JP5579515B2 - Spray gun for electrostatic coating with counter electrode - Google Patents

Description

  The present invention relates to a spray gun for electrostatic coating suitable for a paint having a relatively large electrical resistance such as a solvent-based paint, and a counter electrode is detachably attached to the atomizing head of the spray gun in the vicinity of the charged electrode. Is.

  Generally, an air atomizing type spray gun for electrostatic coating is composed of an atomizing head having a tip provided with a paint nozzle and an air cap for atomizing paint with compressed air, a grounded grip portion, and the atomizing head. And a body part for insulating the grip part. A high voltage generator for generating a high voltage is built in the body part, and a charging electrode is projected from the paint nozzle of the atomizing head at the tip. An ionized sphere is formed by charging the electrode with a negative high voltage of several tens of kilovolts, and the atomized paint that is atomized by the injection of compressed air from the air cap is passed through the ionized sphere to the paint. In addition to negative charging, the paint is applied to the object by the electric field formed between the charged electrode and the object to be coated, and the conveying force of atomization and pattern forming air.

  Here, the charging effect on the paint varies greatly depending on whether or not the ionized sphere region formed by the charged electrode is effectively formed. For this reason, a counter electrode has been used as a means for forming a strong ionization sphere region by forming another electric field between the charged electrode and the object to be coated. That is, in order to improve the coating efficiency, dispose the counter electrode on the top or side of the spray gun body that is grounded and separated from the tip charging electrode so that discharge is promoted from the tip charging electrode. Yes.

  For example, as shown in FIG. 7, there is a handheld spray gun in which a counter electrode A is provided at the tip of a hook portion C protruding above the gun body B. In this case, since the current from the charging electrode D at the tip flows along the creeping surface E along the gun body B, there is a defect that the surface of the gun body made of an insulating resin is easily eroded. In addition, since the distance between the charged electrode and the counter electrode is long, the flowing current is easily affected by humidity and it is difficult to obtain stable ionization. Since the grounded counter electrode is located near the booster circuit of the high voltage generator F in the gun barrel, the breakdown of the gun barrel is likely to occur. Further, the counter electrode may be damaged by the hook portion coming into contact with the metal fitting to which the gun is hooked.

  Japanese Patent Laid-Open No. 8-84942 of Patent Document 1 is an electrostatic automatic spray gun, in which a counter electrode with a built-in resistor is provided on the outer side of the gun body and projects toward the tip of the charged electrode protruding at the tip. Is disclosed. Japanese Patent Application Laid-Open No. 2007-203158 of Patent Document 2 discloses a technique in which a conductive ring that acts as a counter electrode is detachably attached on the outer circumference of an air cap centered on a pin electrode that serves as a charging electrode. . In addition, as a prior art using a counter electrode, for example, Japanese Patent Application Laid-Open No. 58-80470 using a metal paint pipe as a counter electrode, a part of a metal paint pipe or a part of a conductive hook part Japanese Examined Patent Publication No. 61-40470 has been proposed.

JP-A-8-84942 JP 2007-203158 A Japanese Patent Laid-Open No. 58-80470 Japanese Patent Publication No.61-40470

  As described above, when the counter electrode is disposed on the upper part or the side part of the spray gun body, ions discharged from the charged electrode at the tip are discharged along the creepage surface of the gun body, resulting in the gun body. The part will be eroded. If the counter electrode is arranged in front of the gun to prevent electric corrosion, the distance from the charged electrode at the tip is reduced, and the discharge is promoted to lower the voltage of the charged electrode, so that a sufficient discharge cannot be obtained. Further, when the counter electrode is arranged at a location where the electric corrosion can be prevented and the voltage can be maintained, the counter electrode A obstructs the painting work because the charged electrode D at the tip is turned far away as shown in FIG.

  The present invention has been made in view of such problems, and prevents electric corrosion of the body of the spray gun and maintains an effective discharge of the charged electrode to form an ionization zone and maintain charging efficiency. It is an object of the present invention to provide a spray gun for electrostatic coating in which the counter electrode is attached to a position outside the spray gun so as not to obstruct the painting operation and to be detachable with one touch. In that case, when the counter electrode is placed at the tip of the spray gun, since the distance from the charged electrode is close, the resistor is built in the counter electrode so that the voltage does not drop due to excessive current flow. The counter electrode unit can be controlled and can be attached to and detached from an existing spray gun with a single touch.

