OBUS POUR CANON A AME LISSE

SHELL FOR GUN WITH SMOOTH-BORE BARREL

Abrégé français

Procédé permettant de convertir des obus (1) de mortier destinés à être utilisés comme obus non rotatifs stabilisés avec des ailettes dans des canons lisses. Selon la présente invention, on ajoute au cône de charge (14) de l'obus de mortier initial un sabot de guidage ou sabot détachable (6, 17) adapté au nouveau canon. Le cône de charge est, en outre, doté d'un empennage (12, 15) sans charge de propulsion interne, ainsi que d'une charge de poudre propulsive classique pour le canon en question. La présente invention concerne également l'obus fini.

Abrégé anglais

The present invention relates to a method for converting mortar shells (1) for use as non-rotating, fin-stabilized shells in guns with
unrifled barrels. According to the invention, the warhead (14) of the original mortar shell is supplemented with a guide casing or discarding
sabot (6, 17), adapted to the new barrel, and is provided with a tail fin (12, 15) without internal propellant charge, together with a
conventional propellant powder charge for the gun in question. The finished shell is also included in the invention.

Revendications

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CLAIMS:
1. A method for converting mortar shells into shells
for use in smooth-bore gun barrels having an interior
surface, the mortar shells including a warhead having a
front end, a rear end, a tail fin, and a propellant charge,
said method comprising the steps of:
attaching a guide casing to at least the rear end
of the warhead, said guide casing including an outside
surface, said guide casing supporting at least the rear end
of the warhead, said guide casing adapted to the caliber of
the smooth-bore gun barrel that the converted shells are to
be fired from; and
attaching a bourrelet to said outside surface of
said guide casing for sealing between the converted shells
and the interior surface of the smooth-bore gun barrel that
the converted shells are to be fired from.
2. The method according to claim 1, further
comprising the steps of:
removing the tail fin from the rear end of the
warhead; and
attaching to the rear end of the warhead a new
tail fin for use with increased exit velocity of the
smooth-bore gun barrel, said new tail fin not including a
propellant charge.
3. The method according to claim 2, wherein said
warhead includes a threaded portion for securing said tail
fin to said warhead, said guide casing includes an inner
threaded portion and a rear portion including a rearwardly
projecting externally threaded cylinder, said method further
comprising the steps of:

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attaching said inner threaded portion of said
guide casing to said threaded portion of said warhead; and
attaching said new tail fin to said rearwardly
projecting externally threaded cylinder of said guide
casing.
4. The method according to claim 1, wherein said
mortar shell is of a smaller caliber than the smooth-bore
gun barrel that the converted shells are to be fired from,
and said guide casing comprises a multi-part guiding sabot
for adapting said smaller caliber mortar shell for use with
said smooth-bore gun barrel, ram air pressure created as
said converted shell passes through said smooth-bore gun
barrel causing said guide casing to separate from said
smaller caliber mortar shell as the converted shell passes a
muzzle of the smooth-bore gun barrel.
5. The method according to claim 4, further
comprising the step of:
attaching at least one connector ring to said
multi-part sabot for connecting said sabot parts together.
6. The method according to claim 1, wherein the
smooth-bore gun is an artillery piece.
7. The method according to claim 1, wherein the
smooth-bore gun is a tank gun.
8. A method for converting a mortar shell including a
propellant charge into a shell for use in a smooth-bore gun
barrel having an interior surface, said method comprising
the steps of:
providing a mortar shell including a warhead having
a front end, a rear end, an outer surface, and a tail fin;

