Propellant

Abstract

A propellant in the form of a pellet includes adjoining pellet sections. Each pellet section includes a smokeless powder, a burnable metal, and a polymer. The smokeless powder in each pellet section will in many examples be different from the burn rate of the smokeless powder in other pellet sections. A nonignitable tube passes through the center of the pellet. When the pellet is used within a firearm cartridge, the ignition products from the primer travel through the nonburnable tube, igniting the pellet sections sequentially from the front to the rear of the cartridge. The pressure generated by the propellant within a cartridge casing can be maximized and controlled through the selection of the burn rate for each pellet section.

Claims

1. A propellant pellet, comprising: a first pellet section, comprising: a first smokeless propellant powder having a first burn rate; a burnable metal adjacent to the first smokeless powder; a polymer adjacent to the first smokeless powder or the burnable metal, the polymer having a melting temperature below an ignition temperature of the first smokeless powder; a second pellet section joined to the first pellet section, the second pellet section, comprising: a second smokeless propellant powder having a second burn rate, the second burn rate being different than the first burn rate; a burnable metal adjacent to the second smokeless powder; and a polymer adjacent to the second smokeless powder or the burnable metal, the polymer having a melting temperature below an ignition temperature of the second smokeless powder.

2. The propellant pellet of claim 1, wherein the burn rate of the second smokeless powder is faster than the burn rate of the first smokeless powder.

3. The propellant pellet of claim 2, further comprising a nonignitable tube extending from the primer to a position within the first pellet section, the nonignitable tube being structured to direct reaction products from the primer to the position within the first pellet section.

4. The propellant pellet of claim 1, further comprising a nonignitable tube extending from the primer to a position within the first pellet section, the nonignitable tube being structured to direct reaction products from the primer to the position within the first pellet section.

5. A firearm cartridge, comprising: a propellant pellet, comprising: a first pellet section, comprising: a first smokeless propellant powder having a first burn rate; a burnable metal adjacent to the first smokeless powder; a polymer adjacent to the first smokeless powder or the burnable metal, the polymer having a melting temperature below an ignition temperature of the first smokeless powder; a second pellet section, the second pellet section, comprising: a second smokeless propellant powder having a second burn rate, the second burn rate being different than the first burn rate; a burnable metal adjacent to the second smokeless powder; a polymer adjacent to the second smokeless powder or the burnable metal, the polymer having a melting temperature below an ignition temperature of the second smokeless powder; a projectile secured adjacent to the first pellet section; a primer secured adjacent to the second pellet section; and a nonignitable tube extending from the primer to a position within the first pellet section, the nonignitable tube being structured to direct reaction products from the primer to the position within the first pellet section.

6. The propellant pellet of claim 5, wherein the burn rate of the second smokeless powder is faster than the burn rate of the first smokeless powder.

7. A method of making a propellant pellet, the method comprising: providing a first smokeless powder; providing a burnable metal; providing a polymer; providing a solvent; placing the first smokeless powder, burnable metal, and polymer within the solvent, whereby the first smokeless powder, burnable metal, and polymer are combined; removing the solvent; and hot pressing the combined first smokeless powder, burnable metal, and polymer into a pellet.

8. The method according to claim 7, further comprising: providing a second smokeless powder, the second smokeless powder having a different burn rate than the first smokeless powder; providing a burnable metal; providing a polymer; providing a solvent; placing the second smokeless powder, burnable metal, and polymer within the solvent, whereby the second smokeless powder, burnable metal, and polymer are combined; removing the solvent; hot pressing the combined second smokeless powder, burnable metal, and polymer into a pellet; and joining the pellet having the first smokeless powder to the pellet having the second smokeless powder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG. 1 is a perspective view of a propellant pellet.

[0062] FIG. 2 is a side cross-sectional view of a cartridge for a firearm containing the propellant pellet of FIG. 1.

[0063] FIG. 3 is a side partially cross sectional view of a cartridge being discharged within the barrel of a firearm.

[0064] FIG. 4 is a side partially cross sectional view of a cartridge being discharged within the barrel of a firearm.

[0065] FIG. 5 is a side partially cross sectional view of a cartridge being discharged within the barrel of a firearm.