  In order to achieve the above object, the spray gun according to claim 1 has a high voltage generator built in the body, a charging electrode is provided at the tip of the paint nozzle, and high voltage is charged to the fine particles of the sprayed paint. This is an air atomizing spray gun for electrostatic coating that forms an ionized sphere, and is close to the charged electrode at the tip and in a position where there is no interference at the corners of the air cap when connected with the charged electrode in a straight line. The counter electrode is detachably attached.

  The spray gun according to claim 2 is the spray gun according to claim 1, wherein the counter electrode is held by the electrode support body together with the resistor, and can be attached to the holding member and the gun stay that can be attached to and detached from the atomizing head. What was formed as a counter electrode unit which has a fitting piece was made to be detachable by one touch.

  According to the present invention, since the distance between the charged electrode and the counter electrode is reduced, current fluctuation due to humidity (current value that flows is different between dry air and wet air) is suppressed. There is an effect. In addition, by controlling the current value by inserting a resistor and suppressing current fluctuation, it is possible to eliminate wasteful current, effectively charge the paint fine particles, and reduce the load on the transformer of the high voltage generator. Leads to. In addition, the counter electrode has a unit structure that can be fixed with a clip type that does not use screws for attaching to off-the-shelf spray guns, so it can be attached and detached with a single touch, making it easy to replace the air cap and clean the tip of the gun. Can be easily removed and dealt with easily. Furthermore, since the counter electrode unit is attached at a position overlapping the paint pipe, the paint pipe serves as a guard and prevents the counter electrode unit from being damaged.

It is a side view of the spray gun for electrostatic painting (henceforth an electrostatic gun) which attached the counter electrode unit which shows the example of the present invention. It is a front view of the electrostatic gun. It is sectional drawing to which the atomization head of the electrostatic gun was expanded. It is explanatory drawing before attaching the counter electrode unit. It is the perspective view which expanded the atomization head of the electrostatic gun, and shows the positional relationship of the charging electrode and counter electrode in the state where the air cap is blown vertically. It is the front view which expanded the atomization head of the electrostatic gun, and shows the positional relationship of a charging electrode and a counter electrode. It is explanatory drawing which shows the creeping discharge of the conventional electrostatic gun which provided the counter electrode in the hook part. It is a perspective view of the conventional electrostatic gun which shows an example which avoids creeping discharge and secures the distance which does not drop a voltage, but a counter electrode obstructs a painting operation.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a side view showing an outline of an electrostatic gun according to an embodiment of the present invention. An electrostatic gun main body 1 includes an atomizing head 2 at the tip, a body 3 formed of an insulating material, a grip 4 and the like. It consists of A cartridge-type high-voltage generator 5 that contains a booster circuit, a transformer, and a protective resistor and is molded with an insulating resin is accommodated in the body 3. The output terminal 5a of the high voltage generator 5 is connected to the conductor 5b, and is connected to the grounded needle valve 7 that advances and retreats in the paint nozzle 6 in the atomizing head 2 at the tip, and is connected to the tip of the needle valve 7. It is electrically connected to the projecting pin-shaped charging electrode 8. Thus, the high voltage generated by the high voltage generator 5 is supplied to the pin-shaped charging electrode 8 protruding from the tip of the paint nozzle 6.

  Reference numeral 9 denotes an air cap fitted to the paint nozzle 6, which is provided with an annular air outlet 10 between the paint nozzle 6 and atomizes the paint with compressed air and forms pattern forming air at the opposite corners 11. An oval spray pattern suitable for coating is formed by compressed air injected from the holes 11a. 12 is a cover for holding the air cap 9 from the outside, and is screwed into the front end of the body portion 3. By loosening the cover 12, the direction of the air cap 9 is rotated by an angle of 90 degrees to thereby change the direction of spraying. It can be changed to vertical blow or side blow. 13 is an auxiliary air hole provided in the air cap 9, and 14 is an air passage formed in the atomizing head 2.

