Patent Publication Number: US-9833797-B2

Title: Electrostatic coating apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an electrostatic coating apparatus for atomizing paint in a state of applying a high voltage thereto. 
     BACKGROUND ART 
     In general, there is known an electrostatic coating apparatus that is provided with, for example, a rotary atomizing head that is rotatably provided on the front side of an air motor by the air motor, external electrode units provided in the periphery of the rotary atomizing head, and a high voltage generator that applies a high voltage to the external electrode unit to indirectly charge paint particles atomized from the rotary atomizing head with the high voltage (Patent Document 1). 
     Patent Document 1 discloses the configuration in which an air motor is mounted to a housing member, and the housing member and the external electrode unit are covered with a cover made of an insulating material. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: WO 2007/015335 A1 
     SUMMARY OF THE INVENTION 
     Incidentally, in the electrostatic coating apparatus according to Patent Document 1, the cover for covering the housing member and the external electrode unit is formed as a covering member that corresponds to an outer shape of the housing member and the external electrode unit and is slightly larger than them. In this case, since the housing member and the external electrode unit are covered with the cover, adhesion of paint to the housing member or external electrode unit can be prevented. Further, adhesion of paint to the cover can also be suppressed by causing the cover to take charge with a high voltage. 
     However, it is difficult to completely prevent the adhesion of the paint to the cover. When any paint adheres to the cover, contamination of the cover increases around the paint that has adhered thereto. Therefore, in a coating line, the coating line is periodically stopped and it is necessary to manually clean off the paint having adhered to the cover with waste clothes, thus leading to a problem with decline in productivity. 
     The present invention is made in view of the foregoing problems in the conventional art, and an object of the present invention is to provide an electrostatic coating apparatus that can eliminate paint having adhered to a cover in a simple work and enhance productivity at a coating work. 
     (1) According to the present invention, an electrostatic coating apparatus comprises: a motor; a rotary atomizing head that is provided on the front side of the motor to be rotatable by the motor; an external electrode unit that is provided in the periphery of the rotary atomizing head; and a high-voltage applying unit that applies a high voltage to the external electrode unit to indirectly charge paint particles atomized from the rotary atomizing head with the high voltage, characterized in that: a film cover is provided to be formed with a resin material in a film shape for covering an outer peripheral side of the motor; wherein the film cover includes a cylindrical rear cover that covers the rear side from the external electrode unit and a cylindrical front cover that is mounted to the front side of the rear cover to cover the front side from the external electrode unit. 
     With this arrangement, there are some cases where a part of paint particles atomized from the rotary atomizing head adheres to the film cover. In this case, since the film cover includes the cylindrical rear cover that covers the rear side from the external electrode unit and the cylindrical front cover that is mounted to the front side of the rear cover to cover the front side from the external electrode unit, the film cover can be removed by separating the front cover from the rear cover even if the paint article adheres to the film cover. In replacement of it, a new front cover and rear cover or a front cover and rear cover from which the paint is already eliminated are attached to be opposed to each other in a front-rear direction, and thus the clean front and rear covers can be attached. 
     As a result, since the front cover and the rear cover that form the film cover can be removed/attached in a simple work, it is possible to shorten removal work hours of the paint as compared to a cleaning-off work. Thereby, since stopping hours of the coating line can be shortened, the productivity at coating work can be enhanced. 
     On the other hand, in a case of forming the front cover and the rear cover with, for example, a semi conductive material, it is possible to prevent intensive large electrical current from acting on these covers for a short time to suppress degradation of each cover, particularly the front cover, thus enhancing durability thereof. 
     (2) According to the present invention, a rear combining part is provided on the front side of the rear cover, and a front combining part is provided on the rear side of the front cover, wherein the film cover is formed to be integrated by attaching the rear combining part of the rear cover to the front combining part of the front cover. 
     With this arrangement, the rear cover and the front cover can be integrated by attaching the rear combining part provided on the front side of the rear cover to the front combining part provided on the rear side of the front cover. Thereby, the external electrode unit arranged in the outermost diameter side can be efficiently covered by interposing the external electrode unit between the front and rear covers. 
     (3) According to the present invention, the front cover is mounted to the rear cover in a state a front end part of the external electrode unit is exposed. 
     With this arrangement, when the front cover is mounted to the rear cover, only the front end part of the external electrode unit can be exposed to outside. Thereby, the front cover can cover the other parts except the front end part of the external electrode unit to prevent the contamination of the external electrode unit. 
     (4) According to the present invention, the external electrode unit includes an electrode support arm, and a needle electrode member that is provided in the electrode support arm and to which a high voltage is applied from the high-voltage applying unit, the film cover covers the electrode support arm of the external electrode unit together with the motor, and the needle electrode member of the external electrode unit is exposed from an electrode opening formed in the front cover of the film cover. 
     With this arrangement, since the needle electrode member of the external electrode unit is exposed from the electrode opening formed in the front cover of the film cover, ions from the needle electrode member can be securely supplied to the paint particle. Further, since the film cover covers the electrode support arm of the external electrode unit together with the motor, the contamination of the electrode support arm can be prevented. 
     (5) According to the present invention, the motor is supported to a housing member, the film cover covers the housing member and the external electrode unit. 
     With this arrangement, the film cover can prevent the paint particle from adhering to the housing member, and in addition, the film cover can be removed from the housing member by separating the front cover from the rear cover even if the paint article adheres to the film cover. Therefore, the film cover can be easily replaced to enhance the maintenance properties. 
     (6) According to the present invention, the rear cover is provided with a cutting part in which the rear cover is axially cut, and two separating parts that are separated by the cutting part. 
     With this arrangement, since the cylindrical rear cover is provided with the two separating parts that are separated by the cutting part, when the rear cover covers the external electrode unit, the motor and the like, the rear cover is deformed in a deflecting manner to separate the two separating parts from each other. Thereby, the rear cover can be mounted to surround the external electrode unit by widening the cutting part. As a result, also in a state where the coating apparatus is mounted to a robot or the like, the rear cover can be easily mounted. 
     (7) According to the present invention, the two separating parts are removably coupled by a coupling member. Thereby, since the two separating parts are coupled by the coupling member, the separating parts pull away from each other by releasing the coupling by the coupling member, thus making it possible to remove the rear cover. On the other hand, the rear cover is fixed to the front cover in a state of being mounted to the front cover by coupling the two separating parts with the coupling member. Therefore, the rear cover can be easily replaced to enhance the maintenance properties. 
     (8) According to the present invention, a shaping air ring is provided on the rear side of the rotary atomizing head, the shaping air ring being provided with an air spout hole formed to spout shaping air and being connected to ground, and the front cover is formed by a semi conductive member and is connected to the shaping air ring. 
     With this arrangement, since the shaping air ring is grounded to the earth electrical potential, it is not necessary to provide another member only for grounding the front cover. In addition, since the discharge is generated also in the periphery of the grounded shaping air ring, ions can be supplied to the periphery of the air spout hole to accelerate the charging of the paint particles through the shaping air. 
     On the other hand, the corona ions by the corona discharge are generated in the vicinity of the external electrode unit to form a minus ionization zone by the corona ions. Therefore, the paint particles atomized from the rotary atomizing head pass through the ionization zone to be charged with the minus high-voltage and to be charged paint particles. 
     In this case, ions from the external electrode unit tend to easily concentrate on the grounded front cover. However, since the front cover is a resistive element that is formed of a resin material and has higher volume resistivity and higher surface resistivity as compared to a metallic material, an electrical potential gradient is formed in the front cover. That is, the part in contact with the shaping air ring of the front cover becomes in a state where an electrical potential thereof is low, and parts except it become in a state where the electrical potential is high. At this time, since the front cover is charged with same polarity as that of the charged paint particles, the charged paint particle is more difficult to adhere thereto as compared to the shaping air ring, making it possible to suppress the contamination of the front cover. 
