JPS5922358B2 - Safety electric field curtain device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to safety measures for electric field curtain devices,
By placing a resistor in the electric field curtain, spark discharge caused by a failure in a part of the electric field curtain will not develop into an ignition explosion of powder, and will only result in a local performance deterioration and will have little effect on the overall performance. without affecting the power source, without disconnecting that part from the power source, or disconnecting or stopping the power source for the entire device, while continuing a continuous minute spark discharge below the safe limit for the necessary time after the failure occurs, It has been improved to make it easier to use.

The outline of the electric field curtain device is already known as in Japanese Patent Publication No. 49-18308, Japanese Patent Publication No. 49-24106, Japanese Patent Publication No. 50-34582, and Japanese Patent Application Laid-Open No. 48-43735. No. 78219, patent application 1978-1978
No. 222, Japanese Patent Application No. 49-78226, and other applications filed by the present inventor, etc. have begun to embody the invention in detail.

However, safety issues as a high-voltage device remained.

Many power-consuming devices use safety measures to disconnect the power supply, such as fuses and circuit breakers, while non-power-consuming devices use measures such as lightning arresters to prevent abnormal increases in power supply voltage.

Electric field curtain devices are inherently microcapacitive loads.

In some cases, as in Japanese Patent Application No. 49-78219, the device is used with a silent discharge load in a particularly limited range, but even in this case, the capacitive load of the device remains as a standard.

Electric field curtain devices are not safe if only overvoltage countermeasures are taken in accordance with general principles for non-power consuming devices.

In other words, in order to effectively form an unequal electric field in the space near adjacent electrodes, the electrodes must be bare or have extremely thin insulation, so sparks may occur due to foreign matter adhering to them or deterioration of the insulation. The basic problem is that electrical discharge is likely to occur, and since this device is intended for floating powder, measures against dust explosions are essential.

Unless the capacitance of the device is extremely small, C■2 [C
It is natural to divide the electrode arrangement structure so that the capacitance is reduced and the voltage is appropriately reduced. However, if the divided units become smaller, it becomes difficult to detect short-circuit accidents, and countermeasures such as disconnection are required. It is difficult to operate, and even if careful measures are taken, it cannot be said to be safe if a single short circuit or a short circuit that continues for a short period of time can lead to ignition and explosion.

Also, excessive resistance naturally causes a decline in functionality.

The present invention provides an electric field curtain device arranged to ensure a minimum resistance that safely allows permanent continuous short circuits without deteriorating overall performance and can be used safely until an appropriate period of suspension and repair.

The electric field curtain device is used in various forms as described above, but a flat rectangular unit is shown below as a drawing for explaining the safety device and other examples.

What is shown in FIG. 1 is a plan view of a well-known electric field curtain device seen from the back side, and FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. FIG. 3 is a cross-sectional view taken along the line lll-1 in FIG. 2.

In FIGS. 1 to 3, linear electrodes 3-1.3-2.3 are arranged parallel to each other at equal intervals near the surface of the insulator layer 1.
-3, 4-1, 4-2, and 4-3 are buried shallowly under the surface layer, and are connected every other wire in the same phase as shown in the figure. When an alternating current voltage of Since the charged particles vibrate on the outwardly curved lines of electric force, they float under the repulsion force from the surface of the insulating layer, and a cloud 5' of charged particles is generated in the space 5 near the surface of the insulating layer.

The above-mentioned electric field curtain panel, which is made by embedding linear electrodes in a panel-shaped insulating layer, can be used, for example, as a lining for an electrostatic powder coating booth to prevent the adhesion of overspill powder. Alternatively, it has extremely useful industrial applications by taking advantage of its transportation function.

However, when using the electric field curtain device described above for the lining of an electrostatic powder coating device, fine particles of flammable paint powder that can easily ignite are present near the surface of the electric field curtain. A dense cloud 5' of combustible fine particles is formed near the surface by the repulsive action of the particles.

However, it is desirable that the power supply voltage used in the electric field curtain device is 15,000 V or less from the viewpoint of wiring safety and the cost of the device.In order to manufacture an electric field curtain device that operates effectively with this level of applied voltage, The thickness t2 of the thin insulating layer on the surface of the electric field curtain device is normally required to be approximately 0.5 mm.

