Abstract:
An explosive matrix includes a grid structure formed from a single length of detonating cord with one set of spaced-apart detonating cord sections lying in one plane that perpendicularly overlays a second set of spaced-apart sections lying in a second plane such that at each section crossing location the crossing consists of no more than two perpendicular sections of detonating cord. A tool for forming the matrix includes a frame comprising four side members, each having identical castellated edges in which are defined a plurality of notches for receiving a section of detonating cord.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. application Ser. No. 13/786,682, filed Mar. 6, 2013. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates generally to detonating cord, and more particularly to explosive assemblies formed from detonating cord, and further, to explosive assemblies forming a grid from detonating cord, and still further to a tool for forming such explosive assemblies. 
         [0004]    2. Description of the Problem and Related Art 
         [0005]    The general concept of using detonating cord to make an explosive matrix as an explosive counter charge is well known, as exemplified by U.S. Pat. Nos. 2,455,354; 3,242,862; 4,768,417; 5,437,230; and 6,182,553; and by the U.S. Navy&#39;s Distributed Explosives Technology, described in “Distributed Explosive Technology (DET) Mine Clearance System (MCS) Ex 10 Mod 0 Program Life Cycle Cost Estimate for Milestone III” (Jun. 4, 1999). These prior designs were created for large military applications. Such applications require significant manpower and financial resources. These prior art explosive matrices must be manufactured well in advance of their usage. Field assembly is not practical because they are a complex of multiple lengths of detonating cords joined together. Moreover, due to cost, complexity and time of manufacturing, these prior art explosives matrices have been infeasible for commercial use as a blasting charge. In addition, these prior art explosive matrices are heavy and cumbersome to transport. They use rope or cord to hold the detonating cord together, creating undesirable bulk and weight. 
         [0006]    Another shortcoming of these matrices results from the fact that detonating cord detonates linearly from the point of initiation, proceeding therefrom along the cord. Consequently, detonating cord can fail to propagate the detonation wave where the cord makes sharp turns, especially when large grain detonating cord is used. In some prior art designs, in order to assure sufficient transfer of the detonating wave between intersecting cords, clamps were used at all points of intersection of detonating cord. This adds further complexity and bulk to these prior art designs. 
         [0007]    On the other hand, use of low grain non-propagating detonating cord is not always possible in prior art explosive matrices. Some prior art devices initiate at one point, in one direction, and use multiple lengths of detonating cord coupled together, which compromises reliability. To increase reliability, other explosive matrices incorporate multiple initiation points and multiple lengths of detonating cord, again making the design more complex and the assembly more complicated and expensive. 
         [0008]    A later example that addressed many of these shortcomings is taught in U.S. Pat. No. 7,913,624 to the inventor hereof, wherein the explosive matrix assembly permits the construction of explosives counter charges which are more efficient, safer and less costly than the above mentioned prior art explosive matrices. It is typically assembled from a single length of detonating cord formed into a grid-like matrix pattern, and a small number of cable ties and or tape are required to force the detonating cord into 90 degree angles and to hold the assembly together. However, the detonating cord must be forced into position, which may be made easier with a field assembly tool, but the design of the field assembly tool sometimes creates less than perfect right angles throughout the matrix assembly. Furthermore, due to the geometric design of the grid, the matrix will always have intersections that consist of four over-laid sections of detonating cord, while two of the outer sides will always have three over-laid sections of detonating cord. This makes the charge non-uniform. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
           [0010]      FIG. 1  illustrates two options for an exemplary embodiment of an explosive matrix assembly using a single length of detonating cords as disclosed herein; 
           [0011]      FIG. 2  illustrates an exemplary embodiment in which two or more explosive matrix assemblies may be fastened together; 
           [0012]      FIG. 3  depicts a one side member of an exemplary tool useful for forming an explosive matrix assembly as disclosed herein; 
           [0013]      FIG. 3A  is an end view of an exemplary side member comprising two identical members slidingly engaged with one another; 
           [0014]      FIG. 4  depicts assembly of an exemplary tool useful for forming an explosive matrix assembly as disclosed herein; 
           [0015]      FIG. 5  depicts an exemplary side member comprising two slidingly engaged members showing an exemplary embodiment of an adjustably extendable side member; 
           [0016]      FIG. 6  depicts assembly of an exemplary tool useful for forming an explosive matrix assembly as disclosed herein comprised of the exemplary side members for  FIG. 5 ; 
           [0017]      FIG. 7  depicts another exemplary embodiment of an explosive matrix assembly as disclosed herein; 
           [0018]      FIG. 8  depicts yet another exemplary embodiment an explosive matrix assembly as disclosed herein; 
           [0019]      FIG. 9  is a perspective view of the embodiment depicted in  FIG. 8 ; 
           [0020]      FIG. 10  shows another exemplary embodiment of an explosive matrix assembly as disclosed herein; 
           [0021]      FIG. 11  illustrates yet another exemplary embodiment of the explosive matrix assembly as disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The various embodiments of the disclosed explosive matrix and their advantages are best understood by referring to  FIGS. 1 through 11  of the drawings. The elements of the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. Throughout the drawings, like numerals are used for like and corresponding parts of the various drawings. 
