JPS5829149B2 - Electrostatic spray equipment for powder application - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic spraying device for powder coating, and more particularly, to an electrostatic spraying device for powder coating, which includes a passage connected to a discharge port and at least one pair of charging electrodes provided in the passage. The present invention relates to an electrostatic spraying device for use.

Conventionally, in this type of apparatus, an electrostatic field is formed between the surface of the object to be coated and a sharpening discharge electrode provided at the discharge port of the powder coating material, whereby the coating material is electrostatically It was adsorbed onto the surface of the object to be coated.

Typically, the electrostatic field maintains the workpiece at ground potential;
It is constructed by applying a high voltage of about 60 to 100 KV to the sharpened discharge electrode.

Therefore, such conventional devices are subject to potential hazards due to high voltages.

Furthermore, in connection with the use of high voltage, an expensive high voltage generator and a relatively thick high voltage cable with withstand voltage are required. It's not something you get.

Furthermore, if the distance between the surface of the object to be coated and the sharpening discharge electrode changes, the electric field strength will inevitably change, and as a result, the amount of charge on the coating material will also change, making it impossible to obtain stable coating efficiency.

This problem is particularly noticeable in hand-held electrostatic spray devices.

Furthermore, in the conventional apparatus, the electrostatic deposition of the coating material is performed along the lines of electric force of the electrostatic field formed between the surface of the object to be coated and the sharpening discharge electrode. When the surface is uneven, particles of the coating material are concentrated and deposited on the protrusions (including edges) where electric lines of force are strongly concentrated, and almost no particles of the coating material are deposited on the concave areas in the vicinity. Shortcomings are also often recognized.

However, in recent years, in order to solve the drawbacks of this type of conventional device, an internal charging method has been proposed3.
It has a structure in which at least a pair of charging electrodes are provided in a passage connected to a discharge port, and a typical device thereof is known as, for example, an electric gas dynamic gun (electric gas dynamic device). Japanese Patent Application Publication No. 50-22839,
JP-A-52-78249).

Admittedly, by adopting this method, the various drawbacks of the conventional device mentioned above are solved, but on the other hand, the particles of the coating material are immediately deposited on the counter electrode surface which is maintained at ground potential.
As a result, the corona discharge at the charging electrode portion is significantly weakened and a non-charging phenomenon occurs, which has the fatal disadvantage that the counter electrode must be frequently cleaned.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic spraying device for powder coating in which the drawbacks of the internal charging method described above are effectively eliminated.

Another object of the present invention is to provide an electrostatic spraying device for powder coating that can perform corona discharge in a pair of charging electrode sections with high efficiency and stability over a long period of time.

Therefore, in the present invention (according to the present invention), in the electrostatic spraying device for powder coating, which includes a passage connected to a discharge port and at least a pair of charging electrodes provided in the passage, the charging electrode is provided in the passage. separated from a sharpened discharge electrode provided along the axial direction and a counter electrode constituting at least a part of the circumferential surface of the passage, and the counter electrode is formed of a blend of a fluororesin and a conductive lateral side. An electrostatic spraying device is provided.

According to the present invention, in the electrostatic spraying device for powder application, further comprising a passage connected to a discharge port and at least a pair of charging electrodes provided in the passage, the charging electrode is arranged in an axial direction of the passage. comprising a sharpened discharge electrode provided along the passage, and a counter electrode forming at least a part of the circumferential surface of the passage,
The counter electrode is formed of a blend of a fluororesin and a conductive side, the sharpened discharge electrode has a barrier tube surrounding it and having an open tip, and the rear end of the barrier tube is connected to an air supply. An electrostatic spray device is provided, the device being connected to a mechanism.

One of the important features of the present invention is that the counter electrode constituting the charging electrode is formed of a blend of a fluororesin and a conductive side.

That is, fluororesins such as polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, and polyvinyl fluoride, especially the polytetrafluoroethylene, are coated with carbon black. , carbon fibers or carbon fiber powders, metal powders, semiconductor powders, especially carbon black, are blended as a conductive side, thereby forming a counter electrode that is maintained at ground potential. It is possible to create an electrostatic field in which a stable and sufficient corona current flows, and it also has the effect of repelling powder coating materials such as powder coatings and powdered pesticides, so it is reliable and effective in preventing stains. This is because it becomes possible.

Incidentally, the blend of the above composition in the present invention usually has a content of 0.
From the viewpoint of electrical properties, it is preferable to form the conductive lateral side of 5 to 10% by weight, more preferably 1 to 8% by weight, and the remaining fluororesin.

That is, the ratio of the conductive lateral side to the fluororesin is 0.
When the proportion is less than 5% by weight, the electrical resistance value becomes high, and as a result, it becomes difficult to actively generate corona discharge between the sharpened discharge electrode, and on the other hand, when the proportion is more than 10% by weight, powder coating becomes difficult. This is because the repelling effect on the material is significantly reduced.

