U.S. patent application number 11/459250 was filed with the patent office on 2007-09-20 for thin walled, two component cartridge casing.
This patent application is currently assigned to SNC TECHNOLOGIES CORP.. Invention is credited to William A. Dittrich.
Application Number | 20070214992 11/459250 |
Document ID | / |
Family ID | 38516399 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070214992 |
Kind Code |
A1 |
Dittrich; William A. |
September 20, 2007 |
THIN WALLED, TWO COMPONENT CARTRIDGE CASING
Abstract
A cartridge or ammunition casing is made of two components, one
forming the outer casing sleeve and head end and the other
comprising a plug seated within the head end to protect the outer
casing material from propellant gases. The outer cylindrical
sidewall and end panel of the casing may be made of a material
selected from the group consisting of stainless steel, steel,
pre-coated carbon steel, brass or brass-type alloys, aluminum,
hardened aluminum alloys, and suitable polymeric plastic material
such as nylon derivatives and VECTRA.TM.. The inner plug may be
made of a material selected from the group consisting of aluminum,
brass, steel, stainless steel, and suitable polymeric
materials.
Inventors: |
Dittrich; William A.;
(Denville, NJ) |
Correspondence
Address: |
WILLIAM H. EILBERG
THREE BALA PLAZA, SUITE 501 WEST
BALA CYNWYD
PA
19004
US
|
Assignee: |
SNC TECHNOLOGIES CORP.
Avon
CT
|
Family ID: |
38516399 |
Appl. No.: |
11/459250 |
Filed: |
July 21, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60921487 |
Jul 22, 2005 |
|
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Current U.S.
Class: |
102/469 ;
102/470 |
Current CPC
Class: |
F42B 5/36 20130101 |
Class at
Publication: |
102/469 ;
102/470 |
International
Class: |
F42B 5/26 20060101
F42B005/26 |
Claims
1. A casing for cartridge ammunition, the casing having a head end
and an interior volume for containing propellant comprising: a) a
generally cylindrical sleeve portion that forms the sidewall of the
casing with a casing sidewall inner surface, the casing being
further substantially closed at the head end by a casing end panel
having a circumferential boundary joined with the sidewall, the
casing end panel having a centrally located end panel opening to
receive a primer, and b) an inner reinforcing plug seated against
the head end to provide support to the casing against the high
pressures experienced in the firing of the ammunition, the inner
plug having a primer recess formed therein and aligned with said
end panel opening to receive a primer, the recess being provided
with one or more perforations through the inner plug to permit gas
from the primer to enter into the interior of the casing wherein
the inner plug extends laterally between the primer well recess and
the casing sidewall whereat the plug is provided with an
outwardly-directed cylindrical plug surface fitted to bear against
the inner surface of the casing sidewall to seal-off the casing
sidewall and casing end panel from propellant gas arising upon
firing of the ammunition.
2. The casing as in claim 1 wherein the inner plug is a solid body
which extends laterally between the primer recess and the casing
sidewall where the plug is fitted to bear against the inner surface
of the casing sidewall to seal-off the casing sidewall and casing
end panel from propellant gas arising up on firing of the
ammunition.
3. The casing as in claim 1 wherein the casing end panel is
provided with an inwardly depressed, cup-shaped primer pocket
defining a primer well fitted into the primer recess in the plug,
the primer well having a cylindrical sidewall connected to the
casing end panel at the head end and formed therein to accept a
primer, the primer well having a seating surface for the primer in
the form of an annular base that closes-off the inner end of the
cylindrical wall of the primer well, the primer pocket having a
perforation there through aligned with or in communication with the
one or more perforations in the inner plug to allow the primer
gases to ignite propellant within the inner volume of the casing
upon firing.
4. The casing as in any one of claims 1, 2 or 3 wherein said
outwardly-directed cylindrical plug surface extends forwardly
towards the open end of the casing, past the depth of the primer
recess.
5. The casing as in claim 4 wherein the inner plug comprises an
outer cylindrical extension in the form of a flange that is
positioned to extend upwardly towards the open end of the casing
forwardly beyond the depth of the primer recess while lying
sealingly against the inner surface of the casing sidewall.
6. The casing as in claim 5 wherein the material forming such a
flange is of a dimension and of a material sufficiently ductile to
engage intimately with the casing sidewall and ensure the seal
between the plug and the casing sidewall under the pressure of
expanding propellant gases.
7. The casing as in claim 6 wherein the flange tapers with reducing
thickness as it extends towards the forward end of the casing.
8. The casing as in claim 1 wherein the inner plug is in the form
of a layer which provides the primer pocket which defines the
primer well, and conforms to the inner face of the end panel and an
initial portion of the inner surface of the casing sidewall to
seal-off the casing sidewall and casing and panel from propellant
gas arising upon firing of the ammunition.
9. The casing as in claim 1 wherein the casing end panel is joined
seamlessly in a unitary manner to the casing sidewall around the
circumferential boundary of the casing end.
10. The casing as in claim 9 wherein the outer casing sidewall and
outer casing end panel are all formed from one piece of common
material.
11. The casing as in claim 10 wherein the thickness of the casing
sidewall is equal to or greater than the thickness of the casing
and wall panel.
12. The casing as in claim 10 wherein the outer casing sidewall and
end panel are of nearly the same relatively constant thickness.
13. The casing as in claim 1 wherein the plug engages with the
inner surface of the casing sidewall through an interference
fit.
14. The casing as in claim 1 wherein to keep the plug in place
within the casing, the casing sidewall is provided with a slight
inward taper towards its forward end, forward of the plug.
15. The casing as in claim 3 wherein the inner plug is in the form
of a sheet shaped to fit over and embrace the primer well,
extending to and along the inside surface of the casing end panel
at the head end, and extending upwardly along the casing sidewall
in the form of an outer a cylindrical extension of the sheet to
seal-off the casing sidewall and casing and panel from propellant
gas arising upon firing of the ammunition.
16. The casing as in claim 3 wherein the plug embraces the
cylindrical sidewall of the primer well around its outside surface
strengthening the primer well against expansion when the primer is
pressed therein and helping to retain the primer in the primer well
by a friction fit.
