Electrostatic deposition apparatus

Abstract

The present invention provides an electrostatic film deposition apparatus that prevents the powder supplied from the hopper from being repelled by the rubbing member and can supply the powder to the rubbing member. [Solution] The electrostatic film deposition apparatus comprises a screen 10 on which a mesh 11 is formed, a rubbing member 12 having a rubbing surface 12a for rubbing powder into the screen 10, a first power supply DC1 for applying a voltage between the screen 10 and the object 1, a hopper 14 for supplying powder to the rubbing member 12, and a second power supply DC2 for applying a voltage to the hopper 14. The second power supply DC2 is configured to apply a voltage to the hopper 14 that has the opposite polarity to the voltage applied to the screen 10 by the first power supply DC1.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electrostatic film forming apparatus that adheres powder such as edible powder or functional powder to a target object using electrostatic force. BACKGROUND ART

[0002] Electrostatic film forming apparatuses are used in various applications such as food printing and industrial product manufacturing. The principle of this electrostatic film forming apparatus will be described with reference to FIG. 15. As shown in FIG. 15, the electrostatic film forming apparatus includes a screen 202 having a mesh, a rubbing member 203 on the screen 202, and a hopper 204 that supplies powder to the rubbing member 203. A target object 200 is moved by a conveyor 201 to a printing position below the screen 202.

[0003] The screen 202 is connected to the negative electrode of a DC power supply, and the conveyor 201 is connected to the positive electrode of the DC power supply and grounded. A high voltage is applied between the screen 202 and the conveyor 201 by the DC power supply, thereby forming an electrostatic field between the screen 202 and the target object 200 on the conveyor 201. The powder in the hopper 204 is pushed by a rotating hopper roller 205 into a powder outlet (not shown) formed at the bottom of the hopper 204, passes through this powder outlet, is supplied onto the rotating rubbing member 203, and is further fed onto the screen 202 by the rotating rubbing member 203.

[0004] The powder on the screen 202 is rubbed into the mesh of the screen 202 by the rotating rubbing member 203, and is pushed out to the lower side of the screen 202 through the mesh. At this time, the powder is negatively charged by friction with the rotating rubbing member 203. Therefore, the powder is attracted to the grounded target object 200 and adheres to the surface of the target object 200, forming a film of uniform thickness on the target object 200.

[0005] Because such electrostatic film deposition equipment can uniformly form a film made of powder on an object 200, it is increasingly being used in the manufacture of various industrial products such as fuel cells, solid-state batteries, secondary batteries, and cosmetics. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-347221 [Overview of the project] [Problems that the invention aims to solve]

[0007] Figure 16 is an enlarged view of the hopper 204 and the sliding member 203. As shown in Figure 16, the powder is pushed into the powder outlet 204a of the hopper 204 by the rotating hopper brush 205, and as a result the powder becomes negatively charged due to friction. Since the hopper 204 is grounded, some of the powder pushed out of the hopper 204 is attracted to the hopper 204 and adheres to the bottom of the hopper 204, which can block the powder outlet of the hopper 204.

[0008] A negative voltage is applied to the screen 202 by the DC power supply, and the rubbing member 203 in contact with the screen 202 is negatively charged. Furthermore, due to the friction between the rotating rubbing member 203 and the screen 202, the powder on the rubbing member 203 also becomes negatively charged. Since the powder that falls from the hopper 204 is negatively charged, it repels the negatively charged rubbing member 203. As a result, the powder may scatter, and it may not be possible to uniformly supply the powder to the rubbing member 203. This problem is particularly likely to occur when the humidity of the air is low.

[0009] Therefore, the present invention provides an electrostatic film deposition apparatus that prevents the powder supplied from the hopper from being repelled by the rubbing member or screen, and that can supply the powder to the rubbing member or screen. [Means for solving the problem]

[0010] In one embodiment, an electrostatic film deposition apparatus is provided for depositing powder onto an object by electrostatic force, comprising: a screen with a mesh formed thereon; a rubbing member having a rubbing surface for rubbing powder onto the screen; a first power supply for applying a voltage between the screen and the object; a hopper for supplying the powder to the rubbing member or the screen; and a second power supply for applying a voltage to the hopper, wherein the second power supply is configured to apply a voltage to the hopper that is opposite in polarity to the voltage applied to the screen by the first power supply.

[0011] In one embodiment, the hopper comprises a hopper box for containing the powder, a metal plate placed on an insulating plate forming the bottom of the hopper box, and hopper rollers placed inside the hopper box. The metal plate has a powder outlet that allows the powder to pass through, and the metal plate is electrically connected to the second power supply. In one embodiment, the metal plate is electrically insulated from the hopper box by the insulating plate.

