GB2432344A

GB2432344A - An airbag with a releasable tether

Info

Publication number: GB2432344A
Application number: GB0522602A
Authority: GB
Inventors: Klaus Peter Kuhne; Karl Heinz Sommer; Johansson Anders
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2005-11-04
Filing date: 2005-11-04
Publication date: 2007-05-23
Also published as: GB0522602D0

Abstract

A safety arrangement for a motor vehicle, the safety arrangement comprising an airbag unit 1 incorporating a housing 2, an airbag 5 and an inflator 4 for inflating the airbag, the arrangement further comprising a restraining tether 11 secured to the housing at a first anchor region 15 and to a restrainable portion of the airbag at a second anchor region 12, the tether being releasable from at least one of the first and second anchor region to releasably anchor the restrainable portion of the airbag to the housing, whereby, during inflation of the airbag, the restraining tether is placed under tension to restrain inflation of the restrainable portion of the airbag until such time as the restraining tether is released, the restraining tether being released by means of a release cord 14 connected to the airbag such that, upon sufficient inflation of the airbag, the airbag pulls on the release cord to release the restraining tether. If a vehicle occupant is located close to the expanding airbag the release cord is not fully tensioned, thus the tether is not released and the airbag does not fully expand. The release cord may be attached to the tether by various means including a knot, a sliding bolt, rotatable catch, tearable seams etc.

Description

"A SAFETY ARRANGEMENT" THE PRESENT INVENTION relates to safety

arrangement, and more particularly relates to a safety arrangement for a motor vehicle intended to provide protection for a passenger in the motor vehicle.

It has been proposed previously to provide an air-bag located in front of a passenger in a motor vehicle, the air-bag being arranged to inflate in the event of an impact involving the vehicle in order to provide protection for the passenger. Such "passenger air-bags" are generally located within the dashboard of the motor vehicle and, in normal use, are covered by a region of dashboard trim in a manner well known per Se.

Whilst it is known that such an air-bag may provide good protection for an occupant who, at the instant of impact, is sitting in an "ordinary" position, it has been found that the air-bag may actually injure a seat occupant who, at the moment of impact, is not in the "ordinary" position but, instead, might be leaning forwards, for example, to gain access to a glove box mounted in the dashboard of a motor vehicle.

It has therefore been proposed previously that an arrangement should be provided to detect when a vehicle occupant is out of the ordinary position and to moderate inflation of the air-bag, or even inhibit inflation of the air-bag in such a situation, in order to reduce the risk of the air-bag itself injuring the occupant. Various such proposals have been proposed previously which involve the use of detectors to detect when a vehicle occupant is "out of position", the detectors being in some way operatively connected to the air-bag in order that the inflation of the air-bag can be controlled in response to signals received from the detectors. Such an arrangement is, therefore, an "active" system, in the sense that it actively monitors the position of a vehicle occupant.

In some instances, it is considered desirable to provide a safety arrangement in which an air-bag is configured to inflate in such a manner as to avoid significant injury to an "out of position" occupant, without the need for complicated and expensive detector or sensor arrangement.

The present invention seeks to provide an improved safety arrangement for a motor vehicle.

According to the present invention, there is provided a safety arrangement for a motor vehicle, the safety arrangement comprising an airbag unit incorporating a housing, an airbag and an inflator for inflating the airbag, the arrangement further comprising a restraining tether secured to the housing at a first anchor region and to a restrainable portion of the airbag at a second anchor region, the tether being releasable from at least one of the first and second anchor region to releasably anchor the restrainable portion of the airbag to the housing, whereby, during inflation of the airbag, the restraining tether is placed under tension to restrain inflation of the restrainable portion of the airbag until such time as the restraining tether is released, the restraining tether being released by means of a release cord connected to the airbag such that, upon sufficient inflation of the airbag, the airbag pulls on the release cord to release the restraining tether.

Conveniently, the arrangement is provided in a motor vehicle, wherein the release cord is attached to a region of the airbag which, during a given crash impact, is prevented from undergoing said sufficient inflation by an "out-of-position" vehicle occupant.

Optionally, the restraining tether is releasably secured to the housing at the first anchor region and fixed to the restrainable portion at the second anchor region.

Alternatively, the restraining tether is secured to the restrainable portion in the region of one end of the tether and releasably secured to the housing in the region of the opposite end of the tether.

In one envisaged embodiment, the restraining tether is indirectly secured to the restrainable portion via a restraint element, the restraint element being attached to an end of the tether.

Conveniently, the restraint element extends inwardly of the airbag to attach to the tether.

Optionally, the airbag unit comprises a securing arrangement to releasably secure the restraining tether to the housing at the first anchor region.

In a preferred embodiment, the securing arrangement comprises the tether being secured to the housing by a knot, the release cord being coupled to the knot so as to pull on the knot during said sufficient inflation, the knot being configured such that said pulling of the release cord on the knot undoes the knot and releases the tether from the housing.

Preferably, the securing arrangement includes a release member, the cord being fixedly attached to the release member such that, as the air-bag pulls the cord during inflation, the cord pulls on the release member to release the tether from the securing arrangement.

Optionally, the securing arrangement includes a retaining member within the air-bag unit, the tether being releasably secured to the retaining member.

In a preferred embodiment, the retaining member is in the form of a cleat fixed within the air-bag unit and wherein, prior to inflation of the air-bag, the cleat extends through a loop formed by the tether, and the release member is positioned to prevent the loop or eyelet passing over the free end of the cleat, the release member being configured such that, as the cord pulls on the release member during inflation of the air-bag, the release member moves to a position allowing the loop to pass over the free end of the cleat to release the tether.

Optionally, the release member is configured such that, during inflation of the air-bag, the release member engages the tether to force the loop or eyelet over the free end of the cleat and release the tether.

In a preferred embodiment, the release member is in the form of a pivotally mounted catch comprising an end stop and guide member, the catch being pivotable, as the cord pulls on the catch during inflation of the air-bag, between a first position in which the end stop prevents the loop or eyelet from passing over the free end of the cleat, and a second position in which the end stop is spaced away from the projection to allow the loop or eyelet to pass over the free end of the cleat, wherein as the catch moves from the first position to the second position, the guide member engages the tether to guide the loop or eyelet off the free end of the cleat and release the tether.

Optionally, the retaining member is rotatably mounted within the air-bag unit, the retaining element being rotatable between a first position, in which the tether is secured to the retaining member, and a second position in which the tether may disengage from the retaining member, wherein the retaining element moves from the first position to the second position as the cord pulls on the release member during inflation of the air-bag.

Preferably, the retaining member is in the form of a shaft mounted for rotation about a longitudinal axis of the shaft, the release member being in the form of a key configured to engage a key-way in the shaft wherein, prior to inflation of the air-bag, a portion of the tether is wound around the shaft and the key engages with the key-way to prevent rotation of the shaft, thereby securing the tether, and, upon sufficient inflation of the air-bag, the cord pulls on the key to retract the key from the key-way, whereby inflation of the air-bag causes the tether to rotate the shaft such that the tether unwinds from the shaft and is released.

In an alternative embodiment, the retaining member is in the form of a rotatable arm, and wherein prior to inflation the tether is secured to the arm by means of a loop formed in the tether, and the release member engages the arm to prevent rotation of the arm, the release member being configured such that, as the cord pulls on the release member upon sufficient inflation of the air-bag, the release member disengages the arm, whereby inflation of the air-bag causes the tether to rotate the arm such that the arm is aligned generally with the tether thereby releasing the tether from the arm.

In an alternative embodiment, the securing arrangement comprises a guide aperture formed through a fixed part of the air-bag unit, the release member being in the form of a bolt passing through the guide aperture, the tether being secured to the bolt, prior to inflation of the air-bag, by means of a loop formed by the tether, whereby as the cord pulls on the bolt during inflation of the air-bag, the bolt is pulled through the guide aperture and retracted through the loop to release the tether.

