GB2364674A

GB2364674A - A vehicle air-bag arrangement in which the air-bag is deployed in front of and from above the occupant

Info

Publication number: GB2364674A
Application number: GB0017134A
Authority: GB
Inventors: Dick Eriksson; Bengt Pipkorn
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2000-07-12
Filing date: 2000-07-12
Publication date: 2002-02-06
Anticipated expiration: 2020-07-12
Also published as: GB2364674B; GB0017134D0

Abstract

An air-bag arrangement in a motor vehicle to protect an occupant (7) of the vehicle incorporates an air-bag (8) initially retained in a folded position above and in front of the occupant to be protected. On inflation the air-bag (8) is deployed in front of the occupant (7) of the vehicle. The air-bag (8) is provided with an inflatable chamber (30) mounted on the rest of the air-bag, which can have its own gas generator (32) if needs be, that constitutes an inflatable apron to be located between the knees (17) of the occupant of the vehicle and a dashboard (5). The apron (30) can also form an integral part of the air-bag (8). The inflatable apron (30) provides protection fro the knees of the occupant and also retains the main part of the air-bag (8) in a desired position if the air-bag becomes totally separated from the roof of the vehicle.

Description

<Desc/Clms Page number 1> 4IVIPROVEMENTS IN OR RELATING TO AN AIRBAG ARRANGEMENT" THE PRESENT INVENTION relates to an airbag arrangement, and in particular relates to an airbag arrangement for use in a motor vehicle, such as a motor car, to provide protection for the driver or an occupant of the vehicle in the event that an accident should arise.

It has been proposed previously to provide an airbag arrangement in a motor vehicle in which an air-bag-is mounted in the roof of the vehicle and is adapted, when deployed , to occupy a position in which at least part of the air- bag is located in front of the occupant of the vehicle to be protected.

US A 3795412 discloses an airbag arrangement in which a plurality of inflatable tubes are provided which are initially stored in the roof of a vehicle, above the driver. The tubes are associated with netting that interconnects the tubes. In the event that an accident arises the tubes are inflated and extend downwardly from the roof of the car forming a cage that surrounds the occupant of the car and also the back of the seat in which the occupant of the vehicle is sitting. Thus the head and torso of the occupant are prevented from moving forwardly or laterally relative to the back of the seat. It is thought that

if this system were to be used, in an accident situation, the head of the occupant, which typically moves forwardly relative to the torso - since the torso is usually restrained by a seat belt - will engage the combination of the inflatable tubes and the netting and will be bent rearwardly relative to the torso, which may lead to undesirable injuries. At the conclusion of the accident, the occupant will still be encased by the netting, even if the inflatable tubes. deflate, and thus may have great problems in leaving the vehicle. This is undesirable since in many cases it is desirable for the occupants of a vehicle to leave the vehicle as soon as possible after an accident has occurred. A further problem with this arrangement is that if the occupant of the vehicle is leaning forwardly at the instant that the airbag arrangement is deployed, they may be held in the forward position, instead of in the upright position, which may lead to an increase in the injuries sustained, rather than a decrease.

US A 3774936 discloses an arrangement in which an airbag is mounted in the roof of a vehicle in a housing that extends transversely of the rear seat. The airbag, when deployed, is located in front of an occupant of the vehicle seat. The airbag is associated with wires on each side of the vehicle. Each wire is an endless loop which is connected to anchoring points in the roof and behind the shoulder of the occupant of the seat, there being a loop of fabric on the airbag that surrounds the wire of the endless wire loop. The arrangement guides. the inflating airbag so that, when inflated, the airbag applies a downward and rearward force on the pelvic area of the occupant of the seat, as well as providing a physical barrier in front of the seat occupant to restrain forward movement.

US A 4536008 also discloses an airbag arrangement in which an airbag is mounted on the roof of a motor vehicle to be deployed to occupy a position in front of an occupant of the vehicle in the event that an accident occurs. The

airbag is designed so that the lower end of the airbag engages and applies a downward force to the lap of the occupant of the vehicle to retain the occupant of the vehicle in the desired position, whilst also forming a barrier in front of the occupant. The upper part of the airbag is mounted to the roof of the vehicle in such a way that the upper part of the airbag can move forwardly, from its initial position, by up to a predetermined distance if the occupant of the vehicle applies a substantial force to the inflated airbag. The upper part of the airbag moves against a bias provided by springs. Again it is thought that if the head of the occupant makes contact with the airbag after is has been deployed, even though the top part of the airbag can move forwardly slightly, nevertheless, there is still a severe risk that the neck of the occupant will be bent back as the torso continues to move forwardly while the head is restrained.

