JP4499588B2 - Spray gun for electrostatic painting - Google Patents

Description

  The present invention relates to a spray gun for electrostatic coating suitable for a paint having a relatively low electrical resistance.

  Paints used for electrostatic coating of automobile bodies and the like include solvent-based paints (oil-based paints), water-based paints (water-based paints), and metallic paints. Water-based paints and metallic paints have lower electrical resistance than solvent-based paints. Therefore, when using the water-based paint or metallic paint, a current flows through the paint tank grounded through the paint supply path, so a high voltage is directly applied to the charged electrode of the electrostatic paint gun body in contact with the paint. Can not do it.

  Therefore, an electrostatic coating gun for water-based paint or metallic paint employs a so-called “external electrode system” in which one or a plurality of external electrodes are arranged outside the gun body and a high voltage is applied to the external electrodes. Yes. However, since the external electrode type electrostatic coating gun requires an external electrode separately from the gun body, the electrostatic coating gun is enlarged. In addition, there is a problem that the atomized paint particles adhere to the vicinity of the external electrode or the periphery of the electrostatic coating gun body due to electrostatic force.

As a solution to such a problem, there is provided an air spray type electrostatic coating gun in which an electrode to which a high voltage is applied is arranged inside an air cap attached to the front end surface of the electrostatic coating gun ( For example, see Patent Document 1).
International Publication No. 2004/085078 Pamphlet

  However, also in the above configuration, the atomized paint particles adhere to the surface of the air cap. In particular, when the paint adhering to the air cap accumulates and becomes a lump, the lump is blown off to the object to be coated, which causes a coating failure. For this reason, Patent Document 1 proposes a configuration in which a floating electrode is provided on the air cap to reduce the amount of paint particles adhering to the surface of the air cap, but a sufficient effect cannot be obtained. It was.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spray gun for electrostatic coating that prevents the paint from adhering to the air cap as much as possible.

The present invention is an electrostatic coating spray gun for applying paint to an object by atomizing the paint with compressed air and charging it, the barrel having a paint supply path connected to a paint supply source, A paint flow path that is attached to the front end of the barrel and communicates with the paint supply path, an atomizing air flow path that is located around the paint flow path , and a paint discharge port that is located at the front end of the paint flow path A nozzle, a high voltage generating means for generating a DC high voltage for charging the paint discharged from the paint discharge port, and a front end of the barrel so as to cover the paint nozzle, the barrel and the paint An air cap having a space between the nozzle and having the paint discharge port inserted therethrough and communicating with the atomizing air flow path in the center; and the high voltage generating means disposed in the space. An electrode to which the generated high voltage is supplied, a pin electrode disposed in the paint flow path of the paint nozzle and grounded so that a front end portion projects forward from the paint discharge port, and provided on the air cap. a generally annular conductive member around the coating material delivery port, characterized by Tei Rukoto and a connecting member electrically connecting the paint supply path and the conductive members.

  According to the present invention, when the high voltage generated by the high voltage generating means during the electrostatic coating operation is supplied to the electrode, a strong electric field from the surface of the pin electrode to the electrode is generated, and the surface of the paint that travels through the pin electrode A charge having the opposite polarity to that of the electrode is induced. For this reason, the coating material atomized by the atomizing air discharged from the coating material discharge port and ejected from the atomizing air ejection hole jumps out into the air with the charge induced in the pin electrode. At this time, since the conductive member connected to the paint supply path by the connecting member has the same potential as the paint, the paint that has jumped out into the air and the conductive member are electrically repelled. Therefore, it becomes difficult for the paint to approach the air cap, and the paint is prevented from adhering to the surface of the air cap.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
1 to 3 show a first embodiment of the present invention. The spray gun 1 for electrostatic coating according to the present embodiment is composed of a barrel (barrel) 2 made of an insulating synthetic resin material, and a grip 3 provided at the rear end portion (right end portion in FIG. 1) of the barrel 2. Has been. A cascade 4 (corresponding to high voltage generating means) in which a step-up transformer constituting a high voltage generating circuit and a high voltage rectifier circuit (both not shown) are integrally molded is housed in the upper portion of the barrel 2.

