GB2413113A

GB2413113A - An air bag vent with a deformable membrane

Info

Publication number: GB2413113A
Application number: GB0408541A
Authority: GB
Inventors: Laurent Hellot; David Stow
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2004-04-16
Filing date: 2004-04-16
Publication date: 2005-10-19
Also published as: GB0408541D0

Abstract

An air-bag arrangement for use in a motor vehicle, which incorporates a vent. The vent has at least one first aperture (7 to 10) and at least one second aperture (2), and a chamber (11) being in fluid communication with the first aperture (7 to 10) and the second aperture (2) to define a gas flowpath from the first aperture (7 to 10) to the second aperture (2). The first aperture (7 to 10) is of smaller cross-sectional area than the second aperture (2). A deformable membrane (18) is positioned to deform into the chamber (11) when the gas pressure within the air-bag 24 exceeds a predetermined level, to restrict the flow of gas along the gas flowpath (27). Thus, the air-bag (24) remains inflated, as a heavy occupant moves against the air-bag (24) at a high speed, and the heavy occupant is prevented from passing through the space defined by the inflated air-bag (24) and striking part of the vehicle behind. The vent may comprise a hollow cylindrical tubualr housing (1), or a fabric flap (33 figures 5 to 7).

Description

DESCRIPTION OF INVENTION

"IMPROVEMENTS IN OR RELATING TO AN AIR-BAG ARRANGEMENT" THE PRESENT INVENTION relates to an air-bag arrangement, and more particularly relates to an air-bag arrangement to provide protection for an occupant of a vehicle in the event that an accident should occur.

It has been proposed previously to provide an air-bag arrangement for the protection of a vehicle occupant in the event that an accident should arise.

An air-bag arrangement can offer protection to an occupant of a vehicle during a crash situation, by rapidly inflating an air-bag adjacent to the occupant and in a position towards which the occupant is likely to be thrown as a result of the crash. In order to inflate an air-bag rapidly gas must be injected into it at a high pressure from a source such as a gas generator.

Once the air-bag has been inflated it must provide a cushioning effect, to gently decelerate the moving occupant, thus preventing injury. When the occupant initially comes into contact with the inflated air-bag, the occupant will compress the air-bag and the pressure within the air-bag will rise. It is l important that the gas pressure within the air-bag should not reach a very high level which may cause the occupant to bounce off the inflated air-bag.

In order to provide an air-bag with a desirable characteristic, it is well known to incorporate vents into the air-bag to release gas. Conventional air-bag vents are usually of a fixed size in order to allow an air-bag to deflate gently as a person of average size and weight moves against it.

A problem can occur if the occupant is of larger than average weight. If an occupant of larger than average weight moves rapidly against the inflated air-bag a large force will be exerted on the air-bag, causing the gas pressure within the air-bag to rise rapidly. The high pressure within the air-bag may cause substantial quantity of gas to be vented through the open vent.

In an extreme case so much gas may be vented that the air-bag begins to deflate and the occupant passes through the region occupied by the airbag, thus striking part of the vehicle behind the air-bag.

The present invention seeks to provide an improved air-bag arrangement.

According to the present invention, there is provided an air-bag arrangement comprising an air-bag having a vent, the vent incorporating at least one first aperture and at least one second aperture, a chamber being in fluid communication with the first aperture and the second aperture to define a gas flowpath from the first aperture to the second aperture, the first aperture being of smaller cross-sectional area than the second aperture, wherein a deformable membrane is positioned to deform into the chamber in response to a gas pressure within the air-bag in excess of a predetermined level, the deformed membrane acting to prevent or restrict the flow of gas along the said gas Towpath.

Preferably the vent incorporates a hollow cylindrical open ended tubular housing, with the interior of the housing defining the chamber, wherein the or each said first aperture is formed in the wall of the housing, and the said second aperture is defined by one open end of the housing.

Conveniently the other end of the housing incorporates a radially outwardly directed flange, a groove being defined in the flange, and a peripheral part of the membrane being fixed in the groove, the main part of the membrane extending across an open end of the chamber.

Advantageously said first aperture is formed in part of the air-bag and a second aperture is formed in part of the air-bag adjacent the said first aperture, the membrane extending across the second aperture, wherein an element is secured to the exterior of the air-bag to form a chamber extending over the said first aperture and the membrane, the end of the chamber closest to the membrane being open.

Preferably the element is a fabric flap.

Conveniently the element is secured to the exterior of the air-bag by stitching.

Advantageously the membrane is made of an elastically deformable material.