  Reference numeral 15 denotes a counter electrode attached to the outside of the air cap 9 in the vicinity of the charging electrode 8 of the atomizing head 2. An electrode pin 16 projects from the tip, and a resistor 17 is provided in the vicinity of the electrode pin 16. A counter electrode unit 20 built in the electrode support 18 is configured. The resistance value of the resistor 17 may be appropriately determined according to various conditions, but the resistance value was calculated so that a current value of about 20 μA flows at a voltage of −40 kV. According to this example, the resistance value was around 3 GΩ, and a remarkable effect on improving the coating efficiency was confirmed.

  As shown in the exploded view of FIG. 4, the counter electrode unit 20 holds the counter electrode 15 at the base of the gripping member 19 whose section made of insulating resin is C-shaped, and the cover 12 of the air cap 9 is fitted. The gripping member 19 is attached to the peripheral surface of the recessed step portion 21 with the body portion 3 in a clipped manner, and the proximal end serving as the grounding side is attached to the conductive gun stay 24 by the fitting piece 22.

  The fitting piece 22 is constituted by an attachment piece having a resilience formed of, for example, a metal thin plate and connected to the electrode support 18 by a conductor 23 so that it can be attached to the gun stay 24 by one touch. The gun stay 24 is a connecting member that is below the grip portion 4 and integrally holds the air hose joint 25, the power connector 26, and the paint hose joint 27. Thus, the counter electrode unit 20 is detachably attached to the electrostatic gun body 1 in a one-touch manner. Therefore, it can be mounted on an existing electrostatic gun as it is, that is, without changing the structure of the gun.

  The counter electrode 15 is preferably located at the peripheral edge of the air cap 9 as close as possible to the charged electrode 8 at the tip in a linear distance from the viewpoint of preventing electrolytic corrosion of the body 3. However, when it is attached to the upper part of the air cap 9, it is located on the near side of the hook, so that there is a risk of getting in the way or breaking when using the hook. Therefore, it is essential that the position satisfies the following condition. That is, as shown in FIG. 6, when the charged electrode 8 at the tip and the tip of the counter electrode 15 are connected by a straight line X, the location Y must be in the range Y1 to Y2 where there is no interference of the corner 11 of the air cap 9. There is.

  That is, the air cap 9 is provided with corner portions 11 having pattern forming air holes 11a for forming a spray pattern so as to oppose each other, and a vertical spray pattern or a horizontal spray pattern is selected depending on the shape of the object to be coated. In addition, the air cap 9 may be rotated at an angle of 90 degrees with respect to the central charged electrode 8. The direction of the air cap 9 in the front view of FIG. 2 is at a position for forming a horizontal blowing pattern, and the corner portion 11 is at a vertical position. Further, the position of the air cap 9 in the enlarged perspective view of FIG. 6 is a position for forming a vertical spray pattern, and the corner portion 11 is in a horizontal position. Therefore, an oblique position (in the range of Y1 to Y2 in FIG. 6) that is 90 degrees vertical and horizontal with respect to the charged electrode 8 is a position where there is no interference by the corner 11 of the air cap 9.

  The structure of the electrostatic gun body 1 is well known and will not be described in detail. In the figure, reference numeral 28 denotes a paint pipe, and the tip is connected to a paint flow path 6a in the paint nozzle 6 in the atomizing head 2 by a paint joint 29. The rear end is connected to a paint hose joint 27 attached to the gun stay 24. The paint nozzle 6 opens and closes by the advancement and retreat of the needle valve 7 inserted therein, and controls the paint ejected from the central ejection port 6a. Reference numeral 30 denotes a compressed air introduction passage formed in the grip portion 4. The needle valve 7 is operated by pulling the trigger 31 and the air valve 32 is operated, and compressed air is supplied to the air passage 14 of the atomizing head 2. Then, the compressed air is ejected from the air outlet 10 of the air cap 9 to atomize the paint ejected from the paint nozzle 6 and form a spray pattern suitable for painting. An electric circuit 33 is connected to the power connector 26. When the trigger 31 is pulled, a high frequency voltage is supplied to the high voltage generator 5 in the body 3. Reference numeral 34 denotes a hook for hooking the electrostatic gun 1 projecting from the upper portion of the body 3.

  As is apparent from FIGS. 1 and 2, the counter electrode unit 20 is attached so as to overlap the paint pipe 28 with substantially the same inclination as the paint pipe 28. Accordingly, the paint pipe 28 serves as a guard even if it comes into contact with peripheral equipment by mistake during operation of the electrostatic gun, and damage to the counter electrode unit 20 can be prevented.

