An airbag for a motor vehicle safety arrangement

Abstract

There is proposed an airbag (11) for a motor vehicle safety arrangement. The airbag (11) comprises a pair of superimposed layers (7a, 7b) of flexible material interconnected by a peripheral seam (8) to define an inflatable chamber (9) for receipt of inflating gas between the layers (7a, 7b). The airbag (11) is initially provided in an uninflated condition in which at least a region of the airbag (11) is rolled to form a spirally-wound roll (13) which includes a wound length (e.g. an arcuate or spirally-wound length) of said peripheral seam (8). Within said roll (13), overlying regions of the airbag (11) are secured to one another adjacent the wound length of said peripheral seam (8).

Description

[0001] AN AIRBAG FOR A MOTOR VEHICLE SAFETY ARRANGEMENT

[0002] Field of the Invention

[0003] The present invention relates to an airbag for a motor vehicle safety arrangement.

[0004] Background

[0005] Inflatable airbag arrangements are well known in the automotive industry. For many years now, airbags have been provided within the interior cabins of vehicles such as passenger cars to protect occupants in the event of accidents such as crashes. Such airbags are deployed by rapid inflation in the event of an imminent or ongoing vehicle crash, to cushion the impact of a vehicle occupant against elements of the vehicle such as the steering wheel or the dashboard. Over time, it has become common to provide additional airbags at various positions throughout the cabin of a motor vehicle to provide additional or improved protection in the case of various types of accidents such as, for example, rollover accidents and oblique impact crashes. For example, it is now common practice to provide motor vehicles with airbags in the form of inflatable curtains, side airbags, knee airbags, and airbags of different configurations for rear seat passengers. Some vehicles even comprise airbags arranged to deploy across parts of the exterior of the vehicle to protect pedestrians or so-called Vulnerable Road Users (VRUs), such as cyclists or motorcyclists, in the event that they might be struck by the vehicle in an accident. As will be appreciated, to provide effective protection, it is important that such airbags are inflated rapidly, so that they will achieve substantially full deployment very quickly.

[0006] Regardless of the particular type of airbag in question, in order to inflate an airbag sufficiently quickly in order to provide adequate crash-protection, inflating gas must be injected into the airbag at a very high pressure from a source such as a gas generator. Acceptable inflation times vary between particular types of airbag, depending on their intended function. Purely by way of example, so-called inflatable curtain airbags, which are arranged to deploy within the cabin of a motor vehicle across the side windows, to provide protection to vehicle occupants in the event of a roll-over accident, are required to inflate very rapidly indeed. This is because the space between the occupants of a motor vehicle and the side windows of the motor vehicle is very limited, thereby reducing the time available for the inflatable curtain to achieve full inflation, and limiting the inflated depth of the airbag. These factors combine to require inflatable curtains not only to inflate very rapidly, but also to inflate with a particularly high pressure relative to other types of motor vehicle airbags. Also, due to the potentially prolonged period of a roll-over type accident for which inflatable curtains are intended to provide occupant protection, inflatable curtain airbags are required to maintain a substantially fully inflated condition for a considerably longer period than most other types of motor vehicle airbags. Accordingly, inflatable curtain airbags are generally required to have the highest pressure-retention performance of any type of motor vehicle airbag.

[0007] The above-noted performance characteristics of inflatable curtain airbags means that the integrity of the seams of such airbags is of particular importance to prevent leakage of inflating gas during the period for which the airbag is required to remain substantially fully inflated. Accordingly, it is known to configure inflatable curtain airbags (as well as some other types of high-performance motor vehicle airbags) as so-called ‘one-piece-woven’ (“OPW”) airbags, in which seams of the airbag (such as the peripheral seam) are integrally formed from the woven structure of the two layers of woven fabric defining the airbag. In such OPW airbags, the inflatable chamber of the airbag is defined between a pair of woven layers of fabric (in a so-called “2D” manner), and the seams of the airbag are defined by regions in which the yarns of the weave one layer of fabric are interwoven with yarns of the weave of the other layer such that the seams are provided as an integral feature of the woven structure of the fabric. Such a structure provides very good seam integrity.

[0008] However, whilst ‘one-piece weaving’ has been found to be particularly suitable for inflatable curtain airbags, it represents a rather complicated and specialist production technique which (although suitable for automation on specially configured looms) can be expensive and may thus not be considered suitable for all types of airbags. Furthermore, whilst ‘one-piece weaving’ is readily suitable for the production of airbags which have a slim inflated profile (e.g. so-called “2D” airbags) achieved by the provision of an inflatable chamber between two superimposed layers of fabric material, it can often be unsuitable for airbags required to have a more voluminous inflated shape (e.g. so-called “3D” airbags) and which may be fabricated from more than two interconnected flexible panels in order to achieve a desired inflated shape and / or volume.

[0009] So-called “3D” airbags must generally be fabricated via a manual sewing process to interconnect their individual panels via the creation of stitched seams. Such stitched seams have less integrity than the above-noted OPW seams. Furthermore, stitched seams can be prone to gas leakage during or upon inflation, which can lead to damage of the seams and possible rupture of the airbag either during inflation or upon substantially full inflation. Another phenomenon to which some airbags are susceptible is ‘clocking’ or ‘bouncing’, which is the tendency of inflated airbags (particularly voluminous 3D airbags) to move about under inertia arising from high inflation forces during deployment. This phenomenon can be problematic because an airbag prone to moving or bouncing upon inflation may be difficult to position reliably relative to the surfaces of the vehicle from which it is intended to protect the occupant.

[0010] Furthermore, it can be complicated and time consuming (and thus expensive) to fold a 3D airbag reliably on a production line in order to package the airbag ready for installation in an airbag module.

[0011] The present invention has been devised in light of the above considerations.

