Air bag with improved tear stitch

1. An apparatus for helping to protect an occupant of a vehicle, the apparatus comprising:

an inflatable vehicle occupant protection device having a deflated condition and an inflated condition; and

tear stitching interconnecting first and second overlying portions of the protection device to each another, the tear stitching comprising first and second stitch lines positioned next to each other and extending through both the first and second overlying portions, the first stitch line being adapted to rupture in response to tension of a first magnitude exerted on the interconnected portions while inflating to an initially deployed condition, the second stitch line being adapted to remain intact and being capable itself of maintaining the protection device in the initially deployed condition subsequent to rupture of the first stitch line and throughout inflation and deployment of the protection device.

2. The apparatus recited in claim 1 , wherein the second stitch line is adapted to remain intact in response to obstructed deployment of the protection device and to rupture in response to unobstructed deployment and pressurization of the protection device.

3. The apparatus recited in claim 1 , wherein each of the first and second stitch lines comprises a break point and first and second segments that extend away from the break point, the first stitch line having a configuration that is different than the second stitch line so that the rupture strength of the second stitch line is greater than the rupture strength of the first stitch line.

4. The apparatus recited in claim 1 , wherein the first line has a V-shaped configuration and the second stitch line has an arc-shaped configuration.

5. The apparatus recited in claim 1 , wherein the first line has a first arc-shaped configuration and the second stitch line has a second arc-shaped configuration.

6. The apparatus recited in claim 1 , wherein the apparatus has an adaptive condition in which the second stitch line is adapted to rupture in response to deployment of the protection device beyond initial deployment of the protection device, the apparatus being adapted to be placed in the adaptive condition in response to at least one of sensed vehicle and occupant conditions.

7. The apparatus recited in claim 6 , wherein the adaptive condition comprises actuation of at least one of an actuatable fastener and a vent.

8. The apparatus recited in claim 1 , wherein the second stitch line is adapted to maintain the interconnection of the portions of the protection device in response to vented pressurization of the protection device, and to rupture in response to non-vented pressurization of the protection device.

9. An apparatus for helping to protect an occupant of a vehicle, the apparatus comprising:

an inflatable vehicle occupant protection device having a deflated condition and an inflated condition; and

tear stitching interconnecting first and second overlying portions of the protection device to each another, the tear stitching comprising first and second stitch lines positioned next to each other and extending through both the first and second overlying portions, the first stitch line being adapted to rupture in response to initial deployment of the protection device, the second stitch line being adapted to remain intact in response to obstructed deployment of the protection device and to rupture in response to unobstructed deployment and pressurization of the protection device.

10. The apparatus recited in claim 9 , wherein the second stitch line is capable itself of maintaining the protection device in an initially deployed condition subsequent to rupture of the first stitch line, subsequent to the obstructed deployment, and throughout inflation and deployment of the protection device.

11. The apparatus recited in claim 9 , wherein each of the first and second stitch lines comprises a break point and first and second segments that extend away from the break point, the first stitch line having a configuration that is different than the second stitch line so that the rupture strength of the second stitch line is greater than the rupture strength of the first stitch line.

12. The apparatus recited in claim 9 , wherein the apparatus has an adaptive condition in which the second stitch line is adapted to rupture in response to deployment of the protection device beyond initial deployment of the protection device, the apparatus being adapted to be placed in the adaptive condition in response to at least one of sensed vehicle and occupant conditions.

13. The apparatus recited in claim 12 , wherein the adaptive condition comprises actuation of at least one of an actuatable fastener and a vent.

14. The apparatus recited in claim 9 , wherein the second stitch line is adapted to maintain the interconnection of the portions of the protection device in response to vented pressurization of the protection device, and to rupture in response to non-vented pressurization of the protection device.

15. An apparatus for helping to protect an occupant of a vehicle, the apparatus comprising:

an inflatable vehicle occupant protection device having a deflated condition and an inflated condition;

a vent that is actuatable to vent inflation fluid from the protection device; and

tear stitching comprising first and second stitch lines positioned next to each other that form an interconnection that connects first and second overlying portions of the protection device to each another, the first stitch line extending through both the first and second overlying portions and being adapted to rupture in response to deployment of the protection device, the second stitch line extending through both the first and second overlying portions and being adapted to maintain the interconnection in response to vented pressurization of the protection device, and to rupture and thereby break the interconnection in response to non-vented pressurization of the protection device.

16. The apparatus recited in claim 15 , wherein the second stitch line is capable itself of maintaining the interconnection and thereby maintaining the protection device in an initially deployed condition subsequent to rupture of the first stitch line and throughout inflation and deployment of the protection device.

17. The apparatus recited in claim 15 , wherein each of the first and second stitch lines comprises a break point and first and second segments that extend away from the break point, the first stitch line having a configuration that is different than the second stitch line so that the rupture strength of the second stitch line is greater than the rupture strength of the first stitch line.

18. The apparatus recited in claim 1 , wherein the first stitch line is formed from a first thread having a first tensile strength and the second stitch line is formed from a second thread having a second tensile strength greater than the first tensile strength.

19. The apparatus recited in claim 1 , wherein the overlying portions of the protection device comprise a vent that is actuatable to vent inflation fluid from the protection device and a side panel of the protection device to which the vent is secured by the first and second stitch lines.

20. The apparatus recited in claim 9 , wherein the overlying portions of the protection device comprise a vent that is actuatable to vent inflation fluid from the protection device and a side panel of the protection device to which the vent is secured by the first and second stitch lines.

21. The apparatus recited in claim 9 , wherein the first stitch line is formed from a first thread having a first tensile strength and the second stitch line is formed from a second thread having a second tensile strength greater than the first tensile strength.

22. The apparatus recited in claim 15 , wherein the first stitch line is formed from a first thread having a first tensile strength and the second stitch line is formed from a second thread having a second tensile strength greater than the first tensile strength.