To produce a counter electrode from a blend of fluororesin and conductive side, for example, molding of polytetrafluoroethylene (
Methods that have been widely used in the past, such as a compression molding method consisting of pre-compression molding, firing and cooling steps, an extrusion molding method, or even a tispersion molding method, can be used as appropriate depending on the type of fluororesin. Can be used.

Another important feature of the invention is that the sharpened discharge electrode is covered with an electrically insulating barrier tube in which an air passage is formed.

That is, this is because it is possible to reliably and effectively prevent the powder coating material from being deposited on the tip of the sharpened discharge electrode.

Further, the diameter of the sharpened electrode is set to 1 pair or less, preferably 0.6
This is because even if the length is set to be less than M and the length is extended and supported at one end, the shaft can be maintained horizontally without loosening.

Additionally, when the air flow inside the barrier tube is discharged from the axis of the paint passage into the paint passage, the ionized air is preferably agitated and dispersed in the coating material passing through the passage, thereby further enhancing the charging effect. This is because it can be improved.

The barrier tube in the present invention is preferably made of fluororesin, particularly polytetrafluoroethylene.

That is, this prevents the powder coating material dispersed in the air flow from being deposited on the outer peripheral surface of the barrier tube, or in other words, prevents the generation of coarse particles.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an electrostatic spraying device 5 for powder coating, which is equipped with a passage 2 connected to a discharge port 1 and a charging electrode consisting of at least a pair of sharpened discharge electrodes 3 and a counter electrode 4 provided in the passage 2. One of the features of this device is that the sharpened discharge electrode 3 is provided along the axial direction of the passage 2, and the counter electrode 4 has an annular shape constituting at least a part of the circumferential surface of the passage 2. Moreover, the counter electrode 4 is formed of a blend of a fluororesin and a conductive side.

Further, one of the other features of the device 5 is that the sharpened discharge electrode 3
is covered with an electrically insulating barrier tube 7 in which an air passage 6 is formed.

Usually, the sharpened discharge electrode 3 has a diameter of 0.2 to 2W.
11, preferably a thin metal wire of about 0.5 to 1.5'1 m.

Thermal theory, the shape and material of this type of sharpened discharge electrode 3 in the present invention are not limited to these, and various known ones can be appropriately adopted.

The sharpened discharge electrode 4 in this embodiment has an applied voltage of 1
Since a low value of about 0 to 20 KV is sufficient, it is small and lightweight, and electricity is supplied to the high voltage generator 8 integrally attached to the device 5 via the conductive connecting member 9 and the annular electrode support 10. connected.

The high voltage generator 8 in this embodiment uses a piezoelectric element which is known per se and is suitable for reduction in size and weight.
is not limited to this, and various types called transformer type, Kotscroft type, or electrostatic generator type can be adopted as appropriate.

The electrically insulating barrier tube 7 in this embodiment may be made of various insulating materials such as polytetrafluoroethylene, polyethylene, polypropylene, Delrin, vinyl chloride, etc.; It is preferable to use polytetrafluoroethylene, commonly known as Teflon.

The barrier tube 7 is connected to the electrode support 10.
concentrically with the discharge electrode 4, and approximately 0.
It is removably disposed so as to protrude from the front about 5 to 5 layers.

Further, the inner diameter of the barrier tube 7 is larger than the outer diameter of the discharge electrode 4 by at least 0.5M, thereby forming an air passage 6.

The air passage 6 receives a portion of the compressed air flow from a compressed air supply 12 with an air flow control valve 11 in communication with a distribution air flow supply passage 13 in the device 5 and the electrode support passage 13I. The air flow is supplied via an air flow supply passageway 14 within device 10.

Further, the counter electrode 4 in this example has a value of 0.5 to 10
It is a blend of carbon black, preferably 1 to 8% by weight, and the remainder polytetrafluoroethylene, and is formed into a ring shape.

The thickness of the counter electrode 4 is not particularly limited, but the function as a counter electrode in the present invention can be sufficiently achieved by forming the counter electrode 4 so that the electrical resistance value between the thicknesses is 0.3 to 2 Ω. This is preferable in terms of achieving this effect.

Note that the counter electrode 3 includes a conductive ring 15 and the ring 1.
It is connected to the ground pole of the high voltage generator 8 through a connector 16 that is electrically connected to the high voltage generator 5 .

The ring 15 has a large number of air passages 1 for forming an air flow for preventing the coating material from adhering along the inner surface G of the counter electrode 4.
7, and a groove 1 in the contact portion with the counter electrode 4 for making the air flow flowing out through the air passage 17 into an annular shape.
8 is formed.

The air passage 17 communicates with the compressed air supply source 12 via an air supply passage 19 formed within the device 5 .

FIG. 2 shows the arrangement of the charging electrodes in this example.