17. The casing as in claim 1 wherein, to provide rimmed ammunition,
the casing sidewall, at its juncture with the circumferential
boundary of the end panel, extends outwardly to provide that the
diameter of the end panel is greater than the diameter of the
cylinder defined by the casing sidewall to form a protruding
annular rim to provide an extraction rim for the casing.
18. The casing as in claim 1 wherein, to provide rimless ammunition
with an extractor groove formed therein adjacent to the head end,
the inner plug has an annular groove, step or recess formed therein
to provide a space and the casing wall overlying the groove, step
or recess in the plug is deformed to fit within such space to
provide an extraction groove for the casing.
19. The casing as in claim 18 wherein the plug has upper and lower
portions with a straight-footed cylindrical support in its lower
portion that extends to the inside surface of the end panel at the
head end of the casing, the diameter of the cylindrical foot being
reduced from the main diameter of the upper portion of the plug to
provide room for the formation of the extraction groove in the
sidewall of the casing.
20. The casing as in claim 19 wherein the plug comprises a plug-rim
at the head end portion of the cylindrical foot and wherein the
outer casing sidewall is rolled or crimped over this plug-rim to
lock the plug in place and to form an extraction rim.
21. The casing as in any one of claims 17 or 20 wherein the rim is
bent slightly forwardly so that it protrudes at less than a right
angle from the casing sidewall to better engage with the extractor
mechanism of a weapon.
22. The casing as in claim 1 wherein the outer cylindrical sidewall
and end panel of the casing are made of the material selected from
the group consisting of stainless steel, steel, pre-coated carbon
steel, brass or brass-type alloys, aluminum, hardened aluminum
alloys, and suitable polymeric plastic material such as nylon
derivatives and VECTRA.TM..
23. The casing as in claim 1 wherein the outer cylindrical
sidewall, end panel of the casing and primer well are made
exclusively of polymeric material.
24. The casing as in any one of claims 22 or 23 wherein the inner
plug is made of the material selected from the group consisting of
aluminum, brass, steel, stainless steel, and suitable polymeric
materials.
25. A method of manufacturing a casing as in claim 1 wherein the
inner plug has upper and lower portions and outer circumferential
sidewall surfaces with upper and lower portions and an annular
indentation to serve as a plug groove is formed in the lower
portion of plug, comprising the steps of: 1) providing an outer
cylindrical tube with a sidewall to form the eventual casing
sidewall, the tube being closed at one end to provide the casing
end panel; 2) inserting the plug into the base end of the casing
sleeve portion 3) pressing the tube sidewall into the annular
indentation to provide an extractor groove for the casing.
26. A method of manufacturing a casing as in claim 1 wherein the
inner plug has upper and lower portions and outer circumferential
sidewall surfaces with upper and lower portions and an annular
indentation formed in the lower portion of plug, terminating in an
outwardly extending plug annular rim, comprising the steps of: 1)
providing an outer cylindrical tube with a sidewall to form the
eventual casing sidewall, the tube being closed at one end to
provide the casing end panel and having a diameter which is larger
than the casing sidewall diameter; 2) inserting the plug into the
base end of the casing sleeve portion; 3) pressing the tube
sidewall over the plug annular rim to provide a rim for the casing,
and 4) reforming the diameter of the cylindrical tube above the rim
to the diameter of the casing sidewall.
27. A method of manufacturing a casing as in claim 1 wherein the
inner plug has upper and lower portions and outer circumferential
sidewall surfaces with upper and lower portions and an annular
indentation formed in the lower portion of plug, comprising the
steps of: 1) providing an outer cylindrical tube with a sidewall to
form the eventual casing sidewall, the tube being closed at one end
to provide the casing end panel and having a diameter which is
smaller than the eventual casing sidewall diameter; 2) forming an
outwardly extending casing rim at the closed end of the cylindrical
tube, the rim having the diameter of the eventual casing sidewall;
3) expanding a portion of the tube sidewall commencing at a point
above the end panel sufficient to provide an extractor groove for
the casing and a casing sidewall of a final diameter for the
casing; and 4) inserting the plug into the base end of the casing
sleeve portion.
28. A method of manufacturing a casing for cartridge ammunition,
the casing having a cylindrical casing sidewall of final diameter
and a head end closed by an end panel comprising the steps of: 1)
providing an outer cylindrical tube with a sidewall to form the
eventual casing sidewall, the tube being closed at one end to
provide the casing end panel and having a diameter which is smaller
than the eventual, final, casing sidewall diameter; 2) forming in
outwardly extending casing rim at the closed end of the cylindrical
tube, the rim having the diameter of the eventual casing sidewall;
and 3) expanding a portion the tube sidewall commencing at a point
above the end panel sufficient to provide an extractor groove for
the casing and a casing sidewall of the final diameter for the
casing.
Description
[0001] This invention pertains to the field of ordnance. More
particularly, it describes a cartridge casing and process for
manufacturing the same which is directed towards cartridge casings
typically used in small and artillery caliber ammunition.
BACKGROUND OF THE INVENTION
[0002] Cartridge casings used in small caliber to artillery caliber
weapons provide the function of containing the other major
components of the cartridge, including propellant, projectile or
bullet and primer. In addition to being a container, the casing
must expand slightly and act as a seal to prevent gases, generated
by the propellant, from leaking from the forward or mouth end of
the casing, along the sidewall of the casing, and through the
breach or bolt face at the rear of the casing. The head end of the
casing must also absorb the striking force of the firing pin
without deforming excessively.
[0003] In the case of rimless cartridges, a portion of the head end
typically will extend beyond the support of the chamber wall of the
weapon barrel. This is to provide access by an extractor mechanism
on the weapon bolt to engage with an extractor groove formed in the
sidewall of the casing of the rimless ammunition.
[0004] As observed in U.S. Pat. No. 2,774,283 by Harvey, the bolt
face of such a typical weapon supports and rests against the base
or head of the cartridge but does not completely provide support
for sealing-in the gases. The casing must therefore be made heavier
at the rear or head end to prevent it from bursting in the
locations where it is not fully supported or enclosed. The drawing
in that patent also describes the engagement of the extractor,
which removes the casing from the weapon after firing, with the
extractor groove of the casing.
