JP5400995B2 - Electrostatic painting spray gun - Google Patents

Description

  The present invention relates to a spray gun for electrostatic coating, and more particularly to a spray gun for electrostatic coating suitable for electrostatic coating using a water-based paint or metallic paint having a relatively low electrical resistance.

  In general, paints used for electrostatic coating of car bodies and the like are solvent-based paints (oil-based paints) having a relatively high electrical resistance, water-based paints (water-based paints) having a relatively low electrical resistance, and metal powders dispersed therein. There are metallic paints. When electrostatic coating is performed using water-based paints or metallic paints with relatively low electrical resistance, a high voltage is applied directly to the charging electrode of the electrostatic coating gun body that comes into contact with these paints. Current flows to the ground via the path and paint tank. Therefore, corona discharge does not occur between the charged electrode and the grounded object, so that the paint particles cannot be charged and electrostatic coating cannot be performed.

  As a conventional technique for solving this problem, for example, one or a plurality of bare external electrodes are arranged radially outside the electrostatic coating gun main body, and a high voltage is applied thereto to cause corona discharge. There is a system called an external electrode system. This method includes a method using a rotary atomizing head for atomizing paint in the electrostatic coating gun body (for example, see Patent Document 1) and an air spray method using compressed air (for example, see Patent Document 2). is there. In both systems, the external electrode to which a high voltage is applied does not come into contact with the paint having a low electrical resistance, so that the paint particles can be charged by causing a corona discharge while the paint tank is grounded. However, in the case of this external electrode method, the external electrode is attached to the outside of the electrostatic coating gun body, so that the electrostatic coating gun becomes large and there is a bare electrode to which high voltage is applied. The danger of is high. There is also a problem that the atomized paint particles adhere to the vicinity of the external electrode or around the electrostatic coating gun main body due to electrostatic force.

  In order to solve the problem of the external electrode system, an electrostatic coating gun of a system that generates paint particles charged by electrostatic induction instead of corona discharge has been proposed. For example, in Patent Document 3, a positive or negative high voltage is applied to an electrode provided at a position closer to the coating atomization head than the position of a conventional external electrode, and a charge having a polarity opposite to the high voltage of the electrode is applied to the coating particles. Is charged by electrostatic induction. A rotary atomizing electrostatic coating apparatus is disclosed in which the charged paint particles are conveyed to the vicinity of the object by air and then applied to the object by the self electric field of the charged paint particles. However, in the case of this apparatus, there is a problem that the structure becomes complicated due to the use of a rotary paint atomizing head.

  In Patent Document 4, the rotary paint atomizing head is replaced with a liquid spray orifice, low-pressure, high-volume air is supplied to the air orifice in the vicinity thereof, and a charging electrode is disposed in the immediate vicinity of the outlet of the liquid spray orifice. A spraying method is disclosed. The paint is atomized in a state of being charged to a polarity opposite to the voltage polarity of the charging electrode by electrostatic induction. Although this device has a simpler structure than a device using a rotary paint atomizing head, a partially bare charging electrode is arranged in the immediate vicinity of the outlet of the liquid spray orifice, so that it is charged with a polarity opposite to that of the charging electrode. There is a problem that a part of the paint particles easily deposits on the charging electrode.

  Furthermore, as an electrostatic coating gun employing an electrostatic induction method, an air cap attached to the front surface of the gun body in the state in which the inventors of the present application covered an electrode that causes electrostatic induction with an electrically insulating material in Patent Document 5. Or a spray gun for electrostatic coating that is housed in a corner portion that protrudes forward from the upper and lower radial positions of the air cap.

Japanese Patent Laid-Open No. 06-134353 Japanese Patent Laid-Open No. 09-136047 Japanese Patent Laid-Open No. 7-251097 JP 9-502647 A Japanese Patent Application No. 2005-504030

  The present invention has been made from such a background, and is an electrostatic coating spray gun for electrostatic coating using a water-based paint or a metallic paint having a relatively low electrical resistance. It is an object of the present invention to provide a spray gun for electrostatic coating that can be made into a small amount, has a low risk of electric shock, consumes less power, and can be easily replaced.

