Air bag

A side air bag is disclosed for a motor vehicle, and takes the form of a three-dimensional airbag which is formed from two super-imposed layers of fabric. The super-imposed layers of fabric, when laid flat, have a substantial common area of super-imposition. Infill pieces formed from either at least one gusset forming insert or from a portion or portions of fabric of one or both of the fabric layers which extend beyond the area of super-imposition are provided. The air-bag has an inflatable region towards the upper part of the air-bag and an inflatable region towards the lower part of the air-bag. The two inflatable regions are separated by a part of the air-bag which is constrained when the air-bag is inflated, to have a thickness less than the thickness of either of the said regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Great Britain patent application 0314505.9, filed Jun. 20, 2003 and PCT/EP2004/006275, filed Jun. 9, 2004.

FIELD OF THE INVENTION

The present invention relates to an air-bag for use in a motor vehicle, such as a motor car, and more particularly the present invention relates to a side air-bag.

BACKGROUND OF THE INVENTION

A side air-bag is an air-bag which initially is stored within part of a vehicle seat, typically the back-rest of the vehicle seat, or in a side part of the vehicle adjacent the seat.

A side air-bag is of particular value in a side impact situation and, as is known, air-bags which are to provide protection for an occupant of a vehicle during a side impact must be inflated extremely swiftly. Consequently it is desirable for such air-bags to require a minimum amount of gas to inflate.

Various types of side air-bag have been proposed previously.

Many prior proposed side air-bags are so-called “two-dimensional” air-bags. A two-dimensional air-bag is formed from two superimposed layers of fabric of identical size and shape that are secured together at their common periphery to form an air-bag which, in the uninflated state, can be laid out flat. The two superimposed layers may be stitched together with a peripheral seam or, alternatively, a one-piece weaving process may be utilized to produce an air-bag of corresponding form, again having two superimposed layers of identical size and shape that are secured together at their periphery.

In spite of the fact that a side air-bag should be inflated with a minimum amount of gas in order to facilitate rapid inflation, it is also desirable that a side air-bag should have substantial “depth” so that, upon inflation, the air-bag will engage with a seat occupant as soon as possible and provide a maximum lateral “cushion” to protect an occupant in a side impact situation.

A two-dimensional air-bag can be inflated until the opposed sides of the air-bag bulge outwardly away from each other, providing depth or thickness for the air-bag. As the air-bag is inflated in this way, a substantial amount of gas has to be injected into the air-bag, creating an almost cylindrical form, and resulting in the pressure of gas in the air-bag quite high. When inflated in this way, the air-bag may not provide the desired cushioning effect but, instead may cause a seat occupant to “bounce” off the air-bag.

It has been proposed to provide a side air-bag which is a two-dimensional air-bag of the type discussed above. The air-bag has a transverse seam in a central region dividing the air-bag into an upper inflatable region or chamber and a lower inflatable region or chamber. The two inflatable regions or chambers each have a thickness or depth, but near the seam, each has a much lower thickness or depth. The presence of the central seam helps minimize the amount of gas needed to fully inflate the air-bag. Also, the presence of the seam may make it possible, as appropriate, to inflate the two chambers to different internal pressures. However, the presence of the seam in the two-dimensional air-bag means that the overall thickness of the inflatable region or chamber of the air-bag, when it is inflated, is rather small.

It is an object of the present invention to provide an improved side air-bag for a motor vehicle.

SUMMARY OF THE INVENTION

In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a side air-bag for a motor vehicle. The side air-bag being a three-dimensional air-bag formed from two superimposed layers of fabric which, when laid flat, have at least a substantial common area of superimposition. Infill pieces are formed from at least one gusset forming insert or from a portion of the fabric of one or both of the fabric layers which extend beyond the common area of superimposition. The air-bag has an inflatable region towards the upper part of the air-bag and an inflatable region towards the lower part of the air-bag, each inflatable region being separated by a part of the air-bag which is constrained, when the air-bag is inflated, to have a thickness less than the thickness of either of the said regions.

