JPH07194998A - Painting spray gun - Google Patents

Abstract

PURPOSE:To prevent potential difference occurrence due to high voltage in a seat part even if a paint to be sprayed out of a paint spraying outlet is stopped under a condition that high voltage is applied to a needle--like electrode. CONSTITUTION:A conductive layer 23 of a conductive ceramic is formed in a valve part 21A installed in the tip side of a needle valve body 21. Consequently, since the residual paint TB charged at high voltage by a needle-like electrode 22 and the residual paint TA connected to an earth side are electrically communicated to each other by the conductive layer 23, potential difference occurrence due to the high voltage VH between a valve seat 5E of a paint nozzle 5 and the conductive layer 23 of the needle valve body 21 is prevented at the time of closing the valve of a paint spraying outlet 5D. Electrolytic corrosion occurrence on the surface of the valve part 21A of the needle valve body 21 is thus prevented and the life of the needle valve part 21 is extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating spray gun for spraying a coating material from a coating nozzle onto an object to be coated.

[0002]

2. Description of the Related Art Generally, a spray gun for painting of this type (hereinafter referred to as "spray gun") includes a spray gun body, a paint nozzle provided on the tip side of the spray gun body, and a tip of the paint nozzle. And an air nozzle for ejecting atomized air and pattern air, a paint valve provided on the proximal end side of the paint nozzle for opening and closing a needle valve element with respect to the paint nozzle, and sprayed from the paint nozzle. In order to apply a high voltage to the paint, the needle valve electrode is provided to be inserted into the needle valve body and has a tip end protruding from the paint nozzle, and a paint supply pipe for supplying the paint to the paint nozzle. .

The paint supplied to the paint nozzle provided on the tip side of the spray gun body through the paint supply pipe is sprayed from the paint spray port of the paint nozzle. Further, atomized air supplied from the spray gun body through the atomizing air passage in the paint nozzle is ejected from an atomizing air ejection port provided in the air nozzle so as to surround the paint atomizing port, thereby atomizing the paint. Promote the transformation. Further, the pattern air supplied from the spray gun main body is ejected from, for example, a pattern air ejection port provided vertically opposed to the air nozzle so that the spray pattern of the paint is formed into an elliptical or oval pattern. The coating film on the substrate is uniform.

Further, a prescribed high voltage (for example, -60 kV) is supplied to the needle electrode from a high voltage generator, and a corona discharge region is formed on the tip side of the needle electrode. Then, the corona discharge region charges the paint sprayed from the paint nozzle and patterned by the atomizing air and the pattern air, and the paint flies toward the object to be grounded to improve the coating efficiency. It is designed to improve.

Here, an electrostatic atomization type spray gun for coating in the prior art will be described with reference to FIG. 5 by exemplifying a case where a metallic paint having a low electric resistance is used.

In the figure, reference numeral 1 denotes a spray gun main body, which is formed of an insulating resin material in a long cylindrical shape, and a nozzle main body 4 to which a nozzle main body 4 which will be described later is attached is provided on a tip end side of an inner peripheral surface thereof. It becomes the mounting hole 1A, and a screw portion 1B is formed on the outer peripheral surface thereof, and a cylindrical spray gun cover 2 is attached to the screw portion 1B so as to cover the spray gun body 1. Further, the base end side of the inner peripheral surface of the spray gun main body 1 is a high voltage generator mounting hole 1C in which the high voltage generator 3 is mounted, and from the high voltage generator 3 a high voltage is applied to a needle electrode 14 described later. VH is applied.

In the nozzle body mounting hole 1A of the spray gun body 1, a nozzle body 4 which will be described later, a paint nozzle 5 provided on the tip side of the nozzle body 4, and a paint nozzle 5 provided on the tip side of the paint nozzle 5 are provided. The air nozzles 7 thus formed are sequentially provided via a retainer ring 10.

Reference numeral 4 denotes a nozzle main body provided in the nozzle main body mounting hole 1A of the spray gun main body 1. The nozzle main body 4 is formed in a stepped cylindrical shape, and the inner peripheral side from the tip side to the paint nozzle fitting portion. 4A, a seal insertion portion 4B, a paint valve mounting hole 4C having a large diameter is formed on the base end side, and a female screw portion 4D is formed on the tip end side of the paint nozzle fitting portion 4A.

