WO2008105694A1

WO2008105694A1 - An air-bag module and method of mounting an air-bag module

Info

Publication number: WO2008105694A1
Application number: PCT/SE2007/000197
Authority: WO
Inventors: Laurent Hellot
Original assignee: Autoliv Development Ab
Priority date: 2007-03-01
Filing date: 2007-03-01
Publication date: 2008-09-04

Abstract

An air-bag module (1) which comprises a housing (2) for storing an air-bag and a generally planar cover (14) which is attached to the housing (2) by an attachment arrangement. The attachment arrangement being configured to provide a high attachment force which fixes the cover (14) relative to the housing (2) or a low attachment force which allows the cover (14) to be moved relative to the housing (2). The attachment arrangement allows for the cover (14) to be moved to a correct position relative to the housing (2) to align the cover (14) with an aperture (23) in a dashboard (22) when the air-bag module (1) is mounted to the dashboard (22).

Description

Title: "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 to be installed in a motor vehicle to protect an occupant of the vehicle in the event that a crash situation occurs.

It is well known to mount an air-bag module within the dashboard of a motor vehicle. A typical dashboard mounted air-bag module incorporates a housing for storing an air-bag and a cover which seals an opening in the housing to retain the air-bag within the housing. The cover usually incorporates one or more split lines which are configured to rupture when the air-bag module is actuated to define an opening in the cover out of which the air-bag can inflate.

The cover of the air-bag module can itself form part of the dashboard so that when the air-bag module is actuated the air-bag can inflate through the opening in the cover into the interior of the vehicle. In an arrangement of this type the cover of the air-bag module is visible to a person sitting in the vehicle.

In an alternative arrangement the air-bag module is mounted behind part of the dashboard and thus the cover of the air-bag module is not visible to a person sitting in the vehicle. The part of the dashboard which conceals the air- bag module is configured to rupture to provide an opening to allow the air-bag to inflate into the interior of the vehicle.

It is important for the dashboard of a motor vehicle to have a neat appearance to make the interior of the vehicle aesthetically pleasing. In order to achieve a neat appearance the visible parts of a dashboard must be designed in such a way that it is not obvious that a part of the dashboard or a visible cover of an air-bag module is configured to rupture to define an opening out of which an air-bag can inflate.

An air-bag module which has a cover that is designed to be visible when the air-bag module is mounted to a dashboard is disclosed in US-A-5588669. In this prior proposed arrangement the cover of the air-bag module is manufactured separately from the housing of the air-bag module and the cover is only attached to the housing during the final stage of assembly when the air- bag module is mounted to the dashboard of a motor vehicle. The air-bag module is thus not fully assembled before it is mounted to the dashboard. A transport cover is attached to the housing to protect the air-bag stored within the housing before the air-bag module is assembled fully. The cover is clipped to the housing via a hook and window arrangement in which hooks provided on the housing are hooked through windows provided on side walls of the cover.

This arrangement allows the air-bag module to function whilst providing a neat dashboard appearance, but the arrangement is expensive and heavy because it incorporates many parts. Vehicle manufacturers are constantly trying to reduce the complexity and weight of components in vehicles in order to lower manufacturing costs and to make vehicles lighter and hence more efficient to run.

An arrangement in which an air-bag module is installed behind part of a dashboard so that the cover of the air-bag module is not visible is disclosed in

US-A-6644685. In this prior proposed arrangement an air-bag module is assembled fully before it is mounted to a dashboard, that is to say the cover of the air-bag module is attached to the housing before the air-bag module is mounted to the dashboard. This arrangement allows the dashboard to have a neat appearance because the dashboard is one continuous surface.

However, this arrangement is difficult to assemble because the air-bag module must be aligned accurately with the part of the dashboard which is configured to rupture so that both the cover of the air-bag module and the part of the dashboard rupture cleanly to allow the air-bag to inflate into the vehicle in a correct manner. The difficult assembly of this arrangement results in a lengthy assembly time and hence a high assembly cost. Another problem with this arrangement is that the "double wall", constituted by the air-bag module cover and the part of the dashboard which is configured to rupture, is heavy as compared with a "visible cover" arrangement such as the arrangement discussed above where there is only one "wall" to rupture.

