JP2598767B2 - Spray gun for painting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spray gun for spraying paint from a coating nozzle onto a workpiece.

[0002]

2. Description of the Related Art In general, this type of spray gun for painting (hereinafter referred to as "spray gun") includes a spray gun body, a paint nozzle provided at the tip side of the spray gun body, and a tip of the paint nozzle. Air nozzles that spray atomized air and pattern air, a paint valve that is provided on the base end side of the paint nozzle, opens and closes a needle valve body with respect to the paint nozzle, and is sprayed from the paint nozzle. In order to apply a high voltage to the paint, it is provided to be inserted into the needle valve body, and is generally constituted by a needle-like electrode whose tip side protrudes from the paint nozzle, and a paint supply pipe for supplying the paint to the paint nozzle. .

[0003] The paint supplied via a paint supply pipe to a paint nozzle provided on the tip side of the spray gun body is sprayed from a paint spray port of the paint nozzle. Further, the atomizing air supplied from the spray gun body through the atomizing air passage in the paint nozzle is ejected from an atomizing air outlet provided in the air nozzle so as to surround the paint spray port, and the atomization of the paint is performed. Promotes Further, the pattern air supplied from the spray gun body is ejected from a pattern air ejection port provided in the air nozzle, for example, in a vertically opposed manner, so that the paint spray pattern is formed into an oval or oval pattern, The coating on the substrate is evened.

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. The corona discharge region sprays the paint from the paint nozzle, charges the paint that has been patterned by the atomizing air and the pattern air, and the paint flies toward the workpiece connected to the ground, thereby improving the coating efficiency. To improve it.

Here, an electrostatic atomization type coating spray gun 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 drawing, reference numeral 1 denotes a spray gun main body, which is formed of an insulating resin material in a long cylindrical shape, and a tip end of an inner peripheral surface is provided with a nozzle main body 4 to be described later. A screw hole 1B is formed on the outer peripheral surface of the mounting hole 1A, and a cylindrical spray gun cover 2 is attached to the screw portion 1B so as to cover the spray gun body 1. 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. VH is applied.

The nozzle body mounting hole 1A of the spray gun body 1 has a nozzle body 4 to be described later, a paint nozzle 5 provided at the tip side of the nozzle body 4, and a paint nozzle 5 provided at the tip side of the paint nozzle 5. Provided air nozzles 7 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 is a paint nozzle fitting portion from the front end side. 4A, a seal insertion portion 4B, a large-diameter paint valve mounting hole 4C is formed on the base end side, and an internal thread portion 4D is formed on the distal end side of the paint nozzle fitting portion 4A.

Reference numeral 5 denotes a paint nozzle fitting portion 4A of the nozzle body 4.
The paint nozzle 5 is formed from a single material made of a resin material, and has a stepped cylindrical nozzle body 5A and a paint nozzle located at a base end side of the body 5A. A peripheral groove 5B formed so as to communicate with an atomizing air passage (not shown) of the spray gun body 1; and a tapered nozzle located closer to the base end than the peripheral groove 5B. A fitting portion 5C fitted to the paint nozzle fitting portion 4A of the main body 4, a paint spray port 5D located at the tip side of the nozzle body portion 5A and formed to have a small diameter, and the paint spray port 5D
And a valve seat 5E formed on the inner peripheral surface on the proximal end side of the nozzle body 4A, and a valve seat 5E formed on the outer peripheral surface on the proximal end side of the nozzle main body 5A.
A male thread portion 5F screwed with the female screw portion 4D; a tapered surface 5G formed in an annular shape on the distal end side of the nozzle main body portion 5A;
And a plurality of atomizing air flow passages 5H, 5H,... Which are formed so as to communicate with the circumferential groove portion 5B.
A needle valve 13 described later is inserted into the inner peripheral surface of the paint nozzle 5 in the axial direction, and a paint passage 6 is formed between the needle valve 13 and the needle valve 13. The paint is supplied to the paint spray port 5D. I do.