Therefore, it is virtually impossible to ensure that this thin insulating layer 2 on the surface will not be mechanically destroyed. In such cases, there is a risk of spark discharge 10 occurring between a grounded object in the vicinity of the electric field curtain device, such as the support frame 8 of the electric field device, and in other such cases, the grounded foreign object 12 may be destroyed. If the surface is approached, a spark discharge 11 may occur between it and the electrode, and if the surface layer is destroyed between electrodes of different phases, a spark discharge 9 will occur between the electrodes. There is a danger.

When such a spark discharge occurs, if the concentration of the powder paint particle cloud 5' existing near the surface is within the explosive ignition limit, an ignition explosion will occur immediately, resulting in a major accident.

This type of problem is always a problem when treating flammable particles with an electric field curtain device, and unless there is a measure to treat combustible particles with an electric field curtain device, the electric field curtain device cannot be used industrially. Although it is completely impossible to put this into practical use as a device, no consideration has been given to this point in conventionally known electric field curtain devices.

As described in detail above, the present invention provides an extremely simple method for preventing the risk of ignition and explosion of fine particles that occurs when combustible particles are handled in the electric field curtain device itself. The present invention relates to a successful and intrinsically safe electric field curtain device.

4 to 9 show examples of the single-phase electric field curtain according to the present invention, and FIG. 4 shows an example of the single-phase electric field curtain according to the present invention, with the insulating material remaining only on the surface layer and other insulating material being removed. Figure 5 is a cross-sectional view taken along the ■-v line in Figure 4, and Figure 6 is the same as ■-■.
FIG. 7 is a cross-sectional view of the line section, FIG. 8 is a cross-sectional view of the line section II--■, and FIG. 9 is an electric circuit representation of FIG. 4.

In the two-phase electric field curtain according to the present invention, as is clear from FIGS. 4 to 9, the electrodes buried near the surface of the insulating layer 1 are arranged at equal intervals at a substantially constant depth t2 from the surface as shown in the figure. Buried, every other tree 4-1', 4-2'
, 4-3' total, and 3-1', 3-2', 3
-3' are grouped into another group, the electrodes belonging to the same group are connected to the protective resistor at one end, and the electrodes of the other group are connected to the protective resistor at one end on the opposite side to the protective resistor side of the group. is connected to each protective resistor, and each protective resistor is embedded in a sufficiently thick and mechanically strong insulating layer 16 on the back side of the electrode of the insulating layer 1, and the end opposite to the electrode is They are connected to power supply terminals 7 and 6 by conductive wires 38 and 37, respectively, from which two-phase AC high voltage is applied.

Furthermore, in the electric field curtain device according to the present invention, the electrode 3
-1', 3-2', 3-3', 4-1', 4-
2'.

4-3' is composed of high resistance electrodes appropriately selected by the method according to the present invention which will be described in detail later, and protective resistors 3-1'-36, 3-2'-36, 3-3'-36
, 4-1'-35, 4-2'-35, and 4-3'-35 are also constructed of resistors having high resistance values as determined by the method according to the invention which will be described in detail later.

The conductive wires 38 and 3γ are made of ordinary conductors.

Further, as shown in FIG. 1, the electrode and the protective resistor may be constructed separately and connected by conduction, but they may be constructed integrally using the same electrode material as shown in FIG. 8.

The electric field curtain device according to the present invention constitutes an intrinsically safe electric field curtain device that does not cause ignition explosion of treated particles and electric shock accidents against any dielectric breakdown that may actually occur for the reasons described in detail below.

In other words, dielectric breakdown accidents that occur in electric field curtain devices occur between dielectric breakdown that occurs between electrodes of different phases and objects that are substantially grounded in terms of higher voltage than each electrode. In these cases, spark discharge occurs between the electrodes or between the electrodes and the grounded object, and this It was not possible to avoid an accident in which the processed particulate cloud ignited and exploded.

However, in the electric field curtain device according to the present invention, short-circuit accidents occurring between electrodes can be avoided by appropriately selecting the power feeding points of the electrode groups having different phases according to the present invention, and by constructing the electrodes themselves with a high-resistance electrode material. For reasons explained in detail below, the structure is such that the amount of energy released at the short-circuit point is always smaller than the ignition energy of the treated particulate cloud, so ignition explosion accidents can be reliably prevented.

That is, in FIG. 9, the feeding point of electrode 4-3 is 4-3.
'-35', whereas the electrode 3- which has a different phase
The feeding point of electrode 3' is selected at 3-3'-35' on the opposite side, which is farthest from the feeding point of electrode 4-3'.

