Note: Descriptions are shown in the official language in which they were submitted.
~L226171
6903 A
CEB:JS:JF
1 No 8
ANTI-PERSONNEL FRAGMENTATION LINER
by
Anthony M. Caruso
This invention relates to improvements in anti-
personnel weapons and, more particularly, to controlled
grooves in the casing of a fragmentation munition to rug-
late the size, weight and effective radius of the resulting
shrapnel, and the like.
Anti-personnel weapons are subject to a number of
conflicting needs. Unquestionably, anti-personnel weapons
should disintegrate into individual fragments, or shrapnel,
of such shape that maximum damage is inflicted to human
flesh. For reasons considered subsequently in more detail,
and particularly with respect to hand grenades, these
fragments also should enjoy shapes that will permit air
resistance to dissipate fragment energies in short distances
in order to render the fragments harmless at some predator-
mined distance beyond the point of explosion that produced the
fragments in question. Naturally, adaptability to assembly
into a complete munition is a further manufacturing con-
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side ration that must be taken into account in the develop-
mint ox a satisfactory anti-personrlel weapon.
Clearly, these requirements have been the subject of
considerable study and development for many years.
With respect to the effective radius of the
fragments, hand grenades constitute a hazard to the person
throwing them unless they are thrown from prepared post-
lions. because of this hazard, the North Atlantic Treaty
orcyanization, (IOTA), has expressed the idea that hand grew
nudes should be letilal within five meters of the bursting
point, yet inoffensive at 20 to 25 meters, Various ways
have been tried to satisfy this need but none ox these
attempts sully meet the requirements.
The ~ierlilans produce plastic bodies grenades In the
grella~le interior, cast intecJrally with the explosive kirk,
are several thousand steel spheres of small diameter, While
this crank is lethal at the 5 meter distance, some spheres
reach as far as 30 meters. In the United States and Great
Britain a thin welled sheet metal casino encloses a coil of
thin wire that is an ovoid sprincJ with closed spirals to
form a liner. it definite small intervals the wire is
scored. Lowe explosive courage, moreover, is internal to the
coil. It is Relieved in these circumstances that the
explosion will break the wire at the scrounge to produce
incJiviciual ruminates ox small size. In practice, however,
breaks at each Score do not result and many fragments,
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instead ox byway sirlgle are multiples These multiples have
writer mass and consequently travel further to become
lethal beyond the desired distance from the bursting point.
In Italy, experiments have been conducted with
plastic bodied grenades in Welch individual fragments are
shaped to have negative aerodynamics by cementing the
fragments in a thin layer to the internal surface of the
grenade body or outer casing and then loading the interior
of the casing Whitehall the explosive change.
Although this last method produces the desired
results, millions of fragments of suitable aerodynamic shape
must be manufactured because each grenade contains approxi-
mutely 1000 fragments. And finally, each fragment must be
cemented in place in what is presumably, a laborious, dip-
faculty and explosive manufacturing procedure
It has been determined that in order to achieve these
desired aims, it is necessary to have fragments ox as low a
mass as possible and to impart to them as high an initial
velocity as possible. Isle velocity is achieved by having a
high ratio of brisant explosive to mass of fragments and to
shape these ruminates so that air resistance will rapidly
deplete the fragment energy.
Therefore high initial fragment velocity will produce
lethality at close range and the fragment mass and high air
resistance will dissipate energy at the longer ranges.
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attention is invited to additional considerations.
Artillery and mortar projectiles, bombs, land mines, hand
grenades end similar munitions are high density devices end
hence exhibit extremely heavy unit wits. Naturally,
reductions in these unit weights are kowtow desirable in
order to achieve efficiencies in shipment, handling and
actual delivery to the tarcJet. Weight reductions in these
munitions, however, most often are achieved throucJh
decreases in the size of the bursting charge and the weight
of the fragmentation casincJ. In these circumstances effi-
sciences in transportation and handlincJ are attained only at
the cost of a marked decrease in the effectiveness of the
weapon.