     Further, when the front cover takes charge, there is a possibility that discharge is generated between the charged front cover and the grounded shaping air ring. At this time, since the front cover is formed by the semi conductive material, even if the electrical current by discharge flows in the front cover, the electrical current does not become intensive large electrical current for a short time, but slow electrical current. As a result, degradation of the front cover can be suppressed to enhance the durability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a rotary atomizing head type coating apparatus according to a first embodiment in the present invention. 
         FIG. 2  is an exploded perspective view showing a state where a rear cover, a front cover and a semi conductive member in the rotary atomizing head type coating apparatus in  FIG. 1  are exploded. 
         FIG. 3  is a cross section showing the rotary atomizing head type coating apparatus in  FIG. 1 . 
         FIG. 4  is a partially enlarged cross section showing the periphery of a shaping air ring and a semi conductive member in  FIG. 3  in an enlarging manner. 
         FIG. 5  is a front view showing the semi conductive member to be enlarged from the front side. 
         FIG. 6  is a cross section showing the semi conductive member as viewed in a direction of arrows VI-VI in  FIG. 5 . 
         FIG. 7  is an explanatory diagram showing characteristics of various kinds of resin materials. 
         FIG. 8  is a partially enlarged cross section showing a rotary atomizing head type coating apparatus according to a second embodiment in the present invention in a position similar to that of  FIG. 4 . 
         FIG. 9  is a perspective view showing a rotary atomizing head type coating apparatus according to a third embodiment. 
         FIG. 10  is an exploded perspective view showing the rotary atomizing head type coating apparatus in  FIG. 9  in a state where a front cover and a rear cover are exploded. 
         FIG. 11  is a partially enlarged cross section showing the periphery of a rotary atomizing head, a shaping air ring and a front cover in a position similar to that of  FIG. 4 . 
         FIG. 12  is a perspective view showing the rear cover in  FIG. 9  as a single unit. 
         FIG. 13  is a partially enlarged perspective view shown by enlarging binders in  FIG. 12 . 
         FIG. 14  is a side view showing the rear cover in  FIG. 12  in a state where a cutting part is opened. 
         FIG. 15  is a perspective view showing a rear cover according to a first modification as a single unit. 
         FIG. 16  is a cross section showing a surface fastener of the rear cover as viewed to be enlarged in a direction of arrows XVI-XVI in  FIG. 15 . 
         FIG. 17  is a perspective view showing a rear cover according to a second modification as a single unit. 
         FIG. 18  is a cross section showing a hook of the rear cover as viewed to be enlarged in a direction of arrows XVIII-XVIII in  FIG. 17 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an electrostatic coating apparatus according to an embodiment of the present invention will be in detail explained with reference to the accompanying drawings by taking a rotary atomizing head type coating apparatus as an example. 
       FIG. 1  to  FIG. 7  show a first embodiment of an electrostatic coating apparatus in the present invention. 
     In the figure, designated at  1  is a rotary atomizing head type coating apparatus (hereinafter, referred to as coating apparatus  1 ) according to the first embodiment. As shown in  FIG. 2  and  FIG. 3 , the coating apparatus  1  includes an atomizer  2 , a housing member  6 , a shaping air ring  9 , external electrode units  13 , a high voltage generator  15 , a film cover  17 , and a semi conductive member  21 , which will be described later. 
     Indicated at  2  is the atomizer that atomizes paint toward an object to be coated (not shown) having an earth potential. The atomizer  2  includes an air motor  3  and a rotary atomizing head  4 , which will be described later. 
     The air motor  3  drives the rotary atomizing head  4  for rotation, and the air motor  3  is made of a conductive metallic material such as an aluminum alloy, and is connected to ground. As shown in  FIG. 3 , the air motor  3  includes a motor housing  3 A, a hollow rotary shaft  3 C rotatably supported in the motor housing  3 A through a static pressure air bearing  3 B, and an air turbine  3 D fixed to a base end side of the rotary shaft  3 C. The air motor  3  supplies drive air to the air turbine  3 D to rotate the rotary shaft  3 C and the rotary atomizing head  4  in a high speed of, such as 3000 to 150000 rpm. 
     The rotary atomizing head  4  is rotatably provided on the front side of the air motor  3 . That is, the rotary atomizing head  4  is mounted to a front end side of the rotary shaft  3 C of the air motor  3 . The rotary atomizing head  4  is formed of a conductive metallic material such as an aluminum alloy, and is connected to ground through the air motor  3 . The rotary atomizing head  4  is provided with a paint releasing edge  4 A formed therein to be positioned in a front end part of the outer peripheral side for releasing paint. Therefore, in a state where the rotary atomizing head  4  is rotated in a high speed by the air motor  3 , when the paint is supplied to the rotary atomizing head  4  through a feed tube  5  to be described later, the rotary atomizing head  4  atomizes the paint from the paint releasing edge  4 A by a centrifugal force. 
     The feed tube  5  is provided to be inserted in the rotary shaft  3 C, and a front end side of the feed tube  5  projects from a front end of the rotary shaft  3 C and extends into the rotary atomizing head  4 . A paint passage (not shown) is provided in the feed tube  5 , and the paint passage is connected to a paint supply source and a washing fluid supply source (none of them are shown) through a color change valve device and the like. Thereby, the feed tube  5  supplies paint from the paint supply source through the paint passage to the rotary atomizing head  4  at coating. On the other hand, the feed tube  5  supplies washing fluids (thinner, air or the like) from a washing fluid supply source toward the rotary atomizing head  4  at washing or color changing. 
     The housing member  6  accommodates the air motor  3  therein, and the rotary atomizing head  4  is arranged on a front end side thereof. The housing member  6  is formed in a substantially columnar shape by, for example, an insulating resin material. A motor accommodating hole  6 A accommodating the air motor  3  is formed on the front side of the housing member  6 . The motor housing  3 A is mounted in the motor accommodating hole  6 A, and thereby the air motor  3  is supported to the housing member  6 . 
     The air passage member  7  is provided to cover an outer peripheral surface in a front side part of the housing member  6 . The air passage member  7  is formed in a cylindrical shape using, for example, an insulating resin material similar to that of the housing member  6 . A first air passage  8  is formed between the air passage member  7  and the housing member  6  to supply first shaping air. 
     Indicated at  9  is the shaping air ring that spouts shaping air toward the outer peripheral surface of the rotary atomizing head  4 . The shaping air ring  9  is provided on a front end side of the housing member  6  to be positioned backward of the rotary atomizing head  4 . The shaping air ring  9  is formed in a cylindrical shape by, for example, a conductive metallic material, and is connected to ground through the air motor  3 . As a result, the shaping air ring  9  forms an earth member according to the present invention. It should be noted that the shaping air ring  9  may be directly connected to ground or indirectly connected to ground though a resistance. 
     As shown in  FIG. 4 , a plurality of groove parts  9 B are formed on the outer peripheral surface  9 A of the shaping air ring  9  to mount an adaptor  16  thereto. The plurality of groove parts  9 B are arranged to be spaced by equal intervals in the circumferential direction. A stepped part  9 C is formed on a front end part of the shaping air ring  9  by protruding a radial inside part thereof to the forward side. 
     The shaping air ring  9  is provided with first air spout holes  10  and second air spout holes  11  formed therein. The first air spout holes  10  are arranged closer to a radial inside part (front side projecting part) than the stepped part  9 C of the shaping air ring  9  and are provided along a paint releasing edge  4 A of the rotary atomizing head  4 . These first air spout holes  10  are arranged to line up annularly. Each of the first air spout holes  10  is communicated with the first air passage  8  provided between the housing member  6  and the air passage member  7 . The first shaping air is supplied to each of the first air spout holes  10  through the air passage  8 , and the air spout hole  10  spouts the first shaping air to the vicinity of the paint releasing edge  4 A of the rotary atomizing head  4 . 
