Note: Descriptions are shown in the official language in which they were submitted.
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Shock-Insusceptible Smoke Projectiles
The present invention relates to smoke projectiles.
Smoke projectiles having the form of smoke grenades or so-called
smoke cups are fundamentally known, e.g., from DE 28 41 815 C2. In
accordance with this prior art, a projectile charge consists of smoke cups
stacked one above the other in discharging direction in the shell jacket and
comprised of a closed metal casing and a smoke composition charge
accommodated therein on the basis of hexachloroethane, zinc oxide and
metallic powder. The smoke active mass is ignited with the aid of so-called
priming cartridges and lit in the flight of the projectile, with the
projectile then
releasing vapors of smoke upon impact on the ground.
The significance of smoke generation in military terms is to interrupt the
line-of-sight connection between an object to be protected and an attacker.
Concurrently with the further development of modern weapons systems
it became necessary to also obtain interruption of the line-of-sight in the
infrared range.
To this end, combined smoke composition charges on the basis of red
phosphorus were used which result in interruption of the line-of-sight in both
the visible and infrared ranges.
Smoke projectiles for the self-protection of military vehicles are
commonly launched from dischargers, where the smoke active mass is
projected about 25 meters ahead of the vehicle and initiated. The smoke
effect taking place is to interrupt the line-of-sight for the opponent to the
vehicle to be protected in the visual and infrared ranges so as to prevent an
opponent's weapon from taking effect. The introduced smoke measure has
to take effect as quickly as possible. Desired reaction times for building the
smoke screen following initiation of the smoke active mass are within approx.
1 - 2 seconds.
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The smoke projectiles for the protection of military vehicles as
described at the outset include an ammunition body having active masses
incorporated into it. As a result of actuating the firing key in the vehicle,
an .
ejector charge is ignited in the ammunition by means of an electrical primer
which ejects the active mass, or submunition, from the discharger. By means
of a pyrotechnical delay element, which equally was initiated by the ejector
charge, the active mass is lit, still in flight, after lapse of the delay
time, or a
separator charge is initiated as in other systems. In the case of smoke
projectiles including a separator charge, a pressure is generated in the
submunition on the trajectory, which pressure ruptures the metal sheath
enclosing the active mass, lights the smoke active mass contained therein,
and ejects it from the sheath. Any existing smoke projectile systems of the
prior art comprising ammunitions with separator charges present the
drawback that the pressed pellets of smoke active mass ignited on the
trajectory are susceptible to shock on impact. Following separation of the
containers, the ignited active mass pressed pellets drop to the ground from
heights of up to 12 meters. Upon impact on the ground, the impact velocity is
as high as 16 m/s.
Due to the deceleration impulse acting at impact, the flame front is
disrupted, and the active mass pressed pellets are extinguished almost
completely. The same phenomenon is observed in the case of a candle
having its rear side hit against a surface while in the burning condition.
Several seconds pass by until the proper combustion progression required
for smoke generation is re-established. This time span, referred to as the
"gap" in international usage, may be as long as 15 seconds. Line-of-sight
interruption is not provided until the proper combustion progression required
for smoke generation is re-established, and the vehicle to be protected
hence is exposed to an opponent's attack without defence.
The reason for these dangerous delays of up to 15 seconds between
ignition and smoke formation is founded in the fact that the prior-art active
mass pressed pellets comprise about 90% of smoke active mass on the
basis of red phosphorus having an igniter charge pressed thereon. The
pressed pellets are initiated at their surface by the igniter charge during
separation. The ignited charge then lights up the smoke composition charge
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located underneath. The combustion behavior of the pressed pellets thus
has to be rated an end burner. The combustion velocity may at given
dimensions be accelerated within certain limits by increasing the oxygen
donor content, however a variation of the oxygen donor content is subject to
narrow limits, for otherwise smoke will not be formed any more on the one
hand, and the detonation tendency will increase on the other hand, so that
the smoke active mass ceases to release smoke or at the least fails to form
smoke in a sufficient concentration.
Starting out from this prior art it accordingly was an object of the
present invention to furnish a smoke projectile allowing to significantly
reduce
the gap period, to thereby afford protection for the vehicle to be protected
as
quickly as possible.
This object is attained through the characterizing features of claim 1.
In the smoke projectile in accordance with the invention, at least part of
the smoke active mass includes regions having an increased concentration
of at least one igniter charge, wherein the regions have a diameter distinctly
smaller than the diameter of the smoke active mass.
Accordingly in the present invention, the igniter charge is not pressed
on in surface contact as in the prior art, but the smoke projectile of the
invention contains a pressed pellet of active mass provided with so-called
nests of at least one igniter charge. These nests are regions having an
increased concentration of at least one igniter charge mixture and are
embedded into the smoke active mass proper.
