WO1998007520A1 - Electric discharge shock breakdown method and apparatus therefor - Google Patents

Abstract

An electric discharge shock wave generating method and an apparatus therefor, which can break down a large rock and concrete in a short time. The electric discharge shock breakdown method comprises first having positive and negative electrodes (3a, 3b) approach a portion being broken down, the portion being surrounded by a liquid atmosphere or an object being (4) broken down being rendered a liquid atmosphere, and subsequently applying a high voltage pulse between the positive and negative electrodes (3a, 3b) to generate an electric discharge therebetween so that the portion being broken down is broken down by shock waves generated by the electric discharge. In the method, an atmosphere with bubbles is formed in a liquid between the positive and negative electrodes (3a, 3b) before the electric discharge.

Description

 Description Discharge impact destruction method and device Technical field

 TECHNICAL FIELD The present invention relates to a method and an apparatus for destroying a discharge impingement used for breaking rock and concrete. Background technology

 The discharge impact destruction device has a high-voltage pulse generator, and a pair of positive and negative discharge electrodes that receive a high-voltage pulse from the high-voltage pulse generator and discharge. The discharge electrode is referred to as "positive / negative electrode" when the positive electrode and the negative electrode are to be paired, and "electrode" when either one or the pair is acceptable. In other words, this discharge impact destruction device is designed to protect against rocks, concrete, etc. (hereinafter simply referred to as “destroyed objects”) in which the surroundings of the destroyed portion are in liquid or in liquid. First, the positive and negative electrodes are brought close to the portion to be destroyed, and then a high voltage pulse is applied between the two electrodes from a high voltage pulse generating device, thereby causing a discharge between the two electrodes and being destroyed by a shock wave generated by the discharge. This is a device for crushing parts (ie, objects to be destroyed). As the electrodes, conventionally, for example, needle-like, spherical, planar, concave, and combinations thereof are known.

 The above-mentioned conventional electrode is a shape improvement for extending the life and facilitating the discharge, and can be expected to have a considerable improvement in economic efficiency and work efficiency. However, conventional electrodes do not directly contribute, for example, to large blasts, which destroy even large rocks and concrete objects in a short time. Disclosure of the invention

The present invention has been made to solve the problems of the related art, and An object of the present invention is to provide a method and an apparatus for generating a discharge impact rupture that can destroy rocks and concrete in a short time.

 In a first configuration of the discharge impact destruction method according to the present invention, first, a positive electrode and a negative electrode are brought close to the destruction part with respect to the destruction object in which the surrounding of the destruction part is a liquid atmosphere or the liquid atmosphere. Then, a high-voltage pulse is applied between the positive and negative electrodes to cause a discharge between the positive and negative electrodes, and in a discharge impact crushing method in which a portion to be destroyed is crushed by an impulsive wave generated by the discharge,

It is characterized in that the liquid in the liquid between the positive and negative electrodes is made to have bubbles before the discharge.

 A second configuration of the method is that the bubble atmosphere is an atmosphere containing bubbles having an average particle diameter of 1 mm or less.

 A first configuration of the discharge impact destruction device according to the present invention is a discharge impact destruction device including a high-voltage pulse generator, and a positive / negative electrode to which a high-voltage pulse is applied from the high-voltage pulse generator to discharge.

It is characterized by having a bubble introduction device for introducing bubbles into the liquid between the positive and negative electrodes. The second configuration of the device is characterized in that a hollow tube for introducing a bubbled liquid flow between the positive and negative electrodes is provided at or near one of the positive and negative electrodes. The third configuration of the device is characterized in that the high-voltage pulse generating device ffi can apply a current weaker than the high-voltage pulse current between the positive and negative electrodes before generating the high-voltage pulse. . A fourth configuration of the device is characterized in that a bubble holding member is provided between the positive and negative electrodes. A fifth configuration of the device is characterized in that the high-voltage pulse generator can apply a high-voltage pulse to the positive and negative electrodes at 20 Hz or more. The sixth configuration of the device includes a trigger voltage electrode disposed between the positive and negative electrodes, and a trigger voltage generator connected to the trigger voltage electrode. The high-voltage pulse generator has a high voltage between the positive and negative electrodes. It is characterized in that a trigger voltage is generated by a trigger voltage generator and a trigger voltage is applied to a trigger voltage electrode when a creeping pulse is applied.

