Electrostatic atomization coating apparatus

Abstract

In an electrostatic atomization coating apparatus including a nozzle head including a plurality of coating material ejection ports; a coating material chamber that is provided inside the nozzle head and to which a coating material is supplied via a coating material supply path, each of the coating material ejection ports being in communication with the coating material chamber via an individual branch coating material path; and a voltage application device that provides a potential difference between the nozzle head and an object to be coated, the coating material ejected from each of the coating material ejection ports via the coating material supply path, the coating material chamber, and the branch coating material path being brought into a charged state through application of a voltage by the voltage application device, an open/close valve device that opens and closes all of the branch coating material paths, or opens and closes a specific subset of a plurality of branch coating material paths out of all of the branch coating material paths is provided. Thus, it is possible to prevent external air from entering the nozzle head, and the coating material from leaking to the outside of the nozzle head.

Claims

1. An electrostatic atomization coating apparatus comprising: a nozzle head including a plurality of coating material ejection ports; a coating material chamber that is provided inside the nozzle head and to which a coating material is supplied via a coating material supply path, each of the coating material ejection ports being in communication with the coating material chamber via an individual branch coating material path; and a voltage application device that provides a potential difference between the nozzle head and an object to be coated, the coating material ejected from each of the coating material ejection ports via the coating material supply path, the coating material chamber, and the branch coating material path being brought into a charged state through application of a voltage by the voltage application device, wherein a supply-side switching valve that opens and closes the coating material supply path is provided, wherein an open/close valve device that opens and closes all of the branch coating material paths, or opens and closes a specific subset of a plurality of branch coating material paths out of all of the branch coating material paths is provided, wherein the open/close valve device includes one common valve body housed in the coating material chamber, and the common valve body performs an opening/closing operation between a valve closing position at which respective inlets of the branch coating material paths that are open to the coating material chamber are simultaneously closed, and a valve opening position at which the respective inlets of the branch coating material paths are simultaneously opened.

2. The electrostatic atomization coating apparatus according to claim 1, wherein a circumferential groove portion is formed on a chamber-wall portion of the coating material chamber, the inlets of the branch coating material paths are disposed on a bottom surface of the circumferential groove portion so as to be equidistantly arranged in a circumferential direction of the circumferential groove portion, the common valve body has an annular shape configured to be fitted to the circumferential groove portion, and the common valve body moves inside the circumferential groove portion in a piston-like manner in directions away from and toward the bottom surface of the circumferential groove portion, as the opening/closing operation between the valve closing position and the valve opening position.

3. The electrostatic atomization coating apparatus according to claim 2, wherein a communication groove extending continuously from one end face side to another end face side of the annular shape of the common valve body is formed in an inner circumferential surface or an outer circumferential surface of the annular shape of the common valve body.

4. The electrostatic atomization coating apparatus according to claim 1, wherein a circumferential groove portion is formed on a chamber-wall portion of the coating material chamber, the inlets of the branch coating material paths are disposed on a bottom surface of the circumferential groove portion so as to be equidistantly arranged in a circumferential direction of the circumferential groove portion, the common valve body has an annular shape configured to be fitted to the circumferential groove portion, the common valve body includes a plurality of communication holes formed extending therethrough from one end face side to another end face side of the annular shape of the common valve body, the communication holes are disposed so as to be equidistantly arranged in a circumferential direction of the annular shape of the common valve body, at positions in one-to-one correspondence with the respective inlets of the branch coating material paths, and the common valve body pivots inside the circumferential groove portion in a circumferential direction of the circumferential groove portion, as the opening/closing operation between the valve closing position and the valve opening position.

5. An electrostatic atomization coating apparatus comprising: a nozzle head including a plurality of coating material ejection ports; a coating material chamber that is provided inside the nozzle head and to which a coating material is supplied via a coating material supply path, each of the coating material ejection ports being in communication with the coating material chamber via an individual branch coating material path; and a voltage application device that provides a potential difference between the nozzle head and an object to be coated, the coating material ejected from each of the coating material ejection ports via the coating material supply path, the coating material chamber, and the branch coating material path being brought into a charged state through application of a voltage by the voltage application device, wherein a supply-side switching valve that opens and closes the coating material supply path is provided, wherein an open/close valve device that opens and closes all of the branch coating material paths, or opens and closes a specific subset of a plurality of branch coating material paths out of all of the branch coating material paths is provided, and wherein the coating material ejection ports are disposed on the same circumference at a distal end face portion of the nozzle head so as to be equidistantly arranged in a row in a circumferential direction.