In the invention according to claim 1 for solving the above-mentioned problem, when the means is given the reference numeral of an embodiment described later, the paint atomized with compressed air is charged using a high voltage. A spray gun for electrostatic coating to be applied to an object to be coated, a cylindrical portion 20 formed to protrude forward from a front end portion of a substantially cylindrical gun main body portion 2 having at least a front end outer surface layer portion made of a dielectric. A coating material nozzle 7 attached to the inside of the cylindrical portion 20 and having a coating material discharge port 13 at its tip; an air cap 14 covering the coating nozzle 7 and the front end surface of the cylindrical portion 20; and an electrostatic induction electrode 33. The air cap 14 has an atomizing air ejection hole 16 through which the paint discharge port 13 is inserted at the center and the compressed air that atomizes the paint discharged from the paint discharge port 13 is ejected from the periphery of the paint discharge port. Is further drilled A pair of corner portions 25 are provided so as to protrude forward from the upper and lower portions of the front end of the cap 14, and compressed air supplied through a pattern air flow path 28 provided inside the corner portion is provided at the tip portion of the corner portion 25. A pattern air ejection hole 30 that is ejected obliquely inward and forward is provided, and the electrostatic induction electrode 33 is a rod-shaped electrode portion 34 and a rod-like shape that extends perpendicularly to the ring surface from one ring outer peripheral portion of the ring-shaped electrode portion. The support electrode part 35 is composed of a ring-shaped electrode part 34 and the support electrode part 35, and the entire surface of the support electrode part 35 excluding the other end face part 36 is covered with a dielectric. The other end side is detachably attached to a projection (32) at the upper front end portion of the gun main body 2 so as to be inserted into and removed from the front end side. In the inserted state, the other end side end face portion 36 is at a high voltage. In contact with the supplied terminal portion 37 Serial projections work to prevent missing presses the insulating screws 40 fitted in threaded holes formed toward the outer surface of the supporting electrode portion 35, the ring-shaped electrode portion 34 to the ring inside a state which attained該抜only prevention When the pair of corners (25) are inserted, the paint outlet is close to the paint discharge port. When electrostatic coating is performed, the paint in the paint nozzle 7 is electrically connected to the paint. The paint is discharged from the paint discharge port 13 in a state in which a high voltage with reference to the ground potential is applied to the electrostatic induction electrode 33 by grounding via a grounding wire or via a ground wire. At the same time, the spray gun for electrostatic coating is characterized in that compressed air is ejected from the atomizing air ejection holes 16 and the pattern air ejection holes 30 to atomize the paint.

  In the spray gun for electrostatic coating with such a configuration, the outer surface of the electrostatic induction electrode is covered with a dielectric material, so that no direct current flows out. There is little danger of. Moreover, since the space | interval between the ring-shaped electrode part of an electrostatic induction electrode and a coating material discharge outlet can be narrowed, the strong electric field required for electrostatic induction can be generated with a low voltage. Further, since the electrostatic induction electrode can be easily attached to and detached from the gun body, the electrostatic induction electrode can be replaced in a short time even if it is stained with paint.

Further, according to a second aspect of the present invention, in the spray gun for electrostatic coating according to the first aspect, instead of the ring-shaped electrode portion 34, the tip of the support electrode portion 35 is perpendicular to the support electrode portion 35. the outer surface using the electrostatic induction electrode 33a fitted with a rod electrode portion 34a covered with dielectric extending and fixedly inserted into the insertion hole 38 provided with electrostatic induction electrode 33a to the front end upper portion of the gun main body 2 The electrostatic coating spray gun is characterized in that the tip end portion of the rod electrode portion 34a is positioned close to the paint discharge port 13 in the state.

  Even in such a configuration, since the outer surface of the electrostatic induction electrode is covered with a dielectric and direct current does not flow out, an extremely small capacity is required and the risk of electric shock is small. Moreover, since the space | interval between the rod electrode part of a static induction electrode and a coating material discharge outlet can be narrowed, the strong electric field required for static induction can be generated with a low voltage. Further, since the electrostatic induction electrode can be easily attached to and detached from the gun body, the electrostatic induction electrode can be replaced in a short time even if it is stained with paint.

  According to a third aspect of the present invention, in the spray gun for electrostatic coating according to the first or second aspect, the high voltage generating circuit 4a using a battery 70 as a power source is connected to the terminal portion 37 to which the high voltage is supplied. This is a spray gun for electrostatic coating characterized in that the battery 70 is detachably housed in the gun body 2.

