GB2426230A

GB2426230A - An airbag module with venting means

Info

Publication number: GB2426230A
Application number: GB0509167A
Authority: GB
Inventors: Marcus J Ward
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-05-05
Filing date: 2005-05-05
Publication date: 2006-11-22
Also published as: GB0509167D0; DE102006020575A1

Abstract

An airbag module 20 is disclosed for venting inflation gas if an out of position vehicle occupant is too close to the module 20 for proper airbag deployment. The airbag module 20 has an airbag canister comprising a rear wall 23 having gas port 27 to communicate with the ambient air, an airbag 26, a spacer means 30 defining a gas flow passage 32 connecting an interior of the airbag 26 to the gas port 27 and an inflator 25 located within the airbag 26. The spacer means 30 permits venting of gas through the gas port 27 when an out of position occupant applies sufficient force to the airbag 25 and prevents the airbag 26 from blocking or inhibiting flow through the gas port 27. A spacer 230 may also constrain the airbag such that a vent remains coincident with a port in a canister 223.

Description

An Airbag Module This invention relates to airbags and in particular to a

passenger airbag module for a motor vehicle.

Occupant restraint systems for motor vehicles employing airbag modules for passengers are well known. During a collision of a predetermined magnitude, an airbag cushion is inflated by an inflator and is deployed in the vehicle for protection of the vehicle occupant.

The airbag cushion is deployed at a high rate of speed and force optimized to protect a wide range of occupants under various conditions. However, there are circumstances when deploying an airbag cushion is not desirable. Such a circumstance is when a vehicle occupant is so close to the airbag that normal deployment of the airbag may cause injury to the occupant.

An occupant that is too close to the airbag is said to be out of position' and various airbag module designs have been developed to reduce the amount of pressure and force caused by an airbag deployment to an out of position vehicle : *** occupant. e. *

**,. 25 4 I I... For example, some systems use vents in the airbag that : are exposed when the airbag is partially deployed and I.. * * release gases generated by the inflator as the bag is S. deploying through holes in the rear of a canister forming * 30 part of the airbag module. S. *Se

It is a problem with such an arrangement that if the airbag moves in an unexpected manner during deployment the vents in the airbag are either misaligned with the holes in the canister which will considerably restrict the flow of gases from the airbag through the holes or the holes in the canister can become blocked or restricted by the airbag so that no gas can flow therethrough or the flow is restricted.

It is desirable to have an occupant restraint system employing an airbag cushion that deploys with reduced force when an occupant is out of position and is of a simple design.

It is an object of this invention to provide an improved airbag module for a motor vehicle and a motor vehicle including same.

According to a first aspect of the invention there is provided an airbag module comprising a canister for storing an airbag having free ends attached to a wall of the canister, an inflator located within the airbag for providing inflation gas during deployment of the airbag, at least one gas port in the wall of the canister communicating with ambient air pressure and at least one airbag vent positioned in close proximity to a respective gas port so as to permit gas to escape from the airbag through the adjacent gas port to limit the pressure within the airbag during deployment wherein at least one spacer means is provided to : maintain a free gas passage between the airbag and the or ::.. 25 each gas port at least during the later stages of airbag deployment.

I * S * *.S *

The or each airbag vent may be located such that it is SIe only exposed to the gases from the inflator when the airbag ": * 30 is partially deployed by being located at or near to the position of attachment of the airbag to the wall of the IS..

canister.

The inflator may be used to attach the airbag to the wall of the canister.

The wall of the canister may be a rear wall of the canister.

The or each vent may be a single vent formed between two free ends of the airbag and the spacer means is interposed between the two free ends of the airbag.

The spacer means may be a tubular spacer having a body defining at least one gas flow passage, each gas flow passage being in communication at one end with an interior of the airbag and being located at an opposite end near to the or each gas port.

The canister may have a like number of gas ports as there are gas flow passages in the tubular spacer.

The tubular spacer may define a single gas flow passage which is in communication at one end with an interior of the airbag and is positioned at an opposite end near to the or each gas port.

The inflator may be attached to the wall of the canister by one or more elongate fasteners each of which : *. extends through respective apertures formed in the airbag

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25 and in the tubular spacer means.

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: The inflator may clamp one free end of the airbag to *.. I * the tubular spacer and the other free end of the airbag may be clamped between the tubular spacer and the wall of the canister. * I

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The spacer means may comprise of a number of spacers that are spaced apart to define respective gas flow passages the rebetween.

