U.S. patent application number 12/281594 was filed with the patent office on 2010-01-28 for explosive charge.
This patent application is currently assigned to Alford Research Limited. Invention is credited to Alford Roland, Alford Sidney.
Application Number | 20100018427 12/281594 |
Document ID | / |
Family ID | 36694615 |
Filed Date | 2010-01-28 |
United States Patent
Application |
20100018427 |
Kind Code |
A1 |
Roland; Alford ; et
al. |
January 28, 2010 |
Explosive Charge
Abstract
Container (10) is generally cylindrical except for a
longitudinal concave groove (11) extending along its entire length.
Upon explosion, the contour of this groove (11) results in a
focussing effect on the wall material due to the oblique angle at
which the expanding cylindrical detonation wave front impacts upon
its inner wall. This produces the forging of a rough rod-like
projectile (11.sub.1) which, being coherent, maintains its velocity
and consequently travels much further than the randomly shaped
projectiles (10.sub.1).
Inventors: |
Roland; Alford; (Wiltshire,
GB) ; Sidney; Alford; (Wiltshire, GB) |
Correspondence
Address: |
MCANDREWS HELD & MALLOY, LTD
500 WEST MADISON STREET, SUITE 3400
CHICAGO
IL
60661
US
|
Assignee: |
Alford Research Limited
Chippenham, Wiltshire
GB
|
Family ID: |
36694615 |
Appl. No.: |
12/281594 |
Filed: |
March 5, 2007 |
PCT Filed: |
March 5, 2007 |
PCT NO: |
PCT/GB2007/000776 |
371 Date: |
December 15, 2008 |
Current U.S.
Class: |
102/305 |
Current CPC
Class: |
F42B 12/24 20130101;
F42B 12/367 20130101; F42B 1/032 20130101; F42B 3/08 20130101; F42B
1/028 20130101; F41H 11/11 20130101; F42B 12/10 20130101; F42B
1/024 20130101; F42B 3/22 20130101 |
Class at
Publication: |
102/305 |
International
Class: |
F42B 3/00 20060101
F42B003/00; F42B 3/02 20060101 F42B003/02; F42B 1/00 20060101
F42B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2006 |
GB |
0604408.5 |
Claims
1. An explosive charge for producing directed fragments upon
explosion, the charge comprising a casing having a compartment
portion for explosive material, the casing having a concave wall
section adjacent and exterior to the compartment portion.
2. An explosive charge for producing directed fragments upon
explosion, the charge comprising a casing having a compartment
portion for explosive material, and a wall section with an interior
concave shape adjacent and exterior to the compartment portion.
3. An explosive charge for producing directed fragments upon
explosion, the charge comprising a casing having a compartment
portion for explosive material, and a shockwave refracting element
adjacent and exterior to the compartment portion.
4. A charge according to claim 1, wherein the concave wall section
comprises a groove.
5. A charge according to claim 1, wherein the concave wall section
forms part of the exterior wall of the charge.
6. A charge according to claim 1 wherein the concave wall section
comprises two flat planar wall elements connected together along
one common edge to describe an angle therebetween up to
180.degree..
7. A charge according to claim 1 comprising a plurality of concave
wall sections.
8. A charge according to claim 1 in which the concave wall section
has a cross-sectional thickness profile to provide and/or enhance
directionality of flight of fragments of the concave wall section
after explosion.
9. A charge according to claim 8, wherein the cross-sectional
thickness profile of the concave wall section includes a thickness
which reduces with increased distance from the central point of the
explosive compartment.
10. A charge according to claim 9 comprising an inert liner between
the explosive and a projectile portion of the charge for
attenuating the shock wave.
11. A charge according to claim 10 comprising a rubber lining of a
metal tube forming the casing for the explosive charge.
12. A charge according to claim 1 wherein the concave wall section
comprises a wall element and means to interlock with another such
wall element or a standard wall element.
13. A charge according to claim 10 comprising a corner piece to
interconnect the concave wall section with another such concave
wall element or standard wall element.
14. (canceled)
Description
[0001] The present invention relates to an explosive charge.
BACKGROUND
[0002] Barbed wire fences or entanglements consisting of one or
more extended rolls of barbed wire have long been used in theatres
of war as obstacles to infiltration or attack by opposing
forces.
