Abstract:
A hybrid ammunition cartridge for a firearm is includes a substantially cylindrical casing defining a body portion having a neck at a forward end and a base at a rearward end, the base including a rim. A projectile is mounted in the neck. Brass is used in the casing at the neck to hold the projectile at the proper crimp. Brass is also used in the rim to house the primer and to provide a surface at which a hook or any suitable mechanism can be used to extract the cartridge from the firearm. The remaining body portion is then manufactured from a composite material having suitable mechanical properties.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/175,906, filed on May 6, 2009, the content of which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to ammunition and, more particularly, to ammunition that can be assembled in a modular fashion from separate components and methods for assembling such ammunition. 
       BACKGROUND OF THE INVENTION 
       [0003]    Standard ammunition cartridges for firearms are typically unitary in construction with the structural components of the cartridge being made from metal. In general, the cartridge includes four sections, namely, a casing of a generally cylindrical shape and terminated at a rearward end by a rim, a propellant contained in the casing, a primer located at the rearward end, and a bullet or projectile frictionally held in a forward end of the casing. The casing is sized to a particular caliber, which closely approximates the diameter of the projectile and is less than the diameter of the bore defined by the barrel of the firearm through which the projectile moves. When the cartridge is in a firing chamber located at a rearward end of the bore, operating the firearm causes the primer to be ignited (e.g., via impact from a firing pin), which in turn ignites the propellant (usually gunpowder). Gases from the ignition of the gunpowder, when contained, increase the pressure within the casing and cause it to expand. As the casing expands, it seals against the wall resulting in a buildup of pressure in the casing. The built-up pressure causes the projectile to separate from the casing and travel through and out of the bore. The empty casing can then be removed from the chamber. 
         [0004]    At present most small arms ammunition is manufactured with drawn brass casings. Brass generally allows for proper neck retention of the projectile, provides suitable elastic qualities, and has acceptable abrasion characteristics, thereby minimizing damage to the internal surfaces of the firearm. 
         [0005]    One of the material properties of brass that makes it suitable for use in casings is its elasticity. During firing of the cartridge, large loads are imparted to the casing. The elasticity of the material of the casing allows the casing to quickly deform under pressure to provide a suitable seal in the firing chamber and then to quickly return to its original (or near original) condition. This quality, which is known as the “springback” of the casing, facilitates the extraction of the casing from the firing chamber. Without sufficient springback, the casing would plastically deform, thereby hindering or preventing extraction of empty casings. 
         [0006]    Another desirable material property of brass is that it limits the cook off of cartridges. Cook off, also known as thermally-induced firing, occurs when the propellant is ignited due to heat in the surrounding environment. Cook off is especially limiting in automatic weapons, although semi-automatic weapons can also be affected. This is due at least in part to a final round being fed to the firing chamber after the trigger is released. The round will be “cooked off” if the temperature in the firing chamber, due to the firing cycle, is sufficiently high to cause the propellant to ignite. The use of brass as the casing material inhibits the amount of heat transferred from the firing chamber through the wall of the casing to the propellant, thus minimizing the opportunity for cook off to occur. 
         [0007]    The brass casing in a standard cartridge typically comprises a substantial portion of the total weight of the cartridge. For example, in a standard 5.56 mm (NATO) cartridge, the brass accounts for about half of the total weight of the cartridge. Any reduction in the weight of the cartridge beyond the nominal weight would enable a person carrying large quantities of rounds to either be laden with less weight or to carry additional cartridges. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect, a hybrid ammunition cartridge for use in a firearm is disclosed herein. This hybrid ammunition cartridge includes a substantially cylindrical skeleton casing defining a body portion having a neck at a forward end and a base at a rearward end, the base including a rim. A projectile is mounted in the neck of the skeleton casing. A suitable material such as (but not limited to) brass is used in the skeleton casing at the neck to frictionally retain the projectile at the proper crimp. This suitable material can also be used in the rim to house the primer and to provide a surface at which a suitable mechanism can be used to extract the cartridge from the firearm. As will be explained in greater detail below, a charge vessel, manufactured from a polymer having suitable mechanical properties, is located in the skeleton casing. The polymer weighs less than traditional cartridge materials such as brass, thereby resulting in a reduction in cartridge weight. 
