JP2010284618A - Coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent paint particles dispersed in an atmosphere from adhesion to a spray gun and to prevent the deterioration in coating quality of an object to be coated from occurring. <P>SOLUTION: A coating apparatus 1 atomizes a paint supplied from a paint supply source 5 by compressed air supplied from a compressed air supply source 6, and at the same time, shapes the atomized paint particles to a shape suitable for coating to spray the object to be coated 11. Then, an electrostatic generator 3 charges the paint particles to a negative polarity by generating a predetermined direct voltage Vdc of the negative polarity corresponding to an alternating voltage Vac supplied from an AC source apparatus 4 in a cascade 15 to apply to an electrode 16, and at the same time, generates electromagnetic force lines m1 centering the electrode 16 to produce electric repulsive force between the paint particles charged negatively and the electrode 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coating apparatus including a spray gun that atomizes a paint into fine particles.

  Conventionally, paint (liquid paint such as solvent paint and water-based paint and powder paint) supplied to a spray gun is finely divided, and the finely divided paint (hereinafter referred to as paint particles) is applied to the surface of an object to be coated. 2. Description of the Related Art A coating apparatus that performs painting by wearing is known. In such a coating apparatus, one configured to spray compressed paint by supplying compressed air to a spray gun is widely used. To improve the coating quality at the time of painting, Patent Document 1 discloses, for example, Further, there is disclosed a technique in which a paint is uniformly applied to the surface of an object to be coated by making the spray pattern uniform.

JP 2007-21449 A

  By the way, in the case of a coating apparatus that uses compressed air, if the sprayed paint particles deviate from the air flow or bounce off the surface of the object to be sprayed and scatter in the atmosphere, the paint particles staying in the atmosphere are spray guns. May adhere to the body or the vicinity of the nozzle. In this case, not only does the surface of the spray gun become dirty with the paint, but the attached paint dries and peels off, and the paint piece is transported by compressed air and adheres to the surface of the object to be coated. May decrease.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to effectively prevent the paint particles scattered in the atmosphere from adhering to the spray gun, and as a result, the coating caused by the adhering paint. An object of the present invention is to provide a coating apparatus that can prevent a reduction in coating quality of a coated object.

  In order to achieve the above object, a coating apparatus of the present invention is a coating apparatus having a spray gun for atomizing paint and spraying from a nozzle, and is applied in the vicinity of the nozzle to apply a positive or negative DC voltage. And an electrostatic generator that charges the paint sprayed from the nozzle to a predetermined low voltage having the same polarity as the electrode (invention of claim 1).

  According to the coating apparatus of the present invention, the electrostatic generator applies a DC voltage to the electrode to charge the paint particles to a predetermined low voltage having the same polarity as the electrode. An electric repulsive force is generated between the paint particles and the paint particles scattered in the atmosphere can be prevented from adhering to the nozzle (spray gun). In this case, as the predetermined low voltage, for example, a voltage within a range of −1 V to −50 kV can be set as appropriate. More preferably, it is in the range of -1 kV to -10 kV. In short, the predetermined low voltage may be a voltage that generates an electric repulsive force between the charged paint particles and the electrode (spray gun side).

  By the way, in this kind of coating field, a method (apparatus) called electrostatic coating is known in which a paint is applied to an object to be coated using electrostatic force. This electrostatic coating device (electrostatic coating gun) incorporates a DC high voltage generator called a cascade in the body of the spray gun, and paints sprayed from a nozzle are fed into a negative high voltage by the DC high voltage generator. Some are charged to a voltage (e.g., -80 kV) and adsorbed to an object to be coated as an anode.

  At this time, the biggest difference between the above-described electrostatic coating apparatus and the present invention is the magnitude of the voltage for charging the paint. That is, the voltage required for electrostatic coating is generally a considerably high voltage of −60 kV to −100 kV, whereas the voltage charged to the paint in the present invention is sufficiently lower than that. As a result, in the present invention, a large-scale and large-scale DC high-voltage generator such as a general electrostatic coating apparatus is not necessary, and the electrostatic generator can be made compact, lightweight, and inexpensive. In addition, safety is high.

  In the present invention, the electrostatic generator is externally attached to the spray gun and generates a DC voltage corresponding to the input AC voltage, and the AC voltage is supplied to the DC voltage generator. It can be set as the structure provided with the alternating current power supply device (invention of Claim 2).

