Note: Descriptions are shown in the official language in which they were submitted.
CA 02563392 2006-10-06
CARTRIDGE MUNITION, PARTICULARLY ONE OF MEDIUM CALIBER
SCOPE OF THE INVENTION
The invention relates to a cartridge munition, particularly to
one of medium caliber, and here particularly to a practice
round, with a cartridge shell and a projectile inserted into it,
and with the cartridge shell mechanically attached to the
projectile. A propulsion chamber is provided at the base of the
cartridge shell to receive a propulsive charge that, for
example, may be ignited using an igniter cap. After ignition,
the propulsive gases from the propulsive charge act on the base
of the projectile so that, after release of the mechanical bond
between cartridge shell and projectile, the projectile is driven
out of the cartridge shell.
BACKGROUND OF THE INVENTION
Such a cartridge munition is described in the U.S. Patent No.
5,936,189. This cartridge munition is used with rapid-fire
weapons of medium caliber (about 40mm). Many such cartridges are
received into a belt that is fed to the rapid-fire weapon. The
propulsion chamber in the cartridge shell is sub-divided into a
high-pressure chamber into which the propulsive charge is placed
and a low-pressure chamber that is connected with the high-
CA 02563392 2006-10-06
pressure chamber via exhaust apertures. Cartridge shell and
projectile are mechanically connected via a central threaded
connection that is formed as an intended-break point.
When the propulsive charge is ignited pyrotechnically in the
high-pressure chamber by means of an igniter cap, the propulsive.
charge burns and propulsive gases are created at high pressure
that then act on the projectile base in both chambers,
eventually driving the projectile out of the cartridge shell,
after the intended-break point between cartridge shell and
projectile is broken-
A similar cartridge munition is described in the U.S. Patent No.
4,892,038.
Furthermore, practice rounds of this type are known in which
only a low-pressure propulsion chamber is provided; such
cartridges are known as low-velocity cartridges (Low Velocity
Ammunition).
Such cartridge munitions are used in large quantities, and must
both be safely stored and safely transported from the
manufacturer to the user. Storage and transport are generally
performed using larger cases, e.g., metal oases that hold a
large quantity of such cartridges.
2
CA 02563392 2006-10-06
In spite of the considerable quantity of igniter material for
igniter caps and propulsive charge located within a storage or
transport container, storage and transport are generally simple.
However, a fire in the storage or transport system during which
temperatures reach and exceed 220 C presents a risk.
At such temperatures, the pyrotechnic igniter charge of the
igniter cap 'combusts spontaneously, igniting in turn the
propulsive charge that otherwise would have ignited at a
temperature from 320 C to 400 C_ After the propulsive charge
ignites, as during regular firing, enough pressure develops in
the propulsion chamber to act on the base of the projectile
eventually to rupture the mechanical connection between
cartridge shell and projectile, causing them to fly apart
explosively.
Significant damage may result simply from the quantity of
exploded propulsive charges of a large number of cartridges.
However, the cartridge shell and projectile may cause great
damage while flying apart. Cartridge shell and projectile here
act quasi as projectiles. Any receiver containers involved will
be destroyed, whereby the separated cartridge shells and
projectiles may endanger humans and cause major mechanical
damage-
3
CA 02563392 2011-12-08
50235-4
During testing, such cartridges are placed into a heater, and heat is
gradually supplied to the heater. After the igniter-cap ignition temperature
of about
220 C is reached, as illustrated, the igniter cap and thereby the propulsive
charge of
the cartridges are ignited. The cartridge shell and projectile were blown
apart and
thrown up to 100 meters as a result of the pressure buildup in the propulsion
chamber, so that the energy released when many such cartridges catch fire is
considerable.
OBJECT OF THE INVENTION
It is the object of some embodiments of the invention to present
measures intended to prevent separation of the cartridge shell from the
projectile
when there is a sharp increase in ambient temperature above the ignition
temperature of the pyrotechnic igniter charge.
Another object of some embodiments of the invention is to present
measures intended to prevent damage to the environment caused by a collection
of
many such cartridges, e.g., in a storage or transport container, upon sharp
increase
in ambient temperature such as caused by a fire.
Another object of some embodiments of the invention is to weaken the
effect of the main charge after ignition of the igniter charge so that neither
large
pressure damage nor major mechanical damage results.
Yet another object of some embodiments of the invention is to so
configure the cartridge munition that the characteristics of the cartridge
munition are
not influenced by these preventive measures.
