GB2522413A

GB2522413A - Improvements in or relating to shaped charges

Info

Publication number: GB2522413A
Application number: GB1401039.1A
Authority: GB
Inventors: Roland Alford; Sidney Alford
Original assignee: Alford Research Ltd
Current assignee: Alford Research Ltd
Priority date: 2014-01-22
Filing date: 2014-01-22
Publication date: 2015-07-29
Anticipated expiration: 2034-01-22
Also published as: GB2522413B; FI130391B; FI20155049L; GB201401039D0

Abstract

A user-fillable shaped charge (110) comprises: a main container (115) for receiving main explosive material (125) and a projectile (120); and an auxiliary container (130) for receiving auxiliary explosive material (145) and an initiator (135). The auxiliary container (130) is connectable to the main container (115) to allow initial detonation in the auxiliary explosive material (145) to propagate to the main explosive material (125) and cause formation of the projectile (120). The charge (110) comprises a wave shaper (160) for controlling the initial detonation propagation across the interface (155) between the auxiliary explosive material (145) and the main explosive material (125), to improve the efficiency and/or accuracy of projectile formation in use.

Description

IMPROVEMENTS IN OR RELATING TO SHAPED CHARGES

The present invention relates generally to shaped charges. which are explosive charges shaped to focus the effect of an explosive's energy, and particularly to user-filled shaped charges in which a user is required to perform some assembly and/or explosives loading step prior to use.

Shaped charges are used for a variety of purposes, including explosive ordnance disposal, armour penetration and ground penetration.

One known type of shaped charge is shown in Figures 1 and 2. The charge 10 has a cylindrical main container 15 which houses a conical metal liner 20 and "front" explosive 25. The charge also has a separate auxiliary container 30 which is conical and receives a detonator 35 at its narrow end (which terminates with a tubular section 40). The container 30 is filled with "rear" explosive 45. The auxiliary container must be joined and connected to the main container, which in this case is done using a screw-threaded consolidation ring 50. As a result of the two containers 15, 30 joining together the front and rear explosive will contact along the joint line or interface 55.

In use the charge 10 is initiated by the detonator 35 so that an explosive wave front will propagate through the rear explosive material. The advancing wave front must necessarily cross the interface 55 between the rear and front explosive materials 25, 45. Once the wave passes into the front explosive material 25 the pressure generated by detonation of the explosive drives the liner 20 inward to collapse upon its central axis. The resulting collision fonns and projects a high-velocity jet of metal particles forward along the axis.

In Figure 1A the pattern of the detonation front for a conventional shaped charge is shown. This illustrates how the detonation wave front 12, as it impinges on the projectile cone 20, is moving roughly parallel to it.

In order to achieve the highest accuracy and efficiency of jet formation the advancing detonation wave must propagate evenly through the main explosive. However, it is known that the horizontal joint line 55 behind the liner 20 often has discontinuities i.e. the interface is often incomplete. This results is a reduction in the efficiency with which the jet is formed and the accuracy of the resulting projectile. Furthermore, the charge 10 has a large volume behind the liner 20 so it has a very tall profile.

The present invention seeks to address the problems with known shaped charges.

According to the present invention there is provided a user-fillable shaped charge, comprising: a main container for receiving main explosive material and a projectile; and an auxiliary container for receiving auxiliary explosive material and an initiator; the auxiliary container being connectable to the main container to allow initial detonation in the auxiliary explosive material to propagate to 1 5 the main explosive material and cause formation of the projectile, in which the charge comprises a wave shaper for controlling the initial detonation propagation across the interface between the auxiliary explosive material and the main explosive material whereby to improve the efficiency and/or accuracy of projectile formation in use.

The wave shaper, which may also be referred to as a track plate, is inserted within the explosive material for the purpose of modifying the path of the detonation wave as it advances from the auxiliary container into the main container. The present invention uses the wave shaper to control the propagation of the wave front across the interface and into the main container. This can be used to help form a more uniform interface region between the two bodies of explosive.

It has been found by the inventors that using the wave shaper allows less explosive to be used and also improves jet formation.

