Caseless Ammunition And Ignition Means Therefor

Abstract

A caseless charge for firearms and a firearm therefor, said charge being porous and made from comminuted or particulated combustible materials having the surface of each particle thereof softened with a solvent. The softened material is consolidated in a combustible pyroxylin tube and inserted in the firearm. Ignition is provided from an electrical discharge between the end of an ignition probe and the projectile attached to the charge.

Description

This invention relates to ammunition and firearms. More particularly this invention relates to caseless charges or ammunition useful for firing projectiles or the like from firearms or other ballistic launching devices.

Caseless ammunition has in the past proved feasible in caliber sizes ranging from 22 caliber through large artillery rounds. However, the use of caseless charges as ammunition in small arms has not been entirely successful, particularly in rapid fire applications. Reasons for this lack of success stem from many factors, the chief one being improper, incomplete or otherwise faulty burning of the propellant charge material and resulting lack of sufficient gas generation to adequately propel the projectile.

Prior art caseless ammunition has been prepared by molding granules, powder or the like, of combustible oxygen bearing substance mixed with a binder of nitrocellulose and dissolved in a solution of ethanol or ethyl ether. The mixture is formulated to a semisolid constituency and thereafter subjected to a pressure of 3,000-- 9,000 p.s.i. for short periods of about 15 seconds and dried at about 50.degree. C. A nonporous substance results having relatively poor burning characteristics because of unsatisfactory flame propogation. Other workers in the art sought to overcome this problem by preparing the charge by foaming the mixture to induce porosity or by mechanically manipulating the charge by machining cavities and channels therein to create larger burning surfaces. These solutions while improving the burning quality of small arms ammunition, still did not provide a fully satisfactory round because, though porosity helped, the degree thereof and its control to form a reproducible propellant surface and web thickness of the particles were inadequate.

Another problem with prior art caseless ammunition was ignition, which either was too time consuming for small arms ammunition or relatively ineffective in accomplishing combustion. Ignition means encompassed all known means including; hot electrical resistance wire, exploding bridge wire, hot air blast, auxiliary charges and spark gap electrical discharge. While success of varying degree has been achieved, a completely satisfactory ammunition round performing at least as well as metal cartridge type rounds has eluded those concerned.

Accordingly it is an important object of this invention to provide an improved round of caseless ammunition which performs at least as well as ordinary ammunition and is capable of being reproduced in large quantities with no appreciable performance deviations from round to round.

It is still another object of this invention to provide an improved round of caseless ammunition having a porous propellant wherein the degree of porosity thereof is controlled reproducibly from round to round to bring about improved burning characteristics.

It is still another object of this invention to provide a round of caseless ammunition of the character above referred to wherein an electrical ignition system is used to significantly enhance the overall performance of the round.

It is a still further object of this invention to provide an improved closed breech type firearm which accommodates the improved propellant charge of this invention and also serves as an important part of the ignition system therefor.

Other objects and advantages of this invention will be readily apparent upon perusal and consideration of the following description and the drawings annexed wherein;

FIG. 1 is a longitudinal section of a portion of a firearm illustrating the position of the caseless ammunition round of the invention therein at the time of initiation of combustion;

FIG. 2 is a magnified view of a portion of the charge of the invention along Section 2-2 of FIG. 1;

FIG. 3 is a sectional view similar to FIG. 1 of another embodiment of the invention;

FIG. 4 is a view of the invention taken along Section 4-4 of FIG. 3; and

FIG. 5 is a view similar to FIGS. 1 and 3 of still another embodiment of the invention.

Referring now to the drawings, and in particular to FIG. 1 thereof, there is shown the interior breech portion of a firearm 10 with a round 11 in a preferred form of the invention. Round 11 includes a projectile 12 attached to a hollow caseless charge 13 of propellant by an adhesive 14 (heavy black line in this FIG.). Projectile 12 has a rearwardly projecting portion 15 which is provided to increase the adhesive surface and for ignition purposes as will be hereafter more fully explained. Round 11 is positioned in the bore 16 of firearm 10 with the forward edges of charge 13 abutting the annular wall 17 of a recess 18 in bore 16.