Therefore, electrode 3-3'c! If a short circuit occurs between =4-3' and In this case, the energy released at this short-circuit point is caused by the current limiting effect of the electrode 3-3' and the high resistances 4-3'-35 and 3-3'-36, which act as current limiting resistors in series. These shorting points 9−
If the electrode resistance and protective resistance are selected so that the energy released at point 9-1 is sufficiently smaller than the ignition energy of the treated powder, an ignition explosion accident at short-circuit point 9-1 can be reliably prevented.

Similarly, the short circuit accident 9-3 that occurred near the feed point of the electrode 3-3', 4-3'-35, was caused by the resistance of the electrode 4-3', the protective resistor 4-3'-35, and the protective resistor 3. -3'
-36 in series acts as a current-limiting resistor to limit the energy released at the short-circuit point 9-3, and by appropriately selecting these electrode resistances, the short-circuit point 9-3 essentially prevents the ignition and explosion of the treated particles. Accidents can be prevented.

Similarly, if a short-circuit accident occurs at an arbitrary intermediate point 9-2 between electrodes 4-3' and 3-3', the connection will be made from the feed point 4-3'-35' to the short-circuit point 9-2. Electrode 4-3'
electrical resistance, from short-circuit point 9-2 to feed point 4-3'-35'
The electric energy released at the short-circuit point 9-2 is the electrical resistance of the electrode 3-3' itself and the resistances of the protective resistors 4-3'-35 and 3-3'-36, all connected in series. becomes the current limiting resistance of the amount.

Normally, the electrical resistance of each electrode is selected to be uniform, so the amount of electrical energy released at each short circuit point is the same due to the three short circuit accidents described in detail above, and the current limiting resistance value in that case is always equal to the series resistance of the protective resistance of each electrode and the resistance of the entire electrode when it collapses.

Therefore, by configuring the structure as described above and providing each electrode and protective resistor with an electrical resistance having a value as described in detail later, the energy released in the event of a short circuit occurring between the electrodes can be used to prevent the ignition and explosion of unprocessed particulates. The electric field curtain device according to the present invention can reliably prevent this from occurring.

Next, regarding the prevention of short circuit accidents that occur between electrodes and grounding objects, the most dangerous is between the power supply point and the grounding point of a resistor where the resistance of the electrode itself cannot be expected to act as a current limiting resistor. This is an ignition explosion caused by a short circuit accident.

That is, in FIG. 9, this type of short circuit occurs at electrode 4-3.
This is a short circuit accident 10 that occurs between the power feeding point 4-3'-35' and the grounding object 8.

In such locations, the electrical energy released at the short-circuit point 10 is determined by determining the value of the current limiting resistor 4-3'-35 by the method according to the present invention as described in detail below, and by determining the value of the current-limiting resistor 4-3'-35 by the method according to the present invention as described in detail below. Due to the current limiting effect, the ignition and explosion energy of the treated particles is kept below the minimum energy.

In the case of a short circuit between the electrode 4-3' and the grounding point that occurs at any point on the electrode other than the feed point 4-3'-35', the protective resistor 4-3'-35 is added. The electrode 4-3' between the feed point 4-3'-35' and the short circuit point
Since its own electric resistance further acts as a current limiting resistance, it is possible to reliably prevent an ignition explosion caused by an electrode short-circuit to ground.

Next, details of the method for determining the magnitude of the protective resistance and the magnitude of the electrode resistance of the electric field curtain device used in the present invention will be explained.

FIG. 10 extracts and shows the main parts of the connections for adjacent electrodes of different phases and respective protective resistors of the electric field curtain device according to the present invention.

Next, FIG. 11 illustrates the main part of the structure on the electric circuit shown in the electrode system shown in FIG. 10.

That is, in FIG. 11, the adjacent electrodes 4-1' and 3-1' are 4-1'-1, 4-1'-2, and 4-1'-2, respectively.
4-1'-3...4-1'-n, and 3-1'
-1, 3-1'-2, 3-1'-3...3-1
21'-1, 21 which is divided into the electric resistance of each minute portion shown by '-n, and the capacitance between the electrodes 4-1' and 3-1' is divided into n pieces. '-2
, 21'-3, . Furthermore, a voltage is applied to the electrode 3-1' from the power supply 17 via the conductors 38 and 39 and the protective resistor 3-1'-36, and the voltage is applied to the electrode 4-1'. is the protective resistance 4-1'
A voltage is applied through -35.

