Primers for firearms and other munitions

Abstract

The primer includes a layered thermite coating consisting of alternating layers of metal oxide and reducible metal (thermite) deposited on a substrate, with the carbide-containing ceramic layer disposed within the alternating layers of metal oxide and reducible metal.

Description

[Technical field]

[0001] <CROSS REFERENCE TO RELATED APPLICATIONS> This application claims the benefit of U.S. Provisional Patent Application No. 63 / 150,017, filed February 16, 2021, entitled "Primer for Firearms and Other Munitions."

[0002] The present invention relates to primers for firearms and munitions, and more particularly, a primer is provided that is layered with a metal oxide and a reducible metal with a layer of a carbide-containing ceramic. [Background technology]

[0003] Firearm cartridges and other munitions such as larger projectile cartridges and explosives are often ignited by a primer. Currently available primers and detonators have a brass anvil and are made from a copper or brass alloy cup containing lead azide or lead styphnate. When the bottom of the cup is struck by the firing pin, the primer material is crushed between the bottom of the cup and the anvil, igniting the primer charge. The burning primer then ignites another combustible material such as smokeless powder or an explosive material. Lead azide and lead styphnate are dangerous due to their toxicity and high explosiveness. In addition, current manufacturing methods are very labor intensive and the manual processes required increase costs and make quality control more difficult to maintain.

[0004] Energetic materials such as thermite are currently used when a highly exothermic reaction is required. Applications include cutting, welding, refining metal ores, and enhancing the effect of high explosives. Thermite reactions occur between metal oxides and reducible metals. Examples of metal oxides include La2O3, AgO, ThO2, SrO, ZrO2, UO2, BaO, CeO2, B2O3, SiO2, V2O5, Ta2O5, NiO, Ni2O3, Cr2O3, MoO3, P2O5, SnO2, WO2, WO3, Fe3O4, CoO, Co3O4, Sb2O3, PbO, Fe2O3, Bi2O3, MnO2, Cu2O, and CuO. Examples of reducible metals include Al, Zr, Th, Ca, Mg, U, B, Ce, Be, Ti, Ta, Hf, and La. The reducing metals may also be in the form of alloys or intermetallic compounds of the above metals.

[0005] There is a need for primers made from materials that do not have the toxicity of lead.There is a further need for primers made from materials that are suitable for automated processes.There is a further need for primers made from energetic materials that serve for ignition via strike by a firing pin or that otherwise benefit from the stability of thermite. Summary of the Invention

[0006] The above needs are met by a thermite primer. The primer has a substrate having a deposition surface and a back surface. Alternating layers of metal oxide and reducible metal are deposited on the substrate. The alternating layers of metal oxide and reducible metal are configured to react with each other in response to an impact applied to the back surface of the substrate. A carbide-containing ceramic layer is disposed within the alternating layers of metal oxide and reducible metal.

[0007] The above needs are also met by a cartridge for a firearm. The cartridge includes a casing having a front end, a rear end, and a hollow interior. The cartridge includes a bullet secured to the front end of the casing, a propellant disposed in the hollow interior, and a primer secured to the rear end of the casing. The primer is in communication with the propellant. The primer includes a substrate having a deposition surface and a rear surface. The primer further includes alternating layers of metal oxide and reducible metal deposited on the substrate. The alternating layers of metal oxide and reducible metal are configured to react with each other in response to an impact applied to the rear surface of the substrate. The primer further includes a carbide-containing ceramic layer within the alternating layers of metal oxide and reducible metal.

[0008] These and other aspects of the present invention will become more apparent through the following description and drawings. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional side view of a layered thermite structure, a carbide-containing ceramic layer, and a primer passivation coating.

[0010] [Diagram 2] FIG. 2 is a cross-sectional side view of an alternative layered thermite structure, a pair of carbide-containing ceramic layers, and a passivation coating of a primer.

