JP2004275976A - Electrostatic coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic coating method by which a conductive coating material to be discarded is reduced to the minimum upon washing and economical and efficient electrostatic coating operation is carried out by using a simple process. <P>SOLUTION: In this electrostatic coating method, a prescribed coating material is charged by a predetermined amount from a color change valve mechanism 12 to an intermediate storage tank 26 via a block valve mechanism 20, thereafter, supply of the conductive coating material from the color change valve mechanism 12 is stopped and, at the same time, a servo motor 36 of the intermediate storage tank 26 is driven. Therefore, the conductive coating material in a supply path 18c is drawn into a cylinder chamber 30 in the intermediate storage tank 26 and the conductive coating material remaining at least in the electric insulating pipe path 18b of the block valve mechanism 20 is replaced and air is present there. As a result, when washing the block valve mechanism 20, it does not occur that unused conductive coating material is discarded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is to supply the conductive paint to a coating gun after supplying the conductive paint from the paint supply unit to the storage unit once, and electrically disconnecting the paint supply unit and the storage unit. The present invention relates to an electrostatic coating method for performing electrostatic coating by using an electrostatic coating method.
[0002]
[Prior art]
As a method of applying a high voltage to a conductive paint to apply an electrostatic coating to an object to be coated such as an automobile body, for example, a voltage block method is known. In this method, the conductive paint is first introduced into an intermediate storage tank (reservoir) that is insulated from the ground potential, and then supplied to the intermediate reservoir and a paint supply source (paint supply unit). The tracks are washed and dried to form a voltage block. In this state, an electrostatic coating operation is performed on the object to be coated by supplying the conductive gun to which the high voltage is applied from the intermediate storage tank to the coating gun.
[0003]
As an electrostatic coating apparatus used for this type of coating, for example, Patent Document 1 is known. In Patent Document 1, as shown in FIG. 7, a pump 1 is provided as a storage part, and a paint inlet 1a of the pump 1 is filled with a conductive paint from a paint supply path 2. On the other hand, a predetermined amount of the conductive paint is fed to the coating machine 3 from the paint discharge port 1b of the pump 1.
[0004]
The pump 1 includes a piston 4, which can be advanced and retracted by high-pressure air supplied from an air supply source 5 via a pressure regulating valve 6. The moving speed of the piston rod 4a connected to the piston 4 is detected by a non-contact sensor 7, and the flow rate of the conductive paint supplied to the coating machine 3 is measured based on the moving speed of the piston rod 4a. Is done.
[0005]
Then, the measured flow rate of the conductive paint is compared with a flow rate set in advance according to the paint discharge amount of the coating machine 3, and the pressure of the high-pressure air supplied to the pump 1 is determined according to the difference value. It is variably adjusted via the pressure adjusting valve 6. Thereby, the size of the pump 1 can be reduced, and the quantitativeness of the pump 1 can be ensured.
[0006]
[Patent Document 1]
JP-A-6-60452 (FIG. 1)
[0007]
[Problems to be solved by the invention]
By the way, in this type of electrostatic coating apparatus, for example, as shown in FIG. 8, an insulating section 8 is provided between the pump 1 and the paint supply section 2a. The insulating section 8 includes valve mechanisms 8a and 8b, and an insulating pipe 2b that forms the supply path 2 is connected between the valve mechanisms 8a and 8b. The valve mechanism 8a can be connected to a dump path D1, while the valve mechanism 8b is provided with a paint supply section 2a, a cleaning section 9, and a dump path D2 so as to be switchable.
[0008]
For example, when performing coating with the same color of conductive paint using the above-described electrostatic coating apparatus, first, the paint supply unit 2a is connected to the supply path 2 via the valve mechanisms 8a and 8b. Then, the conductive paint is filled into the pump 1 through the supply path 2. Next, the valve mechanism 8a is driven to connect the insulating pipe 2b to the dump path D1, and the washing unit 9 is connected to the insulating pipe 2b under the action of the valve mechanism 8b.
[0009]
In this state, after the cleaning liquid is supplied from the cleaning unit 9 to clean the insulating tube 2b between the valve mechanisms 8a and 8b, the drying air is supplied from the cleaning unit 9. Therefore, the inside of the insulating tube 2b is washed and dried, and the paint supply unit 2a and the pump 1 are electrically insulated. Then, the pump 1 is driven to supply the conductive paint in the pump 1 to the coating machine 3, and a high voltage is applied to the conductive paint, so that the object to be coated (not shown) is statically applied. Electric painting is being performed.