The modern hand grenade, for example, typifies many
of these dilemmas in munition design. For example, hand
c3renades should be light in weight in order to avoid Anne-
cessarily burdening combat personnel. Reduce the weicJht anal
the grenade loses its lethality because a lighter fracJmen-
station casino and a smaller bursting charge are less likely
to produce a suitable distribution of shrapnel with
appropriate impact effect. Better regulation of the shape
and mass of the fragments in order to control more closely
the effective renege end the result on fragment impact is
clearly desirable, but, as noted above with respect to
Italian grenades, have been attained only through the adopt
lion of costly and time consumincJ manufacturing procedures.
lo
In the past it was common to cast the outer fragment
station casing for hand grenades from heavy cast iron.
Usually these casings had segmented outer surfaces that
somewhat resembled small pineapples. The crevice between
the segments were expected to form fracture lines when the
charcJe within the casing exploded in order to produce strap-
not of predetermined shape, mass and distribution or dispel-
soon. The results frequently were less than desirable.
Depending upon the quality ox the particular casting, the
case might fragment in a uniform pattern of shrapnel of
suitable mass. If the casting was in any way defective,
however, the casing might burst along only one groove. In
this latter instance, the grenade produced only a loud noise
and either no shrapnel or a very irregular pattern of strap-
not distribution, thus failing completely in its purpose.
This problem could be overcome, if at all, through
costly and careful inspection of each cast iron case before
it alas willed With hurstin(3 charge and detonator.
Accordingly, the need still exists to provide
lighter, less extensive munitions without compromising the
effectiveness of these weapons. Better control over
fragment shape, mass and dispersion patterns also is needed.
As these problems relate to the hand grenade, moreover,
there remains a further need for greater lethality at close
range and greeter safety at longer rink.
These l~ro~lems are solved, to a large extent, through
,
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the practice of the invention. The munition liner that
characterizes the invention produces fragments that offer
suitable air resistance and which would be very difficult to
manufacture individually. The liner, as applied to hand
grenades, may be fabricated of a material that is less dense
than steel, e.g. hard anodized aluminum, titanium, ceramic
material and the like.
A typical munition fragmentation casing that embodies
principles of the invention is formed through a stacked
array of finals. One transverse surface of each of these
rings has at least one deep groove. The opposite Sirius of
each of these rings has an array of grooves formed in its
own surface. The grooves in this array are angularly
disposed relative to the groove (or grooves) on the other
surface of toe ring. By varying the number of grooves,
their respective depths and angular orientations the size,
shape, mass and dispersion pattern of the resulting shrapnel
can be carefully controlled.
Through careful control of the depths of the Greece
on opposite sides of the rings, apertures, or holes, can be
formed in the rink structure at mutual groove intersections.
As the munition is filled with explosive, a limited amount
of the explosive will flow through the apertures and fill the
volumes formed between the outer grooves and the munition
casing. As a consequence, the explosion, occurring on both
sides of the fragmentation liner, insures that the liner
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will break up into the individual regiments of predetermined
size and shape.
Further, the grooves promote sharp apices of freemen-
station material that are characterized by high stress con-
cent rations together with weak metal bonds This compels
the fragmentation liner to break into individual fragments
and not into clusters. The stress concentrations at the
apices, moreover, can be even further increased through heat
treatment, e.g. rapid quenching after heating.
The cJrooves from which the apices are developed form
a grid which can be shaped to suit specific requirements in
which, for instance, lighter weight fragments of greater
mass and volume than that which heretofore had been possible
in mass predilection munitions are now available.
The sharp-pointed apices that typify the embodiment
of the invention under consideration ace clearly more effect
live upon impact and are superior to the spherical or
cylindrical fragments that have characterized much of the
prior art.
Reese rinks, as mentioned above, can be manufactured
from hard anodized aluminum in order to produce suitably
large, low weight fragments. In this way, the resulting
: I:
large fragments are subject to greater air resistance.
These large fragments produce improved effectiveness at
close range while, for hand grenades, providing better
safety to the person who threw the grenade prom a greater
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distance because air resistance more rapidly dissipates the
energy ox these larcJer lighter fragments thereby reducing
the effective radius of the burst.
because the fragmentation casing is assembled from
individual reneges there is much greater flexibility in
arranging these rings to achieve a desired shrapnel pattern.
These rings are also more readily inspected and at lower
cost than a single massive cast troll casing. A manufac-
luring defect in any one ring leads only to a failure in
that ring when the burstillg charge is exploded in contrast
to a defective monolithic case in which a flaw in the
casting is likely to produce an entirely ineffective weapon.
