U.S. patent application number 16/683635 was filed with the patent office on 2020-05-21 for cartridge and cartridge case.
The applicant listed for this patent is General Dynamics OTS - Canada, Inc.. Invention is credited to John MacDougall, Yann Routhier.
Application Number | 20200158480 16/683635 |
Document ID | / |
Family ID | 70727490 |
Filed Date | 2020-05-21 |
United States Patent
Application |
20200158480 |
Kind Code |
A1 |
Routhier; Yann ; et
al. |
May 21, 2020 |
CARTRIDGE AND CARTRIDGE CASE
Abstract
Cartridges and cartridge cases adapted to be chambered in weapon
systems are provided. In one example, a cartridge case includes a
front shell having a case base end portion, a case body portion
extending forward from the case base end portion towards a case
mouth portion that is configured for holding a projectile. The case
base end portion has a first interlocking feature. A reinforcing
cap is disposed adjacent to the case base end portion on a side
opposite the internal volume. The reinforcing cap has an annular
extraction groove, a primer pocket, a flash hole for providing
fluid communication between the primer pocket and the internal
volume, and a second interlocking feature that engages the first
interlocking feature to couple the reinforcing cap to the case base
end portion.
Inventors: |
Routhier; Yann; (Quebec,
CA) ; MacDougall; John; (Quebec, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Dynamics OTS - Canada, Inc. |
Repentigny |
|
CA |
|
|
Family ID: |
70727490 |
Appl. No.: |
16/683635 |
Filed: |
November 14, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62767795 |
Nov 15, 2018 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42C 19/083 20130101;
F42B 5/36 20130101; F42B 5/285 20130101; F42C 19/0807 20130101 |
International
Class: |
F42B 5/285 20060101
F42B005/285; F42B 5/36 20060101 F42B005/36; F42C 19/08 20060101
F42C019/08 |
Claims
1. A cartridge case adapted to be chambered in a weapon system, the
cartridge case comprising: a generally cylindrical front shell
having a shell wall that surrounds an internal volume for
containing a propellant, wherein the shell wall defines a case base
end portion, a case body portion extending forward from the case
base end portion towards a case mouth portion that is configured
for holding a projectile, and wherein the case base end portion has
a first interlocking feature; and a reinforcing cap disposed
adjacent to the case base end portion on a side opposite the
internal volume, wherein the reinforcing cap has an annular
extraction groove, a primer pocket, a flash hole for providing
fluid communication between the primer pocket and the internal
volume, and a second interlocking feature that extends inwardly
towards the first interlocking feature to define a rib edge that is
rounded, radiused, relatively sharp or pointed and that engages the
first interlocking feature to couple the reinforcing cap to the
case base end portion of the generally cylindrical front shell.
2. The cartridge case of claim 1, wherein the generally cylindrical
front shell comprises a first metallic material and the reinforcing
cap comprises a second relatively lightweight metallic
material.
3. The cartridge case of claim 2, wherein the second relatively
lightweight metallic material is different than the first metallic
material.
4. The cartridge case of claim 2, wherein the first metallic
material is selected from carbon steel, stainless steel, brass,
aluminum, aluminum alloys, nickel, and nickel alloys.
5. The cartridge case of claim 4, wherein the first metallic
material is stainless steel.
6. The cartridge case of claim 2, wherein the second relatively
lightweight metallic material is selected from aluminum and alloys
thereof, titanium and alloys thereof, magnesium and alloys
thereof.
7. The cartridge case of claim 6, wherein the second relatively
lightweight metallic material is an aluminum alloy.
8. The cartridge case of claim 1, wherein the shell wall has a
substantially constant wall thickness.
9. The cartridge case of claim 1, wherein the case base end portion
has a bulge section that forms at least part of the first
interlocking feature.
10. The cartridge case of claim 9, wherein the bulge section
comprises an annular bulge section.
11. The cartridge case of claim 9, wherein the reinforcing cap
comprises a locking rib that includes the rib edge and that forms
at least part of the second interlocking feature.
12. The cartridge case of claim 11, wherein the locking rib
comprises an annular locking rib.
13. The cartridge case of claim 11, wherein the case base end
portion has a recessed feature that forms at least part of the
first interlocking feature.
14. The cartridge case of claim 13, wherein the recessed feature is
an annular recessed feature.
15. The cartridge case of claim 13, wherein the first interlocking
feature has a plurality of spaced apart recessed features and the
second interlocking feature has a plurality of spaced apart locking
ribs that correspondingly engage the plurality of the spaced apart
recessed features.
16. The cartridge case of claim 1, wherein the first and second
interlocking features are directly engaged with each other to
ensure an air-tight seal between the reinforcing cap and the front
shell without the presence of any liquid and/or solid seal(s).
