GB2389822A

GB2389822A - Airbag with internal seam enclosures

Info

Publication number: GB2389822A
Application number: GB0214394A
Authority: GB
Inventors: Michael Golling; Elke Nixdorf; Halit Oezek; Dick Olsson
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2002-06-21
Filing date: 2002-06-21
Publication date: 2003-12-24
Anticipated expiration: 2022-06-21
Also published as: GB2389822B; GB0214394D0

Abstract

An airbag is comprises two superimposed sheets of fabric 1,2 secured together by a stitched seam 3 which is enclosed in a sealed pocket 7 or 8 formed by part of at least one of the sheets 1,2 or by a reinforcing element (23, fig 3) (see also items 34,35, fig 4). The part which forms the pocket is held in place by further stitching 6, and preferably comprises a folded back edge 4,5 of one of the sheets 1,2 or of the reinforcing element (23). Alternatively, the sheets may be joined by two lines of stitching (24,25, fig 3). The edges of both sheets may then be folded together to form a double protection of one side of the seams, which are enclosed by a reinforcing element (23). Both sides of the seam 3 or seams (24,25, fig 3) may be enclosed. The invention reduces the risk of seam damage from impinging hot gas on airbag inflation.

Description

DESCRIPTION OF INVENTION

"IMPROVEMENTS IN OR RELATING TO AN AIR-BAG"

THE PRESENT INVENTION relates to an air-bag, and more particularly relates to an air-bag formed from fabric elements which are sewn together.

It is known to make an air-bag for use in a vehicle from elements of fabric which are secured together by stitching to form seams. Typically a seam is provided adjacent the superimposed edges of two elements of fabric, the stitching passing through the two elements of fabric. The thread that passes through the fabric to form the stitching has portions thereof on the exterior of each of the fabric elements, the exposed portions forming a stitch-line which is visible from either side of the seam.

Most commonly, whilst an air-bag may initially be fabricated with the seams visible on the exterior of the air-bag, the air-bag is then turned "inside-

out" so that the seams are directed inwardly towards the interior of the air-bag, so that the risk of a seam imparting injury to an occupant of a vehicle is minimised. Because the seams are thus directed on to the inner side of the air-bag, gas flow from a gas generator or inflator may damage the seams. For example,

the seams may be burnt by the heat or damaged by the pressure of the gas generated. It has been proposed to coat the seams on an air-bag with, for example, silicone, but this is expensive and the silicone may make the bag more difficult to fold. Consequently the folded air-bag may require a greater volume when the seams are coated with silicone.

It has been proposed to use a fabric reinforcing element.

FR 2,767,763-A discloses various types of seam reinforcement, but in each of the arrangements disclosed the gas within the air-bag can still gain ready access to the stitching which secures elements of fabric together.

The present invention seeks to provide an improved air-bag.

According to the present invention, there is provided an air-bag comprising two sheets of fabric which are superimposed and secured together by a stitched seam, the stitched seam forming a stitch-line on each side of the superimposed layers of fabric, at least one said stitchline being contained within a substantially sealed pocket formed by part of one of the fabric sheets, or a reinforcing element, the said part of the fabric sheet or reinforcing element being held in position by stitching.

Preferably at least one of the fabric sheets is provided with an extending flap defined between the said stitched seam and the peripheral edge of that sheet of fabric, the flap being folded-back to lie adjacent the said sheet and being secured to the sheet by stitching passing through the peripheral edge portion of the flap and the sheet of fabric to form a said pocket, the said pocket containing the stitch-line of the seam associated with the said sheet.

( Advantageously the other sheet is also provided with a flap between the stitched seam and the peripheral edge of the said sheet, that flap also being folded-back and being secured in position by stitching passing through the peripheral edge portion of the flap and the respective sheet to form a second pocket, the second pocket containing the stitch-line of the seam associated with said other sheet.

Conveniently the same stitching is used to secure both flaps in position.

Preferably the other sheet is associated with a reinforcing element, both the seam and the stitching holding the flap in position passing through the reinforcing element.

Advantageously a reinforcing element is provided, part of the reinforcing element being located adjacent one of the superimposed sheets of fabric, the reinforcing element and the superimposed layers of fabric being interconnected by a seam, the main part of the reinforcing element being folded-back so as to cover the stitch-line formed by the seam on the reinforcing element, and extending over the stitch-line formed by the seam on the other layer of fabric, the edge part of the reinforcing element being secured, by stitching, to the other layer of fabric.

Conveniently two reinforcing elements are provided, one on each side of the superimposed layers of fabric; the reinforcing elements being secured by two stitchings, one on either side of the seam; the stitchings passing through the reinforcing elements and the superimposed layers of fabric.

Preferably the or each reinforcing element is formed from fabric equivalent to that used to form the air-bag.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE I is a diagrammatic view of a seam region of an air-bag in accordance with the invention, FIGURE 2 is a view corresponding to Figure I illustrating a further embodiment of the invention, FIGURE 3 is a view corresponding to Figure 1 illustrating another embodiment of the invention, and FIGURE 4 is a view corresponding to Figure I illustrating yet another embodiment of the invention.

