GB2115909A - A fragmentation body for fragmentation projectiles and warheads - Google Patents

Abstract

A hollow body, for use as a fragmentation case for a warhead or missile, comprises preformed fragments 2, 15 and a cast or moulded matrix. The fragments have basal recesses 4 by means of which the fragments are located in a predetermined pattern upon projections of a mould during casting or moulding of the matrix in a mould cavity. The fragments have a ballistic shape and optional stabilising fins 16, and the pattern is selected to enhance fragmentation of the matrix and to improve the performance of the fragments. The mould projections and recesses 4 enable disadvantages of known spherical fragments and known casings to be avoided. The recesses 4 may contain an incendiary filling 10. <IMAGE>

Description

SPECIFICATION A fragmentation body for fragmentation projectiles and warheads The invention relates to a fragmentation body for fragmentation projectiles and warheads in which prefabricated fragments are incorporated into a hollow fragmentation case, which may be employed, for example, to provide the wall of a projectile.

German Patent No. 2536308 discloses a fragmentation body for fragmentation projectiles and warheads in which spherical fragments are held in a lattices hollow cylinder for the purpose of being cast around with metal. The expenditure for producing such a fragmentation body is cost intensive on account of the latticework and, upon the disintegration of the fragmentation body, the lattice impairs the energy transfer from the explosive to the spherical fragments.

The problem underlying the invention is to provide a fragmentation body having great effect.

In accordance with the present invention there is provided a hollow fragmentation body, for a projectile or warhead, comprising a matrix of moulded material in which are embedded a multiplicity of fragments, wherein each fragment is preformed is of elongate ballistic shape, has a base contiguous with a surface of said matrix, and has a recess which is open at said base.

The invention also provides a method of making a hollow fragmentation body for a projectile or warhead, comprising the steps of: (a) forming a multiplicity of fragments such that each fragment has an elongate ballistic shape, a base, and a recess which is open at said base, (b) mounting or locating said fragments upon projections provided upon a first mould so that the projections engage in the recesses, (c) locating said first mould with respect to a second mould to define therebetween a moulding cavity in which said fragments are located, (d) moulding in said cavity a material to form a body in which said fragments are embedded in a matrix of said material, and (e) separating said moulds to release the body.

As a result of the ballistic shape of the fragments, a high penetrating capacity exists.

The base-side recess of the fragments enables each of the fragments to be arranged in the intended position, direction and desired spacing relative to the neighbouring fragments.

The mutual spacing of the fragments has to be ascertained empirically, taking into account, for example, the nature of the casting material used for casting around the fragments with respect to its casting-technology mould-filling ability, and poss ihty also the employment of the casting material to provide fragmentation material in addition to the prefabricated fragments.

Besides the increased penetrating capacity of the fragments of the fragmentation bodies, the effect of the fragments can be increased by pressing known "per se" pyrotechnical or explosive materials or devices, e.g. incendiary fillings, into the recesses of the fragments. By appropriate selection of the fillings the result can be achieved that an incendiary or other effect is added to the penetrating capacity, so that, for example, combustible fluids emerging from ruptured pipelines and containers can be ignited. For example the recesses may be filled with incendiaries, explosives, fuzes, illuminating compositions or smoke substances.

The fragments may have flightpath-stabilising fins. In this way the result is achieved that the fragments are stabilised aerodynamically over their flightpath. Upon the moulding or casting of the matrix there are formed, in the course of the production of the fragmentation body, reproductions of the fins in the matrix material, which reproductions serve as rupture notches, so that, upon the cooling down of the material, high tensile stresses arise in the notch bases. The coefficient of thermal expansion of the shaped fragments is preferably considerably lower than that of the matrix material to stress the material at the notches, so that the notches have a particularly great influence on the fragmenting of the material, more especially formation of fragments of the material, during the initial rupturing of the hollow body.In addition, the predetermined notching of the matrix material is decisive for commencement of rupture and course of rupture of the matrix material and thus decisive for the attitude of the prefabricated fragments flying away.

