Dual stage inflator

• US 6,474,684 B1
• Filed: 02/23/1999
• Issued: 11/05/2002
• Est. Priority Date: 04/24/1997
• Status: Expired due to Term

• Current Assignee: Nammo Talley, Inc. (Nammo AS)
• Original Assignee: Nammo Talley, Inc. (Nammo AS)
• Inventors: Bednarz, John, Scaven, Gregory J., Willhelm, Robert S., Hansen, Glade L., Muir, Martin J., Ludwig, Christopher P.
• Primary Examiner(s): CULBRETH, ERIC D
• Application Number:
  US09/255,834
• Time in Patent Office: 1,351 Days
• Field of Search: 280/741, 280/742, 280/736, 280/740
• US Class Current: 280/741
• CPC Class Codes: B60R 2021/26064 characterised by auto-ignition means
• CPC Class Codes: B60R 2021/2633 with a plurality of inflation levels
• CPC Class Codes: B60R 2021/2648 comprising a plurality of combustion chambers or sub-chambers
• CPC Class Codes: B60R 21/264 using instantaneous generation of gas, e.g. pyrotechnic B60R21/268 takes precedence
• CPC Class Codes: B60R 21/2644 using only solid reacting substances, e.g. pellets, powder
• CPC Class Codes: C06C 9/00 Chemical contact igniters; Chemical lighters
• CPC Class Codes: C06D 5/06 by reaction of two or more solids

Abstract

A non-hybrid pyrotechnic filterless inflator, i.e., gas generator, for an automotive passive restraint air bag having a generally discoidally-shaped pressure vessel having a diameter that preferably is greater than or about equal to its height formed of a cup-shaped closure cap and a base member and having at least one exhaust nozzle for directing gaseous products out of the inflator and into the air bag. The pressure vessel contains two separated and independently initiated initiator assemblies. By initiating either one or both initiator assemblies, the inflator can generate a modulated gas output between a first minimum output level and a second maximum output level in response to passenger and driver conditions.

Claims

1. A dual stage inflator capable of producing a gas output modulated between at least a first output level and a second output level, said dual stage inflator comprising:

(a) a single pressure vessel, said pressure vessel comprising at least one exhaust nozzle adapted to permit passage of gases within said pressure vessel out of said pressure vessel;

(b) a first non-pressurizable chamber within said pressure vessel, said first non-pressurizable chamber comprising;

(i) a first gas-generant charge present in an amount sufficient to generate the first output level;

(ii) a first initiator assembly adjacent said first gas-generant charge and capable of initiating said first charge;

(iii) a first gas-generant cup comprising at least one sidewall, and containing the first gas-generant charge; and

(iv) a lid positioned across an open top of the first gas-generant cup; and

(c) a second non-pressurizable chamber within said pressure vessel, said second non-pressurizable chamber comprising;

(i) a second gas-generant charge present in an amount sufficient to combine with the first gas-generant charge to generate the second output level; and

(ii) a second initiator assembly adjacent said second gas-generant charge and capable of initiating said second charge independent of said first charge;

wherein

said second chamber is separated from said first chamber by a one-way seal comprising a second chamber lid, said second chamber lid configured and adapted to inhibit passage of gas from said first chamber to said second chamber prior to initiation of said second gas-generated charge, and, upon combustion of said second gas-generant charge, to at least partially open, thereby forming an opening defined by said second chamber lid and said second chamber to permit passage of gas from said second chamber to said first chamber upon initiation of said second gas-generant charge, and wherein

the second chamber is disposed within the at least one sidewall, and the first and second chambers do not add structural support to the pressure vessel.

2. The inflator of claim 1, wherein the pressure vessel is discoidal in shape.

3. The inflator of claim 1, wherein the first gas-generant cup further comprises a plurality of gas ports disposed around the sidewalls, the gas ports not aligned with the exhaust ports.

4. The inflator of claim 1, wherein the second chamber comprises a cylinder having a bottom and a top and extending into the first chamber, the cylinder bottom sealed against the pressure vessel and the cylinder top sealed by the one-way gas seal.