17. A cartridge adapted to be chambered in a weapon system, the
cartridge comprising: a cartridge case comprising: a generally
cylindrical front shell having a shell wall that surrounds an
internal volume, wherein the shell wall defines a case base end
portion, a case body portion extending forward from the case base
end portion towards a case mouth portion, wherein the case base end
portion has a first interlocking feature; and a reinforcing cap
disposed adjacent to the case base end portion on a side opposite
the internal volume, wherein the reinforcing cap has an annular
extraction groove, a primer pocket, a flash hole for providing
fluid communication between the primer pocket and the internal
volume, and a second interlocking feature that extends inwardly
towards the first interlocking feature to define a rib edge that is
rounded, radiused, relatively sharp or pointed and that engages the
first interlocking feature to couple the reinforcing cap to the
case base end portion of the generally cylindrical front shell; a
projectile disposed in the case mouth portion; a propellant
disposed in the internal volume and ignitable to propel the
projectile from the case mouth in a forward direction; and a primer
disposed in the primer pocket and ignitable for igniting the
propellant.
18. The cartridge case of claim 17, wherein the reinforcing cap has
a locking rib that includes the rib edge and that forms at least
part of the second interlocking feature.
19. The cartridge case of claim 18, the case base end portion has a
recessed feature that forms at least part of the first interlocking
feature.
20. The cartridge case of claim 19, wherein the first interlocking
feature has a plurality of axially spaced apart recessed features
and the second interlocking feature has a plurality of axially
spaced apart locking ribs that correspondingly engage the plurality
of the axially spaced apart recessed features.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to and claims all available
benefit of U.S. Provisional Patent Application 62/767,795 filed
Nov. 15, 2018, the entire contents of which are herein incorporated
by reference.
TECHNICAL FIELD
[0002] The technical field relates generally to cartridge cases and
cartridges for weapon systems, and more particularly, relates to
relatively lightweight cartridge cases including a front shell and
a reinforcing cap that is coupled to the front shell for weapon
systems, and cartridges including such cartridge cases.
BACKGROUND
[0003] Cartridges include a cartridge case that contains other
major components of the cartridge used in weapon systems, including
a propellant, a projectile or bullet, and a primer. Prior art small
caliber cartridge cases can be divided into 3 groups; brass
cartridge cases, other metallic cartridge cases that are lighter
weight than brass cartridge cases, and polymer lightweight
cartridge cases.
[0004] Conventional cartridge cases made of brass are typically
deep drawn, resulting in good mechanical properties, but are
relatively heavy. For example, typical conventional cartridge cases
used by military forces and/or commercial users are often made from
C26000 brass or other similar alloys, which is relatively heavy,
since brass has a density of around 8.53 g/cc. Furthermore, brass,
containing about 70% copper and 30% zinc, is subject to frequent,
rapid commodity market price fluctuations and is considered one of
the costlier common use metals in ammunition products.
[0005] Lightweight cartridge cases have been of interest for many
years, for example, to lessen the load on soldiers or to increase
their ammo carrying capacity for a given weight to be carried into
battle. A reduced load translates into less soldier fatigue and
better mobility for the soldier, while more ammunition being
carried into battle on the other hand increases the odds of
successful combat engagements by allowing for more, heavy
ammo-consuming strategies.
[0006] Prior art lightweight cartridge cases have been produced
using various manufacturing processes with different materials, but
all present some sort of trade-off when compared to conventional
brass cartridge cases. For example, some of the more significant
trade-offs are a reduced internal cartridge case volume and/or
significant initial capital investment to industrialize a new
manufacturing process.
[0007] Prior art lightweight cartridge cases made of polymers or
combinations of polymers and metals may have varying levels of
functional mechanical resistance. These varying levels depend on
the weapon system used to fire the cartridge including all of the
mechanical interactions that occur between the cartridge and the
feeding, firing and extracting components in those weapon
systems.
[0008] Typically, polymer cartridge cases require a thicker wall to
compensate for reduced mechanical strength properties compared to
conventional brass cartridge cases. This means a smaller inside
diameter at the case body section is available for polymer
cartridge cases. A reduced internal case volume is of concern for
end users of polymer lightweight cartridge cases due to the
performance specification requirements of each small caliber
cartridge. Reduced internal case volume translates to less
propellant powder capacity and therefore, reduced muzzle velocity,
resulting in less kinetic energy in the projectile at any distance
after firing.
[0009] Additionally, once a cartridge case is adopted by the
military or even commercial markets, enormous quantities need to be
manufactured to keep up with the demand. This makes the cartridge
case manufacturing process critical to its viability for sustained
use over time. Without adequate high-capacity and high-accuracy
manufacturing equipment and processes, production costs and quality
levels cannot be brought to a point where it is favorable to switch
to polymer cartridge cases. Presently, polymer cartridge cases
cannot be produced as quickly or as reliably as their conventional
brass counterparts. Brand new, state of the art, controlled polymer
injection molding machines could replace all currently existing
brass cartridge case manufacturing equipment on a 1 to 1 ratio and
still only generate just a fraction of the required production
output required to sustain the world military and commercial
demand. Currently, there is no polymer cartridge case manufacturing
machinery capable of delivering the same production output provided
by production equipment for conventional brass cartridge cases for
the same shop floor space.