There may be first second and third spacers and a first gas flow passage may be defined between the first and second spacers and a second gas flow passage may be defined between the second and third spacers.

The spacers may be joined together by bridge members.

The first spacer may be joined to the second spacer by a first bridge member and the second spacer may be joined to the third spacer by a second bridge member.

The canister may have a like number of gas ports as there are gas flow passages.

The inflator may be attached to the wall of the canister by one or more elongate fasteners each of which extends through respective apertures formed in the airbag and in one of the spacers.

The inflator may clamp one free end of the airbag to the spacers and the other free end of the airbag may be clamped between the spacers and the wall of the canister.

The or each spacer means may be a depression in the rear wall of the canister formed adjacent to each gas port so as to space the airbag away from the rear wall in the region of the gas port. S * S..

: The free ends of the airbag may be clamped to the rear S..

* wall of the canister by the inflator and the or each vent is * S. * formed in the airbag near to one of the free ends of the *::: : 30 airbag. * S *

Each depression may extend across the width of the canister.

Each depression may surround a respective gas port.

The inflator may clamp the free ends of the airbag to the depressions in the rear wall Each vent may be formed by an aperture in a wall of the airbag.

In accordance with a second aspect of the invention there is provided an airbag module comprising a canister for storing an airbag having free ends attached to a wall of the io canister, an inflator located within the airbag for providing inflation gas during deployment of the airbag, at least one gas port in the wall of the canister communicating with ambient air pressure and at least one vent in the airbag to vent gas during deployment of the airbag wherein each vent is positioned coincident with a respective gas port so as to permit gas to escape from the airbag through the gas port to limit the pressure within the airbag during deployment and an alignment means is provided to maintain the alignment of each vent with the adjacent gas port.

The or each vent may be located such that it is only exposed to the gases from the inflator when the airbag is partially deployed by being located at or near to the : **., position of attachment of the airbag to the wall of the

I

25 canister.

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: o. The inflator may be used to attach the airbag to the a., * wall of the canister.

Each vent may be formed in a wall of the airbag.

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S... Each alignment means may comprise of a tubular body portion for engagement with a respective vent and gas port and a circumferentially extending flange for abutment against an inner surface of the airbag.

Each alignment means may include a fastening means to hold the alignment means in the respective gas port.

The fastening means may comprise a number of flexible arms which are biased against a rear face of the wall of the canister so as to hold the alignment mean in position.

Alternatively, the fastening means may comprise a screw thread formed on the outer surface of the alignment means and a nut for engagement with the screw thread.

The alignment means may further comprise a tubular extension extending away from the circumferential flange in the opposite direction to the tubular body.

According to a third aspect of the invention there is provided a motor vehicle having an airbag module in accordance with said first aspect of the invention.

According to a fourth aspect of the invention there is provided a motor vehicle having an airbag module in accordance with said second aspect of the invention.

: *s The invention will now be described by way of example 5** * 25 with reference to the accompanying drawing of which:- * 5** : Fig.l is a pictorial representation of the 510 * * dashboard of a motor vehicle according to one aspect of the *0S * invention; IS * Fig.2 is a partial cross-section along the line X-X

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showing an airbag module according to the invention; Fig.3 is a pictorial representation of the airbag module shown in Fig.2; Fig.4 is a partial cross-section through the airbag module shown in Fig. 3 Fig.5 is a pictorial representation of a spacer means forming part of the airbag module shown in Figs 3 and 4; Fig.,6 is a pictorial representation of an alternative spacer means; Fig.7 is a pictorial view of a second embodiment of an airbag module according to the invention; Fig.8 is a partial cross-section along a longitudinal axis of the airbag module shown in Fig.7; Fig.9 is a pictorial view of a third embodiment of an airbag module according to the invention; Fig.10 is a partial cross- section along a longitudinal axis of the airbag module shown in Fig.9; Fig.11A is a pictorial representation of an alignment means forming part of the airbag module shown in Figs.9 and * *. 10; * S S 0*S I *a** Fig. 11B is a cross-section through the alignment means : ** shown in Fig.11A; I.. * * 5I0 * Fig.12A is a pictorial representation of an *::: : 30 alternative alignment means for use as part of the airbag module shown in Figs.9 and 10; and *S Fig.12B is a cross-section through the alignment means shown in Fig.12A.