5. The inflator of claim 4, wherein the first and second gas-generant charges have an ignition temperature, and comprising an auto-ignition powder for igniting the gas-generant charge at a temperature lower than the ignition temperature of the gas-generant charges.

6. The inflator of claim 5, wherein the auto-ignition powder is disposed adjacent the cylinder bottom in the second chamber and is bounded by cylinder walls, an internal collar of the second initiator assembly sealing the cylinder bottom, and a pad.

7. The inflator of claim 5, wherein the auto-ignition powder is disposed within a cartridge, and the cartridge passes through the first gas-generant cup into the first chamber.

8. The inflator of claim 1, wherein the pressure vessel further comprises a plurality of exhaust nozzles disposed in the pressure vessel and arranged to produce a net force on the pressure vessel of about zero.

9. The inflator of claim 8, further comprising a shroud covering the pressure vessel, the shroud comprising a plurality of vents disposed around the shroud, the vents not aligned with the exhaust nozzles.

10. The inflator of claim 9, wherein the vents are spaced around the shroud at an angle from about 42°

to about 48°

.

11. The inflator of claim 1, further comprising a sensor connected to the first and second initiator assemblies and capable of initiating the initiator assemblies either independently or simultaneously.

12. The inflator of claim 11, wherein the sensor detects rapid vehicle deceleration and initiates the initiator assemblies based on vehicle speed, crash severity, seat position, passenger weight, passenger size, seat belt use, passenger location, or combinations thereof.

13. The inflator of claim 11, wherein the second initiator assembly is initiated after the first initiator assembly to produce at least one intermediate output level.

14. The inflator of claim 13, wherein the second initiator assembly is initiated after the first initiator following a delay after the initiation of the first initiator of about greater than 0 milliseconds to about 40 milliseconds.

15. The inflator claim 1 further wherein the gas-generant charges comprise a non-azide, low-solids producing gas-generating composition, said composition producing a gaseous product upon combustion.

16. The inflator of claim 15 wherein said gas-generating composition further comprises an ignition material coating.

17. The inflator of claim 16 comprising from 54 to about 67 percent guanidine nitrate and from about 33 to about 46 percent oxidizer wherein the oxidizer comprises ammonium perchlorate and sodium nitrate in a mole ratio of about 1 mole of ammonium perchlorate to about 1 to about 4 moles of sodium nitrate.

18. The inflator of claim 17 wherein the gas-generating composition comprises about 55-65 percent guanidine nitrate, about 20-25 percent ammonium perchlorate and about 15-20 percent sodium nitrate.

19. The inflator of claim 16 wherein the gas-generating composition comprises about 59 percent guanidine nitrate, about 23 percent ammonium perchlorate and about 18 percent sodium nitrate.

20. The inflator of claim 1, wherein the inflator is a filterless inflator.

21. An air bag system for use in an automobile, comprising:

(a) an air bag having an open end; and

(b) the dual stage inflator according to claim 1 disposed in the open end for inflating the air bag at either a first or a second rate to either a first or a second peak upon detection of rapid vehicle deceleration.

22. The dual stage inflator of claim 1, wherein said pressure vessel comprises a base member defining at least a first aperture and a second aperture, wherein said first aperture of said base member is configured and adapted to position said first initiator assembly adjacent said first gas-generant charge, and said second aperture of said base member is configured and adapted to position said second initiator assembly adjacent said second gas-generant charge.

23. The inflator of claim 1, wherein the dual stage inflator is filterless.

24. The dual stage inflator of claim 23, wherein the first and second gas-generant charges produce no more than about 15 percent by weight solids on combustion.