  A cylindrical insulator 5 having a through hole 5a is disposed at the upper front portion in the barrel 2. The front half of the insulator 5 is larger in diameter than the rear half, and the front half is exposed at the front part of the barrel 2. Holes 6 and 7 are provided between the cascade 4 and the insulator 5, and conductive springs 6 a and 7 a are accommodated in the holes 6 and 7, respectively. The rear end of the spring 6 a is attached to an output terminal 8 located at the front end of the cascade 4.

  Conductive contacts 9 and 10 are attached to the front and rear ends of the spring 7a, respectively. The spring 6 a is in contact with the rear surface of the conductive contact 10. The conductive contact 9 is attached to the insulator 5. A conductive connecting rod 11 is inserted into the through hole 5 a of the insulator 5, and a rear end portion of the connecting rod 11 is supported by a conductive contact 9. The front end portion of the connecting rod 11 protrudes slightly forward from the front end surface of the insulator 5.

  An electrode support 12 is detachably attached to the front end of the insulator 5. Although not shown in detail, the electrode support 12 has a substantially fan shape when viewed from the front, and is attached to the insulator 5 in the vicinity of the center thereof. A semicircular electrode 13 is fixed to the center of the rear surface of the electrode support 12. The protruding end of the connecting rod 11 is in contact with the rear surface of the electrode 13.

On the other hand, the lower portion of the grip 3 and the connecting member 16a, a cylindrical paint hose joint 17 through 16b are connected with the power supply connector 1 4及 beauty hose joint 15 is attached. The connecting members 16 a and 16 b are fixed to the lower end surface of the grip 3 by screws 50. Both the connecting member 16a and the screw 50 are made of a conductive material. Further, a screw 52 connected to the ground wire 14 a in the power connector 14 via the lead wire 51 is screwed into the connecting member 16 a. Thereby, the joint 17 and the earth wire 14a are electrically connected.

  A high frequency voltage necessary for generating a high voltage is taken from the power connector 14 and supplied to a step-up transformer in the cascade 4 through a wiring cable (not shown) in the grip 3. The supplied high-frequency voltage is boosted by a step-up transformer, further boosted by a high-voltage rectifier circuit using a Cockcroft-Walton voltage doubler rectifier circuit, and simultaneously rectified to generate a DC high voltage of tens of thousands of volts. The

  The generated DC high voltage is guided from the output terminal 8 of the cascade 4 to the conductive contact 10 through the spring 6a. Then, it is guided from the conductive contact 10 to the conductive contact 9 via the spring 7 a and supplied to the electrode 13 through the connecting rod 11.

  Further, a hole 18 extending in the front-rear direction is provided in the lower portion of the barrel 2. A mounting recess 19 is provided at the front end of the barrel 2, and the hole 18 is open at the rear end surface of the mounting recess 19. A paint valve 20 is disposed at the front of the hole 18. A hollow guide member 21 is disposed in the hole 18 at a rear portion of the paint valve 20 with a space.

  The paint valve 20 includes a conductive valve body 22, a valve port 23 that passes through the valve body 22 in the axial direction, and a needle 24 that opens and closes the valve port 23. A space between the paint valve 20 and the guide member 21 in the hole 18 is a valve chamber 25.

  The needle 24 penetrates through the valve chamber 25, and its front end is formed in a taper shape. The rear portion of the needle 24 is inserted into the guide member 21 and moves in the front-rear direction along the guide member 21. The valve port 23 is opened and closed when the front end of the needle 24 abuts and separates.

  The needle 24 is always urged in a direction to close the valve port 23 by a return spring 27 provided at the rear end portion of the barrel 2. Then, only while the trigger 28 provided on the barrel 2 is pulled, the needle 24 moves backward against the return spring 27 and the valve port 23 is opened. A communication passage 25 a communicating with the valve chamber 25 is provided below the valve chamber 25 in the barrel 2, and the communication passage 25 a and the paint hose joint 17 are connected by a paint tube 26. The valve chamber 25, the communication path 25a, and the paint tube 26 correspond to the paint supply path of the present invention.

