An air-bag is disclosed which incorporates regions of fabric which define a mouth, the mouth being mounted to an air-bag housing such that at least part of the mouth is mounted to the housing by a mount initially positioned to hold an edge part of the fabric defining the mouth adjacent the housing. The mount is capable of movement to move to a position in which the edge of the fabric defining the mouth is spaced from the housing to define a vent between the edge of the mouth and housing.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to GB 0309215.2, filed Apr. 23, 2003 which is currently pending.

BACKGROUND OF THE INVENTION

The present invention relates to an air-bag, and more particularly relates to an air-bag to be mounted on a motor vehicle, the air-bag including a vent.

It is known that it is desirable to provide an air-bag with a vent. The vent may perform one or more various functions. The vent may be a permanently open vent, provided to ensure that an air-bag will deflate slightly when impacted, for example, by an occupant of a vehicle when the vehicle is involved in an accident. This helps prevent the occupant of the vehicle from simply bouncing back away from the air-bag and provides the air-bag with a desirable energy-absorbing characteristic.

Controllable vents may be provided on an air-bag, the vents being opened in response to specific signals or specific situations. A controllable vent may, consequently, open when a pressure in excess of a predetermined threshold is experienced within an air-bag. A vent may also be opened in response to a specific situation such as a seat being occupied by a very heavy occupant, or the occupant of a seat leaning forwardly so as to be located close to the air-bag.

The present invention seeks to provide an improved air-bag which incorporates a vent.

According to the present invention there is provided an air-bag, the air-bag incorporating regions of fabric which define a mouth, the mouth being mounted to an air-bag housing, at least part of the mouth being mounted to the housing by a mount initially positioned to hold an edge part of the fabric defining the mouth adjacent the housing, the mount being capable of movement to move to a position in which the edge of the fabric defining the mouth is spaced from the housing to define a vent between the edge of the mouth and the housing.

Preferably the mount comprises a rigid element, the element having two spaced-apart substantially linear arms, one arm of the element being received within a retainer slot formed in the housing so as to be pivotal about its axis, the other edge of the loop being connected to the edge of the fabric.

Advantageously a release mechanism is provided adapted initially to retain the mount in a first predetermined position, and to release the mount to permit the mount to move.

The release mechanism may be a frangible device which breaks when a predetermined pressure is present within the air-bag.

The release device may also be device which releases the mount in response to a predetermined signal from a sensor.

Advantageously the air-bag takes the form of a passenger air-bag for a front-seat passenger of a motor vehicle.

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:

Whilst the invention is being described specifically with reference to a passenger air-bag intended for use by a front-seat passenger, the invention might find applications in other air-bags for use in other situations.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially toFIG. 1, a housing1is shown which is intended to be mounted within the dashboard of a motor vehicle with the housing containing an air-bag which, when inflated, will be located in front of a front seat passenger in the vehicle. The housing1includes a generally cylindrical rear region2which contains a cylindrical gas generator3. The interior workings of the gas generator3are not shown in the drawings for the sake of simplicity of illustration. The interior of the housing1includes an integral diffuser4. The diffuser4helps define a chamber to contain the gas generator3. The diffuser4is provided with apertures5to permit the gas generated by the gas generator3to escape from the diffuser4.

Projecting forward from the generally cylindrical region2of the housing1is a “scoop”-shaped region6which receives a folded air-bag.

As illustrated inFIG. 2, The air-bag is provided with two fabric regions7,8, each provided with an edge bead9,10. The beads are received within bead-receiving slots11,12formed on the housing1close to the cylindrical region2thereof. The air-bag may then be folded and stored within the scoop-shaped region6. The air-bag is spaced from the gas generator3, thus minimising the risk of the air-bag burning when the gas generator is actuated, and an open mouth of the air-bag, defined between the fabric portions7and8is adjacent the apertures5and the diffuser4so that the air-bag may be readily inflated.

The arrangement as discussed above is conventional.

In an air-bag in accordance with the invention, one element of fabric which defines the mouth of the air-bag is mounted to the air-bag housing by a mount which is capable of moving away from the housing to open a vent between the edge of the bag and the housing.

Turning now toFIG. 3, one edge of the sheet of fabric7of an air-bag in accordance with the invention is illustrated. Instead of the edge being provided with a linear bead (such as bead9), the edge is provided with a mount element in the form of a wire loop13. The wire loop13has a first arm14which is received within a stitched pocket15defined at the edge of the layer of fabric7and has a second arm16, parallel with the first arm14, which is spaced from the first arm14.

When the air-bag in accordance with the invention is mounted to the housing1as shown inFIG. 1, the second arm16of the loop13is inserted in the bead-receiving slot11, as shown inFIG. 4, and the loop13is caused to lie adjacent part of the housing so that the first arm14is located towards the interior of the housing, with the fabric7lying across the bead-receiving slot11. The situation is shown quite clearly inFIG. 5.

It is to be appreciated that the air-bag still presents an open mouth adjacent the apertures5of the deflector4so that gas from the gas generator will flow through the mouth of the air-bag and inflate the air-bag.

On inflation of the air-bag, when the pressure within the air-bag reaches a predetermined level, the force applied by the fabric7to the loop13is sufficient to cause the loop13to rotate about the axis of the arm16. This is shown inFIG. 6. The loop is rotating in the direction of the arrow A. The loop continues to rotate until the arm14is located on the exterior of the housing, with the result that the loop13itself forms an open vent17through which gas from the interior of the air-bag may escape.

The situation is shown clearly inFIG. 8.

Referring now toFIG. 9, the housing1is shown together with the air-bag having the upper and lower fabric layers. The upper layer ofFIG. 9is connected to the housing by means of a loop13, and the lower layer of fabric is connected to the housing by means of a bead10which is equivalent to the bead10described inFIG. 2.

A release device18is provided which serves initially to retain the loop13in its initial position. The release device18may be a frangible element adapted to release the loop13when sufficient force is applied thereto through the fabric region7, so that the vent17does not open prematurely, or when there is an insufficient level of pressure present within the air-bag. The release device18may alternatively release the loop13in response to a signal from a sensor, the sensor, for example, being a sensor which senses the weight of a seat occupant, or a sensor which senses the position of the occupant. It is most desirable to have a vent which is open in a passenger air-bag if the passenger is leaning forwards or “out of position” when the air-bag is deployed.

FIG. 10shows the air-bag ofFIG. 9when the release device18has released the loop13and the loop13has moved to the position in which the vent17is open.