The present invention seeks to provide an improved airbag arrangement. According to this invention there is provided an airbag arrangement in a motor vehicle to protect an occupant of the vehicle in the event that an accident should occur, said arrangement incorporating an airbag, the airbag initially being retained in a folded condition within a recess at a position above and in front of the occupant to be protected, the airbag being associated with at least one gas generator and a sensor, the sensor being adapted to sense an accident and to activate the gas generator to inflate the bag, the airbag, on inflation, being deployed in front of the occupant of the vehicle, the airbag being provided with an inflatable chamber mounted on the rest of the airbag that constitutes an inflatable apron to be located between the knees of the occupant of the vehicle and a dashboard provided in the vehicle on deployment of the airbag.

In one embodiment the apron forms an integral part of the airbag.

In an alternative embodiment the apron forms a separate chamber secured to the airbag, the separate chamber being associated with a second chamber, the second gas generator being actuated by the sensor.

Preferably the second gas generator is actuated at a different instant in time from said first gas generator.

Conveniently the apron, on inflation, is inflated to a higher pressure than the rest of the airbag. The apron may be inflated to a pressure of at least 3 bar. Conveniently flexible hose means extend between the or each gas generator and the airbag, the means retaining the airbag in the recess being adapted to release the airbag from the recess so that the entire airbag is free to move forwardly and downwardly away from the recess.

Preferably the means to retain the airbag in position within the recess are adapted to release the airbag from the recess when a force in excess of a predetermined force is applied to the airbag.

Conveniently the upper part of the airbag is secured to frangible means adapted to break to release the airbag.

Preferably the means retaining the airbag within the recess include a plurality of loops in the upper part of the airbag, each loop passing through an aperture formed in a release block, the release block being adapted to break to release the loop and thus to release the upper part of the airbag.

Advantageously the release block is provided with a line of mechanical weakness adjacent said aperture, the release block breaking at the line of mechanical weakness to release the loop.

Alternatively the airbag is initially retained in a folded condition, and the means retaining the airbag in the recess comprise a door which initially closes the recess, the door being adapted to be opened on inflation of the air- bag to release the airbag during inflation thereof.

Preferably the airbag is constrained to be inflated in such a way that during the initial stages of inflation, the airbag is relatively thin (as measured in the direction of the axis of the vehicle) and is located in front of. the occupant, and subsequently the thickness of the airbag (as measured in the direction of the axis of the vehicle) increases.

Conveniently the airbag is provided with one or more breakable means extending from the part of the airbag closest to the occupant to the part of the airbag furthest from the occupant, said breakable means being dimensioned to maintain the airbag in a relatively thin condition (as measured in the direction of the axis of the vehicle) until a predetermined pressure is present within the airbag.

Advantageously the apron is constrained to be inflated in such a way that during the initial stages of inflation of the airbag, the apron is relatively thin (as measured in a distance extending between the knees of an occupant and the dashboard) and subsequently, the thickness of the apron increases.

Preferably the apron is provided with one or more breakable means extending from part of the apron closest to the knee of the occupant to part of the apron located adjacent the dashboard.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 is a diagrammatic view of an airbag arrangement in a motor vehicle illustrating a problem that the present invention seeks to overcome, FIGURE 2 is a diagrammatic view of an airbag arrangement mounted in a motor vehicle in accordance with the invention with the airbag in an initial phase of deployment, FIGURE 3 is a view corresponding to Figure 2 showing a subsequent stage of deployment of the airbag, FIGURE 4 is a view corresponding to Figure 3 showing the occupant of a vehicle moving into contact with the airbag, FIGURE 5 is a diagrammatic illustration showing how the top of the air- bag of Figures 2 to 4 is going through the roof of the motor vehicle, FIGURE 6 is a view corresponding to Figure 5 showing how the top part of the airbag of Figures 2 to 4 become released, and

FIGURE 7 is a view, corresponding to Figure 2, illustrating an alternative embodiment of the invention.

