A frequent requirement of explosive demolition operations is the initiation of a multiplicity of explosive charges either simultaneously or in rapid succession. One means of achieving this is provided by electronic delay detonators, each of which explodes a predetermined time after initiation by an electric pulse. Another is the use of shock tube non-electric detonators with a pyrotechnic delay. Another means of initiation of a multiplicity of charges is by interconnection by means of detonating cord, in which case delays are controlled by varying the lengths of detonating cord to control the time at which the initiation front arrives at an individual charge.

Detonating cord consists of a cord spun from plastics thread and usually clad by a sheath of thermoformed plastics all of which inert components confine a core of powdered explosive, which is most commonly pentaerythritol tetranitrate (PETN). Such cord usually has a diameter between three and six millimetres and an explosive load between five and twenty grams a metre.

A shock tube detonator is similar to a detonator initiated by shock tube except that the firing signal is sent using shock tube instead of detonating cord. Shock tube consists of flexible plastics tubing, typically having an external diameter of only 3mm, with its inner surface lined with a very thin coating of a mixture of a high explosive such as HMX mixed with fine aluminium powder. This is initiated at its proximal end by a relatively small initiating charge, such as a percussion cap, and an explosively generated shock wave travels its length without bursting the tube. The distal end of the shock tube is crimped into the mouth of a detonator which is initiated by the shock wave. The shock wave travelling through shock tube does not have sufficient energy to convey its shock to an adjacent length of shock tube and thus bring about its initiation.

Such detonating cord is reliably initiated either by a detonator which is usually attached to the side of the cord or by means of another strand of detonating cord held in contact with it. In the latter case a single strand of detonating cord can transfer the detonation to a multiplicity of strands of detonating cords suitably attached to it.

Attachment of one length of detonating cord to one or more other strands to which it is intended to convey detonation may be conveniently and reliably accomplished by taping them together using slightly elastic plastics tape, such as is commonly used for bunching and insulating electrical wires, or by means of plastics or metal clips which urge them into contact with each other. The first strand of detonating cord in such a sequence is itself initiated by a single detonator similarly attached.

The application of tape or plastic or metal clips for this purpose depends upon all the explosive components being easily accessible and bare hands being sufficiently agile to apply the tape or other means of attachment with firmness and accuracy. This requirement for dexterity is most difficult in low temperatures and in very wet conditions.

Particular difficulty occurs if the interconnection of detonating cords or shock tube for the initiation of a multiplicity of explosive charges is in a place where manual approach is impossible or unacceptable either because of inaccessibility or because danger of human access. Examples of such situations are the presence of intense radioactivity, dangerous toxins, the possibility of explosion, or a significant probability of premature collapse of a seriously damaged building or other structure following an earthquake or a previous failed attempt at demolition.

In such circumstances all on-site preparations for the demolition may have to be carried out using remote-controlled vehicles (RCVs). The use of such vehicles means that the operator or operators may not be able to see directly the objects to be targeted by the explosive charges but have their vision limited to viewing no more than the images transmitted from cameras carried by the RCVs to computer screens. This remoteness renders impossible the use of tape to interconnect separate lengths of detonating cord.

An additional problem caused by the presence of one or more RCVs is that the usual practice of running lengths of detonating cord, shock tube and electric cables along the ground to one or more groups of explosive charges, each of which is attached to a separate structure to be explosively severed or otherwise deformed, carries the risk of damage of such connecting means by the tracks or wheels of the RCVs. Such damage may be caused by snagging or breaking or by the displacement of one length of detonating cord to such juxtaposition to another strand that it causes severance of the latter but failure to transfer detonation to it.

It is the purpose of the present invention to provide a reliable means of connecting one or more lengths of detonating cord which have been previously attached to each individual charge or group of charges to a common means of their simultaneous initiation after each such charge has been secured to the part of a target upon which they are to function. According to the present invention there is provided a device for common initiation of a multiplicity of explosive devices, comprising a shareable dock to which a plurality of explosively initiatable links (receptors) (see Figure 4) can be attached. The dock comprises or can receive an explosive donor for initiating all attached receptor links in use leading to onward initiation of explosive devices connected thereto.

The "initiator" can be a detonator or other charge (see Figure 3) that initiates the donor and starts the explosive detonation chain. The dock may comprise a panel, for example a generally flat structure. In some embodiments, for example, the dock is formed as a board-like article.

In some embodiments links are attachable to the dock by magnetic means. For example the dock may include a metal grill to which links are attached magnetically in use.

The device may further comprise link attachments for receiving a link and which are attachable to the dock. For example the link attachments may include magnetic means for attaching to the dock. The link attachments may be formed separately from the dock; for example the attachments may comprise carriers into, onto or through which a link is passed so as to be held securely adjacent the dock in use.