The mounting recess 19 has a smaller diameter in the rear half than in the front half, and a paint nozzle 29 is detachably screwed into the small diameter part. The paint nozzle 29 is made of an insulating synthetic resin material, and the front half of the paint nozzle 29 projects forward from the mounting recess 19. A paint flow path 30 penetrating in the front-rear direction is provided at the center of the paint nozzle 29. The rear end portion of the paint channel 30 communicates with the valve port 23 of the paint valve 20. A portion corresponding to the front end of the paint flow path 30 in the front end portion of the paint nozzle 29 is configured to have a small diameter and serves as a paint discharge port 31.
In addition, an annular space is formed around the paint nozzle 29 by mounting the paint nozzle 29 in the mounting recess 19. This annular space is used as the pattern air flow path 44. The electrode support 12 is disposed in the pattern air flow path 44.

  With the above configuration, when the trigger 28 is not operated, it is supplied from a paint tank as a paint supply source to the paint hose joint 17 via a paint hose (both not shown) and passes through the paint tube 26 to the valve chamber. The paint guided to 25 is prevented from being discharged to the paint nozzle 29 by the needle 24. On the other hand, when the trigger 28 is operated to open the paint valve 20, the paint supplied into the valve chamber 25 is discharged to the paint flow path 30 in the paint nozzle 29.

  A pin electrode 32 is inserted into the paint channel 30. The front end of the pin electrode 32 projects forward through the paint discharge port 31. A rear end portion of the pin electrode 32 is connected to the valve body 22 via a holding member 38 having conductivity. When a water-based paint or metallic paint having a relatively low electrical resistance is supplied into the paint nozzle 29, the pin electrode 32 is electrically connected to a grounded paint tank (not shown) due to the conductivity of the paint, and is grounded. To be maintained.

  A plurality of atomizing air flow paths 33 are formed in the paint nozzle 29 around the paint flow path 30. Both front and rear end portions of the atomizing air flow path 33 communicate with annular atomizing air flow paths 33 a and 33 b provided at front and rear end portions of the paint nozzle 29.

  An air valve 34 is provided at the rear end of the barrel 2. An air flow path 36 that connects the air valve 34 and the air hose joint 15 is provided in the grip 3. Compressed air for atomized air and pattern air is supplied from the compressed air generator to the air hose joint 15 via a high pressure air hose (both not shown), and guided to the air valve 34 through the air flow path 36. .

  The air valve 34 is opened and closed by a valve body 37 that moves back and forth integrally with the needle 24. That is, when the paint valve 20 is opened, the air valve 34 is also opened, and when the paint valve 20 is closed, the air valve 34 is also closed. When the air valve 34 is opened, the compressed air passes through an atomizing air supply path and a pattern air supply path (both not shown) provided in the barrel 2, and the atomizing air path 33 b at the rear end of the paint nozzle 29. , Are supplied to the pattern air flow paths 44, respectively.

  The front end of the paint nozzle 29 is covered with an air cap 40 attached to the front end of the barrel 2. A housing recess 41 is provided at the center of the rear surface of the air cap 40, and the front end of the paint nozzle 29 is fitted in the housing recess 41. An annular step 40a is provided on the outer periphery of the rear portion of the air cap 40, and a retaining nut 42 is engaged with the annular step 40a. A screw thread 43 is provided on the outer periphery of the front end of the barrel 2, and the retaining nut 42 is screwed to the screw thread 43.

  A cap ring 53 is detachably attached to the outer periphery of the air cap 40. The cap ring 53 includes a ring body 54 made of a synthetic resin, for example, polyacetal, and a stainless steel conductive ring 55 (corresponding to a conductive member) fixed to the front end of the ring body 54. The conductive ring 55 covers the entire front end surface of the ring main body 54 and the front portion of the outer peripheral surface, and the inner peripheral surface thereof is in contact with the outer peripheral surface of the air cap 40. One end of a lead wire 56 (shown only in FIG. 1) is screwed to the conductive ring 55. The other end of the lead wire 56 is connected to the screw 50. Thereby, the conductive ring 55 and the paint hose joint 17 are electrically connected via the lead wire 56, the screw 50, and the connecting member 16a. The paint hose joint 17 is also electrically connected to the paint because the paint passes through the inside. That is, in the present embodiment, the lead wire 56, the screw 50, the connecting member 16a, and the paint hose joint 17 constitute a connecting member.