Situated aftwardly of charge 13 in breech 20 is a reciprocating bolt 21 of the type found in most firearms. However in this instance bolt 21 is modified to include within its structure an electrical conductor 22 together with its associated insulation 23. Conductor 22 is a two-piece high tension line, one piece being within bolt 21, the other piece leading from a power source 25. The two pieces are electrically joined at a terminal head 22-a when bolt 21 is in the position shown in FIG. 1. Insulation 23 (not shown on the piece of conductor 22 leading from power source 25) is selected to provide full insulation of electrical energy therein from the surrounding metal of bolt 21. Conductor 22 terminates in electrical contact with an ignition probe 24 which is transported by and moves with bolt 21 in its reciprocating motion. As shown in FIG. 1, bolt 21 and probe 24 are in their extreme forward positions and in firing (breech 20 closed) mode. Conductor 22 is connected to high tension electrical power source 25 by means of a switch 26 activated by a firearm trigger 27, shown in schematic form in the various figures.

Charge 13, as shown in the drawings, is a cylindrically shaped combustible mass composed of any of the usual substances well known in the art of ammunition propellants but of modified form for the purposes of this invention, being a porous combustible body made from gun propellant, preferably a homogeneous, solvent type, which is uniquely treated to induce and control porosity and to insure reproducible burning surfaces and particle web thicknesses. This treatment involves contacting the particles forming the charge mass with a solvent, preferably acetone, to soften the surfaces thereof, and thereafter consolidating them under a light load of a few ounces to a few pounds, e.g. 2 ounces to about 25 pounds. The sizes, i.e., diameters, thicknesses and the like are selected in accordance with the desired end use and burning rate required. In small arms ammunition spherical particles from 5 to about 100 mills diameter are preferred. Other particle shapes also usable in this invention are rods, both hollow and solid, flat plates and mixtures of all of these. Since burning time is related to the so-called "web thickness" or web, which in spherical particles is the diameter thereof, contact time of the solvent and subsequent consolidation load determines web thickness in the completed charge. In hollow rod particle shapes burning on all surfaces, web thickness is one-half the distance from the outer surface to the inner surface. In solid rod particles it is one-half the diameter, and in flat plate particles it is one-half the distance from one side to the other. Thus it can be seen that the novel treatment of this invention permits a predictable and reproducible web thickness in the particles and therefore provides the means to produce a charge having a degree of predictable combustion performance not heretofore available.

FIG. 2 illustrates in a magnified view, a portion of charge 13, in this instance the particles being selected from ball propellant and therefore spherical. However, any particle shape above-mentioned can be used. Referring to FIG. 2 the particles or spheres 28 have been softened by, for example, passing them through a solvent for a short period of a few seconds depending on the temperature thereof and on the type of solvent. The particles are then collected in a protective cylinder 18 and consolidated while still softened, consolidation pressure on the other above referred to being sufficient to result in the formation of mutual impregnations or penetrations 29. In the consolidating step, excess material 30 flows into the interconnecting channels or interstices 31 between particles 28, and by careful control thereof a mass having a predictable and reproducible degree of porosity, and therefore consistant burning characteristics, results. It should also be evident that similar results can be obtained regardless, within the above stated limitations, of the particle shape selected.

In practice charge 13 is contained (and consolidated) in protective cylinder 32 cut from thin wall tubing of pyroxylin (low nitrogen content cellulose nitrate with plasticizer) which is itself consummable in the burning of charge 13. Charge 13 when consolidated after softening in tube 32 can be in a hollow form having a central perforation 33 of substantially the same diameter as rearwardly projecting projectile portion 15 and can be attached thereto by adhesive 14. An end cover 34 also of pyroxylin can be adhesively attached to the rearward end of charge 13 to seal it against moisture and damage due to handling.

Alternatively, charge 13 can be made separately in a mold or the like, and protective tube 32 and end cover 34 formed on its outer surface by spraying or dipping to obtain a skinlike covering thereon. Other means for containing and protecting charge 13 will no doubt occur to skilled artisans.

