JPS6082162A - Electrostatic powder painting head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating head for electrostatic powder coating, and more particularly to a coating head having a slit-shaped nozzle.

Recently, in the light electrical industry, etc., machining of pre-painted metal plates (Zoreccord Metal: pcM) has been carried out in order to shorten the process, save labor, and save space. . Conventionally, solvent-based paints were applied for this type of painting (PCM painting), but with solvent-based paints, it is difficult to finish with one coat, and there is a risk of fire or poisoning due to organic solvents, causing pollution problems. There is a problem that the resistance to machining is high, and the resistance to machining is low.
The application of powder coatings that have excellent coating film performance and are highly resistant to severe mechanical processing such as bending and drawing processing or RT-Sores processing has been attracting attention.

The performance that is particularly required of the coating equipment used in PCM powder coating is to be able to finely adjust the amount of powder ejected, to obtain stable ejection, and to maintain stability of the ejection pattern even when the amount of ejected powder is changed. It must not collapse.

The present invention aims, in particular, to form a coating film having a desired uniform thickness at high speed and continuously by an improved structure of the coating head of a PCM powder coating device.

The purpose of the above is that two powder transport pipes are disposed close to each other and substantially parallel to each other, and each of the two powder transport pipes has a slit shaped in the opposing pipe wall along its length. A powder discharge port is formed between the two powder transport pipes, and a slit-shaped air discharge port is formed along the length direction toward the gap between the two powder transport pipes. The discharge port is connected to a compressed air source, and a position (a: This is achieved by a coating head for electrostatic powder coating, characterized in that a slit-shaped nozzle is formed so as to communicate with a powder discharge port, and a charging mechanism is provided at an appropriate position. .

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a partially cutaway perspective view of an embodiment of the coating head according to the present invention in a used state. Reference numerals 1 and 2 indicate paint powder transport tubes, in which tube bodies preferably having a circular cross section are generally arranged substantially parallel to each other in the horizontal direction. The gap is not very wide, ie, the powder transport pipes 1 and 2 are close to each other. Powder discharge ports 3 and 4 are formed in the opposing walls of the powder transport pipes 1 and 2, respectively. The powder discharge ports 3 and 4 extend along the length of the powder transport pipes 1 and 2 and form slits. An air discharge port 5 is formed between the powder transport pipes 1 and 2.

In the embodiment with 11 holes, this air outlet 5ti
tBy the pipe walls of powder transport pipes 1 and 2! The air discharge port 5 is also configured to open downward between the powder discharge ports 3 and 4.
Similarly to 0' and 0'4, the slit 9 extends along the length of the powder transport pipes 1 and 2 to form a slit. The air outlet 5 is connected to compressed air, JGi, and is connected to 9 in Figure 1 (
In the example, an air chamber 6 is formed for this connection. The air chamber 6 is formed along the length direction of the powder transport pipes 1 and 2, and has a t'M structure in which both Qlli parts are closed. A perforated plate 7 is provided in the air chamber 6 to divide the air chamber 6 vertically.The perforated plate 7 is also formed substantially along the length direction of the powder transport pipes 1 and 2. This perforated plate 7 receives the compressed air flow from one side and sends an average air flow over the entire surface to the other side, and the size and density of the small holes are as follows. It can be set as appropriate depending on the purpose.One or more air inlets 8 are attached at appropriate positions in the second part of the air chamber 6, and the air inlets 8 are connected to a compressed air source (not shown). A nozzle 9 is formed below the powder discharge ports 3 and 4 and communicates with the powder discharge ports 3 and 4 and the air discharge port 5.

This nozzle 9 also extends along one length of the powder transport tubes 1 and 2 and forms a slit. It is preferable to form a ventilium 10 inside the nozzle 9 close to the powder discharge ports 3 and 4. The venturi 10 has the same shape in all cross sections perpendicular to the length direction of the powder transport tubes 1 and 2.

The coating head is also provided with a charging mechanism at an appropriate position to ionize the air. The charging mechanism It can be formed from a porous electrode or a linear electrode provided between the compressed air source and the air discharge port 5, at or near the nozzle section 9.

In FIG. 1, a porous electrode is provided on a porous plate 7, and an air chamber 12 is formed below the body transport tubes 1 and 2 near the outer periphery of the nozzle 9. This shows an example in which a porous electrode 11 is provided at the boundary between the chamber 12 and the nozzle part 9. The porous electrode 11 and the air chamber 12 are also formed along the length of the powder transport tubes 1 and 2. Note that one or more air inlets 8' are provided at appropriate positions on the side of the air chamber 120.