[0005] Conventional cartridge casings are generally manufactured
from brass, steel or aluminum by a process in which a thick walled
cup is formed from a coin or cylinder of metal, after which it is
headed, drawn, trimmed, annealed and otherwise formed in a series
of operations, resulting in the shape and physical properties
required to interface with conventional weapons. A typical process
used for manufacture is described by Offutt et al in U.S. Pat. No.
1,296,842. The large number of steps in the process and the scrap
produced, e.g. during machining the extractor groove, substantially
add to the end item cost. There have been many attempts to reduce
the cost and also to reduce the weight of cartridge casings by the
use of alternate materials and processes, but the majority of
casings are still manufactured using materials and processes based
on techniques developed nearly a century ago.
[0006] The continual need for lighter weight in military
applications has initiated numerous studies of aluminum as an
alternate material for conventional brass and steel casings. Some
success has been achieved in 20-40 mm size casings, which have been
in use for nearly half a century. However, in the smaller sizes
used in rifles, machine guns and other man-portable high velocity
systems, aluminum has not been shown practical. Under the high
pressures and physical stresses encountered in such systems,
aluminum has been shown to catastrophically fail in the event of
even minor material defects. The failure mode often results in
ignition of the aluminum, causing a "burn through" that can be
hazardous to the user. Numerous attempts have been made to mitigate
this behavior through the use of coatings and ablative materials
(e.g. U.S. Pat. No. 3,765,297 by Skochko et al), but those methods
have not been shown to be fully reliable.
[0007] Much work has also gone into investigation of plastic as an
alternate material. Two part casings, using a metallic base
combined with a plastic upper sidewall, have also been tried to
reduce weight and cost. They have been successful in lower pressure
weapons, such as shotguns. Processes for the manufacture of such
metallic bases for shot shells are described by Buxton in U.S. Pat.
No. 2,193,245. In such applications, the metallic head or base is
formed from thin steel, brass or brass coated/clad steel strip in a
progressive process, beginning with a thin coin of the metal. The
plastic sidewall is then molded into the interior of the resulting
base cup. Similar configurations have been tried for high-pressure
casings, but they have required heavier base cups to retain the
high pressures and attachment to the plastic sidewall to the
metallic base cup is a problem.
[0008] Multipart casings having an all-plastic sidewall, (U.S. Pat.
No. 4,726,296 by Leshner/Donnard & U.S. Pat. No. 4,614,157 by
Grelle et al) have also been tried. Under the greater temperatures
and more severe physical environments experienced in military
weapons these designs have shown a propensity to fail at the joint
of the plastic-to-metal base, causing jammed or damaged weapons.
All-plastic cases have also not been shown to be as capable of
sustaining the high pressures experienced in small caliber
cartridges. Some applications have been successful, e.g. low
pressure blank/training ammunition, but in general, success has not
been achieved with higher pressure, conventional, ball/tracer
ammunition.
[0009] Steel has been used as an alternate to brass as the casing
material for nearly a century. However, the process used to
manufacture a steel casing requires even more operations than that
used for brass. Some success has been attained (see U.S. Pat. No.
4,041,868 by Rayle et al) in reducing the weight of a steel casing
through the use of higher strength boron steel in a design that
minimizes the amount of steel in the head end or base area.
However, this still requires performing all the major operations,
including applying the lubrication coatings needed for forming
steel casings from thicker initial billets.
[0010] U.S. Pat. No. 1,082,975 describes a cartridge casing with a
simplified construction and reduced cost. It describes a center
fire cartridge comprising an outer shell that extends continuously
from the cylindrical to base-end portions of the casing, and an
internal base cup. This cartridge is intended to operate on the
basis of a Burdan-style primer. The internal base cup, which is
"formed of a single piece of metal", is in the form of a thin,
conically shaped plate that is, effectively, pleated. This base cup
is positioned internally at the base of the cartridge casing at its
head end and is held in position along its outer circumferential
edge by an "inwardly extending circular rib rolled in the shell."
Thus the primer is held in place by the internal base cup: "the
metal of the base cup is bent inwardly to form a circular pocket
which receives the primer . . . . At the bottom of the primer
pocket are holes 17 through which the flame of an exploded primer
passes to ignite the power charge in the shell." This '975 patent
provides a simplified cartridge construction having a single outer
member and a one-piece internal base cup. However, the base cup is
not of a design to assist the outer shell in resisting gas
pressures in the vicinity of the head end particularly when exposed
to the high pressures associated with modern propellants.
[0011] U.S. Pat. No. 933,030 describes a center fire cartridge
which comprises The casing with a cylindrical sidewall fitted into
a base cup at the head end of the casing. The base cup includes a
pocket for the primer of the Boxer type. As illustrated in this
'030 patent, the casing sidewall is fitted within a round rim at
the point where it engages with the base cup. An outer, secondary
head-end cup with an extended sleeve embraces both the base cup and
the casing sidewall. The sleeve portion of the secondary cup
extends along the casing sidewall, extending partially towards the
forward end of the casing. Pressed paper surrounds the primer
pocket on the inner side of the casing, extending to the inner
surface of the casing sidewall.
[0012] The '030 patent ostensibly provides a cartridge that is not
substantially reinforced or protected from propellant gas pressure
at its base end because of the low structural strength of the paper
filler.
[0013] Accordingly, it is an objective of this invention to provide
an alternate design for a lightweight and low cost cartridge casing
primarily for use in the higher-pressure small caliber individual
and crew-served weapons. It may also have applications in larger
caliber artillery weapons.
[0014] The invention in its general form will first be described,
and then its implementation in terms of specific embodiments will
be detailed with reference to the drawings following hereafter.
These embodiments are intended to demonstrate the principle of the
invention, and the manner of its implementation. The invention in
its broadest and more specific forms will then be further
described, and defined, in each of the individual claims which
conclude this Specification.
SUMMARY OF THE INVENTION
[0015] One object of the invention is to provide a cartridge casing
for either rimmed or rimless ammunition with an outer casing wall
that is protected or reinforced within the interior of the base or
head end of the casing in order to resist the high pressures of
propellant gases in the locations where the casing wall isn't
supported completely on the outside of the casing by the weapon
chamber and bolt interface.
