JPS6144544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves sending solid or liquid fine particles dispersed and suspended in a gas toward an object to be coated through a loop-shaped ionic current generating electrode placed opposite to and separated from the object to be coated. The present invention relates to an electrostatic coating device characterized in that a DC voltage is applied between an ionic current generating electrode and an object to be coated.

Electrostatic powder coating has recently begun to be widely used because of its excellent coating film quality and for the purpose of preventing air pollution caused by coating methods using other liquid paints. However, because the paint is expensive and it is difficult to change the color, its applications are limited.To solve this problem, it is necessary to dramatically improve the coating efficiency and quickly and reliably change the color in the coating equipment. There is a strong need for the development of a new method. For example, when applying powder coating to the top coating of an automobile body, if the powder coating efficiency is 80% or more, the paint cost will be profitable even if the overspray powder is discarded, and the coating efficiency will be 85% or more. It is said that if efficiency can be achieved, it will be more economical than painting with liquid paints using conventional thinners, but when using conventional electrostatic powder coating guns,
%, and in order to continuously switch between applying powder coatings of different colors using the same electrostatic powder coating gun, the current electrostatic powder Body painting guns are extremely unreliable in their operation. The present invention solves these problems and provides an electrostatic powder coating device that enables highly efficient electrostatic powder coating and reliable and rapid color change, and also has extremely good throwing performance. This is what we provide.

In a conventional electrostatic powder applicator painting gun, as shown in Fig. 1, powder is sent to the gun body 1 through a pipe 2 by a powder supply device 3, and is dispersed into a gas from its tip. A corona discharge electrode 4 such as a corona bottle or a corona edge is provided at the tip of the gun body 1, and a DC voltage is applied to it by a power source 5. The corona current generated in the discharge electrode 4 charges the floating powder in the process of flying toward the object to be coated 6, and is driven by the electric field from the tip of the gun toward the object to be coated,
Powder is usually applied to the object to be coated.
However, in this case, as shown in Figure 2, the current density of the corona discharge current is extremely high near 8 on the center line, which is closest to the object to be coated than the corona discharge electrode at the tip of the electrostatic powder coating gun, and For example 9
The current density is extremely small at . On the other hand, the powder ejected from the gun is extremely dense near its tip 7, and the powder is not sufficiently dispersed when it reaches the corona discharge electrode 4.
Since the discharge ion current flows, this dense powder prevents the stable generation of ion current, and the dense powder particles mask the ion current from each other, causing the powder to be coated from the tip of the gun. The electric field towards the object is also very strong only above the central axis 8, but rapidly weakens as it moves away from the center, so that particles that are not sufficiently charged will be affected by the wind speed required for ventilation in the booth, as shown by arrow 10, for example. As a result, a large amount of particles deviate from the conical area surrounded by lines 12 and 13, that is, the effective area of the power line from the gun to the workpiece, before being charged, as shown by arrow 11. This phenomenon causes a significant decrease in coating efficiency, and is relatively easy to occur if the area is slightly off the center. Therefore, in a conventional electrostatic powder coating gun, a work piece with a diameter of about 30 cm is coated in a booth where ventilation is performed at a wind speed of about 0.5 m per second in the vertical direction as shown by arrow 10. of
The coating efficiency obtained when painting from a distance of about 30 cm is usually about 75 to 80%, but when applied to the painting of an automobile body, for example, it actually becomes about 65 to 70%. It is normal to put it away.

To summarize the above, in conventional electrostatic powder coating guns, the charging device is usually located in the center of the powder spout, so the concentration of powder in the charging area is too large and the charging is not sufficient. If the electric field distribution is not carried out, the electric field distribution is significantly large in the center part 8, becomes weaker rapidly as it deviates from the center part, and becomes significantly smaller in the peripheral part 9. Furthermore, the corona discharge electrode 4 installed in a region with a high concentration of powder will soon become powdery. Corona discharge tends to become unstable due to body fusion and other causes, and when these three causes overlap, the uncharged powder becomes more effective in the electric field, especially under the influence of the wind speed in the booth. It can be said that the proportion of powder that escapes from the area increases and this hinders the improvement in efficiency. In order to overcome the causes of low efficiency in conventional electrostatic powder coating guns as described in detail above, the voltage applied to the tip of the coating gun is usually increased by step 5. It is common to maintain a strong electric field strength and at the same time increase the corona current by applying a high voltage, thereby accelerating the charging of the powder. In this case, the corona discharge electrode at the tip of the gun Not only does this increase the voltage applied to the workpiece, causing other stability and handling problems, but also increases the current flowing from the gun tip to the workpiece, which can lead to premature formation of a powder layer on the workpiece. This causes serious defects such as reverse ionization and the inability to obtain a smooth powder layer. Therefore, it is essentially difficult to maintain the conventional electrostatic powder coating gun, in which a corona discharge electrode is installed at the center of the powder outlet and its vicinity, and expect higher efficiency than the current level. I have to say that there is.

