AN AIR-BAG MODULE

Description of Invention

The present invention relates to an air-bag module and, more particularly, relates to an air-bag module for use as a safety device in a motor vehicle, the module comprising a housing, an inflatable air-bag and an inflator configured to inflate the air-bag.

It is now common practice to provide motor vehicles with one or more safety devices in the form of inflatable air-bag arrangements. For example, most cars manufactured today are provided with a driver's side air-bag arrangement and a passenger side air-bag arrangement, each arrangement being configured to inflate an air-bag in the event of a crash situation in order to provide protection for the driver and/or passenger of the motor vehicle respectively. Each air-bag arrangement is typically manufactured as a substantially self-contained air-bag module which is then shipped to the motor vehicle production line for subsequent installation into the motor vehicle.

As will be appreciated, it is desirable to provide air-bag modules for simple and inexpensive manufacture, whilst also ensuring that the essential components of the air-bag module, such as the housing, inflatable air-bag and inflator, are properly and securely installed so as to prevent failure of the air- bag module in the event that it comes to be actuated in a crash situation.

A number of different forms of air-bag modules have been proposed previously, some of which require the use of screws, rivets or other similar

mechanical fastening means in order to interconnect the air-bag housing, air- bag and inflator within the self-contained air-bag module.

EP1506896 discloses an air-bag arrangement in which the inflatable air-bag is clamped between an inflator and an edge of the air-bag housing which has been found to be a relatively unreliable form of fastening.

It is an object of the present invention to provide an improved air-bag module.

According to the present invention, there is provided an air-bag module comprising a housing, an inflatable air-bag and an inflator configured to inflate the air-bag, wherein: a mounting opening is formed through a mounting-part of the housing, said mounting-part being provided with a plurality of mounting hooks; the air-bag having an inlet opening and being provided with a plurality of mounting apertures formed through the air-bag, the air-bag being connected to the housing such said inlet opening and said mounting opening are substantially aligned and such that each said mounting hook is received through a respective said mounting aperture; the inflator being secured to the housing in fluid communication with the air-bag via the inlet opening by engagement of said hooks over part of the inflator.

Preferably, said mounting hooks extend rearwardly from a rear-side of said mounting part such that the inflator is secured to the rear-side of the mounting part, and wherein a plurality of mounting slots are provided through the mounting part; said air-bag extending from said hooks, so as to pass through said mounting slots such that the main part of the air-bag is located on the opposed front-side of the mounting part. Advantageously, the air-bag is clamped between said part of the inflator and the rear-side of the mounting part.

Conveniently, said mounting-part is provided with a gripping formation on said rear-side.

Preferably, said mounting hooks are provided at positions around and substantially adjacent the periphery of the mounting opening, and wherein said mounting apertures are provided at positions substantially adjacent the periphery of said inlet-opening.

Advantageously, each said mounting slot is located substantially adjacent at least one said mounting hook, on the opposite side of the hook to the mounting opening.

Conveniently, each said mounting slot is substantially arcuate.

Preferably, said air-bag is provided with a plurality of flaps extending from said inlet opening, each said flap being provided with at least one said mounting aperture therethrough and passing through a respective mounting slot so as to be folded back against the rear-side of said mounting part.

Advantageously, said mounting part is provided with a plurality of secondary hooks, each said secondary hook being received through a respective mounting aperture in the air-bag, but not engaging said inflator.

Conveniently, each said secondary hook extends rearwardly from said rear- side of the mounting-part.

Preferably, said secondary hooks are provided at positions around and substantially adjacent the periphery of the mounting opening, such that each said secondary hook is located substantially between a pair of neighbouring mounting hooks.

Advantageously, each said secondary hook is spaced from the inflator.

Conveniently, said housing is provided with a gas-deflector, the gas-deflector being positioned so as to lie substantially around the inflator, between the inflator and the regions of the airbag which pass through said mounting slots.

Preferably, said gas-deflector is fixed to the front-side of the mounting part.

