Title: Fin-stabilized shell
Abstract: The present invention relates to a fin-stabilized artillery shell (
Patent Number: 6,886,775 Issued on 05/03/2005 to Johnsson, et al.
| Inventors:
|
Johnsson; Stig (Karlskoga, SE);
Hellman; Ulf (Ornskoldsvik, SE);
Holmqvist; Ulf (Karlskoga, SE)
|
| Assignee:
|
Bofors Defence AB (Karlskoga, SE)
|
| Appl. No.:
|
312667 |
| Filed:
|
June 13, 2001 |
| PCT Filed:
|
June 13, 2001
|
| PCT NO:
|
PCTSE01/01332
|
| 371 Date:
|
July 14, 2003
|
| 102(e) Date:
|
July 14, 2003
|
| PCT PUB.NO.:
|
WO0206760 |
| PCT PUB. Date:
|
January 24, 2002 |
Foreign Application Priority Data
| Current U.S. Class: |
244/3.27; 244/3.3; 244/3.29; 102/385 |
| Intern'l Class: |
F42B 010//14 |
| Field of Search: |
244/323,324,325,326,327,328,329,33
102/384,385
|
References Cited [Referenced By]
U.S. Patent Documents
| 3819132 | Jun., 1974 | Rusbach.
| |
| 3861627 | Jan., 1975 | Schoffl.
| |
| 4944226 | Jul., 1990 | Wedertz et al.
| |
| H905 | Apr., 1991 | Rottenberg.
| |
| 6126109 | Oct., 2000 | Barson et al.
| |
| 6454205 | Sep., 2002 | Niemeyer et al.
| |
| 6571715 | Jun., 2003 | Bennett et al.
| |
| Foreign Patent Documents |
| 3344402 | Jun., 1985 | DE.
| |
| 0076990 | Apr., 1983 | EP.
| |
| 2265443 | Sep., 1993 | GB.
| |
Primary Examiner: Carone; Michael J.
Assistant Examiner: Sukman; Gabriel S.
Attorney, Agent or Firm: Connolly Bove Lodge & Hutz LLP, Hume; Larry J.
Claims
1. A fin-stabilized artillery shell, comprising:
a shell body;
a body part mounted in an annular space in a rear of the shell body, the body
part having a plurality of stabilizing fins; and
an expansion chamber between a front part of the shell and the body part where
gas expansion takes place; and
at least one channel connecting the expansion chamber to the annular space, wherein
the body part is axially displaceable from a space in the rear of the shell body
from a first position to a second outer position that extends the length of the
shell rearward,
the body part is tubular and fits in the annular space when the body part is
in the first position,
the fins are deployable when the body part is in the second outer position, and
the gas expansion comes from a charge, wherein the gas expansion displaces the
body part from the first position to the second position.
2. The fin-stabilized artillery shell of claim 1, wherein the body part comprises:
a track mounted in the annular space when the body part is in its first position,
wherein the plurality of fins are pivotably mounted to the track by axles, wherein
the annular space extends forward in the shell body to accommodate substantially
the whole of the body part and the fins when the body part is in the first position.
3. The fin-stabilized artillery shell of claim 1, wherein the rear of the shell
body houses a powder charge and a gas outlet for the powder charge.
4. The fin-stabilized artillery shell of claim 1, wherein the plurality of fins
are pivotably mounted about a periphery of the body part.
5. The fin-stabilized artillery shell of claim 1, comprising:
a pyrotechnic charge in the expansion space.
6. The fin-stabilized artillery shell of claim 1, wherein the fins are mounted
on axles arranged along a longitudinal direction of the shell and are incurved
transversely and wrapped around the body part when the body part is in the first
position and wherein the fins are deployable radially outward from the body part.
7. A fin-stabilized artillery shell, comprising:
a shell body;
a body part mounted in a space in a rear of the shell body, the body part having
a plurality of stabilizing fins and comprising a first section and a second section
rotatably connected to the first section, wherein the fins are mounted to the first
section; and
an expansion chamber between a front part of the shell and the body part where
gas expansion takes place, wherein
the body part is axially displaceable from a space in the rear of the shell body
from a first position to a second outer position that extends the length of the
shell rearward,
the fins are deployable when the body part is in the second outer position,
the gas expansion displaces the body part from the first position to the second
position,
a deformable inner edge of the first section deforms and engages an edge of the
second section when the body part is in the second position.
8. The fin-stabilized artillery shell of claim 7, wherein the first section is
rotatably mounted to the second section by a ball bearing.
9. The fin-stabilized artillery shell of claim 7, wherein the first section houses
a powder charge and a gas outlet for the powder charge.