         [0009]    In another aspect, the present invention resides in a method for manufacturing a hybrid ammunition body. This method includes providing a skeleton casing formed from a first material, the skeleton casing defining an interior area and a first distal end portion adapted to frictionally receive a projectile. A charge vessel is also provided and is molded from a second material. The charge vessel is removably positioned in, and retained by the skeleton casing. A propellant is located in an interior area defined by the charge vessel. 
         [0010]    In still another aspect, the present invention resides in a method of assembling live ammunition. The method includes the steps of retrieving a skeleton casing from a casing inventory; retrieving a charge vessel from a charge vessel inventory; inserting the charge vessel into the skeleton casing so that the charge vessel is retained therein, thereby providing an assembled skeleton casing and charge vessel. A primer is inserted into the assembled skeleton casing and charge vessel, and a thermal barrier and/or a waterproof coating is applied thereto. 
         [0011]    In another aspect, the present invention resides in a hybrid ammunition cartridge. Such a cartridge includes a skeleton casing formed from a first material. The skeleton casing includes a base portion defining a pocket therein. A charge vessel formed from a second material is inserted into the skeleton casing. A propellant is located in the charge vessel, and a projectile is frictionally mounted in an end of the skeleton casing. The hybrid ammunition cartridge can be rendered live upon insertion of a primer, at least a portion of which is in communication with the propellant. 
         [0012]    In another aspect, a method of manufacturing a hybrid ammunition body includes providing a skeleton casing formed from a first material, the skeleton casing defining an interior area. A charge vessel is molded into the interior area defined by the skeleton casing. The charge vessel is formed from a second material. A propellant is located in an interior area defined by the charge vessel, and a projectile is positioned in and frictionally retained by a first distal end portion of the skeleton casing. 
         [0013]    In yet another aspect, the present invention resides in an ammunition body including a skeleton casing formed from a first material, the skeleton casing defining an interior area. A charge vessel is formed from a second material, the charge vessel being positioned in the interior area defined by the skeleton casing. A propellant is located in the charge vessel. The skeleton casing also includes a first distal end portion defining a pocket therein adapted to receive a primer. 
         [0014]    In another aspect, the present invention resides in a hybrid ammunition cartridge including a skeleton casing formed from a first material and having a base portion defining a pocket therein. A charge vessel is formed from a second material molded directly into the skeleton casing. A propellant is located in the charge vessel, and a projectile is frictionally mounted in the skeleton casing. The hybrid ammunition cartridge can be rendered live upon insertion of a primer, at least a portion of which is in communication with the propellant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is perspective view of a modular cartridge of the present invention. 
           [0016]      FIG. 2  is sectional view of the modular cartridge of  FIG. 1 . 
           [0017]      FIG. 3  is a flow chart illustrating a first method of forming a skeleton casing of a modular cartridge of the present invention. 
           [0018]      FIG. 4  is a flow chart illustrating a second method of forming a skeleton casing of a modular cartridge of the present invention. 
           [0019]      FIG. 5  is a side sectional view of a skeleton casing of a modular cartridge made by the method of  FIG. 3 . 
           [0020]      FIG. 6  is a top sectional view of the skeleton casing of the modular cartridge made by the method of  FIG. 3 . 
           [0021]      FIG. 7  is a side sectional view of a skeleton casing of a modular cartridge made by the method of  FIG. 4 . 
           [0022]      FIG. 8  is a top sectional view of the skeleton casing of the modular cartridge made by the method of  FIG. 4 . 
           [0023]      FIG. 9  is a perspective view of a charge vessel. 