[0003] Whereas furtive incursion may sometimes be accomplished by
cutting strands, one by one, with hand operated wire cutters, such
a method exposes the infiltrators to extreme danger if their
activity is noticed by the enemy. For this reason, when it has been
considered necessary for a body of men to traverse a fence rapidly,
manual severing of the fence is typically replaced in favour of
using explosives.
[0004] Since the First World War, the preferred type of explosive
charge to breach wire obstacles with advantageous rapidity has been
a device known as "Bangalore Torpedo" used both as a factory-filled
item and in improvised versions. The Bangalore Torpedo consists of
a thin-walled, cylindrical, metal tube, or arrays of such tubes
joined end to end, filled with explosive. Most commonly such tubes
are steel and they are filled with a mixture of ammonium nitrate
and TNT (amatol) or with TNT alone; improvised versions have
consisted of steel pipes filled with guncotton primers. These
charges are thrust or thrown beneath, through or above the obstacle
and, once the operator has retired to a safe distance, are
detonated by means of safety fuse or electric detonators.
[0005] Individual factory-made charges, which are typically about
1.8 metres long, and of approximately 38 mm diameter, with a wall
thickness of approximately 2 mm, and containing approximately 2 kgs
of explosive in each unit, are provided with bayonet fittings or
screw threads at their ends so that they can be quickly assembled
into a linear array when this is necessary. One end of the charge,
or the charge array, is provided with a pointed, rounded, or ogival
nose in order to facilitate the sliding over possibly rough ground
or the easy insertion into a wire entanglement without
snagging.
[0006] The charge depends for its effectiveness upon the blast
effect of the explosive it contains which both stretches adjacent
strands of wire to the extent that they break and displaces them to
either side, thereby forming a gap in the obstacle wide enough for
one or more combatants to pass through. The effect is enhanced by
the impact of fragments of the tubular case which are projected at
high velocity in radial directions.
[0007] Such charges may also be used for the displacement or the
destruction and consequent rendering safe of anti-personnel or
anti-vehicle mines lying on the ground's surface or buried a short
distance beneath and also as a tool for general demolition.
[0008] It will be understood by those skilled in the art that this
type of explosive charge suffers several limitations. The first of
these is that the length of the unit charge of the existing
Bangalore Torpedo is such that it is awkward to carry and
unnecessarily large to use as a means of severing, for example,
just a few strands of wire or destroying a small object such as an
unexploded projectile or electrical installation.
[0009] Another disadvantage derives from the fact that, as a
consequence of scaling, in order to double the range at which blast
from such a charge would sever a length of wire of a given strength
situated to one side, the diameter of the charge would also need to
be doubled. This would increase the explosive load four-fold. In
practical terms this means that the ability of a charge of given
size to sever wire diminishes rapidly with distance.
[0010] A further disadvantage of the device is the danger presented
to the operator and his colleagues by the very sharp and jagged
steel tube fragments of the bursting tube, this danger being
exacerbated by the frequent need of an operator intending to breach
an obstacle to be as close to the obstacle as possible in order to
advance immediately afterwards.
[0011] One known way of greatly extending the effective range of
charges of high explosive employs the principle of the shaped
charge in which the advancing detonation wave front progressively
collapses a metal-lined cavity provided in the outer border of the
explosive. Collision of the consequently converging increments of
the material lining the cavity has a mutually reinforcing effect on
their mean velocity. Thus a generally cylindrical mass of
explosive, initiated on the long axis at one end and having a
metal-lined conical cavity with an apex angle typically between
40.degree. and 100.degree. at the other, squeezes the liner into a
"jet", consisting of narrow wire of extremely high velocity with a
considerable velocity gradient along its length, the tip travelling
much faster than the rear end. Such jets have great penetrating
power, but the velocity gradient causes them to break up in flight
and the effective range is therefore usually limited to a distance
equivalent to a few charge diameters.