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providing a guide casing including an inner
surface for engaging at least a portion of the outer surface
of the warhead, said guide casing having an outer surface
adapted to be utilized with a smooth-bore gun barrel of a
caliber that the converted shell is to be utilized with;
providing a bourrelet for attaching to the outer
surface of said guide casing to seal a space between the
converted shell and the interior surface of the smooth-bore
gun barrel that the converted shell is to be fired from;
attaching the guide casing to at least the rear
end of the warhead, said guide casing supporting at least
the rear end of the warhead; and
attaching said bourrelet to said guide casing.
9. A converted shell converted from a form for use
with a mortar and including a propellant charge to a fin-
stabilized non-rotating shell for use with a smooth-bore gun
barrel said converted shell comprising:
a warhead of the mortar shell, said warhead
including a front end, a rear end, and an outer surface;
a guide including an inner surface engaging at
least a portion of the outer surface of the warhead, said
guide having an outer surface adapted to be utilized with a
smooth-bore gun barrel of a caliber that the converted shell
is to be utilized with; and
a tail fin attached to one of said warhead or said
guide.
10. The converted shell according to claim 9, further
comprising:

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a bourrelet adapted to the caliber of the smooth-
bore gun barrel that the converted shell is to be fired from
and attached around the outer surface of said guide casing
to seal a space between the converted shell and the interior
surface of the smooth-bore gun barrel that the converted
shell is to be fired from; and
wherein said warhead narrows toward said rear end
and said guide casing encloses at least said narrowing
portion of said warhead, and wherein said tail fin does not
include a propellant charge.
11. The converted shell according to claim 9, wherein:
said warhead includes a threaded portion for
securing a tail fin of the mortar shell to said warhead;
said guide casing includes an inner threaded
portion and a rear portion including a rearwardly projecting
externally threaded cylinder;
said guide casing is secured to said warhead by
engaging said inner threaded portion of said guide casing
with said threaded portion of said warhead; and
a new tail fin is attached to said rearwardly
projecting externally threaded cylinder of said guide casing
to replace a tail fin of the shell before conversion.
12. The converted shell according to claim 9, further
comprising:
a bourrelet adapted to the caliber of the smooth-
bore gun barrel that the converted shell is to be fired from
and attached around the outer surface of said guide casing
to seal a space between the converted shell and the interior

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surface of the smooth-bore gun barrel that the converted
shell is to be fired from; and
wherein said guide includes a collar portion
having a substantially constant external diameter, a front
portion of said collar being adapted to adjoin the warhead.
13. The converted shell according to claim 9, wherein
said converted shell is converted for use with a smooth-bore
gun of a larger caliber than the mortar that the shell was
originally intended to be utilized with, said guide
comprises a multi-part sabot for adapting said shell for use
with said larger caliber smooth-bore gun, said sabot being
separated from said warhead by ram air pressure created as
said converted shell passes through said larger caliber
smooth-bore gun barrel.
14. The converted shell according to claim 13, wherein
said guide further comprises a cup-shaped front portion
opening in a direction of firing of said converted shell,
said cup-shaped portion being separated from the front end
of the warhead so as to form an annular space between the
cup-shaped portion and the front end of the warhead.
15. The converted shell according to claim 13, further
comprising:
at least one connector ring to said multi-part
sabot for connecting said sabot parts together.
16. The converted shell according to claim 9, wherein
the smooth-bore gun is an artillery piece.
17. The converted shell according to claim 9, wherein
the smooth-bore gun is a tank gun.

Description

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Shell for gun with smooth-bore barrel
The present invention relates to a method for
converting certain mortar ammunition for use as fin-
s stabilized, non-rotating shells in smooth-bore guns, in
particular tank guns. The invention also includes
ammunition which has been converted in accordance with
this method.
The invention thus includes, on the one hand, a
method for converting mortar shells for use as fia
stabilized, non-rotating shells in smooth-bore gun
barrels, in particular tank guns, of essentially the same
calibre as the mortars for which the shells in question
were originally intended, and, on the other hand, a
method for converting mortar shells, of smaller calibre
than the gun barrels in question, to subcalibre non-
rotating shells provided with discarding sabots, where
the discarding sabots are separated in a known manner
from the shells outside the muzzle of the gun barrel.
The invention is considered to be of great value
since there is plenty of mortar ammunition in stockpiles,
and the high-explosive mortar shells in particular have
well-designed shell bodies with good fragmentation
properties, and at the same time there is some need for
high-explosive shells for the tank divisions, who
generally have artillery pieces with smooth-bore barrels.
Of course, the invention also includes the converted
shells and the complete rounds of which these form part.