In order to gain the optimum performance from a cone of any angle, the wave shaper may be adapted to cause the detonation front to be travelling generally normal to the surface of the cone.

The projectile may be formed by a liner. A typical device may consist of a solid cylinder of explosive with a metal-lined conical hollow in one end and a central detonator at the other end.

Explosive energy is released directly away from (normal to) the surface of an explosive, so shaping the explosive will concentrate the explosive energy in the void.

The liner may be conical, for example with an internal apex angle of 40 to 110 degrees. Other possible shapes may include hemispheres, tulips, tmmpets, ellipsoids, and bi-conics. The various shapes yield jets with different velocity and mass distributions.

A projectile-forming liner may be formed from any suitable material, including various metals, metal alloys and glass. Very deep penetrations can be achieved with a dense, ductile metal, and a very common choice for this purpose is copper.

The main and auxiliary explosive charge materials may be the same or different. A high explosive material with a high detonation velocity and capable of generating high pressure may, for example, be chosen for the auxiliary and/or main explosive material. In some emdiments plastic explosive material may be used. Plastic explosive is a soft and hand-mouldable solid form of explosive material.

One issue when using a wave shaper in a device which is intended to be assembled by an end-user is to ensure that the wave shaper is correctly positioned. For this purpose the main container and/or the auxiliary container and/or the wave shaper comprise locating means for locating the wave shaper in a required position within the charge. The locating means may locate the wave shaper in a required position and orientation relative to the main container.

In some embodiments the locating means may comprise one or more ribs provided on or by the auxiliary container. Additionally or alternatively the locating means may comprise one or more prongs provided on or by the wave shaper.

The wave shaper may be formed from material which impedes an initial detonation wave front so as to cause that portion of the wave front which passes around it to reach the interface before that which passes through it.

The wave shaper may provide for initial detonation propagation of a wave front which is generally radially symmetrical. In some embodiments a leading wave front which is generally annular is formed.

The wave shaper may fom a radially symmetrical initiation pattern, although it need not be simultaneously initiated all around. Embodiments which having different initiation timings around the periphery of an EFP may be used to produce canted or veined projectiles which are spin stabilised.

The wave front formed by the wave shaper may be generally normal to the cone axis.

The wave shaper may be a body such as a disc or cylindrical block.

The wave shaper may be fluted.

Tlie wave sliaper may be formed from an inert material such as solid or foamed plastic. In some embodiments the wave shaper comprises or includes metal, such as aluminium. The wave shaper may be solid or hollow; laminar structures (for example a metal layer encased in or sandwiched between plastics material) may be used.

The main container and/or auxiliary container may be formed from plastics material, such as polypropylene, polyethylene or ABS. Other suitable materials for the container/s may include metal, metal alloys or high density foam.

The main container and auxiliary container may be connectable together with a screw-threaded consolidation ring.

The charge may be generally cylindrical.

It has been found by the inventors that charges with a significantly lower profile can be formed as a result of the wave shaper. For example the rear wall of the auxiliary container may be substantially flat.

The auxiliary charge may be initiatable with a detonator.

In some embodiments the charge is configured so that the wave shaper may be receivable in the auxiliary container for fitting as a unit to the main container. In other embodiments the charge is configured so that the wave shaper may be receivable in the main container in advance of fitting the auxiliary container.

The wave shaper may be formed as a composite of two or more interlocking elements which are located and aligned by the charge containers. This gives the ability to tune the charge to give different performance or to work with different types of projectile e.g. different angles. This would allow a charge to be tuned for, example, ground or metal penetration. This could also allow, for example for the size and/or shape and/or thickness of the shaper to be varied, by including more or less elements.

If the back of the auxiliary container is itself formed as a track plate, it may not be necessary in all cases to have the ancillary explosive filling the whole rear of the charge. For example, radiating strips of explosive may be used in the auxiliary container to give simultaneous initiation at multiple points around the periphery of the charge rather than all around it.

Different aspects and embliments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims.

