US Patent 7543850 Airbag

The disclosed airbag comprises an upper airbag layer, a lower airbag layer, and an intermediate layer dividing the interior of the airbag into a first chamber and second chamber. An outlet is provided through which gas from the first chamber is able to enter the second chamber. The outlet is configured such that, according to an amount of gas introduced into the airbag through the inlet aperture, gas selectively fills substantially only the first chamber or both first and second chambers.