Description:
BACKGROUND OF THE INVENTION
1. Field of Art
This invention relates to the ignition of ammunition, and is especially adapted to combustible caseless ammunition.
2. Prior Art
Modern firearms conventionally have utilized a movable firing pin in the bolt to actuate the igniter of the round of ammunition. In a firearm utilizing cased ammunition, the case has served to seal the aft end of the chamber to prevent the flow of combustion gas to the face of the bolt. In the case of a percussion actuated igniter, movement of the firing pin relative to the bolt is required to percuss the igniter. Similarly, in the case of an electrically actuated igniter, movement of the firing pin relative to the bolt is required to insure a good electrical connection between the pin and igniter contact. In each case the firing pin is disposed for movement in a passageway, and this passageway must be sealed from the combustion gases. In caseless ammunition, obviously, a case is not available for this function.
In U.S. Pat. No. 3,114,290, issued Dec. 17, 1963, E. M. Harvey et al proposed a dished cup, similar to a Belleville washer, having a central protuberance, which would seal the aft end of the chamber, around the aft end of the caseless round, and which would be snapped forward by a firing pin, to percuss the igniter. In U.S. Pat. No. 3,354,780 issued Nov. 28, 1967, M. Ramsey proposed a true Belleville washer to seal the aft end of the chamber to the face of the bolt, and a protuberance integral from the bolt face passing through the center hole of the washer, to percuss the igniter.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a system for the ignition of caseless ammunition which obviates moving pins and firing pin seals, and that accommodates dimensional tolerances between the round of ammunition, the chamber and the bolt face of the gun.
The advantages of this invention are: (1) the provision of a combustible electric primer for electric ignition in caseless ammunition systems; (2) the elimination of moving parts in the gun bolt, providing a sealed, flush bolt face; (3) the accommodation to a variable gap between the round and the bolt by use of a high voltage current source; and (4) the adaptability to multiple ignition systems with increased reliability of ammunition performance.
A feature of this invention is an electrical ignition system utilizing two electrical contacts in the bolt face; and a primer having an electrically conductive priming mix, and a consumable dielectric disc having two annular consumable conductors therethrough, the gap or effective impedance between the two conductors being significantly greater than twice any gap between the bolt face and the disc.
BRIEF DESCRIPTION OF THE DRAWING
These and other objects, features, and advantages of this invention will be apparent from the following specification thereof taken in conjunction with the accompanying drawing in which:
FIG. 1 is a partial view, in side elevation, in cross-section of an ignition system embodying this invention;
FIG. 2A is a view in side elevation in cross-section of the igniter of FIG. 1;
FIG. 2B is a view in end elevation of the primer of FIG. 2A; and
FIG. 3 is a view in side elevation of another embodiment of a primer embodying this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, the forward end of a bolt 10 is seated against the aft face of the barrel extension 12 to close the chamber 14. A seal 16 may be disposed between the barrel extension and the bolt.
A caseless round 18 of ammunition is disposed in the chamber, and the aft end of the round, due to dimensional tolerance, is spaced from the bolt face 20 by a gap 22. The aft end of the round is shown in the chamber and includes a main charge 24 of molded propellant, a booster charge 26 of booster powder disposed in an aft recess in the main charge and captured by a plug 27 of molded propellant, and a primer 28 disposed in an aft recess in the plug. On ignition, the primer communicates its flame and heat via a bore 29 in the plug in the powder of the booster charge, and to the propellant gains of the main charge and the plug.
The bolt 10 includes a central insulator 30 which may be made of a hard ceramic, a central electrode 31 which is disposed along the longitudinal axis of the insulator, and an annular ground electrode 32 which is spaced from the central electrode by the insulator. The two electrodes and the insulator are ground flush with the bolt face.
The primer 28 may be composed of any suitable materials that are completely consumable during the interval of the combustion of the round in the chamber and the barrel, a matter of three to ten or more milliseconds. They may be moulded, extruded, or cut from colloided nitrocellulose of any typical propellant composition. Other self oxidizing consumable plastics that on combustion yield largely gaseous products are equally suitable, including composite materials compounded of separate fuel and oxidizers, such as some rocket propellants and some artillery gun propellants.
The primer 28 includes an outer tubular casing 33, an inner, forward, closure annulus 34, an electrically conductive priming mixture 35, which may be tableted, or if loose, then retained by a thin, forward, consumable disk and an outer aft closure disk 36. The disk 36 is made of consumable insulative material 38 such as nitrocellulose and has an annular, longitudinal portion 40 and a central, longitudinal portion 42 of electrically conductive material. The transverse cross-sections of the electrically conductive portions 40 and 42 are substantially congruent with the bolt face sections of the bolt electrodes 32 and 31 respectively. The conductive portions 40 and 42 may be composed of nitrocellulose mixed with 40 to 60 percent powdered graphite. Other conductive materials may be used such as acetylene black or other forms of amorphous carbon, powdered copper or silver, although carbon has the advantage of being largely consumed or reduced to carbon dioxide/monoxide when the nitrocellulose base material burns.
The bolt electrodes 31 and 32 are axially aligned with the primer disk electrically conductive portions 42 and 40 and serve as the conductive path for a high voltage current from a power supply, 44, which is coupled through the bolt electrodes, to the electrically conductive primer mix. The radial distance between the primer disk electrically conductive portions 42 and 40, and between the bolt electrodes, is arranged to be sufficiently greater than twice the maximum air gap that may obtain between the bolt face and the primer disk so that arcing from the bolt electrodes to the primer disk electrically conductive portions will occur with high reliability and will result in igniting the primer mix at the selected firing voltage, without any possibility of arcing between the bolt electrodes. The high voltage current source may be a capacitance circuit delivering a pulse of the order of 1 to 5Kv.
It will be appreciated that the invention can be applied to any type of electrically fired weapon, but is particularly suited to caseless ammunition wherein (1) the ground connection to the gun is not provided by a metallic case, and (2) the ammunition to weapon tolerances are large. Most importantly, the invention permits a complete sealing of the bolt face to provide an unbroken surface which obviates the conventional requirement for pressure seals around the moving parts of a conventional firing pin.
An additional advantage of the invention is illustrated in FIG. 3. The combustible electric primer may be located elsewhere than on the outer aft surface of the round. The firing current may be conducted from the bolt electrodes through short lengths of wire or metallic inserts 50 imbedded in through the combustible propellant bodies. These metallic inserts need not establish conventionally good electrical contacts, insolong as any gaps are small, and an efficient circuit path is provided which will avoid large power losses. Short lengths of aluminum, magnesium or other pyrophoric wire may be used as conductors, and will be consumed in the combustion of the propellant, at most leaving a powdered residue. This advantage permits retention of a closed surface over the aft end of the round during the ignition and burning of the booster charge, thereby aiding this process by added confinement. Further a plurality of primers may be provided which are spaced from each other but electrically connected to the power supply by an efficient independent circuit and thus significantly increase the ignition reliability of the round.