JPH09192545A - Rotary atomizing electrostatic applicator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary atomizing electrostatic applicator which can prevent the generation of eddies and improve the adhesive efficiency of coating material. SOLUTION: In a rotary atomizing electrostatic applicator which has a rotary cap 21, a coating nozzle 23 for supplying coating material on the front surface of the cap 21, and the first and second air ejection openings 15, 16 which respectively eject air around the cap 21 from behind the cap 21 forward and are both arranged on a concentric circle different from the axis of a spray head, an open space 4 is formed between the first and second air ejection openings 15, 16, and an arc-shaped oblong hole 5 is formed upstream from the space 4 as a vent hole. Constitution in which a discharge electrode 32 is installed near the outlet of the second air ejection opening 16 so that dehumidified air is ejected from the second air ejection opening 16 is provided, while wet air is ejected from the first air ejection opening 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary atomizing electrostatic coating device and, more particularly, to a device which improves the coating efficiency on an object to be coated.

[0002]

2. Description of the Related Art In the electrostatic coating method, a grounded object is used as an anode and a coating device is used as a cathode. A negative high voltage is applied to this to create an electrostatic field between both electrodes, and the sprayed paint particles are negatively charged. This is a method of efficiently adsorbing the paint to the object to be coated, which is the opposite pole. The reason why the object to be coated is the anode and the coating device is the cathode is based on the practical reason for safety that it is difficult to shift to spark discharge as compared with the opposite case.

Electrostatic coating devices can be roughly classified into two types. One is a rotary mist which atomizes the paint by the force of rotation and static electricity and adsorbs the paint particles to an object by electrostatic attraction. The other is a static electricity electrostatic coating device. The other is to atomize the paint by the force of compressed air or mechanical force such as high paint pressure, and to give an electric charge to the atomized paint and use electrostatic attraction. It is a gun-type device that is adsorbed to an object to be coated.

Of these, the rotary atomizing electrostatic coating device atomizes the coating material by the centrifugal force of a rotating metal cup (sometimes called a "bell cup") and a spray head such as a disk. Generally, a method of applying a high voltage for forming a charge and an electrostatic field of the paint to such a metal spray head is adopted. Therefore, the metal cup simultaneously fulfills the function of atomizing the paint and the function of maintaining an electrostatic field between the cup and the object to be coated.

FIG. 3 is a sectional view showing a schematic structure of a conventional rotary atomizing electrostatic coating apparatus (Japanese Patent Laid-Open No. 58-104656).
Reference).

In this apparatus, a metal spray head 5 is attached to the tip of a rotary shaft 52 of a motor incorporated in the apparatus.
1 is fixed. On the other hand, a paint nozzle 53 that communicates with a paint pump (not shown) is arranged, and its tip opening is located inside the annular space 54 of the spray head 51. This annular space 54 is located in the central portion on the front side of the spray head 51. It communicates with the front surface side of the spray head 51 through a paint outlet hole 55 (a large number of pores are annularly arranged) that opens.

A disk-shaped air jetting device 56 is disposed behind the spray head 51, and the air jetting device 56 includes a first air jet group consisting of a large number of air jets 57. A second air ejection port group including a large number of air ejection ports 58 is formed. These air jets 57,
58 communicates with the annular air passages 59, 60, respectively, and the annular air passages 59, 60 respectively have an air supply port 6
It is connected to an air supply pump (not shown) via 1, 62. Further, the rotary shaft 52 is connected to a high voltage generator (not shown) electrically by a cable or the like, and the rotary shaft 5
A predetermined applied voltage can be applied to the spray head 51 that is electrically connected to the nozzle 2.

In this apparatus, the paint is supplied from the paint outlet hole 55 to the front surface of the spray head 51 (hereinafter, also referred to as the inner surface of the cup) through the paint nozzle 53. This spray head 5
Since No. 1 is rotated at a high speed by a motor, the paint supplied to the inner surface of the cup is thinly spread along the inner surface of the cup by centrifugal force, and is directed toward the outer peripheral edge of the spray head 51. Is released in the form of.