In addition, in this embodiment, in order to charge the coating material in a more stable state, a portion of the compressed air flow is directed into the air supply passage 19 along the inner surface of the ring 15 by approximately 1.5 cm. It is provided with a so-called ejector-type suction section that allows the air to flow out at a pressure of 9/d.

Thus, the powder coating material supplied from the powder coating material supply source 20 to the passage 2 in the device 5 in a state dispersed in the air flow is arranged between the sharpening discharge electrode 3 and the counter electrode 4. While being charged by the action of an electrostatic field and being discharged in the form of a mist from the discharge port 1 (in this passage 2, the amount of electricity is further increased by an electro-gas-dynamic conversion action, and is efficiently deposited on the surface of the article).

In the present invention, in order to effectively obtain the electro-gas-dynamic action, at least the front side of the charging electrode portion of the device 5 is made of an insulating material, such as an acetal resin or a fluororesin.

In addition, in the device 5, the passage 2 portion located on the side of the discharge port 1 from the charging electrode portion has a divergent O shape, thereby slowing down the flow rate of the powder coating material discharged from the discharge port 1. to form the cloud.

Further, in front of the discharge port 1, a collision dispersion member 21 is provided adjacently, thereby more reliably slowing down the flow rate of the powder coating material and making the cloud concentration uniform.

This example (the powder coating material supply source 20 used here was
It consists of the main parts of the coating material storage tank 22, the floatron 23, and the fluidization tank 24, and usually has a capacity of 30 to 150
Approximately fl/1iltπ of coating material is supplied to the device 5.

In the powder coating material supply source 20, the coating material contained in the tank 22 is dropped and supplied to the floatron 23 by the vibration action of a pie break 25 disposed at an appropriate location in the tank 22.

Note that 26 is an opening/closing mechanism, and the opening/closing mechanism 26 is provided to control the coating material supplied from the tank 22 to the floatron 23.

The coating material dropped into the flowtron 23 is further stably controlled in supply amount by a diaphragm (not shown) disposed within the floatron 23, and is then dropped into the fluidization tank 24 in the same manner as described above. Ru.

The coating material dropped into the fluidized tank 24 is air-flow conveyed to the passage 2 of the device 5 by an ejector coupon (not shown) disposed in the fluidized tank 24.

The supply of compressed air flow to the Ezeku coupon pump is carried out via the compressed air supply source 12 or another compressed air supply source (not shown), the choice of which is free and unrestricted.

In this embodiment, even if four spray devices 5 are used, a distribution mechanism 27 is provided between the floatron 23 and the fluidization tank 24 so that only one supply source 20 is required. has been done.

In addition, since the supply source 20 supplies excess compressed air to the fluidization tank 24, an exhaust pipe 2 is provided for discharging the excess air to the outside.
It is equipped with 8.

According to the present invention having the above configuration, no staining of the counter electrode was observed even after continuous operation for 8 hours, and highly efficient and stable coating work could be performed.

[Brief explanation of the drawing]

FIG. 1 is an overall diagram including a partial system diagram for explaining the device of the present invention, and FIG. 2 is an enlarged view of the charging electrode in FIG. 2 is a passage, 3 is a sharpened discharge electrode, 4
5 is a counter electrode, 5 is an electrostatic spray device for powder coating, 7 is a barrier tube, 8 is a high voltage generator, 12 is a compressed air supply source, 2
0 indicates the powder coating material supply source, respectively.

Claims (1)

[Scope of Claims] 1. In an electrostatic spraying device for powder application comprising a passage connected to a discharge port and at least a pair of charging electrodes provided in the passage, the charging electrode is arranged in an axial direction ( separated from a sharpened discharge electrode provided along the passageway and a counter electrode forming at least a part of the circumferential surface of the passage, and the counter electrode is formed of a blend of a fluororesin and a conductive lateral side. 2. The electrostatic spraying device according to claim 1, wherein the fluororesin is polytetrafluoroethylene. 3. The electrostatic spraying device according to claim 1, wherein the conductive side is carbon black. 4. The device according to claim 1, wherein the counter electrode is formed from a blend of 0.5 to 10% by weight of a conductive side and the remainder fluororesin. 5. A passageway connected to the discharge port. and an electrostatic spraying device for powder application comprising at least one pair of charging electrodes provided in the passageway, wherein the charging electrode is a sharpened discharge electrode provided along the axial direction O of the passageway; a counter electrode forming at least a part of the circumferential surface of the passage, the counter electrode is formed from a blend of a fluororesin and a conductive side, and the sharpened discharge electrode covers the periphery thereof and has an open tip. 6. An electrostatic spraying device comprising an electrically insulating barrier tube, the rear end of which is connected to an air supply mechanism. 6. The barrier tube is made of fluororesin. The apparatus of claim 5. 7. The apparatus of claim 5, wherein the fluororesin is polytetrafluoroethylene.