JP2006326452A - Spray gun for powder coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spray gun for powder coating which enables an adjustment of a pattern width easily, and enables a stable spray. <P>SOLUTION: An adjustment air port 31 blowing out compressed air toward a central spray flow is provided on both sides of a jet port 22 to enable the adjustment of the compressed air flow. The jet port is provided with an auxiliary air port 23 blowing out along a powder spray flow around a center mouth 21 for the powder, and can correspond to a shape and coating section of a coating object under optimal conditions depending on conditions of the compressed air from the auxiliary air port. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

TECHNICAL FIELD The present invention relates to a technique for enabling a spray pattern to be adjusted in accordance with spraying conditions in a powder coating spray gun in which a powder coating is sprayed and applied to an object to be coated by the action of static electricity.

Among many coating methods, powder coating uses a solvent and does not use a solvent compared to coating with a liquid paint that forms a coating film by drying. Therefore, it can save resources and prevent the emission of volatile organic compounds. Therefore, there are advantages such as being environmentally friendly and having excellent coating strength. Further, it is known as a coating method that can collect and reuse a paint that has not been applied to an object to be coated, and is excellent in effective use of resources.

On the other hand, among various powder coating methods, powder coating by a spray gun is widely used as a coating method that is highly versatile and can handle a wide range of objects to be coated. Usually, a spray gun for powder coating has a configuration in which the sprayed powder paint is applied to an object to be coated using high-voltage static electricity, and the powder paint is fluidized by compressed air and applied to the spray gun. It is fed in and sprayed from a spray port provided at the tip.

Since the supply of general powder paint is sent together with a relatively large amount of air by an ejector-type pump, the spray port has a relatively large diameter to control the flow rate, and a baffle is placed in front of the spray port to go straight ahead. The spraying flow rate is suppressed so that the effect of static electricity is not disturbed.

On the other hand, in order to perform efficient coating, the spray flow must be adjustable depending on the shape of the object to be coated. The spray flow speed is mainly taken up as a factor of the coating efficiency, the spray pattern shape is a factor for forming a uniform coating surface, and when performing efficient coating according to the size of the coating surface It is considered important. In other words, it is possible to obtain an average film thickness by spraying with a uniform pattern with a large spread over a large area, and the workability is also improved. These are also apparent in spray guns for liquid paints with a long history. It is said that.

In powder coating, powder paint that has not been applied to the object to be coated is characterized by being collected and reused. However, reused powder is inevitable to be contaminated with impurities, so new powder paint is used. It is important to improve the coating efficiency in the case of, and it is desirable to spray efficiently in an optimum pattern for the object to be coated.

As described above, powder spray guns have been supplied with compressed air since the powder coating is supplied with compressed air, and the spray pattern depends on the size, shape, and arrangement of the baffle. A way to adjust is taken.

Needless to say, a small spread pattern is necessary for narrow gaps or narrow shapes in the object to be coated, and a large spread pattern is required for objects having a flat and wide painted surface. The pattern can be changed by using the technique described in Japanese Patent Application Laid-Open No. 54-24953, which obtains the spread of the pattern by colliding the spray flow from the two opposing spray ports, and the slit-shaped spray port. As a technique, a method disclosed in Japanese Patent Laid-Open No. 62-163758 has been developed.

However, all of these techniques change the spray port, and are insufficient in spray state and operability as pattern adjustment, and some improvements are required for practical use.

JP 62-163758 A JP 54-24953 A Japanese Patent Publication No. 6-85895

The present invention solves the problem that in the past, it was difficult to adjust the pattern width in a spray gun for powder coating using static electricity, and the pattern width could not be adjusted widely. An object of the present invention is to provide a spray gun for powder coating that can be easily performed and that can achieve an optimum spray state for coating, and can improve coating quality and productivity.

Specifically, the coating efficiency and coating can be easily adjusted to the optimum pattern width for the powder coating sprayed from the powder spray gun according to the coating conditions including the shape and part of the object to be coated. It is to improve quality. It is another object of the present invention to provide a powder spray gun capable of always performing spray coating in an optimum state without any adverse effect on the coating conditions caused by changes in the spray pattern.

This is a powder coating spray gun that mixes air and sends fluidized powder to a spray port provided at the tip of the spray gun and sprays it onto the object to be coated. By providing an adjustment air port for ejecting compressed air toward the center, the central spray flow is crushed into a flat shape by the compressed air so that the spray pattern can be adjusted to a wide range. The size of the pattern is adjusted so that the flow rate of the compressed air can be adjusted.

The central jet port is provided with a central port of a powder nozzle that forms the auxiliary nozzle, and an auxiliary air port that jets along the powder flow is provided on the circumference. A powder spray flow from the central air port is sprayed from the jet port while being surrounded by compressed air from the auxiliary air port. The adjustment air supply amount to the adjustment air port and the auxiliary air supply amount to the auxiliary air port are variable independently.
As the most preferable configuration for practical use, electrostatic coating does not impair operability by placing a high-voltage charged electrode at the center of the nozzle and connecting a high voltage from a high-voltage generator built in the spray gun. Is possible.