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According to one aspect of the present invention,
there is provided a method for converting mortar shells into
shells for use in smooth-bore gun barrels having an interior
surface, the mortar shells including a warhead having a
front end, a rear end, a tail fin, and a propellant charge,
said method comprising the steps of: attaching a guide
casing to at least the rear end of the warhead, said guide
casing including an outside surface, said guide casing
supporting at least the rear end of the warhead, said guide
casing adapted to the caliber of the smooth-bore gun barrel
that the converted shells are to be fired from; and
attaching a bourrelet to said outside surface of said guide
casing for sealing between the converted shells and the
interior surface of the smooth-bore gun barrel that the
converted shells are to be fired from.
According to another aspect of the present
invention, there is provided a method for converting a mortar
shell including a propellant charge into a shell for use in a
smooth-bore gun barrel having an interior surface, said
method comprising the steps of: providing a mortar shell
including a warhead having a front end, a rear end, an outer
surface, and a tail fin; providing a guide casing including
an inner surface for engaging at least a portion of the outer
surface of the warhead, said guide casing having an outer
surface adapted to be utilized with a smooth-bore gun barrel
of a caliber that the converted shell is to be utilized with;
providing a bourrelet for attaching to the outer surface of
said guide casing to seal a space between the converted shell
and the interior surface of the smooth-bore gun barrel that
the converted shell is to be fired from; attaching the guide
casing to at least the rear end of the warhead, said guide
casing supporting at least the rear end of the warhead; and
attaching said bourrelet to said guide casing.

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According to still another aspect of the present
invention, there is provided a converted shell converted
from a form for use with a mortar and including a propellant
charge to a fin-stabilized non-rotating shell for use with a
smooth-bore gun barrel said converted shell comprising: a
warhead of the mortar shell, said warhead including a front
end, a rear end, and an outer surface; a guide including an
inner surface engaging at least a portion of the outer
surface of the warhead, said guide having an outer surface
adapted to be utilized with a smooth-bore gun barrel of a
caliber that the converted shell is to be utilized with; and
a tail fin attached to one of said warhead or said guide.
According the invention, the actual conversion is
carried out in such a way that the warhead of the original
shell is kept unchanged, while its original tail fin, with
internal propellant charge chamber, is either replaced by a
new tail fin adapted to the new and higher velocity of exit
(Vo) of the projectile, or is merely deprived of its
internal propellant charge, at the same time as which the
warhead is always provided with a guide

vJ0 95130875 218 9 3 .~ ~ PCTISE95100364
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part or guide casing which is adapted to the calibre
gauge of the smooth-bore barreltin question and Which is
preferably provided with ;'a.s~ bourrelet of the type
regularly used as a powder gaa seal is barrels of the
type is question here.
Ia purely general terms, the ordinary tail fin of
the mortar shell is usually secured oa the warhead by
means of a screw thread. Particularly in those cases
where the tail fin is to be replaced by a new one, the
1D said screw thread can be used for securing the guide
casing on the warhead, while the guide casing is is turn
provided with a screw thread for the screwing-on of the
tail fin.
Moreover. the shells converted in accordance with
the present invention are always intended to be
supplemented with the propellant powder charge which is
appropriate for the gun in question sad which, is the
case of task guns. generally involves fixed propellant
charges, and with which they can be combined to form
complete rounds.
The invention further includes two alternative
possibilities for converting the mortar shell for use in
smooth-bore barrels. The first variant is based on mortar
shells intended for mortars of the same, or essentially
the same, calibre as the smooth-bore guns in which the
converted shells are intended to be used. and in this
case the guide casing is mainly is the form of a casing
which encloses and supports the rear part of the warhead
of the original shell, the inside of which casing is
shaped matching the outer shape of the warhead in order
to increase the strength of the warhead against the
firing stresses. and the rear portion of Which casing is
designed to be relatively strong, and the front portion
of which casing consists of an approximately tubular and
relatively thin-walled portion which adjoins the outer
periphery of the warhead is the vicinity of its maximum
diameter. In the more solid rear portion of the guide
casing. there is also a bourrelet groove which is
provided with a conventional bourrelet.