[0012] Summary of the Invention

[0013] According to a first aspect of the invention, there is provided an airbag for a motor vehicle safety arrangement, the airbag comprising a pair of superimposed layers of flexible material interconnected by a peripheral seam to define an inflatable chamber for receipt of inflating gas between the layers, the airbag being initially provided in an uninflated condition in which at least a region of the airbag is rolled to form a spirally-wound roll which includes a wound length of said peripheral seam, characterised in that: within said roll, overlying regions of the airbag are secured to one another adjacent the wound length of said peripheral seam.

[0014] According to a second aspect of the present invention, there is provided an airbag for a motor vehicle safety arrangement, the airbag comprising a pair of superimposed layers of flexible material interconnected by a peripheral seam to define an inflatable chamber for receipt of inflating gas between the layers, the airbag being initially provided in an uninflated condition in which at least a region of the airbag is rolled to form a roll which includes a spirally-wound length of said peripheral seam, wherein: within said roll, overlying regions of the airbag are secured to one another adjacent the spirally-wound length of said peripheral seam.

[0015] An airbag configured in the manner of either the first aspect, or the second aspect has been found to demonstrate an advantageous characteristic upon inflation by the injection of a volume of inflating gas into the inflatable chamber defined between the superimposed layers of flexible material. Due to the manner in which overlying regions of the airbag are secured to one another adjacent the wound length (e.g. spirally-wound length) of the peripheral seam within the roll, the seam will become twisted as the roll unfurls during inflation, under the action of the inflating gas. This seam-twisting effect has been found to reduce gas leakage through the seam, which thereby improves the integrity of the seam. For example, in embodiments in which the peripheral seam is a stitched seam, the twist induced into the seam region of the airbag serves to hide the stitching of the seam behind some of the material of the airbag, within the twist. It is to be appreciated, however, that the peripheral seam interconnecting the superimposed layers of flexible material need not be formed by stitching and could instead (for example) be formed by adhesively bonding or heat fusing the two layers to one another, in which case the twist induced into the seam region of the airbag will similarly serve to hide the adhesive or fused region of the seam behind some of the material of the airbag, within the twist.

[0016] Furthermore, it has been found that the twisted seam creates a line of high tension in the material of the airbag, towards the side of the airbag, which provides an advantageous effect of improving the stability of the inflated airbag.

[0017] In some embodiments, the pair of superimposed layers may each take the form of a respective region of the same sheet of flexible material. For example, a single sheet of flexible material could be folded so as to bring two regions of the sheet into superimposition, whereupon the two resulting layers could be interconnected by a peripheral seam. Alternatively, however, other embodiments are envisaged in which each layer may be defined by a respective sheet of flexible material. For example, two discrete sheets of flexible material (optionally of substantially identical or similar shape) could be arranged in superimposition and interconnected by a peripheral seam.

[0018] As will be appreciated by those of skill in the art, the flexible material of the layers (or sheets) could take any suitable form such as, for example: woven fabric material or a suitable thin- film material such as a thin-film of plastic. In embodiments in which the layers (or sheets) are formed of fabric material, it is envisaged that the peripheral seam may be formed by stitching the two layers together. Alternatively, however, some embodiments may be formed by weaving the two layers simultaneously on a single loom, via a so-called ‘one-piece weaving’ technique in which yarns of one of the layers are interwoven with yarns of the other layer in specific areas to define the peripheral seam.

[0019] In some embodiments, the airbag may comprise a pair of peripheral seam regions which are opposed from one another across at least a region of the inflatable chamber; wherein in the uninflated condition said roll includes a respective wound (e.g. spirally-wound) length of each peripheral seam region; and wherein, within the roll, overlying regions of the airbag are secured to one another adjacent the wound length of each peripheral seam region. This arrangement may effectively provide the above-noted advantages at two opposed sides of the airbag. In particular, this may allow a relatively simple 2D airbag construction comprising a pair of superimposed layers of flexible material to achieve a 3D shape upon inflation. In such arrangements, the resulting respective lines of high tension in the material of the airbag, towards each side of the airbag, may provide a particularly stable airbag which is well-suited for accurate and reliable positioning within or against a surface of the motor vehicle upon deployment.

[0020] Optionally, in said uninflated condition the roll is formed about a roll axis extending from one peripheral seam region to the other peripheral seam region, across the airbag.

[0021] In some embodiments, each said wound length of a seam region may be located at a respective end of the roll.

[0022] The overlying regions of the airbag within the roll may be secured together in several different ways and / or by several different means including, for example, stitching, adhesive bonding, heat fusion and mechanical clamping.

[0023] In some embodiments, the overlying regions of the airbag within the roll are secured to one another by stitching. In some such examples, the stitching may be formed through both layers of the airbag, which may provide a first inflation characteristic (e.g. inflated shape). In further examples, the stitching may be formed through at least four overlying thicknesses of the flexible material arising from the airbag being rolled to form the roll, which may provide a second inflation characteristic (e.g. a different inflated shape). For example, in embodiments in which the roll gives rise to a multiple-turn spirally wound length of a seam or seam region, the stitching may be formed through more than four overlying thicknesses of the flexible material.

[0024] In some alternative embodiments, a set of securing holes may be formed through the airbag adjacent said peripheral seam. The securing holes may be spaced apart from one another along the wound length (e.g. a spirally-wound or arcuate length) of the peripheral seam so as to be substantially aligned with one another within the roll. In such embodiments, a fastener may be provided through the substantially aligned securing holes to secure the overlying regions of the airbag within the roll. Similarly, in embodiments comprising a pair of said peripheral seam regions opposed from one another across a region of the inflatable chamber, a respective set of securing holes may be formed through the airbag adjacent each said peripheral seam region. The securing holes of each set may be spaced apart from one another along the wound length (e.g. a spirally-wound or arcuate length) of the respective peripheral seam region and may be substantially aligned with one another within said roll. In such an arrangement, a respective fastener may be provided through the substantially aligned securing holes of each set to secure the respective overlying regions of the airbag within the roll.

[0025] Optionally, at least some of the securing holes of the or each set are substantially radially aligned with one another across a region of the roll.