[0012] If, however, such a charge is provided not with a
metal-lined conical cavity but with a shallow indentation, which
may be conical but is more commonly approximately spherical or
hyperbolic, then the liner material is squeezed along the long axis
of the charge but no jet is formed. The consolidated material is
projected at a lower velocity than a corresponding jet but, since
it is less elongate, it travels as a coherent mass, undergoes much
less disintegration and consequently has a very much greater
effective range. The projectiles generated by such charges are
generally known as "explosively formed projectiles" or EFPs.
[0013] This principle of a collapsing metal lined cavity can also
be applied to elongate, or linear, shaped charges in which case the
cavity consists of a groove running the length of the elongate mass
of explosive. Such liners are usually angular in transverse section
but cylindrical grooves are also effective. Such charges are most
commonly used for making long cuts in flat, circular or undulate
steel targets.
[0014] Much less frequently used are linear charges with such
shallow lined grooves as produce linear EFPs. These produce
elongate, rod-like, projectiles which, though less penetrating at
close range than linear cutting charges, are capable of producing a
practical effect at ranges much greater than those at which linear
cutting charges produce useful effects. The shape of the
projectiles depends upon the cross-sections of the liner and of the
explosive charge.
[0015] In order to make wire fences and entanglements more
resistant to cutting by whatsoever means, during recent decades
types of wire have been introduced which are harder and stronger
and thus more resistant to cutting and snapping.
OBJECTS OF THE INVENTION
[0016] An object of the present invention is to overcome these
disadvantages.
SUMMARY OF THE INVENTION
[0017] The present invention provides an explosive charge for
producing directed fragments upon explosion, the charge comprising
a casing having a compartment portion for explosive material, the
casing having a concave wall section adjacent and exterior to the
compartment portion.
[0018] The present invention provides an explosive charge for
producing directed fragments upon explosion, the charge comprising
a casing having a compartment portion for explosive material, and a
wall section with an interior concave shape adjacent and exterior
to the compartment portion.
[0019] The present invention provides an explosive charge for
producing directed fragments upon explosion, the charge comprising
a casing having a compartment portion for explosive material, and a
shockwave refracting element adjacent and exterior to the
compartment portion.
[0020] The present invention may include any one or more of the
following preferred features:-- [0021] the concave wall section
comprises a groove; [0022] the concave wall section forms part of
the exterior wall of the charge; [0023] the concave wall section
comprises two flat planar wall elements connected together along
one common edge to describe an angle therebetween up to
180.degree.; [0024] a plurality of concave wall sections; [0025]
the concave wall section has a cross-sectional thickness profile to
provide and/or enhance directionality of flight of fragments of the
concave wall section after explosion; [0026] the cross-sectional
thickness profile of the concave wall section includes a thickness
which reduces with increased distance from the central point of the
explosive compartment; [0027] an inert liner between the explosive
and a projectile portion of the charge for attenuating the shock
wave; [0028] a rubber lining of a metal tube forming the casing for
the explosive charge; [0029] the concave wall section comprises a
wall element and means to interlock with another such wall element
or a standard wall element; [0030] a corner piece to interconnect
the concave wall section with another such concave wall element or
standard wall element.
[0031] The present invention combines the practicability of a
tubular metal container filled with high explosive with the
extended effective range of a linear EFP.
[0032] Each charge unit may consist of an explosive filled metal
tube whose wall thickness is such that it will burst when the
explosive is initiated at one end. The wall of the tube is provided
with one or more concave wall sections forming longitudinal
grooves.
[0033] In one embodiment of the invention, the cross section of
each groove is such that it forms a rod-like projectile when the
charge detonates. In a preferred embodiment, the tube has three,
four or five such grooves spaced equidistantly round the tube.
[0034] A significant proportion of the energy generated by the
explosive is transferred to the metal case. If the case consists of
a circular array of linear EFP liners, joined edge to edge, then
most of the explosive energy will be directed along radial planes
equally spaced round the tube, the position of each plane
corresponding to one of the grooves. The severing of the individual
wires constituting a wire entanglement will not therefore be
dependent only upon sudden deformation caused by a cylindrical
blast wave and randomly distributed fragment impact, as with a
conventional Bangalore torpedo, but adjacent wires will be cut by
linear projectiles at a distance at which blast alone would be
unlikely to cause breakage. The greater the number of wire strands
cut, and the greater the number of cuts made in each strand, the
less the energy required to blow apart the wires and supporting
structures on either side of the line of attack.
