JPH1052656A - Electrostatic coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic coating device which is capable of uniformly directing fine coating particles atomized by a spray head toward a matter to be coated and improving the coating efficiency of a coating material. SOLUTION: This electrostatic coating device atomizes a coating material through a rotating spray head 4, and electrically charges coating material particles atomized through the spray head 4 and deflects the coating material particles toward a matter to be coated with the help of an air current to transport and coat the matter. In this case, an air jet orifice 16 which spews out air is positioned adequately far behind the rotating spray head 4 in the rotating shaft direction, so that the air jet orifice 16 is concentrically arranged, in circular form, with the rotating shaft of the rotating spray head 4. In addition, an almost cylindrical guide face 17 extending from a position near the air jet orifice 16 to a position near the outer peripheral edge part of the spray head 4 is provided on the peripheral side located inwardly from the air jet orifice 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic coating apparatus and, more particularly, to an improvement in a mechanism for forming an air flow for deflecting paint particles atomized by a spray head toward an object to be coated.

[0002]

2. Description of the Related Art In an 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. In this method, the paint is efficiently adsorbed on 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 practical reasons for safety that it is difficult to shift to spark discharge as compared to the opposite case.

[0003] Electrostatic coating apparatuses can be broadly classified into two types. One is a rotary mist that atomizes paint by the force of rotation and static electricity, and attracts paint particles to a substrate by electrostatic attraction. The other is an atomizing type electrostatic coating device. The other is to atomize paint by the force of compressed air or mechanical force such as high paint pressure, and to give a charge to the atomized paint, and to generate electrostatic attraction. This is a gun-type device that adsorbs to the object to be coated.

[0004] A rotary atomizing electrostatic coating apparatus is a metal cup (sometimes called a "bell") that rotates at a high speed.
The paint is supplied to the inner surface side of the spray head such as a disc, and the paint is atomized by the centrifugal force of the spray head, and a high voltage for forming a charge and an electrostatic field of the paint on such a metal spray head. Is generally applied. Further, in such a rotary atomizing type electrostatic coating apparatus, particularly in a bell type coating apparatus, the paint atomized by the spray head as described above is sprayed by a high-speed air flow blown from the back side of the spray head called shaping air. It is directed to the direction of the object located in front of the head, and imparts momentum reaching the vicinity of the object, thereby having a relatively uniform atomization ability and high coating efficiency. Can be demonstrated. Such a structure is described in detail in, for example, JP-A-6-218301.

FIG. 3 is a sectional view schematically showing a tip structure of an example of a conventional rotary atomizing electrostatic coating apparatus.

In this device, a metal bell cup 22 is fixed to the tip of a hollow rotary shaft 21 of a motor incorporated in the device, while a hollow paint pump (not shown) is mounted inside the hollow rotary shaft 21. A paint nozzle 23 communicating with the paint nozzle 23 is disposed, and the tip end of the paint nozzle 23 is located inside the cup 22. ). An air ring 25 that surrounds the outer periphery of the hollow rotary shaft 21 at regular intervals is attached to the cup 22 in the immediate vicinity of the back side thereof. A ring-shaped manifold is formed which connects a number of air outlets 26 opening to the air and an air inlet 27 opening to the side.
The air inlet 27 communicates with an air supply pump (not shown). The hollow rotary shaft 21 is electrically connected to a high-voltage generator (not shown) by a cable or the like, so that a predetermined applied voltage can be applied to the cup 2 that is electrically connected to the hollow rotary shaft 21.

In this apparatus, the paint is supplied to the inner surface of the cup 23 from a paint outlet hole 24 through a paint nozzle 23 positioned at the center of the rotation axis of the cup. This cup 2
3 is a high-speed rotation by the motor, the paint supplied to the inner surface of the cup is stretched thinly along the inner surface of the cup by centrifugal force, and directed to the outer edge of the cup, from the outer edge of the cup thin film or many It is atomized into fine particles by being released in the form of a thread. The finely divided paint is supplied to the air outlet 26 of the air ring 25.
The path can be bent in the direction of the object to be coated by the shaping air which is jetted in the direction of the rotation axis of the cup. On the other hand, since a high voltage is applied to the metal cup, corona discharge is performed from the tip of the cup toward the object to be coated. Therefore, the paint liquid before atomization is charged by contact charging,
Further, the atomized paint particles are also charged by ions obtained by corona discharge, and the thus-charged paint particles are efficiently conveyed to the object to be coated by the Coulomb force.