The present invention will now be more particularly described, by way of example. with reference to the accompanying drawings, in which: Figure 1 is a section of a known shaped charge; Figure 1A is a schematic section of the charge of Figure 1 illustrating an advancing wave front; Figure 2 is an exploded view of the charge of Figure 1; Figure 3 is a section of a shaped charge formed according to an embodiment of the present invention; Figure 4 is an exploded view of the charge of Figure 3; Figure 5 is a perspective view of one end of the charge of Figures 3 and 4 during assembly; Figure 6 is a perspective view of the charge of Figure 3 following assembly of a wave guide; Figure 7 schematically illustrates the charge of Figure 3 when filled; Figure 7A is a schematic section of the charge of Figure 7 illustrating an advancing wave front; Figure 8 is a section of a charge formed according to a further embodiment; Figure 9 is an exploded view of the charge of Figure 8; Figure 10 is a perspective view of an auxiliary container as a wave shaper is fitted; Figure 11 is a perspective section showing the auxiliary container of Figure 10 fitted with the wave guide and a detonator; Figure 12 is a perspective view showing an auxiliary container and a wave shaper formed 1 5 according to an alternative embodiment; and Figure 13 is a perspective view of the auxiliary container of Figure 12 shown with the wave shaper partially fitted.

Referring first to Figures 3 and 4 there is shown a shaped charge generally indicated 110. The charge 110 has a cylindrical main container 115 which 115 houses at one end a conical metal liner 120 and behind it a filling of main explosive 125, which in this embodiment is a plastic explosive material.

The container comprises a cylindrical sidewall 116 that is open at both ends. One end of the sidewall 116 terminates with a flange 117 that extends radially inwards to form a step on which the wide end of the liner 120 rests. In addition, around the exterior of that end three spaced attachment lugs 118 are provided for the purpose of allowing the charge to be secured to a surface (e.g. the ground or a wall) using fixings (such as screws. bolts and the like).

The other end of the container is provided with an external screw thread 119.

The charge 110 also has a separate auxiliary container 130. The container 130 is a truncated cylindrical shape. with a cylindrical sidewall 131 open at one end and at the other end closed by a back plate 132 with a central upstanding tubular section 133 extending from a central aperture 134. The section 133 receives an initiator 135. The free end of the sidewall 131 terminates with a flange 136 which extends radially outwardly.

The container 130 is user-filled with auxiliary explosive 145.

The charge further comprises a wave shaper 160. The shaper 160 is a generally disc-shape body 161 formed from a plastics material. In this embodiment the shaper includes three prongs 162 which extend radially outwards to an extent that they just fit inside the main container sidewall 116.

As illustrated in Figures 5 and 6, to fit the shaper it is pressed into the main explosive material 125. The prongs 162 are pushed into the main explosive material. Because of the radial extent of the prongs, when the shaper is pushed down it must necessarily be located in a required position relative to the container, as determined by fit of the prongs within the sidewall 116.

In this embodiment this means that when the shaper is fitted into the container 115 the bcdy 161 is centrally located with great accuracy. In practical tenns this means that a user does not need to be concerned about accurate placement of the body 161 within the charge; it will always be located in the desired position. After placement of the shaper 160 further explosive material is loaded behind the shaper.

The auxiliary container 130 is now ready to be fitted onto the main container 115. The container is presented to the container 115 with the body 161 facing towards it and thereafter as the containers are pressed together the body 161 will be pressed into the auxiliary explosive material 145.

The auxiliary container 130 is connected to the main container 115 using a screw-threaded consolidation ring 150. The ring includes a cylindrical sidewall 146 with an internal screw thread 147 and at one end a flange 148 extends radially inwards. The auxiliary container sidewall 131 has a diameter slightly less than that of the main container sidewall 116, but the sidewall flange 136 is of an extent so that in use it can rest on top of the screw threaded end of the sidewall 116.