[0066] FIG. 6 is a side partially cross sectional view of a cartridge being discharged within the barrel of a firearm.

[0067] FIG. 7 is a side partially cross sectional view of a cartridge being discharged within the barrel of a firearm.

[0068] FIG. 8 is a graph showing a pressure curve generated by a prior art propellant.

[0069] FIG. 9 is a graph showing a pressure curve that is obtainable utilizing a propellant pellet of FIG. 1.

[0070] Like reference characters denote like elements throughout the drawings.

DETAILED DESCRIPTION

[0071] Referring to the drawings, a propellant is illustrated. The propellant is a combination of either single base (nitrocellulose) or double base (nitrocellulose and nitroglycerin) smokeless powder; a burnable metal, for example, magnesium; and a low temperature thermoplastic, for example, ethylene vinyl acetate. The propellant is formed into a single pellet, which is ignited from one end, and burns to the other end in order to produce the desired gas. The composition of the propellant, and thus the burn rate of the propellant, may vary along the length of the pellet, as described in greater detail below. The shape of the pellet may also be structured to provide varying gas production along the length of the pellet during ignition, thus controlling the pressure generated as the pellet is ignited, in the manner described below in greater detail.

[0072] The pellet is made from a combination of a burnable metal such as magnesium, aluminum, boron, beryllium, or zirconium; nitrocellulose; and possibly nitroglycerin. The illustrated examples herein use magnesium as the burnable metal, because as compared to other burnable metals, magnesium has a lower hardness level, and therefore places less wear and tear on the interior of firearm barrels when used as an additive to a propellant. Other burnable metals, such as aluminum, may be used without departing from the scope of the invention. The primary purpose of the low temperature thermoplastic is to bind the propellant components into a single pellet having the desired shape, with the desired materials in the desired location along the length of the pellet. Ethylene vinyl acetate is an example of a suitable polymer, with one example being marketed by DuPont under the trademark ELVAX 410. Although binding the pellet together is the primary purpose of the polymer, the polymer does contribute to gas production as the pellet burns.

[0073] In the example of a single base propellant, magnesium will react with nitrocellulose as follows:

3Mg+2C.sub.6H.sub.10O.sub.10N.sub.3->3MgO+6H.sub.2O+3N.sub.2+12CO

[0074] Thus, an example combination of magnesium and single base propellant, disregarding the polymer, should consist of about 10.9% magnesium and 89.1% nitrocellulose, +/2%.

[0075] In the example of a double base propellant, disregarding the polymer, magnesium will react with nitrocellulose as shown above, and will react with nitroglycerin as follows:

2C.sub.3H.sub.5N.sub.3O.sub.9+7Mg->6CO+5H.sub.2O+3N.sub.2+7MgO

[0076] Thus, an example combination of magnesium and double base propellant, based on a double base propellant having about 40% nitroglycerin, would include about 13% magnesium, 52% nitrocellulose, and 35% nitroglycerin. Double base propellants having different proportions of nitrocellulose and nitroglycerin may be used, with the percentages of nitrocellulose, nitroglycerin, and magnesium varying accordingly. Other burnable metals will react similarly during ignition of the propellant, so the portions of ingredients for other variations of the propellant can be similarly determined.

[0077] The ethylene vinyl acetate, or other polymer, will typically form about 2% of the total combination. Since the above formulas and compositions are based on the combination of smokeless powder and magnesium only, without taking the polymer into account, a slightly higher percentage of nitroglycerin and/or nitrocellulose would be used in conjunction with the polymer in order to provide a source of oxygen for burning the polymer during ignition of the propellant. The additional nitrocellulose or nitroglycerin required would be calculated using the chemical reaction caused by the burning of the polymer, and then supplying a sufficient amount of nitroglycerin or nitrocellulose to supply a sufficient amount of oxygen to complete the chemical reaction for the amount of polymer provided.

[0078] The magnesium or other burnable metal, as well as the ethylene vinyl acetate or other polymer, are added to the single base or double base smokeless powder by placing the powder within a solvent along with the burnable metal and polymer. An example of a suitable solvent is cyclohexane. When the solvent is removed, for example, by evaporating the solvent, the result is smokeless powder particles with a burnable metal and polymer coating.

