AMMUNITION UNIT

Abstract: The disclosure relates to an ammunition unit (1) in the form of a projectile, shell, missile or the like, of the type which includes a penetrator (5) for mechanical penetration of reactive armour, and an impact sensor (4) for initiation of a shaped hollow charge upon impact against the target. The impact sensor (4) is located in the tip of the ammunition unit for immediate contact upon impact against a target portion. The penetrator (5) is located behind the impact sensor in the forward region of the ammunition unit and is tubular for minimum material in the part of the shaped hollow charge jet before the target is hit. The ignition system includes an integral time-lag device offering choice between time lag and immediate function depending upon target types.

Description: AMMUNITION UNIT, The present invention relates to an ammunition unit in the form of a projectile, shell, missile or the like of the type which incorporates a shaped hollow charge portion and in which the forward portion of the ammunition unit includes a penetrator for mechanical penetration of reactive armour, and an impact sensor incorporated in the ignition system of the ammunition unit for initiation of the warhead upon impact against a target. BACKGROUND ART For combatting armoured vehicles, primarily tanks, it is previously known in this art to employ different types of anti¬ tank ammunition. Such ammunition is designed and constructed to penetrate through even extremely thick armour plating. Anti-tank shells constitute a specific type of anti-tank ammunition, featuring a shaped hollow charge. A shaped hollow charge comprises in principle an outer casing, a metal cone and an explosive. When the explosive detonates, the metal cone collapses and a metal jet is formed which, with immense force, penetrates through even very thick and hard armour plating. In consequence of their good effect in armoured targets, shaped hollow charges have long constituted a serious threat to armoured vehicles. The development which has taken place in the protection field, with the introduction of composite armour, reactive armour etc., has created a need for effective warheads with a high penetration capability even against these types of armour. Armoured targets may thus be provided with a reactive armour of the skirt type placed immediately ahead of or at a distance from the main armour of the target. Such a reactive armour may consist of two metal plates with an interjacent layer of explosive. Normally, such a reactive armour will disrupt the shaped hollow charge jet from a shell and its penetration capability will be greatly reduced. Swedish patent number 446483 discloses an anti-tank shell in which increased penetration capability through reactive armour has been realized -in that the nose cone of the shell has been given such a configuration that it is capable of mechanically penetrating the reactive armour before the shaped hollow charge is initiated. This implies that the penetration jet of the shaped hollow charge will remain undisturbed by the reactive armour, with the result that full penetration capability is achieved into the main target. The nose cone of the shell has a reinforced tip (penetrator) for mechanical penetration of the reactive armour, and an impact contact device is disposed in the nose cone in such a manner that contact is not obtained until after the reinforced tip has forced aside the reactive armour without this being detonated. In the embodiment illustrated in the above-mentioned patent, the tip of the nose cone is solid and sharper than in conventional armour-piercing shells, and the impact contact device is not advanced rfght to the tip of the shell. This arrangement achieves the delay which is normally required in order for the shell to have time to penetrate through the reactive armour before the shaped hollow charge is initiated. Armour-piercing shells of the aforesaid type are highly effective against a- specific target and at typical impact angles. At very low impact angles, for example, there may nevertheless be a tendency for deteriorated functioning of the shell. Moreover, when firing at targets which do not have reactive armour, a certain time lag occurs on account of the reinforced nose cone and the retracted contact device, which entails that the so- called stand-off distance, i.e. the distance from the base of the shaped hollow charge cone to the target, is shortened and penetration capability is reduced. The very fact that the shaped hollow charge jet is to penetrate the strengthened nose cone may also result in optimum penetration not being achieved. OBJECTS OF THE INVENTION One object of the present invention is therefore to realize an ammunition unit which retains a high penetration capability through reactive armour within a large range of impact angles against varying target types and at different ranges. A further object of the present invention is to provide good effect even against targets which are not fitted with reactive armour. In this case, the ignition system must be so arranged that immediate initiation is obtained. The present invention is substantially characterized in that the impact sensor is located in the forward portion of the ammunition unit for immediate signal on striking a target portion; and that the ignition system incorporates a built-in time-lag device for initiation of the warhead of the ammunition unit; and that the penetrator is substantially tubular and located behind the impact sensor in the forward portion of the ammunition unit. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying Drawings, and discussion relating thereto. In the accompanying Drawings: Fig. 1 is a schematic illustration of an ammunition unit in the form of a fin-stabilized anti-tank shell in which the present invention may beneficially be applied; Figs. 2-5 illustrate four different examples of how the forward region of such an anti-tank shell can be designed; and Figs. 6-9 illustrate in block diagram form the appearance of the ignition system. DESCRIPTION OF PREFERRED EMBODIMENT Referring to the Drawings, the anti-tank shell 1 illustrated in Fig. 1 is intended to give effect against an armoured target fitted with reactive armour of the skirt type placed immediately ahead of the main armour of the target. The shell includes a relatively elongate forward portion (nose cone) 2 which is capable of entering into the reactive armour before the warhead of the shell, in the form of a shaped hollow charge disposed in the intermediate portion 3 of the shell, is initiated. In this way, the shaped hollow charge jet can have its normal effect, since the reactive armour has not been detonated by the nose cone of the shell . As opposed to the shell illustrated in SE-PS 446 483, the shell according to the present invention is provided with a comparatively "soft" tip where the impact sensor 4 of the shell is located, whereas the penetrator 5 of the shell is located immediately , behind the impact sensor. The penetrator is substantially tubular, i.e. has a through aperture to allow passage of the shaped hollow charge jet, and also provides space for the inner casin of the impact contact device when such is employed. The penetrator may either consist of a separate body or be integral with the main casing of the shell - see also the various examples illustrated in Figs. 2-5. Since the impact sensor is disposed in the tip of the shell, a very rapid signal will be obtained upon hits against both "soft" and hard targets, i.e. a signal is obtained both on impact against reactive armour and against the main armour of the target. An immediate signal is also obtained even at very small impact angles ("glancing shots"). In order to prevent the shaped hollow charge function from being triggered before the nose of the shell has forced aside the reactive armour, a time-lag device is built into the ignition system. Examples of the appearance of this time-lag device are shown in Figs. 6-9. The time lag commences as soon as contact is obtained in the impact sensor 4. A suitable time lag may be of the order of between 80 and 200 μs , although in certain types time lags of.up to the order of magnitude of 1,000 μs may occur. During this time, the penetrator 5 penetrates through the reactive armour. The ignition system is designed and constructed so as to offer freedom of choice between time-lag and immediate function. Immediate function is selected on firing at targets which do not carry reactive armour. The ignition system is further advantageously designed so that different time lags may be selected (adjusted). The examples illustrated in Figs. 6-9 demonstrate more closely how this may be achieved. Figs. 2-5 illustrate in greater detail how the forward region (the nose portion) may be designed in the anti-tank shell. While we have selected by way of example an anti-tank shell, the skilled reader of this specification will readily perceive that the present invention is also applicable to different types of ammunition units such as rockets, missiles or the like. The nose cone 2 in Fig. 2 comprises two parts, a rear portion 2a which is threaded onto the shell body by means of a thread, and a forward portion 2b which is threaded on the rear cone portion 2a by means of a thread 7. As will be apparent from Fig. 2, the forward portion 2b includes a separate, tubular penetrator 8 secured in the front of the rear cone portion 2a, whose front 9 is reinforced and provided with a central hole 10. Furthermore, the rear cone portion 2a is of considerably greater wall thickness than the forward portion 2b so as to provide a firm anchorage portion for the penetrator 8 which is made of heavy alloy, high-strength steel or the like. As will also be apparent from Fig. 2, the forward region of the tube penetrator is bevelled so as to follow the wall of the forward nose cone. The tubular penetrator, however, does not extend all the way out into the tip of the shell, but leaves there a space 11 for an impact sensor. Because of the relatively thin-walled tip, an impact sensor will be actuated immediately on impact even against a thin-walled reactive armour plating. In Fig. 2, the ignition system consists of an impact contact device in the form of a full-calibre double shell, an outer shell included in the outer casing of the shell proper and an inner shell 12. The outer and inner shells are insulated from one another in order when the nose tip strikes a target to enter into mutual co- operation and establish electric contact with each other. The shells form a passive making contact in the ignition system of the ammunition unit for initiating the shaped hollow charge. The inner shell 12 is drawn through the tubular penetrator and extends right up to the tip of the nose cone. Fig. 3 illustrates a variation of the nose cone according to Fig. 2, in which instance the tubular penetrator is integral with the shell of the nose cone proper. The reason for this is that the nose cone is provided with a forwardly increasing wall thickness which terminates with a front portion 13 in the form of a truncated cone with a central elongate recess 14. Ahead of this front portion 13, a thin-walled tip cap 15 is disposed for the impact sensor. Instead of an impact contact device in the form of a full-calibre double shell, use is here made of another type of per se known impact sensor 12' which is connected to the time-lag device of the ignition system. In this case the wall of the nose cone is preferably made of a high-strength material, for instance steel. Fig. 4 illustrates a variation in which the leading portion of the shell consists of a cylindrical, small-calibre body 16, a so-called spike, the spike being, in this instance, divided into a forward portion 16a, for example of heavy alloy, which forms the penetrator, and a rear portion 16b, for example of steel, which connects to the full calibre shell body with the shaped hollow charge by means of a transitional portion 17. A short, thin-walled tip cap 18 is disposed on the forward region of the