In a yet further embodiment, the securing arrangement includes a retaining member in the form of a fixed cleat and wherein, prior to inflation of the air-bag, the projection extends through a loop formed by the tether, or an eyelet attached to the tether, the securing arrangement further comprising an obstructing member to prevent the loop or eyelet passing over the free end of the projection prior to inflation of the air-bag, the release cord being attached to the tether such that, as the air-bag inflates, the release cord pulls the tether past the obstructing member and off the free end of the cleat to release the tether.

Optionally, the restraining tether is releasably secured at the first or second anchor region by means of a releasable joint, release of the tether from the joint being triggered by the airbag pulling on the release cord upon said sufficient inflation of the airbag.

Conveniently, the restraining tether is releasably secured to the restrainable portion at the second anchor region via a releasable joint and the tether is fixedly attached to the housing at the first anchor region.

Conveniently, the restraining tether is releasably secured to the housing at the first anchor region via a releasable joint and the tether is fixedly attached to the restrainable portion at the second anchor region.

In one embodiment, the releasable joint comprises a fastening element to secure the tether at the respective anchor region, the release cord being operably connected to the fastening element such that, upon said sufficient inflation of the airbag, the release cord pulls on the fastening element along a release direction so as to undo the fastening element, thereby sufficiently weakening the joint to allow the tether to separate from the housing or restrainable portion.

Advantageously, the fastening elements are configured such that the release direction is substantially perpendicular to the principal tension-bearing direction of the fastening element, whereby release of the fastening element is decoupled from the tension in the tether during inflation of said airbag.

Optionally, the releasable joint comprises a plurality of said fastening elements.

Conveniently, the fastening element is a hook and loop fastener, mechanical fastener, heat weld or stitching.

In one embodiment, the release cord is coupled to the fastening element or elements via a release member, the release member comprising a flexible band incorporating a peel panel coupled to the fastening element or elements for pulling and undoing the fastening element or elements upon pulling of the release cord, the peel panel portion being attached to the release cord via two strap portions extending from respective opposing edges of the peel panel to meet one end of the release cord such that, as the release cord is pulled during inflation of the airbag, the release element adopts a generally triangular form.

Conveniently, the release member is pre-formed in the general shape of an isosceles triangle comprising two strap portions of equal length.

Optionally, the releasable joint further comprises one or more reinforcing elements additionally securing the tether to the house or restrainable portion, whereby upon said undoing of the fastening elements and consequent weakening of the joint, the tension in said tether during inflation is sufficient to allow the tether to break free of the reinforcing elements.

In one embodiment, the tether is indirectly secured to the housing at the first anchor region via a flexible attachment element fixed to the housing, the tether being secured to the attachment element via the releasable joint.

Conveniently, the attachment element is a fabric element formed integrally with the airbag.

Preferably, one or more fastening elements are provided in the form of stitched trigger seams securing the tether to the attachment element, whereby pulling the release cord along the release direction unpicks the respective seam or seams.

Optionally, the release cord is coupled to the seam or seams via a release member, the release member comprising a flexible band incorporating a peel panel covering the seam or seams and being coupled thereto for pulling and unpicking the seam or seams upon pulling of the release cord, the peel panel portion being attached to the release cord via two strap portions extending from respective ends of the peel panel to meet one end of the release cord such that, as the release cord is pulled during inflation of the airbag, the release member adopts a generally triangular form.

Conveniently, the release member is formed integrally with the release cord.

Preferably, the releasable joint comprises at least two stitched seams securing the tether to the attachment element along different lengths, the seams being orientated such that as the strap portions pull on the opposing edges of the peel portion in response to the pulling of the release cord, one of said two seams starts to be unpicked before the other of said two seams.

Optionally, the attachment element or tether incorporates a tapered section, said two seams being spaced apart along the length of the tapered section and each spanning the width of the tapered section.

In a preferred embodiment, the releasable joint is provided with one or more reinforcing elements in the form of additional stitched reinforcing seams securing the tether to the attachment element, the reinforcing trigger seams being configured to resist the tension in the tether as the airbag inflates until such time as the release cord unpicks the trigger seams whereby, upon consequent weakening of the joint, the tension in said tether during inflation is sufficient to allow the tether to break free of the reinforcing seams.

Optionally, the safety arrangement comprises a plurality of said release cords.

Optionally, the safety arrangement comprises a plurality of said tethers.

Optionally, the safety arrangement comprises a respective plurality of said securing arrangements.

In order that the present invention may be more readily understood, and so that further features thereof may be appreciated, certain embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure Ia is a schematic cross-sectional illustration showing a safety arrangement in accordance with a first embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure lb is an enlarged view of a section of Figure Ia, showing a portion of the safety arrangement in more detail; Figure 2 is a view corresponding generally to Figure Ia, showing a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 3a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a second embodiment of the invention during an initial stage of deployment, in which an air-bag is partially inflated; Figure 3b is an enlarged cross-sectional view of a section of Figure 3a showing a part of the safety arrangement in more detail; Figure 4 is a view corresponding generally to Figure 3a, showing a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 5 is a schematic cross-sectional illustration showing an alternative form for a part of the safety arrangement shown in Figures 3a and 3b; Figure 6a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a further embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure 6b is an enlarged cross-sectional view showing a part of the safety arrangement of Figure 6a in more detail; Figure 7 is a view corresponding generally to Figure 6a, illustrating a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 8a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a yet further embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure 8b is an enlarged cross-sectional view showing part of the safety arrangement of Figure 8a in more detail; Figure 9 is a view corresponding generally to Figure 8a, illustrating a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure lOa is a schematic cross-sectional illustration showing a safety arrangement in accordance with another embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure lOb is an enlarged cross-sectional view showing part of the safety arrangement of Figure lOa in more detail; Figure 11 is a view corresponding generally to Figure lOa, illustrating a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 12a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a further embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure 12b is an enlarged cross-sectional view showing a part of the safety arrangement of Figure 12a in more detail; Figure 13 is a view corresponding generally to Figure 12a, illustrating a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 14a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a further embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure 14b is an enlarged view showing a part of the safety arrangement of Figure 14a in more detail; Figure 15 is a view corresponding generally to Figure 14a, showing a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 16a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a further embodiment of the present invention, during an initial stage of deployment, in which an air-bag is partially inflated; Figure 16b is an enlarged view showing part of the safety arrangement of Figure 16a in more detail; Figure 17 is a view corresponding generally to Figure 16a, showing a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 18a is a schematic cross-sectional illustration showing a safety arrangement in accordance with a yet further embodiment of the present invention, during a initial stage of deployment, in which an air-bag is partially inflated; Figure 18b is an enlarged view showing part of the safety arrangement of Figure 18a in more detail; Figure 19 is a view corresponding generally to Figure 18a, showing a subsequent stage of deployment, in which the air-bag is substantially fully inflated; Figure 20a is a schematic perspective view showing one aspect of a safety arrangement; Figure 20b is an enlarged, schematic plan view corresponding to Figure 20a; Figure 21 is a schematic, perspective view showing a yet further aspect of a safety arrangement.

Referring initially to Figure 1, there is illustrated a first embodiment of a safety arrangement in accordance with the present invention, showing the arrangement during an initial stage of its deployment.

The safety arrangement illustrated in Figure Ia comprises an air-bag unit I which comprises a housing 2, shown mounted in the upper part of the dashboard 3 of a motor vehicle. It should be appreciated that the present invention can find application in regions of a motor vehicle other than the dashboard, not only in the dashboard region. Nevertheless, for simplicity, the present invention will be described hereinafter with specific reference to an installation mounted in the dashboard of a motor vehicle such as, for example, a front impact "passenger air-bag".

The air-bag unit I further comprises an inflator 4 which may, for example, take the form of a gas generator of a type known per Se. The inflator is mounted within the housing 2 for inflating an air-bag 5.

A deflector 6 is provided (see Figure 1 b) which is mounted generally adjacent an exit port of the inflator 4 and which is configured to direct the flow of inflating gas from the inflator 4 into the air-bag 5 in an appropriate manner. In the embodiment shown in Figures Ia, lb and Figure 2, the free end of the deflector 6 which is located towards the uppermost surface of the dashboard 3 is provided with apertures 7a, 7b (see Figure Ib), the purpose of which will be described in more detail below. It should be appreciated that the apertures 7a, 7b are fixed by virtue of being provided through the gas deflector 6, which is fixed with respect to the housing 2, so that the apertures 7a, 7b are formed through a fixed part of the air-bag unit 1. In an alternative embodiment, however, the two apertures 7a, 7b, could be replaced by a single aperture.

