Header with overlying eyelet

#The present invention relates to the field of pyrotechnic initiators, and more particularly to a pyrotechnic initiator having an eyelet that overlies the glass insulator.

#Pyrotechnic initiators have many uses in industrial and consumer applications. One important use is the inflation of airbags in motor vehicles. As airbag production has steadily increased, significant efforts have been made to reduce the cost of reliable airbag initiators. Nevertheless, there remains a substantial need in the automotive airbag industry in particular as well as in other applications, for further reduction in the costs of manufacturing reliable initiators.

#In accordance with the present invention, a header for an initiator is provided that includes an eyelet overlying the glass insulator. A smaller second glass insulator aspect can also be provided, or the bridgewire can be suspended and encapsulated in an ignition droplet.

#The FIGURE is a side sectional view of an embodiment of the present invention.

#In conventional sealed-glass headers, there is a single insulator that is flush with the top surface of a generally cylindrical eyelet. As shown in the FIGURE, however, a preferred embodiment of a header 20 according to the present invention includes a ground pin 30, a central isolated pin 40, a primary glass insulator 50, an overlying eyelet 60, and a bridgewire 70, with the primary glass insulator 50 being recessed below and substantially covered over by the eyelet 60. Consequently, the top of the pin 70 is flush with the top surface of the eyelet 60, and separated therefrom by an annular region that is filled with a secondary glass insulator 80, or, alternately (not shown), with an ignition pyrotechnic charge.

#Although eyelets in conventional sealed-glass headers are typically machined from stainless steel, the eyelet of the present invention may desirably be fabricated of nickel-plated 1010 carbon steel. Further, the eyelet can be stamped or cold-formed (preferably into a cup-like shape as shown), and then plated with nickel using a standard plating process. The eyelet should have a wall thickness that is sufficient to sustain a compression seal and to sustain ballistic firing forces without creating undue stress in the glass. However, it should be thin enough that the header can fit within the allotted space for the initiator assembly, and thin enough to facilitate any desired stamping or cold-forming. The hole in eyelet 60 (which includes the upper portion of the isolated pin 40 and the annular region around it) may also simply be punched, preferably after the stamping or cold-forming of the eyelet 60, and may even be done on the same press.

#The primary glass insulator 50, pins 30 and 40, and eyelet 60 are preferably of materials that are selected to result in a compression seal, or less preferably, a matched seal. For example, a suitable compression seal would result with a 1010 carbon steel eyelet, a sodasilicate (e.g., TM9) primary glass insulator, and pins of a 52 alloy (or less preferably 42-6 alloy). The primary glass insulator can be made of drawn or pressed glass. The ground pin 30 may be press fit into a corresponding hole (not shown) in the eyelet 60, or it can be welded on, or it can be brazed with a solder ring during the sealing process. Both pins are preferably gold-plated, either individually, or as part of the header in “barrel” plating process.