JPH0824726A - Low pressure atomizing spray gun - Google Patents

Abstract

PURPOSE:To increase the gas-liquid contact area to promote the atomization of a coating material without changing the basic nozzle bore diameter and to improve the finish coating by forming the opening end of a coating material nozzle into a taper which broaden toward the outlet thereof. CONSTITUTION:A coating material nozzle 1 is arranged in the center of a body 2 of an air spray gun and at the tip of a needle valve 3. Incidentally, a coating material is introduced into the coating material nozzle 1 from behind, and a needle valve seat 10 which is an abutted part on a needle valve 3 is formed, and also a basic bore diameter part for determining the jetted quantity of the coating material in front thereof. In the basic bore diameter part, a parallel part is provided. Further, the opening end of the coating material nozzle 1 is formed into a taper which broadens toward the outlet thereof. The tip of the coating material nozzle 1 is arranged in a position projecting from the end surface of the central opening of an air cap 5. In this way, the gas-liquid contact area is increased to promote the atomization of the coating material to improve the finish coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerosol spray gun (2) for atomizing paint with compressed air and spraying it toward an object to be coated.
It relates to a low pressure atomizing spray gun when used at a low pressure of f / cm2 or less.

[0002]

2. Description of the Related Art An air spray gun that atomizes paint by compressed air usually sprays the paint from a circular nozzle,
The basic structure is that atomized by the compressed air flow from the central annular air hole of the air cap formed around the nozzle. Further, in order to form a spray pattern suitable for the coating conditions, various air holes for changing or adjusting the pattern shape are provided, and have a function of spraying the atomized paint particles.

These air spray guns usually have 2.5
The paint used at a spraying air pressure of ˜3.5 kgf / cm 2 is pumped by an air pressure of 0.5 to 3 kgf / cm 2 except the specially viscous paint, and jetted from the paint nozzle. The diameter of the paint nozzle is 0.
The diameter is 5 to 3.0 mm, and the diameter is selected according to the area of the sprayed amount of the paint, and this is a general size.

In order to atomize the paint in the air spray gun, basically, the air flow velocity by the central annular air hole of the air cap and the paint jet velocity from the paint nozzle largely depend on the relative velocity ( It depends largely on the air jet velocity-paint jet velocity. However, in the conventional air spray gun of this type, if the paint ejection speed is made small in order to achieve atomization, the paint ejection amount will be small and the workability of coating will be reduced, and it will not be put to practical use. . Therefore,
Atomization is promoted by increasing the air ejection speed (high air pressure).

[0005]

However, in this case, the traveling speed of the atomized paint becomes high, and the paint rebounds from the surface of the article to be coated (3) or the air for atomizing the material is exposed. The splashing of the coating material and the splashing of the coating particles reduce the coating efficiency, and the scattering of the coating material tends to deteriorate the working environment.

A low pressure atomizing spray gun is considered as a means for improving the spray particle scattering of paint, which is one of the major problems of the conventional air spray gun as described above, and is being put to practical use. As an example, a paint swirling means is provided in the paint passage between the paint nozzle ejection port and the needle valve seat, and the paint ejected from the paint nozzle is positively made into a thin film by centrifugal force, so that the air cap central annular air flow velocity and It is known to improve the relative velocity of gas and liquid and raise the atomization efficiency to lower the air supply pressure to about 1.5 kgf / cm2 / ∧.

However, in the air spray gun having such a structure, a component for imparting a centrifugal force to the paint is added between the paint nozzle ejection port and the needle valve seat, so that the paint flow path is complicated and the paint color is changed. The cleaning efficiency is reduced, and a large amount of paint remains between the paint nozzle ejection port and the needle valve seat, resulting in spits (coarse paint particles) at the beginning of blowing the air spray gun. In addition, as the outer diameter of the paint nozzle becomes larger, it becomes difficult to maintain the uniformity of the paint jet and the central air flow, and it becomes difficult to maintain the stability of the pattern shape at the same time. Absent.

