Rf immune firing circuit employing high-impedance leads

Claim 2

A firing circuit for an electroexplosive device which is immune from radiofrequency induced currents comprising: an energizing source; an electroexplosive device; a current control means operatively connected to said electroexplosive device; and high impedance carbon impregnated plastic leads for transmitting energy from said energizing source to said current control means.

Claim 3

The firing circuit of claim 1 wherein said current control means comprises: an energy storage capacitor operatively connected to said energizing source by means of said high impedance leads; a current path between said energy storage capacitor and said electroexplosive device; and switch means in said current path responsive to energy buildup on said capacitor to close said current path, whereby said electroexplosive device is actuated.

Claim 4

The firing circuit of claim 2 wherein said switch means comprises: a zener diode responsive to said energy buildup so as to breakdown at a predetermined energy level; and a silicon controlled rectifier connected in series with said electroexplosive device and responsive to breakdown of said zener diode to close said circuit path whereby said electroexplosive device is actuated.

Claim 5

The firing circuit of claim 3 wherein said switch means further comprises a variable reactance interposed between said energy storage capacitor and said zener diode permitting manual control of the energy level required on said capacitor to cause said zener diode to breakdown.

Claim 6

The firing circuit recited in claim 3 wherein said electroexplosive device and said current control means are packaged in a package comprising: a tubular enclosure of minimum size; an explosive charge occupying an end portion of said enclosure; said electroexplosive device arranged in intimate contact with said explosive charge; said zener diode and silicon controlled rectifier connected into a circuit with said electroexplosive device and arranged in close proximity to said electroexplosive device; and said energy storage capacitor connected into the circuit with said electroexplosive device and arranged to seal said previous elements into said enclosure, said capacitor also connected to said energizing source by means of high impedance leads, whereby said charge, electroexplosive device, diode, rectifier and storage capacitor are all contained within said tubular enclosure.

Claim 7

The firing circuit recited in claim 1 wherein said high impedance leads comprise: a pair of metal wires operatively connected to said energizing source; a pair of carbon impregnated plastic wires operatively connected to said current control means; and a pair of crimp-on connectors electrically connecting said metal wires with said plastic wires, whereby an impedAnce mismatch occurs at the splice.

Claim 8

The firing circuit recited in claim 6 wherein said high impedance leads further comprise a capacitor shunting said metal wire pair whereby a great impedance mismatch occurs at the splice.