Electrical Initiation Of Percussive-primed Cartridges

Abstract

Disclosed is an electrical firing circuit for initiating percussive-primed artridges wherein the base of the cartridge forms one electrode of a spark gap which has connected thereacross an RF pulse generating means and a charged capacitor. When energized, the pulse means ionizes the air in the spark gap whereupon the capacitor discharges thereacross causing heating of the cartridge base containing the primer mix whereby the primer mix is initiated and hence the cartridge.

Description

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

The invention relates to electrical firing means for munitions and more particularly to electrical firing means and apparatus for electrical initiation of small arms cartridges, particularly percussive-primed cartridges.

In one instance small arms cartridges are each provided with an electrical primer which is electrically coupled through firing pin means, breech mechanism in cooperation with switching means to a primer source such as a charge capacitor or an induction circuit means for activating the electrical primer. Such an arrangement not only involves complicated mechanical firing mechanism and erosion of the firing pin, but also the susceptibility of the electrical primer to radio frequency fields with probable ignition of the primer and subsequent premature firing of the cartridge. In another known means, a cartridge is fired by means of an electric spark which jumps a gap disposed in the proximity to an ignitable fuse. However, such means is not only impractical from military use, but also involves the use of a special cartridge, not standard in civilian or military use.

Percussive-primed cartridges are normally initiated by the action of a firing pin, but can also be initiated by "cook-off" of the primer mix by virtue of external heating. Caliber .22 percussive-primed cartridges have been fired in a modular firing device, but module firing once started was generally unpredictable in action and could not be controlled or stopped. One such moduler firing device consists of 360 aluminum tubes or barrels to accommodate caliber .22 cartridges bound together by epoxy resin in a box-like configuration having the approximate dimension of 71/2 .times. 5 .times. 2 inches. A sheet of pyrotechnic material was caused to burn across the basis of the caliber .22 percussion primed cartridges assembled in the tubes of the modular firing device whereby the heat thus generated caused the primers of the cartridges to "cook-off". While this means does cause ignition of the primers of percussive primed cartridges, its use is highly undesirable particularly since it has been found that it is not only unreliable and uncontrollable but also highly hazardous from a safety standpoint. Percussive primed cartridges may also be fired in a direct contact circuit. For example, a caliber .22 percussive prime cartridge connected directly across a 40 volt source required a current of 300 amperes over a period of 10 seconds for firing. Obviously, the inadequacy of employing such a firing means is apparent. Also, it has been found possible to fire percussive primed cartridges utilizing the spark plug principle wherein the cartridge comprises the electrodes of the spark gap. This system requires 2000-2500 volts for high-frequency ionization of the gap while at the same time providing sufficient electrical energy to fire the cartridge in the order of 10 joules for a caliber .22 percussive primer cartridge. Thus the energy requirements of this system are high, limiting the practicality thereof for military requirements.

An object of the invention is a new and novel electrical firing circuitry for electrical initiation of percussive primers.

Another object of the invention is a new and novel means for electrical initiation of percussive primed cartridges.

A further object of the invention is an electrical firing system for ignition of percussive prime cartridges which permits operation of weapons systems at a high rate of fire without employment of complex mechanical movement and complex electrical circuitry and switches.

A still further object of the invention is a new and novel electrical ignition means for ignition of percussive primed cartridges of extreme simplicity wherein the energy requirement thereof is relatively low.