Reference numeral 5 is a paint nozzle fitting portion 4A of the nozzle body 4.
2 shows a paint nozzle provided so as to be fitted into the nozzle body. The paint nozzle 5 is formed of a single material by a resin material, and has a stepped tubular nozzle main body 5A and a base end side of the main body 5A. However, the peripheral groove portion 5B formed so as to communicate with the atomizing air passage (not shown) of the spray gun main body 1 and the taper-shaped nozzle located at the base end side of the peripheral groove portion 5B. A fitting portion 5C fitted into the paint nozzle fitting portion 4A of the main body 4, a paint spray port 5D formed on the tip side of the nozzle main body part 5A and formed to project in a small diameter, and the paint spray port 5D.
The valve seat 5E formed on the inner peripheral surface side on the base end side of the nozzle body and the outer peripheral surface on the base end side of the nozzle body 5A,
A male screw portion 5F screwed into the female screw portion 4D, a taper surface 5G formed in an annular shape on the tip side of the nozzle body portion 5A, and in contact with an air nozzle 7 described later, and the nozzle body portion 5A.
A plurality of atomizing air flow passages 5H, 5H, ... Are formed so as to communicate with the peripheral groove portion 5B.
Further, a needle valve body 13 described below is inserted into the inner peripheral surface of the paint nozzle 5 in the axial direction, a paint passage 6 is formed between the needle valve body 13 and the needle valve body 13, and the paint is supplied to the paint spray port 5D. To do.

Reference numeral 7 denotes an air nozzle provided on the tip side of the paint nozzle 5, and the air nozzle 7 is provided inside with the paint spray port 5
A tapered concave portion 7A positioned on the tapered surface 5G so as to surround D, a front wall portion 7B formed so as to cover the front surface side of the concave portion 7A, and a vertical position of the front wall portion 7B are opposed to each other. And the horn portions 7C, 7C formed so as to project toward the tip side, and the retainer ring 10 to be described later via the annular ring 8 and the locking ring 9 formed over the entire circumference of the outer peripheral surface. A locking stepped portion 7D that is locked to the fitting protrusion 10A, pattern air flow passages 7E and 7E that are formed from the base end side in each of the horn portions 7C and that communicate with a pattern air chamber 11 described later, and Pattern air jets 7F, 7F, which open diagonally inward from the horn 7C,
, And a plurality of atomizing air ejection ports 7G, 7G, ..., which are formed on the inner peripheral side of the front wall portion 7B so as to surround the paint spray port 5D of the paint nozzle 5.

Reference numeral 10 denotes a ring-shaped retainer ring. On the inner peripheral side of the tip of the retainer ring 10, an engaging projection 10A that engages with the air nozzle 7 via an annular ring 8 is formed, and at the base end. A female screw portion 10B screwed to the screw portion 1B of the spray gun body 1 is formed on the side inner peripheral surface. The paint nozzle 5 is fixed by screwing a female thread portion 4D of the nozzle body 4 with a threaded portion 5F, and the nozzle body 4 is attached to the spray gun body 1 by a positioning plug 18 described later. . Further, since the air nozzle 7 is attached to the spray gun body 1 by the retainer ring 10, the space defined by the nozzle body 4, the paint nozzle 5, the air nozzle 7 and the retainer ring 10 becomes an annular pattern air chamber 11. ing.

Reference numeral 12 denotes a paint valve provided at the base end side of the nozzle body 4, and the paint valve 12 is a cylinder 12A formed in a paint valve mounting hole 4C of the nozzle body 4 and the inside of the cylinder 12A. A piston 12B that is slidably provided in the air chambers A and B, and a closing portion 12C that is provided to close the opening of the paint valve mounting hole 4C of the nozzle body 4, and the closing. The cylinder 12A is roughly composed of a conductive spring 12D formed of a conductive material that electrically connects the portion 12C and the piston 12B, and a V packing 12E inserted into the seal insertion portion 4B.
The (paint valve mounting hole 4C) is provided with a T.ON supply / discharge port 12F communicating with the air chamber A and a T.OFF supply / discharge port 12G communicating with the air chamber B.

The paint valve 12 is provided with compressed air T.ON.
, T.OFF is configured as a 2-port 2-position air switching valve that can be switched by supplying / discharging, and compressed air T.ON is supplied from the T.ON supply / discharge port 12F into the air chamber A, and compressed air T.OFF is supplied. By exhausting air from the T.OFF supply / discharge port 12G, the valve is switched to the open position. On the other hand, compressed air T.OFF is supplied to T.OFF supply / discharge port 1
The compressed air T.ON is supplied to the inside of the air chamber B from 2G.
By exhausting air from the supply / discharge port 12F, the paint valve 12 switches to the closed position.