Preferably the membrane is made of a plastically deformable material.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a sectional view of part of an air-bag vent in accordance with a preferred embodiment of the invention, in a normal condition; FIGURE 2 is a sectional view of part of an air-bag vent in accordance with the preferred embodiment of the invention, in a high pressure condition; FIGURE 3 is a plan view of a partially fabricated airbag vent in accordance with a second embodiment of the present invention; FIGURE 4 is a plan view of the air-bag vent of Figure 3, in a fully fabricated form; FIGURE 5 is a sectional view through the air-bag vent of Figure 4, before the air-bag has been inflated; FIGURE 6 shows a sectional view of the air-bag vent of Figure 4, with the air-bag having been inflated; and FIGURE 7 is a sectional view through the air-bag vent of Figure 4, after the air-bag has been inflated, with a heavy occupant moving rapidly against the inflated air-bag. s

Figure 1 shows a vent in part of an air-bag arrangement. The vent incorporates a hollow cylindrical open ended tubular housing 1. The lower end of the housing 1, as shown in Figure 1, defines an aperture 2. At a position further along the length of the housing 1, and above the aperture 2, a pair of mounting brackets 3,4 extend radially outwardly from the outer surface of the housing 2. The mounting brackets 3,4 each incorporate an aperture 5,6.

At a position further still along the length of the housing 1 apertures7tolO extend through the wall of the housing 2. A chamber 11, which is defined by the interior of the housing 1, provides fluid communication between the apertures 7 to 10 and the aperture 2. A gas flowpath is thus formed from the exterior of the housing, into the chamber 11, and out from the lower end of the chamber 11, through the aperture 2.

The upper end of the housing 1 has a radially outwardly directed flange 12. The upper surface of the flange 12 defines a circular recess 13 and a peripheral groove 14 extends into the flange 12 around the edge of the circular recess 13. The upper open end of the chamber 11 forms an aperture 15, located towards the centre of the circular recess 13.

A relatively thin planar collar 16 extends radially outwardly from the periphery of the flange 12, outwardly beyond the groove 14.

The groove 14 receives a bead 17 which forms a peripheral part of a deformable rubber membrane 18. In this preferred embodiment the bead 17 is glued into the recess 14, but may alternatively be fixed within the groove by another technique such as welding. The membrane 18 is made of a relatively thin elastic material such as rubber, in particular a silicone rubber, but may alternatively be formed of a plastically deformable material such as metal. The membrane 18 is circular and is positioned so that the lower surface of the membrane 18 is in contact with the upper surface 13 of the recess 13 within the flange 12. The main part of the membrane 18 extends across an open end of chamber 11.

A holding plate 19 is attached to the upper surface of the planar collar 16 of the flange 12. The holding plate 19 is a circular disk with an aperture 20 at its centre. The aperture 20 is of larger diameter than the aperture 15 at the upper end of the chamber 11, but is of smaller diameter than the diameter defined by the groove 14. Part of the holding plate 19 sits over the bead 17, to help retain the bead 17 within the groove 14. The aperture 20 in the holding plate 19 allows gas to flow through the aperture 20 to come into contact with the upper surface of the membrane 18.

The housing 1 is mounted in position on part of a vehicle body 21 using bolts 22 and 23. Part of an air-bag 24 is sealingly retained between the lower side of the mounting brackets 3 and 4 and part of the air-bag module housing21 which may be secured to the vehicle body. Nuts 25 and 26 are attached to the lower ends of bolts 22 and 23 to ensure that the housing 1 is securely attached to part of the vehicle air-bag module housing 21, whilst also retaining the air-bag 24 in position.

In the event that the vehicle is involved in a crash, the air-bag 24 is inflated. Once the air-bag 24 has been inflated, gas is vented from within the air-bag 24 out through apertures 7 tolO, along the path generally indicated by arrows 27.

The deceleration of the vehicle in the crash situation will cause the occupant of the vehicle to move against the inflated air-bag 24. As an occupant of the vehicle moves against the inflated air-bag 24 the gas pressure within the air-bag 24 rises. The rise in gas pressure within the air-bag 24 results in gas passing more rapidly through apertures 7 to 10 in the housing 1 and out through the aperture 2 in the base of housing 1. The gas escapes from the vent and the air-bag 24 gradually deflates, thus cushioning the occupant. It is important that the air-bag 24 deflates as the occupant moves against it, to prevent the occupant from bouncing off the inflated air-bag 24.