[0010] Because the military is unlikely to be reducing its
ammunition consumption in the foreseeable future, more floor space
would need to be dedicated to polymer cartridge case manufacturing.
This means that much larger buildings would be required to house
the additional required machines, which represents a considerable
initial capital investment. Furthermore, the overhead costs
associated with these buildings would also be higher than current,
smaller buildings used for manufacturing brass cartridge cases, as
well as higher costs for heating, security, maintenance, and other
related recurring costs.
[0011] Moreover, polymers are typically much weaker than metals and
therefore, using polymers to form lightweight cartridge cases would
normally require a thickening of the wall section along the length
of a cartridge case to resist the forces imparted onto the
cartridge case during weapon firing. This translates into a reduced
cartridge internal volume, thus imposing a reduced maximum
propellant charge weight that can be loaded into the cartridge
case. In turn, this reduces the maximum velocity at which a
projectile leaves a weapon system, resulting in reduced kinetic
energy delivery to the target.
[0012] Another consequence of polymers typically being weaker than
metals is that polymer lightweight cartridge cases can have a
reduced safe maximum operating pressure due to the lower cartridge
case mouth mechanical resistance. Along the shoulder and body of
the cartridge case, the wall can be thickened to compensate for
this weakness, trading off internal volume capacity for the
propellant powder. However, because a conventional weapon chamber
and corresponding projectile each have a fixed geometry, as
determined by industry standards such as CIP (Commission
Internationale Permanente Pour l'Epreuve Des Armes A Feu
Portatives) and SAAMI (Sporting Arms and Ammunition Manufacturers'
Institute), a physical constraint restricts the thickness of
additional polymer material that can be used to achieve the desired
mechanical resistance at the cartridge case mouth wall. This often
translates into split cases around the case mouth area. To solve
this problem, existing weapon systems would need to have their
chambers reamed out to allow for increased polymer cartridge case
thickness around the weaker case mouth areas.
[0013] Yet another consequence of polymers typically being weaker
than metals is that polymer lightweight cartridge cases can have a
reduced retention of the primer within the cartridge case primer
pocket. Polymers normally do not offer enough press-fit mechanical
resistance to suit this type of assembly without the use of an
additional bonding agent.
[0014] Further, gluing projectiles to the cartridge case mouth of
polymer lightweight cartridge cases to meet the CIP, SAAMI or
military specification mandatory bullet extraction force
requirements, such as the NATO (North Atlantic Treaty Organization)
STANAG (STANdardization Agreement), is another concern with this
sub-category of cartridge case designs. Without some sort of
bonding agent, polymers do not offer enough spring back force on
their own as compared to metals to adequately hold a projectile in
the case mouth using standard mechanical assembly methods.
Projectiles held too lightly by the case mouth normally exhibit
more variable bullet extraction forces and thus, tend to increase
the projectiles' standard deviation with respect to muzzle
velocity, which then negatively affects accuracy and dispersion on
the target.
[0015] Additionally, heat removal from the weapon chamber is also a
big concern with polymer lightweight cartridge cases. A brass or
steel cartridge case effectively functions as a thermal sink in
conventional weapon systems. When firing, heat generated from the
burning gases gets absorbed by a highly conductive brass or steel
cartridge case and the heat gets expelled out of the weapon with
the brass or steel case during the post-firing extraction cycle.
Since a polymer cartridge case does not conduct heat very well, the
polymer case will not absorb the heat as efficiently as a brass or
steel cartridge case and therefore, does not remove heat as
effectively upon being ejected from the weapon system. This, in
turn, causes the weapon system to heat up quicker and imposes a
more controlled and shorter firing sequence in order to not
overheat the weapon system components.
[0016] Once heated, polymers tend to rapidly lose their mechanical
properties. This can be problematic when a weapon has been heated
due to sustained firing and a polymer cartridge is then left for a
time within the cartridge chamber. Past a certain temperature
point, the polymer cartridge case could melt in the hot chamber or
even rupture upon subsequent firing.
[0017] Unlike metals, there is also some uncertainty regarding
creep resistance of polymer cartridge cases. Most conventional
machinegun cartridges are assembled with metallic links that allow
for high rates of feeding and firing. These links are typically
made of spring steel and the cartridge is basically captured by the
link in a press-fit condition. Linked cartridges can be stored for
many years before being used. Once linked, cartridges are subject
to a constant pressure along the surface area where the link holds
the cartridge. Since the polymer cartridge case is much softer than
the metallic link, the cartridge case may bulge or creep over time,
causing the cartridge case to become permanently deformed,
resulting in irregular diameters directly above and below the upper
and lower edges of the link where the link is in contact with the
cartridge case. In some instances, this creeping effect over time
can result in cartridge case stress-induced failures upon
firing.