Further, since air is ejected forward from the air ejection ports 57 and 58, the rotating shaft 52 is rotated by centrifugal force.
The paint particles discharged in a direction substantially perpendicular to are deflected toward the object by the jet air flow. Here, when only the first air jet group including the air jets 57 is installed, the jet speed of the air is increased in order to maintain the spread of the paint spray at an appropriate spread angle as the rotation speed of the spray head 51 increases. Although it has to be high, if the jet speed is too high, the jet air flow may bounce after colliding with the object to be coated, or the paint particles may scatter with the air flow. The paint particles discharged from the outer peripheral edge portion of the head 51 are first deflected to some extent by the air flow from the first air ejection port group, and the speed of the paint particles is somewhat decreased, so that the ejection speed of the air is increased to such a high level. Even if not, it is easily deflected by the air flow from the second air jet group,
The paint particles are controlled in a desired pattern and are carried toward the object to be coated.

On the other hand, since a high voltage is applied to the spray head 51, corona discharge is performed from its tip toward the object to be coated. The paint particles are further charged by corona discharge in addition to the charge obtained by contacting the front surface of the spray head 51, and the paint particles thus charged efficiently adhere to the object to be coated by the clonal force.

[0011]

However, in such a conventional rotary atomizing electrostatic coating apparatus, as shown in the drawing, the air flow A from the air jet 57 and the air from the air jet 58 are shown. The flow B causes a negative pressure on the disk-shaped plate 63 of the air ejecting device 56, so that ambient air flows in to generate a vortex and the paint particles released thereby are entrained, so that the coating efficiency is increased. There was a problem that it decreased. Note that, in FIG. 3, for simplification, the flow of air is shown by arrows only in the lower half of the cross section.

Further, since the paint particles thus sprinkled adhere to the disk-shaped plate 63 of the air ejecting device 56, the air ejecting device 56 itself is contaminated, and
There is a possibility that dirty paint particles adhering to the disk-shaped plate 63 may fly off and cause a coating failure on the object to be coated.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to prevent the generation of eddy currents and improve the coating efficiency of the coating material. An object of the present invention is to provide a rotary atomizing electrostatic coating device that can be used.

[0014]

The present invention for achieving the above object is specified as follows for each claim. The invention according to claim 1 is characterized in that a rotating spray head, a means for supplying paint onto the front surface of the spray head, and air around the outer peripheral edge portion of the spray head from the rear to the front of the spray head. In a rotary atomizing electrostatic coating device having a jetting air jet, and the air jets are respectively arranged on a plurality of different concentric circles with respect to the axis of the spray head, the plurality of air jets. A ventilation port through which air passes is provided on the inner diameter side of the outermost position of the air ejection port. In the invention thus specified, the paint is supplied on the front surface of the spray head, and since the spray head is rotated at a high speed,
The supplied paint is thinly stretched along the front surface of the spray head by centrifugal force, and is discharged in a mist form from the outer peripheral edge portion of the spray head. The discharged paint particles are first deflected in the direction of the coating object by the jet air flow from the air jet port on the inner diameter side, and then, sequentially by the air flow jet from the air jet port on the outer diameter side. It is deflected in the direction and carried toward the object to be coated. Here, since it is possible to pass air before and after the vent hole, the jet air flow from the air jet port forms an air flow that flows through the vent port from the rear side to the front side, thereby preventing generation of a vortex flow. Since the paint particles are directed toward the object to be coated without flowing backward, the coating efficiency of the paint can be improved.

