GB2241309A - Sabot projectile - Google Patents

Abstract

A penetrator for an APFSDS round comprises a rod having a nose at its front end, at its rear end a formation for attachment of a fin tail and, adjacent to its front end, a plurality of circular grooves 43 each formed around the surface of the rod. <IMAGE>

Description

PROJECTILES AND COMPONENTS THEREFOR The present invention relates to projectiles and components therefor particularly for armour piercing fin stabilised discarding sabot (APFSDS) ammunition rounds which are rounds generally fired from a tank gun.

APFSDS projectiles are known and in current military use. They comprise a heavy metal penetrator or sub-projectile having a nose at its front end and carrying fins at its rear end which stabilise the flight of the penetrator and a segmental sabot formed around the penetrator. The sabot permits an increased kinetic energy to be imparted to the projectile but is discarded by breaking up in flight and separating from the penetrator soon after the projectile has left the gun so that the sabot does not cause a drag on the penetrator during flight.

Although the performance of known APFSDS projectiles is satisfactory we have discovered that the performance mayA be improved by use of a novel penetrator.

According to the present invention in a first aspect a penetrator for an APFSDS round comprises a rod having aE nose at its front end, at its rear end a formation for attachment of a fin tail to be carried by the penetrator in use and, adjacent to its front end, a plurality of circular grooves each formed around the surface of the rod.

Preferably, a first of the said grooves is formed in the surface of the nose and a second of the said grooves is formed behind the nose.

Preferably, the grooves are formed forward of the portion of the rod on which the sabot is secured in use.

The depth of the grooves may be between 0.01 and 0.1, preferably from 0.04 to 0.08, times the diameter of the rod where the groove exists. Thus, for a rod diameter of between 20 mm and 40 mm the depth may be between 0.2 mm and 4 mm.

The width of the grooves may be between 0.1 and 10 times their depth, preferably between 0.5 and 3.0 times the depth.

Preferably, each groove has a cross-sectional shape in a plane including the rod axis which has a sloping rear edge relative to the rod axis; the front edge may be perpendicular to the rod axis. These two edges may be joined directly or by a connecting edge parallel to the rod axis, or by a suitable radius.

As described in a copending UK Patent Application of even date by the present applicants the penetrator rod may have along a substantial portion of its length a screw thread such that at the mid-diameter of the screw thread the average space between adjacent thread turns is greater than the average thickness of the thread turns.

By the "mid-diameter" (which is usually approximately equal to the "effective diameter" or "pitch line") of the thread is meant the diameter which is midway between the diameter of the penetrator rod at the crests of the thread turns and the diameter of the rod at the roots of the thread turns.

According to the present invention in a second aspect an APFSDS projectile comprises a penetrator according to the first aspect and a sabot secured on the penetrator by a screw thread complementary to that of the penetrator. The sabot may for example be made of any suitable high strength light material known in the art for use as sabots, e.g.

aluminium or a high strength aluminium or magnesium alloy.

The screw thread of the penetrator rod preferably has at the mid-diameter a thread turn spacing-to-thickness ratio of 1.5, e.g. 2 or more. For example, the pitch of the penetrator screw thread may be approximately four times the thread turn thickness at the mid-diameter. For conventional screw threads this ratio is two.

The penetrator rod screw thread may be of a buttress type, i.e. having (relative to the nose of the penetrator) thread turns which are steeper in axial cross-section at their rear surface facing the fin tail than at their front surface facing the penetrator nose. For example, the thread turns of the penetrator rod may have front and rear surfaces which make angles of 45" and 7" respectively relative to the normal to the penetrator rod axis.

Preferably, in order to reduce stresses further, the diameter of the penetrator rod beyond the threaded portion of the rod at its front and rear ends is no greater than the minimum diameter of the threaded portion, i.e. the diameter at the thread roots. The diameter at the front end preferably tapers to a point to provide the nose.

The nose may comprise a pointed tip.

The fin tail may be a known construction, e.g. made of aluminium or an aluminium alloy which may be attached to the rear end of the penetrator rod by a screw thread joint. The tail may include a known epoxy resin coating.

A charge of tracer material may be embedded in this component.

We have discovered that an APFSDS projectile comprising a penetrator rod according to the invention has improved penetration properties. The grooves assist the rod to penetrate multi-layer armour structures by avoiding excessive bending at the front end of rod when the rod encounters the respective layers, especially if the rod has an oblique angle of incidence.

The penetrator road may be made of any suitable dense material known for use in penetrator rods, e.g. tungsten alloy or a dense steel.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a partly cross-sectional side elevation of an APFSDS projectile; and Figure 2 is an enlarged cross-sectional side elevation of part of the projectile shown in Figure 1.