[0008]

In such a conventional rotary atomizing electrostatic coating apparatus, the paint particles emitted from the rotating spray head are arranged at a position very close to the outer periphery of the spray head. Due to the structure in which it is deflected in the direction of the object to be coated by shaping air ejected from the air outlet, the amount of deflection greatly differs due to a slight difference in the particle size of the atomized paint particles, and the relatively large paint particles There is a problem in that the protrusion penetrates outside the flow of the shaping air, and the momentum in the direction of the object to be coated is not sufficiently given, so that a so-called "umbrella" is formed.

In order to solve such a problem, if the blowing pressure of the shaping air is increased, relatively large paint particles can be directed toward the object to be coated.
The relatively small paint particles are blown off by the air flow that spreads outward along the surface of the workpiece, which is formed by the collision of the shaping air with the surface of the workpiece, thereby increasing the coating efficiency. The result is that you cannot do it. In addition, when the rotation speed of the spray head is increased, finer paint particles are released, so the number of umbrellas decreases, but the finer paint particles are more susceptible to the effect of air flow,
Even when the air flow along the surface of the object to be coated is weak as described above, the coating efficiency is lowered.

Accordingly, it is an object of the present invention to provide an improved rotary atomizing electrostatic coating apparatus. The present invention also provides
Irrespective of the size of the atomized paint particles at the spray head, all particles can be imparted with an inertia force that is almost evenly directed toward the workpiece, and the paint particles are held from the vicinity of the workpiece surface to other areas. It is an object of the present invention to provide a rotary atomizing electrostatic coating apparatus capable of reducing the amount of transport and improving coating efficiency of paint.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the problems in the conventional apparatus as described above, and as a result, the paint particles atomized in the spray head were moved in the direction of the object to be coated. Focusing on the shape of the shaping air flow that changes to a relatively slow and wide shape at the outer edge of the spray head from which the paint particles are released, Inertia force can be evenly applied to the workpiece direction, and the velocity difference between the shaping air and the surrounding stationary air is small. It is found that the paint particles that move toward the surface of the object to be coated are reduced, and the flow velocity of the air flow near the surface of the object to be coated is also low, so that the amount of paint particles carried away from the surface of the object to be coated can be reduced and the coating efficiency can be increased. Which has led to the present invention.

Further, in order to form a relatively slow and thick shaping air at the outer peripheral edge of such a spray head, the present inventors specifically require that the shaping air outlet be located at a position where the outlet of the shaping air is disposed. Paying attention, this is offset sufficiently rearward from the position of the outer peripheral edge of the spray head, and further from the outlet to the vicinity of the outer peripheral edge of the spray head, substantially located on the inner peripheral side from the outlet. It has been found that when a cylindrical guide surface is provided and the air flow blown from the outlet is caused to flow along the guide surface, the desired shaping air as described above is formed, and the present invention has been achieved. is there.

That is, the present invention which solves the above-mentioned problems,
(1) Paint is atomized by a rotating spray head, the paint particles to be atomized at the spray head are charged, and the paint particles are deflected in the direction of the object to be coated by an air stream, and are conveyed to perform electrostatic coating. A coating apparatus, wherein the air flow is formed as a relatively slow, thick, steady flow at a position passing near the outer peripheral edge of the spray head.

