Electrostatic discharge device

Abstract

The present invention provides an electrostatic dispensing device that can disperse powder materials and adhere them to a workpiece. [Solution] The electrostatic discharge device comprises a main body through which powder material can pass, a discharge section having a plurality of nozzles for discharging the powder material that has passed through the main body, and discharge electrodes for charging the powder material discharged from the nozzles by corona discharge. The discharge section has discharge ports at the tips of each nozzle arranged in a predetermined direction, and a plurality of discharge electrodes are provided around the discharge section.

Description

Technical Field

[0001] Embodiments of the present invention relate to an electrostatic discharge device.

Background Art

[0002] Patent Document 1 discloses a powder coating method in which a charged powder coating is discharged from a coating gun together with a carrier gas to coat an object to be coated. The coating gun of Patent Document 1 has a plurality of nozzle tubes that branch radially from the gun body and extend. The plurality of nozzle tubes are converged so as to be aligned in series by a tube support.

[0003] The powder coating that has passed through the plurality of nozzle tubes is discharged from the discharge port toward the object to be coated together with the carrier air. Also, by using a plurality of nozzle tubes, it is possible to easily secure a wide spray pattern width.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in a coating gun in which a plurality of nozzle tubes are aligned, when a powder material is conveyed to the nozzle tubes at a low air volume and the powder material is discharged toward the object to be coated in a state where the discharge air velocity is reduced, the powder material after being discharged from the discharge port may not disperse around. In this case, there is a risk of adversely affecting the coating film quality, such as the coating film thickness on the object to be coated not becoming uniform.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrostatic discharge device capable of dispersing a powder material and adhering it to an object to be coated.

Means for Solving the Problems

[0007] The electrostatic discharge device of the embodiment comprises a main body through which a powder material can pass, a discharge section having a plurality of nozzles for discharging the powder material that has passed through the main body, and discharge electrodes for charging the powder material discharged from the nozzles by corona discharge, wherein the discharge ports at the tips of each nozzle are arranged in a predetermined direction, and a plurality of discharge electrodes are provided around the discharge section. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram schematically shows an example of the configuration of an electrostatic discharge device according to one embodiment. [Figure 2] A front view showing an example of an electrostatic discharge device according to one embodiment, in which multiple discharge electrodes are arranged on both sides of the nozzle. [Figure 3] This diagram shows the coating process when powder material is applied to a workpiece without arranging multiple discharge electrodes around the nozzle. [Figure 4] This figure shows the coating process when a powder material is applied to an object to be coated using an electrostatic dispensing device according to one embodiment. [Modes for carrying out the invention]

[0009] The following describes one embodiment with reference to the drawings. Note that, for the sake of explanation, the dimensions of each component may be enlarged in the drawings as needed, and the dimensional ratios between components may not be the same as in reality.

[0010] The electrostatic discharge device 1 shown in Figure 1 coats or applies powder materials, such as powder paint, to a workpiece 90 by electrostatic attraction due to corona discharge. The powder material contains conductive substances, such as metal or carbon. Powders also include granular materials. In this embodiment, powder materials with small particle size or low electrical resistance, resulting in a small charge, can be used.

[0011] As shown in Figure 1, the electrostatic dispensing device 1 includes a dispensing gun 10, a material supply device 20, and a discharge unit 30. The dispensing gun 10 is an automatic gun capable of automatically coating or applying powder material to the object to be coated 90. The electrostatic dispensing device 1 may also be a manual gun operated manually by an operator. The object to be coated 90 is grounded via an earth wire 91.

[0012] In this embodiment, the discharge gun 10 is used fixed to a fixed member, for example (not shown). The discharge gun 10 may also be mounted on a moving mechanism, such as a reciprocator, and configured to be movable relative to the object to be coated 90. In Figure 1, the left side of the paper is the direction in which the powder material is discharged and is the tip side of the discharge gun 10, while the right side of the paper is the opposite side of the direction in which the powder material is discharged and is the base end side of the discharge gun 10.

[0013] The discharge gun 10 is connected to the material supply device 20. The discharge gun 10 receives powder material supplied from the material supply device 20 and discharges the powder material toward the object to be coated 90. The material supply device 20 receives powder material contained in the material tank 201 and supplies the powder material to the discharge gun 10. For example, fluidized air 201a is supplied to the material tank 201, and the fluidized air 201a loosens and dehumidifies the powder material in the material tank 201.