Figure 1 illustrates, schematically, part of a vehicle 1. The vehicle has a roof, 2, a windscreen or windshield 3 and an associated A-Post 4. Incorporated within the vehicle is a dashboard 5. The front seat 6 of the vehicle is occupied by an occupant 7, and is illustrated as wearing a seat belt. Figure 1 illustrates an arrangement in which an airbag 8 is provided which is initially mounted in a recess which is formed in the roof at a position extending across the top of the windshield 3. The airbag 8 is illustrated in the inflated condition, showing the situation that exists some milliseconds after the commencement of a frontal- impact accident.

It can be seen that as a consequence of the frontal impact, the airbag 8 has been inflated and has been deployed to occupy a position in front of the occupant 7 of the vehicle. As a consequence of the deceleration of the vehicle, caused by the frontal impact, the occupant 7 of the seat 6 has moved forwardly relative to the seat. The seat belt has become tightened, thus retaining the pelvic region of the occupant of the seat. The main torso of the occupant of the seat has thus inclined forwardly.

The head of the occupant has been the first part of the occupant to make contact with the airbag. Thus, the forward motion of the head of the occupant, relative to the vehicle, has been retarded, whilst the forward motion of the main torso of the occupant continues. Because the torso of the occupant was moving forwardly relative to the head of the occupant, the neck of the occupant became bent rearwardly, with the head of the occupant effectively being moved pivotally towards the rear, relative to the main torso of the occupant. Such a

movement of the neck of the occupant is very undesirable, and may cause substantial injuries.

Figure 2 which illustrates an embodiment of the invention again shows, schematically, part of a vehicle 1, and illustrates the roof 2, windscreen or windshield 3, and an associated A-Post 4, dashboard 5 and front seat 6. The front seat is occupied by an occupant 7 who is not wearing a seat belt.

The vehicle 1 is provided with an airbag arrangement in accordance with the invention. The arrangement includes an airbag 8 which is initially retained, in a folded state in a recess 9 which extends transversely across at least part of the top of the windscreen or windshield 3 within the roof 2 of the vehicle 1 at a position above and in front of the occupant 7 who is to be protected. The recess may be formed in the roof of the vehicle, or in a housing mounted in the roof. The airbag is connected, by means of a flexible hose 10 to a gas generator 11 and an associated crash sensor 12. The gas generator 11 and crash sensor 12 are shown as being mounted behind the dashboard 5 of the vehicle, but may alternatively be positioned at another location within the vehicle. The flexible hose 10 extends from the gas generator 11 along the A- Post 4 to the airbag 8. The hose 10 is releasably mounted in position on the A- Post 4.

As shown in Figure 2 the sensor 12 has sensed an accident and has activated the gas generator 11. Gas is being supplied by the gas generator 11, through the hose 10 to inflate the airbag 8.

The airbag 8 is partially inflated, and extends downwardly from the roof 2 of the vehicle. Thus the airbag has initially occupied a position in

which the main part of the bag is located in front of the occupant 7 before the occupant 7 has moved significantly forwardly relative to the vehicle.

The occupant of the vehicle could have been in a relatively forward position at the beginning of the accident. If the illustrated occupant is the driver, and if the occupant is short in stature, the seat of the occupant could be in a forward position. If the occupant were the front seat passenger, then the occupant could be leaning forwardly, for example to gain access to the glove box. Thus it is desirable that the airbag 8, as it inflates, is as far forward as possible, to minimise the risk that the airbag cannot be deployed in front of the occupant. Also the airbag, during this phase of deployment should have a minimum thickness, where thickness is understood to be the distance between the part 13 of the airbag closest to the occupant 7 and the part 14 of the airbag closest to the windscreen or windshield 3, as shown by the line T in Figure 2. It is to be understood that the thickness of the airbag, as shown by the line T, is measured in a direction parallel to the axis of the vehicle.

Whilst it is possible to control the deployment characteristics of an airbag by folding the airbag in an appropriate manner, in the described embodiment of the invention the airbag 8 is provided with a plurality of tear straps 15 each of which extends from the part 13 of the bag closest to the occupant 7, to the part 14 of the bag which is furthest from the occupant and closest to the windscreen or windshield 3. The tear straps hold the bag in the illustrated configuration during the initial phase of deployment. The tear straps are provided with regions of mechanical weakness (or are designed to have only a predetermined strength) and are adapted to tear or break when the pressure within the inflating airbag 8 reaches a predetermined threshold. It is to be understood that instead of tear straps interconnecting the relevant parts 13,14 of the airbag 8 tear threads could be used instead, these being

threads adapted to snap when subjected to a predetermined force on inflation of the airbag.

