JPH04247252A - Low-pressure wide-angle pattern spray gun - Google Patents

Abstract

PURPOSE:To enable a spray coating at low pressure and at a short distance by a spray gun in which an annular air center hole around a coating nozzle and a side air hole for injecting the air to change of spray pattern on both sides of the hole by specifying the area of the side air hole are provided. CONSTITUTION:A coating nozzle 2 having an injection port 1 at its tip is freely detachably screw-joined to the tip of the main body 3 of a spray gun, and an air cap 5 is freely detachably mounted coaxially with the nozzle 2 to form an annular air hole 6 outside the injection port 1. The inside of the cap 5 is used as a center air passage 9 and communicated with the air passage 10 of the main body 3. Side air holes 14 and 15 for pattern adjustment are formed in a couple of horns 11 on both sides of the center air hole 6 to inject air against the center axis 16. The area of the side air holes 14 and 15 is controlled to >=2/3 of the total air hole area, hence a more divergent pattern is formed, and spraying at a short distance is facilitated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air spray gun that atomizes paint using compressed air and sprays the paint onto an object to be coated.

0002

[Prior Art] There are two types of air spray guns: one is to spray compressed air onto the sprayed paint and atomize it, and the other is to mix the paint and compressed air inside the spray gun and atomize it. It is being said. The former is widely used for general-purpose finishing coatings because it can produce finer atomized particles and the spray pattern can be variably adjusted than the latter.

This type of spray gun has a structure in which a central annular air hole is provided around a central paint spout to blow out compressed air to atomize the paint. In order to make it elliptical or oblong, side air holes are provided to direct the spray toward the center from both sides of the central air hole.

[0004] Generally used spray guns have a nozzle diameter of 3 mm or less and a standard spray air pressure of 3 to 3.5 k.
gf/cm2 Maximum paint ejection volume is 1l/min, maximum pattern opening is approximately 40cm (when spraying distance is 25cm)
It is. The amount of air ejected from the side air holes is usually around 50% of the total amount of air used, and ranges from 36 to 63%.

[0005]

[Problems to be Solved by the Invention] In these conventional spray guns, priority was given to atomization, so the amount of air coming from the center air hole was relatively large, and therefore the velocity component moving forward from the center was also large. Spraying at short distances has not been possible due to the high flight speed of the spray particles, which increases the number of blowbacks after collision with the painted surface, and the difficulty in enlarging the pattern. Therefore, there is a problem in that the flying distance of the paint particles becomes longer until the coating is applied, leading to an increase in the number of scattered particles.

[0006] The problem of short-distance spraying has become particularly important recently because it reduces scattering and improves coating efficiency, and it is also desired to reduce scattering by further reducing the blowing air pressure. . However, under low pressure conditions, it becomes more difficult to enlarge the pattern, and when working with small patterns, the density within the pattern becomes large, making it difficult to control the film thickness and intercoating, and the paint film may sag. There are also problems such as it being easy to do and causing a decrease in work efficiency. Under these circumstances, there has been a desire for a spray gun that can spray short distances with low spray air pressure and that can provide atomization similar to conventional spray guns.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems and enable low-pressure, short-distance spraying, the present invention sets the ventilation cross-sectional area of the side air holes to at least 2/3 of the total air hole area. By reducing the amount of air ejected from the central air hole, it is possible to spray at low pressure and over short distances. More preferably, there are two pairs of side air holes, and the intersection angle at the center is in the range of 110° to 150°, and they are assembled at substantially the same location.

[0008]

[Operation] With the above configuration, the paint ejected from the paint nozzle is atomized by the air jetted from the central air hole, and the atomization is further promoted by a large amount of compressed air from the side air holes, and a pattern is formed. and head towards the object to be coated. At this time, compared to the flow that is injected from the center and heads forward, the flow rate of the airflow that collides from the sides is more than double, so the forward flow velocity is significantly restricted, and the crushing force is strong, causing the spray particles to collapse. The rate of flattening is large, resulting in spraying in a wide, low-density pattern suitable for short distances.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing is a sectional view showing an atomizing device of an air spray gun showing an embodiment of the present invention. Many examples of spray gun structures are already known. Therefore, the operating section will be omitted, and the atomization device will be explained in detail here.

