GB2410925A

GB2410925A - Air bag with central tethers

Info

Publication number: GB2410925A
Application number: GB0403398A
Authority: GB
Inventors: Hugh Finn; David Stow; Christian Lang
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2004-02-16
Filing date: 2004-02-16
Publication date: 2005-08-17
Also published as: GB0403398D0

Abstract

An air bag is disclosed for use as a safety device in a motor vehicle, said air bag being especially intended for use in protecting the knees (figure 8) of the driver of the vehicle. The air bag incorporates a layer of fabric material 22 defining a front face and a layer of fabric material 21 defining a rear face. The air bag also incorporates at least two connecting means or tethers 23, 24, each tether extending from the front face to the rear face to restrict the width of the central region of the air bag. The tethers do not extend to the side areas of the air bag, and so said side areas are configured to become substantially fully inflated so as to extend rearwardly from the front face, past the central region of the air bag. Prior to inflation the air bag may be located in a housing present on a steering column shroud.

Description

241 0925

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 intended to provide protection for the knees of the driver of a motor vehicle.

It has been proposed previously to provide an air-bag to provide protection for the knees of the driver of a vehicle. Figure 1 illustrates, schematically, a prior proposed arrangement.

FIGURE 1 illustrates a dashboard 1 of a vehicle and a steering wheel 2 which is mounted on the vehicle. The upper part of the steering column associated with the steering wheel is covered by a movable shroud 3 to enable the degree of tilt of the steering wheel to be adjusted. The lower part of the steering column is contained within a fixed shroud 4. The fixed shroud 4 presents a generally arcuate rearwardly directed face 5. Mounted on the fixed shroud 4 is an air-bag unit 6 containing an air-bag which is to be inflated in the event that an accident should occur.

FIGURE 2 is a view, partly in section, illustrating the arrangement of Figure 1 when the air-bag is inflated. A lower part of the dashboard 1 is

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shown, on which is mounted the fixed shroud 4. The steering column 7 for the steering wheel is visible within the shroud 4. An air-bag 8, from the air-bag unit 6, is shown in its inflated form. The air-bag 8 is a generally "flat" air-bag presenting a rectangular front face and being of substantially uniform thickness.

The air-bag is located in front of the knees 9 of a seat occupant to provide protection for the seat occupant.

It has been found, however, that if the knees of the occupant advance, the two opposed end parts of the air-bag 8, that is to say the parts 10 and 11 which are located to either side of the shroud 4, become deflected forwardly as illustrated schematically in Figure 3, enabling the knees of the seat occupant to move apart, and thus permitting the occupant to move forwardly. This is undesirable and the present invention seeks to provide an improved air-bag.

According to the present invention, there is provided an air-bag, the air bag incorporating a layer defining a front face of the air-bag and a layer defining a rear face of the air-bag, the air-bag incorporating at least two connecting means, each connecting means extending from the front face to the rear face, the connecting means being configured to restrict the width of a central region of the bag on inflation of the bag, the connecting means not extending to the two side areas of the bag on either side of the central region, the side areas of the bag being configured to become substantially fully inflated upon inflation of the air-bag, so as to extend rearwardly from the front face, past the central region of the rear face.

Preferably, said connecting means are located at positions intermediate an upper edge and a lower edge of the air-bag, the upper connecting means having a smaller dimension than the lower connecting means as considered in the direction extending across the air-bag substantially parallel to the upper and lower edges.

Advantageously, each connecting means takes the form of a tether of trapezoidal form.

Conveniently, the tethers are parallel with each other, each end of each tether being secured to the respective front and rear faces of the airbag.

The air-bag in accordance with the present invention can be provided mounted in a motor vehicle adjacent a shroud surrounding part of the steering column of the vehicle, the shroud presenting a curved or arcuate face directed towards an occupant of the vehicle.

Preferably, the air-bag is initially mounted in a housing present on the shroud and orientated so that, on inflation of the air-bag the side regions of the air-bag are located to either side of the shroud.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, an embodiment of the invention will now be described, by way of example, with particular reference to Figures 4 to 8 of the accompanying drawings in which: FIGURE 1 is a schematic perspective view of a prior proposed air-bag arrangement, FIGURE 2 is a part-sectional view, from above, of the arrangement of Figure 1 after deployment, FIGURE 3 is a view corresponding generally to that of Figure 2, showing the knees of an occupant impacting the air-bag, FIGURE 4 is an exploded view of the principal components of an air bag in accordance with the invention, FIGURE 5 is a schematic view illustrating the air-bag of the invention, when inflated, FIGURE 6 is a front view of the air-bag of the invention, when inflated, FIGURE 7 is a rear view of the air-bag of the invention, when inflated, and FIGURE 8 is a sectional view, corresponding generally to Figures 2 and 3, showing the air-bag of the present invention in position in a motor vehicle.

Referring initially to Figure 4 of the accompanying drawings, an air bag20 in accordance with the invention is formed from two substantially identical layers or sheets of fabric 21, 22 which are both shown as being rectangular. The sheets may be of slightly different sizes in certain embodiments of the invention, but it has been found that two identical sheets will provide an adequate air-bag.