Preferably, the air-bag includes an upper chamber forming said upper region and a lower chamber forming said lower region, the upper chamber and the lower chamber being separated by a transversely extending seam.

Advantageously, the air-bag is formed from two layers of fabric of substantially identical configuration interconnected by means of a peripheral seam, there being at least one insert in said peripheral seam between the layers of fabric to form a gusset.

Conveniently, there are two inserts, one insert forming a gusset associated with one chamber and the other insert forming a gusset associated with a second chamber.

Preferably, an insert is provided with at least one vent aperture.

Advantageously, each vent aperture is initially sealed by means of a tear-seam.

Conveniently, the superimposed layers of fabric have a substantial common area of superimposition, each layer of fabric having one or more portions thereof which project beyond the area of superimposition, the peripheries of the areas being interconnected by means of a seam.

Preferably, a gas generator is present within the air-bag, the combination of the seam and the gas generator substantially sealing the two chambers from each other, the gas generator being configured to inflate the two chambers to different pressures.

Advantageously, the superimposed layers of fabric each have two portions which project beyond the area of common overlap, the resultant air-bag having, when inflated, an upper chamber and a lower chamber, there being a narrow inflated neck between the upper chamber and the lower chamber.

Conveniently, the two layers of fabric form part of a single fabric element.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially toFIGS. 1 to 3of the accompanying drawings, a side air-bag having an upper inflatable region and a lower inflatable region will be described.

Referring initially toFIG. 1, a side air-bag1is formed from two superimposed identical layers of fabric2,3(only the layer2being visible inFIG. 1). The layers of fabric2,3are co-aligned so that the common area of superimposition is the total area of each layer, with no portion of either layer extending beyond the common area of superimposition.

As will be described, the two layers of fabric2,3are secured together around their periphery to form an inflatable part to the air-bag, and the inflatable part is itself divided into two inflatable regions, namely an upper chamber4and a lower chamber5by means of a transversely extending seam6. The seam6extends from about the middle (in a vertical sense) of part of the air-bag1which will be the forward-most part of the air-bag1when inflated, towards a mid part of a region which will be a rear part7of the air-bag when the air-bag is inflated. The seam6is upwardly inclined. At the rear part7, of the air-bag1a flap8is provided having two apertures9,10formed therethrough.

A generally cylindrical gas generator11is provided which is to be inserted into the air-bag through an aperture (not shown) formed near the flap8. The gas generator11is provided with two radially projecting studs12,13which are positioned and dimensioned to be received through the apertures9,10formed in the flap8. When the apertures9,10formed in the flap8are engaged with the studs12,13the air-bag1may be sealed. The gas generator11is provided with a plurality of gas outlet apertures14. A cylindrical gas deflector15(shown in phantom in FIG.1) is preferably provided which surrounds the gas generator11and defines gas outlets16,17.

The combination of the gas generator11and the gas deflector15is to be inserted into the air-bag1through the opening provided near the flap8. The apertures9,10in the flap8may be engaged with the radially projecting studs12,13so as to seal the air-bag. The inner-most end of the seam6may engage the gas deflector16, thus separating the upper chamber4from the lower chamber5. Gas from the gas generator11may be injected into the upper chamber4through the gas outlet16and into the lower chamber5through the gas outlet17.

FIG. 2illustrates the sheet of fabric2used to form the air-bag ofFIG. 1, showing the position of the seam6and also showing the position of a peripheral seam19which serves to join the fabric layer2to the other identical fabric layer3.FIG. 2also shows a separate fabric insert20of generally oval form, the insert20having opposed pointed ends.

It is to be understood that when the fabric layers2,3are joined together by the peripheral seam19, the insert20is introduced into the peripheral seam19in the lower-most part of the air-bag, between the fabric layers2,3extending from a point A, at the end of the transversely extending seam6, to a point B adjacent the base of the flap8. The insert20has one side edge connected to the first fabric layer2, and the other side edge connected to the other fabric layer3, thus forming a gusset.