[0026] The or each said fastener may be provided through the substantially radially aligned securing holes of the or each respective set to secure the overlying regions of the airbag to one another on one side of the roll, and such that overlying regions of the airbag on a diametrically opposite side of the roll are not secured to one another.

[0027] Alternatively, or additionally, at least some of the securing holes of the or each set may be substantially diametrically aligned with one another across the roll.

[0028] The or each said fastener may be provided through the substantially diametrically aligned securing holes of the or each respective set to secure the overlying regions of the airbag to one another across the roll.

[0029] The or each said fastener may provided in the form of a mechanical fastener. For example, the or each fastener may be provided in the form of a metal or plastic shackle, a cable tie, or indeed any other convenient mechanical fastener capable of interconnecting said aligned holes of the airbag.

[0030] According to a third aspect, there is provided an airbag according to the first aspect or the second aspect in combination with an inflator configured to direct inflating gas into the inflatable chamber in a primary inflow direction, wherein: the wound length of the peripheral seam, or the wound lengths of the peripheral seam regions, are spaced from the primary inflow direction such that said inflating gas does not impinge directly thereon. Such an arrangement may serve to further reduce the risk of damage to the peripheral seam or seam regions and / or leakage of inflating gas through the peripheral seam or seam regions. The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

[0031] The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and / or combined with any other feature or parameter described herein.

[0032] Summary of the Figures

[0033] So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

[0034] Figure 1 is a schematic plan view of a pair of superimposed layers of fabric used to form an airbag in accordance with the invention;

[0035] Figure 2 is a view corresponding generally to claim 1 , illustrating the layers of fabric after interconnection to define an inflatable chamber of the airbag;

[0036] Figure 3 is a schematic perspective view showing the creation of a roll in the airbag, and one way in which overlying regions of the airbag within the roll may be secured to one another;

[0037] Figure 4 is a schematic cross-sectional view through the roll of the airbag shown in Figure 3;

[0038] Figure 5 is a perspective view showing the airbag in an inflated (e.g. deployed) condition;

[0039] Figure 6 is a perspective view from above showing another form of airbag prior to the formation of a roll;

[0040] Figure 7 is a perspective view similar to that of Figure 6, but which shows the airbag in a rolled condition and wherein overlying regions of the airbag within the roll are secured to one another;

[0041] Figure 8 is a schematic cross-sectional view through the roll of the airbag shown in Figure 7, denoting one way in which overlying regions of the airbag within the roll may be secured to one another; Figure 9 is a perspective view from above showing the rolled airbag of Figure 7 following a subsequent connection step;

[0042] Figure 10 is a perspective view from one side of the airbag shown in Figures 6 to 9, showing the airbag in an uninflated (e.g. undeployed) condition and in combination with an airbag module housing;

[0043] Figure 11 is a perspective view similar to that of Figure 10, showing the airbag during an early stage of inflation;

[0044] Figure 12 is a perspective view similar to that of Figure 11 , showing the airbag during a subsequent stage of inflation;

[0045] Figure 13 is a perspective view similar to that of Figure 12, showing the airbag during a subsequent stage of inflation;

[0046] Figure 14 is a perspective view similar to that of Figure 13, showing the airbag in a substantially fully inflated (e.g. substantially fully deployed) condition;

[0047] Figure 15 is a perspective view from the front showing the airbag of Figure 14 in the substantially fully inflated (e.g. substantially fully deployed) condition;

[0048] Figure 16 is schematic cross-sectional view similar to that of Figure 8, but which shows an alternative way in which overlying regions of the airbag within the roll may be secured to one another; and

[0049] Figure 17 is a schematic plan view of another form of airbag, which is somewhat similar to that shown in Figure 6, the airbag being shown prior to the formation of a roll.

[0050] Detailed Description of the Invention

[0051] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

[0052] Figure 1 illustrates a single sheet of flexible material in the form of a sheet of woven fabric 1 . The sheet 1 has a generally rectangular and somewhat elongate shape, with a projecting inlet tab 2 formed at each end. A pair of spaced-apart mounting apertures 3 are formed through each inlet tab 2. In the configuration illustrated in Figure 1 , the sheet 1 is substantially mirror-symmetrical about a central transverse axis 4 of the sheet.

[0053] Turning now to consider Figure 2, the sheet 1 is shown having been folded in half about a fold line 5 coincident with the transverse axis 4 shown in Figure 1 . As will be appreciated, the sheet 1 is thus shown in a folded configuration comprising a fold 6, in which each half of the sheet 1 defines a respective layer 7a, 7b, and such that the two layers 7a, 7b are arranged in superimposition (only the uppermost layer 7a, as viewed, being visible in Figure 2). As will also be noted, the two inlet tabs 2 are thus superimposed and aligned with one another, as indeed are their respective mounting apertures 3.

[0054] After superimposition of the two layers 7a, 7b as described above, the layers are interconnected by the creation of a pair of peripheral seam regions 8a, 8b. In the illustrated embodiment, each peripheral seam region 8a, 8b is a stitched seam, and extends from a respective end region of the fold 6, along and adjacent a respective side edge of the superimposed layers 7a, 7b, and terminates at the aligned inlet tabs 2. As will be noted, the end edges of the two inlet tabs 2 are not interconnected.

[0055] The fold 6 and the two peripheral seam regions 8a, 8b collectively define a peripheral seam 8 interconnecting the superimposed layers 7a, 7b around their aligned peripheries, except at the ends of the two inlet tabs 2 which remain unconnected. The peripheral seam 8 will be understood to extend around substantially the entire periphery of the folded sheet 1 , except at the superimposed ends of the two inlet tabs 2. As will be appreciated, an inflatable chamber 9 is thus defined between the layers 7a, 7b, for receipt of inflating gas between the layers 7a, 7b, with the peripheral seam regions 8a, 8b being opposed from one another across the inflatable chamber 9. The inlet tabs 2 cooperate to define an inlet region 10 (e.g. a necked region) of the inflatable chamber 9, which may be connected to an inflator (e.g. in the form of a gas generator, not shown) via the mounting apertures 3 in a manner known per se.