According to a second aspect of the present invention, in the rotary atomizing electrostatic coating apparatus according to the first aspect of the invention, the air ejected from the air ejection port passes near the outer peripheral edge of the spray head. And a first air outlet arranged to
A second air ejection port arranged on the outer diameter side at a predetermined distance from the air ejection port, wherein the ventilation port is formed between the first air ejection port and the second air ejection port. It is characterized in that it is provided on the upstream side of the open space. In the invention thus specified, since the open space is formed between the first air ejection port and the second air ejection port, the air flow passing through the ventilation port is further rectified. The paint particles are prevented from being incorporated.

According to a third aspect of the present invention, in the rotary atomizing electrostatic coating apparatus according to the first or second aspect, an electric discharge is generated in the vicinity of at least one of the air ejection ports. An electrode is provided. In the invention specified in this way, the degree of freedom in designing the device increases.

According to a fourth aspect of the present invention, in the rotary atomizing electrostatic coating apparatus according to the third aspect, the dehumidified air is ejected from the air ejection port provided with the discharge electrode. Characterize. In the invention specified in this way, the amount of charge of the paint particles increases, and the paint particles adhere to the object to be coated more efficiently.

According to a fifth aspect of the present invention, in the rotary atomizing electrostatic coating apparatus according to the fourth aspect, humidified air is ejected from an air ejection port not provided with the discharge electrode. Is characterized by. In the invention specified in this way, the charge easily escapes from the surface of the coating object where the coating material tends to accumulate and the electric charge is accumulated, and the adhesion of the coating particles to the coating object is promoted, The occurrence of sparks is prevented.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing a schematic structure of a rotary atomizing electrostatic coating apparatus according to an embodiment of the present invention, FIG.
FIG. 3 is a diagram viewed from the left side of FIG. 1.

As shown in FIG. 1, in this apparatus, a cup 21 as a spray head is fixed to the tip of a hollow shaft 22 connected to a motor (not shown) incorporated in the apparatus. Reference numeral 21 denotes a bowl shape that opens toward the front and is made of an insulating material such as resin. On the other hand, a paint nozzle 23 communicating with a paint pump (not shown) is arranged inside the hollow shaft 22, and a tip opening portion thereof is located inside the cup 21 and a paint outlet hole which is opened at a central portion on the front surface side of the cup 21. 24 (a large number of pores are annularly arranged).

On the rear surface side of the cup 21, an air ring 25 is attached which surrounds the outer circumference of the hollow shaft 22 at regular intervals, and the first air ejection port 15 is arranged at the tip of the air ring 25. The ejected air is formed so as to pass near the outer peripheral edge of the cup 21. The first air ejection port 15 has a slit shape continuous in the circumferential direction, and the first air ejection port 15 communicates with an air introduction port 17 opening to the side surface side via a rectifying chamber group 18. . The air introduction port 17 communicates with an air supply pump (not shown). The rectification chamber group 18 is composed of a plurality of ring-shaped manifolds 19 and an axially extending passage 20 connecting them, and the air supplied from the air introduction port 17 is rectified and then forwards from the first air ejection port 15. It is adapted to be uniformly ejected around the outer peripheral edge portion of the cup 21.

On the outer surface of the air ring 25, a substantially cylindrical outer air nozzle 26 is fixed by screwing screw members 27 from three directions, as shown in FIG. At the tip of the outer air nozzle 26, a second air ejection port 16 is arranged on the outer diameter side at a predetermined distance from the first air ejection port 15. Similar to the first air outlet 15, the second air outlet 16 also has a slit shape that is continuous in the circumferential direction, and the second air outlet 16 has an air inlet 28 that opens to the side surface side. The air introducing port 28 communicates with an air supply pump (not shown) while communicating with the rectifying chamber group 29. The rectification chamber group 29 includes a plurality of ring-shaped manifolds 30 and an axially extending passage 31 that connects the ring-shaped manifolds 30. The air supplied from the air introduction port 28 is rectified and then forwards from the second air ejection port 16. Towards cup 2
Around the outer peripheral edge of No. 1, the first air ejection port 15 is uniformly ejected at a position separated by a predetermined distance.

