JPS5940071B2 - Electrostatic coating equipment for metallic paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for electrostatically applying metallic paint.

This type of electrostatic coating device generates an electric field by applying a DC high voltage between the object to be coated and a charged electrode provided in the spray head, and the spray head contains a conductive pigment such as an aluminum pigment. The metallic paint is supplied through a non-conductive paint passage, the metallic paint is sprayed from a spray head equipped with a charged electrode to charge the paint, and the charged paint particles run along the lines of electric force of the electric field to form an object to be painted. Adhere to painted surfaces.

However, at the start of spraying the metallic paint, the conductive pigment contained in the metallic paint tends to form chain-like lumps and spew out, and the quality of the painted surface deteriorates due to the occurrence of the spittle. The cause of smearing is that the conductive pigments contained in the metallic paint in the paint path leading to the spray head are arranged along the lines of electric force of the electric field, and the arranged conductive pigments are dispersed as chain-like lumps. This is because the liquid is ejected from the spray head without being sprayed.

While the metallic paint flows through the paint path and is sprayed from the spray head, the conductive pigments are aligned along the lines of electric force because the metallic paint is agitated by its own flow within the paint path. However, while the spraying of the metallic paint is stopped, the metallic paint does not flow and is not stirred, so the conductive pigments tend to align along the lines of electric force, and therefore, when the spraying of the metallic paint starts, the metallic paint does not flow and is not stirred. is more likely to occur. Therefore, in order to prevent the occurrence of spitting, the electrical resistance value of metallic paint can be reduced by lowering the DC high voltage applied to the charging electrode to weaken the strength of the electric field, or by selecting a solvent depending on the type of paint. Adjustment methods have been considered, but these methods reduce the coating efficiency and waste a lot of metallic paint.

In addition, when the supply of metallic paint to the spray head and the supply of power to the DC high voltage generator that applies DC high voltage to the charged electrode are simultaneously stopped, the remaining metal remains in the DC high voltage circuit of the DC high voltage generator. A method has been devised in which the charge is immediately discharged to earth through a high resistor or switch. However, in this method, at the start of painting, the supply of metallic paint to the spray head and the application of DC high voltage to the charged electrode are started simultaneously, so the spray head is Metallic paint is sprayed from the surface of the surface and the coating must be applied under unstable corona discharge, reducing coating efficiency and making it impossible to obtain a high-quality painted surface. Also,
If so-called paint cuts, in which the supply of metallic paint is temporarily stopped during painting work, are repeated frequently, painting without obtaining a stable corona discharge may result in low coating efficiency and a high-quality painted surface. Furthermore, the DC high voltage generator frequently repeats opening and closing operations and is prone to failure. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic coating apparatus for metallic paint that eliminates the drawbacks of the prior art as described above, prevents the occurrence of spittle, and provides a coated surface of excellent quality.

The present invention focuses on the fact that the cause of spitting is that when metallic paint stagnates in an electric field, the conductive pigments in the metallic paint tend to overflow the lines of electric force of the electric field and are arranged. However, the metallic paint remaining in the turtle area is stirred to prevent the conductive pigment from arranging along the lines of electric force.

That is, a metallic paint supply device is connected via a non-conductive paint passage to a spray head equipped with a charged electrode connected to a DC high voltage generator, a DC high voltage is applied to the charged electrode, and a high DC voltage is applied to the spray head. In an electrostatic coating device for metallic paint that supplies metallic paint, a grounding section is provided in the paint passage or the metallic paint supplying device, and at least The present invention is characterized in that a metallic paint stirring device is provided which is driven while a DC high voltage is being applied to the charging electrode and the supply of metallic paint to the spray head is stopped, thereby making it possible to stir the metallic paint at that location. This is an electrostatic coating device for metallic paint. Since the apparatus of the present invention is equipped with a device for stirring the metallic paint that remains in the electric field, the conductive pigments in the metallic paint are prevented from arranging along the lines of electric force of the electric field, and the spit This prevents the quality of the painted surface from deteriorating due to spitting.