[0056] It is to be noted at this juncture that whilst the illustrated embodiment is formed by folding a single sheet 1 to form two superimposed layers 7a, 7b, other embodiments are envisaged in which each layer may instead be defined by a respective sheet of flexible material. For example, two discrete sheets of flexible material could be arranged in superimposition and interconnected by a single peripheral seam extending all of the way around their edges (except for at the ends of the inlet tabs 2, as explained above). In such an arrangement, it will be understood that the resulting single peripheral seam may nevertheless still be considered to comprise a pair or seam regions opposed to one another across the inflatable chamber 9 in a similar manner.

[0057] Alternative embodiments are also envisaged in which the two superimposed layers may be woven simultaneously on a single loom, via a so-called ‘one-piece weaving’ technique in which yarns of one of the layers are interwoven with yarns of the other layer in specific areas to define the peripheral seam. In such embodiments, the resulting peripheral seam is thus woven as an integral part of both layers of fabric, whilst the layers remain separate from one another inside the bounds of the peripheral seam to thereby define the inflatable chamber. In a one-piece woven embodiment of this type, the resulting integrally-formed peripheral seam may also extend all of the way around the edges of the superimposed layers (except for at the ends of the inlet tabs 2, as explained above). In such an arrangement, it will again be understood that the resulting single peripheral seam may still be considered to comprise a pair of seam regions opposed to one another across the inflatable chamber 9 in a similar manner.

[0058] Returning now to consider the illustrated embodiment, Figure 3 shows a partially formed airbag 11 which is created by rolling up the superimposed and interconnected layers 7a, 7b illustrated in Figure 2. Arrow F denotes the intended primary inflow direction for inflating gas from an inflator. In particular, Figure 3 shows the airbag 11 in an uninflated condition in which the region of the airbag distal to the inlet region 10 (i.e. proximal to the fold 6) is rolled (as denoted by the arrow in Figure 3) about a roll axis 12 to form a roll 13. During formation of the roll 13, a respective line of stitching 14 is formed at each end of the roll 13 to secure together overlying regions of the airbag implicated in the roll 13. As illustrated, the lines of stitching 14 are each located adjacent and slightly inwardly of a respective peripheral seam region 8a, 8b. The resulting arrangement is illustrated more clearly in Figure 4, which is a schematic transverse sectional view through one end of the roll 13. As will be appreciated, formation of the roll 13 serves to roll-up the airbag 11 in a spiral manner such that the roll 13 will include a spirally-wound length of each peripheral seam region 8a, 8b at a respective end of the roll 13. As will be appreciated, each spirally-wound length of a respective peripheral seam region is wound in a spiral manner about the roll axis 12 of the roll 13. The resulting overlying regions of the airbag 11 are thus secured to one another by the lines of stitching 14 adjacent each respective spirally-wound length of the peripheral seam. The lines of stitching 14 are each formed through both layers of fabric 7a, 7b (the layers being denoted in intimate contact in Figure 4), and thus through a total of four thicknesses of the fabric material from which the airbag 11 is formed. As will be noted from Figure 4, in the illustrated embodiment the lines of stitching may be of sufficient length to extend around a whole turn of the airbag 11 around the roll axis 12, although it is to be appreciated that this is not considered essential in all embodiments.

[0059] Figure 5 illustrates the above-described airbag 11 in combination with an airbag module housing 15 and in a substantially fully inflated condition. As will be appreciated by those of skill in the art, the rolled airbag 11 shown in Figures 3 and 4 may be further packed (e.g. by further rolling and / or folding), so as to be initially tightly packed within the airbag module housing 15 for deployment therefrom via inflation. Upon inflation by the rapid inflow of inflating gas along inflow direction F, through the inlet region 10 of the airbag and into the inflatable chamber 9, the airbag 11 is inflated and thus deployed from its initial tightly packed condition and into the inflated condition illustrated in Figure 5 in which the superimposed layers 7a, 7b are urged apart from one another. As will be appreciated, during inflation, the inflating gas is directed along the primary direction F and urged around and through the initially tightly-wound roll 13, which serves to unfurl the roll 13 and ultimately unfold the fold 6 at the heart of the roll 13. The position of the unfolded fold 6 is denoted by the dashed line around the inflated airbag shown in Figure 5. As will also be appreciated, particularly having regard to Figures 3 and 5, because the initially spirally-wound lengths of the peripheral seam regions 8a, 8b which are secured to one another are located at opposite ends of the roll 13, they are effectively spaced from the primary inflow direction F such that the inflating gas will not directly impinge on them during inflation.

[0060] Because of the manner in which overlying regions of the airbag 11 within the initial roll 13 are secured to one another by the lines of stitching 14 adjacent the initially spirally-wound lengths of the peripheral seam regions 8a, 8b, the ends of the roll 13 are not able to unfurl along the lines of stitching 14 in the same manner as the rest of the roll. This results in the peripheral seam regions 8a, 8b becoming twisted along the length of the interconnecting lines of stitching 14, such that the peripheral seam regions 8a, 8b become effectively shrouded in surrounding regions of the airbag fabric. Indeed, it can be seen in Figure 5 that the peripheral seam region 8a visible in the inlet region 10 of the airbag 11 is hidden from view by the shrouding fabric of the airbag (the path of the peripheral seam region 8a thus being denoted in dashed line). The twist induced into the seam regions 8a, 8b of the airbag thus effectively serves to hide (and thereby protect) the stitching of the peripheral seam 8 behind some of the material of the airbag, within the resulting twist. This has been found to reduce gas leakage through the seam 8 and thus improve the integrity of the seam 8.

[0061] Turning now to consider Figures 6 to 16, another embodiment will be described, with the same reference numbers being used to denote identical or equivalent parts or regions.

