JPH08131906A - Nozzle set for preventing paint accumulation in inside mixing type spray gun - Google Patents

Abstract

PURPOSE: To prevent paint accumulation caused by paint sticking in a mixing chamber by forming a ringlike slit in which both a tip cap taper and the external taper of the tip part of a paint nozzle are formed to have a specified angle respectively in an inside mixing type spray gun constituted by joining a tip cap having the mixing chamber and the single-hok paint nozzle. CONSTITUTION: Paint force-fed and supplied from a single-hole paint nozzle 1 is spouted into the mixing chamber 2a of a tip cap 2 and mixed with compressed air injected from a ringlike slit 4 formed between an external taper 1a of the tip part of the paint nozzle and a tip cap taper 2b and thereby a mixed stream is obtained. In this case, the ringlike slit 4 is formed by regulating the tip cap taper 2b at about 180 deg.C, and regulating the external taper 1a of the tip part of the paint nozzle at an obtuse angle of >=90 deg.. Thereby, the central paint jet is diffused by air injector through the ringlike slit 4 and fresh paint is allowed to always flow on the wall surface of the mixing chamber 2a. Paint accumulation caused by paint sticking in the mixing chamber 2a is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal mixing type spray gun, in particular, an internal mixing type atomizing mechanism for spraying air pressure of 1 k.
When used in a low pressure spray gun of g / cm2 or less, a nozzle set at the tip of an internal mixing type spray gun that mixes paint and air in the tip cap and prevents paint accumulation due to sticking of paint in the mixing chamber. Regarding the improvement of.

[0002]

2. Description of the Related Art General spray guns are classified into an internal mixing type and an external mixing type. The external mixing type atomizes by mixing paint and air immediately after injection from an air cap, but the internal mixing type does A spray gun in which air and paint are mixed inside the tip cap (air cap), and the dispersed paint is atomized at the same time as spraying. There are various types of internal mixing methods of this internal mixing type spray gun, which are roughly divided into those with an air nozzle in the center,
There is a paint nozzle in the center. The prior art of the present invention is
In the form with a paint nozzle in the center, compressed air of several atmospheres is ejected from a ring-shaped slit on the outer periphery of the tip of the paint nozzle, together with the paint pressurized from the center paint nozzle,
In the mixing chamber immediately after the paint nozzle is jetted, the air and the paint are mixed, and the paint is atomized at the same time as being jetted from the jet port of the tip chip cap. This internal mixing method mixes air and paint in a pressurized state inside the tip cap, and a high shearing force acts on the paint, so it has the characteristic of good atomization efficiency compared to the external mixing type spray gun. is there.
That is, the paint can be efficiently atomized with a small amount of air or low pressure air. Therefore, it is often used for painting high-viscosity paints and special paints.

In recent years, the scattering of mist in air spray coating and the discharge of organic solvents into the atmosphere have become a socially serious problem (3). As one of the measures for reducing the scattering of the mist of the air spray, a method of reducing the scattering of the mist and improving the coating efficiency by making the spraying pressure 1 atmosphere or less has been attracting attention. However, the external mixing low-pressure spray gun requires a large amount of air to atomize the paint, even at low pressure. I am trying. Therefore, a low-pressure low-pressure spray gun with a small air volume has been developed by adding an internal mixing type atomization mechanism to this low-pressure spray gun. This low-pressure spray gun is already known from the low-pressure atomization spray gun of Japanese Patent Application Laid-Open No. 3-60753 filed by the present applicant. In the internal mixing type low-pressure atomization spray gun, the air flow ejected from the ring-shaped slit on the outer circumference of the paint nozzle into the mixing chamber flows so as to wrap around the paint flow from the central paint nozzle, and the lip of the tip cap at the tip is flown. It is sprayed from the spray port. At this time, the mixing chamber has a slightly high pressure because it is squeezed by the lip-shaped spray port. However, the pressure in the mixing chamber is reduced to at least 1 atm or less than the supplied compressed air pressure of 2 to 3 atm by the ring-shaped slit formed between the tip cap and the paint nozzle.