  According to this, since an electrostatic generator can be externally attached to a spray gun that has been used conventionally, it is easy to carry out without having to change the configuration of the painting equipment etc. (and its installation status) greatly. Can do. Therefore, it is possible to easily add an excellent function of preventing the adhesion of the paint to the coating apparatus having a conventional configuration while being relatively inexpensive.

  Alternatively, the electrostatic generator is built in the spray gun and generates a DC voltage corresponding to the input AC voltage; and an AC power supply apparatus that supplies the DC voltage to the DC voltage generator It is good also as a structure provided with (Invention of Claim 3).

  According to this, since the DC voltage generator is built in the spray gun, there is no need to install a separate device, and the DC voltage generator built-in structure in the spray gun, the insulation structure, and the electrode to the nozzle With respect to various items such as position and wiring connection structure, a suitable design can be performed in advance. At this time, as described above, the DC voltage generator itself can be made relatively compact, so that the entire spray gun can be made relatively small and light, without increasing its size and weight. You can do it.

  According to the coating apparatus of the present invention, coating is performed such that the paint is sprayed onto the object to be coated in a state where the paint is charged at a predetermined low voltage, so that it is effective that the paint particles scattered in the atmosphere adhere to the spray gun. As a result, it is possible to prevent the deterioration of the coating performance and the coating quality due to the adhesion of the coating material.

The 1st Embodiment of this invention is shown, and the figure which shows schematically the whole structure of a coating device Side view schematically showing spray gun Circuit diagram schematically showing the electrical configuration of the electrostatic generator FIG. 2 shows a second embodiment of the present invention and is equivalent to FIG.

Hereinafter, the present invention will be specifically described with reference to a plurality of embodiments.
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.
FIG. 1 is a diagram schematically showing the entire coating apparatus 1 according to the present embodiment. The coating apparatus 1 includes a spray gun 2, an electrostatic generator 3 externally attached to the spray gun 2, an AC power supply device 4 connected to the electrostatic generator 3, and a paint supply source connected to the spray gun 2. 5 and a compressed air supply source 6.

  The spray gun 2 includes a substantially cylindrical body 7 made of a synthetic resin such as polyacetal resin or fluorine resin having electrical insulation. A paint supply hose 8 connected to the paint supply source 5 and a compressed air supply hose 9 connected to the compressed air supply source 6 are connected to the rear end (right side in the figure) of the body 7 of the spray gun 2. . The spray gun 2 is supplied with paint from a paint supply source 5 by a pump (not shown) or the like, and compressed air used for spraying paint or forming a paint pattern is supplied from the compressed air supply source 6.

  A nozzle 10 is attached to the front end (the left side in the drawing) of the body 7 of the spray gun 2, and the paint supplied from the paint supply source 5 is applied to the coating object located in front of the spray gun 2 from the nozzle 10. A certain object 11 is sprayed. An attachment member 12 is provided at the rear end portion of the body 7, and the spray gun 2 is predetermined by holding the attachment member 12 on a holding member (not shown) provided in the painting line. It is installed in the position.

  The static electricity generator 3 includes a substantially annular main body 13 made of a resin material having electrical insulation. The main body 13 of the electrostatic generator 3 is formed so that its inner diameter is slightly larger than the outer diameter of the body 7 of the spray gun 2, and the body 7 of the spray gun 2 is inserted, that is, attached to the spray gun 2 ( It is in an externally attached state. A power cable 14 connected to the AC power supply device 4 is connected to the rear end portion of the main body 13 of the electrostatic generator 3. The main body 13 of the electrostatic generator 3 includes a protruding portion 13a in which a part (upper end portion) in the circumferential direction protrudes forward (left side in the figure). The protruding portion 13a includes a cascade 15 (direct current) described later in detail. The electrode 16 is provided so as to protrude from the front end portion thereof.

Next, the details of the spray gun 2 and the electrostatic generator 3 will be described.
FIG. 2 is a side view schematically showing the spray gun 2 and the electrostatic generator 3. A tubular paint channel 17 is formed inside the body 7 of the spray gun 2, and the paint supplied from the paint supply source 5 through the paint supply hose 8 flows through the paint channel 17 to the nozzle 10. It discharges from the provided discharge hole 18. In the paint channel 17, a needle 19 having a tapered tip and movable in the paint channel 17 in the front-rear direction is disposed. The tip of the needle 19 is formed so as to be able to come into contact with the small diameter portion 17a of the paint channel 17 in a watertight manner. When the needle 19 moves forward in the small diameter portion 17a, the paint channel 17 is closed. When moved rearward, the paint channel 17 is opened. Note that FIG. 2 shows a state where the needle 19 closes the paint channel 17.

