Explosive devices

Abstract

An explosive device is provided, containing an explosive formulation or explosive ink, which is capable of being disposed of onto a substrate for the device by well known printing and depositing techniques, such as screen printing, ink jet printing or gravure methods. The formulation contains an ink resin binder, a metal and a non-metal in particulate form where the diameter of the particles is less than 10 μm, such that when the formulation is heated, a reactive output results. The substrate can be chosen from any inert material or alternatively an energetic material for which the formulation provides a means of initiation. Preferred metals are aluminum iron or titanium and non-metals are carbon, silicon, boron or metal oxides such as copper oxide, nickel oxide or molybedenum oxide. Devices according to the invention may take the form of a; pyrotechnic train, initiators, fuseheads, initiators for gas generators, microthrusters, and may form part of a larger system containing energetic materials.

1 . An explosive device comprising a substrate on which one or more explosive formulations is deposited, wherein at least one of the explosive formulations comprises a binder, at least one metal and at least one non-metal, wherein the non-metal is selected from a metal oxide, or any non-metal from Group III or Group IV, wherein the metal and non-metal particles are 10 μm or less in diameter.  
   
   
       2 . An explosive device according to  claim 1  wherein the metal and/or non metal particles are 1 μm or less in diameter  
   
   
       3 . An explosive device according to  claim 2  wherein the metal and/or non-metal particles are 0.1 μm or less in diameter.  
   
   
       4 . An explosive device according to  claim 1  wherein the deposited formulation comprises an insensitive explosive composition having a figure of insensitiveness greater than 60.  
   
   
       5 . An explosive device according to  claim 4  wherein the figure of insensitiveness is greater than 150.  
   
   
       6 . An explosive device according to  claim 1  wherein the metal is selected from aluminium, titanium or iron.  
   
   
       7 . An explosive device according to  claim 1  wherein the non metal is selected from silicon, boron or carbon  
   
   
       8 . An explosive device according to  claim 1 , wherein the metal oxide is selected from copper oxide, molybdenum oxide or nickel oxide.  
   
   
       9 . An explosive device according to  claim 1 , wherein the metal is silicon and the non-metal is boron or carbon.  
   
   
       10 . An explosive device according to  claim 1 , wherein the binder is selected from an ink resin Polyscreen®, Nylobag®, an epoxy resin or urethane.  
   
   
       11 . An explosive device according to  claim 1 , wherein the binder is an energetic binder.  
   
   
       12 . An explosive device according to  claim 11 , wherein the energetic binder is selected from Polyglyn (Glycidyl nitrate polymer), GAP (Glycidyl azide polymer) or Polynimmo (3-nitratomethyl-3-methyloxetane polymer).  
   
   
       13 . An explosive device according to  claim 1 , wherein the binder is present in the range of from 10% to 50% by volume.  
   
   
       14 . An explosive device according to  claim 13 , wherein the binder is present in the range of from 30% to 40% by volume.  
   
   
       15 . An explosive device according to  claim 1 , wherein the substrate is an inert substrate such as polyester, polyimide, paper, PET, polystyrene or ceramic.  
   
   
       16 . An explosive device according to  claim 1 , wherein the substrate comprises a surface of a consolidated explosive material.  
   
   
       17 . An explosive device according to  claim 1  and being in the form of an initiator, wherein the deposited explosive formulation is connected to a heating element, such that, in use, the heating element ignites the explosive formulation.  
   
   
       18 . An explosive device according to  claim 1  wherein the deposited explosive formulation is connected to a heating element and to an explosive material such as, in use, to form an explosive train connecting said heating element with said explosive material.  
   
   
       19 . An explosive device according to  claim 18  wherein the explosive formulation is disposed on the substrate in an elongate pattern having a length which is chosen to provide in use a desired delay time prior to ignition of the explosive material.  
   
   
       20 . An explosive device according to  claim 19  wherein the explosive formulation is disposed on the substrate in a spiral or zig-zag pattern.  
   
   
       21 . An explosive device according to  claim 17  wherein the deposited explosive formulation is disposed on the substrate in a shape such that when it is ignited by a heating element, the explosive formulation burns with an increasing output of energy until the explosive formulation is exhausted.  
   
   
       22 . An explosive device according to  claim 21  wherein the deposited explosive formulation is formed substantially in the shape of a circle, with the heating element located at the centre thereof.  
   
   
       23 . An explosive device according to  claim 21  wherein the deposited explosive formulation is disposed on the substrate in a shape that is substantially a segment of a circle with the heating element located at the apex thereof.  
   
