Low-mount inflatable knee airbags having serial chambers

1. An inflatable knee airbag configured to be mounted in a vehicle at a bottom portion of an instrument panel, wherein the inflatable knee airbag comprises:

a first inflatable chamber; and

a second inflatable chamber fluidly coupled to the first inflatable chamber in a serial configuration, such that during inflatable knee airbag deployment, the second inflatable chamber is at least partially inflated before the first inflatable chamber,

wherein a lower portion of the first inflatable chamber is attached to the second inflatable chamber at an upper portion of a rear face of the second inflatable chamber,

wherein each of the first and second inflatable chambers comprise single panels of material,

wherein the lower portion of the first inflatable chamber comprises a folded middle portion of the single panel of material from which the first inflatable chamber is formed,

wherein in the deployed configuration, the first inflatable chamber is located above the second inflatable chamber, and

wherein in the deployed configuration, an angle between a rear face of the first inflatable chamber and the rear face of the second inflatable chamber is greater than 90°.

2. The inflatable knee airbag of claim 1 , wherein a perimeter seam of the second inflatable chamber is located on a front face of the inflatable knee airbag.

3. The inflatable knee airbag of claim 1 , wherein the second inflatable chamber comprises a plurality of inflator apertures that are located on the rear face of the second inflatable chamber.

4. An inflatable knee airbag configured to be mounted in a vehicle at a bottom portion of an instrument panel, wherein the inflatable knee airbag comprises:

a first inflatable chamber; and

a second inflatable chamber fluidly coupled to the first inflatable chamber in a serial configuration, such that during inflatable knee airbag deployment, the second inflatable chamber is at least partially inflated before the first inflatable chamber,

wherein the second inflatable chamber comprises a front face and a rear face, wherein the front face and the rear face are opposite from each other,

wherein the second inflatable chamber comprises an inflator insert aperture and an inflator stem aperture that are each located on the rear face of the second inflatable chamber,

wherein a lower portion of the first inflatable chamber is attached to the second inflatable chamber at only an upper portion of the rear face of the second inflatable chamber,

wherein in the deployed configuration, the first inflatable chamber is located above the second inflatable chamber,

wherein in the deployed configuration, an angle between a rear face of the first inflatable chamber and the rear face of the second inflatable chamber is greater than 90° as determined by the attachment of the first inflatable chamber and the second inflatable chamber,

wherein the upper portion of the second inflatable chamber and the lower portion of the first inflatable chamber each comprise a plurality of chamber-to-chamber vents,

wherein the first and second inflatable chambers are attached such that each chamber-to-chamber vent of the second inflatable chamber aligns with a chamber-to-chamber vent of the first inflatable chamber,

wherein stitching attaches the first inflatable chamber and the second inflatable chamber together, and

wherein the stitching extends around the plurality of chamber-to-chamber vents.

5. The inflatable knee airbag of claim 4 , wherein the inflator insert aperture has a greater diameter than the inflator stem aperture.

6. The inflatable knee airbag of claim 4 , wherein the inflator insert aperture is located between about 25 mm and about 125 mm from a distal edge of the second inflatable chamber when the airbag is in a flattened configuration and the inflator stem aperture is located between about 25 mm and about 125 mm from a distal edge of the second inflatable chamber when the airbag is in a flattened configuration.

7. The inflatable knee airbag of claim 4 , wherein the second inflatable chamber comprises an internal tether that is oriented such that it extends across a portion of the second inflatable chamber along an axis that is substantially parallel with a lower edge of the second inflatable chamber.

8. The inflatable knee airbag of claim 7 , wherein the internal tether extends from a front face to the rear face of the second inflatable chamber, and wherein the internal tether comprises an aperture that allows inflation gas to flow from one side of the tether to another side of the tether.

9. The inflatable knee airbag of claim 8 , wherein centers of the inflator insert and inflator stem apertures are located between about 30% and about 60% of a distance between the lower edge of the second inflatable chamber and stitching that couples the internal tether to the second inflatable chamber.

10. The inflatable knee airbag of claim 9 , wherein the first inflatable chamber comprises an internal tether that extends across a portion of the first inflatable chamber along an axis that is substantially parallel with a lower edge of the first inflatable chamber, and wherein the internal tether extends from a front face to a rear face of the first inflatable chamber.

11. The inflatable knee airbag of claim 4 , wherein the location of the stitching and the location of the perimeter seam of the second inflatable chamber relative to each other assist in determining the angle between the rear face of the first inflatable chamber and the rear face of the second inflatable chamber.

12. The inflatable knee airbag of claim 4 , wherein each of the first and second inflatable chambers comprise single panels of material.

13. The inflatable knee airbag of claim 12 , wherein the lower portion of the first inflatable chamber comprises a folded middle portion of the single panel of material from which the first inflatable chamber is formed.

14. The inflatable knee airbag of claim 4 , wherein in the deployed configuration, the angle between the rear face of the first inflatable chamber and the rear face of the second inflatable chamber is greater than 90° and up to about 160° as determined by the attachment of the first inflatable chamber and the second inflatable chamber.