In order to overcome the essential drawbacks of the conventional electrostatic powder coating gun described in detail above, the present invention provides an outlet for supplying powder dispersed and suspended in a gas toward the object to be coated. The first feature is that a loop-shaped ion-generating electrode is provided surrounding the ion-generating electrode from the outside. At the same time that an ionic current flows toward the object to be coated from at least the surface of the loop-shaped electrode facing the object to be coated, a voltage is simultaneously applied to generate an electric field directed from the loop-shaped electrode toward the object to be coated. This creates a skirt-like ionic current and electric field that envelops the powder particles supplied toward the object to be coated, ensuring that the powder particles are well-dispersed and charged, and at the same time, the electric field By reliably enclosing the particles, the particles are charged and driven reliably, thereby successfully increasing the coating efficiency of the powder particles significantly.

Next, the configuration of a basic embodiment of the present invention will be explained in detail. In FIG. 3, the object to be coated 26 is held in contact with the ground as in normal powder coating.
Opposing this, a loop-shaped electrode 16 is provided separately, and from the surface of this electrode facing the object to be coated, an ionic current flows seamlessly toward the object to be coated. A voltage is applied to the electrode 16 so that a DC electric field is formed toward the object to be coated. As a means for concretely constructing the loop-shaped electrode 16 having such a function, for example, a planar silent discharge electrode as shown in Japanese Patent Publication No. 51-8347 may be used, and as shown in FIG. In the figure, 17 uses a planar silent discharge electrode as the loop electrode 16, and 18 uses a DC power source to generate a DC potential difference between it and the object to be coated. This is what is shown. Further, a powder delivery port 15 and the like is provided as a device for delivering solid or liquid fine particles, which is provided separately from the loop-shaped electrode 16 and whose distance from the loop-shaped electrode can be changed relatively. ing. In the electrostatic powder coating apparatus according to the present invention configured as described above, the ionic current and electric lines of force flowing from the loop-shaped electrode 16 toward the object to be coated 26 are configured in a skirt shape as shown in 32. ,
As shown in Fig. 33, there is a slight core in the center where no electric field or current exists, and the loop-shaped electrode is formed to wrap around this core with a relatively uniform distribution and no breaks. A skirt of ionic currents and electric field lines is formed that ends in the object to be coated. FIG. 4 shows the loop-shaped electrode 1 in FIG.
6. Only the weak electric field weak current part 33, that is, the continuous skirt of the ionic current and electric lines of force with the core formed between the objects 26 to be coated is taken out and shown as a schematic diagram, FIG. 5 shows the distribution of current density from the loop-shaped electrode on the object to be coated. Powder particles to be coated are delivered as indicated by arrow 19 by powder delivery ports 15 facing toward the inner edge of the loop-shaped electrode, and a powder storage hopper 24 21 is used for powder delivery. The ejector 25 is a powder transport pipe, etc., and these may be appropriately carried out according to a conventional method. Powder particles 19 delivered through the inner edge of the loop electrode 16 in FIG.
2, 23, etc., it advances toward the object to be coated 26, but as it is dispersed, it immediately rushes into the region 20 where ionic current and electric lines of force exist, where it is well dispersed and forms a skirt-like structure. The uncharged particles are immediately charged by the shower of ion current and proceed toward the object to be coated, and the uncharged particles are pushed by the airflow that follows and gradually escape toward the outer circumference inside the ion skirt. For example, arrow 27, only uncharged particles come.
28, 29, 30, 31 etc., it escapes to the outside of the ion skirt,
Before they escape from the outer surface of the ion skirt, they are well dispersed at the outer periphery of the ion skirt, so they are reliably charged and form a skirt shape, forming lines of electric force that coexist with the ion current. The action immediately drives them toward the object to be coated, and the uncharged particles that have escaped to the outside of the ion skirt are selectively and reliably charged and driven toward the object. The electrostatic powder coating device according to the invention makes it possible to achieve extremely high efficiency. This means that the ionic current and electric lines of force flowing toward the object to be coated all start from the loop-shaped electrode 16, form a continuous ion skirt, and terminate at the object to be coated. This was only made possible by feeding the powder in a dispersed state to the destination, and this is the most distinctive feature of the present invention, which allows for extremely high coating efficiency. It will be done.