           [0024]      FIG. 10  is a schematic representation of a dynamic insertion process of the present invention. 
           [0025]      FIG. 11  is a flow chart illustrating a process of dynamically inserting a charge vessel into a skeleton casing. 
           [0026]      FIG. 12  is a flow chart illustrating a first method of assembling live ammunition. 
           [0027]      FIG. 13  is a schematic representation of a press used in a direct molding process of assembling a modular cartridge of the present invention. 
           [0028]      FIG. 14  is a flow chart illustrating a second method of assembling live ammunition. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    Referring to  FIGS. 1 and 2 , a modular cartridge for use in a firearm is shown generally at  10  and comprises a skeleton casing  12  and a charge vessel  14  located in an interior area defined by the skeleton casing. A projectile  16  is mounted (e.g., frictionally) in a neck  18  at a forward end of the skeleton casing. The skeleton casing  12  includes a base  20  having a rim  22  that defines a primer pocket  26 . A primer is positioned in the primer pocket  26  for igniting a propellant carried in the charge vessel  14 . 
         [0030]    As shown in  FIG. 2 , the skeleton casing  12  defines a channel  27  via which the primer positioned in the primer pocket  26  is in communication with the charge vessel  14 . 
         [0031]    As illustrated in  FIG. 3 , the skeleton casing  12  may be formed from a suitable material such as, but not limited to, brass via a metal stamping operation  30  in which a flat blank is taken from a continuous coil and separated into two target portions for the neck and rim, each portion being separately drawn and extruded into the form of the skeleton casing. In this operation  30 , raw material is obtained in an acquisition step  32 . If not already done so, the raw material is cut or otherwise formed into strips and manipulated in a formation step (if necessary) to have a uniform thickness or elevation. The skeleton casing  12  is then formed in a manufacturing step  36  in which the strips are folded to define the primer pocket  26 . A secondary step  38  is then performed in which the rim  22  is machined, any desired cutting is performed, and the channel  27  extending from the primer pocket  26  to the interior of the skeleton casing  12  is formed. Degreasing operations may also be performed. 
         [0032]    In another embodiment as is shown in  FIG. 4 , the skeleton casing  12  may be formed via a multi-elevation stamping operation  40  from a multi-elevation strip in which the material at one end of the strip is thicker than the material at the other end and in which the difference in elevation is either a constant taper or a flat-taper-flat configuration. In this operation  40 , raw material is obtained in an acquisition step  32 . If not already done so, the raw material is then cut or otherwise formed into strips that are thicker (more elevation) at one end than the other in an engineering step  42 . One manner of engineering the raw material is via the use of a planish mill. Subsequent to the engineering step  42 , a manufacturing step  44  is carried out in which a skeleton casing  12  having a solid primer pocket  26  is formed. After the manufacturing step  44 , a secondary step  46  is then performed in which the rim  22  is machined, any desired cutting is performed, and a channel extending from the primer pocket  26  to the interior of the skeleton casing  12  is formed. Degreasing operations may also be performed. 
         [0033]    Referring now to  FIGS. 5 and 6 , the skeleton casing  12  manufactured using the metal stamping operation  30  is a substantially cylindrical member defined by a wall  48  and has two elongated openings  50  extending lengthwise along generally opposing sides of the cylindrical member and in the wall intermediate the neck  18  and the base  20 . The peripheral edge of the rearward surface of the base  20  forms the rim  22 . As can be seen in  FIG. 6 , an interior surface of the wall  48  is tapered such that the wall is thicker at the rearward end and thinner at the forward end. The degree of taper is determined by the particular manufacturing process. In this embodiment, the material used to fabricate the skeleton casing  12  is folded via the manufacturing step  36  to define the primer pocket  26 . 
