JPH0128320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric detonator provided with safety against static electricity applied between two terminals of conductors of two leg wires. Normally, both terminals of the two leg wires of an electric detonator are short-circuited when not in use, and in this state it can be said to be quite safe against static electricity. However, after the short-circuit condition is released for use, if static electricity is applied between the two terminals of the conductor, the electric detonator will ignite even with relatively slight electrical energy. Conventionally, as a method for preventing an electric detonator from exploding due to static electricity applied between two terminals of a conducting wire, it has been common to make the ignition part of the electric detonator less sensitive to electric energy. Specifically, this meant increasing the diameter of the heat-generating resistance wire in the ignition part, or making the ignition charge composition less sensitive to thermal ignition. However, such a method has problems in actual use. In other words, by making the thermal ignition sensitivity insensitive to electrical energy due to static electricity in the ignition part,
They also became insensitive to the electrical energy provided by the blaster, and there was a risk of failure to detonate when blasting multiple electric detonators connected in series. The present invention has superior safety to the above-mentioned conventional method by being able to prevent unexpected ignition even if static electricity is applied between two terminals of a conductor, and also enables a large number of electric detonators as described above to be connected in series. To provide an electric detonator that does not cause misfires even during blasting. That is, in the electric detonator of the present invention, a heat-generating resistance wire is provided between the leading ends of the two leg wires, an igniter is attached around the heat-generating resistance wire, and the igniter is passed through the leg wires and fixed in the tube body. In an electric detonator having an ignition part made of an insulating embol, an inductor having an inductance of 3 to 90 μH is connected in series to the heating resistance wire, and further in parallel to the circuit consisting of the heating resistance wire and the inductor. It is characterized in that a resistor having a volume resistivity of 7×10 ⁰ to 1×10 ⁴ Ω·cm is connected to the tube body in an insulated state. Next, the structure of the electric detonator of the present invention will be specifically explained with reference to FIG. 1, which schematically shows the structure. In FIG. 1, 1 is a tube body, 2 is an insulating embolus,
3, 3' are leg wires, and leg wires 3, 3' are a pair of conducting wires 4,
4' and an insulating sheath 5, 5' covering the conductors 4, 4', which penetrate the insulating embolus 2. 4 _a , 4' _a indicates the terminals of the conducting wires 4, 4'. 6
A heating resistance wire is connected between the leading ends of the conducting wires 4 and 4' inside the tube body 1, and the ignition charge 7 is attached around the wire. Further, an inductor 8 having an inductance of 3 to 90 μH is connected in series with the heating resistance wire 6 in the middle of one of the conductive wires 4 inside the tube body 1 . 7×10 ⁰ in parallel to the circuit consisting of this inductor 8 and heating resistance wire 6
Resistor 9 having a volume resistivity of ~1×10 ⁴ Ω・cm
are arranged and connected in the range A to A' within the tube body 1. At this time, the resistor 9 must be arranged and connected to the tube body 1 so as to be in an insulated state.
That is, the resistor 9 and the tube body 1 are arranged and connected so that the insulating layer 10 is interposed therebetween so that they do not come into contact with each other. In FIG. 1, the resistor 9 is shown at position A, so the insulating layer 10 in this case is air. In the embodiment described later (FIG. 3), the resistor 9 is arranged and connected inside the insulating embolus 2, so the insulating embolus 2 becomes the insulating layer 10. Furthermore, the second
In the illustrated embodiment, the resistor 9 is bonded to the lower end surface of the insulating embolus 2, and the insulating layer 10 in this case is the insulating embolus 2 and air. Next, the relationship between the constituent features of the electric detonator of the present invention and its effects will be explained. The basic constituent elements of the present invention are an inductor 8 connected in series to the heating resistance wire 6, and a resistor 9 connected in parallel to these.
The electric detonator has the ability to protect against static electricity applied between the two terminals _4a and _4'a . That is, when static electricity is applied between the two terminals 4 _a and 4' _a of the conductors 4 and 4', inductance acts because di/dt (the rate of change of current i with respect to time t) is large, and the current flows through the inductor 8. It is difficult for the resistor 9 to pass through the resistor 9, which is in parallel with the heating resistance wire 6.
Since current flows through the heating resistance wire 6, the ignition powder 7 does not ignite. Therefore, the electric detonator of the present invention can ensure safety against the application of static electricity as described above. The resistor 9 used here can be made of, for example, a conductive resin, a conductive rubber, a conductive coating film, etc., but these are necessary in order to guarantee the static electricity resistance performance of the electric detonator due to their volume resistivity. The inductance of the inductor 8 is made different. In other words, the smaller the volume resistivity of the resistor 9, the smaller the required inductance.
This is advantageous because it allows for a corresponding reduction in size.