Advantageously, the gas-deflector is formed integrally with the mounting part.

Conveniently, the housing and the gas-deflector are co-moulded from plastics material.

Preferably, the inflator is provided with a peripheral mounting flange, the inflator being secured to the housing by engagement between the flange and said hooks.

Advantageously, said flange and said hooks engage one another as snap-fit.

Alternatively, said flange and said hooks engage one another as a bayonet-fit.

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

FIGURE 1 is a plan view from above of an inflatable air-bag forming part of the air-bag module of the present invention, illustrating detail of the air-bag's inlet- opening;

FIGURE 2 is an enlarged view of a mounting aperture formed through part of the air-bag illustrated in Figure 1 ;

FIGURE 3 is a perspective view from the front of an inflator forming part of an air- bag module in accordance with an embodiment of the present invention;

FIGURE 4 is a rear view of the inflator illustrated in Figure 3, showing particular detail of a mounting flange forming part of the inflator;

FIGURE 5 is a rear view of a housing forming part of an air-bag module in accordance with an embodiment of the present invention;

FIGURE 6 is an enlarged perspective view of part of the housing illustrated in Figure 5;

FIGURE 7 is a view corresponding generally to that of Figure 5, illustrating the manner in which the inflator of Figure 4 is engaged with the housing of Figure 5;

FIGURE 8 is a rear perspective view of an air-bag module in accordance with the present invention, showing interconnection between the housing, air-bag and inflator;

FIGURE 9 is a front perspective view of the air-bag module illustrated in Figure 8, with parts of the air-bag itself removed for sake of clarity, and illustrating a gas deflector provided around the inflator;

FIGURE 10 is a part cut-away perspective view of the air-bag module illustrated in Figure 9, again with parts of the air-bag removed for the sake of clarity;

FIGURE 11 is a rear view of an inflator forming part of an air-bag module in accordance with another embodiment of the present invention; and

FIGURE 12 is a rear perspective view illustrating the inflator of Figure 11 connected to the housing.

Referring initially to Figure 1 , an inflatable air-bag 1 is illustrated which has a generally square configuration. It will be appreciated, however, that other shaped air-bags can be used in the present invention. The rear layer of fabric 2 defining the air-bag is provided with a substantially centrally located inlet opening 3 through which inflating gas generated by an inflator (not illustrated in Figure 1 ) is directed into the air-bag 1 , generally in a direction into the page as viewed in Figure 1. The inlet opening 3 is of generally circular configuration, but has four substantially equi-spaced cut-outs 4 around its periphery. Between each adjacent pair of cut-outs 4 there is thus defined a generally elongate and arcuate flap 5, each of the four flaps 5 extending inwardly towards the centre of the inlet opening 3.

As illustrated in Figure 1 , each of the flaps 5 is provided with a generally centrally located mounting aperture 6 formed through the fabric of the air-bag in the region of the respective flap 5. Each central mounting aperture 6 takes the form of a slightly elongated slot. Additionally, each flap 5 is provided with a pair of larger mounting apertures 7 such that one larger aperture 7 is formed through the fabric of the air-bag in the region of the respective flap on either side of the central aperture 6. It will therefore be appreciated that the mounting apertures 6, 7 together define a plurality of mounting apertures formed through the fabric of the air-bag at positions generally adjacent the central inlet opening 3.

It can be seen from Figure 1 , however, that the larger mounting apertures 7 do not all have an identical profile. Five of the larger mounting apertures 7

(identified in particular by reference numeral 7a) take the form of generally straight, elongated slot. However, the remaining three larger mounting apertures (identified in particular by reference numeral 7b) take a different form having a generally "bent" profile comprising a generally straight, elongate first part 8 and a shorter second part 9 set at an angle relative to the first part 8, the shorter part 9 being directed generally inwards, towards the inlet opening 3. This is shown in more detail in Figure 2.

