Method for making a propellant having a relatively low burn rate exponent and high gas yield for use in a vehicle inflator
First Claim
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1. A method for making propellant for use in an inflator located in a vehicle, comprising:
- providing phase-stabilized ammonium nitrate by integrating potassium nitrate with ammonium nitrate such that said ammonium nitrate and said potassium nitrate are fused together;
mixing said phase-stabilized ammonium nitrate with at least fibrous cellulose to form a mixture, wherein said fibrous cellulose is between 6% and 12% by weight of said mixture of said phase-stabilized ammonium nitrate and said at least fibrous cellulose;
forming a thin, continuous length of propellant having a first density from said mixture of said phase-stabilized ammonium nitrate and said at least fibrous cellulose; and
working said thin, continuous length of propellant to provide said thin, continuous length of propellant with a second density greater than said first density.
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Abstract
A method for making a propellant composition that results in a desirable gas output when combusted. The propellant can be part of an inflator used in a vehicle for inflating an air bag. The propellant has a relatively low burn rate exponent of no greater than about 0.7. The propellant is substantially dense, with the propellant having a density that is at least 85% of theoretical density. In making the propellant, its density can be reduced using a roller mill that flattens the propellant to a controlled thickness. The propellant preferably includes phase-stabilized ammonium nitrate and fibrous cellulose.
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Citations
21 Claims
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1. A method for making propellant for use in an inflator located in a vehicle, comprising:
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providing phase-stabilized ammonium nitrate by integrating potassium nitrate with ammonium nitrate such that said ammonium nitrate and said potassium nitrate are fused together;
mixing said phase-stabilized ammonium nitrate with at least fibrous cellulose to form a mixture, wherein said fibrous cellulose is between 6% and 12% by weight of said mixture of said phase-stabilized ammonium nitrate and said at least fibrous cellulose;
forming a thin, continuous length of propellant having a first density from said mixture of said phase-stabilized ammonium nitrate and said at least fibrous cellulose; and
working said thin, continuous length of propellant to provide said thin, continuous length of propellant with a second density greater than said first density. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
cutting said thin, continuous length of said propellant into a number of propellant pieces.
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3. A method, as claimed in claim 1, wherein:
said second density is at least 85% of theoretical density.
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4. A method, as claimed in claim 1, wherein:
said second density is a predetermined density related to a burning rate of said propellant.
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5. A method, as claimed in claim 1, wherein:
said working step includes causing said propellant to have a thickness in a range of about 0.4 mm-6 mm and a burning rate in a range of about 5 mm/sec-100 mm/sec at about 5000 psi.
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6. A method, as claimed in claim 1, wherein:
said propellant is a substantially uniform mixture in which, for each selected cross-section of said substantially uniform mixture, any 1,000-micron portion of said selected cross-section has the same composition as any other 1,000-micron portion of said selected cross-section.
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7. A method, as claimed in claim 1, wherein:
said forming step includes extruding said mixture of said phase-stabilized ammonium nitrate and said at least fibrous cellulose.
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8. A method, as claimed in claim 1, further including:
grinding said phase-stabilized ammonium nitrate before said mixing step.
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9. A method, as claimed in claim 1, wherein:
said phase-stabilized ammonium nitrate further includes at least one of the following;
potassium fluoride, magnesium carbonate, copper/nickel amine complexes, potassium dinitramide, ammonium polyphosphates and cesium nitrate.
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10. A method, as claimed in claim 1, wherein:
said phase-stabilized ammonium nitrate includes a copper material.
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11. A method, as claimed in claim 1, wherein:
said working step includes continuously flattening said propellant using a roller mill having at least a first press element that is in contact with said propellant.
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12. A method, as claimed in claim 11, wherein:
said roller mill includes a second press element over which said propellant moves and said working step includes controlling said second density to a predetermined density by a force applied to one of said first and second press elements.
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13. A method for making a propellant for use in an inflator located in a vehicle, comprising:
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providing phase-stabilized ammonium nitrate by integrating potassium nitrate with ammonium nitrate such that said ammonium nitrate and said potassium nitrate are fused together;
forming a propellant having a first density that includes at least said phase-stabilized ammonium nitrate mixed with fibrous cellulose having amounts by weight as follows;
(a) ammonium nitrate 76.65%±
5%;
(b) potassium nitrate 9.35%±
3%;
(c) fibrous cellulose 9.00%±
3%; and
working said propellant to provide said propellant with a second density that is at least about 85% of theoretical density. - View Dependent Claims (14, 15, 16)
said first density is less than 80% of theoretical, density.
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15. A method, as claimed in claim 13, wherein:
said working step includes flattening said propellant using a roller mill having at least a first press element.
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16. A method, as claimed in claim 13, wherein:
said propellant has a burn rate exponent no greater than 0.7.
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17. A method for making a propellant for use in an inflator located in a vehicle, comprising:
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providing phase-stabilized ammonium nitrate by integrating potassium nitrate with ammonium nitrate such that said ammonium nitrate and said potassium nitrate are fused together;
forming a propellant having a first density that includes at least said phase-stabilized ammonium nitrate mixed with fibrous cellulose, said propellant being a substantially uniform mixture in which, for each selected cross-section of said substantially uniform mixture, any 1000-micron portion of said selected cross-section has the same composition as any other 1000-micron portion of said selected cross-section; and
working said propellant to provide said propellant with a second density that is at least about 85% of theoretical density, with a thickness in a range of about 0.4 mm-6 mm and with a burning rate in a range of about 5 mm/sec-100 mm/sec at about 5000 psi. - View Dependent Claims (18, 19, 20, 21)
said working step includes flattening said propellant using a roller mill having at least a first press element.
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19. A method, as claimed in claim 17, wherein:
said propellant has a burn rate exponent no greater than 0.7.
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20. A method, as claimed in claim 17, wherein:
said phase-stabilized ammonium nitrate further includes at least one of the following;
potassium fluoride, magnesium carbonate, copper/nickel amine complexes, potassium dinitramide, ammonium polyphosphates and cesium nitrate.
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21. A method, as claimed in claim 17, wherein:
said phase-stabilized ammonium nitrate includes a copper material.
Specification