Usually, when the powder particles 21 are conveyed with gas and ejected into the air by a conventional method as shown in FIG. One part is charged with a polarity that is immediately driven toward the object to be coated by the line of force, the other part is charged with the opposite polarity, and the remaining part is almost uncharged. Usually, particles with three different charged states are mixed. In this case, there is no problem with the polarly charged particles that immediately fly toward the object to be coated due to the electric field directed from the loop electrode 16 toward the object 26, and the uncharged particles are explained in detail above. There is no problem with this as the ion current is selectively charged and driven to the object as it escapes to the outside of the skirt-like ion current through the process described in . However, particles charged with opposite polarity,
If there is a part of the loop electrode that is not emitting ion current toward the workpiece, it will accumulate and grow there, creating a tear in the ion skirt through which uncharged particles can flow. A situation occurs in which the particles escape and reduce the coating efficiency. Therefore, it is necessary for the loop-shaped electrode 16 used in the present invention to reliably generate a continuous ionic current at least on its surface facing the object to be coated. For the first time, it has become possible to reliably demonstrate the performance of the coating device, and this is achieved by using the electrostatic powder coating device, which has a corona edge or a corona bottle around the outer periphery of the powder delivery port found in certain types of existing powder coating guns. This is essentially different from a paint gun.

In other words, in a powder coating gun that has a ring-shaped corona edge around the powder delivery port, it is actually impossible to reliably generate corona discharge over the entire length of the corona edge, and there is always a cut there. The aspect of the present invention cannot be satisfied. That is, in the case where a corona bottle is provided around the powder delivery port, a large tear is created in the area where the corona bottle is not present, and an ion skirt cannot be formed, so it is also impossible to achieve the effects of the present invention. Therefore, it is essentially different from the present invention. As the loop-shaped electrode 16 used in the present invention, as mentioned above, for example, JP-A-51-8347
Although it is best to use a planar silent discharge electrode configured in a loop shape as shown in the above publication, it is also possible to use a harmonic bow-shaped glow corona electrode. The ions of opposite polarity necessary to apply a voltage that creates a positive potential to the workpiece and generate a harmonious glow corona are usually supplied from a powder layer formed on the workpiece. Therefore, it is often not necessary to provide a supply device for ions of opposite polarity. Even when the loop-shaped electrode 16 is configured with a harmonic glow corona discharge electrode or a planar silent discharge electrode, it is completely impossible to deposit extremely fine powder particles on the surface of the loop-shaped electrode 16, albeit gradually. In this case, it is possible to continuously remove the fine particles deposited on the surface of the loop-shaped electrode 16 (not shown in the figure) for a long period of time by installing a device to remove or prevent the fine particles from accumulating on the surface of the loop-shaped electrode 16 (not shown in the figure). In some cases, it may be possible to bring about good results for realizing safe driving. In addition, the powder particles that are sent out from the powder outlet 15 toward the inner edge of the loop-shaped electrode and are dispersed and suspended in the gas in the skirt may be pulled back depending on the direction of the wind inside the booth. , in such a case, the auxiliary airflow 23 and 22
By using either one or both of these, highly efficient electrostatic powder coating can be achieved by reliably feeding powder particles into the interior of the unbroken skirt of ionic current and electric lines of force. This is also a major feature of the present invention. be.

In the present invention, the method of supplying powder particles by dispersing and suspending them in gas toward the inner edge of the loop-shaped electrode is usually carried out using a transporting gas according to a conventional method, as shown in FIG. However, without being limited thereto, it is of course possible to introduce the powder particles towards the inner edge of the loop-shaped electrode without entraining gas by gravitational or electrostatic methods; This can sometimes lead to very high efficiencies. Note that the loop-shaped electrode used in the present invention is not limited to the annular plate-shaped electrode exemplified in the above explanation, and a loop-shaped electrode with a slit-shaped inner edge is also possible.
7 and 7 show such an embodiment.

That is, when painting a wide object 42 moving in the direction of arrow 43, a potential difference _E
This is a slit-shaped electrode whose inner edge extends in the width direction of the object 42 to be coated, and is spaced apart from the object 42 to be coated. , 37, and 38 are attached in series by a frame 39, and are arranged to perform reciprocating motion as shown by arrow 46 in order to achieve uniformity of the coating film. Note that 40 indicates the ionic current flowing from the loop-shaped electrode 44 toward the object to be coated, and the outer surface of the electric flux skirt.
Reference numeral 41 indicates a weak portion of the ionic current and electric lines of force formed therein. In this way, the loop-shaped electrode 44 is formed on a wide object to be coated so that its inner edge forms an elongated slit shape,
First, the powder particles 47 suspended in the gas blown into the slit are passed through the nozzles 37, 38, and 39 as indicated by the arrows.
By performing reciprocating motion as shown in 6, it becomes possible to form a powder layer of uniform thickness on the object 42 with high coating efficiency, as indicated by arrow 48 in FIG. Almost no powder particles escape from the skirt of the ionic current and come out to the outside, and it is easy to achieve a coating efficiency of 90% or more. Note that if the slit portion 49 opening at the inner edge of the loop-shaped electrode 35, 35' is extremely thin, the end electrodes 44, 45 present at both ends or one end thereof are not necessarily present; Of course, the loop-shaped electrode used in the present invention also includes a slit-shaped electrode in which 44 and 45 in FIG. 6 are removed, and which has substantially the same function as the loop-shaped electrode.

