JPS6242673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic powder coating method and apparatus, and particularly to an electrostatic powder coating apparatus suitable for coating objects supported in a wide width manner.

In conventional general electrostatic powder coating, a coating booth with a box-shaped casing is used, and the object to be coated, which is suspended from a moving conveyor, passes through the coating booth from the left and right entrances of the coating booth. When applying powder, powder is usually applied from the front side of the coating booth using a coating gun, and in order to prevent unapplied paint from scattering outside, the powder is applied from the bottom of the coating booth, and sometimes from the sides. The uncoated powder and its carrier gas are sucked out. However, if powder is required to be applied to only one side of a heavy article that needs to be supported on a conveyor device over a wide area from below, the powder coating may adhere to the conveyor. This makes long-term continuous operation difficult, and the powder coating unnecessarily wraps around the back side of the product, making it uneconomical. An example of such powder coating is the powder coating of cement tiles.In this case, the cement tiles that are coated are heavy and require mass processing, so powder coating is used. It is appropriate to use a chain conveyor that moves horizontally to load the tiles onto the conveyor for applying the paint, and the parts of the tiles that are overlapped to cover the roof are coated. There are cases where it is functionally better without it, and there is no need to paint the back side at all.
Therefore, when painting tiles, the tiles are loaded like a roof on a conveyor that moves horizontally, and electrostatically applied from above, and the good throwing effect is used to coat the top and sides. is sufficiently painted,
On the other hand, it is required to prevent powder coating from being applied to the overlapping part, back part, and conveyor. This problem is difficult to solve in ordinary powder coating booths. Furthermore, in the case of painting cement tiles, it is necessary to preheat the object to be coated to a high temperature of about 130 to 300 degrees Celsius in order to prevent foaming due to moisture and gas contained in the tiles. For this reason, when painting work is carried out in a normal booth, the powder coating is blown up by the air convection generated by the preheated object to be coated, reducing efficiency, and the powder adhering inside the booth is A serious problem arises in that radiant heat causes melting, which impedes long-term operation.
In particular, if the object to be coated is preheated to a high temperature, the paint once ejected from the gun will continue to cure due to radiant heat even if it is recovered, so a large amount of paint will not be mixed into new paint. A particular problem arises in that it cannot be reused. In this regard, the coating efficiency of the gun is required to be at least 85% or more, preferably about 95%. In other words, if the gun's coating efficiency is 85% or more, preferably around 95%, the excess recovered paint can be mixed with new paint and used almost 100%; If the efficiency is 70%, the amount reused cannot exceed 10%, so 23
% of the recovered paint has to be discarded, and in the end, the total usage rate of the paint is about 77%, which is extremely uneconomical, but if you use a normal powder coating gun and booth, it will be 77%. %, which hinders the large-scale practical application of powder coating for roof tiles.

The purpose of this invention is to solve the various problems mentioned above, by preheating cement tiles to a temperature of 130 to 300°C, and applying powder to the areas where a large amount is needed and the areas where it is not needed. Preheated workpieces can be used without painting, and can be operated continuously for long periods of time while minimizing contamination of the conveyor and booth interior walls, making it possible to achieve nearly 100% total paint utilization. a coating booth that surrounds a part of the movable member to form a coating chamber for electrostatically applying powder to the coating material and has an entrance and exit for the coating material; A coating device is installed inside the coating booth to electrostatically apply powder to objects, and a coating device is installed inside the coating booth to create a rectified airflow as an atmosphere inside the coating chamber, covering almost all of the main parts of the interior of the coating booth. a rectifying device installed along the rectifying device; an air blowing discharge section connected to an air supply duct installed behind the rectifying device; and an air intake for the internal atmosphere provided at the inlet and outlet of the object to be coated in the coating booth. The object of the present invention is to provide an electrostatic powder coating device characterized by having a This method can be widely applied to perform powder coating with high efficiency only on the upper side of moving articles.

The above and other objects, features and advantages of the invention will become apparent from the following detailed description of one embodiment of the invention, taken in conjunction with the accompanying drawings.

1 to 3 of the drawings, an embodiment of the electrostatic powder coating apparatus of the present invention is shown. A coating booth 10 forming a coating chamber 11 for electrostatic powder coating on the placed object 1 to be coated;
It mainly consists of a coating gun 4 for coating powder. In the illustrated example, the conveyor 2 is wide and can place a large number of objects 1 to be coated, such as roof tiles, in a row, and the tiles of the objects 1 to be coated are preheated to the required temperature in an appropriate preheating furnace (not shown). The roof tile itself is dehumidified and electrostatic powder coating is performed well.

