JPH0416258A - Electrostatic coating nozzle - Google Patents

Abstract

PURPOSE:To achieve an increase in a paint emitting amount and the enhancement of coating efficiency, while the fine pulverization of paint is accelerated and to prevent the adhesion of paint droplets to the front surface of a nozzle, by providing an annular jet orifice part, a finely pulverizing air blowoff orifice part and a pattern width-variable air blowoff orifice part. CONSTITUTION:Paint is injected in a thin film form from the annular gap of an annular jet orifice part 21, and a finely pulverizing air blowoff orifice part 24 is formed so as to surround the outer periphery of the annular jet orifice pat 21 and sprays compressed air to the injected paint to accelerate the fine pulverization of the paint. Further, pattern width-variable air blowoff orifice parts 29, 30 are respectively positioned outside the blowoff orifice part 24 to be provided on both side of the jet orifice part 21 to the diameter direction thereof, to spray compressed air onto the finely pulverized paint from both sides thereof to make the coating pattern of the paint ovally flat. As a result, the emitting amount of the paint can be increased while the fine pulverization of the paint is accelerated and coating efficiency can be enhanced, and the adhesion of paint droplets to the front surface of a nozzle can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electrostatic coating nozzle that can improve atomization with a large discharge amount.

(Prior Art) Generally, electrostatic coating nozzles can be roughly divided into two types: round nozzles and flat nozzles. As shown in Japanese Utility Model Publication No. 57-29893, for example, a round spray nozzle has an annular spray nozzle formed on the outer circumferential side of the nozzle, and sprays paint in an annular shape from this annular spray nozzle. By spraying compressed air onto the sprayed paint from air outlets around the outer periphery of the annular nozzle, the paint is atomized to form a nearly circular coating pattern.

On the other hand, as shown in Japanese Patent Publication No. 51-39906, for example, a flat spray nozzle has a small hole-shaped injection port formed in the center of the nozzle, and paint is sprayed forward from this small hole-shaped injection port. Compressed air is sprayed onto the sprayed paint from air outlets provided on both sides of the small hole-shaped injection opening, thereby flattening the coating pattern of the paint into an elliptical shape.

(Problems to be Solved by the Invention) The round spray nozzle described above can spray paint in the form of a thin film from the annular spray nozzle, so it is possible to spray a larger amount of paint than a flat spray nozzle. However, on the other hand, a relatively large negative pressure area is formed on the inner circumferential side of the annular injection port near the front of the round nozzle, which causes the paint to become atomized to some extent. In some cases, the paint became droplets and adhered to the front surface of the round nozzle, and the droplets dripped onto the object to be painted, staining the painted surface of the object.

On the other hand, hand-blown nozzles spray paint from a small nozzle formed in the center, so no negative pressure area is formed on the front of the nozzle, which has the advantage of avoiding the problem of paint droplets mentioned above. However, on the other hand, since the paint is sprayed intensively through the single fine hole that forms the small nozzle, the atomization performance of the paint is inferior to that of a round spray nozzle, and the amount of paint discharged is increased. The drawback was that it could not be done.

The present invention was made in consideration of these circumstances, and its purpose is to increase the amount of paint discharged while promoting atomization of the paint, thereby improving coating efficiency and improving the nozzle size. To provide an electrostatic coating nozzle capable of preventing paint drops from adhering to the front surface and improving the finished quality of a painted surface.

[Structure of the Invention] (Means for Solving the Problems) The electrostatic coating nozzle of the present invention comprises: an annular injection port that injects paint in the form of a thin film from an annular gap; an atomizing air outlet that is formed around the outer periphery of the part and that blows compressed air onto the sprayed paint to promote atomization of the paint; The annular injection port is equipped with air outlets for variable pattern width provided on both sides in the radial direction, and the compressed air blown from the air outlets for variable pattern width on both sides is applied to the atomized paint. The paint is sprayed from both sides to flatten the coating pattern into an ellipse.