FIG. 6 is a perspective view of an embodiment in which the powder coating apparatus according to the present invention is applied to a wide continuous object, and FIG. 7 is a horizontal cross-section of FIG. 6.

In the electrostatic powder coating device according to the present invention, it is possible to have an extremely large degree of freedom in the relative positional relationship between the loop electrode and the means for feeding the powder. It is possible to obtain high performance not found in other devices. For example, in FIG. 8, reference numeral 15' is a powder feeding nozzle made of an insulating material, which is inserted through the loop electrode 16' to a position quite close to the object to be coated 26'. Therefore, the loop-shaped electrode 16'
is located quite far from the object to be coated 26', so that the skirt 32' of the ion and electric lines of force can be sufficiently wrapped around the back of the object to be coated, and at the same time, the skirt 32' of the loop-shaped electrode 16' can be The central core 33' where there is no ionic current and electric field starting at the inner edge and terminating at the workpiece 26' becomes extremely thin, and at its end 27' to the workpiece 26' there is virtually no current-free section. It turns out. In such an arrangement, the powder fed into the nozzle by arrow 25' is separately fed with a pattern adjusting gas shown by arrow 92' inside the tip 15'a of the nozzle. , a rapid swirling flow is generated inside the tip of the nozzle, whereby the powder is ejected from the tip of the nozzle into the ion skirt 32' forming extremely widely spread patters 28', 28'', etc. In this case, it is possible to apply uniform coating to the back side of the object 26' as shown in the figure, and it is possible to apply the coating evenly to the back side of the object 26' as shown in the figure. Even in the case where the front surface is coated well, the lines of electric force starting from the outer edge of the loop-shaped electrode 16', which is placed far away, as shown by the arrows 30' and 30'', can be obtained. Since the skirt 32' wraps sufficiently around the back side of the object to be coated 26', the sufficiently charged powder goes around to the back side of the object to be coated, so that the coating work can be completed in an extremely short time. In this way, in the powder coating apparatus according to the present invention, the loop-shaped electrode 1
By constructing an insulating material through the inner edge of the 6' and adjusting the spouting pattern of powder in various ways at the tip, it is possible to eliminate coatings that could only be achieved with extremely insufficient coverage using conventional electrostatic powder coating guns. An extremely important feature is that it can provide good coverage on coated objects.

In many cases, it is appropriate to adjust the powder ejection pattern from the nozzle by using a swirling airflow generator installed inside the tip of the nozzle, as described above. may be provided.

Next, it will be explained that the powder coating apparatus according to the present invention can extremely easily solve the difficulty in changing colors, which has been a major problem in conventional electrostatic powder coating guns. Figures 9 and 10 show an example of a case where three colors are changed in the electrostatic powder coating apparatus according to the present invention, and Figure 9 is a cross-sectional view. , FIG. 10 is a longitudinal section. The loop-shaped electrode is a long object to be coated 55 in the vertical direction.
A potential difference E _L is applied to the loop-shaped electrodes 50, which have longitudinally long inner edges facing each other, and are spaced apart from each other. Nozzles 51, 52, and 53 of different colors are attached to a shaft 58, which is shaped like a cylindrical shape, and this shaft 58 is attached to a mounting frame 54 that makes a reciprocating movement in the vertical direction as indicated by an arrow 56. In such a case, the loop-shaped electrode 50 according to the present invention can be applied to the coated object 55.
The nozzles 51, 52, 53
It is sufficient to simply send the powder suspended in gas toward the object to be coated through the inner edge of the loop-shaped electrode, and therefore, the structure of the nozzle is extremely simple, compact, and lightweight. Preparing this for each color of powder coating to be used does not place an excessive burden on the reciprocating device and at the same time does not increase the economic burden. Therefore, in the present invention, nozzles 51, 52, and 53 are prepared for each color of paint, and the nozzles are changed by switching the nozzles 51, 52, and 53 to the inner edge of the loop-shaped electrode 50 as necessary by using the rotary fixing device 57 to open the nozzles. The problem of color change in the system is very reliably solved and eliminates the problems associated with changing the powder supply line, such as those found in conventional powder coating guns, and the need to clean the inner surface of the nozzle system after each color change. This makes it possible to reliably prevent the problem of paint loss due to drying. In this case, the problem of powder paint adhering to the loop electrode can be solved by using an electrode that has the property of repelling powder by itself, such as a planar silent discharge electrode, as the loop electrode 50. In addition, the prevention and cleaning of the powder from adhering to the loop electrode can be carried out by means of an air flow flowing through the loop electrode or by other means with the aid of an auxiliary device (not shown).