     The second air spout holes  11  are formed in the shaping air ring  9  together with the first air spout holes  10 . The second air spout holes  11  are respectively arranged closer to a radial inside than the first air spout holes  10  and are arranged to line up annularly. Each of the second air spout holes  11  is communicated with a second air passage  12  provided in the housing member  6 . Thereby, the second shaping air having the same pressure as or a pressure different from the shaping air is supplied to the second air spout holes  11  through the air passage  12 , and the second air spout hole  11  spouts the second shaping air to the back surface of the rotary atomizing head  4 . 
     Thereby, the first and second shaping air shears liquid thread of paint released from the rotary atomizing head  4  to accelerate formation of paint particles, and shapes an atomizing pattern of paint particles atomized from the rotary atomizing head  4 . At this time, the pressure of the first shaping air and the pressure of the second shaping air are adjusted as needed, thus making it possible to change the atomizing pattern to a desired size or shape. 
     Indicated at  13  are the external electrode units that are provided on the outer peripheral side of the housing member  6 . As shown in  FIG. 2 , the external electrode units  13  are mounted to a collar-shaped support member  14  arranged on the rear side of the housing member  6 . The support member  14  is formed by, for example, an insulating resin material as similar to that of the housing member  6 , and projects to a radial outside from the housing member  6 . For example, eight external electrode units  13  are provided to be spaced by equal intervals in the circumferential direction to be positioned in a projecting end side (outer diameter side) of the support member  14 . These eight external electrode units  13  are annularly arranged coaxially with the rotary atomizing head  4 , and are arranged along a circle around the rotary shaft  3 C. It should be noted that not only the eight external electrode units  13  but also nine or more or seven or less external electrode units  13  may be adopted. 
     Here, the external electrode unit  13  includes an electrode support arm  13 A extending in a long, bar-shape to the front side from the support member  14  and a needle electrode member  13 B provided in a front end of the electrode support arm  13 A. The electrode support arm  13 A is formed using an insulating resin material as similar to, for example, the housing member  6  or support member  14 , and its front end is arranged in a backward outer peripheral side of the rotary atomizing head  4  on the periphery of the rotary atomizing head  4 . On the other hand, the needle electrode member  13 B is formed in a needle shape using a conductive material such as metal to have a front end thereof as a free end, and is arranged in a shallow accommodation recessed part provided in a front end of the electrode support arm  13 A. The needle electrode member  13 B is connected to a high voltage generator  15  to be described later through a resistance (not shown) provided in the electrode support arm  13 A. 
     The eight needle electrode members  13 B are annually arranged coaxially with the rotary atomizing head  4 , and are provided in a position along a large diameter circle having a large diameter dimension around the rotational shaft  13 C. The eight needle electrode members  13 B are arranged on the rear side of the atomizer  2  than the shaping air ring  9 . Therefore, the external electrode units  13  charge paint particles atomized from the rotary atomizing head  4  with a minus high voltage by generation of corona discharge from the needle electrode members  13 B. 
     Designated  15  is a high voltage generator as a high voltage applying unit that is connected to the external electrode unit  13 . The high voltage generator  15  is formed by, for example, a multiple stepped rectification circuit (what is called cock croft circuit), and is connected electrically to each needle electrode member  13 B of the external electrode units  13 . In addition, the high voltage generator  15  generates a high voltage of a direct current voltage of −10 kV to −150 kV, for example, and supplies this high voltage to each needle electrode member  13 B of the external electrode units  13 . 
     The adaptor  16  is provided in the shaping air ring  9 , and the adaptor  16  is formed by an insulating material or semi conductive material. Specifically, the adaptor  16  is formed in a ring shape, and is mounted to the shaping air ring  9  to cover the outer peripheral surface  9 A of the shaping air ring  9 . A ring-shaped engaging groove part  16 A is formed on an outer peripheral side of the adaptor  16  over an entire periphery for mounting the semi conductive member  21  to be described later. 
     Further, a plurality of projections  16 B projecting toward a radial inside are provided on an inner peripheral side of the adaptor  16  in positions corresponding to the groove parts  9 B of the shaping air ring  9 . The plurality of projections  16 B are arranged to be spaced by equal intervals in the circumferential direction. 
     When the adaptor  16  is mounted to the shaping air ring  9 , the adaptor  16  is pushed into the outer peripheral side of the shaping air ring  9  from forward to backward, and the adaptor  16  is rotated by a predetermined angle in the circumferential direction in this state. Therefore, the projection  16 B of the adaptor  16  is inserted in the groove part  9 B of the shaping air ring  9  to cause both to be engaged with each other, thus mounting the adaptor  16  to the shaping air ring  9 . The adaptor  16  can be removed from the shaping air ring  9  by the reverse operation to the above. 
     It should be noted that the adaptor  16  can be mounted to or removed from the shaping air ring  9  by an engaging mechanism composed of the projections  16 B and the groove parts  9 B. However, the present invention is not limited thereto, and the engaging mechanism may be configured such that a female screw is formed on an inner peripheral side of the adaptor  16  and a male screw is formed on an outer peripheral side of the shaping air ring  9  to screw the adaptor  16  and the shaping air ring  9  with each other for fixation. Further, if it is not necessary to remove the adaptor  16 , the adaptor  16  may be fixed to the shaping air ring  9 . 
     Designated at  17  is the film cover that is formed of a resin material in a film shape for covering the outer peripheral side of the air motor  3 . The film cover  17  is formed in a thin film shape using an insulating resin material, such as polypropylene (PP), polyethylene terephthalate (PET) or polyethylene (PE). The film cover  17  is formed by a resin film having a thickness dimension of 2 mm or less, preferably about 0.1 mm to 1.5 mm. For reducing the material cost, preferably the thickness dimension of the film cover  17  is as thin as possible within a range where a mechanical strength of the film cover  17  can be secured. 
     A material of the film cover  17  has flame retardation and self-extinguishing properties, and is selected as needed in consideration of workability and solvent resistance. Considering a case of vacuum-molding the film cover  17 , when water-based paint is used, it is preferable to use, for example, polyvinyl chloride (PVC), and when solvent-based paint is used, it is preferable to form the film cover  17  with a material excellent in solvent resistance, such as polypropylene (PP). 
     Various kinds of resin materials containing these insulating resin materials have characteristics as shown in an explanatory diagram of  FIG. 7 , and a material suitable for certain conditions can be applied to the film cover  17 . Also, any material, which is suitable for the film cover  17 , can be applied other than the resin materials described in the explanatory diagram in  FIG. 7 . 
     In a case of ejection molding or extrusion molding, the film cover  17  can be formed with polyvinyl chloride (PVC), polycarbonate (PC), fluorine resin materials (PTFE: polytetrafluoroethylene, ETFE: tetrafluoroethylene/ethylene copolymer, FEP: tetrafluoroethylene/hexafluoropropylene copolymer or the like) or polyphenylene sulfide (PPS), having self-extinguishing properties. In a case of ejection molding or extrusion molding, a flame retardation resin material formed by adding an additive to a thermoplastic resin material or a thermosetting resin material can be used. The thermoplastic resin material may include, for example, acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene (PS), polypropylene (PP), polyethylene (PE), ABS/PC aroyl, polybutyleneterephthalate (PBT), variant polyphenylene ether (m-PPE), polyamide (PA), or polycarbonate (PC). The thermosetting resin material may include, for example, an epoxy resin material or phenol resin material. 
