EXPLOSIVE CHARGE
An explosive charge (1) comprising an elongate casing (2) with elongate grooves (3,4) running along the casing, each groove locally reducing the thickness of the casing. The grooves are distributed in two or more groups around the circumference of the casing and the edge-to-edge spacing between each adjacent pair of grooves in a group is less than the edge-to-edge spacing between each pair of adjacent groups. Detonation causes the casing to break at a pair of grooves in one of the groups and form a fragment from material between the pair of grooves, the fragment cutting an obstacle (28).
The present invention relates to an explosive charge, particularly a charge suitable for use in a so-called “Bangalore Torpedo”.
BACKGROUND OF THE INVENTIONA conventional explosive charge is described in WO 2007/099362. The charge has one or more longitudinal concave grooves. Upon explosion, the contour of the groove results in a focussing effect on the wall material. The groove does not reduce the local thickness of the wall of the charge.
Another conventional explosive charge is described in GB-A-2214618. The inner face of the lining is formed with a set of V-shaped grooves interlinked around the axis of the charge. The grooves reduce the local thickness of the lining and result in material being ejected in a plurality of shaped charge jets one from each outward facing V-shaped region of the lining.
SUMMARY OF THE INVENTIONA first aspect of the invention provides an explosive charge comprising an elongate casing with elongate grooves running along the casing, each groove locally reducing the thickness of the casing, wherein the grooves are distributed in two or more groups around the circumference of the casing and the edge-to-edge spacing between each adjacent pair of grooves in a group is less than the edge-to-edge spacing between each pair of adjacent groups.
A second aspect of the invention provides a kit of parts comprising two or more charges according to the first aspect of the invention, each charge having a head end adapted to be coupled to the tail end of an adjacent charge, and a tail end adapted to be coupled to the head end of an adjacent charge.
A third aspect of the invention provides a method of cutting an obstacle using the explosive charge of the first aspect of the invention, the method comprising detonating explosive material in a compartment of the casing, the detonation causing the casing to break at a pair of grooves in one of the groups and form a fragment from material between the pair of grooves, the fragment cutting the obstacle.
In GB-A-2214618 the grooves are distributed uniformly around the circumference of the lining. In contrast, according to the present invention the grooves are distributed non-uniformly around the circumference of the casing so that they are bunched together in two or more groups. The relatively small edge-to-edge spacing between each adjacent pair of grooves in a group results in the generation of high energy fragments which can cut efficiently through an obstacle.
The edge-to-edge spacing between each groove in a group may be zero, but preferably it is greater than zero so that each groove has an edge which is separated from an adjacent edge of an adjacent groove by a non-grooved portion of the casing.
Various other preferred features of the invention are set out in the dependent claims.
Embodiments of the invention will now be described with reference to the accompanying drawings, in which:
An explosive charge 1 shown in
The grooves 3, 4 are separated from each other by a small non-grooved portion 10 of the casing in which the thickness of the casing is substantially constant. The grooves 3, 4 are relatively narrow, as is the width of the non-grooved portion 10 which separates the groove 3 from the groove 4. Specifically, each groove subtends an angle θg1 of only about 4° and the edge-to-edge angular spacing θg2 between the edges of adjacent grooves within a pair is only about 2°. Therefore each pair subtends an angle θg3 between its two outer edges of about 10°, and the edge-to-edge angular spacing θp1 (shown in
The internal wall of the casing is circular in cross-section for ease of manufacture and to maximise the space available for explosive material.
Referring to
The charge is then detonated, causing the casing to break initially at the bases of the eight grooves where the thickness t1 is at a minimum. The casing material between the grooves forms four small pre-defined fragments which are ejected at approximately +/−45° to the vertical. The fragments from the two downwardly pointed pairs of grooves impact the ground and are not shown in
Note that
Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.
Claims
1. An explosive charge comprising an elongate casing with elongate grooves running along the casing, each groove locally reducing the thickness of the casing, wherein the grooves are distributed in two or more groups around the circumference of the casing and the edge-to-edge spacing between each adjacent pair of grooves in a group is less than the edge-to-edge spacing between each pair of adjacent groups.
2. The charge of claim 1 wherein each group of grooves has no more than two grooves.
3. The charge of claim 1, wherein there are no more than four groups of grooves distributed around the circumference of the casing.
4. The charge of claim 2 wherein there are no more than four pairs of grooves distributed around the circumference of the casing.
5. The charge of claim 1, wherein the grooves are distributed in three or more groups around the circumference of the casing
6. The charge of claim 1, wherein the edge-to-edge spacing between each groove in a group is greater than zero, so that each groove has an edge which is separated from an adjacent edge of an adjacent groove by a non-grooved portion of the casing.
7. The charge of claim 6 wherein the average angle subtended by the non-grooved portions at the centre of the casing, when viewed in transverse cross- section, is less than 5°.
8. The charge of claim 1, wherein the average edge-to-edge spacing between the adjacent edges of each groove within a group is less than the average edge-to-edge spacing between the adjacent edges of adjacent groups by a factor of 10 or more.
9. The charge of claim 1, wherein the grooves taper outwardly when viewed in transverse cross-section.
10. The charge of claim 1, wherein the average angle subtended by each groove at the centre of the casing, when viewed in transverse cross-section, is less than 10°.
11. The charge of claim 1, wherein the total angle subtended by the grooves at the centre of the casing, when viewed in transverse cross-section, is less than 90°, preferably less than 60°, and most preferably less than 30°.
12. The charge of claim 1, wherein the casing has an internal wall and an external wall; and wherein the grooves are formed in the external wall.
13. The charge of claim 12 wherein the internal wall is substantially circular in cross-section.
14. The charge of claim 1, wherein the casing has a threaded head end adapted to be coupled to the tail end of an adjacent charge, and a threaded tail end adapted to be coupled to the head end of an adjacent charge.
15. A kit of parts comprising two or more charges according to claim 1, each charge having a head end adapted to be coupled to the tail end of an adjacent charge, and a tail end adapted to be coupled to the head end of an adjacent charge.
16. A method of cutting an obstacle using the explosive charge of claim 1, the method comprising detonating explosive material in a compartment of the casing, the detonation causing the casing to break at a pair of grooves in one of the groups and form a fragment from material between the pair of grooves, the fragment cutting the obstacle.
17. The method of claim 16 further comprising coupling two or more of the charges head to tail; and detonating explosive material in each charge.
Type: Application
Filed: Mar 26, 2010
Publication Date: Apr 19, 2012
Applicant: CHEMRING ENERGETICS UK LIMITED (Stevenston, Ayrshire)
Inventor: Colin Douglas Young (Ayrshire)
Application Number: 13/258,815
International Classification: F42B 3/00 (20060101); F42B 3/02 (20060101);