In the mixing chamber, the mixed flow of the paint and the air has a high paint density in the central part and a low paint density in the outer peripheral part. Then, a backflow region which becomes a vortex is formed on the wall surface of the mixing chamber by the air jet from the slit. In the backflow region, the paint density is low and the flow of the mixed flow is poor, so the paint adhering to the wall surface dries and sticks. Even if new paint comes in, the once-adhered paint is not washed or replaced with new paint, and is gradually laminated to close the mixing chamber, change the spray pattern shape, and reduce the amount of paint spray. Problems such as deterioration occur. And, this paint accumulation appears remarkably in a paint which dries quickly, for example, an aqueous emulsion paint or a lacquer paint. In such a case, there is a problem that the tip cap must be frequently washed or the condition must be set unless a paint which dries quickly can not be used. Page (4)

[0005]

In the set configuration of the tip cap of the internal mixing type spray gun and the paint nozzle described above, as described above, the spray is ejected from the paint nozzle and the ring-shaped slit around the paint nozzle. In the mixing chamber where air and paint are mixed, the density of the coating is high in the central part and thin in the outer peripheral part, and the backflow region is formed on the peripheral wall of the mixing chamber, and the mixed flow is stagnant. The paint adheres to the peripheral wall of the paint and is dried and fixed by the air with a low paint density, which gradually builds up thickly, and finally the paint spray amount decreases, and the balance of the spray from the lip-shaped spray port is disturbed, resulting in a pattern. There is a problem that pattern defects such as unevenness or deformation are generated, and atomization defects that partially form coarse particles occur. And, this tendency has a problem that it becomes more noticeable as the coating material dries faster.

Therefore, in order to prevent the coating material gradually deposited on the wall surface of the mixing chamber from drying and sticking, the backflow region formed by the air jet from the slit is eliminated or the influence of the backflow region is ignored. Reduce as much as possible,
At the same time, in order to make the distribution density of the mixed flow in the mixing chamber as uniform as possible, paint that contains solvent, water, etc. is always made to collide with the wall of the mixing chamber, and the wall is kept wet so that it does not stick. Is what you are trying to do.

[0007]

SUMMARY OF THE INVENTION The present invention has a single-hole paint nozzle screwed to a spray gun body of an internal mixing type spray gun and a lip-like spray port, and a paint is provided immediately before the spray port. A tip cap with a mixing chamber that mixes air
In a tip nozzle configuration of an internal mixing spray gun joined to the paint nozzle by a taper, when forming a ring-shaped slit for introducing compressed air leading to the mixing chamber, the tip cap taper is set to about 180 °, and the paint nozzle tip is Ring-shaped slip with an outer surface taper of 90 ° or more obtuse angle
A page (5) is formed, and the central paint jet is diffused by the air jet from the ring-shaped slit so that the paint directly collides with the wall of the mixing chamber, and new paint is constantly applied to the wall of the mixing chamber. This is a nozzle set for preventing paint accumulation in an internal mixing type spray gun that is made to flow.

Also, a mixing chamber having a single-hole paint nozzle screwed into the spray gun main body of the internal mixing type spray gun and a lip-like spray port, and mixing the paint and air immediately before the spray port is provided. In the tip nozzle structure of the internal mixing type spray gun, in which the tip cap having the taper is joined to the paint nozzle, the tip cap has an inner surface taper portion and a paint nozzle tip end outer surface taper portion which communicates with the inside of the mixing chamber. When forming a ring-shaped slit for introducing compressed air, a large number of obtuse angles of 90 ° or more are formed on the outer surface taper of the paint nozzle, and by air injection from the grooves,
The central paint jet flow is diffused so that the paint directly collides with the wall surface of the mixing chamber, and the obtuse-angled grooves are symmetrical grooves passing through the center of the paint nozzle. This is a nozzle set for preventing paint accumulation in an internal mixing type spray gun that makes the density distribution in the mixing chamber uniform and allows new paint to always flow on the walls of the mixing chamber.