According to the configuration of the method and the apparatus of the present invention, the following effects can be obtained. If the material to be crushed is simply destroyed, an ultra-high voltage and high current pulse should be applied to the electrode. However, this In such a case, the electrode becomes large. In addition, high-voltage pulse generators have become ultra-high-voltage and high-current, and have become larger, which is disadvantageous for transportation, safety and maintenance. In other words, the mere increase in energy is only a continuation of the conventional technology. By the way, if the high-voltage pulse is constant, the longer the discharge distance, the more effective it is to excavate large holes and crush large rocks. In other words, if a certain discharge distance can be obtained, the high-voltage pulse can be reduced in voltage, cost, and noise, and the crushing can be performed safely and efficiently. That is, the present invention is configured to increase the discharge distance, and these effects can be obtained. Details are as follows. For example, if there is rock in the liquid, a discharge distance of about 1 Omm can be obtained with a high-voltage pulse of about 35 kV due to creeping discharge on the rock surface. If there are no rocks here (that is, a mere submerged discharge), a high voltage pulse of about 50 kV is required. If there are no more liquids (ie air discharges), only 10 kV high voltage pulses are needed. From the above, it can be seen that, even with the same high voltage pulse, if there is a bubble between the positive and negative electrodes, the dischargeable distance is extended several times due to a synergistic effect with the creeping discharge. According to the first configuration of the method, since the liquid atmosphere between the positive and negative electrodes is made a bubble atmosphere before the separation, the discharge distance becomes long. Therefore, if the high-voltage pulse is constant, the discharge distance can be made longer than in the conventional technology, making it possible to cut large holes and break large rocks. Conversely, if the discharge distance can be short, the object to be destroyed is crushed with a high-voltage pulse lower than in the prior art.

According to the second configuration of the method, the following effects can be obtained. Bubbles not only extend the discharge distance, but also collapse due to cavitation due to the discharge shock wave, and the water hammer pressure generated during this collapse causes a synergistic effect that is emphasized by the discharge shock wave. However, depending on the size of the bubbles, there is a problem that the discharge shock wave is absorbed. This will be described with reference to FIG. Figure 7 is a logarithmic graph showing the relationship G1 between the bubble radius (horizontal axis [mm]) obtained from experiments and simulations and the pressure of bubble collapse water in water (horizontal axis [MPs]). . The bubble collapse water hammer pressure is a pressure generated in water when bubbles collapse by cavitation. Pressure is generated and superimposed on the discharge shock wave. On the other hand, on the large diameter side, It does not easily collapse and absorbs discharge shock waves. The maximum water hammer pressure is obtained at a radius of about 0.1 mm (particle diameter of about 0.2 mm), but the practical range is at a radius of about 0.5 mm or less (particle diameter of about 1 mm or less, indicated range P). . In actual use, large and small bubbles are mixed, but if the average particle size is 1 mm or less, it can be considered that the above-mentioned "synergistic effect in which the water pressure is superimposed on the discharge impulse wave" can be obtained. That is, according to the present configuration, since the atmosphere is a “bubble atmosphere having an average particle diameter of 1 mm or less”, in addition to the effect of the first configuration of the method, the above “synergistic effect that the water hammer pressure weighs on the discharge shock wave” is obtained. Can be

 The first to fourth configurations of the device are examples of the first configuration of the above-described method, and achieve “being in the liquid between the positive and negative electrodes to a bubble atmosphere before discharging”. Details are as follows. The first configuration of the device has a bubble introduction device that introduces bubbles into the liquid between the positive and negative electrodes. On the other hand, the second configuration of the device has bubbles between the positive and negative electrodes at or near one of the electrodes. Since there is a hollow tube through which the liquid flows, the liquid between the positive and negative electrodes becomes a bubble atmosphere before discharging. The third configuration of the device is that, before the high-voltage pulse generator oscillates the high-voltage pulse, a current weaker than the high-voltage pulse current can be applied between the positive and negative electrodes. For example, water produces bubbles of oxygen and hydrogen. That is, the liquid in the liquid between the positive and negative electrodes becomes a bubble before the discharge.

