GB2281429A - A gas generator for a vehicle safety system. - Google Patents

Abstract

A sensor 1, which is adapted to sense an accident, provides an output in the form of a shock to be transmitted along shock tubes 3, 5 to two gas generators 2, 4. The shock tube 5 leading to one gas generator 4 incorporates a delay 6. Thus when an accident is sensed, one gas generator 2 is activated before the other gas generator 4. The two gas generators may inflate the same air-bag or may inflate separate air-bags or may activate separate safety devices in the motor vehicle. <IMAGE>

Description

DESCRIPTION OF INVENTION "IMPROVEMENTS IN OR RELATING TO A GAS GENERATOR" ARRANGEMENT" THE PRESENT INVENTION relates to a gas generator arrangement and more particularly relates to a gas generator arrangement for use in connection with a safety device provided in a motor vehicle.

Various safety devices have been provided for use on a motor vehicle which incorporate the use of a gas generator. One type of device is an air-bag which is inflated with gas from the gas generator and another type of device is a seat-belt pre-tensioner which tensions a seat-belt when a piston moves along a cylinder in response to the generation of gas by a gas generator.

It has been proposed previously to provide an electrical triggering arrangement for a gas generator, but more recently a non-electric triggering arrangement has been proposed including a sensor adapted to sense an impact on the vehicle and generate a shock which is transmitted, through a shock tube to the igniting squib of a pyrotechnic gas generator.

The present invention seeks to provide an improved gas generator arrangement utilising a non-electric sensor.

According to this invention there is provided a gas generator arrangement for use with a safety system in a motor vehicle, the gas generator comprising a sensor adapted to sense an impact on the vehicle, or deceleration in excess of a predetermined limit and adapted to provide an output transmissible in the form of a shock along a shock tube, the sensor being connected, by two or more respective paths defined at least partly by shock tube means to two or more gas generators, one or more of the paths being associated with a pyrotechnic delay in series with the shock tube so that each gas generator receives the shock wave from the sensor at a different respective time.

Preferably one gas generator is connected directly to the sensor by a shock tube, and the or each other gas generator is connected to the sensor by means of a respective shock tube which is associated with a respective delay.

Conveniently the gas generators are adapted to inflate a single air-bag.

Alternatively the gas generators are adapted to activate separate safety devices. The separate safety devices may both comprise air-bags or may comprise different types of safety device. Thus, one gas generator may be adapted to activate an air-bag and another gas generator may be adapted to activate a pre-tensioner.

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 block diagram of one embodiment of the invention, and FIGURE 2 is a diagrammatic representation of one embodiment of the invention.

A gas generator arrangement in accordance with the invention comprises a sensor 1 adapted to sense an impact on a vehicle and to provide an output in the form of a pulse to be transmitted along a shock tube. One example of a sensor of this type is shown in British Patent Publication No. 2255535 but other equivalent types of sensor exist. Further types of sensor may generate a shock in a shock tube in response to a deceleration in excess of a predetermined limit.

The sensor is connected directly to a first gas generator 2 by a first path comprising a shock tube 3 which may of the type sold under the Trade Mark NONEL. The shock tube 3 is connected to the gas generator in such a way that when a shock travels along the shock tube it activates the gas generator.

A shock from the sensor 1 will travel very swiftly through the shock tube 3 to the gas generator 2 and thus the gas generator 2 will be triggered virtually immediately after a crash is sensed by the sensor 1.

The sensor 1 is connected in a similar manner to a second gas generator 4 by a second path comprising of a length of shock tube 5, such as that sold under the Trade Mark NONEL. The length of shock tube 5 incorporates a pyrotechnic delay line 6. The effect of the pyrotechnic delay line 6 is to delay the shock wave travelling along the shock tube 5 for a predetermined period of time.

It will thus be appreciated that whereas the gas generator 2 will be triggered by a shock wave present in the shock tube 3 virtually immediatel when the sensor 1 senses an accident, the gas generator 4 will not be triggered until after a predetermined delay.

The gas generators 2 and 4 may be used in connection with the same safety device or in connection with different safety devices within a motor vehicle. It is thus envisaged that the gas generator 2 and the gas generator 4 may both be utilised to inflate the same airbag. The gas generator 2 may be adapted to provide a flow of gas at a relatively low flow rate, as is appropriate when the bag only has a small volume, to accomplish the initial part-inflation of the bag, and the gas generator 4 may be adapted to supply gas at a much higher flow rate, thus swiftly completing the inflation of the bag once it has been partly inflated by the gas generator 2. It has been found inappropriate to provide a high rate of flow of gas to an air-bag when the air-bag is fully un-inflated, since this may cause the bag to tear in an undesirable manner. It is envisaged that the provision of two gas generators adapted firstly to partially inflate the bag and secondly to complete inflation in a very swift manner, will prove to be very advantageous.