  In the spray gun for electrostatic coating having such a configuration, the outer surface of the electrostatic induction electrode is covered with a dielectric and no direct current flows out, so that the power supply capacity of the high voltage generating circuit can be very small. Therefore, even a power source using a battery can sufficiently generate a high voltage and a necessary output current necessary for electrostatic coating. Since the battery is detachably housed in the gun body, the power cable for supplying power from the outside can be eliminated, and the workability when painting with the spray gun held in hand is remarkably improved.

  According to a fourth aspect of the present invention, in the spray gun for electrostatic coating according to the first or second aspect, the high voltage generating circuit 4 that receives power from the outside is supplied to the terminal portion 37 to which the high voltage is supplied. The high voltage generating circuit 4 is connected to a capacitor 50 that is charged by the high voltage current generated by the high voltage generating circuit 4. The spray gun for electrostatic coating.

  In the spray gun for electrostatic coating with such a configuration, the outer surface of the electrostatic induction electrode is covered with a dielectric material, and direct current does not flow out, so the high voltage generating circuit has a very small capacity that can supply a leakage current. That's it. Therefore, once the capacitor is charged, the capacitor can maintain a high voltage for a long time even if the power supply cable is disconnected and the power supply to the high voltage generation circuit is cut off. Can do. Since painting can be performed with the power cable disconnected, the workability when painting with a spray gun in hand is significantly improved.

It is an outline side view of spray gun 1 concerning a 1st embodiment. 1 is an external plan view of a spray gun 1. FIG. 2 is a front view of a tip portion of the spray gun 1. FIG. 1 is a longitudinal sectional view of a spray gun 1. 2 is an enlarged longitudinal sectional view of a tip portion of the spray gun 1. FIG. 3 is a perspective view of a ring-shaped electrostatic induction electrode 33. FIG. It is a block diagram of a high voltage supply circuit. It is explanatory drawing about operation | movement and an effect | action of the spray gun. It is an external appearance perspective view of the electrostatic induction electrode 33a which concerns on 2nd Embodiment. It is an external side view of the spray gun 1a which concerns on 2nd Embodiment. It is a front view of the tip part of spray gun 1a concerning a 2nd embodiment. It is a circuit block diagram of the high voltage generation circuit 4a which uses the battery 70 as a power supply.

Hereinafter, the configuration of a spray gun for electrostatic coating according to the present invention (hereinafter simply referred to as a spray gun) will be described by dividing it into embodiments.
(First embodiment)
The spray gun according to the present invention is a gun suitable for electrostatic coating mainly using a water-based paint or metallic paint having a relatively low electric resistance. 1 is an external side view of a spray gun 1 according to the first embodiment, FIG. 2 is an external plan view, FIG. 3 is a front view of a tip portion, FIG. 4 is a longitudinal sectional view, and FIG. FIG.

  As shown in FIG. 1, the spray gun 1 includes a gun body 2, a grip 3 provided at the rear end thereof, and an atomizing device portion described in detail after being attached to the front end of the gun body 2. Has been. The gun body 2 is covered with an insulating synthetic resin and has a substantially cylindrical shape as a whole. The spray gun 1 is a spray gun with a built-in high voltage generation circuit, and is long in the front-rear direction in which a step-up transformer and a high voltage rectifier circuit required for generating a high voltage are integrally molded in the upper part of the gun body 2. A high voltage generating circuit 4 having a shape is accommodated.

  At the center of the front end face of the gun main body 2, a mounting recess 6 having a circular cross section and a two-stage depth change is formed. A paint nozzle 7 made of an insulating synthetic resin material is inserted into the recessed portion on the back side of the mounting recess 6 in a posture protruding forward with its rear end face in contact with the paint discharge side surface of the paint valve 8.

  The paint nozzle 7 is provided with a central hole penetrating between the front and rear end faces. The central hole communicates with the central hole of the paint valve 8 and functions as a paint flow path 10 reaching the paint valve 8. The front end of the paint nozzle 7, that is, the portion corresponding to the front end of the paint flow path 10, is formed so as to protrude in a small diameter, and is inserted as a paint discharge port 13 into an atomizing air ejection hole 16 provided in an air cap 14 to be described later. Has been. The paint supplied from the paint valve 8 passes through the paint flow path 10 and is discharged forward from the paint discharge port 13.

