IMPROVEMENTS TO AMMUNITION UNITS

Abstract: The disclosure relates to an ammunition unit in the form of a projectile, shell, missile or the like of the type which includes a shaped hollow charge, a reinforced, solid tip (3, 6) for mechanical penetration of reactive armour and an ignition system so disposed that initiation of the shaped hollow charge portion is not obtained until after the reinforced tip has forced aside the reactive armour. The ignition system then includes a pyrotechnic or electronic ignition time-lag device as a complement or alternative to a mechanical time-lag device disposed in the forward portion of the ammunition unit.

Description: IMPROVEMENTS TO AMMUNITION UNITS TECHNICAL FIELD The present invention relates to an ammunition unit in the form of a projectile, shell, missile or the like, for example an anti-tank shell of the type which includes a shaped hollow charge portion, and in which the forward portion of the ammunition unit is provided with a reinforced tip for mechanical penetration of reactive armour, and an ignition system disposed so that initiation of the shaped hollow charge is not obtained until after the reinforced tip has forced aside the reactive armour without this being detonated. BACKGROUND ART An anti-tank shell of the aforesaid type is previously known from Swedish patent No. 446483. The nose cone of the shell has a solid and sharper tip than in conventional anti-tank shells, and the ignition system includes an impact contact device which is not advanced right to the tip of the shell. By this means the time lag is accomplished 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. An anti-tank shell of the aforesaid type has a high kill rate against specific targets and at typical impact angles. However, it has proved that the integrated "mechanical" time lag provides, in certain target types, an excessively indeterminate time lag. OBJECTS OF THE INVENTION One object of the present invention is therefore to realize an ammunition unit possessing a better-defined time lag 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. According to the present invention, the ignition system of the ammunition unit therefore comprises a pyrotechnical or electronic ignition delay device as a complement or alternative to a mechanical time-lag device disposed 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 shows an anti-tank shell whose nose cone is fitted with a solid tip and impact contact device; Fig. 2 shows an alternative embodiment with a spike-shaped tip; and Figs. 3-6 show in block-diagram form how the ignition system may be constructed. DESCRIPTION OF PREFERRED EMBODIMENT Referring to the drawing, the anti-tank shell 1 illustrated in Fig. 1 is intended to give effect against an armoured target provided with reactive armour of the skirt type placed ahead of the main armour of the target. In the figure, the elongate forward portion (nose cone) 2 of the shell is shown, this being capable of penetrating into the reactive armour before the warhead of the shell in the form of a shaped hollow charge located in the intermediate portion (not shown) of the shell, is initiated. In this way the metal jet of the shaped hollow charge can provide its normal effect, since the reactive armour has not been detonated by the shell tip. In analogy with the anti-tank shell disclosed in the above- mentioned Swedish patent No. 446483, the tip 3 is optimated so as to be capable of forcing aside the reactive armour without this being detonated. The tip 3 is thus solid and has a comparatively small tip radius, in addition to which its material thickness in the longitudinal direction amounts to at least 4 to 5 times the wall thickness of the rest of the nose cone. The nose cone also includes an impact contact device in the form of a full-calibre double shell which consists of an outer shell included in the outer casing of the projectile proper, and an inner shell 4. The outer and inner shells are, in a per se known manner, disposed at a distance from and insulated from one another in order when the projectile 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 projectile for initiating the shaped hollow charge. However, as opposed to the impact contact device in the above- mentioned Swedish patent No. 446 483, the contact device in this case may be drawn right up to the tip of the nose cone so that contact is obtained immediately upon impact of the projectile against a target, either against the reactive armour or against the main armour of the target. The requisite time lag for detonating the shaped hollow charge is instead realized by a pyrotechnic or electronic time lag device included in the ignition system. Instead of an integral, fixed mechanical time lag, there will then be obtained a better-defined time lag, ideally with freedom of choice between immediate function and time lag and with the possibility of adjusting the requisite time lag in response to target type. Figs. 3-6 illustrate more closely how the time-lag device may be arranged. Alternatively, the impact contact device may also in this case be disposed so that its inner shell is not advanced right up to the tip of the nose cone, i.e. so that a certain mechanical time lag is built-in to the system. According to the present invention, however, an additional time-lag device as disclosed below is also included in this case. Fig. 2 illustrates a variant in which the forward portion of the projectile consists of a cylindrical, under-calibre body, a so- called spike 5, whose tip is reinforced. The tip consist of a separate body 6, preferably of heavy alloy, and with increased material thickness in the longitudinal direction so as to be able to force aside the reactive armour without this being detonated. The body 6 is preferably fixedly screwed to the spike. The spike 5 connects rearwardly with the full-calibre shell body by means of a conical transitional portion 7. The contact device includes a tubular inner shell 8 which extends throughout the entire spike 5 out into the separate body 6. The spike length may suitably be selected to be between 2 and 4 times the calibre. A thin-walled ballistic cap 9 is disposed so as to surround the spike and connect rearwardly to the full-calibre projectile body. Figs. 3-6 illustrate in block-diagram form a number of different examples of how the ignition system of the shell with time-lag device may be designed. The ignition system comprises a source 10 which generates electrical energy, a storage apparatus 11 for the electrical energy, an AND function 12, an igniter 14 with built-in time lag 13, for example a pyrotechnical igniter which initiates ignition of the shaped hollow charge portion. A signal is impressed on the AND function from the impact contact device 15 disposed in the tip of the shell, and from an arming circuit 16. The components included in the ignition system are per se previously known and will therefore not be described in detail here. Various pyrotechnical ignition delay charges may be selected. A suitable time lag may lie within the range between 80 and 200 μs , but, 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. 4 differs from that described in the foregoing in that the ignition time lag 13' is purely electronic and is disposed in the contact path between the impact sensor 15 and the AND function 12. Electronic ignition time lags are per se previously known in this art and adjustment may, for example, be effected with the aid of a timing ring. In Fig. 5, the pyrotechnical time-lag charge has been replaced by a selector unit 17 which is reversed for adjustment of immediate or delayed initiation of the shaped hollow charge portion. By this means, a suitable mode may be set on the shell according to the type of target. Fig. 6 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 disclosed. In this case, a primary impact sensor 18 is included, being located forwardmost in the tip of the shell, and a further, secondary impact sensor 19. The primary impact sensor 18 is connected to the time-lag portion of the ignition time-lag selector 17' and thereby provides for a selectable time lag on tip impact. The secondary impact sensor 19 is connected to the immediate function of the time-lag selector and, on contact function, emits an immediate ignition signal. This ignition system constitutes the most flexible. An ignition signal is, for example, emitted from the secondary impact sensor on "hard" impact, even if a time lag has 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, for example an anti-tank shell, of the kind which includes a shaped hollow charge, a strengthened, solid tip (3,6) for mechanical penetration of reactive armour, and an ignition system disposed so that initiation of the shaped hollow charge portion is not obtained until after the reinforced tip has forced aside the reactive armour, characterized in that the ignition system of the ammunition unit includes a pyrotechnic or electronic ignition time-lag device as a complement or alternative to a mechanical time-lag device disposed in the forward region 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 mechanical time-lag device consists of an impact contact device which is not advanced up to the tip of the shell. 5. The ammunition unit as claimed in Claim 1, characterized in that the solid tip for mechanical penetration consists of a separate body (6) with increased material thickness in the longitudinal direction of the shell.

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