[0009]

The operation obtained by the above means will be described with reference to FIGS. The paint that is pressure-fed and supplied from the single-hole paint nozzle (1) screwed to the spray gun body is jetted into the mixing chamber (2a) of the tip cap (2) by pulling the needle valve (5). On the other hand, it is momentarily faster than the needle valve is pulled, and the outer taper of the paint nozzle tip (1a) and the tip cap taper (2b)
Compressed air is jetted from a ring-shaped slit (4) formed between the and. Then, in the mixing chamber (2a), the air and the paint are mixed to form a mixed flow. When the compressed air is jetted from the ring-shaped slit (4), a backflow region is generated on the wall surface of the mixing chamber (2a), and the flow of the mixed flow in the backflow region is stagnant.
When the paint adheres to the backflow area and sticks to dryness, the tip of the paint nozzle
Page (6) By making the outer surface taper (1a) an obtuse angle of 90 ° or more, compressed air collides with the paint jet intersecting the obtuse angle so as to block the paint jet in the central portion. As a result, the central paint jet diffuses and collides with the wall surface of the mixing chamber (2a). The new paint containing the diffusing solvent constantly collides with the wall surface, whereby the paint adhering to the wall surface is washed and replaced with the new paint, so that the dry adhesion on the wall surface is prevented.

Further, four or six grooves having an obtuse angle than the taper angle are symmetrically provided on the outer tapered surface (1a) of the paint nozzle so as to more effectively diffuse the central paint jet. Symmetrically 4 or 6 means that compressed air collides with the paint jet and the mixing chamber (2a)
This is because the paint jet is dispersed as evenly as possible.
This uniform dispersion is a necessary condition for obtaining a flat and uniform mist distribution when spraying from the lip-shaped spray port (2c). For example, to simply remove the effect of the backflow region of the mixing chamber, tangentially inject compressed air into the mixing chamber,
By swirling the mixed flow in the mixing chamber, it is possible to prevent the paint from sticking in the backflow region, but in this case, the uniformity of the spray from the lip-shaped spray port cannot be obtained, which is suitable for spray painting. The spray shape cannot be obtained. Therefore, it has been confirmed that the obtuse-angled groove (1b) is preferably a V-shaped groove symmetrical with respect to the central axis, and an even number of 4 or 6 even grooves.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a cross-sectional view showing the entire structure of an internal mixing low-pressure atomization spray gun as an example of the present invention. The main body 10 has a barrel 20 and a grip 30, and a grip 30
The air nipple 31 is attached to the lower part of the above, and compressed air is sent through the through hole 32 to the air valve part provided in the upper part.
The air valve portion is configured by providing an air valve 12 inside the air conditioning pipe 11 that is bored from the rear portion of the barrel 20. The air-conditioning pipe 11 is provided with a hole 13 communicating from the outside to the inside, and the rotation of the air-conditioning pipe 11 causes the amount of air to change depending on how the page 13 (7) of the hole 13 and the through-hole 32 match. A knob 14 is provided to rotate the air conditioning pipe 11. The air valve 12 is pressed against the main body sheet 16 by the spring 15 to stop the compressed air. A needle valve 5 extending to the tip of the barrel 20 penetrates through the center of the air valve 12, a spring 17 is provided at the rear portion thereof, and an air valve rod 19 is provided outside the needle valve 5 for elastically holding the spring 17. There is. Operate the trigger 9 to retract the air valve,
Compressed air is sent to the air distribution chamber 21 in the front. When the trigger 9 is further pulled, the needle valve 5 is moved by the rear end of the air valve 12.
Are configured to retract.

An air distribution chamber 21 shown in a sectional view taken along the line BB of FIG.
The distribution valve 22 is rotatably fitted, and the external knob 2
It is rotated by 3. This air distribution chamber 21
Therefore, there are three air passages toward the front of the barrel 20, one of which is always in communication with the distribution chamber 21, while the other two are of the recess 24 provided in the distribution valve 22. The flow area varies depending on the moving position, and the flow rate can be adjusted. Therefore, the change of the distribution area in the rotating contact portion is controlled by the distribution valve 22.
If it is determined by the concave portion 24 of the above, it is possible to control the distribution amount arbitrarily.

An atomizing device is provided at the tip of the barrel 20. The paint nozzle 1 for spraying paint is screwed into the tip of the main body 10 so that the tip of the needle valve 5 tapers the inner surface of the paint nozzle 1. Sheet and turn the paint on and off. The lower taper 1e of the paint nozzle 1 is a main body 1
And two air passages 25 and 26 which are joined to the main body are defined and are supplied to the air passage 1c to the mixing chamber divided by the distribution valve 22 described above and the side air holes 3a at the corners of the air cap 3. An air passage 1d is formed for this purpose.
The air passage 28 is a passage for pressurized air for supplying the paint under pressure. The air passage 28 is sent to a paint container (not shown) via the paint joint 27 so as to pressurize the paint with compressed air.