 According to the fourth configuration of concealment, the following effects are obtained. In the first to third configurations of the above-described device, the liquid between the positive and negative electrodes is forced to have a bubble atmosphere before discharging. However, without force, bubbles and plasma are generated between the positive and negative electrodes during discharge. However, when the discharge interval is long, these bubbles are scattered from between the positive and negative electrodes and disappear. However, since the fourth configuration of the apparatus has the bubble holding member between the positive and negative electrodes, the bubble holding member maintains the bubble generated by the previous discharge between the positive and negative electrodes and uses the bubble for the next discharge, thereby extending the discharge distance. That is, before discharge, the liquid between the positive and negative electrodes becomes a bubble atmosphere.

According to the fifth configuration of the device, the following effects can be obtained. As described in the fourth configuration of the device, at the time of discharge, bubbles and plasma are generated between the positive and negative electrodes. Plasma leaves ions and radicals as residues. Figure 8 shows the elapsed time t sec after plasma generation obtained by experiments and simulations, and the density of ions and radicals (the reciprocal of the number N, 1 is a logarithmic graph showing a relationship G2 with N). As shown in Fig. 8, the ion radical is reduced to about 50 ms ec to a level that is not practical. In this configuration, the high-voltage pulse generator can apply high-voltage pulses to the positive and negative electrodes at a frequency of 20 Hz or more, so that ions and radicals can be used for the next discharge before they disappear. In this case, ions, radicals, etc. extend the discharge distance more than bubbles.

 According to the sixth configuration of the device, the following effects can be obtained. For example, air gap switches, gas-filled gap switches, vacuum gap switches, and the like include a three-electrode system having a positive and negative main electrode and a trigger electrode. In the three-electrode system, applying a trigger voltage to the trigger electrode lowers the breakdown voltage, but also has the property of increasing the discharge distance between the main electrodes. This configuration is based on this principle, and has a trigger voltage electrode between the positive and negative electrodes, and the high voltage pulse generator applies a trigger voltage to the trigger voltage electrode when applying a high voltage pulse between the positive and negative electrodes. It has a trigger voltage generator to apply. Therefore, the discharge distance can be lengthened.

 By appropriately combining the above inventions, the discharge distance can be synergistically increased. Therefore, large rocks and concrete can be destroyed in a short time without increasing the high voltage pulse. Conversely, small rock and concrete can be crushed with a small high-voltage pulse. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is an explanatory diagram of the overall configuration of the first case according to the present invention.

 FIG. 2 is a block diagram of a second example according to the present invention.

 FIG. 3 is a graph showing the application time of the high voltage pulse P and the weak current state on the time axis for explaining the second case according to the present invention.

 FIG. 4 is an explanatory diagram of the entire configuration of the third example according to the present invention.

 FIG. 5 is a block diagram of a fourth example according to the present invention.

 FIG. 6 is a circuit diagram of a fourth example according to the present invention.

FIG. 7 is a diagram for explaining the operation of the present invention. It is a logarithmic graph which shows the relationship with a landslide hammer pressure.

 FIG. 8 is a diagram for explaining the operation of the present invention, and is a logarithmic graph showing the relationship between the elapsed time after plasma generation and the density of plasma residues. BEST MODE FOR CARRYING OUT THE INVENTION

 Preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

 FIG. 1 shows the first case, in which positive and negative electrodes 3 a and 3 b are connected to the respective ends of the lead wires 2 a and 2 b led from the high-voltage pulse generator 1. Positive electrode 3a is just iron plate. The negative electrode 3b is a hollow tube. The positive electrode 3a and the negative electrode 3b are opposed to each other with a destructible object 4 such as a rock interposed therebetween, and both are submerged. The outer periphery of the hollow tube 3 is covered with an insulating member 31, and a hollow insulating flexible tube 5 is connected to the top. The other end of the insulating flexible tube 5 is connected to a bubbled water flow generator 6. The operation and effects are as follows.