The present invention also provides (2) atomizing a paint by a rotating spray head, charging the paint particles to be atomized at the spray head, deflecting the paint fine particles toward an object to be coated by an air flow, An electrostatic coating apparatus that conveys and performs coating, wherein an air outlet that ejects the air flow is located sufficiently behind in the direction of the rotation axis of the rotating spray head, and the rotating spray head is It is arranged substantially annularly coaxially with the rotation axis, and further provided on the inner peripheral side of the air outlet, a substantially cylindrical guide surface extending from near the air outlet to near the outer peripheral edge of the spray head. It is an electrostatic coating device characterized by the above.

The present invention further provides (3) the electrostatic coating apparatus as described in (2) above, wherein the guide surface is constituted by a smooth continuous surface.

According to the present invention, (4) the guide surface may be 4 °.
An electrostatic coating apparatus according to the above (2) or (3), wherein the electrostatic coating apparatus does not have the above-mentioned projecting step shape.

The present invention also provides (5) a tip of the guide surface located rearward of an outer edge portion of the spray head, and in a cross section along the rotation axis, a cross section line of the guide surface on the spray head side. Any one of (2) to (4) above, wherein an extension line from an end and a cross-sectional line of the back surface of the spray head reaching the outer peripheral edge of the spray head intersect at an angle of less than 4 °. 1 shows an electrostatic coating apparatus according to the present invention.

(6) The electrostatic coating apparatus according to any one of the above (2) to (5), wherein (6) the outer diameter of the tip of the guide surface is smaller than the diameter of the spray head. It shows.

The present invention is further characterized in that (7) the offset amount of the air outlet from the tip of the guide surface in the rotation axis direction is larger than 30 mm. It shows the electrostatic coating device described in any one of the above.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments.

The rotary atomizing electrostatic coating apparatus according to the present invention is basically an air called shaping air for deflecting paint particles emitted from an outer peripheral portion of a spray head toward an object to be coated. The formation of the flow is different from that in the conventional rotary atomizing electrostatic coating apparatus, and in other respects, there is essentially no difference from the conventional one. Therefore, the present invention can be applied to any of the various types of conventionally known rotary atomizing electrostatic coating apparatuses by making improvements as described below.

In the rotary atomizing electrostatic coating apparatus according to the present invention, shaping air for turning the atomized paint particles toward the object to be coated at the spray head is applied to the outside of the spray head from which the paint particles are discharged. A relatively slow and thick steady airflow is formed at the periphery.

In order to form such shaping air, there is no particular limitation. However, the air outlet for ejecting the shaping air is positioned sufficiently behind the rotary spray head in the direction of the rotation axis thereof. A substantially cylindrical guide that is arranged substantially coaxially with the rotation axis of the rotary spray head in an annular manner, and further on the inner peripheral side than the air outlet, from the vicinity of the air outlet to the vicinity of the outer peripheral edge of the spray head. It is desirable to adopt a configuration in which a surface is provided.

It is desired that the front end of the guide surface, that is, the end on the spray head side be located behind the outer edge of the spray head, but the position of the air outlet is determined by the position of the front end of the guide surface. At least 30 mm rearward in the rotation axis direction of the spray head, more preferably at least 60
mm behind. In this manner, the position of the air outlet is sufficiently offset from the position of the guide surface tip or the position of the outer peripheral edge of the rotary spray head, and the shaping air is blown from the rear as in the case of the conventional apparatus. However, not only is the shaping air too thin to bend large paint particles in the direction of the object to be coated, but also small particles collect around the center of the rotation axis, resulting in the disappearance of the umbrella. Because you can't. Since the upper limit of the offset amount depends on the flow rate of the air to be jetted out, it cannot be specified unconditionally. However, from the viewpoint of preventing the device itself from becoming longer, for example, a guide may be used. It is appropriate that the position is about 120 mm rearward from the position where the front end of the surface exists.

When the air outlet of the shaping air is offset sufficiently rearward from the position of the outer peripheral edge of the rotary spray head in this way, the flow velocity of the shaping air near the rotary spray head naturally decreases, but the thick air flow is reduced. Obtainable. The reason that large particles can be bent in spite of such a slow air flow is that the atomized paint particles emitted from the outer peripheral edge of the spray head rapidly increase the velocity while flying in almost still air. This is considered to be caused by dropping and giving an inertial force in the direction of the object to be coated in the thick air flow as described above. On the other hand, the smaller paint particles are also bent in the direction of the substrate by this slow airflow, so that all the particles are directed almost uniformly in the direction of the substrate.