(Function) During painting, the paint is sprayed in the form of a thin film from the annular injection nozzle, and compressed air is blown onto the sprayed paint from the atomization air outlet on the outer periphery of the annular nozzle. Promotes atomization of paint. In this case, the coating pattern becomes circular, which is the same as the conventional round spray nozzle, but according to the above configuration, the air is blown from the pattern width variable air outlet provided on both sides of the atomization air outlet. The compressed air is sprayed onto the atomized paint from both sides so as to flatten the paint pattern into an ellipse. As a result, the negative pressure area on the front of the nozzle is almost eliminated or becomes extremely small, suppressing the droplet formation effect due to negative pressure, preventing paint droplets from adhering to the front of the nozzle, and preventing paint from dripping. Eliminates the problem of surface stains. On the other hand, since the paint is sprayed in a thin film form from the annular injection port and is atomized by compressed air blown from the atomization air outlet,
It is possible to increase the amount of paint discharged while promoting atomization of the paint.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, the general structure of a spray gun of an electrostatic coating machine will be explained based on FIG. 3. A nozzle 2 is attached to the tip of a gun body 1. As shown in FIG. A needle valve 4 for opening and closing the paint flow path 3 is provided within the gun body 1. This needle valve 4 is attached to a bellows 5, and is biased by a spring 6 in a direction to open the paint flow path 3 (leftward in FIG. 3). A bushing rod 7 is provided coaxially with the needle valve 4 at the rear (left side in the figure).
When stopping painting, this bushing rod 7 can be slid forward (to the right in the figure).
The tip of the bellows 5 is pushed forward to close the paint flow path 3 with the needle valve 4.

The gun body 1 is also provided with a joint 8 for a paint hose (not shown), and the joint 8 and the valve chamber 9 of the needle valve 4 are communicated through a communication passage 1o.

Furthermore, two air passages 11 (only one is shown) are formed within the gun body 1.

Next, the configuration of the nozzle 2 will be explained based on FIGS. 1 and 2. This nozzle 2 has an outer shell attached to a body mounting nut 12.
The body mounting nut 12 is connected to the gun body 1.
It is tightened to the threaded part 13 of. A jet 15 and an air guide 16, which are integrated by a locking nut 14, are housed inside the body mounting nut 12, and the jet 15 is tightened to a cylindrical threaded portion 17 of the gun body 1. Two integrated paint guides 18 and 19 are screwed into the center of the jet 15, and the inner paint guide 1
8 and the center of the jet 15, a paint flow path 20 is formed which communicates in a straight line with the paint flow path 3 of the gun body 1. A fine gap is formed along the entire circumference of the front end outer periphery of both paint guides 18 and 19, and this annular gap serves as an annular injection port 21. This annular injection port 21 is inclined outward at an angle of about 45'', for example, and forms a thin film of paint from this annular injection port 21 and outwardly forms a truncated cone at an angle of about 45''. It starts to gush out. Further, a pressure chamber 22 is formed in the inner part of the annular injection port 21 so as to equalize the discharge pressure of the paint. It is now being supplied.

On the other hand, a fine gap is formed over the entire circumference between the outer periphery of the front end of the outer paint guide 19 and the air guide 16, and this annular gap is used as the atomization air outlet part 24,
This atomizing air outlet section 24 surrounds the outer periphery of the annular injection port section 21 . Unlike the annular injection port 21, the atomization air outlet 24 is oriented straight ahead, so that the compressed air injected from the atomization air outlet 24 is directed straight ahead. The paint is sprayed in a thin film form from the jet nozzle 21 at an angle of, for example, about 45@, so that the paint is atomized.

A pressure chamber 25 is formed in the back part of this atomization air outlet 24 so as to equalize the discharge pressure of the compressed air. It is supplied as shown.

Furthermore, a gap is formed over the entire circumference between the inside of the body mounting nut 12 and the locking nut 14, and this cylindrical gap is used as an air passage 27. Compressed air is supplied from the passage 11. Air passages 28 are also formed in the air guide 16 on both sides in the radial direction, parallel to the axis of the nozzle 2.
Air outlet portions 29 and 30 for variable pattern width having two diameters, large and small, are formed at the front end of the air conditioner 8 so as to be located at the front and rear. As a result, two sets of pattern width variable air outlet portions 2 are provided.
9 and 30 are located outside of the atomization air outlet section 24 and provided on both sides of the annular injection port section 21 in the radial direction.

Then, each set of pattern width variable air outlet portion 29.3
0 is inclined at an angle of, for example, about 600 degrees toward the axis of the nozzle 2, and the pattern width variable air outlet portion 29 located inside is formed to have a diameter approximately twice as large as that of the pattern width variable air outlet portion 29. The opening center of the air outlet section 29 for variable pattern width is located slightly forward of the position of the annular injection port section 21 . Each of these air outlet portions 29 and 30 for variable pattern width includes an air passage 1 of the gun body 1.
1, compressed air is sent through an air passage 27 in the body mounting nut 12 and an air passage 28 in the air guide 16. Air outlet part 29.30 for each of these variable pattern widths
The discharge pressure of compressed air is, for example, 1 to 2 kg/c-
On the other hand, the discharge pressure of compressed air from the atomization air outlet section 24 is set to, for example, 1.5 to 3 kg/c.
is set to . An O-ring 31 is attached to the circular edge 12a of the body mounting nut 12 to press against the outer peripheral surface of the air guide 16 to prevent air leakage.

