Method of and apparatus for speeding the response of an air bag inflator at low temperatures

• US 4,380,346 A
• Filed: 04/24/1981
• Issued: 04/19/1983
• Est. Priority Date: 04/24/1981
• Status: Expired due to Fees

• Current Assignee: Thiokol Corporation (Howmet Aerospace, Inc.)
• Original Assignee: Thiokol Corporation (Howmet Aerospace, Inc.)
• Inventors: Kirchoff, George F., Schneiter, Fred E., Dahle, David P., Davis, Leland E.
• Primary Examiner(s): Mitchell, David M.
• Application Number:
  US06/257,285
• Time in Patent Office: 725 Days
• Field of Search: 280/740, 280/741, 280/742, 280/737, 280/736, 280/735, 280/738, 422/166, 180/274
• US Class Current: 280/736
• CPC Class Codes: B60R 21/2644 using only solid reacting substances, e.g. pellets, powder
• CPC Class Codes: F42B 3/04 for producing gas under pressure generators of inflation fluid especially adapted for vehicle air bags B60R21/26

Abstract

An air bag inflator for the passenger side of an automobile includes an elongated, tubular housing having a plurality of perforations in its cylindrical wall for discharging gas. Within the housing are a gas generant composition, an igniter and filtering screens. The perforations are normally sealed with 0.003 inch (0.0762 mm.) thick non-tempered aluminum foil which is easily ruptured by the gas pressure when the inflator is ignited. The foil, in addition to serving as a hermetic seal for protecting the gas generant and igniter from moisture and dust, insures that the gas pressure will reach a certain, threshold level before being discharged into an air bag. In very cold weather the inflator attains its peak pressure considerably more slowly than in warm weather. As a result, the air bag may be inflated either too slowly or insufficiently to perform its intended purpose. In order to preclude this from happening at least some of the perforations in the housing are covered with an additional or buttressing layer of thicker (0.006 inch; 0.1524 mm.) non-tempered aluminum foil, so that the threshold gas pressure necessary to rupture these seals is raised. This shortens the time for attaining peak gas pressure within the tubular housing and results in faster, more satisfactory inflation of the air bag when the ambient temperature is low.

Claims

1. In a method for inflating an air bag comprising,

igniting combustible gas generant material in a sealed housing having walls that rupture when the pressure of the generated gas, in the rise thereof to a peak value, reaches a certain threshold value that is lower than the peak value,

filtering the generated gas, and

discharging the filtered gas to the air bag to be inflated,

the generation of gas within the housing being characterized in that the rise in pressure to the peak value tends to be attained more slowly when the ambient temperature is low so that the air bag then may be inflated too slowly or insufficiently to perform its intended purpose,

the improvement comprising the use of a multiple strength barrier to allow selected areas of the walls of the sealed housing to rupture at a low threshold pressure early in the event to provide gas flow for early bag movement and delaying the rupture of the walls of the sealed chamber in other areas until the pressure of the generated gas therein reaches a predetermined value,

restriction of the major inflator flow area during pressure build up having only a minor impact on inflator function during normal or high ambient temperature operation but having the effect of greatly increasing the rate of pressure build up at low ambient temperature operation when pressure buildup would normally be slow.

2. In an inflator for an air bag comprising housing means having wall means that define a combustion chamber, said wall means having gas discharge perforations formed therein and including rupturable means for normally sealing said perforations,

a combustible gas generant composition disposed in said combustion chamber, said composition being operable upon ignitition to produce gas and combustion products, the generation of gas within said housing being characterized in that the rise in pressure to a peak value tends to be slowed when the ambient temperature is low, said rupturable means of said wall means of said housing rupturing upon the attainment of a certain threshold value that is less than said peak value,

means for filtering the generated gas, and

means for discharging the filtered gas to an air bag,

the improvement comprising

means buttressing said rupturable means to delay the rupture thereof unitl the pressure of the generated gas therein reaches a predetermined value that is higher than the certain threshold value thereby to shorten the time for attaining the peak gas pressure value within the combustion chamber, and resulting in faster, more satisfactory generation of gas and inflation of the air bag when the ambient temperature is low and the rate of gas generation tends to be slowed,

said means for buttressing said rupturable means comprising a layer of foil, said layer of foil buttressing said rupturable means with respect to some only of said perforations.

3. In an inflator as specified in claim 2 wherein said rupturable means comprises the wall of a hermetically sealed cartridge that is positioned within said housing means, said layer of foil being disposed in contacting relation with the wall of said cartridge.

4. In an inflator as specified in claim 3 wherein said housing means is an elongated tubular housing and said cartridge is similarly elongated and tubular, and wherein said layer of foil is disposed in contacting relation with the wall of said cartridge internally thereof.