Electrostatic coating gun

Abstract

To provide an electrostatic coating gun that can achieve improvement in coating efficiency while suppressing occurrence of electrostatic repulsion.SOLUTION: An electrostatic coating gun comprises: a body part; a paint passage provided in the body part; a rectification part which generates revolution flow in powered paint flowing in the paint passage; a discharge electrode to which a high voltage is applied; and a nozzle having a plurality of ejection ports which are provided around the discharge electrode and eject the powered paint flowing the paint passage. The ejection port is formed into a shape that is twisted with respect to a flow direction of the powered paint in the paint passage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to an electrostatic paint gun. [Background technology]

[0002] Electrostatic coating is a coating method in which powder paint is sprayed from an electrostatic coating gun operated directly by an operator and applied to the substrate, such as an automobile body, by electrostatic attraction. In this type of electrostatic coating, a coating film is formed on the surface of the substrate by the accumulation of charged paint particles and free ions that did not contribute to charging. When the electric field strength in the powder layer increases and exceeds the dielectric breakdown field strength of the powder layer, a small-scale discharge occurs. This so-called electrostatic repulsion causes problems because it impairs the smoothness of the coating surface.

[0003] Conventionally, in order to suppress the occurrence of electrostatic repulsion, the amount of free ions generated has been suppressed or the free ions have been prevented from moving toward the object to be coated. Patent Document 1 discloses a method of coating powder paint by electrostatically charging it using an electrostatic powder coating device equipped with a free ion trap device and an electrode for forming an induction field. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-57405 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional configuration, the use of an induction field-forming electrode is used to improve the efficiency of coating on the surface of the workpiece, but the electrode must be positioned appropriately, which can lead to a complex device configuration. Therefore, there is room for improvement in terms of improving coating efficiency while suppressing the occurrence of electrostatic repulsion.

[0006] The present invention has been made in consideration of the above circumstances, and its object is to provide an electrostatic coating gun that can improve coating efficiency while suppressing the occurrence of electrostatic repulsion. [Means for solving the problem]

[0007] The electrostatic coating gun of the embodiment comprises a main body, a paint path provided inside the main body, a rectifying section that generates a swirling flow in the powder paint flowing through the paint path, a discharge electrode to which a high voltage is applied, and a nozzle provided around the discharge electrode and having multiple outlets for spraying the powder paint flowing through the paint path, and the outlets are formed in a twisted shape with respect to the flow direction of the powder paint in the paint path. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of an example of an electrostatic coating gun according to an embodiment. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of a swirling flow generating section of an electrostatic coating gun according to an embodiment. [Figure 3] FIG. 1 is a diagram showing an example of a nozzle configuration of an electrostatic coating gun according to an embodiment. [Figure 4] 1 is a front view of a nozzle of an electrostatic spray gun according to an embodiment; [Figure 5] 5 is a cross-sectional view showing a schematic configuration of the electrostatic spray gun according to one embodiment near the tip of the nozzle, taken along line X5-X5 in FIG. [Figure 6] FIG. 1 is a diagram illustrating a flow of paint sprayed from a nozzle of an electrostatic coating gun according to an embodiment. [Figure 7] 1 is a diagram illustrating an electrostatic paint gun according to an embodiment, in which the charging electrode is densely surrounded by paint particles; DETAILED DESCRIPTION OF THE INVENTION

[0009] An electrostatic coating gun according to one embodiment will be described below with reference to the drawings. The electrostatic coating gun 10 shown in Fig. 1 is used to apply powder paint to a substrate by, for example, applying the powder paint to the substrate by electrostatic attraction. The electrostatic coating gun 10 may be an automatic gun that automatically applies powder paint to the substrate, or a manual gun that is manually operated by an operator. As shown in Fig. 1, the electrostatic coating gun 10 includes a main body 11, a paint passage 12, a high-voltage generator 13, a discharge electrode 14, a nozzle cap 15, and a nozzle 20.