[0011] [Diagram 3] FIG. 3 is a cross-sectional side view of another alternative layered thermite structure, a carbide-containing ceramic layer, and a primer passivation coating.

[0012] [Figure 4] FIG. 4 is a cross-sectional side view of a cup for use with the primer material of FIGS.

[0013] [Diagram 5] FIG. 5 is a side cross-sectional view of a cartridge using the primer cup of FIG.

[0014] Like numbers refer to like elements throughout the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1-3, there is shown a primer structure 10. The primer structure 10 is deposited on a substrate 12. The primer structure includes a layered thermite coating 14, one or more carbide-containing ceramic layers 16 within the layered thermite coating 14, and a passivation coating 18.

[0016] The substrate 12 in the illustrated example is a malleable disk made from a material such as brass, copper, mild steel, and / or stainless steel and has a deposition surface 20 on which the layered thermite coating 14 is deposited, and a back surface 22 (FIG. 4). The substrate 12 is thin and malleable enough so that a strike of a firing pin against the back surface 22 will ignite the layered thermite coating 14 and the carbide-containing ceramic layer 16, as described below, yet is thick enough to facilitate the manufacture of the primer structure 10 and to secure a primer made from the primer structure 10 within a cartridge case, ammunition, modified primer cup, or other location as described below. A preferred substrate thickness is from about 0.005 inches to about 0.1 inches, and more preferably from about 0.01 inches to about 0.025 inches.

[0017] The layered thermite coating 14 includes alternating layers of metal oxides and reducible metals (only a few layers are shown for clarity). Examples of metal oxides include La2O3, AgO, ThO2, SrO, ZrO2, UO2, BaO, CeO2, B2O3, SiO2, V2O5, Ta2O5, NiO, Ni2O3, Cr2O3, MoO3, P2O5, SnO2, WO2, WO3, Fe3O4, CoO, Co3O4, Sb2O3, PbO, Fe2O3, Bi2O3, MnO2, Cu2O, and CuO. Examples of reducible metals include Al, Zr, Th, Ca, Mg, U, B, Ce, Be, Ti, Ta, Hf, and La. The metal oxide and reducible metal are preferably selected to resist abrasion and other damage by avoiding reaction products that may cause damage to the barrel of the firearm in which the cartridge containing the primer is used. One example of such a metal oxide and reducible metal combination is cupric oxide and magnesium oxide.

[0018] The thickness of each of the metal oxide layer and the reducible metal layer is determined to ensure that the proportions of the metal oxide and the reducible metal are both substantially consumed by the exothermic reaction. As an example, for a metal oxide layer made of CuO and a reducible metal layer made of Mg, the chemical reaction is "CuO+Mg->Cu+MgO+heat". Thus, for every mole of Mg (weight 24.305 grams / mole), one mole of CuO (weight 79.5454 grams / mole) is required for this reaction. The density of CuO is 6.315 g / cm 3 and the density of magnesium is 1.74 g / cm 3 Therefore, the volume of 1 mole of CuO is 12.596 cm 3 Similarly, the volume of 1 mole of Mg is 13.968 cm 3 Thus, in the illustrated example, each layer of metal oxide is about the same thickness as, or slightly thinner than, the corresponding layer of reducible metal. If other metal oxides and reducible metals are selected, the relative thicknesses of those metal oxides and reducible metals can be determined similarly.