With particular reference to Figs. 1 to 5 there is shown a dashboard 11 of a motor vehicle. An airbag module is fastened to a rear surface of the dashboard 11. The dashboard 11 is locally weakened by the provision of two grooves 12, 13 to form a cover or door for the airbag module 20. However, it will be appreciated that a separate door or cover could be used.

The airbag module 20 comprises of a canister having four side walls 21 and a rear wall 23 defining a receptacle for an airbag 26 which is folded up and stored in the canister ready for deployment. The canister has a peripheral flange 22 extending around a free edge of the side walls 21 to define a mouth or opening 24 from which the airbag 26 is deployed. The peripheral flange is used to fasten the air bag module 20 to the rear surface of the dashboard 11 and to increase the stiffness of the canister.

An inflator 25 is located within the airbag 26 and is attached to the rear wall 23 of the canister by means of two spaced apart elongate fasteners in the form of threaded studs 28 which are threadingly engaged with nuts 29. It will be appreciated that an alternative form of fastening could be used and either more or less fasteners could be used. * S S S.. *

Each of the elongate fasteners 28 extends through

I

respective apertures formed in the airbag 26, the rear wall 23 and a spacer means 30 interposed between free ends of the

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* airbag 26. **0

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The inflator 25 is used to attach the airbag 26 to the rear wall 23 of the canister by clamping one free end of the

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airbag 26 to one surface of the spacer means 30 and using the spacer means 30 to clamp an opposite free end of the airbag 26 to the rear wall 23.

The rear wall 23 has a number of apertures forming gas ports 27 which are exposed to the atmospheric or ambient pressure surrounding the canister. It will however be appreciated that if required a single elongate gas port could be used.

The spacer means is in the form of a tubular spacer 30 having a body 31 defining a gas flow passage 32. The gas flow passage 32 is in communication at one end with an interior of the airbag 26 and is located at an opposite end near to the gas ports 27.

The gas ports 27 and the gas flow passage 32 have in combination a predetermined restricting effect on the flow "F" exiting the canister which is dependent upon the pressure within the airbag 26.

The tubular spacer 30 is positioned between the two free ends of the airbag 26 which form a single large vent from the airbag 26. The tubular spacer 30 has a number of holes 33, 34 formed in the body 31 through which the elongate fasteners 28 extend. The position of the tubular spacer 30 near to the gas ports 27 is therefore ensured by the engagement of the elongate fasteners 28 and by the fact that the tubular spacer 30 is clamped to the rear wall 23 by * the inflator 25. * . . *.. 4

*., 25 When the airbag 26 is folded into a stored state it : *s covers over one end of the gas flow passage 32 in the I.. * * tubular spacer 30 and so, during the initial stages of *** * airbag deployment, gas cannot escape through the gas flow *::: : 30 passage 32 to the gas ports 27. However, as soon as the airbag 26 is partially deployed the gas flow passage 32 is uncovered and gas can now flow out through the gas ports 27 to limit the pressure within the airbag 26 if required.

During normal deployment the rate at which gas is being generated by the inflator is such that the pressure within the airbag 26 is kept within acceptable limits even though - 10 - some gas will escape through the gas ports 27. It will be appreciated that because the free ends of the airbag 26 are positioned to either side of the tubular spacer 30 there is little risk of the airbag 26 obscuring the gas flow passage 32 once the airbag 26 is partially inflated. This is because the airbag 26 will expand away from its positions of attachment which are on either side of the tubular spacer 30. In addition, the gas will tend to flow away from the inflator 25 into the airbag 26 and, provided the expansion of the airbag 26 is unrestricted, the inertia of the gas will tend to carry it away from the gas flow passage 32.

Therefore, even when the gas flow passage is unobstructed, little gas will flow out through the gas flow passage and the gas ports 27.

In the case of contact with an out of position occupant the expansion of the airbag 26 will be severely restricted and the pressure will rise rapidly within the airbag 26 due to the restriction to expansion of the airbag 26 imposed by the presence of the occupant. However, as the pressure rises within the airbag 26 gas will escape through the gas ports 27 due to the pressure difference that exists there and because the restriction to expansion will cause the gas flow from the inflator 25 to be deflected back towards the

S S S.. *

rear wall 23 of the container. The pressure within the a * airbag 26 is therefore maintained within the airbag 26 at a * .. lower level than would otherwise be the case. * S * a.. * *55

* The presence of the tubular spacer 30 ensures that the gas ports 27 cannot become obscured by the airbag 26 and because of the gas flow passage 32 in the tubular spacer 30 the gas within the airbag 26 always has an unobscured flow path to the gas ports 27. In addition, because the free ends of the airbag 26 form the vent and these are secured to the rear wall 23 of the canister, it is ensured that the vent from the airbag 26 is always maintained close to the gas ports 27.