[0012] In one embodiment, an electrostatic film deposition apparatus is provided for depositing powder onto an object by electrostatic force, comprising: a screen with a mesh formed thereon; a rubbing member having a rubbing surface for rubbing powder onto the screen; a power supply for applying a voltage between the screen and the object; and a hopper for supplying the powder to the rubbing member or the screen, wherein the hopper comprises a hopper box for containing the powder, a metal plate disposed on an insulating plate forming the bottom of the hopper box, and hopper rollers disposed inside the hopper box, the metal plate having a powder outlet that allows the powder to pass through, and the metal plate being grounded via an earth wire. In one embodiment, the metal plate is electrically insulated from the hopper box by the insulating plate.

[0013] In one embodiment, an electrostatic film deposition apparatus is provided for depositing powder onto an object by electrostatic force, comprising: a screen with a mesh formed thereon; a rubbing member having a rubbing surface for rubbing powder onto the screen; a power supply for applying a voltage between the screen and the object; a hopper for supplying the powder to the rubbing member; and a static elimination metal bar in contact with the rubbing surface of the rubbing member, wherein the static elimination metal bar is grounded by an earth wire. In one embodiment, the static-eliminating metal bar is located upstream of the powder supply position from the hopper to the rubbing member in the direction of movement of the rubbing surface.

[0014] In one embodiment, an electrostatic film deposition apparatus is provided for depositing powder onto an object by electrostatic force, comprising: a screen with a mesh formed thereon; a rubbing member having a rubbing surface for rubbing powder onto the screen; a first power supply for applying a voltage between the screen and the object; a hopper for supplying the powder to the rubbing member; an electrostatically charged metal bar in contact with the rubbing surface of the rubbing member; and a second power supply for applying a voltage to the electrostatically charged metal bar, wherein the second power supply is configured to apply a voltage to the electrostatically charged metal bar that is opposite in polarity to the voltage applied to the screen by the first power supply. In one embodiment, the electrolyzed metal bar is located upstream of the powder supply position from the hopper to the rubbing member in the direction of movement of the rubbing surface.

[0015] In one embodiment, an electrostatic film deposition apparatus is provided for depositing powder onto an object by electrostatic force, comprising: a screen with a mesh formed thereon; a rubbing member having a rubbing surface for rubbing powder onto the screen; a first power supply for applying a voltage between the screen and the object; a hopper for supplying the powder to the rubbing member; an electric wire disposed between the hopper and the rubbing member or the screen; and a second power supply for applying a voltage to the electric wire, wherein the second power supply is configured to apply a voltage to the electric wire with a polarity opposite to that of the voltage applied to the screen by the first power supply. [Effects of the Invention]

[0016] The second power supply charges the powder coming out of the hopper by applying a voltage to the hopper that is opposite in polarity to the voltage applied to the screen by the first power supply. The charged powder is attracted to the screen, or to the charged rubbing member on the screen, to which a voltage of the opposite polarity is applied, thus preventing the powder from scattering into the surroundings. As a result, the rubbing member can rub the stably supplied powder into the screen, and a powder film of uniform thickness can be formed on the object.

[0017] The hopper's powder outlet is made of a metal plate, and a voltage is applied to the metal plate from a second power supply, so powder is less likely to accumulate at the outlet. As a result, clogging of the powder outlet by powder can be prevented. Some of the powder that comes out of the hopper may adhere to the insulating plate that makes up the bottom of the hopper. Once the surface of the insulating plate is covered with powder, any powder that approaches the insulating plate is charged with the same polarity as the powder covering the insulating plate, so it is repelled by the powder covering the insulating plate and does not accumulate further on the insulating plate.

[0018] There is a potential difference between the powder that has passed through the powder outlet of the grounded metal plate and the voltage-applied screen. Accordingly, the powder is attracted to the rubbing member on the screen, and the powder falls onto the rubbing member without scattering to the surroundings. As a result, the rubbing member can rub the stably supplied powder into the screen, and a powder film with a uniform thickness can be formed on an object.

[0019] The static-eliminating metal bar can eliminate static electricity from the rubbing surface of the rubbing member on the screen. Accordingly, the powder discharged from the hopper is supplied onto the rubbing surface of the rubbing member without repelling the rubbing member. As a result, the rubbing member can rub the stably supplied powder into the screen, and a powder film with a uniform thickness can be formed on an object.

