ARMOUR PIERCING SHELL

Abstract: The present invention relates to an armour piercing explosive shell of the kind which comprises a hollow charge and an impact contact member placed in the nose cone (1) of the shell an arranged to provide electrical contact for initiation of the hollow charge upon impact of the shell against the target. To improve the penetrative performance of the shell against targets protected by active armour the nose cone (1) of the shell is provided with a reinforced tip (2) for mechanical penetration of the active armour and the impact contact member does not extend all the way to the tip but positioned behind an inner shoulder (8) made in the wall of the nose cone (1).

Description: The present invention relates to an armour piercing shell of the kind comprising a nose cone with a reinforced tip for mechanical penetration of active armour and an impact contact member placed in the nose cone of the shell arranged to provide initiation of the charge upon impact of the shell against a target and wherein the nose cone comprises an inner shoulder, reference is made to EP-A-0 196 283. For combating of armoured vehicles, particularly tanks, it is previously known to use different types of antitank ammunition. Such ammunition is designed to penetrate even thick armour plates. Armour piercing shells are a special type of anti-tank ammunition which is provided with a hollow charge warhead. In principle, a hollow charge warhead comprises an outer casing, a metal cone and an explosive. When the explosive detonates, the metal cone is squeezed together and a metal jet is formed which, with great force, penetrates even very thick and hard armour. By virtue of its good effect in armoured targets, the hollow charges have long constituted a serious threat to armoured vehicles. In consequence of the development that has taken place on the protection side through the introduction of composite armour, active armour, etc, the importance of improving the penetrability of the warhead has, however, increased. Armoured targets can be equipped with active armour in the form of separate mountings placed in front of and at a distance from the main armour of the target. Such active armour may typically comprise two steel plates with an intermediate layer of pentyl explosive paste. Normally, active armour of this kind will disturb the hollow charge jet of the shell, its penetrative ability being drastically reduced owing to the fact that the jet is broken up into fragments which tumble and are dispersed. An armour piercing shell with improved penetrative ability against active armour is previously known by EP 0 196 283. In this case the improved penetrative ability has been accomplished by means of a specific design of the nose cone of the shell so that it is able to mechanically penetrate the active armour before the hollow charge is initiated. This means that the penetration jet of the hollow charge can pass undisturbed by the active armour so that full penetrability is obtained in the main target. Specifically, the nose cone has a reinforced tip for mechanical penetration of the active armour and the impact contact member is so positioned in the nose cone that contact is obtained only when the reinforced tip has penetrated aside the active armour without this detonating. In said European patent publication a preferred embodiment is illustrated in which the tip of the nose cone is solid and sharper than in conventional anti-tank shells and the impact contact member is not extended all the way to the tip of the shell. By this means, the delay is accomplished which is required in order for the shell to have time to penetrate the active armour before the hollow charge is initiated. Armour piercing shells of the above-mentioned type have a very good effect at typical angles of impact, i e angles within the range of 20°-60°. At very small angles of impact, 20°-30°, there is a tendency, however, that the shell case is twisted at the impact with a deteriorated contact function as a consequence. Also on impacts perpendicular to the armour there is a tendency to a deteriorated contact function for the above-mentioned armour piercing shell which might depend on a certain bending of the walls of the nose cone on impact with an undesired delay of the contact function as a result. The object of the present invention is therefore to provide an armour piercing shell for which an increased penetrative ability against active armour is maintained at small angles of impact as well as at an impact of right angle. A main characterizing feature of the invention is that the nose cone wall is changed via said shoulder to a front part with increased wall thickness and that the front part of the impact contact member is positioned behind said shoulder. In a preferred embodiment of the invention said shoulder comprises an annular surface in a plane perpendicular to the longitudinal axis of the shell. Upon impact of the shell at right angle against a target the front part of the contact member hits the shoulder and the ignition system of the shell is closed and the hollow charge warhead is initiated. In the following the invention will be described more in detail in connection with the accompanying drawings in which figure 1 illustrates a first embodiment of the invention having a solid, sharp tip and figure 2 a second embodiment with a solid, cut-off tip. Figure 1 shows the front part of an armour piercing explosive shell comprising a nose cone 1 with a reinforced tip 2. The nose cone is screwed onto the shell body by means of a thread 4. The nose cone could also comprise two parts, a rear part which is screwed onto the body of the shell and a front cap. Like the previously known armour piercing explosive shell according to EP 0 196 283 the reinforced tip is optimated to be able to penetrate aside the active armour without this detonating. As already mentioned the tip is solid and has a decidedly small tip radius and the material thickness of the tip in the longitudinal direction is thus at least 4-5 times the wall thickness of the rear part of the nose cone. The nose cone wall is also made of a harder material than for a conventional shell. If the nose cone is divided then at least the front part (cap) is made of a harder material. The tip 2′ of the shell illustrated in figure 2 is also solid but cut-off in contrast to the sharp tip illustrated in figure 1. Such a cut-off tip could in some applications increase the penetrative ability as the risk for bending of the tip against an inclined target surface is less for this type of tip. Otherwise there is no difference between the two nose cones. Like the previously known armour piercing explosive shell the nose cone also comprises an impact contact member in the form of a full-calibre double sheath, an outer sheath incorporated in the outer casing of the shell and an inner sheath 5. The outer and inner sheaths are disposed in an unused shell at a distance from and isolated from each other so as upon impact of the shell against the target to be able to enter into coaction and make electrical contact with each other. The sheats form a passive end contact in the ignition system of the shell for initiation of the hollow charge. The nose cone comprises a rear, larger spacing 6 in which the impact contact member is disposed and a front, smaller spacing 7 with increased wall thickness. The change in wall thickness, i e the change from the comparatively thin walls of the rear spacing 6 of the nose cone and the thicker walls of the front spacing 7, is formed as an inner shoulder 8 having an annular surface 9 in a plane perpendicular to the longitudinal axis 10 of the shell. The cylindrical front part 11 of the impact contact member is located just behind the shoulder 8 and isolated therefrom, but so arranged that it upon impact against a target is able to enter into coaction with the annular surface of the shoulder and make electrical contact with the outer casing. The front spacing 7 comprises a rear cylindrical part 7a and a front conical part 7b. The length of the spacing 7 is within 10-20% of the length of the spacing 6. The increased wall thickness of the front spacing 7 of the nose cone improves the penetrative ability of the shell for very small angles of impact thanks to the increased torsional strength as well as for impacts at a right angle so that the risk for a bending and a corresponding mis-function of the impact contact member is reduced.

Claims: Armour piercing explosive shell comprising a hollow charge a nose cone (1) with a reinforced tip (2) for mechanical penetration of active armour and an impact contact member (5) located in the nose cone (1) and arranged to initiate the hollow charge upon impact of the shell against a target, the nose cone (1) comprising an inner shoulder (8) characterized in that the wall of the nose cone via the inner shoulder (8) is changed to a front part (7) with increased wall thickness and that the front part of the impact contact member (5) is positioned behind said shoulder (8). Armour piercing explosive shell according to claim 1 characterized in that said shoulder (8) comprises an annular surface (9) in a plane perpendicular to the longitudinal axis (10) of the shell. Armour piercing explosive shell according to claim 2 characterized in that the front part (7) of the nose cone having a wall with increased thickness comprises a rear cylindrical spacing (7a) and a front conical spacing (7b).

Inventors: ANDERSSON, KENNETH, GUSTAFSSON, HANS, KROPP, HANS-ERIK
Applicants: AB BOFORS
Application year: 1988
Main classification: F42C19
IPC codes: F42B12, F42C19