JPS5940072B2 - Electrostatic painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic coating method, and its purpose is to provide an electrostatic coating method that allows safe and efficient coating.

The configuration of an embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 indicates a spray gun, which includes a nozzle body 2, a gun head 3, an extension pipe 4, a cable pipe 5, a gun body 6, and a gun handle T.
, the trigger 8 is the main component, and in particular, in this example, the nozzle body 2, extension pipe 4, and cable pipe 5 are made of aluminum or a light metal such as an aluminum-based metal, and the entire surface thereof is coated with a high-quality metal by hard anodizing. A resistive coating is applied.

The nozzle body 2 is removably attached to the gun head 3,
Further, a cylindrical extension pipe 4 and a cable pipe 5 are respectively fixed to the gun head 3.

However, in this example, the gun head 3 is made of an insulator made of synthetic resin or the like. The rear end portions of the extension pipe 4 and the cable pipe 5 are respectively fixed to the gun body 6, and one end portion of the trigger 8 is pivotally attached 6a to the upper end portion of the gun body 6.

Further, a gun handle 7 is integrally formed in the lower part of the gun body 6, and in this example, a high resistance coating is formed on the entire surface thereof by hard anodizing treatment. In this example, this high resistance film is formed to a thickness of about 60 micrometers, and the 60 micrometer film has a resistance value of about 100 MΩ. Note that this high-resistance coating normally only needs to be coated on the nozzle body (in this example, the coating is applied to almost the entire spray gun in consideration of safety. However, the above-mentioned integrally formed gun body 6 and the gun handle □ are made of aluminum or a light metal such as aluminum, and are connected to the OV for safety.

Incidentally, the gun body 6 and the gun handle □ may be formed of an insulator made of synthetic resin or the like. On the other hand, the lower end of the gun handle □ is for paint.

A joint 9, an air joint 10, and a high voltage cable connector 11 are provided, respectively. One end of a paint tube 12 is connected to the paint joint 9, and the other end is connected to the nozzle body 2 via a paint valve 13 which is opened and closed by the trigger 8.

The other end of the air tube 14 connected to the air joint 10 is connected to the pattern tube 16 through the air valve 15 provided on the back side of the paint valve 18 as shown in FIG. It is branched into an atomization tube 17 which is provided almost parallel to each other.

These two tubes 16 and 17 are both connected to the nozzle body 2, but the pattern tube 16 is connected to the nozzle body 2 through a pattern adjustment valve 18 for adjusting the amount of air. However, in this example, the amount of air in the pattern adjustment valve 18 is adjusted by the rotation of the Asiast screw 18a, and the air valve 15 is opened and closed by the trigger 8. A high voltage cable 19 is connected to the connector 11, and the other end is connected to a spring 2 within the cable pipe 5.
0 to a high resistance 21 (approximately 200 MΩ in this example), and the other end of the high resistance 21 is connected to the nozzle body 2 via a conductive wire 22.

In this example, high pressure is also applied to the workpiece tension pipe 4 via the resistance of the gun head 3.

However, high pressure may be applied to the cable pipe 5. In this example, the nozzle main body 2 includes a main body 23 with a paint nozzle opened to the left in the figure, a jetting element 24 for adjusting the amount of paint flowing out, and an inner cap 2 for adjusting the amount of air.
5 and an outer cap 26 for changing the spray pattern of the sprayed paint, and in this example, each of the above-mentioned members is coated with a high-resistance coating by hard anodic oxidation.

However, the main body 23, the ejector 24, the inner cap 25, and the outer cap 26 are also made of aluminum or an aluminum-based alloy. A screw hole portion 23a into which the screw portion 24b of the blower 24 is adjustably screwed is provided near the center inside the main body 23, and a plurality of air grooves 27 for jetting air are provided on the outer periphery on the left side in the figure. It is recessed in a diagonal shape. Next, the spout 24 is formed into a bottomed cylindrical shape with an opening on the right side in the figure, and a paint port 2 on the left side in the figure.
4a are opened in the radial direction (in this example, four are shown as circles), and the threaded part 24b provided on the right side in the figure is screwed into the threaded hole part 23a of the main body 23, so that this ejector 24
When the ejector 24 is rotated left and right by the engagement groove 28 for a driver (not shown) provided on the left end face of the
The amount of paint flowing out from the paint spout 29 is adjusted.

Reference numeral 25 denotes an inner cap that is adjustably screwed into the main body 23, and is connected to the air outlet 3 at the left end of the main body 23 in the figure.
It is possible to adjust the air outflow amount of 0.

However, the air ejected from the air ejection port 30 is mainly used to atomize the paint ejected from the paint ejection port 29. Reference numeral 26 denotes the outer cap, which is formed into a substantially cylindrical shape in this example, and the right side barrel thereof in the figure has a threaded portion 26a for adjustably screwing into the gun head 3.
is formed.