SUMMARY OF THE INVENTION
According to some embodiments of the invention, it is recommended
that a cartridge munition consisting of a projectile and a cartridge shell,
possessing a
propulsion chamber to provide passages that exit from the propulsion chamber
and
4
CA 02563392 2011-12-08
50235-4
penetrate the wall of the cartridge shell, to be filled with a solid, pressure-
tight fusible
filler material whose melting point is lower than the minimum ignition
temperature of
any pyrotechnic charge in the munition, i.e., lower than the ignition
temperature of the
pyrotechnic igniter charge and the propulsive charge.
Such a fusible material is preferably a fusible metal. Such fusible
metals include alloys of bismuth and tin, whereby other metals such as lead
etc. may
be included.
If a cartridge of the type under discussion is heated to the melting
temperature of the fusible material or metal, for example, 180 C, then the
fusible
material in the passages within the cartridge shell that connect the
propulsion
chamber to the outside melts. If the temperature continues to increase and the
5
CA 02563392 2006-10-06
igniter cap and thereby the propulsive charge are ignited, then
no pressure may build up within the propulsion chamber because
the freed passages function as pressure-relief apertures. The
result is that propulsive charge merely burns, whereby the
propulsive gases thus created may escape via the pressure-relief
apertures. Cartridge shells and projectiles are thus not
separated from each other, so that neither pressure damage nor
mechanical damage may occur.
This was confirmed by a test in which a large quantity of such
cartridges was placed into a conventional transport box made of
lead. The lead box was not damaged even once-
The passages between the propulsive charge and the outside of
the cartridge shell may be configured in many different ways:
e.g., the housing of the igniter cap may be made of such a
fusible material or metal; also, pressure-relief apertures
around the igniter cap that are filled with the fusible material
are a possibility. Either two or four apertures are recommended
for this embodiment. Another option is to provide apertures from
the propulsion chamber penetrating the sidewall of the cartridge
shell.
However configured, the passages must be so shaped that during a
normal shot of the projectile out of the cartridge shell, the
6
CA 02563392 2011-12-08
50235-4
fusible material withstands the high pressures within the propulsion chamber.
Resistance to pressure may be increased by configuring the passages to be
conical,
decreasing toward the outside, as stepped or threaded holes, etc.
In accordance with an aspect of this invention, there is provided a
cartridge munition with a cartridge shell and a projectile inserted into the
cartridge
shell and mechanically connected to it whereby a pyrotechnic propulsive charge
is
located in a propulsion chamber of the cartridge shell that is ignited by
means of a
pyrotechnic igniter, and whose propulsive gases exert a force on the base of
the
projectile when they burn, by means of which the projectile is driven out of
the
cartridge shell, wherein channels exit from the propulsion chamber that
penetrate the
cartridge shell and that are filled with a fusible, solid, pressure-tight
material whose
melting temperature is lower than the ignition temperatures of the pyrotechnic
igniter
and the propulsion charge of the projectile and that the channels narrow as
they
progress from the base of the propulsion chamber to the exit.
BRIEF DESCRIPTION OF THE FIGURES
The invention will be explained in greater detail using illustrations of
embodiments, which show:
Figure 1 a longitudinal section through a cartridge munition consisting of a
projectile
and a cartridge shell that incorporates a propulsion chamber with a propulsive
charge
whereby, according to the invention, pressure-relief apertures are provided
between
the propulsion chamber and the outer wall of the cartridge shell that receive
a fusible
metal, and in this case possess a conical progression;
Figure 2 a second embodiment of a cartridge munition with stepped pressure-
relief
apertures between the propulsion chamber and the outer wall of the cartridge
shell;
and
Figure 3 a third embodiment according to the invention whereby the housing of
an
igniter cap for the propulsive charge is made of a fusible metal.
7
CA 02563392 2006-10-06
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A cartridge munition 1 shown in Figure 1 consists of a
projectile 2 and a cartridge shell 3. The cartridge shell 3
includes a propulsion chamber 4 in which a propulsive charge 5
is positioned.
The wall of the propulsion chamber 4 is provided with overflow
openings 6 that feed into a low-pressure chamber 7 positioned
below the projectile base 8. The propulsion chamber 4 is
provided with a central threaded stud 9 that engages in an inner
thread in the projectile base. In addition, a tracer composition
11 is connected with the projectile base 8 that extends through
the threaded stud 9 into the propulsion chamber.
The cartridge 1 possesses a caliber of from 40mm, for example,
and is fired from a tube weapon (not shown) with a twist, for
which purpose the projectile possesses a guide- or twist-band
(indicated only).
