JP2006263594A - Atomizing air cap for air spray gun - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an atomizing apparatus in an air atomization spray gun by which spots in spraying are decreased to reduce the ununiformity of the film thickness on a coated surface and particularly the disorder of the coated surface easily occurring in thin film coating with a low viscosity coating material or the like is eliminated to form a smooth high grade coating film. <P>SOLUTION: In the center air and the side air of the spray gun which are atomized by the compressed air, the quantity of the side air is controlled to be larger than that of the center air and 3 pairs of side air ports are arranged and provided to increase the opening area gradually toward the tip. Respective side air ports face the center atomizing stream at almost the same crossing angle and are arranged to jet weaker and to spread wider toward the tip compared to the center atomizing stream. When 3 pair of the side air ports are provided, it is preferable that the opening area of the 2nd side air port is made 2 times that of the 1st side air port and that of the 3rd side air port is made 2 times that of the 2nd side air port with the spread of the atomizing air stream. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an air spray gun that atomizes a paint or the like with compressed air and performs spray coating toward an object to be coated, and in particular, uniformly forms atomized particles at the time of spraying to form a coating film free from spots. The present invention relates to an atomizing air cap of an external mixing type air spray gun that enables the above.

Air spray guns for atomizing paint using compressed air to form a painted surface are widely used in various fields. Above all, industrial spray guns used for finish painting of metal, woodwork, plastic products, etc. have a basic structure defined by JIS standards, and in addition, due to the recent diversification of paints and improvement of required quality for objects to be coated. The functions and performance required for guns have been improved.

These industrial spray guns atomize the paint into a mist and spray it onto the object to be coated, so that a uniform smooth surface can be obtained regardless of whether it is a complex painted surface or a flat surface. On the other hand, there is a big problem that paint particles scattered without adhering to the object to be coated are wasted. By improving the coating efficiency, resources are effectively used, the coating environment is prevented from deteriorating, and the work efficiency is improved. There are many problems to be solved, such as improvement of productivity and improvement of atomization performance that leads to improvement of coating film quality, and it can be said that many of these depend on the atomization structure of the spray gun.

Usually, the atomizing structure is mainly composed of a paint nozzle having a paint outlet and an air cap provided with an atomizing air hole, and the combination of these is a state in which the paint is atomized and sprayed on an object to be coated, that is, a spray. The performance of the pattern is determined. In an actual spray gun, a paint valve for controlling the paint sprayed from the paint nozzle, a control valve for adjusting the compressed air ejected from each air port of the air cap, and an air passage are combined with necessary functions. Yes.

The typical structure of the atomization structure is, as can be understood in many cases, a paint nozzle having a jet port formed in the center, and an annular air port is formed around the jet port so that the center of the air cap is formed. In general, the air ports are combined so as to be arranged. The atomization of the paint is performed by jetting and colliding compressed air from the annular central air port in a wrapping form with respect to the paint ejected from the center. Further, the air cap is formed with a pair of projections called corners on both outer sides, provided with side air ports that eject toward the center from these corners, and compressed air is supplied from both sides to the atomized flow at the center. Colliding to form a spray flow pattern. The side air ports are configured to intersect at an obtuse angle so as to crush the spray flow from the center from both side surfaces. Normally, the larger the amount of air from the side air port that is sprayed for the purpose of crushing from both sides, the more the spray pattern spreads, which is convenient when painting a large area, and it can be painted at a distance close to the object to be painted. It is also effective in preventing particle scattering.

Various configurations of the direction and strength of the side air to be collided with, the amount of air, etc. have been considered from many experiences, and those that suit various conditions such as paint, coating quality, coating surface condition etc. have been proposed. Yes. Usually, the simplest configuration has a pair of side air ports with respect to the central air port, and is used in general spray guns that do not require high coating quality and spray guns with a small pattern width. When it is desired to broaden the pattern width, the side air ports are enlarged to increase the collision air from both side surfaces, and further, two pairs of side air ports are provided. However, even if the air from the side air port is strengthened, only the central part of the spray pattern is crushed in the flow concentrated in the central part of the spray flow, and the central part called so-called middle crack is transparent and averaged. The film thickness cannot be painted.