Page (8) FIG. 1 is an enlarged view of the tip of a low pressure atomizing spray gun.
The same components as those in FIG. 2 are designated by the same reference numerals. Body 10
In the paint nozzle 1 that is screwed in, the paint passage 7 and the air passage 1d to the mixing chamber are blocked by the lower taper 1e. The tip cap 1f of the paint nozzle 1 covers the tip cap 2 and is joined by a taper. The air passage supplied to the mixing chamber 2a and the air passage supplied to the air cap 3 are blocked by a taper joint. The air cap 3 that covers the chip cap 2 is configured such that the cap cover 6 simultaneously tightens the chip cap 2 and the air cap 3 on the main body 10. Air cap 3 that covers the tip cap 2
The O-ring 8 prevents air leakage from the fitting portion. The air cap 3 enters the pair of air passages 3b of the air cap 3 through the air passage 1d of the paint nozzle and is jetted from the side air holes 3a. Then, the spray pattern is adjusted by applying it to the mist ejected from the lip-shaped spray port 2c of the tip cap 2. The elliptical pattern ejected from the lip-shaped spray port is adjusted by adjusting the amount of air from the side air holes 3a by the pattern adjusting knob 23 on the main body side. And the pattern is adjusted to the proper pattern.

The mixing chamber 2a according to the gist of the present invention includes a ring-shaped slit 4 formed between the tip outer taper 1a of the paint nozzle 1 and the tip cap taper 2b, and a chip immediately after the single-hole paint nozzle 1. It is formed in the cap 2. The outer surface taper 1a of the paint nozzle tip is formed at an obtuse angle of 90 ° or more with respect to the central axis of the paint nozzle 1. The tip cap 2b is coaxial and is formed at an angle of approximately 180 ° so as to be orthogonal to the axis. It has been confirmed that an approximate effect can be obtained within the angle range of + 10% and -20% for the angle of about 180 °. In addition, the tip of the paint nozzle enters and exits on the same surface as the surface of the tip cap 2b. The gap between the ring-shaped slits 4 varies greatly depending on the entrance and exit of the paint nozzle. The injection hole area of the ring-shaped slit 4 is important for setting an appropriate pressure for atomizing the mixing chamber 2a, in association with the opening area of the lip-shaped spray page (9) mouth 2c of the tip cap. is there. In this configuration, the paint jet from the paint nozzle 1 is diffused to the surroundings by the air jet having an obtuse angle of 90 ° or more from the ring-shaped slit 4 on the outer periphery, and the diffused paint is created by the air jet. Destroy the watershed and mix room 2a
The paint that has collided with the wall surface of the mixing chamber and has adhered to the wall surface of the mixing chamber is always replaced with new paint. This uniformly diffused mixed flow is ejected in an elliptical spray pattern from the elliptical lip-shaped spray port 2c in the top view of the tip of the tip cap 2.

FIG. 4 relates to another gist of the present invention and is a detailed view of the groove portion provided on the outer tapered surface 1a of the paint nozzle tip. FIG. 4A is a sectional view, and FIG.
Shows the top view. In the figure, a V-shaped groove is provided at an angle α which is more obtuse than the angle of the outer surface taper 1a of the paint nozzle. Without limiting the invention, the angle α is designed to be 120 °. The V-shaped groove is
In order to uniformly disperse the paint jet, it is processed at a cutter angle β of 90 °. Of course, the cutter angle β does not limit the present invention. And four V-grooves are provided with exact symmetry passing through the central axis of the paint nozzle. The reason why they are provided symmetrically is that the diffusion of the paint jet is not made uneven by the compressed air jetted from the groove. If it becomes non-uniform, the spray from the elliptical lip-shaped spray port 2c of the tip cap 2 causes unevenness or shading of mist, and a normal spray pattern cannot be obtained. Also, this V
The reason for limiting the number of grooves is that if the number of grooves is three or less, it becomes difficult to secure the uniformity of the fog. And for seven or more, V
This is because the effect of the groove cannot be obtained. In the present invention, the effect of destroying the reverse flow region can be obtained by making the coating nozzle tip outer surface taper 1a an obtuse angle of 90 ° or more, but by providing the V groove, a more reliable effect can be obtained. It is provided for this purpose.