As will be appreciated by those skilled in the art, the air-bag 5 is initially packed, for example by folding, rolling or a combination of both, so as to reside entirely within the housing 2 which, in normal use, is covered by a region of dashboard trim (not shown) in a manner known per Se.

Figure Ia illustrates the air-bag 5 in a condition after actuation of the inflator 4, during the initial stages of inflation of the air-bag 5.

During the early stages of inflation of the air-bag 5, the upper region of the air-bag quickly bears against the under surface of the vehicle's windscreen 8, an instant before the air-bag becomes entirely unfolded or unrolled from its packed condition. Indeed, Figure 1 shows part of the air-bag 9, which is located closest to a front seat occupant 10 of the motor vehicle, still folded.

A restraint element 11 is provided within the air-bag 5, the restraint element 11 being of a generally "parachute shaped" form presenting a panel which is secured, for example via an area of stitching, to a restrainable portion 12 of the inner surface of the air-bag 5, in this case in a region which, at the instant of inflation illustrated in Figure 1, lies substantially adjacent the windscreen 8, above the folded part 9 of the air-bag 5.

The restraint element 11 extends inwardly of the air-bag 5 to attach to a tether 13, being an elongate flexible element, the tether extending inwardly of the restraint element 11 towards the housing 2, where it passes through the guide apertures 7a, 7b formed through the deflector 6 so as to define a loop between the two apertures.

A release cord 14, being an elongate flexible element, is also provided within the air-bag 5, the release cord 14 being attached to the air-bag at one end in the region of the folded part 9 and extending inwardly through the interior of the air-bag towards the deflector 6 of the housing 2.

Referring primarily to Figure Ib, the tether 13 is releasably secured to the housing 2 at a first anchor region by means of a securing arrangement. Thus, the release cord 14 is directly coupled to the tether 13 by means of a suitable knot 15 (illustrated only very schematically in Figure Ib) which, on the one hand, prevents dis-engagement of the tether 13 from the release cord 14 upon pulling of the tether but, on the other hand, allows the release cord and tether to dis-engage from one another upon pulling of the release cord in a direction generally indicated at A in Figure lb. Suitable knots will be appreciated by those skilled in the art, but the arrangement illustrated in Figure Ia comprises a loop formed in the tether 13 between the two apertures 7a, 7b, through which a folded over-end region of the release cord passes. The presence of the release cord 14 in the loop thus prevents withdrawal of the tether 13 from the apertures 7a, 7b.

It is to be appreciated, referring to Figures Ia and Ib, that, with the tether 13 passing through the apertures 7a, 7b, and being coupled to the release cord 14 in the manner shown, the tether is releasably secured to the housing 2 of the air-bag unit I at a first anchor region (specifically, by means of the apertures 7a, 7b and release cord 14). Equally, it will be appreciated that the tether is secured to the restrainable portion 12 of the air-bag at a second anchor region.

The operation of the embodiment shown in Figures 1 and 2 will now be described.

Thus, in the event of a suitable crash impact, the air-bag unit acts to deploy the air-bag 5, commencing inflation of the air-bag 5 by means of the inflator 4 in known manner. During this initial stage of deployment, the air-bag 5 inflates and quickly bears against the under surface of the vehicle's windscreen 8, in the region of the restrainable portion 12, whilst part 9 of the air-bag 5, in the region of the end of the release cord 14, remains completely or partially folded. Thus, referring to Figure Ia, it will be appreciated that, during initial deployment, the degree of inflation of the air-bag 5 (specifically the degree of inflation of the air-bag in the folded region 9) is insufficient to take up the slack in the release cord 14, with the result that the release cord does not pull on the knot 15 and the release cord remains coupled to the restraining tether 13 adjacent the deflector 6. On the other hand, the degree of inflation of the air-bag 5 in the region of the panel 12 occurs sufficiently quickly to take up any slack in the restraint element II and restraining tether 13, so that the restraint element 11 and restraining tether 13 are placed under tension between the wall of the air-bag 5 in the region of the restrainable portion 12, and the deflector 6. It will be appreciated that, as the knot 15 cannot pass through the guide aperture 7, the tether releasably anchors the restrainable portion 12 of the air-bag 5 to the housing 2, thus restraining inflation of the restrainable portion 12.

Referring specifically to the case where the occupant 10 is moving forwardly with respect to the dashboard 3, but from a generally "ordinary" seating position (shown in solid lines in Figure Ia), it will be appreciated that there is sufficient space between the occupant 10 and the air-bag 5 for the folded part 9 of the air-bag 5 to continue to inflate, so that slack in the release cord 14 is taken up as the inflating air-bag 5 begins to unfold in the part 9 and pull on the release cord. As inflation of the air-bag continues, a point will be reached whereby the degree of inflation of the air-bag, specifically the degree of inflation in the region 9 of the air-bag, is such that the release cord 14 is pulled taut and, as inflation of the air-bag continues beyond this point, the release cord will be pulled generally in the direction A (Figure Ib) thereby loosening the knot 15 to dis-engage the release cord 14 from the restraining tether 13.

Thus, referring to Figure 2, which illustrates the air-bag 5 in a substantially fully inflated condition after dis-engagement of the restraining tether 13 and release cord 14, the restraining tether 13 isallowed to run through the apertures 7a, 7b formed in the gas deflector 6 (in the absence of the knot 15) and the air-bag 5 adopts a fully inflated configuration, providing a cushioning effect for the applicant moving from a generally "ordinary" seating position.

On the other hand, if the occupant 10 is "out of position" and is, for example, located significantly closer to the dashboard 3 (as might be the case if the occupant were attempting to retrieve something from the "glove box" of the motor vehicle) then, in contrast to the case where the occupant is in an "ordinary" seating position, the folded part 9 of the air-bag would not have sufficient space to become completely unfolded. In this situation, therefore, because the folded part 9 of the air-bag is prevented from unfolding completely, the release cord 14 will not be pulled taut by the air-bag 5, with the result that the release cord will not pull on the knot 15, so that the knot 15 will not be undone and the tether will continue to be under tension between the deflector 6 and the air-bag 5, releasably anchoring the restrainable portion 12 of the airbag 5 to the housing 2 so that inflation of the air-bag 5 will continue to be restrained by the restraining tether 13. Thus, the occupant 10 of the motor vehicle prevents a full inflation of the air-bag (in this case in the region 9 of the air-bag 5) and, consequently, the air-bag does not pull on the release cord to release the restraining tether. In this manner, the portion of the air-bag adjacent the panel 12 is prevented from advancing too far towards the "out of position" occupant, thereby helping to avoid possible injury to the occupant.

Figures 3a, 3b and 4 show a second embodiment of the present invention.

This arrangement is similar in several respects with the arrangement described above with reference to Figures 1 and 2, and the same reference numerals will be used for like features for the sake of simplicity.

The arrangement illustrated in Figures 3 and 4 differs from that illustrated in Figures 1 and 2 in the form of the securing arrangement which releasably secures the tether 13 to the housing. Principally, the tether 13, is not directly coupled to the release cord 14, but rather, prior to inflation of the air-bag, the release cord 14 is attached to a release member, in the form of a bolt 16, with the tether 13 being releasably secured to the bolt 16 by means of a loop 13a formed by the tether.

More particularly, and with reference to Figures 3a and 3b, the deflector 6 is provided with a guide aperture 17, the deflector 6 supporting a cantilevered guide portion 18 extending generally perpendicular to the deflector portion in a direction away from the release cord 14, and incorporating the guide aperture 7. In similar manner to the embodiment shown in Figures 1 and 2, the tether 13 passes through the guide aperture 7 in the cantilevered guide portion 18 of the deflector 6 but, rather than being directly coupled to the release cord 14 as in the arrangement shown in Figures 1 and 2, the tether 13 is instead releasably secured to the bolt 16 by means of an "open" loop formed in the end of the tether 13. Referring again to Figure 3b, the bolt 16 is received through the guide aperture 17 where it attaches to the release cord 14.