[0062] Figure 6 shows a single sheet of fabric 1 which is substantially identical to the sheet described above with reference to Figures 1 to 5, and which is shown in a folded configuration comprising a fold 6 and in which each half of the sheet defines a respective layer 7a, 7b. As will be appreciated, the two layers 7a, 7b are thus arranged in superimposition (only the uppermost layer 7a, as viewed, being visible in Figure 6). The resulting layers 7a, 7b are again interconnected by a pair of stitched peripheral seam regions 8a, 8b in the same manner as described above with reference to figures 1 to 5.

[0063] In the same manner as that described above, the fold 6 and the two peripheral seam regions 8a, 8b collectively define a peripheral seam 8 interconnecting the superimposed layers 7a, 7b around their aligned peripheries, except at the ends of the two inlet tabs 2 which remain unconnected. Again therefore, in this embodiment the peripheral seam 8 will be understood to extend around substantially the entire periphery of the folded sheet 1 , except at the superimposed ends of the two inlet tabs 2. As will be appreciated, an inflatable chamber 9 is thus defined between the layers 7a, 7b, for receipt of inflating gas between the layers 7a, 7b, with the peripheral seam regions 8a, 8b being opposed from one another across the inflatable chamber 9. The inlet tabs 2 cooperate to define an inlet region 10 (e.g. a necked region) of the inflatable chamber 9, which may be connected to an inflator (e.g. in the form of a gas generator, not shown) in a manner known perse.

[0064] A significant difference between the arrangement shown in Figure 6 and the previously described embodiment is that in the arrangement shown in Figure 6, two sets of spacedapart securing holes 16 are formed through both layers 7a, 7b, such that each securing hole 16 extends entirely through the airbag 11 , within the bounds defined by the peripheral seam 8. In more detail, it will be noted that each set of securing holes 16 is formed along and adjacent a respective peripheral seam region 8a, 8b, such that the securing holes 16 of each set are spaced apart along the respective peripheral seam region 8a, 8b. In preferred embodiments it is proposed that the securing holes 16 of each set may be substantially equispaced along the respective peripheral seam region 8a, 8b, but this may not be essential in all implementations. In the arrangement illustrated, each securing hole 16 of one set is arranged opposite a respective securing hole 16 of the other set, across a transverse direction (i.e. substantially parallel to the fold 6) of the airbag 11 . As will also be noted, in the particular arrangement illustrated in Figure 6, a circular seam is formed around each securing hole 16 which may, as illustrated, take the form a loop in one of the peripheral seam regions 8a, 8b. Alternatively, however, the circular seams around the securing holes 16 may be formed separately to the peripheral seam regions 8a, 8b.

[0065] It is to be noted at this juncture that in an alternative construction of the embodiment illustrated in Figure 6, two superimposed layers 7a, 7b may be woven simultaneously on a single loom, via a so-called ‘one-piece weaving’ technique in which yarns of one of the layers are interwoven with yarns of the other layer in specific areas to define the peripheral seam 8. In such embodiments, the resulting peripheral seam 8 and its loops around respective securing holes 16 (or separate circular seams around the securing holes) are thus woven as integral parts of both layers of fabric, whilst the layers remain separate from one another inside the bounds of the peripheral seam to thereby define the inflatable chamber. In a one- piece woven embodiment of this type, the resulting integrally-formed peripheral seam 8 may also extend all of the way around the edges of the superimposed layers (except for at the ends of the inlet tabs 2, as explained above). In such an arrangement, it will again be understood that the resulting single peripheral seam 8 may still be considered to comprise a pair of seam regions 8a, 8b opposed to one another across the inflatable chamber 9 in a similar manner.

[0066] Figure 7 shows a partially formed airbag 11 which is created by rolling up the superimposed and interconnected layers 7a, 7b illustrated in Figure 6 in the same manner as described above in connection with the embodiment of Figures 1 to 5. Arrow F denotes the primary inflow direction for inflating gas from an inflator. In particular, Figure 7 shows the airbag 11 in an uninflated condition in which the region of the airbag distal to the inlet region 10 (i.e. proximal to the fold 6) is rolled about a roll axis 12 to form a roll 13. During formation of the roll 13, at least some of the securing holes 16 along each peripheral seam region 8a, 8b are brought into alignment with one another as they become implicated in the roll 13, as shown more clearly in Figure 8 which is a schematic transverse sectional view through one end of the roll 13. In particular, as shown in Figure 8 (in which a total of five securing holes 16 of each set are implicated in the roll 13), the securing holes 16 which are implicated in the roll 13 are substantially diametrically aligned with one another across the roll 13.

[0067] As will be appreciated, formation of the roll 13 serves to roll-up the airbag 11 in a spiral manner such that the roll 13 will include a spirally-wound length of each peripheral seam region 8a, 8b at a respective end of the roll 13, in a similar manner to the previously described embodiment. It will therefore be understood that each spirally-wound length of a respective peripheral seam region is wound in spiral manner about the roll axis 12 of the roll. The resulting overlying regions of the airbag 11 are then secured to one another by passing a respective fastener 17 (denoted schematically in Figure 8) through the diametrically aligned securing holes 16 of each set, adjacent the spirally-wound length of the respective peripheral seam region 8a, 8b. In the arrangement illustrated in Figure 7, the fasteners 17 are each shown in the form of a conventional tie-wrap, but it is to be appreciated that alternative forms of mechanical fasteners could be used instead such as, for example, shackles, clamps, clips, staples or the like. As illustrated in Figure 8, in this embodiment each fastener 17 is provided through all of the diametrically aligned securing holes 16 implicated in the roll 13, and thus serves to interconnect diametrically opposed sides of the roll 13 and thereby secure the overlying regions of the airbag 11 within the roll 13 to one another. It is to be appreciated that whilst the fastener 17 is illustrated schematically in Figure 8 as extending across the diameter of the roll 13, in practice each fastener 17 will be effective (e.g. may be drawn tight) to pull the securing holes 16 on one side of the roll 13 into intimate adjacent proximity with the securing holes 16 on the diametrically opposite side of the roll 13, so as to flatten the ends of the roll 13 - as may be appreciated from Figure 9 considered in more detail below.

