Air bag inflator

• US 20040051284A1
• Filed: 09/13/2002
• Published: 03/18/2004
• Est. Priority Date: 09/13/2002
• Status: Active Grant

• Current Assignee: Island Pyrochemical Industries Corp.
• Original Assignee: Island Pyrochemical Industries Corp.
• Inventors: Parizat, Amnon, Tarczynski, Marek
• Granted Patent: US 6,889,614 B2
• Time in Patent Office: Days
• US Class Current: 280/736
• CPC Class Codes: B60R 21/264 using instantaneous generation of gas, e.g. pyrotechnic B60R21/268 takes precedence

Abstract

The air bag inflator employs an injection piston assembly in which liquid propellant is delivered through nozzles in the injection piston to the combustion chamber. Metering of the liquid propellant is accomplished in a manner that is not sensitive to changes in ambient temperatures. A plug is sladably mounted between the propellant chamber and the nozzles to prevent flashback at startup. The plug is pushed forwardly to expose the nozzles to the propellant chamber in response to a predetermined pressure in the propellant chamber. A plug may also be fitted into each nozzle to be expelled into the combustion chamber upon opening of the nozzle. A tape may also be provided over the outlet of the nozzle to prevent flashback into the propellant chamber.

Claims

1. An air bag inflator comprising

a housing having a combustion chamber therein and at least one port for expelling combustion gas from said combustion chamber;

an initiator mounted on said housing for introducing a combustion gas into said combustion chamber;

an injection piston slidably mounted in said combustion chamber of said housing for movement between an initial position and a second position in response to the introduction of a combustion gas into said combustion chamber from said initiator, said piston including a propellant chamber therein for containing a charge of liquid propellant therein, at least one nozzle communicating said propellant chamber with said combustion chamber to deliver liquid propellant thereto, and means for releasably closing said nozzle to prevent communication between said propellant chamber and said combustion chamber; and

a plug mounted in said housing coaxially of said piston to slidably receive said piston.

2. An air bag inflator as set forth in claim 1 wherein said means includes a tape secured to said injection piston over said nozzle on a side facing said combustion chamber to prevent a flow of combustion gas from said combustion chamber through said nozzle during startup.

3. An air bag inflator as set forth in claim 2 wherein said tape is a thin metal tape.

4. An air bag inflator as set forth in claim 3 wherein said tape is made of aluminum.

5. An air bag inflator as set forth in claim 2 wherein said means further includes a plug fitted into said nozzle, said plug being expellable from said nozzle into said combustion chamber in response to a pressurized flow of liquid propellant from said propellant chamber.

6. An air bag inflator as set forth in claim 5 wherein said plug is made of Nylon.

7. An air bag inflator as set forth in claim 1 wherein said injection piston is made of metal and which further comprises a coating on said injection piston within said propellant chamber to prevent contact between a liquid propellant in said propellant chamber and said metal piston.

8. An air bag inflator as set forth in claim 7 wherein said coating is made of a polytetrafluoroethylene plastic.

9. An air bag inflator as set forth in claim 1 wherein said injection piston has a reduced nose projecting into said combustion chamber and having a conically shaped section extending towards said skirt and wherein said nozzle has an outlet located in said conically shaped section.

10. An air bag inflator as set forth in claim 9 wherein injection piston has a plurality of said nozzles in said conically shaped section and said means includes a conically shaped tape secured to said conically shaped section over said nozzles.

11. An air bag inflator as set forth in claim 9 which further comprises an injection plug slidably mounted in said nose to move from a first position blocking communication between said propellant chamber and said nozzle to a second position to permit communication between said propellant chamber and said nozzle in response to a pressurized flow of liquid propellant from said propellant chamber.

12. An air bag inflator as set forth in claim 1 wherein said injection piston has a circumferential skirt defining said propellant chamber and further comprising a pump piston mounted in abutment with one end of said plug and slidably receiving said skirt of said injection piston thereon.

13. An air bag inflator comprising

a cylindrical housing having a combustion chamber therein and at least one exhaust port for expelling combustion gas from said combustion chamber;

an initiator mounted on one end of said housing for introducing a combustion gas into said combustion chamber;

an injection piston slidably mounted in said combustion chamber of said housing for movement between an initial position and a second position in response to the introduction of a combustion gas into said combustion chamber from said initiator, said piston including a propellant chamber therein for containing a charge of liquid propellant therein, at least one nozzle communicating said propellant chamber with said combustion chamber to deliver liquid propellant thereto, and means for releasably closing said nozzle to prevent communication between said propellant chamber and said combustion chamber; and

a plug threadably mounted in an opposite end of said housing from said initiator and coaxially of said piston to slidably receive said piston.