From the above, the conventional general-purpose air spray gun is the easiest to use and has a good coating finish, but the problem of the spraying of coating spray particles is the most inferior, and improving it has a great effect. It will be. In the case of air spraying, the main cause of scattering of paint spray particles is high spray air pressure. INDUSTRIAL APPLICABILITY The present invention achieves the atomization of the paint to such an extent that it can be used for finish coating by the compressed air pressure of 1 kgf / cm2, preferably 0.7 kgf / cm2 or less in the air spray. The purpose is to obtain a low-pressure atomizing spray gun with less scattering without changing the basic diameter of the paint nozzle on page (4).

[0009]

To this end, according to the present invention, a needle valve disposed in an air spray gun body is attached to a center of a tip opening of the air spray gun body, and the needle valve is brought into contact with or separated from the tip of the needle valve. And a center hole that surrounds the paint nozzle, forms a circular air passage coaxially and in parallel with the paint nozzle exit cylinder outer circumference, around the paint nozzle, and the center. In a low pressure atomizing spray gun equipped with an atomizing head composed of an air cap having a pattern forming air hole forming a flat pattern at a position diagonally forward of the hole, a basic caliber portion is provided inside the paint nozzle. And a parallel portion is further provided to the basic diameter portion, and a tapered shape is formed so as to extend toward the outlet opening end of the coating nozzle continuously to the parallel portion. The tip of the nozzle is configured as a position protruding from the center hole open end face of the air cap.

The coating nozzle has a basic bore C formed therein in the range of 0.5 mmφ to 3.0 mmφ, and the basic bore parallel portion length D is at least 0.6 mm or more and is formed at the inner diameter of the tip opening. The divergent taper angle α is 2
The outer diameter A of the tip of the paint nozzle is in the range of 0 ° to 60 °.
Is a paint nozzle in the range of 2.0 mmφ to 5.5 mmφ.

The tip end opening end surface of the paint nozzle projects at least 0.3 mm or more from the air cap center hole opening end surface, and the total area of all air ejection holes of the air cap is 35 to 45 mm 2, and the air cap at the time of spraying. Is characterized in that the internal pressure is 1 kgf / cm2 or less, and the structure of such a low pressure atomizing spray gun is used as a means for solving the above-mentioned conventional problems. Page (5)

[0012]

According to the above-mentioned constitutional means, the paint sprayed from the paint nozzle with a paint pressurization pressure sufficient for spraying has a taper shape in which the open end of the paint nozzle widens toward the outlet. Therefore, a much larger passage area (1.
2 to 4 times), it is easy to disperse, and the contact area with the surrounding compressed air is large, and mixing is sufficiently performed even under low pressure conditions, and fine atomization is achieved by improving atomization efficiency. It will be possible. That is, the atomization improving efficiency can be obtained without changing the basic nozzle diameter.

Since the atomizing air is appropriately throttled in the middle of the process, the air pressure is lower and the air flow is weaker than in the case without throttling. That is, by making the cross-sectional area of the blowing air passage small at least in part and making the downstream flow passage and the opening area of the blowing air injection port relatively wide, the atomized air flow can be made into a low pressure and soft injection air flow. Therefore, a combination of this low pressure action and the divergent inner diameter tapered paint nozzle forms a low pressure atomizing spray gun with less scattering.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings of the embodiments. FIG. 1 shows a cross-sectional view of the atomizing device section. FIG. 2 shows a dimensional relationship diagram of the main parts of the respective parts of FIG. FIG. 3 shows a sectional view of the entire low pressure atomization spray gun.