It is to be appreciated, therefore, that when the air-bag as shown inFIGS. 1 and 2is inflated, the fabric layers2,3will bow outwardly due to the pressure of gas within the chambers4,5, but because of the presence of the gusset formed by the insert20, the lower chamber5, as shown in phantom inFIG. 3, may have a substantial transverse dimension or depth whereas the upper chamber4, again as shown in phantom inFIG. 3, will have a lesser dimension or depth. The lower chamber5, which incorporates the gusset, can therefore be inflated to have a desirable substantial thickness or depth. The presence of the transverse seam6serves to minimize the volume of gas required to fully inflate the air-bag, and, in the arrangement shown, the gas generator may be designed so the upper chamber4may be inflated to a different pressure than the lower chamber5on actuation of the gas generator.

FIG. 4illustrates a modified embodiment of the invention. In this embodiment, instead of having two separate fabric elements2,3, a single fabric element30is provided adapted to be folded along a fold-line31so that a first part32of the fabric element overlies a second, but substantially mirror image part33. Thus, when superimposed, the common area of superimposition is the total area of each part32,33, with no portion of either part extending beyond the area of superimposition. The first part32has a configuration corresponding generally to that of the fabric element2described above with reference toFIG. 2, including an upper area34that is to form the side-wall of an upper inflatable chamber of a side air-bag and a lower area35that is to form the side-wall of a lower inflatable chamber of the side air-bag, the areas34,35being separated by a region which is to accommodate a transversely extending seam36corresponding to the seam6of the air-bag1described above. The second part33of the fabric element has similar features and, in a central area37, where the two parts32and33are conjoined, there are two apertures38,39formed through the fabric element to receive mounting studs mounted on a gas generator. A slit40through which the gas generator may be inserted into the air-bag is also formed through the central area37of the fabric element. Again there is a peripheral region41where a seam is to be provided.

In this embodiment of the invention there are two infill elements or inserts42,43. The first insert42is of oval form with pointed ends and corresponds with the insert20of the embodiment described with reference toFIGS. 1 to 3. This insert42is intended to be inserted into the seam36between the areas35that are to form the side-walls of the lower inflatable chamber when the air-bag is assembled, extending from a point A adjacent the end of the seam36to a point B at the base of the central region37where the two separate parts32,33of the fabric element30are conjoined. One side of the insert42is connected to a first part32of the fabric element30, and the other side is connected to the other part33of the fabric element30, again to form a gusset.

The second insert43is of somewhat larger size, but again is of generally oval form having pointed ends, this insert being configured to be inserted into the seam36between the areas34that are to form the side-walls of the upper chamber, extending from a point C adjacent the end of the seam36to a point D at the upper-most part of the region37in which the two parts32,33of the fabric element are conjoined. Thus, the insert43forms a second gusset. The insert43is provided with a plurality of vent holes44.

It is to be appreciated, therefore, that in the embodiment ofFIG. 4not only is the lower inflatable chamber provided with a gusset constituted by the infill element42but also the upper inflatable chamber is provided with a gusset constituted by the infill element43.

The gussets would initially be tucked into the interior of the air-bag, thus being trapped between the two parts32,33of the fabric element30. Thus the vent holes44would initially be closed, and no gas would be able to pass out through the vent holes44. The vent holes would, however, become exposed on inflation of the air-bag and gas would then be able to escape through the vent holes.

In the embodiment ofFIG. 4, both the lower chamber and the upper chamber may have substantial thickness or depth whilst requiring a minimum quantity of gas for the inflation of the air-bag. In the region of the seam36the air-bag has a lesser thickness or depth.

Turning now toFIG. 5, a modified insert45is shown intended to replace the insert43as described above. The insert45is provided with a plurality of vent holes46, but the region of the insert provided with the vent holes46has been pinched and closed by means of a tear-seam47(seeFIG. 6). The tear-seam47thus serves initially to seal the vent holes46. On inflation of the air-bag, when the pressure of gas within the air-bag reaches a predetermined pressure sufficient to break the tear-seam, the tear-seam breaks and gas may then escape through the vent holes46.

