JPH0424115B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic coating apparatus that can perform electrostatic coating satisfactorily even on objects having a high electrical resistance value.

In general, an electrostatic coating device is equipped with support members such as hangers made of a good electrical conductor at predetermined intervals on a conveyor line that is at ground potential, and the workpiece is supported by the support members. is held at ground potential, an electrostatic atomizer is installed in the paint booth, and a high voltage (e.g. -90 [KV]) from a high voltage generator is applied to the atomizer to atomize the paint. The atomized paint particles are electrically charged, and the charged paint particles are directed toward the object to be coated, which is at ground potential, and are applied by flying along the lines of electric force.

By the way, in such an electrostatic coating device, when the object to be coated is a good electrical conductor such as a metal body, the object to be coated is always maintained at ground potential via a support member made of a good electrical conductor. Therefore, coating with sufficiently high electrostatic effect can be performed over the entire circumference.

However, the surface of the object to be coated is an electrically poor conductor, i.e. materials with high electrical resistance such as various synthetic resins, glasses, ceramics, wood, and insulating sintered metals (hereinafter referred to as "synthetic resins"). If there is,
Or, if the surface of the metal plate is treated with these synthetic resins, negatively charged paint particles may adhere to the object even if the object is set to be at ground potential through the support member. so that the charge imparted by the paint particles does not escape to the ground,
The surface of the object to be coated becomes saturated with static electricity and becomes negatively charged, and even if charged paint particles are discharged from the paint sprayer, they do not coat the object and no electrostatic effect is obtained. Become.

For this reason, in conventional technology, in order to apply electrostatic coating to synthetic resin materials, a conductive treatment liquid, which is a type of antistatic agent, is applied in advance to cover the surface of the synthetic resin with a conductive coating film. The coating process was performed in the following order: electrostatic coating was then carried out by spraying charged paint particles, and then the coated object was placed in a baking oven and baked.

However, in the prior art described above, a conductive treatment liquid is applied to the surface of the object to be coated to give it conductivity, and then the object is supported on a support member made of a good electrical conductor such as a metal hanger. Since the object to be coated is held at ground potential through a . Firstly, when applying a conductive treatment liquid to the surface of an object to be coated, if the object to be coated has a complex shape such as an automobile part or furniture, the conductive treatment is applied uniformly over the entire circumference. It may not be possible to apply the liquid.
In such a case, among the electric charges charged on the object to be coated, the electric charges near the support member can escape to the ground via the support member, but the electric charges in the parts distant from the support member cannot escape. However, it has the disadvantage of causing uneven coating.

Secondly, since the support member is made of a good electrical conductor, an electrostatic field is also formed between the support member and the paint machine, causing paint to adhere to the support member. As a result, when the support member is a hanging hanger, the adhered paint flows down along the hanger and drips onto the surface of the object to be coated, a so-called "drip" phenomenon, which occurs. There are drawbacks that reduce quality. For this reason, it is necessary to remove the hanger from the conveyor line and wash off the paint that has adhered to it with thinner etc. after each painting job.
The drawback is that this cleaning operation requires a great deal of time and effort.

Thirdly, if a large amount of paint is left on a support member and used to support the next object to be painted, this paint will form an insulating layer and no electrical conduction will occur between the support member and the object to be painted. There is. As a result, even if the object to be painted is supported by a support member so that it is at ground potential, the object to be painted made of synthetic resin material will immediately become electrically saturated, making it difficult to apply the paint. The disadvantage is that it cannot be done.

The present invention has been made by paying attention to the points of the prior art mentioned above, and it is not necessary to apply a conductive treatment liquid in advance as a preliminary step, and it is not necessary to use a support member made of a good electrical conductor. By applying a positive or negative high voltage to the back side of the object to be coated, and spraying paint from the surface side of the object with a normal paint sprayer that is substantially at ground potential, the object to be coated becomes electrically charged. It is an object of the present invention to provide an electrostatic coating device that can improve coating efficiency even when it is made of an insulating material with a high resistance value.

In order to achieve the above-mentioned object, the present invention provides a non-contact device that is disposed facing away from the surface side of an object to be coated having a high electrical resistance value, and that sprays paint toward the object while maintaining it at ground potential. An electrostatic coating machine, a support member formed using an insulator with a high electric resistance value and supporting the object to be coated, and a support member provided on the back side facing the coating machine with the object to be coated in between. and a high voltage generator that applies a positive or negative high voltage to the electrode to form an electrostatic field between the electrode and the coating machine.