  Inside the paint nozzle 7, a plurality of atomizing air passages 15 arranged concentrically with the paint passage 10 are formed in a hole shape penetrating between both front and rear end faces of the paint nozzle 7. The front end of the atomizing air flow path 15 communicates with an annular atomizing air flow path 17 surrounded by the front end face of the paint nozzle 7 and the back surface of the air cap 14.

  The back surface side of the paint nozzle 7 is formed in a concave shape in order to secure the annular atomizing air flow path 17 between the front end side outer surface of the paint nozzle 7, and the end surface of the concave portion is the front end surface of the paint nozzle 7. The annular atomizing air flow path 17 and the atomizing air flow path 15 are communicated with each other. In this state, the air cap 14 is pressed against the paint nozzle 7 by a retaining nut 48 that engages with a screw thread provided on the outer peripheral surface of the cylindrical portion 20 formed to protrude forward from the outer peripheral edge of the front end of the gun body portion 2. It is fixed in the state. As a result, the paint nozzle 7 is fixed in a state where the end surface around the paint flow path 10 on the rear end side is pressed against the paint discharge side surface of the paint valve 8.

  The above-described atomizing air ejection hole 16 is formed in the central portion of the air cap 14 and the above-described paint discharge port 13 is inserted therethrough. The atomizing air ejection hole 16 communicates with the annular atomizing air flow path 17 and passes through an annular gap between the inner circumferential surface of the atomizing air ejection hole 16 and the outer circumferential surface of the paint discharge port 13. Air is jetted forward. In addition, two upper and lower sub-atomization air ejection holes 23 communicating with the annular atomization air flow path 17 are formed in the upper and lower positions close to the atomization air ejection hole 16 so that the atomization air flow The compressed air supplied from the path 15 is jetted forward as sub-atomized air.

  Further, a pair of corner portions 25 are formed from the upper and lower ends of the surface of the air cap 14 so as to protrude forward in the vertical direction. Inside, there is a corner pattern air flow path 28 communicating with a pattern air flow path 27 formed between the inner surface of the inlet portion of the mounting recess 6 at the center of the front end surface of the gun body 2 and the outer surface of the paint nozzle 7. Is formed. A plurality of pattern air ejection holes 30 (two in each corner 25 in FIG. 5) communicating with the corner pattern air flow path 28 are formed at the tip of the corner 25. The compressed air supplied through the pattern air passage 27 and the corner pattern air passage 28 is ejected from the pattern air ejection hole 30 obliquely forward and inward as pattern air that determines the spray shape of the atomized paint. The

  A protrusion 32 is provided on the upper front end of the gun body 2, and a ring-shaped electrostatic induction electrode 33 as shown in FIG. 6 is attached to the protrusion 32 toward the front. The electrostatic induction electrode 33 includes a ring-shaped electrode portion 34 and a rod-shaped support electrode portion 35 that extends from one ring outer peripheral portion of the ring-shaped electrode portion 34 at a right angle to the ring surface. The other end side of the support electrode portion 35 is removably inserted into an insertion hole 38 provided from the front surface side in the projection portion 32. In the inserted state, the end surface portion 36 on the other end side is a terminal portion to which a high voltage is supplied. 37 is brought into contact. A screw hole is provided from the upper outer surface of the protrusion 32 toward the support electrode 35, and the support electrode 35 is pressed by the screw 40 made of an insulating material screwed into the screw hole. The induction electrode 33 is prevented from coming off.

  As a feature of the electrostatic induction electrode 33 according to the present invention, the electrode is entirely covered with an insulating dielectric except for the end face portion 36 on the other end side. Therefore, the surface of the metal electrode is not exposed to the outside when the electrostatic induction electrode 33 is attached to the gun body 2. Further, in the attached state, the ring-shaped electrode portion 34 is in a state in which the tip portions of the pair of corner portions 25 are inserted into the inside of the ring and positioned as close as possible to the paint discharge port 13 of the paint nozzle 7. The external dimensions have been adjusted.