Reference numeral 13 denotes a needle valve body whose tip side extends to the paint spray port 5D of the paint nozzle 5 and whose base side is fixed to the piston 12B. The needle valve body 13 minimizes the charging energy. For example, the needle valve 13 is made of an insulating ceramic material such as alumina or zirconia in a rod shape, and has a tapered valve portion 13A on the front end side. Opens and closes the paint nozzle 5. When the valve is closed, the valve portion 13 of the needle valve body 13 is closed.
By A, the paint passage 6 and the paint spray port 5D are electrically insulated.

Reference numeral 14 denotes a needle-shaped electrode inserted in the axial direction of the needle valve body 13, and the base end of the needle-shaped electrode 14 is the plug 1
It is fixed to the piston 12B by 5, and the tip side projects from the paint spray port 5D of the paint nozzle 5.

Reference numerals 16 and 17 denote a paint supply passage and a paint discharge passage formed in the spray gun body 4, respectively.
The passages 16 and 17 are connected to the base end of the paint nozzle 5 and the paint valve 12.
To the annular chamber C between the V packing 12E, and the paint nozzle 5 and the needle valve body 1 at the position of the annular chamber C.
3 communicates with a paint passage 6 formed therebetween.

Further, 18 is a positioning plug which is inserted in the radial direction of the spray gun body 1 and positions the nozzle body 4, and 19 electrically connects the closed portion 12C of the paint valve 12 and the high voltage generator 3. It is a plug for connection.

In the coating spray gun of the prior art constructed as described above, the paint is supplied from the color changing valve device provided outside in the paint preparatory step, whereby the paint is supplied to the paint supply passage 16 The annular chamber C, the paint passage 6 and the paint discharge passage 17 are filled via the. When the coating process is started, the needle valve body 13 is supplied by supplying compressed air T.ON to the paint valve 12 into the air chamber A.
Is separated from the valve seat 5E of the paint nozzle 5, and the paint spray port 5
Spray paint from D. At this time, the sprayed paint is
The atomization air discharged from each atomization air ejection port 7F of the air nozzle 7 promotes atomization of the atomized paint, and the pattern air ejected from each pattern air ejection port 7F makes the spray pattern of the paint uniform. To coat the object.

At this time, a high voltage portion VH is applied from the high voltage generator 3 to the needle electrode 14 to form a corona discharge region on the tip side of the needle electrode 14 and the atomized paint is applied. The paint is applied to the object to be electrically charged and short-circuited to the ground so that the paint is applied.

In the above description of the operation, the case where a metallic paint is used as the paint has been described. The paints are roughly classified into a solvent-based paint having a relatively large electric resistance value and a water-based paint having a small electric resistance value. , There are metallic paints in which metal powder is dispersed, but in water-based paints,
The needle electrode 14 is operated as a spray gun without supplying the high voltage VH.

[0021]

By the way, in the above-mentioned conventional spray gun for coating, when the spray gun is moved to change the coating position on the object to be coated, a high voltage is applied to the needle electrode 14. The valve seat 5 of the paint nozzle 5 between the paint passage 6 and the paint spray port 5D with VH still applied.
By spraying the valve portion 13A of the needle valve body 13 on E and closing the paint spray port 5D, spraying of the paint is stopped. At this time, as shown in FIG. 6, there are residual paints TA and TB in the paint passage 6 and the paint spray port 5D, respectively, and at the seats of the valve seat 5E and the valve portion 13A, paint pigments (for example, metallic paint). In case of, aluminum powder) etc. will be sandwiched. Then, the residual paint T in the paint passage 6
A is connected to the ground via an external color changing valve device, and the residual paint TB at the paint spray port 5D is charged to a high voltage VH by the needle electrode 14, but the needle valve body 13 is made of an insulating ceramic material. Since it is formed by
There is electrical insulation between A and TB. Therefore, a potential difference VH is generated between the valve portion 13A and the valve seat 5E, and this potential difference VH acts on the conductive pigment sandwiched between the seat portions,
A bridge phenomenon occurs on the surface of the seat by energizing the remaining paint TA and TB. As a result, electrolytic corrosion occurs on the surface of the valve portion 13A of the needle valve body 13 made of a ceramic material.

When this electrolytic corrosion progresses, cracks K are generated on the surface of the valve portion 13A, as shown in FIG.
Due to the crack K, the sealability of the seat portion between the valve portion 13A and the valve seat 5E is deteriorated, paint leakage occurs, and the life of the needle valve element 13 is shortened.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention can extend the life of the needle valve body by preventing electrolytic corrosion from occurring on the surface of the valve portion of the needle valve body. The purpose is to provide a spray gun for painting.