Figure 3 illustrates an inflator 10 which preferably takes the form of a gas generator and which is configured to be actuated upon receipt of an appropriate crash signal from a crash sensor (not shown). The inflator 10 comprises a generally cylindrical body part 11 around which is provided a peripheral mounting flange 12 in a manner generally known per se. In the orientation illustrated in Figure 3, the housing body 11 is provided with a plurality of gas outlet apertures 13 at radial positions such that, upon actuation of the inflator 10, gas is directed radially outwardly through each of the apertures 13.

As clearly illustrated in Figure 3, but also shown in Figure 4, the mounting flange 12 of the inflator 10 is provided with a number of outwardly-directed tabs 14 at spaced apart positions around its peripheral edge. One of the mounting tabs 14 is provided with a cut-out locating notch 15, the purpose of which will be described in more detail hereinafter.

Figure 5 illustrates a housing 16 of the air-bag module, viewed from the rear- side of the housing, that is the side which will face away from an occupant of a motor vehicle intended to be protected by the air-bag module, when the module is properly installed within the motor vehicle. The housing 16 is preferably moulded from plastics material and presents a generally planar rear-side face 17. The housing 16 also has a peripheral side-wall 18 (visible most clearly in Figure 8) from which extend a plurality of fixing hooks 19. The

fixing hooks 19 serve to connect the housing with a cover panel (not shown) of a type generally known per se, to protect the airbag in normal use.

A relatively large, centrally located, mounting opening 20 is formed through the rear-side face 17 of the housing 16 and, as illustrated, preferably takes the form of a substantially circular opening. Around the outside of the mounting opening 20, there are also provided four substantially equi-spaced mounting slots 21 , each of which is also formed through the rear-side face 17 of the housing 16 so as to provide access to the front side of the housing 16 (that is the side which will be facing an occupant of the motor vehicle when the air- bag module is properly installed in the motor vehicle) from the rear-side of the housing. Each of the mounting slots 21 is generally elongate and of arcuate form, so as to be centred on the centre point of the mounting opening 20.

Around the outside of the mounting opening 20, but in a region inside the mounting slots 21 , the rear-side face 17 of the housing is provided with an array of gripping formations which, in the preferred embodiment illustrated, take the form of a plurality of upstanding spikes or serrations 22. The spikes 22 are visible most clearly in Figure 6 which is a perspective view of part of the rear-side of the housing 16, looking in the direction indicated generally by arrow A in Figure 5. As will be explained in more detail hereinafter, the spikes 22 are provided to securely grip regions of the fabric forming the air-bag 1 , by "biting into" the fabric of the air-bag. It should readily be appreciated, however, that other alternative forms of gripping formation could be provided on the rear-side face 17 such as, for example, some form of serration or the like.

Referring once again to Figure 5, the housing is provided with four substantially equi-spaced minor mounting hooks 23, each of which extends rearwardly from the rear-side face 17 at a position immediately adjacent a respective mounting slot 21 and located mid-way along the length of the

respective mounting slot 21. One of the minor mounting hooks 23 is illustrated in more detail in Figure 6. Each of the minor mounting hooks 23 is of substantially identical form and comprises a rearwardly-extending wall part 24 which terminates with an inwardly-directed end part 25 so as to define a jaw 26 which is open towards the central mounting opening 20.

The housing 16 is also provided with a plurality of major mounting hooks 27. The arrangement illustrated in Figure 5 comprises eight such major mounting hooks 27, which are arranged in four pairs, each pair of major mounting hooks 27 being associated with a respective mounting slot 21. Each major mounting hook 27 extends rearwardly from the rear-side face 17 of the housing at a position immediately adjacent its associated mounting slot 21 , to one side of the respective minor mounting hook 23 associated with that mounting slot 21. Each minor mounting hook 23 is thus located between a respective pair of major mounting hooks 27.

As illustrated most clearly in Figure 6, each major mounting hook 27 has a form generally similar to that of the minor mounting hooks 23, but is enlarged. Each major mounting hook 27 thus comprises a rearwardly-extending wall part 28 from which extends a jaw part 29 which is directed inwardly towards the centre of the mounting opening 20.