[0018] Lastly, little is known about long-term storage behavior
under various environmental conditions for polymer cartridge cases.
For example, certain types of polymers may be susceptible to UV
radiation, which could become an issue if cartridges with polymer
cartridge cases were to be left outside exposed to the UV radiation
for prolonged periods of time. Further, solvent exposure is also of
concern because some solvents are incompatible with certain grades
of polymers and can completely dissolve the polymer. For example,
if cartridges with polymer cartridge cases are left in the
proximity of an open fuel tank, there could be possible
interactions between the polymer cartridge case and the fuel or
fuel vapors from the fuel tank.
[0019] Prior art lightweight metallic cartridge cases can be
divided into two main categories. The first category includes a
shell with an interior reinforcement and a second category includes
a shell with an exterior reinforcement.
[0020] Lightweight metallic cartridge cases with an interior
reinforcement may use lightweight aluminum for the interior
reinforcement component. However, doing so may result in instances
of aluminothermic reaction whereby the aluminum combusts when
exposed to high temperatures and gas pressures above 40,000 PSI,
which are typical conditions experienced during cartridge firing.
The combusting aluminum can then no longer hold back the gas
pressure and can split completely though the interior
reinforcement, transferring the pressure to the outer shell which
then stretches to failure.
[0021] Furthermore, obtaining a perfect gas seal between the outer
shell and its interior reinforcement has proven to be unreliable.
It is interesting to note that both the flash hole junction as well
as the reinforcement junction are both equally susceptible to
improper sealing. The slightest geometric defect in either
component can result in an inadequate seal that can then cause a
cartridge to swell, inducing extraction issues, or to completely
fail upon firing.
[0022] Because the outer shells of lightweight metallic cartridge
cases are stamped and formed using a set of dies and punches,
rounded edges all around the cartridge case extraction groove may
result at every bend in the metal. This makes extracting the fired
cartridge cases more difficult because the weapon extractor cannot
grab the cartridge case as firmly and "slips" on the rounder case
base edges.
[0023] Since stainless steel, which is typically used for the shell
material, is harder than the typical steels used in weapon
extractors, a premature wear of the extractor is unavoidable when
firing this design of interior reinforcement lightweight
cartridges. This accentuates the "slipping" motion of the extractor
as the gripping surface is further reduced over time.
[0024] Lightweight metallic cartridge cases with an exterior
reinforcement often have assembly strength issues. Prior art
designs, for example as disclosed in U.S. Pat. No. 9,939,236 B2,
use a small diameter hollow rivet through the cartridge case flash
hole to hold both halves together. However, doing so severely
limits the sectional area available to handle the stresses imposed
on the cartridge case extraction post firing. This is because,
during the extraction cycle, the firing pressure gases are not
fully vented out when the weapon system starts to apply an
extraction force on the cartridge case. This force increases until
the cartridge case becomes free from the chamber but may induce
separation of the two parts, and thus, a failure can occur before
case extraction is complete. This greatly limits the viability for
the use of this type of cartridge case in machine guns which
experience high extraction forces.
[0025] Another prior art design, U.S. Patent Application
Publication No. 2019/0226817 A1, utilizes a third component to
achieve a strong coupling of two main components of the lightweight
cartridge case. This additional third component is required to
prevent a flange failure when under substantially maximum
extraction or pressurization force(s) as it is not only the only
deformation mechanism of the manufacturing process used to build
such cartridge cases, but also the main stress reducing and
therefore supporting feature of the design. Furthermore, this
design fails to create an airtight seal between the two main
components without the use of a fourth part, a gasket between the
shell and the reinforcing cap, as no satisfactory definition of
boundary conditions are given to achieve this mandatory goal. It is
also to be noted that the manufacturing method disclosed is
satisfactory to properly construct this prior art's cartridge case,
but the opposite does not hold true; this prior art's described
manufacturing process is insufficient to achieve the innovation
discussed in the present disclosure. In a high rate manufacturing
situation, it is desired to have fewer components to assemble to
reduce costs and increase throughput.
[0026] Accordingly, it is desirable to provide relatively
lightweight cartridge cases that address one or more of the
foregoing concerns, and cartridges including such cartridge cases.
Furthermore, other desirable features and characteristics of the
various embodiments described herein will become apparent from the
subsequent detailed description and the appended claims, taken in
conjunction with the accompanying drawings and this background.