[0024]

A feature of the structure adopted by the first invention to solve the above-mentioned problems is that a conductive layer is provided on the valve portion of the needle valve body.

The feature of the configuration adopted by the second invention is that the needle valve body has one end connected to the needle electrode,
This is because a radial electrode whose other end reaches the outer peripheral surface of the needle valve body is provided.

[0026]

With the above structure, the conductive layer or the radial electrode is
When the valve is closed, the residual paint from the paint spray port charged to high voltage on the needle electrode side and the residual paint that acts as ground on the paint side are electrically connected, and a potential difference is created between the valve and the seat. You can prevent it from happening.

[0027]

Embodiments of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the above-described conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

First, the first embodiment will be described with reference to FIGS. 1 and 2.

In the figure, reference numeral 21 denotes a needle valve body of this embodiment, and the needle valve body 21 is a needle valve body 13 of the prior art.
Is formed into a cylindrical shape with a ceramic material,
A valve portion 21A is formed on the tip side thereof, and the base end side thereof is fixed to the piston 12B of the paint valve 12.

Reference numeral 22 denotes a needle-shaped electrode that is inserted into the needle valve body 21 and is provided so as to project from the valve portion 21A of the needle valve body 21 toward the tip end side. Similar to the needle electrode 14, the high voltage VH supplied from the high voltage generator 3 is applied to form a corona discharge region in front of the needle electrode 22.

Reference numeral 23 is a valve portion 21A of the needle valve body 21.
The conductive layer 23 is formed of a conductive ceramic material, for example, and is formed by coating with a thickness of about 5 μm.

The operation of the coating spray gun of this embodiment having the above-mentioned structure is the same as that of the above-mentioned conventional technique.

However, according to this embodiment, the needle valve body 21 is seated on the valve seat 5E of the paint nozzle 5 while the high voltage VH is applied to the needle electrode 22 when the spray gun is moved, and the paint spray port is opened. Close valve 5D to stop spraying paint. At this time, as in the prior art, the residual paint TA is present in the paint passage 6 and the residual paint TB is present in the paint spray port 5D. The residual paint TA is electrically connected to a color changing valve device connected to an external ground, and the residual paint TB is charged to a high voltage VH by the needle electrode 22. However,
Due to the conductive layer 23 formed on the valve portion 21A of the needle valve body 21, the residual paints TA, TB are electrically connected even in the closed state, and the high voltage VH of the needle electrode 22 causes the residual paint TB,
It is connected to the color change valve device (earth) through the conductive layer 23, the residual paint TA, the paint passage 6, the paint supply passage 16 and the like. On the other hand, the paint passages 6, 16 and the like are filled with paint having an electric resistance, and the voltage drops to the color change valve device.
The short circuit phenomenon is not caused to destroy the high voltage generator 3 and the like.

Since the conductive layer 23 is made of conductive ceramic, it has excellent wear resistance.

Thus, the spray gun for painting according to the present embodiment has the construction in which the conductive layer 23 is formed on the valve portion 21A of the needle valve body 21, so that the high voltage VH is applied to the needle electrode 22 when the spraying of the paint is stopped. Even if it is left as it is, no potential difference is generated at the seating portion between the valve seat 5E of the paint nozzle 5 and the conductive layer 23 of the needle valve body 21 when the paint spray port 5D is closed, and the needle valve body 21 It is possible to reliably prevent electrolytic corrosion from occurring on the surface of the conductive layer 23.
Then, the occurrence of cracks can be effectively prevented, and the life of the needle valve 21 can be remarkably extended.

Next, the second embodiment will be described with reference to FIGS. 3 and 4, which is characterized in that one end side of the needle valve body is connected to the needle electrode and the other end side of the needle valve body is This is because a radial electrode reaching the outer peripheral surface is provided. In this embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 31 denotes a needle valve body of this embodiment, which needle valve body 31 has substantially the same structure as the needle valve body 31 of the first embodiment and has a tapered valve on the tip side. The portion 31A is formed.

Reference numeral 32 denotes a needle-shaped electrode which is inserted into the needle valve body 31 and is provided so as to project from the valve portion 31A of the needle valve body 31 to the tip side. The needle-shaped electrode 32 is the above-mentioned first electrode. In the same manner as the needle-shaped electrode 22 of the embodiment, the high-voltage VH supplied from the high-voltage generator 3 causes the needle-shaped electrode 3 to
A corona discharge region is formed in front of 2.

