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This application claims the benefit of Korean Patent Application No. 1999-6821, filed on Mar. 2, 1999, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The present invention relates to a plasma blasting system, more particularly, to an electrode assembly of a plasma blasting system. 
     2) Description of Related Arts 
     Generally, in blasting for construction work, public works, or excavating works, explosives (such as dynamite), machinery (such as hydraulic jacks and breaker), or chemicals (expandable demolition material) have been used. 
     However, when explosives, such as dynamite, are used for blasting, the blasting is very difficult to perform in crowded or urban areas (i.e. downtown) and is restricted in time and working area, since vibration and noises are very high. Broken pieces are scattered and a large quantity of dust is generated. 
     Accordingly, when blasting is performed using explosives such as dynamite, anti-pollution facilities and safety appliances must be installed, thereby increasing cost. Still, in spite of these safety precautions, it is very dangerous. 
     Recently, a plasma blasting method using electric energy has been disclosed. This method involves instantly discharging very large electric energy into electrodes in a rock thereby producing an explosion. 
     FIGS. 1 and 2 show an electrode assembly of a conventional plasma blasting system. 
     As shown in FIG. 1, the plasma blasting system has an electrolyte  80  and a coaxial cable of an electrode assembly comprising an inner electrode  10 , outer electrodes  12  and  13  and an insulating member  11  therebetween, which is disclosed in U.S. Pat. No. 5,773,750. 
     FIG. 2 shows another electrode assembly according to prior art, which has two parallel electrodes  21  that are soaked or inserted into the electrolyte  80  in an electrolytic cell  22 . 
     High current is introduced from a capacitor bank or power supply into the electrode assembly  21  and is discharged into the electrolyte  80  to increase blasting force capable of generating an instantaneous reaction energy. 
     At this point, the application of the high electrical energy to the electrolyte  80  must occur at a rate sufficient to cause sudden reaction energy production. The sudden reaction energy produced must be sufficient in strength to cause blasting. 
     In the conventional plasma blasting system or pulse power system, however, when the high current flows through the electrode assembly  21  and is discharged into the electrolyte  80 , reaction occurs locally. And most of the electrolytes  80  react by the generated chemical energy induced by the locally discharge. And the rest of the electrolytes  80  even do not react. 
     Therefore, this system is limited in blasting force by the supply of electric energy, and it is difficult to generate a short pulse pressure essential to a plasma blasting system. Further, this system is not efficient to use in construction work, public works and excavating works due to the large size of the machine required. Particularly, since the amount of electrolyte reacting during work is so limited, the efficiency of the system is deteriorated. 
     In addition, since a connecting wire and the electrolytic cell  22  are integrally formed, the connecting wire must be disused after the blasting work. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been made in an effort to solve the above-described problems. 
     It is an object of the present invention to provide an electro-power impact cell with improved blasting efficiency. 
     It is still another object of the present invention to provide an electro-power impact cell with a removable transmission wire. 
     To achieve the above objects, in its one aspect, the present invention provides an electro-power impact cell including, a first electrode to which a first voltage is applied; a second electrode to which an opposite voltage to the first voltage is applied; an eletrolyte enclosing the first and second electrodes; and wherein there is at least one gap between the first and the second electrods and the at least one gap is supported by a nonconductive piece. 
     To achieve the above objects, in its another aspect, an electro-power impact cell includes a first electrode to which a high voltage is applied, the first electrode having a plurality of conductive piece between which nonconductive pieces are disposed so that when the high voltage is applied to the first electrode, arc occur at the nonconductive piece; a second electrode spaced away from the first electrode; and a closed-cartridge enclosing the first and second electrodes while containing electrolyte. 
     To achieve the above objects, in its another aspect, the present invention provides a plasma blasting system, including a electro-power impact cell having first and second electrodes and an electrolyte; a power supply for generating electric energy; a transmission wire for transmitting electric energy to the electro-power impact cell; and a connector for removably connecting the transmission wire to the electro-power impact cell. 
     The cartridge comprises a cylindrical conductive part integrated with the second electrode and having an open end, and an insulating part for insulating the second electrode from the first electrode, the insulating part being close-tightly fitted on the open end of the conductive part. 
     The first and second electrodes are inserted in the cartridge in a state where the first and second electrodes are facing each other. 
     The electro-power impact cell further includes a connector for connecting the first and second electrodes to an external transmission wire and a jack for removably mounting the connector to the first and second electrodes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principle of the invention: 
     FIG. 1 is a schematic sectional view illustrating an electrode assembly of a conventional plasma blasting system; 
     FIG. 2 is a schematic sectional view illustrating another electrode assembly of a conventional plasma blasting system; 
     FIG. 3 is a schematic sectional view of an electro-power impact cell according to a preferred embodiment of the present invention; 
     FIG. 4 a  is a schematic exploded view of a coupling structure of a connector and a transmission wire according to the present invention; 
     FIG. 4 b  is a schematic exploded view of another coupling structure of a connector and a transmission wire according to the present invention; 
     FIG. 5 is a partially broken perspective view of an electro-power impact cell depicted in FIG. 3; and 
     FIG. 6 is a partially broken perspective view of an electro-power impact cell according to another embodiment of the present invention. 