SUMMARY
[0027] Cartridge cases and cartridges adapted to be chambered in a
weapon system are provided herein. In an exemplary embodiment, a
cartridge case adapted to be chambered in a weapon system includes
a generally cylindrical front shell having a shell wall that
surrounds an internal volume for containing a propellant. The shell
wall defines a case base end portion, a case body portion extending
forward from the case base end portion towards a case mouth portion
that is configured for holding a projectile. The case base end
portion has a first interlocking feature. A reinforcing cap is
disposed adjacent to the case base end portion on a side opposite
the internal volume. The reinforcing cap has an annular extraction
groove, a primer pocket, a flash hole for providing fluid
communication between the primer pocket and the internal volume,
and a second interlocking feature. The second interlocking feature
extends inwardly towards the first interlocking feature to define a
rib edge that is rounded, radiused, relatively sharp or pointed and
engages the first interlocking feature to couple the reinforcing
cap to the case base end portion of the generally cylindrical front
shell.
[0028] In an exemplary embodiment, a cartridge adapted to be
chambered in a weapon system includes a cartridge case. The
cartridge case includes a generally cylindrical front shell having
a shell wall that surrounds an internal volume. The shell wall
defines a case base end portion, a case body portion extending
forward from the case base end portion towards a case mouth
portion. The case base end portion has a first interlocking
feature. A reinforcing cap is disposed adjacent to the case base
end portion on a side opposite the internal volume. The reinforcing
cap has an annular extraction groove, a primer pocket, a flash hole
for providing fluid communication between the primer pocket and the
internal volume, and a second interlocking feature. The second
interlocking feature extends inwardly towards the first
interlocking feature to define a rib edge that is rounded,
radiused, relatively sharp or pointed and engages the first
interlocking feature to couple the reinforcing cap to the case base
end portion of the generally cylindrical front shell. The cartridge
further includes a projectile disposed in the case mouth portion. A
propellant is disposed in the internal volume and is ignitable to
propel the projectile from the case mouth in a forward direction. A
primer is disposed in the primer pocket and is ignitable for
igniting the propellant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The various embodiments will hereinafter be described in
conjunction with the following drawing figures, wherein like
numerals denote like elements, and wherein:
[0030] FIG. 1 is a side cross-sectional view illustrating a
cartridge case in accordance with an exemplary embodiment;
[0031] FIG. 2 is a side cross-sectional view illustrating a
cartridge in accordance with an exemplary embodiment; and
[0032] FIG. 3 is a side cross-sectional view illustrating a
cartridge case in accordance with an exemplary embodiment.
DETAILED DESCRIPTION
[0033] The following Detailed Description is merely exemplary in
nature and is not intended to limit the various embodiments or the
application and uses thereof. Furthermore, there is no intention to
be bound by any theory presented in the preceding background or the
following detailed description.
[0034] Various embodiments contemplated herein relate to relatively
lightweight cartridge cases as compared to conventional brass
cartridge cases, and cartridges including such relatively
lightweight cartridge cases. The exemplary embodiments taught
herein provide a cartridge case for a cartridge adapted to be
chambered in a weapon system. The cartridge case includes a
generally cylindrical front shell having a shell wall that
surrounds an internal volume for containing a propellant. The shell
wall defines a case base end portion, a case body portion extending
forward from the case base end portion, and a case mouth portion
that extends forward of the case body portion and that is
configured for holding a projectile. The case base end portion has
a first interlocking feature. A reinforcing cap is disposed
adjacent to the case base end portion on a side opposite the
internal volume. The reinforcing cap has an annular extraction
groove, a primer pocket, a flash hole for providing fluid
communication between the primer pocket and the internal volume. A
second interlocking feature engaging the first interlocking feature
to couple the reinforcing cap to the case base end portion of the
generally cylindrical front shell.
[0035] In an exemplary embodiment, the generally cylindrical front
shell includes a first metallic material and the reinforcing cap
includes a second, relatively lightweight metallic material that is
different than the first metallic material. Advantageously, in an
exemplary embodiment, this novel, bi-metallic, multi-part cartridge
case including the reinforcing cap locked onto a relatively
thin-wall front shell allows for a redistribution of mass to
reinforce critical, stress supporting areas of the cartridge case
as compared to conventional lightweight cartridge cases.
[0036] Another additional advantage of the cartridge case disclosed
herein is that, in some embodiments, a significant weight reduction
of the cartridge case is achieved. Additionally, as such, the
cartridge including the cartridge case has a significant weight
reduction while maintaining all appreciable features of the
conventional brass design.
[0037] In an exemplary embodiment, the cartridge case includes the
metallic reinforcing cap and the metallic front shell that has a
relatively constant wall thickness through its entire length.
Further, the front shell is dimensioned to fit properly into
typical, existing small arms weapon system chambers and properly
seals the chambers upon firing the cartridge. In an exemplary
embodiment, the reinforcing cap is dimensioned to ensure that
conventional weapon extractor systems can reliably grab and extract
the spent cartridge case after firing. Further, the reinforcing cap
is designed to prevent case failures at peak pressure and
temperature during the firing cycle by effectively supporting the
aft end of the steel case body of the front shell of the cartridge
case. In an exemplary embodiment, both the front shell and the
reinforcing cap are effectively joined together by means of plastic
deformation of the front shell within the reinforcing cap.
