Note: Descriptions are shown in the official language in which they were submitted.
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CARTRIDGE CASING
The present disclosure relates to a cartridge casing.
In particular it relates to a cartridge casing for a projectile.
Background
A conventional cartridge casing 10 is shown in Figure 1. The cartridge
assembly 10
comprises a casing 12 and a projectile 14. The casing 12 has a hollow section
16
which will contain propellant for displacement of the projectile 14. The
casing 12 further
comprises a head 18 at the end opposite to the projectile 14 which comprises a
chamber 20 for a percussion cap, and a flash tube 22 for communication of an
ignition
charge from the percussion cap to the inside of the casing 12 and thus the
propellant.
The walls of the chamber 16 are formed integrally with the head 18. Such a
cartridge
casing may typically be formed of brass. This material choice has many
advantages, for
example, it is relatively easy to form into the desired shape. However, brass
has
demerit in that it is also relatively dense, and hence the casing 12 forms a
relatively
large percentage of the mass of the whole cartridge.
It is beneficial to reduce the mass of cartridges in order to reduce transport
costs and
mass burden on soldiers who carry them.
Hence a cartridge case and a method of manufacture of a cartridge case which
is of
relatively low weight is highly desirable.
Summary
According to the present disclosure there is provided an apparatus and method
as set
forth in the appended claims. Other features of the invention will be apparent
from the
dependent claims, and the description which follows.
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Accordingly there may be provided a cartridge casing comprising: a casing tube
having
a first end; wherein the tube bounds at least part of a head cap entered into
its first end;
the head cap being fixed relative to the tube by a welding process.
The casing tube may be substantially cylindrical and have an internal diameter
at the
first end which receives the head cap; and the head cap may have an external
diameter
at least part way along its outer periphery sized such that it fits within the
first end of the
casing tube.
The relative dimensions of the internal diameter at the first end of the
casing tube and
the external diameter of corresponding region of the head cap may be such that
when
the head cap is located in the casing tube they form an interference fit with
one another.
The casing tube may further comprise a corrugation towards the first end of
the casing
tube which extends at least part way around the circumference of the casing
tube.
The corrugation may be provided spaced apart from the first end of the casing
tube
such that the inner circumference of the first end is substantially constant
in a region
between the first end and the corrugation.
When assembled, the head cap may extend along the inside of the casing tube
towards
the corrugation.
The external diameter of the outer periphery of the head cap that is
configured to fit
within the first end of the casing tube may terminate in an outwardly
protruding
shoulder, and when the casing tube and head cap are assembled, the casing tube
may
extend towards the outwardly protruding shoulder.
There may also be provided a cartridge comprising a projectile mounted to a
cartridge
casing according the present disclosure.
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There may also be provided a method of manufacturing a cartridge casing
comprising
the steps of: forming a casing tube by a first process; forming a head cap by
a second
process; and joining the casing tube and head cap by third process.
The first process may comprise the steps of: providing a material sheet; and
deforming
the material sheet into a substantially cylindrical tube.
The material sheet may be deformed such that the cylindrical tube is open at a
first end
and closed at a second end opposite to the first end; and removing the closed
end of
the cylinder such that the tube is open at both ends.
The third process may comprise the steps of: entering the head cap into the
first end of
the casing tube; and bonding the head cap and casing tube together using a
welding
process.
The casing tube and head cap may be welded to one another by applying a
welding
process to the external surface of the casing tube, radially outward of where
the casing
tube is in contact with the external diameter of the head cap.
The casing tube and head cap may be welded to one another around a internal
circumference of the casing tube at an interface between the casing tube and
head cap.
The casing tube and head cap may be welded to one another by applying a
welding
process to an interface between the casing tube and head cap on the external
surface
of the casing tube and head cap.
Hence there is provided a light weight cartridge casing configuration and
method of
manufacture for a light weight cartridge casing.
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Brief Description of the Drawings
Examples of the present disclosure will now be described with reference to the
accompanying drawings, in which:
Figure 1 shows a conventional cartridge casing, as described previously;
Figure 2 shows an example of a cartridge casing according to the present
disclosure;
Figure 3 shows an alternative example of a cartridge casing according to the
present disclosure;
Figure 4 shows an example process for the manufacture of a cartridge casing
according to the present disclosure; and
Figure 5 shows an example forming process for a casing tube of the cartridge
casing of the present disclosure.