FIGS. 11 and 12 show an embodiment in which the powder coating apparatus according to the present invention is applied to an automobile body, including a booth where coating is performed. FIG. 11 is a cross-sectional view along the direction of movement of the automobile body to be painted.
Figure 2 is a sectional view perpendicular to the direction of movement of the body to be painted. In FIGS. 11 and 12, an automobile body 75, which is an object to be coated, moves in the direction of an arrow 80 inside a booth 60, and inside the booth there is a super-air conditioning device 61 installed on the ceiling. Air is blown into the booth through the booth as shown by arrow 62, and is exhausted from the bottom as shown by arrow 79. As is clear from FIG. 11, a loop-shaped electrode 63 and nozzles 64, 65 are mainly used to paint the upper surface of the body.
and loop-shaped electrode 6 for painting the side of the body.
6, 68, 71, 78 and nozzles 67, 69, 7
0 and 72 are located at positions shifted with respect to the traveling direction of the body to be coated. The loop-shaped electrode 63 and the nozzles 64 and 65 for coating the upper surface are different in height from the upper surface of the object to be coated between the bonnet portion 75a and the loop portion 75b. 6 in Figure 11 when painting the bonnet part to adjust the distance to the object to be painted almost constant.
Go down to positions 3, 64, and 65, and when painting the loop section, go up to positions 63', 64', and 65',
Its height is now adjustable. Note 7
7 removes the overspray powder that was not coated by 63, 64, and 65 when it falls along the side of the object to be coated by the air moving from top to bottom in the booth. It is provided for coating and may be considered as a part of the loop-shaped electrode 63. In addition, in order to maintain a more uniform distribution of current and electric field on the object to be coated and obtain a homogeneous powder layer, the present invention is arranged at an angle with respect to the progress line of the object to be coated, as shown in 77'. There is a large degree of freedom in adapting to the implementation mode regarding the arrangement of the device.

The nozzles 64 to 72 can improve the uniformity of the coated powder layer by performing reciprocating motion as required, for example, as shown by arrow A64, and as shown in FIGS. 9 and 10. The nozzle color can be changed by the following methods.
By applying the present invention to automobile body painting in this manner, it is possible to maintain the coating efficiency in an automatic painting booth at 85% or more, and it is also easy to change colors, which makes it possible to The low coating efficiency and difficulty in changing colors, which were major bottlenecks when applying powder coating guns to automobile bodies, have now been definitely solved.

Inside the automobile paint booth, the air flows from top to bottom due to the ventilation system, so no special consideration is given to the upper nozzles 64, 65, upper nozzle 67, etc., and the air is ejected from the nozzles. It is possible to reliably feed the powder into the space surrounded by the ion skirt through the inner edge of the loop-shaped electrode. However, the side nozzles 69,7
0 and the undercarriage nozzle 72, etc., it may be difficult to reliably feed the powder ejected from the nozzle through the inner edge of the loop-shaped electrode.
In FIG. 2, the auxiliary airflow is directed to the inner or outer edge of the loop electrode as shown in the directions of arrows 73 and 74.
Alternatively, suitable results may be obtained by using it through the loop electrode itself, and these auxiliary air flows are a very important element in the present invention.

In addition, depending on the combination of conditions such as the ventilation air speed in the booth, the speed of progress of the object to be coated, and the thickness of the coating, the current flowing from the loop electrode to the object to be coated may become excessive, and as a result, the current flowing from the loop electrode to the object to be coated may become excessive. In this case, preferable results can be obtained by arranging the loop electrode obliquely with the longitudinal direction of the loop electrode parallel to the direction of movement. There is.

Unlike conventional electrostatic powder coating guns, the powder feeding device used in the present invention does not require voltage to be applied to the feeding device itself. Further, since it is provided close to the loop electrode to which a high voltage is applied, it is usually desirable to construct it from an insulating material.

The above description describes the basic configuration of the electrostatic coating device according to the present invention and an example in which this is applied as a stationary device; however, the application of the present invention is limited only to a stationary device. Instead, it is possible to configure this as a so-called handgun, and an embodiment thereof will be described below. 13, 14, and 15 are a plan view, a side view, and a sectional view taken along line 101 of the plan view, respectively, of the handgun according to the present invention. As shown by the arrow 91 in the figure, the powder simply fed or the powder conveyed by the gas passes through the body 86 of the handgun and from the outlet 93 at the tip of the body 86, the oblique hole 93' is opened diagonally. The arrow 92 indicates an inlet for auxiliary air used for dispersing the powder or changing the pattern as needed. The loop-shaped electrode is indicated by 85 in the figure, and has a skirt-like configuration in which the ionic current and electric lines of force are directed toward the object to be coated from at least this surface, and if necessary, there is a delivery port. By means of a device 87 that adjusts and fixes the relative position of the loop-shaped electrode 85 and the loop-shaped electrode 93, the formation of the skirt-shaped ion current and electric lines of force can be adjusted according to the shape of the object to be coated, the coating speed, etc. . Note that arrow 90
1 collectively shows the power supply cables used in this handgun, 89 is a handle, and 100 is a power converter.