The first air ejection port 15 and the second air ejection port 16 do not necessarily have the slit shape continuous in the circumferential direction as described above. For example, a plurality of pores may be circular. It may be formed in the circumferential direction. The paint particles are deflected toward the object to be coated by the jet air flows A and B from the first air jet port 15 and the second air jet port 16. Further, the flow direction of the paint particles can be changed by changing and adjusting the radial positions of the air ejection ports 15 and 16 and the air pressure to be ejected, and the film thickness distribution can be controlled.

In the present embodiment, in particular, the open space 4 is formed between the first air jet port 15 and the second air jet port 16, and the upstream side of the open space 4, that is, the outer air nozzle. In the vicinity of the inner diameter side of 26, arcuate elongated holes 5 serving as ventilation holes through which air passes are formed at equal intervals in the circumferential direction. As a result, the air flow between the ejection ports 15 and 16 is rectified to prevent the paint particles from being entrapped. In addition,
A large number of circular holes may be formed in place of the arc-shaped elongated hole 5, and the outer air nozzle 26 is fixed to the outer diameter side member having the second air ejection port 16 by the screw member 27 and the inner diameter side. It is also possible to form a vent hole through which air passes as a result of separating the members and connecting them by a rod-shaped arm member that extends radially.

A discharge electrode 32 for electrostatic coating is provided near the outlet of the second air jet port 16. The discharge electrode 32 has a ring-shaped conductive coating formed of a conductive coating material. The discharge electrode 32
Can be made of a thin plate of a conductive material instead of the conductive paint. The discharge electrode 32 is electrically connected to a high voltage generator (not shown) by a cable or the like so that an applied voltage (for example, −30 kv to −90 kv) can be applied, and the paint particles discharged from the cup 21 are removed. It can be charged by corona discharge.

Further, in the present embodiment, the discharge electrode 32
The dehumidified air is ejected from the second air ejection port 16 provided with, and the humidified air is ejected from the first air ejection port 15 not provided with the discharge electrode. Therefore, a dehumidifier (not shown) is installed between the second air ejection port 16 and the air supply pump (not shown),
The absolute water content of the air supplied toward the second air ejection port 16 can be controlled to decrease. Note that a heater may be provided instead of the dehumidifier to directly control the water so that the moisture can be removed. On the other hand, a humidifier (not shown) is installed between the first air ejection port 15 and an air supply pump (not shown) to increase and control the absolute water content of the air supplied toward the first air ejection port 15. You can The dehumidifier and the humidifier can be installed at any position, and they can be installed close to the air supply pump, but in view of the function of controlling the amount of water in the air, they should be located as close to the upstream side of the air outlet as possible. It is preferable to install.

Next, the operation of the embodiment of the present invention will be described. In this apparatus, the paint passes through a paint nozzle 23 located at the center of the rotating shaft of the cup 21 and passes through the paint outlet hole 2
4 to the front surface of the cup 21 (hereinafter, also referred to as the inner surface of the cup)
Is supplied to. Since the cup 21 is rotated at a high speed by the motor, the paint supplied to the front surface of the cup is thinly spread along the front surface of the cup by the centrifugal force, and is directed toward the outer peripheral edge portion of the cup. Is released to.

The released paint particles are indicated by the solid arrow P in FIG.
As shown in FIG. 1, first, the air is ejected from the first air ejection port 15 of the air ring 25 so as to be deflected toward the object to be coated, and then the air ejected from the second air ejection port 16 of the outer air nozzle 26 is ejected. It is further deflected in the direction of the object to be coated by the flow B, and is controlled in a desired direction and conveyed toward the object to be coated. In this way, the two-stage jet air flow A, B
As a result, the flow of the paint particles is deflected in the direction of the object to be coated, so that even if the paint particles are ejected in a mist at a high speed, the flow can be sufficiently deflected in the desired direction.