The present invention seeks to provide an improved air-bag module and an improved method of mounting an air-bag module to part of a vehicle.

According to one aspect of the present invention, there is provided an air-bag module comprising a housing for storing an air-bag and a generally planar cover which is attached to the housing by an attachment arrangement, the level of force applied to the cover and the housing by the attachment arrangement being selectable between a high attachment force and a low attachment force, the cover and the housing being configured so that the cover is not moveable relative to the housing when the high attachment force is applied by the attachment arrangement, characterised in that the cover and the housing are configured to allow the cover to be moved relative to the housing in a plane which is substantially parallel to the plane of the cover when the low attachment force is applied by the attachment arrangement.

Preferably the housing is provided with a generally planar flange, the plane of the flange being substantially parallel to the plane of the cover when the cover is attached to the housing, wherein the force applied by the attachment arrangement biases the flange and the cover towards one another.

In one embodiment the cover comprises at least two hooks, each hook being configured to hook around part of the flange of the housing to attach the cover to the housing, the hooks being configured to allow movement of the cover relative to the housing in a direction which is substantially parallel to the plane of the cover when the low attachment force is applied by the attachment arrangement.

Preferably the housing is provided with a stop element which engages the cover to restrict movement of the cover in a direction which is substantially parallel to the plane of the cover.

In a further embodiment the attachment arrangement comprises a clamp which extends around the edge of part of the cover and part of the flange, the clamp being configured to act on a surface of the cover and a surface of the flange to bias the flange and the cover towards one another.

Preferably the clamp is defined by a plurality of generally hook shaped members which are provided on part of a dashboard of a motor vehicle, each hook shaped member being dimensioned to hook around part of an edge of the flange to attach the air-bag module to the dashboard, each hook shaped member being configured to apply the high attachment force to the cover and the housing when the air-bag module is attached to the dashboard.

In a yet further embodiment the flange and the cover are each provided with respective apertures, the apertures being at least partially aligned with one another when the cover is attached to the housing, the attachment arrangement comprising an elongate attachment element which has a first enlarged end and a second enlarged end, the attachment element extending through the aperture in the flange and the aperture in the cover with the first enlarged end acting on the flange and the second enlarged end acting on the cover to apply the attachment force to the flange and the cover.

Preferably the aperture in the cover is larger in one dimension than a part of the attachment element which extends through the aperture to allow the cover to move relative to the attachment element in a plane substantially parallel to the plane of the cover when the low attachment force is being applied by the attachment element.

Conveniently the aperture in the flange is larger in one direction than a part of the attachment element which extends through the aperture to allow the attachment element to move relative to the flange when the low attachment force is being applied by the attachment element.

In one embodiment one of the enlarged ends is formed integrally with the attachment element and the other enlarged end is defined by a member which is releasably mounted to the attachment element.

Preferably the flange and the cover are each provided with a plurality of apertures, each aperture in the cover being configured to align at least partially with a respective aperture in the flange when the cover is attached to the housing, there being a plurality of attachment elements which each extend through an aperture in the flange and an aperture in the cover to attach the cover to the housing, the attachment arrangement comprising an elongate bracket which is configured to be connected to at least two of the attachment elements to define one of the enlarged ends of the at least two attachment elements.

Conveniently the bracket is received in a recess in the cover, the shape of the recess corresponding to the shape of the bracket, at least one dimension of the recess in a direction substantially parallel to the plane of the cover being larger than a corresponding dimension of the bracket to permit the bracket to be moved in the recess in a plane substantially parallel to the plane of the cover when the low attachment force is applied by the attachment arrangement.

In one embodiment the bracket is mounted moveably to part of a dashboard. In another embodiment the air-bag module is mounted to part of a dashboard of a motor vehicle by generally hook shaped members provided on the dashboard.

Preferably an air-bag is stored within the housing, the air-bag module further comprising a retaining element which is attached to the housing, the retaining element extending over part of the air-bag to retain the air-bag within the housing.