[0010]
By the way, as described above, every time the conductive paint is pumped to the coating machine 3 under the action of the pump 1 to perform the electrostatic coating, the insulating portion 8 is cleaned in the insulating tube 2b. At this time, the conductive paint remains in the insulating pipe 2b, and the conductive paint is discarded from the insulating pipe 2b to the dump path D1 every time the insulating pipe 2b is washed.
[0011]
As a result, there is a problem that the unused conductive paint in the insulating tube 2b is unnecessarily discarded for each cleaning operation, and the amount of the conductive paint used increases. In particular, it has been pointed out that when the electrostatic coating operation is performed for a long period of time, the amount of the conductive paint discarded from the inside of the insulating tube 2b considerably increases, which is extremely uneconomical.
[0012]
The present invention solves this kind of problem, and can reduce the amount of conductive paint discarded during cleaning with a simple process as much as possible, thereby performing an economical and efficient electrostatic coating operation. It is an object to provide a possible electrostatic coating method.
[0013]
[Means for Solving the Problems]
In the electrostatic coating method according to the present invention, first, when a predetermined amount of the conductive paint is supplied from the paint supply unit to the storage unit via the supply path, the supply of the conductive paint from the paint supply unit is stopped. On the other hand, at least the conductive paint remaining in the insulating section is supplied to the storage section side. That is, air is present in the insulating part, being replaced by the conductive paint. Next, in a state where the insulating section is cleaned and the paint supply section and the storage section are electrically disconnected, the conductive paint in the storage section is supplied to the coating gun to perform a desired electrostatic coating.
[0014]
As described above, since the conductive paint remaining in the insulating section is once supplied to the storage section side, the conductive paint does not remain in the insulating section when the insulating section is washed. Therefore, it is possible to prevent unused conductive paint from being discarded as much as possible when cleaning the insulating portion, and it is possible to perform an economical and efficient electrostatic coating operation.
[0015]
Further, when a conductive paint of the same color is used, the conductive paint in the storage section is supplied to the coating gun, and after the electrostatic coating is performed, the conductive paint remaining in the storage section is changed to an insulating section. Once returned to the side. This makes it possible to effectively prevent air from being mixed in the conductive paint when the storage section is filled with the conductive paint, and to satisfactorily avoid defective coating pattern formation in a simple process. It becomes possible to do.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic configuration explanatory view of an electrostatic coating apparatus 10 for performing an electrostatic coating method according to the present invention.
[0017]
The electrostatic coating apparatus 10 includes a grounded color changing valve mechanism 12, and the color changing valve mechanism 12 controls supply of drying air (A), water (W), a cleaning liquid (S), and the like. One washing valve 14 and a plurality of paint valves 16a, 16b and 16c capable of supplying conductive paint of different colors are provided. A block valve mechanism 20 is connected to the color changing valve mechanism 12 via a supply path 18a, and a first discharge path 23 is connected to the supply path 18a via a first dump valve 21.
[0018]
The block valve mechanism 20 has a resin electrically insulating pipe (supply path) 18b, and switching valves 22a and 22b are connected to both ends of the electrically insulating pipe 18b. The color change valve mechanism 12 and the second cleaning valve 24 for controlling the supply of air (A), water (W), cleaning liquid (S), and the like are switched by the switching valve 22a on the inlet side, and the switching valve on the outlet side. 22b switches between the second discharge path 25 and the intermediate storage tank (reservoir) 26 via the supply path 18c.
[0019]
The intermediate storage tank 26 forms a cylinder chamber 30 for injecting a conductive paint and a cleaning liquid via a piston 28, and an inlet 32 and an outlet 34 communicate with the cylinder chamber 30. A servo motor 36 is connected to a rod 28a extending from the piston 28 via a ball screw means 37, so that the piston 28 can advance and retreat in the direction of arrow A.
[0020]
A coating gun 40 is connected to the cylinder chamber 30 of the intermediate storage tank 26 via a delivery path 38. The coating gun 40 includes a second dump valve 42 and a trigger valve 44, and is connected to a high voltage applying unit (not shown). The second dump valve 42 is connected to a third discharge path 46 for discharging a waste liquid containing a conductive paint and a cleaning liquid generated during cleaning to the outside of the delivery path 38.
[0021]
The third discharge path 46 is connected to a third cleaning valve 48 that controls the supply of air (A), water (W), cleaning liquid (S), and the like.
[0022]
Next, the operation of the electrostatic coating apparatus 10 thus configured will be described with reference to the flowchart shown in FIG. 2 in relation to the electrostatic coating method according to the present invention.