[0019] The illustrated example of the layered thermite coating 14 in FIGS. 1 and 2 is divided into an initial ignition portion 24 deposited directly on the substrate 12 and a secondary ignition portion 26 deposited on the initial ignition portion 24. The illustrated example of the initial ignition portion 24 includes layers of metal oxide 28 and reducible metal 30 that are thinner than the layers of metal oxide 32 and reducible metal 34 in the secondary ignition portion 26. In the illustrated example, the thickness of each pair of layers of metal oxide 28 and reducible metal 30 is preferably between about 20 nm and about 100 nm, with the illustrated example having a layer pair thickness of about 84 nm. In the illustrated example, the thickness of each pair of metal oxide layer 32 and reducible metal layer 34 is greater than about 100 nm. Thinner layers burn faster and are easier to ignite, while thicker layers burn slower. The thinner layers 28, 30 in the initial ignition portion 24 are more sensitive to physical shock, making them easier to ignite in response to a firing pin strike on the back surface 22 of the substrate 12, and thus to ignite the secondary ignition portion 26. The thicker layers 32, 34 in the secondary ignition portion 26 burn slower, enhancing the reliability of ignition of a smokeless powder, explosive, or other desired ignitable material. The illustrated example of the layered thermite coating 14 has a total thickness of about 25 μm to about 1,000 μm.

[0020] The illustrated example of the thermite coating 14 in Figures 1 and 2 shows a generally uniform thickness for all layers 28, 30 in the initial ignition section 24. Similarly, the layers 32, 34 in the secondary ignition section 26 show a generally uniform thickness. Other examples include metal oxide layers and reducible metal layers of different thicknesses. For example, Figure 3 shows a primer structure 10 with a thermite layer that increases generally in proportion to the distance of the layer from the substrate 12 (only a few layers are shown for clarity). The thicknesses of layers 36 and 38 close to the substrate 12 are small, for example, about 20 nm to about 100 nm. The thicknesses of layers 40 and 42 are increasing. The thicknesses of layers 44 and 46 further from the substrate 12 are greater than layers 40 and 42. Layers 48 and 50, adjacent to the passivation coating 18 and furthest from the substrate 12, are the thickest layers, with thicknesses greater than about 100 nm. As before, the illustrated example of the layered thermite coating has a total thickness between about 25 μm and about 1,000 μm. Such thermite coatings provide essentially the same advantages of rapid ignition near the substrate 12 and relatively slow burning away from the substrate 12 and near smokeless powder, explosives, or other ignitable materials. With this gradual increase in thickness, there may not be a sharp boundary between the initial and secondary ignition sites, and a sharp boundary is not essential to the functioning of the invention.

[0021] In another example, the thickness of all layers of metal oxide and reducible metal may be less than about 100 nm, and the time required to consume all layers of metal oxide and reducible metal may be made sufficiently long to ignite conventional propellants and explosives by simply increasing the number of layers of metal oxide and reducible metal.

[0022] Other examples of layered thermite coatings 14 may include layers 28, 30, 32, 34, or layers 36, 38, 40, 42, 44, 46, 48, 50 that are deposited at different temperatures such that each layer is deposited at a temperature that is either significantly higher or lower than the adjacent layers, which, when temperature is equalized within the layered thermite coating, induces thermal expansion and contraction stresses within the layered thermite coating 14. Such expansion and contraction stresses are expected to increase sensitivity to ignition by physical shock.

[0023] The passivation layer 18 covers the layered thermite coating 14 and protects the metal oxides and reducible metals within the layered thermite coating 14. One example of a passivation layer 18 is silicon nitride. An alternative passivation layer 18 can be made from reactive metals that are self-passivating, such as aluminum or chromium. When an oxide forms on the surface of such a metal, it is self-sealing. Thus, when the exposed surface of the metal is completely covered with oxide, oxide formation stops.

[0024] The carbide-containing ceramic layer 16 is disposed within the thermite coating 14. In the illustrated example, one carbide-containing ceramic layer 16 is disposed approximately 1 / 3 of the distance to the top of the thermite coating 14. In other examples, the carbide-containing ceramic layer 16 may be disposed elsewhere in the thermite coating 14, such as at the bottom, middle, top, bottom, or other locations on the top of the thermite coating 14. In some examples, multiple layers of the carbide-containing ceramic layer 16 disposed at different locations throughout the thermite coating 14 may be included. Although one or two layers are illustrated, three or more layers may be utilized. The thickness of the carbide-containing ceramic layer 16 is thicker than the metal oxide layer or the reducible metal layer, and in the illustrated example is between about 100 nm and about 2 μm. In other examples, the carbide-containing ceramic layer 16 may be between about 500 nm and about 1 μm thick.

