CA1226171A - Anti-personnel fragmentation liner - Google Patents

Abstract

ABSTRACT

Illustrative embodiments of the invention are directed to a fragmentation casing for a munition in which the size and distribution pattern of the shrapnel is care-fully controlled. Typically, the casing is formed from a stacked array of rings in which angularly oriented inner and outer surface grooves form apertures at the mutual intersec-tions. Through control of ring size, groove depth and shape, a light-weight, efficient fragmentation casing is provided in which the size, shape and bursting pattern of the resulting shrapnel is regulated in a predetermined manner.

Description

~L226171 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-~z2~

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, ~2~6~7~

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.

SLY

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 , 122~L7~

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 ~226~71 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 ~2Z617~

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 - 12~6~

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 SLY

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 ~22~6~

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.

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 ~226~

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 ~2~6:~7~

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.

Claims (6)

I Claim:

1. A fragmentation liner comprising a ring having a plurality of grooves formed in the outer surface thereof and a plurality of grooves formed in the inner surface thereof, said inner surface grooves being angularly oriented with respect to said outer surface grooves to form mutual intersections therewith, and another ring stacked against said ring, said another ring having a plurality of grooves formed in the outer surface thereof and a plurality of grooves formed in the inner surface thereof, said inner sur-face grooves being angularly oriented with respect to said outer surface grooves to form mutual intersections therewith in order to form a fragmentation casing, all of said plu-ralities of grooves being sufficiently deep within said respective rings in order to form apertures at said mutual intersections to enhance liner disintegration into individual fragments.

2. A fragmentation liner according to Claim 1 wherein said rings each have different diameters.

3. A fragmentation liner according to Claim 2 wherein transverse flanges join said rings together at said adjacent stacked surfaces.

4. A fragmentation liner according to Claim 2 wherein said rings are formed of anodized aluminum.

5. A hand grenade comprising a plurality of stacked rings, each of said rings having respective diameters that are different from the diameters of the adjacent rings in said stack, each of said rings having a plurality of grooves formed in the outer surface thereof and a plurality of angu-larly disposed grooves formed on the inner surface of each of said rings, said respective inner and outer grooves forming a plurality of mutual interactions therewith to pro-duce a plurality of apertures at said intersections, and a bursting charge fill within said rings and in said outer grooves to enhance complete fragmentation of the grenade.

6. A structure for producing anti-personnel fragments comprising a liner, said liner having an inner surface and an outer surface, a plurality of grooves formed in the inner surface thereof, and a plurality of grooves formed in the outer surface thereof, said grooves being angularly oriented with respect to each other in order to establish a plurality of points of mutual intersection, said grooves being sufficiently deep to form an aperture in said liner at said mutual intersection points in order to produce an anti-personnel fragment of predetermined size and shape.