Ammunition and explosives – Igniting devices and systems – Accidental fuse ignition prevention means
Reexamination Certificate
1999-11-29
2001-10-16
Tudor, Harold J. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Accidental fuse ignition prevention means
C102S702000, C102S202500, C102S202900, C102S530000
Reexamination Certificate
active
06302023
ABSTRACT:
The invention relates to an igniter for a pyrotechnical inflator, comprising a squib arranged therein, contact leads to the squib, and a high-frequency choke for preventing spurious release, the high-frequency choke being formed by at least one ferromagnetic body surrounding at least one contact lead.
Igniters for pyrotechnical inflators of vehicle occupant restraint systems are relatively expensive to manufacture. Manufacturing is done in numerous individual steps and hitherto, due to the complexity of the various components, this also necessitates production by different manufacturers each having the know-how for the individual components concerned. Since, however, the individual components are secured to and based on each other, the parts need hitherto to be shipped from one manufacturer to another for further processing, which is complicated.
The generic document GB 2 198 816 A describes the structure of an igniter comprising a high-frequency filter for inflators, in which small tubes of a ferrite material and small tubes of a dielectric ceramic material are pushed over the contact leads and over each other. While the soldering of the ferrite sleeves is avoided in this way, this structure is still very complicated.
In order to simplify the production of gas-tight high-frequency filters, U.S. Pat. No. 5,367,956 proposes that the leads be surrounded by an electromagnetically absorbent sintered glass ceramics. The entire arrangement including the housing, wires and ceramic mass however needs to be heated to a temperature of 600° C., which would raise the number of manufacturing steps again if this method is used for igniters of a pyrotechnical material.
The invention provides an igniter which is configured substantially simpler than those known hitherto and which necessitates fewer steps in fabrication than hitherto so that the overall expense of fabrication is less. This is achieved in an igniter of the aforementioned kind by the contact leads being configured as at least one printed circuit board, preferably with an electrically non-conductive substrate material on which an electrically conducting material is applied, by the contact leads, for constituting a base body, being molded in an electrically non-conductive material or sealed in such a material, and by the ferromagnetic body and the base body being combined to form a unit serving as the high-frequency choke.
In many of the igniters used hitherto, the high-frequency choke is purchased as a complete item needing to be arranged in relation to the contact leads relatively complicatedly, whereas in the case of the igniter in accordance with the invention individual steps in fabrication can be eliminated since first a base body is formed by molding or sealing the contact leads in an electrically non-conductive material, preferably plastic material, and no separate high-frequency choke needs to be assembled, but merely a ferromagnetic body such as for instance a small tube as known from GA 2 198 816 A is combined with the base body such that the resulting unit acts as the high-frequency choke. In this arrangement the contact leads extending through the ferromagnetic body function as a coil winding, with each contact lead extending through the ferromagnetic body/bodies acting as approximately half a coil winding. As a result of this, the ferromagnetic body is no longer required to be fully covered, as hitherto, and assembly of the individual components is simplified. The molded or sealed contact leads have a dual function.
Fabrication of the contact leads can be simplified further by these being configured completely as at least one printed circuit board. The printed circuit board is made of an electrically non-conductive material which is termed the substrate material. The electrically conductive material is then applied on the substrate material by using a known method, for instance by rolling or printing.
The invention is not restricted to merely an igniter, it also relates to an inflator with the igniter in accordance with the invention integrated therein, the squib being surrounded by a propellant charge. The igniter in accordance with the invention also permits facilitated, cheaper production of a unit comprising inflator and igniter.
Advantageous embodiments of the invention constitute the subject matters of the sub-claims.
Joining the base body and the ferromagnetic body to a single unit is done preferably by bonding, by means of an interlocking fit or with a force-transmitting connection.
The base body comprises preferably a recess adapted to the geometry of the ferromagnetic body into which the latter can be inserted and arrested. The arresting can be realized for example by means of a latching or clip connection formed on the base body, holding the ferromagnetic body in its fitted position. A latching or clip connection has furthermore the advantage that the body is held in place under pretension, so as to avoid rattling.
In the preferred embodiment the ferromagnetic body is inserted into the base body from an end of the base body opposite the squib. The ferromagnetic body is thus inserted axially into the recess preferably formed as a cavity in the base body.
The ferromagnetic body may surround at least one contact lead annularly, or a separate ferromagnetic body may also be provided for each contact lead.
To achieve an adequate inductance the longitudinal extent of the ferromagnetic body corresponds to at least its transverse extent.
In addition, a circuit board may be secured to the base body, this circuit board being connected to the contact leads and featuring at least one contact lead of its own, via which the circuit board communicates with a control unit in the vehicle, thus making it possible to continually monitor the operativeness of the igniter. Due to the circuit board being in the vicinity of the squib the currents necessary for monitoring the operativeness can be kept very low, as desired.
The circuit board, too, is secured to the base body preferably by a plug or latching connection. Circuit board and contact leads may be formed of separate parts which are not interconnected electrically until the base body and the circuit board are joined together. In addition to this, circuit board and contact leads may also be configured integrally.
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Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Occupant Restraint Systems GmbH & Co. KG
Tudor Harold J.
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