Referring to Figures 3 and 4, it will be appreciated that the embodiment of Figures 3 and 4 operates in a generally similar manner to the embodiment shown in Figures 1 and 2. Thus, upon a suitable crash impact, the inflator 4 is triggered to inflate the air-bag 5 in known manner whereupon the air-bag 5 quickly bears against the under surface of the windscreen 8 in the region of the restrainable portion 12, whilst a part of the air-bag 9, in the region of one end of the release cord 14, remains completely or partially folded. It will be appreciated that, in a similar manner to the embodiments shown in Figures 1 and 2, the degree of inflation of the air-bag 5, in Figure 3a, (specifically the degree of inflation of the air-bag in folded region 9) is insufficient to take up the slack in the release cord 14, with the result that the release cord 14 does not pull on the bolt 16. On the other hand, it will also be appreciated that the degree of inflation of the air-bag 5 in the region of the restrainable portion 12 occurs sufficiently quickly to take up any slack in the restraint element 11 and restraining tether 13. Moreover, it will be appreciated that, with the bolt 16 in the position shown in Figure 3B, the tether 13 remains secured with respect to the air-bag unit 1 by means of being secured to the bolt 16, the bolt being prevented from moving upwardly (in a direction generally perpendicular to the direction B in Figure 3b) by the cantilevered guide portion 18. In the position shown in Figure 3a, during initial deployment of the air-bag 5, the tether 13 is placed under tension between the wall of the air-bag 5 in the region of the restrainable portion 12, and the deflector 6 (specifically the cantilevered guide portion 18 thereof). In this manner, the restraining tether 13 releasably anchors the restrainable portion 12 to the housing 2.

In the case where the occupant is moving forwardly with respect to the dashboard 3, but from a generally "ordinary" seating position, it will again be appreciated that there is sufficient space between the occupant 10 and the air-bag 5 for the folded part 9 of the air-bag to continue to inflate, so that slack in the release cord 14 is taken up as the inflating air-bag 5 begins to unfold in the part 9 and pull on the release cord 14. As inflation of the air-bag 5 continues, a point is reached whereby the degree of inflation of the air-bag 5 in the region 9 is such that the release cord 14 is pulled taut and, as inflation of the air-bag continues, the air-bag 5 begins to pull on the release cord generally in the direction B (Figure 3b), thereby withdrawing the bolt 16 through the guide aperture 17 and through the loop 13a in the tether 13 to release the tether 13 from the first anchor region.

Referring now to Figure 4, which illustrates the air-bag 5 in a substantially fully inflated condition after release of the restraining tether 13 from the bolt 16, the restraining tether 13 is allowed to run through the guide aperture 17 formed through the gas deflector 6 and the air-bag 5 is free to adopt a fully inflated configuration, providing a cushioning effect for the occupant moving from a generally "ordinary" seating position.

On the other hand, if the occupant 10 is "out of position" and is, for example, located significantly closer to the dashboard 3, then, in similar manner to the embodiment illustrated in Figures 1 and 2, the folded part 9 of the air-bag would not have sufficient space to become completely unfolded and, in this situation, the release cord 14 would not be pulled taut by the air-bag 5, with the result that the release cord does not pull on the bolt 16, so that the bolt 16 remains generally in the position shown in Figure 3b and the tether continues to be held taut between the deflector 6 and the air-bag 5 such that inflation of the air-bag 5 consequently continues to be restrained by the tether 13 in the region of the restrainable portion 12. In this manner, the portion of the air-bag adjacent the restrainable portion 12 is prevented from advancing too far towards an "out of position" occupant, thereby avoiding possible injury to the occupant.

Whilst the bolt 16 in Figures 3 and 4 has a generally cylindrical body, it is envisaged that any manner of suitably shaped bolts may be used. For example, the bolt may incorporate a tapered body, as illustrated in Figure 5, to promote a "cleaner" release of the tether 13 from the bolt.

Figures 6 and 7 show a further embodiment of the present invention, being similar to the embodiment shown in Figures 3 and 4, but employing a slightly different securing arrangement for the tether 13.

Thus, rather than the tether 13 being secured to the bolt 16 by means of an "open" loop, as in Figures 3 and 4, the tether 13 is releasably secured to the bolt 16 by means of a "closed" loop, which in Figure 6b is shown in the form of a closed loop formed by knotting the tether 13 at an appropriate point 19, but which may take the form of a separate eyelet or ring attached to the tether. In a similar manner to the embodiments shown in Figures 3 and 4, the bolt 16 is again slidably received through a guide aperture 17 in the deflector 6; however, rather than there being provided a cantilevered guide portion, as in Figures 3 and 4, the air-bag unit is instead provided with a secondary deflector portion 20, running generally parallel to the deflector 6, the secondary deflector portion 20 comprising a second guide aperture 21, aligned with the guide aperture 17 for slidably receiving the bolt 16 in like manner.

It will be appreciated that, aside from the manner in which the tether 13 is secured to the bolt 16, the embodiment of Figures 6 and 7 is very much the same as the embodiment of Figures 3 and 4, and that these two embodiments operate in a very similar way, such that the tension applied to the release cord 14 is effective to withdraw the bolt 16 from the apertures 17,21 and from the loop 19.

Turning to Figures 8 and 9, a yet further embodiment is illustrated including an alternative form of securing arrangement for the tether 13.

Thus, referring to Figure Sb in particular, a securing arrangement is shown comprising a cleat 22 projecting from the deflector 6 generally perpendicular thereto and rigidly affixed to the deflector. A release member is provided in the form of a catch 23 rotatably mounted to the air-bag unit I at a pivot point 24. The catch 23 comprises a body portion 25, which in a first position shown in Figure 8b extends generally perpendicular to the deflector 6 and parallel to the cleat 22. The body portion 25 is provided, at one end, with an end stop 26 in the form of an annular barrier portion 26 which, in the first position shown in Figure 8b extends generally parallel to the deflector 6, that is perpendicular to the body portion 25. The barrier portion 26 has an aperture significantly larger than the maximum dimension of the cleat 22 and which receives the cleat 22 therethrough. At the end of the body portion opposite the annular barrier portion 26 there is provided a hook portion 27 which is secured to one end of the release cord 14 by means of a "closed" loop in the release cord 14 (see Figure 8b).

The catch also comprises an annular guide member 28, extending generally perpendicular to the elongate body portion, and parallel to the deflector 6, at a point along the body portion between the hook 27 and annular barrier portion 26. In similar manner to the annular barrier portion 26, the annular guide portion 28 also receives the cleat 22 therethrough in the first position shown Figure 8b so that, in this position, the cleat 22 extends from the deflector 6 generally horizontally through, in turn, the annular guide member 28 and annular barrier portion 26, whereby the tether 13 is prevented from sliding off the free end of the cleat 22 so that it is (releasably) secured to the housing at a first anchor region.

During operation of the safety arrangement according to the embodiment shown in Figures 8 and 9, it will be appreciated that, so long as the release cord 14 remains slack and does not pull on the hook portion 27 of the catch 23, the tether 13 will be prevented (by means of the annular barrier portion 26) from sliding off the cleat 22, whereby in the case where an "out of position" occupant prevents unfolding of the part 9 of the air-bag 5, the tether is placed under tension between the cleat 22 and air-bag 5 in the region of the panel 12 so as to prevent the air-bag 5, in the region of the panel 12, from advancing too far towards the "out of position" occupant.

Alternatively, where an occupant is moving forward from an "ordinary" position, so that the part 9 of the air-bag 5 is free to inflate and, eventually, pull on the release cord 14, the release cord 14 will in turn pull on the hook portion 27 of the catch 23 in a direction generally indicated at D in Figure 8b, thereby causing the catch to rotate in a direction E (Figure 8b) about the pivot point 24. As the catch 23 pivots about the pivot point 24, it will be appreciated that, provided the annular guide portion 28 and annular barrier portion 26 are sufficiently large, the catch will be free to move to a second position shown in Figure 9, whereby the annular barrier portion is spaced away from the cleat (which does not move) allowing sufficient space for the loop in the tether 13 to pass over the free end of the cleat, releasing the tether from the securing arrangement.