Each of the major mounting hooks 27 are substantially identical with one another. However, one of the major mounting hooks 27 is provided with a small locator formation 30 which extends downwardly from the jaw part 29 of that hook so as to present a ramp surface 31 which faces the region of the rear-side face 17 located under the jaw 29 of that hook 27.

As can be seen from Figure 5, all of the mounting hooks 23, 27 (i.e. both the minor and major mounting hooks) are located around the outside of the array of gripping formations but inside, and immediately adjacent, the arcuate

mounting slots 21. Because the minor mounting hooks 23 are smaller than the major mounting hooks 27, the minor mounting hooks 23 are spaced further from the peripheral edge of the mounting opening 20 than the major mounting hooks 27.

The housing 16 is also provided with three rearwardly-directed stop projections 31 , each of which is located generally adjacent a respective major mounting hook. As can be seen from Figure 5, each stop projection 32 is, in fact, located slightly inwardly, and to the same side, of its associated major mounting hook 27. This positioning can also be seen clearly in Figure 6. As also clearly seen in Figure 6, each stop projection 32 defines a generally planar stop surface 33 which is perpendicular to the rear surface 17 of the housing 16 and which is directed towards the adjacent major mounting hook 27.

As illustrated in Figure 6, one of the three stop projections 32 is provided adjacent the major mounting hook 27 which is provided with the locator formation 30. The other two stop projections 32 are provided adjacent other major mounting hooks 27 such that the three stop projections 32 are provided at the corners of a notional isosceles triangle.

Figure 7 illustrates the inflator 10 connected to the housing 16 (with the air- bag 1 omitted for the time being for the sake of clarity).

As can be seen from Figure 7, each mounting tab 14 provided around the periphery of the inflator flange 12, is located beneath the jaw of a respective major mounting hook 27. The inflator 10 is manoeuvered into the position illustrated in Figure 7 by first being offered up to the rear-face 17 of the housing 16 in an orientation rotated counter-clockwise relative to the orientation of the inflator 10 illustrated in Figure 7. It will thus be appreciated that the inflator 10 is offered up to the housing 16 such that each mounting tab

14 is presented out of alignment with a respective major mounting hook 27. In this orientation, the inflator 10 is advanced towards the housing 16 such that the mounting flange 20 approaches the rear surface 17, whereafter the entire inflator 10 is rotated in a clockwise sense (as viewed in Figure 7) such that each mounting tab 14 moves under the jaw of a respective major mounting hook 27.

The mounting tab 14 which is provided with the locating notch 15 must be positioned under the jaw the major mounting hook 27 which is provided with the locator formation 30. As this mounting tab 14 is moved underneath the jaw of the major mounting hook (as the inflator is rotated in the clockwise sense), the advancing edge of the mounting tab bears against the ramp surface 31 of the locator formation 30 and is hence urged downwardly towards the rear surface 17 of the housing. As the inflator 10 continues to be rotated in a clockwise sense, the locating notch 15 will become aligned with the locator formation 30 whereupon the mounting tab 14 will snap over the locator formation 30. The provision of the locator formation 30 and the locating notch

15 thus ensures that the inflator 10 can only be mounted to the housing 16 in one particular orientation.

Simultaneously with the locator formation 30 being received in the locating notch 15, an end surface of each mounting tab 14 engages and bears against the stop surface 33 of a respective stop projection 32. The stop projections 32 thus prevent over-rotation of the inflator 10 as it is connected to the housing 16 in the manner described above.

It should therefore be appreciated that the arrangement illustrated in Figure 7 provides for a "bayonet-fit" between the mounting flange 12 of the inflator 10 and the major mounting hooks 27.

Turning now to consider Figure 8, the inflator 10 is again shown connected to the housing 16, but in this drawing, the air-bag 1 is also illustrated.

