Primer cup for a thermite primer

Abstract

A primer cup includes a substantially flat disk retained in the bottom of a tube. Prior to installation in the tube, alternating layers of reducing metal and metal oxide, and in some examples one or more layers of a carbide-containing ceramic, are deposited on one surface of the disk. The bottom end of the tube includes a folded over portion forming a disk retaining structure. The disk is pressed into this disk retaining structure with the layered thermite structure facing the hollow interior of the tube, and then staked into place. The resulting primer cup facilitates the use of thermite while fitting within a standard primer pocket of a standard ammunition casing.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of US provisional patent application serial number 63 / 746,967, which was filed on January 18, 2025, and entitled "Primer Cup for a Thermite Primer."TECHNICAL FIELD

[0002] The present invention relates to cups for primers for firearms and other munitions. More specifically, a primer cup permits a layered thermite primer material to be deposited upon a flat substrate and then combined with a cup to fit within a primer pocket of a conventional firearm cartridge or munition primer pocket.BACKGROUND INFORMATION

[0003] Cartridges for firearms, as well as other munitions such as larger projectile cartridges and explosives are often ignited by a primer. Presently available primers and detonators are made from a copper or brass alloy cup with a brass anvil and containing lead azide or lead styphnate. When the base of the cup is struck by a firing pin, the priming compound is crushed between the cup's base and the anvil, igniting the primer charge. The burning primer then ignites another flammable substance such as smokeless powder, explosive substances, etc. Lead azide and lead styphnate are hazardous due to their toxicity as well as their highly explosive nature. Additionally, present manufacturing methods are very labor-intensive, with the necessary manual processes raising costs, causing greater difficulty in maintaining quality control.

[0004] Energetic materials such as thermite are presently used when highly exothermic reactions are needed. Uses include cutting, welding, purification of metal ores, and enhancing the effects of high explosives. A thermite reaction occurs between a metal oxide and a reducing metal. Examples of metal oxides include La2O3, AgO, ThO2, SrO, ZrO2, UO2, BaO, CeO2, B2O3, SiO2, V2O5, Ta2O5, NiO, Ni2O3, Cr2O3, M0O3, P2O5, SnO2, WO2, WO3, Fe3O4, COO, C03O4, Sb2O3, PbO, Fe2O3, Bi2O3, MnO2, Cu2O, and CuO. Example reducing metals include Al, Zr, Th, Ca, Mg, U, B, Ce, Be, Ti, Ta, Hf, and La. The reducing metal may also be in the form of an alloy or intermetallic compound of the above-listed metals.

[0005] A properly designed energetic material would provide an effective alternative to presently used primer materials, as well as being safer to manufacture. Examples of such energetic materials and methods of making the energetic materials are disclosed in US 10,882,799, which was issued to K. R. Coffey et al. on January 5, 2021, and US 11,650,037, which was issued to D. Yates on May 16, 2023. Additionally, primers may be made using the procedures described within US 2024 / 0361113, which was invented by D. Yates, published on October 31, 2024, and resulted in US 12,385,727, which was issued on August 12, 2025. The entire disclosure of each of the above references is expressly incorporated herein by reference. In addition to the structures and methods disclosed therein, a primer cup is disclosed herein for easily installing such a primer within a conventional cartridge casing, or within another location that is designed to receive a conventional primer.PURPOSE OF THE INVENTION

[0006] Layered thermite structures are optimally deposited upon flat substrates. However, conventional ammunition casings as well as other munitions typically include a primer pocket which is dimensioned and configured to secure a conventionally shaped primer cup therein. Accordingly, there is a need for a primer cup structure and method of manufacturing the primer cup which securely holds a flat substrate within a primer cup. The flat substrate must be positioned within the cup so that when the cup is installed within an ammunition casing or other munition, the substrate side opposite the deposition side is positioned to be struck by a conventional firing pin. The manufacturing method must facilitate deposition of the thermite on one side of the substrate, and must then facilitate simplified, secure installation of that substrate within the remaining cup structure to produce a suitable primer.SUMMARY

[0007] The above needs are met by a cup for a thermite primer. The cup comprises a tube having at least one sidewall defining a hollow interior therein and a sidewall interior surface. The tube further has a tube first end and a tube second end. The tube second end includes a first foldover portion and a second foldover portion. The first foldover portion extends along the sidewall interior surface towards the first end. The second foldover portion extends away from the at least one sidewall and into the hollow interior of the tube. The cup further comprises a disk defining a disk first surface, a disk second surface, and at least one disk edge between the disk first surface and disk second surface. The at least one disk edge abuts the first foldover portion, and the first surface of the disk abuts the second foldover portion.