In FIG. 10, the protective resistor 3-1'-3 according to the present invention
The required resistance value of 6 is determined as follows.

That is, from the feeding point of electrode 3-1' to the grounding point, arrow 10
When a short circuit shown by occurs, the protective resistor 3 is set so that the electrical energy released at this short circuit point is smaller than the ignition energy of the treated particulate cloud existing in the vicinity.
A value of -1'-36 may be determined.

In FIG. 11, if only the main parts of the circuit components directly related to this problem are arranged, a circuit diagram as shown in FIG. 12 will be obtained.

In the figure, a power supply 17 is connected to a capacitor 4 via a resistor 45.
7, and a short circuit point 4 is connected in parallel to this capacitance 47.
8 exists, and an untreated particulate cloud 5 exists around the short circuit point 48.
′ exists.

In this circuit, capacitance 47 represents the ground capacitance of electrode 3-1', resistance 45 represents the resistance of power supply protection resistor 3-1'-36 of electrode 3-1', and short-circuit gap 48 represents the ground capacitance of electrode 3-1'. -1' power supply point 3-1'-36' toward the grounding point 8.In an AC circuit with such a configuration, combustible material exists around the short-circuit gap 48. Capacitance 47 for ignition of particle cloud 5'
What effect the value of the resistor 45 has on the value of the AC applied voltage 49 is still completely unknown in conventional safety engineering.

The inventors have experimentally studied this problem and have completed the present invention by obtaining practically necessary and sufficient knowledge in order to determine the value of the protective resistance of the electric field curtain device according to the present invention. It is.

That is, in the experimental apparatus shown in FIG. 12, 5'
The fine particle cloud to be treated, represented by A test spark gap 48 is installed in a part of the spark gap 48, and tests are conducted to determine whether or not the fine particle cloud to be treated ignites and explodes in the spark gap 48 using various combinations of capacitance 47, electrical resistance 45, and applied voltage 49. Figure 13 shows the arrangement.

That is, in FIG. 13, the horizontal axis represents the resistance value R of the resistor 45 in FIG. 12 in MΩ, and the vertical axis represents the value of the voltage 49 applied by the power source 17 in FIG. 12 in KV. The three lines plotted on this RV plane have a capacitance of 4
7 as a parameter, and above each line there is always a cloud of treated particles (in this case, acrylic granule paint with an average particle size of 30μ)
A line is shown that indicates the boundary below which ignition of the treated particulate cloud occurs, and below which ignition of the treated particulate cloud does not occur.

Since the value of the ground capacitance that a single electrode of a practical electric field curtain device normally has is in the range of about 5 to 100 PF, an example of the experimental results shown in FIG.
Typical experimental examples in which the values of are 15PF, 4.5PF, and 61PF, respectively, are represented by curves 51, 52, and 52, respectively.
It is shown in FIG. 13 as 53.

The treated fine particle cloud 5' is adjusted to a predetermined ignition concentration by an electric field curtain device (not shown in the figure), and each fine particle is charged and moves extremely actively within its confined space due to the electric field of the electric field curtain. Since the particle cloud 5' forms a particle cloud with an extremely uniform concentration, the experimental results obtained using the experimental apparatus shown in Fig. 12 are extremely reproducible and reliable. I can do it.

The method for determining the value of the high resistance 3-1'-36 (which is shown in FIG. 11) according to the experimental results shown in FIG. 13 using the test equipment shown in FIG. 12 according to the invention is as follows. This is done as detailed below.

That is, when the maximum value of the ground voltage applied to the electrodes of this electric field curtain is 8 KV, the ground capacitance of the electric field curtain device is 15 to 61 PF, as is clear from Fig. 13.
If the capacitance 47 or 33 is in the range of
It is clear that this has almost no effect on the ignition of the curves, so a horizontal line 56 is drawn from the voltage 8KV on the vertical axis of FIG.
3, the point 54 that intersects with 53 is a perpendicular line drawn from 54 of this treated fine particle toward the R axis, and the value 28 obtained by the intersection with the R axis is defined as the minimum AC ignition resistance of this treated fine particle cloud. do.

That is, the minimum AC ignition resistance of the powder to be treated shown in FIG. 13 is IOMΩ.