In addition, unlike the conventional technology described above, in order to prevent the occurrence of spitting, there is no need to waste metallic paint or increase the number of openings and closings of the DC high voltage generator. It can be painted, and a high-quality painted surface can be obtained without reducing coating efficiency. Furthermore, the apparatus of the present invention has a simple structure, as it is constructed by attaching a metallic paint agitating device to the paint passage of the electrocoating apparatus.

Next, examples of the present invention will be described.

FIRST EXAMPLE (See FIG. 1) (The electrostatic coating apparatus of this example is equipped with a manual air atomization type sprayer 1, and the sprayer 1 is made of a non-conductive material such as nylon. An insulating tube fitting hole 3, a paint passage 4, and an air passage 5 are formed in the cylindrical body 2 along its axial direction, and a needle-shaped charging electrode 8 is connected to the tip of the cylindrical body 2 in the central cylindrical part. A paint nozzle 6 made of a non-conductive material such as nylon inserted into the paint hole 7 is screwed on, the tip of the paint passage 4 of the cylindrical body is communicated with the paint hole 7 of the paint nozzle, and the paint nozzle 6 is screwed on. A paint hole 7 with a charged electrode 8 of a paint nozzle is inserted into the tip of the cylindrical body 2, and an atomizing air hole 10 for atomizing paint and a pattern for adjusting the jetting angle or pattern of the atomized paint are inserted around the paint hole 7. An air nozzle 9 made of a non-conductive material such as nylon with air holes 11 is screwed onto the air nozzle.
11 is connected to the tip of the air passage 5 of the cylindrical body, a spray head 12 is formed by the paint nozzle 6 and the air nozzle 9 at the tip of the cylindrical body 2, and the insulating pipe fitting hole 3 of the cylindrical body is connected to the spray head 12. Then, the conductor wire 14 covered with polyethylene, the high resistor 15 and the helical spring 16 are successively connected in a line, and the built-in insulating tube 13 is fitted, and the helical spring 16 at the tip of the insulating tube 13 is connected to the charging head of the spray head. The outlet of the paint flow control valves 19 and 20 connected to the end of the electrode 8 and operated by the trigger 18 pivoted to the handle part 17 attached to the end of the cylindrical body 2 is connected to the end of the cylindrical body 2. It is connected to the ends of the paint passage 4 and the air passage 5.

A DC high voltage generator 21 is connected to the end of the wire 14 in the insulated pipe 13 of the sprayer, and the paint flow control valve 1 of the sprayer is connected to the end of the wire 14.
A metallic paint supply device 23 is connected to the inlet of 9 through a nylon hose 22 that forms a non-conductive paint passage, and a paint pressure reducing valve 24 is provided in the middle of the nylon hose 22, and the paint pressure reducing valve 24 is grounded. This grounding part 24, which also serves as a grounding part and is located on the most downstream side of the paint passage, and the sprayer 1
A metallic paint stirring device 25 is provided in the middle of the nylon hose 22 located between the two, and a paddle-shaped stirring blade 26 rotatably driven by a motor 27 with a switch 28 is supported, and the part that comes into contact with the paint is insulated. Sprayer air flow control valve 20
High pressure air supply device 30 via air pressure reducing valve 29 at the inlet of
The high pressure air supplied from the high pressure air supply device 30 passes through the air flow control valve 20 of the atomizer and the air passage 5 to the atomization air hole 10 of the air nozzle and the pattern air hole 1.
The DC high voltage generator 21 is driven as the liquid is ejected from the fuel cell 1. When using the electrostatic coating device of this example, first drive the metallic paint supply device 23 and high pressure air supply device 30, then close the switch 28 of the metallic paint stirring device and drive the motor 27 to drive the stirring blades. 26 is rotated, and after driving the metallic paint stirring device 25, the trigger 18 of the sprayer is slightly pulled to open the air flow control valve 20. Then, the pressure of the high-pressure air supplied from the high-pressure air supply device 30 is regulated by the air pressure reducing valve 29, and the air flows through the open air flow control valve 20 of the atomizer and the air passage 5 to the atomizing air hole 10 of the air nozzle. They are ejected from the pattern air holes 11, respectively. As this high-pressure air is ejected, the DC high voltage generator 21 is driven, and a DC high voltage is applied to the charged electrode 8 of the spray head via the wire 14 in the insulating tube 13 of the sprayer, the high resistor 15, and the spiral spring 16. is applied, an electric field is generated, and a corona discharge occurs. Then,
A high DC voltage is applied to the charging electrode 8 while the metallic paint in the nylon hose 22 is not flowing, but since the metallic paint stirring device 25 has already been driven, the metallic paint in the nylon hose 22 is not flowing. Paint still stirring. This prevents the conductive pigments in the metallic paint from aligning along the lines of electric force of the electric field.