The shape of the air outlet of the shaping air is not particularly limited as long as the air jetted from the outlet flows along a guide surface as described later. It is appropriate to have a structure that blows out substantially flush with or substantially parallel to the guide surface.

Further, as for the position of the air outlet of the shaping air in the radial direction of the rotary spray head, the release pattern of paint substantially radially released from the outer peripheral edge of the rotary spray head is regulated. It is not particularly limited as long as it forms shaping air that can be a desired spray pattern directed in the direction,
It may be any position on the outer peripheral side from the outer peripheral edge of the spray head, almost the same position as the outer peripheral edge, or any position on the inner peripheral side from the outer peripheral edge, but is usually slightly smaller than the outer peripheral edge of the spray head. The position is on the outer peripheral side. Further, in the present invention, the shaping air ejected from the air outlet is caused to flow along a guide surface as described below until reaching the outer peripheral edge of the spray head, and the desired shaping air is rotated around the rotation axis of the spray head. Since the air flow is formed into a thick circular cross section, the shape of the spray head is adjusted so that the shaping air ejected from the air outlet reaches the outer peripheral edge of the spray head without separating from the guide surface. It is desirable to arrange the air outlet so that the angle between the straight line connecting the outer peripheral edge and the air outlet and the rotation axis of the spray head does not become so large, particularly desirably less than 4 °. .

The shaping air outlet mechanism is provided behind the air outlet as described above, and has an air reservoir having a cross-sectional area that is sufficiently larger than the opening area of the outlet, specifically, for example, twice or more in cross section. Is effective in simply forming a uniform air flow. However, when such a shape cannot be obtained due to the structure, a size-regulating plate or a similar structure may be provided inside the air pocket to substitute the same.

The air flow rate of the shaping air ejected from the air outlet depends on the offset amount (distance in the rotation axis) of the air outlet from the spray head, the radial distance from the rotation axis, and the like. , Approximately 100-80
A flow rate of 0 L / min is required, and it is necessary to have a means for varying the flow rate because it is necessary to form a paint spray pattern by this air flow.

In the electrostatic coating apparatus according to the present invention, the air outlet of the shaping air is offset sufficiently rearward in the direction of the rotation axis from the position of the outer peripheral edge of the spray head. On the inner peripheral side than the air outlet,
A substantially cylindrical guide surface is provided from the vicinity of the air outlet to the vicinity of the outer periphery of the spray head. The guide surface is provided with a housing surrounding the tip portion of the electrostatic coating device from the vicinity of the air outlet to the vicinity of the outer periphery of the spray head, for example, as in an embodiment described later, and is formed by the outer surface thereof. Is possible, but is of course not limited to such an embodiment. For example, more simply, a thin plate is processed into a substantially cylindrical shape, and the thin plate is fixed to an arbitrary stationary portion of the electrostatic coating device located on the inner peripheral side from the air outlet, and the spray head is located near the air outlet. An embodiment in which a guide surface reaching the vicinity of the peripheral portion is formed can also be adopted.

It should be noted that the guide surface must be formed of a smooth continuous surface, and even if a portion where the angle changes unavoidably is provided, the angle of the portion should not exceed about 4 °. It is desirable to do. In particular, the separation angle must be avoided. If the guide surface is not formed by such a smooth continuous surface, the shaping air ejected from the air outlet does not flow along the guide surface.

In the cross section along the rotation axis, an extension line of the cross section line of the guide surface from the spray head side end and a cross section line of the back surface of the spray head reaching the outer periphery of the spray head are as follows:
It is desirable that the intersection angle is less than 4 °.

Further, in order for the shaping air flowing along the guide surface to stably change the paint particles emitted from the outer peripheral edge of the spray head toward the object to be coated, the tip of the guide surface is required. Is preferably smaller than the diameter of the spray head.