6. The electrostatic atomization coating apparatus according to claim 5, wherein, at the distal end face portion of the nozzle head, a plurality of coating material ejection nozzles each including the coating material ejection port are provided on the same circumference so as to be equidistantly arranged in a row in a circumferential direction in a state in which the coating material ejection nozzles each protrude independently.

7. The electrostatic atomization coating apparatus according to claim 5, wherein an annular protruding portion is provided at the distal end face portion of the nozzle head, and the coating material ejection ports are disposed at the annular protruding portion so as to be equidistantly arranged in a row in a circumferential direction of the annular protruding portion.

8. The electrostatic atomization coating apparatus according to claim 5, wherein the coating material ejection ports are disposed on each of a plurality of concentric circumferences at the distal end face portion of the nozzle head so as to be equidistantly arranged in a row in a circumferential direction.

9. The electrostatic atomization coating apparatus according to claim 5, wherein the open/close valve device includes one common valve body housed in the coating material chamber, and the common valve body performs an opening/closing operation between a valve closing position at which respective inlets of the branch coating material paths that are open to the coating material chamber are simultaneously closed, and a valve opening position at which the respective inlets of the branch coating material paths are simultaneously opened.

10. The electrostatic atomization coating apparatus according to claim 5, wherein each of the branch coating material paths is provided with an individual open/close valve as the open/close valve device, and common operation means that simultaneously operates the open/close valves to open or close is provided.

11. The electrostatic atomization coating apparatus according to claim 5, wherein the nozzle head is formed of an electrically insulating material or a slightly conductive material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a vertical cross-sectional view of an electrostatic atomization coating apparatus.

(2) FIG. 2 is a front view of a distal end face portion of a nozzle head.

(3) FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1.

(4) FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 1.

(5) FIG. 5 is a perspective view of a common valve body.

(6) FIG. 6 is a front view of a distal end face portion of a nozzle head, showing an alternative embodiment.

(7) FIG. 7 is a structure diagram of an open/close valve device, showing an alternative embodiment.

(8) FIG. 8 is a front view of a distal end face portion of a nozzle head, showing an alternative embodiment.

(9) FIG. 9 is a schematic vertical cross-sectional view of a nozzle head, showing an alternative embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

(10) FIG. 1 shows an electrostatic atomization coating apparatus 1 that coats an object to be coated by atomizing a coating material, and the electrostatic atomization coating apparatus 1 includes a main body portion 2 coupled to a distal end portion of a work arm of a coating robot, and a nozzle head 3 attached to a distal end of the main body portion 2.

(11) In a coating operation using the electrostatic atomization coating apparatus 1, the coating operation is advanced while sequentially moving a target location of the coating material atomization on the object to be coated. At this time, the position and the posture of the electrostatic atomization coating apparatus 1 are sequentially adjusted by operations made by the coating robot such that the separation distance between the object to be coated and the nozzle head 3 is kept constant, and a state in which a distal end face portion of the nozzle head 3 is perpendicular to and directly faces the object to be coated is maintained.

(12) A coating material chamber 4 is formed inside the nozzle head 3, and the coating material chamber 4 is disposed concentrically with the columnar nozzle head 3. In addition, an open/close valve device 5 is provided inside the nozzle head 3.

(13) On the other hand, inside the main body portion 2, a coating material supply path 7a and a coating material feedback path 7b that extend to the coating material chamber 4 inside the nozzle head 3 are provided, and a supply-side switching valve 6A that opens and closes the coating material supply path 7a and a feedback-side switching valve 6B that opens and closes the coating material feedback path 7b are provided.