  The high voltage required for electrostatic coating applied to the electrostatic induction electrode 33 is generated by the control circuit 42 and the high voltage generation circuit 4 shown in FIG. The control circuit 42 is installed near a paint tank (not shown) and includes a high frequency oscillation circuit 44 and an output transformer 45. When commercial power is supplied to the high frequency oscillation circuit 44, a high frequency voltage is generated on the secondary side of the output transformer 45 connected to the output side. The generated high frequency voltage is supplied to the primary side of the step-up transformer 48 in the high voltage generation circuit 4 attached in the gun body 2 through the power cable 47. The high-frequency voltage boosted by the step-up transformer 48 is rectified by a Cockcroft-Walton voltage doubler rectifier circuit 49 to generate a DC high voltage of 20,000 to 20,000 V. The polarity of the generated high voltage can be positive (plus) or negative (minus) by changing the direction of the diode in the Cockcroft-Walton voltage doubler rectifier circuit 49. One end of the secondary coil of the step-up transformer 48 is grounded. As a feature of the present invention, a capacitor 50 is additionally connected between the voltage doubler rectifier circuit 49 and a grounded secondary coil. The high voltage generated at the output terminal of the voltage doubler rectifier circuit 49 is supplied to the terminal portion 37 through the high resistor 51, and the electrostatic induction electrode 33 through the other end surface portion 36 of the support electrode portion 35 that contacts therewith. Is supplied with a high voltage.

  The paint is supplied from a paint tank (not shown) to a paint hose joint 53 attached to the lower part of the grip 3 by a paint hose (not shown), and is guided to the paint valve 8 through the paint tube 54. . The paint valve 8 is opened and closed by a needle 57 that moves back and forth in conjunction with the operation of the trigger 56, and the supplied paint is opened and discharged to the paint channel 10 in the paint nozzle 7 only while the trigger 56 is being pulled. Let

  Compressed air for atomized air and pattern air is supplied from a compressed air generator (not shown) to an air hose joint 60 attached to the lower part of the grip 3 by a high-pressure air hose, passes through an air flow path 61 in the grip 3, and after the gun body 2 It is guided to an air valve 62 attached to the end. The air valve 62 opens and closes compressed air in accordance with the opening and closing of the paint valve 8 by a valve body 63 that moves back and forth integrally with the needle 57. The compressed air that has passed through the air valve 62 is supplied to the atomizing air passage 15 and the pattern air passage 27 through a passage (not shown) provided in the gun body 2.

  Next, the operation and action of the spray gun 1 of the present embodiment configured as described above will be described with reference to FIG. When the trigger 56 is pulled, the paint valve 8 opens and the paint supplied from the joint 53 is discharged to the paint flow path 10 and is discharged from the paint discharge port 13 at the front end of the paint nozzle 7. At the same time, the high-frequency voltage fed by the power cable 47 is supplied to the high voltage generation circuit 4. The DC high voltage of tens of thousands of volts generated by the high voltage rectifier circuit 49 charges the capacitor 50 and is applied to the electrostatic induction electrode 33 via the high resistor 51.

  The paint is grounded via the paint tank due to its conductivity. If the polarity of the high voltage applied to the electrostatic induction electrode 33 is positive, a strong electric field is generated from the ring-shaped electrode portion 34 of the electrostatic induction electrode 33 toward the ground potential paint of the paint discharge port 13. As a result, a large amount of negative charges having a polarity opposite to the high voltage of the electrostatic induction electrode 33 is induced by electrostatic induction on the surface of the paint just before it becomes mist particles away from the paint discharge port 13. The paint pushed out from the paint discharge port 13 is atomized by the atomization principle by the atomizing air ejected from the atomizing air ejection hole 16 and the sub-atomization air ejection hole 23. The atomized paint particles retain the negative charge induced just before leaving. That is, the atomized paint particles 64 are negatively charged.

  The negatively charged paint particles 64 receive a force directed toward the ring-shaped electrode portion 34 along the lines of electric force due to the electric field directed from the ring-shaped electrode portion 34 toward the paint discharge port 13. However, there is a strong flow of atomized air toward the front on the entire surface of the paint discharge port 13. In addition, the compressed air supplied to the pattern air flow path 28 is ejected to the front of the air cap 14 through the pattern air ejection hole 30, and the paint particles 64 just atomized are carried on the air flow and forward. try to. Due to such a strong air flow, the paint particles 64 cannot reach the ring-shaped electrode portion 34 and are transported to the vicinity of the object 65 placed in front of the air flow.