- 11 - Although the tubular spacer shown in Fig.5 has only a single gas flow passage it will be appreciated that it could have several gas flow passages separated by dividing walls.

In this case the canister could have a like number of gas ports as there are gas flow passages in the tubular spacer or could have only a single gas port.

With particular reference to Fig.6 there is shown a spacer means 40 that is intended to be a direct replacement for the spacer means shown in Fig. 5.

However, in this case, instead of the spacer means 40 being of a tubular construction it comprises of first, second and third spacers 41, 42 and 43 which are spaced apart with respect to one another to form two gas flow passages 44, 45.

Each of the spacers 41, 42, 43 is made as a solid block of material although they could also be of a hollow construction. It will also be appreciated that there could only be two spacers or there could be more than three spacers. ** * * I.. *

25 The first spacer 41 is connected to the second spacer

I

42 by a first bridge member 47 and the two spacers 41, 42 : *** define a first gas flow passage 44 therebetween. The second II. * * spacer 42 is connected to the third spacer 43 by a second S..

* bridge member 46 and the two spacers 42, 43 define a second gas flow passage 45 therebetween.

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In this case each of the first and third spacers 41 and 43 has an aperture 50, 49 therein through which an elongate member (not shown) extends in use to fasten the inflator 25 to the wall 23 of the canister as described previously.

- 12 - As before the inflator 25 is used to clamp the airbag 26 to the wall 23 of the canister and the spacer means 40 is interposed between the free ends of the airbag 26. That is to say, the inflator 25 clamps one free end of the airbag 26 to the spacers 41, 42, 43 and the other free end of the airbag 26 is clamped between the spacers 41, 42, 43 and the rear wall 23 of the canister.

It will be appreciated that the canister could have a like number of gas ports 27 as there are gas flow passages 44, 45 defined between the spacers 41, 42, 43 or could have only a single gas port 27 large enough to span both of the gas flow passages 44, 45.

As before the spacers 41, 42, 43 secure the vent defined by the free ends of the airbag 26 near to the gas ports 27 and ensure that a flow path from the airbag 26 to the gas ports 27 is maintained after initial deployment of the airbag 25.

With particular reference to Figs.7 and 8 there is shown an airbag module 120 that is intended to be a direct replacement for the airbag module previously described. * S. * a a

The airbag module 120 comprises of a canister having a.' four side walls 121 and a rear wall 123 defining a receptacle for an airbag 126 which is folded up and stored in the canister ready for deployment. The canister has a a..

* peripheral flange 122 extending around a free edge of the side walls 121 to define a mouth or opening 124 from which ::., the airbag 126 is deployed. The peripheral flange 122 is used to fasten the air bag module 120 to the rear surface of a dashboard such as the dashboard 11 shown in Fig.1 and to increase the stiffness of the canister.

An inflator 125 is located within the airbag 126 and is attached to the rear wall 123 of the canister by means of a - 13 - single centrally positioned elongate fastener in the form of a threaded stud 128 which is threadingly engaged with a nut 129. It will be appreciated that an alternative form of fastening could be used and that, if required, more fasteners could be used.

The elongate fastener 128 extends through respective apertures formed in the airbag 126 and the rear wall 123.

The inflator 125 is used to attach the airbag 126 to the rear wall 123 of the canister by clamping the free ends of the airbag 126 to the rear wall 123.

The rear wall 123 has a number of apertures therein each forming a gas port 127 which is exposed to the atmospheric or ambient pressure surrounding the canister.

The airbag 126 has a number of apertures or vents 131 formed in it near to its free ends where it is fastened to the canister. Each of the vents 131 is positioned or located near to one of the gas ports 127 so that the flow "F" exiting the airbag 126 and canister has a relatively direct path. S. * . S *.a *

** 25 When the airbag 126 is folded into a stored state it covers over the vents 131 and so during the initial stages of airbag deployment gas cannot escape through the vents 131 S.. * * to the gas ports 127. However, when the airbag 126 is lie * partially deployed the vents 131 are uncovered and gas can then flow out through the gas ports 127 to limit the pressure within the airbag 126. Si.