Therefore, no spitting occurs at the start of spraying of the metallic long-lasting paint, which will be described below. After the corona discharge generated in the charging electrode 8 is stabilized, the trigger 18 of the sprayer is further pulled to open the paint flow control valve 19 as well.

Then, the pressure of the metallic paint supplied from the metallic paint supply device 23 is regulated by the paint pressure reducing valve 24 which also serves as the grounding part, and is stirred by the metallic paint stirring device 25 which is being driven, and the paint flow rate is controlled when the sprayer is opened. The paint passes through the valve 19 and the paint passage 4 and is ejected from the paint hole 7 with the charged electrode 8 of the paint nozzle. The metallic paint sprayed from the paint nozzle 6 is
The air is atomized by the air ejected from the atomizing air holes 10 of the air nozzle, charged by the DC high voltage applied to the charging electrode 8', and the air ejected from the pattern air holes 11 of the air nozzle. The ejection angle or pattern is thus adjusted, and the charged metallic paint particles adhere to the painted surface of the object (not shown). To temporarily stop spraying the metallic paint from the spray head 12, the user releases the trigger 18 of the sprayer and closes the paint flow control valve 19.

Then, the supply of metallic paint to the spray head 12 is stopped, and the metallic paint in the nylon hose 22 stops flowing while the DC high voltage is applied to the charging electrode 8.
Because the metallic paint stirring device 25 is still operating. The metallic paint in the nylon hose 22 continues to be agitated, and the conductive pigments in the metallic paint are prevented from aligning along the lines of force of the electric field. Therefore, no spitting occurs when the sprayer resumes spraying the metallic paint by pulling the trigger 18 of the sprayer again and opening the paint flow control valve 19. However, in the electrostatic coating apparatus of this example, the metallic paint agitating device 25 is operated even during spraying of the metallic paint.
Since the sprayer is driven, there is no chance of spitting during spraying of metallic paint.

Second Embodiment (See Figure 2) The electrostatic coating device of this embodiment is equipped with a rotary atomizing type sprayer 31, and the sprayer 31 has an air motor 33 attached to the end of a base body 32. A substantially cup-shaped hub member 37 is inserted into the tip of the rotating shaft 36, and the center of the disk portion 38 of the hub member is fixed to the tip surface of the rotating shaft 36 with a bolt 41, and the center of the disk portion 38 of the hub member is fixed to the tip of the rotating shaft 36 with a bolt 41. A base end portion with a center hole of a bell-shaped paint discharge member 42 which also serves as a charging electrode is fitted, and a large number of paint holes are formed in the end portion of the cylindrical portion 39 of the hub member on the side of the disk portion 38 to communicate with the tip portion of the paint discharge member 42. A spray head 43 is formed by a paint discharge member 42 such as a hub member 37 at the tip of the rotary shaft 36 of the air motor, and
Attach the paint tube 44 to the tip of the paint tube 44.
Insert the tip opening into the substantially cup-shaped hub member 37,
An air passage 45 is formed at the tip of the base body 32, and the air passage 45
A large number of pattern air holes 46 facing the outer periphery of the tip of the paint discharge member 42 are provided at the tip.