[0035] The preferred number of longitudinal grooves in the tube is
a compromise between a large number of shallow and narrow grooves,
which would generate a large number of projectiles and therefore
strike the wires of an entanglement at more places, and a small
number of grooves which, being wider, would produce heavier
projectiles which would strike the wires at fewer points but would
do so more energetically and thus be more likely to sever them. The
former arrangement would have the additional advantage of best
approximating a cylindrical array which would accommodate the
greatest amount of explosive for an outer envelope of a given
diameter.
[0036] Though the principal application of the Bangalore torpedo is
the breaching of wire fences and entanglements, it will be
understood that the invention may also be used for such other
applications as the clearing of a path through a minefield and also
for general disruption of mechanical and electronic equipment and
for the disruption of containers of, for example, fuel.
[0037] The addition of igniferous substances to the inside or, more
conveniently, the outside of the explosive containing tube provides
a means of enhancing the incendive capabilities of the charge. This
is of particular advantage when it is required to perforate
containers or conductors of inflammable liquids or gases and to
ignite the liberated contents.
[0038] Conventional Bangalore torpedoes are made using simple steel
tubes. These have the advantage of cheapness, hardness and strength
and their relatively high density favour the production of
fragments of high cutting power. Since, however, the torpedo is
intended for short-range applications, the production of sharp
fragments of material of high density extends the range at which
they constitute a hazard to the users. In one embodiment of the
present invention the body is formed by extruding aluminium. This
not only facilitates manufacture but, given the relatively low
density of aluminium (2.7 g/cm.sup.3 compared with 7.9 g/cm.sup.3
for steel) produces fragments of very high initial velocity and
hence cutting power but which lose their velocity as a result of
drag much more quickly so remain potentially dangerous for shorter
distances.
[0039] For general use and the most consistent performance, it
would be preferable for the charges to be factory-filled with
explosive. This would preferably be an insensitive explosive, such
as a plastic-bonded explosive, for the sake of safety with respect
to accidental initiation by shock or excessive heating. In some
circumstances, however, it would be advantageous to provide the
torpedoes empty but with one end temporarily removable. This would
enable the charges to be transported and stored without invoking
considerations of explosive hazard. The user would then load the
charges in anticipation of an imminent requirement using plastic
explosive or, for ease and rapidity of filling, a liquid explosive
such as nitromethane, suitably sensitised to initiation by mixing
with such sensitising agents as aliphatic amines or as glass
microspheres together with a suitable dispersing and thickening
agent. The use of such user-filled charges in this way
significantly reduces the total amount of explosive needed to be
held in or near the place of use. Indeed, unsensitised nitromethane
is not generally subject to the restrictions of transportation and
storage proper to explosives.
[0040] In order to render the unit charges more easily carried, it
is preferable that they be provided in shorter lengths than the
presently usual 1.5 metres. By providing both ends of each charge
unit with suitable joining means, such as a push fit, matching
threads or a bayonet fitting, linear arrays of charge units can be
readily assembled. Detonation propagation from one charge unit to
the next can be facilitated either by abutting thin diaphragms or
by arranging the insertion of an explosive-filled axial extension
on one unit charge into a matching cavity on the axis of the next.
Such a shortening of the body length of each unit charge also
greatly facilitates the hand stemming of the interior with plastic
explosive.
[0041] The present invention includes a kit of parts including any
one or more component elements of the charge as described in the
present specification.
[0042] The present invention is a replacement to the Bangalore
Torpedo which has been used for over a hundred years. It is
configured as a linear explosively formed projectile (EFP) which is
capable of cutting wire obstacles including those made in razor
wire which conventional Bangalore Torpedos are incapable of
breaching.
[0043] The system is a lightweight Anti-Obstacle and General
Explosive Engineering Charge to be used in an identical manner to
the original Bangalore Torpedo but which offers a number of
inherent advantages over the original design.
[0044] The present invention incorporates into the design advanced
shaped charge technology which enhances the performance by giving
the charge a cutting, as well as blasting, effect.
[0045] The system makes good many of the perceived shortcomings in
the current Bangalore Torpedo without introducing into service any
new energetic materials or systems.