         [0034]    As can be best seen in  FIG. 5 , the edges  52  of each opening intermediate the forward and rearward ends of the skeleton casing  12  define strap arm portions  56  that connect the neck  18  and the base  20 . Each strap arm portion  56  defines a slight “S” bend that improves flexing of the skeleton casing  12  and facilitates the insertion of the charge vessel  14 . Also, the “S” bends of the strap arm portions  56  allow for the provision of additional length or stretch, which increases the amount of allowable interference between the skeleton casing  12  and the charge vessel  14 . In any embodiment, the openings  50  allow a substantial amount of material to be removed from the casing, thereby reducing the weight of the casing. 
         [0035]    Referring now to  FIGS. 7 and 8 , the skeleton casing  12  manufactured from the multi-elevation strip of the multi-elevation stamping operation  40  comprises a substantially cylindrical member also having two elongated openings  50 . In this embodiment, however, the material used to fabricate the skeleton casing  12  is tooled accordingly to provide a solid primer pocket  26  (no folded material). The skeleton casing  12  of this second embodiment provides a hardness gradient having a value that is greater than the skeleton casing of the folded embodiment. Furthermore, material used to manufacture this skeleton casing  12  has a split elevation, is taper planed, rolled, or otherwise manipulated to provide for the multiple thicknesses or elevations in the material. 
         [0036]    As can be seen in  FIG. 7 , the edges  52  of each opening  50  again define strap arm portions  56  that connect a neck  18  and a base  20 , as with the embodiment of  FIGS. 5 and 6 . Again, the strap arm portions  56  are configured to define slight “S” bends to facilitate several factors in the manufacturing process. 
         [0037]    In either of the above-described methods of forming the skeleton casing  12 , the primer pocket  26  in the base  20  of the skeleton casing allows the primer to be press fit into the primer pocket. The present invention is not limited in this regard, however, as other configurations are within the scope of the present invention. The specific types of the other configurations depend upon the actual hardness of the material in the area of the primer pocket  26  and whether an extrusion process can reliably retain a standard press fit type of primer. If such a primer cannot be reliably retained, an alternate construction may be used (for example, the primer may be mechanically fastened or the press fit type of primer may be augmented using mechanical fasteners). Furthermore, in order to afford a margin of safety and to accommodate the logistics of handling and transportation of the materials used in construction, the primer configuration may be otherwise changed in consideration of the manufacturing process such that the cartridge  10  is not “live” until the primer is inserted. 
         [0038]    The projectile  16  can be of any suitable configuration (for example, hollow point, armor piercing, tracer, and the like). The neck  18  in which the projectile  16  is mounted is appropriately sized. One advantage of providing the neck  18  of the cartridge  10  as described herein is that projectile retention values commensurate with current practice can be achieved to yield ballistics data that is equivalent or superior to ballistics data of non-modular cartridges. 
         [0039]    The areas proximate the neck  18  and the base  20  are connected via strap arm portions  56 . The areas at which the strap arm portions  56  connect to the neck area and base area define points of articulation for the rotation of the neck  18  and base  20  about the common centerline C. The present invention is not limited to the specific configuration as shown, as the strap arm portions  56  are modifiable to facilitate any articulable rotation of the neck  18  and base  20  that is desired for a specific design of the cartridge  10 . 
         [0040]    Referring now to  FIG. 9 , the charge vessel  14 , which is located in the skeleton casing  12 , can be manufactured via a stand alone molding process. After being molded, the charge vessel  14  is charged with the propellant, purged of any air, sealed with foil, and stored as a component for incorporation into the skeleton casing  12 . In the alternative, the charge vessel  14  can be insert-molded directly into the skeleton casing  12 . In this embodiment, any flashing is removed from the charge vessel  14 , a thermal waterproof coating can be applied, and the assembled charge vessel and skeleton casing  12  are stored as a component. The stand alone molding process of molding the charge vessel  14  is preferable for a method of assembling the modular cartridge  10  of the present invention using dynamic insertion techniques (in which the charge vessel is dynamically inserted into the skeleton casing  12  after being molded). For at least the dynamic insertion method, the charge vessel  14  can be molded using the stand alone molding process in a basic single cavity mold, and the inside shape of the charge vessel can be designed to increase the velocity of the projectile  16  upon firing. 