A DC high voltage generator 47 is connected to the charging electrode 42 which also serves as a paint discharge member of the sprayer, and the air outlet 35 of the air motor 33 is
while opening the air inlet 34 of the air motor 33 to the atmosphere.
The high pressure air supply device 5 is connected to the high pressure air supply device 5 via a pressure reducing valve 48 and an on/off valve 49.
0 is connected to the terminal opening of the air passage 45 of the sprayer, and the above-mentioned high-pressure air supply device 50 is connected to the terminal opening of the air passage 45 of the sprayer via a pressure reducing valve 51 and an on-off valve 52, and furthermore, a non-conductive terminal is connected to the terminal opening of the paint tube 44 of the sprayer. A metallic paint supply device 54 is connected via a nylon hose 53 forming a transparent paint passage;
A pressure reducing valve 55 is provided in the middle of the nylon hose 53, and an on-off valve 56 is provided downstream of the pressure reducing valve 55 of the nylon hose 53.
A switch 60 is installed in the middle of the nylon hose 53 located between the grounding part 56 located at the most downstream side of the paint passage and the sprayer 31. A metallic paint stirring device 57 is provided in which a propeller-shaped stirring blade 58 rotatably driven by a motor 59 is supported and the portion that contacts the paint is insulated. When using the electrostatic coating device of this example, first close the switch 60 of the metallic paint stirring device, drive the motor 59 to rotate the stirring blade 58, and then turn on the metallic paint supply device 54 and high pressure air supply device 50. The on-off valve 49 is opened, the air motor 33 is driven, and the spray head 43 is connected to the pressure reducing valve 4.
The sprayer rotates in one direction at the rotation speed adjusted in step 8, opens the on-off valve 52, and blows out the air whose pressure is regulated by the pressure reducing valve 51 from the pattern air hole 46 through the air passage 45 of the sprayer.

Next, the DC high voltage generator 47 is driven to apply a DC high voltage to the charging electrode 42 of the spray head. After the corona discharge generated in the charging electrode 42 is stabilized and the rotation of the spray head 43 is stabilized, the paint passage opening/closing valve 56 is opened. Then, the pressure of the metallic paint supplied from the metallic paint supply device 54 is regulated by the pressure reducing valve 55, and the metallic paint is stirred by the metallic paint stirring device 57 which is being driven through the open on-off valve 56 which also serves as the grounding part. Sprayer paint tube 44
The paint passes through the hub member 37 and the paint hole 40 of the hub member, reaches the tip of the paint discharge member 42, and is discharged from the periphery of the tip of the paint discharge member 42.

The discharged metallic paint is atomized by the rotation of the paint discharge member 42, and the charged electrode 42 also serves as the paint discharge member.
The discharge angle is adjusted by the air ejected from the pattern air holes 46. When performing a so-called paint cut, in which the spraying of paint from the spray head 43, etc. is temporarily stopped, the opening/closing valve 56 of the paint passage is closed.

Then, the supply of the metallic paint to the spray head 43 is stopped, and the metallic paint in the nylon hose 53 stops flowing while the DC high voltage is applied to the charged electrode 42, but the metallic paint agitating device 57 stops driving. As the stirring continues, the metallic paint in the nylon hose 53 continues to be stirred, and the conductive pigments are prevented from being arranged by the electric lines of force. Therefore, no spitting occurs when spraying of the metallic paint is started when the on-off valve 56 of the paint passage is opened. In addition, in the static coating apparatus of this embodiment, as in the first embodiment, no spitting occurs during spraying of the metallic paint.