With this configuration, when a high voltage is applied to the electrode from the high voltage generator, an electrostatic field is formed between the coating machine at ground potential and the electrode via the object to be coated. When paint is sprayed from a coating machine in this state, paint particles fly along the electrostatic field and are applied to the surface of the object to be coated. At this time, since the support member is made of an insulator, by applying one of the high voltages of plus and minus to the back side of the object to be coated, the back side of the object to be coated can be Due to the induction phenomenon, it is induced to one potential, and the surface side is induced to the opposite potential. As a result, a potential difference is maintained between the front surface of the object to be coated and the coating machine, and the paint sprayed from the coating machine is efficiently applied to the surface of the object to be coated.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In the drawings, 1 is a resin material (hereinafter referred to as "resin plate") made of synthetic resin material as the object to be coated,
The resin plate 1 is suspended from a conveyor 3 via a hanger 2 as a support member. Here, the hanger 2 is made of an insulator having a high electric resistance value, such as plastics using various synthetic resin materials, a coated insulator made of a metal body coated with synthetic resin, ceramics, etc., wood, or the like.

Reference numeral 4 denotes a coating machine disposed facing the resin plate 1 at a predetermined distance in order to coat the surface 1A of the resin plate 1. The coating machine 4 is connected to a reciprocator 6 via an arm 5.
It is installed so that it can move up and down. The coating machine 4 is connected to a paint pump 8 via a paint hose 7. Here, as the coating machine 4, a non-electrostatic coating gun, such as an air atomization type coating gun or a hydraulic atomization type coating gun, which is held at substantially ground potential is used, and the spray from these coating guns is used. Paint particles are not charged with an electric charge. Incidentally, even when an electrostatic atomizer is used as the atomizer 4, a high voltage is not applied to the electrostatic atomizer, and the electrostatic atomizer may be used while being held at ground potential.

Further, reference numeral 9 indicates a plurality of needle-like electrodes 9 provided on the back side 1B facing the coating machine 4 with the resin plate 1 in between.
A, 9A, . t is approximately 10 to 200 [mm], preferably 100 [mm]
It is set to be about.

In addition, 10 boosts the commercial power supply, plus or minus high voltage, such as + or -30~120
[KV] is a high voltage generator that generates a direct current high voltage, and the high voltage generator 10 is connected to a high voltage cable 11.
The electrode 9 is connected to the electrode 9 through the electrode 9, and a predetermined high voltage, for example, +45 [KV] can be applied to the electrode 9. Note that 12 in the figure indicates the ground potential.

The present invention is constructed as described above, but in order to carry out painting work using this painting device, first a positive or negative high voltage, for example a +45 [KV] high voltage, is generated from the high voltage generator 10. is applied to the electrode 9. As a result, each needle-shaped electrode 9 of the electrode 9
An electrostatic field having electric lines of force E as shown in the figure is formed between A and the coating machine 4, which is a protruding object and is held at substantially ground potential, via the resin plate 1.

Next, when the paint is supplied from the paint pump 8 to the coating machine 4, this paint is atomized by air or hydraulic pressure by the coating machine 4. However, paint machine 4
Since no voltage is applied to and is substantially at ground potential, the atomized paint particles are not electrically charged. However, the back surface 1 of the resin plate 1
The back surface 1 is charged by an electrode 9 on the B side.
Due to the electric potential B, an electrostatic field is formed between the paint sprayer 4 and the resin plate 1, and as a result, the paint particles move along the lines of electric force E formed between the needle electrode 9A to which a high voltage is applied. , and coats the surface 1A of the resin plate 1.

However, unlike the prior art, the resin plate 1 is not coated with a conductive treatment liquid, and the hanger 2 is formed of an insulator, so by applying a positive high voltage to the back side 1B, the back side is 1B is negatively induced by the induction phenomenon, and the surface 1A
On the contrary, it is induced in a positive direction. Moreover, since the hanger 2 is made of an insulator at this time, the polarization direction of the electric dipoles of the resin plate 1 is arranged not to face the hanger 2 but between the front surface 1A and the back surface 1B. Ru. As a result, the surface 1A side of the resin plate 1 is always maintained at a positive potential, and an effective potential difference is maintained between the entire surface of the resin plate 1 and the coating machine 4. The sprayed paint particles fly along the lines of electric force E and can be efficiently applied to the resin plate 1.

