JP3357189B2 - Low pressure atomizing spray gun - Google Patents

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 for atomizing a paint by compressed air and spraying the paint toward an object to be coated.
The present invention relates to a low-pressure atomizing spray gun when used at a low pressure of less than kilopascal.

[0002]

2. Description of the Related Art An air spray gun for atomizing paint by compressed air usually sprays paint from a circular nozzle.
The basic structure is such that the air is atomized by a compressed air flow from a central annular air hole of an 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.

[0003] These air spray guns are usually 250
It is used at a spray air pressure of ~ 350 kPa and the paint is 50 ~ 300 kPa except for high viscosity paint.
And is sprayed from the paint nozzle. According to JIS, the diameter of the paint nozzle is 0.5 to 3.0 mmφ, and the diameter is selected according to the paint ejection area and is a general size.

[0004] The atomization of paint in the above-mentioned air spray gun basically depends greatly on the air flow velocity through the center annular air hole of the air cap and the paint jet velocity from the paint nozzle, and its relative velocity (air jet velocity). -Paint jet velocity). However, in this type of conventional air spray gun, if the spraying speed of the paint is reduced in order to achieve finer particles, the spraying amount of the paint is reduced, and the workability of the coating is reduced, which is not practical. . Therefore, atomization is promoted by increasing the air ejection speed (increase air pressure).

[0005]

However, in this case, the running speed of the atomized paint increases, and the paint rebounds from the surface of the object to be coated, or the air for atomizing the surface of the object to be coated is hit. The coating efficiency is lowered due to the rebound and the repelling of the paint particles, and the work environment is liable to be deteriorated due to the scattering of the paint.

A low-pressure atomizing spray gun has been considered as a means for improving the scattering of the spray particles of the paint, which is one of the major problems of the conventional air spray gun as described above, and its practical use is progressing. As an example, a paint swirling means is provided between the paint passage between the paint nozzle ejection port and the needle valve seat, and the paint ejected from the paint nozzle is positively thinned by centrifugal force, so that the air cap center annular air flow rate and A structure is known in which the relative pressure of the gas and liquid is increased to increase the atomization efficiency, thereby reducing the blowing air pressure to about 150 kPa .

However, in the air spray gun having such a structure, a part for imparting the centrifugal force of the paint is added between the paint nozzle outlet and the needle valve seat. The washing efficiency is reduced, and a large amount of paint remains between the paint nozzle ejection port and the needle valve sheet, and spits (coarse paint particles) are generated at the beginning of blowing the air spray gun. Also, as the outer diameter of the paint nozzle increases, it becomes difficult to maintain the uniformity of the paint jet and the center air flow, and it is also difficult to maintain the stability of the pattern shape at the same time, resulting in a costly air spray gun. Absent.

As described above, the conventional general-purpose air spray gun is the device which can be used most easily and has good coating finish. However, the problem of the scattering of the coating spray particles is the least inferior. Will be. The largest cause of the dispersion of paint spray particles in the case of air spray is the high spray air pressure. The present invention relates to the use of 100 kPa, preferably 70 kPa in air spray.
The following compressed air pressure Cal, achieved to the extent that can be used to finish painting atomization of the paint, based on a conventional general-purpose air spray gun near facile construction, without changing the basic diameter of the paint nozzle, scattering It is an object of the invention to obtain a low-pressure atomizing spray gun.

[0009]

Means for Solving the Problems] Therefore, in the present invention, a needle valve disposed in an air spray gun body, attached to the distal end opening center of the air spray gun body, and the tip abutment of the needle valve It has a sheet that separates and has a paint nozzle that introduces the liquid paint, surrounds the paint nozzle, and surrounds the periphery of the paint nozzle outlet cylinder around the paint nozzle outlet cylinder outer periphery, coaxially and parallel to the annular air. In a low-pressure atomizing spray gun having an atomizing head including a center hole constituting a passage and an air cap having a pattern forming air hole forming a flat pattern at a position obliquely forward of the center hole, Liquid paint is introduced into the paint nozzle, and has a basic diameter having a parallel portion.
The liquid paint is formed by forming a portion to maintain a stable ejection of the liquid paint, and forming a tapered shape diverging toward the outlet opening end of the paint nozzle continuously to the parallel portion .
It is easy to spread and has a large increase in the distribution cross section.
The area of contact with the compressed air ejected from the surrounding area
Promotes the effect of atomization. Further, by forming the tip of the paint nozzle so as to protrude from the end face of the opening of the center hole of the air cap, compressed air spouting from the surroundings is formed.
Instability of paint ejection caused by back pressure
Can be avoided.

