JPH02280858A - Internally mixed spray gun - Google Patents

Abstract

PURPOSE:To enable a general spray coating by using low pressure atomization by installing an atomizing head, which is furnished with a conical inner face, a V-shaped groove, a lip-shaped opening, divergent taper, etc., at its center hole part, in a main body of spray gun. CONSTITUTION:Paint ejected from a nozzle 1, which is opened in a cap 8, is atomized from the center hole of the cap 8 after mixed and atomized by a compressed air stream flowing from a circumferential path. The inner face 3 of the center hole is formed into a cone or nearly same shape, the outer face 13 is also formed into a cone or nearly same shape, and a lip-shaped opening 11 is formed by engraving a nearly V-shaped groove 14 at the center part of the cap 8 which has nearly the same thickness. An atomizing performance with external mixing at 3 to 4kgf/cm<2> is attained by a spray with internal mixing at such a low pressure not higher than 1kgf/cm<2> that the spray with usual internal mixing is impossible. It is possible, as a result, to carry out a general spray coating by atomizing at a low pressure and to prevent an undesirable emission of paint fume etc.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an internal mixing spray gun that atomizes and sprays liquid such as paint using compressed air. This relates to a spray gun used as a spray gun.

<Prior Art> In general, many spray guns called so-called air spray guns are used for spraying paints and the like. Air spray guns that use compressed air as atomization means are broadly divided into internal mixing methods and external mixing methods, depending on the atomization means.

In this internal mixing method, the paint and compressed air are mixed inside the atomizing head of the spray gun, and the mixture is atomized from the spray nozzle.In the external mixing method, the paint and air jets are connected to the atomizing head, and the paint and air jets are connected to the outside. It is open to the outside, and disperses and atomizes the liquid paint stream ejected from the paint spout by the paint stream that is diffused and ejected around the paint stream.

These spray guns use the suction power of compressed air to spray paint, but the spray is forced by a supply device such as a pump at a pressure of several kJ' crn, and paint is not atomized by spraying it alone. In addition, air is used as energy to atomize the paint, and usually a pressure of 2 to 5 kgf/CrrI'' or around it is used.

For example, an internal mixing type spray gun as shown in FIGS. 2A and 2H has a structure in which a paint nozzle a opens into an air cap b, and a nozzle opening d is opened and closed by a needle valve C to control the spraying of paint. The paint is dispersed inside the air cap b by the compressed air sent around the nozzle port d, and the paint is dispersed outside through the spray port e that opens in the center of the air cap I facing the nozzle port d. is sprayed on.

The spray nozzle e is generally circular, but depending on the spray conditions, an oval or rectangular opening is often used. Since the particle size of this type of spray gun is coarser than that of the external mixing type, it is used as a special spray gun for building wall paints and adhesives where the smoothness of the painted surface is not required.

On the other hand, the external mixing type is generally used as a so-called spray gun, and there are already known ones that are compatible with various paints and coating conditions. What these spray guns have in common are:
There is a paint nozzle 1 in the center, which faces the outside of the atomizing head. An annular air hole is provided around the ejection port, and compressed air is ejected so as to surround the paint stream ejected from the ejection port. That is.

Paint and compressed air are ejected separately and mixed and atomized in front of the atomizing head.Normally, most spray guns of this type have a pair of spray guns on both sides for the atomized paint. Side air holes are provided, and compressed air is sprayed from both sides of the spray stream to adjust the shape of the spray pattern.

In other words, the flattening of the spray stream sprayed in a circular pattern at the center can be adjusted by changing the jet pressure or jet amount of the side air holes. Moreover, since mixing is performed externally, the particles can be made finer as the amount (pressure) of compressed air is increased.

<Problem to be solved by the invention> However, since conventional spray guns use air to atomize, there is a problem of paint scattering, which has unfavorable results in terms of coating efficiency, environmental hygiene, etc. It is occurring. In particular, this tendency becomes more pronounced as the air blowing pressure is increased, so blowing at a low pressure is desired. However, when considering the finish of the painted surface, it is important to make the atomized particles finer, and for this purpose it is necessary to make the paint finer using high-pressure air, which are contradictory phenomena. In most cases, efficiency and environmental health are sacrificed.

However, effective use of resources and conservation of the environment are becoming more and more important in the future, and spray guns with low-pressure atomization are becoming necessary.

Since the method of atomizing paint etc. is not limited to air only, 1.
For example, a method in which high-pressure paint is injected into the atmosphere from a nozzle and atomized by collision with the atmosphere has become common. However, the industrial spray gun in this case is 100 kg/
It requires a high paint pressure called "crn" and uses a special pump.

Moreover, there are problems such as being dangerous. For this reason, spray guns that use compressed air have been used instead, reducing the paint pressure to several tens of kg/crn', but the above problems still remain and the air pressure is not low enough. This is the current situation, and a satisfactory spray gun has not been obtained.

In order to realize such a spray gun, the present invention sets the spray pressure to a low pressure of 1 kg/crn'' or less, and makes the spray particles equivalent to those of conventional spray guns.

The object is to provide an internal mixing spray gun that does not impair the finish.

Means for Solving the Problems> The present invention provides an internal mixing spray gun that mixes and sprays the paint spouted from a nozzle opening in the cap with a stream of compressed air from the surroundings, and then sprays the paint outward from the center hole of the cap. In this case, the inner surface of the center hole has a conical or similar shape, the outer surface has a conical or similar shape, and a substantially V-shaped groove is provided from the outside of the center of the cap having a substantially coaxial wall thickness. It has an almost lip-shaped opening.

It is also an internal mixing spray gun with a lip-shaped cap opening, and the internal paint nozzle opening is tapered to widen toward the end, so that air is mixed in from the outer surface of the tip.