Although the present invention has been described in detail with reference to an internal mixing type low pressure atomizing spray gun as an example (10), it is not limited to the low pressure atomizing spray gun, but a mixing chamber of a general internal mixing type spray gun. Adhesion of paint to the surface is a common phenomenon and is a major drawback of internally mixed spray guns. Therefore, the external mixing type spray gun
Despite the large amount of fog scattered, it is one of the major causes of widespread use. The present invention has a principle applicable to high pressure general internal mixing spray guns, and is not limited to low pressure atomizing spray guns.

[0018]

According to the present invention, the paint nozzle tip taper of the internal mixing type spray gun is set to an obtuse angle of 90 ° or more, or
Alternatively, by providing four or six obtuse V-grooves on the tapered surface of the paint nozzle, compressed air is jetted into the paint jet at an obtuse angle to diffuse the paint jet, and the diffused paint is dispersed in the reverse direction of the mixing chamber. By destroying the basin and colliding with the wall of the mixing chamber, the paint adhering to the wall is constantly washed and replaced, preventing dry adhesion to the wall of the mixing chamber, and conventional cleaning or unusable conditions. The attached use conditions are eliminated, and a stable normal pattern is obtained for a long period of time.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of the tip of an internal mixing low-pressure atomization spray gun showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an internal mixing low-pressure atomization spray gun showing an embodiment.

3 is a cross-sectional view of the air distribution chamber taken along the line BB of FIG.

FIG. 4A is a detailed cross-sectional view of a V groove portion provided on a tapered surface of a paint nozzle tip. (B) is a top view of (a).

[Explanation of symbols]

 Page (11) 1 Paint nozzle 1a Paint nozzle tip outer surface taper 1b Groove 2 Tip cap 2a Mixing chamber 2b Tip cap taper 2c Lip spray nozzle 3 Air cap 3a Side air hole 4 Ring slit 10 Main body 20 Barrel 30 Grip

Claims (3)

[Claims] 1. A single-hole paint nozzle (1) screwed to a spray gun body of an internal mixing type spray gun and a lip-shaped spray port (2c) are provided, and paint and air are supplied immediately before the spray port. Tip cap (2) with mixing chamber (2a) for mixing
In a tip nozzle configuration of an internal mixing type spray gun, which is joined to the paint nozzle (1) by a taper, when a ring-shaped slit (4) for introducing compressed air leading to the mixing chamber (2a) is formed, A ring-shaped slit having a cap taper (2b) of about 180 ° and an outer taper (1a) of the paint nozzle tip portion of 90 ° or more at an obtuse angle is formed, and a central paint jet is diffused by air injection from the ring-shaped slit. Then, a nozzle set for preventing paint accumulation of an internal mixing type spray gun in which the paint directly collides with the wall surface of the mixing chamber (2a). 2. A single-hole paint nozzle (1) screwed to a spray gun body of an internal mixing type spray gun and a lip-shaped spray port (2c), and paint and air are sprayed immediately before the spray port. Tip cap (2) with mixing chamber (2a) for mixing
In a tip nozzle configuration of an internal mixing type spray gun, which is joined to the paint nozzle (1) by a taper, a mixing chamber is provided between a tip cap taper (2b) and a paint nozzle tip outer surface taper (1a). When forming the ring-shaped slit (4) for introducing compressed air leading to (2a), 90 ° on the outer taper (1a) of the paint nozzle tip.
A large number of the obtuse-angled grooves (1b) described above were formed, and the central paint jet flow was diffused by air injection from the grooves (1b) so that the paint directly collided with the wall surface of the mixing chamber (2a).
Nozzle set for preventing paint accumulation in internal mixing type spray gun. 3. A ring-shaped slit (4) for introducing compressed air.
Outer surface taper (1a) that forms the paint nozzle
When a large number of obtuse-angled grooves (1b) of 90 ° or more are formed, the obtuse-angled grooves (1b) are symmetrical grooves that pass through the center of the paint nozzle (1) and are four or six. The paint accumulation prevention for an internal mixing type spray gun according to claim 2.
Page (2) Stop nozzle set.