         [0023]    Furthermore, reference in the specification to “an embodiment,” “one embodiment,” “various embodiments,” or any variant thereof means that a particular feature or aspect described in conjunction with the particular embodiment is included in at least one embodiment. Thus, the appearance of the phrases “in one embodiment,” “in another embodiment,” or variations thereof in various places throughout the specification are not necessarily all referring to its respective embodiment. 
         [0024]    This invention may be provided in other specific forms and embodiments without departing from the essential characteristics as described herein. The embodiments described above are to be considered in all aspects as illustrative only and not restrictive in any manner. The following claims rather than the description below indicate the scope of the invention. 
         [0025]    Referring to the drawings,  FIG. 1  depicts a preferred embodiment of the explosive matrix assembly  1 . The explosive charge is provided by a single length of detonating cord  2  that is configured into a first set of at least three parallel straight portions  3  lying in a first plane. There are equal spaces  4 , which can altered in size depending upon the desired size of the overall matrix assembly, but will always be equal to each other within the same explosives matrix assembly, separating the straight portions from each other. The detonating cord is further configured so that there is a second set of at least three more parallel straight portions  5  that are perpendicular to the first set and lying in a second plane. The second set of straight portions  5  are spaced in a manner similar to the first set of straight portions  3 . At one end of each parallel straight portions  3 ,  5  of detonating cord, there is a looped portion  11 . 
         [0026]    In one embodiment, the detonating cord  2  is further configured so that two ends of the detonating cord,  6   a  and  6   b,  are fastened together with ties or tape  7  to form a closed loop  8 , or as depicted in Option  2 , looped back such that the ends  6   a  and  6   b  meet and abut one another. This arrangement may be secured with sheet tape or polyethylene foam sheets  22 , as depicted in  FIG. 7  secures the closed loop. 
         [0027]    The explosive initiator  9  can be attached to the detonating cord  2  at any point within the explosives matrix assembly  1 . In a preferred embodiment, each of the first and second sets comprises an odd number of parallel straight portions  3 ,  5 . The reason for the odd number of parallel straight portions is so that a single looped portion  10  of detonating cord may run between the two sets of parallel detonating cords at a point that is diagonally across from the looped ends  6   a  and  6   b  that are secured to each other. 
         [0028]    Typically, the perimeter of each explosive matrix assembly  1  roughly defines a rectangular panel, the maximum size of which may be made according to the intended function, the minimum size dependent upon the limited flexibility of detonating cord  2 . Alternatively, in the event a larger explosive matrix  1  is desired, assembly panels may be joined together. For example, if the explosive matrix must cover a larger surface area, two or more explosive matrix assemblies are secured to one another by cable ties  12 , as depicted in  FIG. 2 . All explosive matrix assembly panels  1  are secured to one another can be initiated by the same initiator as would be appreciated by those skilled in the relevant arts. 
         [0029]    The first step in deploying the claimed invention is for the explosives technician to decide how large an explosive matrix  1  area is needed to completely cover the surface area required. If the surface area required is greater than the surface area of a single explosives matrix assembly  1 , a sufficient number of explosive matrix assembly panels  1  may be made and secured to one another by additional cable ties  12  as depicted in  FIG. 2 . 
         [0030]    The explosives technician determines the N.E.W. of the counter charge needed to perform the explosives work required. The N.E.W. of the matrix charge is based on the area of the matrix charge and detonating cord grain weight. Charts or diagrams may be prepared to provide users of the matrix tool detailed information on the assembly of the matrix charge, the amount of detonating cord needed for a specific size matrix charge, and the N.E.W. for the matrix charge based on the grains per foot of detonating cord and the areal size of the matrix charge. 
         [0031]    In order to quickly and conveniently assemble the explosive matrix  1  in the field, an assembly tool  21  may be provided, as shown in  FIGS. 3 through 6 . The assembly tool  21  is designed so that it may be carried disassembled to the place where it will be used to deploy the matrix  1 . An exemplary assembly tool  21  may include four or eight substantially identical side members  13 , an example of which is illustrated in  FIG. 3 . In the illustrated embodiment, each of the side members  13  comprises an elongated member having at least one castellated edge  28  along a long edge defining a set of recesses  15  and interstitial tabs  22 . The castellated edge  28  should define at least three, and preferably six, or more recesses  15 , each of which are dimensioned to receive and engage detonating cord and accommodate the diameter of the cord. 