Two internal tethers or straps 23, 24 are provided. Each tether or strap is in the form of a sheet of fabric having a trapezoidal form. Each sheet of fabric has two parallel sides, one of which is longer than the other. The tether 24 is somewhat larger than the tether 23, having a greater length and having a greater width. Thus the parallel sides of the tether 24 are each longer than the equivalent one of the parallel sides of the tether 23.

The air-bag 20 is assembled by stitching the short side of tether 23 to a stitch-line 25 formed on the sheet of fabric 21 and stitching the short side of the tether 24 to a stitch-line 26, which is located beneath the stitch-line 25 and which is parallel with the stitch-line 25, on the first fabric sheet 21. The long side of the tether 23 is stitched to a stitch-line 27 formed on the secured fabric sheet 22 and the long side of the tether 24 is stitched to a stitch-line 28 formed on the second fabric sheet 22. The stitch-lines 25, 26, 27 and 28 are parallel with one another and are also parallel with the upper and lower sides of each of the fabric sheets 21, 22. The sheets 21, 22 are secured together to form a substantially air-tight air-bag by means of a peripheral seam 29. An inflator may be provided within the air-bag or may be connected to the air-bag by means of a gas supply duct 30.

When the air-bag is inflated, because of the construction of the air-bag, the air-bag will adopt a specific form.

The effect of the tethers 23, 24 is to prevent the central regions of the fabric layers 21, 22 from moving away from one another by more than a predetermined extent. Thus the central region of the inflated air-bag is of limited thickness. Because the lower tether 24 has greater dimensions than the upper tether 23 the lower part of the central region of the inflated air-bag has a rather greater thickness than the upper part of the central region of the inflated air-bag. At each side of the air-bag, where the tethers are not present, the air bag may become fully inflated, and thus the side parts of the air-bag form two substantially cylindrical inflated regions 31,32 as illustrated in Figure 5.

Figure 8 illustrates the air-bag in position in a motor vehicle. The airbag is mounted so as to be located immediately in front of a shroud 4 surrounding the steering column 7 of the vehicle. It can be seen that the central region of the air-bag, provided with the tethers 23, 24, is located immediately in front of an arcuate part of the shroud 4. The substantially cylindrical inflated regions 31, 32 are located to either side of the arcuate region, and thus the rear surface of the bag generally conforms to the shape of the arcuate fixed shroud 4. It is believed that the bag will have a better operating characteristic than the prior proposed bag described above, there being less risk of the knees of the occupant being spread apart in the event of an accident situation, to enable the occupant to move forwardly.

Whilst the invention has been described with reference to an embodiment in which two tethers or straps are provided, each being formed from a single trapezoidal element of fabric, it is to be appreciated that each of the upper and lower tethers or straps may be formed from a plurality of discrete strap elements of appropriate length.

It may be advantageous for the tethers to be "tear tethers" - that is to say that the tethers be designed to rupture, for example by the breaking of one or both stitch-lines securing the tether in position, in the event that a very high pressure is experienced within the bag.

It is to be appreciated that the lower tether is of a greater dimension than the upper tether so that the rear surface of the bag can have an inclined face, the inclined face co-relating with the inclined face of the shroud 4 against which the air-bag is to be located when inflated. Thus the front face of the air-bag may have a desired angular orientation, such as an upright or vertical orientation, even though the air-bag is mounted on an inclined shroud 4.

It is also to be appreciated that an air-bag in accordance with this invention could be provided with one or more vent holes in order to ensure safe cushioning of an occupant impacting with the air-bag in an accident situation.

Whilst the invention has been described with reference to a bag incorporating stitched seams, the bag may be made using a one-piece weaving 1 0 process.

When used in this Specification and Claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

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, the air-bag incorporating a layer defining a front

face of the air-bag and a layer defining a rear face of the air-bag, the air-bag incorporating at least two connecting means, each connecting means extending from the front face to the rear face, the connecting means being configured to restrict the width of a central region of the bag on inflation of the bag, the connecting means not extending to the two side areas of the bag on either side of the central region, the side areas of the bag being configured to become substantially fully inflated upon inflation of the air-bag, so as to extend rearwardly from the front face, past the central region of the rear face.
2. An air-bag according to Claim 1 wherein said connecting means are located at positions intermediate an upper edge and a lower edge of the air-bag, the upper connecting means having a smaller dimension than the lower connecting means as considered in the direction extending across the air-bag substantially parallel to the upper and lower edges.
3. An air-bag according to Claiml or Claim 2 wherein each connecting means takes the form of a tether of trapezoidal form.
4. An air-bag according to Claim 3 wherein the tethers are parallel with each other, each end of each tether being secured to the respective front and rear faces of the air-bag.
5. An air-bag according to any one of the preceding Claims when mounted in a motor vehicle adjacent a shroud surrounding part of the steering column of the vehicle, the shroud presenting a curved or arcuate face directed towards an occupant of the vehicle.
6. An air-bag according to Claim 5 wherein the air-bag is initially mounted in a housing present on the shroud and orientated so that, on inflation of the air- bag the side regions of the air-bag are located to either side of the shroud.
7. An air-bag substantially as herein described with reference to and as shown in Figures 4 to 8 of the accompanying drawings.
8. Any novel feature or combination of features disclosed herein.