[0079] The resulting particles can then be hot pressed into a desired configuration at a temperature below the ignition temperature of the propellant. For example, if ELVAX 410 is the polymer used, then the resulting particles can be hot pressed at a temperature of about 70 C. The results of the hot pressing process is a single propellant pellet having the desired configuration.

[0080] Other methods of making the propellant can include adding only the single base or double base powder, as well as the polymer, to the solvent. After the solvent has been removed, the burnable metal can be added in a powder form, and the resulting mixture can be hot pressed into the desired shape. As another alternative, if the single base or double base powder, burnable metal, and polymer are all in the form of a powder, they can be hot pressed directly into the desired configuration.

[0081] Such a single propellant pellet can be configured to provide varying burn rates along its length. Presently available single base and/or double base smokeless powders are already designed to have specific burn rates, through controlling of the particle size as well is the specific chemical composition. These powders can be arranged into a single pellet as illustrated in FIG. 1. The illustrated example of the pellet 10 is generally cylindrical in shape, having a tapered configuration with a narrow front end 12 and a wide back end 14. A passageway 16, which in the illustrated example is substantially coaxial with the pellet 10, has been molded within the pellet 10. At least the back end 18 of the central passageway 16 is open.

[0082] Smokeless powders having different burn rates have been incorporated into different sections of the pellet 10. In the illustrated example, the section having the slowest burning rate is at the front end 12 of the pellet 10, with increasing burn rates progressing towards the back end 14 of the pellet 10. Thus, in the illustrated example of a pellet 10 having five sections with different burn rates, forwardmost section 19 has the slowest burn rate. Section 20, which is adjacent to section 18, has a faster burn rate than section 18. Section 22, which is adjacent to section 20, has a faster burn rate than section 20. Section 24, which is adjacent to section 22, has a faster burn rate than section 22. Section 26, the rearmost section, has the fastest burn rate.

[0083] In the illustrated example of a pellet 10, the pressure generated by ignition of the pellet 10 is controlled not only by the burn rate of the smokeless powder component used in the individual sections, but also by the relative diameter of each section as compared to the adjacent sections. Thus, a smaller diameter section, resulting in less propellant material within that section, will be used to generate a lower pressure, and a larger diameter section, which will have more propellant material within that section, will be used to generate a higher pressure. In the illustrated example, the front end 12 of the pellet 10 will not only generate the slowest burn rate, but also the lowest overall pressure. As both burn rate and propellant volume increase as burning progresses rearward within the pellet 10, progressively greater pressure is generated.

[0084] FIG. 2 illustrates a firearm cartridge utilizing a propellant pellet 10. The firearm cartridge 28 is conventional in many respects, utilizing a casing 30 having a side wall 32, a back end 34 defining a rim 36 and primer pocket 38 containing a primer 40, and a bullet 42 secured at the front end 44 of the casing 30. The casing 30 in the illustrated example is made from brass, but in other examples may be made from another metal such as a soft steel, aluminum, aluminum alloy, or a polymer material. Some examples of the casing 30 may include a back end 34 that is a separate piece from the side wall 32 at least during manufacture of the cartridge, permitting the pellet 10 to be inserted into the casing from the back end 34. A tube 46 made from a non-burning material, for example, brass, extends from the forward end 48 of the primer pocket 38, through the passageway 16, and terminates at a forward end 50 adjacent to the front end 12 of the pellet 10. Thus, when the primer 40 is ignited, the ignition products travel through the tube 46, igniting the pellet 10 first within the forward most section 18. Ignition of the pellet 10 then progresses sequentially through sections 20, 22, 24, and 26.