[0010] The main body 11 constitutes the main body of the electrostatic paint gun 10. The main body 11 is made of, for example, an electrically insulating synthetic resin. In this embodiment, the left side of the paper in FIG. 1 is the tip side of the main body 11, which is the direction in which the powder paint is sprayed, and the right side of the paper in FIG. 1 is the base side of the main body 11, which is the opposite side to the direction in which the powder paint is sprayed. The paint path 12 is provided inside the main body 11. The paint path 12 extends along the axis of the main body 11. The paint path 12 guides powder paint supplied by conveying air from an external paint supply source (not shown) via a paint hose or the like to the nozzle 20. The "outside" refers to the outside of the electrostatic paint gun 10.

[0011] As shown in FIG. 1, a rectifying section 121 is provided on the upstream side of the paint path 12. The rectifying section 121 constitutes the inlet of the paint path 12. The rectifying section 121 generates a swirling flow in the powder paint flowing through the paint path 12. The rectifying section 121 has a rectifying section inlet 121a, a rectifying section main body 121b, a rectifying section outlet 121c, and a rectifying plate 121d. As shown in FIG. 2, the rectifying section inlet 121a, the rectifying section main body 121b, and the rectifying section outlet 121c are formed with a tubular outer shape, for example, a cylindrical outer shell. The inner diameters of the rectifying section inlet 121a and the rectifying section outlet 121c are set slightly smaller than the inner diameter of the rectifying section main body 121b. The rectifying section inlet 121a constitutes the inlet of the rectifying section 121 and is connected to the base end side of the rectifying section main body 121b. The rectifier outlet 121c constitutes the outlet of the rectifier 121, and is connected to the tip side of the rectifier main body 121b.

[0012] The flow rectifying plate 121d is housed inside the flow rectifying unit main body 121b. The flow rectifying plate 121d is made of a highly wear-resistant material. The flow rectifying plate 121d is fitted, for example, to the inner circumferential surface of the flow rectifying unit main body 121b. In this case, the portion of the flow rectifying unit main body 121b where the flow rectifying plate 121d is attached is formed in a straight shape with a constant inner diameter. The flow rectifying plate 121d rectifies the powder paint that flows into the flow rectifying unit 121 from the flow rectifying unit inlet 121a to create a swirling flow. The flow rectifying plate 121d has an outer shape that is twisted, for example, into a spiral shape, and generates a swirling flow in a desired direction. In this embodiment, the flow rectifying plate 121d is formed in a clockwise spiral shape in the flow direction of the powder paint. In this case, the flow rectifying unit 121 generates a clockwise swirling flow in the paint flowing through the paint path 12.

[0013] The high voltage generating unit 13 is provided within the main body 11. The high voltage generating unit 13 is configured with a boost circuit, a rectifier circuit, etc., and receives a predetermined AC voltage from an external power supply (not shown). The high voltage generating unit 13 can then output a DC high voltage proportional to the AC voltage. The discharge electrode 14 is configured, for example, of a conductive metal material and includes a pin-shaped member. The output side of the high voltage generating unit 13 is connected to the discharge electrode 14, and a negative high voltage generated by the high voltage generating unit 13 is applied to the discharge electrode 14. This forms an electrostatic field between the discharge electrode 14 and the substrate. Due to the action of this electrostatic field, the paint sprayed from the nozzle 20 is negatively charged, allowing electrostatic painting to be performed on the substrate.

[0014] The nozzle cap 15 is located at the tip side of the main body 11. The nozzle cap 15 is formed, for example, in a cylindrical shape overall, and is removably attached to the main body 11. The base end side of the nozzle 20 is housed inside the nozzle cap 15. The nozzle 20 is provided at the tip of the main body 11 and is used to spray the powder paint flowing through the paint path 12. The nozzle 20 is made of, for example, an electrically insulating synthetic resin. The central axis of the nozzle 20 coincides with the central axis of the discharge electrode 14. The axis of the main body 11, the central axis of the nozzle, and the central axis of the discharge electrode 14 are all oriented in the same direction.

[0015] 3 to 5, the nozzle 20 has a nozzle body 21, a tip side member 22, and a cover portion 23. The nozzle body 21 forms the base end side of the nozzle 20 and is connected to the paint path 12. In this case, a swirling flow of the powder paint that has passed through the paint path 12 flows into the nozzle body 21, as shown by the dashed arrow in FIG.