  When the negatively charged paint particles 64 approach the grounded object 65, a positive charge is induced on the surface of the object 65 by electrostatic induction. Then, an attractive force due to static electricity acts between the negative charge on the paint particles 64 and the induced positive charge, and the paint particles 64 receive a force toward the object 65. The paint particles 64 are applied to the surface of the object 65 by both the electrostatic attraction force and the pattern air blowing force. Since the suction force due to static electricity works in addition to the spraying force due to the pattern air, the paint particles 64 also wrap around the back side of the object 65 and the paint particles 64 are also applied to the back side part of the object 65 not facing the spray gun 1. To wear. Electrostatic coating is performed on the workpiece 65 by the operation as described above.

  Since the negatively charged paint particles 64 move from the paint discharge port 13 to the coating object 65, a current flows from the coating object 65 toward the coating material discharge port 13, and returns to the coating object 65 through the ground. An electromotive force is generated along the route. This electromotive force is not caused by the high voltage applied to the electrostatic induction electrode 33, but is generated by the kinetic energy of compressed air blown out as atomized air or pattern air.

The spray gun 1 of the present embodiment that performs electrostatic coating by the configuration and action as described above has the following advantages.
(Advantage 1) In the spray gun 1 of this embodiment, the ring-shaped electrode part 34 can be disposed at a position close to the paint discharge port 13. The support electrode part 35 is extended forward from the front end protrusion part 32 of the gun body part 2 so that it can be placed at a close position, and the ring electrode part 34 is suspended by the support electrode part 35. ing. The electric field strength between the ring-shaped electrode portion 34 and the coating material discharge port 13 is a value obtained by dividing the potential difference therebetween (voltage applied to the electrostatic induction electrode 33) by the distance therebetween. A short distance between the ring-shaped electrode portion 34 and the paint discharge port 13 means that a small potential difference is required to generate the same electric field strength. Therefore, the spray gun 1 of this embodiment has an advantage that the voltage generated by the high voltage generation circuit 4 can be lowered.

  (Advantage 2) In the spray gun 1 of this embodiment, the electrostatic induction electrode 33 is configured to be easily attached to and detached from the gun body 2. That is, the support electrode portion 35 of the electrostatic induction electrode 33 can be inserted into and removed from the insertion hole 38 provided from the front side of the front end protrusion portion 32 of the gun body portion 2, and the screw 40 made of an insulating material in the inserted state. This prevents the electrostatic induction electrode 33 from coming off. For this reason, the electrostatic induction electrode 33 can be easily attached and detached. As described with reference to FIG. 8, the coating particles 64 that are negatively charged and atomized receive a force directed to the ring-shaped electrode portion 34 by an electric field, but are pushed by the strong flow of atomized air and pattern air to form a ring shape. It cannot flow toward the electrode part 34 but flows in the direction of the workpiece 65. However, some paint particles 64 reach the surface of the ring-shaped electrode portion 34 and are applied. For this reason, if the coating is continued for a long time, the surface of the ring-shaped electrode portion 34 becomes dirty with the paint. Since the spray gun 1 of the present embodiment employs a configuration in which the electrostatic induction electrode 33 is easily detached, it can be replaced with a new spray gun in a short time.

  (Advantage 3) In the spray gun 1 of the present embodiment, the entire surface of the electrostatic induction electrode 33 exposed to the outside of the gun body 2 is covered with a dielectric material that does not pass a direct current. Therefore, no current flows out from the electrostatic induction electrode 33. The high voltage applied to the electrostatic induction electrode 33 only induces static electricity of the opposite polarity on the surface of the paint to be separated from the paint discharge port 13 by electrostatic induction, and does not perform any work. That is, no energy is consumed. For this reason, the output current of the high voltage generation circuit 4 is basically zero in the paint state, and it is sufficient to have a slight output that can compensate for the leakage current in the gun body 2. This means that the high voltage generation circuit 4 can be manufactured in a very small size, which is a great advantage.

  (Advantage 4) In the spray gun 1 of the present embodiment, the entire surface of the electrostatic induction electrode 33 exposed to the outside of the gun body 2 is covered with a dielectric material that does not pass a direct current. Therefore, there is an advantage that there is less risk of electric shock.

