Seatback-mounted restraint system

1. A restraint system comprising:

a seatback; and

an airbag including two lateral portions and a central chamber connecting the lateral portions;

wherein when the airbag is inflated, each lateral portion includes a plurality of lateral chambers arranged consecutively from the seatback to the central chamber, and the lateral portions and central chamber define a gap positioned directly above and directly in front of space for a head of a 50th-percentile dummy sitting against the seatback;

the seatback includes a left lateral side, a right lateral side opposite the left lateral side, and a headrest;

the airbag is inflatable from an uninflated position; and

the airbag in the uninflated position extends along the right lateral side, above the headrest, and along the left lateral side.

2. The restraint system of claim 1 , wherein the lateral portions are each inflatable from one of the lateral sides.

3. The restraint system of claim 1 , wherein the central chamber extends from the left lateral side to the right lateral side when the airbag is inflated.

4. The restraint system of claim 1 , wherein the central chamber extends vertically from space for hips to space for a chest of a 50th-percentile dummy sitting against the seatback when the airbag is inflated.

5. The restraint system of claim 1 , wherein the lateral portions extend vertically from above to below space for a head of a 50th-percentile dummy sitting against the seatback when the airbag is inflated.

6. The restraint system of claim 1 , wherein the lateral portions extend forward from the seatback to in front of space for a head of a 50th-percentile dummy sitting against the seatback when the airbag is inflated.

7. The restraint system of claim 1 , wherein the lateral portions include a left lateral portion and a right lateral portion; and when the airbag is inflated, the gap extends from the headrest to the central chamber and from the left lateral portion to the right lateral portion.

8. The restraint system of claim 1 , wherein the lateral portions include a left lateral portion and a right lateral portion; and the left lateral portion includes a first chamber bordering the left lateral side and a second chamber bordering the central chamber when the airbag is inflated.

9. The restraint system of claim 8 , wherein the first chamber does not border the central chamber when the airbag is inflated.

10. The restraint system of claim 8 , wherein the first chamber is fluidly connected to the second chamber, and the second chamber is fluidly connected to the central chamber.

11. The restraint system of claim 10 , wherein the first chamber is fluidly connected to the central chamber only via the second chamber.

12. The restraint system of claim 1 , further comprising an inflatable tube attached to the central chamber.

13. The restraint system of claim 12 , wherein the inflatable tube is disposed below the central chamber when the airbag is inflated.

14. The restraint system of claim 12 , wherein the seatback includes a left lateral side and a right lateral side opposite the left lateral side, and the inflatable tube extends from the left lateral side to the right lateral side.

15. The restraint system of claim 12 , wherein the inflatable tube is fluidly isolated from the central chamber.

16. The restraint system of claim 12 , wherein the inflatable tube and airbag are arranged so that during inflation the inflatable tube inflates before the airbag inflates.

17. A restraint system comprising:

a seatback; and

an airbag including two lateral portions and a central chamber connecting the lateral portions;

wherein when the airbag is inflated, each lateral portion includes a plurality of lateral chambers arranged consecutively from the seatback to the central chamber, and the lateral portions and central chamber define a gap positioned directly above and directly in front of space for a head of a 50th-percentile dummy sitting against the seatback;

the seatback includes a left lateral side and a right lateral side opposite the left lateral side;

the lateral portions include a left lateral portion and a right lateral portion;

the left lateral portion includes a first chamber bordering the left lateral side and a second chamber bordering the central chamber when the airbag is inflated;

the first chamber is fluidly connected to the second chamber, and the second chamber is fluidly connected to the central chamber; and

the first chamber is fluidly connected to the central chamber only via the second chamber.

18. A restraint system comprising:

a seatback;

an airbag including two lateral portions and a central chamber connecting the lateral portions; and

an inflatable tube attached to the central chamber;

wherein when the airbag is inflated, each lateral portion includes a plurality of lateral chambers arranged consecutively from the seatback to the central chamber, and the lateral portions and central chamber define a gap positioned directly above and directly in front of space for a head of a 50th-percentile dummy sitting against the seatback; and

the inflatable tube is fluidly isolated from the central chamber.

19. A restraint system comprising:

a seatback;

an airbag including two lateral portions and a central chamber connecting the lateral portions; and

an inflatable tube attached to the central chamber;

wherein when the airbag is inflated, each lateral portion includes a plurality of lateral chambers arranged consecutively from the seatback to the central chamber, and the lateral portions and central chamber define a gap positioned directly above and directly in front of space for a head of a 50th-percentile dummy sitting against the seatback; and

the inflatable tube and airbag are arranged so that during inflation the inflatable tube inflates before the airbag inflates.