According to another aspect of the present invention, there is provided a dashboard of a motor vehicle to which is mounted an air-bag module according to any one of the claims defined hereinafter, the dashboard being provided with an aperture so that part of the cover of the air-bag module is visible from outside of the dashboard.

According to a further aspect of the present invention, there is provided a method of mounting an air-bag module to part of a vehicle, the air-bag module comprising a housing for storing an air-bag, a generally planar cover and an attachment arrangement, the method comprising the steps of: attaching the cover to the housing using the attachment arrangement; adjusting the attachment arrangement so that the attachment arrangement applies a low attachment force to the cover and the housing; attaching the air-bag module to the part of the vehicle; moving the cover relative to the housing in a plane which is substantially parallel to the plane of the cover to align part of the cover with the part of the vehicle; and adjusting the attachment arrangement so that the attachment arrangement applies a high attachment force to the cover and the housing so that the cover is not moveable relative to the housing.

In order 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: FIGURE 1 is a diagrammatic perspective view of parts of an air-bag module in accordance with a preferred embodiment of the invention,

FIGURE 2 is a diagrammatic sectional view of part of an air-bag module in accordance with the preferred embodiment of the invention,

FIGURE 3 is a diagrammatic sectional view of part of an air-bag module in accordance with a further embodiment of the invention,

FIGURE 4 is a diagrammatic perspective view of parts of an air-bag module in accordance with a yet further embodiment of the invention during a first stage of assembly,

FIGURE 5 is a diagrammatic perspective view of a cover of the air-bag module of Figure 4,

FIGURE 6 is a diagrammatic perspective view from below the air-bag module of Figure 4 during a second stage of assembly, and

FIGURE 7 is a diagrammatic sectional view of the air-bag module of Figure 4 mounted to a dashboard.

Referring initially to figures 1 and 2 of the accompanying drawings, an air-bag module 1 comprises a housing 2 for storing an air-bag. The housing 2 incorporates a body portion 3 which, in this embodiment, is of a plastics material. The body portion 3 is defined by a generally rectangular base 4 and four upstanding side walls 5 (only one of which can be seen in figure 1) which are formed integrally with the base 4 and which each extend upwardly from an edge of the base 4. The housing 2 has two mounting formations 6 (only one of which is visible in figure 1 ) which are formed integrally with the body portion 3 at opposite ends of the housing 2. Each of the mounting formations 6 is configured to be mounted to a respective one of two mounting tabs 7 which are provided on a part of a vehicle 8.

The base 4 and the side walls 5 define a storage chamber 9 for storing an air- bag. A generally cylindrical support element 10 is mounted to the inner face of the base 4. The support element 10 is configured to support a gas generator (not shown) which, when actuated, is configured to inflate an air-bag stored within the housing 2.

The upper edges of the side walls 5 define a generally rectangular opening 11 in the housing 2. A generally planar flange 12, which is tilted with respect to the base 4, is formed integrally with the upper edges of the side walls 5 and the flange 12 extends outwardly from around the periphery of the opening 11.

The flange 12 is provided with six apertures 13. Three of the apertures 13 are provided in the flange 12 on one side of the housing 2 and the other three apertures 13 are provided in the flange 12 on an opposing side of the housing 2. The purpose of the flange 12 and the apertures 13 will become clear from the description below.

The air-bag module 1 further comprises a generally planar cover 14. The cover 14 is generally rectangular in shape to correspond with the shape of the periphery of the flange 12 on the housing 2. The cover 14 is, in this embodiment, of a plastics material.

A generally rectangular door section 15 of the cover 14 is defined in a central region of the cover 14 by lines of mechanical weakness. The lines of mechanical weakness are configured to split or rupture when an air-bag within the housing 2 is inflated and exerts a force on the door section 15. When some of the lines of mechanical weakness split, the door section 15 is configured to pivot about one of the lines of mechanical weakness which does not split so that the door section 15 moves to define an opening in the cover 14 out of which the air-bag can inflate.