The smoke projectile of the invention may, for example, have a first
layer comprising smoke active mass including regions of increased
concentration of at least one igniter charge, and underneath this layer
provided with igniter charge nests, the smoke active mass proper is arranged
as a main smoke active mass in a second layer.
Based on practical considerations, the igniter charge, other than in the
prior art, is not pressed on but mixed at certain mixing ratios of smoke
active
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mass and igniter charge, and this mixture is press compacted jointly with the
pure smoke active mass that was introduced into the pressing mold in
advance.
Due to the fact that the active masses (smoke active mass and igniter
charge) are present in granulated form prior to pressing, what is formed is a
pressed pellet of active mass comprising a layer of smoke active mass and
an overlying layer of smoke active mass including nests of igniter charge.
The pressed pellet thus produced is also ignited during separation. Other
than in the prior art, however, it is not the end face that burns, but
starting
out from the surface the igniter charge nests inside the active mass. The
igniter charge nests (hot spots) burning in the active mass burn with a larger
free surface. As a result of the igniter charge nests burning within the smoke
active mass, the pressed pellet becomes insusceptible to impact on the
ground and thus to shock. At the same time, higher energy is consequently
introduced into the smoke active mass, and the combustion velocity
increases without requiring to this end an increase of the oxygen donor
content in the active mass that would otherwise be necessary.
Reaction of the smoke projectile pressed pellets of the invention is
spontaneous, so that the above described gap between separation and
onset of the smoke effect approaches Zero.
As a particular advantage, the combustion period may at given masses
and dimensions of the pressed pellets be adjusted through the ratio of
smoke active mass and igniter charge in the mixed charge on the one hand,
or at a given ratio for the mixed charge on the other hand, e.g. 2:1 (smoke
active mass to igniter charge) may be adjusted on the basis of the mass ratio
of mixed charge and pure smoke active mass.
An important precondition applying to the present invention is the
relationship of the combustion velocities D of smoke active mass and igniter
charge:
DAS " DNW
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with AS standing for igniter charge, and NW standing for smoke active
mass.
In the smoke projectile in accordance with the invention, the flame front
is shifted from the surface into the active mass by introducing igniter charge
nests into the active mass (mixed charge). The flame front accordingly is
closed in or screened so as to be no longer torn off by the delay impulse
during impact on the ground. The pressed pellets of active mass accordingly
continue to burn in the absence of any slump, and line-of-sight interruption
thus is ensured by the resulting smoke generation from activation of an
ammunition until completion of combustion.
In a particularly advantageous manner, igniter charge nests are
distributed to a depth of up to 50% of the overall height of the active mass.
The concentration in the regions/nests of igniter charge may amount to
as much as 100% of the igniter charge mixture.
!n accordance with the invention it is preferred if the smoke active mass
is based on red phosphorus, as hereby infrared line-of-sight interruption
takes place on top of visual line-of-sight interruption.
In the smoke projectiles of the invention, the smoke active mass itself
and the mixed charge of smoke active mass and igniter charge nests
preferably is in the form of a pressed pellet.
It is particularly preferred if the smoke active mass contains nests of
igniter charge having a mixing ratio of smoke active mass and igniter charge
of approx. 5:1 to 1:5, in particular of approx. 2:1.
It is another advantage of the instant smoke projectile that the burn time
is adjustable through selection of the mixing ratio of smoke active mass and
igniter charge and/or through the concentration of the nests.
It is a central point of the invention that the smoke projectile is not
susceptible to shock following ignition, i.e. substantially insusceptible to
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impact on the ground, so that the flame front will not be extinguished any
more on impact, and the smoke screen builds up without a gap within 0 to 2
seconds.
A preferred embodiment of the smoke projectile of the invention
comprises a mixed charge of smoke active mass with igniter charge nests
which is arranged in several layers.
In another embodiment of the present invention, the nests of igniter
charge inside the smoke active mass present a gradient-type concentration
profile, with the concentration being highest in the direction of ignition.
The gradient-type concentration profile may, for example, be
represented as a preformed steep gradient, with the one gradient step
arranged in the direction of ignition comprising igniter charge nests, whereas
the further steps facing away therefrom contain about 100% smoke active
mass.
Here it is moreover preferred if the single steps of the gradient also
have the form of pressed pellets.
Further advantages and features of the present invention become
apparent through the description of an embodiment and through the drawing,
wherein:
Fig. 1 is a longitudinal sectional view of a smoke active mass in
accordance with the prior art in schematic representation; and
Fig. 2 is a schematic longitudinal sectional view of a smoke projectile in
accordance with the invention.