     Here, the film cover  17  includes a cylindrical rear cover  18  mounted to the housing member  6  to cover the rear side from the external electrode unit  13  and a cylindrical front cover  19  mounted to the front side of the rear cover  18  to cover the front side from the external electrode unit  13 , that is, the air motor  3 . That is, the film cover  17  is integrated by attaching the front side of the rear cover  18  to the rear side of the front cover  19 . 
     The rear cover  18  is provided with a fixing part  18 A that is formed in a cylindrical shape and is fixed to the housing member  6  and a flared part  18 B that extends to flare in a bell shape forward from a front end of the fixing part  18 A. The fixing part  18 A is mounted on an outer peripheral side of the support member  14  using a fixing means (not shown) such as a bolt or lock pin and is fixed to the housing member  6 . At this time, the flared part  18 B covers a radial outside of the external electrode unit  13 , and eight electrode support arms  13 A are arranged inside the flared part  18 B. Further a flange part  18 C as a rear combining part that spreads radially outward is provided in a front side opening end of the flared part  18 B. 
     The front cover  19  is provided with a disc part  19 A that is positioned in a rear part outer peripheral side and is formed in a disc shape and a cylindrical part  19 B that is successively formed to an inner peripheral edge of the disc part  19 A to extend forward. The disc part  19 A covers a front end part of each of the electrode support arms  13 A forming the external electrode units  13  from a radial outside. The disc part  19 A is provided with electrode openings  20  formed in positions corresponding to the front end parts of the respective electrode support arms  13 A to expose the front end parts of the electrode support arms  13 A. The needle electrode member  13 B of the external electrode unit  13  is exposed to the front side from the electrode opening  20 . As shown in  FIG. 3 , preferably the front end of the needle electrode member  13 B projects having a projection dimension d of about 1 mm to 10 mm from the electrode opening  20 , for example. 
     An annular combining groove part  19 C as a front combining part is formed on a rear side opening end of the disc part  19 A to extend over the entire circumference to be positioned on the inner peripheral side. The flange part  18 C of the rear cover  18  is inserted and fitted in the combining groove part  19 C. As a result, the front cover  19  is pushed against the front side of the rear cover  18  to be attached in an outer peripheral side position of the external electrode units  13 . In this way, the front cover  19  and the rear cover  18  are attached to be positioned closer to the radial outside than the external electrode unit  13 . Therefore, in a state where the front cover  19  is attached to the rear cover  18 , the external electrode units  13  can be accommodated to be interposed between the disc part  19 A and the flared part  18 B. On the other hand, the flange part  18 C of the rear cover  18  is flexibly deformed by pulling the front cover  19  forward, thus making it possible to separate the flange part  18 C from the combining groove part  19 C. Thereby, the front cover  19  can be removed from the rear cover  18 . 
     The cylindrical part  19 B covers the outer peripheral side of the air motor  3  including the housing member  6  and the air passage member  7 . A front end part  19 D of the cylindrical part  19 B is arranged near the rear end of the shaping air ring  9  to be positioned to be radially spaced from the shaping air ring  9 . That is, the film cover  17  is not in contact with the shaping air ring  9 , and a radial or axial gap is formed between the film cover  17  and the shaping air ring  9 . 
     Designated at  21  is the semi conductive member formed of a semi conductive material. The semi conductive member  21  is formed of a semi conductive resin material having a surface resistance of 10 10  to 10 7  Ωm or volume resistance of 10 8  to 10 5  Ωm, for example. Specifically, the semi conductive member  21  is formed using a semi conductive resin sheet in which a semi conductive resin is kneaded in amorphous-polyethylene terephthalate (A-PET), a three-layered resin film in which a polystyrene semi conductive film is interposed between two polypropylene (PP) films or the like. The semi conductive member  21  may be formed by a resin material having semi conductivity by blending a conductive element with the same material as that of the film cover  17 , for example. The semi conductive member  21  has a thickness dimension of, for example, 2 mm or less, preferably about 0.1 mm to 1.5 mm, and flares from forward to backward to be formed in a substantially conical shape or in a substantially cylindrical shape. 
     A plurality (for example, five) of engaging projections  21 A are formed in the intermediate position of the semi conductive member  21  in the front-rear direction to project toward a radial inside. The plurality of engaging projections  21 A extend in an arc shape along the engaging groove parts  16 A of the adaptor  16  in the circumferential direction, and are arranged to be spaced by equal intervals from each other in the circumferential direction. When the semi conductive member  21  is pushed against the adaptor  16  from forward to backward, the plurality of engaging projections  21 A are inserted in the engaging groove part  16 A of the adaptor  16 . Thereby, the semi conductive member  21  is mounted to the outer peripheral side of the adaptor  16 . When the semi conductive member  21  is pulled forward, the engaging projection  21 A is flexibly deformed to pull the engaging projection  21 A out of the engaging groove part  16 A. Thereby, the semi conductive member  21  can be removed from the adaptor  16 . 
     A rear end part  21 B that is one end part of the semi conductive member  21  is in contact with the front end part  19 D of the front cover  19 . Specifically, the rear end part  21 B of the semi conductive member  21  covers the front end part  19 D of the front cover  19  from outside to be in surface contact with the front end part  19 D, and the semi conductive member  21  can be conductive to the front cover  19 . 
     On the other hand, a front end part  21 C that is the other end part of the semi conductive member  21  is in contact with the shaping air ring  9 . Specifically, the front end part  21 C of the semi conductive member  21  is formed as a ring-shaped flat plate extending radially inside, is in surface contact with an end surface of the stepped part  9 C provided on a front outer peripheral side of the shaping air ring  9 , and the semi conductive member  21  can be conductive to the shaping air ring  9 . 
     It should be noted that the rear end part  21 B of the semi conductive member  21  is in surface contact with the front end part  19 D of the front cover  19 , and the front end part  21 C of the semi conductive member  21  is in surface contact with the stepped part  9 C of the shaping air ring  9 . However, the present invention is not limited thereto, and only if the rear end part  21 B of the semi conductive member  21  and the front end part  19 D of the front cover  19  are electrically connected to each other, they may be in line contact or in point contact. Similarly, the front end part  21 C of the semi conductive member  21  may be in line contact or point contact with the stepped part  9 C of the shaping air ring  9 . For increasing an electrical resistance of the semi conductive member  21  between the shaping air ring  9  and the front cover  19 , the front end and the rear end of the semi conductive member  21  is preferably in line contact or point contact with each other. On the other hand, for securing the electrical connection, the semi conductive member  21  is preferably in surface contact with the shaping air ring  9  or the front cover  19 . 
     The coating apparatus  1  according to the first embodiment has the aforementioned configuration, and next an explanation will be made of an operation at the time of performing a coating work using the coating apparatus  1 . 
     First, the rotary atomizing head  4  is rotated at a high speed by the air motor  3 , and the paint is supplied to the rotary atomizing head  4  through the feed tube  5  at this state. Therefore, the atomizer  2  micro-particulates the paint by a centrifugal force when the rotary atomizing head  4  rotates, and atomizes the paint as the paint particles. At this time, the first and second shaping air is supplied from the first and second air spout holes  10 ,  11  provided in the shaping air ring  9 , and the shaping air controls an atomizing pattern composed of the paint particles. 
     Here, a minus high voltage is applied to the needle electrode member  13 B of the external electrode unit  13  by the high voltage generator  15 . Therefore, an electrostatic field is regularly formed between the needle electrode member  13 B and the object to be coated having the earth potential. Therefore, corona discharge is generated in the front end of the needle electrode member  13 B to generate the ionization zone caused by the corona discharge in the periphery of the rotary atomizing head  4 . As a result, the paint particles atomized from the rotary atomizing head  4  pass through the ionization zone, and thereby are indirectly charged with a high voltage. The paint particles charged with the high voltage (charged paint particles) fly along the electrostatic field formed between the needle electrode member  13 B and the object to be coated and adhere to the object to be coated for paint. 
