This invention relates to a blasting apparatus for blasting a to-be-blasted object such as a concrete construction or a rock base by melting and vaporizing a melting/vaporization a melting/vaporization substance (e.g., metallic fine wire) by supplying electrical energy for a short time and then exploding an explosive blasting substance by a phenomenon of a process accompanying the vaporization.

EP-A-0 872 317 discloses a method comprising a step to form a hole for charging a breaking substance into an object to be fractured, a step to insert a pair of electrodes having a thin metal wire connected between ends thereof into the hole, a step to dispose the breaking substance and the thin metal wire into a bag-like container made of rubber at a stage to supply electric energy accumulated in a capacitor to the electrodes for fusing and vaporizing the thin metal wire, thereby swelling a volume of the breaking substance and breaking the object to be fractured, and a step to fit the bag-like container into the hole. This method assures secure transmission of an expansion force to the object to be fractured even when the hole formed in the object to be fractured is deformed.

An apparatus known from EP-A-0 955 427 is constituted to supply electrical energy to a melting and vaporizing material so as to cause the melting and vaporizing material to melt and vaporize, thereby demolishing an object to be demolisched using the vaporization and expansion force generated at the time of melting and vaporization of the material; wherein either by providing a granular material which ejects from a container following the generation of the vaporization and expansion force, or by using an inflammable material as demolishing material in which the melting and vaporizing material is immersed, a to-be-demolished object is demolished with a strong demolishing force.

From FR-A-2 362 261 a detonator is known which comprises a conductive wire that is volatilised by a HT electrical discharge. The current initiating detonation of an explosive with two components. The detonator is completely inert prior to mixing. A conductive wire is mounted in a support and connected to a HT generator which volatilises the wire, creating a shock wave. The detonator, which is immersed in a liquid explosive, ignites the latter. The detonator consists of a small reservoir which, at the moment of use, receives a two-component explosive mixture which is ignited by HT discharge through a wire.

It is the object of the present invention to provide a blasting apparatus, especially for blasting a concrete construction or a rock base, whereby the safety in handling the blasting apparatus is improved.

The present invention provides a blasting apparatus in which a liquid filled in a blasting container is ignited by melting/vaporizing a melting/vaporization substance and its explosive force causes a to-be-blasted object to be blasted. The blasting apparatus comprises

   the blasting container for holding the liquid and providing the melting/vaporization substance exposed in the liquid, the substance being melted/vaporized rapidly when an electric energy of a predetermined amount is supplied thereto for a short time;

   a lid member for closing an opening of the blasting container, the member inserting a pair of electrodes through;

   wherein each end of the electrodes is connected by the melting/vaporization substance and each other end is connected to an electric energy supply circuit for supplying the electric energy to the melting/vaporization substance,

   whereby the liquid comprises nitromethane.

According to the invention the liquid comprises nitromethane. Nitromethane is not explosive and does not explode even if ignited. Since nitromethane never explodes under ordinary handling conditions, there is no need to do such a dangerous work as to make a blast as described for example in FR-A-2 362 261.

Further, nitromethane does not explode only by an impulse generated when melting/vaporization substance is melted and vaporized, but it explodes when high-electric energy is supplied all at once so that more than 70 ton · f/cm² impulse be generated. Therefore, as long as such amount of high-electric energy is not stored in an electric energy supply circuit before usage, safety is maintained.

The present invention will be described in detail with reference to the accompanying Figures 1 and 2.

In a blasting apparatus 1 according to the present invention, metallic fine wire of copper: Cu formed to be 0.3 mm in diameter as melting/vaporization substance is vaporized rapidly and a blasting substance 3 is exploded by a shock caused by a phenomenon accompanying the vaporization, such as discharge, spark, heat and vaporization expansion, so as to blast a to-be-blasted object such as a concrete construction or a rock base.

As the blasting substance 3, explosives or explosive compounds other than the explosives are used. The explosives mean an explosive, a high explosive and an ammunition as described in the "New Edition: Industrial Explosives" issued by the Industrial Explosives Society of Japan. In this style, blasting powder and smokeless powder are used as explosive, and DDNP, mercury fulminate and the like are used as high explosive. Explosive compounds other than the explosives include, for example, methyl nitrate, nitro-compound, gasoline and the like as described in "Chemical Handbook" complied by the Chemical Society of Japan.

In the blasting apparatus 1 of the present invention, the aforementioned blasting substance 3 is filled in a blasting container 6 mounted in a mounting hole 5 formed in a to-be-blasted object 4. An opening side of this blasting container 6 is sealed by a lid member 7 and a pair of electrodes 8 are inserted through this lid member 7. Ends of these electrodes 8 are connected with each other by the aforementioned metallic fine wire 2 exposed to the blasting substance 3.