Figure 1 illustrates part of an air-bag. The air-bag is formed from an upper sheet of fabric 1 and a lower sheet of fabric 2. The sheets of fabric have been superimposed with their edge regions co-aligned, and a seam 3, constituted by stitching, has been provided to secure the upper sheet of fabric I to the lower sheet of fabric 2. A flap 4, constituted by that part of the upper sheet of fabric l between the seam 3 and the very edge of the sheet of fabric has been folded-back to overlie the seam 3, so that the very edge of the flap 4 lies adjacent the upper surface of the upper sheet of fabric 1. Similarly, a flap 5 formed by that part of the lower sheet of fabric extending from the seam 3 to

( the very edge of the sheet has been folded-back to underlie the seam 3, again with the very edge of the flap 5 lying adjacent the under-surface of the lower sheet of fabric 2. Further stitching 6 has been utilised to secure together the edge region of the flap 4 with the edge region of the flap 5, with the further stitching 6 passing through not only the edge region of the flaps 4, 5, but also through the superimposed sheets of fabric I, 2.

Thus the upper folded-back flap 4 defines a substantially sealed upper pocket7, and the folded-back flap 5 defines a substantially sealed lower pocket 8. The two stitch-lines of the stitched seam 3 are contained within the pockets 7, 8, with the stitch-line on the upper fabric sheet I being located within the upper pocket 7, and the stitch-line on the lower fabric sheet 2 being located within the lower pocket 8.

The stitched seam 3, shown in the orientation of Figure 1, has the position that it will occupy when the fabricated air-bag has been turned "inside-

out" so that the seam 3 is directed inwardly towards the interior of the air-bag.

The seam 3 may be subjected to a very aggressive flow of gas during inflation of the air-bag. However, because the stitch-lines of the seam 3 are located within the respective substantially sealed pockets 7, 8, the stitching of the seam 3 will not be directly damaged by the flow of gas, because it will be protected by the upper and lower flaps 4, 5.

Figure 2 illustrates a second embodiment of the invention. In the embodiment of Figure 2, the air-bag is formed from an upper sheet of fabric 11 and a lower sheet of fabric 12. The sheets of fabric 11, 12 are superimposed, with the lower sheet of fabric 12 leaving a protruding flap 13 which extends beyond the edge of the upper sheet of fabric 11. A reinforcing element 14 of fabric is provided which lies adjacent the edge of the upper sheet of fabric 11.

A stitched seam 15 is provided which extends through the reinforcing element 14, through the upper sheet of fabric 11 and the through the lower sheet of fabric 12. The protruding flap 13 defined by the lower sheet of fabric 12 is then folded-back to underlie the seam 15, forming a pocket 16 and a second stitching 17 is utilised which passes through the reinforcing element 14, the upper sheet of fabric 11, the lower sheet of fabric 12 and the edge part of the folded-back flap 13, to secure the folded-back flap 13 in position. Thus, a substantially sealed pocket 16 is defined by the folded-back and stitched flapl3, and the lower stitch- line of the seam 15 is contained within the pocket 16.

In this embodiment, whilst the upper stitch-line of the seam 15 that is visible on the reinforcing element 14 is exposed in the interior of the air-bag, the lower stitch-line associated with the lower sheet of fabric 12 is contained within the sealed pocket 16. On inflation of the air-bag, it is anticipated that gas will flow upwardly from below, as indicated by the arrow 18. The lower stitch-line of the seam 15 that would ordinarily be expected to be exposed to the flow of gas is protected by the foldedback flap 13 which forms the substantially sealed pocket 16.

Figure 3 illustrates an embodiment of the invention in which an air-bag is formed from an upper sheet of fabric 21 and a lower sheet of fabric 22. A reinforcing element 23 of fabric is also provided. Initially the upper sheet of fabric 21 and the lower sheet of fabric 22 are superimposed with their edges substantially in alignment. The reinforcing element 23 is positioned with one edge thereof spaced slightly inwardly from the aligned free edges of the sheets of fabric 21, 22. Two stitched seams 24, 25 are then utilised to secure together the reinforcing element 23, the upper sheet of fabric 21 and the lower sheet of fabric 22. The reinforcing element 23, which has effectively been secured to

the under-side of the lower sheet 22, is then folded away from the lower sheet 22 and around the free edges of the upper and lower sheets 21, 22, so that the edge of the reinforcing element 23 that has not been connected to the fabric sheets by the two seams 24, 25 then lies immediately adjacent the upper surface of the upper sheet 21. The free edges of the upper and lower sheets 21, 22 are curled back with the reinforcing element 23.

The free edge of the reinforcing element 23 is then secured to the upper sheet of fabric 21, by means of stitching 26 which passes through the reinforcing element 23 in the region of its free edge and also through the upper layer of fabric 21 and the lower layer of fabric 22.