In the drawings, a projectile comprises a penetrator rod 1 carrying a sabot 3. The sabot 3 comprises three segments or petals (the division between the segments not being shown) held together by bands 5 and 7. The sabot 3 is secured on the penetrator rod 1 by a screw thread joint 9 which is shown enlarged in Figure 2. This joint comprises a male thread 11 on the rod 1 and a female thread 13 inside the sabot 3. The male thread 11 has a buttress type profile, its thread turns making angles of 45" and 7" respectively at their front and rear surfaces to the normal to the axis of the rod 1. The male thread 11 has a 12 turns per inch form (0.305 turns per mm) and the ratio of the spacing between adjacent turns to the thickness of the turns at the mid-diameter is 2.8.The male thread 11 is in fact equivalent to a two-start thread (whose pitch is half the thread turn lead distance) having one thread omitted.

The threads 11 and 13 are separated into two portions by slots 15 and 17 respectively in which is fitted a collar 19. The collar 19 serves to lock the sabot 3 in position on the rod 1.

The rod 1 has a nose 21 and an extruded aluminium alloy fin tail 23 attached to the rod 1 by a screw thread joint 25. The fin tail 23 which has six blades incorporates a known tracer charge 27 which illuminates the flight of the penetrator during use.

The projectile is fitted in the end of a cartridge case 29 containing a charge of propellant (not shown), the cartridge case 29 being crimped into the band 7 which also serves an obturator ring. The band 7 may be made of nylon. A seal 31 is fitted on the sabot 3 behind the band 7. The seal 31 is manufactured as a separate item and, during assembly, is pressed onto the sabot 3 being located thereon by an annular slot 33 in the outer surface of the sabot 3 and a complementary annular flange 35 on the seal 31. The seal 31 is provided to prevent gases generated by burning of the propellant from entering the gap between the segments of the sabot 3 and thereby damaging the sabot 3.

A foam plastics support bush 37 is provided between the rear end of the seal 31, the fin tail 23 and the cartridge case 29 providing padding which protects the rear end of the projectile in the event of accidental mechanical damage, e.g. by dropping.

The diameter of the rod 1 in its unthreaded regions is nowhere greater than the minimum diameter of the portions where the thread 11 exists. At the front end of the rod 1 a nose portion 41 is formed and an annular groove 43 is formed in the outer surface of the rear end of the nose portion 41.

The tip of the nose portion 41 is made of steel.

The rod 1 may be made of a tungsten alloy. The sabot 3 and fin tail 23 may be made of a commercial high strength aluminium alloy, e.g. the alloy having the UK designation DTD5124. The seal 31 may be made of silicone rubber and the bush 37 may be made of expanded polyurethane foam.

Claims (6)

Claims:

1. A penetrator for an APFSDS round comprising a rod having a nose at its front end, at its rear end a formation for attachment of a fin tail to be carried by the penetrator in use and, adjacent to its front end, a plurality of circular grooves each formed around the surface of the rod.

2. A penetrator rod as claimed in claim 1 and wherein a first of the said grooves is formed in the surface of the nose and a second of the said grooves is formed behind the nose.

3. A penetrator rod as claimed in claim 1 or claim 2 and wherein the depth of each of the grooves is between 0.01 and 0.1 times the diameter of the penetrator rod where the groove exists.

4. A penetrator rod as claimed in any one of the preceding claims and wherein each groove has a width between 0.1 and 10 times the depth of the groove.

5. A penetrator rod as claimed in any one of the preceding claims and wherein each groove has a cross-sectional shape in a plane including the axis of the rod which has a sloping rear edge relative to the rod axis.

6. A penetrator rod as claimed in any one of the preceding claims and wherein each groove has a cross-sectional shape in a plane including the rod axis which has a front edge perpendicular to the axis of the rod.

6. A penetrator rod as claimed in any one of the preceding claims and wherein each groove has a cross-sectional shape in a plane including the rod axis which has a front edge perpendicular to the axis of the rod.

Amendments to the claims have been filed as follows 1. A penetrator for an APFSDS round comprising a rod having a nose at its front end, at its rear end a formation for attachment of a fin tail to be carried by the penetrator in use, means positioned between the front end and the rear end for securing a sabot to the rod, and, adjacent to the front end, a plurality of circular grooves each formed around the surface of the rod wherein the depth of each of the grooves is between 0.01 and 0.1 times the diameter of the penetrator rod at the site of the groove.

2. A penetrator rod as claimed in claim 1 wherein the nose is tapered and a first of the said grooves is formed in the surface of the nose and a second of the said grooves is formed behind the nose.

3. A penetrator rod according to claim 1 or claim 2 wherein the grooves are formed forward of the means for securing the sabot to the rod.

4. A penetrator rod as claimed in any one of the preceding claims and wherein each grovve has a width between 0.1 and 10 times the depth of the groove.

5. A penetrator rod as claimed in any one of the preceding claims and wherein each groove has a cross-sectional shape in a plane including the axis of the rod which has a sloping rear edge relative to the rod axis.