As a material of the aforementioned blasting container 6, a non-metal such as wood, paper or synthetic resin, or a metal such as aluminum or iron is used.

An electric energy supply circuit 10 is connected to the metallic fine wire 2 so as to supply electric energy of a predetermined amount (e.g., 5,000 V) enough to melt and vaporize the metallic fine wire 2.

This electric energy supply circuit 10 comprises a power supply unit 11, a capacitor 14 connected between this power supply unit 11 and both terminals 8a, a charge control circuit 12 which is connected between the power supply unit 11 and one side terminal 8a so as to control the capacitor 14 to store an electric energy of a predetermined amount (e.g., 400 µF), and a discharge switch 13 which is connected between this charge control circuit 12 and the one terminal 8a.

The aforementioned blasting apparatus 1 is manufactured by connecting both ends of the electrodes 8 to each other with the metallic fine wire 2, inserting the electrodes 8 through the lid member 7, filling the blasting container 6 with the blasting substance 3, fitting the lid member 7 to the blasting container 6 to seal the blasting substance 3, and connecting the electric energy supplying circuit 10 to the terminals 8a of the electrodes 8. Then, the blasting container 6 is mounted in the mounting hole 5 formed in the to-be-blasted object 4.

Then, an electric energy of a predetermined amount necessary for melting and vaporizing the metallic fine wire 2 is stored in the capacitor 14 and the discharge switch 13 is turned on. As a result, the aforementioned electric energy is supplied to the metallic fine wire 2 for a short time so that the metallic fine wire 2 is melted and vaporized. By the aforementioned phenomenon accompanying the process of melting and vaporization, the blasting substance 3 is exploded. Then, the explosive force of the blasting substance 3 is combined with a shock caused by the melting and vaporization of the metallic fine wire 2, whereby the to-be-blasted object 4 is securely blasted and made fragile.

According to the present invention, the blasting container is filled with the blasting substance 3 and instead of the detonator, the metallic fine wire 2 connected to the electrodes 8 is used. Therefore, even if leakage current occurs from surrounding devices and is supplied to the metallic fine wire 2, as long as electric energy enough for melting and vaporizing the metallic fine wire 2 is not supplied, the blasting substance 3 is not exploded. Thus, the blasting apparatus can be handled under the safety.

Meanwhile, since nitromethane is not exploded until a large shock of more than about 70 ton · f/cm² is supplied thereto, an explosive needs be used to explode this nitromethane. Therefore, nitromethane has seldom been used in the prior art. However, a sufficient shock for exploding nitromethane can be secured by a shock caused when the metallic fine wire 2 is melted and vaporized, thereby allowing nitromethane to be used as the blasting substance 3. By using nitromethane, the same explosive force as when dynamite is used can be obtained, so that the to-be-blasted object can be securely blasted and made fragile by the great explosive force of nitromethane.

Although an example of using the metallic fine wire 2 as the melting/vaporization substance has been described in the above embodiment, it is permissible to use a small piece of metal or a conductive material such as carbon formed in an appropriate shape, as other example of the melting/vaporization substance. When such materials are used, the blasting substance 3 is also exploded by the phenomenon caused in a process of melting and vaporization in the same manner as in the above embodiment, so that the to-be-blasted object 4 can be securely blasted or made fragile.

Although according to the above embodiment, the blasting container 6 is mounted in the mounting hole 5 formed in the to-be-blasted object 4, it is permissible, without being restricted to this example, to butt the blasting container 6 to the surface of the to-be-blasted object 4 or to hoist the blasting container with an appropriate hoisting tool so that it is disposed in the vicinity of the surface of the to-be-blasted object 4. In any case, by supplying electric energy to the metallic fine wire 2 (a small piece of metal or a conductive material such as carbon), the metallic fine wire 2 is melted and vaporized rapidly so that the blasting substance 3 is exploded by the phenomenon accompanying that process. As a result, the to-be-blasted object 4 is blasted and made fragile by the shock caused in the process of melting and vaporization of the metallic fine wire 2 and the explosive force of the blasting substance 3.

Further, by adjusting the blasting force of the blasting apparatus 1 of the above embodiment, this blasting apparatus 1 can also be used as a focus apparatus for geophysical prospecting.

As described above, the blasting apparatus of the present invention is suitable for blasting a to-be-blasted object requiring a massive blasting force.