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The second variant of the invention is based on
a mortar shell of smaller diameter than the gun barrel in
question, sad this shell is provided with a'guide casing
designed in~accordaace with the principles applying to
discarding sabots for subcalibre projectiles, i.e. it is
designed is three or more parts is the longitudinal
a
direction, these parts being held together by mesas of
locking bands which are intended to be torn off by the
effect of the ram pressure when the projectile leaves the
barrel. As in the first variant of the invention, the
guide casiag/discarding sabot is question here is also
given a relatively strong rear portion, with as inner
shape adapted to the outer shape of the warhead in order
to increase the strength of the warhead against the
firing stresses, and With associated guide grooves for a
conventional bourrelet, and a more thin-walled front
portion which expediently opens out is a cup shape at the
front is order to offer a good point of attack for the
relative wind.
The method and the arrangement according to the
invention, and the finished round which is obtained in
accordance therewith, are defined is the attached patent
claims sad will now be described in somewhat greater
detail is connection With the attached figures.
Fig. 1 shows a side view of the starting point,
namely a conventional high-explosive mortar shall, and
Fig. 2 shows a partially cut-away side view of
the converted high-explosive shell adapted for use in
unrifled gun barrels.
Fig. 3 shows a partially cut-away side view of a
converted subcalibre-type shall provided with discarding
sabot.
The mortar shell 1 shown is Fig. 1 comprises a
front warhead 2 (also seen is Fig. 2) and a rear tail fin
3 with inner propellant charge.
The shall 4 shown in Fig. 2, sad modified for use
in unrifled barrels, comprises the explosive-filled
warhead 2, while the tail fin 3 has been disassembled and
its assembly screw thread 5 has been used for screwing-on

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of the guide casing 6. The latter has relatively thin-
walled, tubular front part 7, a more solid rear portion 8,
which encloses the rearwardly narrowing rear part 2a of the
warhead 2, and a rear part 11 on which a new tail fin 12 is
firmly screwed, the said tail fin 12 being adapted to the
new and higher velocity of exit (Vo) of the converted shell.
A bourrelet 9 is further arranged in a bourrelet groove 10
in said solid rear portion 8. The finished shell also
includes a fuse 13, which can be the original mortar fuse or
a newly constructed mortar fuse.
Fig. 3 shows the second variant of the shell
according to the invention. In this case the starting point
is a shell 14 of smaller calibre than the barrel in
question, and here the original tail fin 15 has been
retained, but deprived of its original internal propellant
charge. The fuse 16 has also been retained in its original
form. In contrast, the shell has been supplemented with a
discarding sabot (guide casing) 17 a-c, which is divided in
three equal parts in the longitudinal direction and is held
together by connection rings 18 and 19 and also the
bourrelet 20. These come to be torn off by the ram pressure
when the shell leaves the barrel muzzle, after which the
discarding sabot parts leave the shell in a known manner,
with the shell continuing its trajectory alone. The three
parts 17 a-c of the discarding sabot are designed in such a
way that the latter has a relatively solid rear and central
portion 21, which fits closely against, and supports, those
parts of the original shell body which, upon firing, are
exposed to the greatest stresses, while its front portion 22
is relatively thin-walled and opens out in a cup shape at
the front around the forward part of the shell body 14, in
order to give the ram pressure a good point of attack there.

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The shells which are converted according to the
invention are always supplemented with a conventional
propellant powder charge for the artillery piece in
question.

Dessin représentatif