In some embodiments the explosive donor comprises a sheet of explosive material. It may, for example, be sandwiched between a back board and a front grill. The receptor links may comprise detonating cord, shock tube or other such means of conducting detonation from one component to another.

In some cases charges may be remotely placed using robots and then connected together using lengths of detonating cord or shock tube.

In some embodiments the present invention is provided in the form of an explosive board into which the ends of detonating cord links are stuck using magnets.

A main board may be made from a piece of wood with magnets on the back to attach it to the target. On the front is a layer of sheet explosive and on top of that is a layer of steel mesh. The detonating cord tails are terminated with a magnetic connector that sticks onto the mesh. A variant has two opposing magnetic pads that self-align to connect two lengths of detonating cord or detonating cord to shock tube It will be understood that detonating cord is shown as a means of conducting detonation from one component to another. Shock tube may alternatively be employed.

In some embodiments the device is deployed and used as follows. A connector device formed in accordance with the present invention is deployed by an ROV and positioned on a target. The connector device is a magnetic board with a steel mesh cover which can be loaded with sheet explosives.

Demolition charges are fitted with detonating cord or shock tube and detonator on the end of which is a magnetic pad.

The charges are positioned and the magnetic pads thereof are then attached to the connector.

The present invention also provides an underwater multi-charge placement system comprising a weighted container for housing a plurality of explosive charges and a shareable dock to which a plurality of explosively initiatable links, which are associated or associable with the charges, are or can be attached, the dock comprises or can receive an explosive initiator for initiating all attached links in use leading to onward initiation of explosive devices connected thereto. In some embodiments the system is deployed in a safe state i.e. there is no initiator connected. For example the container could comprise a box (such as a wooden box filled with concrete). The box houses or holds a dock or "bunch connector" and a magazine of explosive charges. The dock is not connected to an initiator and the charges are not connected to the dock. The container can therefore be deployed safely, for example from the side of a marine vessel such as a boat, so that it sinks to the bottom of a marine environment. In some embodiments such a container is deployed with a line of detonating cord attached to the dock, the line pays out from the boat but is not at that stage connected to a detonator on the boat.

With the sunken container in position an ROV could then pick up a charge and take it to a target. The charge may have detonating cord, shock tube or the like connected to it so that it pays out as the ROV travels out to the target. For example reels of cord may be provided on or by the container (for example by the link). The other end of the cord may be pre-attached to the dock via a link, or the ROV may travel back to the container and attached the link to the dock. If shock tube is used, it can have a tendency to float. In some embodiments lengths of shock tube are pre-fitted with weights, or weights are attached as the shock tube pays out.

When all required charges are in position, at that point the system may be armed. For example the line from the container to the vessel may be connected to an initiator. In some embodiments an acoustic initiation system is used and could be armed once all charges are positioned.

A single initiation event is then used and all of the links on the dock are actuated so that the initiation event is then propagated to each of the charges deployed on targets.

In some embodiments the system is presented as a gravity-driven "clump". The clump could be likened to a toolbox which can be accessed by an ROV. Depending on how the system is configured, the charges are not "live" during transport and deployment and even until after they are all deployed, which can be used to improve safety.

In some embodiments the initiator for initiating the links is situated remotely of the container. For example the initiator may be provided on a marine vessel from which the container is deployed. The initiator may comprise a detonator or the like.

The links may be formed separately of and be attachable to the dock.

The links may be attachable to the dock by magnetic means. One or more magnets may be provided for this purpose.

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 combinations 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.

The example embodiments are described 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 alternative 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. 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, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention.

Referring now to Figures I to 4, the present invention incorporates a plate of rigid material ( I ) which for the sake of convenience may, for example, be rectangular. This is provided with one or more magnets (2). One convenient configuration consists of an array of four, one being located at each corner and located on the side of the plate which is to be placed in contact with the target structure, for example. It will be understood that, for target structures of little or no magnetic susceptibility, the attachment of the pads to the plate may be enabled by the use of a suitable adhesive. Upon the other side of the plate ( I ) is a sheet of explosive donor (3) which may most conveniently have a contour slightly smaller than that of the rigid plate ( I ). Upon the explosive sheet (3) is placed a steel plate which may advantageously bear a multiple array of perforations and thus constitute a grille (4). The three components ( I ), (3) and (4) are held together by four threaded rods (5) which may be made of plastics material and each may be integral with rectangular plastics enclosures (6) containing the magnets (2) on all but one large surface. A nut (7) applied to each threaded rod (5) secures each corner of the array of components ( I ), (3) and (4) and urges each on them into contact with its fellows (this could be replaced by a screw).

The assembly comprising components ( I ) to (7) may conveniently be provided with a projecting handle which enables the assembly to be easily gripped by the jaws of an RCV and offered to a suitable, preferably elevated, point on the structure to be acted upon by the explosive charge or charges to which it attaches itself by means of the array of magnets (2).