In the electrostatic coating apparatus according to the present invention,
As a method for charging the paint particles, it is effective to provide a discharge portion in or on the boundary surface of the air flow as the shaping air as described above to increase the discharge amount. It is effective to form a discharge electrode made of an insulating material and formed of a conductive material that rotates with the spray head on the rear surface, that is, the portion where the shaping air collides, and discharge from the outer peripheral edge of the spray head. is there. However, the effect of the present invention is not particularly impaired even if a general type made of metal as the whole is used as the spray head, and the charging efficiency is slightly reduced.

The main body is made of an insulating material.
The structure of the spray head having a discharge electrode on the rear surface is described in detail in Japanese Patent Application No. 7-291394 previously filed by the present inventors, but will be briefly described below. .

The insulating material constituting the spray head is not particularly limited as long as it has sufficient resistance to the coating composition to be used, in particular, a solvent and the like and is insulating. Although it depends on the type of the coating composition to be formed, for example, various synthetic resins such as polyetheretherketone can be preferably used.

The discharge electrode provided on the rear surface of the spray head may be formed by directly contacting the rear surface of the spray head, or may be formed at a predetermined distance from the rear surface of the spray head, for example,
Although it is possible to form them separately at a distance of about 1 to 10 mm, it is desirable to form them by directly contacting the rear surface of the spray head. For example, the discharge electrode can be formed by a conductive paint, a metal deposited film, a conductive metal oxide deposited film, an electroless plated film, a sputtered film, a CVD film, or the like. Of course, a mode in which a thin metal plate is attached can also be adopted. Among them, in particular, when a conductive paint is used, an electrode having a predetermined shape can be formed inexpensively and easily in workability. In the conductive coating composition,
As the conductive filler, existing ones such as carbon particles, silver particles, and conductive ceramic whiskers may be used, and as the resin component, for example, an epoxy-based or fluorine-based one having excellent solvent resistance is preferable. However, since it is not a portion to which a solvent such as a thinner is directly applied, extremely high solvent resistance is not required, and various known materials can be used.

Such a discharge electrode may be formed on the entire rear surface of the spray head. However, it is preferable that the discharge electrode be formed in a plurality of specific directions from the center of the spray head, for example, two to six. Locally extended form only in the degree direction,
To put it plainly, it is desirable to have a substantially star shape.

In the electrostatic coating apparatus according to the present invention, for the components other than those described above, any of the various aspects of the conventionally known electrostatic coating apparatus can be used. As a motor for rotating the electrodes, any of an electric motor by electric power, an air motor by air pressure, etc. can be used, and any high voltage generator capable of generating an appropriate voltage according to such a driving method can be used. An apparatus can be used.
In addition, as the paint supply system, a pump having an appropriate capacity and discharge amount, such as a gear pump, depending on the type of paint to be applied, such as an aqueous system, an organic solvent system, a high solid type, a two-liquid high solid type, or the like. It is possible to use a driving device for controlling the pump rotation speed remotely, a mixing device such as a static mixer, or the like, as appropriate. In addition, various known modes are used for the use of a spark guard system, a control device for monitoring the device and performing a sudden stop when an abnormality occurs, a safety device such as a constant voltage device, a fire extinguishing device, and other various insulating and explosion-proof components. I can do it. Also, as the installation method, it is possible to adopt any method such as a fixed type and a reciprocating type.

[0040]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

FIG. 1 is a sectional view schematically showing the structure of the tip portion in an embodiment of the electrostatic coating apparatus according to the present invention.

