS. 3-5. This gas generator may be constructed for example from aluminum and have the structure as described in copending application Ser. No. 715,493 identified above. Gas generator 54 includes a cylindrical body 56 with a plurality of holes 58. The body 56 has a bottom plate 60 with three arcuate tongues 62, 64 and 66 dimensioned to fit into notches 28, 30, and 32 of backing plate 26, respectively. Tongue 66 is provided with a lateral projection 68 having a round hole 70. Within gas generator 54 there is an acceleration sensor 72 with a a rotary member 74A having D-shaped hole 74. This sensor may be for example a mechanical sensor as described in U.S. patent application Ser. No. 715,493 identified above. When gas generator 54 is not installed, the rotary member 74A is positioned so that the sensor 72 is disarmed so that the generator is not set off even if it is accidentally dropped, hit with a hammer, and so on.

The gas generator 54 is installed into the wheel 10 as follows. First, the gas generator 54 is positioned in the 22 with shaft 53 inserted in hole 74 and tongues 62, 64, 66 inserted into notches 28, 30, 32 as shown in FIG. 6. The gas generator 54 is then rotated clockwise, as indicated by arrow A, causing the tongues 62, 64, 66 to slip under the lip 26 of plate 24. The gas generator 54 and plate 24 are dimensioned so that an interference fit is formed therebetween to maintain the gas generator 54 in place. Importantly, as gas generator 54 is rotated, shaft 53 remains fixed, thereby arming the sensor 72. In addition, as shown in FIG. 7, as the gas generator reaches the end of its travel, projection 68 pushes the slide plate 48 to the right, uncovering hole 42. Thus, when the gas generator 54 is in its secured and armed position shown in FIG. 7, hole 42 is uncovered since sliding plate 44 is pushed aside, and is aligned with hole 70.

The cover 20, as shown in FIGS. 9 and 10, includes a top panel 80. This panel 80 is made of plastic or leather and has several parallel grooves 82, 84, 86 (shown in FIG. 1). On its bottom surface 88, cover 20 has a cylindrical wall 90. Inside cover 20, there is a folded air bag 91 (FIG. 10). The cover 20 also has five downwardly extending or protrusions studs 92, 94, 96, 98 and 100 which fit into holes 34, 36, 38, 40 and 42 respectively when the cover is installed over well 22. Studs 92, 94, 96 and 98 are preferably threaded. Once the cover 20 is installed over the well 22, its studs extend under the steering wheel so that it may be secured by nuts such as nut 102 (FIG. 10). Wall 90 is arranged to fit telescopically about gas generator 54.

Once the cover 20 is secured, the air bag assembly is armed and operational. If the motor vehicle is involved in a crash, the acceleration sensor 72 triggers the gas generator which emits an inflator gas through its holes 58. The cover 20 is arranged over the generator, so that this gas is channeled into the air bag 91. The air bag 91 then quickly expands breaking panel 80 along its parallel grooves.

The gas generator assembly described above has a number of very advantageous features. When disassembled, its gas generator is disarmed and therefore the components of the assembly are safe to handle. The cover 20, generator 54 and the backing plate 24 cooperate to prevent an improper or incomplete installation. More particularly, the cover 20 cannot be installed into well 22 without the gas generator being installed properly of the operation of the sliding plate 44. Plate 44 allows the proper installation and securing of cover 20 only after gas generator 54 is seated and armed within the well 22. Finally, if the air bag assembly has to be dismounted, the gas generator cannot be removed from the well before it is disarmed by rotating it counterclockwise with respect to shaft 53. If the gas generator 54 is not disarmed, it is prevented from being removed by backing plate 24.

In the above-described embodiment the air bag assembly is shown installed on a steering wheel; however, it may be installed on other parts of a motor vehicle, for example over a glove compartment. Obviously numerous other modifications may be made to the invention without departing from its scope as defined in the appended claims.