In such a case, before the side air collides, the distribution of the central spray flow is adjusted in advance by auxiliary air or the like in a direction different from the side air by 90 °, or the side air jet has a wide width to the central spray flow. An auxiliary air port is provided so as to collide. The auxiliary air port is provided close to the central air port and is injected as part of the same central air. The auxiliary air port 11 shown in FIGS. 4 and 5 promotes spraying in a direction perpendicular to the side air port so that an average spray distribution is formed when the side air acts on the central portion. The auxiliary air port 12 is made to act on the central spray flow as a diffused air flow by colliding with the side air flow before the side air acts on the spray flow. In the field of industrial coating, including these combinations, an air cap capable of obtaining a required pattern is used. With regard to the arrangement of these auxiliary air ports, an example considered to achieve specific painting requirements can be found in JP 2000-343004.

In this way, the structure of the air cap has been improved according to the requirements of various coatings, but there is still room for improvement due to the appearance of new paints and objects to be coated, or higher required coating quality. Yes. In particular, in recent years, the quality of the finished product has been higher than ever because of the high-quality orientation of the object to be coated, and the value of the product is often influenced by the final finish. Now, the added value of painting tends to depend on the stable performance of the painting machine, regardless of skilled painters, and it is strongly desired to improve the performance of the spray gun that affects the finish. In addition to seeking smooth surfaces and shine, spray guns play a major role in developing paints that create beautiful surfaces such as pearls and other beautiful surfaces that are more natural and deep. Value-added paint can also be extracted with a spray gun.

Conventionally, aiming to apply a uniform film thickness at the time of painting on average, the sprayed pattern shape has been required to be uniform. It is important not only to make the film thickness distribution uniform, but also to make it uniform in the sprayed state. Particularly in the automotive industry and thin film resin coating, which have a relatively large area, the unevenness of the flow in the spray state directly affects the coating surface, so the formation of a uniform coating surface without coating spots is the biggest issue.

Until now, spraying with compressed air has a mist turbulence due to the relationship between the process of atomizing the paint and the flow of compressed air, resulting in mist unevenness. When done, it has been empirically done to reduce the overall fog rate. However, as described above, when spraying high-grade paint in resin coating with a thin film, or when finishing the final finish surface with high-grade paint in automobile coating, mechanically reduce fog unevenness that occurs during spraying. It is clear that these problems can be solved, resulting in a reduction in waste of resources and an industrial and economic effect.
JP 2000-343004 A

As described above, improvements have been made to maintain the spray pattern thickness distribution properly and to maintain the pattern shape normally, but the technology for reducing the mist unevenness during spraying has not been sufficient. The present invention is an air atomizing spray gun in which unevenness during spraying is reduced, resulting in a non-uniform film thickness on the coating surface, and there is no disturbance in the coating surface, which is likely to occur particularly in thin-film coating in low-viscosity paints. It is a problem to obtain an atomizing device that can easily form a high quality coating film.

As an atomizing device incorporated in an air spray gun that atomizes with compressed air, a central air port that forms an annular air port on the outer periphery of the paint nozzle tip of the paint nozzle arranged at the center, and the outside of this central air port A pair of corner portions provided symmetrically to each other, and three or more pairs of the side air ports are formed in each of the air caps provided with side air intersecting at an obtuse angle from the corner portion toward the center portion. The jet flow from the side air port is formed so as to gradually spread as it moves away from the mouth, and is arranged so as to collide with the spray flow from the center.

The formation of the side air ports that form a gradually expanding jet width is obtained by sequentially arranging the side air ports that gradually increase from the side air ports close to the center air port. That is, in the case of a normal circular hole, the injection width of the small hole is narrow, and the injection width increases as it increases. Therefore, by forming at least three or more gradually increasing side air ports, the synthesized jet can be made into a jet having a jet width that gradually widens.