[0016] According to one embodiment of the invention the casing for
ammunition in the form of a cartridge having a head end and
containing propellant in its interior for use in small caliber and
artillery caliber weapons comprises: [0017] a) a generally
cylindrical sleeve portion that forms the sidewall of the casing,
the casing being further substantially closed at the head end by
the casing end panel having a circumferential boundary joined with
the sidewall, the casing end panel having a centrally located end
panel opening, preferably in the form of a well, to receive a
primer, and [0018] b) an inner reinforcing plug preferably seated
against the head end to provide support to the casing against the
high pressures experienced in the firing of the ammunition, the
inner plug having a primer well recess formed therein and aligned
with said end panel opening to receive a primer, the recess
terminating in one or more perforations through the inner plug to
permit gas from the primer to enter into the interior of the casing
wherein the inner plug extends laterally between the primer well
recess and the casing sidewall whereat the plug is provided with an
outwardly-directed cylindrical plug surface fitted to bear against
the inner surface of the casing sidewall to seal-off the casing
sidewall and casing end panel from propellant gas arising upon
firing of the ammunition. Preferably said outwardly-directed
cylindrical plug surface extends forwardly towards the open end of
the casing, past the depth of the primer well recess.
[0019] According to a preferred variant the inner plug is a solid
body which extends laterally between the primer well recess and the
casing sidewall where the plug is fitted to bear against the inner
surface of the casing sidewall to seal-off the casing sidewall and
casing end panel from propellant gas arising up on firing of the
ammunition. Alternately, the inner plug may be in the form of a
layer which conforms to the sidewall of the primer well recess, the
interface of the end panel, and an initial portion of the inner
surface of the casing sidewall to seal-off the casing sidewall and
casing and panel from propellant gas arising upon firing of the
ammunition.
[0020] According to another preferred variant, the casing end panel
is joined seamlessly in a unitary manner to the casing sidewall
around the circumferential boundary of the casing end. That is, the
sleeve or sidewall portion of the casing and the casing end panel
are preferably "integrally formed". The expression "integrally
formed" indicates that there is continuity of material between the
casing sidewall and the circular casing end panel. Preferably, the
outer casing sidewall and outer casing end panel are all formed
from one piece of material. The thickness of the casing sidewall
may be equal to or greater than the thickness of the casing and
wall panel, which is converse to the configuration of most standard
ammunition. This feature conveniently integrates with the metal
forming procedure described further below.
[0021] According to another preferred variant, the inner plug
engages with the inner surface of the casing sidewall through an
interference fit. One advantage of the interference fit, e.g.
having a sealing, preferably voidless, contact between the inside
surface of the outer casing sidewall and the outside surface of the
plug, is to prevent propellant gas on firing from having access to
the head end. Another advantage of providing such a coupling
between the plug and casing sidewall is that it will help ensure
that both parts are extracted as a unit from the chamber after
firing. Alternately, to keep the plug in place within the casing,
the casing sidewall may be given a slight inward taper towards its
forward end, forward of the plug, after the plug is fitted in
place. Further or alternately, an inwardly protruding ring may be
formed into the casing sidewall above the upper boundary of the
plug to prevent shifting of the plug.
[0022] In a simple variant of the invention the casing end panel
has a centrally located end panel opening and the inner plug
provides the recess to receive a primer. According to a further
preferred variant, the casing end panel is provided with an
inwardly depressed, cup-shaped primer pocket or well formed therein
to accept a primer. This is an alternative to having the inner plug
define the primer recess. The primer well when formed integrally
with the casing end panel includes a cylindrical sidewall provided
by/connected to the casing end panel at the head end. Such a primer
well preferably also includes a seating surface for the primer in
the form of an annular base that closes-off the inner end of the
cylindrical wall of the primer well, (except for a perforation
therethrough to allow the primer gases to ignite propellant within
the inner volume of the casing upon firing). This seating surface
for the primer is also preferably an integral extension of the
casing end panel.
[0023] The plug is primarily seated against the inside surface of
the end panel of the casing. The plug in this latter variant is
preferably shaped to overlie at least a portion of the inner side
of the primer seating surface formed at the base of the primer well
where it may optionally be further seated. The primer gas
perforations in the inner plug are aligned or are in communication
with the perforation in the primer well seating surface to allow
for the passage of propellant gases. In cases where the plug
overlies the primer well cylindrical sidewall, the plug may be
partly supported by such wall as well as by the base of the primer
well. However, it is preferable that the primary support for the
plug is provided by the fact the plug extends to contact securely
against the inside surface of the head end of the casing.
[0024] When the casing end panel extends inwardly to form the
cylindrical sidewall of the primer well, it is advantageous for the
plug to embrace this cylindrical sidewall of the primer well around
its outside surface. This will strengthen the primer well against
expansion when the primer is pressed therein, helping to retain the
primer in the primer well by the friction fit.
[0025] According to another feature of the invention, in the
variant of rimmed ammunition the casing sidewall, at its juncture
with the circumferential boundary of the end panel, extends
outwardly to provide that the diameter of the end panel is greater
than the diameter of the cylinder defined by the casing sidewall.
This forms a protruding annular rim to provide an extraction rim
for the casing. In this variant, the inner plug does not conform to
the casing sidewall in the region of the annular rim.
[0026] As is customary in rimless ammunition, the casing sidewall
has an extractor groove formed therein adjacent to the head end. To
accommodate this groove, the inner plug may itself have an annular
groove, step or recess formed therein and the casing wall overlying
the groove, step or recess in the plug may be deformed to fit
within such space to provide an extraction groove for the casing.
The fit between the casing wall within the groove and the inner
plug need not be intimate, which is to say that the casing wall and
the inner plug do not necessarily need to be in complete, sealing
contact along the entire outer surface of the inner plug.
[0027] The plug may have a straight-footed cylindrical support that
extends to the inside surface of the end panel at the head end of
the casing. The diameter of this cylindrical foot may be reduced
from the main diameter of the plug to provide room for the
formation of the extraction groove in the sidewall of the casing.