Here, since the arc-shaped elongated hole 5 is formed between the first air ejection port 15 and the second air ejection port 16, the passage of air before and after the arc-shaped elongated hole 5 is prevented. It becomes possible, and there is no possibility that a vortex will be generated and paint particles will be sprayed as in the conventional case, and the jet air flows A and B will flow from the rear of the outer air nozzle 26 through the arc-shaped elongated hole 5 to the front. Since the air flow C is formed, it is possible to prevent the paint particles from flowing backward and direct them toward the object to be coated. In addition, since the open space 4 is formed between the first air ejection port 15 and the second air ejection port 16, the air flow C that has passed through the arc-shaped elongated hole 5 is further rectified and the paint particles Prevent rolling. Therefore, it becomes possible to significantly improve the coating efficiency of the paint.

On the other hand, since a high voltage is applied to the discharge electrode 32 provided in the vicinity of the outlet of the second air ejection port 16, from the tip of the discharge electrode 32 to the object to be coated is almost constant. Corona discharge is performed toward the outside, and a discharge current is formed toward the object to be coated in the entire outer peripheral region of the cup 21. The paint particles atomized at the outer peripheral edge of the cup and jumping to the front space are charged by this corona discharge, and the paint particles thus charged efficiently adhere to the grounded object by the cloning force.

Further, the dehumidified air is discharged from the second air outlet 16 provided with the discharge electrode 32 (for example, 40% or less of the saturated water vapor amount at the ambient temperature, more specifically, the ambient temperature 2).
At 0 ° C, 0.01729 mg / cm ³ (40% or less) is ejected, so the discharge current increases in dehumidified air and the charge amount of the paint particles also increases, so the suction force due to the clonal force of the paint particles increases. However, there is an advantage that it can be more efficiently attached to the object to be coated.

In the process where the coating material is applied to the object to be coated in this way, as the electric charge accumulates on the surface of the object to be coated, the coating particles released later tend to gradually become difficult to adhere. , Humidified air from the first air outlet 15 (for example, 60 to 70 of saturated water vapor amount at ambient temperature).
%) Is ejected, when the ejected airflow A reaches the object to be coated, a water film is formed and charges easily escape from the surface of the object to be coated, and the adhesion of paint particles to the object to be coated is promoted. At the same time, the spark can be prevented from occurring.

The above-described embodiments are described for facilitating the understanding of the present invention and are not described for limiting the present invention. Each element disclosed in the embodiment is intended to include all design changes and equivalents within the technical scope of the present invention.

For example, in the above-described embodiment, the second
Although the discharge electrode 32 is provided in the vicinity of the outlet of the air jet port 16, the dehumidified air is jetted from the second air jet port 16 and the humidified air is jetted from the first air jet port 15. On the contrary, the discharge electrode is provided in the vicinity of the outlet of the first air outlet 15 and
It is also possible that the dehumidified air is ejected from the air ejection port 15 and the humidified air is ejected from the second air ejection port 16. In addition, the air jets 15 and 1
Instead of providing a discharge electrode near the outlet of 6, the cup 21
It is also possible to use a metal as a discharge electrode. That is, the discharge electrode is composed of the first air ejection port 15 and the second air ejection port 15.
The same effect as that of the above-described embodiment can be obtained regardless of whether the air jet port 16 or the cup 21 is provided, and the degree of freedom in designing the device is large. Therefore, the present invention can be configured relatively easily by fixing the outer air nozzle 26 to the conventional rotary atomizing electrostatic coating device that does not have the outer air nozzle 26 by screwing or the like.

Further, it is possible to use the discharge electrode 32 provided in the vicinity of the outlet of the second air ejection port 16 as it is, and also to make the cup 21 made of metal so that the same voltage is applied to it. . By doing so, a repulsive force is applied to the charged paint particles, and the paint particles are further prevented from flying behind the cup 21.

Further, in the above-described embodiment, the first air ejection port 15 and the second air ejection port 16 are used as the air ejection ports.
However, it is also possible to increase the number of air outlets and arrange them on three or more different concentric circles.