A paint nozzle 2 having a paint spout 1 at its tip
is removably screwed into the center of the tip of the main body 3 of the spray gun, only the tip of which is shown. The tip of a needle valve 4 that moves back and forth from the inside comes into contact with the spout 1, and the paint is stopped in this state. When the needle valve 4 retreats to the right, paint is ejected.

An air cap 5 is removably attached coaxially with the paint nozzle 2 so as to form an annular central air hole 6 outside the spout 1. In the embodiment, the tapered surface 7 of the paint nozzle 2 and the band-shaped spherical sheet 8 of the air cap 5 are set concentrically. This annular central air hole 6 has an outer diameter of 2.3 to 2.0 mm.
8mm, air cap center hole diameter 2.6~3.6
mm, and the clearance is 0.15 to 0.4 mm. In order to increase the efficiency of atomization, it is better to make the gap smaller and the diameter larger in order to increase the surface area, but since the precision of processing and combination affects the pattern shape, it is set within the possible range.

Inside the air cap 5 is a central air passage 9.
It communicates directly with the air passage 10 of the spray gun body 1. The outer side closed by the tapered surface 7 and the spherical sheet 8 communicates with a pattern adjustment air passage 12 formed in a pair of corners 11 protruding from the air cap 5, and is different from the air passage 10 in a pattern. They are configured to communicate via a control valve 13.

Side air holes 14 and 15 for pattern adjustment are formed in a pair of corners 11 formed on both sides of the central air hole 6 so as to face each other and emit air toward the central axis 16. In the case of the embodiment, two pairs of side air holes are formed, and the angles of the side air holes 14 and 15 are determined so that the respective injection axes intersect at one point of the central axis 16. These angles are in the crossing angle range of 110° to 150°, and two pairs provide better stability than one pair. The total opening area of these side air holes 14 and 15 is more than twice the opening area of the central air hole 6. Therefore, more than 2/3 of the total air hole area, that is, 66%
That's all.

[0014] Furthermore, no air holes that obstruct side air, ie, auxiliary air holes, are provided around the central air hole so that the air on the sides directly collides with the spray flow from the center and promotes atomization. Therefore, the atomization can be efficiently promoted by the side air as well. However, the stronger the influence of the side air holes, the more strongly only the central part acts on the center spray flow, and the pattern may lack stability. Therefore, two pairs of side air holes are provided as described above, and these They are provided at different angles so as to intersect with each other, and are formed so as to substantially merge in the middle of injection and collide with the spray stream.

[0015]

As described above, according to the present invention, the side air holes account for 67% or more of the total air hole area, that is, 2/3 or more, and the amount of air is more than twice that of the conventional method compared to the spray flow from the center. Since it is crushed from both sides, it is possible to form a pattern with a large spread. Therefore, a relatively large pattern, or in other words, a pattern with low density, can be formed with a short spraying distance, making it easier to perform spraying work at short distances. Spraying at a short distance can significantly reduce the scattering of spray particles, thereby increasing coating efficiency and reducing environmental pollution. In addition, the pattern can be expanded without increasing the pressure like in the past, and atomization can be promoted by side air, so the spraying work that was conventionally done at 3 to 3.5 kgf/cm2 is reduced to about 1/2. 1.8 kgf/cm2 is possible, and is highly effective in preventing scattering due to low-pressure spraying.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a tip atomizing device portion of a spray gun showing an embodiment of the present invention.

FIG. 2 shows a left side view of FIG. 1.

[Explanation of symbols]

5 Air cap 6 Center air hole 9 Central air passage 12 Pattern adjustment air passage 14 Side air hole 15 Side air hole

Claims (2)

[Claims] Claim 1: An annular central air hole is provided around a paint nozzle that opens at the center of the tip of the spray gun, and the paint is atomized, and air is ejected from both sides of the central hole to form and adjust the spray pattern. In the air spray gun, the air hole area of the side air holes provided on both sides is
Air spray gun with more than 2/3 of the total air hole area. [Claim 2] Two or more pairs of side air holes are provided on both sides, and there is no air flow that obstructs the flow direction of each jet flow.
The air spray gun according to claim 1, wherein the intersection angle of the centers of the jets is in the range of 110° to 150°.