     Next, an explanation will be made of effects of suppressing degradation, contamination or the like of the film cover  17  by the semi conductive member  21 . 
     Here, a description will be made of a case of omitting the semi conductive member  21 , for example. In this case, a surface of the film cover  17  made of the insulating material collides with ions from the external electrode unit  13  for charge to increase the electrical potential. At this time, when a difference in electrical potential between the charged film cover  17  and the grounded shaping air ring  9  increases and thus the insulating state cannot be maintained, the discharge is generated. Several micro seconds of pulse discharge is generated in air to release energy accumulated by the charging in a short time. 
     Thereby, ozone is generated by plasma, collision of electrons by the discharging, local heat generation of joule by electrical current, and by release of electromagnetic wave by transition from energized state to base state, and the like, oxidation or reduction of molecular weight is generated in peripheral materials such as the film cover  17  and the peripheral materials are degraded. Particularly, since the shaping air ring  9  or rotary atomizing head  4  has the fixed electrical potential and an electrical line of force is pulled therein from the external electrode unit  13 , ion particles concentrate thereon. As a result, the front end part  19 D of the film cover  17  near the shaping air ring  9  or the rotary atomizing head  4  is more easily charged than other parts and is remarkable in degradation progress. 
     In contrast to this, in the first embodiment, the boundary between the front end part  19 D of the film cover  17  made of an insulating material and the shaping air ring  9  made of a conductive material is covered with the semi conductive member  21 , and the rear end part  21 B of the semi conductive member  21  is made in contact with the front end part  19 D of the film cover  17  and at the same time the front end part  21 C of the semi conductive member  21  is made in contact with the stepped part  9 C of the shaping air ring  9 , while the semi conductive member  21  is connected to ground. 
     In this case, the electric charge charged to the film cover  17  is discharged to the semi conductive member  21 , but the electrical current does not become intensively large for a short time, as in the case of discharge to the shaping air ring  9  made of the conductive material, and becomes slow electrical current. Therefore, degradation of the film cover  17  is suppressed. On the other hand, the electrical current flows also in the semi conductive member  21  following the discharge from the film cover  17 , but this electrical current becomes several ten μA or less. Therefore, there is no possibility that the semi conductive member  21  itself may be eventually degraded due to supply of the electrical current thereto. 
     Further, since the shaping air ring  9  has an earth potential, ions from the external electrode unit  13  tend to easily concentrate on the semi conductive member  21  in contact with the shaping air ring  9 . However, since the semi conductive member  21  is a resistance having a higher volume resistance or a higher surface resistance as compared to that of a metallic material, an electrical potential gradient is formed in the semi conductive member  21 , an electrical potential of which becomes in a higher state as compared to that of the shaping air ring  9 . At this time, since the semi conductive member  21  takes charge with the same polarity as the charged paint particle, the charged paint particle becomes difficult to adhere thereto as compared to the shaping air ring  9 , making it possible to suppress the contamination. 
     Thus, according to the first embodiment, the film cover  17  made of an insulating resin material includes the cylindrical rear cover  18  that covers the rear side from the external electrode unit  13  and the cylindrical front cover  19  that is mounted to the front side of the rear cover  18  to cover the front side from the external electrode unit  13 . Therefore, the film cover  17  can be removed by separating the rear cover  18  from the front cover  19  even if the paint article adheres to the film cover  17 . In replacement of it, the new rear cover  18  and front cover  19  or the rear cover  18  and front cover  19  which the paint is already removed are attached to be opposed to each other in a front-rear direction, and thereby the clean rear cover  18  and front cover  19  can be integrated. 
     As a result, since the rear cover  18  and the front cover  19  that form the film cover  17  can be attached/separated in a simple work, it is possible to shorten removal work hours of the paint as compared to a cleaning-off work. Thereby, since stopping hours of the coating line can be shortened, the productivity at coating work can be enhanced. 
     The flange part  18 C is provided on the front side of the rear cover  18 , and the combining groove part  19 C is provided on the rear side of the front cover  19 , wherein the flange part  18 C of the rear cover  18  and the combining groove part  19 C of the front cover  19  are attached to be positioned closer to the radial outside than the external electrode unit  13 , so that the flange part  18 C and the combining groove part  19 C can be integrated. Therefore, the flange part  18 C can be fitted in the combining groove part  19 C by pushing the front cover  19  on the front side of the rear cover  18  to simply attach the front cover  19  to the rear cover  18 . On the other hand, the flange part  18 C of the rear cover  18  can be flexibly deformed by pulling the front cover  19  forward to be pulled out of the combining groove part  19 C of the front cover  19 , so that the front cover  19  can be simply removed from the rear cover  18 . Here, in a state where the rear cover  18  and the front cover  19  are attached, the external electrode units  13  arranged on the outermost diameter side (outermost periphery of the coating apparatus  1 ) are interposed by the front and rear covers  19 ,  18 , thereby effectively covering the external electrode units  13 . 
     On the other hand, the rear end part  21 B of the semi conductive member  21  is made in electrical contact with the film cover  17  and the front end part  21 C of the semi conductive member  21  is made in electrical contact with the shaping air ring  9 . Therefore, the discharge between the film cover  17  and the shaping air ring  9  is prevented by the semi conductive member  21  to suppress degradation of the film cover  17 , thus making it possible to enhance the durability. In addition thereto, since the semi conductive member  21  takes charge with the same polarity as the charged paint particle, the adhesion of the charged paint particle can be suppressed. 
     In this way, since the shaping air ring  9  is connected to ground, it is not necessary to provide another member only for grounding the front end part  21 C of the semi conductive member  21 . Further, since the discharge is generated also in the periphery of the grounded shaping air ring  9 , ions can be supplied in the periphery of the air spout holes  10 ,  11  to accelerate charge of paint particles through the shaping air. 
     The adaptor  16  made of an insulating material or semi conductive material is provided in the shaping air ring  9 . Thereby, even when the front end part  19 D of the film cover  17  is arranged in the periphery of the shaping air ring  9 , insulation properties between the film cover  17  and the shaping air ring  9  can be enhanced to suppress direct discharge therebetween. 
     On the other hand, since the front end part  21 C of the semi conductive member  21  is in electrical contact with the shaping air ring  9 , the semi conductive member  21  has the electrical potential closer to earth than the film cover  17 , and paint particles tend to easily adhere thereto. However, since the semi conductive member  21  is replaceably mounted to the adaptor  16 , only the semi conductive member  21  that tends to be easily contaminated can be replaced to enhance the maintenance properties. 
     Since the needle electrode member  13 B of the external electrode unit  13  is exposed outside from the electrode opening  20  formed in the front cover  19  of the film cover  17 , ions from the needle electrode member  13 B can be supplied to the paint particles. Since the film cover  17  covers the electrode support arm  13 A of the external electrode unit  13  in addition to the air motor  3 , the film cover  17  can prevent the contamination of the electrode support arm  13 A and keep it clean. 
     Further, the film cover  17  is configured of the rear cover  18  mounted to the housing member  6  and the front cover  19  attached on the front side of the rear cover  18  to cover the air motor  3 . Thereby, even if the paint particle adheres to the film cover  17 , the film cover  17  can be removed from the housing member  6  by separating the front cover  19  from the rear cover  18 . Therefore, the film cover  17  can be easily replaced to enhance the maintenance properties. 