         [0032]    In the illustrated embodiment, the side member  13  terminates in a protrusion  16  extending from one end  30 , with the opposing end  31  including a cut-out  17  defined perpendicularly to the long axis of the side member  13 . The cut-out  17  is dimensioned to snugly receive the protrusion  16  comprised in a second side member  13 . Bore holes  29   a  are defined through the protrusion  16  and corresponding bore holes  29   b,  are defined in the walls defining the cut-out with the end most holes opening to the outer end of the member  13 . As illustrated in  FIG. 4 , the tool  21  may be assembled by fitting the protrusion  16  of a first member  13  into the cut-out  17  of another such that the corresponding bore holes  29   a,    29   b  align. Fastener pins  14  may then be inserted into the aligned bore holes  29   a,    29   b  from the open outer thereof, thus fastening one end of one member with a counterpart end of a second member, forming a right angle. Assembly of the members  13  is repeated in this manner until a generally rectangular loom results with the castellated edges oriented away from the center of the tool shape. See  FIG. 4 . It will be appreciated that the ends of the members  13  may be fastened together in any suitable manner to form a secure perpendicular connection, including lap joints, hinged couplings, etc. Additionally, although bore holes  29   a,    29   b  are depicted in the exemplary embodiment in corresponding pairs, more or less holes may be used. 
         [0033]    In another embodiment, each side member  13  may comprise two parallel side members,  13   a,    13   b  slidingly engaged with one another with their corresponding castellated edges  28  oriented in the same direction. The sliding attachment of the two members  13  may be accomplished by any suitable means known in the art. For example, with reference to  FIG. 3A , one member  13  is paired with another member  13 , using a sliding dovetail joint  18  to form a sliding pairs  20  with one member  13   a  having an elongated dovetail slot  18   a  lengthwise defined in a planar surface and the second member  13   b  having an elongated dovetail pin  18   b  extending from the opposing surface thereof. As depicted in  FIGS. 5 , and  6 , the sliding pairs  19  may be assembled in the manner described earlier creating an adjustable assembly tool  21  facilitating the formation larger explosives matrix assemblies. 
         [0034]    Once the matrix tool  21  is assembled it may be used to assemble the explosive matrix  1 , by weaving a length of detonating cord  2  on the tool by inserting the cord into a first recess  15 , stretching the cord across the tool and inserting the cord  2  into an opposite second recess  15 , bending the cord around the adjacent interstitial tab  22  to insert into a third recess  15  adjacent the tab  22 , and so on until the form depicted in  FIG. 1  is complete. The matrix  1  grid is complete with end  6   b  back at the starting point. 
         [0035]    Once the grid is complete, ties or tape  7  are used to hold ends  6   a  and  6   b  together in a closed loop  8 , or abutted together and secured with adhesive sheet tape, or, for example, polyethylene foam sheets  23  with one surface coated with an adhesive which is place on either side of the grid and then pressed together to bond the grid  1  and sheets  23  together, as shown in  FIG. 7 . 
         [0036]    The tool may be removed from the completed matrix assembly  1  by removing the fasteners  14  allowing the matrix assembly  1  to slide off the assembly tool. 
         [0037]    In yet another alternative embodiment, the explosives matrix assembly  1  may be combined with a plurality of point explosives  24 , such as sheet explosives, as shown in  FIG. 8  and  FIG. 9 . The explosives matrix assembly  1  only needs to be of sufficient strength to initiate the point explosives  24 . Because the point explosives  24  are the effective explosives charge, not the explosives matrix assembly  1 , a lower grain of cord  2  may be used. Using the matrix assembly  1 , point explosives  24  are placed at the points in the matrix assembly  1  where lengths of detonating cord  2  cross. Initiation of the detonating cord  2  will result in substantially simultaneous initiation of the the point explosives  24  creating a shotgun effect with the point explosives  24 . Thickness, weight, size, and type of the point explosives  24  may vary depending upon the needs of the explosives work to be done. 
         [0038]    Yet another embodiment employs the explosives matrix assembly  1  to initiate insensitive blasting agents  25 , such as ANFO (Ammonium Nitrate and Fuel Oil) in place of primers, as shown in  FIG. 10 . By using the explosives matrix assembly  1  to initiate the blasting agents  25 , the critical diameter of the blasting agent  25  can be reduced below its normally accepted critical diameter without a low order detonation. If a greater surface area of the charges is desired or required, matrix assembly  1  panels may be connected together using cable ties or tape  12 , as described above. All explosive charges so secured to one another can be initiated by the same explosives initiator  9 . 
         [0039]    In a further embodiment and with reference to  FIG. 11 , the explosives matrix assembly  1   e  may be connected with other matrix assemblies  1   j,  e.g., attaching at least three panels, and preferably five or six panels, in a mutually perpendicular shape, i.e., a cube  27 , advantageous as an explosives device  26  disruption charge (render safe) to defeat electronic switches and power sources, as shown in  FIG. 11 . A low energy detonating cord  2  may be employed in this example. The explosives device  26  is either placed in the cube  27  or the cube  27  is placed over the explosives device . All explosive matrix assemblies  1  so secured to one another can be initiated by the same explosives initiator  9 . 
         [0040]    As described above and shown in the associated drawings, the present invention comprises an explosive matrix assembly. While particular embodiments of the invention have been described, it will be understood, however, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is, therefore, contemplated by the appended claims to cover any such modifications that incorporate those features or those improvements that embody the spirit and scope of the assembly.