Detailed Description
Figure 2 shows an example cartridge casing 30 according to the present
disclosure.
The cartridge casing 30 comprises a casing tube 32 having a first end 34 which
is
closed by a head cap 36. The casing tube 32 is substantially cylindrical and
has an
internal diameter at the first end 34 which receives the head cap 36. The
casing tube 32
bounds at least part of the head cap 36 entered into its first end 34. The
head cap 36 is
configured to support and reinforce the base of the casing tube 32 to prevent
it from
swelling and rupturing during operation. As will be described in more detail
later, the
head cap 36 is welded to the casing tube 32, thereby fixing the head cap 36
and casing
tube 32 relative to one another.
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In the context of the present disclosure, "welding" is intended to cover
joining processes
that produce bonding of materials by heating, which may be done with or
without
pressure or filler material. For example, the term is intended to encompass
brazing and
soldering. It may also be taken to encompass a process in which the material
of one or
more articles being joined are brought into a molten state to facilitate
bonding. It may
include a process in which the base materials melt along with a filler
material.
The casing tube 32 further comprises a second end 38, which is open and
configured to
receive a projectile (as shown in Figure 1) opposite to the first end 34. The
second end
38 has a diameter which may be substantially the same as, or less than, the
diameter
of the first end 34. In the example shown the diameter of the second end 38 is
substantially less than the diameter of the first end 34.
The walls of the casing 32 define a substantially cylindrical thin walled
chamber 40. The
tube casing 32 has a substantially constant diameter along a first region of
its length
between the first end 34 and the second end 38. However, the cylindrical thin
walled
chamber 40 may have a taper (for example <10) along at least part or all of
its length.
That is to say, although having a substantially constant diameter along its
length, the
diameter of the casing 32 may decrease slightly in a direction away from the
first end
34, reducing in diameter from the first end 34 to the second end 38. The
casing tube 32
also comprises a transition region 42 towards or at the second end 38 wherein
the
transition region 42 of the casing tube 32 reduces in diameter in a direction
away from
the first end 34 to the second end 38. Hence the diameter of the casing tube
32 will be
different on either side of the transition region 42. The diameter of the
casing tube 32 is
substantially constant along its length to either side of the transition
region 42.
The head cap 36 defines a passage 46 which extends all of the way through the
head
cap 36 which in use will be a flash tube (or "flash passage"). The flash
tube/passage 46
extends into a chamber 47 which, in use, will house a percussion cap
(sometimes
referred to as a "primer"). Thus the head cap 36 has a percussion side 48
which, in use,
faces away from the casing tube 32.
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The head cap 36 further comprises a charge side 49 which, in use, defines part
of the
internal surface of the cartridge casing 30. Thus the flash passage 46 extends
between
the percussion side 48 and the charge side 49.
The head cap 36 has an external diameter at least part way along its outer
periphery
sized such that it fits within the first end 34 of the casing tube 32. The
relative
dimensions of the internal diameter at the first end 34 of the casing tube 32
and the
external diameter of corresponding region of the head cap 36 may be such when
the
head cap 36 is located in the casing tube 32 they form an interference fit
with one
another.
The casing tube 32 and head cap 36 may comprise a welded join which bonds them
together in a region where they form an interference fit with one another. For
example,
the join may be provided around the circumference of the casing tube 32 and
head cap
36 in a region where they interface with one another. Such a region is
indicated with
arrows "A" in Figure 2. The join may be a through weld or stake weld.
Alternatively the casing tube 32 and head cap 36 may comprise a join which
bonds
them together in the interior of the casing tube 32, for example in a region
around a
circumferential edge of an interface between the casing tube 32 and the head
cap 36.
Such a region is indicated with arrows "B" in Figure 2.
The weld may achieved by laser welding. Alternative weld joins may be provided
which
brought only material of the casing tube 32 into a molten state, or brought
material of
both the casing tube 32 and head cap 36 into a molten state. The weld join may
have
been provided by any one of the welding processes as hereinbefore defined.