Moreover, it is to be appreciated that, as the catch moves from the first position shown in Figure 8b to the second position shown in Figure 9, the annular guide portion 28 will come into contact with the loop of the tether 13 so as to guide the loop of the free end of the cleat and release the tether through the space between the spaced apart annular barrier portion 26 and the cleat 22 (see Figure 9). In this manner, pulling of the release cord 14 releases the tether 13 from the securing arrangement of the air-bag unit 1, allowing the air-bag to inflate substantially fully towards the occupant moving from an "ordinary" position.

Referring now to Figures 10 and 11, a yet further embodiment of a safety arrangement according to the present invention is shown, incorporating yet another envisaged securing arrangement for the tether 13. Thus, referring to Figures lOa and lOb, the air-bag unit is provided with a second deflector portion 29, opposite the deflector 6 and extending upwardly and generally parallel to the deflector 6. A cleat 30 extends generally horizontally from the secondary deflector 29 towards the deflector 6, terminating before reaching the deflector 6 so as to define a space between the free end of the cleat 30 and the deflector 6. The deflector 6 is provided, at its upper end, with a cantilevered guide portion 31 extending towards the secondary deflector portion 29, in a direction generally perpendicular thereto, the cantilevered portion 31 projecting beyond the free end of the cleat 30 such that the cleat 30, deflector 6 and cantilevered portion 31 together define a labyrinth-like structure.

Referring to Figures lOa and lOb, the tether 13 is releasably secured at a first anchor region to the housing 2, more specifically to the cleat 30 by means of a closed loop formed in the tether via a knotted point 19. The release cord passes between the cantilevered portion 31 and the cleat 30, and between the cleat 30 and the deflector 6 so as to be fixedly attached to the tether at the bottom of the closed loop (distal from the knotted point 19). Thus, provided the release cord 14 remains slack, (for example because the part 9 of the air-bag 5 is prevented from unfolding by an "out of position" occupant), the tether 13 is placed under tension, as the air-bag 5 inflates, between the cleat 30 and the air-bag 5 in the region of the restrainable portion 12, whereby the tether 13 serves to releasably anchor the restrainable portion 12 to the housing 2 so as to restrain inflation of the restrainable portion 12.

However, when the folded part 9 of the air-bag 5 is allowed to freely inflate and unfold, for example in the case where the occupant is moving forward from an "ordinary" position, the air-bag 5 pulls on the release cord 14 such that the release cord 14 drags the tether 13 along the cleat 30 (to the left in Figure lOb) and then, as the tether 13 passes over the free end of the cleat 30, pulls the tether upwardly beyond the free edge of the cantilevered guide portion 31, as indicated by the direction F in Figure lOb. In this manner, the tether 13 is released from the first anchor region and, consequently, the air-bag 5 is free to inflate to a substantially fully inflated position, shown in Figure 11.

Referring now to Figures 12 and 13, a yet further embodiment of a safety arrangement according to the present invention is shown, the arrangement comprising an alternative form of securing arrangement for releasably securing the tether to the air-bag unit.

Thus, referring to Figure 12a, a shaft 32 is provided, mounted for rotation about a longitudinal axis 33, within the guide apertures 17 and 21 formed through the deflector 6 and secondary deflector 29. The deflector 6 is also provided with a cantilevered bracket portion 34 extending generally perpendicular to the deflector 6, away from the deflector portion 29. A release member is provided in the form of a key 35, slidably received through a clearance hole in the cantilevered bracket portion 34 and being attached at one end to the release cord 14, whilst being configured, at the opposite end, to be received in a key-way 36 formed in the shaft 32.

Prior to inflation, and in the deployment position shown in Figures 12a and 12b, the tether 13 is wound around the shaft 32, between the deflector 6 and the secondary deflector 20 and the key 35 is engaged in the key-way 36 to prevent rotation of the shaft 32, whereby the tether 13 is releasably secured to the housing 2 at a first anchor region. It will be appreciated that, provided the release cord 14 remains slack during inflation, (as will be the case for example if the occupant of the vehicle is "out of position" and restricts inflation of part 9 of the air-bag 5), the key 35 will remain engaged with the key-way 36 in the shaft 32, thereby continuing to prevent rotation of the shaft 32. Thus, as the air-bag 5 inflates, the tether 13 is placed under tension between the air-bag 5 (in the region of the restrainable portion 12) and the (non-rotating) shaft 32, restraining inflation of the restrainable portion 12, and preventing the air-bag from advancing too far towards the "out of position" occupant.

On the other hand, if the part 9 of the air-bag 5 is free to inflate, as would be the case where the occupant was moving from an "ordinary" position, the air-bag 5 pulls on the release cord 14 which, in turn, will eventually pull on the key 35 as the air-bag inflates, thereby releasing the key 35 from the key-way 36 in the shaft 32, allowing the shaft 32 to rotate such that the tether 13 unwinds from the shaft and is thereby released from the first anchor region. In this manner, the air- bag 5 is allowed to inflate substantially fully to adopt the position shown in Figure 13.

In a yet further embodiment shown in Figures 14 and 15, the retaining member is in the form of a rotatable arm 37 mounted to a boss portion 38 extending upwardly and generally parallel to the deflector 6, for rotation about apivotpoint39.

A release member is provided in the form of an abutment member 40, which is slidably received through a clearance hole 41 formed through the deflector 6 at a position below the pivot point 39.

The abutment member 40 passes through the clearance hole 41 in the deflector 6 and extends towards the boss portion 38 and into the rotational path of the arm 37, thereby preventing free rotation of the arm 37. Prior to inflation of the air-bag 5, the tether 13 engages with the arm by means of a closed loop, which is passed over the free end of the arm 37, on the opposite side of the pivot point 39 to the abutment member 40.

Referring now to Figures 14a and 14b, as the air-bag 5 initially inflates, the air-bag in the region of the panel 12 quickly bears against the under surface of the windscreen 8 and the region of the air-bag 9 remains completely or partially folded such that the release cord 14 is slack. The upward movement of the air-bag 5, in the region of the panel 12, serves to take up any slack in the tether 13 and, consequently, the tether 13 pulls on the rotatable arm 37 to rotate the arm 37 in the direction I (Figure 14b). As will be appreciated, once the arm 37 abuts against the abutment member 40, further rotation of the arm 37 is prevented and the rotatable arm 37 adopts a generally horizontal position, as shown in Figure 14b, whereby further rotation of the rotatable arm 37 in an anticlockwise sense (indicated by I in Figure 14b) is prevented by the abutment member whilst, at the same time, rotation of the arm 37 in a clockwise sense is prevented by the upward pulling motion of the tether 13. In this manner, the tether 13 is secured to the housing at a first anchor region.

Thus, the tether 13 is placed under tension between the air-bag 5, in the region of the restrainable portion 12, and the rotatable arm 37 such that the tether anchors the restrainable portion to the housing and serves to restrain inflation of the restrainable portion 12, thereby preventing the air-bag from advancing too far towards the "out of position" occupant.

In the alternative scenario, where an occupant is moving forward during the crash impact from an "ordinary" position, so that the part 9 of the air-bag 5 is substantially fully inflated and unfolded, the release cord pulls on the abutment member 40 (once a sufficient degree of inflation of the region 9 of the air-bag has occurred) and withdraws the abutment member 40 through the clearance hole 41 in the deflector 6, thereby allowing the upward pulling motion of the tether to further rotate the arm 37 in an anticlockwise direction (I). Referring now to Figure 15, it will be appreciated that the tether 13 will continue to rotate the arm 37 in an anticlockwise direction until such time as the arm becomes generally aligned with the tether 13, at which point the tether 13 is pulled off the end of the rotatable arm 37, releasing the tether 13 and thereby allowing a substantially full inflation of the air-bag 5, as shown in Figure 15.

Referring now to Figure 16 and 17, an arrangement is shown comprising an alternative form of securing arrangement for releasably securing the tether to the housing at a first anchor region.

