GB2259480A

GB2259480A - An air bag with the closed end folded and secured

Info

Publication number: GB2259480A
Application number: GB9119419A
Authority: GB
Inventors: Michael George Litton; Raymond Graham
Original assignee: Airbags International Ltd
Current assignee: Airbags International Ltd
Priority date: 1991-09-11
Filing date: 1991-09-11
Publication date: 1993-03-17
Anticipated expiration: 2011-09-11
Also published as: GB2259480B; GB9119419D0

Abstract

An inflatable airbag has the closed end folded back over at least pan of its upper surface and secured to said surface so that at least part of its upper surface is effectively three-ply. its lower surface is single-ply, and there is no seam at its folded end. The airbag is preferably made from a blank so shaped that when folded back each side overlies itself. Preferably the airbag is made from a blank of double woven fabric with those areas constituting the sides and closed end woven as single fabric. This arrangement prevents abrasion of the vehicle occupant by seams, and vents the hot gas of the inflator away from the occupants face. <IMAGE>

Description

AN INFLATABLE AT RAG This invention relates to inflatable airbags for the protection of vehicle occupants in the event of a crash. Such airbags are made of fabric, are conventionally substantially lens shaped when inflated, and are stowed in front of the respective occupants of a vehicle. They are arranged to be inflated almost instantaneously by a gas generator if a crash occurs and to commence to deflate immediately, so as temporarily to restrain the occupants and thus prevent them from being injured by being thrown against hard interior surfaces of the vehicle.

Known airbags do not have an end seam in the area of deployed contact with the vehicle occupant because this seam can cause abrasions where it hits the occupant, and there is a risk that it can leak hot gas or even burst open thereby burning the occupant. Known airbags also have relatively complex arrangement to ensure safe deflation by venting the hot gas in areas remote from the occupant's face, involving for example, the punching out of vent holes, the use of a different more permeable fabric or the use of a different weave pattern in such areas.

The object of the present invention is to avoid the disadvantages referred to in the preceeding paragraph.

The invention comprises an inflateable airbag the closed end of which is folded back over at least part of its upper surfac and secured to said surface so that at least part of its upper surface is effectively three-ply, its lower surface is single-ply, and there is no seam at its folded end.

The airbag is preferably made from a blank so shaped that when folded back each side overlies itself.

Preferably the airbag is made from a blank of double woven fabric with those areas constituting the sides and closed end woven as single fabric.

Preferably, also, the fabric is woven as a continuous web with mirror image pairs of blanks along its length.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings of which: Figure 1 is a plan view of a length of fabric woven as part of a continuous web; Figure 2 is a sectional side view on a larger scale of an airbag made from part of said length of fabric, the airbag being uninflated but not compacted into its stowed inoperative condition; and Figure 3 is a sectional side view of said airbag when inlated into its deployed condition.

Referring now to Figure 1, a continuous web 10 of fabric is double-woven, that is to say two separate layers of fabric are simultaneously, except in the cross-hatched areas 12 which are woven as a single layer of fabric. The technology for weaving in this manner is known. The weave pattern and the thread size and material throughout the two separate layers of fabric are uniform. The cross-hatched areas 12 define interconnected mirror-image pairs of blanks, each blank being flask-shaped as most readily seen to the right of the dotted line 14. The web 10 is cut along each dotted line 14, and each blank is then produced by cutting around the outside of each flask-shaped singlewoven area. Those parts 16 of the web 10, including two short lengths of single-woven fabric, which lie between the closed ends 18 of two adjacent blanks are cut at 29 and 30.

Referring now to figure 2, the closed end 18 of each blank is folded back a substantial distance, say two-thirds of the way, towards the open end 20 thereof to form the upper surface of an airbag. The fold is made along such a line (see 21 in figure 1) that each side of the blank exactly overlies itself due to the blank being flask-shaped. The closed end 18 is then secured by the short lengths of single fabric 16 to the adjacent layer 22 of the blank as indicated at 24, by stapling, sewing, rivetting, welding or the like. The open end 20 constitutes a throat-hole adapted to be surrounded in known manner by an attachment flange for a gas generator (not shown). There is thus formed an airbag, a substantial part of the upper surface of which is effectively of three-ply construction while the lower surface 26 is single-ply, there being no seam at the folded end 28.

Referring now to figure 3, inflation and subsequent deflation of the airbag occurs so rapidly in the event of a crash that the hot gas deploys the airbag as illustrated and the pressure on the lower side of the layer 22 largely prevents the gas from entering the folded-back portion of the upper surface. Thus the gas vents through the singleply surfaces and mainly through the lower surface 26 into the foot well of the vehicle, away from the occupant's face which is protected from the hot gas by the much less permeable three-ply portion of the upper surface. The occupant is also protected from abrasion by the absence of a seam at the folded end 28 of the airbag, which in addition avoids the risk of leakage or even bursting in that area. Due to the provision of the three-ply area the fabric can be made less dense.

The invention enables airbags to be made much wider than hitherto and of adequate depth, which is a great advantage in the case of airbags for vehicle passengers. Airbags for car drivers are usually circular as they need to fit in the steering wheel and have to fill a relatively small space between said wheel and the driver. Airbags for passengers, however, which have a much greater space to fill, must be larger and so tend to spread into the foot well and above the dashboard, and require a correspondingly larger gas generator for rapid inflation. A passenger airbag according to the invention can be made as wide as necessary without being correspondingly deep and thus spreading unnecessarily into the foot well or above the dashboard when deployed, and can therefore be inflated rapidly using a smaller gas generator.

In a modification, the open end 20 of the airbag is sealed and a throat hole adapted to be surrounded by an attachment flange for a gas generator is cut either in the lower surface 26 or in the single-ply portion of the upper surface.

In another modification, the unwanted parts 16 are eliminated by consolidating the closed ends 18 of two adjacent blanks into one double-width area of single-woven fabric and subsequently cutting it precisely down the middle.

In a further modification, the flask-shaped blank can be formed from separate upper and lower layers of fabric seamed together along the sides and the closed end, and then folded and secured as hereinbefore described.

Claims

CLAINS

1. An inflatable airbag the closed end of which is folded back over at least part of its upper surface and secured to said surface so that at least part of its upper surface is effectively three-ply, its lower surface is single-ply, and there is no seam at its folded end.

2. An airbag as claimed in claim 1 which is made from a blank so shaped that when folded back each side overlies itself.

3. An airbag as claimed in either of claims 1 or 2 which is made from a blank of double woven fabric with those areas constituting the sides and closed end woven as single fabric.

4. An airbag as claimed in claim 3 in which the fabric is woven as a continuous web with mirror image pairs of blanks along its length.

5. An airbag as claimed in any of claims 1 to 4 which is for the passenger side of avehicle and which is wide as necessary without being correspondingly deep and thus does not, in use, spread unnecessarily into the foot well or above the dashboard when deployed, and can therefore be inflated rapidly using a smaller gas generator.

6. An airbag as claimed in any if claims 1 to 5 in which an open end opposite the folded end constitutes a throat hole for attachment to a gas generator.

7. An airbag as claimed in any of claums 1 to 5 in which the open end is sealedd and a throat hole adapted to be surrounded by an attachment flange for a gas generator is cut either in the lower surface of the bag or in a singleply portion of the upper surface.

8. An airbag as claimed in claim 1 in which a flask-shaped blank is formed from separate upper and lower layers of fabric seamed together along the sides and the closed end, and then folded and secured.

9. An airbag substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.