  After the paint nozzle 29 is inserted into the mounting recess 19, the air cap 40 is fitted to the front end, and a retaining nut 42 is inserted from the front end of the air cap 40 and screwed into the thread 43. Is fixed to the barrel 2 together with the air cap 40. Thereafter, the cap ring 53 is fitted from the front of the air cap 40. At this time, an annular space located around the paint nozzle 29 is formed between the air cap 40 and the barrel 2. This space is used as the pattern air flow path 45 together with the pattern air flow path 44.

  An atomized air ejection hole 46 is formed in the center of the air cap 40. The paint discharge port 31 of the paint nozzle 29 is inserted into the atomizing air ejection hole 46. The atomizing air ejection hole 46 communicates with the atomizing air flow path 33a, and the atomizing air supplied to the atomizing air flow path 33a is connected to the inner peripheral surface of the atomizing air ejection hole 46 and the paint discharge port 31. It is ejected forward through an annular gap between the outer peripheral surface of each of them.

  A plurality of sub-pattern air ejection holes 47 are provided in the air cap 40 around the atomizing air ejection holes 46. The sub-pattern air ejection hole 47 communicates with the atomizing air flow path 33a, and the compressed air supplied to the atomization air flow path 33a is ejected forward from the sub-pattern air ejection hole 47 as sub-pattern air. .

  Further, a pair of corner portions 48 projecting forward are formed on the upper and lower portions of the front end surface of the air cap 40 with the atomizing air ejection hole 46 interposed therebetween. A plurality (two in FIG. 2) of pattern air ejection holes 49 that respectively communicate with the pattern air flow path 45 are formed in the corner portion 48. The pattern air ejection hole 49 is inclined obliquely forward toward the central axis of the air cap 40. Accordingly, the pattern air as the compressed air supplied to the pattern air flow path 45 is ejected obliquely forward from the pattern air ejection hole 49.

  Next, the operation when electrostatic coating is performed using the spray gun 1 having the above-described configuration will be described. When the trigger 28 is pulled, the paint valve 20 is opened, and the water-based paint supplied from the joint 17 is discharged to the paint flow path 30, and is transmitted from the paint discharge port 31 at the front end of the paint nozzle 29 to the surface of the pin electrode 32. It is discharged in the form of a film. At the same time, a high frequency voltage is supplied to the high voltage generation circuit in the cascade 4 and a DC high voltage of tens of thousands of volts generated by the high voltage rectification circuit is applied to the electrode 13. Since the pin electrode 32 is grounded using the conductivity of the paint, a strong electric field is generated from the surface of the pin electrode 32 toward the electrode 13 to which a high voltage is applied. As a result, a charge having a polarity opposite to the polarity of the high voltage of the electrode 13 is induced on the surface of the paint having conductivity that is transmitted through the surface of the pin electrode 32.

Further, when the trigger 28 is pulled, compressed air is supplied to the atomizing air flow path 33, and this compressed air passes through a narrow gap between the inner periphery of the atomizing air ejection hole 46 and the outer periphery of the paint discharge port 31. Is blown forward as converted air. The atomized air collides with the paint traveling on the surface of the pin electrode 32 and atomizes the paint by the principle of spraying. Simultaneously with the ejection of the atomizing air, the compressed air supplied from the atomizing air flow path 33 is also ejected from the sub pattern air ejection hole 47 as the sub pattern air. This sub-pattern air also plays an auxiliary role in the atomization of the paint.
The atomized paint particles thus ejected into the air with the charge induced by contacting the surface of the pin electrode 32. That is, the atomized paint particles are charged with a polarity opposite to the polarity of the electrode 13.