(14) As shown in FIGS. 1 and 2, an annular protruding portion 11 disposed concentrically with the nozzle head 3 is formed in a distal end face portion of the nozzle head 3 that is made to directly face the object to be coated, and many coating material ejection ports 12a are formed in the annular protruding portion 11. The many coating material ejection ports 12a are disposed so as to be equidistantly arranged in a row in the circumferential direction of the annular protruding portion 11.

(15) Note that, at the distal end face portion of the nozzle head 3, a plurality of coating material ejection nozzles N each including a coating material ejection port 12a may be disposed on the same circumference so as to be equidistantly arranged in a row in the circumferential direction in a state in which the coating material ejection nozzles N each protrude independently as shown in FIG. 6, instead of providing the above-described annular protruding portion 11.

(16) Each of the coating material ejection ports 12a is in communication with the coating material chamber 4 via an individual branch coating material path 13, and a coating material T that is supplied to the coating material chamber 4 via the coating material supply path 7a is ejected from the coating material ejection ports 12a via the branch coating material paths 13.

(17) Meanwhile, in a state in which the supply-side switching valve 6A and the feedback-side switching valve 6B are open, the coating material T flows through the coating material supply path 7a, the coating material chamber 4, and the coating material feedback path 7b, and a portion of the flowing coating material T is fed from the coating material chamber 4 to the coating material ejection ports 12a via the branch coating material paths 13.

(18) In the electrostatic atomization coating apparatus 1, a voltage application device 14 that provides a potential difference ΔV between the object to be coated, which is a coating target, and the nozzle head 3 is provided, and the coating material T that is ejected from the coating material ejection ports 12a via the coating material supply path 7a, the coating material chamber 4, and the branch coating material paths 13 is brought into a charged state as a result of a high voltage being applied by the voltage application device 14.

(19) Due to the application of a high voltage by the voltage application device 14, an electric field is formed around the coating material ejection ports 12a, and the coating material T in the charged state that has been ejected from the coating material ejection ports 12a, is atomized by the action of the electric field formed around the coating material ejection ports 12a, as the so-called electrostatic atomization, and the atomized coating material T in the charged state is electrostatically attracted to and flies to the object to be coated due to the potential difference between the nozzle head 3 and the object to be coated, and is thus applied onto the surface of the object to be coated.

(20) In the electrostatic atomization coating apparatus 1, many coating material ejection ports 12a are disposed at the distal end face portion of the nozzle head 3 so as to be equidistantly arranged in the circumferential direction. Accordingly, an electric field is formed uniformly without any imbalance around the coating material ejection ports 12a even if electric field interference occurs between adjacent coating material ejection ports 12a. Thus, the atomization of the coating material T in the charged state that has been ejected from the coating material ejection ports 12a is uniform, resulting in enhanced coating quality of the object to be coated.

(21) In addition, it is possible to effectively prevent a situation where the atomization of the coating material T in the charged state that has been ejected from a subset of the coating material ejection ports 12a is insufficient due to imbalances in the electric field, whereby the insufficiently atomized coating material T adheres to the nozzle head 3. Thus, the burden of performing cleaning and maintenance on the nozzle head 3 is reduced.

(22) The open/close valve device 5 provided in the nozzle head 3 is a valve device that opens and closes the branch coating material paths 13 for the coating material ejection ports 12a, and the open/close valve device 5 is constantly biased to the valve opening side by a spring 18.

(23) As shown in FIGS. 1 and 4, inside the nozzle head 3, the coating material chamber 4 includes a circumferential groove portion 15 that is concentric with and has substantially the same diameter as the annular protruding portion 11, and the respective inlets 13a of the many branch coating material paths 13 are open to the circumferential groove portion 15 serving as the coating material chamber 4 on the bottom surface of the circumferential groove portion 15. The many inlets 13a are disposed so as to be equidistantly arranged in a row in the circumferential direction of the circumferential groove portion 15, in correspondence with a ring-shaped row of the coating material ejection ports 12a.

(24) In this respect, a valve body 16 of the open/close valve device 5 is formed in an annular shape configured to be fitted to the circumferential groove portion 15, and is housed in a fitted state in the circumferential groove portion 15, and the annular valve body 16 serves as a common valve body for the many branch coating material paths 13.

