Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A propellant charge for tubular weapons and a process
for the production thereof
BACKGROUND OF THE INVENTION
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FIELD OF THE INVENTION
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This invention relates to propellant charges
consisting of propellant charge powders, the energy
carriers of which consist of nitrocelluloses or
nitrocelluloses and nitroglycerols or nitrocelluloses,
nitroglycerols, nitroguanidine and/or hexogen or
octogen, that is of propellant charge powders which are
designated as mono-, di- or tri basic propellant eharge
powders.
D SCRIPTION OF THE PRIOR ART
Propellant cnarge powders with the above compositions
can be prepared as solid- porous- or tubular-
type powders. Mono-basic propellant charge powders have
to be prepared with suitable solvents, such as ether,
alcohol and acetone to gelatinate the nitrocelluloses~
Di- and tri-basic propellant charge powders having a
suitable composition can be prepared without solvents.
They are known as PoL powders.
It is generally held that, all components are most
auitab1y mixed toyether in the production of mono-, di~
or tri-basic propellant charge powders, so that the base
compos~ition uf the finished powder has a homogeneous
composition.
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The surface treatment optionally carried out on
bulk powders can be left out of consideration in this
case.
These conventional propellant charge powders
generally used in tubular weapons are designated as
"homogeneous powders" within the context of the present
application.
A characteristic of "homogeneous powders" is that
their rate of combustion increases as the firi~g or
surrounding temperature rises. This means that, when
the weapon is fired, the projectile speed is substantially
slower at a firing temperature of, for example, -40 C
than at a iring temperature of, for example, ~60 C
when propellant charges of "homogeneous powders" are
used. The temperature-dependent performance of the
propellant charges causes substantial problems for
guns for armoured vehicles, for example with regard to
reliable first strike capability and to the projectile
performance which is restricted by the weapon pressure
produced at high temperatures, such as +60 C.
Propellant charge powders which do not experience
~ the increase in the rate of combustion as the
: temperature rises, oharacterlstic ~of "homogeneous
powders", are described in DE-PS 17 71 087, DE-PS
2~ 42 457 and DE-OS 30 08 196.
The energy carriers of these propellant charge
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pWders are the same as those used in conventional"homogeneous powders". The fundamental difference is
in the material structure of the powder composition.
The production of the powder composition
S illustrates this point. Mono-, di- or tri-basic bulk
powders, termed granulate, of suitable dimensions are
incorporated into the kneading composition, termed base
composition, of a monobasic propellant charge powder.
The degree of nitration of the nitrocelluloses used
for the production of granulate and base composition
are selected, such that the granulate remains as
granulate during production of the powders.
These types of powder are known as "HET powdersl ~
owing to the heterogeneous structure of the grain of
the powder which becomes a powder base composition
by the incorporation of a granulate.
"HET-powders" have a funda~entally different
temperature-dependence from "homogeneous powders'l.
As the firing temperature rises, their rate of
combustion descreases.
The "negatlve" temperature-dependence of the
rate of combustion of HET powders can be explained
by the fact that the connection between t:he base
composition and the granulate is temperature-
dependent. If, for example, the base compositlon ismonobasic and the granulate is dibasic~ the connection
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becomes stronger as the temperature rises, through the
expansion of the thermoplastic granulate into the
comparatively rigid base composition. Consequently
the combustion surface forming in the grain of the
powder becomes smaller. Larger combustion surfaces
are formed in the grain of the powder at sub-freezing
temperatur~ due to the greater contraction of the
granulate~ The given fall in the rate of combustion
as the temperature drops is over-compensated into a
rise, at least down to a specific low firing temperature
of, for example, -15 C,as a result of the increase in
the combustion surfaces at sub-freezing temperatures
and the reduction in the combustion surfaces as the
temperature rises.
The composition of the base mass and the granulates,
the proportion of granulate and the size of the granules
are factors by which the temperature behaviour of an
"HET powder" may be controlled, that is to what extent
the rate of combustion falls as the temperature rises
and rises as the temperature falls.
/ Burning "HET-powders n should advantageously be
completely temperature-neutral. However, this is
imposs1ble with known types of powder, within a
relati~ely large firing temperature range of several
tens of C,~with predetermined heat of explosion, force
and propellant charge powder dimensions.