In Fig. 1, 1 designates a smoke projectile which comprises a smoke
active mass 2 and associated igniter charge 3. The igniter charge 3 is lit on
the ignition side 4 with the aid of a primer as an igniting means which is not
designated more closely in Fig. 1, to then burn in the combustion direction
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represented by an arrow in Fig. 1. The igniter charge 3 then in flight ignites
the smoke active mass 2.
In the example of Fig. 1, igniter charge 3 and smoke active mass 2 are
arranged annularly around a center passage 5.
In accordance with the prior art, the igniter charge 3 is pressed on the
smoke active mass 2 in surface contact. The combustion behavior of the
pressed pellet according to the prior art in accordance with Fig. 1 acts as an
end burner. As soon as the prior-art smoke projectile impacts on the ground,
the flame front is inhibited or extinguished almost entirely, resulting in a
delay
of up to 15 seconds after which the smoke is then actually released. This
causes a dangerous gap that may be utilized by an attacker for a successful
attack on the vehicle to be protected.
In contrast, Fig. 2 shows a schematic longitudinal sectional view of a
smoke projectile in accordance with the invention, in which identical parts
are
provided with the same reference symbols.
Other than in the prior-art embodiment, the active mass of the smoke-
generating pellet of the invention contains a mixed charge 6 which contains
igniter charge nests 7.
In an exemplary case, one chooses as the igniter charge mixture a
mixture having the following ingredients as described, e.g., in EP 106 334
A2:
magnesium powder 12.00% (wt.)
iron blue 9.00% (wt.)
boron, amorphous 2.39% (wt.)
powder-type chloroparaffin 8.00% (wt.)
finely ground black powder 47.00% (wt.).
In the exemplary case, this igniter charge mixture is mixed with a
smoke mixture in a mass ratio of 2:1 (smoke mixture : igniter charge mixture)
and then granulated.
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As the smoke active mass one uses in the exemplary case one in
accordance with EP 106 334, which may have the following ingredients:
red phosphorus 55% (wt.)
cesium nitrate 23% (wt.)
zirconium/nickel alloy 70 : 30 12% (wt.)
polybutadiene binder 10% (wt.)
It is, as a matter of fact, also possible to use other smoke active
masses, e.g. those as disclosed in DE 30 31 369 A1 and containing a
chlorine donor, metal oxide and ammonium chloride as well as 5 - 40% (wt.)
of thiourea, 20 - 70% (wt.) of ammonium perchlorate, 1 - 3% (wt.) of
aluminum powder having a grain size of less than 100 Vim, and 5 - 30% (wt.)
of binding agent. Further smoke active masses are, for example, those
described in DE 199 36 054 A1 and making use, e.g., of hexachloroethane
as the chlorine donor.
According to the present invention, the igniter charge is not pressed on
in surface contact like in the prior art, but mixed in a mixing ratio of 2:1
of
smoke active mass and igniter charge, and this mixture is pressed jointly with
pure smoke active mass filled into the pressing mold in advance.
Due to the fact that the smoke active mass and the igniter charge active
mass are present in granulated form prior to press compacting, a pressed
pellet of active mass comprised of a layer of smoke active mass and an
overlying mixed layer of smoke active mass with so-called nests of igniter
charge is formed.
A pressed pellet thus obtained is also ignited during separation of the
smoke ammunition. Other than with the smoke ammunition of the prior art, it
is not the end face that burns, but four igniter charge nests burn starting
out
from the combustion side with a much larger free surface in comparison with
the prior art. As a result of the igniter charge nests burning inside the
smoke
active mass, the pressed pellet becomes insusceptible to impact on the
ground because the introduction of igniter charge nests into the smoke active
mass shifts the flame front from the surface into the smoke active mass. The
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flame front accordingly is closed in or screened and is no longer torn off by
the delay impulse during impact on the ground. As a result, the pressed
pellets of smoke active mass burn through without a slump, and line-of-sight
interruption from activation of the ammunition until completion of combustion
is ensured through the related smoke generation. In particular, gaps virtually
do not occur any more, but the smoke emanates within 1 - 2 seconds at the
longest, to thus be available momentarily, as it were, and in a concentration
ensuring secure line-of-sight interruption without a gap.
Thus with the present invention, smoke projectiles are for the first time
available which do not give rise to dangerous gaps even with a ground
impact velocity of up to 16 m/s.
The smoke projectile of the invention may be formed into ammunitions
for all customary launchers of most variegated calibers, such as 66 or
76 mm.
