GB2116298A - Shaped charges - Google Patents

Abstract

A shaped charge for a rocket, mortar, rifle grenades, mines etc., has an essentially conical cladding (2') which is truncated at the top (10) and/or the bottom (9) to improve space and weight characteristics. The liner may have a conical shape of constant slope, a conical shape of multiple slopes, an ogival or bell shape, or a tulip shape. The thickness of the liner may be constant, progressive, or regressive. <IMAGE>

Description

SPECIFICATION Improvements to shaped charges The present invention relates to improvements to shaped charges. The development of armourplates for more efficient protection of tanks, notably obtained by complex assemblies of several layers of different materials, spaced apart or not-so-called "composite" armour-plates, leads to a requirement for improved performance of shaped charges.

Several means for improving the intrinsic performance of a shaped charge are known, the effect of such improvements being more easily and more immediately measured by trials against homogeneous steel armour-plates. However, it appears preferable, within the scope of a modern application to infantry antitank projectiles or rockets, and also to antitank missiles, to adapt the shaped charge to the largest possible calibre compatible with the weapon system envisaged, and to try, in this configuration, to reduce the mass as far as possible, while respecting the two following requirements: -keeping the same performance on modern composite targets; -keeping an armour-piercing power still sufficient for armour-plate steel homogeneous targets.

The present invention relates to various improvements to shaped charges provided, notably, for weapon systems such as rocket launchers, missiles, mortars, closed breech guns, recoilless guns, rifles, grenades, multiple element heads, sub-ammunitions, mines, etc., and provides said shaped charge with a cladding truncated at the top and/or at the base. Due to this arrangement there is obtained a reduction in weight of the charge which allows increasing its calibre while keeping a mass compatible with its use on a rocket, a missile, etc.

The various features and advantages of the invention will become more apparent from the following description. It relates to a shaped charge head with a conical cladding of simple and constant slope.

Without departing from the scope of the invention, it can apply to all other forms of cladding conical with multiple slopes, convex or concave, as seen by an observer notionally placed inside the cavity formed by the cladding "tulip", "ogival", or "bell" shaped, concave, as seen by an observer notionally placed inside the cavity formed by the cladding conical with a constant slope, with an angle very closed (less than 600) or very open (more than 609), etc.

The shaped charge which is hereafter described and shown in the accompanying drawings relates more especially to a missile. It is made clear that the invention applies, without departing from its scope, to heads for all other weapons: rockets, mortar shells, closed breech gun shells, recoil less guns, rifles, grenades, subammunitions, mines, etc.

It is also made clear that only examples are shown, and that other modes of construction, proportions, arrangements, can be used without departing from the scope of the invention.

Particularly, the embodiments described and shown herein relate to shaped charges primed by a "disc", by an "ogival" screen and a toroidal, annular detonation wave. It is made clear that the invention applies to all other types and forms of priming, of screens and detonation wave, of central priming, without screen and spherical wave for example, etc.In the following description, reference is made to the accompanying drawings wherein: Figure 1 is a longitudinal sectional view of a shaped charge head provided with a standard conical cladding; Figure 2 is a longitudinal sectional view similar to Figure 1, but showing a shaped charge provided with a frustoconical cladding according to the invention; Figure 3 shows the schematic evolution of the speed of the elements of the jet as a function of their initial position in the coating; and Figure 4 shows, in longitudinal cross-section, a frustoconical cladding according to the invention, in correspondence with the speed curves of Figure 3.

In the drawings, the cladding is conical, according to a constant thickness law.

Without departing from the scope of the invention, it is also possible to use any other form of cladding, following a thickness law which is progressive, regressive or others.

As stated hereabove, the present invention proposes, due to the truncation of the shaped charge cladding at its top and/or at its base, length reductions of the assembly, whereby gains are derived for the charge mass, the cladding itself, the explosive and the body or envelope.

Such gains can reach a significant proportion of the charge mass (10, 15 or 20%, said values not being a limitation).