[0085] FIG. 3 illustrates the beginning stage of ignition, wherein the primer has ignited the propellant section 19. This section, containing the smallest diameter of the slowest burning powder, burns, generating gas to raise the pressure to a predetermined maximum pressure, forcing the bullet 42 forward within the barrel 52. As the bullet 42 progresses down the barrel 52, additional volume of space 56 behind the bullet 42 is available for the expanding gases. To maintain a pressure that is near the maximum predetermined pressure within the available space, the propellant section 20, containing a slightly greater amount of a faster burning propellant, is ignited from the burning of section 19, as shown in FIG. 4. As the bullet progresses farther down the barrel as shown in FIG. 5, leaving behind even more volume 56 to be filled by the expanding gases, propellant section 22 burns. Because section 22 contains a slightly greater amount of an even faster burning propellant, pressure is maintained at or near the predetermined maximum pressure. The process continues in FIG. 6, wherein the volume 56 left behind by farther bullet travel is filled by gas from the ignition of propellant section 24, which contains a slightly greater volume of even faster burning propellant. As the bullet approaches the muzzle 54, as shown in FIG. 7, propellant section 26 is ignited. Since propellant section 26 contains the largest diameter of the fastest burning propellant, the maximized volume 56 within the barrel 52 behind the bullet 42 is filled sufficiently to maintain the pressure at or near the predetermined maximum pressure until the bullet exits the muzzle.

[0086] As explained above, the use of progressively increasing amounts of progressively faster burning powders as the bullet travels farther down the barrel maintains the pressure level behind the bullet near the maximum safe pressure level, without exceeding the safe pressure level. Thus, increased velocity and energy is imported to the bullet without exceeding the safe pressure limits of the firearm. FIG. 8 illustrates a pressure curve generated by a presently available smokeless powder within a conventional firearm casing. As can be seen, the pressure reaches its maximum quickly, remains at the maximum for a relatively short time, and gradually decreases as the bullet progresses down the length of the barrel. As the pressure decreases, an opportunity to increase the velocity and energy of the bullet is lost. FIG. 9 illustrates a pressure curve that can be generated by a pellet 10. It is anticipated that the inclusion of magnesium or other burnable metals as described herein can increase the energy output of the propellant pellet 10 by about 80%.

[0087] The number of sections, specific polymer and burnable metal coated smokeless powder used within each section, and the diameter of each section (which would vary the amount of propellant within each section) can be varied to produce a variety of pressure curves. As few as one section, or several sections, may be utilized depending on the desired pressure curve. In some examples, a generally cylindrical pellet having a uniform diameter may be utilized. In other examples, the diameter may vary uniformly or nonuniformly along the length of the pellet, depending upon the desired pressure at various points in the ignition cycle. The direction of taper may be from a narrow front to a wide rear in some examples or from a wide front to a narrow rear in other examples. In other examples, the direction of taper may be nonuniform. Although the examples illustrated herein are generally cylindrical or tapered cylindrical, other shapes, for example, rectangular, may be utilized without departing from the invention. The shape of the pellet may in some examples conform to the interior of a cartridge casing, thus maximizing the available propellant. As another example, propellant blocks such as square propellant blocks could be used, combining them to produce a desired pressure curve. The individual ignition cycle, and thus the pressure generated, can thus be varied and customized in order to optimize the performance of each individual caliber of ammunition with which the propellant described herein is utilized. If, for example, a given firearm includes a gas port in a given location within the barrel, the pellet 10 can be configured so that an increased amount of faster burning propellant is ignited after the bullet passes the gas port, thus compensating for gases that flow into the gas port. Although the illustrated example commences ignition from the front of the pellet, ignition may be commenced from the rear of the pellet without departing from the invention.

[0088] The propellant described herein provides for significantly increased energy, with a smaller volume of propellant. As one example, a combination of single base smokeless powder, magnesium, and ethylene vinyl acetate will produce about 22% more energy than a propellant consisting solely of single base smokeless powder. As another example, a combination of double base smokeless powder, magnesium, and ethylene vinyl acetate will produce about 100% more energy than a propellant consisting solely of double base smokeless powder. A propellant pellet as described above may have up to 100% more density than loose powder. The propellant may therefore be utilized in applications wherein volume available for propellant is limited. If a pellet is structured to vary the burn rate throughout ignition to produce a pressure curve that maintains without exceeding a predetermined maximum pressure, additional energy may be transferred to a bullet as compared to the same pressure generated by presently available smokeless powder. Because the predetermined pressure level can be controlled as described above, the propellant may not only be used with presently available brass, aluminum, or steel cased ammunition, but also with other less common, or yet to be developed casing materials, such as plastic or polymer.

[0089] 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.