The cover 14 is provided with six mounting apertures 16. Three of the mounting apertures 16 are provided in the cover 14 at spaced apart positions along one edge of the cover 14 and the other three mounting apertures 16 are provided in the cover 14 at spaced apart positions along an opposing edge of the cover 14. The position of the mounting apertures 16 is such that the mounting apertures 16 at least partially align with the apertures 13 in the flange 12 when the cover 14 is superimposed on the flange 12. As will become clear from the description below, the size of each of the mounting apertures 16 is important to the operation of the preferred embodiment of the invention.

The upper surface of the cover 14 is provided with two generally rectangular elongate recesses 17. One of the elongate recesses 17 extends into the upper surface of the cover 14 on one side of the cover 14 so that the three of the mounting apertures 16 on that side of the cover 14 extend through the housing 14 at the base of the recess 17. The other elongate recess 17 extends into the upper surface of the cover 14 on the other side of the cover 14 so that the other three mounting apertures 16 extend through the housing 4 at the base of the other recess 17.

Each of the recesses 17 is shaped to receive an elongate generally planar mounting bracket 18 which, in this embodiment, is of metal. The mounting brackets 18 are identical to one another and are each provided with three spaced apart generally cylindrical hollow open ended threaded collars 19. The collars 19 protrude from one side of each of the brackets 18 and the collars 19 are positioned so that, when each bracket 18 is placed within a corresponding one of the recesses 17 in the cover 14, the collars 19 in the bracket 18 each extend into one of the mounting apertures 16 provided in the cover 14. The brackets 18 define components of an attachment arrangement for attaching the cover 14 to the housing 2. The other components of the attachment arrangement are six attachment elements in the form of bolts 20. Each bolt 20 is configured to be screwed into one of the collars 19 of one of the brackets 18 so that at least two of the bolts 20 are connected to each bracket 18. The bolts 20 together with the mounting brackets 18 define the attachment arrangement for attaching the cover 14 to the housing 2.

The cover 14 is mounted to the housing 2 by superimposing the cover 14 on the flange 12 and aligning the mounting apertures 16 in the cover 14 with the apertures 13 in the flange 12. The mounting brackets 18 are positioned within the recesses 17 in the cover 14 so that the collars 19 in the brackets 18 extend into the mounting apertures 16 in the cover 14. The bolts 20 are then pushed upwardly through the apertures 13 in the flange 12 to engage and connect with the threaded collars 18 of the brackets 19.

The bolts 20 each define an elongate attachment element. The head of each bolt 20 defines a first enlarged end of the elongate attachment element. Once each bolt 20 has been connected to one of the brackets 18, the bracket 18 defines a second enlarged end of the attachment element. The head of the bolt 20 acts on the underside of the flange 12 and the bracket 18 acts on the upper surface of the cover 14. As the bolt 20 is tightened by screwing the bolt 20 into the bracket 18, the attachment arrangement defined by the bolt 20 and the bracket 18 applies an attachment force which biases the cover 14 and the flange 12 towards one another. The level of the attachment force is dependent upon the tightness by which bolt 20 is screwed into its respective bracket 18.

The size of each of the mounting apertures 16 in the cover 14 is selected to be larger than the outer diameter of the collar 19 and the part of each bolt 20 which extends through the mounting aperture 16. This results in a gap 21 being present between the edge of the mounting aperture 16 and the collar 19 and the periphery of the bolt 20.

If each bolt 20 is only screwed loosely into its respective bracket 18 then the attachment arrangement only applies a low attachment force (which may be zero) to the cover 14 and the flange 12. When the low attachment force is applied, the cover 14 is moveable relative to the housing 2. The gap 21 between the mounting apertures 16 and the bolt 20 allows the cover 14 to move relative to the housing 2 in a direction which is substantially parallel to the plane of the cover 14. If the bolts 20 are tightened then the attachment arrangement applies a high attachment force to the cover 14 and the flange 12 which attaches the cover 14 firmly to the flange 12 so that the cover 14 is not moveable relative to the housing 2. The significance of the ability to position the cover 14 relative to the housing 2 will become clear from the description below.

