GB2241307A

GB2241307A - Sabot projectile

Info

Publication number: GB2241307A
Application number: GB8604203A
Authority: GB
Inventors: James Chattley George; Ian Gardner; Robert Wheatley
Original assignee: Royal Ordnance PLC
Current assignee: BAE Systems Global Combat Systems Munitions Ltd
Priority date: 1986-02-20
Filing date: 1986-02-20
Publication date: 1991-08-28
Anticipated expiration: 2006-02-20
Also published as: GB2241307B

Abstract

A penetrator rod for an APFSDS round, having a nose at its front end and at its rear end a formation for attachment of a fin tail, has on its surface along a substantial portion of its length a male screw thread 11 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. The ratio of screwthread pitch to thickness of screwthread turn at the mid-diameter may be greater than 3. The sabot has a complementary female screwthread 13. <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 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.

It is known to secure the sabot on the penetrator by complementary screw threads on these two components.

Projectiles constructed in this way have hitherto been made with generally conventional screw thread forms. Although the performance of such projectiles is satisfactory we have discovered that the performance may be improved by use of a novel construction.

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

By providing a novel penetrator having a screw thread as defined above and a sabot having a complementary screw thread the properties of the round incorporating such a penetrator are improved. The sabot interfaces between the fin and the penetrator. It transmits the propulsion forces, which comprise a combination of axial and angular acceleration forces, from the gun to the penetrator. The screw thread as defined, together with a complementary screw thread on the sabot, is better suited to the transmission of large axial and angular forces. The sabot is generally made of a weaker material than the penetrator and we have found that it is beneficial to reduce the number of stress raising screw thread roots in the sabot thereby distributing stresses between the two components more favourably according to their respective strengths.

The present invention allows the level of stress generated in the roots of the screw threads of both components to be reduced. Furthermore, it aids separation of the sabot from the penetrator since the radial movement of the two components relative to one another is less restricted than with conventional screw threads, by virtue of the fact that there are less contact points which may interrupt separation.

It is preferred that the penetrator rod is any suitable dense material known for use in the art, e.g. a tungsten alloy or a dense steel.

For a conventional screw thread, e.g. as incorporated on known penetrator rods, the ratio of the screw thread pitch to the thickness of the thread turn when measured at the mid-diameter is typically about 2. For penetrator rods according to the first aspect of the present invention the corresponding ratio is greater than 2, e.g. 3 to 4 or more.

The screw thread in the penetrator rod according to the invention 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 sabot may be made of any suitable high strength light material, e.g. one of the materials known in the art for use as sabots, e.g. aluminium or magnesium alloy.

The fin tail may be a known construction, e.g. made of aluminium 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.

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 70 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 the gap between the sabot 3 and the rod 1 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

Claims:

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

2. A penetrator as claimed in claim 1 and wherein the ratio of the screwthread pitch to the thickness of the screwthread turn when measured at the mid-diameter of the penetrator rod is greater than 3.

3. A penetrator as claimed in claim 1 or claim 2 and wherein the thread is of buttress form having thread turns which are steeper at their rear surface facing the fin tail than at their front surface.

4. A penetrator as claimed in claim 1, claim 2 or claim 3 and wherein the diameter of the penetrator rod at its front and rear ends is no greater than the minimum diameter of the rod at its threaded portion.

5. A penetrator having a sabot having a female screwthread complementary to that of the penetrator rod.

Amendments to the claims have been filed as follows Claims: 1. A penetrator for an APFSDS round comprising a rod having a nose at its front end and at its rear end a formation for attachment of a fin tail to be carried by the penetrator in use, the penetrator rod having on its surface along a substantial portion of its length a screw thread such that the ratio of the screwthread pitch to the thickness of the screwthread turr; when measured at the mid-diameter of the screwthread is at least 3.

2. A penetrator as claimed in claim 1 wherein the thread is of buttress form having thread turns whcih are steeper at their rear surface facing the fin tail than at their front surface.

3. A penetrator as claim in claim 1, or 2 wherein the diameter of the penetrator rod at its front and rear ends is no greater than the minimum diameter of the rod at its threaded portion.

4. A penetrator as claimed in any one of claims 1 to 3 wherein the penetrator rod is of tungsten or hard steel.

5. A penetrator as claimed in any one of claims 1 to 3 and having assembled thereto a sabot having a female screwthread closely conforming to that of the penetrator rod.

6. A penetrator as claimed in claim 5 wherein the sabot is of a material less dense then that of the penetrator rod such as aluminium or magnesium alloy.