Therefore, it is desired to reduce the volume resistivity of the resistor 9 as much as possible, but in order to prevent misfires when using the electric detonator, it is necessary to consider the following two points. To prevent insufficient heating of the heating resistance wire 6 due to the blasting current being consumed by the resistor 9. To prevent the blasting current from leaking to the outside of the detonator due to contact between the resistor 9 and the tube body 1, thereby causing insufficient heating of the heat generating resistance wire 6. As a basic consideration for the above, in the present invention,
The condition is that the resistor 9 and the tubular body 1 be insulated. That is, for example, an insulating embolus 2 and an insulating layer 1 such as an air layer are provided between the resistor 9 and the tube body 1.
0 to intervene. On the other hand, in order to satisfy the above, it is necessary to find the following: Volume resistivity, which is the electrical property of the material of the resistor 9 Characteristic values such as the shape of the resistor 9 and the spacing between the conductors 4 and 4' Resistance of the resistor 9 In completing the present invention, various experimental studies were conducted to determine the lower limit value, and by determining the lower limit value within that value, the following results were obtained. In other words, the lower limit value of the volume resistivity of the resistor 9 is 7×
10 ⁰ Ω・cm, and the conductor 4 at this lower limit value
The lower limit of resistance of the resistor 9 between the two terminals 4 _a and 4' _a of 4' (the circuit excluding the heating resistance wire 6) is 25 Ω (the resistor 9 has a volume resistivity of 7 × 10 ⁰ Ω cm). (This use is possible only by interposing the insulating layer 10). The lower limit inductance of the inductor 8, 3 μH, corresponds to the lower limit value of the volume resistivity of the resistor 9, and is the lowest limit value for guaranteeing the anti-static performance of the electric detonator of the present invention. On the other hand, if the volume resistivity of the resistor 9 is increased,
It is also necessary to increase the inductance of inductor 8, but the relationship between the two is that the volume resistivity is 1
When the volume resistivity becomes larger than this, the required inductance increases rapidly, so a resistor exceeding 1×10 ⁴ Ω^・cm is required.
Using this would require a large inductor 8 with large inductance,
This is undesirable in electric detonators, where each component must be housed in a limited space. Therefore, the volume resistivity of the resistor 9 is 1×10 ⁴ Ω・cm or less (corresponding to this, the resistance value between terminals 4 _a and 4' _a of the resistor 9 is 1
×10 ⁶ Ω or less), and the inductance of the inductor 8 is preferably 90 μH or less. Specifically, the inductor 8 having the above-mentioned performance has the following aspects (FIGS. 2 to 4).
can be used. (a) A coil-shaped inductor 8 (the embodiment shown in FIG. 2) formed by winding an insulated conductor wire 8 _b such as enamelled copper wire around a ferrite magnetic core 8 _a as a support (b) An insulating embolus 2 A coil-shaped inductor ₈ (a third Embodiment shown in the figure) ( _c ) An inductor 8 ( _no . Embodiment in Figure 4) The effects of the electric detonator of the present invention will be described below with reference to Examples and Comparative Examples. The leg wire length of the electric detonator in each example was 1.5 m, and the heating resistance wire 6 was a platinum wire with a diameter of 28 μm unless otherwise specified. The test results for each example are summarized in Table 1. Example 1 According to the embodiment shown in FIG. 2, a conductive coating film made of silver powder and epoxy resin and having a volume resistivity of 2×10 ¹ Ω・cm was formed on the lower end surface of an insulating embolus 2 made of polyethylene. Using the resistor 9 having a resistance of 50 to 90 _Ω , we also created an inductance by winding an enamelled copper wire as an insulated conductor _8b in a coil around a ferrite magnetic core 8a as a support.
An electric detonator was created using an inductor 8 with a voltage of 12μH. Electrical energy charged to a 2000PF capacitor to a specified voltage (applied voltage shown in Table 1) is applied to this electric detonator between the two terminals 4a _{and 4'a} of conductive terminals 4 and 4' to check for ignition. test (hereinafter referred to as antistatic test), and using a blaster with an output voltage of 600V with a 32 μF capacitor, an electric detonator 150
A test was conducted to determine the number of electric detonators that were completely detonated by connecting books in series and submerging the tubes in water (hereinafter referred to as the "blasting test"). Hereinafter, the electrostatic resistance test and blasting test for each example were conducted by the above-mentioned method. Example 2 A conductive resin of 2×10 ² to 7×10 ² Ω was obtained by molding a conductive resin made of copper powder and polypropylene with a volume resistivity of 5×10 ² Ω・cm according to the embodiment shown in FIG. A resistor 9 having resistance is used, and an insulating embolus 2 made of polyethylene is used to enclose the resistor 9 and have a recess 2'.The recess 2' is used as a support, and an insulated conductor is attached to this As _8b , an electric detonator was prepared using an inductor 8 having an inductance of 35 μH by winding an enamelled copper wire, and an electrostatic resistance test and a blasting test were performed on the inductor 8. Example 3 A conductive resin made of carbon black and polyethylene with a volume resistivity of 6×10 ³ Ω·cm was molded according to the embodiment shown in FIG. 3, and had a resistance of 1×10 ⁵ to 7×10 ⁵ Ω. Using a resistor 9, an insulating embolus 2 made of ethylene-vinyl acetate copolymer is used, which encloses the resistor 9 and has a recess 2'.