The water flow generator 6 with bubbles is operated to flow the water flow 8 with bubbles 7 from the opening of the tip of the negative electrode 3b toward the positive electrode 3a. As a result, before the discharge, the liquid between the positive and negative electrodes 3a and 3b has a bubble atmosphere. Then, the high-voltage pulse generator 1 is driven. The high-voltage pulse generated by the high-voltage pulse generator 1 is applied to the positive and negative electrodes 3a and 3b and discharged. This discharge generates a shock wave and breaks the rock. In addition, since the discharge path has bubbles 7, the discharge distance increases. Therefore, a larger rock 4 can be crushed as compared with the state without the bubble 7. In addition, the discharge shock wave causes the bubble 7 to collapse into a cavity, and the collapse causes a water hammer pressure. Since this water pressure is superimposed on the discharge shock wave, more efficient destruction can be performed. The size of the bubbles 7 is desirably set to an average particle size of 1 mm or less as described above with reference to FIG. Otherwise, the bubbles 7 are unlikely to cause the collapse of the cavitation, and the bubbles 7 absorb the discharge shock wave. Therefore, the crushing efficiency decreases. The high-voltage pulse from the high-voltage pulse generator 1 is periodically applied to the positive and negative electrodes 3a and 3b, crushes the rock 4, and moves the positive and negative electrodes 3a and 3b as the crush progresses. . This achieves continuous crushing.

 In the first case, the negative electrode 3 b itself is hollow, but a conduit for guiding the fluid 8 containing the bubbles 7 may be provided on the positive electrode 3 a side, or may be provided on both sides. Alternatively, a fluid 8 containing bubbles 7 may flow from a separately prepared nozzle toward the space between the positive and negative electrodes 3a and 3b. It is not necessary to limit to the fluid 8 containing the bubbles 7, and a bubble introducing device for guiding the bubbles 7 into the liquid between the positive and negative electrodes 3 a and 3 b may be used. This bubble introduction device has, for example, a tube having a hollow fiber tip, and this hollow fiber is arranged in the vicinity between the positive and negative electrodes 3a and 3b. With this bubble introduction device, compressed air may be sent into the tube, and bubbles 7 may be released from the pores on the outer wall of the hollow fiber into the liquid between the positive and negative electrodes 3a and 3b.

 FIG. 2 shows a second case, in which the high-voltage pulse generator 1 has therein a high-voltage pulse generator 11 and a low-current generator 12 that outputs a weak current 〖0. These generators 11 and 12 are connected to the positive and negative electrodes 3a and 3b, respectively. The operation and effect will be described below with reference to FIG.

 FIG. 3 shows the time t, the application timing of the high-voltage pulse P to the positive and negative electrodes 3a and 3b, and the state of the current I0 from the low current generator 12. The high-voltage pulse generator 11 applies a high-voltage pulse P to the positive and negative electrodes 3a and 3b periodically, as in the case of the high-voltage pulse generator 1 in the first case described above, and continuously applies the material 4 to be broken. Crush. On the other hand, the low current generating section 12 constantly supplies a weak current Io to the positive and negative electrodes 3a and 3b. Therefore, due to the current Io, bubbles 7 are generated by electrolysis from the positive and negative electrodes 3a and 3b immersed in the water 9, and the liquid between the positive and negative electrodes 3a and 3b becomes a bubble atmosphere before discharging. The bubbles 7 due to electrolysis are mainly oxygen and hydrogen. This enables the discharge distance to be extended as in the first case described above. In addition, superimposition of the water hammer pressure due to the cavitation collapse of bubble 7 on the discharge shock wave is also obtained.

In the second case, the low-current generator 12 is incorporated in the high-voltage pulse generator 1, but may be provided independently. Instead of flowing the current Io constantly, the current Io may be caused to flow before the application of the high-voltage pulse P and earlier by the time when the bubbles 7 are sufficiently generated. Fig. 4 shows the third case, in which the positive and negative electrodes 3a and 3b are fixed to the insulating base 32 separately from each other, and the bubble holding member 10 such as a net or sponge is fixed between them. There is. The operation and effects are as follows.

 In the first and second cases described above, the liquid in the liquid between the positive and negative electrodes 3a and 3b was forced to bubble before discharge, but even if not forced, the positive and negative electrodes 3a3 Bubble plasma is generated in b. However, if the discharge interval is long, these bubbles are scattered from between the positive and negative electrodes 3a and 3b, and do not exist between the positive and negative electrodes 3a and 3b. However, according to the third case, since the bubble holding member 10 such as a net or a sponge is provided between the positive and negative electrodes 3a and 3b, these bubbles can be held without being scattered. Therefore, before the next discharge, the liquid between the positive and negative electrodes 3a and 3b can be made to have a bubble atmosphere. Since the net or sponge only holds generated bubbles, it does not care much about the size (for example, mesh size) of the gap that becomes the passage portion. It is desirable to have This is because if the gaps are small, if small bubbles become dense, they will come into contact with each other and grow into large-sized bubbles.