FIG. 2 shows a porous electrode attached to a porous plate 7, and a nozzle part 9.
This shows an example in which a linear electrode 14 is installed.

FIG. 3 shows an example in which a porous electrode is installed on the perforated plate 7 and a linear electrode 13 is installed near the air outlet 5.

- Figure 54 shows a linear electrode 13 installed near the air outlet 5;
'? L also shows an example in which a porous electrode 11 is installed on the outer periphery of the nozzle part 9.

FIG. 5 shows an example in which a linear electrode 13 is placed near the air discharge port 5 and a linear electrode 14 is installed in the nozzle portion 9.

Table 1 qualitatively compares the cost, capacitance, and charge amount of each method shown in FIGS. 1 to 5.

The number of electrodes may be single, but as described above, a combination of a plurality of electrodes is desirable. Further, it is preferable to provide a potential difference between the plurality of electrodes. That is, in the example of FIG. 1, if the ratio of the potentials between the porous electrode 7 in the upper part and the porous electrode 11 in the nozzle part 9 is set to 07 to 0.8:l, the movement of the charged powder coating material will be reduced. is accelerated and straightness improves, reducing scattering and further improving coating efficiency to the object to be coated.

FIG. 6 is a system diagram of a powder coating apparatus using the coating head according to the present invention as described above. 20 is a painting head;
The powder transport pipes 1 and 2 are arranged in the left-right direction along the plane of the paper. Reference numeral 21 denotes a conveyor for transporting the dust and the object 22 to be coated at a constant speed in a direction perpendicular to the plane of the paper. 23 is a powder coating supply machine, from which powder is supplied through a conduit 24 into the powder transport pipes 1 and 2 of the coating head 2o so that the powder is usually 0.18 to 2.5 vot%. . Here, as shown in FIG. 1, the powder transport pipe 1
In the powder transport pipes 1 and 2, the conduit 24 is branched so that the moving direction of the powder is opposite as shown by the arrow.
Connect to. As the powder feeder 23, a pressure vessel type, a scree set, an ejector set, a rotating disk type, etc. are generally used. Capacity of powder feeder 23 and conduit 2
Although the size of 4 can be set as appropriate, it is preferable that, for example, the size of the powder feeder 23 can be changed as appropriate within the range of 500 g to 7 g. In addition, the pressure of the air fed into the air chamber 6 of the painting head 2o from the compressed air source is usually about 0.5 to 2.0 kg/L:rn.
Therefore, the appropriate supply pressure for each powder in powder transportation V1 and 2 is normally about 0.2 to 0.5 kg/crn. When increasing the conveyor speed and increasing the coating speed while maintaining the same, high pressure should be applied.Furthermore, by providing a secondary air inlet 25, the powder will be dispersed better and the discharge will be lower. It is possible to prevent pulsation in the image, make the discharge f uniform, and make fine adjustment of the discharge h) easier. 31 is a high voltage generator, which supplies a high DC voltage to the electrode of the paint rad 20 via a high voltage cable 32. 7.11.13 or 14. On the other hand, the powder that is not ejected from the nozzle in the coating head is led to the cyclone 27 through the conduit 26 and collected there. The fine powder is removed by the container 28, and the reusable powder is sent to the powder feeder 2.
3 and supplied to the coating head 20 again. Dust is removed from the exhaust air of the cyclone 27 by a bag filter 29, and the exhaust air is
It is discharged by i130.

According to the coating head of the present invention as described above, powder transport 'ry
A part of the powder that has passed through 1 and 2 is discharged from the powder discharge ports 3 and 4 as air is discharged from the air discharge port 5 to the nozzle 9, and is ejected from the nozzle 9 onto the object to be coated 22. It will be done. Here, powder transport pipes 1 and 2. Since the powder discharge ports 3 and 4° and the air discharge port 5 and the nozzle 9 have the same shape in all cross sections perpendicular to the length direction of the powder transport pipes 1 and 2, the powder jet nozzle from the nozzle 9 The turns can be the same in all cross sections. At this time, as shown in FIG. 1, if the directions of powder movement are reversed between the powder transport pipes 1 and 2,
This eliminates the phenomenon that the amount of powder discharged from the powder outlet 3 or 4 differs between the connection tilt with the conduit 24 (powder inlet) and the connection with the conduit 26 (powder outlet) when the JJ13 is long. , uniform powder ejection 1i can be obtained in the longitudinal direction of the coating head.