However, it is equally envisaged that the gas generator 2 may be associated with one air-bag in one predetermined position, and the gas generator 4 may be associated with another air-bag located at another position. Thus, for example, the gas generator 2 may be adapted to inflate an air-bag located in front of a passenger in a motor vehicle, whereas the gas generator 4 may be adapted to inflate an air-bag located to the side of that passenger. Thus, the air-bag in front of the passenger will be inflated initially and the air-bag to the side of the passenger will be inflated at a later instant in time.

Referring now to Figure 2 which is a diagrammatic representation of the embodiment of Figure 1, the same reference numerals apply to the same parts.

It can be seen, from Figure 2, that the shock tube 3 is connected directly to a repeater charge 7 located within a housing 8 containing the pyrotechnic material 9 that, when ignited, generates the gas which emerges from the gas generator 2. The housing 8 is provided with a weakened portion 10 which, when the pyrotechnic material 9 is ignited, forms an outlet port communicating with the interior of an air bag 11.

The pyrotechnic delay line 6 comprises a slow burning pyrotechnic material 12 contained within a housing 13 which is mounted on a housing 14 which contains a squib 15 and a pyrotechnic charge 16 which, when ignited, generates the gas to be generated by the gas generator 4.

The housing 14 has a relatively thin area 15 which, when the pyrotechnic material 16 is ignited, forms an outlet port 15 communicating with the interior of the bag 11.

In operation of the gas generator 4 a shock passing through the shock tube 5 initially ignites the slow burning pyrotechnic material 12 within the housing 13, and after a delay that material ignites the squib 15 which subsequently ignites the gas generating pyrotechnic material 16.

In a further alternative arrangement, the gas generator 2 may be adapted to actuate a pre-tensioner, whereas the gas generator 4 may be adapted to inflate an air-bag.

It is to be appreciated that whilst a simple embodiment of the invention has been illustrated, with only two gas generators and one delay line, three or more gas generators could be provided, each gas generator being associated with a different delay. Of course, a delay line could be incorporated in the shock tube 3, the delay line and the shock tube 3 having a different period of delay to the delay line in the shock tube 5.

Whilst the delay can be at any point in the path between the sensor and the respective gas generator, the delay could be associated directly with the gas generator.

A single shock tube could then be connected from the sensor to the input of the or each delay, as well as being connected directly to a gas generator which is not associated with a delay.

An arrangement in accordance with the invention must have two or more gas generators that receive the shock wave from the sensor, and are thus activated at different times. The arrangement could also additionally contain further gas generators that receive the shock wave at the same time that other gas generators receive the shock wave.

Claims (9)

CLAIMS:

1. A gas generator arrangement for use with a safety system in a motor vehicle, the gas generator comprising a sensor adapted to sense an impact on the vehicle, or deceleration in excess of a predetermined limit and adapted to provide an output transmissible in the form of a shock along a shock tube, the sensor being connected, by two or more respective paths defined at least partly by shock tube means to two or more gas generators, one or more of the paths being associated with a pyrotechnic delay in series with the shock tube so that each gas generator receives the shock wave from the sensor at a different respective time.

2. An arrangement according to Claim 1 wherein one gas generator is connected directly to the sensor by a shock tube, and the or each other gas generator is connected to the sensor by means of a respective shock tube which is associated with a respective delay.

3. An arrangement according to any one of the preceding Claims wherein the gas generators are adapted to inflate a single air-bag.

4. A gas generator arrangement according to Claim 1 or 2 wherein the gas generators are adapted to activate separate safety devices.

5. An arrangement according to Claim 4 wherein the separate safety devices both comprise air-bags.

6. An arrangement according to Claim 4 wherein the two different safety devices comprise different types of safety device.

7. An arrangement according to Claim 4 wherein one gas generator is adapted to activate an air-bag and another gas generator is adapted to activate a pre-tensioner.

8. A gas generator arrangement substantially as herein described with reference to and as shown in the accompanying drawings.

9. Any novel feature or combination of features disclosed herein.