Whilst the embodiments described above have all included at least one insert or infill to form a gusset in a three-dimensional air-bag, a three dimensional air-bag may alternatively be formed using two layers of fabric superimposed to define a common area of superimposition. In this embodiment, at least one of the layers of fabric has a region which extends beyond the common area, with the periphery of the first layer of fabric being secured to the periphery of the second layer of fabric, thus forming an air-bag with three-dimensional properties. Preferably the length of the periphery of one of the layers of fabric is identical to the length of the periphery of the other layer of fabric.

FIGS. 7 and 8show, from opposite sides, a single fabric element50having two parts51,52which have been folded about a fold-line53so as to be superimposed as an intermediate step in the fabrication of the air-bag. The part51is shown to be on the top inFIG. 7and the part52is shown to be on the top inFIG. 8. It can be seen that there is a very substantial area of common overlap in which the part51partially overlies the part52, but there are protruding portions54,55,56,57of the part51which protrude beyond the area of common overlap, and also it can be seen that there are protruding portions58,59,60,61of the part52which extend beyond the area of common overlap.

It is to be appreciated that adjacent the fold-line53, a region is provided having mounting apertures62,63in the part51, there being a slit or opening in the region of the fold-line53to enable a gas generator of the type shown inFIG. 1to be introduced into the air-bag, with the studs on the gas generator being engaged with the apertures62,63to hold the gas generator in position and to seal the air-bag.

It is to be understood that an internal transversely extending seam66is provided which interconnects the two parts51,52of the fabric element50so the seam extends across the area of common overlap and terminates adjacent the said apertures62,63. Here it is to be understood that when the gas generator is mounted in position within the air-bag, a gas deflector provided on the gas-generator may contact the seam66thus separating the air-bag into two separate inflatable regions or chambers, the chambers being separated by the seam66.

It is to be appreciated that as the air-bag is assembled from an intermediate position shown inFIGS. 7 and 8, the peripheries of the two superimposed parts51,52are brought into alignment with an appropriate manipulation of the fabric of the air-bag, and the aligned peripheries are interconnected, for example by stitching, thus forming an air-bag in which there is a lower three dimensional inflatable region or chamber defined by the superimposed fabric layers in the region67and a corresponding upper inflatable region or chamber in the region68. The protruding portions54-61all form infill elements, equivalent to the inserts of the embodiments described above. The inflatable regions or chambers67,68may have a significant thickness or depth, when the air-bag is inflated, but the air-bag will have a minimum thickness or depth in the region of the seam66.

FIG. 9illustrates another embodiment of the invention in which a single fabric element is used to form a three-dimensional air-bag. In this embodiment, however, there is no transverse seam dividing the air-bag into separate chambers.

Referring toFIG. 9, a single element of fabric70is shown having two substantially mirror-image parts71,72interconnected by a connecting region73. Within the connecting region73there are two apertures74,75to engage studs provided on a gas generator and an access slit76to enable a gas generator to be inserted into the air-bag.

It is to be understood that during the fabrication process the fabric element70will be folded about a fold-line77which passes through the interconnecting region73, so that the part71is partially superimposed over the part72as shown in phantom inFIG. 9. Here it is to be appreciated that when in the folded condition there is a substantial common area of overlap. As such, the part72will have regions78and79which extend beyond the area of common overlap, and the part71will have portions80,81which extend beyond the area of common overlap. Again the fabric layers are interconnected by means of a peripheral seam82, with the fabric being manipulated so that the peripheries of the areas are brought together.

An air-bag, fabricated from a fabric element as shown inFIG. 9will, when inflated (seeFIG. 10), tend to have an upper inflatable region83of relatively large thickness and depth, and a lower inflatable region84also of relatively large thickness and depth, interconnected by a neck region85of much less width or depth. Again the air-bag may be inflated using a minimum quantity of gas, but is provided with inflatable regions which have a substantial thickness or depth, thus enabling the air-bag to be brought into physical contact with a seat occupant relatively swiftly on deployment of the air-bag, and also enabling the air-bag to provide an adequate protective or cushioning effect.