After the cover 14 has been attached to the housing 2 by the attachment arrangement, the air-bag module may be mounted to the dashboard of a motor vehicle. Initially the air-bag module 1 is mounted by the mounting formations 6 to tabs 7 provided on part of the vehicle 8 which may, for instance, be a support beam situated within a dashboard. The air-bag module 1 is then also mounted to the instrument panel 22 which defines a part of the dashboard of a motor vehicle which is visible to a person seated within the vehicle. The instrument panel 22 is provided with a generally rectangular aperture 23 which is of a shape that corresponds with the shape of the door region 15 of the cover 14 of the air-bag module 1. In this embodiment the air-bag module 1 is mounted to the underside of the instrument panel 22 by hooks 24 which are formed integrally with the underside of the instrument panel 22. The hooks 24 extend around the edge of the cover 14 and the flange 12 to clip the air-bag module 1 to the underside of the instrument panel 22. It is important that the door region 15 of the cover 14 aligns accurately with the aperture 23 in the instrument panel 22 so that when the air-bag module 1 is actuated the door region 15 may open through the aperture 23 in the instrument panel 22 to allow the air-bag to inflate into the vehicle. If the door region 15 is not aligned correctly with the aperture 23 in the instrument panel 22 then the instrument panel 22 may overlap with the edge of the door region 15 and obstruct movement of the door region 15.

After the air-bag module 1 has been clipped to the instrument panel 22 the bolts 20 are loosened so that the attachment arrangement only applies a low attachment force to the cover 14 and the housing 2. The cover 14 can then be moved relative to the housing 2 in a plane substantially parallel to the plane of the cover 14 so that the edge of the door region 15 may be aligned correctly with the edge of the aperture 23 in the instrument panel 22. Once aligned, the bolts 20 are tightened so that the attachment arrangement applies a high attachment force to the cover 14 and the housing 2 so that the cover 14 is no longer moveable relative to the housing 2.

The provision of the generally planar cover 14 and the attachment arrangement which allows for high or low attachment forces to be selected allows for the position of the cover 14 to be adjusted relative to the housing 2 to minimise the effect of manufacturing tolerances which might otherwise result in the cover 14 being positioned incorrectly.

The generally planar nature of the cover 14 allows for the cover 14 to be moved relative to the housing 2 in a plane which is substantially parallel to the plane of the cover 14. The cover 14 is not provided with any side walls which might otherwise obstruct movement of the cover relative to the housing 2. The fact that the cover 14 does not need to have side walls to mount the cover 14 to the housing 2 means that the cover 14 is lighter and less complex than an equivalent cover which has side walls to mount the cover to a housing. The cover and flange arrangement of embodiments of the invention helps to minimise the height of the air-bag module 1 and hence minimise the space occupied by the module when the module is mounted within a dashboard.

Referring now to figure 3 of the accompanying drawings, an air-bag module in accordance with a further embodiment of the invention has many parts which are identical to the preferred embodiment described above and equivalent reference numerals will be used when describing this further embodiment.

The cover 14 of this further embodiment is identical to the cover 14 of the preferred embodiment described above except that the cover 14 of this further embodiment does not incorporate the recesses 17. In this further embodiment, the mounting brackets 18 are held loosely within channels 25 of generally T-shaped cross-section which are formed in the instrument panel 22.

In addition to this, the instrument panel 22 of this further embodiment does not have hooks to hook the air-bag module 1 onto the instrument panel 22.

The air-bag module 1 of this further embodiment is mounted to the instrument panel 22 via the bolts 20 which serve to attach the air-bag module 1 to the instrument panel 22 as well as applying the attachment force to attach the cover 14 to the housing 2. The loose fit of the mounting brackets 18 within the channels 25 in the instrument panel 22 allows for the position of the brackets 18 and the air-bag module 1 to be adjusted relative to the instrument panel 22 when the attachment arrangement applies the low attachment force. The mounting apertures 16 in the cover 14 are enlarged relative to the diameter of the collars 19 and the bolts 20 so that the position of the cover 14 can be altered relative to the housing 2 as described above in relation to the preferred embodiment.