Third Embodiment (See Figure 3) The electrostatic coating device of this example is equipped with an automatic air atomization type sprayer 61 that incorporates a metallic paint stirring device 70, and the sprayer 61 is a non-conductive An insulating tube fitting hole 63, a paint passage 64, and an air passage 65 are formed in a cylindrical body 62 made of two members made of material, and a needle-shaped charging electrode 66 is connected to the paint hole (not shown) at the tip of the cylindrical body 62. The inserted paint nozzle is screwed on, and the paint nozzle (not shown) with a charged electrode 66 is inserted through the paint hole, and an air nozzle 67 (not shown) provided with an atomizing air hole and a pattern air hole (not shown) is screwed around it. , the tip of the paint passage 64 of the cylindrical body is communicated with the paint hole of the paint nozzle, and the tip of the air passage 65 of the cylindrical body is communicated with both air holes for atomization and patterning of the air nozzle 67. A spray head 68 is formed by a paint nozzle such as a nozzle 67, and an insulating tube 69 containing a built-in high resistance resistor (not shown) is fitted into the insulating tube fitting hole 63 of the cylindrical body, and the tip of the insulating tube 69 is sprayed. A screw-like stirring blade is connected to the end of the charged electrode 66 in the head and is placed in the middle of the non-conductive paint passage 64 in the cylindrical body, and is rotatably driven by an air motor 72 built into the end of the cylindrical body 62. A metallic paint agitating device 70 is provided with a metal paint stirring device 71 pivotally supported.

A DC high voltage generator 74 is connected to a high resistor (not shown) in the insulating tube 69 of the sprayer, and an air outlet (not shown) of the air motor 72 is opened to the atmosphere, while a pressure reducing valve 75 is connected to the air inlet 73 of the air motor 72. A high-pressure air supply device 77 is connected to the air passage 65 of the sprayer via an on-off valve 76, and a high-pressure air supply device 80 is connected to the end opening of the air passage 65 of the sprayer via a pressure reducing valve 78 and an on-off valve 79. A metallic paint supply device 82 is connected to the end opening of the paint passage 64 via a nylon hose 81 that forms a non-conductive paint passage similar to the paint passage 64, and a pressure reducing valve 83 is connected in the middle of the nylon hose 81. A pressure reducing valve 8 with a nylon hose 81 is provided.
3. An on-off valve 84 is provided at a downstream position to be opened and closed by a signal from a reciprocator 85 that reciprocates the sprayer 61,
The on-off valve 84 is grounded and also serves as a grounding part, and the metallic paint built in the cylindrical body 62 is installed in the non-conductive paint passage 64 between the grounding part 84 located at the most downstream side of the paint passage and the sprayer 61. A stirring device 70 is provided. When driving the electrostatic coating device of this example, first, both high-pressure air supply devices 77 and 80 and the metallic paint supply device 82 are driven respectively, one of the on-off valves 76 is opened, and the air motor 72 of the metallic paint stirring device is driven. is driven to rotate the stirring blade 71, and the other on-off valve 79 is opened to blow out high-pressure air through the air passage 65 of the atomizer and from both the atomization and pattern air holes (not shown) of the air nozzle 67. . Next, the DC high voltage generator 74 is driven to apply a DC high voltage to the charging electrode 66 of the spray head. After the corona discharge generated in the charging electrode 66 is stabilized, the reciprocator 85 is driven to cause the sprayer 61 to reciprocate. Then, the paint passage opening/closing valve 84 is opened by a signal from the reciprocator 85, and the metallic paint supplied from the metallic paint supply device 82 is
The pressure is regulated by a pressure reducing valve 83, and an on-off valve 84 also serves as a grounding part.
The metallic paint agitating device 70 in operation in the atomizer
The liquid is agitated by the atomizer, passes through the paint passage 64 of the sprayer, is atomized from the paint hole with the charging electrode 66 in the spray head, and is charged and sprayed. If paint cutting is performed, reciprocator 8
5, the paint passage opening/closing valve 84 is temporarily closed.