Due to the above structure, the paint ejected from the nozzle is mixed and dispersed by the compressed air sent from the surrounding area and heads towards the spray nozzle, where it forms a flat pattern rather than the flat opening. However, since the inner and outer surfaces of the opening have almost the same shape and a uniform thin wall thickness, the dispersed paint particles are dispersed by the edge effect, and the surrounding air is shaped like a cone by the mixed air flow. It will be absorbed along the outer surface, further promoting paint dispersion at the edge of the opening. Therefore, sufficient atomization can be achieved even at a low pressure of 1 kg'/crn' or less.

In addition, since the opening end of the nozzle is tapered to widen at the end, the paint ejected from the sheet section has a much larger passage area when it is ejected from the nozzle opening end, making it easier to disperse and spread around the surrounding area. The contact area with the compressed air becomes extremely large, allowing sufficient mixing and fine atomization. As a result, this atomized paint is sprayed from the spray port of the cap, but by making the outer diameter of the nozzle slightly larger than the diameter of the passage leading to the spray port, the mixed air flow of the sprayed paint is maximized. This will increase the atomization effect. In other words, if it is smaller than the passage diameter, it will be atomized without sufficient mixing contact with compressed air, and if it is too large, recombination will occur in the passage, and the effect of internal mixing and atomization will be lost. .

<Example> The present invention will be described below based on the drawings of the example.

FIG. 1 is a cross-sectional view showing the atomizing heads, which are the main parts. These atomizing heads are attached to a known spray gun, and paint and air are fed through their respective passages. l is the paint nozzle,
It is made of relatively hard steel, but recently, as water-based paints are often used, opaque steel is often used.A paint passage 2 is formed inside the center of this paint nozzle 1, and a paint passage 2 is formed at the tip. A spout 3 is provided. A sheet 4 is provided inside the spout 3, and a needle valve 5 in contact with the sheet 4 controls the spouting of paint. A passage 7 is formed on the outside of the paint nozzle 1, which communicates with an air passage 6 when attached to the spray gun body 1O. The paint nozzle 1 protruding from the front end of the spray gun body 10 is covered with an air cap 8 and is used while being fixedly integrated with the spray gun body 10 by a cover 9.

Inside this air cap 8 is a paint nozzle l as described above.
is accommodated, and a spray nozzle 1 is located at the center tip facing the nozzle 3.
The spray nozzle 11 has a cylindrical inner surface 12 followed by a conical inner surface 13, and a V-shaped groove 14 is cut from the outside at the center of the nozzle 11 to form an approximately lip-shaped opening. The six-conical inner surface 13 may be, for example, bullet-shaped or spherical, and the ■-shaped groove 14 may be trapezoidal or the like.

Here, the compressed air introduced through the passage 7 is transferred to the inner surface 15 of the cap and the spout 3 of the paint nozzle l.
It flows into the center through the gap between the outer diameter of the spray nozzle 3, mixes with the paint sprayed at the tip of the spray nozzle 3, and is dispersed in a mist.
It is sprayed from 1. Since the spray port 11 has a lip-shaped opening as described above, the spray pattern is approximately oval.

In this case, since the outer surface of the air cap 8 is formed of a conical outer surface 18 similar to the conical inner surface 13, the surrounding air is easily sucked along the outer surface 16 by the spray flow, and the surrounding air is drawn to the open end. It will flow in.

Further, since the opening has substantially the same pressure portions sandwiched between the inner and outer conical surfaces around the entire circumference, uniform distribution is achieved as a whole. In order to enhance this effect, it is possible to form it thinly, and in the example, it is about 0.6 tall. This wall thickness is preferably 1 mm or less, and the thinner the thinner the better,
Wall thickness is determined based on strength and durability.

In addition, in the embodiment, a side air hole 17 is provided which communicates with the air passage 7', similar to other external mixing spray guns.
The spray pattern can be adjusted.

<Effects of the Invention> As described above, the internal mixing spray gun of the present invention has a conical inner surface, a V
This is because the structure has a groove, a lip-like opening, a tapered end, etc.

By spraying at a low pressure of 1 kg/cm' or less, which was impossible with conventional internal mixing, 3 to 4 kg can be achieved with external mixing!
/ am' spray performance can be achieved.

This makes it possible to perform general spray painting using low-pressure atomization, which can be highly effective in solving social problems such as undesirable scattering of paint and environmental destruction.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main part of the present invention, and FIGS. 2A and 2B are a sectional view and an enlarged sectional view of the main part of a conventional spray gun. 109. Paint nozzle 209. Paint passage 300. spout 410. Seat 500. Needle valve 7016 passage 803. Air cap 10, Spray gun body 11, Spray nozzle 12, Cylindrical inner surface 13, Conical inner surface 14, V-shaped groove 17, Air hole

Claims (1)

[Claims] 1. In an internal mixing spray gun in which the paint sprayed from a nozzle opening in the cap is mixed with a compressed air flow from the surrounding area and then sprayed outward from the center hole of the cap, The inner surface has a conical or similar shape,
An internal mixing spray characterized in that the outer surface is also conical or similar in shape, and a substantially V-shaped groove is provided from the outside in the center of the cap with a substantially coaxial wall thickness to form a substantially lip-shaped opening. gun. 2. In an internal mixing spray gun that mixes and sprays the paint ejected from a nozzle opening in the cap with a stream of compressed air from the surrounding area, then sprays the paint outward from the center hole of the cap, the cap opening is formed into a lip shape. An internal mixing spray gun characterized in that the internal paint nozzle opening is tapered to widen toward the end, and air is mixed from the outer surface of the tip.