 As mentioned in the operation and effect of the third example, plasma is generated on the positive and negative electrodes 3a and 3b during discharging, in addition to bubbles. This plasma leaves ions and radicals as residues. If these ions and radicals can be used, the discharge distance can be further extended. However, as described above with reference to FIG. 8, the usable existence period of these ions and radicals is about 50 msec. On the other hand, if the high voltage pulse generator 1 applies high voltage pulses to the positive and negative electrodes 3a and 3b at a cycle of 20 Hz or more, the discharge distance can be reduced using ions and radicals. It can be extended further.

Figure 5 shows the fourth case. The electrode of the fourth example has a trigger voltage electrode 3c between the positive and negative electrodes 3a, 3b in addition to the positive and negative electrodes 3a, 3b in the first, second, and third examples. ing. Trigger voltage generator 13 is connected to high-voltage pulse generator 1 by lead wire 2c. And the trigger voltage electrode 3c is connected by the lead wire 2d. Connected to trigger voltage generator 13. The operation and effects are as follows.

 When the high-voltage pulse generator 1 applies a high-voltage pulse to the positive and negative electrodes 3a and 3b, a synchronous operation signal is given to the trigger voltage generator 13 via the lead wire 2c. Then, the trigger voltage generator 13 uses the high-voltage pulse generator 1 to output the high-voltage pulse to the positive and negative electrodes.

Prior to (or simultaneously with) the application of 3a, 3b, a trigger voltage is applied to the trigger voltage electrode 3c. Then, first, the trigger voltage electrode 3c starts discharging to the positive and negative electrodes 3a (or 3b) having polarities different from those of the trigger voltage electrode 3c. Then, the positive and negative electrodes 3a and 3b start the main discharge with a smaller voltage than the high voltage pulse applied in the first, second and third cases. That is, if the high-voltage pulse in the fourth case has the same voltage as the high-voltage pulse in the first, second, and third cases, the discharge distance in the fourth embodiment is extended several times.

 Details of such a configuration example will be described with reference to FIG. First, differences in the basic configuration between FIG. 6 and FIG. 5 will be described. In the configuration of Fig. 5, the positive and negative electrodes 3a and 3b are directly applied with the high voltage pulse from the high voltage pulse generator 1, while the trigger voltage electrode 3c is directly applied with the trigger voltage from the trigger voltage generator 13 . In other words, they are independent of each other except for synchronous control. On the other hand, in the configuration of FIG. 6, the high-voltage pulse from the high-voltage pulse generator 1 is applied to the positive and negative electrodes 3a and 3b and the trigger voltage electrode 3c, and the self-synchronization is controlled. ing. That is, the configuration of FIG. 6 is as follows.

 Lead wires 14 a and 14 b are connected to the high-voltage pulse generator 1. The lead wire 14a is connected to a lead wire 2 connected to the negative electrode 3b via the secondary side L2 of the transformer T and one side of the capacitor C via the primary side L1 of the transformer T. Branch to lead wire 2e connected to terminal. On the other hand, lead 14b is connected to lead 2f connected to the other terminal of capacitor C, lead 2d connected to trigger voltage electrode 3c, and positive electrode 3a. Branched to lead line 2a. The operation and effects are as follows.

When a high-voltage pulse is applied from the high-voltage pulse generator 1 to the lead wire 14a with a negative potential and the lead wire 14b with a positive potential, the capacitor C is connected to the primary side L1. And gradually charged. Due to the current change at this time, a trigger voltage is generated on the secondary side L2, and a pre-discharge occurs between the trigger voltage electrode 3c and the negative electrode 3b. The pre-discharge induces a main discharge between the positive and negative electrodes 3a and 3b. Note that the trigger voltage occurs only when the capacitor C is charged. That is, the electrodes of the first, second, and third cases are of two-electrode type. In this case, unless a large breakdown voltage (that is, a large high-voltage pulse) is applied, the positive and negative electrodes 3 a , 3b cannot initiate main discharge. On the other hand, the fourth case has the trigger voltage electrode 3c, so that the main discharge can be started even with a small breakdown voltage (ie, a small high-voltage pulse). However, once the main discharge has occurred, the compress pulse is at the same level. Fig. 6 shows a simple structure in which a trigger voltage is generated only by the high-voltage pulse from the high-voltage pulse generator 1 using an LC series circuit. Therefore, a large trigger voltage generator 13 as shown in FIG. 5 is not required.