In other words, in an electric field curtain device that processes untreated powder, if a short circuit occurs from a single electrode of the electric field curtain device to a grounded object and a spark discharge occurs, the spark discharge causes a flaming explosion of the treated particles. The minimum resistance value necessary to prevent the induction of is 10 MΩ, and if the value of the protective resistance is smaller than this, ignition and explosion of the treated particles will occur in the gap 48 in FIG.
When the value of the resistance 45 is larger than this, the powder to be treated does not explode in the gap 48.

Therefore, we also looked at the safety factor, and in this case, the safety factor was set to 2.
If you use a protection resistor of 20MΩ for the gap 48
It can be guaranteed that practically no ignition explosion of the treated particles will occur.

In this way, depending on the voltage applied to the electric field curtain and the value of the grounding capacity of the single electrode of the electric field curtain, the ignition of the powder to be treated is prevented. This makes it possible to reliably prevent ignition of the powder to be treated.

The protective resistors selected through the above procedure are arranged geometrically as shown in Figures 5 to 9, and power is supplied to the power supply point of each electrode via the protective resistors selected through the above procedure. Ignition and explosion of the processed particulate cloud in the event of a short circuit accident with a grounded object at the feeding point of the electrode of the electric field curtain device according to the invention can be virtually completely prevented.

Next, we will discuss how to find the resistance value that the electrodes themselves should have against short circuits caused by capacitance between adjacent electrodes.If the obtained value is lower than the effective earthing protection resistance value, the electrodes will have resistance. There is no need to have

That is, the grounding protection resistor acts as a protection resistance in series with respect to the inter-electrode spark, and if the electrode itself has resistance, it can share the required resistance amount.

Furthermore, if the resistance value determined from the inter-electrode capacitance is greater than the resistance value determined from the ground capacitance, safety is maintained even if the electrode is a good conductor if the former is used as a reference for the earth protection resistance value.

The resistance value given to the electrodes for preventing ignition and explosion of the treated fine particle cloud due to a short circuit occurring between the electrodes according to the present invention will now be described in detail.

In FIG. 11, electrodes 4-1' and 3-1 having different phases
If a short circuit 18 occurs in the middle of ',
The energy released here is that the electrostatic energy stored in the minute capacitance 21'-4 of the distributed capacitance between the two electrodes existing nearby is first released, and then the electrostatic energy is connected in series to this capacitance. The minute resistance of each part of both electrodes connected to 3-1'-1...3-1'-3, 4-1-n.
. . . The short circuit 1 is caused by a spark discharge caused by the AC voltage supplied from the power supply 17 through the combined resistance of 4-1'-4.
The energy released at 8 will trigger an ignition explosion of the process particulate cloud present in its vicinity.

However, in this case, 4
Assume that the protection resistors -1'-35 and 3-1'-36 are not present.

Considering this, both electrodes 4-1' and 3-1
The electrostatic distributed capacitance existing between 21'-1...
Assume that 21'-4...21'-n are all connected in parallel to the capacitance of 21'-4 without using a resistor, making it the same as the total capacitance between both electrodes. However, from a safety point of view, considering that the situation will proceed in a safer direction, the short circuit 18 between the electrodes in Fig.
When this occurs, the value of resistor 45 in Figure 12 is used as a model for determining the electrical resistance of the electrode in order to prevent the short circuit from igniting and exploding the treated particles, using the resistance of the electrode itself. is the minute resistance 3-1 in Figure 11 and 1+...3-1'-3+
4-1'-4+...4-1'-n is equal to the value of resistor 45 in Figure 12, and capacitance 47 in Figure 12 is equal to the total capacitance between both electrodes. You can think about it.

Therefore, the voltage 49 applied by the power source 17 and the resistor 45
The resistance 45, the capacitance 47, and the applied voltage 49 should be selected based on the relationship between the ignition of the fine particle preshock 5b processed by the electric field curtain and the relationship between the resistance 45 and the capacitance 47. This is the basic content of the present invention.

This model is exactly the same as the one used to determine the protective resistance 3-1'-36 for safety against ignition of the processed particulate cloud due to a short-circuit accident at both ends of the ground capacitance of a single electrode of an electric field curtain device. Therefore, by making the value of the resistor 45, that is, the resistance value that the electrodes should have, larger than the AC minimum ignition resistance that has already been explained in detail, the electric field curtain device according to the present invention can reduce the mutual resistance between the electrodes. It is possible to reliably prevent ignition of the processed particulate cloud due to a short circuit accident that occurs during the process.