10. The fin-stabilized artillery shell of claim 7, wherein the fins are mounted
about axes of rotation extending transverse to a width direction of the fins.
11. The fin-stabilized artillery shell of claim 7, wherein the fins are folded
forwards and inwards about axes of rotation in grooves extending in a longitudinal
direction of the shell when the body part is in the first position, and wherein
the fins execute a rotational movement of at least 90° about said axes outwards
and rearwards in the direction of flight of the shell.
12. The fin-stabilized artillery shell of claim 7, comprising:
canard fins at a front part of the shell that are deployable substantially simultaneously
with the deployment of the plurality of fins.
13. The fin-stabilized artillery shell of claim 7, wherein the space is cylinder-shaped
and the fins are secured along the outer periphery of the body part in the space,
and comprising: a base-bleed unit having a powder chamber containing a slow-burning
powder, an igniter which initiates the powder, and a gas outlet arranged at a rear
plane of the cylinder-shaped body part.
14. The fin-stabilized artillery shell of claim 7, wherein an axis of rotation
of the first section with respect to the second section coincides with a longitudinal
axis of the shell, and the first section is locked relative to the shell body when
the body part is in the second position.
15. The fin-stabilized artillery shell of claim 7, wherein the plurality of fins
are pivotably mounted about a periphery of the body part.
16. A fin-stabilized artillery shell, comprising:
a shell body;
a body part mounted in a space in a rear of the shell body, the body part having
a plurality of stabilizing fins, a base-bleed charge located therein and a gas
outlet;
an expansion chamber between a front part of the shell and the body part where
gas expansion takes place; and
pyrotechnic means in the expansion chamber for generating the gas expansion and
initiating the base-bleed charge, wherein
the body part is axially displaceable from a space in the rear of the shell body
from a first position to a second outer position that extends the length of the
shell rearward,
the fins are deployable when the body part is in the second outer position, and
the gas expansion displaces the body part from the first position to the second
position before initiating the base-bleed charge.
17. The fin-stabilized artillery shell of claim 16, wherein the body part comprises
a first section and a second section rotatably connected to the first section,
wherein the fins are mounted to the first section.
Description
The present invention relates to a novel type of fin-stabilized artillery shell
of the general type which is provided with a drive band as its direct contact with
the inside of the barrel from which it is fired and which is therefore fired only
at a low speed of rotation about its longitudinal axis and which, in order to stabilize
it in its continued trajectory towards the target, is provided with stabilizing
fins which are arranged at its rear end, are retracted initially and until the
shell has completely left the barrel, and can then be deployed when the shell has
fully left the barrel.
Fin-stabilized shells are mechanically more complicated than conventional
rotation-stabilized shells, but they can be given longer ranges of fire since the
fins included in them can be designed to give the shell an increased lifting force.
It is also much easier to correct the flight path of a fin-stabilized nonrotating
or slowly rotating shell than it is for corresponding rotation-stabilized shells
rotating at high speed. These two properties have meant that development work on
new long-range shells guided in their final phase has increasingly concentrated
on making them fin-stabilized.
However, one problem which has had to be dealt with in connection with shells
of this type is that the flight of the fin-stabilized shell in its trajectory towards
the target is all the more stable, the further the fins are situated behind its
centre of gravity in the direction of flight of the shell. In addition, the fins
in the retracted position block a not inconsiderable space in the rear part of
the shell, a space which it would often be desirable to use for some other purpose.
The need to have the fins lying as far back as possible behind the centre of gravity
of the shell additionally often conflicts with the maximum dimensions which are
stipulated for artillery shells of different calibres and which must be complied
with since they cannot otherwise be loaded into conventional artillery weaponry,
which as a rule is an absolute requirement.
The present invention now relates to a novel type of fin-stabilized artillery
shell of the abovementioned general type, that is to say one which is provided
with a drive band and is thus intended to be fired at low rotation about its longitudinal
axis, and which is additionally provided with stabilizing fins which are retracted
in its rear end until it has completely left the muzzle of the barrel and which
are designed in such a way that they are automatically deployed as soon as the
shell is free of the barrel and the muzzle brake. According to the basic concept
of the invention, the whole fin system is now designed in such a way that the fins
are not only deployed when the shell has left the barrel: before they are deployed,
they are additionally displaced to a new position which is situated behind the
original rear plane of the shell during launch and where they are deployed. According
to the basic concept of the invention, we thus obtain an extension of the distance
to the centre of gravity of the shell and therefore a more stable flight for the shell.