 In the first, second, third, and fourth cases, the positive electrode 3a and the negative electrode 3b are all unified and described in the drawings, but the polarities may be opposite. In addition, the coils L l and L 2 of the transformer T in the fourth case, when charging the capacitor C, make sure that the directions of the currents flowing through both coils L 1 and L 2 match when viewed from the high-voltage pulse generator 1. Need to be wound around. Industrial applicability

 INDUSTRIAL APPLICABILITY The present invention is useful as a method and apparatus for generating a discharge implosion that can destroy even a large rock concrete in a short time.

Claims

The scope of the claims 1. With respect to the object to be destroyed (4) in which the surroundings of the portion to be destroyed are in air or in liquid, first, the positive and negative electrodes (3a, 3b) are brought close to the portion to be destroyed. The discharge impingement method of applying a high-voltage pulse between the positive and negative electrodes (3a, 3b) to cause a discharge between the positive and negative electrodes (3a, 3b) and crushing the portion to be destroyed by a shock wave generated by the discharge. And  A discharge shock destruction method, characterized in that a bubble atmosphere is formed in the liquid between the positive and negative electrodes (3a, 3b) before discharging. 2. The method of claim 1, wherein  The method according to claim 1, wherein the bubble atmosphere is an atmosphere containing bubbles (7) having an average particle diameter of 1 mm or less. 3. In a discharge impact destruction device including a high-voltage pulse generator (1) and positive and negative electrodes (3a, 3b) to which a high-voltage pulse is applied from the high-voltage pulse generator (1) to discharge.  A discharge impact destruction device comprising a bubble introducing device for guiding bubbles (7) into the liquid between the positive and negative electrodes (3a, 3b). 4. In a discharge impact destruction device including a high-voltage pulse generator (1) and positive and negative electrodes (3a, 3b) to which a high-voltage pulse is applied from the high-voltage pulse generator (1) to discharge. A hollow tube (3b) for introducing a liquid flow (8) containing bubbles (7) between the positive and negative electrodes (3a, 3b) at or near any one of the electrodes (3b) of the positive and negative electrodes (3a, 3b). ), Characterized in that it comprises a discharge mouthpiece and a crushing device. 5. In a discharge impact destruction device including a high-voltage pulse generator (1) and positive and negative electrodes (3a, 3b) to which a high-voltage pulse is applied from the high-voltage pulse generator (1) to discharge,  The high-voltage pulse generator (1) can apply a current weaker than the high-voltage pulse current between the positive and negative electrodes (3a, 3b) before generating the high-voltage pulse. Discharge impact destruction device. 6. In a discharge impact destruction device including a high-voltage pulse generator (1) and positive and negative electrodes (3a, 3b) to which a high-voltage pulse is applied from the high-voltage pulse generator (1) to discharge.  A discharge impact destruction device comprising a bubble holding member (10) between the positive and negative electrodes (3a, 3b). 7. Discharge shock destruction including a high-voltage pulse generator (1) and positive and negative electrodes (3a, 3b) to which a high-voltage pulse is applied from the high-voltage pulse generator (1) and discharges.  The high-voltage pulse generator (1) is capable of applying a high-voltage pulse to the positive and negative electrodes (3a, 3b) at a frequency of 20 Hz or more. 8. A discharge impulse destruction device including a high-voltage pulse generator (1), and positive and negative electrodes (3a, 3b) to which a high-voltage pulse is applied from the high-voltage pulse generator (1) to release heat. ,  A trigger voltage electrode (3c) disposed between the positive and negative electrodes (3a, 3b); A trigger voltage generator (13) connected to the trigger voltage electrode (3c), wherein the high voltage pulse generator (1) applies the high voltage pulse between the positive and negative electrodes (3a, 3b). A trigger voltage is generated by the trigger voltage generator (13), and the trigger voltage is applied to the trigger voltage electrode (3c). apparatus,