Patent Application
20180135953
The present invention relates to an ammunition cartridge incorporating a venting system in the munition's base, a method to manufacture the cartridge case and a package configuration to store and transport vented ammunition cartridges.
Introduction: The term “Insensitive Munitions” refers to a generic body of munitions knowledge that includes guidance practices, regulations, technology, methodologies and standards for complying with the following objective:
Insensitive Munitions (“IM”) technology includes new energetic materials with less sensitivity to unplanned stimuli as well as mechanical and functional designs that mitigate the undesired reactions against such unplanned stimuli. Two key IM tests required by the U.S. Department of Defense (“DOD”) in qualification of ammunition are slow cook-off and fast cook-off tests where the ammunition is exposed to heat and/or fire and the results are documented. DoD's requirement to identify new safety technology that can be broadly incorporate into an array of munitions remains a primary goal, this application focuses on applying venting solutions in a narrow range of ordnance, gun fired ammunition cartridges.
Accordingly, it is desired that an ammunition cartridge will not exhibit a substantial reaction when naked or packaged ammunition cartridges are heated when exposed to an external fuel fire event which is, for the purpose of this specification, identified as an emergency mode.
While we intend to introduce new survivability technology into ammunition cartridges, all cartridges must continue to function in all normal operational modes, being fired from a cannon or machine gun. Normal modes of operation include:
A—Logistics Package Storage
B—Tactical Stowage
C—Feeding
C—Chambering
D—Function Fire
E—Extraction
F—Ejection of a “Spent” cartridge case
Prior Art: The prior art in the field of Insensitive Munitions and venting of ammunition propulsion includes a number of articles and patents that are relevant to the present invention. Typical of such prior art is the U.S. Pat. No. 5,936,189 to Lubbers and an article “IM Solutions for Projectiles Crimped to Cartridges for Artillery Application—Phase II, Transition from Cartridge Case Venting to Insensitive Propellant” by Carl J. Campagnuolo, Christine M. Michienzi, Edward G. Tersine, Christine D. Knott, William J. Andrews—NDIA IM/EM Symposium, May 11-14, 2009.
Also relevant are the following prior art patents:
U.S. Pat. No. 7,322,295 (Haeselich) introduced modifications and configuration of venting cartridge cases using a fusible material in a channel.
U.S. Pat. No. 8,028,826 teaches use of a unique internal packaging configuration for 25 mm ammunition allowing for venting of cartridge cases using a high density package methodology.
U.S. Pat. No. 8,322,286 discloses a “contracting” memory metal incorporated into the base of a projectile's propulsion allowing for venting.
U.S. Pat. No. 8,381,656 discloses a cartridge or grenade venting mechanism that uses interlocking components coupled with a fusible material that liquefies at elevated temperatures, releasing a encapsulated spring imparting a rotational force that activates a vent.
U.S. Pat. No. 8,550,004 teaches an insensitive cartridge munition having a base plug in the cartridge case. The base plug is held in place by a “separate solder” that, at elevated temperatures, releases the base plug, thus providing a void for venting propellant gasses.
U.S. Pat. No. 8,573,127, entitled “Pressure Relief System,” discloses embodiments for partially or fully encapsulating a fusible material or plug that loses strength at elevated temperatures thus providing a method of venting a cartridge case.
WO 2012/126554A1, also published as DE 10 2011 014402 A1 and EP2686636 A1 and B1 disclose a solid base plug crimped or riveted with a fusible material that is configured in a channel in the manner taught in U.S. Pat. No. 8,573,127. The device retains the base plug in position during normal operating conditions, but at elevated temperatures a bismuth tin material releases the plug from a channel.
U.S. Pat. No. 8,720,722, entitled “Venting Mechanism for Containers,” teaches a design to vent containers.
U.S. Pat. No. 8,925,463 discloses the use of expanding memory metal, incorporated into a munition's cartridge case, that releases a base plug with a primer. This patent provides a useful discussion of the operating context and requirements for cartridge case operating and venting in emergency storage or cook-off conditions.
U.S. Pat. No. 9,410,782 teaches use of an encapsulated spring fitted into the ogive of a projectile that, upon reaching an elevated temperature, mechanically separates the fuze from the warhead, thus venting and separating the detonator or booster from the primary explosive.