The air passage 31 formed by the outer cap 26 and the inner cap 25 includes the pattern tube 16.
Air is supplied from the air and is ejected from the pattern ejection port 32. The air ejected from the pattern ejection port 32 restricts the outward spread of the paint ejected from the paint ejection port and atomized by the air from the air ejection port, so the pattern adjustment By adjusting the amount of air ejected from the pattern ejection port 32 by adjusting the spray valve 18, it is possible to arbitrarily change the spray angle of the atomized paint. The air outlet 30 is connected to the atomizing tube 17 via an atomizing air passage 30a,
The paint spout 29 is connected to the paint tube 12 via a paint passage 29a. Further, the high voltage from the conductor 22 is applied to a cylindrical electrode body 3 which is depressed in the gun head 3.
3 to the nozzle body 2. Next, a power supply device for supplying high voltage to the spray gun 1 in this example will be explained based on FIG. 7.

In the figure, the high voltage rectifier circuit 34 converts AClOOV to DClOOV.
At the same time, this DClOOV is supplied to the power amplification circuit 37 via the air flow switch 38. The low voltage rectifier circuit 35 converts AClOO to AC6.3V, rectifies it, and supplies it to the oscillation circuit 36 as DO6.3V.

The oscillation circuit 36 oscillates a high frequency of approximately 22 to 23 KHz in this example, and this high frequency is amplified by the power amplification circuit 37. The high frequency amplified by the power amplification circuit 37 is boosted by a step-up transformer 39 and then applied to a Kotscroft circuit 40 to be boosted in multiple stages, and is then sent to the spray gun 1 via a resistor R1 and a high-voltage supply cable 41. supplied to In this way, in this example, the commercial AC power supply is first replaced with DC, and the oscillation circuit 36 is powered by this DC.
Since the power is amplified after oscillating and replacing it with a high frequency current of about 22 to 23 KHz, the current supplied to the clock clock circuit via the step-up transformer 39 becomes a high frequency current, and The high frequency ripple component is superimposed on the DC high voltage applied to the spray gun 1.

In this example, the power amplification degree of the power amplification circuit 37 is set to the minimum necessary level, so even if the nozzle body 2 is electrically short-circuited, the voltage drop will be large and the discharge current will be extremely small. The output power in this example is 13W. Note that the air flow switch 38 is interposed between the compressor 1 that supplies compressed air and the spray gun 1.

Therefore, in conjunction with the operation of the trigger 8, the spray gun 1
The high pressure supplied to is turned on and off. Next, the resistance R and capacitance C of the high-resistance coating formed by the anodic oxidation treatment in this example will be explained based on FIG. 9.

Hereinafter, the resistance R and capacitance C of this high-resistance coating will be referred to as specific resistance R and specific resistance C. The pair of resistance R and capacitance C shown in the figure is a schematic diagram showing the specific resistance R and the specific capacitance C when considering a minute portion of the high-resistance film.

A natural resonance frequency exists in the high-resistance film due to the specific resistance R and the specific capacitance C, and the ripple component superimposed on the DC high voltage has a crystal structure due to the specific resistance R and the specific resistance C. Above, the frequency is set to be the same as the resonant frequency of the circuit configured as a parallel resonant circuit. Next, the operation will be explained with reference to FIG. 8 showing the overall configuration.

Compressed air from a compressor (not shown) is supplied to the air joint 1 of the spray gun 1 via an air operator 43.
0.

The power supply device 42 supplies high voltage to the connector 11 via the high voltage supply cable 41, and its remote line 38a connects to an air flow switch 38 built in the air operator 43.
It is connected to the.

The other end of the paint supply hose 44 connected to the paint joint 9 of the spray gun 1 is connected to a paint pump (not shown). First, the power supply device 42 and the paint pump and compressor (not shown) are started.

When the trigger 8 is pulled in this state, paint and air are ejected from the nozzle body 2, the air flow switch 38 is turned on, and a high voltage is applied to the nozzle body 1. The way the atomized paint spreads in the radial direction can be adjusted by rotating the Asiast screw 18a to increase or decrease the amount of air ejected from the pattern ejection port 32. When the trigger is released, the ejection of air and paint from the nozzle body 2 is stopped, and the air flow switch 38 is turned off due to the stoppage of the air flow, and the power supply 4 is turned off.
The oscillation of the second oscillation circuit 36 is stopped, and the generation of high voltage is stopped.

Incidentally, the state of the electric field generated around the spray gun 1 is shown in FIG.

In this example, since a high voltage is applied particularly to the cable pipe 5, a negative electric field is also generated behind the nozzle body 2, causing a repulsive force to act on the ejected negatively charged paint. The object to be coated is moved forward, that is, by the lever.

For this reason, conventionally the distance t from the nozzle body 2 to the object to be coated is
1 and the distance T2 from the nozzle body 2 to the handle 7 is t
1 × T2 was required, but in this example, t1>
Even at T2, painting can be done satisfactorily. Next, the effects of the embodiment will be explained.