In the apparatus of the embodiment shown in FIG. 1, an air motor 2 is incorporated inside the apparatus main body case 1.
The hollow rotary shaft 3 of the air motor is rotated at high speed by air supplied from an air supply source (not shown). A resin cup 4 is fixed to the tip of the rotating shaft.
On the other hand, a paint nozzle 5 communicating with a paint pump (not shown) is arranged inside the hollow rotary shaft 3, and its tip opening is located inside the resin cup 4, and the paint is opened at a central portion on the front side of the cup 4. It communicates with the outlet hole 6 (a number of small holes are arranged in a ring). A substantially star-shaped conductive film (not shown) having a plurality of tips extended to the outer peripheral edge of the cup is formed on the rear surface of the resin cup 4 by a conductive paint. This conductive coating is
Is electrically connected to the rotation shaft 3 on the center side. Since the rotating shaft is electrically connected to a high-voltage generator (not shown) by a cable or the like, an applied voltage can be applied to a discharge electrode formed of a conductive film that is electrically connected to the rotating shaft. Discharge occurs from the outer periphery of the head.

The shaping air supply mechanism in this apparatus has the following configuration. That is, the outer periphery of the main body case 1 of this device is provided with two concave portions at a position roughly located on the side surface of the air motor 2, and further includes a front end portion further forward than the front concave portion of the two concave portions. The outer peripheral surfaces of the portions immediately behind the rear recess are male screw portions 7 and 8, respectively.

A female screw portion 10 formed on the inner periphery of the rear end of a substantially cylindrical air buffer case 9 surrounding the outer periphery of the front end side of the main body case 1 is screwed with the male screw portion 8 on the rear side. Case 1
A first air reservoir 11 and a second air reservoir 12 are formed by two recesses on the outer periphery of the main body case 1 and the inner surface of the air buffer case 9. Furthermore, a thin gap (slit) is formed between the first air reservoir 11 and the second air reservoir 12 by the convex portion on the outer peripheral surface of the main body case 1 and the convex portion on the inner peripheral surface of the air buffer case 9 opposed thereto. This gap functions as a rectifying unit 13 that connects the first air reservoir 11 and the second air reservoir 12.

On the other hand, the male screw portion 7 on the front side of the main body case 1
The female screw part 15 formed on the inner periphery of the rear end of the substantially cylindrical tip casing 14 is screwed into the casing, and the tip casing 14 is connected to the front of the main body case 1. This tip casing 1
The rear end of the air buffer case 9 is located within the front end of the air buffer case 9, and the gap between the rear end outer peripheral surface of the front casing and the front inner peripheral surface of the air buffer case causes the second air reservoir 12 to be closed. An air outlet 16 communicating with the air outlet is formed. On the other hand, the distal end of the distal casing 14 is located near the rear surface of the outer peripheral edge of the cup 4, whereby the outer peripheral surface of the distal casing 14 extends from near the air outlet to near the outer peripheral edge of the spray head. , And a guide surface 17 for shaping air. In this embodiment, since the guide surface 17 and the inner surface of the air outlet 16 are both formed by the outer peripheral surface of the distal end casing 14, the guide surface and the air outlet are flush. In this embodiment, the air outlet 16 is located on the radially outer side from the outer peripheral edge of the cup 4, and the guide surface 17, that is, the outer peripheral surface of the distal casing 14 is gradually reduced toward the distal side. Although it is a tapered surface having a diameter, it has a smooth continuous surface without any steps or the like as shown in the figure. In this embodiment,
A straight line connecting the outer peripheral edge of the cup 4 and the air outlet 16 substantially coincides with the guide surface 17 and, in a cross section along the rotation axis, from the cup-side end of the sectional line of the guide surface 17 Is an angle of less than 4 °.
It intersects at 5 °.

The inner peripheral surface of the distal casing 14 has a cross-sectional shape separated from the rotating shaft 3 and the cup 4 with an appropriate gap so as not to hinder the rotation of the rotating shaft 3 and the cup 4.

In this embodiment, the guide surface 17
The offset amount of the air outlet 16 in the direction of the rotation axis from the tip end is 40 mm, which is a distance of 30 mm or more.