[0008] The above needs are also met by a cartridge. The cartridge comprises a casing having a front end, a back end, and a hollow interior. The cartridge has a propellant disposed within the hollow interior, and a primer cup secured within the back end of the casing. The primer cup is in communication with the propellant. The primer cup comprises a tube having at least one sidewall defining a hollow interior therein and a sidewall interior surface. The tube further has a tube first end and a tube second end. The tube second end includes a first foldover portion and a second foldover portion. The first foldover portion extends along the sidewall interior surface towards the first end, and the second foldover portion extends away from the at least one sidewall and into the hollow interior of the tube. The primer further comprises a disk defining a disk first surface, a disk second surface, and at least one disk edge between the disk first surface and disk second surface. The at least one disk edge abuts the first foldover portion, and the first surface of the disk abuts the second foldover portion.

[0009] The above needs are further met by a method of making a cup for a thermite primer. The method comprises providing a cup having at least one sidewall, a first end, and a second end, the first end being open, and the second end being closed by a second end wall. The at least one sidewall has an interior surface. The method further comprises making a hole within the second end wall defined within a peripheral edge of the second end wall. The peripheral edge of the second wall is formed into a first foldover portion disposed adjacent to the interior surface of the at least one sidewall. A terminal section of the first foldover portion is formed into a second foldover portion extending away from the interior surface of the sidewall. The method further includes providing a disk having a disk first surface, a disk second surface, and at least one disk edge extending between the disk first surface and disk second surface. At least one layer of metal oxide and at least one layer of reducing metal are provided on the disk first surface. The disk is secured within the cup so that the at least one disk edge abuts the first foldover portion and the disk first surface abuts the second foldover portion.

[0010] These and other aspects of the invention will become more apparent through the following description and drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is a cutaway perspective view of an example of a primer cup.

[0012] Fig. 2 is a perspective view of a disk for a primer cup of Fig. 1.

[0013] Fig. 3 is a perspective view of a tube for a primer cup of Fig. 1.

[0014] Fig. 4 is a partially schematic side elevational view showing a first step of making the tube of Fig. 3.

[0015] Fig. 5 is a partially schematic side elevational view showing a second step of making the tube of Fig. 3.

[0016] Fig. 6 is a partially schematic side elevational view showing a third step of making the tube of Fig. 3.

[0017] Fig. 7 is a perspective view of a substrate sheet for making the disk of Fig. 2.

[0018] Fig. 8 is a side elevational view of the substrate sheet of Fig. 7, showing a mask applied to a top surface of the sheet.

[0019] Fig. 9 is a partially schematic side elevational view showing a first step of installing the disk of Fig. 2 into the tube of Fig. 3.

[0020] Fig. 10 is a partially schematic side elevational view showing a second step of installing the disk of Fig. 2 into the tube of Fig. 3.

[0021] Fig. 11 is a partially schematic side elevational view showing a third step of installing the disk of Fig. 2 into the tube of Fig. 3.

[0022] Fig. 12 is a partially schematic side elevational view showing a fourth step of installing the disk of Fig. 2 into the tube of Fig. 3.

[0023] Like reference characters denote like elements throughout the drawings.DETAILED DESCRIPTION