     Next,  FIG. 8  shows a second embodiment of an electrostatic coating apparatus according to the present invention. The second embodiment is characterized in that a shaping air ring is provided with an inside engaging part, and an outside engaging part engaging with the inside engaging part is provided in the midway part between one end part and the other end part of a semi conductive member. In the second embodiment, the component elements that are identical to those of the foregoing first embodiment will be simply denoted by the same reference numerals to avoid repetitions of similar explanations. 
     Designated at  31  is a rotary atomizing head type coating apparatus (hereinafter, referred to as coating apparatus  31 ) according to the second embodiment. The coating apparatus  31  includes, as substantially similar to the coating apparatus  1  according to the first embodiment, an atomizer  2 , a housing member  6 , a shaping air ring  32 , external electrode units  13 , a high voltage generator  15 , a film cover  17 , a semi conductive member  33  and the like. 
     Indicated at  32  is the shaping air ring according to the second embodiment. The shaping air ring  32  is formed as substantially similar to the shaping air ring  9  according to the first embodiment, and is provided with first and second air spout holes  10 ,  11 . The shaping air ring  32  forms part of the earth member according to the present invention. Therefore, the shaping air ring  32  is formed in a cylindrical shape using, for example, a conductive metallic material, and is connected to ground through the air motor  3 . 
     An annular flange part  32 B is formed on an outer peripheral surface  32 A of the shaping air ring  32  to project radially outside. The flange part  32 B is arranged in a position opposed to the midway part between a rear end part  33 B and a front end part  33 C of the semi conductive member  33  to be described later. That is, the flange part  32 B forms an inside engaging part engaging with an engaging projection  33 A. It should be noted that for preventing discharge between the front end part  19 D of the front cover  19  and the flange part  32 B, for example, the flange part  32 B is preferably arranged in a position closer to a stepped part  32 C than the front end part  19 D. 
     Indicated at  33  is the semi conductive member according to the second embodiment that is formed by a semi conductive material. The semi conductive member  33  is formed as substantially similar to the semi conductive member  21  according to the first embodiment. Therefore, the semi conductive member  33  flares from forward to backward to be formed in a substantially conical shape or substantially cylindrical shape. 
     A plurality (for example, five) of engaging projections  33 A are formed in the intermediate position of the semi conductive member  33  in the front-rear direction of the semi conductive member  33  to project radially inside. The plurality of engaging projections  33 A form an outside engaging part engaging with the flange part  32 B of the shaping air ring  32 . Specifically, the plurality of engaging projections  33 A extend in an arc shape along the flange part  32 B of the shaping air ring  32  toward the circumferential direction, and are arranged to be spaced by equal intervals from each other in the circumferential direction. 
     A rear end part  33 B that is one end part of the semi conductive member  33  is in contact with the front end part  19 D of the front cover  19 . Specifically, the rear end part  33 B of the semi conductive member  33  covers the front end part  19 D of the front cover  19  from outside to be in surface contact with the front end part  19 D of the front cover  19 , and the semi conductive member  33  can be electrically conductive to the front cover  19 . 
     On the other hand, a front end part  33 C that is the other end part of the semi conductive member  33  is in contact with the shaping air ring  32 . Specifically, the front end part  33 C of the semi conductive member  33  is formed as a ring-shaped flat plate extending radially inside, is in surface contact with an end surface of the stepped part  32 C provided on a front outer peripheral side of the shaping air ring  32 , and the semi conductive member  33  can be electrically conductive to the shaping air ring  32 . 
     When the semi conductive member  33  is pushed against the shaping air ring  32  from forward to backward, the plurality of engaging projections  33 A run over the flange part  32 B to be locked on a rear surface of the flange part  32 B. At this time, the front end part  33 C of the semi conductive member  33  is in surface contact with the end surface of the stepped part  32 C of the shaping air ring  32 . Therefore, the flange part  32 B and the stepped part  32 C of the shaping air ring  32  are interposed in the front-rear direction between the engaging projection  33 A and the front end part  33 C of the semi conductive member  33 . As a result, the semi conductive member  33  is mounted to the outer peripheral side of the shaping air ring  32 . 
     On the other hand, when the semi conductive member  33  is pulled forward, the engaging projection  33 A is flexibly deformed and the engaging projection  33 A is pulled out of the flange part  32 B. Thereby, the semi conductive member  33  can be removed from the shaping air ring  32 . 
     Thus, also in the second embodiment as configured above, operational effects substantially similar to those in the first embodiment can be obtained. Particularly, in the second embodiment, since the flange part  32 B is provided in the shaping air ring  32  and the engaging projection  33 A is provided in the semi conductive member  33 , the semi conductive member  33  can be replaceably mounted to the shaping air ring  32  in a state where the engaging projection  33 A is engaged with the flange part  32 B. Therefore, only the semi conductive member  33  that tends to be easily contaminated can be replaced. In addition, the adaptor  16  can be eliminated in contrast to the first embodiment, making it possible to reduce manufacturing costs. 
     Next,  FIG. 9  to  FIG. 14  show a third embodiment of an electrostatic coating apparatus according to the present invention. The third embodiment is characterized in that a front cover of a film cover is formed with a semi conductive material to be connected to a shaping air ring, and a rear cover of the film cover is provided with two separating parts that are separated by a cutting part. In the third embodiment, the component elements that are identical to those of the foregoing first embodiment will be simply denoted by the same reference numerals to avoid repetitions of similar explanations. 
     Designated at  41  is a rotary atomizing head type coating apparatus (hereinafter, referred to as coating apparatus  41 ) according to the third embodiment. The coating apparatus  41  includes, as substantially similar to the coating apparatus  1  according to the first embodiment, an atomizer  2 , a housing member  6 , a shaping air ring  43 , external electrode units  13 , a high voltage generator  15 , a front cover  44 , a semi conductive member  21  and the like. 
     However, a mounting base  42  is provided on a rear end part of the housing member  6  to be positioned closer to the rear side than the support member  14 . The mounting base  42  is bent from an axis line of the housing member  6  to extend downward. Here, the housing member  6  is mounted to an arm (not shown) of a robot, reciprocator or the like through the mounting base  42  and moves integrally with the arm. 
     Designated at  43  is the shaping air ring according to the third embodiment. As shown in  FIG. 11 , the shaping air ring  43  is configured as substantially similar to the shaping air ring  9  according to the first embodiment, and is provided with first and second air spout holes  10 ,  11 . The shaping air ring  43  forms part of the earth member according to the present invention. Therefore, the shaping air ring  43  is formed in a cylindrical shape using, for example, a conductive metallic material, and is connected to ground through the air motor  3 . Further, the shaping air ring  43  has an outer peripheral surface  43 A, and a stepped part  43 B is formed on a front end part of the shaping air ring  43  by protruding a radial inside part of the shaping air ring  43  forward. 
     Designated at  44  is a film cover that is used in the third embodiment. The film cover  44  is formed with a rear cover  45  and a front cover  49  as substantially similar to the film cover  17  according to the first embodiment. That is, as shown in  FIG. 9  and  FIG. 10 , the film cover  44  includes the cylindrical rear cover  45  that is mounted to the housing member  6  to cover the rear side from the external electrode unit  13  and the cylindrical front cover  49  that is mounted to the front side of the rear cover  45  to cover the front side from the external electrode unit  13 . 
     The rear cover  45  is formed as substantially similar to the rear cover  18  according to the first embodiment and is formed in a cylindrical shape to surround the housing member  6 . The rear cover  45  is provided with a fixing part  45 A that is formed in a cylindrical shape to be fixed to the housing member  6  and a flared part  45 B that extends forward from a front end of the fixing part  45 A to flare in a bell shape. The flared part  45 B covers an outer peripheral side of the external electrode units  13 , and eight electrode support arms  13 A are arranged in the inside thereof. On the other hand, a flange part  45 C as a rear combining part widening radially outside is provided in a front side opening end of the flared part  45 B. The flange part  45 C of the rear cover  45  is inserted in a combining groove part  49 C of the front cover  49 . Therefore, the front cover  49  is attached to the front side of the rear cover  45 . 