25. A dual stage inflator capable of producing at least a first output level and a second output level, comprising:

(a) a pressure vessel, said pressure vessel comprising at least one exhaust nozzle adapted to permit passage of gases within said pressure vessel out of said pressure vessel;

(b) a first chamber within said pressure vessel, comprising;

(i) a first gas-generant cup comprising at least one sidewall; and

(ii) a lid positioned across an open top of the first gas-generant cup;

(iii) a first gas-generant charge disposed in the first gas-generant cup and present in an amount sufficient to generate the first output level; and

(iv) a first initiator assembly adjacent said first gas-generant charge and capable of initiating said first charge; and

(c) a second chamber within said pressure vessel and separated from said first chamber by a one-way seal, said second chamber comprising;

(i) a cylinder having a bottom and a top and extending into the first chamber, the cylinder bottom sealed against the pressure vessel and the cylinder top sealed by the one-way gas seal;

(ii) a second gas-generant charge disposed in the cylinder and present in an amount sufficient to generate enough output to combine with the first output level to form the second output level; and

(iii) a second initiator assembly adjacent the second gas-generant charge and capable of initiating said second charge independent of the first charge.

26. A method for producing a total gas output level modulated between a first gas output level and a second gas output from a dual stage inflator having a single pressure vessel comprising at least two non-pressurizable independently initiatable chambers, the dual stage inflator comprising a first mode of operation in which the first chamber only is initiated to produce a minimum gas output level, a second mode of operation in which the second chamber only is initiated to produce a maximum gas output level, a third mode of operation in which the first and second chambers are initiated simultaneously to produce the maximum gas output level, and a fourth mode of operation in which the first chamber is initiated followed by initiation of the second chamber after a delay to produce an intermediate gas output level, comprising:

(a) determining the total output level; and

(b) selecting an appropriate mode of operation, wherein initiation of either one of the second or third modes of operation produces a maximum mass of gas pressure and a maximum mass flow rate and the initiation of the first chamber followed by the second chamber after a delay produces an intermediate mass of gas and an intermediate mass flow rate, and the ratio of the maximum mass of gas to the intermediate mass of gas is less than the ratio of the maximum mass flow rate to the intermediate mass flow rate.

27. A dual stage inflator capable of producing a gas output modulated between at least a first output level and a second output level, said dual stage inflator comprising:

(a) a pressure vessel, having a discoidal shape, and comprising at least one exhaust nozzle adapted to permit passage of gases within said pressure vessel out of said pressure vessel;

(b) a first non-pressurizable chamber within said pressure vessel, said first non-pressurizable chamber comprising;

(i) a first gas-generant charge present in an amount sufficient to generate the first output level; and

(ii) a first initiator assembly adjacent said first gas-generant charge and capable of initiating said first charge; and

(c) a second non-pressurizable chamber within said pressure vessel, said second non-pressurizable chamber, comprising;

(i) a second gas-generant charge present in an amount sufficient to combine with the first gas-generant charge to generate the second output level; and

(ii) a second initiator assembly adjacent said second gas-generant charge and capable of initiating said second charge independent of said first charge;

wherein

said second chamber is separated from said first chamber by a one-way seal comprising a second chamber lid, said second chamber lid configured and adapted to inhibit passage of gas from said first chamber to said second chamber prior to initiation of said second gas generant charge, and, upon combustion of said second gas-generant charge, to at least partially open, thereby forming an opening defined by said second chamber lid and said second chamber to permit passage of gas from said second chamber to said first chamber upon initiation of said second gas-generant charge.

28. A method for producing a total gas output level modulated between a first gas output level and a second gas output level from a dual stage inflator having a single pressure vessel comprising at least two non-pressurizable independently initiatable chambers, the dual stage inflator comprising a first mode of operation in which the first chamber only is initiated to produce a minimum gas output level, a second mode of operation in which the second chamber only is initiated to produce a maximum gas output level, a third mode of operation in which the first and second chambers are initiated simultaneously to produce the maximum gas output level, and a fourth mode of operation in which the first chamber is initiated followed by initiation of the second chamber after a delay to produce an intermediate gas output level, comprising:

(a) determining the total output level; and

(b) selecting an appropriate mode of operation;

wherein

initiation of either one of the second or third modes of operation produces a maximum mass of gas pressure and a maximum mass flow rate and the initiation of the first chamber followed by the second chamber after a delay produces an intermediate mass of gas and an intermediate mass flow rate, and the ratio of the maximum mass of gas to the intermediate mass of gas is less than the ratio of the maximum mass flow rate to the intermediate mass flow rate.