     FIG. 7 is a schematic view of using pluralities of the electro-power impact cells of the invention combined linearly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     As shown in FIG. 3, an electro-power impact cell includes an electrolytic cell or cartridge  20  connected to both outer and inner conductors  31  and  30 . The outer conductor  31  is connected to a first wire  1 , and the inner conductor  31  is connected to a second wire  2 . The outer conductor  31  is hollow cylindrical shaped and has an opening on its one end. The inner conductor  30  is disposed within the cylindrical outer conductor  31 , extending outwardly through the opening of the outer conductor  31  to be connected to the second wire  2 . 
     An insulating plate  32  is located to block the opening of the outer conductor  31 . Electrolyte  70  is accommodated in the closed space of the cylindrical outer conductor  31 . 
     The inner conductor  30  includes first to fourth conductors  37 ,  38 ,  39  and  40  and first to fourth nonconductors  33 ,  34 ,  35  and  36 , which are made of insulating material such as MC-nylon or wood. Each of the nonconductors  33 ,  34 ,  35  and  36  is located at a corresponding gap between adjacent conductors  37 ,  38 ,  39 , and  40 . Each height of the nonconductors  33 ,  34 ,  35  and  36  is several millimeters. The first to fourth conductors  37 ,  38 ,  39  and  40  and the nonconductors are attached to each other using a suitable method such as a screw-tightening or a bonding method. 
     When a switch to apply high voltages is turned on, high current is induced to the inner conductor  30  through the second wire  2  and to the first nonconductor  33 , where it is discharged. Then it is consecutively induced to the second to fourth nonconductors  34 ,  35  and  36  only to be discharged. At this point, since a time delay during the discharge at each gap is very short, it seems that the arc occurs simultaneously at each gap. 
     Further, an inductor  41  may be provided between the fourth conductor  40  and the outer conductor  31  for a uniform discharge. 
     Thus, according to the invention, since the arc occurring at the gaps can make ignition occur at a plurality of points of the electrolyte  70 , an impact force is increased as compared with a conventional blasting system in which the ignition occurs only at a point of the electrolyte  70 . In addition, attained is the short impact time independent of the length of the inner electrode. 
     Further, the electrolytic cell  20  is designed to be connected to the first and second wires  1  and  2  by a connector  42  so that the electrolytic cell  20  can be separated from the first and second wires  1  and  2 . The inner and outer conductors or electrodes  30  and  31  also can be separated from the connector  42  using a jack  80 . 
     FIGS. 4 a  and  4   b  show various examples of a coupling structure of connecting the wire to the connector. 
     As shown in FIG. 4 a , the first wire  1  may be forcedly fitted into the connector  42  such that after connecting the wire  1  to the connector  42  the outer surface of the connector  42  is pressed to fix the wire  1 . 
     As shown in FIG. 4 b,  a depressing plate  42   a  can be disposed between the wire  1  and the connector  42  so that the wire can be tightened into the connector  42  by screws. 
     Accordingly, after the blasting work is finished, the first and second wires  1  and  2  and the connector  42  can be re-used by separating them from the electrolytic cell  20 . 
     The shape of the electro-power impact cell can be varied according to conditions of a blasting place. FIG. 5 is a partially broken perspective view of the electro-power impact cell depicted in FIG.  3 . The electro-power impact cell shown is generally used in general blasting work. 
     FIG. 6 shows an electro-power impact cell according to another embodiment of the present invention. 
     First and second wires  1  and  2  facing each other are coupled to a electrolytic cell  51  of nonconductive material. High current flows along a central electrode  60  which is connected to the first and second wires  1  and  2 . The central electrode  60  is shaped one line, but has several gaps  61  spaced regularly. 
     The electro-power impact cell shown in FIG. 6 is effective when used in blasting work of a penetrated rock. 
     In the above described electro-power impact cell, since the central electrode  60  is divided into a plurality of pieces, ignition occurs at a plurality of portions of electrolyte, increasing impact force. In addition, since impact time is independent of the length of the central electrode  60 , the shape of the cell can be varied in accordance with blasting conditions. Furthermore, since the electro-power impact cell is designed so that the electrolytic cell  51  can be separated from wires by using the connectors  42 , costs can be reduced. 
     As described until here, the electro-power impact cell according to the present invention can increase blasting force by simultaneous ignition at a plurality of points of the electrolyte. Cost can be reduced due to the removable connector for connecting the wire to the electrode. 
     Other embodiments of the invention will be apparent to the skilled in the art from consideration of the specification and practice of the invention disclosed herein. That is, without cartridge enclosing the two electrodes, the electro-power impact cell can work if it is enclosed by soil or sand after depositing the cell and the electrolyte therein. 
     Further, FIG. 7 shows that pluralities of the electro-power impact cells of the invention can be used if it is combined linearly. 
     First and second wires  1  and  2  are coupled to another wires of electro-power impact cells. 
     The electro-power impact cells shown in FIG. 7 is used in simultaneous blasting for more effective blasting. 
     It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Summary:
An electro-power impact cell used in blasting works includes a first electrode to which a high voltage is applied, the first electrode having a plurality of conductive piece between which nonconductive pieces are disposed so that when the high voltage is applied to the first electrode, arc occur at the nonconductive piece; a second electrode spaced away from the first electrode; and a closed-cartridge enclosing the first and second electrodes while containing electrolyte.