In the paint nozzle, the length D of the parallel portion of the basic diameter formed inside is at least 0.6 mm,
Divergent taper angle α formed at the inner diameter of the tip opening
Are you on the application nozzle by 20 ° to 60 ° range
Spray coating suitable for improving the spraying amount and atomization efficiency
The spread of the fee is obtained.

The end face of the tip opening of the paint nozzle is at least 0.3 mm from the end face of the opening of the air cap center hole.
The above-mentioned protruding causes fluctuation of the compressed air pressure.
Reduces the effect on the paint nozzle tip due to
It allows spraying with the amount of paint sprayed out.

[0012]

According to the above means, the paint ejected from the paint nozzle with a paint pressurizing pressure sufficient to eject the paint has a tapered shape that widens as the opening end of the paint nozzle approaches the outlet. , The passage area (1.2 mm) is much larger than when it is ejected from the basic diameter of the needle valve seat.
Up to 4 times), easy to disperse, and large contact area with the compressed air ejected to the surroundings, sufficient mixing even under low pressure conditions, and fine atomization by improving atomization efficiency Becomes possible. That without changing the basic nozzle diameter, atomization enhancing effect is obtained. Needle valve
A basic diameter part and a taper part are formed continuously to the seat part.
So that there is no problem with the accumulation of paint,
No coarse particles splatter.

[0013] Further, the tip of the paint nozzle is extended
The outer shape of the tip inevitably becomes larger due to the par shape,
Effect of compressed air pressure injected around the paint nozzle tip
The compressed air pressure fluctuated.
In this case, the disadvantage that the spraying stability is impaired
Stick out the end of the air cap center hole opening end
It is stabilized by that.

[0014]

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

Reference numeral 1 denotes a paint nozzle disposed at the center of the main body 2 of the air spray gun and provided at the tip of a needle valve 3. The paint nozzle 1 introduces paint from the rear and contacts the needle valve 3 provided inside. A needle valve seat 10 as a contact portion is formed, and a paint nozzle basic diameter φC for determining 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 in the range of 0.5 to 3.0 mmφ (0.8, 1.2, 1.4 in the embodiment). , 1.8,
2.5 mmφ), and the parallel length D of the paint nozzle basic diameter C should be at least 0.
It is configured to keep at least 6 mm. The tip end of the paint nozzle 1 is opened at a tapered angle α ゜ diverging from the center axis.

A center air hole 7 formed of an annular parallel slit is formed between the outer periphery of the tip end of the paint nozzle 1 and a center hole 6 of an air cap disposed outside thereof. The air cap 5 is provided on the axis of the paint nozzle 1 in addition to the center hole 6.
At least one pair of square air holes 8 that cross and collide with each other is provided in front of the paint outlet, and a center air passage 9 to the center hole 6 and a square air passage 9 ′ to the square air hole 8 are separately provided. The position of the valve body 4 provided on the main body 2 is determined by the pattern adjusting device 12 to determine the opening degree, so that the square air holes 8
It is configured such that the supply amount of pattern air to the nozzle can be changed. The center 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 throttle section 13 is provided in the middle of the atomizing air passage 14, and the total area of the cross section of the compressed air passage of the square air hole 8 and the center hole 6 of the air cap 5 is 35 to 44 mm 2, which is larger than that of a general-purpose spray gun (1.5 times). Above), the high-pressure compressed air pressure (generally 3 ) at the inlet of the air spray gun.
( Around 50 kPa ) at the pressure inside the air cap of 7
It is configured to be 0 kilopascal . Note that the other mechanisms of the air spray gun are the same as those of the known air spray gun, and thus the description is omitted.

Next, the path of the paint will be described. First, the paint is supplied to the paint nozzle 1 from a separately provided pressure feeding device (not shown), and the needle valve is provided to the needle valve seat 10 provided in the paint nozzle 1. The tip 3 contacts and separates to control the amount of paint sprayed. The supply of compressed air to the air cap 5 is controlled by an air valve 15. As with the general-purpose air spray gun, the operation of the trigger 11 sends the compressed air flow to the air cap 5 and the paint is ejected by the paint nozzle 1 when the needle valve 3 separates (retreats).