A paint nozzle 1 is provided at the center of a main body 2 of the air spray gun and is provided at the tip of a needle valve 3. The paint nozzle 1 introduces paint from the rear side and contacts the needle valve 3 provided inside. A needle valve seat 10 that is a contact portion is formed, and a paint nozzle basic diameter φC that determines a paint ejection amount is formed in front of the needle valve seat 10. Similar to the paint nozzle diameter of a general-purpose spray gun defined by JIS, the basic diameter C is set to several types within the range of 0.5 pages (6) to 3.0 mmφ (in the example, 0.
8, 1.2, 1.4, 1.8, 2.5 mmφ), and the parallel length D of the paint nozzle basic diameter C is kept at least 0.6 mm or more in order to obtain a stable ejection amount. Has been done. The tip of the paint nozzle 1 is opened with a taper angle α ° diverging toward the central axis.

Further, the outer periphery of the tip of the paint nozzle 1 is formed with a central air hole 7 formed of an annular parallel slit with a central hole 6 of an air cap arranged on the outer side thereof. This air cap 5 is provided on the shaft of the paint nozzle 1 in addition to the central hole 6 and
At least one pair of crossing collision angular air holes 8 are provided in front of the paint ejection port, and a central air passage 9 to the central hole 6 and an angular air passage 9'to the angular air hole 8 are provided separately. The position of the valve body 4 provided on the main body 2 is determined by the pattern adjusting device 12 so that the angular air hole 8 is opened.
The pattern air supply amount to the pattern is variable. The central air passage 9 and the square air passage 9 ′ communicate with the atomizing air passage 14 inside the tip of the main body 2.

In the low pressure spray gun of this embodiment, the main body 2
The atomizing air passage 14 is provided with a throttle part in the middle thereof, and the square air hole 8 of the air cap 5 and the central hole 6 have a total sectional area of the compressed air passage of 35 to 44 mm2, which is larger than the spray gun (1.5 times or more). As a result, the high pressure compressed air pressure (generally 3.5kgf /
(around cm2) is 0.7 kgf / cm2 at the internal pressure of the air cap. The other mechanism of the air spray gun is the same as that of the known air spray gun, and the description thereof is omitted.

Next, the route of the coating material will be explained. First, the coating material is supplied to a portion of the coating material nozzle from a separately provided pressure feeding device (not shown), and a needle valve seat 10 provided in the coating material nozzle 1 is needled. The tip of the valve 3 contacts and separates to control the amount of paint sprayed. Page (7) The compressed air supply to the air cap 5 is controlled by the air valve 15. Like the general-purpose air spray gun, when the trigger 11 is operated to send the compressed air flow to the air cap 5, the needle valve 3 is separated (retracted) and the paint is ejected from the paint nozzle 1.

Since the opening end of the paint nozzle 1 is formed in a taper shape that widens toward the exit, the paint which is stably applied from the parallel part of the opening through the needle valve seat portion 10 is ejected from the opening end of the nozzle. At that time, the coating area is much larger (1.2 to 4 times), and the paint is easily dispersed, and the contact area with the surrounding compressed air is large, so that the gas and liquid are mixed sufficiently. In addition, the paint flow velocity at the paint nozzle outlet becomes slower by the area increase, the relative velocity generated with the air flow increases, the shear force received from the air flow increases, and the atomization of the paint is promoted.

Further, since the opening end of the paint nozzle 1 projects from the end face of the center hole 6 of the air cap 5 by "T" as shown in FIG. 2, the expansion air flow and the angle from the center air hole 7 of the air cap 5 are increased. Since the back pressure generated in the vicinity of the paint nozzle outlet due to the flat air flow from the air holes 8 is not affected, the balance of the paint pressurization pressure is stably maintained, and the stable supply of the paint ejection amount is obtained. In general-purpose pressure-feed air spray guns, it is common to position the paint nozzle opening outlet end on the negative surface within the range forming the air cap center hole (nozzle concave) in order to promote atomization. When the nozzle diameter is large, the back pressure action of the central air flow and the angular air flow on the tip of the nozzle is strong, so that the variation in the amount of paint sprayed is large.