(25) Specifically, all of the branch coating material paths 13 are simultaneously closed as a result of the inlets 13a of all of the branch coating material paths 13 being closed by the annular common valve body 16 due to the annular common valve body 16 moving in a piston-like manner in the circumferential groove portion 15 to the bottom surface side of the circumferential groove portion 15, and all of the branch coating material paths 13 are simultaneously opened as a result of the inlets 13a of all of the branch coating material paths 13 being simultaneously opened by the annular common valve body 16 moving in a piston-like manner to the side away from the bottom surface of the circumferential groove portion 15.

(26) That is, if the coating material supply path 7a and the coating material feedback path 7b are simply closed at the supply-side switching valve 6A and the feedback-side switching valve 6B when the atomization of the coating material onto the object to be coated is stopped in order to suspend or end the coating operation, depending on the posture of the nozzle head 3 at the time, external air may enter the coating material chamber 4 via the branch coating material paths 13 from a subset of coating material ejection ports 12a located at an upper portion out of the many coating material ejection ports 12a. As a result of this, the coating material T remaining in the coating material chamber 4 may leak to the outside from another subset of coating material ejection ports 12a located at a lower portion via the branch coating material paths 13.

(27) In this respect, in the electrostatic atomization coating apparatus 1, when the atomization of the coating material onto the object to be coated is stopped, the open/close valve device 5 is operated to close, and all of the branch coating material paths 13 are closed by the annular common valve body 16. Thus, regardless of the posture of the nozzle head 3 at that time, the entry of external air via a subset of coating material ejection ports 12a, and the leaking out of the remaining coating material T via another subset of coating material ejection ports 12a as described above can be reliably prevented.

(28) As shown in FIGS. 4 and 5, many communication grooves 17 are formed in the outer circumferential surface and the inner circumferential surface of the annular shape of the common valve body 16, and the communication grooves 17 are formed extending from one end face of the annular common valve body 16 to the other end face thereof. On the one end face of the common valve body 16, the communication grooves 17 are open to a region on the bottom surface side of the circumferential groove portion 15 and, on the other end face of the common valve body 16, the communication grooves 17 are open to a region on the side opposite to the bottom surface of the circumferential groove portion 15 on.

(29) In other words, in a state in which the open/close valve device 5 is open, the coating material T supplied to the coating material chamber 4 flows into the region on the bottom surface side of the circumferential groove portion 15 from the region on the side opposite to the bottom surface thereof via the many communication grooves 17. When the open/close valve device 5 performs an opening/closing operation in a piston-like manner, the coating material T moves between the region on the bottom surface side of the circumferential groove portion 15 and the region on the side opposite to the bottom surface thereof via the many communication grooves 17 so as to follow the opening/closing operation.

(30) The annular common valve body 16 is coupled to a cross-shaped support member 20 via four coupling rods 19, and the four coupling rods 19 are equidistantly disposed in the circumferential direction of the circumferential groove portion 15.

(31) The cross-shaped support member 20 is coupled to a valve operation piston 22 via a valve operation shaft 21 disposed on a central axis q of the nozzle head 3.

(32) In other words, when the valve operation piston 22 is moved, through the application of air pressure for a valve-opening operation, to the distal end face side of the nozzle head 3 against the biasing force of the valve-opening biasing spring 18, the resulting parallel movement of the support member 20 and the four coupling rods 19 causes the annular common valve body 16 to operate so as to close the inlets 13a of all of the branch coating material paths 13.

(33) As shown in FIG. 3, a guide hole 23 for the cross-shaped support member 20 is formed inside the nozzle head 3, and the guide hole 23 is formed in a cross shape as viewed in the direction of the central axis q of the nozzle head.

(34) In other words, the cross-shaped support member 20 moves inside the cross-shaped guide hole 23 so as to reciprocate in the direction of the central axis q of the nozzle head.

(35) The nozzle head 3 is formed of a non-conductive material or a slightly conductive material. Thus, even if the nozzle head 3 under application of a high voltage by the voltage application device 14 is inadvertently brought close to another object, it is possible to prevent the occurrence of discharge between the nozzle head 3 and the other object.

Alternative Embodiments

(36) Next, alternative embodiments of the present invention will be listed.