The plug may also be made with its own rim at the head end portion
of the cylindrical foot. Then the outer casing sidewall may be
rolled or crimped over this plug-rim to lock it in place. This
configuration will have the advantage of allowing the rim-forming
operation to provide a sharper radius on the forward corner of the
outer edge of the casing rim, stiffening the rim and providing a
preferred shape to better engage with the extractor mechanism of
the weapon. As a further feature to improve engagement with the
extractor mechanism of the weapon, the cartridge rim, whether
formed on rimmed ammunition or defining one side of the extraction
groove, can be bent slightly forwardly so that it protrudes at less
than a right angle from the casing sidewall.
[0028] As stated above, the thickness of the casing sidewall may be
equal to or greater than the thickness of the casing and wall
panel. As a further preferred variant, the outer casing sidewall
and end panel can be made of nearly the same relatively constant
thickness. Either result can conveniently be obtained by forming
the side and end walls from a single piece of material which
initially has a thickness which is near or equal to that of the
final thickness of the end panel. Starting with a thinner sheet of
material, particularly a metal, allows formation of the cylindrical
sidewall of the casing by progressive stamping operations that are
not interrupted by as many annealing and lubrication treatment
steps as would be required if a thicker sheet of material were used
initially. This process is to be distinguished from the traditional
casing forming operation in which a thick sheet of the initial
material is used to form a thick head end and the thinner casing
sidewall is re-formed out of the annular material around the head
end.
[0029] Materials which may be used for the outer cylindrical
sidewall and end panel of the casing in accordance with the
invention include stainless steel, steel (preferably pre-coated
carbon steel to provide corrosion resistance), brass or brass-type
alloys, aluminum and hardened or tougher forms of aluminum alloys,
and equivalent suitable polymeric plastic materials. For the inner
plug, appropriate materials include aluminum, brass, steel,
stainless steel, and appropriate polymeric plastic materials. The
use of stainless steel or a precoated carbon steel should reduce
the need for a final coating on the case. Use of precoated steel
may be able to reduce the number of operations and cost by applying
the coating to the rolled steel strip in a continuous process
before any forming operations are begun. Such coated strip is
commonly used for shot shell bases, lamp parts, etc. to reduce
costs and provide the appearance of brass.
[0030] Generally, but particularly where the plug is formed of
higher strength carbon steel or stainless steel, the plug may not
necessarily need to be a fully solid body which extends between the
primer recess and the casing sidewall (where it is fitted to bear
against the inner surface of the casing side wall). Instead, it may
be in the form of a sheet shaped to fit over and embrace the primer
well, extending to and along the inside surface of the casing end
panel at the head end, and extending upwardly along the casing
sidewall in the form of an outer a cylindrical extension to this
sheet. An inner plug according to this design is intended to
provide a combined thickness in the casing sidewall and the base
area of the casing at the head end as well as well as a sealing
effect sufficient to withstand and seal-off the outer surface of
the casing at its head end from propellant gas pressure. This outer
cylindrical extension to the plug may be in the form of a flange
that is positioned to extend upwardly towards the open end of the
casing while lying against the inner surface of the casing
sidewall. Preferably, this outer cylindrical extension extends
forwardly of the depth of the primer well or recess.
[0031] Even where a solid body is employed, this solid body may
have its own forwardly directed cylindrical extension in the form
of a cylindrical sleeve or flange that lies sealingly against the
casing. The material forming such a flange is preferably of a
dimension and sufficiently ductile to improve the seal between the
plug and the casing sidewall under the pressure of expanding
propellant gases. To provide this function, it may taper with
reducing thickness as it extends towards the forward end of the
casing.
[0032] Manufacture of casings according to the invention may be
achieved in a variety of manners. According to one method of
manufacture, a rimmed metal base cup, initially formed from a thin
coin in the manner similar to that disclosed in U.S. Pat. No.
2,193,245 by Buxton but preferably being thinner than normal, is
re-formed to provide the outer sidewall of the casing, with the
base panel at the head end of the casing. This may be achieved
through progressive stamping operations. In the case of rimless
ammunition, the inner plug, having provision for an extractor
groove in the form of a plug groove or annular indentation formed
in the lower portion of its outer circumference sidewall, is then
pressed-in or inserted into the base portion of the casing
sidewall. Then the outer casing is crimped or deformed into the
plug groove to provide an appropriately shaped extractor groove for
the casing.
[0033] According to another method of manufacture, a rimless casing
according to the invention may be similarly manufactured by
progressively forming from a sheet-metal sheet a cylindrical
precursor to the cylindrical portion of the casing, closed-off the
cylindrical precursor at the head end by an end panel. At the
circumferentially boundary between the end panel and the
cylindrical wall of the precursor casing, an outwardly protruding
rim is formed in the normal manner for forming a rim on rimmed
ammunition. Thereafter, the precursor casing is expanded to its
normal, full, diameter in the region above the location of the
extraction groove which is to be present in the final rimless
cartridge. Then the plug in accordance with the invention may be
inserted into the bottom of the casing. In this manner, the
unexpanded portion of the material of the casing sidewall defines
the extraction groove. This is the reverse process from that of
providing an initial casing with a full diameter sidewall and then
deforming the sidewall inwardly to form the extraction groove.
[0034] If a rim type casing is needed, as an alternative to forming
the rim before insertion of the inner plug, such a plug of
appropriate final diameter, preferably having its own rim which
will ensure centering, can be inserted into the casing. The casing
outer wall is then deformed at the head end to form the protruding
rim by reducing the diameter of the casing above the rim present on
the plug. In this metal forming operation the casing sidewall is
reduced to an inside diameter which is able to mate intimately with
that of the outer wall of the plug. By providing a rim on the
bottom end of the plug the outer casing layer may then be rolled
over this plug rim. This configuration of the invention helps
ensure that the plug is locked into place inside the cartridge
casing.
[0035] The presence of a bottom, footing rim on the inner plug
permits the outer casing rim, either on rimmed ammunition or as the
rim bordering an extraction groove, to be formed with a sharper
forward corner which is better suited for engagement by the
extraction finger on a firearm.