Thus, referring to Figures 16a and 16b, the tether 13 is indirectly secured to the housing 2 at the first anchor region via a flexible attachment element in the form of a fabric attachment element 42 which is formed integrally with the air-bag 5.

The tether 13 is secured to the attachment element by means of a releasable joint comprising a plurality of fastening elements in the form of stitched trigger seams 43 and a plurality of reinforcing elements in the form of stitched reinforcing seams which, in the embodiment shown in Figure 16 are arranged generally parallel to one another, positioned along the length of the attachment element 42 (as most clearly seen in Figure 16b). Referring to Figure 16b, the release cord 14 is also stitched to the tether 13 by means of the trigger seams 43, so that the release cord 14 is effectively coupled to the release seams 43. Alternatively, the release cord 14 may be coupled to the trigger seams 43 by means of a strong adhesive or the like.

The operation of the embodiment shown in Figures 16 and 17 will now be described.

Thus, in the event of a suitable crash impact, the air-bag unit acts to deploy the air-bag 5, commencing inflation of the air-bag 5 by means of the inflator 4 in known manner. During this initial stage of deployment, the air-bag 5 quickly bears against the under surface of the vehicle's windscreen 8, in the region of the panel 12, whilst part of the air-bag 9, in the region of one end of the release cord 14 remains completely or partially folded. Thus, referring to Figure Ia, it will be appreciated that, during initial deployment, the degree of inflation of the air-bag 5 (specifically the degree of inflation of the air-bag in the folded region 9) is insufficient to take up the slack in the release cord 14. As a result, the release cord 14 does not pull on the trigger seams 43 and therefore remains coupled to the trigger seams 43 which in turn continue to secure the tether 13 to the attachment element 42. On the other hand, the degree of inflation of the air-bag 5 in the region of the restrainable portion 12 is sufficient quickly to take up any slack in the restraint element II and restraining tether 13, so that the restraint element II and restraining tether 13 are placed under tension between the wall of the air-bag 5 in region of the restrainable portion 12, and the attachment element 42. It will be appreciated that, so long as the trigger seams 43 and reinforcing seams 44 are configured to be strong enough to resist the tension in the tether 13, (indicated at A in Figure 16b) and the resulting reaction force B (indicated in Figure 16b) exerted on the attachment element 42, then the restraining tether 13 will be placed under tension between the restrainable portion 12 and the attachment 42, thereby anchoring the restrainable portion 12 to the housing 2 to restrain inflation of the restrainable portion 12.

Referring specifically to the case where the occupant 10 is moving forwardly with respect to the dashboard 3, but from a generally "ordinary" seating position (shown in solid lines in Figure 16a), it will be appreciated that there is sufficient space between the occupant 10 and the air-bag 5 for the folded part 9 of the air-bag 5 to continue to inflate, so that slack in the release cord 14 is taken up as the inflating air-bag 5 begins to unfold in the region and 9 and pull on the release cord 14. As inflation of the air-bag 5 continues, a point will be reached whereby the degree of inflation of the air-bag 5, specifically the degree of inflation in the region 9 of the air-bag, is sufficient to pull the release cord 14 taut and as inflation of the air-bag continues beyond this point, the release cord will be pulled generally in the direction C (Figure 16b) thereby unpicking the trigger seams 43 to disengage the release cord 14 from the tether 13 and, moreover, partially disengage the tether 13 from the attachment element 42. It will be appreciated that, by pre-configuring the reinforcing seams 44 so that they alone are unable to withstand the tension in the tether 13 during inflation of the air-bag, unpicking of the trigger seams 43 will allow the tether 13 to break free of the reinforcing seams 44 and the air-bag 5 will continue to inflate and eventually adopt the general configuration shown in Figure 17, whereby the release cord 14 and tether 13 have each separated from the housing 2 at the first anchor region. It is to be appreciated that, in the substantially fully inflated condition shown in Figure 17, after disengagement of the restraining tether 13 at the first anchor region, the air-bag 5 will provide a cushioning effect for the applicant moving from a generally "ordinary" seating position.

On the other hand, if the occupant 10 is "out of position" and is, for example, located significantly closer to the dashboard 3 (as shown in the dotted lines in Figure 16a) then, in contrast to the case where the occupant is in an "ordinary" seating position, the folded part 9 of the air-bag would not have sufficient space to become completely unfolded. In this situation, therefore, because the folded region 9 of the air-bag is prevented from unfolding completely, the release cord 14 will not be pulled taut by the air-bag 5, with the result that the release cord will not, in turn, pull on the trigger seams 43, so that the trigger seams 43 will continue to secure the tether 13 to the attachment element 42 (in combination with the reinforcement seams 44), thereby anchoring the restrainable portion 12 of the air-bag to the housing 2. In this manner, the occupant 10 of the motor vehicle prevents a sufficient degree of inflation of the air-bag to release the restraining tether and, consequently, the restrainable portion of the air-bag is prevented from advancing too far towards the "out of position" occupant, thereby helping to avoid possible injury to the occupant.

Referring now to Figures 18 and 19, a yet further safety arrangement is illustrated including an alternative form of securing arrangement for thetether 13. In many respects, the arrangement shown in Figure 18a and 18b is similar to the arrangement shown in Figures 16 and 17, and like numerals have been used to denote like features for the sake of clarity and conciseness.

Thus, referring to Figures 18a and 18b, the tether 13 is fixedly attached to the housing 2 at a first anchor region and releasably secured to the restrainable portion 12 of the air-bag at a second anchor region via a releasable joint. In similar manner to the embodiment shown in Figures 16 and 17, the releasable joint comprises a plurality of fastening elements in the form of trigger seams 43, and a plurality of reinforcing elements in the form of reinforcing stitched seams 44. Similarly, the release cord 14 is coupled to the trigger seams 43 as in the embodiment described with reference to Figures 16 and 17.

It will be appreciated that the embodiments shown in Figures 18 and 19 operate in a very similar way to the embodiments shown in Figures 16 and 17, save that the tether 13 is releasable from the air-bag 5 at the second anchor region, rather than being releasable from the housing 2 (via the attachment element 42) at the first anchor region.

Thus, briefly, so long as the release cord 14 remains slack (as will be the case where the region 9 of the air-bag is prevented from unfolding), then the release cord 14 will not pull on the trigger seams 43, so that the trigger seams 43 will continue to secure the tether 13 to the air-bag 5 (along with the reinforcing seams 44) and, consequently, the tether 13 will be placed under tension between the restrainable portion 12 of the air-bag 5 and the housing 2, thereby anchoring the restrainable portion to the housing 2.

Alternatively, where the region 9 is permitted to undergo sufficient inflation to pull the release cord 14 taut, the release cord 14 will in turn pull on the trigger seams 43 to unpick the trigger seams 43, and as a consequence the releasable joint will be sufficiently weakened such that the tension in the tether 13 will be sufficiently high to allow the tether (via the restraint element 11) to break free of the reinforcing seams 44, so that the air-bag 5 may continue to substantially fully inflate as shown in Figure 19.

In the embodiments shown in Figures 16, 17, 18 and 19, it is to be noted that the release direction C (see Figures 16b and 18b) is perpendicular to both the tension A in the tether 13 and the reaction force B exerted on the attachment element 42 in the case of (Figure 16b) or air-bag 5 in the case of (Figure 18b).

Thus the force required to unpick the trigger seams 43 is perpendicular to the principle load bearing direction of the releasable joint (specifically, the load bearing direction of the trigger seams 43 and reinforcing seams 44). In this manner, it will be appreciated that the resistance of the releasable joint to the tension in the tether 13 (as the air-bag 5 inflates) can very easily be tuned simply by adding a number of additional trigger seams 43 or reinforcing seams 44, without effecting the force required to unpick the trigger seams, and thereby trigger release of the tether, along the direction C. In effect, release of the tether 13 is decoupled from the tension in the tether 13 during deployment.

Turning now to Figures 20a and 20b, an alternative arrangement of securing the release cord 14 to the trigger seams 43 is shown.