At this stage it is to be noted that the lowest part of the airbag, as initially inflated, is constituted by a region 16 which is located between a knee 17 of the occupant, and the under-part of the dashboard 5. The region 16 forms an inflatable chamber mounted on the rest of the airbag that constitutes a "apron" and the function of the apron 16 will become clear from the following description. The apron 16 is provided with one or more of the above-described tear straps 15. The tear straps 15 within this region maintain the apron 16 in a relatively "thin" condition during the initial stages of inflation, so that the apron 16 may be inserted into the space between the knees 17 of the occupant and dashboard 5, and then break to permit the apron 16 to inflate.

Figure 3 illustrates the phase of deployment of the airbag 8 following the tearing of the tear straps 15. The thickness of the bag as measured in a direction parallel to the axis of the vehicle is now increasing, with the part 13 moving towards the occupant 7 and with the part 14 moving towards the windscreen or windshield 3. The occupant 7 is still in the initial position as during this initial phase of atypical accident the vehicle is decelerated relatively slowly as the crumple zone of the vehicle crumples.

The tear straps 15 in the apron 16 have torn or broken. The apron 16 is inflated and is thus gripped firmly between the knees 17 of the occupant 7 and the dashboard 5. Thus the lower part of the airbag 8 is securely located in position. The apron 16 will provide cushioning for the knees 17 of the occupant 7.

Subsequently the vehicle decelerates more rapidly and, as shown in Figure 4, the occupant 7 moves forwardly relative to the seat 6 and the rest of the vehicle 1. The occupant 7 impacts with the bag 8. Because the occupant is not wearing a seat belt the torso 18 and the head 19 of the occupant engage the airbag virtually simultaneously. At this time the knees 17 of the occupant move forwardly, thus trapping the apron 16 even more securely between the knees and the under-surface of the dashboard 5. Thus the apron is held very firmly in position, retaining the lower part of the airbag 8 in position.

The torso 18 of the occupant may have a substantial mass and thus a substantial momentum relative to the vehicle 1. Thus the torso, even though it has impacted with the airbag 8, will continue to move forwardly, as shown in Figure 4, thus compressing the airbag 8. The head 19 of the occupant is engaging a part of the airbag 8 which is close to the roof, and if the torso 18 moved forwardly while the head 19 was retained in the position shown in Figure 4 there would be a risk that the neck of the occupant 7 of the vehicle would be bent backwardly. This bending of the neck might lead to injuries that could permanently damage the occupant of the vehicle.

In the illustrated embodiment of the invention the upper part of the air- bag 8 is releasably connected to the recess within the roof 2 of the vehicle 1 in which the airbag was initially stored or retained, as will be described below with reference to Figures 5 and 6. The arrangement is such that when the force, in a forward direction of the vehicle, applied to the airbag by the occupant 7 exceeds a predetermined threshold the upper part of the airbag 8 becomes disconnected from the recess within the roof 2 of the vehicle. The entire air- bag 8, which is still connected to the gas generator 11 by the flexible hose 10 is thus released from and thus becomes separated from the recess within the roof 2 of the vehicle. The head 19 of the occupant can thus move forwardly,

whilst being protected and retarded by the airbag 8, with a greatly reduced risk that the neck of the occupant 7 will be bent back in an undesirable way.

There is no real risk of the airbag leaving the desired position generally in front of the occupant 7 of the vehicle, since when the airbag is released from the roof of the vehicle the main part of the airbag 8 is trapped between the torso 18 of the occupant 7 and the dashboard 5, and also the apron 16 provided at the lower part of the airbag 8 is trapped between the knees 17 of the occupant 7 and the dashboard 5.

Thus the airbag provides the desired protection for the occupant 7 of the vehicle whilst minimising the risk of the occupant suffering from undesired injuries as a consequence of backward bending of the neck. Because the apron 16 formed at the lower part of the airbag is trapped between the knees 17 of the occupant 7 and the under-surface of the dashboard 5, the inflated airbag 8 is retained in position even though the airbag 8 has been substantially or completely released from the roof of the vehicle.

