GB2246621A - Hollow charge - Google Patents

Abstract

A hollow armour-piercing charge 3 is provided with a penetrator-forming liner 4 and an inert body forming a guide for the detonation wave front from a propagation charge 7 detonated by a primer 10. In order to reduce the overall length required the body 12 of inert material is made up of a stack of plates 14 to 19 comprising alternate materials of low compressibility and of high compressibility such as metal 14, 15, 17, 19 and plastic 16, 18. A further inert body 13 may be included. <IMAGE>

Description

TITLE flollow Charge This invention relates to a hollow charge such as are used in armour piercing ammunition.

It is known to provide hollow charges with a body of inert material serving to guide the detonation wave front and located between a propagation charge and the hollow charge liner. The body is usually constructed in the form of a spherical shaped cap or is ogival in cross section, the base of the cap or ogive rests against the propagation charge. The detonation of the main charge by the propagation charge thus takes an annular course.

The detonation wave then moves over the inert body surface from the annular zone of the main charge to the liner which is encountered at an angle to produce an optimum penetrator spike.

In order to ensure that the shock wave front propagating through the body of inert material will not reach a point at the outer surface of the said body before the detonation wave which is moving around the surface in the explosive material, known bodies of inert material serving as detonation wave guides are made of a substance of low specific gravity, such as plastics, foamed materials or the like.

Certain length and diameter ratios have to be adhered to if the detonation wave is to encounter the liner in the required manner and the speed of the shock wave propagating in the body of inert material is to be reduced accordingly. Such conditions include a certain ratio for the axial length of the said body to its diameter and a certain distance from the latter to the apex of the lining. This, however, necessitates a certain overall length for a given diameter of the hollow charge. The greater the overall length the greater will be the weight of the hollow charge. With certain types of warhead, great importance is attached to a reduction of weight and length for ballistic and other reasons.

EP 91 860 Al makes known a hollow charge with a conical-cylindrical propagation charge with a metal disc embedded in that side of the body of inert material which faces towards the propagation charge. As the shock wave propagates faster in metal than in plastic or similar material of low specific gravity the inert body has to be made still longer.

One object of this invention is to reduce the weight of a hollow charge without substantial detriment to the performance.

According to this invention there is provided a hollow charge including a propagation charge and at least one body of inert material serving as a detonation wave guide and positioned between the propagation charge and a liner of the hollow charge, the inert body comprising or including a number of layers concentrically positioned along the longitudinal axis of the charge, alternate layers having differing compressibility.

According to this invention, therefore, the inert body serving as a detonation wave guide has a number of layers preferably comprising plates in a stack with alternate higher and lower degrees of compressibility or deformability with the layer or plate facing the propagation charge and the layer or plate facing the hollow charge liner being only slightly compressible.

The layers or plates of low compressibility preferably comprise a hard metal, particularly one of relatively high density, such as steel, tungsten or the like, while the low-density compressibility layers or plates are preferably made of plastic, particularly a thermoplastic, such as polytetrafluorethylene, rubber or a comparatively soft metal.

A relatively thin stack of plates thus suffices for ample alteration of the shock wave, that is ensures that the latter will not detract from the performance of the hollow charge. This can no doubt be explained by the fact that each compressible plastic plate provided between two non-compressible metal plates absorbs the energy of the shock wave by plastic deformation.

The thickness of the individual plates is preferably 0.5 to 5mm, a particularly advantageous range being 1 to 2mm. In general thinner plates undergo a greater degree of plastic deformation than thick ones. On the other hand the greater number of thin plates required in order to obtain the same alternation effect increases production costs in consequence of the greater total number of plates involved. The ratio of the height of the stack of plates to the diameter of the propagation charge is preferably between about 1:4 and 1:40, advantageously 1:10 to 1:30. The number of plates or the height of the stack depends on the detonation wave guiding action required for the hollow charge in question.

The shock wave starts from the priming point of the propagation charge. In other words, if this priming zone has a relatively small diameter the plates likewise can be made to a smaller diameter than in the case of a large diameter priming point. Furthermore, a smaller diameter suffices for plates forming a relatively high stack than for plates of which the stack is comparatively low. The maximum diameter of the plates is about 0.9, preferably 0.8, of the diameter of the disc shape propagation charge, thus corresponding to that of a conventional inert detonation wave guide body consisting, for example, of plastic.

The metal plate having such a large diameter, or at all events a greater diameter than the remaining plates, will preferably be the first one which bears against the propagation charge. This metal plate at the same time obstructs the detonation wave propagating in the propagation charge, as a result of which the said charge may have a smaller critical layer thickness and can be made thinner, thus reducing the overall length of the hollow charge still further.

The disc shaped propagation charge can be made particularly thin if the covering plate over the hollow charge at the rear, and which is thus positioned on that end face of the propagation charge which faces away from the body of inert material, is likewise made of material of low compressibility such as a metal, to thereby exert an obstructing effect over a wide area.