  In addition, a plurality of air flow paths 20 through which compressed air supplied from the compressed air supply source 6 flows are provided in the body 7 of the spray gun 2. The compressed air supplied to the spray gun 2 flows through the air flow path 20 provided in the body 7 and is discharged from the pattern forming air hole 21 to be used as pattern forming air. Further, the compressed air flows through another air flow path (not shown), is discharged from an atomizing air hole (not shown) provided in the vicinity of the discharge hole 18, and is used as atomizing air. Further, the compressed air is also used as drive air for driving the needle 19 described above in the front-rear direction.

  FIG. 3 is a circuit diagram schematically showing an electrical configuration of the entire electrostatic generator 3 including the AC power supply device 4 and the cascade 15. The AC power supply device 4 includes a high frequency power supply circuit 22 and an output transformer 23. The high frequency power supply circuit 22 connected to the commercial power supply has a direct current power supply and an inverter circuit (not shown), converts the output voltage of the direct current power supply into alternating current by the inverter circuit, and outputs the alternating current voltage Vac through the output transformer 23. Output. In the present embodiment, the output voltage of the DC power supply is 2 V, the inverter circuit is driven at a frequency of 20 kHz, and the AC power supply device 4 outputs a low-voltage AC voltage Vac of about 2.4 V / 20 kHz.

  The cascade 15 includes a step-up transformer 24, a voltage doubler rectifier circuit 25, and an output resistor 26, and generates a predetermined low voltage DC voltage Vdc. Specifically, the cascade 15 boosts the AC voltage Vac supplied from the AC power supply device 4 by the step-up transformer 24, rectifies it by a voltage doubler rectifier circuit 25 made of, for example, a Cockcroft-Walton type circuit, and generates a predetermined low voltage. Conversion to a DC voltage Vdc. An output resistor 26 is connected to the output terminal of the voltage doubler rectifier circuit 25, and the DC voltage Vdc generated in the cascade 15 is supplied to the electrode 16 through the output resistor 26. At this time, the electrode 16 has a needle-like tip, is located at the top of the nozzle 10 and is provided so as to protrude forward. Note that the voltage doubler rectifier circuit 25 can make the polarity of the output voltage positive or negative with respect to the ground potential by changing the direction of the diode in the circuit.

  According to the study by the present inventors, if a voltage within a range of, for example, -1 V to -50 kV is appropriately set as the predetermined low voltage generated by the cascade 15, a corona discharge is generated in the electrode 16, and the paint The particles can be charged to a low voltage. More preferably, it is in the range of -1 kV to -10 kV. In the present embodiment, the cascade 15 is configured so that the polarity of the output voltage is negative with respect to the ground potential. For example, when an AC voltage Vac of 2.4 V / 20 kHz is supplied, A DC voltage Vdc of about −5 kV is generated.

  Such a coating apparatus 1 is installed in a painting line where a painting operation is performed. Although not shown in the drawing line, a conveying device for holding and conveying the object 11 to be grounded (grounded), a line control device for controlling the entire operation including the coating device 1, etc. Is provided. In this state, the object to be coated 11 is moved relative to the nozzle 10 in front of the spray gun 2 (the direction in which the paint particles are sprayed, leftward in FIG. 1). Painting is performed while moving sequentially.

Next, the operation of the coating apparatus 1 having the above configuration will be described.
As shown in FIG. 1, the coating apparatus 1 is supplied from the paint supply source 5 by discharging the compressed air supplied from the compressed air supply source 6 from an atomizing air hole and a pattern forming air hole 21 (not shown). The paint is atomized (micronized), and the atomized paint particles are formed into a shape (paint pattern) suitable for painting and sprayed. In this embodiment, for example, a water-based paint having a small electrical resistance is used, and the paint is grounded in the paint supply source 5 through the paint supply hose 8 due to the conductivity of the paint itself.