     As shown in  FIG. 12  to  FIG. 14 , the rear cover  45  is provided with a cutting part  45 D that axially cuts the rear cover  45  and two separating parts  45 E,  45 F separated by the cutting part  45 D. The separating parts  45 E,  45 F are respectively provided with projected pieces  45 E 1 ,  45 F 1  alternately projecting to each other. When the rear cover  45  is mounted to the housing member  6 , the projected pieces  45 E 1 ,  45 F 1  are fitted to each other. Therefore, the projected pieces  45 E 1 ,  45 F 1  suppress the separating parts  45 E,  45 F from being position-shifted in the front-rear direction. 
     The separating parts  45 E,  45 F are provided with two binders  46  as coupling members that are spaced from each other. One of the binders  46  is provided, for example, in a position of the fixing part  45 A of the rear cover  45  and the other of the binders  46  is provided in a position of the flared part  45 B. Each of the binders  46  includes a binding wire  47  a base end part of which is fixed to the separating part  45 E and a receiver  48  fixed to the separating part  45 F of the opponent. 
     The binding wire  47  is formed in a string shape by using a resin material having flexibility, for example and a front end part thereof is configured as a free end. Further, the binding wire  47  is provided with a plurality of knot parts  47 A arranged along a length direction. 
     On the other hand, the receiver  48  is provided with a substantially cylindrical engaging projection  48 A an upper side of which is opened and a notched part  48 B formed by notching a part of the engaging projection  48 A in the opening side. At the time of coupling the separating parts  45 E,  45 F to each other, any one of the knot parts  47 A in the binding wire  47  is inserted in the engaging projection  48 A. At the time of releasing the coupling of the separating parts  45 E,  45 F, the knot part  47 A of the binding wire  47  is pulled out of the engaging projection  48 A. Thereby, the two separating parts  45 E,  45 F are removably coupled by the binder  46 . 
     As shown in  FIG. 9  to  FIG. 11 , designated at  49  is the front cover of the film cover  44 . The front cover  49  is formed, for example, using a semi conductive material as similar to that of the semi conductive member  21  according to the first embodiment. Except for this material, the front cover  49  is formed as substantially similar to the front cover  19  according to the first embodiment. Therefore, the front cover  49  includes a disc part  49 A formed in a disc shape to be positioned in a rear part outer peripheral side and a cylindrical part  49 B that is formed to be connected to an inner peripheral edge of the disc part  49 A in series and extends forward. The disc part  49 A is provided with electrode openings  50  formed in positions corresponding to front end parts of the external electrode units  13 . The needle electrode member  13 B of the external electrode unit  13  is exposed to the front side from the electrode opening  50 . 
     As shown in  FIG. 11 , the cylindrical part  49 B covers an outer peripheral side of the air motor  3  including the housing member  6  and the air passage member  7 . A ring-shaped front end part  49 D extending to a radial inside is provided in a front end position of the cylindrical part  49 B, and the front end part  49 D is in surface contact with an end surface of the stepped part  43 B of the shaping air ring  43  and is electrically conductive thereto. 
     The combining groove part  49 C as a front combining part that is positioned in the inner peripheral side to extend over the entire periphery is formed on a rear side opening end of the disc part  49 A. At the time of pressing the front cover  49  against the rear cover  45  from the front side, the flange part  45 C is inserted in the combining groove part  49 C. Thereby, the front cover  49  is attached to the front side of the rear cover  45 . Thus, the front cover  49  and the rear cover  45  are attached to be positioned closer to a radial outside than the external electrode unit  13 . Therefore, in a state where the front cover  49  is attached to the rear cover  45 , the external electrode units  13  can be accommodated to be interposed between the disc part  49 A and the flared part  45 B. On the other hand, when the front cover  49  is pulled forward, since the flange part  45 C is flexibly deformed, the flange part  45 C can be pulled out of the combining groove part  49 C. Thereby, the front cover  49  can be removed from the outer peripheral side of the housing member  6 . 
     Thus, also in the third embodiment as configured above, operational effects substantially similar to those in the aforementioned first embodiment can be obtained. Particularly, in the third embodiment, the front cover  49  of the film cover  44  is formed by the semi conductive material, and the front end part  49 D is connected electrically to the stepped part  43 B of the shaping air ring  43 . 
     Accordingly, since the front cover  49  is charged with same polarity as that of the charged paint particles as substantially similar to the semi conductive member  21  according to the first embodiment, the charged paint particle is more difficult to adhere thereto as compared to the shaping air ring  43 , making it possible to suppress the contamination. 
     Further, when the front cover  49  takes charge, there is a possibility that discharge is generated between the charged front cover  49  and the grounded shaping air ring  43 . At this time, since the front cover  49  is formed by the semi conductive material, even if the electrical current by discharge flows in the front cover  49 , the electrical current does not become intensive large electrical current for a short time, but slow electrical current. As a result, degradation of the front cover  49  can be suppressed to enhance the durability. 
     On the other hand, in the third embodiment, the cylindrical rear cover  45  is provided with the two separating parts  45 E,  45 F that are separated by the cutting part  45 D. Therefore, the rear cover  45  can be easily mounted to the housing member  6  from the lateral side (for example, upper-lower direction or left-right direction) by coupling the two separating parts  45 E,  45 F to each other by using the binder  46 . Thereby, for example, even in a state where the housing member  6  is mounted to a robot or the like through the mounting base  42 , the rear cover  45  can be easily mounted to the housing member  6 . 
     Since the two separating parts  45 E,  45 F are coupled by the binder  46 , the separating parts  45 E,  45 F pull away from each other by releasing the coupling by the binder  46 , thus making it possible to remove the rear cover  45  from the housing member  6 . On the other hand, the rear cover  45  is fixed to the housing member  6  by coupling the two separating parts  45 E,  45 F with the binder  46 . Therefore, the rear cover  45  can be easily replaced to enhance the maintenance properties. 
     Moreover, in the third embodiment, it should be noted that the two separating parts  45 E,  45 F of the rear cover  45  are removably coupled using the binder  46  composed of the binding wire  47  and the receiver  48 . However, the present invention is not limited thereto, and, for example, as in a case of a first modification as shown in  FIG. 15  and  FIG. 16 , a surface fastener  61  as a coupling member may be used to removably couple two separating parts  45 E′,  45 F′. 
     In a case of the first modification, the separating parts  45 E′,  45 F′ have such a length dimension as to be able to overlap. A hook part  62  of the surface fastener  61  is mounted to an inner peripheral surface of the separating part  45 E′, and a loop part  63  of the surface fastener  61  is mounted to an outer peripheral surface of the separating part  45 F′. Thereby, the separating parts  45 E′,  45 F′ are coupled to each other by engagement of the hook part  62  and the loop part  63 . In such a coupled state, the surface fastener  61  can suppress positional shifts in the front-rear direction as well as in the circumferential direction of the housing member  6 . Therefore, it is not necessary to provide a projecting piece for suppressing the positional shift in the front-rear direction on the separating parts  45 E′,  45 F′. 
     Further, as in a case of a second modification as shown in  FIG. 17  and  FIG. 18 , the two separating parts  45 E′,  45 F′ may be removably coupled by using hooks  71  as coupling members. In this case also, the two separating parts  45 E′,  45 F′ each have such a length dimension as to be able to overlap. An outer side recess  72  of the hook  71  is mounted to the separating part  45 E′, and an inner side projection  73  of the hook  71  is mounted to the separating part  45 F′. As a result, the separating parts  45 E′,  45 F′ are coupled to each other by inserting the inner side projection  73  in the outer side recess  72 . 