The use of anodized aluminum in accordance with the
invention end the superior fraglnentation control that this
invention provides further permit the use of munitions with
lighter unit weights but of unimpaired effectiveness.
To summarize a liner according to the principles of
the inventioll is easier to manufacture than single fragments
cemented to thy inside of a casino or the scored wire coil.
The tragmerlts producect through a liner ox the type
under consideration have (to better dissipate force imparted
in the explosion) poor aerodynamic coefficients These
fragments also ennui superior impact effect arc desired the
fragment shape is readily obtained.
lthoucJh the liner may be formed of dense ferrous
material for Swahili applications (mortar and artillery project
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tiles, for instance), for individual munitions, of which the
hand or rifle grenade is typical, non-ferrous materials ox
lower specific weight can be used to reduce the unit weight
of the particular munition without impairing its
effectiveness.
y filling all of the grooves in the liner, both
inside and outside, the explosive forces bearincJ against all
of the groove surfaces generate respective resultant forces
that concentrate at each of the fragment apices. These
resultant forces thereby enhance the possibility of complete
liner disintec3ration into individual fragments, rather than
clusters.
The insertion of a one piece liner into a casino is a
relatively inexpensive process, in contrast with the Italian
system of cementing individual fra~rnents to the inside of a
casing.
munition casincJ weight also can be reduced. Plastics
or other low density materials now can be substituted for
the relatively thick steel or cast iron casings that hereto-
fore had been recolored and, which, more dense materials,
generally failed to burst into the desired more-or-less unit
form fragments.
Consequently, the invention permits the creation of
fragments of predetermined shape, which shape (or shapes)
can be quite complicated, with ease and at low cost.
Complete and uniform fracJmentation now also is possible
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because of thy presence ox an explosive charge on both sides
of the fragmentation liner.
These other advantages of the invention are more
completely described in the following detailed description
when taken in conjunction with the accompanying drawing.
The scope of the invention is nevertheless limited only by
the appended claims.
GRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a side elevation of a portion of a fragtnen-
station liner embodying features of the invention;
Fig. 2 is a plan view of the portion of the fragment
station liner that is shown in Fig. l;
Fig. 3 is a typical fragment from the liner shown in
Figs. I and 2;
Fig. 4 is a side elevation in half section of a port
lion of a hand grenade fragmentation liner assembled in
accordance with the invention; and
Fig. 5 is a side elevation in half section of a port
lion of a hand grenade liner that typifies a different
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For a more thorough understanding of the invention
attention is invited to Fig. 1 which shows a fragmentation
--10--
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rink 10 that has a cylindrical axis 12. In accordance Wilt
the invention, the outer circumference of the ring 10 has
two circumferential, V-shaped concave grooves 13, 14 the
depths ox the (grooves and the dimensions of the ring being
selectee to Rhodes shrapnel, or fragments, of predetermined
size and shave as described subsequently in more complete
detail. At this point it should be further noted that the
ring It, is formed preferably from anodized aluminum to pro-
vise a lighter weight fragmelltation casing that will burst
into leerier, low mass fragments.
As best shown in Fig. 2, the ring 10 has an array of
grooves 15 formed on its inner circumference. These indivi-
dual crevice that form the array lo also have V-shapes, each
of which is general perpendicular to the concave apex of
the grooves 13, I in the outer circumference of the ring
10 it 1).
It will he recalled Tut the size, shape and duster-
bushily ox to ;hra~rlel created as the bursting charge (not
shown in its I and 2) causes the rink 10 to fragment is
controlled by the depths ox the grooves 13, 14 and the
grooves in the array lo, as well as the dimensions of the
ring 10. Illustratively, the depths of the apices of the
concave grooves 13, I at points of common intersection with
the perpendicularly oriented (Grooves in the array 15 form
diamond -shaved shrapnel apertures of which apertures 17, 20
are typical. These apertures 17, 20 not only permit the
Lo
charge ox bursting explosive to be loaded on either side ox
the Ryan I as described subsequently, but also define
fragment size and shape by establishing the fracJment eon-
news. Isles, as the ring 10 bursts, the concave apices of
the grooves that connect adjacent apertures form predator-
mined fracture lines to generate fracJments of generally Ulli-
form size and shape. A typical fragment 21 is shown in Fig.