[0068] Figure 9 illustrates another possible step in which the end regions of the roll 13 (which are shown somewhat flattened by the fasteners 17 as explained above) are folded (denoted at 18) and the two uppermost (in the orientation illustrated) corners 19 of the airbag are brought into close proximity with one another. These two corners 19 may then be secured to one another by inserting a third fastener 20 through the respective corner securing holes 16c, which are not implicated in the roll 13. By securing the corners 19 together in this way, a funnel shape may be imparted to the airbag 11 , adjacent the inlet region 10, during inflation.

[0069] Figure 10 illustrates the above-described airbag 11 in combination with an airbag module housing 15 and in a partially packaged and uninflated condition somewhat similar to the condition illustrated in Figure 9. In particular, it will be noted that the inlet region 10 is connected to the housing 15, and the airbag 11 is folded loosely such that the roll 13 is folded at 18 into thirds. In the orientation illustrated, the secured corners 19 of the airbag are located underneath the airbag 11 , proximate the module housing 15. As will be appreciated by those of skill in the art, the rolled and folded airbag 11 shown in Figure 10 may be further packed (e.g. by further rolling and / or folding), so as to be initially tightly packed within the airbag module housing 15 for deployment therefore via inflation.

[0070] Figure 11 is a view similar to that of Figure 10, but which shows the airbag 11 partially inflated, and thus adopting a shape and configuration representative of an early stage of inflation during deployment from the module housing 15. It is to be appreciated, however, that Figure 11 , and also Figures 12 to 14, show the airbag 11 being manually inflated by a blower 21 inserted through a makeshift inlet aperture 22 in the airbag 11 , rather than under the action of an inflator (e.g. a gas generator) provided within the module housing 15 as would the case during operational inflation of the airbag 11 . As will be understood, in an operational installation it is proposed that the airbag 11 will be inflated by a rapid inflow of inflating gas from an inflator located within the module housing 15 and configured to direct the flow of gas in a primary inflow direction F which will not impinge on the initially spirally- wound lengths of the peripheral seam regions 8a, 8b which are secured to one another by the mechanical fasteners 17 at opposite ends of the roll 13. Nevertheless, Figure 11 accurately shows initial inflation of the airbag 11 urging the layers 7a, 7b apart from one another and unfurling the roll 13 of the airbag 11 . Indeed, Figure 11 shows the roll 13 almost completely unfurled in the central region between its two opposite ends, and shows the initially spirally-wound lengths of the peripheral seam regions 8a, 8b along which overlying regions of the airbag 11 are secured together by the mechanical tasters 17 being prevented from unfurling in the same manner. As shown, the peripheral seam regions 8a, 8b (only 8b being visible in Figure 11) thus begin to twist in a similar manner to that described above in connection with the embodiment of Figures 1 to 5.

[0071] Figures 12 and 13 show views similar to Figure 11 but illustrate the airbag 11 in successive stages of inflation. Figure 12 therefore shows the airbag 11 inflated to a higher internal inflation pressure than Figure 11 , and Figure 13 similarly shows the airbag 11 inflated to a higher internal inflation pressure than Figure 12. Figures 12 and 13 show the initially visible peripheral seam region 8b becoming progressively more twisted as pressure inside the airbag 11 increases, and the development of lines of tension radiating outwardly from the mechanical fastener 17 and the tightening twisted seam region 8b which it creates - one such line of tension extending generally along the untwisted region of the peripheral seam region 8b (along which the securing holes 16 were not secured within the roll 13) and another extending generally in a radially opposite direction along the path of the (now unfolded) fold line 6.

[0072] Figure 14 is another similar view, but which shows the airbag 11 in a substantially fully inflated condition at maximum inflation pressure. Figure 15 shows the airbag 11 in the same condition, as viewed from the front. In this condition, the initially visible seam region 8b is hidden from view and effectively shrouded by fabric of the airbag 11 along substantially its entire length (the path of the seam region 8b being denoted in dashed line in Figure 14). As will be appreciated, the same effect is produced on the opposing seam region 8a on the other side of the airbag 11 not visible in Figure 14. Figure 14 also shows the above-noted primary lines of tension extending: i) generally along the untwisted region of the peripheral seam region 8b (along which the securing holes 16 were not secured within the roll 13), and ii) generally in a radially opposite direction along the path of the (now unfolded) fold line 6 (also denoted in dashed line in Figures 14 and 15). In a similar manner to that described above in connection with the embodiment of Figures 1 to 5, the twist induced into the seam regions 8a, 8b of the airbag 11 thus effectively serves to hide (and thereby protect) the stitching of the peripheral seam 8 behind some of the material of the airbag 11 , within the twist. This has been found to reduce gas leakage through the seam 8 and thus improve the integrity of the seam 8.

[0073] Whilst an embodiment of the invention has been described above with reference to Figures 6 to 15 (and with particular reference to Figure 8) in which all of the diametrically aligned securing holes 16 of each set implicated in the roll 13 are interconnected by a respective fastener 17 extending therethrough, other ways of using fasteners 17 to secure overlying regions of the airbag 11 within the roll are envisaged. Figure 16 illustrates one such example, and shows a schematic transverse sectional view through one end of the roll 13 in a similar manner to Figure 8. However, as will be noted, in this example, a fastener 17 is provided which extends only through a group of radially aligned securing holes 16 on one side (at A) of the roll 13. The fastener 17 does not extend through the other group of radially aligned securing holes 16 on the diametrically opposite side of the roll 13 (at B). In this arrangement, it will therefore be appreciated that the fastener 17 serves to secure overlying regions of the airbag 11 to one another on only one side (A) of the roll 13 such that overlying regions of the airbag 11 on the diametrically opposite side (B) of the roll 13 are not secured to one another. This type of arrangement will provide a different inflation characteristic to the airbag 11 , characterised by a somewhat looser twist being induced in the seam regions 8a, 8b.