[0023]
First, the supply path 18a, the electrically insulating pipe 18b, and the supply path 18c are connected via the switching valves 22a and 22b of the block valve mechanism 20 (step S1). Then, for example, the paint valve 16a of the color changing valve mechanism 12 is opened (Step S2), and the servomotor 36 of the intermediate storage tank 26 is driven (Step S3).
[0024]
For this reason, as shown in FIG. 1, a conductive paint of a predetermined color is pumped from the paint valve 16a. The conductive paint fills the cylinder chamber 30 of the intermediate storage tank 26 through the supply path 18a, the electrically insulating pipe 18b, and the supply path 18c, and is further supplied to the coating gun 40 via the delivery path 38. (Step S4). During this supply, the trigger valve 44 is closed while the second dump valve 42 is closed.
[0025]
In the state where the supply of the conductive paint is completed as described above (YES in step S4), at least the capacity of the conductive paint remaining in the electrically insulating conduit 18b is stored in the cylinder chamber 30 of the intermediate storage tank 26. Only a small amount of conductive paint is supplied.
[0026]
Then, the process proceeds to step S5, where the paint valve 16a is closed, and the driving of the servomotor 36 is continued. At this time, the first dump valve 21 is driven, and the supply path 18a is connected to the first discharge path 23 (see FIG. 3). For this reason, the conductive paint remaining in the supply passage 18c is drawn into the cylinder chamber 30 by the movement of the piston 28 in the direction of the arrow A1, and at least in the electrically insulating pipe 18b, the conductive paint is replaced with the conductive paint. Air is introduced.
[0027]
In step S6, when the filling of the conductive paint into the cylinder chamber 30 of the intermediate storage tank 26 is completed (YES in step S6), the work of cleaning the block valve mechanism 20 is performed (step S7). Specifically, as shown in FIG. 4, the switching valves 22a and 22b of the block valve mechanism 20 are switched, and the second cleaning valve 24 is connected to the second discharge path 25 via the electrically insulating pipe 18b. You.
[0028]
Therefore, when the cleaning liquid (water or thinner) is supplied from the second cleaning valve 24, the inside of the electrically insulating conduit 18b is cleaned, and the waste liquid is discharged to the second discharge path 25. Further, air is supplied from the second cleaning valve 24 to dry the inside of the electrically insulating conduit 18b, and the switching valves 22a and 22b are electrically insulated (YES in step S8).
[0029]
Next, as shown in FIG. 5, when the trigger valve 44 is opened and the piston 28 moves in the direction of the arrow A2 under the driving action of the servo motor 36, the conductive path is transferred from the cylinder chamber 30 to the delivery path 38. The paint is pumped. For this reason, the conductive paint is discharged from the coating gun 40 via the trigger valve 44, and a high voltage is applied to the conductive paint to perform electrostatic coating on a workpiece (not shown) (step S9). .
[0030]
When the above-described electrostatic coating is completed, the process proceeds to step S10, in which the conductive coating remaining in the intermediate storage tank 26 is returned to the block valve mechanism 20 once. Specifically, as shown in FIG. 6, the trigger valve 44 is closed. On the other hand, the supply path 18c, the electrically insulating pipe line 18b and the supply path 18a are connected via the switching valves 22a and 22b constituting the block valve mechanism 20, and the supply path 18a is connected via the first dump valve 21. It is connected to the first discharge path 23.
[0031]
In this state, when the piston 28 moves in the direction of the arrow A2 under the action of the servomotor 36, the conductive paint remaining in the cylinder chamber 30 is pushed out to the supply passage 18c, and the conductive paint is supplied to the electrically insulating conduit 18b. The paint is returned once. At this time, the air remaining in the electrically insulating pipe 18b and the supply path 18c is pushed out to the supply path 18a by the conductive paint, and is discharged to the first discharge path 23 connected to the supply path 18a.
[0032]
Therefore, when the paint valve 16a is opened and the conductive paint is supplied to the supply path 18a in order to perform the coating operation with the conductive paint of the same color, air does not mix in the conductive paint. . This effectively prevents air from being introduced into the intermediate storage tank 26, and satisfactorily avoids poor formation of a coating pattern and the like in a simple process.
[0033]
In this case, in this embodiment, as shown in FIG. 1, a predetermined conductive paint is supplied from the color changing valve mechanism 12 to the intermediate storage tank 26, and the cylinder chamber 30 of the intermediate storage tank 26 is filled with a predetermined amount. Is done.
[0034]
Next, as shown in FIG. 3, while the supply of the conductive paint from the color changing valve mechanism 12 is stopped, the servomotor 36 is driven to draw the conductive paint in the supply path 18 c into the cylinder chamber 30. . Thus, at least in the electrically insulative conduit 18b, air is present instead of the conductive paint, and when the block valve mechanism 20 is washed, the electrically insulative conduit 18b is placed in the electrically insulative conduit 18b. Does not remain.