As shown best in Figure I , each explosive charge to be initiated simultaneously or in rapid succession (not shown) is attached to a length of detonating cord (8) of which one end serves to initiate the charge, with or without a supplementary explosive booster. The free end of each length of detonating cord (8) is attached to a generally flat plastics component (9) with an elongate groove ( 10) on one side in which a length of detonating cord can be secured by plastic tape and which incorporates magnets ( I I ) - see Figure 4. When this component (9) is addressed by the RCV to the exposed surface of the steel grill (4) it becomes magnetically attached thereunto. When each charge of an array to be initiated is thus individually connected to the grill (4) the assembly is ready for the means of initiation off all charges attached thereunto. Referring to Figure 3, to this end the robotic arm delivers the charge's initiator ( 12) consisting of a plastics moulding which incorporates one or more magnets ( 1 3) and which contains a sufficiently powerful mass of explosive ( 14) to transfer detonation to the sheet of explosive (3) across the metal grille (4).The detonating sheet of explosive (3) in turn transmits detonation back through the metal grille (4) and thus initiates the detonation of each strand of detonating cord (8) which is urged against the surface of the grille (4) and thus brings about the initiation of each explosive charge attached thereunto. The explosive ( 14) within the initiator ( 12) may incorporate an electric detonator or, alternatively, the distal end of a long length of detonating cord to be paid out by the withdrawing RCV or led from the point of initiation by the RCV as it approaches the array of explosive charges for the last time before withdrawal, only when all main charges have been put in position and require no more adjustment before they are detonated. If detonating cord is thus employed it will either be deployed by the RCV back to the point of initiation.

In Figure 5 a connector ( 100) formed according to a further embodiment is shown and includes:

Initiator = detonator or booster assembly that initiates the sheet explosive.

Donor = the sheet explosive in the magnetic board.

Receptor = detonating cord/shock tube link that picks up from the magnetic board and goes to the main charges.

Three lengths of detonating cord ( 108) are shown. Each length is fitted into an open conduit ( 109) on a plastic pad fitted with a strong magnet. When attached to the front steel mesh on the connector the detonating cord is in close proximity to the underlying sheet explosive ( 103), but there is a gap between the two corresponding to the thickness of the grille). A final initiator ( 1 14) is also fitted onto the front of the connector device and when initiated will cause detonation of the explosive sheet/s and onward initiation of the links (and subsequently initiation of main charges attached to a target).

In Figure 6 the connector ( 100) is shown fitted to a target ( 120). Demolition charges ( 1 15) are positioned on the target and detonating cord links extend from the charges to the connector where they are attached using magnetic carriers.

Some advantages of the device and system of the present invention include:

Simplify ROV charge attachment and re-attachment as necessary. - Reduce the total quantity of detonating cord.

By raising all explosive links off of the ground, it will greatly reduce ROV snagging hazards. - Time delay detonators can be fitted for sequential initiation. The connector and detonating cord connections will be visible from outside of the exclusion area.

Figure 7 shows an explosive receptor formed according to an alternative aspect of the present invention.

Each receptor is able to "stick" onto the back of the next one and still be initiated. It is possible thereby to make something consisting of a series of "explosive pucks" (220) that stack up. The receptors need not be round, and may or may not have magnets; for example they could stack on a spigot in order to be aligned.

Figure 8 shows an explosive receptor formed according to an alternative aspect of the present invention.

Two plates (350, 355) are provided and each includes a groove (35 I , 356) into which a length of detonating cord (352, 357) can be pressed and retained. Each plate also comprises a magnet (353, 358) and the opposite side of the plate includes a threaded rod (354, 359) useful for manipulating the plates.

Magnetic polarity can be used to align and position two parallel lines of detonating cord such that one will initiate the other in use.

In Figure 9 a marine vessel (460) is located above a site with two submerged targets A, B.

The vessel (460) carried a clump (465) shown in more detail in Figure 10. The clump (465) comprises a box (470) which is weighted, in this embodiment by concrete blocks (475). The box (470) carries a magazine (480) of charges (481 ). In addition a dock (485) is provided. Attached to the dock (485) are charge links (486) - one for each charge (481 ). The links (486) are connected to their respective charges (481 ) by detonating cord (490), which in this embodiment is provided on reels that can pay out from the links. Attached to the dock is an initiator link (487), which connects to a length of detonating cord 488 that pays out from the vessel. The clump (465) is deployed from the vessel and sinks to the seabed under the weight of the blocks (475) as shown in Figure I I . An ROV (495) can then approach the clump and collect a charge (481 ). The ROV can then travel with the charge to a target A, B and attach the charge thereto. The ROV can then return to the clump and collect another charge for the next target etc.

When all of the charges are placed the cord (488) is then and only then connected to a detonator. When the detonator is activated this causes detonation at the dock, which in turn propagates to each of the attached detonating cords. In turn this therefore causes detonation of the charges on the targets.

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 by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.