Gas generator for vehicle occupant restraint

• US 5,462,306 A
• Filed: 02/22/1995
• Issued: 10/31/1995
• Est. Priority Date: 01/21/1993
• Status: Expired due to Fees

• Current Assignee: TRW Inc. (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Barcaskey, Eric S.
• Primary Examiner(s): Miller, Edward A.
• Application Number:
  US08/392,605
• Time in Patent Office: 251 Days
• Field of Search: 149/35, 280/741, 280/736
• US Class Current: 280/736
• CPC Class Codes: C06B 35/00 Compositions containing a metal azide
• CPC Class Codes: C06D 5/06 by reaction of two or more solids

Abstract

The present invention resides in a vehicle occupant restraint assembly (12). The assembly comprises a vehicle occupant restraint (20), a housing (14), a gas generating composition (16) within the housing, an igniter (18) for igniting the gas generating composition, and gas flow means (22) for directing gas into the vehicle occupant restraint. In a preferred embodiment of the present invention, the vehicle occupant restraint (20) is an air bag. The gas generating composition (16) comprises lithium azide (Li₃ N) and a metal oxidant (MeO), wherein O can be either oxygen or sulfur. The metal oxidant is present in a sub-stoichiometric amount relative to the lithium azide. The gas generating composition (16), on ignition, burns under reaction conditions which produce lithium nitride (Li₃ N) and a combustion product which is essentially free of elemental lithium.

Claims

1. A vehicle occupant restraint assembly comprising:

a vehicle occupant restraint;

a housing;

a gas generating composition within the housing;

an igniter for igniting the gas generating composition; and

gas flow means for directing gas from said housing to said vehicle occupant restraint;

said gas generating composition comprising lithium azide and a metal oxidant (MeO) wherein the metal oxidant is present in a sub-stoichiometric amount with respect to the lithium azide, the ratio of lithium azide to metal oxidant being a ratio effective to produce lithium nitride (Li₃ N).

2. The restraint assembly of claim 1 wherein the gas generating composition burns according to the following equation:

##EQU4## wherein O is either oxygen or sulfur.

3. The restraint assembly of claim 2 wherein z equals approximately 3 plus 2y.

4. The restraint assembly of claim 1 comprising cooling surfaces effective to cool the products of combustion of the gas generating composition to below the melting point of lithium nitride.

5. The restraint assembly of claim 1 comprising cooling surfaces effective to cool the products of combustion of the gas generating composition to below 850°

C.

6. The restraint assembly of claim 1 comprising at least about 15 mol percent excess lithium azide.

7. The restraint assembly of claim 1 wherein the metal oxidant is an oxide or sulfide of a transition metal, or boron, aluminum, or silicon, or mixtures thereof.

8. The restraint assembly of claim 1 wherein said metal oxidant is iron oxide (Fe₂ O₃) present in a sub-stoichiometric amount of about 20-50 mol percent excess lithium azide.

9. The restraint assembly of claim 8 wherein said gas generating composition burns according to the following equation:

space="preserve" listing-type="equation">9LiN.sub.3 +Fe.sub.2 O.sub.3 →

13N.sub.2 +3Li.sub.2 O+Li.sub.3 N+2Fe.

10. The restraint assembly of claim 9 having a cooling surface effective to cool the products of combustion of the gas generating composition to less than about 850°

C.

11. A vehicle occupant restraint assembly comprising:

a vehicle occupant restraint;

a housing;

a gas generating composition within the housing;

an igniter for igniting the gas generating composition; and

gas flow means for directing gas from said housing to said vehicle occupant restraint;

said gas generating composition consisting essentially of lithium azide and iron oxide (Fe₂ O₃) wherein the lithium azide is present in an effective amount to, in reaction with the iron oxide, produce lithium nitride;

heat exchange means in said gas flow means effective to cool the products of combustion of the gas generating composition to less than about 850°

C. to produce lithium nitride solids; and

filter means to entrap the solids of lithium nitride and other solids in the combustion products.

12. A gas generating composition for inflating a vehicle occupant restraint comprising active ingredients consisting essentially of lithium azide and a metal oxidant wherein the lithium azide is present in an effective amount to, in reaction with the metal oxidant, produce an amount of lithium nitride (Li₃ N).

13. The composition of claim 12 wherein said metal oxidant is selected from the group consisting of oxides or sulfides of a transition metal, of boron, of aluminum, of silicon or of mixtures thereof.

14. The composition of claim 12 wherein said metal oxidant is iron oxide (Fe₂ O₃) present in a sub-stoichiometric amount of about 20-50 mol percent excess lithium azide.

15. A gas generating composition for inflating a vehicle occupant restraint comprising active ingredients consisting essentially of lithium azide and a metal oxidant in proportions which react essentially according to the following equation:

##EQU5## wherein O is either oxygen or sulfur.

16. The composition of claim 15 wherein z equals approximately 3 plus 2y.

17. A gas generating composition for inflating a vehicle occupant restraint comprising active ingredients consisting essentially of lithium azide and iron oxide (Fe₂ O₃) in proportions which react essentially according to the following equation:

space="preserve" listing-type="equation">9LiN.sub.3 +Fe.sub.2 O.sub.3 →

13N.sub.2 +3Li.sub.2 O+Li.sub.3 N+2Fe

18. A gas generating composition for inflating a vehicle occupant restraint comprising active ingredients consisting essentially of lithium azide and iron oxide (Fe₂ O₃) in a mol ratio wherein the composition has at least about 15 mol percent excess lithium azide over a stoichiometric ratio of lithium azide to iron oxide, effective to produce Li₃ N reaction product.

19. The composition of claim 18 which burns according to the equation:

space="preserve" listing-type="equation">9LiN.sub.3 +Fe.sub.2 O.sub.3 →

13N.sub.3 +3Li.sub.2 O+Li.sub.3 N+2Fe

20. The composition of claim 18 which, on ignition, burns to produce a reaction product which is essentially free of elemental lithium.