         [0041]    At least in the dynamic insertion methods of the present invention, the charge vessel  14  is molded from a polymer and holds a desired mass of propellant depending on the type and size of the finished cartridge  10 . The weight savings of the modular ammunition of the present invention is attributed at least in part to the density of the polymer used. The polymer selected is considered in view of the characteristics of the final product, such characteristics including mold shrinkage factors and the like. One polymer found to be suitable is a polyphenylsulfone sold as RADEL R-5000, which is available from Solvay Advanced Polymers, L.L.C., of Alpharetta, Ga. 
         [0042]    Referring now to  FIG. 10 , the charge vessel  14  can be dynamically inserted into the skeleton casing  12 . The charge vessel  14  may include a molded blister gate  62  on the rearward end thereof to receive the primer. The outer surfaces of the charge vessel  14  may be relatively smooth, or they may include contours and reliefs or the like to comport with the inner surfaces of the skeleton casing  12  such that after insertion of the charge vessel into the skeleton casing, the contours and reliefs provide a substantially flush outer diameter to the cartridge. The flush outer diameter of the cartridge  10  may facilitate belt feeding of the cartridges and may also ensure efficient extraction of the cartridge during a firing cycle. 
         [0043]    Referring now to  FIGS. 10 and 11 , a process outlining the dynamic method of inserting the charge vessel  14  into the skeleton casing  12  is shown generally at  70  in  FIG. 11  and is hereinafter referred to as “process  70 .” In general, the skeleton casing  12  is securely retained, and the charge vessel  14  is presented to the skeleton casing through one of the openings between the strap arm portions  56  in the direction of an arrow  64  ( FIG. 10 ). The charge vessel is compressed, and the skeleton casing  12  is moved to allow the charge vessel to “slide into” the skeleton casing. An interference fit is thereby created to capture the charge vessel  14  in the skeleton casing  12 . This differs from conventional ammunition manufacturing practice in that with the above-described components, components of an individual cartridge can be manufactured at different times and/or in different locations, stored (if desired), and assembled as desired (for example, in a just-in-time scenario). 
         [0044]    In process  70 , the charge vessel  14  is presented to the skeleton casing  12  in a suitable orientation via tooling and various fixtures. The rim  22  of the base  20  is held fast using a collet. The start point of insertion occurs when the charge vessel  14  makes contact with the skeleton casing  12 , which is likely to be proximate the area where the strap arm portions  56  meet the neck  18 . The charge vessel  14  is urged into the skeleton casing  12  and downward at an angle until the charge vessel is seated in the skeleton casing. 
         [0045]    The seated charge vessel  14  is sized with a die in a sizing step. In this sizing step, the edges of the strap arm portions  56  are radiused, which thereby traps the charge vessel  14  within the skeleton casing  12 . At this time, the charge vessel  14  carries the propellant, with the propellant being dispensed to the charge vessel prior to its insertion into the skeleton casing  12  and being retained therein via the blister gate in the primer pocket region. After being purged of air and the blister gate being put into place, a foil member is ultrasonically welded over the primer pocket. By doing so, the charge vessel  14  is effectively sealed, thereby allowing for an extended shelf life. 
         [0046]    After being sized, the assembled casing  12  and charge vessel  14  could remain as a subcomponent without a projectile and/or without a primer. By allowing the cartridge  10  to remain in this semi-completed state, beneficial features in integration and logistics can be realized. In particular, the type of projectile can be changed to accommodate last-minute changes in the desired use. Also, semi-completed cartridges can be more easily shipped and stored due to their lighter weight and reduced volume. The final assembly can occur when the projectile and/or the primer are fitted to the charge vessel/skeleton casing subassembly. Additionally, the just-in-time aspect of subcomponent assembly has distinct advantages, particularly with regard to the life of ammunition and the costs of demilling live ammunition that does not pass proof testing (the deliberate over-pressuring of ammunition to verify that the ammunition will not explode in an unexpected manner upon firing). With JIT manufacturing, as much as about 80% of the costs associated with demilling live ammunition can be eliminated. 