In order to assemble together the air-bag 1 , the inflator 10, and the housing 16, the air-bag 1 must first be connected to the housing 16 in the absence of the inflator 10. This is done by offering up the \air-bag 1 to the housing 16 from the front side of the housing 16 (that is from the underside as illustrated in Figure 8). Each flap 5 defined around the inlet opening 3 of the air-bag is inserted through a respective mounting slot 21 formed through the housing 16 whereafter the flaps 5 are each folded inwardly so that each of the larger mounting apertures 7 passes over a respective major mounting hook 27, and such that each of the smaller mounting apertures 6 pass over a respective minor mounting hook 23. It will thus be appreciated that each mounting hook is received through a respective mounting aperture formed through the fabric of the air-bag 1.

As will be understood from a comparison of Figure 1 and 5, the bent mounting apertures 7b are shaped so as to receive therethrough not only the respective major mounting hook 27, but also a respective stop projection 32. The rearwardly-extending wall part 28 of the major mounting hook 27 is thus received in the longer part 8 of the bent mounting apertures 7b, whilst the stop projection 32 is received in the shorter part 9.

Once the flaps 5 have been inserted through the respective mounting slots 21 and folded back against the rear-facing surface 17 of the housing 16 such that the mounting hooks are received through respective mounting apertures formed through the fabric of the air-bag, the inflator 10 is connected to the housing 16 in the manner described above such that the mounting flange 12 becomes engaged under the jaws of the major mounting hooks 27 as a "bayonet-fit". This is the configuration illustrated in Figure 8 from which it will be appreciated that the major mounting hooks 27 not only serve to secure the

air-bag to the housing 16, but also serve to secure the inflator to the housing 16. The air-bag is actually securely fastened by the mounting hooks and by virtue of the inner parts of the flaps 5 being clamped between the rear surface 17 of the housing and the mounting flange 12 of the inflator 10. This clamping serves to press the innermost regions of the flaps 5 against the spikes 22 so that the fabric of the air-bag in the these regions of the flaps is securely gripped.

It will also be appreciated, however, that the minor mounting hooks 23, each of which is received through a respective mounting aperture 6, serve to secure the air-bag with respect to the housing 16. However, because the minor mounting hooks 23 are spaced from the peripheral edge of the mounting flange 12, they are effectively thermally isolated from the inflator 10. This is advantageous because the inflator 10 will get extremely hot in the event that it is actuated so as to direct inflating gas into the interior volume defined by the air-bag 1. It is considered possible that the inflator 10 could get so hot as to burn, and hence damage, the fabric of the air-bag in the region of the flaps 5 which are clamped between the flange 12 and the housing. By providing the minor mounting hooks 23 in thermal isolation from the inflator, the minor mounting hooks 23 will continue to hold the air-bag securely to the housing 16 even in the event that regions of the flaps 5 engaged by the major mounting hooks 27 (which are connected to the flange 12 of the inflator) get burned away.

Figures 9 and 10 illustrate the assembled air-bag module with its air-bag, housing and inflator all connected to one another as described above, from the front (that is from the side which will be presented towards an occupant of a motor vehicle to be protected by the air-bag module). However, for the sake of clarity, the major extent of the main part of the air-bag 1 has been omitted, leaving simply the flaps 5 visible through the respective mounting slots 21. As illustrated in Figure 9, the front side of the housing 16 is provided with a gas

deflector 34 of generally annular form. The gas deflector 34 sits around the central cylindrical body part 11 of the inflator 10 but is located inside the four mounting slots 21.

In the preferred arrangement, the gas deflector 34 is formed integrally with the rest of the housing 16 and, most preferably, is co-moulded with the rest of the housing 16 from plastics material.

As illustrated most clearly in Figure 10 which is a part-sectional view of the preferred air-bag module, the gas deflector 34 has a forwardly-extending annular skirt 35 which is spaced from the main cylindrical part 11 of the gas generator 10 and which extends forwardly immediately adjacent the mounting slot 21. In fact, it can be seen from Figure 10 that the major mounting hooks

27 are formed as rearwardly-directed extensions of the forwardly-extending skirt 35.