Thus, referring to Figure 20a, the release cord 14 is indirectly secured to the trigger seams 43 via a release member 45 comprising a flexible band 46 incorporating a peel panel 47 and a pair of strap portions 48. Referring to Figure 20a, the peel panel is coupled to the trigger seams 43 in a manner similar to the coupling between the release cord 14 and trigger seams 43 in Figures 16b and 18b, whilst the two strap portions 48 extend from respective edges of the peel panel to meet one end of the release cord 14.

Referring principally to Figure 20b, which is a view from above of Figure 20a, it will be appreciated that as the release cord 14 is pulled taut by the inflating air-bag 5, the release member 45 will adopt a generally triangular form and, more specifically, the general form of an isosceles triangle (in the case where the strap portions 48 are of equal length). It will also be appreciated, referring to Figure 20b, that by varying the angle between the (taut) strap portions 48 and the peel portion 47 (for example by varying the length X of the strap portions 48), the effective pulling force required along the release direction C to unpick the trigger seams 43 will be correspondingly altered, with a larger angle resulting in a smaller pulling force along the release direction C being required to unpick a given trigger seam. In this manner, it will be appreciated that use of a release member as described with reference to Figures 20a and 20b provides for straightforward tuning of the pulling force required to unpick a given trigger seam and, ultimately, the pulling force required to release the tether from a respective anchor region.

Whilst the arrangements shown in Figures 20a and 20b show the specific situation where the tether 13 is attached to the housing 2 (via the attachment element 42), it will be appreciated that the use of a release member 45 as described with reference to Figures 20a and 20b could equally be employed in the case where the tether 13 is to be releasably secured at the second anchor region to the air-bag 5.

Referring now to Figure 21, a yet further arrangement is shown for coupling the release cord 14 to the trigger seams 43. Thus, in the embodiment shown in Figure 21, the attachment element is provided with a tapered section 49, with the trigger seams 43 being spaced along the length of the tapered section 49 and spanning the width thereof. Considering the two seams 43a, 43b in Figure 21, it will be noted that the seam 43b will secure the tether 13 to the attachment element 42 along a greater length than the trigger seam 43a.

Thus, with the seams 43a, 43b arranged in parallel manner and parallel to the opposing longer edges of the peel portion 47, it will immediately be appreciated that, as the release cord 14 is pulled in the direction C (upon inflation of the air-bag 5) so that the strap portions 48 initially pull on the edges of the peel portion 47, the longer seam 43b will begin to be unpicked before the shorter seam 43a. In this manner, the order in which the trigger seams begin to be unpicked can be readily controlled.

Whilst Figure 21 shows the attachment element 42 comprising tapered section 49, it is to be understood that the tether 13 might alternatively be provided with a tapered section (rather than the attachment element 42), with the trigger seam 43a and 43b similarly being spaced along the length of the tapered section of the tether 13 and spanning the width thereof. Indeed, where it is required to control the unpicking of the trigger seams at the second anchor region (with tether 13 secured to the air-bag 5), it is envisaged that it would be more convenient to provide the tapered section in the tether 13, as opposed to being part of the air-bag 5.

Whilst the arrangement described with reference to Figures 16 and 21 incorporates fastening elements and reinforcing elements in the form of stitching, it is envisaged that other suitable fastening elements could equally be used such as, for example, hook-and-loop fasteners, mechanical fasteners such as "press-studs" or the like, heat welds or any combination of such suitable fastening elements.

It will be appreciated that the safety arrangement described herein, with reference to the embodiments of Figures 1 to 21, comprises a restraining tether secured to a housing at a first anchor region and to a restrainable portion of the air-bag at a second anchor region, and that the tether is releasable from at least one of the first and second anchor regions to releasably anchor the restrainable portion of the air-bag to the housing. In this manner, during inflation of the air-bag the restraining tether is placed under tension and consequently restrains inflation of the restrainable portion of the air-bag until the restraining tether is released by means of a release cord. The release cord is connected to the air-bag such that, upon sufficient inflation of the air-bag, the air-bag pulls on the release cord, with sufficient inflation of the air-bag occurring during a given crash impact when a passenger is moving from a generally "ordinary" position, and sufficient inflation of the air-bag be prevented by the actual vehicle occupant in the case where the occupant is "out of position".

Thus, the safety described herein is a "passive" arrangement, whereby the release of the tether does not depend upon the active detection of a given type of crash situation, but is instead effectively controlled, once inflation of the air-bag has been triggered, by the actual dynamics of the particular crash situation, in particular the interaction of the vehicle occupant with the air-bag.

Whilst, in the foregoing embodiments, the safety arrangement has been described with reference to a single tether, single securing arrangement and single release cord, it is to be understood that this is merely for the sake of clarity and simplicity, and it will be immediately appreciated that the safety arrangement might equally incorporate a plurality of release cords, a plurality of tethers and a plurality of respective securing arrangements, which may restrain inflation of the air-bag in the region of one or more restrainable portions as desired.

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. A safety arrangement for a motor vehicle, the safety arrangement comprising an airbag unit incorporating a housing, an airbag and an inflator for inflating the airbag, the arrangement further comprising a restraining tether secured to the housing at a first anchor region and to a restrainable portion of the airbag at a second anchor region, the tether being releasable from at least one of the first and second anchor region to releasably anchor the restrainable portion of the airbag to the housing, whereby, during inflation of the airbag, the restraining tether is placed under tension to restrain inflation of the restrainable portion of the airbag until such time as the restraining tether is released, the restraining tether being released by means of a release cord connected to the airbag such that, upon sufficient inflation of the airbag, the airbag pulls on the release cord to release the restraining tether.

2. A safety arrangement according to claim 1, the arrangement being provided in a motor vehicle, wherein the release cord is attached to a region of the airbag which, during a given crash impact, is prevented from undergoing said sufficient inflation by an "out-of-position" vehicle occupant.

3. A safety arrangement according to claim 1 or 2, wherein the restraining tether is releasably secured to the housing at the first anchor region and fixed to the restrainable portion at the second anchor region.

4. A safety arrangement according to claim 3, wherein the restraining tether is secured to the restrainable portion in the region of one end of the tether and releasably secured to the housing in the region of the opposite end of the tether.

5. A safety arrangement according to claim 3 or 4, wherein the restraining tether is indirectly secured to the restrainable portion via a restraint element, the restraint element being attached to an end of the tether.

6. A safety arrangement according to claim 5, wherein the restraint element extends inwardly of the airbag to attach to the tether.

7. A safety arrangement according to any of claims 3 to 6, wherein the airbag unit comprises a securing arrangement to releasably secure the restraining tether to the housing at the first anchor region.

8. A safety arrangement according to claim 7, wherein the securing arrangement comprises the tether being secured to the housing by a knot, the release cord being coupled to the knot so as to pull on the knot during said sufficient inflation, the knot being configured such that said pulling of the release cord on the knot undoes the knot and releases the tether from the housing.

9. A safety arrangement according to claim 7, wherein the securing arrangement includes a release member, the cord being fixedly attached to the release member such that, as the air-bag pulls the cord during inflation, the cord pulls on the release member to release the tether from the securing arrangement.

10. A safety arrangement according to claim 9, wherein the securing arrangement includes a retaining member within the air-bag unit, the tether being releasably secured to the retaining member.

11. A safety arrangement according to claim 10, wherein the retaining member is in the form of a cleat fixed within the air-bag unit and wherein, prior to inflation of the air-bag, the cleat extends through a loop or eyelet formed by the tether, and the release member is positioned to prevent the loop or eyelet passing over the free end of the cleat, the release member being configured such that, as the cord pulls on the release member during inflation of the air-bag, the release member moves to a position allowing the loop to pass over the free end of the cleat to release the tether.

12. A safety arrangement according to claim 11, wherein the release member is configured such that, during inflation of the air-bag, the release member engages the tether to force the loop or eyelet over the free end of the cleat and release the tether.

13. A safety arrangement according to claim 12, wherein the release member is in the form of a pivotally mounted catch comprising an end stop and guide member, the catch being pivotable, as the cord pulls on the catch during inflation of the air-bag, between a first position in which the end stop prevents the loop or eyelet from passing over the free end of the cleat, and a second position in which the end stop is spaced away from the projection to allow the loop or eyelet to pass over the free end of the cleat, wherein as the catch moves from the first position to the second position, the guide member engages the tether to guide the loop or eyelet off the free end of the cleat and release the tether.