16, 17, and 18 show other embodiments of the handgun according to the present invention.
17 is a sectional view taken in the direction of arrow 98 in FIG. 16, and FIG. 18 is a side view of the same.
It is a detailed view of part A of the figure. In this embodiment, the powder particles introduced by the arrow 91 are dispersed in a well dispersed state with the help of the air introduced by the arrow 92 as required.
The area where the spray is sprayed from the tip 93 is the same as the embodiment shown in FIGS. 13, 14 and 15, but in FIGS. 16, 17 and 18, the surface of the loop electrode is Depending on the shape of the object to be coated, the outer and inner peripheries of the loop-shaped electrode or Air is supplied from the cover 9 from the air inlet tube 97 through a slit 95 provided in the loop electrode itself 94.
An auxiliary air flow as shown by the arrow 99 is formed by the air introduced into the air chamber 6, thereby achieving the above-mentioned purpose. Note that the auxiliary airflow 99 is not necessarily formed parallel to the nozzle body 86, but can be formed in a shape that widens or tapers as needed, or as a swirling flow. When it is formed into a parallel flow or a tapered flow with a flow velocity of In addition,
The cover 96 also serves as a guide for forming this auxiliary airflow, and the relative position with the outlet 93 can be adjusted by the cover 87, as shown in FIGS. 13, 14, and 15. be.

It should be noted that the powder coating device according to the present invention in which the powder delivery port and the loop-shaped electrode are directly connected as described above is not limited to handguns, and a single type of this type can be used in multiple units. The fact that it can be used as an automatic gun is that it can be used as an automatic gun in combination with a reciprocating device or robot, and it can be used in combination with a stationary loop electrode, and a wide range of other applications are possible. This resulted in significant performance improvements in transfer efficiency and coverage compared to conventional electrostatic powder coating guns.

As explained in detail above, the application of the present invention is extremely flexible depending on the shape of the object to be coated, processing speed, film thickness, etc., but in implementing this, it is necessary to stably and reliably control the ionic current. Select conditions such as the configuration of the loop-shaped electrode that can generate a It is only necessary to select the appropriate amount of powder to be supplied and the application time, and despite the variety of application modes, the basic conditions for implementation are extremely versatile. Therefore, regarding the embodiments of the present invention, the improvement in coating efficiency will be explained with reference to FIGS. 19 and 20, and the improvement in throwing power will be explained with reference to FIGS. 21, 22, and 16.
17 and 18 will be explained.

Figure 19 shows arrow 1 along the horizontal rail 109.
A horizontally moving object 108 as shown in 10
The nozzles 111, 11 are connected to the nozzles 111, 11 through a loop-shaped planar silent discharge electrode 117 which is arranged opposite to and spaced apart from the nozzles 111, 11.
2, 113, 114, 115, and 116, the epoxy powder coating material is fed through a slit toward the object to be coated to form a powder layer on the object to be coated. In this case, the moving speed of the object to be coated, indicated by the arrow 110, is 3.5 m/min, and the average vertical downward wind speed inside the booth where this painting is performed is when there is no object to be coated. It is adjusted so that the speed is 0.3m per second. In this case, the electrical configuration of the planar silent discharge electrode used as the loop-shaped ion generating electrode 117 is shown in FIG. 20, which corresponds to the virtual plane B in FIG.
FIG. 1 schematically shows a cross-sectional view of a planar silent discharge electrode plate and an electrical connection diagram related thereto.
In FIG. 20, the planar silent discharge electrode plates are made of glass insulators 107 and 1 with relatively low volume resistivity.
06, parallel linear electrodes 103 are connected near the surface so that they have the same potential by a connecting device not shown in the figure, and parallel linear electrodes are located deeper than that. Planar electrodes 102 are buried at regular intervals from the group 103, and an AC power source 104 is connected between the planar electrodes 102 and 103.
A high voltage of a commercial frequency is applied by the method, thereby causing a silent discharge in the gas on the surface of the layer 107, and the ions generated by this silent discharge are transferred to the coated object 108. DC power supply 105 connected to generate a DC potential difference with respect to
It is arranged so as to generate an ionic current toward the object to be coated. In the example shown in FIG. 19 above, each nozzle generates a
About 100 g of epoxy powder paint is fed in, each nozzle is moved appropriately, the width of the loop-shaped ion-generating electrode 117 is set to 75 mm, and the width of the mutual slits of the loop-shaped ion-generating electrodes is set to 100 mm. The distance between the loop-shaped ion generating electrode and the object to be coated is 200 mm.
The AC voltage applied by the power source 104 is maintained at 4.5 KV, and the negative DC voltage applied by the power source 105 is maintained at 50 KV. When powder coating is performed under conditions such that the average film thickness of the epoxy film formed after baking is 50μ, the application efficiency is 95%.
%±2%, the coating was extremely stable, the efficiency was significantly higher than that of conventional coating methods, and the smoothness and uniformity of the coating film after baking were also extremely good. Experiments were conducted using other commercially available guns in the same booth and on the same object, selecting conditions such that the wind speed in the booth and the film thickness formed on the object were the same. The coating efficiency obtained in this case was 70 to 80%, and it was confirmed through experiments that the coating efficiency according to the present invention was extremely good.