The first inert body, formed by the plates, is preferably positioned in a corresponding recess in a second detonation wave guide body of inert material, made of a low-density substance. The result is that, on the one hand, the first inert body that is the stack of plates, obstructs the shock wave, while on the other hand the second body of inert material which surrounds the said stack and of which the contour corresponds to a conventional inert body serving to guide the detonation wave, such as a spherical cap or ogive, ensures that the detonation wave will be accordingly guided along the body of inert material from the annular priming zone of the main charge to the liner in such a way as to encounter the latter in an optimum manner.

In an alternative construction the layers are of a conical or like shape with the propagation charge being also of conical shape. Thus the inert body may comprise a nested stack of conical cup-shaped parts.

This invention thus meets the three main requirements for a modern hollow charge, that is short overall length, moderate mass and high performance.

An embodiment of a hollow charge according to this invention is described by way of example with reference to the drawing showing a longitudinal section through the rear part of a hollow charge.

As shown in the drawing, the casing 1 of a rotationally symmetrical hollow charge with a longitudinal or rotational axis 2 contains a main charge 3 of which the front end is provided with a conical recess containing a liner 4.

At the rear end the main charge 3 has a spherical recess 5 and an annular surface 6 surrounds the said recess 5 where the main charge 3 is in contact with a disc shaped propagation charge 7 of the same diameter. A cover 8 closes off the hollow charge towards the rear.

The cover 8 has a central boring 9 containing a pressed booster charge 10. To ensure point ignition of the propagation charge 7 on the rotational axis 2, as far as possible, the said propagation charge 7 extends as a peak into a corresponding shape recess in the booster 10. The arrow 11 indicates the initiation point of the ignition process.

Two bodies 12 and 13 of inert material are provided in the recess 5 of the main charge 3.

The first inert body 12 consists of a stack of plates 14 to 19 extending in the radial direction and positioned in a shaped recess in the rear end face of the second inert body 13 which faces towards the propagation charge. The second inert body 13, apart from the recess serving to accommodate the first inert body 12, is shaped to conform with the recess 5 and consists of a lowdensity material such as a foamed polyurethane.

The plates 14 to 19, which like all other parts of the rotationally symmetrical hollow charge are arranged coaxially, differ in compressibility. In other words, the plate 14, which is the first plate starting from the priming zone 11, consists of metal, as are also the plates 15, 17 and 19, while the plates 16 and 18, situated between the metal plates 15 and 17 respectively, are made of polytetrafluorethylene.

The first metal plate 14, having a relatively large diameter almost equal to that of the base of the body 13, bears against a large area of the propagation charge 7.

In contrast, the diameter of the remaining plates 15 to 19 is only about half that of the base of the second inert body 13. The first metal plate 14 is also thicker than the remaining plates 15 to 19. The first metal plate 14 is thus a means of obstructing the detonation wave moving from the booster 10 through the propagation charge 7 to the annular priming zone 6 of the main charge 3. This obstructing effect is intensified if the plate 8 is made of metal.

According to the structure of the particular hollow charge and/or the level of performance required, the second inert body 13 can be omitted altogether, so that the means for guiding the detonation wave consists solely of the plates 14 to 19.

Claims (12)

1. A hollow charge including a propagation charge and at least one body of inert material serving as a detonation wave guide and positioned between the propagation charge and a liner of the hollow charge, the inert body comprising or including a number of layers concentrically positioned along the longitudinal axis of the charge, alternate layers having differing compressibility.

2. A hollow charge according to Claim 1, wherein alternate layers have high and low compressibility.

3. A hollow charge according to Claim 1 or 2, wherein the outermost layers have low, limited or only slight compressibility.

4. A hollow charge according to Claim 3, wherein the layer or layers adjacent said outermost layers have high compressibility.

5. A hollow charge in accordance with any preceding claim, wherein the layers are between 0.5 and 5mm in thickness.

6. A hollow charge in accordance with any preceding claim, wherein the diameter of the layers is between 0.2 and 0.9 times the diameter of the propagation charge.

7. A hollow charge in accordance with any preceding claim, wherein the propagation charge and the layers of the inert body are plates.

8. A hollow charge in accordance with Claim 7, wherein the diameter of the plate of the inert body facing towards the propagation charge is greater than the diameter of the other plates and at least 0.5 times the diameter of the propagation charge.

9. A hollow charge in accordance with any preceding claim, wherein the ratio of the depth of the body of inert material to the diameter of the propagation charge is between 1:4 and 1:40.

10. A hollow charge in accordance with any preceding claim, wherein the layers of low compressibility are metal and the layers of high compressibility are a plastic material.

11. A hollow charge in accordance with any preceding claim, wherein a first inert body comprising a stack of layers is located within a recess in a second inert body made of a material of lower density and forming a detonation wave guide.

12. A hollow charge constructed and arranged to function as herein described with reference to the drawing.