[0038] Another additional advantage of the cartridge case disclosed
herein is that, in some embodiments, the reinforcing cap, which may
be made from aluminum, is isolated from the hot burning propellant
gases. This provides a positive protection against possible "burn
through" observed in many prior art interior reinforcement
lightweight cartridge case designs.
[0039] An additional advantage of the cartridge case disclosed
herein is that, in some embodiments, an overall weight of the
cartridge case is reduced by roughly 50% while the internal volume
available to receive the propellant powder charge is increased by
about 8% as compared to conventional brass cartridge cases.
Further, the cartridge including such cartridge case has an overall
weight reduction of at least 10% as compared to cartridges that
include conventional brass cartridge cases.
[0040] Another additional advantage of the cartridge case disclosed
herein is that, in some embodiments, the front shell is formed of
305 stainless steel, which has a nominal density of 7.99 g/cc, and
the reinforcing cap is formed of 7075-T6 aluminum, which has a
density of 2.81 g/cc. While maximizing the aluminum to stainless
steel volume ratio, the cartridge case has a weight reduction, when
compared to a typical brass cartridge case, of about 50% for most
conventional small arms ammunition.
[0041] An additional advantage of the cartridge case disclosed
herein is that, in some embodiments, the cartridge case maximizes
internal case volume by introducing a constant wall thickness front
shell, which is supported by the attached external reinforcing cap.
Being deep drawn, conventional brass cartridge cases do not have a
constant wall thickness. The typical brass case is thinnest at the
mouth and shoulder region and becomes progressively thicker as it
nears its base. This is a consequence of the progressive deep
drawing manufacturing process itself and cannot be remedied. In
order to produce a full, solid case base using brass, wall
thickness must smoothly increase from the thin neck area to the
thick base area. As such, the internal case volume of brass
cartridge cases is less than the internal case volume of the
cartridge case disclosed herein.
[0042] Another additional advantage of the cartridge case disclosed
herein is that, in some embodiments, the cartridge case isolates
the aluminothermic sensitive area of the cartridge case so the
cartridge case will not be susceptible to an aluminothermic
reaction. Prior art aluminum interior reinforcement metallic
cartridge cases are susceptible to aluminothermic reactions by the
nature of the sensitivity of aluminum to exposure to high
temperatures and flame. By using a stainless steel front shell to
fully enclose the propellant charge, the exterior aluminum
reinforcing end cap becomes completely insulated from the high
flame temperature exposure and hot gas pressure generated during
the cartridge firing process and therefore, the reinforcing end cap
will not be susceptible to an aluminothermic reaction.
[0043] An additional advantage of the cartridge case disclosed
herein is that, in some embodiments, a stronger mechanical
interlock is formed between the front shell and the reinforcing cap
via the first and second interlocking features. As will be
discussed in further detail below, by designing and exploiting a
unique bulge feature near the base of the front shell which is
securely mated to the reinforcing cap, a significantly increased
stress supporting area is created. As such, the cartridge case is
enhanced to withstand the weapon extraction forces that a cartridge
case will be subjected to in a weapon system. In an exemplary
embodiment, there is no longer any need to pass through the
relatively small cartridge case flash hole to create the locking
feature between the components as with some prior art cartridge
case designs.
[0044] Another additional advantage of the cartridge case disclosed
herein is that, in some embodiments, cartridge case splits are
eliminated. In particular, prior art polymer cartridge cases are
severely limited in respect to possible dimensional changes in the
case mouth area because of the geometrical and physical limitations
imposed by current industrial and military standards regarding the
weapon chamber and the projectile dimensions. The exterior form of
the cartridge case and the corresponding bullet are precisely
defined to ensure commonality and interchangeability between the
various cartridges and weapons (for a given caliber) produced by
the plethora of manufacturers around the world. Polymers, typically
being mechanically weaker than metals, would normally require a
thicker case mouth wall section to sustain the high pressures and
stresses involved in firing a cartridge. However, the previously
mentioned physical dimensional limitations preclude significantly
increasing the case mouth wall thickness and result in a weak
section that often fails on the polymer type of cartridge case when
used in current small arms weapons. The cartridge cases disclosed
herein solve this problem by using high-strength stainless steel in
this area. This allows for an equivalent case mouth mechanical
strength when compared to conventional brass casings.
[0045] An additional advantage of the cartridge case disclosed
herein, is that in some embodiments, the cartridge case does not
experience any material creep when linked. In particular, prior art
polymer cartridges which have undergone material creep after being
linked can be problematic and induce failures when going through a
fully automatic machine gun firing cycle. For example, localized
"bulging" of the polymer case, at sections directly adjacent to the
metallic link edges may occur and generate irregular case exterior
diameters, which may in turn reduce performance reliability. The
material creeping phenomenon is the result of the constant pressure
applied by a metallic link's press-fit on a softer polymer
cartridge case where the link firmly grabs the case. Polymer
cartridge cases have been known to be more susceptible to material
creep or flow when stressed by the metallic links after being
stored for extended periods of time. The cartridge cases disclosed
herein are creep-resistant, for example similar to the creep
resistance of conventional brass cartridge cases.