While the on-off valve 84 is closed, the supply of metallic paint to the spray head 68 is stopped, and the metallic paint in the paint passage 64 of the sprayer stops flowing while the DC high voltage is applied to the charging electrode 66. Since the stirring device 70 is driven, the conductive pigments of the metallic paint in the paint passage 64 are prevented from being aligned along the lines of electric force. In the electrostatic coating apparatus of each of the above embodiments, the metallic paint stirring device is driven not only when the spraying of the metallic paint is stopped but also during the spraying. The quality of the painted surface does not deteriorate due to ζ spit.

In addition, since the DC high voltage generator is kept running when spraying of metallic paint is stopped, even if the paint cut that temporarily stops spraying of metallic paint is repeated, the DC high voltage generator will not open and close more frequently. This will not cause any malfunction. Furthermore, since the metallic paint is sprayed after the corona discharge is stabilized, the coating efficiency is not reduced since the coating is always performed under the stabilized corona discharge, and a coated surface of excellent quality can be obtained. In the electrostatic coating apparatus of each of the above embodiments, the metallic paint stirring devices 25, 57, and 70 are all equipped with rotating blades, but are limited to those that stir by rotation. Rather, for example, as shown in FIG. 4, a non-conductive mesh piston 89 that is slidably fitted into a non-conductive cylinder 88 provided in the middle of a non-conductive paint passage 86 is connected to a steel rod at the tip of the piston rod 90. An electromagnet 92 inserted into the metal rod 91 and a spring 93 between the iron rod 91 and the cylinder 88 cause the metallic paint to reciprocate in the direction of flow.

The metallic paint stirring device 87 may be of the type that performs stirring by reciprocating motion. In short, any type of stirring device may be used as long as it stirs the metallic paint and prevents the conductive pigment from arranging along the lines of electric force.

[Brief explanation of the drawing]

1 to 3 are partial vertical cross-sectional schematic diagrams of electrostatic coating apparatuses according to first to third embodiments of the present invention, and FIG. 4 is a metallic durable paint stirring device of an electrostatic coating apparatus according to another embodiment. FIG. Explanation of symbols, first embodiment 8 shown in FIG. 1: Charged electrode, 1
2: Spray head, 21: DC high voltage generator, 22: Nylon hose, non-conductive paint passage, 23: Metallic paint supply device, 24: Paint pressure reducing valve and grounding section, 25: Metallic paint stirring device . 2nd embodiment shown in FIG. 2, 42: charged electrode serving as paint discharge member, 43: spray head, 47: DC high voltage generator, 5
3: Nylon hose, non-conductive paint passage, 54: Metallic paint supply device, 56: Grounding part that also serves as an on-off valve, 57
: Metallic paint stirring device, third embodiment shown in FIG. 3,
64: Non-conductive paint passage, 66: Charged electrode, 68: Spray head, 70: Metallic paint stirring device, 74: DC high voltage generator, 81: Nylon hose, non-conductive paint passage, 82: Metallic paint supply device, 84: Grounding part that also serves as an on-off valve. Another embodiment shown in FIG. 4, 86: non-conductive paint passage;
87: Metallic paint stirring device.

Claims (1)

[Claims] 1. A metallic paint supply device is connected via a non-conductive paint passage to a spray head provided with a charged electrode connected to a DC high voltage generator, and a DC high voltage is applied to the charged electrode. In an electrostatic coating device for metallic paint that supplies metallic paint to the spray head, a grounding section is provided in the paint passage or the metallic paint supply device, and a non-conductive A metallic paint agitating device is installed in the paint passageway to be driven at least while a DC high voltage is being applied to the charging electrode and the supply of metallic paint to the spray head is stopped, so that the metallic paint at that location can be stirred. This is an electrostatic coating device for metallic paint. 2. The electrostatic coating device for metallic paint according to claim 1, wherein the metallic paint agitating device is driven at least while applying a DC high voltage to the charging electrode.