[0074] Turning now to consider Figure 17, another embodiment will be described which is similar to the embodiment described above with reference to Figures 6 to 16, with the same reference numbers being used to denote identical or equivalent parts or regions.

[0075] Figure 17 shows a single sheet of fabric 1 which is substantially identical to the sheet described above with reference to Figure 6, and which is shown in a similar folded configuration comprising a fold 6 and in which each half of the sheet defines a respective layer 7a, 7b. As will be appreciated, the two layers 7a, 7b are thus arranged in superimposition (only the uppermost layer 7a, as viewed, being visible in Figure 17). In common with the arrangement shown in Figure 6, two sets of spaced-apart securing holes 16 are again formed through both layers 7a, 7b, such that each securing hole 16 extends entirely through the airbag 11 .

[0076] A significant difference between the arrangement shown in Figure 17 and the arrangement described above with reference to Figure 6, however, concerns the extent of the stitched peripheral seam regions 8a, 8b shown at each side of the folded sheet 1 . In this proposal, each peripheral seam region 8a, 8b is effectively discontinuous in the sense that is split into a respective first section 8a’, 8b’ located at the top of the folded sheet (as illustrated) and a respective second section 8a”, 8b” located at the bottom of the folded sheet (as illustrated), with a gap between the two sections along a respective side of the folded sheet 1 .

[0077] In more detail, it will be noted that the first section 8a’, 8b’ of each seam region 8a, 8b extends from the end of the aligned inlet tabs 2, along and adjacent the edge of the folded sheet 1 , around the first (uppermost as illustrated) securing hole 16 in the manner of a loop (in a similar manner to that described above with reference to the embodiment of Figure 6), and then extends downwardly along and adjacent the edge of the folded sheet 1 before terminating in another loop around the second adjacent securing hole 16. Similarly, the second section 8a”, 8b” of each seam region 8a, 8b begins at the fold 6 and extends upwardly along and adjacent the edge of the folded sheetl , around the lowermost securing hole 16 (i.e. proximate the fold 6) in the manner of a loop and then continues to extend upwardly along and adjacent the edge of the folded sheet 1 and forms similar loops around the next three (or optionally more) adjacent securing holes 16. In addition, it will be noted that respective stitched loop seams 23 are formed around the remaining securing holes 16 which are not encircled by loops formed as part of the first and second sections 8a’, 8a”, 8b’, 8b”.

[0078] As will be appreciated, the result of the type of discontinuous seam regions 8a, 8b described above with reference to Figure 17 is that the inflatable chamber 9 of the resulting airbag is not entirely closed by a peripheral seam prior to rolling, with effective vent gaps 24 being formed between adjacent securing holes 16 which are not looped by either the first or second sections 8a’, 8a”, 8b’, 8b” of the discontinuous seam regions 8a, 8b.

[0079] It is to be noted at this juncture that in an alternative construction of the embodiment illustrated in Figure 17, two superimposed layers 7a, 7b may be again be woven simultaneously on a single loom, via a so-called ‘one-piece weaving’ technique in which yarns of one of the layers are interwoven with yarns of the other layer in specific areas to define the peripheral seam regions 8a, 8b and the looped seams 23. In such embodiments, the resulting peripheral seam regions 8a, 8b and looped seams 23 are thus woven as integral parts of both layers of fabric.

[0080] It is proposed that the partially formed airbag 11 described above and shown in Figure 17 will then be rolled in a substantially identical manner to that described above with reference to Figures 7 to 9, and that the resulting overlying regions of the airbag 11 will be secured to one another via fasteners 17 in an identical manner (or alternatively as described above with reference to and as shown in Figure 16). It may be appreciated, however, that because the seam regions 8a, 8b in this embodiment are discontinuous and do not extend all of the way along the side edges of the folded sheet 1 prior to rolling, the second sections 8a”, 8b” of the peripheral seam regions 8a, 8b within the resulting spirally-wound roll 13 may not extend around an entire turn of the airbag 11 about the roll axis 12, and may therefore form an arcuate wound length of the respective peripheral seam region 8a, 8b rather than, for example, a spirally wound length. In other words, in this embodiment, the overlying regions of the airbag 11 within the roll 13 may therefore be secured to one another (by the fasteners) adjacent a somewhat shorter arcuate wound length of each peripheral seam region 8a, 8b rather than the longer spirally wound length of the previously described embodiments.

[0081] It has been found that an airbag configured as described above with reference to and as shown in Figure 17 will perform in a substantially identical (or least very similar) manner to the airbag described above with reference to and as shown in Figures 6 to 16 during normal unobstructed inflation. This is because the initially wound lengths of the second sections 8a”, 8b” of the peripheral seam regions 8a, 8b, along which overlying regions of the airbag 11 are secured together by the mechanical fasteners 17 are again prevented from unfurling, which is sufficient to begin inducing twist to the second sections 8a”, 8b” of the peripheral seam regions 8a, 8b. It has been found that if the second sections 8a”, 8b” are sufficiently long, the seam twisting will propagate along the edges of the airbag 11 to shroud the regions where the securing holes 16 which are not looped by the peripheral seam regions and effectively close or block the vent gaps 24 formed therebetween.

[0082] However, in circumstances where inflation of the airbag 11 is restricted, for example by a so- called ‘out of position’ (‘OOP’) motor vehicle occupant sitting too close to the airbag 11 for its safe deployment, the roll 13 will be prevented (or at least inhibited) from unfurling during an early stage of deployment because it will quickly impinge on the OOP occupant. This will have the effect of preventing, or at least reducing, the development of the above-described twist to the second sections 8a”, 8b” of the peripheral seam regions 8a, 8b. The effect of this is that the seam twisting will not propagate sufficiently along the edges of the airbag 11 to shroud the regions where the un-looped securing holes and vent gaps 24 are formed, such that inflating gas which continues to be directed into the airbag will vent from the airbag through the vent gaps 24, therefore preventing further inflation of the airbag via unfurling of the roll. In this manner, a venting airbag 11 may be provided which will not achieve full inflation in the event of impingement on an OOP occupant, thereby avoiding or at least reducing the likelihood of injury to the occupant.