All the developments of the invention which are defined in the attached patent
claims are based on the fact that the fins, arranged about axles provided for this
purpose, are to be mounted and initially retracted in a body part which is axially
displaceable in the longitudinal direction of the shell relative to the rest of
the shell body and which, until the shell has left the launch barrel, and with
the fins retracted in the body part, occupies a space provided for this purpose
in the rear part of the shell, and which, when the shell has left the barrel, is
axially displaced to a second outer position in which it is locked relative to
the rest of the shell and in which at least that part of the body comprising the
fins and their bearing axles is located, in the direction of flight of the shell,
behind the latter's original rear plane in a position which allows the fins to
be deployed.
The fin-stabilizing unit included in the shell according to the invention can
thus be said to be characterized primarily by the fact that the attachment points
of the fins are formed by an axially displaceable body part which, from a first
retracted position completely in front of the normal rear plane of the shell, can
be pushed out to a second deployed position where the fins and their attachment
points are situated behind the same rear plane and where the fins are free to unfold.
The body part in question can then have the basic shape of a tube along whose
outer periphery the fins are secured and in the original position incurved towards
the inside in an outwardly open annular track in the same and in the original position
retracted into a tubular slit in the rear part of the shell. In the deployed position,
this type of body part thus gives the shell a hollow base, which can be very advantageous,
especially if the space in the actual shell body inside of the abovementioned slit
contains a base-bleed unit.
If the body part instead has the shape of a cylinder which in the original position
is inserted in a cylindrical cavity in the rear part of the shell and the fins
are arranged along its outer periphery, then the base-bleed unit can be arranged
inside the cylinder.
In these two variants of the invention, the fins are expediently of the type
which
are mounted deployably around axles arranged in the longitudinal direction of the
shell, or corresponding components with a hinge function, and in the retracted
position are incurved transversely and wrapped around the body in which the axles
are secured, i.e. in this context the respective body part in each variant, and
it is the inside of that part of the shell body in which the body part is arranged
in the retracted position which, as long as the body part is located in its retracted
position, also holds the fins incurved against the periphery of the respective
body part, and the fins in the deployed and extended position, at least nearest
their bearing axles, extend essentially radially out from the body part.
The fins in question here are therefore of the general type usually referred
to as folding fins or wrap-around fins since, in the retracted position, they are
folded in towards and wrapped around that part of the shell adjoining the retracted
position of the fins, while in the deployed and extended position they extend essentially
radially out from the shell body, at least nearest their bearing axles. In most
of the older types of folding fins and wrap-around fins, especially those included
in the missiles in the older reaction weapons and rocket weapons, these fins retain
a large part of their curved shape even after deployment, but nowadays there are
various light metals, steel and titanium materials available with such good inherent
resilience and such good shape-memory that it is possible to produce fins which,
despite being stored for many years in a curved retracted position, change directly
to their original plane shape after deployment and thus come to extend completely
radially outwards from the missile on which they are secured.
Since the previously mentioned annular gap or the space between the cylindrical
body part, containing the base-bleed unit, and the inside of the shell opens out
in the rear plane of the shell, the space between these and the inside of the shell
is acted upon, during launching of the shell, by the whole of the gas pressure
from the propellant powder charge used unless the space is extremely well sealed.
A way of eliminating the risk of the gas pressure opening the seal between the
mutually movable parts and deforming the fins is for all the space inside the gap
not occupied by the holder part, the axles or the fins, to be filled with a noncombustible,
nonsolidifying gel or the like with low decompressibility and low inherent strength.
For example, certain silicones can be used for this purpose. As soon as the holder
part has been pushed out and the fins have deployed, this gel material is thrown
off from the shell and for this reason does not cause any further problems.
Other fins which can be used in connection with a variant of the invention
are of the type which can be deployed about axles arranged transverse to the direction
of flight of the shell and which, in the retracted position, are folded forwards
and downwards in longitudinal radial tracks in the body part and which, upon deployment,
execute a rotation, of at least 90°, outwards and rearwards about said axles.
This type of fin has the advantage that the fins can be made long and, because
they are angled rearwards in the deployed position, they can be given a further
stabilizing effect. They are also easy to deploy since the relative wind catches
the fins at an early stage of deployment and acts on them in the direction of deployment,
and at the same time they are not affected by any substantial transverse forces
which during the actual deployment phase could affect them in a negative direction.
According to a further variant of the invention, the respective body part
can be divided up into at least two sections which rotate freely relative to each
other, of which one body section ensures the connection with the rest of the shell
when the body part is in the deployed position, while the second body section,
at the rear in the direction of flight of the shell, supports the fins. This variant
affords a shell with a free-spinning tail and fin portion, which can be very advantageous
since it gives the shell much better manoeuvrability (it is quite simply easier
to manoeuvre and thus requires less rudder angle, for example on controllable fins,
for a defined manoeuvre) without thereby losing its directional stability.