An alternative example of a cartridge casing 80 according to the present
disclosure is
shown in Figure 3. The example of Figure 3 is similar in many ways to the
cartridge
case shown in, and as described with reference to, Figure 2. Features common
to the
examples of Figure 2 and Figure 3 are referred to using the same reference
numerals.
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In the example of Figure 3, the casing tube 32 further comprises a corrugation
50
towards the first end 34 of the casing tube 32. The corrugation 50 extends at
least part
of the way around the circumference of the casing tube 32. In the example
shown, the
corrugation 50 extends all of the way around the circumference of the casing
tube 32.
The corrugation 50 extends inwardly from the external surface of the casing
tube 32,
such that it extends into the chamber defined by the thin walls of the casing
tube 32.
The corrugation 50 provides an expansion feature for the casing 32 during
operation of
the cartridge casing 30'. The corrugation 50 may also be provided in the
example of
Figure 2. The corrugation 50 may be provided as a convolution or cannelure
which
extends around the circumference of the casing tube 32. The corrugation 50 is
provided spaced apart from the first end 34 of the casing tube 32 such that
the inner
circumference of the first end 34 is substantially constant in a region
between the first
end 34 and the corrugation 50. When assembled, the head cap 36 extends along
the
inside of the casing tube 32 towards the corrugation 50. In the example shown
in
Figure 3, the external diameter of the outer periphery of the head cap 36 that
is
configured to fit within the first end 34 of the casing tube 32 terminates in
an outwardly
protruding shoulder 52. When assembled, the casing tube 32 extends towards the
outwardly protruding shoulder 52 such that the first end 34 of the casing tube
32 is
proximate to or abuts with the shoulder 52.
The casing tube 32 may be joined to the head cap 36 in the region of the
protruding
shoulder 52 (as indicated by arrow "C" in Figure 3), the join being provided
by a laser
or other welding process as hereinbefore defined.
The convolution or cannelure 50 is provided to act as an expansion joint
positioned just
forward of the weld to eliminate stress on the weld join.
The casing tube 32 and head cap 36 may be formed from a metal, metallic
material or
metal alloy comprising, for example, aluminium or titanium. In one example the
casing
tube 32 and head cap 36 may comprise ferritic alloys, for example stainless
steel. The
casing tube 32 and head cap 36 may alternatively be formed from non metallic
material
and/or metal-plastic composite material. The casing tube 32 and head cap 36
may be
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made of the same or dissimilar materials. The choice of welding process will
be
determined in part by the choice of materials used, as appropriate and as
understood in
the art.
The method of manufacture of a cartridge casing 30, 30' according to the
present
disclosure and as shown in Figure 2 and Figure 3 comprise the steps of forming
a
casing tube 32 by a first process, forming a head cap 36 by a second process
and
joining the casing tube 32 and head cap 36 by a third process. This is
described as a
flow diagram in Figure 4. Figure 5 shows the forming of the casing tube 32 in
more
detail.
A material sheet 100 for example a stainless steel strip 100, is formed on a
transfer
press into a tapered casing tube 32 as shown in Figure 5. In an independent
process a
stainless steel wire, or blank of material, is machined and/or formed into a
cylindrical
head cap 36, perhaps by a cold forming process. The casing tube 32 and head
cap 36
are joined in a third independent process, after the casing tube 32 and head
cap 36 are
assembled.
The material sheet 100 which may be deformed in a series of steps, shown in
sequence from the bottom to the top of the page on Figure 5 in the direction
shown by
the arrow 102. Although details of the process may vary, the material is
gradually
formed through intermediate stages in which the features of the casing tube 32
are
provided. The thin walls of the cylindrical tube 32 are drawn from the
material strip 100,
during which process the tapered transitional region 42 may be formed. The
material
sheet 100 is deformed such that the cylindrical tube 32 is initially formed
open at the
first end 34 and closed at the second end 38 opposite to the first end 34.
Alternatively the casing tube 32 may be formed from a pre-drawn tube.
The transition region 42 of the cylindrical tube 32 is tapered towards the
second end 38
such that the second end has a diameter less than that of the first end 34.
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The second end 38 of the casing tube 32 is then removed such that the second
end 38
is "open".