Reference numeral 7 denotes an air nozzle provided on the tip side of the paint nozzle 5, and the air nozzle 7 has a paint spray port 5 inside.
D, a tapered concave portion 7A positioned on the tapered surface 5G, a front wall portion 7B formed so as to cover the front side of the concave portion 7A, and an upper and lower position of the front wall portion 7B. Horn portions 7C, 7C formed so as to protrude toward the distal end side, and a retainer ring 10 which is formed over the entire outer peripheral surface and which will be described later via an annular ring 8 and a locking ring 9. A locking step 7D locked to the mating projection 10A, pattern air flow passages 7E, 7E formed in the horn portions 7C from the base end side and communicating with a pattern air chamber 11 described later; Pattern air jets 7F, 7F, which open diagonally inward from the horn 7C,
, And a plurality of atomizing air jet ports 7G, 7G,... Formed in 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. An engagement protrusion 10A for engaging the air nozzle 7 via an annular ring 8 is formed on the inner peripheral side of the distal end of the retainer ring 10, and a base end thereof is provided. On the inner peripheral surface, a female screw portion 10B screwed to the screw portion 1B of the spray gun main body 1 is formed. The paint nozzle 5 is fixed to the internal thread 4D of the nozzle body 4 by screwing a screw 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 main body 1 by the retainer ring 10, the space defined by the nozzle main body 4, the paint nozzle 5, the air nozzle 7 and the retainer ring 10 is an annular pattern air chamber 11. ing.

Reference numeral 12 denotes a paint valve provided on the base end side of the nozzle body 4. The paint valve 12 includes a cylinder 12 A formed in a paint valve mounting hole 4 C of the nozzle body 4 and a cylinder 12 A. A piston 12B slidably provided on the nozzle body 4 and defining two air chambers A and B, a closing part 12C provided to close the opening of the paint valve mounting hole 4C of the nozzle body 4, and a closing part 12C. The cylinder 12A is substantially constituted by a conductive spring 12D formed of a conductive material for electrically connecting the portion 12C and the piston 12B, and a V-packing 12E inserted into the seal insertion portion 4B.
In the (paint valve mounting hole 4C), 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 are formed.

The paint valve 12 is provided with compressed air T.ON.
, T.OFF, which is switched by the supply / discharge of 2 ports and 2 positions, to supply the compressed air T.ON into the air chamber A from the T.ON supply / discharge port 12F, and to supply the compressed air T.OFF. By exhausting air from the T.OFF supply / discharge port 12G, the valve is switched to the valve open position. On the other hand, compressed air T.OFF is changed to T.OFF
The compressed air T.ON is supplied from 2G into the air chamber B,
By exhausting air from the supply / discharge port 12F, the paint valve 12 switches to the valve closing position.

Numeral 13 denotes a needle valve body having a distal end extending to the paint spray port 5D of the paint nozzle 5 and a proximal end fixed to a piston 12B. The needle valve body 13 is provided to minimize charging energy. For example, the needle valve body 13A is formed in a rod shape from an insulating ceramic material such as alumina or zirconia, and has a tapered valve portion 13A at the tip end. Opens and closes the paint nozzle 5. When the valve is closed, the valve portion 13 of the needle valve body 13 is closed.
A electrically insulates the paint passage 6 from the paint spray port 5D.

Reference numeral 14 denotes a needle electrode inserted in the needle valve body 13 in the axial direction. The base end of the needle electrode 14 is a plug 1
5, the distal end side protrudes from the paint spray port 5 </ b> D 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 provided between the base end of the paint nozzle 5 and the paint valve 12.
Of the paint nozzle 5 and the needle valve element 1 at the position of the annular chamber C.
3 and a paint passage 6 formed therebetween.

Reference numeral 18 denotes a positioning plug which is inserted from the radial direction of the spray gun main body 1 to position the nozzle main body 4, and 19 electrically connects the closing portion 12C of the paint valve 12 and the high voltage generator 3. Plug for connection.