[0046] The present invention is a multi-patterned linear EFP charge
in which multiple cutting "blades" are formed which travel outwards
radially, severing obstacles in their path. The blast from the
explosive charge then clears the obstacles, leaving a path through
the obstacle for the foot soldier to pass.
[0047] The present invention may have the same explosive load as a
conventional charge, ensuring that the same amount of blast is
provided to push the severed wire apart.
[0048] The system is offered as factory filled charges which
conform to Insensitive Munition Standard STANAG 4439. In addition,
as part of the UK's Future Battlefield Explosive Engineering System
(FBEES) project, the present invention may be a user-filled Charge
Container System. As such, it may be charged with any PE and
initiator. It is much more efficient than bulk PE and perform at
least as well as the in-service equivalent, while offering
capabilities not otherwise available. It is complementary to the
fixed-configuration explosive charge system and a highly
cost-efficient `capability multiplier`.
[0049] Operator safety is an integral part of the design concept.
The charge body is made from extruded aluminium which has excellent
cutting performance at short range but which loses momentum rapidly
and has limited range, making it inherently safe to use.
BRIEF DESCRIPTION OF THE INVENTION
[0050] The invention will be more particularly described with
reference to the accompanying drawings in which:
[0051] FIG. 1 is a transverse section of a simple prior art
cylindrical tubular container, filled with explosive;
[0052] FIG. 2 is a transverse section of a square sectioned tubular
container, filled with explosive;
[0053] FIG. 3 is a generally cylindrical tubular container
according to the present invention provided with an elongate
straight, rounded (in cross-section), groove;
[0054] FIG. 4 is a transverse section of a second embodiment of the
present invention being a tubular charge which is provided with
four equally radially spaced, longitudinal, rounded grooves;
[0055] FIG. 5 is a transverse section of a third embodiment of the
present invention being a tubular charge which is provided with
four equally radially spaced angled grooves;
[0056] FIG. 6 is a transverse section of a forth embodiment of the
present invention being a tubular charge which is provided with
five equally radially spaced angled grooves;
[0057] FIG. 7 is a transverse section of a fifth embodiment of the
present invention being a tubular charge which is provided with
four equally radially spaced faces;
[0058] FIG. 8 is a sixth embodiment of the present invention being
an array of elongate projectile elements joined along their edges
by engagement with corner strips;
[0059] FIG. 9 is a transverse section of a seventh embodiment of
the present invention, being a charge element for combination with
five other such elements.
[0060] FIGS. 10 to 12 show further embodiments of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0061] FIG. 1 shows the cross-section of a cylindrical container 1
constituting an explosive charge indicating, in broken lines, the
resultant fragmentation after detonation of the explosive in the
container.
[0062] Referring now to FIG. 1, it will be seen that such container
or tube 1, being radially symmetrical, expands radially as a result
of the shockwave and gas pressure generated by the detonation
passing along its length. This will progressively expand the wall
of the tube until its elasticity is exceeded and it will suffer
many longitudinal fractures.
[0063] Since there is misalignment between the longitudinal
fractures in adjacent longitudinal increments of tube, many
transverse failures will also result and few, if any, long lengths
of projectile material 1.sub.1, 1.sub.2 and so on will survive
beyond a distance exceeding the diameter of the tube 1. This is the
mode of fracture of conventional Bangalore Torpedoes.
[0064] FIG. 2 shows a container with four flat sides 3 to 6 so
that, upon explosion, the material will tend to be torn along the
corner edges and their radially distributed component increments
will diverge more gradually than is the case of the
equivalent-sized cylinder 1 shown in FIG. 1. This leads to a
greater concentration of projected fragments (3.sub.1, 3.sub.2, and
so on) in each of the four planes passing through the long axis of
the charge and parallel to the flat sides prior to explosion. The
fragments 3.1, 3.2, 3.2, etc, follow paths which are closer than
those that the same pieces of metal would follow had the tube 5
been circular in section rather than square. In other words, the
rate of separation of the elongate fragments in FIG. 2 is lower, so
the metal constituting these (potentially separate) fragments tends
to break up less and it thus forms larger fragments.