However, the arrangement according to the invention can possibly sacrifice, in a small but in any case acceptable way, the armour-penetrating effect of the charge. Recent and most precise studies have in fact demonstrated that the most useful and most efficient portion of the jet corresponds to the "median" portion of the coating (except the areas adjacent the top and the base). Therefore, the means proposed by the invention can be used either for making the charge and therefore the projectile lighter, or for taking advantage from the ballistic viewpoint (speed, range ) without affecting substantially the armour-piercing power, or to use this reduction of weight for increasing the calibre, and therefore finally increase the armour-plate piercing power without modifying the ballistic conditions.

The comparative description which is given hereafter with reference to Figure 1 (known shaped charge) and Figure 2 (a shaped charge with truncated cladding according to the invention) is provided for a better understanding of the invention.

Reference being made to Figure 1, one sees that the shaped charge head 1, of standard definition and having a calibre a, comprises a conical cladding 2, for example of copper, a main explosive 3 (hexolite or octolite for example), a priming "disc-shaped" block 4, made of hexocire or octocire for example, a screen 5 which forms an annular priming wave, a body or envelope 6 made of a metal or of a complex filament winding for example, a nose cone 7 providing a striking distance DA (for example 3 calibres).

The top of screen 5 is situated at a distance d of the top of cladding 2.

Figure 2 shows a shaped charge head according to the invention, of the same calibre a, which uses the same general disposition and the same technology as the known charge shown in Figure 1, but which comprises a frustoconical cladding 2', made of copper for example, a main explosive 3', a priming block 4 in hexocire or octocire for example, which forms an annular priming wave, a screen 5, a body or envelope 6' which is metallic or made of filament winding complex for example, and a nose cone 7 at a striking distance DA.

In the embodiment shown in Figure 2, the cladding 2' is truncated at the base and at the top. Without departing from the scope of the invention, cladding 2', could be truncated either at its base or at its top.

By comparing Figures 1 and 2, the gain of mass obtained by the invention appears clearly: envelope 6' is lighter than envelope 6, cladding 2' is shorter and lighter than cladding 2, and the main explosive 3' is of course less heavy (being shorter) than the main explosive 3. In the embodiment of Figure 2, the screen, the printing block 4 and distance d have been intentionally maintained, but said parameters may be, and preferably once the object of an optimalization in the case of the truncated cladding of the invention.

By referring to claddings 2 and 2' of Figures 1 and 2, it is possible to analyse the generation of the truncated cladding 2' according to the invention from the known cladding 2. In fact, (Figure 1), the known cladding 2 comprises a median region which is the most efficient and has a length T, a region less efficient at its base having a length B and a region less efficient at its top having a length S, the total length or height of the known cladding being: R=T+B+S By doing away with regions B and S (shown in spaced hatchings in the two regions in Figure 1), the truncated cladding 2' has a height T, the gain in length of the charge 1' according to the invention (Figure 2) being thus equal to:B+S, the length L' of the charge according to the invention, having a truncated cladding 2', being related to the length L of the known charge I by the relation: L-L'=B+S Thereby is inferred the corresponding reduction in weight described and explained hereabove.

The truncation of the top of cladding 2' can be closed or not. For example, it can be closed by an integral formation of the cladding as such (chased, forged or flow turned). Without departing from the scope of the invention, thus truncation can also be closed by an insert, preferably of plastics material, defining the cavity of the shaped charge and the explosive 1'.

This truncation can have the shape of a flat disc (Figure 2) or of a hemisphere or basket handle, shown at 8' in dotted lines in Figure 2.

These examples of construction are not limiting and do not depart from the scope of the invention.

The base of the cladding is also truncated, which brings about the subcalibration relative to the body or envelope of the charge. This truncated subcalibrated base connects and provides the centralization of the cladding to the calibre of the head via a flange 9. The flange can be formed integrally with the cladding as such (forging, flow turning, chasing .), or added as an insert. The shape of the flange 9 according to the invention can be plane or curvilinear, or have any other configuration, without departing from the scope of the invention.