   
       24 . An explosive device according to  claim 1  wherein the substrate has one or more voids and the explosive formulation fills said voids.  
   
   
       25 . A microthruster device comprising an explosive device according to  claim 1 , wherein the substrate has a plurality of voids into which the explosive formulation is deposited, further comprising means for selectively igniting said deposits of the explosive formulation to provide thrust.  
   
   
       26 . A microthruster device, according to  claim 25  wherein the voids have diameters in the range 0.25 mm to 11.0 mm.  
   
   
       27 . An initiator for a gas generator, comprising an explosive device according to  claim 17 , wherein the deposited explosive formulation is connected to a heating element and to a gas generating explosive material, such that, in use, the device forms an explosive train connecting said element with said gas generating explosive material.  
   
   
       28 . An initiator for a gas generator according to  claim 27 , wherein in use the gas generated inflates an air bag located in a vehicle, vessel or flying craft.  
   
   
       29 . An initiator for a gas generator according to  claim 28 , wherein the generated gas actuates a seat belt pre-tensioner to restrain a passenger in a vehicle, vessel or flying craft.  
   
   
       30 . A pyrotechnic device comprising an explosive device according to  claim 1 , wherein the deposited explosive formulation further includes one or more Group 1 or Group 2 metal salts to produce, in use, a coloured light or sound emission.  
   
   
       31 . A method of producing an explosive device comprising the steps of: 
 a) mixing a potion of a binder with at least one metal in the form of particles having a diameter of less than 10 μm;    b) mixing a further portion of the binder with at least one non-metal, wherein the non-metal is selected from a metal oxide, or any non-metal from Group III or Group IV in the form of particles having a diameter of less than 10 μm;    c) mixing together the products of a) and b) to provide an explosive formulation;    d) depositing the formulation so produced onto a substrate; and    e) causing the formulation to dry on said substrate.    
   
   
       32 . A method of producing an explosive device according to  claim 31  wherein the process of deposition in step (d) is by spraying, brushing, dipping or printing.  
   
   
       33 . A method according to  claim 32  wherein printing is achieved by a wet printing method.  
   
   
       34 . A method according to  claim 33  wherein the wet printing method is selected from ink jet, bubble jet, screen printing or gravure.  
   
   
       35 . A method according to  claim 33  comprising loading the explosive formulation into a printing apparatus having a nozzle for spraying a jet of explosive ink.  
   
   
       36 . A method of making an explosive device according to  claim 31 , wherein the device is a microthruster device for use in space apparatus or airborne craft and wherein the substrate has a plurality of voids which are filled with deposits of the explosive formulation.  
   
   
       37 . A method of making an explosive device according to  claim 31 , wherein the device is a gas generator device for use in a vehicle, vessel or flying craft, wherein the substrate in step (d) of  claim 31  is a heating element and wherein the method further comprises the steps of: 
 f) placing a gas generating explosive material in intimate contact with the product of step (d); and    g) placing the product of step (f) within a suitable containment means.    
   
   
       38 . A method of depositing an explosive formulation, including the steps of: 
 a) loading a printing apparatus with a mixture of a binder with at least one metal in the form of particles having a diameter of less than 10 μm and with a mixture of a binder with at least one non-metal, wherein the non-metal is selected from a metal oxide, or any non-metal from Group III or Group IV in the form of particles having a diameter of less than 10 μm such that the at least one metal and/or at least one non-metal mixtures are held separate in the apparatus;    b) drawing up selected aliquots of the at least one metal and the at least one non-metal mixtures and mixing the same in-situ immediately prior to operation of the apparatus to deposit an explosive formulation onto a substrate.    
   
   
       39 . A method of depositing an explosive formulation according to  claim 38  wherein the metal and non-metal particles are 1 μm or less in diameter.  
   
   
       40 . A method of depositing an explosive formulation according to  claim 39  wherein the metal and non-metal particles are 0.1 μm or less in diameter.  
   
   
       41 . An explosive ink comprising an explosive formulation as described in  claim 1 , together with a volatile organic solvent.  
   
   
       42 . An explosive ink according to  claim 41  wherein the volatile organic solvent is selected from a lower alkyl alcohol, ketone or ether or from petroleum ethers ranging from C5 to C10.  
   
   
       43 . An explosive ink according to  claim 41 , wherein the metal and/or non-metal particles are 1 μm or less in diameter.  
   
   
       44 . An explosive ink, according to  claim 43 , wherein the metal and/or non-metal particles are 0.1 μm or less in diameter.