The fins preferably extend the length of the fragments and intersect at tips of the fragments to enhance the flightpath-stabilising effect on the fragments and to form notches extending from the outside to the inside of the hollow body, so that a defined fragment formation of the matrix material is achieved.

Some or most of the fins of the fragments may be so aligned and arranged that fins of neighbouring fragments lie opposite and extend towards one another, so that the thickness of the matrix material is very thin between the notches so as to produce weakening in the matrix material, with the result that relatively slight disintegration force is needed to cause the matrix material to fragment. By appropriate positioning of the fins in the matrix material, depending upon the shapes of recesses and projections and the pattern of the projections employed, many variations of the number of and properties of the weakenings are possible.For example, the projections and recesses may be of conical or frusto-conical forms, but are preferably of pyramidal or frusto-pyramidal or other multi-sides forms so as to have polygonal cross sections of, for example, six sided form; the projections may be arranged in a pattern based on the repetition of a polygonal figure preferably having a different number of sides, e.g. of four sided form; and the fragments preferably each have a predetermined number, e.g. four, of the fins arranged at predetermined intervals, e.g. 90 intervals, around the fragments, so that by mounting or locating the fragments on the porjections or selected ones of the projections so that the fins are in selected orientations relative to the sides of the projections, the proportion of said fins which extend towards each other, e.g. to form groups of fins in each of which groups the fins extend towards a centre of the group, can be selected as desired, e.g. to provide an array in which the fins of substantially all of the fragments (except those at the borders of the body) are so directed.

For the moulds, a ceramic composition is needed only for casting high melting point matrix materials.

For other materials having a lower melting point, such as aluminium or brass, use is made of steel moulds which offer the advantage of multiple usability for casting. Also fairly weak matrix materials are suitable for the fragmentation bodies, if the loading of the projectile so allows; for example zinc or a synthetic material, such as a fibre-reinforced and/or filler-lightened material which can be injection moulded, can be employed.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein: Figure lisa perspective view of a portion of a fragmentation body of the invention; Figure 2 is a sectional view of parts of inner and outer moulds, with preformed fragments located therebetween; Figure 3 shows a first form of fragment having an incendiary composition therein; Figure 4 shows a second form of fragment with fins; and Figure 5 is a diagram showing part of an array of fragments in a fragmentation body.

Referring to Figure 1, the fragmentation body 1 comprises preformed fragments 2, e.g. of sintered iron, which are imbedded in a matrix material 3, e.g.

cast iron. Each of the fragments 2 are provided with a recess 4 which is open at the base 11 of the fragment.

Referring to Figure 2, the fragments 2 are held between an outer mould 5, e.g. of steel, and an inner mould 6, e.g. of ceramic, having a support or carrier 7. The inner mould 6 has projections 8 which engage in the recesses 4. The inner mould 6 is supported by, e.g. sintered onto, the support 7, e.g. of ceramic. The prefabricated fragments 2 are located or mounted on the projections which are arranged in a pattern, and the inner mould is located in the outer to hold the fragments therebetween. The fragmentation body 1 is now produced by molten cast iron being poured into the moulding cavity between the moulds to fill the interstices 9 between the fragments. After the cast iron has solidified, the inner mould 6,7 is smashed and the fragmentation body 1 is removed from the outer mould 5.

After casting or moulding of the body 1, a known incendiary filling, e.g. of Thermit, which self-ignites upon impact, is pressed into the recesses 4, as indicated in Figures 3 and 4.

The fragment 15 shown in Figure 4 is similar to the fragment 2, except in that there are provided, over its entire length, four fins 16. Both fragments 2,15 have a ballistic shape and taper from a tip 12 to the base 11. These fins overlap at the tip of the fragment 15, which fragment 15 is also produced by a process using powder pressing and sintering technology.

Each of the recesses 4 shown in Figures 1 and 3 has a hexagonal transverse cross section which is uniform throughout the length of the recess, but each of the recesses 4 may taper so as to be of a frusto-pyramidal form having a hexagonal cross -section as shown in Figure 2. The projections 8 shown in Figure 2 likewise taper (but need not do so) and are hexagonal in cross-section so as to engage in the recesses.