Figure 5 shows the upper part of the airbag 8 following deployment thereof. The airbag 8 was initially retained in a recess 20 above the roof lining 21 behind a flap or door 22. Initially the flap or door 22 formed part of, or was mounted to be flush with or just behind, the roof lining so that the air- bag arrangement was inconspicuous. On inflation of the airbag 8 the door or flap 22 opened to permit the airbag to descend to the position shown in Figure 2. The airbag 8 is provided on each lateral side thereof ( i.e. the side nearest the adjacent door, and the side adjacent the centre of the vehicle) with a loop 23. The loop passes through an aperture 24 formed in a release block 25 mounted within the recess 20. The block 25 may be made of a frangible material which is adapted to break when subjected to a predetermined force,

but in the described embodiment of the invention one part of the block surrounding the aperture is provided with a line of mechanical weakness 26. A force applied to the release block by the loop 23 in excess of a predetermined threshold causes it to break at the line of mechanical weakness 26, thus permitting the loop 23 to escape in a generally forward direction from the aperture 24.

Referring now to Figure 6, when the occupant 7 applies a force to the airbag 8 as a consequence of the forward movement of the head 19 or torso 18 of the occupant 7 the loop 23 will apply that force to the release block 25. If the force is in excess of a predetermined threshold, the block will break along the line 26 of mechanical weakness, thus releasing the top part of the airbag from the roof of the vehicle. The only connection between the airbag and the vehicle is then the flexible hose 10 that extends to the gas generator 11. The flexible hose 10 readily becomes disconnected from the A-Post 4 and the airbag 8 is free to move forwardly and downwardly.

Figure 7 illustrates a modified embodiment of the invention. In this embodiment of the invention, the airbag 8 is generally as described with reference to Figure 2, and thus like references refer to like parts. The airbag 8 in the embodiment of Figure 7 is not provided with an integral apron 16 extending between the knees 17 of the occupant of the seat and the undersurface of the dashboard 5, but instead the airbag 8 is provided with a separate additional inflatable chamber 30 which is secured to the exterior of the main part of the airbag 8 to form an inflatable apron. The separate chamber 30 is provided with a flexible gas flow duct 31 which extends up the part 14 of the airbag 8 which is furthest from the occupant 7 and closest to the windscreen 3, that gas duct 31 then extending in parallelism with the gas duct 10 to a second gas generator 32 that is provided adjacent the principal gas generator 11. The

crash sensor 12 may provide signals both to the principal gas generator 11 and to the second gas generator 32. The second gas generator 32 may be actuated at a slightly different time to the principal gas generator 11, so that the additional inflatable chamber 30 becomes inserted between the knee 17 and the under-surface of the dashboard 5 in an appropriate manner.

As shown in Figure 7, the additional chamber 30 may incorporate at least one tear strap 33 so that the additional chamber 30 is maintained in a relatively "thin" condition until it is located between the knee 17 and the dashboard 5, with the additional chamber then inflating.

The remaining features of the embodiment shown in Figure 7 are the same as the corresponding features of the embodiment shown in Figure 2, and the airbag will operate effectively in the same way as the airbag shown in Figure 2..

It is to be appreciated, therefore, that the apron constituted by the region 16 or by the additional chamber 30, will become trapped between the knees of the occupant and the under-surface of the dashboard to hold the air- bag in position, especially when the upper part of the airbag has become disconnected from the roof 2 of the vehicle. Also, of course, the apron will provide a degree of protection for the knees of the occupant, since the inflated apron will provide a degree of cushioning between the knees of the occupant and the under-surface of the dashboard.

It is envisaged that the additional inflatable chamber 30 may be inflated, on deployment of the described airbag arrangement, to a pressure substantially greater than the pressure within the main part of the airbag 8.

The main part of the airbag 8 is to provide a cushioning effect for the torso and head of the occupant, and thus should be relatively "soft". It is envisaged that a pressure of less than 1 bar would be appropriate for the main part of the airbag 8, such as a pressure of about approximately 0.5 bar.

The inflatable chamber 30, which is to form the inflated apron between the knee 17 and the under-surface of the dashboard should, however, be inflated to a higher pressure such as, for example, a pressure in excess of 3 bar. As the lower part of the torso of the occupant moves forwardly, and the knee 17 moves forwardly, the knee is only spaced by, typically, a very short distance from the dashboard. The knee 17 should be prevented from coming into contact with the dashboard. The knee will apply a force to the inflated chamber 30 over a relatively small surface area, and thus the inflated chamber 30 should be inflated to a high pressure to provide the desired cushioning effect.

