Abstract: An electropyrotechnic initiator comprising a pyrotechnic varnish in contact with a resistive heating element is prepared by preparing an aqueous adhesive composed of a dispersion of an explosive substance and of additives in an aqueous suspension based on a copolymer chosen from ethylene/vinyl acetate copolymers and vinyl acetate/ethylene acetate/ethylene copolymers, depositing the aqueous adhesive on the resistive element, and drying the aqueous adhesive at a temperature of between 55° C. and 75° C., in order to remove the water contained in the adhesive and to obtain the varnish.

Abstract: The present invention relates to the field of very low-energy electropyrotechnic initiators. The initiator (1) according to the invention comprises, in particular: an electrically and thermally insulating support (26) on which is deposited a thin-film electrical circuit comprising a resistive heating element (17) whose thickness is less than 1×10−6 m; an ignition composition (23) consisting of a primary explosive, the particle size of which is less than 30×10−6 m. The initiators according to the invention are very suitable for initiating devices for protecting the occupants of a motor vehicle.

Abstract: The present invention relates to a process for the preparation of an electropyrotechnic initiator (1) comprising a pyrotechnic varnish (6) initiated by a resistive heating element (11). The pyrotechnic varnish is obtained by deposition, on the resistive element, of an aqueous adhesive composed of a dispersion of an explosive substance and of additives in an aqueous suspension based on a copolymer and then by drying the said aqueous adhesive at a temperature of between 55° C. and 75° C. The copolymer is chosen from ethylene/vinyl acetate copolymers and vinyl acetate/ethylene acetate/ethylene copolymers.

Abstract: The electropyrotechnic igniter (1) comprises a body divided into a downstream chamber and an upstream chamber by a discoid metal piece (8), the downstream chamber containing a resistive heating element (11), a pyrotechnic initiating composition (12) and a pyrotechnic ignition composition (7), and the upstream chamber containing a rectangular electronic card (17) extended by three external metal pins (29 to 31), on which electronic card conducting tracks are provided. Two metal connection pins (13, 14) pass through the discoid metal piece (8) and connect the said conducting tracks to the resistive heating element (11). A means of intercommunicating and of triggering a train of specific electric pulses as well as a means of storing electrical energy are connected to the conducting tracks. This igniter is more especially intended to be used in motor-vehicle safety, especially for constituting the device for igniting a gas generator associated with an airbag.

Abstract: The present invention relates to the field of electropyrotechnic initiators comprising a thick-film multifoil circuit. The electrical circuit is photoetched on an insulating support (16). It consists of a resistive first foil having a central part (17) of constant width. This first foil is covered, except on the central part (17), by two conducting areas (28, 29) made of copper. The circuit (18) has an outline consisting of curved lines whose radius is greater than 7×10−4 m and whose shortest distance from the edge of the support (16) is at least 35×10−5 m. Such an initiator has an enhanced electrostatic discharge resistance.

Abstract: The present invention relates to the field of very low-energy electropyrotechnic initiators.

Abstract: The present invention relates to the field of pyrotechnic igniters, especially those intended for motor-vehicle safety. The igniters (1) according to the invention have a thin-film resistive bridge (19) connected via two thin metal areas (17 and 18) to two electrodes (9 and 10). An initiating lacquer (20) covers the resistive bridge (19) and a varistor attached to the said areas protects the igniter from electrostatic discharges. The resistive bridge (19) has a volume resistivity of between 0.5×106 and 2×106 &OHgr;.m and the initiating lacquer is made from a primary explosive. The igniters (1) have a no-fire current of greater than 500 mA and an all-fire current of less than 1200 mA.

Abstract: The electro-pyrotechnic initiation system preferably comprises an electro-pyrotechnic initiator (1) consisting especially of an insulating support (14) over which a flat resistive heating element (3) and two separate conductive metal areas (15, 16) are extended, the said resistive heating element and the said conductive metal areas being electrically connected to a current source (2) by means of two electrodes (9, 10). A conductive filter device (5), connected in parallel with the said resistive heating element (3), is divided into a varistor (6) and into a capacitor (7) which are connected to the electrodes (9, 10). This conductive filter device (5) has an equivalent resistance which varies depending on the measured electric potential difference between the two electrodes (9, 10) and ensures that the initiator (1) is not operated when the latter is subjected to a high-voltage electrostatic discharge.

Abstract: An electro-pyrotechnical initiator comprising a form pyrotechnical charge initiated by a heating resistive element placed in contact with said charge. The resistive element comprises a flat strip of narrow width l, preferably lying in the range 80 micrometers to 300 micrometers, and made of a resistive metal alloy which is deposited on a printed circuit support, said resistive element being connected to two current feeds via two extensive electrically-conductive areas, and the pyrotechnical charge is a thermosensitive substance that is applied in the form of an explosive varnish that covers said resistive element.

Abstract: The present invention relates to a priming charge with annular percussion, free from any toxic metal, which corresponds to the following weight composition:40 to 70% of a dinitrobenzofuroxan salt as impact-sensitive primary explosive,3 to 15% of tetrazene as sensitizing explosive,10 to 30% of cupric oxide as oxidizing agent,5 to 25% of a pulverulent reducing agent,0.5 to 20% of an inert abrasive powder and0 to 5% of a binder.It also relates to a process for its manufacture, wherein the following successive stages are carried out:the cupric oxide and the pulverulent reducing agent and the inert abrasive powder are mixed dry;the dinitrobenzofuroxan salt and the tetrazene are then added to this mixture thus formed, andthe mixture thus obtained is homogenized.If appropriate, a solution of binder, for example in the form of an aqueous solution of gum arabic, is added to the inert mixture.

Abstract: Pyrotechnic compositions having a decreased susceptibility to external influences are obtained by suspending pyrotechnic particles in a dilute solution of a coating polymer and adding a second polymer which is more soluble in the solvent, so that microdroplets of the coating polymer are formed, completely enclosing the pyrotechnic particles. The coated particles are hardened by exposure to air, optionally in the presence of a hardening catalyst.