Reference numerals 33 and 33 denote a pair of radial electrodes provided in the needle valve body 31, respectively.
Has one end connected to the needle electrode 32 and the other end provided so as to reach the outer peripheral surface of the needle valve 31.

In the coating spray gun according to the present embodiment having the above-mentioned structure, since the radial electrodes 33, 33 are formed on the valve portion 31A of the needle valve body 31, the high voltage VH is applied to the needle electrode 32 when the spraying is stopped. Even if the voltage is still applied, the paint passage 6 is formed from the needle electrode 32 through the radial electrodes 33, 33.
Since the high voltage VH is directly applied to the residual paint TA inside,
When the paint spray port 5D is closed, the potential difference VH does not occur in the seat portion between the valve seat 5E of the paint nozzle 5 and the valve portion 31A of the needle valve body 31, and the valve portion 3 of the needle valve body 31 is eliminated.
It is possible to reliably prevent electrolytic corrosion from occurring in 1A. Therefore, it is possible to effectively prevent the occurrence of cracks on the surface of the valve portion 31A of the needle valve body 31, and to prolong the life of the needle valve body 31 remarkably.

Although a ceramic material is used for the needle valve element in the above embodiment, an insulating resin material may be used instead of this, and the point is that the insulating material is formed into a rod shape. Are all applicable to.

[0042]

As described in detail above, according to the present invention, the coating layer is closed while the high voltage is applied to the needle electrode by providing the conductive layer on the valve portion of the needle valve body. Also,
Since the high voltage of the needle-shaped electrode is conducted to the paint in the paint passage through the conductive layer, it is possible to prevent the potential difference of the high voltage from occurring in the seated portion between the valve portion of the needle valve body and the valve seat of the paint nozzle, It is possible to reliably prevent electrolytic corrosion from occurring in the valve portion of the needle valve body. Then, it is possible to effectively prevent the occurrence of cracks in the valve portion of the needle valve body, and to prolong the life of the needle valve body significantly.

Further, by providing the needle valve body with a radial electrode whose one end side is connected to the needle electrode and whose other end side reaches the outer peripheral surface of the needle valve body, the high needle voltage is high by the radial electrode. An electric current can be directly applied to the paint in the paint passage, a high voltage potential difference can be prevented from occurring at the seating part between the valve part of the needle valve body and the valve seat of the paint nozzle, and the electrolytic corrosion of the valve part of the needle valve body is possible. Can be reliably prevented.
Then, it is possible to effectively prevent the occurrence of cracks in the valve portion of the needle valve body, and to prolong the life of the needle valve body significantly.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a needle valve element and a paint nozzle according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a needle valve element in FIG.

FIG. 3 is a cross-sectional view of essential parts showing a needle valve element and a paint nozzle according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a needle valve body in FIG.

FIG. 5 is a cross-sectional view of a main part of a conventional spray gun for painting.

FIG. 6 is a cross-sectional view of essential parts showing a needle valve element and a paint nozzle according to a conventional technique.

7 is a perspective view of the needle valve element in FIG.

[Explanation of symbols]

 4 Nozzle body 5 Paint nozzle 5D Paint spray port 5E Valve seat 7 Air nozzle 12 Paint valve 21,31 Needle valve body 21A, 31A Valve part 22,32 Needle electrode 23 Conductive layer 33 Radial electrode VH High voltage

Claims (2)

[Claims] 1. A nozzle body, a paint nozzle provided on the tip side of the nozzle body, having a valve seat on the inner circumference of the tip side, and having a paint spray port ahead of the valve seat, and an insulating material. A needle valve body that is formed in a rod shape and is inserted in the axial direction of the paint nozzle and has a valve end portion on the tip side, and is inserted and fitted in the axial direction of the needle valve element so that the tip end side projects beyond the needle valve element. A coating spray gun comprising a needle-shaped electrode provided in the coating spray gun, wherein the valve portion of the needle valve body is provided with a conductive layer. 2. A nozzle body, a paint nozzle provided on the tip side of the nozzle body, having a valve seat on the inner circumference of the tip side, and having a paint spray port ahead of the valve seat, and an insulating material. A needle valve body that is formed in a rod shape and is inserted in the axial direction of the paint nozzle and has a valve end portion on the tip side, and is inserted and fitted in the axial direction of the needle valve element so that the tip end side projects beyond the needle valve element. In the spray gun for coating, which comprises a needle-shaped electrode provided on the needle valve body, one end side is connected to the needle-shaped electrode and the other end side is provided with a radial electrode reaching the outer peripheral surface of the needle valve body. A spray gun for painting that is characterized.