Next, the operation of the above configuration will be explained. When painting,
The annular injection port 21 of the nozzle 2 makes the paint into a thin film and injects it outward in the form of a truncated cone at an angle of about 45 inches, for example, and atomization air is blown around the outer periphery of the annular injection port 21. From the outlet part 24, for example, 1.5 to 3 kg/
CD compressed air is blown onto the sprayed paint at an angle of, for example, around 45'' to promote atomization of the paint.For this reason,
Similar to the conventional round spray nozzle, it is possible to increase the amount of paint discharged while promoting atomization of the paint.

By the way, if the paint is only atomized by the compressed air blown out from the atomization air outlet section 24, the coating pattern will become circular and the same as that of a conventional round spray nozzle, but according to the above configuration, the atomization Compressed air of, for example, 1 to 2 kg/c is blown out from the pattern width variable air outlet sections 29 and 30 provided on both outsides of the pattern width variable air outlet section 24.
The coating pattern of the paint is flattened into an ellipse by spraying onto the atomized paint from both sides of the paint. As a result, the negative pressure area on the front surface of the nozzle 2 is almost eliminated or becomes extremely small, suppressing the formation of paint droplets due to negative pressure, and preventing paint droplets from adhering to the front surface of the nozzle 2. This eliminates the problem of stains on painted surfaces due to dripping. On the other hand, as described above, the paint is injected from the annular injection port 21 in the form of a thin film and is atomized by the compressed air blown from the atomization air outlet 24, so that the paint becomes fine. It is possible to increase the amount of paint discharged while promoting the coating process, thereby improving coating efficiency.

Further, in the above embodiment, pattern width variable air outlet sections 29 and 30 of two diameters, large and small, are formed at symmetrical positions on both outer sides of the atomization air outlet section 24, and are arranged in front and behind. Therefore, the aspect ratio of the painting pattern is increased (
This has the advantage that the pattern width can be made wider), coating efficiency can be further improved, and the negative pressure area on the front surface of the nozzle 2 can be more effectively eliminated. Such an effect has been confirmed by the inventor's experimental results.

Moreover, according to the experimental results, as in the above example,
By forming the diameter of the pattern width variable air outlet section 29 located on the inside to be larger than the diameter of the outer air outlet section 30, the coating pattern can be changed while increasing the flatness of the coating pattern (widening the pattern width). It can effectively prevent cracking (where the paint pattern becomes thinner or divided in the center) and reliably prevent uneven paint.

Note that the present invention is not limited to the above embodiments,
For example, the paint jetting angle of the annular jetting port 21 may be changed, or the air blowing angle of the atomizing air blowing port 24 or the pattern width variable air blowing port 29,30 may be changed.
Various modifications are possible.

[Effects of the Invention] As is clear from the above description, the present invention injects paint in the form of a thin film from an annular injection opening, and also includes an air outlet for atomization around the outer circumference of the annular injection opening. Compressed air is sprayed onto the sprayed paint from the part to promote atomization of the paint, and then the compressed air blown from the air outlet for variable pattern width is sprayed onto the atomized paint so as to sandwich it from both sides. Since the coating pattern of the paint is flattened in an elliptical shape, it is possible to increase the amount of paint discharged while promoting the atomization of the paint, improving the painting efficiency, and also making it possible to spread the paint on the front of the nozzle. It has the excellent effect of preventing droplets from adhering and improving the finish of the painted surface.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a longitudinal sectional side view of a nozzle portion, FIG. 2 is a front view thereof, and FIG. 3 is a longitudinal sectional side view of the tip side portion of a spray gun. In the drawing, 1 is the gun body, 2 is the nozzle, 11 is the air passage,
12 is a body mounting nut, 14 is a stop nut, 15 is a jet, 16 is an air guide, 18 and 19 are paint guides,
20 is a paint flow path, 21 is an annular injection port, 24 is an atomization air outlet, 26 to 28 are air passages, 29 and 3
0 is an air outlet for changing the pattern width. Applicant Asahi Okuma Sangyo Co., Ltd.

Claims (1)

[Claims] 1. An annular injection port that sprays paint in the form of a thin film from an annular gap, and a ring-shaped injection port that is formed so as to surround the outer periphery of the injection port, and compressed air is sprayed onto the sprayed paint to create fine particles of the paint. an atomizing air outlet section that promotes atomization; and an atomizing air outlet section located outside the atomizing air outlet section on both sides of the annular injection port section in the radial direction to inject the atomized paint from both sides. An electrostatic coating nozzle comprising a pattern width variable air outlet section which blows compressed air to flatten the coating pattern of the paint into an elliptical shape.