In this further embodiment the air-bag module 1 can be pre-assembled, that is to say the cover 14 can be attached to the housing 2, before the air-bag module 1 is mounted to the instrument panel 22 by screwing nuts onto the ends of the bolts 20 in place of the brackets 18 to attach the cover 14 to the housing 2. When the air-bag module 1 is to be mounted to the instrument panel 22 the nuts are removed so that the ends of the bolts 20 are free to be screwed into the brackets 18 provided on the instrument panel 22.

Whilst in the embodiments described above the mounting apertures 16 in the cover 14 are enlarged, with the apertures 13 in the flange 12 being of a smaller size, in other embodiments the apertures 13 in the flange 12 may be of a larger size with the mounting apertures 16 in the housing 14 being of a smaller size. In a yet further embodiment both the mounting apertures 16 in the cover 14 and the apertures 13 in the flange 12 are of a larger size. In these alternative embodiments the enlarged size of the apertures allows for movement of the cover 14 relative to the housing 2 by moving the cover 14 relative to the bolts 20 or moving the cover 14 together with the bolts 20 relative to the housing 2.

Referring now to figure 4 of the accompanying drawings an air-bag module in accordance with a yet further embodiment of the invention has many parts which are the same as the parts of the air-bag module of the preferred embodiment described above and the same reference numerals will be used when describing this yet further embodiment. The housing 2 of this embodiment is identical to the housing 2 of the preferred embodiment described above except that the flange 12 of this embodiment does not incorporate any mounting apertures. The flange 12 of this embodiment is, however, provided with a generally cylindrical stop element 26 which protrudes upwardly from the upper surface of one end of the flange 12.

The air-bag module 1 of this yet further embodiment has a rectangular generally planar cover 27. A generally rectangular door section 28 is defined in the cover 27 by three lines of mechanical weakness and one already open edge 29 (see figure 7). The cover 27 of this yet further embodiment does not incorporate any mounting apertures, but instead has six opposing hook shaped formations 30 which are formed integrally with the rest of the cover 27. Three of the hook shaped formations 30 depend downwardly from one edge of the cover 27 and the other three hook shaped formations 30 depend downwardly from an opposing edge of the cover 27 so that the hook shaped formations 30 oppose one another. The hook shaped formations 30 are spaced apart from one another with two gaps 31 being defined between the hook shaped formations 30 on each side of the cover 27.

Each of the hook shaped formations 30 is dimensioned to receive an edge of the flange 12 of the housing 2 so that the cover 27 can be slid onto the flange 12 in the direction generally indicated by arrow 32 in figure 4.

The cover 27 is provided at one end with a rounded notch 33. The notch 33 is dimensioned to receive the stop element 26 on the flange 12. The cover 27 is attached to the housing 2 by sliding the cover 27 onto the flange 12 until the stop element 26 engages the notch 33 to stop further movement of the cover 27. The hook shaped formations 30 apply a low attachment force on the flange 12 to attach the cover 27 to the housing 14. The low attachment force allows the cover 27 to be moved relative to the housing 2 in a plane substantially parallel to the plane of the cover 27.

After the cover 27 has been attached to the housing 2 the housing 2 is mounted to part of a vehicle 8, as shown in figure 6. After the air-bag module 1 has been mounted to the part of the vehicle 8 the air-bag module 1 is then clipped onto an instrument panel 22 by hooks 24 which are provided on the underside of the instrument panel 22. The hooks 24 are spaced so that each of the hooks 24 extend around the edge of the cover 27 and the flange 12 in the gaps 31 between the hook shaped formations 30. The hooks 24 on the instrument panel 22 exert a force on the cover 27 and the flange 12 which acts as a high attachment force which biases the cover 27 and the flange 12 towards one another. The hooks 24 on the instrument panel 22 define parts of an attachment arrangement which attaches the cover 27 to the housing 2. The high attachment force exerted on the cover 14 and the housing 2 by the hooks 24 attaches the cover 27 firmly to the housing 2 so that it is not possible to move the cover 27 relative to the housing 2.