FIG. 21 shows a workpiece 11 having a bending rib at one end.
8, and the details of the structure of the rib portion are as shown in FIG. 22, which is a cross-sectional view of virtual cross section C in FIG. 20, and when painted with a commercially available powder coating gun. It was almost impossible to apply the powder to the area indicated by arrow 121. However, this is carried out every minute from the direction shown by the arrow 119 using a handgun as shown in detail in FIGS. 16, 17 and 18 of the present invention.
While spraying about 60g of powder, keep the distance between the object to be coated and the tip of the gun approximately in the direction of arrow 119.
When coating is carried out while maintaining the distance of about 20 cm, the object to be coated 1
As shown by 120 on 18, it is possible to form a uniform powder layer with extremely good uniformity and with complete coverage even inside the bending ribs, which is different from conventional powder coating guns. This was considered completely impossible. The details of the structure of the handgun according to the present invention used in this case are shown in FIG. 18, and the mechanical structure of the loop-shaped ion generating electrode is almost the same as that shown in FIG. 20. 94a, 94b, and 94c are arranged concentrically in an annular shape to form a gap 95, and a gas flow is formed from each gap as shown by the arrow 99.
7 supplies air from behind, and the average wind speed at the outlet of the cover 96 is approximately 0.45 m/sec. In FIG. 18, power supplies and electrodes that perform the same functions as those in FIG. 20 are given the same numbers to clarify their relationships. In this embodiment, the auxiliary airflow indicated by the arrow 99 makes a large contribution to improving the coverage, and the powder delivery device 86
is extremely thin with an outer diameter of approximately 20 mm, and the powder sent out by the swirling airflow at the outlet is extremely well dispersed and flows from the loop-shaped ion generating electrode toward the object to be coated. The powder is sufficiently charged by the ionic current and sprayed onto the object to be coated by the airflow 99, and the sufficiently charged powder travels around to the back side of the object by riding the airflow. At that time, the particles are sufficiently charged and the coating is performed by the electric field that is formed between the particles and the object to be coated due to their own electric charge, so this is not seen at all with conventional powder coating guns. This makes it possible to achieve significantly better throwing power than ever before. Further, by this auxiliary air flow 99, the partial electrodes 94a, 94b, 94c of the ion current forming electrode are always kept clean, and the tip of the powder delivery device 86 is also kept clean in the same way. be.

In this case, the applied AC voltage was 4.5KV and the DC voltage was 45KV.

When painting the object to be coated 118 having the shape shown in FIGS. 21 and 22, the wide area is painted using the method shown in FIG. 19, and only the areas that are difficult to cover are painted. Figures 16 and 17
Coating can be carried out using the methods explained in detail in Figs. By using these methods in combination as appropriate, it is possible to improve overall coating efficiency and coverage, and the present invention improves the performance of powder coating. This will bring about a revolutionary improvement.

When a patterned silent discharge electrode is used as the loop-shaped ion generating electrode in the present invention, the form of the planar silent discharge electrode is of course not limited to the form explained in FIGS. 20 and 15. Various types of planar silent discharge electrodes, such as those listed in Japanese Patent Application Laid-Open No. 51-8347, may be selected and used depending on the purpose of use. In addition, the polarity of the potential difference that exists between the object to be coated and the loop-shaped ion generating electrode may be positive or negative depending on the properties of the paint, and if it is necessary to form a special thick coating film, the polarity of the potential difference that exists between the object to be coated and the loop-shaped ion generating electrode may be positive or negative depending on the properties of the paint. Of course, positive and negative voltages may be used alternately in the intervals, and this may be done in a conventional manner.