[0024] Referring to the drawings, an example of a primer cup 10 is shown. The primer cup 10 includes a disk 12 secured within the bottom of a tube 14. Both the disk 12 and tube 14 in the illustrated example are made from a malleable material such as brass, copper, soft steel, and / or soft stainless steel. Referring to Figs. 1-3, the disk 12 includes a substrate 16 having a top surface 18 upon which an ignitable material 20 has been deposited. The disk 12 also includes a bottom surface 22 opposite the top surface, and an edge 24 which, depending on the shape of the disk 12, may include one or more surfaces surrounding the substrate between the top surface 18 and bottom surface 22. The tube 14, depending on the shape, includes one or more sidewall(s) 26 surrounding a hollow interior 28. The one or more sidewall(s) 26 includes a top end 30 and a bottom end 32. The bottom end 32 includes a disk retention structure which in the illustrated example includes a folded over portion 34 which terminates in a disk positioning protrusion 36, effectively acting as a stop collar via a surface 39 extending away from the sidewall(s) 26 upon which the installed disk 12 may rest. The illustrated example of a disk retention structure further includes inwardly projecting disk retention ribs 38 defined on the interior surface 40 of the fold over portion 32. Although the illustrated number of disk retention ribs 38 is 4, a greater or lesser number may be used. The illustrated example of a disk retention structure also includes an annular groove 42 as a result of staking the bottom end 32 of the tube 14 to compress material from the fold over portion 34 into the side edge 24 of the disk 12 to more securely retain the disk 12 within the tube 14. Other examples of acceptable staking processes may produce a plurality of staking indentations encircling the fold over portion 34.

[0025] As used herein, terms such as top, bottom, right, left, etc. are used for convenience of reference only, recognizing that the portion of any object on top can be changed by simply rotating the object. As used herein, a disk refers to a substantially flat substrate that is structured for installation in the bottom of the tube 14. Although the illustrated example of the disk 12 is round, the disk is not limited to this shape. It is to be understood that terms such as annular as used herein refer to the primer cup 10 shown in the drawing Figures, adapted to house a round disk. In other embodiments of the invention the annular components may be formed to other shapes. As used herein, substantially flat means sufficiently close to flat to facilitate deposition of the ignitable material described below, as well as to form an appropriate striking surface for a firing pin on the opposing side. As used herein, tube is defined as a structure having at least one sidewall surrounding a hollow interior, with one end being dimensioned and configured to secure the disk 12 therein. Although the illustrated example of the tube 14 is cylindrical, other shapes may be used.

[0026] The primer cup 10 is dimensioned and configured to fit within a standard primer pocket within an ammunition cartridge or other munition. As used herein, ammunition includes cartridges for firearms, other small arms, blank cartridges, cartridges for fastener guns such as nail guns, and the like. The cartridge includes a casing having a front end and a back end, with a side wall therebetween. A primer is secured to or within the back wall of the casing. If the cartridge is for use in a firearm, one or more projectiles will be secured within the front end of the casing. In the case of a rifle, handgun, or other small arms utilizing a rifled barrel, the projectile is a single bullet which is secured by friction fit within the front end of the casing. In the case of a shotgun, the projectile(s) may be a plurality of pellets held within a forward portion of the casing or a single, larger slug held within a front portion of the casing, with the casing having a closed front end. A propellant is held in the interior of the casing. In the case of a shotgun, a wad separates the propellant from the pellets or slug. In the case of a blank cartridge or fastener gun cartridge, no projectile is included, and the front end is closed either by the casing itself or by a wad held within the front end of the casing. Primers are also used within larger munitions, for example, larger projectile cartridges as well as explosives.

[0027] Those skilled in the art will recognize that conventional primers are supplied in the form of a cup because such a cup is a convenient container for lead azide and lead styphnate. However, specific thermite compositions are not only suitable ignitable materials for use as a primer, but are also significantly safer and easier to produce than conventional primers made with lead azide and lead styphnate. The thermite compositions disclosed within US 10,882,799, US 11,650,037, and US 2024 / 0361113 (issued as US 12,385,727), and made utilizing the procedures described within these references are sufficiently stable and impact sensitive for use as the ignitable material in a primer. As indicated above, the entire disclosure of each of these references is expressly incorporated here and by reference. Those skilled in the art will recognize that the alternating layers of reducing metal, metal oxide, and the one or more layers of carbide containing ceramic described in the above references are best deposited on a flat surface, rather than within a cup. Accordingly, it is necessary to provide a flat surface for the deposition process, and then to place the substrate and deposited ignitable material within a suitable cup.