It is to be appreciated that in this yet further embodiment the cover 27 is moved relative to the housing 2 to a required position to align with the aperture 23 in the instrument panel 22 just before the air-bag module 1 is clipped to the instrument panel 22. The low attachment force exerted by the hook shaped formations 30 on the cover 27 is sufficient to hold the cover 27 in position relative to the housing 2 whilst the air-bag module 1 is being clipped to the instrument panel 22.

Whilst in the embodiments described above parts of an attachment arrangement are defined by bolts and/or hook shaped formations, it is to be appreciated that part of the attachment arrangement may be defined by a clamp of any type which extends around the edge of the cover and the flange to bias the cover and the flange towards one another. The clamp may take the form of a clip which clips around the edge of the cover and the flange or the clamp may take the form of an adjustable clamp in which a screw is tightened to select the attachment force to be applied to the cover and the flange.

It is to be appreciated that the meaning of the term "not moveable" when used in connection with the cover and the housing means that the cover cannot be moved relative to the housing by a force such as the force which could be exerted manually by a person.

In embodiments of the invention a retaining element in the form of a wrapper may be attached to the housing 2. The retaining element extends over part of an air-bag stored within the housing 2 to retain the air-bag within the housing 2

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.

Claims

1. An air-bag module (1 ) comprising a housing (2) for storing an air-bag and a generally planar cover (14;27) which is attached to the housing (2) by an attachment arrangement, the level of force applied to the cover (14;27) and the housing (2) by the attachment arrangement being selectable between a high attachment force and a low attachment force, the cover (14;27) and the housing (2) being configured so that the cover (14;27) is not moveable relative to the housing (2) when the high attachment force is applied by the attachment arrangement, characterised in that the cover (14;27) and the housing (2) are configured to allow the cover (14;27) to be moved relative to the housing (2) in a plane which is substantially parallel to the plane of the cover (14;27) when the low attachment force is applied by the attachment arrangement.

2. An air-bag module according to claim 1, wherein the housing (2) is provided with a generally planar flange (12), the plane of the flange (12) being substantially parallel to the plane of the cover (14;27) when the cover (14;27) is attached to the housing (2), wherein the force applied by the attachment arrangement biases the flange (12) and the cover (14;27) towards one another.

3. An air-bag module according to claim 2, wherein the cover (14;27) comprises at least two hooks (30), each hook (30) being configured to hook around part of the flange (12) of the housing (2) to attach the cover (14;27) to the housing (2), the hooks (30) being configured to allow movement of the cover (27) relative to the housing (2) in a direction which is substantially parallel to the plane of the cover (27) when the low attachment force is applied by the attachment arrangement.

4. An air-bag module according to claim 3, wherein the housing (2) is provided with a stop element (26) which engages the cover (27) to restrict movement of the cover (27) in a direction which is substantially parallel to the plane of the cover (27).

5. An air-bag module according to any one of claims 2 to 4, wherein the attachment arrangement comprises a clamp which extends around the edge of part of the cover (14;27) and part of the flange (12), the clamp being configured to act on a surface of the cover (14;27) and a surface of the flange (12) to bias the flange (12) and the cover (14;27) towards one another.

6. An air-bag module according to claim 5, wherein the clamp is defined by a plurality of generally hook shaped members (24) which are provided on part of a dashboard (22) of a motor vehicle, each hook shaped member (24) being dimensioned to hook around part of an edge of the flange (12) to attach the air-bag module (1) to the dashboard (22), each hook shaped member (24) being configured to apply the high attachment force to the cover and the housing when the air-bag module (1) is attached to the dashboard (22).

7. An air-bag module according to claim 2, wherein the flange (12) and the cover (14) are each provided with respective apertures (13,16), the apertures (13,16) being at least partially aligned with one another when the cover (14) is attached to the housing (2), the attachment arrangement comprising an elongate attachment element (20) which has a first enlarged end and a second enlarged end, the attachment element (20) extending through the aperture (13) in the flange (12) and the aperture (16) in the cover (14) with the first enlarged end acting on the flange (12) and the second enlarged end acting on the cover (14) to apply the attachment force to the flange (12) and the cover (14).

