Pulsed pressure source particularly adapted for vehicle occupant air bag restraint systems

Claims

We claim:

1. A pulsed pressure source comprising plural chambers holding progressively larger masses of gas generants, said chambers being arranged so that each has an outlet coupled in fluid flow relation with the chamber having the next largest gas generant mass, the gas generant in each chamber being predominantly a non-explosive solid particulate material, the smallest chamber including a metal element in contact with the generant therein and selectively connected to an electric source, the electric source supplying a pulse having sufficient energy and duration when coupled to the element to cause the metal element to rupture and form a plasma discharge in the generant in the smallest chamber, the plasma discharge having sufficient energy and pressure to energize the generant in the smallest chamber to a plasma in response to the surface of the particles being heated by the plasma from the metal flowing between the particles, the chambers and generants being arranged so that gas from each chamber sequentially flows into the chamber having the next largest gas generant mass to sequentially heat the generant mass in the next largest chamber into a gas.

2. The pulsed pressure source of claim 1 wherein the chambers, masses in the chambers and the flow paths between the chambers are arranged so that gas flow from chamber C1 into chamber C2 continues until after gas flow from chamber C2 to chamber C3 is initiated, where C1, C2 and C3 are chambers having progressively larger generant masses therein.

3. The pulsed pressure source of claim 2 wherein the chambers, masses in the chambers and the flow paths between the chambers are arranged so that the pressure and temperature of the generant in chamber C.sub.i are approximately constant while the generant in chamber C.sub.i is being consumed by the gas from chamber C.sub.i, where C.sub.i is selectively each of the chambers.

4. The pulsed pressure source of claim 3 wherein the chambers, masses in the chambers and the flow paths between the chambers are arranged so that the mass flow rate of the gas from chamber C.sub.i to chamber C.sub.i+1 is approximately equal to the consumption rate of the generant in chamber C.sub.i, where C.sub.i+1 is the chamber in downstream fluid flow relation with chamber C.sub.i.

5. The pulsed pressure source of claim 4 wherein chamber C.sub.i has a volume sufficiently small that there is virtually no fluid flow from chamber C.sub.i+1 to chamber C.sub.i.

6. The pulsed pressure source of claim 4 wherein chamber C1 is constructed to confine the flow of gas from the generant in chamber C1 from chamber C1 only into chamber C2 and chamber C2 is constructed to confine the flow of gas from the generant in chamber C2 only into chamber C3.

7. The pulsed pressure source of claim 6 further including a first diaphragm for the gas flow from chamber C1 to chamber C2, the first diaphragm rupturing in response to the pressure in chamber C1 reaching a predetermined level, a second diaphragm in the gas flow path from chamber C2 to chamber C3, the second diaphragm rupturing in response to the pressure in chamber C2 reaching a predetermined level, a third diaphragm in a gas flow path from chamber C3, the third diaphragm rupturing in response to the pressure in chamber C3 reaching a predetermined level.

8. The pulsed pressure source of claim 7 wherein the first, second and third diaphragms respectively include vent holes that change from a closed state to an open state in response to the pressures in chambers C1, C2 and C3 reaching pressures lower than the pressures which respectively rupture the first, second and third diaphragms, the vent holes enabling the pressures in the chambers to continue to increase until rupture of the associated diaphragms.

9. The pulsed pressure source of claim 2 wherein chamber C1 is constructed to confine the flow of gas from the generant in chamber C1 from chamber C1 only into chamber C2 and chamber C2 is constructed to confine the flow of gas from the generant in chamber C2 only into chamber C3.

10. The pulsed pressure source of claim 9 further including a first diaphragm for the gas flow from chamber C1 to chamber C2, the first diaphragm rupturing in response to the pressure in chamber C1 reaching a predetermined level, a second diaphragm in the gas flow path from chamber C2 to chamber C3, the second diaphragm rupturing in response to the pressure in chamber C2 reaching a predetermined level, a third diaphragm in a gas flow path from chamber C3, the third diaphragm rupturing in response to the pressure in chamber C3 reaching a predetermined level.

11. The pulsed pressure source of claim 10 wherein the first, second and third diaphragms respectively include vent holes that change from a closed state to an open state in response to the pressures in chambers C1, C2 and C3 reaching pressures lower than the pressures which respectively rupture the first, second and third diaphragms, the vent holes enabling the pressures in the chambers to continue to increase until rupture of the associated diaphragms.

12. The pulsed pressure source of claim 1 wherein the non-explosive material includes NH.sub.4 NO.sub.3 particles.

13. The pulsed pressure source of claim 1 wherein the NH.sub.4 NO.sub.3 particles are coated with carbon powder.

14. The pulsed pressure source of claim 13 wherein the particles are about 200 micrometers in diameter and the carbon powder has a diameter of about 5 micrometers.

15. The pulsed pressure source of claim 12 further including a hermetic seal around the NH.sub.4 NO.sub.3 particles.

16. The pulsed pressure source of claim 1 wherein the electric source includes a capacitor connected to be charged by a DC power supply, the capacitor being connected in a discharge circuit including said metal element in series with an inductor.