In the prior art coating spray gun constructed as described above, in the preliminary coating process, the coating material is supplied from a color changing valve device provided outside, so that the coating material is supplied to the coating material supply passage 16. Is filled into the annular chamber C, the paint passage 6 and the paint discharge passage 17 through the opening. Then, in the painting process, the compressed air T.ON is supplied to the paint valve 12 into the air chamber A, so that the needle valve 13
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 atomizing air outlet 7F of the air nozzle 7 promotes atomization of the atomized paint, and the pattern air ejected from each pattern air outlet 7F makes the spray pattern of the paint uniform. To paint the object to be coated.

At this time, a high voltage portion VH is applied to the needle electrode 14 from the high voltage generator 3 to form a corona discharge region on the tip side of the needle electrode 14, and the atomized paint is applied. The coating is performed by causing the paint to fly toward the workpiece short-circuited to the ground when charged.

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

[0021]

In the above-described prior art 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. With VH applied, valve seat 5 of paint nozzle 5 between paint passage 6 and paint spray port 5D.
The spraying of the paint is stopped by seating the valve portion 13A of the needle valve body 13 on E and closing the paint spray port 5D. At this time, as shown in FIG. 6, the remaining paints TA and TB are present in the paint passage 6 and the paint spray port 5D, respectively, and a paint pigment (for example, metallic paint) In this case, aluminum powder) is sandwiched. Then, the remaining paint T in the paint passage 6
A is connected to the ground through an external color changing valve device, and the remaining paint TB in 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. , The remaining paint T
A and TB are electrically insulated. 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 current is applied between the remaining paints TA and TB to cause a bridge phenomenon on the surface of the seating portion. As a result, electrolytic corrosion occurs on the surface of the valve portion 13A of the needle valve body 13 formed of the ceramic material.

When the electrolytic corrosion progresses, a crack K is generated on the surface of the valve portion 13A as shown in FIG.
Due to this crack K, there is a problem that the sealing performance of the seating portion between the valve portion 13A and the valve seat 5E is reduced, paint leakage occurs, and the life of the needle valve body 13 is shortened.

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

[0024]

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

The second aspect of the present invention is characterized in that one end of the needle valve body is connected to the needle electrode,
The other end is provided with a radial electrode reaching the outer peripheral surface of the needle valve body.

[0026]

According to the above construction, the conductive layer or the radial electrode is
When the valve is closed, the residual paint in the paint spray port charged to the high voltage on the needle electrode side and the residual paint that is grounded on the paint side are electrically connected, and a potential difference is generated between the valve and the seat of the valve seat. It can be prevented from occurring.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment 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 technology are denoted by the same reference numerals, and description thereof will be omitted.

First, a first embodiment will be described with reference to FIGS.

In the figure, reference numeral 21 denotes a needle valve element according to the present embodiment.
It is formed in a cylindrical shape by a ceramic material almost in the same way as
A valve portion 21A is formed on the distal end side, and the base end side is fixed to the piston 12B of the paint valve 12.

Reference numeral 22 denotes a needle-like electrode which is inserted into the needle valve body 21 and is provided so as to protrude from the valve portion 21A of the needle valve body 21 toward the tip end. Similarly 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 denotes a valve portion 21A of the needle valve body 21.
The conductive layer 23 is formed of, for example, a conductive ceramic material, and is formed by coating with a thickness of about 5 μm.

The operation of the spray gun for coating according to the present embodiment thus configured is not different from that of the prior art described above.

However, according to the present embodiment, the needle valve 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, so that the paint spray port Close 5D to stop spraying paint. At this time, as in the prior art, the remaining paint TA exists in the paint passage 6 and the remaining paint TB exists in the paint spray port 5D. The remaining paint TA is electrically connected to a color changing valve device connected to an external ground, and the remaining paint TB is charged to a high voltage VH by the needle electrode 22. However,
The remaining paints TA and TB are electrically connected by the conductive layer 23 formed on the valve portion 21A of the needle valve body 21 even when the valve is in a closed state, and the high voltage VH of the needle electrode 22 is reduced by the remaining paints TB and
It is connected to a color change valve device (earth) via the conductive layer 23, the remaining 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 electric resistance, and the voltage drops between the paint passages up to the color changing valve device.
It does not cause a short circuit phenomenon and destroy the high voltage generator 3 and the like.