14. A safety arrangement according to claim 10, wherein the retaining member is rotatably mounted within the air-bag unit, the retaining element being rotatable between a first position, in which the tether is secured to the retaining member, and a second position in which the tether may disengage from the retaining member, wherein the retaining element moves from the first position to the second position as the cord pulls on the release member during inflation of the air-bag.

15. A safety arrangement according to claim 14, wherein the retaining member is in the form of a shaft mounted for rotation about a longitudinal axis of the shaft, the release member being in the form of a key configured to engage a key-way in the shaft wherein, prior to inflation of the air-bag, a portion of the tether is wound around the shaft and the key engages with the key-way to prevent rotation of the shaft, thereby securing the tether, and, upon sufficient inflation of the air-bag, the cord pulls on the key to retract the key from the key-way, whereby inflation of the air-bag causes the tether to rotate the shaft such that the tether unwinds from the shaft and is released.

16. A safety arrangement according to claim 14, wherein the retaining member is in the form of a rotatable arm, and wherein prior to inflation the tether is secured to the arm by means of a loop formed in the tether, and the release member engages the arm to prevent rotation of the arm, the release member being configured such that, as the cord pulls on the release member upon sufficient inflation of the air-bag, the release member disengages the arm, whereby inflation of the air-bag causes the tether to rotate the arm such that the arm is aligned generally with the tether thereby releasing the tether from the arm.

17. A safety arrangement according to claim 9 wherein the securing arrangement comprises a guide aperture formed through a fixed part of the air-bag unit, the release member being in the form of a bolt passing through the guide aperture, the tether being secured to the bolt, prior to inflation of the air-bag, by means of a loop formed by the tether, whereby as the cord pulls on the bolt during inflation of the air-bag, the bolt is pulled through the guide aperture and retracted through the loop to release the tether.

18. A safety arrangement according to claim 7, wherein the securing arrangement includes a retaining member in the form of a fixed cleat and wherein, prior to inflation of the air-bag, the projection extends through a loop formed by the tether, or an eyelet attached to the tether, the securing arrangement further comprising an obstructing member to prevent the loop or eyelet passing over the free end of the projection prior to inflation of the air-bag, the release cord being attached to the tether such that, as the air-bag inflates, the release cord pulls the tether past the obstructing member and off the free end of the cleat to release the tether.

19. A safety arrangement according to any of claims I to 7, wherein the restraining tether is releasably secured at the first or second anchor region by means of a releasable joint, release of the tether from the joint being triggered by the airbag pulling on the release cord upon said sufficient inflation of the airbag.

20. A safety arrangement according to claim 19, wherein the restraining tether is releasably secured to the restrainable portion at the second anchor region via a releasable joint and the tether is fixedly attached to the housing at the first anchor region.

21. A safety arrangement according to claim 19, wherein the restraining tether is releasably secured to the housing at the first anchor region via a releasable joint and the tether is fixedly attached to the restrainable portion at the second anchor region.

22. A safety arrangement according to any of claims 19 to 21, wherein the releasable joint comprises a fastening element to secure the tether at the respective anchor region, the release cord being operably connected to the fastening element such that, upon said sufficient inflation of the airbag, the release cord pulls on the fastening element along a release direction so as to undo the fastening element, thereby sufficiently weakening the joint to allow the tether to separate from the housing or restrainable portion.

23. A safety arrangement according to claim 22, wherein said fastening elements are configured such that the release direction is substantially perpendicular to the principal tension-bearing direction of the fastening element, whereby release of the fastening element is decoupled from the tension in the tether during inflation of said airbag.

24. A safety arrangement according to claim 22 or 23, wherein the releasable joint comprises a plurality of said fastening elements.

25. A safety arrangement according to any of claims 22 to 24, wherein the fastening element is a hook and loop fastener, mechanical fastener, heat weld or stitching.

26. A safety arrangement according to any of claims 22 to 25, wherein the release cord is coupled to the fastening element or elements via a release member, the release member comprising a flexible band incorporating a peel panel coupled to the fastening element or elements for pulling and undoing the fastening element or elements upon pulling of the release cord, the peel panel portion being attached to the release cord via two strap portions extending from respective opposing edges of the peel panel to meet one end of the release cord such that, as the release cord is pulled during inflation of the airbag, the release element adopts a generally triangular form.

27. A safety arrangement according to claim 26, wherein the release member is pre-formed in the general shape of an isosceles triangle comprising two strap portions of equal length.

28. A safety arrangement according to any of claims 21 to 27, wherein the releasable joint further comprises one or more reinforcing elements additionally securing the tether to the house or restrainable portion, whereby upon said undoing of the fastening elements and consequent weakening of the joint, the tension in said tether during inflation is sufficient to allow the tether to break free of the reinforcing elements.

29. A safety arrangement according to any of claims 21 to 28, wherein the tether is indirectly secured to the housing at the first anchor region via a flexible attachment element fixed to the housing, the tether being secured to the attachment element via the releasable joint.

30. A safety arrangement according to claim 29, wherein the attachment element is a fabric element formed integrally with the airbag.

31. A safety arrangement according to claims 29 or 30, wherein one or more fastening elements are provided in the form of stitched trigger seams securing the tether to the attachment element, whereby pulling the release cord along the release direction unpicks the respective seam or seams.

32. A safety arrangement according to claim 31, wherein the release cord is coupled to the seam or seams via a release member, the release member comprising a flexible band incorporating a peel panel covering the seam or seams and being coupled thereto for pulling and unpicking the seam or seams upon pulling of the release cord, the peel panel portion being attached to the release cord via two strap portions extending from respective ends of the peel panel to meet one end of the release cord such that, as the release cord is pulled during inflation of the airbag, the release member adopts a generally triangular form.

33. A safety arrangement according to claim 32, wherein the release member is pre-formed in the general shape of an isosceles triangle comprising two strap portions of equal length.

34. A safety arrangement according to claim 32 or 33, wherein the release member is formed integrally with the release cord.

35. A safety arrangement according to any of claims 32 to 34, wherein the releasable joint comprises at least two stitched seams securing the tether to the attachment element along different lengths, the seams being orientated such that as the strap portions pull on the opposing edges of the peel portion in response to the pulling of the release cord, one of said two seams starts to be unpicked before the other of said two seams.

36. A safety arrangement according to claim 34, wherein the attachment element or tether incorporates a tapered section, said two seams being spaced apart along the length of the tapered section and each spanning the width of the tapered section.

37. A safety arrangement according to any of claims 31 to 36, wherein the releasable joint is provided with one or more reinforcing elements in the form of additional stitched reinforcing seams securing the tether to the attachment element, the reinforcing trigger seams being configured to resist the tension in the tether as the airbag inflates until such time as the release cord unpicks the trigger seams whereby, upon consequent weakening of the joint, the tension in said tether during inflation is sufficient to allow the tether to break free of the reinforcing seams.

38. A safety arrangement according to any preceding claim, comprising a plurality of said release cords.

39. A safety arrangement according to any preceding claim, comprising a plurality of said tethers.

40. A safety arrangement according to claim 39, comprising a respective plurality of said securing arrangements.

41. A safety arrangement substantially as herein described with reference to Figures 1 and
2.

42. A safety arrangement substantially as herein described with reference to Figures 3 and 4.

43. A safety arrangement substantially as herein described with reference to Figures 6 and 7.

44. A safety arrangement substantially as herein described with reference to Figures 8 and 9.

45. A safety arrangement substantially as herein described with reference to Figures 10 and 11.

46. A safety arrangement substantially as herein described with reference to Figures 12 and 13.

47. A safety arrangement substantially as herein described with reference to Figures 14 and 15.

48. A safety arrangement substantially as herein described with reference to Figures 16 and 17.

49. A safety arrangement substantially as herein described with reference to Figures 18 and 19.

50. A safety arrangement substantially as herein described with reference to Figure 20.

51. A safety arrangement substantially as herein described with reference to Figure 21.

52. Any novel feature or combination of features described herein.