Ammunition and explosives – Igniting devices and systems – Electrical primer or ignitor
Reexamination Certificate
2001-07-12
2003-01-07
Tudor, Harold J. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Electrical primer or ignitor
C102S202100, C102S202900, C102S202140
Reexamination Certificate
active
06502512
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a secured high-power electro-pyrotechnic initiator.
The high-power electro-pyrotechnic initiator works according to the well-known principle of the “slapper” or “exploding foil initiator” (EFI). In its most standard version, known as a “finite perforated-plate slapper”, it comprises an electrical circuit such as a current pulse equal to some thousands of amperes generated within a few tens of nanoseconds prompting the volatilization of a part of the conductor (fuse bridge) and the formation of a metal plasma. The very sudden expansion of the confined metal plasma is used to impel a projectile against the face of a pyrotechnic filling (a secondary explosive or a low-sensitive pyrotechnic composition). This projectile consists of a plastic disk, some tens of micrometers thick, with a diameter of about one millimeter. This disk is produced by cutting through a bored element (a perforated plate) made of plastic film. The initiation of the pyrotechnic charge (the detonation of the secondary explosive or explosion of the pyrotechnic composition) is prompted by the impact of the projectile driven by an impact speed of several kilometers per second.
In another version of the high-power electro-pyrotechnic initiator, known as a “bubble slapper”, the plastic film is not cut out through the perforated plate but forms a bubble whose diameter is limited by the perforated plate. It is the impact at the peak of the bubble that initiates the pyrotechnic charge.
An EFI type high-power electro-pyrotechnic initiator is commonly formed by a connection device with two contact zones or two pins electrically connected by the fuse circuit. The fuse circuit and the plastic film to be impelled are confined between the perforated plate and an anvil. The compressed pyrotechnic charge is placed in a box facing the perforated plate. The assembly thus formed may be hermetically sealed (French patent 2 669 725).
Parasitic electrical currents may be induced in the electronic control circuits connected upline from the initiator. These parasitic currents may be caused by the fact that these circuits are generally unsheathed or are poorly sheathed. Owing to the low electrical resistance of the fuse circuit (equal to some tens of milliohms), said parasitic electrical current coming through the connection zones may cause deterioration in the fuse bridge or make it melt and thus affect the reliability of the initiator.
SUMMARY OF THE INVENTION
An object of the invention is a slapper type electro-pyrotechnic initiator whose reliability is not affected by parasitic currents induced in the circuits to which it is connected, the initiator having low-cost components that are simple to manufacture and assemble, with triggering characteristics that are precise and independent of the surrounding conditions (such as atmospheric pressure, temperature, air moisture content, etc.).
The slapper type initiator according to the invention, with connection device having control circuits, fuse circuit, perforated plate and pyrotechnic charge, comprises a calibrated electrical discontinuity device between the connection device and the fuse circuit.
REFERENCES:
patent: 3002458 (1961-10-01), Haas
patent: 3117519 (1964-01-01), Hamilton et al.
patent: 3262389 (1966-07-01), Bryla et al.
patent: 3797393 (1974-03-01), Marchandise et al.
patent: 4441427 (1984-04-01), Barret
patent: 4944225 (1990-07-01), Barker
patent: 5204491 (1993-04-01), Auréal et al.
patent: 5347929 (1994-09-01), Lerche et al.
patent: 5431104 (1995-07-01), Barker
patent: 5969286 (1999-10-01), Ward et al.
patent: 0 482 969 (1992-04-01), None
Poulard Eric
Riviere Christophe
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDA Armements SAS
Tudor Harold J.
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