[0028] The tube 14 can be made beginning with a conventional cup 44 made from brass, copper, or other suitable material, which has been formed into the proper shape by procedures well known to those skilled in the art. Referring to Fig. 4, the conventional cup 44 is placed within an appropriate die 46 which supports the bottom edges 48 of conventional cup 44. The die 46 includes a hole 49 below the portion 50 of the cup 44 which will be removed using an appropriate punch 52 as the cup 44 is held in place against the die 46 using a fixture 53 which in some examples may be held in place by spring pressure. Fig. 4 depicts such an arrangement where the portion 50 of the cup 44 has been punched out. Next, as shown in Fig. 5, the cup 44 is inverted upside down and placed over a draw post 54 having a raised annular edge 56 as well as an opening 58 for receiving a punch 60. The cup 44 is held against a draw post 54 by a fixture 62 as the punch 60 pushes the bottom edge 64 of the cup 44 downward to begin creating the fold over portion 34 (Fig. 1) of the primer tube 14. As shown in Fig. 6, in the case of primer cup 10 as shown, the cup 44, which is still inverted, is then placed over another support post 66 having a flat annular surface 68 and held in place by a fixture 70. A punch 72 having an annular surface 74 is then used to create the disk positioning protrusion 36, completing the formation of the tube 14. The disk retention ribs 38 may be formed during one of the above forming steps. As one example, the punch 72 may include cutouts to allow material from the tube 14 to flow into these cutouts as the disk positioning protrusion 36 is created as shown in Fig. 6.

[0029] Turning to production of the disk 12, deposition of the thermite 20 on the substrate 16 is best accomplished by processing a larger substrate plate 76 having multiple individual substrates 16 thereon, as illustrated in Fig. 7. However, extraction of the individual substrates 16 from the plate 76 must then be accomplished without damage to the thermite 20. In the illustrated example process, the individual substrates 16 are precut from the plate 76, and then returned to the plate 76 in a manner that secures them within the locations they originally occupied within the plate 76. Next, as shown in Fig. 8, a mask 78 is placed over the top surface 80 of the plate 76. The mask 78 defines holes 82 therein, with each hole being substantially centered over one of the precut substrates 16. In determining the positions of the holes 82, it must be considered that the example process described within US 2024 / 0361113 positions the plate 76 on a rotating drum which carries the plate 76 from deposition chamber to deposition chamber. Therefore, as the plate 76 is bent to place it on the drum, the plate 76 and masks 78 will slide with respect to each other as shown by the arrows A&B. Therefore, the diameter of the drum and the corresponding change in positions of the holes 82 with respect to the individual substrates 16 must be taken into account when determining the positioning of the holes 82 within the mask 78. Thermite 20 is then deposed on the substrate 16.

[0030] Once deposition of the thermite 20 is complete, the mask 78 is removed, and individual disks 12 are fitted over a punch 84 and aligned with individual tubes 14 as shown in Fig. 9. Next, as shown in Figs. 10-11, the disk 12 is pushed into the central opening of the disk retaining structure at the bottom end of the tube 14 which in the illustrated example is accomplished using the punch 84 while the tube 14 is held in place by the fixture 85. At this point, the disk retention ribs 38 retain the disk 12 within the tube 14. As shown in Fig. 12, a staking tool 86 is utilized to form the annular ring 42, compressing the material of the tube 14 against the edge 24 of the disk 12 to stake the disk 12 in place. At this point, a complete primer cup 10 has been made.

[0031] The primer cup 10 may be placed into the primer pocket of an ammunition cartridge or other munition in exactly the same manner as any other primer cup. Upon a firing pin striking the surface 22, the disk 12 will deform, and the impact and deformation will ignite the thermite 20, subsequently igniting the propellants within the ammunition cartridge or explosive within the munition.

[0032] The present invention therefore provides a primer cup which permits deposition of alternating layers of reducing metal and metal oxide onto a substantially flat substrate, along with one or more layers of a carbide-containing ceramic in some examples. Once deposition is complete, this substrate is incorporated into a cup having substantially the same external configuration as a conventional primer. The resulting primer is not only considerably easier and safer to manufacture than conventional primers, but also provides long term stability and reliable ignition of the munition.

[0033] A variety of modifications to the above-described embodiments will be apparent to those skilled in the art from this disclosure. Thus, the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention. The appended claims, rather than to the foregoing specification, should be referenced to indicate the scope of the invention.