In a severe crash situation, such as a high speed crash, the occupant of the vehicle will move rapidly against the inflated air-bag 24. In this situation, if the occupant of the vehicle is of larger than average weight, the occupant will exert a substantial force on the inflated airbag 24. The large force exerted lS by the heavy occupant moving rapidly will cause the gas pressure within the air-bag 24 to rise to a high level in excess of a predetermined level very quickly.

The high gas pressure within the air-bag 24 results in a high gas pressure being present on the upper side of the membrane 18. As the apertures 7 to 10 together are of relatively smaller cross-sectional area as compared with the cross-sectional area of the aperture 2 in the base of the housing 1, the gas within the chamber 11 can escape from the chamber 11 through aperture 2 at a higher rate than it is introduced into the chamber 11 through the apertures 7 to 10. Thus the gas pressure within the chamber l l will be lower pressure than the gas pressure within the inflated air-bag 24. When the gas pressure within the air-bag 24 rises very quickly, as the air-bag 24 is subjected to a force from the heavy occupant, a very high pressure is exerted on the upper side of membrane 18 and the upward force exerted on the lower side of the membrane 18 by the gas within the chamber 1 1 is much less than the force exerted by the high pressure gas inside the air-bag 24 on the upper side of the membrane 18.

The large force acting on the upper side of the membrane 18 causes the membrane 18 to deform and extend into the chamber 1 1, in response to the gas pressure within the air-bag being in excess of a predetermined level. As the membrane 18 extends into the chamber 11 it covers the apertures 7 tolO in the walls of the housing 1. Once the membrane 18 has fully deformed it covers all of the apertures 7 to 10 in the housing 1, as shown in Figure 2. The membrane 18 thus prevents or restricts the flow of gas along the gas flow path 27.

Whilst the membrane 18 covers the apertures 7 to 10, gas within the air bag 24 can no longer escape through the apertures 7 to 10 and out into the body of the vehicle. The gas pressure within the air-bag 24 is thus maintained. This prevents the heavy occupant from passing through the space defined by the inflated air-bag 24 and striking the vehicle behind.

Once the inflated air-bag 24 has slowed the movement of the heavy occupant, the gas pressure within the air-bag 24 will fall as the force exerted by the occupant decreases.

In this preferred embodiment the membrane 18 is made of rubber, and when the gas pressure within the air-bag 24 falls below a predetermined level, the membrane 18 will elastically return to its normal shape, parallel to the upper surface 13. As the membrane 18 returns to its normal shape the apertures 7 to will become uncovered, and the gas within the air-bag 24 will be able to be vented, thus deflating the air-bag 24.

Alternatively, if the membrane 18 is made of a plastically deformable material, such as a metal foil, the membrane 18 will remain in its deformed shape as shown in Figure 2. In this case, the apertures 7 to 10 will remain covered by the membrane 18, and the gas pressure within the air-bag 24 will be maintained.

Although the preferred embodiment incorporates a vent which is formed from a housing 1, the vent may in an alternative embodiment be formed using fabric. In order to produce such a vent, initially an aperture 28 is formed in part of an air-bag 29, as shown in Figure 3. A second aperture 30, of larger diameter than the aperture 28, is formed in part of the air-bag 29, adjacent the first aperture 28. A bead 31 of a deformable rubber membrane 32 is fixed to the air-bag 29, by a process such as welding or gluing, so that the membrane extends across and seals the second aperture 30.

An element in the form of a fabric flap 33 is placed over the aperture 28 and the membrane 32. The flap 33 is generally formed from a rectangular section 34 with one end of the rectangular section 34 having a semicircular end 35. In this embodiment, the flap 33 is stitched to the air-bag 29 along the upper and lower edges of the rectangular section 34 and along the semi-circular end 35, as shown in Figure 4. The flap 33 may alternatively be secured to the air bag by another means such as by gluing. The semi-circular end 35 is located adjacent the smaller aperture 28. The end of the flap 33, opposite the semi circular end 35, is left free and unstitched to form an open end 36 of a chamber 37, defined between the fabric of the flap 33 and the air-bag 29. The membrane 32 is located between the smaller aperture 28 and the open end 36. The chamber37 extends over the first aperture 28 and the membrane 32, and provides fluid communication between the aperture 28 and the open end 36.

When the air-bag 29 is in an uninflated state, the flap 33 lies generally flat against the upper surface of the air-bag 29, as shown in Figure 5.

In the event that the vehicle is involved in a crash, the air-bag 29 is inflated. Once the air-bag 29 has been inflated, gas is vented from within the air-bag 29 through the aperture 28. As the gas from within the air-bag 29 escapes through the aperture 28 the force exerted by the escaping gas moves the flap 33 away from the outer surface of the air-bag 29, as shown in Figure 6.