         [0047]    Referring now to  FIG. 12 , a system for the assembly of live ammunition is shown generally at  80  and is hereinafter referred to as “system  80 .” System  80  uses JIT principles and fragments the manufacturing process and distributes portions to various parties, thereby allowing for simultaneous subcomponent building. 
         [0048]    In the system  80 , inventory is pulled in a pulling step  82 . In the pulling step  82 , the skeleton casings  12  and the loaded charge vessels  14  are retrieved from storage or otherwise obtained. Three additional steps can then be undertaken, either simultaneously or sequentially. These three steps include a step of puncturing the blister gate  84 , the process  70  of inserting the charge vessel  14  into the skeleton casing  12 , and the step of inserting the projectile and final sizing  86 . 
         [0049]    After the process  70  of inserting the charge vessel  14  into the skeleton casing  12 , a primer installation step  88  is undertaken. Subsequent to the primer installation, a coating step  90  is carried out in which a thermal barrier and/or waterproof coating is applied to the primer pocket. This coating step  90  may include or may be ancillary to the placing of the foil member over the primer pocket. Once completed, the ammunition is live. 
         [0050]    The system  80  depicted is a process that is truncated and/or which includes separate independent processes. As such, the need for a large, unitary manufacturing facility is avoided in favor of smaller, separate operations, many of which may be carried out by diverse private entities. Also, production can be streamlined and a minimum of 50% of demill operations for destroying ammunition that fails proof testing can be avoided. 
         [0051]    The present invention is not limited to the use of a dynamic insertion method of inserting a charge vessel  14  into a skeleton casing  12  (as is shown in process  70  of  FIG. 11 ), as the cartridge  10  can be manufactured by molding the charge vessel into the skeleton casing. More specifically, the charge vessel  14  may be insert molded directly into the skeleton casing  12 , thereby circumventing the dynamic insertion method as described above. One advantage of an insert molding process is that an existing ammunition production line could be used. Any insert molding process generally involves providing a suitable polymer and using a process of extrusion, blow molding, vacuum forming, compression molding, and/or injection molding to dispose the charge vessel into the skeleton casing. The present invention is not limited to any of the foregoing techniques, as other methods, combinations, and variations thereof are within the scope of the present disclosure. 
         [0052]    One embodiment of an insert molding process utilizes a press  90  as is shown in  FIG. 13 . The press  90  employs a machine cycle to produce the cartridges  10 . 
         [0053]    The machine cycle utilizing this press  90  would allow the skeleton casing to be placed in the mold and the charge vessel to be molded into the skeleton casing. The charge vessel would then be filled with the suitable propellant. 
         [0054]    Referring now to  FIG. 14 , a system for the assembly of live ammunition is shown generally at  100  and is hereinafter referred to as “system  100 .” System  100  is a system of enhancing traditional ammunition with weight savings and potential cost savings. It integrates easily into existing SCAMP or other processes and may also solve problems indicative of other systems in a more efficient fashion. 
         [0055]    In the system  100 , inventory is pulled in a pulling step  102 . In the pulling step  82 , the skeleton casings  12  and the loaded charge vessels  14  are retrieved from storage or otherwise obtained. The skeleton casings  12  and the loaded charge vessels  14  are then used in a step  104  in which they are substituted for brass casings in a SCAMP line or other process. A coating step  106  is carried out in which a thermal barrier and/or waterproof coating is applied to the primer pocket. Once completed, the ammunition is live. 
         [0056]    Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.