  (Advantage 5) In the spray gun 1 of this embodiment, as shown in FIG. 7, a capacitor 50 is additionally attached between the output terminal of the voltage doubler rectifier circuit 49 and the ground. The capacitor 50 is charged to the output voltage of the voltage doubler rectifier circuit 49 in a short time when power is supplied to the high voltage generation circuit 4. As described in the third advantage, no current other than the leakage current flows from the electrostatic induction electrode 33. Therefore, even if the power supply to the high voltage generation circuit 4 is cut off after the capacitor 50 is once charged, the capacitor 50 can maintain a high voltage for a long time. This means that the electrostatic coating can be performed for a considerable time even if the capacitor 50 is charged before the electrostatic coating is started and then the power cable 47 connected to the gun body 2 is removed. The ability to paint with the power cable 47 removed is a great advantage because the workability when painting with the spray gun 1 in hand is significantly improved.

(Second Embodiment)
The spray gun according to this embodiment is obtained by changing the shape of the electrostatic induction electrode 33 in the spray gun 1 according to the first embodiment. FIG. 9 is an external perspective view of the electrostatic induction electrode 33a used in the present embodiment. The electrostatic induction electrode 33a is obtained by attaching a rod electrode part 34a extending downward at a right angle to the tip of the support electrode part 35. Similarly to the electrostatic induction electrode 33, the electrostatic induction electrode 33 a is also covered with a dielectric on the entire outer surface except the other end side end surface portion 36 of the support electrode portion 35. Therefore, even if a high voltage is applied, a direct current does not flow out from the electrostatic induction electrode 33a.

  FIG. 10 is an external side view of the spray gun 1a to which the electrostatic induction electrode 33a is attached, and FIG. 11 is a front view of the tip portion. The method of attaching the electrostatic induction electrode 33a is the same as that of the electrostatic induction electrode 33, and the support electrode portion 35 is inserted into the insertion hole 38 provided from the front side of the front end protrusion portion 32 of the gun body portion 2 for insulation. Fix with screws 40 made of material.

  Also in the case of the spray gun 1a of the present embodiment, the dimensions are adjusted so that the tip of the rod electrode portion 34a of the electrostatic induction electrode 33a is positioned close to the paint discharge port 13. For this reason, since the space | interval of the front-end | tip of the rod electrode part 34a and the coating material discharge outlet 13 becomes narrow, a strong electric field can be generated with a low voltage. In addition, since the electrostatic induction electrode 33a can be easily attached and detached, even when the electrostatic induction electrode 33a is contaminated with paint, it can be replaced in a short time. In addition, since the entire outer surface of the electrostatic induction electrode 33a is covered with a dielectric so that a direct current does not flow out, the power supply capacity of the high voltage generation circuit 4 may be extremely small.

(Third embodiment)
The present embodiment is a modification of the high voltage supply circuit shown in FIG. Since the electrostatic induction electrodes 33 and 33a used in the spray guns 1 and 1a according to the first and second embodiments are entirely covered with a dielectric, no current flows out from the high voltage generation circuit 4. Therefore, since the output current capacity of the high voltage generation circuit 4 can be small, it is possible to generate a necessary high voltage using a battery as a power source.

  FIG. 12 shows a circuit configuration of the high voltage generation circuit 4a of this embodiment using the battery 70 as a power supply source. The direct current output from the battery 70 is supplied to the high-frequency oscillation circuit 72 through the switch 71 and converted into a high-frequency current. The high-frequency current is boosted by the high-frequency transformers 45 and 48, then rectified by the voltage doubler rectifier circuit 49, converted into a DC high voltage of 20,000 to 20,000 V, passed through the high resistor 51, the electrostatic induction electrode 33, 33a. The battery 70 is detachably attached to the gun body 2 and the entire high voltage generation circuit 4a is accommodated in the gun body 2.

  With such a configuration, it is possible to eliminate the power cable 47 for supplying power to the gun body 2 from the outside, and the workability at the time of painting with the spray gun held in hand is remarkably improved.

(Other uses)
In the first to third embodiments, the spray gun that atomizes the paint and electrostatically coats the object to be coated has been described. However, as can be seen from the above description, the application of these spray guns is not limited to electrostatic coating using paint, but it is generated by changing a slightly conductive liquid into charged atomized particles. The mist-like particles thus applied can be widely applied to a grounded object or a grounded object that is sprayed on and adhered to the surface. Such applicable fields include, for example, a gun for a cleaning device that sprays cleaning liquid on an object to be cleaned, a gun for an agricultural spraying device that sprays chemicals and fertilizers on plants, and a surface coating agent on an object. There are guns for coating equipment.