The advantages of using such a hexagonal or other appropriate polygonal form as compared with, for example, a conical form of projection and/or recess, in combination with an appropriate arrangement of the projections and an appropriate arrangement of the fins are considerable. For example, referring to Figure 5, the fragments 2 are arranged in a pattern (identical with the pattern in which the projections 8 are arranged), which pattern is based on the repetition of a four-sided figure the hypothetical corners of which arise at the axes of four adjacent fragments 15, e.g. as indicated by the reference suffix letters A, B, C and D.

One fin of each of these fragments 15A, B, C and D extends diagonally of said figure towards the centre 13, so that said one fins collectively form a group around the centre 13. The other fins of these fragments form parts of other groups with other adjacent fragments in the pattern.

In each group, the fins are disposed in opposed pairs, the fins of each pair extending towards each other so that said diagonals represent zones 17, indicated by lines, in said matrix which are inherently weak and in which stresses are concentrated. The zones 17 extend from the centres to bases of fin accommodating notches in the matrix 3.

All the projections in the pattern need not be employed, the fragments being arranged in a selected secondary pattern based on a larger rectangle, e.g. having its corners at the centres of the fragments 1 so, C, E and F, the fragment 1 SD at the centre of the larger rectangle being omitted so that two of the fins of each of these four fragments extend along adjacent sides of this rectangle towards the adjacent fins of two of these fragments so as to provide zones 17 around a portion of the matrix within the rectangle.

Furthermore, the orientation of some of the frag ments on the projections may be varied so that the fins are displaced, from the relative orientation shown, by the angle between the mid-points of two adjacent sides of the polygonal, e.g. hexagonal, cross section, whereby to vary the disposition and effect of said zones.

Thus said zones 17 may be varied within wide limits to provide desired bursting characteristics, e.g. to minimise the bursting charge required, to impart the maximum proportion of the resultant accelerative forces to the fragments, and to maxi mise the fragmentation of the matrix into fragments of predetermined character.

In use, upon the detonation of the bursting explosive of the eventual device incorporating the hollow body, the matrix material fractures at or along the rupture zones 17 and the fragmented matrix material is accelerated separately from the fragments 15. The fragments 15 are stabilised aerodynamically in flight by the fins 16. Upon impact on or penetration of the target, the fragments 15 burst asunder, whereby the incendiary fillings 10 are ignited, so that, if the fragments rupture a conduit or container to release combustible matter, the burning fillings can ignite said matter.

The invention is not confined to the precise details of the foregoing example and many variations are possible within the scope of the invention as defined by the appended claims. For example, depending upon the nature of the matrix material the inner mould 6, with or without the support 7, may be formed as a multipart inner mould of metal, such as aluminium, and may be used, e.g. for injection moulding of the matrix. To remove the fragmentation body 1 from the moulds, the parts of the moulds are suitably coordinated with one another for removal from the fragmentation body without being broken.

Matrix materials other than cast iron may be employed, e.g. aluminium, zinc and synthetic materials.

The projections 8 may be provided on the outer mould as well as or instead of on the inner mould, so that a fragment arrangement is also possible in which the tips of the or some of the fragments 2 and/or 15 are directed inwards. In this way, the incendiary fillings or some thereof are protected from being ignited by the detonation of the bursting explosive so as to ignite only upon impact upon the target. Despite the reverse positioning of the fragments, the same acceleration of the fragments by the explosive is achieved, since the matrix material acts as a sabot, which then comes loose from the fragments. An ignition of the incendiary filling by the bursting explosive may also be prevented by a thin-walled steel case being arranged between the fragmentation body and the bursting explosive.

The aerodynamic stabilising of the fragments may be achieved by any suitable form of the fins and/or by the centre of gravity being disposed in the region of the tip of each fragment.

The number and spacing of the fins on each fragment may be varied to suit the polygonal cross section and pattern selected. The polygonal cross section may be tetragonal.