[0036] In another embodiment, the outer surface of the casing is
made entirely of polymeric plastic which is molded to extend
continuously along the cylindrical sidewall sleeve portion of the
casing and around the head end to form the end panel and embrace
the cylindrical inner plug. This outer surface may be extended to
define a primer well in the head end. This is the reverse of
conventional practice, e.g. as in shot shells, wherein the plastic
sidewall is molded integrally around only the outer periphery of
the metal cup forming the head end of conventional shotshells. This
avoids the need for a junction for the joining of plastic and metal
components at the sidewall, which has been a failure point in prior
configurations. Polymeric materials such as nylon derivatives,
VECTRA.TM., or other equivalent materials can be used as the
polymeric plastic material. In this variant as in all cases of the
invention, the inner plug provides protection for the polymeric
plastic outer surface of the casing at its head end against the
effects of propellant gases.
[0037] In the embodiment consisting of a plastic outer cartridge
casing, the casing can be formed so as to fit into a groove present
in the plug that is shaped to receive the plastic outer layer with
an intimate fit. Alternately, a right-circular cylindrical plug can
be used having no "notches" into which the plastic casing can be
intimately pressed. Instead, the plug has an inward step at its
bottom end to receive the inwardly deformed outer layer, but is not
shaped in the form of a groove to receive the plastic outer layer
with an intimate fit. In this case, an extractor groove can be
formed into the plastic outer shell, independently of the shape of
the plug. This latter shape could be formed by injection molding
the plastic over the plug, or by inserting the plug after injection
molding of the outer casing.
[0038] Using only two pieces to form the supporting casing members
provides an advantage over other prior art processes because it
permits the use of a sheet metal stamping-type process for the
outer member, which is simpler than the common casing production
process wherein a thick metal disk must be drawn and stretched in
several separate operations to provide The casing with a thick base
and a thin sidewall. The use of a thin walled, outer shell or
sleeve of adequate strength surrounding a separate internal
reinforcing plug can closely mimic the function of existing brass
or steel one-piece casings, while providing a number of advantages
over prior art casings. First, the outer component in the current
invention can be produced from a thin sheet of metal e.g.
0.012-0.025 inches of 300 series stainless, rather than the thick
plate e.g. 0.150-0.200 inches as typically used for an equivalent
normal cartridge casing. This permits use of a manufacturing
process similar to those used in tin can and stamping manufacturing
operations, thereby reducing or eliminating eliminate intermediate
annealing operations. This process also permits using smaller,
lighter weight, multi-station forming presses which will reduce
cost. Some annealing of the forward end of necked-down cartridges
may still be required to relieve less than the common brass
casing.
[0039] The current invention also permits the use of relatively
thin stainless steel or pre-coated carbon steel as an outer
material, providing the strength and even the appearance of brass
with the proper coatings. By using a somewhat more expensive per
pound, but lighter, aluminum inner plug to provide the
reinforcement normally provided by a heavier-based brass or steel
conventional casing head end, the current invention can provide
savings in overall weight.
[0040] The foregoing summarizes the principal features of the
invention and some of its optional aspects. The invention may be
further understood by the description of the preferred embodiments,
in conjunction with the drawings, which now follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a cross sectional side view of a prior art 5.56 mm
cartridge case.
[0042] FIG. 2 is a cross sectional side view of one embodiment of
the cartridge case of the current invention.
[0043] FIG. 3 is a cross sectional side view of a cup used as the
initial member in the production of the cartridge case of FIG. 2 in
one embodiment.
[0044] FIG. 4 is a cross-sectional side view of the cup of FIG. 3
after the formation of the primer pocket and part of the extractor
groove.
[0045] FIG. 5 is a cross-sectional side view of a reinforcing
plug.
[0046] FIG. 5A is a cross sectional side view of an alternate
embodiment of the plug of FIG. 5 having a small rim its base
end.
[0047] FIG. 5B is a cross sectional side view of another alternate
embodiment of a plug of FIG. 5 having a circumferential recess.
[0048] FIG. 6 is a cross sectional side view of the cup of FIG. 4
which is being expanded with an expansion punch and supporting
die.
[0049] FIG. 7 is a cross sectional side view of the case sleeve of
FIG. 6 with the reinforcing plug in place.
[0050] FIG. 8 is a cross sectional side view of a cartridge using
the cartridge case of the invention as depicted in FIG. 1.
[0051] FIG. 8A is a cross-sectional side view of a rimless
cartridge using a reinforcing sheet rather than the reinforcing
plug of FIG. 8.
[0052] FIG. 8B is a cross-sectional side view of a rimmed cartridge
using a reinforcing sheet rather than the reinforcing plug of FIG.
8.
[0053] FIG. 8C is a cross-sectional side view of a rimmed cartridge
using the reinforcing plug as depicted in FIG. 5A.
[0054] FIG. 8D is a cross-sectional side view of a rimmed cartridge
using a reinforcing plug that has no rim and wherein the outer rim
is provided entirely by the case sleeve.
[0055] FIG. 8E is a cross-sectional side view of a rimless
cartridge using a reinforcing plug as depicted in FIG. 5B, wherein
the case wall is depressed into the plug's annular recess.
[0056] FIG. 9 depicts a cartridge using the cartridge case of the
current invention which is chambered within a firearm.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0057] FIG. 1 shows a typical prior art cartridge case. A case of
this type is formed by the progressive drawing of an initially
thick "coin", and as a result has a thick base member 200 at the
head end 202 and a tapered cylindrical sidewall 203.
[0058] FIG. 2 depicts a first embodiment of the cartridge casing 1
of the current invention. A cartridge casing 1 is provided with an
cylindrical outer case member 2 having a cylindrical sleeve portion
8 and an end member 7. A cylindrical reinforcing plug 10 is located
at the head end 202 of the cartridge casing 1. The reinforcing plug
10 is arranged such that it will provide additional strength to the
sleeve-like case member 8 in the base area of the cartridge casing
1 needed to withstand the higher stresses in that area of the
cartridge casing 1 occurring as a result of gas expansion at the
area of the cartridge casing 1 where the case 1 is not
substantially supported by the barrel or bolt assembly.