In the present specification "comprise" 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 airbag arrangement in a motor vehicle to protect an occupant of the vehicle in the event that an accident should occur, said arrangement incorporating an airbag, the airbag initially being retained in a folded condition within a recess at a position above and in front of the occupant to be protected, the airbag being associated with at least one gas generator and a sensor, the sensor being adapted to sense an accident and to activate the gas generator to inflate the bag, the airbag, on inflation, being deployed in front of the occupant of the vehicle, the airbag being provided with an inflatable chamber mounted on the rest of the airbag that constitutes an inflatable apron to be located between the knees of the occupant of the vehicle and a dashboard provided in the vehicle on deployment of the airbag.
2. An arrangement according to Claim 1 wherein the apron forms an integral part of the airbag. -
3. An arrangement according to Claim 1 wherein the apron forms a separate chamber secured to the airbag, the separate chamber being associated with a second gas generator to inflate the second chamber, the second gas generator being actuated by the sensor.
4. An arrangement according to Claim 3 wherein the second gas generator is actuated at a different instant in time from said first gas generator.
5. An arrangement according to Claims 3 or 4 wherein the apron, on inflation, is inflated to a higher pressure than the rest of the airbag.

<Desc/Clms Page number 17>
6. - An arrangement according to Claim 5 wherein the apron is inflated to a pressure of at least 3 bar.
7. An airbag arrangement according to any one of the preceding Claims wherein flexible hose means extend between the or each gas generator and the airbag, the means retaining the airbag in the recess being adapted to release the airbag from the recess so that the entire airbag is free to move forwardly and downwardly away from the recess.
8. An airbag arrangement according to any one of the preceding Claims wherein the means to retain the airbag in position within the recess are adapted to release the airbag from the recess when a force in excess of a predetermined force is applied to the airbag.
9. An arrangement according to Claim 7 or 8 wherein the upper part of the airbag is secured to frangible means adapted to break to release the airbag.
10. An arrangement according to Claim 9 wherein the means retaining the airbag within the recess include a plurality of loops in the upper part of the air- bag, each loop passing through an aperture formed in a release block, the release block being adapted to break to release the loop and thus to release the upper part of the airbag.
11. An arrangement according to Claim 10 wherein the release block is provided with a line of mechanical weakness adjacent said aperture, the release block breaking at the line of mechanical weakness to release the loop.

<Desc/Clms Page number 18>
12. An arrangement according to any one of Claims 1 to 8 wherein the air- bag is initially retained in a folded condition, and the means retaining the air- bag in the recess comprise a door which initially closes the recess, the door being adapted to be opened on inflation of the airbag to release the airbag during inflation thereof.
13. An arrangement according to any one of the preceding Claims wherein the airbag is constrained to be inflated in such a way that during the initial stages of inflation, the airbag is relatively thin (as measured in the direction of the axis of the vehicle) and is located in front of the occupant, and subsequently the thickness of the airbag (as measured in the direction of the axis of the vehicle) increases.
14. An arrangement according to Claim 13 wherein the airbag is provided with one or more breakable means extending from the part of the airbag closest to the occupant to the part of the airbag furthest from the occupant, said breakable means being dimensioned to maintain the airbag in a relatively thin condition (as measured in the direction of the axis of the vehicle) until a predetermined pressure is present within the airbag.
15. An airbag arrangement according to any one of the preceding Claims wherein the apron is constrained to be inflated in such a way that during the initial stages of inflation of the airbag, the apron is relatively thin (as measured in a distance extending between the knees of an occupant and the dashboard) and subsequently, the thickness of the apron increases.
16. An arrangement according to Claim 15 wherein the apron is provided with one or more breakable means extending from part of the apron closest to the knee of the occupant to part of the apron located adjacent the dashboard.

<Desc/Clms Page number 19>
17. An airbag arrangement substantially as herein described with reference to Figures 2 to 6 of the accompanying drawings.
18. An airbag arrangement substantially as herein described with reference to and as shown in Figure 7 of the accompanying drawings.
19. Any novel feature or combination of features disclosed herein.