As before, during normal deployment, the rate at which gas is being generated by the inflator 125 is such that the pressure within the airbag 126 is kept within acceptable limits even though some gas will escape through the gas ports 127. However, in the case of contact with an out of - 14 - position occupant, the pressure will begin to rise rapidly within the airbag 126 and more gas will escape through the gas ports 127 so that the pressure within the airbag 126 is at a lower level than would otherwise be the case.

To prevent the airbag 126 from blocking the gas ports 127 the rear wall 123 has a number of depressions 130 formed in it to space the free ends of the airbag 126 away from a plane on which the gas ports 127 lie. That is to say the surface of the rear wall 123 to one side of each gas port is raised compared to the surface of the rear wall 123 at the position where the gas port 127 is formed. This reduces the probability of the airbag 126 obscuring or blocking the gas ports 127.

In the embodiment shown there are two depressions 130 each of which extends across substantially the entire width of the rear wall 123 of the canister. Each of the depressions 130 forms a raised surface within the canister and the free ends of the airbag 126 are clamped to these raised surfaces.

There are a number of vents 131 formed in the airbag 126 near to each free end to allow gas to escape from the airbag 126 through the gas ports 127. The positioning, S*ss number and size of these vents 131 is such that excessive gas loss is prevented during normal deployment while * permitting adequate venting during an out of position * S. * occupant event. * S * I. *

It will be appreciated that there could be a similar * S number of gas ports as there are vents and the vents and gas ports could be aligned or there may be only one gas port to each side of the inflator 125. Furthermore, each of the depressions could extend around a respective one of the gas ports so that the gas port is effectively recessed in the - rear wall or there could be depressions just in the vicinity of each gas port 127.

With particular reference to Figs. 9 to liE there is shown yet another embodiment of an airbag module according to the invention that is intended to be a direct replacement for the airbag module shown on Figs.i and 2.

The airbag module 220 comprises of a canister having side walls 221 and a rear wall 223 defining a receptacle for an airbag 226 which is folded up and stored in the canister ready for deployment. The canister has a peripheral flange 222 extending around a free edge of the side walls 221 to define a mouth or opening 224 from which the airbag 226 is deployed. The peripheral flange 222 is used to fasten the air bag module 220 to the rear surface of a dashboard such as the dashboard 11 shown in Fig.1.

An inflator 225 is located within the airbag 126 and is attached to the rear wall 123 of the canister by means of two elongate fasteners which in this case are threaded fasteners. It will be appreciated that an alternative form of fastening could be used and that more or less fasteners * .. could be used. I * I,, *

Each of the elongate fasteners extends through a : * respective aperture formed in the airbag 226 and the rear 11 * wall 223 and a nut is threadingly engaged with each of the *I) elongate fasteners. s. 30 1 * * I,

The inflator 225 is therefore used to attach the airbag 226 to the rear wall 223 of the canister by clamping the airbag 226 to the rear wall 223.

The rear wall 223 has a number of apertures therein and the airbag 226 has a like number of apertures or vents formed in it near to the position where it is fastened to

-I-

- 16 - the canister. Each of the vents is positioned or located near to one of the apertures in the rear wall 223 and is held in position by a respective alignment means 230.

The alignment means 230 ensure that at all times the vents in the airbag 226 are positioned coincident with the apertures in the rear wall 223.

Each of the alignment means 230 comprises of a tubular body 232 defining a flow passage or gas port therein and has a circumferentially extending flange 233 at one end which in use is located within the airbag 226. The circumferentially extending flange 233 is used to hold the airbag 226 to the rear wall 223.

The tubular body 232 has a number of resilient flexible arms 231 formed integrally therewith. Each of the arms 231 is biased in use against the rear wall 223 of the canister and is used to provide a load to the circumferential flange 233 so as to hold the airbag 226 to the rear wall 223. That is to say, the alignment means 230 snap into engagement with the apertures in the rear wall 223 and hold the airbag 226 in position. It will be appreciated that a different fixing method could be used such as, for example, a screw thread formed on the outer surface of each tubular body 232 and a S. * respective nut for engagement with the screw thread.

When the airbag 226 is folded into a stored state it covers over the vents in the airbag and so during the initial stages of airbag deployment gas cannot escape 0 through the vents to the gas ports formed by the tubular *S.

bodies. However, when the airbag 226 is partially deployed the vents are uncovered and gas can then flow out through the gas ports to limit the pressure within the airbag 226.