[0046] Another additional advantage of the cartridge case disclosed
herein, is that in some embodiments, the cartridge case is
resistant to long-term ultraviolet (UV) light exposure. In
particular, stainless steel and aluminum, for example, which form
the front shell and the reinforcing cap, respectively, are
impervious to UV radiation and as such, their mechanical properties
are not affected by long-term exposure to UV radiation. This is
however not the case with many polymeric materials, which may
experience material strength degradation as a result of long-term
exposure to UV radiation.
[0047] An additional advantage of the cartridge case disclosed
herein, is that in some embodiments, the cartridge case is
corrosion free. In particular, stainless steel and aluminum, for
example, which form the front shell and the reinforcing cap,
respectively, are corrosion-resistant metals. Galvanic corrosion
between these two metals has been extensively studied, for example,
using accelerated aging methods and the minimal resulting corrosion
does not exceed what is currently acceptable for the long-term
storage requirements of a cartridge case.
[0048] Another additional advantage of the cartridge case disclosed
herein, is that in some embodiments, the cartridge case is
compatible with high capacity cartridge loading and packaging
equipment. In particular, an important factor in the design of a
new ammunition is its successful viability industrialization
potential within existing industrial manufacturing facilities, thus
obviating the requirement for new, specialized production
equipment. The cartridge cases disclosed herein can be efficiently
and effectively manufactured on current, existing high-capacity
loading and packing production equipment that is typically used in
ammunition manufacturing plants today. Production cadences for the
cartridge cases disclosed herein are expected to be similar to
those of cartridges made with conventional brass cartridge cases.
This is however not the case with the more sensitive and complex
polymer cartridge case designs.
[0049] An additional advantage of the cartridge case disclosed
herein, is that in some embodiments, the cartridge cases can be
efficiently manufactured at a competitive cost. In particular,
being able to load the cartridge cases disclosed herein on existing
production equipment means only a minimal tooling investment is
required to get up to and achieve typical brass cartridge case
level production rates. The production cadences for the cartridge
cases disclosed herein are similar to those with brass cartridge
cases while steel and aluminum raw base materials are less
expensive than brass. As such, price-wise, the cartridge cases
disclosed herein will be competitive with brass cartridge cases
once fully industrialized. By contrast, polymer cartridge cases,
even when fully industrialized, will still remain much more
expensive due to their special manufacturing process requirements
and resulting lower production cadence.
[0050] FIG. 1 is a side view illustrating a cartridge case 10 that
is adapted to be chambered in a weapon system in accordance with an
exemplary embodiment. FIG. 2 is a side cross-sectional view
illustrating a cartridge 12 including the cartridge case 10
depicted in FIG. 1. The cartridge case 10 includes a generally
cylindrical front shell 14 and a reinforcing cap 16 that is
interlocked with the front shell 14.
[0051] The front shell 14 has a shell wall 18 that surrounds an
internal volume 20 for containing a propellant 22. The shell wall
18 defines a case base end portion 24, a case body portion 26
extending forward (e.g., distal direction 66) from the case base
end portion 24 towards a case mouth portion 30, and optionally a
case shoulder portion 28 extending forward from the case body
portion 26 and tapering inwardly to the case mouth portion 30. For
example, the cartridge case 10 for a pistol may not include a case
shoulder portion 28 and, as such, the case body portion 26 extends
straight forward to and terminates at the case mouth portion 30
without tapering inwardly such that the case mouth portion 30 has a
substantially similar diameter compared to the case body portion
26. In another example, the cartridge case 10 for a rifle may
include the case shoulder portion 28 that tapers inwardly and that
is disposed between the case body portion 26 and the case mouth
portion 30 which has a narrower diameter than the case body portion
26. The case mouth portion 30 holds a projectile 32. As will be
discussed in further detail below, the case base end portion 24 has
a first interlocking feature 34.
[0052] The reinforcing cap 16 is disposed adjacent to the case base
end portion 24 on a side opposite the internal volume 20. The
reinforcing cap 16 has an annular extraction groove 36, a primer
pocket 38, a flash hole 40 for providing fluid communication
between the primer pocket 38 and the internal volume 20, and a
second interlocking feature 42. The second interlocking feature 42
engages the first interlocking feature 34 to couple the reinforcing
cap 16 to the case base end portion 24 of the front shell 14.
