JPH08196950A - Low pressure fine pulverizing spray gun - Google Patents

Abstract

PURPOSE: To obtain a spray pattern high in fine pulverizing efficiency and uniform in particle distribution by boring a large number of air grooves in the leading end of a coating nozzles in a jet direction at an obtuse angle and forming a guide wall expanding in a conical shape in front of them to control coating jet streams in the jet direction. CONSTITUTION: A coating nozzle 1 is threaded with the barrel 20 of a spray gun main body by a coating nozzle screw 1f and, by the joining of a lower taper 1e, the cut-off of coating from a coating joint 8 and the division with air to a ring-shaped slit 4 and a corner part 2a are performed. An air cap 2 is mounted on the barrel 20 by an air cap cover 3 through a cover ring 7 so as to cover the coating nozzle 1. Herein, a large number of grooves 1a are bored in the leading end part of the coating nozzle 1 so as to provide an angle obtuse from the lower part surface of the ring-shaped slit 4 of the air cap 2 to a jet direction. Coating is ejected toward the center part of coating jet streams to be mixed with air to be dispersed and the fine pulverization of the coating is enhanced. In order to prevent the diffusion of coating, a conical guide wall 1b is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly applicable to a blowing air pressure of 1 k.
Mainly used for low pressure atomization spray gun of gf / cm2 or less, external mixing type air spray gun that mixes compressed air and paint outside the air cap. High atomization to improve atomization mechanism of atomization head. It concerns air spray guns.

[0002]

2. Description of the Related Art An external mixing type air spray gun is a coating machine which is defined in JIS of Japanese Industrial Standards and is widely used for general industrial coating. The external mixing type air spray gun has a standard spraying air pressure of 3, 0 to 3, 5 kgf / cm.
In 2, the compressed air is sprayed from the ring-shaped slit on the outer circumference of the paint nozzle, which is formed between the paint nozzle and the air cap, and the paint is atomized, and the paint is sprayed on the object to be coated to form a film. is there. This coating method has the widest application range regardless of the shape of the object to be coated, the type of coating material, and the like. However, this coating method has the drawback that there is a lot of fog scattering and there is a lot of paint loss due to overspray, and due to the work environment and air pollution, the tendency to set restrictions on the usage conditions of air spray spreads worldwide. There is. As one of the countermeasures, a low pressure spray gun which has a spray air pressure of 1 kgf / cm2 or less and suppresses the spray of mist to improve the coating efficiency has been highlighted.

There are several types of low-pressure spray guns in principle, and one of them is a spray pressure of 1
In order to compensate for the insufficient atomization of the paint due to being kept below atmospheric pressure, wide the slit width for air injection formed between the paint nozzle and the air cap, with a large amount of air,
A spray gun is used to atomize the paint. The mechanism of this low-pressure spray gun is basically the same as the mechanism of a general high-pressure spray gun, and widens the slit on the outer periphery of the paint nozzle to inject a large amount of low-pressure air. In addition, few paint nozzles and air caps have undergone special processing.The paint nozzle is a simple cylindrical cutting shape, and the ring-shaped slit width between the air cap and paint nozzle is several times the slit width of the high pressure spray gun. Has become. However, insufficient atomization of the paint by reducing the spray air pressure has some problems that cannot be solved only by increasing the air volume. One of them is that when the amount of paint spray is increased, the sprayed coarse particles of the paint remain in the center of the spray pattern, resulting in an uneven surface called Yuzu skin on the painted surface. In that case, the same phenomenon is likely to occur, and further, when the width of the elliptical spray pattern is adjusted, coarse paint particles tend to fly around the outer periphery of the pattern.

[0004]

As described above,
The present invention, in the low-pressure atomization mechanism of the external mixing type air spray gun, in order to solve the occurrence of partial coarse particles and non-uniformity of atomization due to the low-pressure air flow during paint atomization,
Effectively mixing low-pressure air jetted from a ring-shaped slit on the outer circumference of the paint nozzle formed between the tip of the paint nozzle and the center opening of the air cap with the paint flow ejected from the paint nozzle, thereby making the paint in the center part Atomization mechanism of external mixing type air spray gun to obtain uniform elliptical pattern of atomization, which is not affected by side air flow from the corner of air cap, for uniform atomization and flattening pattern This is the purpose.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a paint nozzle is screwed to an air spray gun body, joined by a taper so as to cover the paint nozzle, and attached to the spray gun body with an air cap cover. With an external mixing type air spray gun that mixes compressed air and paint in the atmosphere immediately after the paint is sprayed to atomize the paint, etc., a large number of airs directed toward the center of the paint nozzle jet at the tip of the paint nozzle. In order to prevent the paint from diffusing in the air grooves, the paint nozzle is provided with a guide wall at the tip of the plurality of air grooves in order to prevent the paint from diffusing in the air grooves. A low-pressure atomizing spray gun installed, and when a plurality of air grooves directed toward the center of the paint nozzle ejection port are formed at the tip of the paint nozzle at an appropriate angle in the injection direction, The angle is 60 ° or more At a square angle, the number of air grooves is 3, 4, or 6 on the outer circumference of the paint nozzle ejection port, and the paint dispersed in a large number of air grooves is diffused. In order to suppress it, a guide wall is provided at the tip of the plurality of air grooves, and the guide wall is a low pressure atomizing spray gun which is an opening surface formed in a conical concave shape.