The coating booth 10 consists of an upper part and a lower part formed to cover a part of this conveyor 2,
The upper part includes intake sections 12 and 14 provided on the entrance and exit sides of the conveyor 2, and these intake sections 12 and 1.
4, a discharge part 15 is provided in the center of the discharge part 15 for forming and discharging a uniformly rectified air flow, and a discharge part 15 is provided in the center of the discharge part 15 so as to be able to reciprocate across the conveyor 2 in a direction perpendicular to the moving direction of the conveyor 2. Painting gun 4
The lower part, corresponding to the upper part, is made up of a lower discharge part 17 which is provided below the conveyance surface of the conveyor 2 and discharges air from below the conveyance surface of the conveyor 2.

The air intake sections 12, 14 of the coating booth 10 are formed of outer hood plates 22, 24 and inner baffle plates 25, 26, and are connected to air intake ducts 27, 28, respectively. Hood plates 22, 24 and deflector plate 2
5, 26, the rectifier 34, etc., are preferably provided in a removable manner so that they can be removed or replaced when they become dirty or damaged. The discharge section 15 provided between these intake sections 12 and 14 is divided into two by the guide path section 30 of the coating gun 4 in the center, and the air sent from the supply duct 32 is passed through an appropriate rectifier 34. The flow is rectified into a uniform flow and discharged toward the object 1 to be coated, thereby gently suppressing the convection generated from the preheated object 10.
The airflow is divided into intake sections 12 and 14 provided at the entrance and exit of the workpiece 1, and is gently sucked in while flowing close to the workpiece 1, and the airflow containing powder is extremely unlikely to deviate in the width direction of the workpiece 1. Therefore, the coating efficiency can be significantly increased. This rectifying device 34 is for uniformly blowing out the air from the supply duct 32. For example, a large number of rods are arranged at narrow intervals to form a row of narrow slits, or a perforated plate, cloth, or wire mesh is used. It can be formed from an appropriate material such as.

The guide path section 30 of the coating gun 4 extends perpendicularly to the moving direction of the conveyor 2, and the coating gun 4, which is fixed to the support stand 5 and extends downwardly, is connected to an appropriate guide rail 6.
It is supported so that it can reciprocate along the Further, an appropriate air supply pipe 35 is connected to the guide path section 30, and is configured to supply air into the guide path section 30 and gently blow out the air from the gap.

The side walls 40 of the coating booth 10 hang down from the upper part to both sides of the conveyor 2 and extend to cover both sides of the conveyor 2, and allow uncoated powder to fall naturally between the side walls 40 of the coating booth 10 and both sides of the conveyor 2. A recovery path 42 for recovery is provided, and an air duct 46 for blowing upward along the side wall portion 40 is connected to each side.
This can prevent powder paint from adhering to the side walls. Note that the airflow that does not contain the powder coating material and flowing along the side wall portion 40 may flow from the top to the bottom.

In addition, the lower discharge part 1 of the lower part of the coating booth 10
Reference numeral 7 consists of an air blowing casing 51 provided immediately below the upper conveying section 2a of the conveyor 2, connected to an air duct 52, and configured to blow air from the air duct 52 through the casing 51. Due to the existence of this airflow, unnecessary powder coating is prevented from passing through the gap between the objects 1 to be coated and adhering to the back side or contaminating the conveyor 2. Unnecessary wrap-arounds and contamination of the conveyor at both ends of the direction are likewise prevented.