The truncated cladding 2' shown in Figure 2, is truncated at its top and at its base. However, it is made clear that the invention applies, without departing from its scope, to claddings which are truncated either at the top or at the base thereof. Likewise, the truncated cladding 2' according to the invention, shown in Figure 2, is conical with a constant angle; however, it remains clear that the invention applies also to a truncation (top and base, or top or base) of any other shape.

The charge is made lighter by using truncated claddings, while preserving without significant reduction its armour-piercing power, as described with reference to Figures 1 and 2. This can be corroborated by theoretical or experimental considerations with reference to Figures 3 and 4.

Figure 3 shows the schematic evolution of speed V of the shaped charge jet elements as a function of their initial position 1 L in the cladding (generating line of length L).

Actually and as already disclosed hereabove, the present invention consists in truncating one of the ends of the cladding, or both ends; in this embodiment, the regions truncated are regions S near the top 0 and region B near the base 0' (Figure 4).

The first portion of the curve (Figure 3) shows an inversion of speed gradient of the jet elements.

The elements issued from the top 0 of the cladding, in the known shaped charge, are therefore caught up by the following elements for forming the head of the jet. About 1/5 (this proportion being given as a non limiting example, taking in account that said value varies according to the definition of the charge) of the length of the generating line of the cladding is involved by said phenomenon.

The present invention, consisting first in truncating said region of the shaped charge, results in eliminating or reducing said phenomenon, the potential reduction of the armour-piercing power by this process at the top being certainly small.

The opposite end B of the speed curve V corresponding to the base of the cladding is strongly inflected and tends toward lower speeds of 2 km/sec., from about 9/1 ooth of the length of the generating line L of the cladding, starting from the top 0. Actually, it is known that a speed of about 2 km/sec. is substantially the limit speed V0 necessary for obtaining the formation of a crater in a homogeneous target made of armor-plate steel (said speed V0 is of the order of the double in modern targets).

The advantages and the improved technical effects brought about by the present invention, consisting in truncating also the base of the cladding, are well justified by said observations of curve 1 V=f, L Figure 3.

A truncation at the base of the order of 10% has only a small effect on the armour-piercing power, while providing an important reduction of weight, as hereabove described.

If truncation B is of the order of 1/1 ooth about, the armour-piercing power is maintained for steel.

If said truncation is more than 1/1 0th, the armour-piercing power is maintained on a modern composite armour-plate, while suffering from a reduction of armour-piercing power in steel.

Claims (9)

Claims

1. A shaped charge, comprising cladding truncated at the top and/or at the base the importance of the end truncations being related, according to the targets attacked, to the evolution of the speed of the shaped charge jet, corresponding to the portion in length of the generating line of said cladding generating the corresponding portion of said jet.

2. A shaped charge according to claim 1 having a truncation of the base, corresponding to the jet speeds lower than those allowing the formation of a crater.

3. A shaped charge according to either of claims 1 or 2, having a truncation of the top corresponding to the region where there is an inversion of the jet speed gradient, the head elements being caught up by the following elements.

4. A shaped charge according to any one of the preceding claims, wherein the top is truncated and has a flat hemispherical or basket-handle shape, whereby said shape can be provided either integrally with the cladding as such (by flow turned, chased or forged) or by an insert, centered in the opening of the truncation, preferably in plastics material.

5. A shaped charge according to any one of the preceding claims, comprising a flange at the truncated base of said coating, said flange providing the centering of the cladding in an envelope-body and being provided integrally with the cladding as such (by flow turning, chasing, forging), or formed by a centering insert.

6. A shaped charge according to any one of the preceding claims, wherein the global reduction of weight of the charge given by the truncation of cladding is used for increasing the calibre for a gain of power, the masses being equal, or for increasing notably the speed, the range, by accepting possibly a slight reduction of power for the same calibre.

7. A shaped charge according to any one of the preceding claims, wherein the truncated claddings have a conical shape of constant slope, a conical shape of-multiple slopes, an ogival or bell shape, or a tulip shape.

8. A shaped charge according to any one of the preceding claims, wherein its cladding follows a law of constant thickness, or a law of progressive or regressive thickness.

9. A shaped charge substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.