Explosive booster

Abstract

An explosive booster body comprises a receptacle body for receiving and retaining a length of detonating cord in a loop configuration. The receptacle body defines a cavity for introducing boosting exp

Description

The present invention relates generally to a booster: a means of initiating insensitive explosives by means of detonating cord. Detonating cord typical comprises a train of finely powdered high explosive constituting the core of a cord in which it is wrapped by such materials as a strip of paper and two or more helically wound plastics threads or strip. This assembly is usually coated with water-proofing wax or a seamless flexible layer of water and abrasion-proof flexible plastics. The explosive most commonly used for this purpose is pentaerythritol tetranitrate (PETN) but cyclic- trimethylenetrinitramine (RDX) is sometimes used for the imparting of greater thermal stability. The explosive load usually ranges from approximately 1.5g a metre to 100g a metre. Detonating cord most commonly employed in military usage contains 10 or 12g a metre. One of the main applications of detonating cords with light or medium explosive loads is the transmission of a detonation wave from the point of initiation to a multiplicity of explosive main charges either in very rapid succession or simultaneously on the scale of the overall event. Whereas a light load of explosive in the detonation cord suffices for the reliable transmission of the detonation to each of the secondary or main charges, for reason of safety the main charges are almost invariably in both military and non military applications made too insensitive to be initiated by mere contact with the outer sheath or the severed end of the detonating cord. To enable the detonating cord reliably to initiate the secondary, or main, charge or charges it is therefore necessary to use a small intermediate charge, which is made from an explosive material that is sensitive enough to be initiated by the detonating cord to convey the detonation from the detonating cord to the main charge. Such a charge is referred to as a booster and is of such shape and size as enables it to be abutted against the end of an elongate main charge or to be inserted in a cavity provided in the end, or at another convenient point, in the secondary charge. A variety of boosters are currently available, including slip-on boosters, knotted detonating cord and cast boosters. One means of improvising a booster is to form a loop at the terminal end of a length of detonating cord by bending this end back on itself and securing it in this position, thereby defining a loop with a profile approximately in the shape of a teardrop. This elongate space is filled with plastic explosive. Such a configuration provides a reliable means of initiation particularly in applications in which it can be applied to the surface of the main explosive charge or can be surrounded by plastic explosive. At present, constraining the detonating cord in a suitably proportioned loop is most commonly achieved by taping the ends together for a short distance immediately before the cusp of the loop. The present invention seeks to provide improvements in or relating to boosters. It is a purpose of the present invention to provide a means of conveying detonation from a length of detonating cord (also known as detcord) to a main charge without the need of an intermediate charge of primary explosive. An aspect of the present invention provides an explosive booster comprising a receptacle body for receiving and retaining a length of detonating cord in a loop configuration. The receptacle body may comprise a base and a lid. The lid may be detachably attachable to the base; for example the lid may be slidably receivable on the body. The body (for example the base of a two-piece receptacle body) may comprise a spigot. In some embodiments the spigot is hollow for receiving explosive material. The spigot may, for example, be partially pre-packed with explosive material before a loop is introduced; then further packing may follow. The spigot may comprise attachment means for connecting the body to a charge. For example a screw thread formation (e.g. M14 thread) may be provided on the spigot. The body (e.g. a base) may comprises a generally semi-circular portion for receiving the bight of the loop. The body (e.g. a base) may comprise an exit gate for holding the ends of the loop together. In some embodiments the loop booster: i) ensures that the detcord loop is approximately the correct size; and ii) ensures that the two sides of the detcord loop initiate substantially simultaneously. The present invention also provides a loop former booster comprising a plastic moulding which is configured to constrain a length of detonating cord in a loop configuration and prevent expansion thereof, and in which boosting explosive material can be received in the loop whereby initiation of the material can be driven by the cord. Different aspects and embodiments 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. Example embodiments are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein. Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate. The terminology used herein to describe embodiments is not intended to limit the scope. The articles “a,” “an,” and “the” are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and / or “including,” when used herein, specify the presence of stated features, items, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and / or groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein. In the following description, all orientational terms, such as upper and lower are used in relation to the drawings and should not be interpreted as limiting on the invention. Referring first to figures 1 to 6 there is shown a booster generally indicated 10. The booster 10 comprises a base 20 and a lid / cover 30. The base 20 comprises a generally teardrop shape upstanding sidewall 21 with a semi-circular portion 22 at one end and at the other end terminating with a pair of spaced, co-operating pinch members 23a, 23b that together define a loop exit 24. The sidewall 21 upstands from a flange 25. Extending from the “bottom” side of the flange 25 is a hollow spigot 26. The exterior of the spigot is provided with a screw thread 27. The lid 30 comprises an arch-shape top plate 31. Along two sides of the top plate an L-shape, L-section sidewall 32a, 32b portion depends and extends inwards to define a gap 33. The lid 30 is a complementary shape to the base 20 and can be slid onto the base so that the L-shape sidewall portions 32a, 32b engage the base flange 25, with the pinch members 23a, 23b passing through the gap 33. Referring now also to Figures 8 to 11, a length of detonating cord 50 can be introduced into the base, with the semi-circular portion 22 defining / determining / constraining the bight 55 of a loop and the two tales 57, 59 of the loop extending along the sidewall portions 32a, 32b. The base therefore defines the required loop size. At the loop exit 24 the pinch members 23a, 23b serve to hold the ends 57, 59 of the loop together (best shown in Figure 11). In this embodiment the detcord tales are held parallel to each other. In use the spigot 26 is packed with boosting explosive material (e.g. plastic explosive) before the loop is fitted into the base; then further explosive material is introduced into the loop before the cover is fitted. The booster can now be fitted to an explosive charge e.g. by screwing on using the spigot. The previously detcord-insensitive plastic explosive material is rendered sensitive due to the loop. The loop booster: i) ensures that the loop is approximately the correct size; and ii) ensures that the two sides of the loop initiate substantially together. Although only an example has been disclosed herein, other alternatives, modifications, uses and / or equivalents thereof are possible.

Claims

1. An explosive booster body comprising a receptacle body for receiving and retaining a length of detonating cord in a loop configuration, in which the5 receptacle body defines a cavity for introducing boosting explosive material in the loop, whereby, in use, initiation of boosting explosive material can be driven by the cord.

2. A booster body as claimed in claim 1, in which the receptacle body 10 comprises a base and a lid.

3. A booster body as claimed in claim 1, in which the lid is detachably attachable to the base.15 4. A booster body as claimed in claim 3, in which the lid is slidably receivableon the body.

5. A booster body as claimed in any preceding claim, in which the receptacle body comprises a spigot.

206. A booster body as claimed in claim 5, in which the spigot is hollow for receiving explosive material.

7. A booster body as claimed in claim 5 or claim 6, in which the spigot 25 comprises attachment means for connecting the body to a charge.23 01 258. A booster body as claimed in claim 7, in which the attachment means comprise a screw thread formation.5 9. A booster body as claimed in any preceding claim, in which the receptaclebody comprises a generally semi-circular portion for receiving the bight of the loop.

10. A booster body as claimed in any preceding claim, comprising an exit gate 10 for holding the ends of the loop together.

11. A booster body as claimed in any preceding claim, in which the receptacle body is configured such that an inserted loop is approximately the correct size.15 12. A booster body as claimed in any preceding claim, in which the receptaclebody is configured such that the two sides of a loop initiate substantially together.

13. A booster body as claimed in any preceding claim, in which the receptacle body comprise a plastic moulding.2014. A booster charge comprising a booster body as claimed in any preceding claim and fitted with detonating cord and boosting material.13

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