[0014] The material supply device 20 also includes a screw feeder unit 21 and an injector 22. The screw feeder unit 21 is located downstream of the material tank 201 in the direction of discharge of the powder material. The screw feeder unit 21 has a well-known configuration, so a detailed explanation will be omitted, but it quantitatively discharges the powder material by rotating the blades of a screw (not shown) in response to the driving force of a drive motor 211. The material supply device 20 quantitatively supplies the powder material at an arbitrarily set discharge amount by changing the rotation speed of the screw blades in response to changes in the rotation speed of the drive motor 211, for example.

[0015] The injector 22 sucks up the powder material discharged from the screw feeder unit 21 and supplies the sucked powder material to the discharge gun 10 via the paint hose 23. The injector 22 is supplied with conveying air 22a from an air supply source (not shown), such as a compressor, and the powder material is sucked up from the screw feeder unit 21 by the conveying air 22a. The airflow rate of the conveying air 22a is controlled by a control device (not shown) for example, according to a predetermined discharge rate. The paint hose 23 is made of a tubular member and is located between the injector 22 and the discharge gun 10.

[0016] The dispensing gun 10 has a main body 11, a material flow path 12, and a dispensing section 13. The main body 11 constitutes the main body of the dispensing gun 10 and is made of, for example, an electrically insulating synthetic resin. The material flow path 12 is provided inside the main body 11. The material flow path 12 extends along the axis of the main body 11. Powder material supplied from the material supply device 20 passes through the material flow path 12 from the base end to the tip end of the main body 11. In other words, powder material can pass through the inside of the main body 11.

[0017] The discharge section 13 is located at the tip of the discharge gun 10. The discharge section 13 discharges the powder material that has passed through the material flow path 12 toward the object to be coated 90. The discharge section 13 has a plurality of nozzles 131 and a support section 132. The nozzles 131 are made of, for example, synthetic resin and are formed in a tubular shape. The nozzles 131 may be made of a material that generates triboelectric charge on the powder material passing inside the nozzle 131, such as tetrafluoroethylene. In this case, the powder material contains a composition that becomes triboelectric charge due to friction with the nozzle 131.

[0018] The nozzle 131 has a discharge port 131a. The discharge port 131a forms the tip of the nozzle 131 and communicates the inside and outside of the nozzle 131. The discharge port 131a forms the powder material that has passed through the material flow path 12 into a desired spray pattern shape and discharges it toward the workpiece 90. The plurality of nozzles 131 branch radially from the main body portion 11 and extend respectively. The plurality of nozzles 131 are provided such that each discharge port 131a is arranged side by side along a predetermined direction. For this reason, the spray gun 10 can secure a wide width of the spray pattern.

[0019] In the present embodiment, as shown in FIGS. 1 and 2, the plurality of nozzles 131 are provided such that each discharge port 131a is arranged side by side in one direction along a direction orthogonal to the direction in which the main body portion 11 extends. However, the present invention is not limited to this. In a front view, the plurality of nozzles 131 may be provided such that each discharge port 131a is curved or bent in an arc shape, or may be provided arranged in an annular shape as a whole. In FIG. 1, for ease of viewing the drawing, only some of the reference numerals of the nozzles 131 and the discharge ports 131a are attached, and the reference numerals of the other nozzles 131 and discharge ports 131a are omitted.

[0020] The support portion 132 aligns and supports each nozzle 131 so that each discharge port 131a faces a predetermined direction. The support portion 132 is formed of, for example, a rod-shaped member. The support portion 132 has a through hole (not shown), and the nozzle 131 is supported by inserting the base end side of the nozzle 131 into the through hole from the discharge port 131a. The distance in the discharge direction from the support portion 132 to each discharge port 131a may be the same or different for each nozzle 131.

[0021] The discharge unit 30 generates an ion wind by corona discharge as an air flow for dispersing the powder material discharged from the nozzle 131. A plurality of discharge units 30 are provided around the discharge gun 10. In the present embodiment, the discharge unit 30 is configured to be separated from the discharge gun 10. The discharge unit 30 may be configured integrally with the discharge gun 10. The discharge unit 30 includes a discharge unit main body 31, a high-voltage generator 32, and a discharge electrode 33. The discharge unit main body 31 constitutes the main body of the discharge unit 30 and is formed of, for example, a synthetic resin having electrical insulation properties.

[0022] The high-voltage generator 32 is provided inside the discharge unit main body 31. The high-voltage generator 32 includes, for example, a boost circuit and a rectifier circuit, and an AC voltage of a predetermined value, for example, 12 to 20 V, is input from a power supply device not shown. Then, the high-voltage generator 32 boosts and rectifies the AC voltage to output a DC high voltage.

