PASSIVE TRAINTS The present invention relates to passive restraints for use in motor cars and, more particularly, to the type of passive restraint which comprises a bag which automatically inflates in front of the driver or a passenger under crash conditions.
Such an inflatable bag is known as a "crash bag". The crash bag is provided with vent panels which break when the passenger impacts with the bag so that the gas used to inflate the bag can escape allowing the bag to deflate in response to the impact of the passenger and thereby safely brake the motion of the passenger and limit injury to him.
In a crash situation in which the crash bag is inflated, there is normally also a considerable risk of fire in the engine compartment. Various types of fire extinguishing systems for automatic operation have been proposed for use in private cars and other vehicles.
Although passive restraints and fire extinguishing systems provide increased safety to the vehicle user, the addition of these systems to cars considerably increases the overall cost. The proliferation of independent safety systems may also give rise to problems in finding the necessary space for all the different components.
The present invention seeks to solve these technical problems by providing a vehicle crash safety system comprising a bag stored in a deflated condition, a source of fire extinguishing gas, and means for connecting the gas source to the bag to inflate the -bag upon actuation of a crash sensor, the bag being provided with vent means for allowing gas to escape therefrom whenever the gas pressure exceeds a predetermined threshold, said vent means being connected to conduct the vented gas to a compartment of the vehicle where there may be a fire risk.
Such a system is advantageous in that it provides the functions of fire suppression and passive restraint in one system using a single gas source. The fire extinguishing gas is preferably Halon 1301 since this is a low boiling point fire extinguishing gas and, therefore, provides a relatively large volume of gas at normal temperatures from a relatively small cylinder of compressed gas. In a preferred embodiment the vented gas is conducted to the engine compartment and/or the fuel tank.
For safety reasons, it is necessary to provide a gas cylinder capable of producing sufficient gas to inflate the bag at the lowest possible operating temperature, for example -200C. This means that there is normally an excess of gas in the cylinder over that necessary to inflate the bag at temperatures in excess of the minimum operating temperature. In the system of the present invention, since the vent means are connected to a fire risk area, this excess gas is fed via the bag and vent means to the fire risk area resulting in a highly inert atmosphere which will prevent initiation of a fire or extinguish any fire that has started as a result of the crash. The risk of fire when the crash takes place at the minimum operating temperature is, of course, considerably reduced.
In a preferred embodiment, secondary means are provided for conducting gas from the gas source directly to a compartment of the vehicle where there may be a risk of fire. Such means may comprise a manual override operable by the driver when a fire is detected, or an automatic fire sensor in the vehicle compartment at risk. In this way an inerting atmosphere can be produced in such a compartment under conditions other than crash conditions. Therefore, the system can provide the benefits of independent passive restraint and fire extinguishing systems as previously proposed.
A vehicle crash safety system will now be described, by way of example only, with reference to the accompanying diagrammatic drawing, which shows the system, partly in section and partly diagrammatically, mounted in the steering column of a vehicle.
The crash safety system illustrated has a bag 2 which is stored in deflated form in the upper part of a steering column 4. Although the embodiment specifically described is intended for the driver, a similar system can be provided for any passenger in the front or rear of the vehicle, in which case the deflated bag will be stored in an appropriate place. An opening of the bag is connected to the outlet of a valve 6 which is connected to a compressed gas cylinder 8 containing Halon 1301. The operation of the valve 6 is controlled by a crash sensor 10 which opens the valve 6 to allow the bag 2 to be inflated by the gas contained within the cylinder 8 on detection of a crash condition.
As so far described, the system is a conventional passive restraint system for inflating a crash bag in crash conditions. Such systems are well known and therefore these components will not be described in any further detail herein. It will be appreciated that the crash sensor 10 may be in accordance with any previous proposal. In particular, it may contain two independent trip switches, for example one for detecting deceleration and another for detecting compression of a part of the vehicle. The valve 6 is not opened unless both switches have been operated in order to minimise the risk of false alarms which could, in themselves, lead to a considerable hazard to the driver if the bag were to inflate unexpectedly during normal driving conditions.
When the valve 6 is opened to allow gas to enter the bag 2, the bag is pushed out through an opening in the centre of the steering wheel 12 and inflates between the driver and the steering wheel so to provide a brake on the driver's movement towards the steering column and windscreen. The inflated position of the bag is shown in dotted lines at 14.
The bag 2 is provided with vent means 16 at its rear end adjacent the opening to which the outlet of the valve 6 is connected. These vent means typically take the form of panels which break to allow gas to escape when the pressure inside the bag relative to the pressure outside in the steering column exceeds a predetermined differential pressure which is set by the construction of the panel itself. This excess pressure in the bag arises in the first case when the gas cylinder has provided sufficient gas to fill the bag at the operating temperature and the cylinder continues to supply gas because it is not yet empty, and in the second case when the driver strikes the bag deforming the bag and causing a pressure wave in the gas inside the bag. The gas escaping from the vent means 16 is conducted along conduit 18 to a spray bar 20 in the engine compartment.It will be appreciated that part of this conduit 18 may be defined by the whole interior of the steering column.
The gas cylinder 8 is provided with a second valve 22 which has an outlet connected directly into the conduit 18. This valve 22 is operated under the control of a manual override switch or a heat detector in the engine compartment 24.
When the valve 22 is opened, gas from the bottle 8 is vented directly into the conduit 18 to the spray bar so that an inerting atmosphere is rapidly produced in the engine compartment.
The gas contained in the bottle 8 is preferably Hal on 1301 or another low boiling point fire extinguishing gas.
Normally dedicated passive restraint systems use nitrogen gas. Nitrogen may be used in the system described provided a sufficient quantity of the gas is available to provide an inerting atmosphere in the engine compartment. An inerting gas generated by pyrotechnic means could also be used as a gas source in place of or in addition to the compressed gas cylinder 8 shown.
Since Hal on 1301 escaping from a compressed gas cylinder cools on expansion, an auxiliary pyrotechnic gas generator can be used to replace some of this heat loss to ensure the bag is filled as quickly as possible. A pyrotechnic nitrogen generator is most suitable for this purpose as the gas produced is inert.