[0016] The tip side member 22 is located on the tip side of the nozzle body 21. The tip side member 22 has a storage section 221, a tip wall 222, a recessed section 223, an inclined section 224, and a spray nozzle 225. As shown in FIG. 5, the storage section 221 is formed in a cylindrical shape with an open base end. The storage section 221 is configured to be able to store the tip side of the nozzle body 21. In this case, the inner diameter of the storage section 221 is set to be slightly larger than the outer diameter of the tip side of the nozzle body 21.

[0017] The tip wall 222 constitutes the tip surface of the tip side member 22, i.e., the tip surface of the nozzle 20. The tip wall 222 is a surface that is perpendicular to the central axis of the nozzle 20. As shown in FIGS. 3 and 4, the tip wall 222 is formed, for example, with a circular outer diameter. The tip wall 222 also has a through hole 222a. The through hole 222a is located approximately in the center of the tip wall 222 and is formed to penetrate the tip wall 222 in the thickness direction. The discharge electrode 14 is inserted into the through hole 222a. In other words, the discharge electrode 14 is exposed to the outside via the through hole 222a.

[0018] The recessed portion 223 is formed by recessing a portion of the tip wall 222 inward, i.e., toward the base end. The recessed portion 223 has, for example, a circular outer diameter. The recessed portion 223 is located in a region overlapping with the through hole 222a. The through hole 222a is located approximately in the center of the recessed portion 223. In this case, the tip of the discharge electrode 14 is located within the recessed portion 223, as shown in FIG. 5. In other words, the tip of the discharge electrode 14 is located closer to the base end than the tip of the nozzle 20.

[0019] The inclined portion 224 connects the storage portion 221 and the tip wall 222. As shown in FIGS. 3 and 5, the inclined portion 224 is formed to widen outward from the tip side toward the base end. The inner diameter of the inclined portion 224 is set smaller than the inner diameter of the storage portion 221. As shown in FIG. 5, the base end of the inclined portion 224 comes into contact with the tip of the nozzle body 21 when the nozzle body 21 is stored in the storage portion 221. The nozzle body 21 comes into contact with the inclined portion 224, thereby determining the axial position of the nozzle body 21. A space S is formed by the inner surface of the tip wall 222 and the inner surface of the inclined portion 224. The space S is a portion into which the powder paint that has passed through the nozzle body 21 flows.

[0020] As shown in Figures 4 and 5, the ejection port 225 is formed to penetrate the inclined portion 224. In this case, the ejection port 225 extends along the radial direction of the tip side member 22. The ejection port 225 communicates between the space S and the outside. The ejection port 225 is for ejecting the powder paint that has flowed through the paint path 12 and the nozzle body 21 and entered the space S. A plurality of ejection ports 225 are provided at predetermined intervals, for example, at equal intervals, around the entire circumference of the inclined portion 224 so as to surround the periphery of the discharge electrode 14. Note that in Figure 4 and other figures, for ease of viewing, reference numerals are assigned to only some of the multiple ejection ports 225, and reference numerals for the remaining ejection ports 225 are omitted.

[0021] The multiple jetting ports 225 are inclined in the same direction in the circumferential direction. In this embodiment, the multiple jetting ports 225 are inclined in the same direction as the swirling direction of the swirling flow generated by the flow straightening section 121, i.e., clockwise in the circumferential direction. Furthermore, the jetting ports 225 extend at an inclination from the base end to the tip end as they move from the inner side to the outer side in the radial direction. The jetting ports 225 are twisted from the inner surface to the outer surface of the inclined section 224 so as to form a spiral around the central axis of the nozzle 20. That is, the jetting ports 225 are formed in a twisted shape with respect to the flow direction of the powder paint in the paint path 12. By forming the jetting ports 225 in this twisted shape, the speed of the paint jetted from the jetting ports 225 can be reduced. The diameter and number of the jetting ports 225, the spacing between adjacent jetting ports 225, and other factors can be appropriately changed depending on the width of the desired pattern shape.

[0022] The powder paint that flows into the nozzle 225 from the space S passes through the nozzle 225 while maintaining a swirling flow, as shown by the black arrow A in Fig. 6, and when it is ejected from the nozzle 225, a large number of powder paints PP fly in an overall twisted trajectory, as shown by the dashed arrow B in Fig. 6. In Fig. 6, to make the drawing easier to understand, only some of the powder paints PP are labeled with reference numerals, and the reference numerals for the other powder paints PP are omitted.

