Abstract:
An air-bag arrangement incorporating an air-bag ( 6 ) and means adapted to inflate the air-bag, so that the air-bag occupies a position generally in front of an occupant ( 2 ) of a front seat of the vehicle, and between the occupant ( 2 ) of the front seat of the vehicle and the windscreen or windshield ( 5 ) of the vehicle, that part of the air-bag ( 6 ) located to contact the interior of the windshield ( 5 ), when the air-bag ( 6 ) is inflated being provided with gas outlet means to inject gas, under pressure, between part of the air-bag and the inside surface of the windscreen or windshield ( 5 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an air-bag arrangement, and more particularly relates to an air-bag arrangement provided in a motor vehicle to give protection to an occupant of a front seat of the vehicle, such as the driver or a front seat passenger of the vehicle. 
     2. Description of the Prior Art 
     It has been proposed previously to provide an air-bag adapted to be inflated in the event that an accident should arise, the inflated air-bag being located in front of the driver or front seat passenger in a motor vehicle, to provide protection for the driver or passenger. A problem with such air-bags is that, in certain situations, when the air-bag has been deployed and the occupant moves forwardly towards the air-bag, as a consequence of deceleration of the vehicle during an accident, the neck of the occupant of the vehicle may be moved rearwardly, relative to the torso, thus injuring the occupant of the vehicle. The present invention seeks to provide an improved air-bag arrangement. 
     SUMMARY OF THE INVENTION 
     According to this invention there is provided an air-bag arrangement in a motor vehicle, the air-bag arrangement incorporating an air-bag initially stored within a housing, and means adapted to inflate the air-bag, so that the air-bag, when inflated, occupies a position generally in front of an occupant of a front seat of the vehicle, and between the occupant of the front seat of the vehicle and the windscreen or windshield of the vehicle, the air-bag being provided with a first region adapted to contact or lie immediately adjacent the interior of the windshield when the air-bag is inflated, and a second region located between the first region and the housing, the first region being provided with gas outlet means adapted to eject gas, from the interior of the air-bag, under pressure, to points between the first region of the air-bag and the inside surface of the windscreen or windshield. 
     Preferably the gas outlet means comprise a plurality of apertures in the air-bag providing a communication between the interior of the air-bag and the exterior of the air-bag. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a diagrammatic side view illustrating an air-bag, following deployment thereof, at a position in front of a front seat passenger in a motor vehicle, 
         FIG. 2  illustrates the passenger impacting with the air-bag, 
         FIG. 3  illustrates the situation that can arise with a prior art air-bag shortly after the occupant has impacted with the air-bag, 
         FIG. 4  is a perspective view of a motor vehicle provided with an air-bag in accordance with the invention, with the air-bag in the deployed state, and 
         FIG. 5  is a view, corresponding to  FIGS. 1 to 3 , illustrating the situation that exists shortly after the occupant of the vehicle has impacted with the inflated air-bag of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1  of the accompanying drawings, an interior part of a motor vehicle is illustrated. A seat  1 , such as the front seat, is provided, and a passenger  2  is located on the front seat. The passenger is retained in an initial position by a seat-belt  3 . The vehicle is provided with a dashboard  4  and a windscreen or windshield  5 . In  FIG. 1 , an air-bag  6 , of a conventional design, is illustrated, the air-bag having been deployed from the dashboard  4  of the vehicle, as is conventional. The dashboard contains an air-bag housing in which the air-bag is stored before inflation. The inflated air-bag  6  is thus located between the passenger  2  and the dashboard  4  of the vehicle. The air-bag  6  is also located between the occupant  2  and the windscreen  5 . It is normal that a section of the air-bag is resting against the windscreen  5 . 
       FIG. 1  thus illustrates the situation that exists shortly after a frontal impact has been detected, and the air-bag  6  has been deployed. 