DE 10 2014 001576 A1 published 2 Feb. 2014 is very similar to U.S. Pat. No. 8,925,463 as it uses a memory metal in combination with a fusible material.
In addition, a great deal of prior art exists for general use of a base plug in munitions, especially in calibers such as 40×53 mm, where fittings for base plugs are often incorporated into cartridge cases forming dual chamber systems. The U.S. Army's M169 40×53 mm propulsion system has a design, allowing for loading of the cartridge case during manufacture, whereby a base plug is fitted to form a high-pressure chamber and, after a propellant is loaded, the primer is inserted into the base plug affixed to a cartridge case. In some circumstances it is advantageous to minimize disruption of well-established supply chains by swapping out existing crimped base plug designs with crimped base plug safety vents configured within a base plug.
Notwithstanding the forgoing references which are applicable to gun fired ammunition cartridges, most prior art venting concepts vent other types of munitions such as large artillery projectiles, bombs, shoulder launched rockets and large tactical rocket motors.
When considering venting of ammunition cartridge, some additional technical context is useful to understand how propellants react when heated. In most cases, auto-ignition of propellants in confinement initiates violent deflagration of medium caliber projectiles.
Solid Propellant Combustion in Confinement: A principal goal in Insensitive Munitions (IM) technology development is the mitigation of violent events where munitions are exposed to external fires. Most modern military ammunition cartridge use modern double-based propellants. It is important to understand some fundamental principles regarding propellants when developing technologies in this field. There are a number of excellent teaching references regarding combustion of solid propellants. One such reference is the NATO publication RTO-EN-023, “Combustions of Solid Propellants” by G Lengelle, J. Duterque and J. F. Tumbert from the National Aerospace Research Institute (ONERA) in France, published in May 2002. This NATO report provides excellent graphics and detail explaining how propellants will burn at different efficiency rates with varying atmospheric pressures. When combustion takes place in a confined state, reactions become more violent and the reaction releases more energy.
Fortunately, it is possible to vent combustion chambers, such that burning propellants do not pressurize combustion chambers. Hence, venting of a high-pressure chamber in an emergency condition, such as a fire, leads to reduced energy being released by unconfined propellant combustion.
Off-gassing and Differential Thermal Analysis: When propellants are heated, solid propellants exhibit a phenomenon known as “off-gassing” or “out-gassing.” Double-base gun propellants typically contain nitrocellulose and nitroglycerine with small amounts of stabilizers and binders. Nitrogen dioxide (NO2), a corrosive gas, and other oxides of nitrogen, are generated in the heating of double-based propellants. The release of results in increased pressures in a confined environment, but the amount and types of gases produced by heating vary greatly. The density of solid propellant in a volume, the type of propellant, age and storage conditions of the propellant, all influence the amount of off-gassing exhibited. The amount of off-gassing and pressurization of a chamber is therefore difficult to predict without exact control of all the variables.
A principal objective of the present invention is to provide a robust ammunition cartridge configuration that will vent the propulsion component of ammunition cartridges in order to minimize collateral damage that results from an auto-igniting propellant when ammunition cartridges are heated by an external fire.
It is a further objective of the present invention to disclose a novel manufacturing process to configure vents incorporated into the base of ammunition cartridges.
It is a further objective of the present invention to provide an improved method for inserting and retaining a base plug with a venting system into a cartridge munition.
It is a further objective of the present invention to provide a cartridge munition that is designed to vent gases under high pressure from cartridge case and, at the same time, to physically separate the igniter (primer or flash tube) from the propellant with the first energetic event.
It is a further objective of the present invention that, upon primer initiation (first energetic event) in either a slow or fast cook-off, a vent mass (base plug) is ejected and an optimized vent void leads to a less efficient propellant burn (second energetic event).
It is a further objective of the present invention to provide a cartridge munition of the above-noted type with an effective and reliable solution to vent propellant gases from the cartridge case in the event the cartridge munition is exposed to temperatures that reach or exceed auto-ignition temperatures of the primer, igniter and/or propellant.