The propulsive charge 5 is ignited pyrotechnically by means of
an igniter cap 13 whereby the igniter cap 13 is mounted in the
center of the base of the cartridge shell 3.
Passages are provided between the propulsion chamber 4 and the
lower base of the cartridge shell 3, in this case conical
CA 02563392 2006-10-06
channels 14 that decrease in size as approach the base of the
cartridge shell. The channels 14 possess a diameter of 7mm for a
40mm-caliber projectile, for example, and narrow down to about
6mm.
For example, two or three or four channels 14 are provided,
symmetrical to the central line of the projectile and to the
igniter cap, that are positioned around the igniter cap.
The passages 14 are filled with a fusible metal 15. ThIF fusible
metal is, for example, a bismuth/tin alloy with 30 to 40%
bismuth by weight and 60 to 70% tin by weight. Depending on the
blend, the melting point of this alloy lies between about 140
and 175 C. The alloy is impact--resistant and not soluble in
water-
The fusible metal 15 is cast into the channels 14 after
appropriate heating, or conical rivets are made of the fusible
metal that are then driven or screwed into the channels 14.
The propulsion chamber is tight and pressure-resistant toward
the exterior by means of the fusible metal 15 so that the
cartridge 1 may be fired from a tube weapon in the same way as a
conventional cartridge- The conical shape of the channels
9
CA 02563392 2006-10-06
prevents the fusible metal 15 from being forced from the
channels 14 by the high pressure in the propulsion chamber.
As mentioned above, when the ambient temperature near the
cartridges rises to 140 to 175 C as the result of a fire, for
example, then the fusible material 15 within the channels 14
melts, freeing them- When the temperature of the igniter cap 13
then continues to rise to above about 220 C, it ignites, also
igniting the propulsive charge 5- The propulsive gases, created
when the propulsive charge burns, may be diverted without
consequence through the free channels 14, so that no pressure
may build up within the propulsion chamber, and therefore the
propulsive charge 5 is also not triggered. Cartridge shell 3 and
projectile 2 further remain mechanically connected via the
threads 9 and 10 so that no major damage can occur, neither
because of high pressure nor because of separation of the
cartridge shell and the projectile.
Figure 2 shows a longitudinal section through a cartridge shell
3 and a portion of the projectile 2; cartridge shell and
projectile are constructed the same as in Figure 1 up to the
channels 14 with the fusible metal 15_ in this case, the
channels are stepped drillings into which the fusible metal 15
is cast. Here also, the fusible metal may either be cast at the
CA 02563392 2006-10-06
time of cartridge manufacture or threaded in, if the channels
and the fusible metal are provided with threads.
Also in this embodiment, the pressure-relief channels 14, as
shown, are positioned either on both sides of the central
igniter cap 13 or in any other configuration around the igniter
cap.
This cartridge may also be fired in the same way as a
conventional cartridge. In case of fire or similar problem, the
function is the same as described by Figure 1.
Figure 3 shows another version of a cartridge whereby only the
cartridge shell 3 and a portion of the projectile 2 are shown,
as in Figure 2. The cartridge shell 3 is constructed the same
way in the area of the propulsion chamber as in the embodiments
shown in Figures 1 and 2.
In this case, the igniter cap 13 is inserted into an igniter-cap
housing 14' that may be threaded into the base of the cartridge
shell 3 in a charge opening 14. The igniter-cap housing 14'
consists of the aforementioned fusible metal 15.
If during a fire, for example, the ambient temperature increases
above the melting point of the fusible metal 15, then the
igniter-cap housing 14' melts and frees a pressure-relief
11
CA 02563392 2011-12-08
50235-4
channel corresponding to the charge opening 14 between the base of the
propulsion
chamber and the base of the cartridge shell. If the igniter cap then ignites
because of
increasing temperature, thereby igniting the propulsive charge 5, then it
merely burns
out without pressure being allowed to increase, so that the cartridge shell
and
projectile are not separated. Pressure damage and major mechanical damage are
prevented.
In the previous text, even if the pressure-relief channels 14 extend from
the base of the propulsion chamber to the outer base of the cartridge shell,
it is
routine for the specialist to configure these channels otherwise, e.g.,
routing them
through the sidewall of the cartridge shell and the propulsion chamber.
It is also possible, of course, to use other low-melting-point materials
instead of the bismuth/tin alloy mentioned as long as it is strong enough to
seal the
pressure-relief channels completely so that a normal shot is possible from a
tube
weapon.
Even though the previous description concerned the preferred
embodiments of the invention, it will be apparent to the specialist that
alterations and
modifications to the embodiments are possible without deviating from the scope
of
the claims.
12
