Vehicle safety device

Claim 1

A vehicle safety device adapted for attachment to a vehicle for protecting an occupant thereof during an accident, said vehicle safety device including impact bag means inflatable on crash impact by fluid flow thereinto, said impact bag means having a collapsed condition and an expanded operative condition for restraining movement of an occupant relative to the vehicle as the result of a crash impact, said impact bag means comprising in part a material from zero to low permeability with respect to the inflating fluid thereof and in part at least one other material having variable permeability which increases and decreases in relation to the fluid pressures within said impact bag means, certain areas of the bag being reinforced for added strength, and wherein the total flow rate of the inflating fluid through the material of the impact bag is within the range of 1800 <ελ i S i < 2300 cubic feet per minute and wherein the area of the material of variable permeability is determined according to the formula: ##EQU5## wherein: ελ i S i is the desired summation of flow through all pieces of fabric (λS for each piece) and λ 1 is the weighted average of the permeability of the material of variable permeability, λ 2 is the weighted average of the permeability of the material of zero to low permeability, S 1 is the total of the design area of the material of variable permeability, S 2 is the total of the design area of material of zero to low permeability, S 3 is the area made relatively impervious by installation of reinforcing, S Tot is the total bag design area, all values of λ are in terms of cubic feet per minute per square foot at 1 p.s.i.g, and all values of S are in terms of square feet.