  The electrostatic generator 3 generates a predetermined negative DC voltage Vdc based on the AC voltage Vac supplied from the AC power supply device 4 and applies the DC voltage Vdc to the electrode 16. As a result, a negative ionization sphere is formed by corona discharge in the vicinity of the paint discharge hole 18, and the paint particles sprayed from the spray gun 2 pass through the ionization sphere to have the same negative polarity as the electrode 16. Is charged. The charged paint particles are conveyed to the air flow of the compressed air, reach the surface of the object 11 to be coated, and are applied to the object 11.

  At this time, the electrostatic generator 3 charges the paint particles and forms an electromagnetic force line m <b> 1 that covers the spray gun 2 around the electrode 16 in the vicinity of the spray gun 2. Therefore, even when the paint particles are scattered in the atmosphere due to deviating from the air flow or rebounding on the surface of the object 11, the negatively charged paint particles are formed by the electrode 16. The movement toward the spray gun 2 is limited by the electric repulsive force generated between the magnetic field lines m1.

  As described above, in the coating apparatus 1 to which the electrostatic generator 3 is externally attached, a kind of protective area is formed so as to cover the spray gun 2 around the electrode 16, and the paint particles scattered in the atmosphere are spray gun 2. It is prevented from adhering to.

As described above, the coating apparatus 1 according to the present embodiment has the following effects.
Since the coating apparatus 1 charges the paint particles to a negative low voltage by the electrostatic generator 3, the potential of the paint particles and the potential on the spray gun 2 (electrode 16) side become the same negative polarity. A repulsive force is generated, and the movement of the paint particles toward the spray gun 2 is restricted. Thereby, it is suppressed that the paint particle scattered in the atmosphere adheres to the spray gun 2 side. Accordingly, it is possible to prevent the coating quality from being deteriorated due to the adhesion of the paint, such as the paint adhering to the spray gun 2 being peeled off and adhering to the surface of the object 11 by the air flow.

  Since the electrostatic generator 3 is externally attached to the spray gun 2, an excellent function of preventing adhesion of paint can be easily added even in a production line using the spray gun 2 having a conventional configuration. . Further, in order to use the electrostatic generator 3, it is only necessary to add the power cable 14, so that the installation cost does not increase significantly.

  Since the generated electrostatic voltage 3 is a low voltage of about −5 kV, the electrostatic generator 3 is a circuit having a low rating (electrical withstand voltage and small capacity) such as the step-up transformer 24 and the voltage doubler rectifier circuit 25. An element can be used, and the electrostatic generator 3 can be reduced in size and weight. Further, the cost can be reduced. Therefore, it is necessary to add a paint adhesion prevention function without significantly changing the existing equipment situation (strength of the holding jig of the spray gun 2, installation space, etc.), that is, without causing a significant increase in cost. Can do.

  Since the paint particles are charged with a low voltage of about −5 kV, the conveyance force by the air flow is stronger than the adsorption force by the electrostatic force. Therefore, for example, it is possible to reduce the possibility of uneven coating without the concentration of charges on the edge portion of the object 11 to be coated. Further, the influence of the electric lines of force m1 on the spray pattern of the paint particles can be reduced.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in that electrodes and cascades are built in the body of the spray gun. In addition, the same code | symbol is attached | subjected to the component substantially the same as 1st Embodiment, and detailed description is abbreviate | omitted. Further, for simplification of description, description will be given with reference to FIG.

  FIG. 4 is a diagram schematically showing the spray gun 32 of the coating apparatus 31 according to the second embodiment. The coating device 31 includes a spray gun 32, an electrostatic generator 33, a paint supply source 5, a compressed air supply source 6 (both see FIG. 1), and the like. The spray gun 32 is connected to the paint supply source 5 and the compressed air supply source 6, and the paint supplied from the paint supply source 5 is made into fine particles by the compressed air supplied from the compressed air supply source 6. It sprays with respect to the coating material 11 (refer FIG. 1).

  The electrostatic generator 33 includes a cascade 34 and an electrode 35 as in the first embodiment. Since the cascade 34 only needs to be able to generate the low DC voltage Vdc as described above, a small circuit element can be used. Therefore, in this embodiment, the miniaturized cascade 34 is provided inside the spray gun 32. The tip of the electrode 35 has a needle shape, and is provided in the vicinity of the outside of the paint channel 17 in the nozzle 10 (lower part in FIG. 4). The electrical configurations of the cascade 34 and the AC power supply device 4 are the same as those shown in FIG.

