Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a training projectile which is
s~abili~ed by i~s own rotational velocity and which comprises a conical nose
section~ a cylindrical intermediate portion and a tail section and which
projectile is provided with braking means for reducing said rotational velocity
after it has been launchedO
For military training purposes the normal live ammunition is commonly
substituted by specific training ammunition for economic reasons. Such training
ammunition often has a more simple design than normal live ammunition in order
to reduce the firing costs. In order to enable military personnel to be trained
under substantially normal iring conditions it is important that the ballistic
properties of the training ammunition substantially correspond to those of the
substituted live ammunition. As a result, the r~;m~l firing range of the
training ammunition corresponds to the r~ l firing range of the live ammu~i-
tion in question. This also means, however) ~hat the military training sessions
must take place on the fe~ very wide proving grounds and that comparatively
large areas must be closed off in order to allow the firing.
As a consequence~ a new type of training projectiles has recently
been proposed which up to a predetermined firing distance has substantially the
same ballistic properties as the live ammLmition in question, but which has a
substantially reduced r~;m~l firing range compared with normal live ammunition.
The advantage of using this new type of training ammunition is that such
amm~mition allows realistic military training sessions on substantially smaller
proving grounds than previouslyO
One example of such training projectile is shown in German ~atent
16 78 197. This type of training projectile is provided with a number o chan-
nels on its nose section3 which channels are made in such a way that an air
stream is formed in the channels and gives the projectile an impulse opposite
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to its direc~ion of rotation. In one alternative embodiment said chann~ls may
be replaced by a n~ber o~ blades but also in thls case :it is the axial air
stream which is utilized to impart to thc projectile an impulse in a direction
which is opposite to the d;rection of rotation of the projectile.
By orming the projectile wi~h such means for deflecting the axial air
stream it is possible to reduce the rotational velocity of the projectile so
much that finally 2 critical value for the rotational velocity is reached where
the projectile is no longer stable in its trajectory but tips or tilts. When
this happens the air resistance is increased considerably, with the result that
the firing range is reduced.
One disadvantage with this type of projectile is that the deflec~ing
channels as well as the blades make the projec~ile comparatively complicated
and expensiveO Furthermore it is difficult to modify the projectile for
diferent firing di.stances. By making such arrangements in the front section
of the projectile there is also a risk that the ballistic properties o~ the
projectile even up to the actual firing distance are changed.
Accordingly, the primary object of the present invention is to provide
a training projectile which is more simple to manufacture and which can be
easily modified for diferent firing distances In accordance with the present
invention the cylindrical intermediate portion of the projectile is provided
with a number of aerodynamic sur~aces radially directed and parallel to the
symmetrical axis of the projectile. The aerodynamic surfaces may be made in
the form of fins, which is appropriate for a sub caliber projectile, or formed
by grooves or notches made directly on the cylindrical surface, for instance in
the case of a full caliber projectileO Common for both of ~he types is that
the air resistance is increased in the direction of rotation which means that
the ro~ational velocity of the projectile is reduced after launching. For a
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specific rotating speed -the projectile becomes ~mstable and tips. By adjust:ing
the location, size and/or n~ber of the surfaces it is possible to make this
critical speed happen at a specific distance~ preferably just behind the target
distance for the practice firing.
In the following the invention will be described more in detail with
reference to the following drawings in which Figure 1 shows three different
examples with the aerodynamic surfaces made in the form of fins on the cylin-
drical intermediate portion and Figure 2 shows an alternative embodiment in
~hich the aerodynamic surfaces are formed by grooves on the cylindrical surface.
1~ The projectile body shown on the drawings is an example of an appro-
priate projectile design and is basically identical for the different embodi-
ments and comprises a conical nose section 1, a cylindrical intermediate portion
~'waist") 2 and a tail section 3O In this case the projectile is intended to be
launched by means of a separate driving band ~not shown) and is therefore
provided with a tail section ~ith grooves for the driving. For a full caliber
projectile the tail section may have another design.
On the cylindrical intermediate portion 2 four fins 4 are distributed
symmetrically over the periphery of the projectile body but in three different
axial positions: at the front tFigure la), in the middle (Figure lb) and at the
back ~Figure lc) of the cylindrical portion 20 The fins are directed axially,
parallel to the symmetrical axis 5 of the projectile, extending radially out
from the surface of the cylindrical portion 2. In the axial direction the fins
are extended to about one third of the length of the cylindrical portion 2 and
in its radial direction extended to about one fifth of the radius of the
cylindrical portion 20 For aerodynamic reasons the front end surface 6 of the
fins has been cut so that it forms an angle of approximately 45 with the
symmetrical axis 5 of the projectile and fur~hermore the edges of this end
surface have been machined at appro~lmately ~5 so that the fin has a sharp
forward edge.
The rotational velocity which has been given to the projectile on
leaving the gun barrel is reduced by the braking effect of the side sur~aces of
the fins due to ai~ resistance. When the rotation has been reduced so much that
the ro~ational speed has reached a specific critical value the projectile is no
longer stable but tips or tilts~ which means a significant and sudden increase
of air resistance for the projectile so that also its movement forwards in its
trajectory is bra~ed~ This in turn means a significant reduction of the ~im~l
firing range compared with normal live ammunition. By varying the size o the
fins, i~eO their extension radially and axially, as well as their axial positions
it is possible to make said instability happen just behind the present target
distance.
~ ompared with the previous types of projectiles with channels or sur-
faces for deflecting an air stream axially, this ne~ type of projectile means a
more simple constructionO The basic form of the projectile body is maintained.
~ach of the fins may be arranged on the cylindrical intermediate portion 2 but
as an alternative they may also be arranged on a replaceable ring which is
threaded on the cylindrical portion 2. Said last-mentioned alternative is
preferred as then a plurality of replaceable rings with different fin configura-
tions adapted to different firing ranges may be used. Such ring 7 has been
indicated in Figure la and in this case the ring is arranged in a corresponding
recess on the cylindrical surface of the intermediate portion 2
In Pigure 2 an alternative embodiment is illustrated in which the
aerodynamic surfaces for braking the rotational velocity of the projectile are
formed by grooves 8 on the cylindrical intermediate portion 2. In conformity
~ith the corresponding fins in Figure 1 the grooves 8 are distributed symmetri-
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cally over the periphery oE the projectile body and the location, depths andaxial extension ma~ be easily adjusted to the d0sired braking effect. If the
grooves ~ are not extended over the entire axial length of the cylindrical
intermediate portion the rear end ~ of the groove is pre-ferably cut to form an
angle of ~5 ~Yith the symmetrical axis of the projectile for aerodynamic reasons.
The embodimen~ illustrated in Figure 2 may be used for sub-caliber as
well as full-caliber projectiles, but the embodiment of Figure 1 with fins ca~
be used for sub-caliber projectiles only. Sub-caliber projectiles are provided
~th separate driving bands and the fins or grooves of the intermediate portion
may~be used as a support for the driving band.
The invention is not limited to the above embodiments but can be
modified within the scope of the following claims. By way of example, four
symmetrically distributed fins have been illustrated but another number of fins
may be used, if a~r~riateO Furthermore the fins or the grooves may have an
axial extension which corresponds to the length of the cylindrical intermediate
portion 2.
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