The gas escaping through the aperture 28 may thus flow through the chamber37, along a Towpath 38, and past the membrane 32 out into the surrounding environment through the open end 36 of the chamber 37. The gas within the air-bag 29 is thus vented and the air-bag 29 is allowed to gently deflate, cushioning the vehicle occupant.

In a severe crash situation, such as a high speed crash, where a larger than average weight occupant moves rapidly against the inflated air-bag 29, the gas pressure within the air-bag 29 will rise to a high level in excess of a predetermined level very quickly.

The high gas pressure within the air-bag 29 will result in a high gas pressure being present on the lower side of the membrane 32, as shown in Figure 6. As the aperture 28 is of smaller cross-sectional area than the open end 36 of the chamber 37, gas can escape from the chamber 37 through the open end 36 at a higher rate than it is introduced into the chamber 37 through the aperture 28. Thus, the gas pressure within the chamber 37 will be lower pressure than the gas pressure within the inflated air-bag 29. When the gas pressure within the air-bag rises very quickly, as the air-bag is subjected to a substantial force by a heavy occupant, a very high pressure is exerted on the lower side of the membrane 32. The downward force exerted on the upper side of the membrane 32 by the gas pressure within the chamber 37 is much less than the upward force exerted by the very high pressure gas inside the air-bag 29 on the lower side of the membrane 32.

The large force acting on the lower side of the membrane 32 causes the membrane 32 to deform and extend into the chamber 37 as shown in Figure 7, in response to the gas pressure within the air-bag 29 being in excess of a predetermined level. As the membrane 32 extends into the chamber 37 it restricts or prevents the flow of gas along flowpath 38. The gas pressure within the air-bag 29 is thus maintained. This is intended to prevent the heavy occupant from passing through the space defined by the inflated airbag 29 and striking part of the vehicle behind the air-bag.

In this alternative embodiment the membrane 32 is made of rubber, and when the gas pressure within the air-bag 29 falls below a predetermined level, the membrane 32 will elastically return to its normal shape, parallel to the fabric of the air-bag 29. As the membrane 32 returns to its normal shape, the flow of gas through the chamber 37 will no longer be restricted or prevented and gas will therefore be vented from within the air-bag 29, allowing it to deflate.

The membrane 32 may alternatively be made of a plastically deformable material, such as metal foil. In this case, the membrane 32 will remain in its deformed state, and will continue to restrict the gas Towpath 38 through the chamber 37, thus maintaining the gas pressure within the airbag 29.

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.

Claims

CLAIMS: 1. An air-bag arrangement comprising an air-bag having a vent, the

vent incorporating at least one first aperture and at least one second aperture, a chamber being in fluid communication with the first aperture and the second aperture to define a gas Towpath from the first aperture to the second aperture, the first aperture being of smaller cross- sectional area than the second aperture, wherein a deformable membrane is positioned to deform into the chamber in response to a gas pressure within the air-bag in excess of a predetermined level, the deformed membrane acting to prevent or restrict the flow of gas along the said gas Towpath.
2. An air-bag arrangement according to Claim 1, wherein the vent incorporates a hollow cylindrical open ended tubular housing, with the interior of the housing defining the chamber, wherein the or each said first aperture is formed in the wall of the housing, and the said second aperture is defined by one open end of the housing.
3. An air-bag arrangement according to Claim 2, wherein the other end of the housing incorporates a radially outwardly directed flange, a groove being defined in the flange, and a peripheral part of the membrane being fixed in the groove, the main part of the membrane extending across an open end of the chamber.
4. An air-bag arrangement according to Claim 1, wherein said first aperture is formed in part of the air-bag and a second aperture is formed in part of the air-bag adjacent the said first aperture, the membrane extending across the second aperture, wherein an element is secured to the exterior of the air-bag to form a chamber extending over the said first aperture and the membrane, the end of the chamber closest to the membrane being open.
5. An air-bag arrangement according to Claim 4, wherein the element is a fabric flap.
6. An air-bag arrangement according to Claim 4 or Claim 5, wherein the element is secured to the exterior of the air-bag by stitching.
7. An air-bag arrangement according to any one of the preceding Claims, wherein the membrane is made of an elastically deformable material.
8. An air-bag arrangement according to any one of Claims 1 to 6, wherein the membrane is made of a plastically deformable material.
9. An air-bag arrangement substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.
10. An air-bag arrangement substantially as herein described with reference to and as shown in Figures 3 to 7 of the accompanying drawings.
11. Any novel feature or combination of features disclosed herein.