14. An air bag inflator as set forth in claim 13 wherein said means includes a tape secured to said injection piston over said nozzle on a side facing said combustion chamber to prevent a flow of combustion gas from said combustion chamber through said nozzle during startup.

15. An air bag inflator as set forth in claim 14 wherein said means further includes a plug fitted into said nozzle, said plug being expellable from said nozzle into said combustion chamber in response to a pressurized flow of liquid propellant from said propellant chamber.

16. An air bag inflator as set forth in claim 13 wherein said injection piston is made of metal and which further comprises a coating on said injection piston within said propellant chamber to prevent contact between a liquid propellant in said propellant chamber and said metal piston.

17. An air bag inflator as set forth in claim 13 wherein said injection piston has a reduced nose projecting into said combustion chamber and having a conically shaped section extending towards said skirt and wherein said nozzle has an outlet located in said conically shaped section.

18. An air bag inflator as set forth in claim 17 wherein injection piston has a plurality of said nozzles in said conically shaped section and said means includes a conically shaped tape secured to said conically shaped section over said nozzles.

19. An air bag inflator as set forth in claim 17 which further comprises an injection plug slidably mounted in said nose to move from a first position blocking communication between said propellant chamber and said nozzle to a second position to permit communication between said propellant chamber and said nozzle in response to a pressurized flow of liquid propellant from said propellant chamber.

20. An air bag inflator as set forth in claim 13 further comprising a second piston mounted in abutment with one end of said plug and slidably receiving said injection piston thereon to pressurize liquid propellant in said propellant chamber in response to sliding of said injection piston onto said second piston

21. An air bag inflator as set forth in claim 20 wherein said second piston is made of plastic.

22. An air bag inflator as set forth in claim 13 having a plurality of said exhaust ports staggered along the length of said housing and said injection piston for sequential exposure to control the mass flow rate of the combustion gas out of said combustion chamber.

23. A liquid propellant comprising hydroxyl ammonium nitrate based liquid monopropellant including hydroxyl ammonium nitrate, triethyl ammonium nitrate and water.

24. A liquid propellant as set forth in claim 23 having 56% by weight hydroxyl ammonium nitrate as an oxidizer, 19% by weight triethyl ammonium nitrate as fuel and at least 20% by weight water as a diluent to provide stability of the propellant

25. A liquid propellant as set forth in claim 23 further comprising a stabilizer consisting of etidronic acid, phosphonic acid and tetrasodium bisphosphonate.

26. An injection piston assembly for an inflator comprising

a piston having a propellant chamber therein for containing a charge of liquid propellant therein,

at least one nozzle in one end of said piston communicating said propellant chamber with a combustion chamber external to the piston to deliver liquid propellant from said propellant chamber thereto, and

means for releasably closing said nozzle to prevent communication between said propellant chamber and the combustion chamber.

27. An injection piston as set forth in claim 26 wherein said means includes a tape secured to said injection piston over said nozzle on a side facing the combustion chamber to prevent a flow of combustion gas from the combustion chamber through said nozzle during startup.

28. An injection piston as set forth in claim 27 wherein said tape is a thin metal tape.

29. An injection piston as set forth in claim 28 wherein said tape is made of aluminum.

30. An injection piston as set forth in claim 26 wherein said means further includes a plug fitted into said nozzle, said plug being expellable from said nozzle in response to a pressurized flow of liquid propellant from said propellant chamber.

31. An injection piston as set forth in claim 30 wherein said plug is made of Nylon.

32. An injection piston as set forth in claim 26 wherein said injection piston is made of metal and which further comprises a coating on said injection piston within said propellant chamber to prevent contact between a liquid propellant in said propellant chamber and said metal piston.

33. An injection piston as set forth in claim 32 wherein said coating is made of a polytetrafluoroethylene plastic.

34. An injection piston as set forth in claim 26 further comprising a pump piston slidably mounted in said injection piston thereon to pressurize liquid propellant in said propellant chamber in response to sliding of said injection piston relative to said pump piston.