[0035]
Therefore, in the present embodiment, when the block valve mechanism 20 is washed, unused conductive paint remaining in the electrically insulative conduit 18b can be prevented from being discarded as much as possible. The effect is that an effective electrostatic coating operation can be easily performed.
[0036]
Moreover, it is only necessary to stop the supply of the conductive paint from the color changing valve mechanism 12 and drive the servo motor 36. Therefore, there is an advantage that it is possible to satisfactorily prevent the conductive paint from being unnecessarily discarded with a simple control. In particular, when the electrostatic coating operation is performed for a long period of time, a large amount of the conductive coating material is discarded from the electrically insulating conduit 18b every time the block valve mechanism 20 is washed. However, according to this type of electrostatic coating apparatus 10, there is an effect that the economic efficiency is greatly improved.
[0037]
By the way, when a new conductive paint of a color different from the above-mentioned conductive paint is used, the application of the high voltage to the coating gun 40 is released after the completion of the above-mentioned coating work, and the block valve mechanism 20 is released. The cleaning liquid is injected into the cylinder chamber 30 of the intermediate storage tank 26 by driving the first cleaning valve 14 by switching the switching valves 22a and 22b. After washing the cylinder chamber 30 and the delivery path 38, the cleaning liquid is discharged from the third discharge path 46 under the action of the second dump valve 42. Then, for example, a conductive paint of a different color is supplied to the cylinder chamber 30 of the intermediate storage tank 26 via the paint valve 16b of the color changing valve mechanism 12, and the painting operation is performed by the same method as described above. Good.
[0038]
【The invention's effect】
In the electrostatic coating method according to the present invention, when a predetermined amount of the conductive paint is supplied from the paint supply unit to the storage unit via the supply path, the supply of the conductive paint from the paint supply unit is stopped. On the other hand, at least the conductive paint remaining in the insulating section is supplied to the storage section side. Therefore, when the insulating portion is cleaned, the conductive paint does not remain on the insulating portion, and it is possible to prevent unnecessary disposal of the unused conductive paint as much as possible. Thus, economical and efficient electrostatic coating work can be reliably performed with simple control.
[Brief description of the drawings]
FIG. 1 is a schematic structural explanatory view of an electrostatic coating apparatus for performing an electrostatic coating method according to the present invention.
FIG. 2 is a flowchart illustrating the electrostatic coating method.
FIG. 3 is an operation explanatory diagram when a conductive paint remaining in a block valve mechanism constituting the electrostatic coating device is sent to an intermediate storage tank.
FIG. 4 is an operation explanatory diagram when the block valve mechanism is cleaned.
FIG. 5 is an explanatory diagram of an operation when electrostatic coating is performed by discharging a conductive paint from a coating gun.
FIG. 6 is an explanatory diagram of an operation when the conductive paint remaining in the intermediate storage tank is once returned to the block valve mechanism side after completion of coating.
FIG. 7 is a schematic configuration explanatory view of an electrostatic coating device according to Patent Document 1.
FIG. 8 is a schematic explanatory view of a block valve mechanism incorporated in the electrostatic coating apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Electrostatic coating device 12 ... Color change valve mechanism 14,24 ... Washing valve 16a-16c ... Paint valve 18a, 18c ... Supply path 18b ... Electrically insulating pipe 20 ... Block valve mechanism 22a, 22b ... Switching valve 26 ... Intermediate storage tank 28 Piston 30 Cylinder chamber 32 Injection port 34 Discharge port 36 Servo motor 40 Painting gun

Claims (2)

A supply section for temporarily storing the conductive paint is provided in a supply path for supplying the conductive paint from the paint supply section to the coating gun, and an insulation for electrically shutting off the paint supply section and the storage section. An electrostatic coating method for performing electrostatic coating by an electrostatic coating apparatus having a part,
Supplying the conductive paint from the paint supply unit to the storage unit via the supply path,
A step of stopping supply of the conductive paint from the paint supply unit, and supplying the conductive paint remaining in at least the insulating unit to the storage unit side,
A step of performing electrostatic coating by supplying the conductive paint in the storage section to the coating gun in a state where the insulating section is washed and the coating supply section and the storage section are electrically disconnected,
An electrostatic coating method comprising: 2. The electrostatic coating method according to claim 1, wherein when the same color conductive paint is used, the conductive paint in the storage is supplied to the coating gun to perform the electrostatic coating, and then the storage is applied. A step of temporarily returning the conductive paint remaining on the insulating portion side to the insulating portion side.

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