Next, a method of using the present invention will be described.
When the trigger 31 is pulled, a high frequency voltage is supplied to the high voltage generator 5 through the power connector 26 and the electric circuit 33, and a negative high voltage of −40 kV is applied to the tip of the atomizing head 2 through the output terminal 5a and the conductive wire 5b. To the pin-shaped charging electrode 8. The paint is atomized by the air injected from between the annular air outlet 10 of the air cap 9 at the same time as the needle valve 7 is pulled and ejected from the center opening 6 a of the paint nozzle 6. Moreover, in order to promote atomization, the air from the auxiliary air hole 13 provided on the circumference of the air outlet 10 is injected. At this time, an ionization sphere is formed by the electric field formed between the pin-shaped charging electrode 8 and the counter electrode 15 having the tip facing the lower outer periphery of the air cap 9, and a negative high voltage is applied to the fine particles of the paint. Is charged.

  The fine particles of the paint charged with a negative high voltage are formed into an oval spray pattern suitable for painting by pattern forming air sprayed from the pattern forming air holes 11a of the opposite corners 11 of the air cap 9, and sprayed. Electrostatic coating is performed by applying the air conveying force and electric lines of force formed between the charging electrode 8 and the object to be coated.

  In the present invention, the counter electrode 15 is attached to a position where there is no interference of the corner portion 11 of the air cap 9 when the counter electrode 15 is close to the charged electrode 8 at the tip and connected to the charged electrode 8 with a straight line. In addition, lines of electric force are formed between the two electrodes, and creeping discharge to the electrostatic gun body 2 at the rear can be prevented. Accordingly, it is possible to prevent electrolytic corrosion on the creeping surface of the electrostatic gun barrel, and to prevent the return of the coating fine particles to the barrel 2.

  Further, in order to make it possible to attach the counter electrode 15 to an existing electrostatic gun, the counter electrode unit 20 in which the electrode support 18 in which the resistor 17 is connected to the counter electrode 15 can be attached in a clip-type manner with one touch is provided. As a result, the counter electrode can be easily attached, and can be easily removed when the air cap is replaced or cleaned.

  In addition, since the resistor 17 is connected to the counter electrode 15 to form the electrode support 18, it is possible to prevent a sudden voltage drop despite the close proximity of the distance between the charging electrode 8 and the counter electrode 15. It is possible to form an ionized sphere with enhanced

  Further, when the counter electrode unit 20 is attached to the electrostatic gun, the counter electrode unit 20 is attached so as to overlap the existing paint pipe 28, so that the paint pipe 28 serves as a guard, and the counter electrode unit 20 can be prevented from being damaged.

DESCRIPTION OF SYMBOLS 1 Electrostatic gun body 2 Atomization head 3 Body 4 Gripping part 5 High voltage generator 6 Paint nozzle 7 Needle valve 8 Charging electrode 9 Air cap 10 Air outlet 11 Corner part 12 Cover 15 Counter electrode 16 Electrode pin 17 Resistance Body 18 Electrode support 19 Holding member 20 Counter electrode unit 22 Insertion piece 23 Conductor 24 Gun stay

Claims (3)

  For air atomization type electrostatic coating with a built-in high-voltage generator in the body, a charged electrode protruding from the tip of the paint nozzle, and an ionization zone where high voltage is charged to the sprayed paint particles A counter electrode, which is a spray gun, wherein the counter electrode is detachably attached at a position close to the charged electrode at the tip and where there is no interference with the corner of the air cap when connected with the charged electrode in a straight line. A spray gun for electrostatic painting.   The counter electrode is held by an electrode support together with a resistor, and is formed as an integrated counter electrode unit provided with an atomizing head of a spray gun and a fixing means that can be attached to and detached from a grounded gun stay. An electrostatic coating spray gun provided with the counter electrode according to claim 1.   The counter electrode is held by an electrode support together with a resistor, and is a one-piece counter electrode that has a gripping member that can be attached to and detached from the atomizing head of the spray gun, and a fitting piece that can be attached to a grounded gun stay. The spray gun for electrostatic coating provided with the counter electrode according to claim 1, wherein the spray gun is formed as a unit.

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