Dual-stage gas generator utilizing eco-friendly gas generant formulation

• US 20040056458A1
• Filed: 09/12/2002
• Published: 03/25/2004
• Est. Priority Date: 09/12/2002
• Status: Active Grant

• Current Assignee: Textron Innovations Incorporated (Textron Inc)
• Original Assignee: Textron Innovations Incorporated (Textron Inc)
• Inventors: Daoud, Sami
• Granted Patent: US 6,877,435 B2
• Time in Patent Office: Days
• US Class Current: 280/736
• CPC Class Codes: B60R 2021/2648 comprising a plurality of combustion chambers or sub-chambers
• CPC Class Codes: B60R 21/2171 specially adapted for elongated cylindrical or bottle-like inflators with a symmetry axis perpendicular to the main direction of bag deployment, e.g. extruded reaction canisters B60R21/2176 takes precedence
• CPC Class Codes: B60R 21/2644 using only solid reacting substances, e.g. pellets, powder
• CPC Class Codes: C06D 5/06 by reaction of two or more solids

Abstract

This invention relates to a gas generator having two or more compartments, each with a separate initiator, with one compartment discharging before another, i.e., the compartments discharge sequentially. Each compartment has the same propellants, but the propellants have different geometries in each compartment, which results in different rates of gas evolution from each compartment.

The new gas generator is designed to reach maximum inflation at the same time as the current, single stage gas generators. However, the new generator has a more rapid initial inflation, followed by a more gradual inflation rate in the subsequent stages, improving safety to occupants.

The propellant used in new generator comprises (1) ammonium nitrate as the oxidizer, which is less toxic and corrosive than the currently-used azide, (2) a fuel such as CL-20, and (3) a binder such as polycaprolactone. No hot metal particles (e.g., CuO) are generated in the new system. This means that the complex, expensive filtering system in the current airbag systems is not needed, nor is there a need to use coated airbags.

Claims

1. A gas generator comprising at least two chambers, each said chamber being capable of discharging gas therefrom at a different time and different volumetric rate, each said chamber containing the same propellant and an initiator,

wherein said propellant comprises on a weight basis approximately (a) 84-95% of an oxidizer, (b) 3.4-13.4% of a fuel, and (c) 1.5-2.6% of a binder,

the products of combustion of said propellant being non-toxic gases.

2. The gas generator of claim 1, wherein said fuel is selected from the group consisting of CL-20, RDX, HMX, GAP, TATB, LLM-105, EDNA, and mixtures thereof.

3. The gas generator of claim 1, wherein said binder is selected from the group consisting of PCL, PIB, GAP, polyvinylpyrrolidone, and mixtures thereof.

4. The gas generator of claim 1, wherein said oxidizer is ammonium nitrate.

5. The gas generator of claim 1, wherein said oxidizer is ammonium nitrate, said fuel is CL-20, and said binder is polycaprolactone.

6. The gas generator of claim 5, wherein said ammonium nitrate comprises approximately 89.5%, said CL-20 comprises approximately 8.4%, and said polycaprolactone comprises approximately 2.1% of said propellant.

7. The gas generator of claim 1, wherein the geometry of said propellant is different from chamber to chamber.

8. The gas generator of claim 7 having 2 chambers, wherein the change of pressure as a function of time from the first of said chambers is at least 2 times greater than the change of pressure as a function of time from the second of said chambers.

9. The gas generator of claim 1, wherein the products of combustion of said propellant consist of water, nitrogen and CO₂.

10. The gas generator of claim 1, wherein said propellant is made by

a. preparing a mixture of the components of said propellant in wet or dry form,

b. forming said mixture into tablets, disks or granules,

c. if wet, allowing said tablets, disks or tablets to dry, and

d. perforating said tablets, disks or tablets to achieve the desired geometry.

11. The gas generator of claim 1, wherein said propellant has density greater than or equal to approximately 92% of theoretical density.

12. A vehicle airbag system comprising

a. the gas generator of claim 1, each said chamber being capable of discharging gas therefrom at a different time, each said chamber containing the same propellant and an initiator,

wherein said propellant comprises on a weight basis approximately (1) 84-95% of an oxidizer, (2) 3.4-13.4% of a fuel, and (3) 1.6-2.6% of a binder,

the products of combustion of said propellant being non-toxic gases and

b. an uncoated airbag.

13. A process for controlling the rate of inflation of a vehicle airbag comprising

a. connecting to said vehicle airbag the gas generator of claim 1, each said chamber being capable of discharging gas therefrom at a different time,

each said chamber containing the same propellant and an initiator,

wherein said propellant comprises on a weight basis approximately (1) 84-95% of an oxidizer, (2) 3.4-13.4% of a fuel, and (3) 1.6-2.6% of a binder,

the products of combustion of said propellant being non-toxic gases,

b. causing each of said chambers to discharge at a different, predetermined time, and

c. causing the effluent of each of said chambers to flow into said airbag.