spike. The contact device includes a tubular inner shell 19 which extends throughout the entire spike out into the tip cap which forms the impact sensor. The spike length may suitably be selected to be between 2 and 4 times the calibre and the length of the penetrator may amount to between 20 and 100 per cent of the length of the spike. A spike may be an advantage as compared with a nose cone for "working up" a hole in the target. Fig. 5 shows a variant of a spike provided with a thin-walled ballistic cap 20 whose rear portion 21 connects to the shell casing. Fig. 6 illustrates in block-diagram form how the time-lag ignition system of the shell may be designed. The ignition system includes a source 22 which generates electrical energy, a storage device 23 for the electrical energy, an AND function 24, an igniter 26 with integral time lag 25, for example a pyrotechnical igniter which initiates ignition of the shaped hollow charge. A signal is impressed upon the AND function 24 from the impact sensor 27 located in the tip of the shell and from an arming circuit 28. The components included in the ignition system are per se previously known in this art and will therefore not be described here in detail. Various pyrotechnical ignition delay charges may be selected. A suitable time lag may lie in the region of between 80 and 200 μs, although in certain target types time lags of up to the order of magnitude of 1,000 μs may occur. The ignition system illustrated in Fig. 7 differs from that illustrated in the foregoing in that the ignition time lag 25' is purely electronic and is disposed in the contact path between the impact sensor 27 and the AND function 24. Electronic ignition time lags are per se previously known and adjustment may, for example, be carried out with the aid of a timing ring. In Fig.8, the pyrotechnical time-lag charge has been replaced by a selector unit 19 with capability for adjustment to- immediate or time-lag initiation of the shaped hollow charge. By this means, a suitable mode may be set for the shell according to the type of target. Fig. 9 finally illustrates yet a further example of how the ignition system may be designed. The same reference numerals have been employed for components analogous with those previously described. In this case, a primary impact sensor 30 is included, being located forwardmost in the tip of the shell, and a further, secondary impact sensor 31. The primary impact sensor 30 is connected to the time-lag portion of the ignition time-lag selector 29' and, thus provides for a selectable time lag on tip impact. The secondary impact sensor 31 is connected to the immediate function section of the time-lag selector and provides, on contact function, an immediate ignition signal. This ignition system constitutes the most flexible. An ignition signal is, for example, emitted from the secondary impact sensor 31 on "hard" strike even if a time lag had been programmed. The present invention should not be considered as restricted to that described above and shown on the Drawings, many modifications being conceivable without departing from the spirit and scope of the appended claims.

Claims: WHAT WE CLAIM AND DESIRE TO SECURE BY LETTERS PATENT IS: 1. An ammunition unit in the form of a projectile, shell, missile or the like of the kind which includes a shaped hollow charge portion and whose forward region includes a penetrator for mechanical penetration of reactive armour, and an impact sensor .incorporated in the ignition system of the ammunition unit for initiation of the warhead upon impact against a target, characterized in that the impact sensor (4) is disposed in the forward region of the ammunition unit for an immediate signal upon impact against a target portion; that the ignition system includes an integrated time-lag device for initiation of the warhead; and that the penetrator (5) is substantially tubular and disposed behind the impact sensor (4) in the forward region (2) of the ammunition unit. 2. The ammunition unit as claimed in Claim 1 characterized in that the ignition system provides freedom of choice between time lag and immediate function. 3. The ammunition unit as claimed in Claim 2, characterized by an autonomous switching between time lag and immediate function of the ignition system upon impact against different target types. 4. The ammunition unit as claimed in Claim 1, characterized in that the tubular penetrator consists of a separate body (8) mounted on an interior anchorage portion (9) in the forward region of the ammunition unit. 5. The ammunition unit as claimed in Claim 1, characterized in that the tubular penetrator is integral with the shell of the ammunition unit in that this has been provided with forwardly increasing wall thickness which terminates with a front portion (13) in the form of a truncated cone with a central recess (14). 6. The ammunition unit as claimed in Claim 1, characterized in that its forward region is designed as an under-calibre tubular body, a so-called spike, (16), at least the forward region (16a) of the spike being made of heavy alloy, high-strength steel or the l ke and serving as a penetrator. 7. The ammunition unit as claimed in Claim 1, characterized in that the ignition system includes a contact device (12) which extends through the penetrator to a thin-walled space (nose cap) ahead of the penetrator. 8. The ammunition unit as claimed in Claim 1, characterized in that the time lag lies in the interval of between 20 and 1,000 μs . 9. The ammunition unit as claimed in Claim 1, characterized in that the time lag is generated by a pyrotechnical delay charge disposed in association with the ignition device of the warhead. 10. The ammunition unit as claimed in Claim 1, characterized in that the time lag is achieved by an electronic time-lag circuit with optional adjustment of the time lag.

Inventors: BRATTSTROEM LEIF, LINDEN SVEN-ERIK, BRATTSTROEM, LEIF, LINDEN, SVEN-ERIK
Applicants: BOFORS AB, AB BOFORS
Application year: 1990
Main classification: F42B12
IPC codes: F42B12