[0025] The carbide-containing ceramic is selected for its tendency to project relatively large particles (compared to thermite reaction products) into the propellant or other pyrotechnic or explosive material of a firearm cartridge when ignited by ignition of adjacent reducible metals and metal oxides. Examples include ceramics such as zirconium carbide, titanium carbide, silicon carbide, aluminum carbide (a metal-ceramic composite, but considered a carbide-containing ceramic herein), and combinations thereof. When multiple carbide-containing ceramic layers are present, the different carbide-containing ceramic layers may be composed of the same carbide-containing ceramic or may be composed of different carbide-containing ceramics. When these carbides (or other suitable carbides) ignite, carbon dioxide is formed by reaction with oxygen from cupric oxide. This gas production helps to propel the thermite and carbide-containing ceramic reaction products into the propellant or other pyrotechnic or explosive material. The large, hot particles produced by the reaction of the carbide-containing ceramic with oxygen continue to burn for a period of time sufficient to ensure reliable ignition of the propellant or other pyrotechnic or explosive material.

[0026] Some examples of primer structure 10 may include an adhesion layer 17 above and below each carbide-containing ceramic layer 16. In the illustrated example, adhesion layer 17 is made from titanium or chromium. In some examples, nickel may be used as the adhesion layer. The thickness of adhesion layer 17 in the illustrated example is about 5 nm to about 10 nm.

[0027] The layered thermite coating 14 can be produced by sputtering or physical vapor deposition. In particular, high power impulse magnetron sputtering can rapidly produce thermite coating 14. Alternatively, certain manufacturing methods described in U.S. Patent No. 8,298,358, issued to Kevin R. Coffey et al. on October 30, 2012, and U.S. Patent No. 8,465,608, issued to Kevin R. Coffey et al. on June 18, 2013, are suitable for depositing alternating metal oxide layers and reducible metal layers in a manner that inhibits the formation of oxides between the alternating layers, the entire disclosures of both patents being expressly incorporated herein by reference. Dr. Coffey's method allows the interface between the alternating metal oxide layers and the reducible metal layers to be substantially free of metal oxide, or, if reducible metal oxide is present, allows the thickness of the reducible metal oxide layer forming the interface to be less than about 2 nm, or even less than 1 nm. In many instances, the interface is sufficiently thin that detection by high resolution transmission electron microscopy does not allow for measurement of a large portion of the interface. Deposition of individual layers of metal oxide and reducible metal at elevated and / or reduced temperatures can optionally be employed which, upon returning to room temperature, create expansion / contraction stresses relative to other layers in the layered thermite coating 14, thereby increasing the sensitivity of the primer 10 to firing pin strikes. If desired, lithography can be used to remove unwanted portions of each layer in areas of the substrate 12 where material deposition is not desired, leaving only those portions intended to be covered by the primer structure 10.

[0028] The layered thermite coating 14 can also be produced using a deposition apparatus that uses a rotating drum. Such a system is described in U.S. Pat. No. 8,758,580 issued June 24, 2014 to R. DeVito, U.S. Pat. No. 5,897,519 issued March 9, 1999 to J.W. Seeser et al., and European Patent No. 0,328,257 invented and published August 16, 1989 by MA Scobey et al., or in other published patents or applications, all of which are expressly incorporated herein by reference in their entirety. The use of a rotating drum system allows the substrate to be rapidly moved between different chambers to deposit different layers of different materials. In one example, one chamber is used for deposition of a reducible metal, another chamber is used for deposition of a metal oxide, and yet another chamber is used for deposition of a carbide-containing ceramic. In a four chamber system, other chambers may be used to deposit adhesion layers above and below the carbide-containing ceramic. In one example, two to four chambers may be used, with two targets per chamber. Atmospheric conditions are maintained within each chamber and isolated from the rest of the system by a baffle that extends close to the drum while maintaining separation from the substrate. The correct pressure and atmospheric conditions are thereby maintained in each chamber throughout the process of depositing multiple layers, while the substrate may be moved between chambers by rotating the drum on which it is located. In addition, the pressure of the inert gas, e.g., argon, in the chamber used to deposit the reducible metal may be higher than the pressure in the chamber used to deposit the metal oxide, which inhibits the ingress of oxygen into the reducible metal chamber. Thus, the need to pump down each chamber between layers of different materials is avoided, speeding up the deposition process.

