Curved airbag and method of manufacturing

1. An airbag comprising:

a plurality of interconnected adjacent inflatable cells, wherein each cell is attached to an adjacent cell by at least two junction seam lines, said at least two junction seam lines being spaced from each other to define a cell area, said cell area comprising a gas passage portion between said adjacent cells,

wherein said airbag has a storage position and a deployed position in which the airbag has an impact zone and an inflator-attachment zone, and wherein said airbag in its deployed position has at least one curved zone, wherein said at least one curved zone is obtained in a gas distribution zone having a curvature radius, whereby in the deployed position of the airbag, said impact zone lies on a plane inclined with respect to the deployment direction of said inflator-attachment zone and wherein each cell is formed by a single pre-cut element closed by a first margin seam line extending entirely along a first edge of said pre-cut element, and by a second margin seam line extending partially along a second edge of said pre-cut element at said curved zone of the airbag, wherein the at least two junction seam lines are curved.

2. An airbag according to claim 1 , wherein in said deployed position of said cell area defines a wall acting as a tether for the airbag.

3. An airbag of claim 2 , wherein said wall extends in a direction that is substantially transverse to a plane defined by said impact zone of the airbag.

4. An airbag according to claim 1 , wherein said pre-cut element comprises a seam allowance portion for said first margin seam line and said second margin seam line.

5. An airbag according to claim 4 , wherein at least part of said seam allowance portion is sewn inside the volume of said cell.

6. An airbag according to claim 1 , wherein several pre-cut elements are sewn together by said junction seam lines at said cell area to provide a line of adjacent cells.

7. A pre-cut element for producing a multi-cell airbag according to claim 1 , said element having an area that provides at least one means for passage of gas and two semi-portions that are symmetrical extending from a central axis (S) of said element, said semi-portions including curved parts, whereby when said semi-portions are folded and superimposed so that a curved cell of an airbag is obtained.

8. An airbag according to claim 1 , wherein the first margin seam line and the second margin seam line are curved.

9. An airbag according to claim 8 , wherein at least a portion of the at least two junction seam lines, at least a portion of the first margin seam line, and at least a portion of the second margin seam line are parallel to each other.

10. An airbag comprising a plurality of interconnected adjacent inflatable cells, wherein each cell is attached to an adjacent cell by at least two junction seam lines, said at least two junction seam lines being spaced from each other to define a cell area, said cell area comprising a gas passage portion between said adjacent cells, wherein said airbag has a storage position and a deployed position in which the air-bag has an impact zone and an inflator-attachment zone, and wherein said airbag in its deployed position has at least one curved zone, wherein said at least one curved zone is obtained in a gas distribution zone having a curvature radius, whereby in the deployed position of the airbag, said impact zone lies on a plane inclined with respect to the deployment direction of said inflator-attachment zone and wherein each cell is formed by at least two pre-cut elements sewn together to provide a cell closed by at least a first margin seam line and second margin seam line, said first margin seam line extending entirely along a first edge of said pre-cut elements and said second margin seam line extending entirely along a second edge of said pre-cut elements, wherein the at least two junction seam lines are curved.

11. An airbag according to claim 10 , wherein the first margin seam line and the second margin seam line are curved.

12. An airbag according to claim 11 , wherein at least a portion of the at least two junction seam lines, at least a portion of the first margin seam line, and at least a portion of the second margin seam line are parallel to each other.

13. An airbag comprising a plurality of interconnected adjacent inflatable cells, wherein each cell is attached to an adjacent cell by at least two junction seam lines, said at least two junction seam lines being spaced from each other to define a cell area, said cell area comprising a gas passage portion between said adjacent cells, wherein said airbag has a storage position and a deployed position in which the air-bag has an impact zone and an inflator-attachment zone, and wherein said airbag in its deployed position has at least one curved zone, wherein said at least one curved zone is obtained in a gas distribution zone having a curvature radius, whereby in the deployed position of the airbag, said impact zone lies on a plane inclined with respect to the deployment direction of said inflator-attachment zone and wherein said gas passage portion in said cell areas comprises holes in the side of said cells, said holes in one cell being at least in part superimposed to the holes in an adjacent cell; said holes being kept in place by said junction seam lines sewing lines stitching together said cells, wherein the at least two junction seam lines are curved.

14. An airbag according to claim 13 , wherein said cell is formed by a single pre-cut element closed by a first margin seam line extending entirely along a first edge of said pre-cut element, and by a second margin seam line extending partially along a second edge of said pre-cut element at said curved zone of the airbag, wherein the first margin seam line and the second margin seam line are curved.

15. A process according to claim 14 , wherein at least a portion of the first junction seam line, at least a portion of the second junction seam line, at least a portion of the first margin seam line, and at least a portion of the second margin seam line are parallel to each other.

16. A process for producing an inflatable airbag comprising a plurality of cells, said process comprising the steps of:

a) providing a plurality of pre-cut elements, said elements having a portion that has at least one means for passage of gas;

b) overlapping two pre-cut elements and aligning at least part of the gas passage portion of said pre-cut elements;

c) sewing together said pre-cut elements with at least a first junction seam line and a second junction seam line, said junction seam lines are spaced and located at opposite sides of said gas passage portion to provide a connection between adjacent cells in a final airbag, wherein said junction seam lines are curved;

d) folding a pre-cut element to superimpose its edges and sewing together the edges of each pre-cut element by means of at least a margin seam line to form one cell of said plurality of cells and wherein steps b) and c) are repeated several times to provide several cells in the final airbag, and wherein said pre-cut elements have two semi-portions that are symmetrical extending from a central axis (S) of said element, said semi-portions including curved parts, whereby when said semi-portions are folded and superimposed, a curved cell of an airbag is obtained and wherein at least a pre-cut element of said pre-cut elements is formed by a plurality of separate semi-portions joined together.

17. A process according to claim 16 , wherein said cell is formed by a single foldable pre-cut element.

18. A process according to claim 16 , wherein said pre-cut elements are obtained by sewing together separate semi-portions along said central axis (S).

19. A process according to claim 16 , wherein in step d) a first margin seam line is provided entirely along a first edge of said superimposed pre-cut element and a second margin seam line extends along the edge of said curved part of the said superimposed pre-cut element.

20. A process according to claim 19 , wherein the first margin seam line and the second margin seam line are curved.