The second process, for forming the head cap 36, comprises the step of
providing the
blank of material, machining and/or forming the material blank into the
cylindrical head
cap 36 such that the head cap 36 has an external diameter substantially
identical to the
internal diameter of the first end 34 of the casing tube 32 to thereby provide
an
interference fit between the two. Alternatively it may be formed with an
external
diameter slightly less than the internal diameter of the casing tube 32 such
that the
interference fit is negligible or completely absent. The head cap 36 is also
formed with
the passage 46 which extends all the way through the head cap 36.
The head cap 36 may be turned, or cold formed, or any other appropriate method
for
the forming of a head cap 36.
The third process may comprise the steps of entering the head cap 36 into the
first end
34 of the casing tube 32. The casing tube and head cap 36 are then bonded
together
using a welding process.
The casing tube 32 and head cap 36 may be welded to one another in a region
where
they form an interference fit with one another. For example, they may be
welded to one
another by applying a welding process around the circumference of the casing
tube 32,
on the external surface of the casing tube 32, radially outward of where the
casing tube
32 is in contact with the external diameter of the head cap 36. Such a region
is
indicated with arrows "A" in Figure 2. This may be achieved by a through weld
or stake
weld process.
Alternatively the casing tube 32 and head cap 36 may be welded to one another
around
the internal circumference of the casing tube 32 at an interface between the
casing tube
32 and head cap 36, as indicated by arrows "B" in Figure 2.
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With reference to the example of Figure 3, the casing tube 32 may be welded to
the
head cap 36 in the region of the protruding shoulder 52 (as indicated by arrow
"C") by a
butt weld or other welding style. That is to say the casing tube 32 and head
cap 36 are
welded to one another by applying a welding process to an interface between
the
casing tube 32 and head cap 36 on the external surface of the casing tube 32
and head
cap 36.
In each example, the welding process may be any one of the welding processes
as
hereinbefore defined. For example the welding process may be one of laser
welding.
Alternative welding processes may employed which bring only material of the
casing
tube 32 into a molten state, or bring material of both the casing tube 32 and
head cap
36 into a molten state.
Prior to assembly the casing tube 32 and head cap 36 may be prepared for
welding, for
example being degreased. Post welding, no subsequent machining may be
required,
and neither may a cleaning of the casing be required.
Post welding the cartridge 30, 30' may be turned to ensure the head cap 36 is
properly
centred on the casing tube 32, and to provide any other additional features
required for
successful functioning of the casing 30, 30'. The assembly is then gauged to
ensure it
meets the correct dimensional tolerances.
Thus there is provided a thin cartridge casing with a thin wall casing tube
which is made
of a material which is inherently lighter than conventional cartridge cases.
The material
choice enables the casing tube to withstand the ignition pressures induced
during
operation whilst also being made by a reliable and repeatable manufacturing
process.
Since the casing may have a thinner wall than that of the related art, and is
made of a
material which has a lower density than that used for conventional casings,
the
resultant cartridge casing will overall be lighter than an equivalent
conventional casing.
Hence for a given amount of powder propellant, a cartridge having a casing of
the
present disclosure will produce the same performance for less overall
cartridge mass
than a conventional cartridge assembly. Additionally, a cartridge casing of
the present
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disclosure may contain a larger volume of powder propellant for delivering the
projectile
over a further distance or with greater force than a conventional cartridge,
and yet,
when assembled, be of the same mass or lower than a conventional cartridge.
While the cartridge cases have been described with reference to propelling a
projectile,
the techniques and materials described may also be used in the production of a
blank
cartridge case, for example one used to contain only a charge but no
projectile.
Attention is directed to all papers and documents which are filed concurrently
with or
previous to this specification in connection with this application and which
are open to
public inspection with this specification, and the contents of all such papers
and
documents are incorporated herein by reference.
All of the features disclosed in this specification (including any
accompanying claims,
abstract and drawings), and/or all of the steps of any method or process so
disclosed,
may be combined in any combination, except combinations where at least some of
such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying
claims,
abstract and drawings) may be replaced by alternative features serving the
same,
equivalent or similar purpose, unless expressly stated otherwise. Thus, unless
expressly stated otherwise, each feature disclosed is one example only of a
generic
series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s).
The
invention extends to any novel one, or any novel combination, of the features
disclosed
in this specification (including any accompanying claims, abstract and
drawings), or to
any novel one, or any novel combination, of the steps of any method or process
so
disclosed.
