Patent Application
20120199033
1. Field of the Invention
This invention relates to the manufacture of ammunition, and specifically relates to methods for producing ammunition that is waterproof and resistant to invasive corrosive materials that may lead to misfiring or fouling.
2. Description of Related Art
Ammunition of the type used in rifles or pistols, as well as ammunition used in larger artillery weapons, generally comprises a casing which houses a primer, a propellent and a projectile. The types of casings, primers, propellants and projectiles used in ammunition varies widely. The size of the unit of ammunition may vary as well from a small caliber ammunition to large military munitions and bombs.
In many, and more traditional, units of ammunition, the casing is made of a metal material, typically brass. Brass is a soft metal that is particularly suited for use as ammunition casings because it does not mar the bore of the firearm and does not harm the firing mechanism. However, brass casings are shiny and, therefore, present a problem in terms of being observable from long distances. The ability to see the casing, particularly spent casings, readily identifies the position of the shooter, which is very undesirable in hunting and in covert or other military operations.
It is known, therefore, to treat the casing of ammunition to produce low-observable ammunition. An example of such ammunition and processes for making the ammunition is disclosed in U.S. Pat. No. 6,672,219, which describes that the brass casings of ammunition are treated or coated to reduce the shine of the brass, or the casing is colored so that the casing is not observable, or is “low-observable.” It is notable that in such processes, only the casing of the ammunition is treated, and not the entire unit of ammunition, including the projectile and casing (hereinafter referred to as a “cartridge.”
It has also been observed by both military and civilian users of firearms and large artillery devices that ammunition is often subject to damage or deterioration by environmental forces in the area in which the ammunition in used. For example, it has often been observed that ammunition can be damaged by high humidity or other sources of moisture. Ammunition is, therefore, stored and handled by methods that attempt to keep the ammunition in a dry state, or to avoid exposure to high moisture levels.
Ammunition has also been rendered useless by other environmental factors, such as sand, dirt or moisture infiltrating into the casing. It has been reported, particularly in military situations in the Middle East, that the very fine sand particles of the desert can infiltrate into the casing of ammunition and cause misfiring of the ammunition. The U.S. military has reported high rates of ammunition failure or misfiring due to ammunition being degraded by desert conditions, and such ammunition failure is critical to lives and wartime expenditures.
Thus, it would be beneficial to provide ammunition, and processes for making such ammunition, that is entirely coated or treated to render ammunition waterproof, low-observable and resistant to degradation from environmental forces.
In accordance with the present invention, ammunition is provided having the entire cartridge coated or treated with a material suitable for rendering the ammunition waterproof, resistant to degradation from environmental forces and having low-observability. Methods for making such ammunition are also disclosed.
In accordance with the invention, fully-assembled ammunition (i.e., the primer, propellant and projectile are positioned in and attached to the casing to form a complete, ready-to-use cartridge) is treated or coated with a coating material that renders the entire cartridge waterproof and resistant to degradation from environmental forces. Particularly, the method of the present invention assures that all crevices or openings of the ammunition are coated to block infiltration of moisture and other undesirable or deleterious environmental elements, such as sand, salt and other corrosive elements, that might cause fouling, ammunition failure or misfiring.
While the invention may be described herein as useful for making smaller caliber cartridges, it is to be understood that any type or size of ammunition or artillery projectile can be manufactured by the disclosed method to render it waterproof, resistant to environmental degradation and low observable. The invention is suitable for both civilian and military weaponry uses.
In the drawings, which illustrate what is considered to be the best mode for carrying out the invention:
While the present invention can be adapted to use in the formation of any type of ammunition, the invention is described and illustrated herein by way of a small caliber ammunition cartridge.