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BRIEF SUMMARY OF THE INVENTION
Propellant charges with burning behavior which is
temperature-neutral within a large firing temperature range
can be obtained in a surprisingly straightforward manner
according to the present invention. According to the
invention, there is provided a propellant charge for tubular
weapons, consisting of a mixture of at least one mono- or
polyhasic homogeneous propellant charge powder, of which the
particles are of homogeneous material, with at least one
heterogeneous propellant charge powder of which the particles
consist of a mono- or polybasic base powder with mono- or
polybasic powder granulates embedded therein and which, by
virtue of its heterogeneous composition, has a pressure
characteristic with a negative firing temperature
coefficient; wherein the propellant charge powders are
adjusted to the same or comparable characteristic values in
regard to heat of explosion, force and dimensions; and
wherein the mixing ratio between the propellant charge
powders is selected so that, in a desired, predetermined
nominal firing temperature range, the positive firing
temperature coefficient of the homogeneous propellant charge
powder is compensated by the negative firing temperature
coefficient of the heterogeneous propellant charge powder to
give substantially constant burning behavior of the
propellant charge.
Outside of the nominal firing temperature range, a
drop in weapon pressure is occasionally consciously sought at
extremely low firing temperatures in order to guarantee
against an accidental rise in weapon pxessure owing to the
powder becoming brittle at such temperatures. Likewise, a
drop in weapon pressure at unusually high, and thus
infrequent, firing temperature is acceptable. Such burning
behavior of the finished propellant charge can be obtained by
suitable selection of the types of powder to be mixed and
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mixing ratio, such that the burning characteristics,
such as weapon pressure ~nd projectile speed are almost
constant within a relatively large firing temperature
rated range, and at least do not increase outside the
rated range.
DETAILED DESCRIPTION OF THE INV~NTION
Advantageous embodimen~ of the present invention
are disclosed in the various sub-claims appended to this
description.
The present invention will be explained in more
detail in the following two Examples with reference to
Figures 1 and 2.
Figures l and 2 show the measured values of weapon
pressure and projectile speed ln the firing temperature
range of from -40 C to +60 C for a 2 cm automatic
weapon. Part A shows the projectile speeds measured at
16 m from the weapon, and part B shows the weapon
pressuresmeasured.
Example 1
An adapted "HET powder" is developed into a
"homvgeneous powder" which ls used in one type of
ammunition for structuring the propel~lantcharge. This
means that the heat of explosion, force and the dimensions
of the "HET powder" are set at the same values as, or
at comparable values to, the "homogeneous powder", by
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a suitable selection of the composition of the base mass
and granulate~ and the quantity of granulate. The "HET
powder" is adjusted to the "homogeneous powder" such
that, when the weapon is fired, at a reference firing
temperature of, for example, from -5 to ~10 C the
same projectile speed is produced, at the same or
comparable pressure pattern,as in the case of propellant
charges consisting of "homogeneou~" or "HET powders".
If these conditions are fulfilled, the pressure and speed
curves of the "homogeneous" and "HET powders" are mirror-
inverted with respect to rising and falling firing
temperatures.
If the propellant charge consists of a mixture,
of the same proportion by weight, of "homogeneous
powder" and "HET powder" which has been adjusted thereto
as explained above, the weapon pressure and the projectile
speed are almost constant in the firing temperature
ra~ge of:from -40 C to +60 C.
In Figure 1~ the curves designated by reference
numeral 1 show the values for weapon pressure and
projectlle speed, obtained with the "homogeneous
: propellant charge powder" used for this ammunition.
The curves designated by reference numeral 2 show
the values obtained with the adjusted "HET powder".
The curves designated ~y reference numeral 3 show the
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values obtalned with a mixture~ of the same proportions
by welght, of both powders.
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Example 2
Example 2 differs from Example 1 in that the
"~ET powder" used is structured, such that from the
reference firing temperature of 0 C, thle weapon pressure
drops as the temperature rises and falls.
In Figure 2, the curves designated by reference
numeral 1 show the values of the "homogeneous powder",
the curves designated by reference numeral 2 show the
10 values of the "HET powder" and the curves deslgnated by
reference numeral 3 give the values with a mixture, of
equal proportions by weight, of both powders.
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