US 3009419 A
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Nov. 21, 1961 F. B. CLAY, JR., Erm. 3,009,419
AMMUNITION FOR ELECTRICALLY FIRED WEAPONS Filed Feb. 27, 1958 2 Sheets-Sheet 1 NQM Nov. 21, 1961 F. B. CLAY, JR., ET AL 3,009,419
AMMUNITION FOR ELECTRICALLY FIRED WEAPONS Filed Feb. 27, 1958 2 Sheets-Sheet 2 INVENTOR. FRAN/UN 7. CLA y .74. BY RVCHAAD A. 54 HL /A/ JL.. N fun f. Mug
t@ t ic 3,009,419 Patented Nov. 2l, 1961 3,009,419 AMMUNITION FOR ELECTRICALLY FIRED WEAPONS Franklin B. Clay, Jr., Westport, and Richard A. Sahlin,
Fairfield, Conn., assignors, hy mesne assignments, to
the United States of America as represented by the 'Secretary of the Army Filed Feb. 27, 1958, Ser. No. 717,930 1 Claim. (Cl. 102-46) The present invention relates in general to firearm ammunition and, more particularly, lto improved electric tiring means for quick firing guns, typical of which is the automatic firearm shown in part in the Birkigt Patents 2,159,126 and 2,159,127. A Vgood example of the electrical firing system with which the present invention can be used is disclosed in U.S. Patent 2,466,929, of April l2, 1949. It will be understood, however, that the particular gun and system shown is by Way of illustration only and that the invention is not limited thereby, but includes all modifications and applications within the scope of the appended claim.
Cartridges have been developed in recent years having electric primers for use in automatic quick firing guns. These cartridges are fired by conducting a high voltage charge, such as the discharge of a condenser to the electric primer. Usually, in -guns utilizing electrical firing systems, the lbolt is provided with a contact pin instead of the usual firing pin, the contact pin being insulated from the bolt and charged by engagement with a conductor carried in the bolt.
One difiiculty encountered in the operation of these electrical firing systems involved small slivers of metal some of which are shaved from portions of the cartridge cases during the feeding and extraction operations. 'I'hese metallic slivers lodge in the gun mechanism and can cause either premature firing by bridging the gap between the contact pin and the primer or, rby short circuiting the contact pin to grounded gun structure, may thus prevent firing of the primer.
It is an object of this invention .to provide means for preventing the firing failures or mishaps mentioned in the previous paragraph and render the operation of such electrical firing systems safer and more dependable.
It is a further object of this invention to prevent the firing of ammunition having electric primers by the effect of stray electrical currents, either in the gun or elsewhere.
These and other objects, features and advantages of the invention will be more particularly described in the following specification, having reference to the drawings in which:
FIGURE 1 is a fragmentary side elevation, partly in section, of an automatic firearm embodying the electric bolt of this invention.
FIGURE 2 is a fragmentary plan view, partly in section, on line 2 2 of FIGURE l.
FIGURE 3 is la vertical section on line 3-3 of FIG- URE l.
FIGURE 4 is a diagram of an induction firing circuit for use with the electric bolt shown in FIGURES l and 2.
FIGURE 5 is a diagram of a capacitative firing circuit adapted for use with the electric bolt shown in FIGURES l and 2.
FIGURE 6 is an enlarged section view of one-half of the electric firing means shown in FIGURE 2.
FIGURE 7 is a fragmentary side elevation of the front end of one of the slides showing the firing means retaining lug.
FIGURE 8 is an isometric View of the forward portion of the right hand slide. The view is from a point to the ture 12. A barrel 13 is received in the forward end ofl rear of the front end and from the inside or to the left of the slide as properly oriented in an assembled gun.
FIGURE 9 is an enlarged portion of the fragmentary plan view of FIGURE 2, partly in sections, showing in detail the improvement of the present invention as applied to the 1base portion of a cartridge casein the gun chamber. The firearm, of known construction, chosen to illustrate an application of the present invention is shown in part in FIGURES l, 2 and 3 and comprises a substantially rectangular receiver 10 provided with an upper cartridge feeding aperture 11 and a lower cartridge ejection aperthe receiver. Mounted in the receiver for reciprocable sliding movement is the breech mechanism which comprises a breech bolt 14 having a longitudinal aperture 14 and a pair of slides 15 and 16, the latter being supported on opposite sides of the bolt and slidable longitudinally relative thereto. Supported within the bolt is an electrical firing means indicated generally at 17 which is cooperatively associated with the pair of slides 15 and 16 so as to be displaced within the bolt by relative movement of the slides and bolt in a manner disclosed fully in the previously mentioned Patent Number 2,466,929, of April l2, 1949.
The cartridges used in the electrical fir-ing system embodying the present invention comprise, as best shown in FIGURE 9, a cartridge case C of the usual configuration containing a propellant charge and a project-ile (not sh-own). The cartridge case C is also provided with a primer cup device 92 containing the material 91 for initiating the combustion of the propellant charge. The initiating material, in the example shown by way of illustration, surrounds an electrical resistance wire 93 which lis heated to incandescence when the firing voltage charge is applied thereto to fire the cartridge. The primer cup element containing the initiation material is open at one end facing the interior of the shell. The other end is closed by a contact disc 94 which is insulated from the primer cup structure and other cartridge structure by a sleeve 95 of dielectric material. The resistance wire is connected to the contact disc at one end and to primer cup structure at the other end. Since the primer cup, cartridge case and gun structure are connected to ground, a path for the firing current is established when a firing voltage impulse is applied to the contact disc from the bolt tiring contact 96 as in the manner described in Patent 2,466,929.
This invention involves the application of a dielectric coating or film 98 across the head of the cartridge case to cover at least the primer portion thereof. Such a coating or film may be of any suitable material such as shellac or polyethylene applied in a thickness which may be determined in a well known manner to give the desired breakdown voltage value in the tiring circuit. Naturally the tiring of each primer will take place only when the dielectric coating or film breaks down under an applied voltage equal to or in excess of breakdown voltage to allow current to pass and complete the firing circuit. This coating or film insures that ordinary stray currents will not accidentally tire a cartridge, and also eliminates the previous firing difficulties which occurred because of small metal slivers shorting the firing contact to the firing disc causing undesired firing or shorting the firing pin to other grounded structure -by-passing the primer and resulting in a failure to fire. A coating of shellac in a thickness of approximately .001 has been satisfactory with a firing voltage of about 350 to 450 volts. The thickness of the dielectrics coating or film necessary to perform as desired will not interfere with normal feeding and ejection of the cartridges.
The material may be applied in any conventional manner such as spraying or brushing. Thus it can be seen 3 that a relatively small change has produced very large and substantial benefits in the safety and reliability of operation of rearms utilizing electrically fired ammunition, as well as improving the safety of the ammunition itself.
A firearm cartridge of the type adapted to be red by the passage of an electric current therethrough, comprising a casing having a head portion and ya tubular body portion, a propellant charge in said -body portion, a primer device in said head portion containing a propellant charge initiating material and electrical means for igniting said initiating material upon the application of an electrical charge thereto, and a lm of solid plastic dielectric material on said head portion shielding and insulating said primer device from all electrical charges below a predetermined voltage to prevent the passage of current through said primer device until a voltage of suflicient magnitude 4 t is applied to said dielectric material to equal or exceed the breakdown voltage of said dielectric material and cause a current to oW through said electrical means contained in said primer to fire the initiating material and said cartridge.
References Cited in the file of this patent UNITED STATES PATENTS