[0006]

In general, the atomization of the paint in the external mixing type air spray gun is to atomize the paint by the jetting force of the compressed air from the ring-shaped slit on the outer periphery of the tip of the paint nozzle. 3,5kgf / cm2
In the high pressure air spray gun of, the jet is jetted at a speed close to the speed of sound, so the jetted flow is completely turbulent, and the mixture of paint and air is completely mixed by this turbulent flow and atomized. To be done. A low-pressure spray gun with a blowing air pressure of 1 kgf / cm2 or less has a low Reynolds number, does not become a complete turbulent flow, and has a flow close to a laminar flow. As a result, atomization becomes very bad, and in order to compensate for this, the width of the ring-shaped slit from the outer circumference of the paint nozzle is widened to increase the amount of jet air. However, when the amount of paint jetted from the paint nozzle is large, the central portion of the paint jet is poorly mixed with the air flow, and complete mixing cannot be obtained. Therefore, the atomization of the paint becomes insufficient, resulting in non-uniform atomization.

Therefore, a large number of air grooves are provided at the tip of the paint nozzle toward the center of the paint jet flow, and the air flow from the plurality of grooves causes the air flow to reach the center of the paint jet flow. By mixing, the homogenization of atomization is achieved. The paint flow that is dispersed and diffused in a large number of air grooves is controlled in the jet direction by a guide wall provided immediately after the large number of air grooves so as not to spread more than necessary.

The effect of the guide wall can be obtained even if the guide wall extends in a cylindrical shape as it is from the paint nozzle ejection port. However, various experimental results have shown that the guide wall is made into a conical concave shape to form fine particles. It has been discovered that the effect is further enhanced. Further, the air groove toward the paint jet is a groove having an obtuse angle of 60 ° or more toward the jet direction, and has a guide length to serve as a guide path for directing the paint jet to the center. is there. This allows
Even when the amount of paint jetted is relatively large, the air jet is mixed up to the center of the paint. Further, the guide wall prevents the particles from being diffused more than necessary, and the relatively thick air flow of the ring-shaped slit from the outer circumference of the paint nozzle atomizes the particles completely and uniformly, and the atomization effect equivalent to that of the high pressure air spray is obtained. At the same time, the atomization mechanism of the low-pressure air spray, which was only dependent on the increase of the central air flow, has the effect of improving atomization efficiency and reducing the air consumption by adding this mechanism. is there.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the overall structure of a low pressure atomizing spray gun. The spray gun body 10 has a barrel 2
The structure is such that it has 0 and a grip 30, an air nipple 31 is attached to the lower part of the grip 30, and compressed air is sent to the tip of the spray gun through the air valve chamber 16 above the air passage 32. The air valve portion has an air valve seat, an air valve 15, and a packing set 19 in an air valve chamber 16, and the coil spring 17 presses the air valve 15 against the valve seat of the air valve chamber 16 to form a seat. 18 is a blind screw for setting these. The valve rod of the air valve 15 extends to the trigger 13, and the air valve 15 is opened a few mm earlier than the needle valve 5 is pulled by the needle valve guide 5a. Compressed air is sent to. A needle valve guide 5a for vertically pulling the needle valve 5 and a needle valve guide 5 for pulling the needle valve 5 vertically on the rear extension of the center of the paint nozzle 1 screwed to the tip of the barrel 20.
A guide chamber 23 for guiding a is provided.
The compressed air is sent through the outer circumference of the guide chamber 23. The needle valve 5 is pressed against the inner surface of the sheet at the paint nozzle ejection port by the coil spring 22 behind the needle valve guide 5a to seal the paint. The coil spring 22 is pressed by the paint ejection amount adjusting knob 21. The paint ejection amount adjusting knob 21 has a guide rod located behind the needle valve guide 5a when the screw is rotated.
When the needle valve 5 is brought into contact with the needle valve 5, the amount of paint sprayed is adjusted by the pulling margin of the needle valve 5, that is, the opening of the gap between the paint nozzle spray port seat and the needle valve 5.