  On the other hand, the compressed air supplied to the pattern air flow paths 44 and 45 is ejected vigorously from the pattern air ejection holes 49 provided at the upper and lower corners 48 as the pattern air toward the obliquely inner front. This pattern air forms a spray pattern of atomized paint particles into an oval or oval shape suitable for painting. Note that the sub-pattern air ejected from the sub-pattern air ejection holes 49 also plays an auxiliary role in forming this spray pattern.

  The paint particles are mainly conveyed to the vicinity of the object by this pattern air. When the charged paint particles approach the object to be coated, a charge having a polarity opposite to the charge of the paint particles is induced on the surface of the object to be grounded by electrostatic induction. Then, an electrostatic force acts between the induced opposite polarity charges, and an attractive force toward the coating object acts on the paint particles. The paint particles are applied to the surface of the object by both the suction force and the spray force of the pattern air. Since the suction force due to the electrostatic force works, the paint particles are also wrapped around and applied to the back side of the object not facing the spray gun 1. Thus, electrostatic coating is performed on the workpiece.

  By the way, according to the experiment of the present inventor, when electrostatic coating is performed using the spray gun 1 of the present embodiment in which the cap ring 54 is mounted on the outer periphery of the air cap 40, a conventional spray gun that is not mounted is used. The amount of the paint attached to the surface of the air cap 40 was clearly reduced than the case. The reason is considered as follows.

  That is, the conductive ring 55 included in the cap ring 54 is electrically connected to the paint hose joint 17 via the lead wire 56, the screw 50, and the connecting member 16a. For this reason, the electric potentials of the conductive ring 55 and the paint hose joint 17 are substantially equal. Since the paint hose joint 17 is electrically connected to the paint passing through the paint hose joint 17, the potentials of the paint particles discharged from the paint discharge port 31 and the conductive ring 55 are substantially equal. Thus, when the potential of the paint particles and the conductive ring 55 becomes equal, the paint particles and the conductive ring 55 are electrically repelled. Accordingly, since the paint particles are transported to the vicinity of the object to be coated by the action of pattern air or the like without approaching the surface of the air cap 40, the amount of the paint adhering to the surface of the air cap 40 can be reduced.

According to this embodiment, since the conductive ring 55 is attached to the outer periphery of the air cap 40 and the electric potential of the conductive ring 55 and the paint particles is equal, the paint particles are formed on the surface of the air cap 40. Is less likely to approach, and the paint particles can be prevented from adhering to the surface of the air cap 40 as much as possible.
Further, the spray gun 1 according to the present embodiment has the same configuration as the conventional spray gun except that it includes a cap ring 53 and a lead wire 56 that connects the cap ring 53 and the paint hose joint 17 (screw 50). is doing. Therefore, the conventional spray gun can be used as it is.

  4 and 5 show a second embodiment of the present invention, which differs from the first embodiment in the following points. That is, in the second embodiment, a pair of corner portions 48 are provided on both left and right end portions of the front end surface of the air cap 40 with the atomizing air ejection hole 46 interposed therebetween. A conductive ring 61 is embedded in the front end surface of the air cap 40. The conductive ring 61 has an annular shape centering on the paint discharge port 31. Although the conductive ring 61 is buried in the air cap 40 at the portion where the corner portion 48 is located, most of the remaining portion is exposed on the front end surface of the air cap 40.

A lead wire 62 is embedded in the front end of the barrel 2 below the mounting recess 19. The lead wire 62 has the entire rear half embedded in the barrel 2 and the rest protruding forward from the front end of the barrel 2. The rear end portion of the lead wire 62 embedded in the barrel 2 extends to the communication path 25 a that connects the valve chamber 25 and the paint tube 26. Therefore, the lead wire 62 is electrically connected to the paint passing through the communication path 25a.

  On the other hand, the front end portion of the lead wire 62 is inserted into a pore (not shown) in the air cap 40, and the tip thereof is in contact with the rear surface of the conductive ring 61. When the air cap 40 is attached to the front end surface of the barrel 2, the front end portion of the lead wire 62 is inserted into the pore of the air cap 40. At this time, the middle portion of the lead wire 62 is located in the pattern air flow paths 44 and 45.