(37) The above-described embodiment has shown an open/close valve device 5 with a structure in which the respective inlets 13a of the branch coating material paths 13 are simultaneously opened/closed relative to the coating material chamber 4 through a piston-like opening/closing operation of the annular common valve body 16. However, instead of this, a structure shown in FIG. 7 may be adopted as the structure of the open/close valve device 5.

(38) That is, in the structure shown in FIG. 7, the annular common valve body 16 includes a plurality of communication holes 24 formed extending therethrough from one end face side to the other end face side of the annular shape of the common valve body 16, and the communication holes 24 are disposed so as to be equidistantly arranged in the circumferential direction of the annular shape of the common valve body 16, at positions in one-to-one correspondence with the respective inlets 13a of the branch coating material paths 13 that are open in the bottom surface of the circumferential groove portion 15.

(39) Then, the annular common valve body 16 is configured to pivot inside the circumferential groove portion 15 in the circumferential direction by rotating about the central axis of the annular shape, as the opening/closing operation.

(40) In other words, in the structure shown in FIG. 7, the common valve body 16 is operated to pivot until the respective inlets 13a of the branch coating material paths 13 are brought into communication with the communication holes 24 of the common valve body 16, whereby the respective inlets 13a of the branch coating material paths 13 are open to the coating material chamber 4 via the communication holes 24. Thus, the branch coating material paths 13 are simultaneously opened.

(41) In addition, the common valve body 16 is operated to pivot until the communication holes 24 are displaced from the respective inlets 13a of the branch coating material paths 13, whereby the respective inlets 13a of the branch coating material paths 13 are closed by the common valve body 16. Thus, the branch coating material paths 13 are simultaneously closed.

(42) The above-described embodiment has shown an example in which only one ring-shaped row of coating material ejection ports 12a in which the coating material ejection ports 12a are disposed on the same circumference so as to be equidistantly arranged in a row in the circumferential direction is provided at the distal end face portion of the nozzle head 3. However, instead of this, coating material ejection ports 12a may be disposed on each of a plurality of concentric circumferences s1 and s2 at the distal end face portion of the nozzle head 3 so as to be equidistantly arranged in a row in the circumferential direction as shown in FIG. 8, or in other words, a plurality of ring-shaped rows of coating material ejection ports 12a may be provided at the distal end face portion of the nozzle head 3 so as to be arranged concentrically.

(43) The plurality of coating material ejection ports 12a may not necessarily be formed in the distal end face portion of the nozzle head 3 so as to be arranged in a ring-shaped row, and may be formed in the distal end face portion of the nozzle head 3 so as to be arranged in a matrix.

(44) The above-described embodiment has shown an example in which a plurality of branch coating material paths 13 are simultaneously opened/closed by one common valve body 16. However, as schematically shown in FIG. 9, each of a plurality of branch coating material paths 13 that are to be opened/closed may be provided with an individual open/close valve 5v as the open/close valve device 5, and the open/close valves 5v may be operated to open/close by common operation means.

(45) The above-described embodiment has shown an example in which all of the branch coating material paths 13 are simultaneously opened/closed by the open/close valve device 5. However, instead of this, a plurality of branch coating material paths 13 into which external air is highly likely to enter and from which the coating material is highly likely to leak out may be selected as a specific subset of a plurality of branch coating material paths out of all of the branch coating material paths 13, and only the selected specific subset of a plurality of branch coating material paths 13 may be simultaneously opened/closed by the open/close valve device 5.

INDUSTRIAL APPLICABILITY

(46) An electrostatic atomization coating apparatus according to the present invention is applicable to coating of a variety of articles in various fields, such as coating of automobile bodies and automobile parts, or coating of casings of electric electronic products and building materials.

DESCRIPTION OF REFERENCE SIGNS

(47) 3: nozzle head 12a: Coating material ejection port 4: Coating material chamber 7a: Coating material supply path T: Coating material 13: Branch coating material path 14: Voltage application device 5: Open/close valve device N: Coating material ejection nozzle 11: Annular protruding portion s1, s2: Circumference 16: Common valve body 15: Circumferential groove portion 17: Communication groove 24: Communication hole 5v: Open/close valve