However, in this case, as is clear from Fig. 11, it can be virtually assumed that the odor short circuit accident 18 between the two electrodes occurs near the shortest distance between the two electrodes, so the short circuit accident 18 may occur between the electrodes. Electrical resistance 4 in Figure 12 no matter where it occurs
The value of 5 is the same value as the electrode resistance.

Therefore, the value of the minimum AC ignition resistance shown in FIG. 13 may be used as the resistance of the electrode itself, taking into account other conditions and giving an appropriate safety factor.

As explained in detail above, in the electric field curtain device according to the present invention, the value of the protective resistance of each electrode and the value of the electrical resistance of the electrode itself are determined by the method explained in detail above, and By selecting the geometrical arrangement of the feed points, it is possible to virtually completely prevent ignition of the treated particle cloud due to short-circuit accidents between the feed point and grounded objects and between electrodes.

In this case, from the standpoint of safety principle, if the length of the electrodes is very short and the value of capacitance between the electrodes is extremely small, the protective resistance of each electrode will cause the particles to be treated to It is clear from the above detailed explanation that cloud ignition and explosion can be prevented.

However, when the length of the electrode is longer than a certain level, it is extremely effective to provide the electrode itself with electrical resistance according to the determination method according to the present invention. If the generated electric field between the electrodes has no electrical resistance, the voltage will completely drop to O over the entire electrode, and the electric field curtain function will be lost over the entire electrode. In an electric field curtain with electrical resistance, the relative voltage decreases only in the vicinity where a short circuit accident occurs, and this does not affect the entire electrode, so the decline in the function of the electric field curtain due to a short circuit accident is extremely small. This is a practically extremely advantageous effect of the present invention.

In the electric field curtain device according to the present invention, the protective resistor is usually thick enough on the back side of the electrode to ensure sufficient safety on the back side of the electric field curtain, which can be expected to provide extremely sufficient protection and insulation ability both mechanically and electrically. In principle, the

Therefore, as a practical matter, it is possible to select the value of the protective resistor to be a sufficiently large current-limiting resistance in order to prevent electric shock accidents at the power feeding point, but by providing resistance to the electrode itself, electric shock accidents can be prevented. It is possible to further improve the prevention of this problem.

Furthermore, in the electric field curtain device according to the present invention, which employs a resistance value larger than the AC minimum ignition resistance as the protective resistance and electrode resistance, if the length of the electrode is about several tens of centimeters, the electrode is a substantially conductive electrode that does not have resistance. The function as an electric field curtain is not inferior in any way compared to the electric field curtain device using the electric field curtain device.

Next, as an example of applying the present invention to multiphase alternating current, an electric field curtain device according to the present invention using three-phase alternating current will be described in detail.

In the electric field curtain device according to the present invention, if the protective resistor is a single phase, and if any one of the phases is always grounded, the protective resistor should not be provided on the electrode of the grounded phase. , a protective resistance having a predetermined magnitude of force other than the contact side may be provided.

However, in general, it is more convenient to divide the protective resistance value into two and install a protective resistor on each phase of both swords, as shown in Figure 9, so that it can be used with either side grounded. There are many.

Next, an electric field curtain device according to the present invention of the type operated by polyphase alternating current will be explained by way of example of an electric field curtain device used with a three-phase alternating current power supply.

Figure 14 shows three-phase AC power supplies 65, 66, 67
The electric field curtain device according to the present invention operated by the electric field curtain device according to the present invention is shown in the same manner as FIG. It is something.

In the three-phase electric field curtain device according to the present invention shown in FIG. 14, every second electrode is connected in the same phase, and is divided into three phases.

The power feeding point of the electrodes of the phase connected by the conducting wire 76 is selected at the upper end of the figure, and the feeding point of the electrode group connected to the conducting wire 77 is fed from a point approximately half the length of the electrode, and the feeding point of the electrode group connected to the conducting wire 77 is The feeding point of the electrode group connected to is selected to be the lowest point of the electrodes.

The electrical resistance of each electrode is determined by the present invention based on FIGS. 12 and 13 for the maximum applied voltage applied to each electrode. It is selected to be held as the resistance value of .

In this way, for example, 9-
In the event of a short circuit accident as shown in 4,
Even if the electrical energy released at this point is considered ignoring the power supply protection resistors 70-1 and 71-2, the amount of electrical energy released at the short circuit point 9-4 is limited by the electrical resistances 61 and 62. , electrical resistance 61 and 62
Since the sum of the above is larger than the AC minimum ignition resistance, ignition explosion of the processed particulate cloud in the short circuit accident that occurred in 9-4 is virtually completely prevented.