According to the powder spray gun of the present invention, the powder is always sprayed from the central spray port in a stable state, and compressed air is blown so as to squeeze the entire surface from both sides against the spray flow. The normal circular spray pattern can be made flat, and the pattern width increases as the amount of compressed air increases. Therefore, if the shape of the object to be coated is widened, the pattern width can be widened to provide uniform coating over the entire surface, less spraying operations can be performed, and coating efficiency can be increased.

The pattern width can be easily adjusted with the supply air amount adjustment device provided in the spray gun, and can be adjusted without interrupting the work. The air amount adjustment device can be automatically controlled or externally adjusted. It is also possible to automatically perform pattern control based on an external control signal by supplying air adjusted by a valve.

Further, in the present invention, an auxiliary air port is provided around the central port from which the powder is ejected, and the compressed air can be ejected to impart a linear force to the spray flow. The flow rate of the compressed air from the auxiliary air port can be adjusted independently of the adjustment air, so that the spray flow can easily obtain the optimal spray flow according to the shape of the object to be coated and the condition of the coating part. Can do.

In particular, when painting in gaps and narrow corners that did not enter with conventional spray guns, it is easy and quick to increase the compressed air from the auxiliary air port and to force straight forward spray, Powder coating is also possible on the object to be coated without impairing workability.

These techniques can obtain an effect as a spray gun for powder coating, but can be most effective in electrostatic powder coating in which coating is performed by electrostatic force. In electrostatic powder coating, various methods can be used to charge the powder, and in addition to internal friction charging, a configuration with a large opening at the center of the jet outlet is possible, so that electrostatic spraying is not affected by spraying. Since it becomes easy to arrange a charging electrode for painting, a method in which a charging electrode is provided at the tip can be used without any problem. When a charged electrode is provided, a high-function, high-productivity spray gun for powder coating can be obtained without sacrificing operator operability by incorporating a high-voltage generator for charging in the spray gun body. Can be obtained.

FIG. 1 shows an overall cross section of a powder coating spray gun according to an embodiment of the present invention. A gun body 1 is attached at its tip with a powder nozzle 3 constituting a spray device, and is attached concentrically with the powder nozzle 3. The air cap 2 is detachably attached with a cover 4. The powder nozzle 3 is connected to a powder passage connected from a powder inlet 10 provided at the rear of the gun body 1 through a supply hose 8 to a powder inlet 7 near the tip. Although the air passage for adjusting the spray is not shown in detail, the adjustment air supply passage 11 opens at the tip of the gun body 1, and an air cap is provided between the powder nozzle 3 and the cover 4 as shown in FIG. The second adjustment air hole 32 is connected. Another auxiliary air supply path 12 is opened to an auxiliary air chamber 24 formed by the attachment of the powder nozzle 3.

In the case of the present embodiment, the high voltage generator 5 is built in the gun body, and the high voltage output is connected from the high voltage terminal 6 to the charging electrode 9 disposed at the center of the powder nozzle 3. It has become.

The details of the spraying apparatus will be described with reference to FIG. A jet port 22 connected by a caliber is formed. An auxiliary air port 23 is formed on the circumference between the center port 21 and the jet port 22, and the air from the auxiliary air chamber 24 is ejected through the auxiliary air passage 25 of the powder nozzle 3. In this embodiment, eight auxiliary air ports 23 are formed on the circumference.

The air cap 2 is configured to be concentrically mounted by a taper sheet that is in contact with the powder nozzle 3 and forms a pair, and the powder nozzle 3 has an opening at the front side of the injection port, and a corner portion opposed to both front sides thereof. 33 is provided with an adjustment air port 31 for spraying toward the spray flow from the center. The size, the injection angle, the number, and the like of the adjustment air port 31 are selected according to the spray adjustment balance. In the embodiment, two each are provided.
The supply of compressed air to the auxiliary air port 23 and the adjustment air port 31 is supplied from the auxiliary air supply path 12 and the adjustment air supply path 11, respectively. Although not shown, these air amounts can be adjusted independently through adjusting means such as each adjusting valve device.

As a spray gun for performing electrostatic coating as powder coating, the entire body including the gun body is made of an insulating resin, and a charged electrode is provided at the tip, as in the configuration of other spray guns for electrostatic coating. In the case of this example, an electrode terminal 91 provided at the rear end of the charging electrode 9 attached to the gun main body 1 is provided at a height built in the gun main body 1 so that the tip protrudes several millimeters at the center of the jet nozzle. It is configured to be electrically connected to a high voltage terminal 6 that is connected to and extends to the high voltage output side of the voltage generator 5.

