Airbag apparatus with multi-ply airbag cushion

1. An airbag apparatus, comprising:

a fastening unit mounted to a portion of a vehicle;

a multi-ply airbag cushion fastened to the fastening unit, the multi-ply airbag cushion being formed by overlapping airbag cushion sheets on each other to form a multi-ply structure, and

an inflator to provide gas to the airbag cushion sheets of the multi-ply airbag cushion,

wherein the multi-ply airbag cushion has an overlapped portion formed by overlapping a margin of a first side thereof with a margin of a second side thereof,

wherein the overlapped portion has a first gas hole formed at a predetermined position through the margin of the first side of the multi-ply airbag cushion, and a second gas hole formed through the margin of the second side of the multi-ply airbag cushion at a predetermined position, and

wherein the inflator supplies the gas to the multi-ply airbag cushion through the first and second gas holes.

2. The airbag apparatus as set forth in claim 1 , wherein the portion of the vehicle is a bumper or a housing connected to the bumper, the housing retaining the fastening unit and the multi-ply airbag cushion therein.

3. The airbag apparatus as set forth in claim 1 , wherein the fastening unit comprises:

a first fastener mounted to the portion of the vehicle, the first fastener having a first through hole to receive a portion of a guide unit therein, wherein the guide unit is connected to the inflator to receive the gas therethrough; and

a second fastener fastened to the first fastener, the second fastener having a second through hole to receive the other portion of the guide unit therethrough,

wherein the overlapped portion is disposed between the first and second fasteners.

4. The airbag apparatus as set forth in claim 3 ,

wherein a plurality of first coupling holes is formed through a perimeter of the first fastener, and locking members are inserted into the corresponding first coupling holes to fasten the first fastener to the portion of the vehicle, and

a plurality of second coupling holes is formed through a perimeter of the second fastener, and locking members are inserted into the corresponding second coupling holes to fasten the second fastener to the first fastener.

5. The airbag apparatus as set forth in claim 3 , wherein a first protrusion protrudes from one surface of the first fastener, the first protrusion extending a predetermined length in a longitudinal direction of the first fastener, and second protrusions protrude from the second fastener in a direction opposing a direction in which the first protrusion protrudes, the second protrusions being spaced apart from each other by predetermined intervals.

6. The airbag apparatus as set forth in claim 1 , further comprising:

a guide unit coupled to the fastening unit, the guide unit being disposed through the first and second gas holes of the overlapped portion of the multi-ply airbag cushion.

7. The airbag apparatus as set forth in claim 1 , wherein a tether is coupled to an inner surface of the multi-ply airbag cushion by sewing to control a shape of the multi-ply airbag cushion.

8. The airbag apparatus as set forth in claim 7 , wherein the tether is coupled to an inner surface of a front portion of the multi-ply airbag cushion and an inner surface of a rear portion of the multi-ply airbag cushion.

9. The airbag apparatus as set forth in claim 1 , wherein the multi-ply airbag cushion has a sewn portion formed by sewing the airbag cushion sheets that are overlapped with each other.

10. The airbag apparatus as set forth in claim 1 , wherein the portion of the vehicle comprises a bumper mounted to the vehicle, and the multi-ply airbag cushion comprises an external airbag cushion provided in the bumper.