JP2006247538A - Atomization structure of air spray gun - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an atomization device of an air spray gun for reducing unevenness formed during spraying, and eliminating formation of coating with an uneven thickness to a surface to be coated, and capable of coating without unevenness in thin film coating using a low viscosity paint or the like and forming a high quality coated surface. <P>SOLUTION: There is provided an atomization structure of an air spray gun in which a plurality of vertical caves 33 that are opened substantially parallel to a center axis of a paint nozzle 3 are provided as a path for supplying air from a center air chamber 13 of a gun body 1 to a center air outlet 42 of an air cap 4, and shielding plates 34, 35 in a collar shape for shielding air from each of the vertical caves 33 from going straight ahead to an outlet portion in the air cap side of each of the vertical caves 33 and directing to an outer periphery of the shielding plates 34, 35 are provided so that an annular concentric path having an axial length and a sufficient volume is formed in order to form a more uniform air flow after air flowing around the outer periphery of the shielding plates 34, 35 reached thereto. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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, forms a coating film without unevenness by uniformly dispersing atomized particles during spraying. It is related with the atomization structure of the tip of an external mixing type air spray gun which makes it possible.

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 jet nozzle and an air cap provided with an atomizing air hole, and a 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.

As can be understood from the example shown in the figure, the typical structure of the atomization structure is a paint nozzle having a jet port formed in the center, and an air hole is formed so that an annular air port is formed around the jet port. It is combined so that the central air port of the cap is arranged. The atomization of the paint is performed by colliding the compressed air from the center 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 compressed air ejected from the central air port and the side air port is divided into two when the paint nozzle is assembled to the spray gun body, and when the air cap is further combined, it is connected to the respective passage of the air cap. It has a configuration that is divided into two. Some examples of these structures are known in addition to FIG.

As for the pattern to be sprayed, the necessary atomization and its distribution state, shape, etc. have a direct influence on the finish of the coating, and many improvements have been made so far. In particular, the balance of the blown air flow greatly affects the fog state, and the pattern is deformed or non-uniform due to the deterioration of the uniformity of the entire circumference of the annular air port, the balance from the air ports on both sides, and the jet stability. become. As a result, the state of the coating film becomes non-uniform, and the coating surface becomes defective, such as unevenness, uneven gloss, and distortion. Although it is indispensable to improve the machining accuracy of each nozzle for these measures, there are still situations where it cannot be improved.

A technique for uniformly stabilizing the balance from the side air ports is distribution of the compressed air from the air passages provided in the gun body to the side air holes communicating with the side air ports arranged on both sides. In order to feed in a uniform and stable flow, an annular air chamber is formed immediately before the side air hole, and a shielding plate is provided so that the compressed air flows uniformly into the air chamber. (For example, the technique described in Japanese Patent Publication No. 63-44019)

In addition, because the supply to the central air port needs to be separated from the outside side air, a partition wall is formed around it, so several air holes are formed on the circumference between the paint passage and the air cap side Need to be sent to. Normally, at least four nozzle holes are provided, but in any case, it is impossible to prevent the air flow toward the annular central air port from being uneven on the circumference. What is considered as a countermeasure is a shield plate for the nozzle well. As shown in Japanese Patent Registration No. 3422625, a brim-shaped shielding plate is provided on the front side of the entrance of the pothole so as to flow into a plurality of drilled holes on average.

In industrial coating, the value of the final product is often influenced by the quality of the appearance coating, and it is always desired to improve the coating quality as the coating quality becomes higher. Particularly in the automotive industry and thin film resin coating, which have a relatively large area, the formation of a uniform coated surface free from coating spots is the biggest issue. Until now, the spraying with compressed air has a variation in the generation of mist due to the relationship between the process of atomization of the paint and the flow of compressed air. It has been empirically performed to reduce the proportion of variegated spots. However, as mentioned above, it is these problems to reduce the spots that occur when spraying, such as when painting a high-grade paint in resin coating with a thin film, or when finishing the final finish coating surface in automobile painting with a high-grade paint. This will result in a resolution, resulting in resource savings, industrial and economic benefits.

Japanese Patent Publication No. 63-44019 Patent Registration No. 3422625

As described above, improvements have been made to maintain the spray pattern thickness distribution properly and to maintain the pattern shape normally, but the technique for reducing the fog during spraying has not been sufficient. In the air atomizing spray gun according to the present invention, unevenness in spraying is reduced, and as a result, nonuniform film thickness on the coating surface is reduced. It is an object to obtain an atomizing device that can easily form a smooth high-quality coating film.