[0020] The second power supply charges the rubbing surface of the rubbing member in contact with the charged metal bar by applying, to the charged metal bar, a voltage having a polarity opposite to that of the voltage applied to the screen by the first power supply. Since the powder and the rubbing surface are charged with opposite polarities, the powder is attracted to the rubbing surface. Accordingly, scattering of the powder to the surroundings can be prevented. As a result, the rubbing member can rub the stably supplied powder into the screen, and a powder film with a uniform thickness can be formed on an object.

[0021] The second power supply applies, to the charged electric wire, a voltage having a polarity opposite to that of the voltage applied to the screen by the first power supply, whereby the charged electric wire can eliminate static electricity from the powder discharged from the hopper. Accordingly, the powder is supplied onto the rubbing member or the screen without repelling the rubbing member or the screen. As a result, the rubbing member can rub the stably supplied powder into the screen, and a powder film with a uniform thickness can be formed on an object. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] [Figure 1] It is a front view showing one embodiment of an electrostatic film forming apparatus. [Figure 2] It is an enlarged view of a hopper and a rubbing member. [Figure 3] It is a diagram showing another embodiment of an electrostatic film forming apparatus. [Figure 4] It is a top view showing one embodiment of a screen transfer device that moves a screen. [Figure 5] It is a diagram showing still another embodiment of an electrostatic film forming apparatus. [Figure 6] It is a diagram showing still another embodiment of an electrostatic film forming apparatus. [Figure 7] It is a side view of the electrostatic film forming apparatus shown in Fig. 6. [Figure 8] It is an enlarged view showing one embodiment of a static elimination metal bar. [Figure 9] It is an enlarged view showing one embodiment of a charging metal bar. [Figure 10] It is a diagram showing still another embodiment of an electrostatic film forming apparatus. [Figure 11] It is a diagram showing still another embodiment of an electrostatic film forming apparatus. [Figure 12] It is a diagram showing still another embodiment of an electrostatic film forming apparatus. [Figure 13] It is a side view of the electrostatic film forming apparatus shown in Fig. 12. [Figure 14] It is a diagram showing still another embodiment of an electrostatic film forming apparatus. [Figure 15] It is a diagram illustrating an example of a conventional electrostatic film forming apparatus. [Figure 16] It is a diagram illustrating problems of a conventional electrostatic film forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0023] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a front view showing one embodiment of an electrostatic deposition apparatus. The electrostatic deposition apparatus comprises a screen 10 having a mesh 11, a rubbing member 12 placed on the screen 10, a hopper 14 for supplying powder to the rubbing member 12, a power supply DC1 for applying a voltage between the screen 10 and the object 1, and a power supply DC2 for applying a voltage to the hopper 14. Examples of powders include edible powders and functional powders. The object 1 is not particularly limited and can be food, or industrial products such as fuel cells, all-solid-state batteries, secondary batteries, and cosmetics.

[0024] The screen 10 is positioned facing the object 1, and the screen 10 and the object 1 are in non-contact. As shown in Figure 1, the screen 10 is positioned horizontally above the object 1. The screen 10 has a mesh 11 through which the powder passes. The powder is rubbed into the mesh 11 of the screen 10 by the rubbing surface 12a of the rubbing member 12. The rubbing surface 12a is made up of the cylindrical outer surface of the rubbing member 12.

[0025] The rubbing member 12 is in contact with the screen 10. In this embodiment, the rubbing member 12 is a rubbing roller having a cylindrical or columnar shape. An elastic material such as urethane sponge is used as the material for the rubbing member 12. In particular, a continuous-cell urethane sponge with good powder retention properties is preferably used. The rubbing member 12 is placed on the screen 10. More specifically, the rubbing member 12 is pressed against the screen 10, and the lower part of the rubbing member 12 is slightly deformed (crushed).

[0026] The rubbing member 12 is rotated by a rubbing member rotating device (not shown), and the rubbing surface 12a of the rubbing member 12 slides against the mesh 11 of the screen 10. In another embodiment, the rubbing member 12 may be a rubbing belt having a rubbing surface instead of a cylindrical rubbing roller. The rubbing belt is circulated by a belt drive device (not shown).

[0027] The hopper 14 is positioned above the smearing member 12. The hopper 14 comprises a hopper box 20 for containing powder, a metal plate 25 positioned on an insulating plate 24 that forms the bottom of the hopper box 20, and hopper rollers 22 positioned inside the hopper box 20. The metal plate 25 has a powder outlet 28 that allows powder to pass through. The metal plate 25 is electrically connected to a power supply DC2. The hopper rollers 22 are connected to a hopper roller rotating device (not shown) and rotated by the hopper roller rotating device.