[0065] FIG. 3 shows a container 10 which is generally cylindrical
except for a longitudinal concave groove 11 extending along its
entire length.
[0066] Most of the wall material derived from explosion of the
container or charge 10 shown in FIG. 3 will be distributed with
approximate radial symmetry in similar manner to that as shown in
FIG. 1 and resulting in fragments 10.sub.1, and so on, with the
exception of the exploded fragments resulting from the longitudinal
groove 11. Upon explosion, the contour of this groove 11 results in
a focussing effect on the wall material from which it is
constituted, as a result of the oblique angle at which the
expanding cylindrical detonation wave front impacts upon its inner
wall. This effect produces the forging of a rough rod-like
projectile 11.sub.1 which, being coherent, and having a much
smaller surface area than the randomly shaped projectiles 10.sub.1
and so on impelled in other directions, maintains its velocity to a
significantly greater extent and consequently travels much further
than the latter.
[0067] Advantageously, the groove 11 in container 10 is should be
straight and not caused to spiral along the tube, since rotation of
the groove about the long axis of the charge would cause adjacent
increments of the projectile to travel along rotationally-spaced
radii. This may produce continuous stretching of the spiral
projectile which could result in it breaking up into a large number
of short pieces to the detriment of any useful cutting power.
[0068] Typically, container 10 has a conical shape at one end to
enable the end to be readily stuck in the ground, if appropriate.
The container may have, at the other end, some form of connection
to another similar container or standard tube, for example a
screw-thread portion. In this way, an extensive length of explosive
charge can be provided to be effective against a long fence or
other obstacle with barbed wire.
[0069] The container 20 of FIG. 4 comprises four concave
longitudinal flutes 21 to 24 shown in cross-section as being linked
by web-portion wall portions 25 to 28.
[0070] Much greater use is made of the focussing effect in the
charge shown in FIG. 4, in which almost all the exploded wall
material 21.sub.1, 22.sub.1, 23.sub.1, 24.sub.1 is constrained
within one or other of the four flutes 21 to 24 in its wall. In the
previous Figure (FIG. 3), no more than a quarter of the metal
constituted the grooved portion and was thus destined to be formed
into a coherent linear projectile: in the shape shown in FIG. 4,
about 90% of the metal ultimately constitutes linear fragment
projectiles. Such an arrangement has the advantage that a cutting
effect will be applied in four equally spaced directions, thereby
increasing the probability of a strike. By way of example, were a
charge unit to be thrown or dragged without regard to its radial
orientation beneath a parked aircraft, upon detonation of the
charge that aircraft would nevertheless be struck by at least one
upwardly directed projectile. In the extreme case of the charge
being passed through a loop in a helical wire fence, then the wire
constituting that loop is likely to be cut in four places.
[0071] The container 30 of FIG. 5 has four longitudinal flutes 31
to 34, each of two flat walls 35, 36 angled at about
145.degree..
[0072] Container 30 produces projectile material 31, consisting of
angular rather than rounded grooves with higher velocities. To some
extent, the velocity of the projectile could be increased by
decreasing the angle of the groove. This would, however, decrease
the volume available for containing the explosive so, beyond an
optimally small angle, the reduced amount of available energy would
cause a loss of velocity of the projectiles 31, 32, and so on.
[0073] FIG. 6 shows a transverse section of a container or charge
40 which is provided with five equally radially spaced angled
grooves 41 to 45, resulting in generally similar properties to
container 30 illustrated by FIG. 5 except that the probability of
impact on a particular target or target component is
correspondingly augmented. The diminution of width of each
projectile element is somewhat balanced by an increase in internal
volume and, hence, of explosive load for a given charge
diameter.
[0074] It will be understood that both round and square-sectioned
steel and aluminium tubes are common articles of commerce. Thus the
bodies of charges based upon the shapes shown in FIGS. 1 & 2
could be bought in items. Containers shaped as shown in FIGS. 3, 4,
5 and 6, however, would need to be made for the purpose. Containers
shaped as shown in FIGS. 3 and 6 can be readily formed by rolling
or pressing round tubes, and those of FIGS. 4 and 5 by rolling or
pressing square tubes.
