Ammunition and explosives – Jacketed or cartridge gas generator
Reexamination Certificate
1998-05-28
2001-12-04
Price, Thomas (Department: 3643)
Ammunition and explosives
Jacketed or cartridge gas generator
C102S202500, C102S202140, C280S741000, C280S737000
Reexamination Certificate
active
06324987
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a pyrotechnic means for vehicle occupant protection systems including a container for an ignitor, propellant and/or compressed gas.
BACKGROUND OF THE INVENTION
Pyrotechnic means in the field concerned are known wherein an electrically actuated ignitor is surrounded by a solid propellant which is capable of spontaneous combustion on being ignited. The resulting hot gas serves, for instance, to ignite further propellant charges or directly for inflating a gas bag or for tensioning a seat belt. Also known are pyrotechnic means wherein an electrically actuated ignitor is surrounded by a minor quantity of solid propellant and ignitor and propellant are arranged within a container filled with compressed gas. Ignitor and propellant serve on ignition to open a bursting diaphragm provided in the container and in subsequent exit of the compressed gas to compensate the losses in temperature and pressure thereof during a specific time span. Typically the container for ignitor, propellant and/or compressed gas is press fitted with a mounting so that ambient effects such as e.g. moisture are kept away from the interior of the container. If the container is required to be gas-tight, for example 0.5% loss in 15 years at 220 bar helium, the container needs to be sealed by complicated and expensive methods, such as e.g. glass potting the joints, due to welding or soldering being prohibitive in view of the high temperatures involved which would otherwise damage or detriment the ignitor, propellant or compressed gas.
It is the intention of the invention to facilitate production of gas-tight pyrotechnic means having long-term stability.
SUMMARY OF THE INVENTION
For this purpose in accordance with the invention a pyrotechnic means is provided for vehicle occupant protection systems including a container for an ignitor, a propellant and/or compressed gas wherein the container includes a container body and at least one container lid and a gas-tight ultrasonic welded joint is provided between the container body and the container lid. This ultrasonic welded joint is gas-tight and in addition has long-term stability. Due to the contact surface areas between container body and container lid being heated up only locally due to friction in ultrasonic welding the remainder of the container remains more or less cold so that ignitor, propellant or compressed gas are not heated up, or merely insignificantly so, during ultrasonic welding. It has been surprisingly discovered that during ultrasonic welding the heating up fails to be propagated to the inner walls in contact with the propellant.
In one aspect of the invention the container body and/or the container lid are made of a non-ferrous heavy metal or an alloy of non-ferrous heavy metal. Using a non-ferrous heavy metal or an alloy of non-ferrous heavy metal offers good conditions for ultrasonic welding between container body and container lid. For example, the application of Cu 99.5, a bronze alloy, or a brass alloy is possible. Preferably a soft material is employed for the container lid and a harder material for the container body. A harder material for the container body promotes a controlled bursting action of a bursting diaphragm provided in the wall thereof.
In an advantageous manner, container body and/or container lid can also be made of aluminium or an aluminium alloy. Container and container lid are preferably made of Al 99.5−99.75 or an aluminum alloy such as e.g. AlMgSi 0.5.
In another aspect the container body comprises a peripheral wall, the face surface area of which locates the container lid. Configuring the container body in this way results in an arrangement of advantage for ultrasonic welding. Due to the desired high surface area pressure during welding the contact surface area between container body and container lid is maintained as narrow as possible, for example <1 mm.
It is of advantage when the face surface area of the peripheral wall is chamfered in the direction of the container opening and the container lid rests against the face surface area and the chamfer. As a result, the container lid is centered in place simply by being mounted on the container body due to the container lid then being in contact with the face surface area and chamfer. Welding is done in the region of the face surface area and in the region of the chamfer or only in one of the two regions. With the container and the container lid being configured like this, it is possible especially with thin-walled containers to prevent lateral buckling of the peripheral wall in case of welding pressure applied from above by lateral support of the peripheral wall.
It is likewise of advantage when the container body comprises a peripheral flange on which the container lid is mounted. Also in the case of very thin-walled containers this creates a contact surface area of sufficient stability for an ultrasonic weld. In addition to this a peripheral flange can be well supported, so that the desired surface area pressure during welding can be produced in a simple manner.
In yet a further aspect of the invention it is provided for that a bursting diaphragm is formed in the container body and/or the container lid. Such a bursting diaphragm simplifies production of the pyrotechnic means since no separate bursting diaphragm needs to be connected gas-tight to the container body or the container lid.
In still another aspect of the invention the region of the bursting diaphragm is surrounded by a notch. As a result, a controlled bursting response of the bursting diaphragm is made possible once a predetermined internal pressure has been attained.
In a final aspect of the invention it is provided for that the region of the bursting diaphragm is offset. Offsetting of the bursting diaphragm may be done, for example, by drawing down. It is likewise possible to produce the complete container lid or container body including the bursting diaphragm by cold extrusion or deep drawing. Offsetting the bursting diaphragm results in strain-hardening of the offset portion so that the bursting diaphragm bursts as defined or is punctured by the internal pressure, instead of bulging in part and bursting without control like a soft material.
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Price Thomas
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Occupant Restraint Systems GmbH & Co. KG
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