3. Note in FicJ. 3 that the mass of the fragment 21 is
determined by sides 22, 23, 24 and 25 of the apertures that
defined its over-all size. The effectiveness of the
fragment 21 is further enhanced by crests or creases 26, 27
on opposite sides of the fragment at the tops of the respect
live cJrooves from which the fragment is formed. In some
circumstances, it also might be desirable to produce high
stress concentrations at the creases 26, 27. Depending on
the materiel selectee for the fragmentation liner, these
stress concentrations can be provided through heat treat-
mint, of which rapid quenching after heating is typical.
As previously noted, the thickness and width of the
ring 10 (Fig. 1), the depths of the grooves 13, 14 and the
individual grooves in the arrays 15, 16 determine the size
and shape ox the resulting fragments. In these circumstan-
cues, the fracJments enjoy an unusual uniformity in shape and
mass. Consequently, the dispersion pattern and the effect
live diameter of this pattern for any given munition is
uniform and quite predictable.
-12-
Lo
The shapes and relative angular orientations of the
grooves lo, 14 and grooves in the arrays 15, 16 also can be
varied to accommodate preferred machining operations, to
produce particular bursting pattern, aerodynamic properties
and the like. thus, instead of the transverse grooves, 13,
I formed in the outer periphery of the ring 10, one or more
spiral Grooves can be substituted. Similarly, the array of
grooves 15 can be oriented at an acute ankle relative to the
Russ 13, 1~1, rather than the relative ~eripendicular
orientation that is shown in the drawing.
As a further illustrative variant of the invention,
concave transverse grooves can be formed on the inner air-
cumference of the rincJ 10 and the concave, axially oriented
grooves can be formed on the outer circumference of the ring
10 .
Attention now is invited to Fig. 4 which shows a
hand yrenclcle fra~1melltation liner 30 assembled in accordance
with principles of the invention. A group of rings 31, 32,
33, 34 each ox which has a different diameter and are
{Grooved in the manner described in connection with Fits. 1
end 2, are aliened relative to longitudinal axis 35. The
rincJs 31, 32, 33 34 are seated in mating recesses in an
outer casino 36. The casing 36 has a stepped cylindrical
con~icJurcltion in order to accommodate the differellt diameters
of the rinks nested within and to impart to the grenade
a general outline of the customary shape that is most sweets
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to bcin~J c~raspec3 in a hand for aiming and throwing. Roy
casino 36, moreover, can be formed of some sturdy, light
weicJht plastic, or other suitable material in order to
further reduce the overall weight of the grenade.
The apertures 17, 20 (shown in Fig. 1 and not shown in
Fig. 4) provide communication between the inside of the
rejective rings 31, 32, 33 34 and the surface that is in
contact with the outer casing oh. Thus, as the molten
bursting charge (not shown in the drawing) is poured into
the hollow cavity that is formed by the rings 31, 32, 33,
I some of this charge flows through the apertures to fill
the grooves in the outer circumferences of the respective
rings. Upon bursting, the charge on both sides of the
grooves explodes to produce a force resultant for each
fragment that concentrates at the outer surface apex or
crease further insuring disintegration of the liner 30 into
individual fragments.
A further embodiment of the invention is shown in
Fake. 5. AS illustrated, each of axially aligned and craved
rings 37, 40, 41 42 for a hand grenade fragmentation casing
I are jointed each to a next adjacent ring by means of
transversely disposed flanges I 45, 46. In this way a
monolithic fragmentation casing is formed from the basic
ring structures. Although the fragmentation liners shown in
the drawing are assembled in stacked rings, a cylindrical or
hexagonal liner, as well as any other suitable shave, can be
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used for the purpose of toe invention which, as mentioned
above, depends to a larcJe extent on the forming of mutually
intersection grooves of appropriate depths and cross sections
on inner and outer fragmentation liner surfaces to provide
suitable shrapnel.
It should be noted in connection with Figs. 4 and 5,
that the different diameters of the rings 31 to I and 37,
and 40 to 42, respectively, to approximate the ovoid shape
of a grenade without producing fragments of smaller size as
the ends of the munition are approached.
Thus, there is provided in accordance with the invent
lion a method and apparatus for forming the fragmentation
casing for a munition. The technique shown arc! described
proc3uces lottery weight munitions of unimpaired effect
tiveness in which the size, shape, mass and distribution
pattern of the shrapnel can be controlled within much closer
limits than those which heretofore were possible.