Claims (24)

1. A method of making a hollow fragmentation body for a projectile or warhead, comprising the steps of: (a) forming a multiplicity of fragments such that each fragment has an elongate ballistic shape, a base, and a recess which is open at said base, (b) mounting or locating said fragments upon projections provided upon a first mould so that the projections engage in the recesses, (c) locating said first mould with respect to a second mould to define therebetween a moulding cavity in which said fragments are located, (d) moulding in said cavity a material to form a body which said fragments are embedded in a matrix of said material, and (d) separating said moulds to release the body.

2. A method as claimed in Claim 1,wherein after step (e) there is performed the step: (f) inserting into the recesses pyrotechnical or explosive compositions or devices.

3. A method as claimed in Claim 1 or 2, wherein during step (a) fins are provided on said fragments; and wherein said first mould is formed so that after completion of step (b) at least some of the fragments are located so that at least one fin of each said fragment extends towards a fin of an adjacent fragment.

4. A method as claimed in Claim 1,2 or 3, wherein said first mould is formed so that the projections are disposed in a predetermined pattern based on the repetition of a four-sided figure, wherein during step (a) each fragment is provided with four fins; wherein step (b) is performed so that substantially all the fragments are located so that at least some of said fins are arranged in groups of four, in each of which groups each fin extends from a respective one of the fragments towards the centre ofthe group.

5. A method as claimed in any preceding claim, wherein said projections are of conical, orfrusto-conical form.

6. A method as claimed in Claim 3 or 4, wherein said projections are of a frusto-pyramidal or other multi-sided form having a hexagonal cross section; and wherein the fragments are positioned during step (b) so that a selected proportion of the fins are disposed so that each thereof extends towards another thereof.

7. A method as claimed in any preceding claim, wherein said first mould is a male mould for forming the interior surface of the body.

8. A method as claimed in any preceding claim, wherein said moulds are formed from steel or ceramics.

9. A method as claimed in any preceding claim, wherein step (d) is performed by casting or injection moulding said material.

10. A method of making a hollow fragmentation body substantially as hereinbefore described with reference to the accompanying drawings.

11. A hollow fragmentation body made by a method as claimed in any one of Claims 1 to 10.

12. A hollow fragmentation body, for a projectile or warhead, comprising a matrix of moulded material in which are embedded a multiplicity of fragments, wherein each fragment is performed, is of elongate ballistic shape, has a base contiguous with a surface of said matrix, and has a recess which is open at said base.

13. A body as claimed in Claim 12, wherein the recesses contain pyrotechnical or explosive compositions or explosives.

14. A body as claimed in Claim 12 or 13, wherein said fragments are provided with fins.

15. A body as claimed in Claim 12,13 or 14, wherein each said fragment tapers to a tip remote from said base.

16. A body as claimed in Claim 15 as appended to Claim 14, wherein said fins intersect at said tip and extend to said base.

17. A body as claimed in Claim 14 or 16, wherein most of said fragments are disposed so that at least one fin of each fragment extends towards a fin of an adjacent fragment to produce weakenings in the matrix.

18. A body as claimed in Claim 14, 16 or 17, wherein said fragments are arranged in a pattern based on the repetition of a polygonal figure, and are disposed in said pattern so that the fins of at least some of said fragments are arranged in groups in each of which groups each fin extends from a respective one of said fragments towards a centre of the group.

19. A body as claimed in Claim 18, wherein said figure is four-sided.

20. A body as claimed in any one of claims 11 to 19, wherein the recesses are of pyramidal or frustopyramidal or other multi-sided form.

21. A body as claimed in Claim 18 or 19, wherein said recesses are polygonal in cross section and have a number of sides which is not the same as the number of fins on each fragment or which is not the same as the number of sides in said polygonal figure.

22. A body as claimed in any one of claims 13 to 21,wherein said surface is the interior surface of the body.

23. A body as claimed in any one of claims 11 to 22, wherein said material has a higher coefficient of thermal expansion than that of the fragments.

24. A hollow fragmentation body substantially as hereinbefore described with reference to Figure 1; Figures 1 and 3; Figures 1 and 4, or Figures 1,4 and 5 of the accompanying drawings.