Further, since the conductive layer 23 is formed of conductive ceramic, it has excellent wear resistance.

Thus, the spray gun for coating according to the present embodiment has a structure 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 when the spray valve 5D is closed, no potential difference is generated 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. The occurrence of electrolytic corrosion on the surface of the conductive layer 23 can be reliably prevented.
Further, cracks can be effectively prevented, and the life of the needle valve 21 can be significantly extended.

Next, a second embodiment will be described with reference to FIGS. 3 and 4. The feature of this embodiment is that one end of the needle valve is connected to the needle electrode and the other end is connected to the needle valve. That is, a radial electrode extending to the outer peripheral surface is provided. In this embodiment, the same components as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the drawing, reference numeral 31 denotes a needle valve element of the present embodiment. The needle valve element 31 has substantially the same construction as the needle valve element 31 of the first embodiment, and has a tapered valve at the tip end. A part 31A is formed.

Reference numeral 32 denotes a needle electrode which is inserted into the needle valve body 31 and is provided so as to protrude from the valve portion 31A of the needle valve body 31 toward the tip end. Similarly to the needle-shaped electrode 22 of the embodiment, the high-voltage VH supplied from the high-voltage generator 3
2, a corona discharge region is formed.

Reference numerals 33, 33 denote a pair of radial electrodes provided in the needle valve element 31, and each of the radial electrodes 33
Is provided such that one end thereof is connected to the needle electrode 32 and the other end thereof reaches the outer peripheral surface of the needle valve 31.

In the spray gun for coating according to the present embodiment having the above-described structure, the radial electrodes 33, 33 are formed on the valve portion 31A of the needle valve body 31, so that the high voltage VH is applied to the needle electrode 32 when the spraying is stopped. Is applied from the needle-shaped electrode 32 through the radial electrodes 33, 33.
Since the high voltage VH is applied directly to the remaining paint TA in the interior,
When the paint spray port 5D is closed, the potential difference VH does not occur at the seating portion between the valve seat 5E of the paint nozzle 5 and the valve portion 31A of the needle valve body 31, so that the valve portion 3 of the needle valve body 31
The occurrence of electrolytic corrosion in 1A can be reliably prevented. Therefore, cracks can be effectively prevented from being generated on the surface of the valve portion 31A of the needle valve element 31, and the life of the needle valve element 31 can be significantly extended.

In the above embodiment, the case where a ceramic material is used as the needle valve body is exemplified. However, the present invention may use an insulating resin material instead. Are all applicable.

[0042]

As described above in detail, according to the present invention, by providing a conductive layer on the valve portion of the needle valve body, the paint spray port is closed while a high voltage is applied to the needle electrode. 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 a potential difference of a high voltage from being generated at a seating portion between the valve portion of the needle valve body and the valve seat of the paint nozzle, Electrolytic corrosion can be reliably prevented from occurring in the valve portion of the needle valve body. Further, it is possible to effectively prevent cracks from being generated in the valve portion of the needle valve body, and to significantly extend the life of the needle valve body.

Also, by providing the needle valve body with one end connected to the needle-shaped electrode and the other end provided with a radial electrode reaching the outer peripheral surface of the needle valve body, the high voltage of the needle-shaped voltage can be reduced by the radial electrode. Electric current can flow directly into the paint in the paint passage, preventing the potential difference of high voltage from occurring at the seating portion between the valve part of the needle valve body and the valve seat of the paint nozzle, and electrolytic corrosion on the valve part of the needle valve body Is reliably prevented from occurring.
Further, it is possible to effectively prevent cracks from being generated in the valve portion of the needle valve body, and to significantly extend the life of the needle valve body.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of 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 body in FIG.

FIG. 3 is a sectional view showing a main part of a needle valve body 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 sectional view of a main part of a spray gun for painting according to the prior art.

FIG. 6 is a sectional view of a main part showing a needle valve element and a paint nozzle according to a conventional technique.

FIG. 7 is a perspective view of the needle valve body in FIG. 6;

[Explanation of symbols]

 Reference Signs List 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)

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