8. An air-bag module according to claim 7, wherein the aperture (16) in the cover (14) is larger in one dimension than a part the attachment element (20) which extends through the aperture (16) to allow the cover (14) to move relative to the attachment element (20) in a plane substantially parallel to the plane of the cover (14) when the low attachment force is being applied by the attachment element (20).

9. An air-bag module according to claim 7 or claim 8, wherein the aperture (13) in the flange (12) is larger in one direction than a part of the attachment element (20) which extends through the aperture (13) to allow the attachment element (20) to move relative to the flange (12) when the low attachment force is being applied by the attachment element (20).

10. An air-bag module according to any one claims 7 to 9, wherein one of the enlarged ends is formed integrally with the attachment element (20) and the other enlarged end is defined by a member which is releasably mounted to the attachment element (20).

11. An air-bag module according to any one of claims 7 to 9, wherein the flange (12) and the cover (14) are each provided with a plurality of apertures (13,16), each aperture (16) in the cover (14) being configured to align at least partially with a respective aperture (13) in the flange (12) when the cover (14) is attached to the housing (2), there being a plurality of attachment elements (20) which each extend through an aperture (13) in the flange (12) and an aperture (16) in the cover (14) to attach the cover (14) to the housing (2), the attachment arrangement comprising an elongate bracket (18) which is configured to be connected to at least two of the attachment elements (20) to define one of the enlarged ends of the at least two attachment elements (20).

12. An air-bag module according to claim 11, wherein the bracket (18) is received in a recess in the cover (14), the shape of the recess (17) corresponding to the shape of the bracket (18), at least one dimension of the recess (17) in a direction substantially parallel to the plane of the cover (14) being larger than a corresponding dimension of the bracket (18) to permit the bracket (18) to be moved in the recess (17) in a plane substantially parallel to the plane of the cover (14) when the low attachment force is applied by the attachment arrangement.

13. An air-bag module according to claim 11 , wherein the bracket (18) is mounted moveably to part of a dashboard (22).

14. An air-bag module according to any one of claims 7 to 13, wherein the air-bag module (1) is mounted to part of a dashboard (22) of a motor vehicle by generally hook shaped members (24) provided on the dashboard (22).

15. An air-bag module according to any one of the preceding claims, wherein an air-bag is stored within the housing (2), the air-bag module (1) further comprising a retaining element which is attached to the housing (2), the retaining element extending over part of the air-bag to retain the air-bag within the housing (2).

16. A dashboard (22) of a motor vehicle to which is mounted an air-bag module (1) according to any one of the preceding claims, the dashboard (22) being provided with an aperture so that part of the cover (14;27) of the air-bag module (1 ) is visible from outside of the dashboard (22).

17. A method of mounting an air-bag module (1) to part of a vehicle (22), the air-bag module (1) comprising a housing (2) for storing an air-bag, a generally planar cover (14;27) and an attachment arrangement, the method comprising the steps of: attaching the cover (14;27) to the housing (2) using the attachment arrangement; adjusting the attachment arrangement so that the attachment arrangement applies a low attachment force to the cover (14;27) and the housing (2); attaching the air-bag module (1) to the part of the vehicle (22); moving the cover (14;27) relative to the housing (2) in a plane which is substantially parallel to the plane of the cover (14;27) to align part of the cover (14;27) with the part of the vehicle (22); and adjusting the attachment arrangement so that the attachment arrangement applies a high attachment force to the cover (14;27) and the housing (2 so that the cover (14;27) is not moveable relative to the housing (2).

18. An air-bag module substantially as herein before described with reference to and as shown in figures 1 and 2 of the accompanying drawings.

19. An air-bag module substantially as herein before described with reference to figure 3 of the accompanying drawings.

20. An air-bag module substantially as herein before described with reference to and as shown in figures 4 to 7 of the accompanying drawings.

21. A method of mounting an air-bag module to a dashboard substantially as herein before described with reference to the accompanying drawings.