Usually, the paint atomized by the injection of the central air port is sprayed forward with a spread. Further, in the injection from the side air port, first, the first side air port near the center is small, and the second and third are formed so as to be farther from the center. As schematically shown in FIG. A fan-shaped jet cross section A is formed, collides from both sides with a central spray flow B sprayed while slightly diffusing, and gradually spreads as a spray flow. For this reason, the pattern of the spray flow is widened by the wider side air stream as it goes forward in a wrapped state without causing the side air stream to collide locally and causing variations in the spray particles.

Up to now, air caps with many forms of air ports have been proposed and used, but since all of them were arranged to act locally on the central spray flow, it was difficult to eliminate fog irregularities, This was dealt with by adjusting the spray shape of the central spray flow by the central air in advance, but in the present invention, the spray flow by the central air is sprayed as a spray flow that spreads in a conical shape without any disturbance, and the side air that spreads forward to this Rather than simply colliding the flow, a generally fan-shaped jet that spreads forward from a jet with a small width collides with it to suppress turbulence and enable spraying with minimal mist unevenness.

In order to obtain a fan-shaped fan that spreads forward, the side air jet has an area of the side air port that is close to the opening area that is approximately twice as large, but this has many advantages that can be provided commercially. In other words, the arrangement of the side air ports that can identify the jet of the present invention can take several forms. However, making a large number of air ports or holes not only causes a cost disadvantage in terms of production technology, but also relates to A new problem occurs in the jet distribution due to the balance and dimensional accuracy of the holes. If these are technically solved and allowed, it is possible to cope with the number and arrangement of holes without greatly changing the size of the holes.

Also, the opening area of the side air opening is larger than the opening area of the central air opening, preferably about 1.5 times or more, so that the spray flow is greatly expanded at a short distance, preventing scattering, It can be made less susceptible to atmospheric influences. When the central spray flow is large, a sufficient pattern width cannot be obtained, and variations are likely to occur partially, and mist unevenness cannot be avoided.

As described above, according to the present invention, the fine particles of the paint atomized by the central air are dispersed by the side air sprayed in a wider range sequentially than the first side air, and become a continuous spray flow. Head for things. For this reason, the flight density of the spray particles is averaged to improve the coating unevenness, and a uniform coating surface can be formed. In particular, paints containing fine particles that affect the appearance of the coating film itself such as metallic paint and mica, which contain metal powder in the paint, will affect the appearance quality and reduce the quality of the coating, By implementing the present invention, a uniform coated surface can be obtained.

In addition, it is possible to achieve a uniform finish even in light-colored paints and thin film paints that are easily affected, enabling finish paints with less paint, and even with resin coatings that use expensive finish paints with a small film thickness High-quality finish painting is possible, and the effects of shortening the painting process and saving paint can be obtained. In addition, the improvement of the coating quality is possible with a spray gun, so that results that can reduce coating costs and improve productivity can be obtained. Even in the field of high-grade finish painting that would otherwise be difficult, it is possible to achieve a great industrial effect, such as enabling stable painting with an automatic spray gun.

FIG. 1 is a sectional view showing an atomizing air cap and a paint nozzle portion of a spray gun according to an embodiment of the present invention. FIG. 2 shows the overall structure of a spray gun using the air cap of FIG. In this embodiment, a hand-type spray gun is shown, and a paint nozzle 2 and an air cap 3 are attached to the tip of a main body 1. A needle valve 4 is incorporated in the center of the paint nozzle 2 so as to be able to advance and retreat, and opens and closes the paint jet nozzle 21. In addition to the handle 5 and the trigger 6, the air valve 7, the pattern adjustment valve 8, and the like are incorporated in the rear portion of the main body 1. This type of spray gun is widely used in general and is also known as a structure, and therefore details thereof are omitted.