Referring to the drawing wherein the electrical ignition means and system of the invention for firing percussive primed cartridges is illustrated in conjunction with a single percussive primed caliber .22 cartridge 10 in the breech of a single barrel firearm 11 for the purpose of simplicity, it being understood that application of the invention is not limited to single barrel firearms and further, that it has been used in conjunction with weapon systems whereby a rate of fire of 10,000 rounds per minute has been attained without a single moving mechanical part and without complex circuitry and switching. An electrical energy source 12 which may consist of two series connect lead-acid type batteries provides means for charging a capacitor 13 and energizing the RF pulse producing means 14 which may consist of an automotive type ignition coil having a primary winding 15 and a secondary winding 16. A resistor 17 has one terminal coupled through a switch 18 to terminal 22 of the electrical energy source on battery 12 and and another terminal by means of conductor 24 to an electrode 20 through an inductor 21. The electrode 20 is aligned with cartridge 10 along its longitudinal axis and spaced from the base thereof to form a spark gap 25 therewith across which electrical energy is discharged. Capacitor 13 has one plate connected to a junction 24' formed on conductor 24 intermediate resistor 17 and inductor 21 whereby it is coupled through resistor 17 and switch 18 to terminal 22 of battery 12 and through inductor 21 to electrode 20. The opposite plate of capacitor 13 is connected to common 26 and thereby to terminal 23 of battery 12 and firearm 11 and hence to cartridge 10. Primary winding 15 of ignition coil 14 has one terminal connected through switch 28 via conductor 27 to an intermediate top 22' of battery 12 and its other terminal connected to terminal 23 of battery 12 by means of common conductor 26. The secondary winding 16 of ignition coil 14 is coupled across spark gap 25, one terminal thereof being connected to electrode 20 and the other terminal thereof to common circuit 26 and hence through firearm 11 to cartridge 10. In operation, switch 18 is closed and capacitor 13 is charged through resistor 17 to the potential of battery 12. The size of capacitor 13 is selected in view of the priming mix of the percussive primed cartridge 10 to provide sufficient arc heat to cause cook-off of the priming mix. After capacitor 13 has been charged by battery 12 switch 28 is closed and a current build up in primary winding 15 inducing a high voltage in the secondary winding 14 thereof it being understood that the voltage induced in the secondary winding may be created by either opening or closing of switch 28, whereby a RF pulse is created and discharges across spark gap 25 causing ionization of the air in said gap thereby producing a highly conductive path across which capacitor 13 then discharges. The energy of capacitor 13 discharge creates sufficient heat in the base of cartridge 10 to cause cook-off of the primer mix in the percussive primed cartridge 10. Resistor 17 functions to prevent battery 12 from maintaining the arc or capacitor discharge across spark gap 25 and indicator 21 prevents the RF pulse of the RF pulse producing means 14 from shorting to ground, common conductor 26, through capacitor 13.

Although a specific embodiment of the invention has been illustrated and described, it will be understood that this is but illustrative and that various modifications may be made therein without departing from the spirit of the invention and the scope of the claims.

Claims

We claim:

1. An low voltage electrical firing circuit for initiating percussive-primed cartridges comprising in combination:

a percussive-primed cartridge affixed in a firearm and having the base thereof serving as one electrode of a spark gap,

a terminal spaced from the base of said cartridge and exterior thereof and in alignment therewith forming the other electrode of said spark gap,

radio-frequency pulse generating means coupled across said electrodes for ionizing said spark gap,

high intensity electrical energy storage means coupled across said spark gap and operable to discharge across said spark gap when it is ionized by the said pulse generating means and heat said base whereby the primer of the percussive-primed cartridge is initiated.

2. The invention in accordance with claim 1 wherein said radio-frequency pulse generating means comprises a high tension induction coil having a primary and secondary winding, said primary winding coupled across a potential source through switching means for connecting and disconnecting said primary winding to or from said potential source, and said secondary winding having one terminal connected to said other electrode and another terminal connected to said one electrode through said firearm.

3. The invention in accordance with claim 2 wherein said high intensity electrical storage means comprises a capacitor coupled in parallel with said potential source and said spark gap.

4. The invention in accordance with claim 3 and means for preventing the potential source from creating an electrical arc across said spark gap when ionized comprising a resistor connected in series with potential source and said other electrode.

5. The invention in accordance with claim 4 and means for preventing the RF pulse generated by said pulse generating means from shorting to ground through said capacitor comprising a blocking impedance coupled between said other electrode and said capacitor.