Explaining the dimensional relationship relating to the paint nozzle 1 and the air cap 5 of the embodiment of the present invention, the paint nozzle basic diameter C = 0.5 to 3.0 mmφ and below, the paint nozzle outer diameter A is 2.0 to. 5.5mmφ, paint nozzle divergent taper outlet diameter B is 1.5 to 4.5mm Page (8) φ paint nozzle basic diameter length D is 0.6mm ≦, divergent taper outlet diameter α ° is 20 ° to 60 ° By doing so, the atomization effect was confirmed. In the above example, the case where the present invention is applied to the low pressure spray gun in which the operator directly grips and performs the coating work is described, but the present invention is also applied to a so-called automatic air spray gun used in an automatic system such as a coating robot. Of course you can.

[0022]

As described above, according to the present invention: 1) The coating nozzle has an opening end that is tapered toward the outlet so that the gas-liquid contact area is increased without changing the basic nozzle diameter. The atomization of paint can be improved by maintaining the atomization suitable for finish coating without increasing the air amount at a low air pressure of 1 kgf / cm2 or less, and the scattering of spray particles can be reduced. The coating efficiency can be improved and the environmental pollution can be reduced. 2) By making the projection of the paint nozzle project from the front surface of the air cap, the stability of the spray amount of the paint can be obtained and the film thickness of the finished surface of the paint can be stabilized. 3) A large amount of paint residue does not occur inside the paint nozzle from the sheet portion to the opening end, cleaning and handling maintenance are easy, and there is a cost advantage due to the component configuration similar to a general-purpose air spray gun.

[Brief description of drawings]

FIG. 1 is a sectional view of an atomizing head of an air spray gun showing an embodiment of the present invention.

FIG. 2 shows a main dimensional relationship diagram of each part in FIG.

FIG. 3 is an overall cross-sectional view of an embodiment of a low pressure atomizing spray gun of the present invention.

[Explanation of symbols]

 1 Paint Nozzle 2 Main Page (9) 3 Needle Valve 4 Valve Body 5 Air Cap 6 Center Hole 7 Center Air Hole 8 Square Air Hole 9 Center Air Passage 9'Square Air Passage 10 Needle Valve Seat 11 Trigger 12 Pattern Adjuster 13 Throttle part 14 Air passage for atomization 15 Air valve

Claims (3)

[Claims] 1. A paint nozzle having a needle valve disposed in an air spray gun body, a sheet attached to the center of a tip opening of the air spray gun body, and having a sheet that is brought into contact with and separated from the tip of the needle valve, and the paint nozzle. Around the outer circumference of the outlet cylinder of the paint nozzle, a central hole that forms an annular air passage coaxially and parallel to the outer circumference of the paint nozzle outlet cylinder, and a flat pattern are formed diagonally forward of the central hole. In a low-pressure atomization spray gun having an atomizing head composed of an air cap having a pattern forming air hole, a basic caliber is provided inside the paint nozzle, and a parallel part is further provided to the basic caliber. And a taper shape which is continuous with the parallel portion and widens toward the exit opening end of the paint nozzle, and the tip of the paint nozzle is the central hole opening of the air cap. A low pressure atomizing spray gun configured to project from the end face. 2. The paint nozzle has a basic bore C formed therein in the range of 0.5 mmφ to 3.0 mmφ, the basic bore parallel portion length D is at least 0.6 mm, and the tip opening inner diameter The divergent taper angle α formed in
The low pressure atomizing spray gun according to claim 1, wherein the range is 20 ° to 60 °, and the outer diameter A of the tip of the paint nozzle is in the range of 2.0 mmφ to 5.5 mmφ. 3. The tip opening end face of the paint nozzle is at least 0.3 mm from the end face of the air cap center hole opening.
The low pressure atomization according to claim 1, wherein the total area of all the air ejection holes of the air cap is 35 to 45 mm 2 and the internal pressure of the air cap during spraying is 1 kgf / cm 2 or less. Spray gun.