[0028] The hopper roller 22 has a cylindrical shape. The hopper roller 22 is made of an elastic material such as urethane sponge. The hopper roller 22 is placed on a metal plate 25. More specifically, the hopper roller 22 is pressed against the metal plate 25 of the hopper box 20, and the lower part of the hopper roller 22 is slightly deformed (crushed).

[0029] The powder outlet 28 is a plurality of through holes or slits. The insulating plate 24 has an opening 24a at the same position as the powder outlet 28 of the metal plate 25, and the insulating plate 24 can allow the powder to pass through. When the hopper roller 22 rotates, the powder in the hopper box 20 is agitated by the hopper roller 22 and pushed into the powder outlet 28 of the metal plate 25 placed inside the hopper box 20, passing through the powder outlet 28 and the opening 24a and falling onto the rubbing surface 12a of the rubbing member 12. The amount of powder supplied to the rubbing member 12 can be adjusted by the rotation speed of the hopper roller 22.

[0030] A conveyor 2 is positioned below the screen 10 to transport multiple objects 1. The conveyor 2 sequentially moves the objects 1 to a position below the screen 10. A belt-type conveyor already installed in the factory can be used as the conveyor 2. The screen 10 is connected to the negative terminal of the power supply (voltage application device) DC1, and the conveyor 2 is connected to the positive terminal of the power supply DC1. The positive terminal of the power supply DC1 and the conveyor 2 are grounded. A high voltage is applied between the screen 10 and the conveyor 2 by the power supply DC1, thereby forming an electrostatic field between the screen 10 and the objects 1 on the conveyor 2.

[0031] The powder is supplied from the hopper 14 onto the rubbing member 12 and carried to the screen 10 by the rotating rubbing member 12. The powder is rubbed into the mesh 11 of the screen 10 by the rubbing surface 12a of the rotating rubbing member 12 and pushed out to the opposite side of the screen 10. At this time, the powder becomes negatively charged due to friction with the rotating rubbing member 12. Therefore, the powder is attracted to the object 1 that is in contact with the ground and adheres to the surface of the object 1, forming a powder film of uniform thickness on the object 1.

[0032] It is preferable to rub the powder onto the screen 10 while oscillating the rubbing member 12 in its axial direction using a rocking mechanism (not shown). Depending on the type of powder, some powders may become positively charged when rubbed onto the mesh 11 of the screen 10 by the rubbing member 12. When using such powders, the screen 10 is connected to the positive terminal of the power supply DC1, and the negative terminal of the power supply DC1 and the conveyor 2 are grounded.

[0033] Power supply DC2 is configured to apply a voltage to the hopper 14 that has the opposite polarity to the voltage applied to the screen 10 by power supply DC1. In this embodiment, since the polarity of the voltage applied to the screen 10 is negative, power supply DC2 applies a positive voltage to the hopper 14. More specifically, the metal plate 25 of the hopper 14 is electrically connected to the positive terminal of power supply DC2, and power supply DC2 applies a positive voltage to the metal plate 25. The negative terminal of power supply DC2 is grounded.

[0034] In another embodiment, when the screen 10 is connected to the positive terminal of power supply DC1 and the negative terminal of power supply DC1 and conveyor 2 are grounded, the metal plate 25 of the hopper 14 is electrically connected to the negative terminal of power supply DC2 and the positive terminal of power supply DC2 is grounded. Power supply DC2 is configured to apply a negative voltage to the metal plate 25.

[0035] The metal plate 25 is in contact with the insulating plate 24 that forms the bottom of the hopper box 20, but not with any other part of the hopper box 20. The parts of the hopper box 20 other than the insulating plate 24 are made of metal and are grounded. The metal plate 25 is electrically insulated from the hopper box 20 by the insulating plate 24. The insulating plate 24 can be made of resins such as MC nylon, acrylic, polyethylene, or polypropylene. The bottom surface of the hopper 14 is formed from the underside of the insulating plate 24.

[0036] Figure 2 is an enlarged view of the hopper 14 and the smearing member 12. Power supply DC2 charges the powder coming out of the hopper 14 by applying a voltage to the hopper 14 that is opposite in polarity to the voltage applied to the screen 10 by power supply DC1. In this embodiment, as shown in Figure 2, power supply DC1 applies a negative voltage to the screen 10, and power supply DC2 applies a positive voltage to the metal plate 25.