In the combination of the air cap and the paint nozzle that forms the spray pattern, the central air and the side air are divided by a partition, and the central axis of the paint nozzle is used as a passage to be supplied from the central air chamber of the gun body to the central air port of the air cap. A plurality of coffin holes are provided that are opened substantially in parallel, and an eaves-shaped shield plate that blocks straight travel from the coffin hole and is directed to the outer periphery is provided at the outlet portion on the air cap side of the coffin hole, and flows around the outer periphery of the shield plate. A sufficient volume of concentric annular passage having an axial length is formed so that the air can be made more uniform after the flange-shaped shield plate.

As a result, the local flow ejected from a plurality of wells can be relaxed and dispersed by the shielding plate, but the variation in pressure distribution caused by the interference from the flow from adjacent wells flows directly into the central air port. Is preventing. In other words, the air that has passed through the outer periphery of the shielding plate is not spouted while reducing the passage area toward the central air port, but rather, by allowing the air to pass through a concentric annular passage having a sufficient volume, the variation can be reduced. Can be formed to reduce the spots in the spray.

In order to ensure that a uniform and stable flow is formed by the cylindrical passage, the present invention forms a slight annular groove at the front and end portions of the cylindrical passage. As a result, the air flow is directed to the groove and temporarily stagnates, or a part of the air flows along the groove, and the flow is changed in a direction perpendicular to the cylindrical passage, further increasing the uniformity and the center. It becomes a contracted flow that converges on the air cap and is ejected from the central air port of the air cap. For this reason, a slight remaining variation is eliminated depending on the cylindrical passage, and the spray can be stabilized as a stable jet.

The average air inflow into the pit is average for a plurality of pits, which provides a more favorable atomization air jet, and a ridge-shaped shielding plate is disposed facing the inlet side of the pit. Thus, the pattern can be stabilized. In addition, a baffle that shields the flow path is provided between the gun body and the air supply port on the side of the air cap. By using it in combination with the other shielding plate, pattern normalization and spray spots are more stable. Reduction can be achieved.

As described above, according to the present invention, the spray pattern shape can be stabilized and the dispersion of the paint particles during spraying can be made uniform by the stabilization of the central atomized air to reduce the spots. The distribution can be averaged over a large area. Therefore, as compared with the conventional case, even when the film thickness is thin, it is possible to obtain a smooth and uniform coating surface by suppressing variations in the coating surface. As a result, high-quality finish coating with a small film thickness is possible in resin coating using an expensive finish paint, and the effect of shortening the coating process and saving paint can be obtained.

In addition, the certainty of stabilizing the spray pattern is increased, and the coating quality can be stabilized, so that the result of improving the productivity can be obtained. In particular, the improvement and stabilization of the coating quality depends on the eyes of conventional workers, and stable painting with an automatic spray gun is possible even in the field of high-grade finish painting, which was difficult without the skill of skilled workers. Can have a great industrial effect

FIG. 1 is a sectional view showing the structure of a spray gun according to an embodiment of the present invention. Although this spray gun is a so-called automatic spray gun in which the spraying operation is automatically controlled by the action of working air, the atomizing device of the present invention is not limited to these types of operation. The spray gun body 1 is provided with an atomization device at the front, an operation and adjustment device at the rear, a paint supply port 2 at the center, and a compressed air introduction port for atomization (not shown). The atomizing device at the tip is mainly composed of a paint nozzle 3, an air cap 4, and a needle valve 5, and the air cap 4 is detachably attached to the gun body 1 by a cover 6.

In the atomizing device, as shown in an enlarged view in FIG. 2, the paint nozzle 3 is screwed into the gun body 1 by a rear screw 31, and the paint supply port 2 and the paint passage 32 at the center of the paint nozzle 3 are tightly connected at the rear end. Connected to. The tip of the paint nozzle 3 is provided with a spout 9 and the inner peripheral surface opens and closes as the tip of the needle valve 5 advances and retreats. In the example of this figure, the operation is controlled by the rear working piston 11. The operation amount is adjusted by an adjustment knob, and these structures have already been shown in many cases.

When the paint nozzle 3 is incorporated in the gun body, the central air chamber 13 formed on the gun body 1 side where the central air passage 12 is opened and the side air chamber 15 where the side air passage 14 is opened are partitioned by a sheet portion. The air from the outer side air chamber 15 goes around the outer periphery of the paint nozzle 3 and communicates with the side air side of the air cap 4, and the air in the inner central air chamber 13 passes through the coffin hole 33 provided in the paint nozzle 3. 4 is configured to communicate with the central air side. The dredging hole 33 is an air hole penetrating forward from the rear part of the coating material nozzle 3, and usually four or more holes are formed on the circumference.