As mentioned above, in this example, the high frequency component included in the DC high voltage applied to the nozzle body 2 resonates with the resonant circuit formed by the resistance R and capacitance C of the high resistance coating applied to the nozzle body 2. can cause When this resonance phenomenon occurs, an electric charge is accumulated in the capacitor C at the same period as the period of the high-frequency voltage. 2, the absolute value of the voltage is increased and a stronger electric field can be formed. On the other hand, when a liquid splits, it is accompanied by a vibrational phenomenon, gives an excessive charge to the liquid flow, and ``when ions vibrate, the liquid flow becomes resonant.'' By applying vibration, it is possible to enhance the atomization phenomenon of the liquid flow, promote the atomization of the paint, and increase the efficiency of coating.

Therefore, in this example, by applying a high-frequency voltage, the electric field strength changes in synchronization with the period of this high-frequency voltage, and (
Regular changes become vibrations. Furthermore, in the case of a high-frequency voltage, the value of the voltage V changes at a predetermined period, and the electric field strength is [electric FEV/electrode distance L]. ) This also changes the electrostatic force applied to the ions, and this change in electrostatic force can give vibration to the ions and increase the effectiveness of the coating. Incidentally, the resonance phenomenon in a high-resistance film occurs regardless of the voltage value applied thereto, but it is not preferable for the voltage value to be too low.

Further, the high resistance coating has a resistance of 100MΩ, and the resistance between the power supply device 42 and the nozzle body 2 is 242MΩ.
If a voltage of 60,000 volts is applied to the nozzle body 2, the current flowing through the human body due to electric shock is approximately 200 ItA, which is 50 mA, which is said to lead to death. It is very safe in comparison.

This example is also effective against discharges caused by charges accumulated in the electrodes, which cannot be prevented by simply inserting a resistor between the electrodes and the high voltage power source.

In other words, the charge accumulated on the electrode is 10
It is impossible to cause a discharge due to the resistance of 0MΩ. Therefore, in this example, the electrode area can be increased compared to the conventional one, so a high voltage can also be applied to the cable pipe 5 to form a backward electric field to prevent paint from adhering to the painter. There is. Moreover, since a backward electric field is formed, paint will not adhere to the human body even if the distance from the high-voltage nozzle to the human body, which is the ground object, is shortened, and therefore the overall length of the spray gun 1 can be shortened and its weight can be reduced. It has its features. Moreover, conventionally, two holes were drilled in one bare rod to provide a passage for the paint and cable, but if the high-voltage cable and the paint were placed close together, there was a possibility of leakage from the paint side. The spacing between the passages could not be closer than a predetermined spacing, thus increasing the diameter and weight of the spray gun.

However, in this example, the spray gun 1 is a twin-barrel type with a pipe structure, and the passages for the paint and cable are separate, so the insulation of the atmosphere can be used, the lightness of the pipes, and the spacing between the two pipes can be used. The weight of the spray gun 1 can be reduced synergistically since there is no increase in weight even if the gun is opened. Furthermore, the nozzle body 2 in this example is provided with a pattern jet port 32 on the outer periphery of the paint jet port 29 and the air jet port 30 in order to change the jet angle of the paint jetted from the main body 2. It has the advantage of allowing you to freely adjust how the paint spreads.

Furthermore, since the power amplification degree of the power amplification circuit 37 is set to the minimum necessary level, even if the nozzle body 2 is electrically short-circuited, the voltage drop will be large and the discharge current will be extremely small.

Next, the effects of the invention will be explained.

That is, the present invention provides an electrostatic coating method in which a high voltage is applied to a spray gun, and an electric field formed by the high voltage leads ionized paint to an object to be coated. A high-resistance coating is applied to the surface by anodizing, and a high DC voltage is applied to the high-resistance coating with a high frequency that is approximately the same as the resonant frequency of a resonant circuit formed from the resistance and capacitance that the high-resistance coating has in its crystal structure. The electrostatic coating method applied to the nozzle body has an excellent feature of being able to provide a safe and efficient electrostatic coating method.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a side sectional view showing an embodiment of the spray gun, FIG. 2 is a rear view thereof, FIG. 3 is a side sectional view showing the nozzle body, and FIG. 4 is a side sectional view showing an embodiment of the spray gun. 5 is a side view without showing the main body of the nozzle, FIG. 5 is a sectional view taken along line AA in FIG. 3, FIG. Figure 8 is an explanatory diagram showing the entire electrostatic coating device, Figure 9 is an explanatory diagram showing the high-resistance coating, Figure 10 is an explanatory diagram showing the state of the electric field, and Figure 11 is a cross section taken along line A-A in Figure 1. It is a diagram. 1... Spray gun, 2... Nozzle body, 4... Machine scrap tension pipe, 26...
...outer cap, 32... pattern spout, 36... oscillation circuit.

Claims (1)

[Claims] 1 An electrostatic coating method in which a high voltage is applied to a spray gun, and an electric field formed by this high voltage guides ionized paint to the object to be coated, and the surface of the nozzle body of the spray gun A high-resistance coating is applied to the nozzle by anodizing, and a DC high voltage superimposed with a high frequency of approximately the same frequency as the resonant frequency of a resonant circuit formed from the resistance of the high-resistance coating due to its crystal structure is applied to the nozzle. An electrostatic painting method characterized by applying an electrostatic voltage to the main body.