With the above configuration, the powder coating material is fed into the powder inlet 10 of the powder spray gun in a state of being fluidized together with the compressed air by the supply pump. In this case, there are various types of pumps. In order to effectively use the present invention, a positive displacement pump using a cylinder / piston is used. According to this pump, powder can be supplied in a fluidized state with a small amount of compressed air, and spraying can be performed in a state where the momentum of the compressed air is low from the ejection port.

In the case of an injector pump that is representative of powder supply, a large amount of compressed air is used for supply, and since the air is supplied to the spray gun by the air, the spraying force by the compressed air is strong. Control becomes difficult. On the other hand, in the case of the positive displacement pump, the amount of air at the time of powder supply is about one-tenth, and the spray flow can be easily controlled. As an example of this type of pump, powder is sucked into the cylinder by the movement of a piston that reciprocates in a cylindrical cylinder, discharged together with a small amount of air jetted into the cylinder for fluidization, and then passed through a supply hose. There is a pump that feeds the body spray gun. The supply amount of the powder is set to a range in which about 50 to 400 g per minute is often used.

The powder sprayed from the central jet port 22 is flattened in a state where the whole is crushed by the adjustment air sprayed from the adjustment air ports 31 provided on both side surfaces. This spread increases as the flow rate of the compressed air increases, and is selected according to the coating width of the object to be coated. Naturally, the amount of adjustment air for adjusting the pattern depends on the amount of powder ejected. In one example, a pattern width of about 400 mm can be obtained with an air amount of about 35 liters per minute for a discharge amount of 300 g. It was.

On the other hand, when the pattern width expanded by the adjustment air exceeds a certain range, the density of the powder is reduced in a state where the central portion is blown away, resulting in a non-uniform finish for coating. In the present invention, the forward spray flow in a state of enveloping the spray flow without increasing the back pressure in the powder nozzle by the compressed air ejected in parallel with the spray flow from the auxiliary air port 23 provided around the center port 21. , That is, the straight running force can be increased, the density reduction of the central portion can be prevented, and the average distribution state can be maintained.

In addition, when spraying deep corners of the object to be coated, an edge effect due to static electricity is also added, and it becomes a situation where the spray flow does not enter unless there is momentum, and uneven coating occurs, but the same as above By adding auxiliary air, the straight running force increases and the amount of spray can be concentrated in the center, and it is possible to select a spray in a convenient state and to improve the problems in the previous period.

Various configurations and balances of the jet port, the adjustment air port, and the auxiliary air port that form the spray state are considered depending on the conditions of the powder spray, and the size and dimensions of each are not limited, and the properties of the powder paint The spraying conditions must be selected according to the various coating conditions. For this reason, the flow rate of the adjustment air and the auxiliary air can be individually adjusted, and the configuration is such that the operator is automatically controlled directly or based on the set conditions, thereby further increasing the application effect. It will be.

The spray structure according to the present invention is not limited to the electrostatic charging method, and the charging method using the charging electrode shown in FIG. In the center of the spray, the charged electrode is in a state that does not affect the spray pattern. Can be arranged. In an electrostatic coating gun that can be made in this way, a high voltage applied to the charged electrode forms an electric field directed to the object to be coated by the discharge, and the periphery of the electrode is ionized and charged to the sprayed powder, It will adhere to the paint. Since these actions have already been clarified by many conventional techniques, details thereof will be omitted.

1 is an overall cross-sectional view of a spray gun for electrostatic powder coating according to the present invention. It is sectional drawing which expanded and showed the spray apparatus part of FIG. It is the side view which looked at the spray apparatus part of FIG. 2 from the left.

Explanation of symbols

1 Gun body 2 Air cap 3 Powder nozzle 5 High voltage generator 7 Powder inlet
9 Charging electrode 11 Adjustment air supply path 12 Auxiliary air supply path 21 Central port 22 Spout 23 Auxiliary air port 24 Auxiliary air chamber 25 Auxiliary air passage 31

Claims (4)

In a spray gun for powder coating, air is mixed and fluidized powder is sent to the spray port provided at the tip of the spray gun and sprayed onto the object to be coated, and compressed toward the spray flow from the spray port. A powder coating spray gun in which an adjustment air port for ejecting air is provided opposite to both sides of the discharge port, and the compressed air is supplied to the adjustment air port via a flow rate adjusting means. The ejection port is formed in a circular shape outside the center port so as to be ejected along a center port provided at the center of the powder nozzle provided at the tip of the spray gun and the flow of powder ejected from the center port. The spray gun for powder coating according to claim 1, wherein an auxiliary air port provided in is incorporated. The spray gun for powder coating according to claim 2, wherein an adjustment air supply amount to the adjustment air port and an auxiliary air supply amount to the auxiliary air port are each independently variable. 2. The spray gun for powder coating according to claim 1, wherein a high voltage charging electrode is arranged at the center of the jet nozzle, and a high voltage from a high voltage generator built in the spray gun is connected to charge the spray flow.

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