This means that in use the auxiliary container can be placed onto the main container and then the ring 150 can pass down over the sidewall 131 until the screw threads 119, 147 engage when the ring is rotated. Thereafter the ring 150 is rotated until the ring flange 148 abuts against the sidewall flange 136. This helps to ensure that the containers are pressed tightly together and helps with forming a gcod interface between the main and auxiliary explosive materials. A thin layer of auxiliary explosive material will remain under the body 161. In this embodiment the materials 125, 145 are the same, both being a plastic explosive.

As shown best in Figure 7. as a result of the two containers 115, 130 joining together the main and auxiliary explosives are pressed together and will contact along an interface 155. It will also be seen that the shaper defines an annulus of auxiliary explosive material which is not subjected to its shielding effect upon detonation.

In use the charge 110 is centrally initiated by the detonator 135 so that an explosive wave front will propagate through the auxiliary explosive material 145. However, the shaper 160 acts to shield the explosive material from sympathetic detonation long enough for an annulus of explosion to foim and propagate across the explosive material interface so that a radially symmetrical detonation wave front is initiated in the main explosive material.

Thereafter the charge functions in a very similar way to the prior art charge in that once the wave passes into the main explosive material the pressure generated by detonation of the explosive drives the liner inward to collapse upon its central axis. The resulting collision forms and projects a high-velocity jet of metal forward along the axis.

In Figure 7A the pattern of the detonation front for the shaped charge with a wave shaper is shown. This illustrates how the detonation front 112, as it impinges on the projectile cone 120, is moving almost normal to the surface (rather than parallel to it). This is more efficient as it drives the cone inwards rather than downwards.

By incorporating the wave shaper and providing for its accurate placement the charge provides an increase in the efficiency with which the jet is formed and the accuracy of the resulting projectile.

Furthermore, the charge 110 has a much reduced volume behind the liner 120 so it has a much shorter profile. A reduction of the explosive load of approximately 20-25% may be achieved.

Referring now to Figures 8 and 9 there is shown a charge 210 formed according to an alternative embodiment. The charge 210 is similar to the charge 110, with the main difference being the auxiliary container.

In this embodiment the back plate 232 is provided with a plurality of "spoke-like" upstanding ribs 233 which extend radially outwards. Each rib is generally L-shape, having an elongate main body 234 terminating with a truncated leg 236.

The container 230 is partially filled with auxiliary explosive 245. Subsequently the wave shaper 260 is pressed into the explosive. The shaper 260 is a generally disc-shape body 261 formed froin a material which prevents transmission of initiation, which in this emlxxiliment is a plastics material. The body 261 is seated onto the ribs, lying on the bodies 233 and within the legs 236 so that the location and orientation of the body 261 is predeternñned and fixed relative to the container 230.

Unlike the charge 110, therefore, in this embodiment the shaper 260 itself does not include any locating/orientating features, as in this erndirnent this function is provided by the ribs 233. This means that when the shaper is fitted into the container the body is centrally located with great accuracy. In practical terms this again means that a user does not need to be concerned about accurate placement of the body 261 within the container 230; it will always be located in the desired position. After placement of the shaper 260 further auxiliary explosive material 245 may be "buttered" around the body 261.

The auxiliary container 230 is now ready to bg fitted onto the main container 115. The container 230 is present to the container 215 with the body facing towards the main explosive material and thereafter as the containers are pressed together the annulus of auxiliary explosive material around th2 p2riphery of the body will be pr2ssed against ±2 main explosive material 225 to form a continuous interface.

1 5 The charge 210 functions in a very similar way to the charge 1 10. In use the charge 210 is centrally initiated by the initiator 235 so that an explosive wave front will propagate through the auxiliary explosive material 245. Th shaper 260 acts to shield tiw explosive material from sympathetic detonation long enough for an annulus of explosion to fomi and propagate across the explosive material interface 255 so that a radially symmetrical detonation wave front is initiated in the main explosive material 225. Once the wave passes into the main explosive material the pressure generated by detonation of the explosive drives the liner inward to collapse upon its central axis. The resulting collision foims and projects a high-velocity jet of metal forward along the axis.