A typical bullet 10, as depicted in
In prior art ammunition coating systems, the casing 12 is formed with a thin coat 24 of material that endows the bullet 10 with low observability. That is, in prior art coating systems, the casing 12 is first coated, and then the ammunition is assembled by placement of the projectile 18 in the open end 16 of the casing 12. As a result, a gap remains between the projectile 18 and the casing 12 at the point of insertion of the projectile 18 into the casing 12. Moisture and other deleterious matter can then infiltrate into the gap and foul the propellant or otherwise lead to a non-functional round of ammunition.
In the ammunition made in accordance with the present invention, a coating 30 is formed on the entire unit of ammunition after the unit of ammunition has been fully assembled for its intended purpose. Consequently, the coating 30 seals the gap that otherwise exists at the open end 16 of the casing 12 where the projectile 18 is inserted into the casing 12. By sealing the entire unit of ammunition, including the at the open end 16 of the casing and the point of insertion of the primer 20 in the closed end 22 of the casing 12, the ammunition is rendered waterproof and resistant to infiltration of deleterious matter, such as sand or salt.
The coating material that is used to coat and seal the cartridge is suitably any coating substance that can provide a thin, and highly adherent coating on the entire cartridge to render the cartridge resistant to infiltration of moisture, sand, and any other undesirable or deleterious matter into the cartridge. Coatings that are particularly suitable for use are those that have high adhesion quality and durability. High adhesion characteristics can be determined by any number of adhesion measurement methods known to those of skill in the art, including ASTM D4541, ISO 4634, ASTM D3359 and ASTM D6677 methodologies. High adhesion may be characterized by one standard as measuring between 800 psi and 4,000 psi adherent force.
The coatings that are most suitable for the invention also demonstrate durability and resistance to environmental challenges, such as abrasion or corrosion. The coating material may preferably be heat stable above 300° F., and may be heat stable up to 2000° F. The coating material may preferably be formulated to have a matte or dull finish to provide low-observability to the ammunition. Notably, low-observability may be an optional feature depending upon the intended use of the ammunition. The coating material may also be desirably formulated with low viscosities and low volatile organic compounds (VOC) content.
Coating materials that are particularly suitable for use in coating ammunition in accordance with the invention include cross linked epoxies, polyurethanes and polysiloxane coating materials, or any other similar coating material that possesses good adhesion properties and resistance to moisture and other environmental challenges, such as abrasive materials or corrosive materials or conditions. Exemplary suitable coating materials that may be used in making ammunition of the present invention are inorganic polymers having the desired characteristics of high heat stability, good adhesion and resistance to environmental degradation. Particularly suitable coating materials are inorganic silicon-based polymers, such as silicon-based epoxies. Zinc silicates, for example, provide the desired characteristics necessary to the production of the ammunition of the present invention, and tend to display inherent low gloss, or matte, characteristics suitable for low-observability.
Another particularly suitable coating material is an essentially inorganic, silicon-oxygen polymer, such as polysiloxane polymers. Polysiloxane polymers have very high heat stability (up to about 2000° F.) and, therefore, provide a heat resistant coating that is desirable in the coating of ammunition. Suitable polysiloxane polymers also provide thin, very durable, highly adherent and hard film coatings that are similar in structure to quartz compound structures. Examples of epoxy polysiloxane coatings that may be useful in the invention are disclosed in U.S. Pat. No. 5,618,860 and U.S. Pat. No. 5,804,616, the contents of which are incorporated herein by reference.
Ammunition coated with polysiloxane is very resistant to environmental degradation. Polysiloxane polymer coatings on the ammunition also render the ammunition resistant to the tars that typically build up in the barrel or bore of firearms, thereby significantly reducing fouling by better than 50%. Other examples of suitable polysiloxane polymers are disclosed in one or more of the following references: U.S. Pat. No. 5,275,645; U.S. Pat. No. 5,618,860; U.S. Pat. No. 5,760,155; U.S. Pat. No. 5,888,280; U.S. Pat. No. 5,942,073; and U.S. Pat. No. 6,169,066. The contents of the referenced patents are incorporated herein by reference.
One particularly suitable coating that may be used in formation of the ammunition of the present invention is Xylexin™ coating, which is available from Shield Master of Provo, Utah.