     In the third embodiment, the two separating parts  45 E,  45 F of the rear cover  45  are removably coupled. However, the present invention is not limited thereto, and, for example, the rear cover  45  may be mounted to the housing member  6  by fixation of the separating parts  45 E,  45 F through adhesion or thermal compression bond. In this case, at the time of replacing the rear cover  45 , for example, the cutting part  45 D is cut to remove the rear cover  45 , and a new rear cover  45  may be mounted to the housing member  6 . 
     Further, in the third embodiment, the cutting part  45 D is provided at one location to the rear cover  45 , but cutting parts may be provided at a plurality of locations in different positions in the circumferential direction. 
     On the other hand, in the respective aforementioned embodiments, a case where five engaging projections  21 A of the semi conductive member  21  and five engaging projections  33 A of the semi conductive member  33  are respectively provided to be spaced in the circumferential direction is explained as an example, but two, three, four, six or more engaging projections may be provided. Further, for example, one engaging projection may be formed over an entire circumference to project in an annular shape or in a C-letter shape. 
     It should be noted that the first embodiment illustrates a case where the flange part  18 C as the rear combining part spreading in the radial outside is provided on the front side opening end of the rear cover  18 , and the combining groove part  19 C as the front combining part is provided on the rear side opening end of the disc part  19 A of the front cover  19  to be positioned on the inner peripheral side and to be fitted in the flange part  18 C by insert thereof. However, the present invention is not limited thereto, and, for example, a flange part may be provided on the rear side opening end of the front cover  19  and a combining groove part may be provided on the front side opening end of the rear cover  18  to be fitted in the flange part by insert thereof. Besides, any component that can integrally mount the rear cover  18  and the front cover  19 , such as screwing, convex/concave fixation of plural locations, adhesion or bonding, may be used as an attachment component. This configuration can be applied also to the second and third embodiments. 
     In the first embodiment, the semi conductive member  21  is replaceably mounted to the adaptor  16  provided in the shaping air ring  9 . However, the present invention is not limited thereto, and, for example, the semi conductive member may be formed by integration of the semi conductive member  21  and the adaptor  16 . In this case, the semi conductive member may be replaceably mounted to the shaping air ring. 
     In the first embodiment, the rear end part  21 B of the semi conductive member  21  is made in contact with the film cover  17  and the front end part  21 C is made in contact with the shaping air ring  9 . However, the semi conductive member may be formed as an annular plate body extending radially, wherein a radial outside end part thereof is made in contact with a film cover and a radial inside end part thereof is made in contact with a shaping air ring. Besides, when the film cover and the earth member are electrically connected using the semi conductive member, positions of one end part and the other end part of the semi conductive member can be set as needed. This configuration can be applied to the second and third embodiments. 
     In the first embodiment, the semi conductive member  21  is in contact with the film cover  17  in a separable state, but, for example, the semi conductive member may be connected or adhere to the film cover in an inseparable state or may be formed integrally. In this case, a contact failure between the semi conductive member and the film cover can be prevented. This configuration can be applied to the second embodiment. 
     The first embodiment is explained by taking a case where the shaping air ring  9  forms the earth member, as an example. However, the present invention is not limited thereto, and, for example, the earth member may be provided separately from the shaping air ring, wherein the semi conductive member is connected to ground through the earth member. This configuration can be applied to also to the semi conductive member in the second embodiment and the front cover in the third embodiment. 
     In each of the aforementioned embodiments, a case where the needle electrode member  13 B is arranged on the rear side of the atomizer  2  is illustrated, however, it may be arranged on the front side of the atomizer  2 . For accelerating supply of ions to the paint particle, the needle electrode member  13 B is preferably arranged on the front side of the atomizer  2 . On the other hand, for downsizing the coating apparatus  1 ,  31  or  41 , the needle electrode member  13 B is preferably arranged on the rear side of the atomizer  2 . 
     In each of the aforementioned embodiments, a case where the electrode support arm  13 A made of the long bar-shaped body of the external electrode unit  13  is provided in the collar-shaped support member  14  arranged on the rear side of the housing member  6  is illustrated. However, the present invention is not limited thereto, and there may be adopted the configuration that the support member  14  is formed as a cylindrical support member extending to the air passage member  7  or the rotary atomizing head  4  and a short electrode support arm is provided in a front end of this cylindrical support member. 
     In each of the aforementioned embodiments, the rotary atomizing head  4  is formed at its entity by the conductive material. However, the present invention is not limited thereto, and there may be adopted the configuration that, the body part having the substantially same shape as the rotary atomizing head  4  is formed using an insulating material, and a conductive or semi conductive coated layer is provided on an outside surface and an inside surface of the body part. In this case, a paint release edge of the rotary atomizing head is connected to ground through the coated layer. 
     In each of the aforementioned embodiments, the external electrode unit  13  is formed using the needle electrode member  13 B. However, the present invention is not limited thereto, and an external electrode member may be formed using a ring electrode that surrounds an outer peripheral side of a cylindrical part of a front cover and is annularly formed with an elongated conductive wire. Besides, an external electrode unit may be formed using a blade ring in a thin blade shape, a star-shaped ring formed in a star shape with an elongated conductive wire, a spiral ring formed spirally with an elongated conductive wire or the like, which are described in Patent Document 1. 
     In each of the aforementioned embodiments, the housing member  6  and the air passage member  7  are separately provided, but the housing member and the air passage member may be formed integrally using an insulating material. 
     In each of the aforementioned embodiments, the motor is explained by taking the air motor as an example, but, for example, an electric motor may be used. 
     Further, in each of the aforementioned embodiments, the first and second air spout holes  10 ,  11  that spout the shaping air are arranged in a double-annular shape in each of the shaping air rings  9 ,  32 ,  43 . However, the present invention is not limited thereto, and, for example, the air spout hole may be arranged in a single annular shape by eliminating any one of the first and second air spout holes, for example. 
     DESCRIPTION OF REFERENCE NUMERALS 
       1 ,  31 ,  41 : Rotary atomizing head type coating apparatus (Coating apparatus) 
       3 : Air motor (motor) 
       3 C: Rotary shaft 
       4 : Rotary atomizing head 
       4 A: Paint release edge 
       6 : Housing member 
       9 ,  32 ,  43 : Shaping air ring (Earth member) 
       10 : First air spout hole 
       11 : Second air spout hole 
       13 : External electrode unit 
       13 A: Electrode support arm 
       13 B: Needle electrode member 
       15 : High-voltage generator (High-voltage applying unit) 
       16 : Adaptor 
       17 ,  44 : Film cover 
       18 ,  45 : Rear cover 
       18 A,  45 A: Fixing part 
       18 B,  45 B: Flared part 
       18 C,  45 C: Flange part (Rear combining part) 
       19 ,  49 : Front cover 
       19 A,  49 A: Disc part 
       19 B,  49 B: Cylindrical part 
       19 C,  49 C: Combining groove part (Front combining part) 
       19 D,  49 D: Front end part 
       20 ,  50 : Electrode opening 
       21 ,  33 : Semi conductive member 
       21 A,  33 A: Engaging projection 
       21 B,  33 B: Rear end part 
       21 C,  33 C: Front end part 
       32 B: Collar part 
       45 D: Cutting part 
       45 E,  45 F,  45 E′,  45 F′: Separating part 
       46 : Binder (Coupling member) 
       61 : Surface fastener (Coupling member) 
       71 : Hook (Coupling member)