According to the electrostatic powder coating apparatus of the present invention configured in this way, the objects 1 to be coated, such as roof tiles, are arranged on the conveyor 2 in order to achieve good powder coating, and then It is preheated in a suitable preheating oven and then conveyed to an electrostatic powder applicator. In the electrostatic powder coating device, synthetic resin powder is sent to a coating gun 4 through a suitable powder supply pipe, and is sprayed out from the coating gun 4 toward the object 1 to be coated. , and the electrostatic coating is performed by an electrostatic field formed by the electrodes of the coating gun 4. In the coating chamber 11 of this electrostatic powder coating device, the object 1 to be coated has been preheated and still has considerable heat, so even if an upward air current is generated in the coating chamber 11 due to the radiant heat, Since the air from the air duct 32 is blown out in a uniform flow by the rectifier 34, good electrostatic coating of the powder is performed by the coating gun 4 in the coating chamber 11. After electrostatic coating is completed, the uncoated powder and carrier gas are transferred to the coating chamber 11.
The uncoated powder is sucked in by the intake air in the intake sections 12 and 14 before and after the powder, passes through the intake ducts 27 and 28, and is collected by an appropriate air filter or air bag. At this time, the intake section 12,
Part of the outside air is also sucked in by the coating chamber 14, so that the inside air, that is, the gas inside the coating chamber 11, does not leak to the outside. In addition, the air blown out from the casing 51 of the lower discharge part 17 below the upper conveyance surface of the conveyor 2 flows out from the gaps between the conveyor 2 and the object 1 and the sides of the conveyor 2, and flows out from the air intake part 12,
The air sucked and discharged from the air duct 14 and blown out from the air duct 46 along the side wall 40 also flows into the air intake section 1.
It is sucked and discharged from 2 and 14. Furthermore, paint gun 4
is moved along the guide path section 30 at an appropriate speed corresponding to the moving speed of the conveyor 2 on which the object to be coated 1 is placed. Painting is possible.

Thus, according to the present invention, the air duct 32
The flow of air in the coating chamber 11 is improved by uniformly blowing the air into the coating chamber 11 through the rectifying device 34, and the air is discharged directly below the upper conveyance surface 2a of the conveyor 2. Together with the blowing of air from the casing 51 of the section 17 and the air duct 46 along the side wall section 40, the suction and recovery of unpainted powder and carrier gas by the suction sections 12 and 14 as well as the gas blown out from each section. As a result, the airflow within the coating device is maintained in a suitable manner, so that no uncoated powder leaks to the outside, contaminates the surrounding area, and scattering of the powder can be prevented. Furthermore, it is possible to suppress the generation of upward airflow in the coating chamber 11 due to the radiant heat of the preheated object 1, such as a roof tile, and to form a good powder coating state. Of course, it is not only applicable to coated objects such as roof tiles.
For other objects to be coated that are not preheated, powder coating can be performed even better at room temperature. Further, an appropriate cooling device may be provided around the coating gun 4 itself to cool the coating gun, or any other coating gun may be used.

If even higher efficiency is required, a high voltage is applied almost perpendicularly to the airflow in the booth as shown in the figure, and corona discharge is generated toward the workpiece 1 as necessary. Advantageous results can be obtained by providing a transparent auxiliary electrode 8, such as a thin wire. In this case, due to the presence of the rectifier 34, there is very little performance degradation due to dirt on the auxiliary electrode 8;
If necessary, a dirt prevention means, for example, a small amount of clean airflow forming device may be provided only in the vicinity of the auxiliary electrode 8. In this case, depending on the dimensional relationship of the device, it is preferable that the gun, the support, and the rectifying device 34 be constructed of an insulating material.

[Brief explanation of the drawing]

The drawings show an embodiment of the electrostatic powder coating apparatus of the present invention, in which FIG. 1 is a longitudinal sectional view, FIG. 2 is a plan view, and FIG. 3 is a partial end sectional view. In the figure, 1:
Object to be coated, 2: Conveyor, 4: Coating gun, 10: Coating booth, 12, 14: Intake part, 15: Discharge part,
17: Lower discharge part, 22, 24: Hood plate, 25,
26: Deflector plate, 27, 28: Intake duct, 3
2: supply duct, 34: rectifier, 40: side wall, 42: recovery path, 46: air duct, 51: casing.

Claims (1)

[Claims] 1. A movable member that supports a preheated object to be coated, and a movable member that surrounds a part of the movable member to form a coating chamber for electrostatically applying powder to the object to be coated. A coating booth with an entrance and exit for objects, a coating device installed inside the coating booth to electrostatically apply powder to objects to be coated, and a coating device that creates a rectified air flow as the interior atmosphere of the coating chamber. A rectifying device installed over almost the main part of the inner surface of the coating booth, an air blowing outlet connected to an air supply duct installed behind the rectifying device, and an inlet and an outlet for the object to be coated in the coating booth. 1. An electrostatic powder coating apparatus comprising: an internal atmosphere suction section provided at the top, and a lower discharge section for blowing out air provided below the moving member. 2. The electrostatic powder coating apparatus according to claim 1, wherein the entrance/exit for the object to be coated in the coating booth is comprised of a removable hood plate.