[0083] The features disclosed in the foregoing description, or in the following claims, or in 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 obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0084] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention. For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0085] Unless otherwise defined herein, scientific and technical terms used in connection with the presently disclosed inventive concept(s) shall have the meanings that are commonly understood by those of ordinary skill in the art.

[0086] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0087] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps than those listed in a claim.

[0088] Throughout this specification, including the claims which follow, unless the context requires otherwise, the words “have”, “comprise”, and “include”, and variations such as “having”, “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0089] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0090] Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements or such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0091] As may be used herein, any reference to “one embodiment,” “an embodiment,” “some embodiments,” “one example,” “for example,” or “an example” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearance of the phrase “in some embodiments” or “one example” in various places in the specification is not necessarily all referring to the same embodiment, for example. Further, all references to one or more embodiments or examples are to be construed as non-limiting to the claims. As may be used herein, the term "substantially" means that the subsequently described event or circumstance completely occurs or that the subsequently described event or circumstance occurs to a great extent or degree. For example, when associated with a particular event or circumstance, the term "substantially" means that the subsequently described event or circumstance occurs at least 80% of the time, or at least 85% of the time, or at least 90% of the time, or at least 95% of the time. For example, the term "substantially adjacent" may mean that two items are 100% adjacent to one another, or that the two items are within close proximity to one another but not 100% adjacent to one another, or that a portion of one of the two items is not 100% adjacent to the other item but is within close proximity to the other item. The words "preferred" and "preferably" are used herein refer to embodiments of the invention that may provide certain benefits under some circumstances. It is to be appreciated, however, that other embodiments may also be preferred under the same or different circumstances. The recitation of one or more preferred embodiments therefore does not mean or imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure, or from the scope of the claims.

Claims

CLAIMS1 . An airbag (11 ) for a motor vehicle safety arrangement, the airbag (11 ) comprising a pair of superimposed layers (7a, 7b) of flexible material interconnected by a peripheral seam (8) to define an inflatable chamber (9) for receipt of inflating gas between the layers (7a, 7b), the airbag (11 ) being initially provided in an uninflated condition in which at least a region of the airbag (11 ) is rolled to form a spirally- wound roll (13) which includes a wound length of said peripheral seam (8), characterised in that: within said roll (13), overlying regions of the airbag (11) are secured to one another adjacent the wound length of said peripheral seam (8).

2. An airbag (11) according to claim 1 , comprising: a pair of peripheral seam regions(8a, 8b) which are opposed from one another across at least a region of the inflatable chamber (9); wherein in said uninflated condition said roll (13) includes a respective wound length of each said peripheral seam region (8a, 8b); and wherein, within said roll (13), overlying regions of the airbag (11) are secured to one another adjacent the wound length of each peripheral seam region (8a, 8b).

3. An airbag (11 ) according to claim 2, wherein in said uninflated condition said roll (13) is formed about a roll axis (12) extending from one said peripheral seam region (8a) to the other said peripheral seam region (8b), across the airbag (11).

4. An airbag (11) according to claim 2 or claim 3, wherein in said uninflated condition, each said wound length of a seam region (8a, 8b) is located at a respective end of said roll (13).

5. An airbag (11) according to any preceding claim, wherein said overlying regions of the airbag (11) within said roll (13) are secured to one another by stitching (14).

6. An airbag (11) according to claim 5, wherein said stitching (14) is formed through both said layers (7a, 7b) of the airbag (11).

7. An airbag (11) according to claim 6, wherein said stitching (14) is formed through at least four overlying thicknesses of said flexible material arising from the airbag (11 ) being rolled to form said roll (13).

8. An airbag (11 ) according to claim 1 , wherein a set of securing holes (16) is formed through the airbag (11) adjacent said peripheral seam (8), said securing holes (16)being spaced apart from one another along the wound length of the peripheral seam (8) so as to be substantially aligned with one another within said roll (13), and wherein a fastener (17) is provided through said substantially aligned securing holes (16) to secure said overlying regions of the airbag (11) within the roll (13).

9. An airbag (11 ) according to any one of claims 2 to 4, wherein a respective set of securing holes (16) is formed through the airbag (11) adjacent each said peripheral seam region (8a, 8b), the securing holes (16) of each set being spaced apart from one another along the wound length of the respective peripheral seam region (8a, 8b) and being substantially aligned with one another within said roll (13), and wherein a respective fastener (17) is provided through the substantially aligned securing holes (16) of each set to secure the respective overlying regions of the airbag (11) within the roll (13).

10. An airbag (11) according to claim 8 or claim 9, wherein at least some of the securing holes (16) of the or each set are substantially radially aligned with one another across a region of the roll (13).

11. An airbag (11 ) according to claim 10, wherein the or each said fastener (17) is provided through the substantially radially aligned securing holes (16) of the or each respective set to secure said overlying regions of the airbag (11) to one another on one side (A) of the roll (13), and such that overlying regions of the airbag (11 ) on a diametrically opposite side (B) of the roll (13) are not secured to one another.

12. An airbag (11) according to claim 8 or claim 9, wherein at least some of the securing holes (16) of the or each set are substantially diametrically aligned with one another across the roll (13).

13. An airbag (11) according to claim 12, wherein the or each said fastener (17) is provided through the substantially diametrically aligned securing holes (16) of the or each respective set to secure said overlying regions of the airbag (11) to one another across the roll (13).

14. An airbag (11) according to any one of claims 8 to 13, wherein the or each said fastener (17) is provided in the form of a mechanical fastener.

15. An airbag (11) according to any preceding claim, the airbag being provided in combination with an inflator configured to direct inflating gas into the inflatable chamber (9) in a primary inflow direction (F), wherein: said wound length of the peripheral seam (8), or said wound lengths of said peripheral seam regions (8a, 8b), are spaced from said primary inflow direction (F) such that said inflating gas does not impinge directly thereon.

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