Since the open end of the paint nozzle 1 has a tapered shape that widens toward the outlet, the paint that has been stably ejected from the parallel portion of the opening through the needle valve seat 10 is ejected from the nozzle open end. At this point, the passage area becomes much larger (1.2 to 4 times), so that the paint is easily dispersed and the contact area with the surrounding compressed air is large, so that the gas and liquid are sufficiently mixed. In addition, the flow velocity of the paint at the paint nozzle outlet is reduced by the increase in the area, the relative velocity generated between the paint flow and the air flow is increased, the shear force received from the air flow is increased, and the atomization of the paint is promoted.

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. Since there is no influence of the back pressure generated near the paint nozzle outlet due to the flat air flow from the air hole 8, the balance of the paint pressurizing pressure is stably maintained, and a stable supply of the paint ejection amount can be obtained. In general-purpose pressure-feeding air spray guns, the outlet end of the paint nozzle opening is generally located on the minus surface within the area where the air cap center hole is formed (the nozzle tip is recessed ) to promote atomization. In particular, when the diameter of the paint nozzle is large, the back pressure action of the center and square air flows on the tip of the nozzle acts strongly, so that the amount of paint ejected greatly fluctuates.

The dimensional relationship relating to the paint nozzle 1 and the air cap 5 of the embodiment of the present invention will be described. When the paint nozzle basic diameter C is 0.5 to 3.0 mmφ or less, the paint nozzle outer diameter A is 2.0 to 5 mm. 0.5 mmφ, paint nozzle divergent taper exit diameter B is 1.5 to 4.5 mmφ, paint nozzle basic diameter length D is 0.6 mm or more , and divergent taper exit diameter α ゜ is 2
By setting the angle to 0 ° to 60 °, the effect of atomization was confirmed. In the above example, the case where the present invention is applied to a low-pressure spray gun in which an operator directly grips and performs a painting operation has been described. However, the present invention is also applied to a so-called automatic air spray gun used in an automatic system such as a painting robot. Of course you can.

[0022]

As described above, according to the present invention, the following effects can be obtained.
Which are important for painting
Environmental conservation, resource saving, and production without impairing
It is possible to obtain a spray gun excellent in workability. 1) Since the opening end of the paint nozzle is formed in a tapered shape that diverges toward the outlet, the atomization of paint can be improved by increasing the gas and liquid contact area without changing the basic nozzle diameter, and 100 kPa or less. At the compressed air pressure of, the atomization suitable for the finish coating is maintained without increasing the amount of air, the scattering of spray particles can be reduced, the coating efficiency is improved, and the environmental pollution is reduced. .
2) By making the protrusion of the paint nozzle convex from the front surface of the air cap, the stability of the paint ejection amount can be obtained, and the film thickness of the finish surface of the paint can be stabilized. 3) Washing without a large amount of paint remaining inside the paint nozzle from the sheet to the open end.
It is easy to handle and maintain, and has a cost advantage because it has a component configuration similar to a general-purpose air spray gun.

[Brief description of the drawings]

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

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

FIG. 3 is an overall sectional view of one embodiment of the low-pressure atomization spray gun of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paint nozzle 2 Main body 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 adjustment device 13 Restrictor 14 Fog Air passage 15 air valve

Claims (2)

(57) [Claims] 1. A and an air spray gun body disposed a needle valve, fitted to the tip opening center portion of the air spray gun body, and a coating nozzle having a sheet tip and those SeHHanareHiraki of the needle valve, paint Around the outer periphery of the outlet cylinder of the paint nozzle around the nozzle, a center hole which forms an annular air passage coaxially and parallel to the outer periphery of the paint nozzle outlet cylinder, and a flat pattern obliquely forward of the center hole. A liquid paint is introduced into the paint nozzle in a low-pressure atomizing spray gun having an atomizing head comprising an air cap having a pattern forming air hole for forming
And a basic aperture with a parallel part formed continuously with the inner sheet part
A portion is provided , and the tapered shape is formed so as to diverge toward the outlet opening end of the paint nozzle continuously to the parallel portion, so that the tip of the paint nozzle projects from a center hole opening end surface of the air cap. Composed low pressure atomizing spray gun. 2. A length D of a parallel portion of a basic diameter of the paint nozzle.
Should be at least 0.6 mm
The divergent taper angle α is in the range of 20 ° to 60 °.
The paint nozzle has a tip opening end face facing the air key.
0.3 mm or more from the end face of the opening of the cap center hole
Protruding and the internal pressure of the air cap during spraying is 10
2. The method according to claim 1, wherein the pressure is 0 kilopascal or less.
The described low-pressure atomization spray gun .