Ammunition and explosives – Shells – Shrapnel
Reexamination Certificate
1998-06-23
2001-08-21
Poon, Peter M. (Department: 3643)
Ammunition and explosives
Shells
Shrapnel
C102S496000
Reexamination Certificate
active
06276278
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a new type of shell intended to increase mainly the effective range of anti-aircraft cannon, in the case of all near misses, to the greatest possible extent by concentrating the fragments formed on detonation of the shell in the direction of the target. The invention involves more specifically a combination of a specially designed explosive-charged shell forming fragments on its detonation and a special type of proximity fuse intended to initiate the explosive charge when a target is detected. The detailed construction of the proximity fuse has nothing to do with the invention, however, the fact that it is available is a prerequisite for the invention. The purpose of the invention is therefore partly to increase the potential of the AA artillery for combating extremely difficult targets such as sea-skimmers etc. and partly to increase the effect of the individual shells on more conventional targets. Also, the purpose is to reduce the dependency of anti-aircraft cannon on entirely accurate range calculations which, in spite of the most modern technology available, can be difficult to achieve in the rapid combat sequences which are now involved in combating air targets. Furthermore the number of targets which are extremely difficult to combat in the form of autonomous guided or self-guiding weapon carriers with small external dimensions can be expected to increase in the future since the air force seeks to an ever increasing extent to be able to combat a selected target without having itself to enter the risk area around the target.
Naval and field barrel-type anti-aircraft weapons of today consist mainly of automatic cannons of 20-76 mm caliber and for these use is as a rule made of explosive-charged high-explosive shells or ball-type high-explosive shells which, at least in the larger 40-76 mm calibers, are usually equipped with proximity fuses for initiation in the case of near misses of the target. For direct hits on the target there are percussion initiation functions.
The generation of proximity fuses in general use today have an antenna pattern with relatively undefined omnidirectional seeking beams, and in the same way the fragments formed on the detonation of the high-explosive shells and ball-type high-explosive shells of today are scattered radially from them about their own longitudinal axis.
The advantage of a combination of the omnidirectional proximity fuse and the omnidirectional fragmentation shell is that, with this combination, there is no need to keep track of the rotational position of the shell which therefore simplifies the initiation system. It is therefore only necessary for the proximity fuse to have ascertained that the shell is sufficiently close to a target for initiation of the explosive to take place. The disadvantage, however, is that the energy of the explosive charge and of the fragments scattered on its detonation is scattered while turning and is therefore directed only to a limited extent towards the target. For a single 40 mm AA shell, this means that it must today be as close to the target as roughly 5 meters in order to ensure that the target is shot down. Considering the rapid targets of today, it will be absolutely clear that such a close hit picture requires extraordinarily accurate prediction.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a method and an arrangement for effectively combating air targets with explosive-filled shells which are provided with proximity fuses, fired from anti-aircraft cannon, and rotate in the trajectory towards the target. In order to increase the effect of the shells on the target, the fragmentation of the previous generation of AA shells, which was distributed symmetrically around their own longitudinal axis, has been replaced by a directed fragmentation where the dynamic scatter direction of the explosive charge and of the fragments has been concentrated in one or more directions which coincide with the seeking direction or seeking directions of the proximity fuse. At the same time, omnidirectional proximity fuses of the conventional Doppler radar type which were used previously have been replaced by a newly developed proximity fuse, the special feature of which is that it has one to four clearly delimited seeking or radiation directions. This proximity fuse may be a socalled optronic proximity fuse, which is actually a laser proximity fuse. It may also be an IR proximity fuse or another direction-sensing proximity fuse with one or possibly a few specifically defined radiation directions aligned with the main direction or main directions of the fragmentation of the shell, which will is therefore produce a concentrated fragment sheaf in the direction of the target on detonation of the shell. The fact that the radiation direction or radiation directions of the proximity fuse is/are aligned with the fragmentation means of course that consideration has been given to the flying speed of the shell and its rotational speed and also to the reaction time of the proximity fuse and its initiation function interacting therewith.
Through this combination, a proximity fuse-initiated shell is capable of effectively combating air targets at up to three times the detonation range from the target of the older types of proximity fuse-initiated shells of the same caliber which they are intended to replace. A further advantage of the combination according to the invention is elimination of the problem which was inherent in earlier types of proximity fuse which, in the outer edge of their range area, had a tendency to trigger the detonation of the shells far too late, when they had already passed the target. As this misfunction was a direct consequence of the antenna pattern of the older types of proximity fuse, it was difficult to avoid it.
The complete shell designed according to the invention may of course also be combined with other functional steps such as time release, initiation on direct hit, miss destruction etc.
In the selection of dynamic main-action direction/main-action directions of the explosive charge and the fragments and with this the aligned radiation direction/radiation directions of the proximity fuse, there are a number of different alternatives. An alternative suitable for a proximity fuse with a single radiation direction is to arrange the main-action direction of the explosive charge and the radiation direction of the proximity fuse at an acute angle forwards in relation to the trajectory direction of the shell. As a result of the rotation of the shell, complete coverage is then obtained for a conical space extending in front of the shell and uniformly distributed around the axis of the trajectory of the shell. A corresponding part of the space will be scanned by the proximity fuse along a spiral path formed as the shell rotates. If on the other hand the seeking direction of the proximity fuse can form an angle which approaches a 90° angle with the projectile trajectory, the proximity fuse will scan the space around the projectile trajectory along a spiral path formed in a corresponding manner.
Lastly, should the proximity fuse be provided with a number of seeking arms, the scanning pattern becomes denser with a number of spiral paths which run into one another. In the case of proximity fuses with a number of seeking directions, the shell must of course also be provided with a number of dynamic fragmentation directions aligned therewith.
In an embodiment of the invention which is suitable for combating larger targets such as aircraft, the proximity fuse is made dependent on its rotation having indicated the target twice before the explosive charge is initiated. This alterative is based on a microprocessor coupled together with the proximity fuse, which has been programmed so that, during the first revolution of the shell in contact with a target, it can calculate the number of samples or contacts with the target in order that, during the second revolution, it can trigger the explosive charge after half the num
Bofors AB
Connolly Bove Lodge & Hutz
Nguyen Son T.
Poon Peter M.
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