In this apparatus, the paint is supplied from the paint outlet hole 6 to the front surface of the cup 4 (the inner surface of the cup) through the paint nozzle 5 positioned at the center of the rotation axis of the cup 4. Since the cup 4 is rotated at a high speed by the air motor 2, the paint supplied to the front surface of the cup is thinly stretched along the front surface of the cup by centrifugal force, directed to the outer peripheral edge of the cup, and sprayed from the outer peripheral edge of the cup. It is released in the form.

On the other hand, the shaping air is guided at a high pressure from an air supply source (not shown) to a first air reservoir 11 communicating via a shaping air flow path 18 formed inside the main body case 1, and further passes through a rectifying unit 13. Then, the air reaches the second air reservoir 12, and is then blown into the atmosphere from the air outlet 16 and is sent along the guide surface 17 to the vicinity of the outer peripheral edge of the cup 4. Here, two air reservoirs 11, 1
The reason for providing 2 is that it is difficult for a single air reservoir to uniformly send high-pressure air sent through a narrow flow path from the air outlet over the entire circumference. This is because the air pressure is distributed by utilizing the pressure gradient. Although such a rectifying section is practically sufficient to be constituted by a slit as in this embodiment,
It may be composed of many pores. In particular, in the case of a large number of pores, providing a rectifying portion not parallel to the rotation axis is also effective in increasing the pressure gradient.

In order to blow air smoothly along the guide surface, the air outlet 16 and the second air reservoir 12 are required.
Is preferably small. In order to blow out uniformly in this state, it is desirable that the entire opening area of the rectifying unit 13 is smaller than the entire opening area of the air outlet.

The shaping air blown into the atmosphere from the air outlet 16 is applied to the guide surface 17 as described above.
Flows forward along the path, but since the offset amount of the air outlet 16 from the tip of the guide surface 17 is 30 mm or more, the flow velocity of the shaping air reaching the vicinity of the outer peripheral edge of the cup 4 is reduced. The thick air flow causes the paint particles discharged in the form of a mist from the outer peripheral edge of the cup 4 so that all the particles are almost uniformly distributed by the slow thick air flow without being greatly influenced by the size of the paint particles. An inertial force in the direction of the object is given.

On the other hand, since a high voltage is applied to the discharge electrode made of a conductive film provided on the back surface of the cup 4, almost constant current is applied from the tip of each discharge electrode present on the outer peripheral edge of the cup. In addition, a corona discharge is performed toward the object to be coated, and the paint particles carried toward the object to be coated by the shaping air atomized at the outer peripheral edge of the cup are charged by the corona discharge, and thus, The charged paint particles efficiently adhere to the object to be coated by the cloning force.

FIG. 2 is a sectional view schematically showing a tip structure in another embodiment of the electrostatic coating apparatus according to the present invention.

The apparatus of the embodiment shown in FIG.
And the air outlet 16 in the apparatus of the embodiment shown in FIG.
And the configuration is almost the same except that there is a slight difference in the position, the shape of the guide surface 17, and the like. Note that the reference numerals assigned to the respective members in FIG. 2 are the same as the reference numerals assigned to the respective common members in FIG.

In the embodiment shown in FIG. 2, the tip of the air buffer case 9 is extended to a position closer to the cup 4 as compared with the embodiment shown in FIG. The length of the rear end of the front casing 14 located in the front end of the airbag case becomes longer, and eventually the air outlet formed by the gap between the rear outer peripheral surface of the front casing and the front inner peripheral surface of the air buffer case. 1
The opening 6 is provided at a position closer to the cup 4, however, at a position offset sufficiently rearward (30 mm or more) from the tip of the guide surface 17. The outer peripheral surface of the distal end casing 14 located forward of the opening of the air outlet 16 forms a guide surface 17 for shaping air from the vicinity of the air outlet to the vicinity of the outer peripheral edge of the spray head. In the example,
The sectional line of the guide surface 17 is substantially curved, that is, the angle changes in the middle of the guide surface. However, the angle change portion on this guide surface is 4 °.
Since it is neither the above angle nor the separation angle, the shaping air blown out from the air blowout port 16 is caused to have a desired good flow by the guide surface as in the case of the embodiment in FIG. is there.