The configuration other than the above is the same as that of the first embodiment. Accordingly, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
Also in the above configuration, the conductive ring 61 and the paint passing through the communication path 25a are electrically connected via the lead wire 62 when performing electrostatic coating. The potentials are almost equal. Therefore, the atomized paint particles discharged from the paint discharge port 31 and the conductive ring 61 are electrically repelled, and the paint particles are prevented from adhering to the surface of the air cap 40 as much as possible.

  In the present embodiment, the lead wire 62 is disposed inside the spray gun 1. For this reason, dust does not adhere to the lead wire 62, and fingers do not get caught on the lead wire 62 during electrostatic coating work. For this reason, the work efficiency and the quality of the painting work can be improved.

The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
The entire conductive ring may be located in the air cap as long as it is near the front end surface of the air cap.
The portion connecting the conductive ring via the lead wire is not limited to a screw or a communication path. In short, it is only necessary that the conductive ring and the paint are electrically connected so that the potentials of both are equal.

In the first embodiment, the entire lead wire 56 is configured to be located outside the spray gun 1. However, a part of the lead wire 56 is embedded in the spray gun 1 (barrel 2), and the paint flow path is formed. You may connect to. Also in the first embodiment, the entire lead wire may be disposed inside the spray gun 1.
A corner | angular part may provide not only a pair but multiple pairs. Further, a pair may be provided on each of the upper and lower portions and the left and right portions of the front end surface of the air cap.

1 shows a first embodiment of the present invention, and is a longitudinal side view showing an overall configuration of a spray gun for electrostatic coating. Longitudinal side view showing enlarged front end Front view of the front end FIG. 1 equivalent view showing a second embodiment of the present invention. 3 equivalent figure

Explanation of symbols

  In the drawings, 1 is a spray gun for electrostatic coating, 2 is a barrel, 4 is a cascade (high voltage generating means), 13 is an electrode, 16a is a connecting member (connecting member), 17 is a joint for paint hose (connecting member), 25a is a communication path (paint supply path), 26 is a paint tube (paint supply path), 29 is a paint nozzle, 30 is a paint flow path, 31 is a paint discharge port, 33 is an atomizing air flow path, 32 is a pin electrode, 40 is an air cap, 44 is a pattern air flow path (space), 46 is an atomizing air ejection hole, 50 is a screw (connection member), 55 and 61 are conductive rings (conductive member), and 56 and 62 are lead wires. (Connecting member) is shown.

Claims (5)

In spray guns for electrostatic coating, where paint is atomized with compressed air and charged by charging it,
A barrel having a paint supply path connected to a paint supply source;
A paint flow path that is attached to the front end of the barrel and communicates with the paint supply path, an atomizing air flow path that is positioned around the paint flow path , and a paint discharge port that is positioned at the front end of the paint flow path A paint nozzle,
High voltage generating means for generating a DC high voltage for charging the paint discharged from the paint discharge port;
An atomized air jet attached to the front end of the barrel so as to cover the paint nozzle, having a space between the barrel and the paint nozzle, and being connected to the atomizing air flow path through which the paint discharge port is inserted An air cap having a hole in the center;
An electrode disposed in the space and supplied with a high voltage generated by the high voltage generating means;
A pin electrode disposed in the paint flow path of the paint nozzle and grounded so that the front end protrudes forward from the paint discharge port;
A substantially annular conductive member provided in the air cap and centering on the paint discharge port;
The conductive member and the connecting member and the spray gun for electrostatic coating, characterized in Tei Rukoto provided with the electrically connects the paint supply passage.   The spray gun for electrostatic coating according to claim 1, wherein the conductive member is detachably attached to an outer peripheral portion of the air cap.   The spray gun for electrostatic coating according to claim 1, wherein the conductive member is embedded in the vicinity of the front end surface of the air cap. The spray gun for electrostatic coating according to any one of claims 1 to 3, wherein the connecting member is connected in the vicinity of a portion of the paint supply path that communicates with the paint flow path. The spray gun for electrostatic coating according to claim 4, wherein the connecting member is connected to the paint supply path via a space between the paint nozzle, the barrel and the air cap.

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