As has already been mentioned, the invention has been defined in its entirety
in the attached patent claims, and the following is only a fairly detailed description
made with reference to the attached figures, where:
FIG. 1 is a partial cross-sectional view showing a shell of a first type in
the launch position,
FIG. 2 is the same partial cross-sectional view showing the same shell after
fin deployment,
FIG. 3 shows the shell from FIG. 2 on a smaller scale and in an oblique projection,
FIG. 4 shows, on an extra large scale, the cross-sectional rear portion of the
shell from FIG. 2,
FIG. 5 shows, on a different scale, an oblique projection of the body part included
in FIGS. 1-4,
FIG. 6 shows, on a large scale and in a cross-sectional view, a variant of the
invention in the original position,
FIG. 7 shows the complete shell according to FIG. 6 with the fins in the deployed position,
FIG. 8 shows a partial cross-sectional view of a shell according to yet another
variant of the invention,
FIG. 9 shows the same shell as in FIG. 8, but with its fins in the deployed
position, and
FIG. 10 shows the rear part of the shell from FIG. 9 on a larger scale.
Where the same components appear in different figures, they have been given
the same reference numbers regardless of whether they are shown on different scales.
The shell
1 shown in FIGS. 1,
2 and
3 and partially in FIG.
4 is provided with a plastic drive band
2 and a base-bleed unit which is
incorporated in the rear part of the shell and is provided with a charge
4
of slow-burning powder and a gas outlet
6 arranged centrally in the rear
plane
5 of the shell. Around the base-bleed unit
3, near the outer
periphery of the shell, there is a tubular or annular gap
7 extending in
the longitudinal direction of the shell. In this gap, a tubular body part
8
(see FIG. 5) can be axially displaced from its first position shown in FIG. 1,
where it is fully retracted inside the gap, to its second position in FIGS. 2,
3 and
4, where it is deployed and its main part lies outside, i.e.
to the rear of, the original rear plane
5 of the shell. The body part
8
is designed such that it is effectively locked in its outer position as soon as
it has reached this position. A pyrotechnic charge arranged in the space
9
has been used to push the body part
8 out to its outer position. This has
been initiated immediately after the shell has left the barrel from which it has
been launched and powder gases formed have forced the body part out to its locked
outer position. The powder gases have been distributed via the channels
10.
As can be seen from FIG. 5, the holder part
8 is provided with a relatively
wide track
11 arranged annularly about its outer periphery and the same
number of axles
12-
17, arranged in the longitudinal direction of
the shell and extending over the track, as the shell has fins. One of the fins
18-
24 (
23 and
24 not shown in the figure) is secured
about each of these axles and the fins are bent into the track
11 in their
retracted position. This track thus has a sufficient depth to ensure that the retracted
fins will have enough space there when the body part is inserted into the gap
7.
As soon as the body part
8 has reached its outer position, the fins spread
out under their own flexibility to their intended deployed positions.
Among the advantages of this construction that may be mentioned, it not only
extends the distance between the stabilizing fins and the centre of gravity of
the shell, it also gives the shell a hollow base, which gives the base-bleed unit
an improved action.
FIGS. 6 and 7 now show a second variant of the invention where the main part
of the shell can still be labelled
1 and its drive band can still be labelled
2. By contrast, the rear part of the shell here is not designed with a gap,
but instead with a cylinder-shaped hollow or space
25 in which a complete
unit
26 is arranged. The unit
26 comprises both the base-bleed unit
and the necessary number of deployable fins and some further components and functions
which will be described below. The base-bleed unit arranged in the unit
26
can also be labelled
3 here, and the same applies to its powder charge
4
and its gas outlet
6. By contrast, the base-bleed unit
3 here is
contained in a cylindrical body
27 whose outer periphery has a peripheral
outer track
28 which corresponds to the track
11 in the body part
according to FIG.
5 and which has the same function as the latter, namely
for attachment of the fins and for providing space for these when they are curved
in against the body in question and the latter is situated in its position fully
inserted in the hollow
25. The figures show only fins
29 and
30,
but they can be of any chosen number. For pushing the complete arrangement
26
out to its outer position, use is made of a pyrotechnic charge
31 suitable
for this purpose and initiated on command. When this is initiated, the powder gases
formed will displace the unit
26 to its outer position, and the pyrotechnic
charge also has a second function in that when it reaches its burnout it initiates
the powder charge
4 of the base-bleed unit.