Claims

What is claimed is:

1. A cup for a thermite primer, the cup comprising:a tube, the tube having at least one sidewall, the at least one sidewall defining a hollow interior therein, the at least one sidewall defining a sidewall interior surface, the tube further having a tube first end and a tube second end, the tube second end including a first foldover portion and a second foldover portion, the first foldover portion extending along the sidewall interior surface towards the first end, the second foldover portion extending away from the at least one sidewall and into the hollow interior of the tube; anda disk, the disk defining a disk first surface, a disk second surface, and at least one disk edge between the disk first surface and disk second surface, the at least one disk edge abutting the first foldover portion, the first surface of the disk abutting the second foldover portion.

2. The primer cup according to claim 1, wherein the first foldover portion includes at least one disk retention rib, the at least one disk retention rib extending towards the at least one disk edge.

3. The primer cup according to claim 1, wherein the second foldover portion is substantially parallel to the at least one sidewall.

4. The primer cup according to claim 1, wherein the disk is retained within the tube by staking the tube second end.

5. The primer cup according to claim 4, further comprising an annular groove formed by the staking process.

6. The primer cup according to claim 1, wherein the disk first surface includes at least one layer of reducing metal and at least one layer of metal oxide.

7. A cartridge, comprising:a casing having a front end, a back end, and a hollow interior;a propellant disposed within the hollow interior;a primer cup secured within the back end of the casing, the primer cup being in communication with the propellant, the primer cup comprising;a tube, the tube having at least one sidewall, the at least one sidewall defining a hollow interior therein, the at least one sidewall defining a sidewall interior surface, the tube further having a tube first end and a tube second end, the tube second end including a first foldover portion and a second foldover portion, the first foldover portion extending along the sidewall interior surface towards the first end, the second foldover portion extending away from the at least one sidewall and into the hollow interior of the tube; anda disk, the disk defining a disk first surface, a disk second surface, and at least one disk edge between the disk first surface and disk second surface, the at least one disk edge abutting the first foldover portion, the first surface of the disk abutting the second foldover portion.

8. The cartridge according to claim 7, wherein the first foldover portion includes at least one disk retention rib, the at least one disk retention rib extending towards the at least one disk edge.

9. The cartridge according to claim 7, wherein the second foldover portion is substantially parallel to the at least one sidewall.

10. The cartridge according to claim 7, wherein the disk is retained within the tube by staking the tube second end.

11. The cartridge according to claim 10, further comprising an annular groove formed by the staking process.

12. The cartridge according to claim 7, wherein the disk first surface includes at least one layer of reducing metal and at least one layer of metal oxide.

13. A method of making a cup for a thermite primer, comprising:providing a cup, the cup having at least one sidewall, a first end, and a second end, the first end being open, and the second end being closed by a second end wall, the at least one sidewall having an interior surface;making a hole within the second end wall, the hole being defined within a peripheral edge of the second end wall;forming the peripheral edge of the second wall into a first foldover portion, the first foldover portion being disposed adjacent to the interior surface of the at least one sidewall;forming a terminal section of the first foldover portion into a second foldover portion, the second foldover portion extending away from the interior surface of the sidewall;providing a disk, the disk having a disk first surface, a disk second surface, and at least one disk edge extending between the disk first surface and disk second surface;providing at least one layer of metal oxide and at least one layer of reducing metal on the disk first surface; andsecuring the disk within the cup so that the at least one disk edge abuts the first foldover portion and the disk first surface abuts the second foldover portion.

14. The method according to claim 13, further comprising forming protrusions extending from the first foldover portion.

15. The method according to claim 13, further comprising staking the second end of the cup, whereby the first foldover portion is pushed against the disk edge to retain the disk therein.

16. The method according to claim 13, wherein said disk is formed by precutting substrates from a plate and returning the substrates to the plate in the locations they originally occupied with the plate prior to providing the at least one layer of metal oxide and at least one layer of reducing metal on the disk first surface.

17. The method according to claim 16, wherein the step of providing at least one layer of metal oxide and at least one layer of reducing metal on the disk first surface is achieved using a mask.

18. The method according to claim 13, further comprising staking the second end wall of the cup.

19. The method according to claim 13, wherein said securing the disk within the cup so that the at least one disk edge abuts the first foldover portion and the disk first surface abuts the second foldover portion creates an annular ring.

20. The method according to claim 13, wherein said securing the disk within the cup so that the at least one disk edge abuts the first foldover portion and the disk first surface abuts the second foldover portion creates a plurality of staking indentations.

Images