As before, during normal deployment the rate at which gas is being generated by the inflator 225 is such that the - 17 - pressure within the airbag 226 is kept within acceptable limits even though some gas will escape through the gas ports 227. However, in the case of contact with an out of position occupant, the pressure will rise rapidly within the airbag 226 and more gas will escape through the gas ports 227 so that the pressure within the airbag 226 is at a lower level than would otherwise be the case. As before, this is because the gas is deflected back towards the rear wall 223 of the canister The alignment means 230 ensure that the vents in the airbag 226 are always correctly located with respect to the apertures in the rear wall 223 and so there is no danger of the vents moving to a position in which the flow of gas from the airbag 226 is unduly restricted.

With respect to Figs.12A and 12B there is shown an alternative embodiment of alignment means 330 which is intended to be a direct replacement for the alignment means shown in Fig.10.

Each of the alignment means 330 comprises of a tubular body 332 defining a flow passage or gas port therein and has a circumferentially extending flange 333 towards one end .: . 25 which in use is located between the airbag 226 and the rear a...

wall 223. The tubular body 332 has a number of flexible arms 331 formed integrally therewith. Each of the arms 331 a. * is biased in use against the rear wall 223 of the canister and is used to provide a load to the circumferential flange * * 30 333 SO as to hold the alignment means 330 to the rear wall a. * 223. as..

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Because of the location of the peripheral flange 333 part way along the tubular body 332 part of the tubular body becomes a tubular extension 334 extending away from the circumferential flange in the opposite direction to the main portion of the tubular body 332. The airbag 226 will tend - 18 - to expand away from these tubular extensions 334 when it is inflated and so there is very little probability of the gas ports defined by the alignment means 330 from being obscured during airbag 226 deployment.

However, if required, apertures can be formed in this tubular extension 334 so that even if the airbag 226 is able to cover the end of the gas passage defined by the tubular body 332 there is still a route for gas to enter the gas passage and escape from the airbag 226.

It will be appreciated by those skilled in the art that although theinvention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention. S. * 4 IS * SC** I... * S. * S S S.. *

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Claims

- 19 - Claims 1. An airbag module comprising a canister for storing an

airbag having free ends attached to a wall of the canister, an inflator located within the airbag for providing inflation gas during deployment of the airbag, at least one gas port in the wall of the canister communicating with ambient air pressure and at least one airbag vent positioned in close proximity to a respective gas port so as to permit gas to escape from the airbag through the adjacent gas port to limit the pressure within the airbag during deployment wherein at least one spacer means is provided to maintain a free gas passage between the airbag and the or each gas port at least during the later stages of airbag deployment.
2. An airbag module as claimed in claim 1 wherein the or each airbag vent is located such that it is only exposed to the gases from the inflator when the airbag is partially *: 20 deployed by being located at or near to the position of *I..

attachment of the airbag to the wall of the canister.
3. An airbag module as claimed in claim 1 or in claim 2 wherein the inflator is used to attach the airbag to the wall of the canister. "S * S5 I. *
4. An airbag module as claimed in any of claims 1 to 3 wherein the wall of the canister is a rear wall of the canister.
5. An airbag module as claimed in any of claims 1 to 4 wherein the or each vent is a single vent formed between two free ends of the airbag and the spacer means is interposed between the two free ends of the airbag.
6. An airbag module as claimed in claim 5 in which the spacer means is a tubular spacer having a body defining - 20 - at least one gas flow passage, each gas flow passage being in communication at one end with an interior of the airbag and being located at an opposite end near to the or each gas port.
7. An airbag module as claimed in claim 6 wherein the canister has a like number of gas ports as there are gas flow passages in the tubular spacer.
8. An airbag module as claimed in claim 6 in which the tubular spacer defines a single gas flow passage which is in communication at one end with an interior of the airbag and is positioned at an opposite end near to the or each gas port.
9. An airbag module as claimed in any of claims 6 to 8 wherein the inflator is attached to the wall of the canister by one or more elongate fasteners each of which extends through respective apertures formed in the airbag * 20 and in the tubular spacer means. I... S...
10. An airbag module as claimed in claim 9 wherein the inflator clamps one free end of the airbag to the tubular spacer and the other free end of the airbag is clamped : 25 between the tubular spacer and the wall of the canister.