It is yet another objective of the present invention to provide an ammunition package configuration for cartridge munitions that facilitates the venting from the ammunition package into the atmosphere of such munitions fitted with special vent plugs.
These objectives, as well as additional objectives which will become apparent from the discussion that follows, are achieved, according to the invention, by providing a cartridge munition comprised of a projectile inserted in, and mechanically connected to, a metal cartridge case having a propulsion chamber and a base, and an energetic propellant disposed in the propulsion chamber. The cartridge base has an internal cavity that is provided with a solid plug in which is mounted an igniter with an energetic primer. During manufacture of the cartridge, the base plug is affixed in the cartridge using a process of injection molding a fusible material through one or more passages into a metal cavity, where the material cools and forms a fusible support for the plug. The fully assembled ammunition cartridge functions in normal operational modes; however, when the cartridge is exposed to external heating the fusible support for the plug loses mechanical strength and an unsupported cartridge, clear of obstructions, vents gases from the base of the cartridge.
The fusible material, which may be a metal or a polymer, is selected so that the cartridge case assembly loses mechanical strength and structural integrity at elevated temperatures such that, when the propellant or primer off-gasses or otherwise pressurizes the propulsion chamber, for example, by auto-igniting, the base plug or lid is ejected from the cavity at the base of the cartridge case, creating a void that allows the ignited primer or propellant to burn itself out in an unconfined space.
A typical ammunition cartridge is comprised of a projectile inserted into the cartridge case that is mechanically connected thereto via crimping or alternative means. Normally, a projectile and cartridge case has a propulsion chambers that contains a solid propellant. The cartridge case includes a primer or igniter in the head or base of the cartridge case. The cartridge case may include one or multiple chambers for ignition, combustion and expansion. A base plug can be used to close a high pressure chamber in a cartridge case. Effective combustion of the propulsion requires containment to optimize burning of the propulsion.
An objective of this design, according to the invention, in an emergency situation, is to allow for activation of a vent creating a channel that is created when the base plug or a base plug component is ejected from the cartridge case, such that the vented high pressure chamber precludes auto-igniting propellant powders from burning in a pressurized environment within a cartridge case.
Accordingly, the safer IM cartridge case, when exposed to heating by a fire, activates an emergency vent that creates a passage at the base of the cartridge case, where any auto-igniting energetic materials eject and vent rearward clear of the propulsion chamber allowing propellant gases to exit through the base plug or through the head of the cartridge case.
Where such a system is incorporated into a dual-chamber propulsion system, and a cartridge is subjected to heating in an emergency storage mode, the fusible material supporting the base plug incorporated into the base of a cartridge case weakens. Off-gassing or combustion of an energetic, such as the propellant, acts to expel part or all of the base plug from the sealed cartridge case assembly. This action, in combination, creates an activated vent channel at the base of the cartridge case.
It would be beneficial, according to the invention, to also couple this propulsion venting system, with a methodology to vent warheads of the type disclosed in the U.S. Pat. No. 9,410,782.
A cartridge case assembly normally has at least two non-fusible components. These include:
According to the invention, the contours at the surfaces the metal non-fusible cylindrical case and a non-fusible base plug provide a cavity with voids and ports that facilitate injection of a fusible material into a cavity where the metal parts act to mold a fusible material. This cavity connects to voids that form one or more passages that facilitate injection of a heated, fusible fluid into the cavity during manufacture. Further cooling of the fusible material to ambient temperatures results in formation of a solid fusible support for the base plug configured in the cartridge case assembly. Subsequent ammunition cartridge fabrication steps are completed in ambient conditions, after injection molding of the cartridge case and will normally include (1) crimping of the projectile to a cartridge case, (2) propellant loading and (3) seating of a primer to close the cartridge case. This fully assembled ammunition cartridge, configured with a fusible material supporting the base plug thus incorporates a melting point that is higher than the operational temperature of the ammunition and lower than the auto-ignition temperature of the energetics contained in the cartridge, which may be about 130° C., for example.
The base plug houses the primer and/or igniter, whereby the cartridge case assembly:
Accordingly, in the emergency storage condition, the ignition and expanding gases produced by the burning propellant do not push the projectile forward from the mouth of the cartridge case, at a high velocity.
