Ported passenger airbag module can

Abstract: A vehicle safety airbag inflation device including an extruded U-shaped housing (10) with sidewalls (12, 14) interconnected by a web (16), an inflatable cushion (28) and an inflator (26) containing autoignition material. One or more ports, each containing a fusible plug (24) of a low melting point alloy or organic material are situated in the sidewalls (12, 14), web (16) or end caps which cover ends of the housing (10). Preferably the ports are positioned to provide ready flame access to the inflator (26) in the region of its autoignition material thereby causing early ignition in the event of exposure of the device to fire. Once opened, the ports allow venting of the housing (10).

Description: This invention relates to an improvement in the extruded aluminum cans which serve as module housings in passenger side airbag installations. More particularly it relates to a module can with means to avoid pressurization of the can during autoignition when the airbag module can is exposed to bonfire conditions. Passenger airbag modules generally comprise a housing or can within which there are an inflator, an undeployed airbag cushion and means for actuating the inflator at the time of a collision. The airbag module housing can also include an auto-ignition package e.g. as described in the following recently issued United States Patents: Adams et al 4,561,675 December 31, 1995 Jasken et al 5,100,174 March 31, 1992 Lindsay et al 5,378,017 January 3, 1995 Kidd et al 5,427,030 June 27, 1995 In the unlikely event that a fire occurs at the storage facility or a bonfire results from an automotive vehicle being involved in a collision, it is undesirable for excessive pressures to build up inside the module housing. The purpose of the autoignition component as described in the Adams et al patent is to provide a mechanism for igniting the inflator contents at temperatures well below those at which the inflator charge reacts to generate large volumes of gas, and thereby moderates the pressures which build up in the module housing can. The several components are assembled and then stored until they are shipped to a location where they are installed in a vehicle. A further prior art airbag module (on which the preamble of claim 1 is based) is described in US 5358272. The module includes an inflator and a housing with air entrainment ports covered by an inwardly displaceable flap valve which opens to allow air entrainment upon normal actuation of the module. The flap valve is made of a material which melts below the ignition temperature of the inflator, thereby allowing venting through the ports under bonfire conditions. The securing of the flap valve to the interior of the housing involves separate securing devices. One object of the invention is to provide an extruded module can or housing for an airbag in which the housing includes means to relieve pressure developed in said housing when it's contents are ignited. Another object of the invention is to provide an airbag module can constructed with ports which provide enhanced access to the contents of said can when the module housing can is exposed to bonfire conditions. Still another object of the invention is to provide a ported airbag module can or housing in which the ports are temporarily sealed with plugs which melt when the ports are exposed to bonfire temperatures. A further object of the invention is to provide an airbag module can construction which is applicable to passenger side airbag modules and to driver side airbag modules. These and other objects of the invention are achieved by an airbag module can provided with ports in the can housing and meltable plugs inserted in said ports. In the present invention pressure build up due to autoignition is avoided by the provision of holes drilled or punched in the extruded module can, the holes being sealed with plugs which block the passage of inflation gases. The plugs are composed of materials intended to melt from the outside during bonfire conditions. During bonfire conditions the plugs melt away creating ports for direct flame and heat impingement on the inflator in the module can. This decreases the time to autoignition of the autoignition package in the housing. The ports relieve the pressures generated within the module can as a result of said autoignition. The invention will become clear and will be better understood from the description which follows taken in conjunction with the drawings in which: Figure 1 is a view in perspective of a passenger side module can;and Figure 2 is a section through a port, in Figure 1. As shown in Figure 1 a module can 10 has a generally U shaped configuration. Preferably the module can is an extrusion of an aluminum alloy as is known in this art. The module can has walls 12 and 14 which extend upwardly from a web 16. Depending on the orientation of the module, can walls 12 and 14 may be either top and bottom walls or side walls and web 16 may either be a side or the bottom of the module. The walls 12 and 14 terminate at their free ends with flanges 18 for mounting the can in an automotive vehicle in the usual way. The extrusion may include ribs 20 to reinforce the can and provide additional stiffness and strength to the module can. Holes 22 are punched or drilled in either web 16 or in a wall 12 or 14, each hole being dimensioned to receive a fusible plug 24. Holes of about 25 mm (1 inch) in diameter have been found suitable in a passenger side airbag module can approximately 254-305 mm (10-12 inches) long. An inflator 26 and airbag cushion 28 are installed in the module housing 10 in the usual way. Plugs 24 are inserted in the holes 22 punched in the can. The plugs are designed to withstand the heat and pressure incidental to a normal inflation when the airbag cushion is deployed in the usual way. Plugs 24 are composed of materials which remain solid at the temperatures to which the module is exposed when stored either in a warehouse or in an automotive vehicle - e.g. temperatures up to about 49°C (120°F) and even the more elevated temperatures to which they may be subjected when an airbag inflator is actuated and airbag cushion 28 is inflated. The plugs maybe a low melting metal alloy such as Wood's metal or an organic material such as a wax designed to melt at 350°K or above. Since the purpose of the ports is to facilitate actuation of the autoignition material when the airbag inflation device is exposed to bonfire conditions, the ports are preferably located adjacent to the autoignition material in the inflator 26 and may even be in the end caps 30 of the module housing if an autoignition package is at one end of the inflation device. In the event that the module can is exposed to bonfire conditions, the plugs will be exposed to temperatures well above the melting point of the plugs and once the plugs melt and the autoignition package in the inflator autoignites, the resulting gas evolution is vented through ports 22 avoiding a pressure build up in the module. It will be seen that the ports formed when plugs 24 melt, enhance the performance of an extuded reaction can during bonfire conditions in several ways. First they allow direct impingement of heat and flames on the inflator cartridge, which decreases the time to autoignition of the inflator and module exposure time is also decreased so that wall strength of the module at ignition is higher. Second the ports act as vents during autoignition inflation, thereby decreasing the load on the module walls. Although the invention has been described and shown in a passenger side airbag module can, it will be understood that it could also be applied to a driver side airbag module housing.