* * S.
11. An airbag module as claimed in claim 5 wherein the spacer means comprises of a number of spacers that are spaced apart to define respective gas flow passages therebetween.
12. An airbag module as claimed in claim 11 wherein there are first second and third spacers and a first gas flow passage is defined between the first and second spacers and a second gas flow passage is defined between the second and third spacers.

- 21 -
13. An airbag module as claimed in claim 11 or in claim 12 wherein the spacers are joined together by bridge members.
14. An airbag module as claimed in claim 13 when dependent upon claim 12 wherein the first spacer is joined to the second spacer by a first bridge member and the second spacer is joined to the third spacer by a second bridge member.
15. An airbag module as claimed in any of claims 11 to 14 wherein the canister has a like number of gas ports as there are gas flow passages.
16. An airbag module as claimed in any of claims 11 to wherein the inflator is attached to the wall of the canister by one or more elongate fasteners each of which extends through respective apertures formed in the airbag and in one of the spacers.

ae, 20 S..
17. An airbag module as claimed in any of claims 11 to 16 wherein the inflator clamps one free end of the airbag to S * the spacers and the other free end of the airbag is clamped between the spacers and the wall of the canister. S. * * .

*
18. An airbag module as claimed in any of claims 1 to *5S.

4 wherein the or each spacer means is a depression in the rear wall of the canister formed adjacent to each gas port so as to space the airbag away from the rear wall in the region of the gas port.
19. An airbag module as claimed in claim 18 wherein the free ends of the airbag are clamped to the rear wall of the canister by the inflator and the or each vent is formed in the airbag near to one of the free ends of the airbag.

- 22 -
20. An airbag module as claimed in claim 18 or in claim 19 wherein each depression extends across the width of the canister.
21. An airbag as claimed in claim 18 or in claim 19 wherein each depression surrounds a respective gas port.
22. An airbag module as claimed in claim 20 or in claim 21 wherein the inflator clamps the free ends of the airbag to the depressions in the rear wall
23. An airbag module as claimed in any of claims 18 to 22 wherein each vent is formed by an aperture in a wall of the airbag.
24. An airbag module comprising a canister for storing an airbag having free ends attached to a wall of the canister, an inflator located within the airbag for providing inflation gas during deployment of the airbag, at ::.: 20 least one gas port in the wall of the canister communicating with ambient air pressure and at least one vent in the airbag to vent gas during deployment of the airbag wherein each vent is positioned coincident with a respective gas *I.

* port so as to permit gas to escape from the airbag through the gas port to limit the pressure within the airbag during deployment and an alignment means is provided to maintain the alignment of each vent with the adjacent gas port.
25. An airbag module as claimed in claim 24 wherein the or each vent is located such that it is only exposed to the gases from the inflator when the airbag is partially deployed by being located at or near to the position of attachment of the airbag to the wall of the canister.
26. An airbag module as claimed in claim 24 or in claim 25 wherein the inflator is used to attach the airbag to the wall of the canister. -

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27. An airbag module as claimed in any of claims 24 to 26 wherein each vent is formed in a wall of the airbag.
28. An airbag module as claimed in any of claims 24 to 27 wherein each alignment means comprises of a tubular body portion for engagement with a respective vent and gas port and a circumferentially extending flange for abutment against an inner surface of the airbag.
29. An airbag module as claimed in claim 28 wherein each alignment means includes a fastening means to hold the alignment means in the respective gas port.
30. An airbag module as claimed in claim 29 wherein the fastening means comprises a number of flexible arms which are biased against a rear face of the wall of the canister so as to hold the alignment mean in position. S.

* 20
31. An airbag module as claimed in claim 29 wherein S...

the fastening means comprises a screw thread formed on the outer surface of the alignment means and a nut for * engagement with the screw thread. S..
32. An airbag module as claimed in any of claims 28 to ::.. 31 wherein the alignment means further comprises a tubular extension extending away from the circumferential flange in the opposite direction to the tubular body.
33. A motor vehicle having an airbag module as claimed in any of claims 1 to 23.
34. A motor vehicle having an airbag module as claimed in any of claims 24 to 32.
35. An airbag module substantially as described herein with reference to the accompanying drawing.

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36. A motor vehicle substantially as described herein with reference to the accompanying drawing. S. * S *. S *S.. *55* * S S a.. * * s Se * St.. S * * SS.