The atomizing device part that influences the spray performance is composed of an air cap 3 and a paint nozzle 2, the needle valve 4 that affects the supply of paint and compressed air, the paint nozzle 2 attachment part of the main body 1, and the air cap 3, the cap cover 9, and the like are related as constituent elements. In the present invention, the air cap 3 is used as a gist, and only the air cap 3 and the paint nozzle 2 are shown for details, and FIG. 1 is omitted. explain. The paint nozzle 2 is provided with a paint jet 21 at the center and a cylindrical outer diameter 22 is formed at the tip. The rear part is attached to the main body 1 so that compressed air divided into atomizing central air and pattern adjusting side air is sent to the air ports of the air cap 3.

When the air cap 3 is assembled to the paint nozzle 2, a center port 32 that forms an annular central air port 31 is provided outside the outer diameter 22 of the paint nozzle 2, and a pair of corners 33 are formed outside the air cap 3. It is formed for the center. Inside the corner portion 33, a square hole 34 is provided, and a side air opening is opened from the central axis side so that compressed air for pattern formation is injected to the spray flow.

In the case of this embodiment, the first side air port 35, the second side air port 36, and the third side air port 37 are opened from the position close to the coating material ejection port 21 in the case of this embodiment. The opening direction of each side air port is the direction that intersects with the obtuse angle toward the central axis as in the case of the conventional spray gun, and is generally opened at an angle of 120 ° to 150 °. It is not always necessary to match.

Each adjacent side air port has an opening area of the second side air port 36 approximately double that of the first side air port 35, and the opening area of the third side air port 37 relative to the second side air port 36. However, the magnification is not limited to this, and it is important that the jet becomes larger and wider toward the tip as shown by B in FIG. It is. As a result, the spray flow of the narrow side air first collided with the central spray flow and then spread is gradually widened as shown by C in FIG. 6, and the wide side air jet corresponding to this spreads. A balanced spray flow is formed.

In addition, the size of the entire side air port by these air ports is selected so as to be clearly larger than the area of the central air port formed in the annular shape. By increasing the air opening area, a flow that wraps the central spray flow in a wide range is formed, and the spray pattern is greatly widened by increasing the amount of air, thereby enabling the effect of spraying at a shorter distance. Actually, it is desirable that the area be about 1.5 times or more.

It is a combination sectional view of an air cap and a paint nozzle of a spray gun showing one embodiment of the present invention. It is a front view which shows the air port of the air cap which looked at FIG. 1 from the left. It is sectional drawing which shows the Example of the spray gun which attached the atomization air cap of this invention. It is a front view which shows the air hole of the conventional air cap. It is sectional drawing which shows the YZX cross section of FIG. It is a schematic diagram which shows the collision of the side air flow and center spray flow of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gun body 2 Paint nozzle 3 Air cap 4 Needle valve 5 Handle 6 Trigger 7 Air valve 8 Pattern control valve 9 Cover 21 Paint outlet 22 Outer diameter 31 Center air port 32 Center port 33 Corner portion 34 Corner hole 35 First side air Port 36 Second side air port 37 Third side air port 38 Auxiliary air port

Claims (4)

As an atomizing device incorporated in an air spray gun that atomizes with compressed air, a central air port that forms an annular air port on the outer periphery of the paint nozzle tip of the paint nozzle disposed in the center, and an outside of the central air port In each of the air caps provided with side air ports that form a spray pattern by injecting side air that intersects at an obtuse angle toward the center from the corner, The side air ports formed at the corners of the nozzles are composed of a plurality of air ports, and when ejected at the same time, a jet air flow that collides with the central jet flow with a wider jet width is formed as the distance from the central air port increases. Atomizing air cap for air spray gun. 2. The atomizing air cap of an air spray gun according to claim 1, wherein three or more pairs of the side air ports are formed, and the opening area gradually increases as the distance from the central air port increases. The atomizing air cap according to claim 1, wherein an opening area of the side air opening is formed larger than an opening area of the central air opening. The atomization according to claim 1, wherein three pairs of side air ports formed gradually larger are provided, and the side air ports adjacent to each other are formed so that the side air ports separated from the central air port have approximately twice the opening area. Air cap.

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