The present invention relates to low permeability airbags. More specifically, the present invention relates to airbags that are required to stay inflated for extended periods of time in order to protect occupants in a vehicle in the event of a sustained collision event, such as a rollover. An example of such an airbag is a side curtain airbag.
Traditional airbags are manufactured by means of sewing panels of fabric together to form a substantially enclosed, three dimensional bag, where the only substantial opening in the bag (other than vents) is designed to receive the inflator means. Typically, airbags are made from woven fabrics, and bags of desired shape have been produced by sewing panels of various shapes and dimensions. Sewn seams may be adequate for some driver and passenger applications because the required time for gas retention on these bags is less than one second.
This manufacturing method is unsuitable for side curtain airbags, and the like, because the holes created in the fabric by the sewing process allow gas to leak out, which reduces the gas retention time to unacceptable levels. Further, in order to obtain fabrics having low air permeability, it has generally been necessary to apply a heavy coating or lamination to the fabric, which is a costly step in the manufacturing process.
One solution that has been proposed to address this leakage issue is to attach the fabric panels together through welding means. While this method may prevent or reduce leakage at the seams, the fabric must still be heavily coated or laminated, and it has proven difficult to weld fabric directly to fabric.
Thus, it would be desirable to provide an airbag having low air permeability, which would not allow significant gas leakage at the seams thereof, and which would not require a minimal amount of lamination or coating on the face of the airbag fabric or substrate.
Accordingly, it is an object of the present invention to provide a low permeability airbag cushion that prevents or reduces leakage along the seams thereof.
Another object of the present invention is to provide a low gas permeability airbag cushion that reduces the use of costly laminates and coatings that must be applied to a face of the airbag fabric.
Yet another object of the present invention is to provide a low gas permeability airbag cushion having an inner bag enclosed in an outer bag, thus forming a double-layered airbag cushion.
Yet another object of the present invention is to provide a low cost fabric or non-woven on the outside, but having a low permeability inner cushion. The fabric component functions primarily as a strength provider rather than as a means to impart low permeability.
Another object of the present invention is to provide an inner bag enclosed in an outer bag, thus forming a double-layered airbag cushion that could be used on the driver, passenger, or side airbag applications.
Still another object of the present invention is to provide a method for producing a low gas permeable airbag, wherein the process prevents the airbag from being punctured in such a way that would allow leakage along the seams thereof.
Another object of the present invention is to provide an inexpensive airbag cushion and method for manufacturing such an airbag cushion, which minimizes or eliminates the use of expensive coatings and laminates, and which addresses other problems associated with the manufacture and production of airbag cushions having low gas permeability characteristics.