[0023] The discharge electrode 33 is formed of, for example, a metallic material having conductivity. The output side of the high-voltage generator 32 is connected to the discharge electrode 33, and a negative or positive high voltage generated by the high-voltage generator 32 is applied thereto. Thereby, an ion wind by corona discharge is generated around the discharge electrode 33. By the action of this ion wind, the powder material discharged from the nozzle 131 is charged with a negative or positive polarity and dispersed with each other, and adheres to the object to be coated 90. Further, since the powder material discharged from the nozzle 131 is charged with the same polarity, the dispersion is promoted by the electrostatic repulsive force acting between the particles.

[0024] Here, if the powder material is supplied to each discharge port 131a at a high airflow rate and discharged into the air at high speed from each discharge port 131a, it is thought that the powder material will disperse due to air resistance, which is the resistance force generated by friction and pressure with the air as it moves through the air. On the other hand, if the powder material is supplied to each discharge port 131a at a low airflow rate and discharged into the air at low speed from each discharge port 131a, it is thought that the powder material will not disperse easily because the air resistance acting on the powder material is small. If the powder material discharged from each discharge port 131a adheres to the object to be coated 90 in a linear pattern without dispersing, linear unevenness will occur as shown by the symbol S in Figure 3, resulting in an uneven coating film thickness.

[0025] Therefore, in this embodiment, multiple discharge electrodes 33 are provided around the discharge section 13. This allows, for example, the ion wind produced by corona discharge to be effectively applied to the powder material discharged from each nozzle 131 at a low speed. This disperses the powder material discharged from each nozzle 131, thereby achieving uniformity in the coating film thickness on the object to be coated 90.

[0026] The inventors have confirmed that, as shown in Figure 4, applying ionized wind from multiple discharge electrodes 33 to powder material discharged at low speed from each nozzle 131 suppresses the occurrence of unevenness in the discharge line. In this embodiment, the multiple discharge electrodes 33 are provided on both sides of the multiple nozzles 131. That is, as shown in Figure 2, the multiple discharge electrodes 33 are provided on both sides of the imaginary line L connecting each discharge port 131a. The arrangement of each discharge electrode 33 may be regular or irregular.

[0027] According to the embodiment described above, the electrostatic dispensing device 1 comprises a main body 11 through which powder material can pass, a dispensing unit 13 having a plurality of nozzles 131 for dispensing the powder material that has passed through the main body 11, and discharge electrodes 33 for charging the powder material discharged from the nozzles 131 by corona discharge. The dispensing unit 13 has discharge ports 131a at the tips of each nozzle 131 arranged in a predetermined direction. Multiple discharge electrodes 33 are provided around the dispensing unit 13.

[0028] According to this method, powder material conveyed at a low airflow rate can be dispersed and adhered to the object to be coated 90 through multiple discharge ports 131a arranged in a predetermined direction. This makes it possible to achieve uniformity in the coating thickness on the object to be coated 90, thereby improving the quality of the coating film. Furthermore, by dispersing the powder material and adhering it to the object to be coated 90, coating efficiency is improved, and the amount of powder material used can be reduced.

[0029] Multiple nozzles 131 are provided with each discharge port 131a aligned in a direction perpendicular to the direction in which the main body 11 extends. Multiple discharge electrodes 33 are provided on both sides of the multiple nozzles 131. This allows ion wind from corona discharge from the multiple discharge electrodes 33 to efficiently act on the powder material discharged from each discharge port 131a. This promotes the dispersion of the powder material.

[0030] The embodiments described above are presented as examples and are not limited to those described above and shown in the drawings. They can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0031] 1...Electrostatic discharge device, 11...Main body, 13...Discharge unit, 131...Nozzle, 131a...Discharge port, 33...Discharge electrode

Claims

1. A main body through which powder material can pass, A discharge unit having a plurality of nozzles for discharging the powder material that has passed through the main body, The device comprises a discharge electrode that charges the powder material discharged from the nozzle by corona discharge, The discharge section is provided with the discharge ports at the tips of each nozzle arranged in a predetermined direction. Multiple discharge electrodes are provided around the discharge section and at positions that straddle the imaginary line connecting each of the discharge ports. Electrostatic discharge device.

2. The plurality of nozzles are provided such that each discharge port is positioned in a direction perpendicular to the direction in which the main body extends. The electrostatic discharge device according to claim 1.

Images