[0023] The cover portion 23 is formed, for example, in a cylindrical shape, and is located outside the tip side member 22. The cover portion 23 is provided so as to cover the multiple ejection ports 225 from the outside. As shown in FIG. 5 , in a cross-sectional view, the inner surface of the cover portion 23 faces the multiple ejection ports 225. The cover portion 23 comes into contact with some of the powder paint ejected from the multiple ejection ports 225. The cover portion 23 is intended to guide some of the powder paint ejected from the multiple ejection ports 225 to the periphery of the discharge electrode 14.

[0024] Figure 7 shows an observation of the state of powder paint being sprayed from the nozzle 20. The powder paint PP sprayed from the nozzle 20 follows a twisted trajectory, as indicated by the two-dot chain arrow in Figure 7. At this time, gaps between the powder paints sprayed from the multiple spray ports 225 are suppressed, and the discharge electrode 14 is covered with the powder paint. The spray pattern is uniformed around the discharge electrode 14. In other words, free ions can be effectively mixed into the paint particles sprayed from the nozzle 20, preventing the free ions from concentrating and accumulating on the workpiece.

[0025] According to the embodiment described above, the electrostatic paint gun 10 includes a main body 11, a paint passage 12 provided inside the main body 11, a rectifying unit 121, a discharge electrode 14, and a nozzle 20. The rectifying unit 121 generates a swirling flow in the powder paint flowing through the paint passage 12. A high voltage is applied to the discharge electrode 14. The nozzle 20 has a plurality of ejection ports 225. The plurality of ejection ports 225 are provided around the discharge electrode 14 and eject the powder paint flowing through the paint passage 12. The ejection ports 225 are formed in a twisted shape with respect to the flow direction of the powder paint in the paint passage 12.

[0026] With this, by spraying the powder paint, which has been made into a swirling flow by the rectifying section 121, from the spray nozzle 225, it is possible to uniformly and densely cover the periphery of the discharge electrode 14 with paint particles. As a result, free ions are mixed in with the paint particles and head toward the workpiece, preventing excessive accumulation of free ions on the surface of the workpiece. This makes it possible to improve coating efficiency while suppressing the occurrence of electrostatic repulsion.

[0027] The nozzle 20 has a cover portion 23. The cover portion 23 is provided so as to cover the outlet 225 from the outside, and comes into contact with a portion of the powder paint ejected from the outlet 225. This makes it easier for the powder paint ejected from the outlet 225 to concentrate around the discharge electrode 14. This allows the periphery of the discharge electrode 14 to be effectively covered with paint particles. This further suppresses the occurrence of electrostatic repulsion.

[0028] The nozzle 20 also has a recessed portion 223. The recessed portion 223 is formed by recessing the tip wall 222 of the nozzle 20 inward. The tip of the discharge electrode 14 is located within the recessed portion 223. This makes it easier for the paint particles ejected from the ejection port 225 to cover the periphery of the discharge electrode 14. This makes it possible to suppress the occurrence of electrostatic repulsion.

[0029] The above-described embodiments are presented as examples, and are not limited to the embodiments described above and shown in the drawings, but can be modified as appropriate within the scope of the gist of the invention. [Explanation of symbols]

[0030] 10... electrostatic coating gun, 11... main body, 12... paint path, 121... rectifying section, 14... discharge electrode, 20... nozzle, 225... spray port

Claims

1. a main body; a paint passage provided inside the main body; a flow straightening section that generates a swirling flow in the powder paint flowing through the paint path; a discharge electrode to which a high voltage is applied; a nozzle provided around the discharge electrode and having a plurality of ejection ports for ejecting the powder paint flowing through the paint path; The ejection port is formed in a twisted shape with respect to the flow direction of the powder paint in the paint path. Electrostatic paint gun.

2. The nozzle has a cover portion that is provided to cover the outlet from the outside and that comes into contact with a part of the powder paint sprayed from the outlet.

2. The electrostatic paint gun of claim 1.

3. the nozzle has a recessed portion formed by recessing a tip surface of the nozzle inward, The tip of the discharge electrode is located within the recess.

3. The electrostatic spray gun according to claim 1 or 2.

Images