In addition, in the painting head of the present invention, if the air chamber 6 is provided as shown at 78 in FIG. 1 and the porous electrode 7 is formed, the air flow from the compressed air source can be made uniform in the length direction of the painting head. Since the air can be simultaneously ionized and supplied to the air discharge port 5, the uniformity of the amount of powder ejected from the nozzle 9 can be increased and the powder can be charged.

Similarly, if the air chamber 12 is provided and the porous electrode 11 is formed, the ionized air flow can be uniformly discharged into the nozzle 9 in the length direction of the painting head, so that the powder inside the nozzle 9 can be uniformly discharged. In addition to increasing the dispersion and mixing of the particles, by applying a potential difference between the porous electrodes 7 and 11, the movement of the powder is accelerated, and the powder can be coated efficiently and in close contact with the object to be coated.

Furthermore, in the coating head of the present invention, by forming a venturi 10 in the nozzle 9 as shown in FIG. The powder can be more effectively sucked, and the powder from the powder discharge ports 3 and 4 can be sufficiently mixed in this part, and the uniformity of the powder jet pattern from the nozzle 9 can be improved. .

Since the coating head of the present invention is as described above, the coating head 2
2 is conveyed at a constant speed while the nozzle 9 is placed above it.
The powder is sprayed by arranging the coating head at a certain distance so that the slits are substantially parallel and the longitudinal direction of the coating head is substantially orthogonal to the direction of movement of the object to be coated. In addition, a coating film with a constant thickness and strong adhesion can be efficiently formed on the :ilz surface of the object 22 to be coated. and,
By appropriately adjusting the pressure of discharged air and/or the powder supply amount, powder coating can be performed by changing the powder ejection rate without impairing the uniformity of the powder ejection pattern. Further, since the coating head of the present invention has a slit-shaped nozzle 9, the powder is ejected in a curtain shape, and by moving the object 22 to be coated in a direction substantially perpendicular thereto, a large area can be coated at high speed. becomes possible.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the painting head according to the present invention (+11
FIG. 3 is a partially cutaway perspective view in a state of use. FIGS. 2 to 5 are partially cutaway perspective views showing other embodiments of the present invention in which the electrode positions are changed. FIG. 6 is a system diagram of a powder coating apparatus using a coating head according to the present invention. 1.2... Powder transport pipe, 3, 4... Powder discharge port, 5
...Air discharge port, 6.12...Air chamber, 7...
Perforated plate and ultimate, 8, 8'...Air inlet, 9...
・Nozzle, 10... Pencil, 11... Porous electrode, 13.14... Linear electric 1lf120... Painting head, 21... Conveyor, 22... To be coated, 23.
... Powder supply, 24.26 ... Conduit, 31 ... High pressure generator, 32 ... High voltage cable.

Claims (5)

[Claims] (1) Two powder transport pipes are arranged close to each other and substantially parallel, and each of the two powder transport pipes has a slit-like powder in the opposing pipe wall along its length. A slit-shaped air discharge port is formed between the two powder transport pipes along the length direction toward the gap between the two powder transport pipes. It is connected to a compressed air source, and is connected to the powder discharge port at a position opposite to the air discharge port with respect to the powder discharge port along the length direction between the two powder transport pipes. A static 14 powder coating head characterized in that a slit-shaped nozzle is formed so as to communicate with the nozzle, and a charging mechanism is provided at an appropriate 11" position. (2) An air chamber is formed along the length of the powder transport pipe between the compressed air source and the air discharge port, and the iq air chamber has the compressed air source side and the air discharge port side. 2. The electrostatic powder coating head according to item 1, wherein a perforated plate is provided along the length of the powder transport pipe so as to partition the powder transport pipe. (3) The electrostatic powder coating head according to item 1, wherein a venturi is formed in the nozzle adjacent to the powder discharge port. (4) The electrostatic powder coating head according to item 1, wherein the charging mechanism comprises a porous electrode or a linear electrode provided between the compressed air source and the air outlet, at or near the nozzle portion. (5) The electrostatic powder coating head of item 2, wherein the perforated plate is an electrode.