[0037] The powder becomes positively charged as it passes through the powder outlet 28 of the metal plate 25 to which a positive voltage is applied. The positively charged powder is attracted to the rubbing member 12 on the screen 10 to which a negative voltage is applied. Since the rubbing member 12 is negatively charged, the powder falls onto the rubbing member 12 without scattering into the surroundings. As a result, the rubbing member 12 can rub the stably supplied powder into the screen 10, forming a powder film of uniform thickness on the object 1.

[0038] The powder outlet 28 of the hopper 14 is made of a metal plate 25, and a voltage is applied to the metal plate 25 from the power supply DC2, so powder is less likely to accumulate at the powder outlet 28. As a result, clogging of the powder outlet 28 by powder can be prevented. Some of the powder that comes out of the hopper 14 may adhere to the insulating plate 24 that makes up the bottom of the hopper 14. Once the surface of the insulating plate 24 is covered with powder, powder that approaches the insulating plate 24 is charged with the same polarity as the powder covering the insulating plate 24, so it is repelled by the powder covering the insulating plate 24 and does not accumulate further on the insulating plate 24.

[0039] Figure 3 shows another embodiment of the electrostatic deposition apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figures 1 and 2, so redundant descriptions are omitted.

[0040] In this embodiment, the hopper 14 is positioned above the screen 10 and supplies powder onto the screen 10 rather than the rubbing member 12. The screen 10 is moved at the same speed and in the same direction as the object 1 on the conveyor 2 by the screen moving device 30 shown in Figure 4. The position of the rubbing member 12 is fixed and operates to rub the powder supplied from the hopper 14 onto the screen 10 into the mesh 11 of the screen 10.

[0041] Figure 4 is a top view showing one embodiment of a screen moving device 30 for moving screens 10. The screen moving device 30 is a conveyor that moves multiple screens 10 along an elliptical path. The configuration of the screen moving device 30 itself can be based on the configuration of a known conveyor.

[0042] The electrostatic film deposition apparatus of the embodiment described with reference to Figures 3 and 4 can achieve the same effects as the electrostatic film deposition apparatus of the embodiment described with reference to Figures 1 and 2.

[0043] Figure 5 shows yet another embodiment of the electrostatic film deposition apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 1, so redundant descriptions are omitted. In this embodiment, the metal plate 25 on the insulating plate 24 is connected to an earth wire 31 instead of the power supply DC2, and the metal plate 25 is grounded via the earth wire 31.

[0044] Since the metal plate 25 is grounded, its potential is 0. However, from the perspective of the negatively charged rubbing member 12, the metal plate 25 has a positive potential relative to the rubbing member 12. Therefore, the powder that passes through the powder outlet 28 of the metal plate 25 also has a positive potential relative to it. The powder is attracted to the rubbing member 12 on the screen 10 to which a negative voltage is applied, and the powder falls onto the rubbing member 12 without scattering into the surroundings. As a result, the rubbing member 12 can rub the stably supplied powder into the screen 10, and a powder film of uniform thickness can be formed on the object 1.

[0045] The embodiment described with reference to Figure 5 can also be applied to the embodiment shown in Figure 3. That is, in the embodiment shown in Figure 3, the metal plate 25 on the insulating plate 24 may be grounded via an earth wire instead of the power supply DC2.

[0046] Figure 6 shows yet another embodiment of the electrostatic film deposition apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 1, so redundant descriptions are omitted.

[0047] As shown in Figure 6, the electrostatic deposition apparatus includes a static elimination metal bar 41 that contacts the rubbing surface 12a of the rubbing member 12. The static elimination metal bar 41 is grounded by an earth wire 42. The static elimination metal bar 41 is located upstream of the powder supply position from the hopper 14 to the rubbing member 12 in the direction of movement of the rubbing surface 12a. In this embodiment, since the rubbing member 12 rotates, the static elimination metal bar 41 is located upstream of the powder supply position from the hopper 14 to the rubbing member 12 in the direction of rotation of the rubbing member 12.

[0048] The electrostatic deposition apparatus further includes an electrostatically charged metal bar 45 that contacts the rubbing surface 12a of the rubbing member 12, and a power supply DC3 that applies voltage to the electrostatically charged metal bar 45. The electrostatically charged metal bar 45 is located upstream of the powder supply position from the hopper 14 to the rubbing member 12 in the direction of movement of the rubbing surface 12a. In this embodiment, since the rubbing member 12 rotates, the electrostatically charged metal bar 45 is located upstream of the powder supply position from the hopper 14 to the rubbing member 12 in the direction of rotation of the rubbing member 12.