[0053] In an exemplary embodiment, the cartridge case 10 is a
bi-metallic cartridge case. In particular, the front shell 14 is
formed of a first metallic material and the reinforcing cap 16 is
formed of a second relatively lightweight metallic material that is
different than the first metallic material. In an exemplary
embodiment, the first metallic material is selected from carbon
steel, stainless steel, brass, aluminum, aluminum alloys, nickel,
and nickel alloys, for example, stainless steel. In an exemplary
embodiment, the second relatively lightweight metallic material is
selected from aluminum and alloys thereof, titanium and alloys
thereof, magnesium and alloys thereof, for example an aluminum
alloy.
[0054] As illustrated, the shell wall 18 of the front shell 14 has
a substantially constant wall thickness. As discussed above,
advantageously having the front shell 14 with a substantially
constant wall thickness allows the front shell 14 of the cartridge
case 10 to have an enhanced internal volume 20 as compared to the
internal volume of conventional brass cartridge cases that are
formed by a deep drawing process or the like and therefore, can
hold an increase volume of the propellant 22.
[0055] In an exemplary embodiment, the case base end portion 24 of
the front shell 14 has an annular bulge section 44 that forms at
least part of the first interlocking feature 34. As illustrated,
the case base end portion 24 has a base 46, the annular bulge
section 44 with an annular tapered forward section 48 (in the
distal direction 66) and an annular flared distal section 50 (in
the distal direction 66) that extends to the aft section of the
case body portion 26. In an exemplary embodiment, the first
interlocking feature 34 is configured at least in part as an
annular recessed feature 134, e.g., groove, annular V-shaped
groove, or the like, that is defined between the annular tapered
forward section 48 and the annular flared distal section 50 of the
case base end portion 24.
[0056] Likewise, the reinforcing cap 16 has a reinforcing cap body
portion 52 that includes the primer pocket 38, the annular
extraction groove 36, and the flash hole 40. As illustrated, a
reinforcing cap sleeve portion 54 extends forward from the
reinforcing cap body portion 52. The reinforcing cap sleeve portion
54 and the reinforcing cap body portion 52 together form a pocket
56 that has the case base end portion 24 disposed therein. The
reinforcing cap sleeve portion 54 has a locking rib 43 that forms
at least part of the second interlocking feature 42. In an
exemplary embodiment, the locking rib 43 is an annular locking rib
that extends or tapers inwardly towards the groove or annular
recessed feature 134, for example tapers inwardly to a rib edge 142
that is rounded, radiused, relatively sharp or pointed (e.g.,
slight radius or non-radius rib edge such as having a radius of
from about 0 to about 0.5 mm), to substantially match the annular
tapered forward section 48 and flares outwardly therefrom to
substantially match the annular flared distal section 50, thereby
defining a substantially V-shaped annular locking rib, and engages
with the annular recessed feature 134 of the case base end portion
24 to securely interlock the reinforcing cap 16 with the front
shell 14. In an exemplary embodiment, advantageously having the
locking rib 43 extend or taper inwardly to a rounded, radiused,
relatively sharp or pointed rib edge in which the locking rib 43
substantially matches and directly interfaces with the annular
tapered forward section 48 and the annular layered distal section
50 of the first interlocking feature 34 ensures an air-tight seal
between the reinforcing cap 16 and the front shell 14, for example
without the use or presence of any liquid and/or solid seal(s).
[0057] As illustrated in FIG. 2, the cartridge 12 includes the
cartridge case 10, the propellant 22, the projectile 32, and a
primer 60. The projectile 32 is disposed in the case mouth portion
30. The propellant 22 is disposed in the internal volume 20 and is
ignitable to propel the projectile 32 from the case mouth 30 in a
forward direction (indicated by single headed arrow 62). The primer
60 is disposed in the primer pocket 38 and is ignitable for
igniting the propellant 22.
[0058] Referring to FIG. 3, a cartridge case 110 is provided
similarly configured as the cartridge case 10 illustrated in FIG. 1
including the front shell 14, the reinforcing cap 16, the first
interlocking feature 34, and the second interlocking feature 42 but
with the exception that the interlocking feature 34 includes a
plurality of annular recessed features 134 and 136 and the
interlocking feature 42 includes a plurality of locking ribs 43 and
68. In an exemplary embodiment, the annular recessed features 134
and 136 are axially spaced apart by the annular bulge section 44
and are independently configured as a groove, annular V-shaped
groove, or the like.
[0059] In an exemplary embodiment, the reinforcing cap sleeve
portion 54 has the locking rib 43 and 68 that are axially spaced
apart from each other and that extend inwardly to rib edges 142 and
144, substantially matching and directly interfacing with the
annular recessed features 134 and 136 of the interlocking feature
34 of the case base end portion 24 to securely interlock the
reinforcing cap 16 with the front shell 14. Advantageously, this
ensures an air-tight seal between the reinforcing cap 16 and the
front shell 14, for example without the use or presence of any
liquid and/or solid seal(s).
[0060] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the disclosure, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the disclosure in any
way. Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the disclosure. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the disclosure as set forth in the appended
claims.
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