[0056]

As described above, in the present invention, a high coating efficiency can be obtained by using slow and thick shaping air as shaping air in the electrostatic coating apparatus.

Further, in the electrostatic coating apparatus of the present invention,
The air outlet for ejecting the air flow is located sufficiently behind the rotary spray head in the rotation axis direction,
A substantially cylindrical guide surface that is arranged substantially coaxially with the rotation axis of the rotary spray head in an annular shape, and further on the inner peripheral side than the air outlet, from near the air outlet to near the outer peripheral edge of the spray head. Is provided, it is possible to easily form slow and thick shaping air which improves the coating efficiency as described above.

Further, in the present invention, the guide surface is constituted by a smooth continuous surface, the guide surface does not have a stepped shape having a projection of 4 ° or more, and the guide surface is formed from an outer edge of the spray head. Also, the tip of the guide surface is located rearward,
In a cross section along the rotation axis, an extension line from a spray head side end of a cross section line of the guide surface and a cross section line of a back surface of the spray head reaching an outer peripheral edge of the spray head are less than 4 °. The guide surface has an outer diameter smaller than the diameter of the spray head, and the offset amount of the air outlet from the tip of the air guide in the rotation axis direction is less than 30 mm. Is large, the shaping air derived from the outlet can be guided stably to the vicinity of the outer peripheral edge of the spray head without peeling off from the guide surface, and more excellent coating efficiency can be expected. Becomes

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a tip structure in an embodiment of an electrostatic coating apparatus according to the present invention;

FIG. 2 is a cross-sectional view schematically showing a tip structure in another embodiment of the electrostatic coating apparatus according to the present invention;

FIG. 3 is a cross-sectional view schematically showing a tip structure of an example of a conventional electrostatic coating apparatus.

[Description of Signs] 1 ... Body case, 2 ... Air motor, 3 ... Rotating shaft, 4 ... Resin cup (spray head), 5 ... Paint nozzle, 6 ... Paint outlet hole, 9 ... Air buffer case, 11 and 12 ... air pool, 13 ... rectification part, 14 ... tip housing, 16 ... air outlet, 17 ... guide surface.

Claims (7)

[Claims] 1. A paint is atomized by a rotating spray head, paint particles to be atomized at the spray head are charged, and the paint particles are deflected in the direction of an object to be coated by an air flow, and are conveyed to perform coating. An electrostatic coating device, wherein the air flow is formed as a relatively slow, thick, steady flow at a position passing near the outer peripheral edge of the spray head. 2. A paint is atomized by a rotating spray head, paint particles to be atomized at the spray head are charged, and the paint fine particles are deflected in the direction of the object to be coated by an air flow, and are conveyed to perform coating. An electrostatic coating apparatus, wherein an air outlet for ejecting the air flow is located sufficiently behind the rotating spray head in a rotation axis direction thereof, and is substantially coaxial with a rotation axis of the rotating spray head. And a substantially cylindrical guide surface extending from the vicinity of the air outlet to the vicinity of the outer peripheral edge of the spray head is provided on the inner peripheral side of the air outlet. Electrocoating equipment. 3. The electrostatic coating apparatus according to claim 2, wherein said guide surface is formed of a smooth continuous surface. 4. The electrostatic coating apparatus according to claim 2, wherein the guide surface does not have a projecting step shape of 4 ° or more. 5. The front end of the guide surface is located rearward of an outer edge portion of the spray head, and in a cross section along the rotation axis, an extension of a cross-sectional line of the guide surface from a spray head side end. The electrostatic coating apparatus according to any one of claims 2 to 4, wherein a cross-section line of the back surface of the spray head reaching an outer peripheral portion of the spray head intersects at an angle of less than 4 °. 6. The electrostatic coating apparatus according to claim 2, wherein an outer diameter of the tip of the guide surface is smaller than a diameter of the spray head. 7. The electrostatic coating according to claim 2, wherein an offset amount of the air outlet from the tip of the guide surface in the rotation axis direction is larger than 30 mm. apparatus.