As can best be seen from FIG. 6, the space
25 is sealed off from the outside
by an inwardly directed conical edge
32, and the unit
26 at the same
time has an inner edge
33 which can be upset and is directed counter to
said conical edge and which, when displaced towards the edge
32 at sufficient
speed, will be deformed and give rise to effective locking between the unit
26
in its deployed position and the main part of the shell
1.
However, the shell shown in FIGS. 6 and 7 is also designed with a further
refinement. The unit
26 is in fact divided up into a first section, which
can again be labelled
27 since it is this section in which the base-bleed
unit is arranged and in which the fins are secured, and a second section
34
which is the section by which the unit
26 in the deployed position is locked
relative to the rest of the shell, and these two sections are joined to each other
via a ball bearing
35.
This arrangement thus means that the fins in the deployed position will spin
freely relative to the rest of the shell.
FIGS. 8-10 show a further variant of the invention which in this case is equipped
with no base-bleed unit but with fins of a completely different type which have
the advantage that they can be made longer and that in the deployed position they
can be folded rearwards in the direction of flight of the shell, which fact further
increases their stabilizing capacity. However, the basic idea remains that of displacing
the fin-supporting body part rearwards and out from the rear plane of the shell
upon launch in order in this way to increase the stabilizing length of the shell.
The shell body here is once again labelled
1 and its drive band is once
again labelled
2. In the rear part of the shell body
1 there is a
cylindrical hollow which can have the same shape as the hollow
25 of the
shell in FIGS. 6 and 7. The hollow has therefore been given the same reference
label in these figures too, i.e.
25. In said hollow
25, a body part
36 can be displaced between a first position and a second position. In its
first position, the whole body part
36 lies inside the hollow
25
and in its second position most of the body part
36 lies behind the original
rear plane of the shell, while still being connected to the shell. The body part
36 further comprises a front section
37 which, when it reaches its
rearmost position in connection with the pushing-out of the body part from the
hollow
25, is locked relative to the rest of the shell body, for example
by means of an abutment joint. In addition, the body part
36 comprises a
rear section
38 which is connected to its front section
37 by means
of rotating ball bearing
39. The rear part
38 of the body, which
in the deployed position thus comes to lie behind the original rear plane of the
shell, is further provided with a number of radial tracks extending in the direction
of flight of the shell, of which the tracks
40 and
41 can be seen
in the figures, and in each of these tracks there is a deployable fin
42-
47
(the fins
42 and
43 are not shown in the figures). Each of these
fins can be deployed about its axle arranged in the rear section of the body part
38 transverse to the direction of flight of the shell. (FIG. 10 shows the
axles
48 and
49 for example). When the fins are deployed, they move
outwards and rearwards about their respective axles, the outer ends of the fins
following an arc-shaped trajectory to a preferably slightly rearward position shown
in FIGS. 9 and 10.
The body part
36 also includes a space
51 in which it is possible
initially to arrange a pyrotechnic charge which generates gas when initiated and,
upon initiation of this charge, the body part is driven from its inner position
to its outer position. There is also a gas outlet
52 for excess powder gas.
According to a variant of the method for displacing the body part from
its inner position to its outer position, an empty chamber is arranged at a suitable
location between the main part of the shell and the displaceable body part. This
empty chamber can thus be arranged at the same location as the chamber
51
and it will be designed in such a way that, during the shell launch phase, it communicates
with the inside of the barrel via an opening of defined size. This opening can
be the same as the opening
52 and it will be adapted such that the full
barrel pressure prevails inside the chamber
51 when the shell leaves the
barrel. When the shell leaves the barrel, the pressure outside the shell drops
more or less instantaneously from the barrel pressure to normal atmospheric pressure.
This very rapid reduction in pressure outside the shell, combined with a high initial
pressure inside the chamber
51 in question, can then be used to force the
body part
36 out from its first position to its second position. As the
counterpressure on the outside disappears, the overpressure inside the chamber
51 is easily able to force the body part
36 out to its outer position.
In order to function satisfactorily, this method requires a correct adaptation
of the dimensions of the chamber
51 and of the connection
52 functioning
as outlet and inlet.
As can be seen from FIG. 9, the shell according to this figure is also provided
with deployable canard fins
53,
54 which are additionally movable
so that their angle relative to the longitudinal axis of the shell can be modified
within certain values, which in turn makes it relatively simple to make the shell
controllable within fairly wide limits. The canard fins can additionally give the
shell extra lifting force, and when a shell is equipped with canard fins it is
advantageous if the distance between these and the normal stabilizing fins is as
great as possible. As has already been mentioned, it is together with control functions,
for example those obtained with canard fins, that the freely rotating fin portion
of the shell gains its full effect since the shell is thereby more easily manoeuvred.
*