[0049] Power supply DC3 is configured to apply a voltage to the electrostatic metal bar 45 that has the opposite polarity to the voltage applied to the screen 10 by power supply DC1. In this embodiment, as shown in Figure 6, power supply DC1 applies a negative voltage to the screen 10, and power supply DC3 applies a positive voltage to the electrostatic metal bar 45.

[0050] In this embodiment, the hopper 14 does not have the metal plate 25 and insulating plate 24 described with reference to Figures 1 and 2. Furthermore, it does not have a power supply DC2. A powder outlet 28 is formed at the bottom of the hopper 14 to allow the powder to pass through. When the hopper roller 22 rotates, the powder in the hopper box 20 is agitated by the hopper roller 22 and pushed into the powder outlet 28, passing through the powder outlet 28 and falling onto the rubbing surface 12a of the rubbing member 12.

[0051] Figure 7 is a side view of the electrostatic deposition apparatus shown in Figure 6. The static elimination metal bar 41 and the electrostatic metal bar 45 extend along the axial direction of the rubbing member 12. In this embodiment, the static elimination metal bar 41 and the electrostatic metal bar 45 are parallel to the screen 10. The static elimination metal bar 41 and the electrostatic metal bar 45 are longer than the powder supply range from the hopper 14 to the rubbing member 12 and are approximately the same as the axial dimensions of the rubbing member 12.

[0052] The static-eliminating metal bar 41 can eliminate static electricity from the rubbing surface 12a of the rubbing member 12 on the screen 10. Therefore, the powder coming out of the hopper 14 is supplied onto the rubbing surface 12a of the rubbing member 12 without being repelled by it. As a result, the rubbing member 12 can rub the stably supplied powder into the screen 10, and a powder film of uniform thickness can be formed on the object 1.

[0053] Power supply DC3 applies a voltage to the charged metal bar 45 that is opposite in polarity to the voltage applied to the screen 10 by power supply DC1, thereby charging the rubbing surface 12a of the rubbing member 12 that is in contact with the charged metal bar 45. Since the powder and the rubbing surface 12a are charged with opposite polarities, the powder coming out of the hopper 14 is attracted to the rubbing surface 12a. Therefore, the powder is prevented from scattering into the surroundings. As a result, the rubbing member 12 can rub the stably supplied powder into the screen 10, and a powder film of uniform thickness can be formed on the object 1.

[0054] In another embodiment, when the screen 10 is connected to the positive terminal of power supply DC1 and the negative terminal of power supply DC1 and conveyor 2 are grounded, the electrostatic metal bar 45 is electrically connected to the negative terminal of power supply DC3 and the positive terminal of power supply DC3 is grounded. Power supply DC3 is configured to apply a negative voltage to the electrostatic metal bar 45.

[0055] As shown in Figure 6, the electrostatic metal bar 45 is located downstream of the static elimination metal bar 41 in the direction of movement of the rubbing surface 12a (the rotation direction of the rubbing member 12). Therefore, the rubbing surface 12a comes into contact with the static elimination metal bar 41 and then the electrostatic metal bar 45. The static elimination metal bar 41 eliminates static electricity from the rubbing surface 12a, and then the electrostatic metal bar 45 applies a positive voltage to the rubbing surface 12a.

[0056] Figure 8 is an enlarged view showing one embodiment of the static elimination metal bar 41. As shown in Figure 8, the static elimination metal bar 41 is held by a holding member 47 and pressed against the rubbing surface 12a of the rubbing member 12. Both sides of the static elimination metal bar 41 are curved outward from the rubbing surface 12a. The static elimination metal bar 41 is made of a highly conductive metal (e.g., aluminum, copper). The static elimination metal bar 41 is connected to an earth wire 42.

[0057] The static-eliminating metal bar 41 is pressed in by a distance W1 of about 2 mm to 3 mm from the rubbing surface 12a of the rubbing member 12. This arrangement increases the contact surface of the static-eliminating metal bar 41, allowing the static-eliminating metal bar 41 to more effectively eliminate static electricity from the rubbing surface 12a.

[0058] Figure 9 is an enlarged view showing one embodiment of the electrostatic metal bar 45. As shown in Figure 9, the electrostatic metal bar 45 is held by a holding member 48 and pressed against the rubbing surface 12a of the rubbing member 12. Both sides of the electrostatic metal bar 45 are curved outward from the rubbing surface 12a. The electrostatic metal bar 45 is made of a highly conductive metal (e.g., aluminum, copper). The electrostatic metal bar 45 is electrically connected to a power supply DC3.