Needless to say, the present invention can be applied to any of various conventionally known rotary atomizing electrostatic coating devices.

[0038]

As described above, according to the present invention, the following effects can be obtained for each claim. In the invention according to claim 1, since the vent hole through which air passes is provided on the inner diameter side of the outermost air ejection port of the plurality of air ejection ports,
Air can be passed before and after the air vent, and there is no risk of vortexes being generated and paint particles being sprayed as in the past, and the air flowing from the rear through the air vent to the front by the jet air flow. Since the flow is formed, it is possible to prevent the backflow of the coating particles and direct them toward the object to be coated, and it is possible to significantly improve the coating efficiency of the coating.

According to the second aspect of the present invention, the air jet port includes a first air jet port arranged so that the jetted air passes near the outer peripheral edge portion of the spray head, and the first air jet port. A second air ejection port, which is disposed on the outer diameter side with a predetermined distance, and the ventilation port includes the first air ejection port and the second air ejection port.
Since it is provided on the upstream side of the open space formed between the air ejection port and the air ejection port, it can be configured by adding a relatively simple element to the existing device, and the first air ejection port and the second air ejection port can be formed. Since the open space 4 is formed between the outlet and
The air flow that has passed through the ventilation holes can be further rectified to prevent the paint particles from being entrapped.

According to the third aspect of the invention, since the discharge electrode is provided in the vicinity of at least one of the air ejection ports, the degree of freedom in designing the device is increased.

In the invention described in claim 4, since the dehumidified air is ejected from the air ejection port provided with the discharge electrode, the electrification amount of the paint particles is increased, and the object to be coated is more efficiently applied. In the invention according to claim 5, which can be adhered, the humidified air is ejected from the air ejection port not provided with the discharge electrode, so that the electric charge easily escapes from the surface of the object to be coated, It is possible to promote the adhesion of the particles to the article to be coated and prevent the generation of sparks.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic structure of a rotary atomizing electrostatic coating device according to an embodiment of the present invention.

FIG. 2 is a diagram viewed from the left side of FIG.

FIG. 3 is a sectional view showing a schematic structure of a conventional rotary atomizing electrostatic coating device.

[Explanation of symbols]

 4 ... Open space, 5 ... Arc-shaped long hole (vent), 15 ... 1st air jet (air jet), 16 ... 2nd air jet (air jet), 21 ... Cup (spray head), 23 ... Paint nozzle (means for supplying paint) 32 ... Discharge electrode

Claims (5)

[Claims] 1. A rotating spray head, a means for supplying paint onto the front surface of the spray head, and an air jet for jetting air around the outer peripheral edge of the spray head from the rear side to the front side of the spray head. In the rotary atomizing electrostatic coating device, which has an outlet, and the air outlet is arranged on a plurality of different concentric circles with respect to the axis of the spray head. The rotary atomizing electrostatic coating device is characterized in that a ventilation port through which air passes is provided on the inner diameter side of the air ejection port at the outer position. 2. The first air jet outlet is arranged so that jetted air passes near the outer peripheral edge of the spray head.
The air outlet includes a second air outlet that is disposed on the outer diameter side at a predetermined distance from the first air outlet, and the ventilation port includes the first air outlet and the second air outlet. The rotary atomizing electrostatic coating device according to claim 1, wherein the rotary atomizing electrostatic coating device is provided on the upstream side of an open space formed between the outlet and the outlet. 3. The rotary atomizing electrostatic coating device according to claim 1, wherein a discharge electrode is provided in the vicinity of at least one of the air ejection ports. 4. The dehumidified air is ejected from an air ejection port provided with the discharge electrode.
The rotary atomizing electrostatic coating device described in. 5. The rotary atomizing electrostatic coating device according to claim 4, wherein humidified air is ejected from an air ejection port not provided with the discharge electrode.