[0029] Once all of the layers of metal oxide 28, 30, reducible metal 32, 34, and carbide-containing ceramic 16 have been deposited, the passivation layer 18 may be deposited on the layered thermite coating 14 using any of the methods described above.

[0030] FIG. 4 shows an example of a primer 52 utilizing the primer structure 10. The illustrated example of the substrate 12 is a disk having an upper surface 54 that defines a recess 56 in which the deposition surface 20 is disposed. The edge of the disk 52 includes a larger diameter portion 58 and a smaller diameter portion 60 with a ledge 62 formed therebetween. The primer structure 10 is deposited on the surface 20 in the recess 56 as described above. The disk (substrate) 12 is then placed into a cup 64 to form the complete primer. The cup 64 includes a sidewall 66 having an upper end 68 and a lower end 70. The lower end 70 includes an inwardly extending protrusion 72 that is sized to abut the ledge 62 and the smaller diameter portion 60 of the disk 12. When the disk 12 is inserted into the cup 64 through the upper end 68 and then placed in position against the lower end 70, the disk 12 is prevented from passing outwardly from the lower end 70 of the cup. The disk 12 may then be retained within the cup 64 by an inward protrusion 74 that engages the disk's top surface 54. The inward protrusion 74 may be formed by punching inwardly into an outer portion of the wall 66 to form a recess 76. In some examples, an adhesive may also or alternatively be utilized to retain the disk 12 within the cup 64.

[0031] Referring to FIG. 5, the primer 52 may then be placed into a conventional firearm cartridge 78. The cartridge 78 includes a casing 80 having a general configuration. The casing 80 includes a front end 82 configured to retain a bullet 84 therein. The casing 80 also includes a rear end 84 having a groove 86 and a rent 88 to aid in extraction of the cartridge 78. Within a hollow center 92 of the casing 80 is a propellant 90. The rear end 84 of the casing 82 defines a primer pocket 94 and an ignition port 96 that extends between the primer pocket 94 and the hollow center 92. Upon striking the face 22 with a firing pin, the primer material 10 ignites and reaction products pass through the ignition port 96 into the propellant 92 which propels the bullet 84.

[0032] In another example, the primer structure 10 can be used as a primer deposit ignition material, as invented by Timothy Mohler and Daniel Yates and disclosed in U.S. Patent Application Publication No. 2020 / 0400415, published December 24, 2020, the entire disclosure of which is expressly incorporated herein by reference.

[0033] Although the illustrated example is for a firearm cartridge, the primer structure 10 can be used for larger projectile cartridges, such as those for artillery, or for other munitions, such as grenades or other explosives, that utilize a primer as part of their detonation mechanism.

[0034] Thus, the present invention provides a primer made from materials that do not have the toxicity or other safety issues of conventional primers. The primer can be easily manufactured in a manner that is suitable for automation. The primer takes advantage of the stability of thermite while providing at least the reliability of conventional primers. By adjusting the thickness of the thermite layer in the primary and secondary ignition parts, and by optionally creating expansion / contraction stresses, the sensitivity of the primer can be adjusted and tailored to a particular application. The location and thickness of the carbide-containing ceramic layer can also be tailored to a particular application. The primer of the present invention is useful not only for firearm cartridges, but also for projectiles such as artillery, grenades, and other explosives and munitions. An example primer fits into a space designed for a conventional primer.