While the preparation of charge 13 has been disclosed as a porous mold of propellant or power treated by contact therewith of acetone, it should be understood that other solvents can be used for applicant's purpose. For example, various alcohols, e.g. ethyl, methyl, propyl and butyl alcohol ether, mixtures thereof and of acetone therewith will also accomplish this end. Other solvents include many of the ketones, e.g., methyl ethyl ketone and many of the halogenated hydrocarbons such as methylene chloride, fluorotrichloromethane difluorodichloromethane and the like. It is preferred to pass the propellant particles through the solvent which is in the vapor form, or in a mist, for sufficient time to obtain the desired surface softening, this being determined by choice of solvent. In the case of acetone, a single pass through the vapor, recovering the particles through a metering valve at the bottom will result in a contact time of at most a few seconds. Temperature conditions during the softening period range from about 50.degree. C. to about 70.degree. although, depending on the solvent used, may range from lower to higher temperatures. Warm air passing through the softened propellant is used to dry the mass and remove excess solvent to prevent over softening.

In other instances the solvent can be passed through the loose propellant in tube 32 either under pressure or under a vacuum for periods from a few seconds to several minutes depending on the desired degree of surface softening (and therefore porosity of the charge) desired. The softened powder is then subjected to warm air for drying and to prevent over softening, and consolidated with any suitable apparatus well known to the art such as a piston and the like under a light compressing load ranging from several ounces to about 25 pounds to obtain the result indicated in FIG. 2 and above described. Softening of the particles can also be achieved by spraying the solvent on the moving material or by flowing the solvent over particles which remain stationary.

While this invention has been described with reference to cellulose nitrate based propellant, other propellant materials are also suitable for application herein. For example, the material known as "Ballistite" or cellulose nitrate mixed with nitroglycerine also can be used. Guanadine nitrate propellants and even black powder are also acceptable candidates in achieving a reproducible charge 13 with the desired predictable porosity.

FIGS. 3 and 4 illustrate an additional embodiment wherein the electrical ignition circuit is modified in that conductor 22 connects to and terminates in a round headed terminal 22-a, passing through the lower part of an insulator collar 35 in breech 20. Terminal 22-a electrically contacts an outer conductive ring cover 36 which is insulated from the surrounding firearm 10 members by collar 35. Conductive ring 36 includes a radially extending central portion 36-a which generally extends from cover 36 to the central area of charge cover 34 over the end of perforation or core 33. Probe 24 (in FIG. 3 and also FIG. 5) is electrically isolated from power source 25 when in the position shown in FIG. 3, and from bolt 21 by insulator bushing 24-a. FIG. 4 shows the relative position of cover 36 and center portion 36-a when viewed from breech 20. It should be noted that regardless of the orientation of round 11 in bore 16, electrical contact will be maintained between ring 36 and conductor 22, and central portion 36-a will always extend over perforation 33.

FIG. 5 illustrates still another embodiment of this invention wherein charge 13 and cover 34 includes an outer sheath 37 of conductive material. Materials selected for sheath 37 (and ring 36) include any conductive material, preferably metal foil or the like which is thin enough to be easily pierced by probe 24 and, as will be later indicated, conductive of electric current and combustible. Candidate materials are magnesium, aluminum, copper, zinc, iron and titanium and the like. Ring 36 and sheath 37 can also be integral with cover 34 by forming cover 34 with carbon or metal particles within the pyroxylin whereby current will be conducted from power source 25.

In operation of the invention charge 13 is prepared by softening particles of commercial propellant with a solvent in vapor form by passing the vapor through the loose powder 28 contained in cylinder 18, dropping the propellant particles into the solvent, or any of the other methods above described. A mandrel (not shown) can be used to form core 33, which can be hollow and integral with cylinder 18 and of combustible pyroxylin, or removable. After a time sufficient to soften the surfaces of particles 28, the solvent vapor is removed and the particles dried and consolidated under light pressure until charge 13 is of the desired porosity and length. End cover 34 is preferably preattached to cylinder 18 and the final length of charge 13 is determined by trimming the opposite end. A projectile 12 is positioned on charge 13 with projecting portion 15 in core 33 and adhesively attached thereto. Round 11 thus prepared is inserted in bore 16 with bolt 21 retracted as shown in FIGS. 3 and 5. Bolt 21 is then moved forwardly causing probe 24 to pierce end cover 24 in FIG. 1, coming to rest at position shown in FIG. 1 to provide an electrical discharge gap A between the ends of probe 24 and projectile portion 15. Firearm 10 is now armed and ready for firing. To ignite charge 13 and fire projectile 12 trigger 27 is pulled closing switch 26. Current from power source 25 flows through lead 22 to ignition probe 24 and discharges across gap A with high energy to ignite charge 15 and fire projectile 12 by the pressurized gas generated thereby.

