Method and apparatus for filling and sealing an inflator for an automotive airbag module

#This invention relates to a method and apparatus for fabricating airbag inflators, and more particularly to the gas filling, assembly and sealing of airbag inflators using a single apparatus.

#Airbag modules employ inflators which house a highly pressurized inert gas. The inflator, when ignited in a vehicular collision, releases the stored pressurized gas into a folded airbag in the module for inflation and deployment of the airbag into the vehicle.

#Airbag inflators normally provide a small opening which is employed as a fill port for the injection of the gas. During one stage of the inflator assembly, a prescribed amount of pressurized gas is provided in an area designed to contain the gas along with the inflator. Such a gas fill method is time-consuming and difficult to control with respect to weight and pressure. In addition, the fill hole must be sealed after the inflator is filled to the desired pressure. One method of closing the fill hole is disclosed, e.g., in U.S. Pat. No. 5,196,669 assigned to RWC Inc. A ball is deposited in the mouth of the gas fill opening in the inflator and is subjected to resistance welding by moving a retracted welding electrode of the machine into an extended welding position into contact with the ball. A welding current is applied to the welding electrode to weld the ball in the fill hole, thereby sealing the same and thereafter retracting the welding electrode and resetting the ball delivery system for the next inflator sealing operation.

#The invention together with further objects, features, aspects and advantages thereof may be more fully understood from the following description taken in connection with the accompanying drawings.

#FIG. 1 is a view of an assembled inflator in accordance with the present invention;

#FIG. 2 is an exploded, perspective view of the inflator of FIG. 1;

#Referring now to FIG. 1, an assembled pressurized gas filled inflator, referred to generally with the reference numeral 10, comprises a base 12 and a canister 14. As will best be seen in FIG. 2, the base 12 includes a shortening clip 16, a diffuser 18, an initiator 20, a diffuser screen 22, a weld ring 24 and a burst disk 26. The canister portion 14 of the inflator 10 has an inflator chamber 15 therein. The base or closure 12 is joined to the canister 14 by the weld ring 24 as shown in FIG. 1 in a manner described hereinafter.

#FIG. 3 shows diagrammatically an apparatus for the assembling, filling and sealing the inflator 10 of FIGS. 1 and 2. The apparatus of FIG. 3 comprises a housing 28 having an upper fill/weld chamber 30 and a lower fill chamber 32 forming an inflator chamber 36 therein when closed. A lower cylinder 34 is connected to the lower chamber 32 for moving the lower chamber 32 down to open the housing 28 for loading the base assembly 12 and the canister 14 in the housing 28. The lower fill chamber 32 has a plurality of canister locators 40 therein for properly positioning and aligning the canister 14 therein and a grounding plate 42 on the bottom thereof on which the canister 14 sits when positioned in the lower chamber 32.

#The upper chamber 30 contains a top press cylinder 44 coupled to a magnet and base press 46. The magnet and base press 46 hold the base assembly 12, i.e., its constituent parts, the shortening clip 16, diffuser 18, initiator 20, weld ring 24 and burst disk 26 in place in the upper chamber 30 in alignment with a canister 14 separated from the base 12 and positioned in the lower chamber 32. As an alternative structure, the magnet could be replaced by a clamping mechanism for holding the base assembly in place. A circular welding electrode 50 is mounted in the upper chamber 30 to which an electrical source 52 is applied via electrical leads 54 through an embedded insulated electrical contact terminal 56 in the wall of the upper chamber 30. A wiper or sliding contact 58 coupled between the terminal 56 and welding electrode 50 applies the electrical source 52 to the welding electrode 50. As an alternative structure, the electrode could be included in the base press 46.