The gas deflector 34 is connected to the main structure of the housing 16 by four radially-directed and equi-spaced bridge formations 36, the rear surface of which can be seen in Figure 8 and extends between adjacent arcuate mounting slots 21. As can be seen in Figure 9, the bridge formations 36 each extend forwardly from the mounting slots 21. It will be appreciated from a consideration of Figure 1 , that when the flaps 5 of the air-bag 1 are inserted through the mounting slots 21 from the front of the structure (that is from above as viewed in Figure 9), the bridge formations 36 each become received within a respective cut-out 4 between adjacent flaps 5.

The gas deflector 34 presents a generally curved surface as viewed in section in Figure 10, extending away and forwardly from the inflator 10. The gas deflector 34 thus serves to deflect the flow of gas coming out through the gas outlet apertures 13 of the inflator 10 in a direction generally forwardly, thereby preventing direct impingement on the region of the air-bag fabric around the

inflator 10. This is important because the flow of gas exiting through the gas outlet apertures 13 in the event of actuation of the inflator 10 is very hot and if not directed away from the immediately adjacent regions of the air-bag fabric can damage the air-bag fabric.

Figure 11 illustrates a modified configuration of the mounting flange 12. In this arrangement, four of the peripheral mounting tabs 14, including the one provided with the locating notch 15, are of a modified form. Each of the thus- modified mounting tabs 14 is provided with a generally radially outwardly- directed projection 37 at one end. Each of the outwardly-directed projections 37 supports a respective elongate arm 38. Between each arm 38 and the respective mounting tab 14, there is thus defined an open-ended elongate slot 39.

Figure 12 shows the modified inflator 10 of Figure 11 connected to the rear- side of the air-bag housing 16, with the air-bag itself omitted for the same of clarity. Here it can be seen that as each of the modified mounting tabs 14 is advanced underneath the jaw of a respective major mounting hook 27, as the inflator 10 is rotated in a clockwise sense in order to effect the "bayonet-fit" with the inflator 16, the upstanding wall part 28 of each major mounting hook 27 becomes received within a respective slot 39. In the condition illustrated in Figure 12, in which the "bayonet-fit" has been fully effected, four of the major mounting hooks 27 are thus engaged on their outside by a respective arm 38. The arms 38 thus serve to resist radially outward deflection of the respective major mounting hooks 27 which serves to provide a more secure connection between the inflator and the housing because it resists deflection of the respective major mounting hooks 27 in the event of actuation of the inflator 10.

Whilst the present invention has been described above with reference to particular embodiments, it should be appreciated that certain modifications or alterations could be made without departing from the scope of the present

invention. For example, it is envisaged that a simplified form of the present air-bag module could be provided in which the mounting flange 12 of the inflator engages the mounting hooks 27 as a snap-fit rather than as a bayonet- fit. In such an arrangement, it is envisaged that the mounting flange 12 of the inflator could simply be advanced towards the rearmost part of the mounting hooks 27, whereupon further advancement of the mounting flange 12 towards the housing could deflect the mounting hooks 27 outwardly to allow passage of the mounting flange 12 therepast. Subsequently, the mounting hooks 27 would snap back over the mounting flange 12 such that the periphery of the mounting flange 12 is securely engaged underneath the jaws 29 of the mounting hooks 27.

The above-described invention provides significant advantages in simplifying the construction and manufacture of air-bag modules. The provision of an arrangement whereby the air-bag and the inflator are both secured to the housing, rear-side of the housing, means that the air-bag and inflator can both be secured to the housing in a single action and only involving access to one side, namely the rear-side of the housing. Also, because the air-bag is secured to the rear-side of the housing, with the main part of the air-bag being located on the front-side of the housing, the pulling forces generated upon actuation of the inflator act in a direction generally 180° from the mounting hooks. This provides a much more secure form of connection between the air-bag and the rest of the air-bag module.

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.