In FIGS. 3 and 5, bolt 21 is shown in its retracted position, probe 24 being physically and electrically separated from power source 25 and electrically from bolt 21 by bushing 24-a. As bolt 21 is moved forwardly probe 24 pierces end cover 34 and conductive central portion 36-a of ring 36, coming to rest in the position shown by the dotted lines in FIGS. 3 and 5, so as to again provide discharge gap A. In piercing central portion 36-a, probe 24 becomes electrically connected to power source 25 and activation of trigger 27 supplies energy thereto, and an electrical discharge across gap A occurs igniting charge 13. Similarly in FIG. 5 probe 24 in piercing shield 37 becomes electrically connected to energy source 25 and activation of trigger 27 causes a discharge across gap A to ignite charge 13.

Thus what has been described and illustrated is a new form of caseless ammunition wherein a porous charge is provided in a combustible protective cylinder. By treating a commercially obtainable propellant by the methods above described, controlled and predictable porosity is obtained, and upon ignition, complete combustion occurs, smoothly and with little or no residue. A protective cylinder being similarly made from combustible, low nitrogen content cellulose nitrate, wherein the nitrogen content is in the 7 to 10 percent range and well known to the art also burns completely and contains the porous charge. The means for ignition of the propellant is a high tension electrical discharge system which, in the preferred embodiment, is a part of the reciprocating bolt common to most firearms. Arming of the projectile occurs when the bolt is in its forward position, and though not shown, the circuitry can easily be provided with safety switching means to prevent premature firing, for example, conductor lead 22 can be provided with a switch mounted at the power source or on the firearm itself.

While only a preferred and several additional embodiments have been presented, it should be understood that other variations and modifications will become apparent to skilled artisans after perusal hereof. Therefore no limitations should be placed upon the scope of this invention except as indicated by the appended claims.

Claims

I claim:

1. A caseless ammunition round adapted for firing from a firearm and the like comprising a projectile, a propellant charge having a central core adhesively attached to said projectile, said charge comprising a combustible mass formed from propellant particles having their outer surfaces softened by contact with a solvent for a period of time of up to 60 seconds and thereafter being consolidated by a force of from 2 ounces to about 25 pounds whereby said mass is sufficiently compacted to cause said particles to become mutually impregnated, and form a unitary mass, a combustible, pyroxylin protective tube containing said mass, and a combustible, pierceable, pyroxylin end cover attached to said tube.

2. The ammunition round of claim 1, wherein said charge is porous.

3. The ammunition round of claim 1, wherein said solvent is selected from the group consisting of acetone, alcohol, ether, methyl ethyl ketone and mixtures thereof, methylene chloride and halogenated fluorocarbon solvents.

4. The ammunition round of claim 1, wherein said solvent is a vapor.

5. The ammunition round of claim 1, wherein said solvent is the form of a mist.

6. The ammunition round of claim 1, wherein said solvent is a liquid.

7. The ammunition round of claim 1, wherein a portion of said end cover is electrically conductive.

8. The ammunition round of claim 1, wherein the material of said protective tube and said end cover is pyroxylin.

9. The ammunition round of claim 1, wherein the propellant material for said charge is selected from the group consisting of cellulose nitrate, ballistite, guanadine nitrate and black powder.

10. The ammunition round of claim 1, wherein the propellant particles are spherical.

11. The ammunition round of claim 1, wherein the propellant particles are rodlike.

12. The ammunition round of claim 1, wherein the propellant particles are flat plates.

13. The ammunition round of claim 1, wherein the propellant material is a mixture of spherical, rodlike and flat plate particles.

14. The ammunition round of claim 7, wherein said conductive material is a metal selected from the group consisting of aluminum magnesium, copper, zinc, iron and titanium.

15. The ammunition round of claim 7, wherein said conductive material is carbon.