A pattern opening adjusting device for branching the compressed air into the central portion and the corner portion of the air cap 2 and adjusting the air amount to the corner portion is provided on the paint ejection amount adjusting portion of the barrel 20. It is provided. The pattern opening adjusting device is screwed to the pattern opening adjusting guide 26 together with the pattern opening adjusting valve 27 and the pattern opening adjusting knob 25. By rotating the pattern opening adjustment knob 25,
Depending on the opening degree of the gap between the pattern opening control valve 27 and the valve seat portion 28 provided in the air passage, the air cap cover 3 causes the side air holes at the corners of the air cap 2 screwed to the barrel 20 to reach the side air holes. The amount of air is adjusted, and the opening of the spray pattern that spreads in a fan shape is adjusted. The compressed air from the air passage 32 is opened parallel to the side of the air passage of the seat portion 28 of the pattern opening control valve 27 (not shown).
Therefore, the air passage is branched at the seat portion 28 into air for the central portion and air for the corner portions of the air cap 2. The air to the center of the air cap 2 has no adjusting part,
The air pressure from the air passage 32 is the same as the air cap 2
It is supposed to be sent to the center of.

In the above structure, the trigger 13 is pulled like a pendulum around the trigger fulcrum 14, so that the air valve 15 is pulled, and then the needle valve 5 is pulled. On the other hand, the paint is supplied to the paint nozzle 1 from a paint container attached to the paint joint 8 or a paint hose (not shown). As for the paint, the needle packing 11 for sealing the paint leakage from the seat portion of the paint nozzle ejection port and the needle valve 5 portion behind the paint nozzle is pressed by the packing adjusting screw 12. The packing adjusting screw 12 is adjusted to an appropriate strength and screwed in order to prevent paint leakage and to operate the needle valve 5 smoothly.

FIG. 2 is an enlarged sectional view of the tip portion of the low pressure spray gun of the present invention. The same reference numerals are given to the components explained in FIG. 1 for explanation. In the figure, a paint nozzle 1 is screwed to a barrel 20 of a spray gun body 10 by a paint nozzle screw 1f, and a lower taper 1e is joined to cut off the paint from a paint joint 8 and to a ring-shaped slit 4 and a corner 2a. It is divided from the air. An air cap 2 is attached to the barrel 20 by an air cap cover 3 via a cover ring 7 so as to cover the paint nozzle 1. By the upper surface taper 1d, the central air and the air to the corners are divided by the taper as in the lower taper. The interior of the paint nozzle 1 is pressed against the inner surface of the paint nozzle by the taper of the tip of the needle valve 5 to form a sheet.

The low-pressure compressed air branched in the barrel 20 and sent through the air passage 9 is symmetrically opened via the collar 6 and the side air passages 2b of the corners 2a of the air cap 2. It is opened to form an elliptical spray pattern by jetting from the side air holes 2c. One or a plurality of side air holes 2C that are opened symmetrically are opened. Then, the fan-shaped opening of the spray pattern is adjusted by adjusting the amount of air injected from the side air holes 2c by the pattern opening adjusting device. The other air branched in the barrel 20 has an air passage 32a.
Further, it is sent to the central portion of the air cap 2 through the central air hole 1c provided in the paint nozzle 1. At the center of the air cap 2, the outer periphery of the tip of the paint nozzle 1 and the air cap 2
The auxiliary air hole 2d is opened so as to intersect with the ring-shaped slit 4 formed between the center slit and the injection extension line of the side air hole 2C. The auxiliary air holes 2d are opened in order to balance the ejection force from the side air holes 2c in forming the spray pattern, and one or more auxiliary air holes 2d are opened.

The main constituent of the paint atomization is the compressed air injected from the ring-shaped slit 4 formed between the outer periphery of the tip of the paint nozzle 1 and the center opening of the air cap 2.
This is a so-called external mixing type atomization in which the paint ejected from the paint nozzle ejection port is mixed in the atmosphere to be atomized. This ring-shaped slit 4 is 3,0-3,5 kgf
In the case of a high pressure spray of / cm2, it is jetted in a complete turbulent flow from a gap of a fraction of that in the case of a low pressure spray. However, in the case of a low pressure spray having a spraying pressure of 1 kgf / cm 2 or less, the gap is wide and the air flow layer is thick, but the air is sprayed at a relatively slow speed. Therefore, in the case of a cylindrical paint nozzle shape,
The air is not completely mixed in the central portion of the paint flow ejected from the paint nozzle, resulting in non-uniform atomization. According to the present invention, a large number of grooves 1a are provided at the tip of the paint nozzle 1 from the lower surface of the ring-shaped slit 4 of the air cap 2 in the jet direction.
By piercing at an obtuse angle of more than ° and spraying toward the center of the paint jet, air is mixed to the center of the paint jet to disperse the paint and improve atomization. It is intended. In order to prevent the paint dispersed by the air grooves 1a from unnecessarily diffusing, a large number of the grooves 1a are formed.
A conical guide wall 1b is provided at the tip of the.