  In the drawings, 1, 1a is a spray gun for electrostatic coating, 2 is a gun main body, 4, 4a is a high voltage generating circuit, 7 is a paint nozzle, 13 is a paint discharge port, 14 is an air cap, and 16 is atomized air. Ejection hole, 18 is a corner, 20 is a cylindrical part, 28 is a pattern air flow path, 33 and 33a are electrostatic induction electrodes, 30 is a pattern air ejection hole, 34 is a ring electrode part, 34a is a bar electrode part, 35 Is a support electrode part, 36 is an end surface part on the other end side, 37 is a terminal part, 38 is an insertion hole, 40 is a screw, 50 is a capacitor, and 70 is a battery.

Claims (4)

A spray gun for electrostatic coating in which a paint atomized with compressed air is charged using a high voltage and applied to an object,
A cylindrical portion (20) formed to protrude forward from a front end portion of a substantially cylindrical gun body portion (2) having at least a front end outer surface layer portion made of a dielectric;
A paint nozzle (7) attached to the inside of the cylindrical portion and having a paint discharge port (13) at the tip;
An air cap (14) covering the paint nozzle and the front end surface of the cylindrical portion;
An electrostatic induction electrode (33),
The air cap has an atomizing air ejection hole (16) through which the paint discharge port is inserted at the center and compressed air for atomizing the paint discharged from the paint discharge port is ejected from the periphery of the paint discharge port. Furthermore, a pair of corners (25) is provided to project forward from the upper and lower parts of the front end of the air cap, and a pattern air flow path (28) provided inside the corners at the tip of the corners. Pattern air ejection holes (30) for ejecting the compressed air supplied through the slanting front and inner side are formed,
The electrostatic induction electrode includes a ring-shaped electrode portion (34) and a rod-shaped support electrode portion (35) extending perpendicularly to the ring surface from one ring outer periphery of the ring-shaped electrode portion, The support electrode part is the entire surface except the other end side end face part (36) of the support electrode part covered with a dielectric, and the other end side of the support electrode part is a protrusion (32 on the front end part of the gun body part). ) In the insertion hole (38) provided from the front end side so that it can be inserted and removed, and in the inserted state, the projecting portion is in a state where the other end side end surface portion is in contact with the terminal portion (37) to which a high voltage is supplied. An insulating screw (40) attached to a screw hole provided from the outer surface toward the support electrode portion is pressed to prevent the removal, and in the state where the removal prevention is aimed at, the ring-shaped electrode portion is located inside the ring. the coating material delivery in a state in which is inserted a pair of corner portions (25) (13) is configured such that a state close to the,
When electrostatic coating is performed, the paint in the paint nozzle is grounded using the conductivity of the paint or via a grounding wire, the object to be coated is grounded, and the ground potential is referenced to the electrostatic induction electrode. The static electricity is characterized in that the paint is discharged from the paint discharge port in a state where a high voltage is applied, and at the same time, the paint is atomized by jetting compressed air from the atomizing air ejection hole and the pattern air ejection hole. Spray gun for electropainting. The spray gun for electrostatic coating according to claim 1, wherein instead of the ring-shaped electrode portion, a rod electrode portion (34a) whose outer surface extending perpendicularly to the support electrode portion from the tip of the support electrode portion is covered with a dielectric. ) using the attached electrostatic induction electrode (33a), in the state in which the electrostatic induction electrode was inserted and fixed in the insertion hole (38) provided in the front end upper portion of the gun main body, the tip of the rod electrode portion A spray gun for electrostatic coating, characterized in that the portion is positioned close to the paint discharge port.   3. The spray gun for electrostatic coating according to claim 1, wherein a DC high voltage generated by a high voltage generation circuit (4a) using a battery (70) as a power source is supplied to the terminal portion to which the high voltage is supplied. A spray gun for electrostatic coating, wherein the battery is detachably housed in the gun body.   3. The spray gun for electrostatic coating according to claim 1, wherein a DC high voltage generated by a high voltage generation circuit (4) that receives power supply from the outside is supplied to the terminal portion to which the high voltage is supplied. A spray gun for electrostatic coating, characterized in that a capacitor (50) charged by a high voltage current generated by the high voltage generation circuit is connected in the high voltage generation circuit.