An enamelled copper wire was wound around the recess 2' in the same manner as in Example 2 to obtain an inductor 8 with an inductance of 80 μH. An electric detonator was made using this, and an electrostatic resistance test and a blasting test were conducted. Comparative Example 1 An electric detonator similar to that of Example 2 was prepared except that the resistor 9 and inductor 8 were not used, and a static electricity resistance test was conducted. Comparative Example 2 An electric detonator similar to that of Example 2 was prepared except that the resistor 9 was not used, and a static electricity resistance test was conducted. Comparative Example 3 An electric detonator similar to that of Example 2 was prepared except that the inductor 8 was not used, and a static electricity resistance test was conducted. Comparative Example 4 An electric detonator similar to Example 2 was made, except that the resistor 9 and inductor 8 were not used, and a platinum wire with a diameter of 60μ was used as the heating resistance wire 6, and an electrostatic resistance test and a blasting test were conducted. Summer. As shown in Table 1, the results of the tests in each of the above examples show that Examples 1 to 3 exhibited almost perfect anti-static performance, and no electric detonators failed to explode in the blasting tests. Ta. On the other hand, Comparative Examples 1 to 3 had no antistatic performance at all. In Comparative Example 4, some electrostatic resistance performance was observed at an applied voltage of 10 KV, but this performance was not observed at all at 20 KV and 40 KV, and moreover, about two-thirds of the samples failed to explode in the blasting test, making it impractical. 【table】

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory view schematically showing the configuration near the ignition part of the electric detonator of the present invention, and FIGS.
4 and 4 are longitudinal sectional views including a partial external view of the vicinity of the ignition part, showing an embodiment of the electric detonator of the present invention. 1: tube body, 2: insulating embolus, 2': recess, 3,
3': Leg wire, 4, 4': Conductor wire, 6: Heat generating resistance wire,
7: Ignition powder, 8: Inductor, 8 _a : Magnetic core, 8
_b : Insulated conductor, 8 _c : Synthetic resin sheet, 8
_d : spiral printed wiring, 9: resistor.

Claims (1)

[Claims] 1. A heating resistance wire is provided between the leading ends of the two leg wires, and an igniter is attached around the heating resistance wire,
In an electric detonator having an ignition part made of an insulating embol that penetrates the leg wire and is fixed in the tube body, an inductor having an inductance of 3 to 90 μH is connected in series with the heat generating resistance wire, and further connected to the heat generating resistance wire. 7×10 ⁰ to 1×10 ⁴ in parallel to the circuit consisting of the inductor and insulated from the tube body.
An electric detonator characterized by connecting a resistor having a volume resistivity of Ωcm. 2. The electric detonator according to claim 1, wherein the resistor is connected in an insulated state to the tube body between the conductors of the two leg wires between the heating resistance wire and the lower end surface of the embolus. 3. The electric detonator according to claim 1, wherein the resistor is connected in an insulated state to the tube body between the conductors of the two leg wires inside the insulating embolus. 4. The electric detonator according to claim 1, wherein the resistor is joined to the lower end surface of the insulating embolus and is connected between the conductors of the two leg wires in an insulated state with respect to the tube body. 5. The electric detonator according to any one of claims 1 to 4, wherein the resistor is made of a conductive resin, a conductive rubber, or a conductive coating. 6. The electric detonator according to any one of claims 1 to 5, wherein the resistor has a resistance value of 25 to 1×10 ⁶ Ω between the terminals of the conducting wires of the two leg wires. 7. The electric detonator according to any one of claims 1 to 6, wherein the inductor is formed by winding an insulated conductive wire around a support to form a coil. 8. The inductor is formed into a coil shape by winding an insulated conductive wire around the recess, using the recess provided along the circumference of the side wall of the lower part of the insulating embolus as a support. Items 1 to 6
Electric detonator described in any of paragraphs. 9. The electric detonator according to any one of claims 1 to 6, wherein the inductor is formed by printing a conductive substance in a spiral shape on the surface of a synthetic resin sheet in which ferrite is dispersed and mixed. .