3 and 4 are enlarged views of the tip portion of the paint nozzle, FIG. 3 is a cross section of the tip portion of the paint nozzle, and FIG. 4 is a projection view from the ejection outlet side of FIG. At the tip of the paint nozzle 1, an air groove 1a is a V groove having an angle α, and the paint nozzle 1
It is drilled toward the center. The angle α is made to be an obtuse angle of 60 ° or more. Although not limited to the present invention, the shape of the air groove 1a is formed such that the V groove angle θ is 90 °. It is understood that the V-groove is used to uniformly intersect the air streams directed to the center of the paint stream from four directions. For example, it is understood that the same effect can be obtained even with a semicircular shape. This is where Further, although the number of the air grooves 1a to be bored is four in the figure, it has been experimentally confirmed that the same effect can be obtained with three or six air grooves. A conical guide wall 1b is provided at the tip of the air groove 1a at an angle β. The angle β of the guide wall 1b is determined from the shape extending in a cylindrical shape from the paint nozzle ejection port,
This is because the atomization effect is enhanced by being formed in the range of the shape in which the angle β spreads to 90 ° as shown in FIG. With the above configuration, the air is mixed to the center of the paint flow and the paint is dispersed. The paint particles that are dispersed and diffused are guided by the guide wall 1b.
The spray pattern is controlled in the advancing direction of the paint flow, and is uniformly atomized to the center of the paint flow by the flow of the relatively thick air flow layer on the outer periphery of the paint nozzle 1, resulting in a uniform particle distribution and a spray pattern with high atomization efficiency. can get.

[0016]

EFFECTS OF THE INVENTION A large number of air grooves are formed at the tip of a paint nozzle of an external mixing type low pressure spray gun at an obtuse angle of 60 ° or more in the injection direction, and a guide wall that spreads in a conical shape is provided at the tip thereof. , By controlling the paint spray flow in the spray direction, it effectively atomizes the paint flow of the low-pressure atomization spray gun to the center of the paint flow, resulting in high atomization efficiency and a spray pattern with a uniform particle distribution. .

Further, since the atomization efficiency becomes high, it is possible to obtain a low-pressure atomization spray gun which can obtain a proper spray pattern with a fine mist, without depending only on an increase in the amount of air used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an overall configuration as an example of a low-pressure atomization spray gun.

FIG. 2 is an enlarged cross-sectional view of the tip of the low pressure atomizing spray gun of the present invention.

FIG. 3 is an enlarged cross-sectional view of an essential part for explaining a paint nozzle tip portion of the present invention.

FIG. 4 is a projection view from the ejection outlet side of FIG.

[Explanation of symbols]

 1 Paint Nozzle 1a Air Groove 1b Guide Wall 2 Air Cap 2a Corner 2c Side Air Hole 2d Auxiliary Air Hole 4 Ring Slit 5 Needle Valve 10 Spray Gun Main Body 20 Barrel 30 Grip

Claims (3)

[Claims] 1. A paint nozzle is screwed onto an air spray gun body, and is joined by a taper so as to cover the paint nozzle,
An air cap attached to the spray gun body with an air cap cover mixes compressed air with paint in the atmosphere immediately after the paint is jetted, and atomizes the paint, etc. In order to prevent the paint from diffusing in the air grooves, a large number of air grooves directed toward the center of the nozzle outlet are formed at an appropriate angle in the injection direction to prevent the paint from diffusing. A low pressure atomization spray gun with a paint nozzle with a guide wall at the end of the groove. 2. When a large number of air grooves directed toward the center of the paint nozzle jet are formed at the tip of the paint nozzle at an appropriate angle in the jet direction, the appropriate angle is an obtuse angle of 60 ° or more. The low-pressure atomization spray gun according to claim 1, wherein the number of the air grooves is 3, 4, or 6 on the outer periphery of the paint nozzle ejection port at various angles. 3. A large number of air grooves directed toward the center of the paint nozzle ejection port are formed at the tip of the paint nozzle at appropriate angles in the ejection direction, and the paint dispersed in the air grooves diffuses. 2. The low pressure atomizing spray gun according to claim 1, wherein, when a guide wall is provided at the tip of the plurality of air grooves to prevent the occurrence of the above, the guide wall is an opening surface formed in a conical concave shape.