As shown in Figures 12 and 13, a wave shaper 360 may be formed as a composite of two elenwnts 363, 364 which ar located and aLigned by the auxiliary charge container 330. The element 363 is a disc, whereas the element 364 is a ring which fits tightly around the element 363. The elements are formed from the same material but in other embodiments different materials may be used.

When compared to the ribs 333 of the charge container 230, to accommodate the elements 363, 364 the ribs 360 of the back plate 332 are formed with an additional step 337 which allows the element 363 to be seated centrally (raised away from the back plate) as shown in Figure 13. The element 364 can then optionally be fitted around the element 363, seated (raised) within the confines of the rib legs 336.

This gives the ability to tune the charge to give different performance or to work with different types of projectile e.g. different angles. This would allow a charge to be tuned for, example, ground or metal penetration.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein 1 5 by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

CLAIMS1. A user-fillable shaped charge, comprising: a main container for receiving main explosive material and a projectile; and an auxiliary container for receiving auxiliary explosive material and an initiator; the auxiliary container being connectable to the main container to allow initial detonation in the auxiliary explosive material to propagate to the main explosive material and cause formation of the projectile, in which the charge comprises a wave shaper for controlling the initial detonation propagation across the interface between the auxiliary explosive material and the main explosive material whereby to improve the efficiency and/or accuracy of projectile formation in use.
2. A charge as claimed in claim 1, in which the main container and/or the auxiliary container and/or the wave shaper comprise locating means for locating the wave shaper in a required position within the charge.
3. A charge as claimed in claim 2, in which the lating means locates the wave shaper in a required position and orientation relative to the main container.
4. A charge as claimed in claim 2 or claim 3, in which the locating means comprises one or more ribs provided on or by the auxiliary container.
5. A charge as claimed in any of claims 2 to 4, in which the lating means comprises one or more prongs provided on or by the wave shaper.
6. A charge as claimed in any preceding claim, in which the wave shaper is formed from material which impedes an initial detonation wave front so as to cause that portion of the wave front which passes around it to reach the interface before that which passes through it.
7. A charge as claimed in any preceding claim, in which the wave shaper provides for initial detonation propagation of a wave front with a generally radial symmetry.
8. A charge as claimed in any preceding claim, in which the projectile is generally cone-shaped.
9. A charge as claimed in claim 8, in which the wave fronf caused by the wave shaper is generally noimal to the cone axis.
10. A charge as claimed in any preceding claim, in which the wave shaper is generally disc-shaped.
11. A charge as claimed in any preceding claim, in which the wave shaper comprises or includes plastics material.
12. A charge as claimed in any preceding claim, in which the wave shaper comprises or includes a metal material.
13. A charge as claimed in any preceding claim, in which the main container and/or auxiliary container are formed from plastics and/or metal material.
14. A charge as claimed in any preceding claim, in which the main container and auxiliary container are connectable with a consolidation ring.
15. A charge as claimed in any preceding claim, in which the charge is generally cylindrical.
16. A charge as claimed in any preceding claim, in which the auxiliary charge is initiatable with a detonator or other initiator.
17. A charge as claimed in any preceding claim, in which the wave shaper is receivable in the auxiliary container for fitting as a unit to the main container.
18. A charge as claimed in any preceding claim, in which the wave shaper is receivable in the main container in advance of fitting the auxiliary container.
19. A charge as claimed in any preceding claim, in which the wave shaper has two or more parts.
20. A charge as claimed in any preceding claim, in which the diameter of the shaper can be varied.
21. A charge as claimed in any preceding claim, in which the wave shaper is fluted.
22. A charge as claimed in any preceding claim, in which initiation occurs at two or more different times within the auxiliary explosive.
23. A charge as claimed in any preceding claim, in which the main and/or auxiliary explosive comprises or includes plastic explosive material.
24. A charge as claimed in any preceding claim, in which the main and auxiliary explosive materials are substantially the same or are different to each other.
25. A charge as claimed in any preceding claim, in which the wave shaper is formed as part of the auxiliary container.
26. A charge substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
27. A charge as claimed in any preceding claims and filled with explosive material.