[0059] The charged metal bar 45 is pressed in by a distance W2 of approximately 2 mm to 3 mm from the rubbing surface 12a of the rubbing member 12. This arrangement increases the contact surface of the charged metal bar 45, allowing the charged metal bar 45 to more effectively charge the rubbing surface 12a.

[0060] In the embodiments shown in Figures 6 and 7, the electrostatic deposition apparatus includes both a static-eliminating metal bar 41 and an electrostatic-adding metal bar 45. In other embodiments, as shown in Figure 10, the electrostatic deposition apparatus may include a static-eliminating metal bar 41 but not an electrostatic-adding metal bar 45. In yet another embodiment, as shown in Figure 11, the electrostatic deposition apparatus may include an electrostatic-adding metal bar 45 but not a static-eliminating metal bar 41. In the embodiments shown in Figures 10 and 11, the powder coming out of the hopper 14 is more likely to fall onto the rubbing surface 12a.

[0061] Figure 12 shows yet another embodiment of the electrostatic film deposition apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 6, so a redundant explanation is omitted.

[0062] In this embodiment, the static elimination metal bar 41 and the electrostatic metal bar 45 are not provided. Instead, as shown in Figure 12, the electrostatic deposition apparatus includes an electrostatic wire 50 positioned between the hopper 14 and the smearing member 12, and a power supply DC4 that applies voltage to the electrostatic wire 50. The power supply DC4 is configured to apply a voltage to the electrostatic wire 50 that is opposite in polarity to the voltage applied to the screen 10 by the power supply DC1. In this embodiment, as shown in Figure 12, the power supply DC1 applies a negative voltage to the screen 10, and the power supply DC4 applies a positive voltage to the electrostatic wire 50.

[0063] The power supply wires 50 are located below the powder outlet 28 of the hopper 14 and above the smearing member 12. In this embodiment, multiple power supply wires 50 are arranged on both sides of the powder path from the hopper 14 to the smearing member 12. That is, multiple power supply wires 50 are arranged on both sides of the powder falling from the hopper 14. These power supply wires 50 are electrically connected to the positive terminal of the power supply DC 4.

[0064] In another embodiment, when the screen 10 is connected to the positive terminal of power supply DC1 and the negative terminal of power supply DC1 and conveyor 2 are grounded, the power supply wire 50 is electrically connected to the negative terminal of power supply DC4 and the positive terminal of power supply DC4 is grounded. Power supply DC4 is configured to apply a negative voltage to the power supply wire 50.

[0065] Figure 13 is a side view of the electrostatic deposition apparatus shown in Figure 12. The power supply wire 50 extends along the axial direction of the rubbing member 12. In this embodiment, the power supply wire 50 is parallel to the screen 10. The power supply wire 50 is longer than the powder supply range from the hopper 14 to the rubbing member 12 and is approximately the same as the axial dimension of the rubbing member 12.

[0066] Power supply DC4 applies a voltage to the power supply wire 50 that is opposite in polarity to the voltage applied to the screen 10 by power supply DC1, thereby allowing the power supply wire 50 to de-staticize the powder coming out of the hopper 14. As a result, the powder is supplied onto the rubbing member 12 without being repelled by it. Consequently, the rubbing member 12 can rub the stably supplied powder onto the screen 10, forming a powder film of uniform thickness on the object 1.

[0067] Figure 14 shows yet another embodiment of the electrostatic film deposition apparatus. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figure 13, so redundant descriptions are omitted.

[0068] In the embodiment shown in Figure 14, the hopper 14 is positioned above the screen 10 and supplies the powder onto the screen 10 rather than the smearing member 12. The power supply wires 5 are positioned between the hopper 14 and the screen 10. In this embodiment, multiple power supply wires 50 are positioned on both sides of the powder path from the hopper 14 to the screen 10. That is, the multiple power supply wires 50 are positioned on both sides of the powder falling from the hopper 14.

[0069] The screen 10 is moved at the same speed and in the same direction as the object 1 on the conveyor 2 by the screen moving device 30 shown in Figure 4. The position of the rubbing member 12 is fixed and it operates to rub the powder supplied onto the screen 10 from the hopper 14 into the mesh 11 of the screen 10.

[0070] The embodiments described with reference to Figures 1 to 14 may be combined as appropriate. For example, the metal plate 25, insulating plate 24, and power supply DC2 shown in Figure 1 may be applied to the embodiments described with reference to Figures 6 to 14. Furthermore, the static elimination metal bar 41 and the electrostatic metal bar 45 described with reference to Figures 6 to 11 may be applied to the embodiments described with reference to Figures 12 to 14.

