JPS6326196Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an air spray gun for painting. In particular, the present invention relates to an air cap having a structure that prevents sprayed paint particles from adhering to the surface of the air cap.

The air cap of an air spray gun used for painting has a paint nozzle at the tip of the spray gun.
The paint nozzle has an ejection hole formed in its center. The air cap has a central hole surrounding the nozzle, and an annular central air hole is formed between the air cap and the outside of the nozzle. Furthermore, a pair of corner portions are provided at symmetrical positions on both sides of the center hole, and at least one pair of side air holes are provided in the corner portions so as to converge and intersect at one point on the paint injection axis. Further, around the center hole, air holes are provided as auxiliary air holes to flatten the spray flow from the center and air holes to flatten the jet flow from the side air holes. When compressed air is injected from each air hole and paint is injected from a nozzle, the paint is atomized, most of which heads toward the object to be painted in front.

However, conventionally, this type of air cap has a central hole and auxiliary air holes on a flat surface, and when air is injected from these air holes with force, the area around the air hole becomes negative pressure, which entrains nearby air. It turns out. At this time, since spray particles are generated immediately before these air holes, the spray particles are also drawn in, and the paint gradually adheres and accumulates on the plane of the air cap where the air holes are formed.

When these adhering paints reach a certain amount, they cause deformation and partial clogging of each air hole, making the shape of the spray pattern abnormal and causing paint film defects.
In addition, coarse particles of paint are blown onto the object to be coated, and these adhere to the painted surface and form stains, making the product defective.

Therefore, if paint buildup occurs on the air cap, it is necessary to stop work and clean or replace it. This not only unnecessarily lowers productivity, but also causes problems such as the hassle of cleaning, preparation of supplementary air caps, and constant monitoring.

The present invention forms the periphery of the central hole of the air cap with as few flat surfaces as possible and most of the conical surfaces,
The accompanying airflow generated when compressed air is injected is generated from the large diameter portion of the conical surface and is flown away forward, thereby preventing spray particles from adhering to the surface of the air cap.

Next, the structure of the present invention will be explained in detail with reference to the drawings based on a specific embodiment of the present invention. Figure 1 shows the tip of the air spray gun. A paint nozzle 1 and an air cap 2 are shown.

The tip of the paint nozzle 1 forms a tubular portion with a nozzle opening 3 at the center and a cylindrical surface 4 at the outside. The air cap 2 has a central hole 5 in the center so as to enclose this tubular portion, and a conical surface 7 is formed around the central hole 5 with a slight flat portion 6 remaining. This central hole 5 forms an annular central air hole 5A between it and the cylindrical surface 4 of the paint nozzle 1. air cap 2
A pair of corner portions 8 are formed at symmetrical positions on both sides of the center hole 5, and at least a pair of side air holes 9 are formed in both corner portions so as to intersect at a point on the axis of the paint spray flow. It is being By applying compressed air to the spray stream from this side air hole 9, the spray pattern is changed from a circular pattern to an oval pattern.

Further, in the conical surface 7, two auxiliary air holes 10 are opened at symmetrical positions on both sides of the center hole 5 to flatten the air jet from the side air holes 9 to stabilize the pattern. Furthermore, these auxiliary air holes 10
Another auxiliary air hole 11 is opened at symmetrical positions on both sides of the center hole 5 on a line orthogonal to the center hole 5 to flatten the spray flow and stabilize the pattern. This auxiliary air hole 11 is commonly called an end mill hole because it needs to be opened toward the central axis in order to direct the spray flow, and a notch 12 is formed in the conical surface for machining. The conical surface 7 widens from the center toward the rear of the air cap 2, and its rear edge 13 is formed at approximately the same position as the position closest to the center of the side air hole 9, or to the outside thereof. The angle of the conical surface 7 is approximately 130°, but it is desirable to make it more acute if possible.

Further, in the corner portion 8 of this embodiment, a flat surface with the smallest possible area is left only in the portion where the side air hole 9 opens, and the surrounding area is chamfered to prevent paint from adhering to this portion.

Figure 2 shows the air cap of a conventional spray gun, but without the conical surface of Figure 1, the center hole 15
An auxiliary air hole 17 is formed in a plane 16 parallel to the surface in which the auxiliary air hole 17 is formed.

In this case, the air around the center hole 15 becomes an accompanying air flow and is drawn by the air flow injected from the center hole 15, but since the area around the center hole 15 is flat, a vortex flow is generated on the plane, and the paint coming out from the nozzle hole is The spray particles entrain the air in the area in which they are present, causing coating to adhere to the flat surface, leading to undesirable results.

On the other hand, in the embodiment of the present invention shown in FIG. 1, the air drawn by the air stream injected from the center hole 5 becomes an air stream that flows along the conical surface 7, and the air that does not contain paint particles at the rear of the air cap is The air is sucked in one after another and travels to the object to be coated in front along with the jet air and spray particles. Therefore, air containing spray particles on the same plane as the center hole 5 of the air cap 2 is not drawn in, and the surface of the air cap is not contaminated by paint.

Moreover, since the conical surface 7 is formed to extend outward from the side air hole 9 closest to the center hole 5, the accompanying airflow caused by the injection from the side air hole 9 also comes from the rear, so paint does not adhere to the surface. decrease in width.

An example of enamel painting of a cylindrical object using a conventional air cap requires spraying the paint for about 20 seconds at a rate of 300 c.c./min. It had become so large that I was worried about the coarse particles scattering, so I had to clean it. When the air cap of this invention is used under exactly the same conditions
Even after applying 60 coats of paint, there was very little adhesion and it was still usable.

Figure 4 shows the state of adhesion after spraying the paint for 20 minutes. Since the paint is made of enamel, it adheres to the paint in large clumps, layered on top of it.

Due to this reduction in paint adhesion,
Not only does this eliminate the need for periodic cleaning and replacement of air caps, but especially in automatic painting, the automatic painting machine can be used for long periods of time without interruption, resulting in greater productivity than ever before.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the tip of the spray gun including the air cap of the present invention, and FIG. 2 is a front view of FIG. 1. Figure 3 is a cross-sectional view of a conventional air cap.
FIG. 4 is an external view showing the state of paint adhesion when a spray test was conducted using the air cap of the present invention and the conventional air cap. 2... Air cap, 5... Center hole, 7... Conical surface,
9...Side air hole, 10...Auxiliary air hole.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. An air cap for a spray gun that sprays paint using compressed air, which has a central hole at a position surrounding the tubular tip of the nozzle that sprays paint, and has a diameter equal to the outer diameter of the nozzle tip. An annular air hole is formed between the
Spray air is sprayed around the center hole and at least a pair of side air holes, which have a pair of corners symmetrically located on both sides of the center hole, and are drilled such that the corners converge and intersect at a point on the paint injection axis. In an air cap that has a plurality of auxiliary air holes to stabilize the shape, the center hole is surrounded by a conical surface, leaving as small a flat surface as possible, and the conical surface extends further outward than the side air holes. An air cap of a spray gun having an auxiliary air hole opening in the conical surface. 2. The air cap according to claim 1 of the utility model registration having a cone angle of 130 degrees. 3. The air cap according to claim 1, in which the flat portion around the center hole has a width of 0.5 mm or less.