  A power cable 14 connected to the AC power supply device 4 (see FIG. 1) is connected to the rear end portion (right side in the drawing) of the spray gun 32 in order to supply the AC voltage Vac to the cascade 34. The cascade 34 converts the AC voltage Vac supplied from the AC power supply device 4 into a predetermined low voltage DC voltage Vdc (about −5 kV) and supplies the converted voltage to the electrode 35. As a result, electromagnetic field lines m1 (see FIG. 1) covering the spray gun 32 around the electrode 35 are generated, and the negatively charged paint particles passing through the negative ionization zone formed by the electrode 35 are generated. Access to the spray gun 32 is prevented.

  According to such a coating apparatus 31, the same effects as those of the first embodiment can be obtained, for example, the paint particles sprayed from the spray gun 32 can be prevented from adhering to the spray gun 32. In particular, in the second embodiment, since the cascade 34 and the electrode 35 are built in the spray gun 32, the built-in structure of the cascade 34, the insulating structure, the position of the electrode 35 with respect to the nozzle 10, the connection structure of the power cable 14, etc. The various designs in the spray gun 32 can be optimized in advance. Moreover, since the cascade 34 itself can be made relatively compact, the entire spray gun 32 can be made relatively small and light.

(Other embodiments)
The present invention is not limited to the embodiments described above and shown in the drawings, and can be expanded or changed as follows without departing from the gist thereof.

The magnitude of the DC voltage, the voltage / frequency of the AC voltage, and the like are not limited to the examples in the embodiments, and may be set as appropriate depending on the flow rate of the paint or compressed air, the type of the object to be coated, or the like.
In each embodiment, although the example which applied this invention to the automatic spray gun was shown, you may apply to a manual spray gun. In this case, for example, if the operation lever (painting start switch) of the manual spray gun is also used as the operation start switch of the electrostatic generator, the operator turns on the operation of the electrostatic generator on the spot. / Because it can be turned off, the work efficiency is improved and the safety when carrying the spray gun is improved.

  Although an example in which one electrode is provided has been described, a plurality of electrodes may be arranged around the nozzle, or may be arranged not only at the front end portion but also at the rear end portion of the spray gun. Various changes can be made to the shape and position of the electrodes. Furthermore, it is good also as a structure which employ | adopts a small generator, such as an air turbine type generator, for example as an alternating current power supply device, integrates this in a spray gun with a cascade, or attaches it externally.

  When using paints with high electrical resistance such as solvent-based paints and powder paints, an electrode for directly charging the paint and an electrode for preventing adhesion are provided, and the output of the DC voltage generator is You may make it the structure supplied to both. In that case, the polarities of both electrodes may be different. In short, it is sufficient that the potential of the charged paint particles and the potential applied to the adhesion preventing electrode have the same polarity.

  The coating apparatus may be configured to include a plurality of paint supply sources (including a paint supply hose) and a plurality of compressed air supply sources (including a compressed air supply hose). Moreover, you may apply to the coating device etc. which were provided with the rotating body and were equipped with the spray gun which atomizes a coating material by centrifugal force. Or, instead of connecting the spray gun and the paint supply source with the paint supply hose, the spray gun and the paint cup are integrated into a powder coating device using a so-called cup type spray gun. You may apply.

  In the drawings, 1 and 31 are coating devices, 2 and 32 are spray guns, 3 and 33 are electrostatic generators, 4 is an AC power supply device, 10 is a nozzle, 11 is an object to be coated, 15 and 34 are cascades (DC voltage) (Generator), 16 and 35 are electrodes, Vac is an AC voltage, and Vdc is a DC voltage.

Claims (3)

In a coating device equipped with a spray gun that atomizes the paint and sprays it from the nozzle,
An electrostatic generator that has an electrode to which a positive or negative DC voltage is applied in the vicinity of the nozzle and charges a paint sprayed from the nozzle to a predetermined low voltage having the same polarity as the electrode A coating apparatus characterized by providing   The electrostatic generator includes a DC voltage generator externally attached to the spray gun and generating a DC voltage corresponding to an input AC voltage, and an AC power supply device that supplies the DC voltage to the DC voltage generator. The coating apparatus according to claim 1, further comprising a coating apparatus.   The electrostatic generator includes a DC voltage generator that is built in the spray gun and generates a DC voltage corresponding to an input AC voltage, and an AC power supply device that supplies the DC voltage to the DC voltage generator. The coating apparatus according to claim 1.

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