Polysiloxane polymers further provide a coating which renders the ammunition resistant to water and other environmental damage or degradation which can cause failure of the ammunition to fire. Such conditions include infiltration of moisture, sand and dirt into the casing. Polysiloxane polymers have low viscosity and are excellent for combining with other compounds or formulas to achieve the desired qualities of the coating material. For example, colorants may be added to provide a selected color or look (e.g., a designated pattern, such as camouflage) to the ammunition. The coloration of the ammunition may also be beneficial in identifying the source of the ammunition.
Additionally, compounds may be added to achieve the desired finish to the ammunition, such as a matte, low-gloss or dulled finish. Polysiloxane polymers, because of their low viscosities, are also low VOC compounds so that they are more environmentally safe, and safe to handle.
Additional compounds or material may be added to the coating to aid in the process of coating the ammunition for later identity or quality assurance. For example, suitable doping agents or specially formulated fluorescing compounds can be added to the coating that enable the coated cartridge to fluoresce upon exposure to ultraviolet (UV) light, thereby providing assurance that the ammunition has been fully and adequately coated. The use of different fluorescing agents may also act as a marker to aid in later identification of the source of the ammunition. Suitable fluorescing agents are available from Beaver Luminescers of Newton, Mass.
The coated ammunition of the present invention is made by coating or otherwise treating an entirely formed cartridge, meaning that the projectile, propellant and primer are completely formed to the casing to produce a “ready-to-use” unit of ammunition. The fully formed ammunition is then coated with a thin layer or film of the coating material. The thickness of the layer or film of coating may be from about 0.01 mm to about 0.045 mm, depending on the size of the ammunition, with smaller caliber ammunition having thinner coating and large artillery shells having a relatively thicker coating. The weight of the coating is less than 0.09% of the total weight of the unit of ammunition.
The layer or film of coating material is applied to the fully formed unit of ammunition by any known method, including but not limited to, spraying, dipping, brushing, rolling, electro-deposition, or combinations of these techniques. A single layer of coating material is sufficient to produce a unit of ammunition with the desired characteristics as described herein.
Once the coating is applied to the unit of ammunition, the coating may be allowed to dry, cure or set under ambient conditions. In a particularly suitable process, however, an anaerobic curable coating is used to coat the ammunition to assure that the coating fully seals all openings or crevices in the ammunition, thereby assuring that the ammunition is waterproof and sealed from deleterious environmental matter, such as sand or salt. An example of the formation of anaerobic curable coatings that may be employed in the present invention is described in U.S. Pat. No. 6,883,413, the contents of which are incorporated herein by reference.
While the described inorganic polymers used in making the ammunition of the invention typically have excellent adherent qualities, or can be blended with other compounds to achieve the desired or necessary adhere characteristics, it may be desirable to pre-treat the fully formed unit of ammunition as a means of improving adhesion of the coating material to the ammunition. For example, the unit of ammunition may be etched by mechanical means to roughen the surface of the ammunition. Alternatively, the ammunition may be acid-etched or subjected to an acid bath to prepare the surface of the ammunition for receipt of the coating material. Other means for preparing or treating the surface of the ammunition are known and usable to produce the desired characteristics in the finished ammunition.
Testing of ammunition having a coating formed in accordance with the processes disclosed herein have proven to be waterproof and resistant to environmental conditions. The ammunition of the present invention has been especially designed to withstand the desert conditions experienced in the conflicts of desert areas such as the Middle East where firing failures are extremely high due to sand, grit and/or moisture infiltrating the ammunition. The ammunition of the present invention is also low-observable, making the ammunition suitable for a wide range of uses and applications, both civilian and military. Reference herein to specific details of the structure of coated ammunition and the methods of making are by way of example only and are not meant to be by way of limitation.
This application is a non-provisional application claiming priority to provisional patent application Ser. No. 60/994,081, filed Sep. 17, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60994081 | Sep 2007 | US |