It can be seen that in this embodiment of the invention, the stitched seams 24, 25 are effectively totally surrounded by the folded-back and secured reinforcing element 23 which defines a substantially sealed pocket having a lower pocket portion 27 adjacent the lower stitch-lines of seams 24, 25, and an upper pocket 28, which contains the folded-back peripheral edge parts of the upper and lower sheets 21, 22 and which covers the upper stitch-line of the seams 24 and 25.

Figure 4 illustrates yet another embodiment of the invention. In this embodiment, an upper sheet of fabric 31 is connected to a lower sheet of fabric 32, by means of a simple stitched seam 33. An upper reinforcing element of fabric 34 is located in position adjacent the upper surface of the upper layer of fabric 31, with the reinforcing element 34 extending over the upper stitch-line of the seam 33. A lower reinforcing element 35 is positioned adjacent the under-surface of the lower sheet of fabric 32, again with the reinforcing element 35 extending over the seam 33. A first stitching 36 is utilised to connect the reinforcing elements 34, 35 to the superimposed sheets

( of fabric 31, 32, with the light stitching 36 extending to one side of the seam 33. A second stitching 37 is also utilised, again to secure the reinforcing elements 34, 35 to the superimposed sheets of fabric 31, 32, with the second stitching 37 extending to the other side of the seam 33. The stitched reinforcing elements 34, 35 thus effectively define an upper substantially sealed pocket 38 adjacent the upper sheet of fabric 31, and a corresponding lower pocket 39 adjacent the lower sheet of fabric 32. The upper and lower stitch-lines of the stitch-seam 33 are contained within the respective substantially sealed pockets 38, 39.

It is to be understood that in all of the above described embodiments, the pocket or pockets which contain the stitch-line or stitch-lines of the seam may have an extremely small internal volume. The stitch-line of the seam is protected by the element of fabric that defines the pocket, and thus the volume of the pocket is not critical.

In each of the embodiments, the pocket, or pockets, are defined by a portion of the fabric from which the air-bag is formed, or from reinforcing elements. The reinforcing elements may also be made from a fabric equivalent to that used to make the air-bag.

It is to be appreciated that in each of the described embodiments of the invention, at least one stitch-line deemed by the seam joining two sheets of fabric together is protected within a substantially sealed pocket. In most of the embodiments the stitch-lines on both sides of the seam are protected by being within a pocket. Thus, one or both stitch-lines of the seam will be protected from any aggressive flow of gas within the air-bag, helping to maintain the integrity of the air-bag.

( In the present Specification "comprises" means "includes or consists of"

and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following

Claims, or the accompanying drawings, expressed in their specific forms or in

terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. An air-bag comprising two sheets of fabric which are superimposed and secured together by a stitched seam, the stitched seam forming a stitchline on each side of the superimposed layers of fabric, at least one said stitch-line being contained within a substantially sealed pocket formed by part of one of the fabric sheets, or a reinforcing element, the said part of the fabric sheet or reinforcing element being held in position by stitching.

2. An air-bag according to Claim 1 wherein at least one of the fabric sheets is provided with an extending flap defined between the said stitched seam and the peripheral edge of that sheet of fabric, the flap being folded-back to lie adjacent the said sheet and being secured to the sheet by stitching passing through the peripheral edge portion of the flap and the sheet of fabric to form a said pocket, the said pocket containing the stitch-line of the seam associated with the said sheet.

3. An air-bag according to Claim 2 wherein the other sheet is also provided with a flap between the stitched seam and the peripheral edge of the said sheet, that flap also being folded-back and being secured in position by stitching passing through the peripheral edge portion of the flap and the respective sheet to form a second pocket, the second pocket containing the stitch-line of the seam associated with said other sheet.

4. An air-bag according to Claim 3 as dependent upon Claim 2 wherein the same stitching is used to secure both flaps in position.

5. An air-bag according to Claim 2 wherein the other sheet is associated with a reinforcing element, both the seam and the stitching holding the flap in position passing through the reinforcing element.

6. An air-bag according to Claim 1 wherein a reinforcing element is provided, part of the reinforcing element being located adjacent one of the superimposed sheets of fabric, the reinforcing element and the superimposed layers of fabric being interconnected by a seam, the main part of the reinforcing element being folded-back so as to cover the stitch-line formed by the seam on the reinforcing element, and extending over the stitch-line formed by the seam on the other layer of fabric, the edge part of the reinforcing element being secured, by stitching, to the other layer of fabric.

7. An air-bag according to Claim 1 wherein two reinforcing elements are provided, one on each side of the superimposed layers of fabric; the reinforcing elements being secured by two stitchings, one on either side of the seam; the stitchings passing through the reinforcing elements and the superimposed layers of fabric.

8. An air-bag according to any one of the preceding Claims wherein the or each reinforcing element is formed from fabric equivalent to that used to form the air-bag.

9. An air-bag substantially as herein described with reference to and as shown in Figure 1 of the accompanying drawings.

10. An air-bag substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.

11. An air-bag substantially as herein described with reference to and as shown in Figure 3 of the accompanying drawings.

12. An air-bag substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings.

13. Any novel feature or combination of features disclosed herein.