In the above explanation, in principle, the loop-shaped ion generating electrodes are arranged on almost the same plane across the powder delivery port or powder delivery slit, and the powder is delivered perpendicularly to this surface. explained. However, this relationship is not limited to this in terms of implementation, and especially when the main purpose is to touch up a recess, the surface containing the loop electrode and the powder delivery direction may be diagonally intersected. In some cases, good results can be obtained, and this is due to the fine particle delivery port, which is an important element of the present invention.
This is included in the configuration in which the relative position with respect to the loop-shaped ion current generator is adjusted and fixed.

All of the above explanations have been made with respect to electrostatic coating of powder, but even when applied to fine particles of liquid, the present invention can obtain significant effects in improving coating efficiency and throwing performance. In this case, the purpose can be achieved very easily by replacing the liquid atomization and delivery device in place of the powder delivery device described above.

[Brief explanation of the drawing]

Figure 1 shows a conventional electrostatic coating device, and Figure 2 shows the 1st type electrostatic coating device.
3 is an electrostatic coating device according to an embodiment of the present invention, FIG. 4 is an explanatory diagram of the main part of FIG. 3,
FIG. 5 is a characteristic diagram for FIG. 4. FIG. 6 shows an electrostatic coating device according to another embodiment of the present invention. FIG. 7 is an explanatory diagram of the main part of FIG. 6, and FIG. 8 is an electrostatic coating apparatus according to another embodiment of the present invention. FIG. 9 is a plan view of an electrostatic coating apparatus according to still another embodiment of the present invention. Figure 10 is the 9th
11 is a sectional view of an electrostatic coating apparatus according to still another embodiment of the present invention, and FIG. 12 is a side view corresponding to the figure.
This figure is another sectional view of the electrostatic coating device corresponding to FIG. 11, and FIG. 13 is a plan view of the electrostatic coating device of another embodiment of the present invention. Fig. 14 is a side view of the electrostatic coating device corresponding to Fig. 13, and Fig. 15 is a side view of the electrostatic coating device shown in Fig. 13.
16 is a side view of an electrostatic coating device according to another embodiment of the present invention; FIG. 17 is a sectional view taken along line 98-98 in FIG. 16; Fig. 18 is a sectional view of the main part of Fig. 16, Fig. 19 is an explanatory diagram of an experimental example of the present invention, Fig. 20 is an electric circuit diagram of the main part of Fig. 19, and Fig. 21 is a cross-sectional view of the main part of Fig. 16. Explanatory diagram of an experimental example. FIG. 22 is an enlarged sectional view and explanatory diagram of the main part of FIG. 21. 15...Powder delivery port, 16...Loop-shaped electrode,
23...Auxiliary airflow, 26...Object to be coated, E _L ...Potential difference, 15'...Insulator nozzle, 57...Rotation fixing device, 58...Shaft, 87...Relative position adjustment device, 93' ...oblique hole.

Claims (1)

[Claims] 1. A loop-shaped electrode for generating ionic current by silent discharge, which is placed opposite to the object to be coated, and which is provided separately from the loop-shaped electrode, and whose distance from the loop-shaped electrode is relatively changed. a means for sending solid or liquid fine particles dispersed and suspended in a gas through the loop-shaped electrode capable of generating an ionic current; An electrostatic coating device comprising: means. 2. The electrostatic coating device according to claim 1, further comprising means for generating an auxiliary airflow flowing through the loop-shaped electrode as means for sending out the fine particles. 3. The device according to claim 1 or 2, characterized in that a nozzle is used as the means for sending out the fine particles, and the nozzle has means for adjusting the sending pattern of the fine particles at the tip thereof. electrostatic coating equipment. 4. The electrostatic coating device according to any one of claims 1 to 3, wherein an internal swirling auxiliary airflow generating device is applied as the particulate delivery pattern adjusting means. 5. The electrostatic coating device according to any one of claims 1 to 3, characterized in that a collision deflection device is applied as the particulate delivery pattern adjusting means. 6. The electrostatic coating device according to any one of claims 1 to 3, wherein an internal swirling auxiliary airflow generating device and a collision deflection device are applied as the particulate delivery pattern adjusting means. 7. The electrostatic coating device according to any one of claims 1 to 6, further comprising a device for reciprocating movement as a means for sending out the fine particles. 8. The electrostatic coating according to any one of claims 1 to 7, further comprising a device for adjusting and fixing the relative position of the device for sending out the fine particles and the ion current generating device. mounting device. 9. The device according to any one of claims 1 to 8, characterized in that a plurality of devices for sending out the fine particles are provided, and a means for selecting and using one of them is added. Electrostatic coating equipment. 10. The electrostatic coating device according to any one of claims 1 to 9, characterized in that a planar silent discharge electrode is used as the ionic current generating electrode. 11. The electrostatic coating device according to any one of claims 1 to 9, characterized in that a harmonic glow corona electrode is used as the ionic current generating electrode.