17. The pulsed pressure source of claim 16 wherein the electric pulse has a duration less than an order of magnitude of the duration required for the generant in the chamber having the smallest generant mass to be consumed by the plasma formed therein.

18. The pulsed pressure source of claim 17 where a maximum of 25 joules is coupled by the pulse to the metal element.

19. The pulsed pressure source of claim 18 wherein the metal element has a segment with a smaller cross-sectional area than the remainder thereof, the smaller cross-sectional area segment initially vaporizing to form the plasma in response to the pulse being supplied to it.

20. The pulsed pressure source of claim 17 wherein the metal element has a segment with a smaller cross-sectional area than the remainder thereof, the smaller cross-sectional area segment initially vaporizing to form the plasma in response to the pulse being supplied to it.

21. The pulsed pressure source of claim 1 wherein the metal element has a segment with a smaller cross-sectional area than the remainder thereof, the smaller cross-sectional area segment initially vaporizing to form the plasma in response to the pulse being supplied to it.

22. The pulsed pressure source of claim 1 wherein a plurality of said pulsed pressure sources are provided, means for sequentially activating the plural pulsed pressure sources in response to a common sensed parameter so that a gas pressure pulse from each of said pulsed pressure sources flows continuously to a load over an interval beginning with flow from the chamber having the largest generant mass of the first source which is activated and ending with flow from the chamber having the largest generant mass of the last source which is activated.

23. The pulsed pressure source of claim 22 wherein the separate pressure pulses overlap in time so that the first pressure pulse has a duration beginning with flow from the chamber having the largest generant mass of the first pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated, the second pulse having a duration beginning with flow from the chamber having the largest generant mass of the second pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated, the third pulse having a duration beginning with flow from the chamber having the largest generant mass of the third pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated.

24. The pulsed pressure source of claim 1 wherein each chamber includes means for partially confining the vapor formed therein to cause the vapor to be resident in the chamber for a sufficient length of time to cause heating of a substantial amount of the generant in the chamber to a vapor.

25. The pulsed pressure source of claim 24 wherein the means for partially confining the vapor includes a frangible diaphragm with vent holes.

26. The pulsed pressure source of claim 1 further including an exit orifice to a load for gas flowing from the chamber having the largest mass, the smallest chamber being constructed so gas flowing from it can flow to the load only through an exit in another of the chambers, the exit orifice being closed by a diaphragm that ruptures only in response to the generant in the chamber having the largest mass being converted in to a gas having a predetermined pressure.

27. An occupant passive restraint system for an automotive vehicle having a battery comprising an air bag, means for sensing deceleration of the vehicle associated with a crash, a pulsed pressure source in fluid flow relation with the air bag, the pulsed pressure source including: plural chambers holding progressively larger masses of gas generates, said chambers being arranged so that each has an outlet coupled in fluid flow relation with the chamber having the next largest gas generant mass, the gas generant mass in each chamber being predominantly a non-explosive solid material, the smallest chamber including a metal element in contact with the generant therein and selectively connected to an electric source energized by said battery, the electric source responding to the deceleration sensing means for supplying a pulse having sufficient energy and duration to the element to cause the metal element to burst and form a plasma discharge having sufficient energy and pressure to the plasma discharge having sufficient energy and pressure to energize the generant in the smallest chamber to a vapor, the chambers and generants being arranged so that gas from each chamber sequentially flows into the chamber having the next largest gas generant mass to sequentially activate the generant mass in the next largest chamber, the gas from the chamber having the largest generant mass flowing into the air bag.

28. The occupant passive restraint system of claim 27 wherein a plurality of said pressure sources are provided, means for sequentially activating the plural pressure sources in response to a crash being sensed so that a gas pressure pulse from each of said pressure sources flows continuously to the bag over an interval beginning with flow from the chamber having the largest generant mass of the first pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated.

29. The occupant passive restraint system of claim 28 the separate pulses overlap in time so that the first pulse has a duration beginning with flow from the chamber having the largest generant mass of the first pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated, the second pulse having a duration beginning with flow from the chamber having the largest generant mass of the second pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated, the third pulse having a duration beginning with flow from the chamber having the largest generant mass of the third pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated.

30. The occupant passive restraint system of claim 29 including temperature sensing means for controlling energization of said pressure pulses.

31. The occupant passive restraint system of claim 30 wherein the temperature sensing means controls when said pressure pulses are derived.

32. The occupant passive restraint system of claim 30 wherein the temperature sensing means controls how many of said pressure pulses are derived.

33. The occupant passive restraint system of claim 27 wherein each chamber includes means for partially confining the vapor formed therein to cause the vapor to be resident in the chamber for a sufficient length of time to cause heating of a substantial amount of the generant in the chamber to a vapor.