[0075] FIG. 7 shows container 50 which, in cross-section, has an
external profile generally square in shape with rounded corners and
a slight concave aperture to the exterior side walls; however the
interior surfaces of the container have greatly pronounced aperture
of the side walls, as shown.
[0076] The container 50 shown in FIG. 7 cannot readily be formed
from commercially available tubes since the wall thickness varies
radially as shown in FIG. 7. Whereas extrusion of the shapes
illustrated in FIGS. 1-6 is a feasible alternative to pressing
round or square tubes in such metals as aluminium or magnesium, it
is the only practicable production method for tubes having varying
wall thickness.
[0077] Container 50 has four walls 51 to 54 which produces
projectiles 51.sub.1, 52.sub.1, 53.sub.1, 54.sub.1 and so on each
with a lens-shaped transverse section. The thickness of an
increment of projectile material determines its inertia and,
thence, its velocity as the detonation wave of the explosive
strikes it. Variation of the thickness of increments of a
projectile therefore modifies the velocity at which these
increments are projected. A tendency for the projectile to
disintegrate as it travels because its individual component
increments are travelling at different velocities, or in different
directions, can therefore be largely mitigated by causing all
increments projected in approximately the same direction to be
travelling at approximately the same velocity. The strength of the
material can therefore suffice to hold the increments together in a
coherent mass. Lens shapes are commonly used to achieve this
incremental velocity adjustment, which can be optimised for the
production of compact elongate masses of maximum stability in
flight.
[0078] Aluminium based alloys are ideal for precise and rapid
manufacture and the advantage in the present case of more rapid
deceleration in flight than heavier metals which implies smaller
danger zones.
[0079] FIG. 8 shows container 60 which is fabricated by joining
separate projectile components 61 to 64 along their edges using any
known means of joining such as welding, brazing, the application of
adhesive or the engagement of interlocking edges. Such interlocking
edges might engage directly with each other or with additional
corner pieces 65. Alternatively, or additionally, such elongate
projectiles may be constrained together, edge to edge, by a
surrounding frame or tube of plastics or metal.
[0080] FIG. 9 shows a transverse section of a charge 70 which may
be used alone, or as a component of an array of such charges to
form a charge of equivalent shape and effect as that of FIG. 6.
Thus FIG. 9 illustrates the use of charge 70 in the assembly of a
radially symmetrical assembly which propels explosively formed
projectiles in five equally spaced directions. It will be
understood that an outward facing array of charges with a variable
number of such charge units could be arranged according to the
perceived requirement at the time of use.
[0081] The intended effects of conventional Bangalore torpedoes are
the blast and fragment damage to adjacent structures. In many
applications the concomitant starting of fires would be
disadvantageous in an already dangerous environment. In those
instances in which an incendiary effect might be advantageous,
however, the use of such incendiary metals as magnesium and its
alloys, titanium or zirconium would be advantageous. Incendiary
effect might also be obtained or augmented by the use of aluminised
plastic or plastic-bonded explosive as the main fill. It will be
understood that aluminium, when used for substantial parts of the
cases of explosive charges, is little oxidised so makes little
contribution to any incendiary effect: when the powdered metal is
incorporated in explosive materials, however, it reacts
exothermically with both endogenous oxygen of the explosive and
with the surrounding air or water.
[0082] Alternatively, to a torpedo whose body is made from
relatively non-incendiary materials, may be applied additional
components made from incendiary materials. Thus, by way of example,
the incendiary effect of such a container as that illustrated in
FIG. 7, itself made from aluminium or steel, may be applied an
external tube of magnesium or, alternatively, strips of magnesium
may be applied, by mechanically interlocking grooves and ribs, or
by adhesive or sticky tape.
[0083] In a container assembled according to FIG. 8, the projectile
components 61 to 64 might be made in steel or aluminium while the
joining edge members 65 are made in magnesium.
[0084] In such applications as may require a minimal amount of
projectile damage, then the tubular components of the container of
the invention may be made from plastics or ceramic materials whose
effective range is limited by stretching and tearing, giving a very
large surface to mass ratio, and by extreme comminution
respectively.