[0035] Various modifications to the above-described embodiments will be apparent to those skilled in the art from this disclosure. For example, the shape of the primer may be circular, square, rectangular, or may have a completely different shape, may or may not have a chamfered edge, or may have a chamfered edge on either side of the primer. The primer may fit into a conventional or non-conventional primer pocket. Thus, the present invention may be embodied in other specific forms without departing from its spirit or essential attributes. The specific embodiments disclosed are intended to be illustrative only and not limiting of the scope of the invention. Reference should be made to the appended claims, rather than the specification, as to the scope of the invention.

Claims

1. a substrate having a deposition surface and a back surface; alternating layers of metal oxide and reducible metal deposited on the substrate, the alternating layers of metal oxide and reducible metal configured to react with each other in response to an impact applied to a backside of the substrate; a carbide-containing ceramic layer within the alternating layers of metal oxide and reducible metal; In a primer comprising: the carbide-containing ceramic layer is titanium carbide, aluminum carbide, silicon carbide, or a combination thereof; when the alternating layers of metal oxide and reducible metal react with each other, the carbide-containing ceramic layer is ignited by the reaction between the reducible metal and metal oxide to produce particles that are reaction products of the carbide-containing ceramic layer; The carbide-containing ceramic layer primer, wherein the particles are ejected from the primer.

2. a substrate having a deposition surface and a back surface; alternating layers of metal oxide and reducible metal deposited on the substrate, the alternating layers of metal oxide and reducible metal configured to react with each other in response to an impact applied to a backside of the substrate; a carbide-containing ceramic layer within the alternating layers of metal oxide and reducible metal; Equipped with The primer further includes an adhesion layer separating the carbide-containing ceramic layer from each of the metal oxide layers or reducible metal layers adjacent the carbide-containing ceramic layer.

3. 3. The primer of claim 2, wherein each adhesion layer is one of titanium, chromium, and nickel.

4. A cartridge a casing having a front end, a rear end, and a hollow interior; a bullet secured to the front end of the casing; a propellant disposed within the hollow interior; a primer secured within the rear end of the casing; Equipped with The primer is in communication with a propellant, the primer comprising: a substrate having a deposition surface and a back surface; alternating layers of metal oxide and reducible metal deposited on the substrate, the alternating layers of metal oxide and reducible metal configured to react with each other in response to an impact applied to a backside of the substrate; a carbide-containing ceramic layer within the alternating layers of metal oxide and reducible metal; Equipped with the carbide-containing ceramic layer is titanium carbide, aluminum carbide, silicon carbide, or a combination thereof; when the alternating layers of metal oxide and reducible metal react with each other, the carbide-containing ceramic layer is ignited by the reaction between the reducible metal and metal oxide to produce particles that are reaction products of the carbide-containing ceramic layer; The particles are fired from the primer, cartridge.

5. A cartridge comprising: a casing having a front end, a rear end, and a hollow interior; a bullet secured to the front end of the casing; a propellant disposed within the hollow interior; a primer secured within the rear end of the casing; Equipped with The primer is in communication with a propellant, the primer comprising: a substrate having a deposition surface and a back surface; alternating layers of metal oxide and reducible metal deposited on the substrate, the alternating layers of metal oxide and reducible metal configured to react with each other in response to an impact applied to a backside of the substrate; a carbide-containing ceramic layer within the alternating layers of metal oxide and reducible metal; an adhesion layer separating the carbide-containing ceramic layer from each of the metal oxide layers or reducible metal layers adjacent the carbide-containing ceramic layer; The cartridge comprises:

6. 6. The cartridge of claim 5, wherein each adhesion layer is one of titanium, chromium, and nickel.

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