This relationship becomes the worst condition for electrodes 70 and 71 when the short circuit accident 9-4 occurs between the power supply points of electrodes 70 and 71, and the short circuit accident occurs below the power supply point of electrode 71 as shown in 9-5. If it occurs on the side, there is no problem because it is much safer.

Next, to explain in detail how to determine the size of the protective resistor for power supply, in a three-phase sine wave AC power supply such as 65, 66° 67 shown in FIG. Since the generated voltage is the heaviest of the phase-to-phase voltage applied between 70 and 71, if it is adopted as a protective resistance TO-1 that is larger than the value of the AC minimum ignition resistance determined by the present invention for this voltage, This relationship is also exactly the same for the protective resistors 71-2 and 72-3, and in general, in the case of multiphase AC, the value of the protective resistor should be chosen smaller than the AC minimum ignition resistance required for the electrode itself. become.

As an embodiment of the three-phase electric field curtain according to the present invention, as shown in FIG. 15, the feeding points of each electrode are taken from both ends of the electrode, and the feeding points of adjacent electrodes are always taken from the opposite side. An electric field curtain device according to the invention is also possible.

In the three-phase electric field curtain device shown in FIG. 15, a short circuit accident 9 occurs between adjacent electrodes 70 and 71.
Regarding -4, its safety is high, but it is not impossible that a short circuit accident may occur by jumping over one phase as shown in 9-5, depending on the falling object onto the surface of the electric field curtain. Therefore, in this case, the safety effect of the electrode resistance may become zero, and there is no point in providing resistance to the electrode.

Compared to short circuit accident 9-4 that occurs between adjacent phases,
Although the probability of an accident as shown in 9-5 occurring is extremely low, generally speaking, the three-phase electric field curtain device according to the present invention of the type shown in Fig. 14 is better than the one according to the present invention shown in Fig. 15. It can be said that the safety is higher than the electric field curtain device.

Also in the three-phase electric field curtain device according to the present invention, depending on the power supply connection, as in the single-phase case, a protection resistor is not required in principle for the electrode group that is supplied with power by the installed phase.

However, in this case, a high voltage is applied to the electrode groups of the other phases, so the protective resistance of the other phases must be set to a correspondingly large value, and the versatility of electrode connection is lost. In many cases, it is more convenient to provide a protective resistor for each electrode, as shown in FIGS. 14 and 15.

In the electric field curtain device according to the present invention having more than three phases, as explained in detail above, the particle cloud is processed according to the voltage applied between the phases and the voltage applied between each phase and the ground point. The determined characteristic values as shown in FIG. 13 are prepared using an experimental apparatus as shown in FIG. 12, and a resistance larger than the determined AC minimum ignition resistance can be selected. It is easy to make the multiphase electric field curtain device according to the invention inherently safe in exactly the same way.

In general, with regard to the protective resistance for the feed point in the electric field curtain device according to the present invention, the capacitance between the phases is not very large, and the capacitance to ground is several points in the range where the electrostatic energy stored therein is smaller than the ignition energy of the direct current. It is also possible to install protection resistors for supplying power collectively to the electrodes of the same phase according to the method specified in detail by the present invention.

However, in this case, if a short circuit occurs between phases or a short circuit occurs between the power supply point and the grounded object, it will lead to sudden danger, so normally power is supplied to each electrode separately. It is preferable to install a protective resistor for power.

For normal purposes, such as electric field curtain panels used for lining electrostatic powder coating booths, the electrodes and protective resistors are lim or less, with an electrical resistance of several hundred kilograms to several MΩ per cfrL. Electrodes for the electric field curtain having a diameter are required, which can be made of polyethylene, vinyl chloride, or other suitable plastic mixed with a suitable conductive material such as carbon powder, carbon fiber, or metal powder. It is easy to obtain a certain degree of resistance, and in fact, by this method it is possible to easily obtain suitable electric field curtain device electrodes and protective resistors that can be used in the electric field curtain device according to the present invention.

An example of an electric field curtain device according to the present invention will be described.