[0071] In the embodiments described with reference to Figures 1 to 14, the voltage and polarity applied to the metal plate 25, the charged metal bar 45, and the charged wire 50 are selected to avoid repulsion of the powder, taking into consideration the surface voltage and polarity of the rubbing member 12 and the screen 10.

[0072] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of Symbols]

[0073] 1. Object 2 Conveyors 10 screens 11 mesh 12. Sliding material 12a Rubbing surface DC1,DC2,DC3,DC4 Power supply 14 Hoppa 20 hopper boxes 22 hopper rollers 24 Insulating board 25 metal plate 28 Powder outlet 30 Screen moving device 31. Ground wire 41 Static-eliminating metal bar 42 Ground wire 45 Electrostatic Metal Bar 47 Retaining member 48 Retaining member 50 Feeding wire

Claims

1. An electrostatic film deposition apparatus that deposits powder onto an object using electrostatic force, A screen with a mesh formed on it, A rubbing member having a rubbing surface for rubbing powder onto the screen, A first power supply for applying a voltage between the screen and the object, A hopper for supplying the powder to the grinding member or the screen, The hopper is equipped with a second power supply for applying voltage, An electrostatic film deposition apparatus, wherein the second power supply is configured to apply a voltage to the hopper that has the opposite polarity to the voltage applied to the screen by the first power supply.

2. The hopper comprises a hopper box for containing the powder, a metal plate placed on an insulating plate forming the bottom of the hopper box, and hopper rollers placed inside the hopper box. The metal plate has a powder outlet that allows the powder to pass through, The electrostatic film deposition apparatus according to claim 1, wherein the metal plate is electrically connected to the second power supply.

3. The electrostatic film deposition apparatus according to claim 2, wherein the metal plate is electrically insulated from the hopper box by the insulating plate.

4. An electrostatic film deposition apparatus that deposits powder onto an object using electrostatic force, A screen with a mesh formed on it, A rubbing member having a rubbing surface for rubbing powder onto the screen, A power supply for applying a voltage between the screen and the object, The system includes a hopper for supplying the powder to the grinding member or the screen, The hopper comprises a hopper box for containing the powder, a metal plate placed on an insulating plate forming the bottom of the hopper box, and hopper rollers placed inside the hopper box. The metal plate has a powder outlet that allows the powder to pass through, The aforementioned metal plate is grounded via an earth wire in an electrostatic film deposition apparatus.

5. The electrostatic film deposition apparatus according to claim 4, wherein the metal plate is electrically insulated from the hopper box by the insulating plate.

6. An electrostatic film deposition apparatus that deposits powder onto an object using electrostatic force, A screen with a mesh formed on it, A rubbing member having a rubbing surface for rubbing powder onto the screen, A power supply for applying a voltage between the screen and the object, A hopper for supplying the powder to the grinding member, The aforementioned rubbing member is equipped with an anti-static metal bar that contacts the rubbing surface, The electrostatic deposition apparatus is characterized by the fact that the static-eliminating metal bar is grounded by an earth wire.

7. The electrostatic film deposition apparatus according to claim 6, wherein the static elimination metal bar is located upstream of the powder supply position from the hopper to the rubbing member in the direction of movement of the rubbing surface.

8. An electrostatic film deposition apparatus that deposits powder onto an object using electrostatic force, A screen with a mesh formed on it, A rubbing member having a rubbing surface for rubbing powder onto the screen, A first power supply for applying a voltage between the screen and the object, A hopper for supplying the powder to the grinding member, An electrostatically charged metal bar that contacts the rubbing surface of the rubbing member, The system includes a second power supply for applying voltage to the aforementioned electrostatic metal bar, An electrostatic film deposition apparatus, wherein the second power supply is configured to apply a voltage to the electrostatic metal bar that has the opposite polarity to the voltage applied to the screen by the first power supply.

9. The electrostatic film deposition apparatus according to claim 8, wherein the electrostatically charged metal bar is located upstream of the powder supply position from the hopper to the rubbing member in the direction of movement of the rubbing surface.

10. An electrostatic film deposition apparatus that deposits powder onto an object using electrostatic force, A screen with a mesh formed on it, A rubbing member having a rubbing surface for rubbing powder onto the screen, A first power supply for applying a voltage between the screen and the object, A hopper for supplying the powder to the grinding member, A power supply wire disposed between the hopper and the sliding member or the screen, The system includes a second power supply that applies voltage to the aforementioned power supply line, An electrostatic film deposition apparatus, wherein the second power supply is configured to apply a voltage to the power supply wire having a polarity opposite to that of the voltage applied to the screen by the first power supply.

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