By way of example:
[0085] A strip of aluminium, 25 mm wide and 5 mm thick, was bent
along its long axis to an angle of 170.degree. and to its convex
surface were stuck three strips of plastic explosive SX2, each 25
mm wide and 3 mm thick. This gave a calculated explosive load
equivalent to 480 g/metre. This charge was fired at a distance of
1000 mm from a length of razor wire and a 5 mm thick plate of 43A
grade steel Both the wire and the plate were cut. The projectile
was not projected in a direction exactly normal to the long axis of
the charge but was inclined forwards an angle of approximately
40.
[0086] It has been shown previously how the randomly shaped and
distributed fragments of a metal cylinder filled with detonating
explosive can be made cohesive and thus form elongate projectiles
by forming the sides of the tube into concave or lens-sectioned
longitudinal elements which remain intact and therefore act as
longitudinal self-forging fragment projectiles. These maintain more
consistent cutting properties at greater stand-off distances than
do the fragments derived from explosive-filled tubes of uniform
wall thickness.
[0087] Then follows an alternative means of mitigating the random
fracture of explosive-filled metal tubes and thus producing similar
elongate projectile elements.
[0088] Referring to FIG. 10, a square-sectioned metal tube 101 is
substantially filled with a detonating explosive 104. Between each
flat face 102 of the tube 1 is placed a shock wave refracting
element 102. This is essentially lens sectioned or prismatic and
the material used for its confection, and its shape, are determined
according to its shock wave propagation velocity. Since the
velocity of shock wave propagation will be lower than that of the
detonation velocity of the explosive 104, the shock front will be
refracted in the manner of light passing through a prism. The
consequence of this refraction is that the otherwise divergent loci
imparted to longitudinal elements of the tube 101 will be made
parallel with, or even convergent towards, the longitudinal plane
passing through the midline of each flat side 105 and normal to its
surface.
[0089] The consequence of this mitigation of radial expansion of
longitudinal elements of the tube 101 is that each side of the tube
101 remains largely coherent and constitutes a longitudinal
projectile 103.
[0090] It will be understood that this principle is not limited to
tubes having four sides.
[0091] An alternative configuration is illustrated in FIG. 11 in
which shock wave refracting elements 107 are applied to the inner
wall of a cylindrical tube 106 containing explosive 105. The inner
surface of the elements 107 may be flat or convex. An elongate
projectile 108 is produced by each refracting element 107.
[0092] The greater the curvature of the inner surfaces of the wave
shaping elements 102 and 107, and the slower the velocity of shock
wave propagation therein, the greater the degree of convergence of
the elements of the projectile material constituting the walls of
the tubes 101 and 106.
[0093] FIG. 12 shows a charge in which a metal tube 110 contains
four refracting elements 110 which are joined by thin-walled
sections 111. The refracting elements 110 and the joining elements
111 thus constitute a flexible lining element 112. This element 112
may be made either with flexible joining elements 111 or may be
made from elastic material. This facilitates the insertion of the
element 112 in the tube 109 before filling with explosive 113.
Tamping or injection of explosive into the lumen of the element 12
inflates the element and urges its outer wall against the inner
wall of the tube 109.
[0094] The use of a flexible or elastic lining element 113 has the
further advantage of facilitating the filling of the charge with
explosives which are initially made in the form of a paste but
which set to form solids. Such explosives are typified by plastic
bonded explosives in which a finely divided particulate explosive
material, such as cyclo-tetramethylene tetranitramine (HMX), is
dispersed in a viscous liquid matrix, such as hydroxyl terminated
polbutadiene, which is mixed with a cross-linking substance, such
as an organic diisocyanate, immediately before filling. Interaction
of the last two components converts the viscous liquid into a
rubbery solid. Such an explosive is typified by the composition
PBXN-110.
[0095] Difficulty is frequently experienced in the filling of
munitions with explosives having such a constituency because of the
difficulty of excluding bubbles of air. By connecting a reservoir
of such an explosive to the end of an evacuated, blind ended and
inflatable element 112, flow of explosive into the tube 109 can be
induced by the application of a vacuum to the space 114 between the
inner wall of the metal tube 9 and the outer surface of the
inflatable element 112. Simultaneous application of positive
pressure to the open end of the element 112 assists the filling
process and, in so doing, urges the outer surface of the element 12
against the inner surface of the tube 109.
* * * * *