Front and rear of the hole 33, that is, the inlet side and the outlet side, are provided with hook-shaped shielding plates 34 and 35 so as to block the passage shaft of the hole 33, respectively. In the example shown in the figure, the front shielding plate 35 on the outlet side is fitted from the front of the paint nozzle 3 for the convenience of processing. However, depending on the processing method and design dimensions, the front is integrated and the rear The shielding plate 34 may be fitted. Further, the outer peripheral side of the paint nozzle 3 forms a cylindrical outer wall portion 36, and a taper sheet that contacts the sheet portion 41 of the air cap at the tip portion so that the air from the central air chamber 13 is blocked from the side air side. 37 is provided. Further, a baffle 38 is provided to prevent the air jetted from the gap between the outer wall portion 36 and the gun body 1 from going straight and to send it to the air cap 4 side while being distributed and supplied to the outer periphery on average. Although the baffle 38 is shown to be fitted as a separate body in the figure, it may be integrally formed or may be provided on the air cap 4 side depending on the size and shape.

As known so far, the air cap 4 is formed with a central air port 42 formed in an annular gap so as to surround the outer periphery of the jet nozzle 33 of the paint nozzle 3 at the center, and the corners projecting on both sides thereof. A side air port 44 that is provided at 43 and injects the side air toward the spray flow at the center is provided. The number, size, direction, and the like of the side air ports 44 are selected according to the spraying conditions and are not limited directly. Further, the present invention can also be applied to the case where two pairs of corners are provided and the direction of the spray pattern is properly used by controlling the blown air.

As a feature characterizing the implementation of the present invention, an in-cap passage 45 leading to the front of the shielding plate 35 of the paint nozzle and the central air port 42 of the air cap is important. That is, the air flow around the outside of the shielding plate 35 is prevented from being directly directed to the central air port 42, and passes through a concentric annular air passage having a sufficient axial length after the shielding plate, The in-cap passage 45 is formed so that the air flows into the air port 42 in a convergent manner. Therefore, in the case of the present invention, the cylindrical portion 39 is formed in front of the shielding plate 35.

The air that has exited from the hole 33 provided in the paint nozzle collides with the shielding plate 35 and flows into the front passage through the gap between the outer periphery of the shielding plate 35 and the inner periphery of the passage. At this time, the gap between the hole 33 and the shielding plate 35 is the outer periphery. The necessary distance must be ensured to be uniform toward. If the amount is too small, the flow from the well will flow into the front passage without being partially uniformized. On the other hand, even when sufficiently separated, a part of the jet flow from the well hole flows into the passage in front through the gap as it is, and the uniformization is hindered. Therefore, the uniformizing means in the passage after exceeding the shielding plate 35 becomes important.

The configuration of the in-cap passage 45 allows the above-mentioned homogenization by providing an annular air passage having a sufficient volume. If jetting while converging as a contracted flow to the central air port as it is, uniform jetting becomes difficult. The same tendency also occurs when the inner passage 45 is short and the inner end is formed in the direction of decreasing the cross-sectional area at the front end. Therefore, if necessary, an annular groove 46 is formed at the inner end of the cap cap passage 45 of the air cap to temporarily stir the flow or to have a circumferential flow, thereby increasing the certainty of uniformity. It becomes possible.

It is sectional drawing of the spray gun which shows one Example of this invention. It is the detailed sectional view which expanded and displayed the atomization apparatus part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gun body 2 Paint supply port 3 Paint nozzle 4 Air cap 5 Needle valve 6 Cover 9 Spout 11 Piston 13 Central air chamber 15 Side air chamber 32 Paint passage 33 Bore hole 34, 35 Shield plate 36 Outer wall 37 Taper sheet 38 Baffle 39 Cylindrical part 41 Sheet part 42 Central air port 43 Corner 44 Side air port 45 Cap passage 46 Annular groove

Claims (4)

In an atomizing device consisting of a combination of an air cap and a paint nozzle that separates central air and side air supplied to the air cap of an air spray gun that atomizes with compressed air, the center of the air cap from the central air chamber of the gun body As a passage to be supplied to the air port, there are provided a plurality of potholes that are opened substantially parallel to the central axis of the paint nozzle. An air spray gun characterized in that a concentric annular passage having an axial length is provided in which a plate is provided and the air flowing around the outer peripheral portion of the shielding plate is made uniform even after the shielding plate. Atomization structure. The mist according to claim 1, wherein an annular groove is formed at a front end of the cylindrical passage, and an air flow that collides with the groove is ejected from a central air port of the air cap in a flow direction that converges at a central portion. Structure. 2. The atomizing device according to claim 1, wherein a shield-like shield plate is disposed facing the inlet side of the well hole, and an outer peripheral portion of the shield plate and an outer inner wall are formed as a concentric annular passage. 2. A baffle for shielding a flow path between a side air outflow portion of a gun body and a passage supplied to a side air port of an air cap and forming a uniform flow path toward an outer peripheral portion. 3. Atomization device.

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