34. The occupant passive restraint system of claim 33 wherein the means for partially confining the vapor includes a frangible diaphragm with vent holes.

35. The occupant passive restraint system of claim 27 further including an exit orifice to the air bag for gas flowing from the chamber having the largest mass, the exit orifice being closed by a diaphragm that ruptures only in response to the generant in the chamber having the largest mass being converted into a gas having a predetermined pressure, for gas flowing from the chamber having the largest mass, the smallest chamber being constructed so gas flowing from it can flow to the load only through an exit in another of the chambers, the exit orifice being closed by a diaphragm that ruptures only in response to the generant in the chamber having the largest mass being converted into a gas having a predetermined pressure.

36. The occupant passive restraint system of claim 27 wherein the chambers, asses in the chambers and the flow paths between the chambers are arranged so that gas flow from chamber C1 into chamber C2 continues until after gas flow from chamber C2 to chamber C3 is initiated, where C1, C2 and C3 are chambers having progressively larger generant masses therein.

37. The occupant passive restraint system of claim 36 wherein the chambers, masses in the chambers and the flow paths between the chambers are arranged so that the pressure and temperature of the generant in chamber C.sub.i are approximately constant while the generant in chamber C.sub.i is being consumed by the gas from chamber C.sub.i, where C.sub.i is selectively each of the chambers.

38. The occupant passive restraint system of claim 37 wherein the chambers, masses in the chambers and the flow paths between the chambers are arranged so that the mass flow rate of the gas from chamber C.sub.i to chamber C.sub.i+1 is approximately equal to the consumption rate of the generant in chamber C.sub.i, where C.sub.i+1 is the chamber in downstream fluid flow relation with chamber C.sub.i.

39. The occupant passive restraint system of claim 38 wherein chamber C1 is constructed to confine the flow of gas from the generant in chamber C1 from chamber C1 only into chamber C2 and chamber C2 is constructed to confine the flow of gas from the generant in chamber C2 only into chamber C3.

40. The occupant passive restraint system of claim 39 further including a first diaphragm for the gas flow from chamber C1 to chamber C2, the first diaphragm rupturing in response to the pressure in chamber C1 reaching a predetermined level, a second diaphragm in the gas flow path from chamber C2 to chamber C3, the second diaphragm rupturing in response to the pressure in chamber C2 reaching a predetermined level, a third diaphragm in a gas flow path from chamber C3, the third diaphragm rupturing in response to the pressure in chamber C3 reaching a predetermined level.

41. The occupant passive restraint system of claim 40 wherein the first, second and third diaphragms respectively include vent holes that change from a closed state to an open state in response to the pressures in chambers C1, C2 and C3 reaching pressures lower than the pressures which respectively rupture the first, second and third diaphragms, the vent holes enabling the pressures in the chambers to continue to increase until rupture of the associated diaphragms.

42. An occupant passive restraint system for an automotive vehicle having a battery comprising an air bag, means for sensing deceleration of the vehicle associated with a crash, a pulsed pressure source in fluid flow relation with the air bag, the pulsed pressure source including: means for generating separate pressure pulses at sequential time intervals in response to the deceleration means sensing a single impact of a crash, pressures from the sequentially generated pulses being combined to produce a flow for inflating the air bag, means for generating the separate pressure pulses including plural sources of pressure pulses, said sources being responsive to the crash sensing means to be sequentially activated, each of said sources of pressure pulses including plural chambers holding progressively larger masses of gas generants, said chambers being arranged so that each has an outlet coupled in fluid flow relation with the chamber having the next largest gas generant mass, the gas generant mass in each chamber being predominantly a non-explosive solid material, the smallest chamber including a metal element in contact with the generant therein and selectively connected to an electric source energized by said battery, the electric source responding to the deceleration sensing means for supplying a pulse having sufficient energy and duration to the element to cause the metal element to rupture and form a plasma discharge in the generant in the smallest chamber, the plasma discharge having sufficient energy and pressure to energize the generant in the smallest chamber to a vapor, the chambers and generants being arranged so that gas from each chamber sequentially flows into the chamber having the next largest gas generant mass to sequentially activate the generant mass in the next largest chamber, the gas from the chamber having the largest generant mass flowing into the air bag.

43. The occupant passive restraint system of claim 42 wherein the separate pulses overlap in time so that the first pulse has a duration beginning with flow from the chamber having the largest generant mass of the first pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated, the second pulse having a duration beginning with flow from the chamber having the largest generant mass of the second pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated, the third pulse having a duration beginning with flow from the chamber having the largest generant mass of the third pressure source which is activated and ending with flow from the chamber having the largest generant mass of the last pressure source which is activated.

44. The occupant passive restraint system of claim 43 wherein each chamber includes means for partially confining the vapor formed therein to cause the vapor to be resident in the chamber for a sufficient length of time to cause heating of a substantial amount of the generant in the chamber to a vapor.

45. The occupant passive restraint system of claim 44 wherein the means for partially confining the vapor includes a frangible diaphragm with vent holes.