[0059] In order to produce the outer case member 2, in one
embodiment, the process for the outer component begins with a strip
of metal from which a coin is punched. The coin is then held
circumferentially as it is initially pressed through a die with a
punch to form a cup with a sidewall having about half the height of
the cup diameter. That cup is then pressed through a number of
smaller and smaller (e.g. 5) dies to further elongate it while
reducing its diameter to that described by FIG. 3.
[0060] FIG. 3 depicts the elongated steel cup 30 from which a
cartridge casing 1 is to be formed in one embodiment of the
invention. The cup 30 initially has a diameter which is less than
the final required diameter, such that the sidewalls of the cup 30
may be expanded through the use of a die and punch or other
appropriate tooling device to conform to the shape which is desired
in the end product. By using a cup 30 having a generally uniform
thickness, it is typically easier to stamp-form the material into
the final shape of a casing.
[0061] The cup 30 is further flattened at the head end to form the
rim 4 or pinched-in to form an extractor groove 12. Then, one or
more punches are successively pressed in from the head end against
rigid pocketed punches inside the case to form the primer pocket 3
and hole. All the operations are normally performed sequentially on
a multiple station (e.g. 13 station) progressive die stamping
press, with completed straight walled case components with rims 4
and primer pockets (FIG. 4) falling off the end of the press.
Alternately, the straight cup 30 of FIG. 3 is left larger in
diameter than the desired diameter of the end product and pinched
in at the bottom after forming the primer pocket 3 defining a
primer well to form a complete, straight-walled, rimless case 1
having an extractor groove 12. After plug insertion, the case is
tapered; the mouth is formed and trimmed on a separate
press(s).
[0062] FIG. 4 depicts the cup 30 of FIG. 3 which has been headed.
The heading step has provided a small annular protrusion 4 at the
head end of the outer case member 2, which is to form a portion of
the extractor groove used in most military weapons. An end panel
opening 31 to accommodate a primer in the form of a primer well or
pocket 3 has been formed, said primer pocket 3 having a centrally
located passageway 6 to allow a gas evolved by the detonation of
the primer 25 contained within the primer pocket 3 to reach a
propellant 22 which is located further towards the front end of the
cartridge casing 1, within the sleeve-like sidewalls 8 of the
cartridge case 1.
[0063] FIG. 5 depicts one embodiment of a reinforcing plug 10 to be
inserted into the cartridge cylindrical sleeve portion 8 to rest
against the end member or end panel 7 of the outer case member 2.
The reinforcing plug 10 is provided with a primer-accommodating
recess 13 which is dimensioned to mate with the primer pocket 3
that is formed in the outer case member 2. Such
primer-accommodating recess has one or more generally centrally
located bores 44 which permit gas evolved during the ignition of
the primer 25 to come into contact with the propellant 22 and to
ignite such propellant 22.
[0064] The reinforcing plug 10 is dimensioned so as to extend from
the wall of the primer pocket 3 to at least the innermost diameter
of the extractor groove 12, such that when the reinforcing plug 10
is inserted into the cartridge casing outer member 2, it becomes
frictionally locked into place through an interference fit between
the outer circumference of the plug 10 with the inside surface of
the generally cylindrical sleeve portion 8 of the outer case member
2. A similar fit may exist between the inner circumference of the
primer recess 13 of the plug 10 and with the sidewalls which define
the primer pocket 3.
[0065] The plug 10 may include a cylindrical flange 11 at its front
end which extends forwardly from the reinforcing plug 10 further
into the outer case member 2. The cylindrical flange 11 is
preferably formed such that it is tapered towards the generally
cylindrical sleeve portion 8 of outer case member 2 in such a
manner, combined with the ductility of the material, to permit it
to expand slightly to conform more intimately with the generally
cylindrical sleeve portion 8 of the outer case member 2 when
exposed to the pressures that arise from the ignition of the
propellant 22 in order to ensure that propellant gas does not pass
between the outer case member 2 and the reinforcing plug 10.
[0066] In an alternate embodiment of the invention (not shown), the
end panel opening 31 does not extend to the inside of the cartridge
casing 1 in the form of a primer pocket 3, but instead is a hole in
the end member 7 which, in combination with the primer recess 13
found in the reinforcing plug 10, forms a primer accommodating
recess to accept a primer cap.
[0067] FIG. 5A depicts an alternate embodiment of a reinforcing
plug 10A having a small rim 14 at its base end. Such a rim 14 may
be enveloped by the outer case member 2 in order to ensure that the
reinforcing plug 10 is retained in its position in relation the
outer case member 2. Forming the rim 14 in this manner also
facilitates providing the rim with the sharper inside corner.
[0068] FIG. 5B depicts another alternate embodiment of a
reinforcing plug 10E for use in rimless ammunition, the plug 10E
having a circumferential recess 15 into which the outer case member
2 can be forced in order to provide an extractor groove 12 and to
ensure proper retention of the reinforcing plug 10E in relation to
the outer case member 2.
[0069] FIG. 6 depicts the outer case member 2 of the invention
after having had its diameter expanded through the use of an
expansion punch 16 and a supporting die 17, while still located
within said punch 16 and die 17. A supporting member 18 holds the
cartridge casing 1 in place while the punch expands the outer
casing member 2 . The case now has a complete extractor groove 12.
If the case is to be a rimmed case, the initial cup 30 may be
provided such that it is initially of the correct diameter. In such
a case, a rim 14 would be formed by crimping the head end of the
cartridge casing 1.
[0070] FIG. 7 depicts the outer case member 2 after it has been
expanded through the use of the punch 16 and die 17. In this
figure, the case is provided with the reinforcing plug 10 which may
be held in place by an interference fit or through the use of an
adhesive or by crimping the outer case member 2 to provide an
inwardly-directed annular rim or "bump" (not shown) to limit the
motion of the plug along the central axis of the cartridge casing 1
and to improve the sealing properties of the reinforcing plug 10.
Alternatively, the flanges 11 of the reinforcing plug 10 may be
"flared" outwardly in order to ensure that the interference fit is
secure.
