Adjustable electrical time delay fuze

Claim 1

In a system comprising a gun and an explosive projectile launched therefrom, delay fuze means for exploding said projectile during flight at a predetermined time after launch, including a firing circuit carried by said projectile, said firing circuit comprising: first and second input terminals; a first capacitor, and means connecting said first terminal, through a blocking diode and an initially-closed setback-actuated single-pole-single throw first switch and said capacitor, to said second terminal; a second capacitor, and means connecting said first terminal, prior to setback, through said second capacitor and one path of a setback-actuated single-pole-double throw second switch, to said second terminal; a timing resistor connected in parallel with said terminals; a detonator for exploding the projectile; a programmable unijunction transistor including an anode, a gate and a cathode and having its anode connected to the junction of said second capacitor and said second switch, its gate connected to said first terminal and its cathode connected, through said detonator, to said second terminal; and means connecting said transistor anode to the junction of said first switch and said first capacitor, through the other path of said second switch, when the latter is actuated by setback; whereby the two capacitors can be charged to two different voltages prior to setback by supplying the two voltages successively to the two terminals, and will discharge in series through the timing resistor after setback until the anode of the transistor is sufficiently positive relative to the gate to cause the transistor to discharge through the detonator and thereby explode the projectile.