On the other hand, paint does not adhere to the hanger 2. That is, since the paint particles sprayed from the paint sprayer 4 are not electrically charged and are outside the range of the electrostatic field between the paint sprayer 4 and the electrode 9, there is no charge between the paint particles and the hanger 2. There is no potential difference between the two, and no paint will stick to it. Further, by making the hanger 2 in the form of a rod or string, a so-called "wrapping phenomenon" of the electric field occurs, thereby preventing paint from adhering to the hanger 2. Therefore, there is no risk of "sagging" phenomenon as in the prior art, and there is no fear of ground failure due to paint stains as in the case of using a hanger made of metal material.

In addition, in the above-mentioned embodiment, the case where three needle-like electrodes 9A are provided as the electrode 9 has been described as an example, but the number of needle-like electrodes 9A may be one. It can be something. Also,
The electrode 9 is not limited to the needle-like electrode 9A, but may be a flat electrode. In this case, an aluminum foil electrode 9' having an uneven surface is used as shown in FIG. By placing it close to 1B, the electrode effect can be enhanced. Furthermore, when using an electrode plate made of aluminum material or the like as an electrode, the electrode plate 9'' may be brought into contact with the back surface 1B of the object to be coated 1 as shown in FIG. Since there is no intervening layer, the electrode plate 9'' can polarize the resin plate 1 more effectively.

Further, in the embodiment, the resin plate 1 was used as an example of the object to be coated, but it is not limited to a plate-like object as shown in the figure, and may be a square-shaped object, a box-like object, or an automobile body, an electric appliance, etc. Of course, any shape can be adopted.

Further, in the embodiment, the hanger 2 suspended from the conveyor 3 as a support member was described as an example, but the conveyor may be a ground traveling type conveyor, and the support member may be provided upwardly from the conveyor. The coating work may be performed by placing the object to be coated on the support member, and any structure may be used as long as it can be supported from above, below, and from the left and right.

The electrostatic coating apparatus according to the present invention is as described in detail above, and when coating an object to be coated which is an electrically poor conductor, the electrostatic coating apparatus uses an ordinary coating machine which is held substantially at ground potential as a coating machine. In addition to using insulators with high electrical resistance for the support members,
The structure is such that an electrode to which a positive or negative high voltage is applied is placed on the back side of the object to be coated, so a constant potential is maintained between the object to be coated and the coating machine, allowing electrostatic painting. can be carried out effectively. In addition, the paint does not adhere to the support member and drip onto the object to be coated, and the support member does not need to be washed frequently, which improves coating quality and work efficiency.

[Brief explanation of drawings]

FIG. 1 is a general block diagram showing an electrostatic coating apparatus of the present invention, FIG. 2 is a partial block diagram showing another embodiment of the electrode, and FIG. 3 is a partial block diagram showing still another embodiment. 1... Resin plate (object to be coated), 2... Hanger (supporting member), 3... Conveyor, 4... Painting machine, 7...
Paint hose, 8...Paint pump, 9...Electrode, 9
A...Acicular electrode, 10...High voltage generator, 11
...High voltage cable, 9'...Aluminum foil electrode, 9''...Electrode plate.

Claims (1)

[Scope of Claims] 1. A non-electrostatic coating that is arranged facing away from the surface side of an object to be coated, which has a high electrical resistance value, and sprays paint toward the object while maintaining it at ground potential. machine and
a support member formed using an insulator with a high electric resistance value and supporting the object to be coated; an electrode provided on a back side facing the coating machine with the object to be coated in between; An electrostatic coating device comprising a high voltage generator that applies a positive or negative high voltage to the electrode in order to form an electrostatic field between the electrostatic coating device and the coating machine. 2. The electrostatic coating apparatus according to claim 1, wherein the support member is a hanger that supports the object to be coated from any direction, such as vertically, horizontally, or vertically. 3. The electrostatic coating apparatus according to claim 1, wherein the electrode is composed of one or more needle-like electrodes, and the needle-like electrodes have their tips facing toward the back side of the object to be coated. . 4. The electrostatic coating apparatus according to claim 1, wherein the electrode is a flat electrode, and the flat electrode is brought close to or in contact with the back surface of the object to be coated.