[0071] FIG. 8 depicts a cartridge 20 which uses the cartridge
casing 1 of the current invention. The cartridge is provided with a
propellant 22 located within the case, a primer 25 containing
primer cap 23 has been inserted into the end panel opening 31 and
is held within the primer well 13. A bullet 21 has been inserted
into the mouth of the projectile. The cartridge 20 comprises the
reinforcing plug 10 of FIG. 5, having an extractor groove 12 formed
within the outer casing member 2 which is partially supported by
the reinforcing plug 10.
[0072] FIG. 8A depicts a cartridge head end having an alternate
plug or reinforcing member 26 which has been formed out of thinner
sheet material than in the previously mentioned embodiments of the
reinforcing plug 10 which are substantially "solid" and which
extend fully from the primer pocket 3 to the outer case member 2.
The strip 26 is shaped to substantially conform to the inner
perimeter of the outer case member 2. Such a strip may be formed
through the use of simpler stamping machines when compared to the
methods or forming the previously mentioned reinforcing plugs
10.
[0073] FIG. 8B depicts a rimmed cartridge head end which has an
alternate plug or reinforcing member 26 which reinforces and
supports the rimmed head end of the cartridge casing 1 in a
substantially similar fashion to that of FIG. 8A. The rim 40 of
this embodiment is formed by crimping the outer cartridge member 2
near the base end of the cartridge casing 1, and there is no
supporting member extending from the reinforcing member 26 into the
rim 40. In a similar variant of the invention, the reinforcing
member 26 may also be crimped to form the rim 40 such that the rim
40 is provided with additional support.
[0074] FIG. 8C depicts a rimmed cartridge head end which has a
reinforcing plug 10C that has a base end which is substantially in
the shape of a right circular cylinder. The outer case member 2 is
crimped to form a rim 40 that can be used by the casing ejection
mechanisms which is typically found in firearms which use rimmed
ammunition. In this variant, the rim 40 is formed solely from the
outer cartridge member 2, that is to say that there reinforcing
plug 10C is not an integral part of the rim 40.
[0075] FIG. 8D depicts a rimmed cartridge head end which has a
reinforcing plug 10D that has a base end which is provided with a
small annular rim 14 that extends around its circumference. The
outer case member 2 is arranged to conform to the peripheral shape
that is provided by the reinforcing plug 10D, and the plug rim 14
in combination with the outer case member 2 forms the rim 40 to be
used in extraction mechanisms in firearms which use such
cartridges. Although FIG. 8D depicts a rimmed cartridge, a rimless
cartridge could
[0076] FIG. 8E depicts a rimless cartridge head end which is
provided with a reinforcing plug 10E which has a circumferential
annular recess 15. The outer case member 2 is pressed into the
annular recess 15 of the reinforcing plug 10E in order to help
restrain the reinforcing plug 10E and to provide an
cationextraction groove 12 to allow the firing mechanism. This
embodiment is unlike the embodiment shown in FIG. 8, as it provides
additional support for the crimped ridge 4 of the extractor groove
12 which engages with the extractor mechanism and may provide
additional support in the head end of the cartridge case 1.
[0077] FIG. 9 depicts a cross section of cartridge 20 using the
cartridge case of the current invention which is in place in
chamber of a firearm, showing that certain sections of the head end
of the cartridge 1 are not supported by the structure of the
firearm. The barrel 100 of the firearm substantially supports the
generally cylindrical sleeve portion 8 of the cartridge casing 1
while the end panel 7 of the cartridge casing 1 is supported by the
bolt assembly 101. This section of the cartridge 1 which is not
supported by the firearm's structure has its structural strength
increased by the reinforcing plug 10.
[0078] The outer case member 2, if made of metal, may be
alternatively formed from thin strip or coin in the manner as a
typical a shot shell base cup. The casing material preferably
comprises a strong, ductile metal, such as brass, steel, brass
coated steel, or any other similarly strong, ductile metal. The
process of forming the outer case member 2 may alternatively be
performed conventionally through the use of progressive die
stamping and drawing presses, beginning with constant thickness
strip. This process is repeated to elongate the case, as depicted
in FIG. 1B and the case is finally headed, as shown in FIG. 1C to
provide a rim 5 at the base end of the elongated case 4.
[0079] It would also be desirable to use polymeric materials or
plastics as the outer case member 2 or as the reinforcing plug 10
or sleeve 26. In such cases, it would be possible to form the outer
case member 2 out of plastic material which is moulded around a
reinforcing plug 10.
[0080] The inner reinforcing plug 10 is typically fabricated using
common crafting practice, by casting, molding, or cold heading.
This reinforcing plug 10 is preferably of a stronger material than
the outer case member 2, such as steel, or certain plastics. It may
also be made aluminum, in which case the outer case member 2 would
provide protection from the "burn-through" often experienced with
all-aluminum cases.
[0081] The above process, involving the combination of a
reinforcing component or plug 7 with an outer case member 4,
permits the use of a much thinner strip material to be used for the
outer case 4 than that used in conventional cartridges. It also
permits the use of bulk pre-coated or clad materials, eliminating
the need for the costly coating operations required for materials
other than brass.
[0082] A configuration similar to that described with reference to
FIG. 4 is also practical for designs using an outer casing made of
a suitable plastic composition instead of the previously mentioned
suitable metal material, as depicted in FIG. 6. In this instance,
the plastic outer casing 16 may be molded around the inner plug 7,
which may be metallic, to provide increased strength in the head or
base area of the cartridge 1, which is hard to achieve with lower
strength plastics. Molding around the higher strength plug
eliminates the need for a joint of the two materials and obviates
the potential failure point at the juncture, which is common in
prior art.
Conclusion
[0083] The foregoing constitutes a description of specific
embodiments showing how the invention may be applied and put into
use. These embodiments are only exemplary. The invention in its
broadest and more specific aspects is further described and defined
in the claims which now follow.
[0084] These claims, and the language used therein, are to be
understood in terms of the variants of the invention which has been
described. They are not to be restricted to such variants, but are
to be read as covering the full scope of the invention as is
implicit within the invention and the disclosure that has been
provided herein.
[0085] While the present invention has been described with respect
to exemplary embodiments thereof, it will be understood by those of
ordinary skill in the art that other variations and modifications
can be effected within the scope and spirit of the invention.
* * * * *