Where multi-chamber cartridge cases are used, the fusible material in a heated condition releases the vents from the passage and (i) does not vent from orifices between multi-chamber systems, and (ii) does not pressurize the low pressure chamber such that projectiles are ejected at high-velocity from a projectile's case. According to the invention, the size of the venting area is chosen in relation to the propellant load.
If a cartridge munition of the type described herein is heated to the melting temperature of the fusible material or metal—a temperature higher than the operational temperature of the ammunition but below the auto-ignition temperature of the primer, igniter or propellant, for example, in the range of about 115° C.—then the fusible material in the void melts. If the temperature continues to increase and the propellant charte, primer and/or the igniter auto-ignite, almost no significant pressure can build up within the propulsion chamber because the opened, free passages function as pressure-relief apertures.
According to the invention, the cartridge ejects a base plug prior to or simultaneous with energetic auto-ignition, such that combustion occurs in an unconfined space. Propellant combustion in an unconfined space disrupts efficient propellant combustion and reduces the violence, severity and shock associated with propellant auto-ignition. Nevertheless, the disruption of a confined propellant combustion does not completely render safe the ammunition and the auto-ignition of solid propellant powders will still generate gases that must be vented from the rear of the cartridge case. When ammunition cartridges include high explosive projectiles, the disclosed method of propulsion venting may be coupled to a separate, but complementary means of warhead venting as disclosed in the aforesaid U.S. Pat. No. 9,410,782.
The ammunition cartridge according to the invention can use solid metal, polymers or fusible metals in combination. During manufacture of the cartridge munition, the selected fusible metal or polymers liquefies at elevated temperatures allowing for injection via ports into channels and cavities in the cartridge case. In a preferred embodiment, the fusible material is positioned substantially outside the venting channel, surrounding the solid base plug.
The preferred embodiment of the invention does not use temperamental rivets and does not use memory metals. The channels, internally configured by a metal part positioned in a seat, provide for fabrication of an internal polymer internal skirt, similar to an O-ring. Cooling of the cartridge case to ambient temperatures allows the fluid fusible material to solidify during manufacture such that the metal cartridge case and base plug are bonded together. After completing the bonding process, the cartridge case can be loaded with propellant, primer and affixed to a projectile, thereby forming a completed ammunition cartridge with a safety vent configured into the base of the cartridge case.
According to a preferred embodiment of the invention, the fusible material surrounding the base plug includes a plurality of outward projections from the O-ring shape that extend radially into respective openings in the base of the cartridge case. This “retention feature” retains the physical connection of the base plug to the cartridge case during ejection after firing and reducing the energy imparted on the ejected base plug.
In preferred embodiments of the invention, the fusible material is selected to lose mechanical strength at an elevated temperature (1) exceeding the ammunition's maximum storage temperature, and (2) below the temperature where an energetic, confined in a high pressure chamber auto-ignites.
A number of new high-melt temperature polymers can be used to fabricate vented cartridge cases. In some cases, the molding ports may be capped or covered.
The present invention thus provides for an ammunition cartridge having a metal cartridge case, with a base plug that is assembled to create and maintain a confined high pressure chamber within the cartridge case in ambient and operational environments. The same cartridge munition, when subjected to elevated heating, ejects the base plug when an energetic primer igniter or the propellant off-gasses, or an auto-ignition momentarily pressurizes the high pressure chamber.
The ammunition cartridge described above is preferably packaged for transportation and storage in such that combustion gases discharge through an opened vent, after ejection of the base plug, such that the vent channel is not impaired. A preferred embodiment of the packaging arrangement, in accordance with the present invention, allows for venting gases, released intermittently from multiple ammunition cartridge undergoing external heating, allowing for gases to vent from each cartridge case, into the ammunition storage box, and subsequently from the temporarily pressurized ammunition storage box into the atmosphere.