     Following the detection of the frontal impact and the initial deployment of the air-bag the vehicle will be decelerated, but the occupant  2  will continue to move forwardly, because of the inertia of the torso  7  and head  8  of the occupant. As the occupant continues to move forwardly, the seat-belt  3  will stretch and the torso  7  will impact with the inflated air-bag  6  and the head  8  will also impact with the inflated air-bag  6 . This is the situation shown in  FIG. 2 . The air-bag, when this stage is reached, will be fully inflated. Now a substantial area  9  of the forward section  13  of the air-bag will be pressed against the windscreen  5  located above the dashboard  4 , whilst a lower portion  10  of the air-bag will be pressed against the torso  7  of the occupant  2  of the seat  1  of the vehicle. 
     In a conventional air-bag, because the large surface area  9  is pressed against the windshield  5 , there is substantial friction between the area  9  and the windshield  5 , and thus the upper part of the inflated air-bag  6  is held stationary in the position that it occupies when inflated, even if subjected to a force that tends to move the air-bag. 
     The torso  7  of the occupant has a substantial momentum or inertia, and as the vehicle continues to decelerate, the torso  7  moves forwardly relative to the vehicle, compressing the inflated air-bag  6 , moving the portion  10  of the air-bag which is at a position remote from the area  9  forwardly. The load on the bag is increased and the pressure on the windscreen is increased thereby. The head  8 , of the occupant, does not have such a great inertia, and the head  8  of the occupant engages an upper part  11  of the air-bag which is very close to the region which is held stationary because of the friction existing between the area  9  and the windshield  5 . Thus the head  8  tends to be kept relatively stationary, whilst the torso  7  is permitted to move forwardly. This leads to a rearward flexing of the neck of the occupant  2  of the seat  1 , as can be seen in  FIG. 3 . This is undesirable. 
     Turning now to  FIG. 4 , it is to be appreciated that in the described embodiment of the invention, the air-bag  6  is provided, within the region  9 , that is to say the region that is to be pressed against the windshield  5  on inflation of the air-bag  6 , with a plurality of small apertures  12 . The small apertures  12  provide a communication between the interior of the air-bag and the exterior of the air-bag and thus permit the exit of gas from the interior of the air-bag. The gas is directed towards the inner surface of the windshield  5  and is consequently injected between the surface of the air-bag and the inner surface of the windscreen or windshield  5 . This tends to ensure that the air-bag  6  is biased away from the windshield  5 . When the pressure in the bag is increased by the occupant moving into the bag more gas will be forced out through the apertures  12 . The effect is, in some respects, similar to that of “hovercraft”. The high pressure gas ejected from the air-bag between the air-bag and the windscreen or windshield tends to separate the air-bag from the windscreen or windshield which is illustrated by the space  14 , thus at least reducing the friction between the airbag and the windscreen or windshield. In a typical situation because the area  9  of the air-bag  6  is spaced slightly from the windshield  5 , there is no friction or grip between the air-bag  6  and the windshield  5 . 
     To obtain a best possible reduction of the friction with a minimum of gas leaving the bag, the openings in the area  9  can be arranged asymmetrically, for example, by larger openings in the center or by the openings  12  arranged closer to each other in selected areas. 
     Thus, as can be seen from  FIG. 5 , when the torso  7  and head  8  of the occupant  2  of a seat  1  in a vehicle provided with an air-bag  6  in accordance with the invention impacts with the air-bag, the upper part of the air-bag actually moves forwardly and downwardly in response to the pressure applied thereto by the head  8  of the occupant  2 . The area  9  of the air-bag, thus “slides” across the interior surface of the windscreen or windshield  5 . Therefore the risk of the neck of the occupant of the vehicle flexing rearwardly is substantially minimised. 
     Whilst the invention has been described with specific reference to an air-bag provided to protect a front seat passenger in a motor vehicle, it is to be appreciated that in an alternative embodiment of the invention, the air-bag may be intended to protect the driver of the vehicle. In such a situation the air-bag would be initially mounted within the hub of the steering wheel of the vehicle. 
     In this specification the term “comprising” means “including or consisting of” and the term “comprises” means “includes or consists of”.