A diameter of 0.5 mm is placed at a depth of 0.5 mm from the surface of a plastic plate with a thickness of 10 rILm. 'IMΩ per cfrL at 5 mm
A conductive plastic electrode having a resistance of In the electric field curtain device according to the present invention, which is embedded with sufficient mechanical strength, holes are made in the surface of the electrode or objects are dropped on the surface of the electrode to damage the surface during operation, and at the same time, the electric field is applied to the surface. When a voltage was applied to a sufficiently concentrated acrylic electrostatic powder paint suspended by a curtain effect, weak spark discharge was observed between the electrodes and between the electrodes and the ground object. No ignition of the powder was observed, demonstrating the extremely high safety of this electric field curtain device.

In addition, the function as an electric field curtain does not use a protective resistor.
Moreover, it was confirmed that the electrodes were almost the same as an electric field curtain made of conductors of the same shape.

Furthermore, in contrast to electric field curtains in which the electrodes are made of conductors, the entire device becomes unusable as soon as dielectric breakdown occurs, the electric field curtain device according to the present invention
It has become clear that the device has an extremely large advantage in that it can be safely continued to be used as it is, with only the function of the portion d being degraded.

[Brief explanation of drawings]

Fig. 1 is a bottom view with a part of the conventional electric field curtain device cut away, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a sectional view taken along the line I-1 in Fig. 2. , FIG. 4 is a partially cut-away bottom view of the single-phase safe electric field curtain device according to the present invention, FIG. 5 is a sectional view taken along the line ■-■ in FIG. 4, and FIG. 6 is a cross-sectional view taken along the line Vl-Vl. 7 is a cross-sectional view of the section lined by ■-■, FIG. 8 is a cross-sectional view of the section lined ■-■, FIG. 9 is an electric circuit diagram of FIG. 4, and FIG. 10 is a cross-sectional view of the section of the present invention. An explanatory diagram of the main parts of the device, Fig. 11 is an electric circuit diagram of Fig. 10, Fig. 12 is an electric circuit diagram extracting the main parts of Fig. 11, and Fig. 13 is a circuit diagram of Fig. 12. Fig. 14 is an electric circuit diagram of a three-phase safety type electric field curtain device according to the present invention, and Fig. 15 is a diagram showing the results of testing on the device shown in Fig. 15. FIG. 3 is an electrical circuit diagram showing another example of the device. 1... Insulator layer, 2... Surface layer, 3-
1'-... Electrode, 3-2'... Electrode, 3
-3'... Electrode, 4-1'... Electrode, 4
-2'... Electrode, 4-3'... Electrode,
3-1'-36...Protection resistor, 3-2'-36
...Protection resistance, 3-3'-36...Protection resistance, 4-1'-35...Protection resistance, 4-2
'-35...Protection resistance, 4-3'-35...
...Protection resistance, 48...Floating dust.

Claims (1)

[Claims] 1. Electrodes in the form of rods, wires, strips, etc. are arranged spatially parallel to and at regular intervals on a virtual surface, and an AC high voltage is applied between adjacent electrodes to In a device that repels charged particles from a virtual surface by an alternating unequal electric field generated in the The minimum AC ignition resistance value to the ground is determined so that floating dust will not be ignited by continuous spark discharge to the ground due to the ground capacitance of the current resistance (protective resistance) and the maximum voltage used. A minimum AC ignition resistance between electrodes is determined to prevent floating dust from being ignited due to continuous spark discharge between the electrodes due to capacitance and the maximum voltage used. A safety electric field curtain device in which a protective resistance with a minimum AC ignition resistance value or higher, which is the higher value of the first two, is inserted into the device. 2 Arrange bar-shaped, wire-shaped, strip-shaped electrodes spatially parallel to the virtual plane and at regular intervals, and apply an AC high voltage between adjacent electrodes to generate an alternating unequal electric field near the virtual plane. In a device that repels charged particles from a virtual surface, the electrode is divided into electrode elements of an appropriate length or less as necessary, and the electrode elements and the series current-limiting resistor (protective resistor) of the electrode element are used. The minimum AC ignition resistance to the ground that will prevent floating dust from being ignited due to continuous spark discharge to the ground based on the ground capacitance of A resistor with a resistance greater than the minimum AC ignition resistance to ground is inserted into the electrode, and the distance between the electrodes is such that floating dust will not be ignited by continuous spark discharge between the electrodes due to the capacitance between adjacent electrode elements and the maximum voltage used. Determine the minimum AC ignition resistance value, choose the feed point of adjacent electrode elements at the far end of each electrode element, and -
A safe electric field curtain device in which the total resistance from the feed point of the electrode element to one end is greater than or equal to the minimum AC ignition resistance between electrodes.