Accordingly, the packaging material used in ammunition containers utilizes packing material that retains form and strength at elevated temperatures and provides an undeterred vent path for release of pressure in the event the base plug is ejected. The package preferably includes dunnage with a configuration allowing for unobstructed venting of the base of the multiple cartridges contained therein, and includes a blow-out panel in a wall of the package that relieves any momentary pressurization within the package by breaking away and allowing gases to vent from a punctured panel into the atmosphere. Advantageously, the dunnage is selected so as not to liquefy or clog vented cartridges.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
The preferred embodiments of the present invention will now be described with reference to
To highlight and distinguish the improvement according to the invention from current state of the art, an example of which is illustrated in
A typical cartridge is also configured with a propellant 34 that is confined in proximity to the primer or igniter 32A. A typical cartridge case sub-assembly 24 normally includes a rim 28 near the base 26 to facilitate extracting and feeding 110B and cartridge extraction 110E and ejection 110F (
Modes of Use, Configuration (Unpackaged and Packaged) and Venting Improvement:
A cartridge munition according to the invention must continue to function in all modes of use (shown in
Fabrication of Fusible Support Plugs in Cartridge Cases:
During assembly, a projectile 12 may be affixed 14 to a cartridge case assembly 22 in either an initial or a final step of fabrication. It is also noteworthy that the assembly process may include insertion of a retention feature or component 72 and a cap 74 (
Incorporation Fusible Support Plugs into Base Plugs:
An alternate construction is provided for in
Heating, Safety Plug and Venting:
Alternatively, heating produces propellant auto-ignition event 128 which ejects the base plug 26 to create a clear vent channel 36. A cross-section illustration of the resulting safety vent function is illustrated in
Alternatively, where adequate propellant out-gassing occurs at an elevated temperature 124, off-gassing from the propellant pressurizes the chamber and the weakened fusible support plug 92 ejects the plug 98 from the cartridge case assembly 22, 22A, 22B, 22c, 22D. In these circumstances, the base plug 92C is ejected by pressurization of off-gassing (or ignition of combustion gases) 36. As the propellant does not combust in a pressurized vessel, the vent compromises the efficiency of the propellant burn and severity of the energetic event.
Multi-Chamber Configurations:
References 3A-3E illustrate other 40×53 mm cartridge configurations with low pressure chamber 54 and high pressure chamber 56 utilizing the techniques identified in this specification. Various configurations may incorporate chamber wall 44, burstable liners 48, and High to Low/Interim Pressure vent orifices 46. A dual chamber case may include a toggle 62 that throttles the passage of propellant, combustion gases into the low pressure chamber 46.
A 40 mm HV cartridge case assembly 22B, 22C and 22D, may include a dual or multi-chamber system with chamber walls 44 where a multi-chamber system includes at least one higher chamber system with a orifice 46. In normal operation, the expanding propellant gases combust in the high pressure chamber bursting a liner 48 or push a toggle component 62 and then pass thru an orifice 46 channeling gases into a low pressure chamber 54.
Form and Injection Molding Fusible Materials into Ports, Channels and Cavities for Safety Plug Fabrication:
A preferred assembly process forms a multi-chamber cartridge with a high pressure chamber 46 with a safety vent cavity 82 where a fabricator can inject a fusible material, preferably a polymer, via ports 88 and molding channels 84 completing fabrication of a cartridge case sub-assembly 24. In fabrication, such a cartridge case and the incorporated fusible support plugs is held in position within the base plug seat 66. The configuration allows the fabricator to first assemble non-energetic components; in a second step to load the propellant 34 into the high pressure chamber 56 via a passage 64 and, in a third step, position and seal the primer or an igniter 32A allowing for automated assembly of a cartridge case 22.
Dunnage and Vented Packaging:
With reference to
Hot Gun Chamber Performance and Retention Features:
With reference to
There has thus been shown and described a novel ammunition cartridge fitted with a base plug that will initiate contingent venting which fulfills all the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow.
Ammunition Cartridge Overview
Cartridge Case Assembly Types and Features
Energetic Material
Special Propulsion Features
Operational Chambers
Typical Metal Propulsion Component Features
Vent Retention Feature
Safety Vent Features
Safety Vent Feature Configured in a Cartridge Case Assembly
Ammunition Packaging Features
Ammunition States and Modes of Use and Handling
Key Venting Temperature Ranges
Heat Transfer
This application claims priority from the U.S. Provisional Application No. 62/422,098 filed Nov. 15, 2016.
| Number | Date | Country | |
|---|---|---|---|
| 62422098 | Nov 2016 | US |