Claims: An airbag inflation device which includes an airbag (28), means (26) to inflate said airbag, a housing (10) for said airbag (28) and said inflation means (26), and fusible means (24) in said housing (10), wherein said inflation means includes an autoignition device which ignites when said inflation means (26) is exposed to bonfire temperatures characterised in that said fusible means comprises a fusible plug (24) inserted in the or each of at least one port (22) in said housing (10). The device of claim 1 in which the or each said fusible plug (24) is made of materials which melt at bonfire temperatures. The device of claim 1 or 2 in which said material is a low melting point metal alloy. The device of claim 1 or 2 in which said material is an organic material. The device of any preceding claim in which said housing (10) is a generally U shaped extrusion. The device of claim 5 in which said extrusion includes two walls (12, 14) joined by a web (16). The device of claim 6 in which the or each said port (22) is in said web (16). The device of claim 6 in which the or each said port (22) is in one of said walls (12, 14). The device of any preceding claim in which said device is a passenger side airbag inflation device. The device of any preceding claim in which the or each said port (22) is located adjacent to autoignition material in said device. A method of facilitating the actuation of an autoignition material in an airbag inflation device containing said material which comprises: enclosing said device in an airbag inflation device module housing (10) ; providing at least one port (22) in said housing (10) and inserting a fusible plug (24) of low melting material in the or each said port (22), whereby when said airbag inflation device is exposed to bonfire conditions, the or each said fusible plug (24) melts and the or each said port (22) provides direct access to said autoignition material for actuation of said autoignition material. The method of claim 11 wherein the or each said port (22) is located adjacent to said autoignition material.

Inventors: DAVIS TERRY R, RAVENBERG MICHAEL J, DAVIS, TERRY R., RAVENBERG, MICHAEL J.
Applicants: AUTOLIV ASP INC, AUTOLIV ASP, INC.
Application year: 1997
Main classification: B60R21
IPC codes: B60R21